FIELD VALIDATION OF SEDIMENT TIE METHODS

EPA Science Inventory

Sediment toxicity is a widely recognized problem in many regions of the world. Frequently, however, the cause of toxicity is not known. The ability to identify the cause(s) of toxicity in sediments allows managers to determine sources of continuing contamination to support sele...

Evaluating Local and Regional Sources of Trace Element Contamination in a Rural Sub Estuary of the Upper Chesapeake Bay

NASA Astrophysics Data System (ADS)

Krahforst, C.; Hartman, S.; Sherman, L.; Kehm, K.

2014-12-01

The distribution of trace elements (V, Cr, Co, Ni, Cu, Zn, As, Ag, Cd, Sn, Ba, W, Pb and U) along with Al and Fe and other sediment characteristics in surface sediment and sediment cores from the Chester River - a sub estuary of the Chesapeake Bay located in a predominantly agricultural watershed of Maryland's upper Eastern Shore, USA - have been determined in order to add to the understanding of contaminant transport and fate and inform management strategies designed to maintain or improve the ecological condition of estuaries. These analyses coupled with the comparison of elemental analysis of 210Pb - dated sediment cores, main stem water quality surveys, and a review of recent EPA National Coastal Condition Assessment sediment data from Chesapeake Bay provide added information about the roles of local and region scale processes on ecosystem condition. The high amount of suspended sediment in the Chester River (5-20 mg L-1) is an important factor controlling water quality conditions of the Chester River and a prime focus for environmental management of this system. Sources of suspended matter include local runoff, atmospheric deposition, local resuspension, and exchange with the Chesapeake Bay. In principle, each of these sources could be distinguished on the basis of chemical composition of surface sediment. Preliminary results from multivariate analytic models indicate that many of the elements investigated display significant covariance with Al (and other predominantly crustal signatures) which may indicate limited exogenic sources of contamination for sediments of this watershed. For example total Pb concentrations are mostly below the NOAA's low toxic effects level and lower than the median value of NCCA data for the upper Chesapeake suggesting that sediments have significant sources from within the watershed. Further, significant higher concentrations of Sn and Cu coincide with sediment collected in or near marinas and point to localized anthropogenic sources for these elements. Elemental enrichment values relative to Al of Chester River sediments are significantly lower than observations in sediments from Chesapeake Bay overall and may indicate that local watershed management strategies may be effective for improving water and habitat quality of the Chester River.

Clay-mineral suites, sources, and inferred dispersal routes: Southern California continental shelf

USGS Publications Warehouse

Hein, J.R.; Dowling, J.S.; Schuetze, A.; Lee, H.J.

2003-01-01

Clay mineralogy is useful in determining the distribution, sources, and dispersal routes of fine-grained sediments. In addition, clay minerals, especially smectite, may control the degree to which contaminants are adsorbed by the sediment. We analyzed 250 shelf sediment samples, 24 river-suspended-sediment samples, and 12 river-bed samples for clay-mineral contents in the Southern California Borderland from Point Conception to the Mexico border. In addition, six samples were analyzed from the Palos Verdes Headland in order to characterize the clay minerals contributed to the offshore from that point source. The <2 ??m-size fraction was isolated, Mg-saturated, and glycolated before analysis by X-ray diffraction. Semi-quantitative percentages of smectite, illite, and kaolinite plus chlorite were calculated using peak areas and standard weighting factors. Most fine-grained sediment is supplied to the shelf by rivers during major winter storms, especially during El Nin??o years. The largest sediment fluxes to the region are from the Santa Ynez and Santa Clara Rivers, which drain the Transverse Ranges. The mean clay-mineral suite for the entire shelf sediment data set (26% smectite, 50% illite, 24% kaolinite+chlorite) is closely comparable to that for the mean of all the rivers (31% smectite, 49% illite, 20% kaolinite+chlorite), indicating that the main source of shelf fine-grained sediments is the adjacent rivers. However, regional variations do exist and the shelf is divided into four provinces with characteristic clay-mineral suites. The means of the clay-mineral suites of the two southernmost provinces are within analytical error of the mineral suites of adjacent rivers. The next province to the north includes Santa Monica Bay and has a suite of clay minerals derived from mixing of fine-grained sediments from several sources, both from the north and south. The northernmost province clay-mineral suite matches moderately well that of the adjacent rivers, but does indicate some mixing from sources in adjacent provinces.

Palynology after Y2K--Understanding the Source Area of Pollen in Sediments

NASA Astrophysics Data System (ADS)

Davis, M. B.

Pollen grains preserved in lake and bog sediment provide a record of past vegetation that has been an important source of information about climate and land cover during the Quaternary Period. Yet from the beginning, questions have been raised about the source area of pollen in sediment. Interpretation has been hampered by the lack of well-developed theory treating the relationship between the spatial distribution of trees on the landscape and the percentages of pollen in sediment. Within the past decade, however, new theory, models, and empirical data show how heterogeneous vegetation is represented by pollen. The distinction between "local" and "regional" pollen is explained by the Prentice-Sugita dispersal/deposition models, which predict how the ratio of regional to local pollen changes with lake size. Sugita's model simulating a landscape with heterogeneous vegetation predicts the size of the relevant source area-the area of vegetation reflected in between-lake variations in pollen loading-while demonstrating that regional pollen from beyond this distance is homogeneous at all lakes of similar size. By predicting the way landscape patterns will be reflected in pollen records, simulation models can improve research design and lead to more detailed and spatially precise records of past vegetation, enhancing continental-scale climate reconstructions.

Coastal Inlets Research Program

DTIC Science & Technology

2015-02-09

maintenance dredging of 216 million cubic yards from Federal navigation channels. Dredging costs are likely to increase in the future because of...beaches, estuaries, ecosystems and regions. Demand for regional sediment management practices and mitigation for engineering activities includes...innovative creation of nearshore berms with dredged sediment intended as a source to nourish neighboring beaches. Renewable, cost- effective placement

Sediment Sources Change for the Past 42 Years in a Small Watershed Located in the Black Soil Region of Northeastern China Based on Fingerprinting Method

NASA Astrophysics Data System (ADS)

Du, P.; Huang, D.; Ning, D.

2017-12-01

The temporal change of sediment source in watershed is very helpful for evaluating the adopted soil conservation measures and the implemented land management practices. For this purpose, a sediment profile from Hebei watershed outlet and 59 samples from the three potential sediment sources were collected. The rediounuclide Pb-210 was then measured to obtain sedimentation rate for the past 42 years. Generally, the sedimentation rate was gradually decreased from 10.83 cm yr-1 in the 1970's to 1.50 cm yr-1in the 2010's. Taken the radiounulide Cs-137 as a fingerprinting identifying tracer, the mean contribution of sediment from cultivated lands, woodlands, and channel banks were 50.60%, 22.26%, and 26.74%, while the ranges varying from 20.16% to 84.02%, from 2.22% to 36.85%, and from 11.61% to 53.28%, respectively. The percentage of sediment sources from cultivated lands was decreased, whereas the percentages from woodlands and channel banks were both increased in the past 42 years. The results indicate that soil conservation measures adopted in the cultivated lands have been played a very important role in reducing erosion, however, more attention on land management practices implementation should be paid to maintain current woodland and to control serious gully erosion in the black soil region. (This paper is a contribution to the project of National Natural Science Foundation of China (No. 41501299), and the non-profit project of Ministry of Water Resources of China (No. 201501045).)

Subduction, erosion and the sediment record: Insights from Miocene sediments, Hengchun Peninsula, Taiwan

NASA Astrophysics Data System (ADS)

Kirstein, Linda; Carter, Andrew; Chen, Yue-Gau

2010-05-01

Detrital sedimentary records include vast archives of material that have been removed from developing tectonically active regions. These archives have been used to investigate challenging questions on continental deformation, exhumation and palaeodrainage using a variety of different techniques including heavy minerals, fission-track dating and palaeocurrent reconstructions. The Hengchun Peninsula of southern Taiwan and offshore Hengchun Ridge form a present day accretionary prism, with accretionary wedge growth occurring both by frontal accretion, with sediments from the continental margin scraped up into the accretionary wedge and by underplating. Miocene sediments in Hengchun include foreland basin deposits, deep marine turbidites and forearc basin deposits. As a result the detrital sediments record details of accretionary prism growth associated with continued Luzon arc-continent collision. Diametrically opposite palaeocurrents are preserved in the Miocene sandstones of the Hengchun Peninsula, southern Taiwan. Controversial explanations include an exotic source terrane to the south and/or 180 ° rotation of a depositional basin. We document the tecto-thermal evolution of the Miocene sediment source(s) using a double dating approach. U-Pb grain ages range from Miocene to Archaean, while zircon fission-tracks record thermal cooling primarily in the Cretaceous with minor peaks in the Miocene, Triassic, Jurassic and Permian. The primary source of the Miocene sediments at the centre of the controversy was similar. Palaeocurrent data are influenced by local basin geometry and submarine topography and suggest that sediment deposition in the Miocene was strongly controlled by incipient subduction, associated structural trends and submarine topography. A similar control on deposition in the modern Taiwan collision zone is apparent in the offshore region today.

Antibiotics in the coastal environment of the Hailing Bay region, South China Sea: Spatial distribution, source analysis and ecological risks.

PubMed

Chen, Hui; Liu, Shan; Xu, Xiang-Rong; Zhou, Guang-Jie; Liu, Shuang-Shuang; Yue, Wei-Zhong; Sun, Kai-Feng; Ying, Guang-Guo

2015-06-15

In this study, the occurrence and spatial distribution of 38 antibiotics in surface water and sediment samples of the Hailing Bay region, South China Sea, were investigated. Twenty-one, 16 and 15 of 38 antibiotics were detected with the concentrations ranging from <0.08 (clarithromycin) to 15,163ng/L (oxytetracycline), 2.12 (methacycline) to 1318ng/L (erythromycin-H2O), <1.95 (ciprofloxacin) to 184ng/g (chlortetracycline) in the seawater, discharged effluent and sediment samples, respectively. The concentrations of antibiotics in the water phase were correlated positively with chemical oxygen demand and nitrate. The source analysis indicated that untreated domestic sewage was the primary source of antibiotics in the study region. Fluoroquinolones showed strong sorption capacity onto sediments due to their high pseudo-partitioning coefficients. Risk assessment indicated that oxytetracycline, norfloxacin and erythromycin-H2O posed high risks to aquatic organisms. Copyright © 2015 Elsevier Ltd. All rights reserved.

Sources and dispersal of land-based runoff from small Hawaiian drainages to a coral reef: Insights from geochemical signatures

NASA Astrophysics Data System (ADS)

Takesue, Renee K.; Storlazzi, Curt D.

2017-03-01

Land-based sediment and contaminant runoff is a major threat to coral reefs, and runoff reduction efforts would benefit from knowledge of specific runoff sources. Geochemical signatures of small drainage basins were determined in the fine fraction of soil and sediment, then used in the nearshore region of a coral reef-fringed urban embayment on southeast Oahu, Hawaii, to describe sources and dispersal of land-based runoff. The sedimentary rare earth element ratio (La/Yb)N showed a clear distinction between the two main rock types in the overall contributing area, tholeiitic and alkalic olivine basalt. Based on this geochemical signature it was apparent that the majority of terrigenous sediment on the reef flat originated from geologically old tholeiitic drainages. Sediment from one of five tholeiitic drainages had a distinct geochemical signature, and sediment with this signature was dispersed on the reef flat 2 km west and 150 m offshore of the contributing basin. Sediment and the anthropogenic metals Cd, Pb, and Zn were entrained in runoff from the most heavily urbanized region of the watershed. Although anthropogenic Cd and Zn had localized distributions close to shore, anthropogenic Pb was found associated with fine sediment on the westernmost part of the reef flat and 400 m offshore, illustrating how trade-wind-driven sediment transport can increase the scale of runoff impacts to nearshore communities. Our findings show that sediment geochemical signatures can provide insights about the source and dispersal of land-based runoff in shallow coastal environments. The application of such knowledge to watershed management and habitat remediation efforts can aid in the protection and restoration of runoff-impacted coastal ecosystems worldwide.

Sources and dispersal of land-based runoff from small Hawaiian drainages to a coral reef: Insights from geochemical signatures

USGS Publications Warehouse

Takesue, Renee K.; Storlazzi, Curt

2017-01-01

Land-based sediment and contaminant runoff is a major threat to coral reefs, and runoff reduction efforts would benefit from knowledge of specific runoff sources. Geochemical signatures of small drainage basins were determined in the fine fraction of soil and sediment, then used in the nearshore region of a coral reef-fringed urban embayment on southeast Oahu, Hawaii, to describe sources and dispersal of land-based runoff. The sedimentary rare earth element ratio (La/Yb)N showed a clear distinction between the two main rock types in the overall contributing area, tholeiitic and alkalic olivine basalt. Based on this geochemical signature it was apparent that the majority of terrigenous sediment on the reef flat originated from geologically old tholeiitic drainages. Sediment from one of five tholeiitic drainages had a distinct geochemical signature, and sediment with this signature was dispersed on the reef flat 2 km west and 150 m offshore of the contributing basin. Sediment and the anthropogenic metals Cd, Pb, and Zn were entrained in runoff from the most heavily urbanized region of the watershed. Although anthropogenic Cd and Zn had localized distributions close to shore, anthropogenic Pb was found associated with fine sediment on the westernmost part of the reef flat and 400 m offshore, illustrating how trade-wind-driven sediment transport can increase the scale of runoff impacts to nearshore communities. Our findings show that sediment geochemical signatures can provide insights about the source and dispersal of land-based runoff in shallow coastal environments. The application of such knowledge to watershed management and habitat remediation efforts can aid in the protection and restoration of runoff-impacted coastal ecosystems worldwide.

A Model-Based Approach to Infer Shifts in Regional Fire Regimes Over Time Using Sediment Charcoal Records

NASA Astrophysics Data System (ADS)

Itter, M.; Finley, A. O.; Hooten, M.; Higuera, P. E.; Marlon, J. R.; McLachlan, J. S.; Kelly, R.

2016-12-01

Sediment charcoal records are used in paleoecological analyses to identify individual local fire events and to estimate fire frequency and regional biomass burned at centennial to millenial time scales. Methods to identify local fire events based on sediment charcoal records have been well developed over the past 30 years, however, an integrated statistical framework for fire identification is still lacking. We build upon existing paleoecological methods to develop a hierarchical Bayesian point process model for local fire identification and estimation of fire return intervals. The model is unique in that it combines sediment charcoal records from multiple lakes across a region in a spatially-explicit fashion leading to estimation of a joint, regional fire return interval in addition to lake-specific local fire frequencies. Further, the model estimates a joint regional charcoal deposition rate free from the effects of local fires that can be used as a measure of regional biomass burned over time. Finally, the hierarchical Bayesian approach allows for tractable error propagation such that estimates of fire return intervals reflect the full range of uncertainty in sediment charcoal records. Specific sources of uncertainty addressed include sediment age models, the separation of local versus regional charcoal sources, and generation of a composite charcoal record The model is applied to sediment charcoal records from a dense network of lakes in the Yukon Flats region of Alaska. The multivariate joint modeling approach results in improved estimates of regional charcoal deposition with reduced uncertainty in the identification of individual fire events and local fire return intervals compared to individual lake approaches. Modeled individual-lake fire return intervals range from 100 to 500 years with a regional interval of roughly 200 years. Regional charcoal deposition to the network of lakes is correlated up to 50 kilometers. Finally, the joint regional charcoal deposition rate exhibits changes over time coincident with major climatic and vegetation shifts over the past 10,000 years. Ongoing work will use the regional charcoal deposition rate to estimate changes in biomass burned as a function of climate variability and regional vegetation pattern.

Effects of legacy sediment removal on hydrology and biogeochemistryin a first order stream in Pennsylvania, USA

EPA Science Inventory

Historic forest conversion to agriculture and associated stream impoundments built for hydropower led to extensive burial of valley bottoms throughout the mid-Atlantic region of the US. These so-called legacy sediments are sources of nutrient and sediment pollutant loads to down...

Regional controls on geomorphology, hydrology, and ecosystem integrity in the Orinoco Delta, Venezuela

USGS Publications Warehouse

Warne, A.G.; Meade, R.H.; White, W.A.; Guevara, E.H.; Gibeaut, J.; Smyth, R.C.; Aslan, A.; Tremblay, T.

2002-01-01

Interacting river discharge, tidal oscillation, and tropical rainfall across the 22,000 km2 Orinoco delta plain support diverse fresh and brackish water ecosystems. To develop environmental baseline information for this largely unpopulated region, we evaluate major coastal plain, shallow marine, and river systems of northeastern South America, which serves to identify principal sources and controls of water and sediment flow into, through, and out of the Orinoco Delta. The regional analysis includes a summary of the geology, hydrodynamics, sediment dynamics, and geomorphic characteristics of the Orinoco drainage basin, river, and delta system. Because the Amazon River is a major source of sediment deposited along the Orinoco coast, we summarize Amazon water and sediment input to the northeastern South American littoral zone. We investigate sediment dynamics and geomorphology of the Guiana coast, where marine processes and Holocene history are similar to the Orinoco coast. Major factors controlling Orinoco Delta water and sediment dynamics include the pronounced annual flood discharge; the uneven distribution of water and sediment discharge across the delta plain; discharge of large volumes of water with low sediment concentrations through the Rio Grande and Araguao distributaries; water and sediment dynamics associated with the Guayana littoral current along the northeastern South American coast; inflow of large volumes of Amazon sediment to the Orinoco coast; development of a fresh water plume seaward of Boca Grande; disruption of the Guayana Current by Trinidad, Boca de Serpientes, and Gulf of Paria; and the constriction at Boca de Serpientes. ?? 2002 Elsevier Science B.V. All rights reserved.

Sources and ages of fine-grained sediment to streams using fallout radionuclides in the Midwestern United States

USGS Publications Warehouse

Gellis, Allen; Fuller, Christopher C.; Van Metre, Peter C.

2017-01-01

Fallout radionuclides, 7Be and 210Pbex, sampled in bed sediment for 99 watersheds in the Midwestern region of the United States and in 15 samples of suspended sediment from 3 of these watersheds were used to partition upland from channel sources and to estimate the age or the time since the surface-derived portion of sediment was on the land surface (0–∼1 year). Channel sources dominate: 78 of the 99 bed material sites (79%) have >50% channel-derived sediment, and 9 of the 15 suspended-sediment samples (60%) have >50% channel-derived sediment. 7Be was detected in 82 bed sediment samples and all 15 suspended-sediment samples. The surface-derived portion of 54 of the 80 (68%) streams with detectable 7Be and 210Pbex were ≤ 100 days old and the surface-derived portion of all suspended-sediment samples were ≤ 100 days old, indicating that surface-derived fine-grained sediment moves rapidly though these systems. The concentrations of two hydrophobic pesticides–DDE and bifenthrin–are correlated with the proportion of surface-derived sediment, indicating a link between geomorphic processes and particle-associated contaminants in streams. Urban areas had the highest pesticide concentrations and the largest percentage of surface-derived sediment. Although the percentage of surface-derived sediment is less than channel sources at most of the study sites, the relatively young age of the surface-derived sediment might indicate that management actions to reduce sediment contamination where the land surface is an important source could have noticeable effects.

Sources and Deposition of Polycyclic Aromatic Hydrocarbons to Western U.S. National Parks

PubMed Central

USENKO, SASCHA; MASSEY SIMONICH, STACI L.; HAGEMAN, KIMBERLY J.; SCHRLAU, JILL E.; GEISER, LINDA; CAMPBELL, DON H.; APPLEBY, PETER G.; LANDERS, DIXON H.

2010-01-01

Seasonal snowpack, lichens, and lake sediment cores were collected from fourteen lake catchments in eight western U.S. National Parks and analyzed for sixteen polycyclic aromatic hydrocarbons (PAHs) in order to determine their current and historical deposition, as well as to identify their potential sources. Seasonal snowpack was measured to determine the current wintertime atmospheric PAH deposition; lichens were measured to determine the long-term, year around deposition; and the temporal PAH deposition trends were reconstructed using lake sediment cores dated using 210Pb and 137Cs. The fourteen remote lake catchments ranged from low-latitude catchments (36.6° N) at high elevation (2900 masl) in Sequoia National Park, CA to high-latitude catchments (68.4° N) at low elevation (427 masl) in the Alaskan Arctic. Over 75% of the catchments demonstrated statistically significant temporal trends in ΣPAH sediment flux, depending on catchment proximity to source regions and topographic barriers. The ΣPAH concentrations and fluxes in seasonal snowpack, lichens, and surficial sediment were 3.6 to 60,000 times greater in the Snyder Lake catchment of Glacier National Park than the other 13 lake catchments. The PAH ratios measured in snow, lichen, and sediment were used to identify a local aluminum smelter as a major source of PAHs to the Snyder Lake catchment. These results suggest that topographic barriers influence the atmospheric transport and deposition of PAHs in high-elevation ecosystems and that PAH sources to these national park ecosystems range from local point sources to diffuse regional and global sources. PMID:20465303

Using geochemical fingerprinting to track the dispersion of radioactive contamination along coastal catchments of the Fukushima Prefecture

NASA Astrophysics Data System (ADS)

Lepage, Hugo; Laceby, J. Patrick; Evrard, Olivier; Onda, Yuichi; Caroline, Chartin; Lefèvre, Irène; Bonté, Philippe; Ayrault, Sophie

2015-04-01

Several coastal catchments located in the vicinity of the Fukushima Dai-Ichi Power Plant were impacted contaminated fallout in March 2011. Following the accident, typhoons and snowmelt runoff events transfer radiocesium contamination through the coastal floodplains and ultimately to the Pacific Ocean. Therefore it is important to understand the location and relative contribution of different erosion sources in order to manage radiocesium transfer within these coastal catchments and the cumulative export of radiocesium to the Pacific Ocean. Here we present a sediment fingerprinting approach to determine the relative contributions of sediment from different soil types to sediment transported throughout two coastal riverine systems. The sediment fingerprinting technique presented utilizes differences in the elemental geochemistry of the distinct soil types to determine their relative contributions to sediment sampled in riverine systems. This research is important as it furthers our understanding of dominant erosion sources in the region which will help with ongoing decontamination and monitoring efforts pertaining to the management of fallout radiocesium migration in the region.

A unified framework for modelling sediment fate from source to sink and its interactions with reef systems over geological times.

PubMed

Salles, Tristan; Ding, Xuesong; Webster, Jody M; Vila-Concejo, Ana; Brocard, Gilles; Pall, Jodie

2018-03-27

Understanding the effects of climatic variability on sediment dynamics is hindered by limited ability of current models to simulate long-term evolution of sediment transfer from source to sink and associated morphological changes. We present a new approach based on a reduced-complexity model which computes over geological time: sediment transport from landmasses to coasts, reworking of marine sediments by longshore currents, and development of coral reef systems. Our framework links together the main sedimentary processes driving mixed siliciclastic-carbonate system dynamics. It offers a methodology for objective and quantitative sediment fate estimations over regional and millennial time-scales. A simulation of the Holocene evolution of the Great Barrier Reef shows: (1) how high sediment loads from catchments erosion prevented coral growth during the early transgression phase and favoured sediment gravity-flows in the deepest parts of the northern region basin floor (prior to 8 ka before present (BP)); (2) how the fine balance between climate, sea-level, and margin physiography enabled coral reefs to thrive under limited shelf sedimentation rates after ~6 ka BP; and, (3) how since 3 ka BP, with the decrease of accommodation space, reduced of vertical growth led to the lateral extension of reefs consistent with available observational data.

Use of spatial statistics and isotopic tracers to measure the influence of arsenical pesticide use on stream sediment chemistry in New England, USA

USGS Publications Warehouse

Robinson, G.R.; Ayuso, R.A.

2004-01-01

Arsenical pesticides and herbicides, principally Pb arsenate, Ca arsenate, and Na arsenate with lesser use of other metal-As pesticides, were widely applied on apple, blueberry, and potato crops in New England during the first half of the twentieth century. Agricultural census data for this time period is used to define an agricultural index that identifies areas that are inferred to have used arsenical pesticides extensively. Factor analysis on metal concentrations in 1597 stream sediment samples collected throughout New England, grouped by agricultural-index categories, indicate a positive association of areas with stream sediment sample populations that contain higher As and Pb concentrations than samples from the region as a whole with sample site settings having high agricultural-index values. Population statistics for As and Pb concentrations and factor scores for an As-Pb factor all increase systematically and significantly with increasing agricultural-index intensity in the region, as tested by Kruskal-Wallis analysis. Lead isotope compositions for 16 stream sediments from a range of agricultural-index settings generally overlap the observed variation in rock sulfides and their weathering products; however, sediments collected from high agricultural-index settings have slightly more radiogenic Pb compositions, consistent with an industrial Pb contribution to these samples. Although weathering products from rocks are likely to be the dominant source of As and metals to most of the stream sediment samples collected in the region, the widespread use of arsenical pesticides and herbicides in New England during the early 1900-1960s appears to be a significant anthropogenic source of As and metals to many sediments in agricultural areas in the region and has raised background levels of As in some regions. Elevated concentrations of As in stream sediments are of concern for two reasons. Stream sediments with elevated As concentrations delineate areas with elevated background concentrations of As from both natural rock and anthropogenic sources that may contribute As to groundwater systems used for drinking water supplies. Conversion of agricultural land contaminated with arsenical pesticide residues to residential development may increase the likelihood that humans will be exposed to As. In addition, many stream sediment sites have As concentrations that exceed sediment quality guidelines established for freshwater ecosystems. Thirteen percent of the New England sediment sample sites exceed 9.79 mg/kg As, the threshold effects concentration (TEC), below which harmful effects are unlikely to be observed. Arsenic concentrations exceed 33 mg/kg, the probable effects concentration (PEC), above which harmful effects on sediment-dwelling organisms are expected to occur frequently, at 1.25% of the sediment sample sites. The sample sites that exceed the PEC value occur predominately in agricultural areas that used arsenical pesticides.

Fingerprinting the main erosion processes delivering sediment to hillside reservoirs: Case of Kamech catchment in Cape Bon, Tunisia

NASA Astrophysics Data System (ADS)

Ben Slimane, A.; Raclot, D.; Evrard, O.; Sanaa, M.; Lefèvre, I.; Ahmadi, M.; Le Bissonnais, Y.

2011-12-01

About 74% of agricultural soils are affected by water erosion in Tunisia. This intense soil degradation threatens the sustainability of food production in the country. It also leads to the siltation of the numerous hillslide reservoirs that were constructed in the 1990s to protect downstream villages against floods and provide a source of water in cultivated areas. Very dense gully systems are observed in Tunisian agricultural land and in other Mediterranean regions, but their contribution to contemporary sediment supply to hillside reservoirs has not been quantified yet. Still, there is a need to quantify the sediment sources in this region in order to guide the implementation of erosion control measures. Sediment can be supplied by gully systems but it can also be provided by erosion of the superficial layer of cultivated soil. We propose a methodology to estimate the relative contribution of gully erosion vs. interrill erosion to the sediment accumulated in hillside reservoirs. This work was conducted in a pilot catchment (i.e., Kamech catchment, 263ha, Cape Bon, Tunisia) to define guidelines on the number and the location of sediment core samples to collect in the reservoirs, in order to provide relevant information on the evolution of sediment sources throughout the last two decades. Once validated, this methodology will be applied to other catchments of the Tunisian Ridge. We applied the sediment fingerprinting method, which consists in measuring conservative and stable properties in both sources and sinks of sediment to outline their origin. Sampling efforts were concentrated on the field surface (cropland and grassland), gullies and channel banks. Thirteen sediment cores were collected along an upstream-downstream transect across Kamech hillside reservoir, in order to estimate the contribution of each potential sediment source to the material accumulated at the outlet, and to investigate the potential spatial differences of sediment origin across the reservoir. Concentration in two types of tracers (i.e., radionuclides and organic matter) was analyzed in all samples to provide potential fingerprinting properties, and a Monte Carlo mixing model was applied. Among the 11 potential tracers, 137Cs, total nitrogen and total organic carbon were selected. Application of the mixing model outlined that a mean homogenized sample provided similar information on the sediment origin as the analysis of all successive sediment layers observed in the core. We subsequently focused on the interpretation of the results obtained for those "mean" homogenised core samples. Those results showed that the dominant sources varied along the reservoir transect. However, the overall dominant source of sediment was interrill erosion. Soil conservation measures need therefore to be applied on cultivated land of Kamech catchment to limit siltation.

Earthquake Signatures in the Modern Sediment Record of Prince William Sound, Alaska

NASA Astrophysics Data System (ADS)

Marshall, N. R.; Kuehl, S. A.; Dellapenna, T. M.; Miller, E. J.

2016-02-01

Geochemical signatures of earthquake-generated sediment gravity flows are investigated using X-ray fluorescence core scanning on a suite of sediment cores from Prince William Sound, Alaska. This study focused on the development of geochemical proxies for earthquake deposits with an emphasis on interpreting deposits initiated from large subduction earthquakes. A north-south transect of sediment cores from Prince William Sound, between Hinchinbrook Island and the Columbia Glacier, was used to examine a record of earthquakes in this tectonically active region for the past century. The sediments in Prince William Sound are sourced from two geologically distinct regions: the metamorphosed turbidites of coastal Prince William Sound, and the Copper River Basin that contains a significant amount of volcanic rocks. Geochemical studies of sediment cores and end-member sediment samples using X-ray fluorescence and inductively coupled plasma mass spectrometry allowed for the development of geochemical proxies for sediment provenance during the past 100 years. Downcore peaks in Sr/Pb are indicative of Copper River Basin sediments, whereas peaks in K/Ca are indicative of inputs of Prince William Sound sediments. Large subduction earthquakes in northern Prince William Sound initiate gravity flows of Prince William Sound provenance into the deep channel. Particularly robust provenance signatures are seen in the northernmost cores in the core transect, which are closer to the earthquake epicenters and the Columbia Glacier source region. The ages of the deposits, from core-averaged 210Pb sediment accumulation rates, correspond to large earthquakes that occurred in 1912, 1964, and 1983. A similar deposit from 1895 in northern Prince William Sound, prior to historical earthquake records, may have also been initiated from a large earthquake in the 1890's.

Sources of suspended-sediment flux in streams of the chesapeake bay watershed: A regional application of the sparrow model

USGS Publications Warehouse

Brakebill, J.W.; Ator, S.W.; Schwarz, G.E.

2010-01-01

We describe the sources and transport of fluvial suspended sediment in nontidal streams of the Chesapeake Bay watershed and vicinity. We applied SPAtially Referenced Regressions on Watershed attributes, which spatially correlates estimated mean annual flux of suspended sediment in nontidal streams with sources of suspended sediment and transport factors. According to our model, urban development generates on average the greatest amount of suspended sediment per unit area (3,928 Mg/km2/year), although agriculture is much more widespread and is the greatest overall source of suspended sediment (57 Mg/km2/year). Factors affecting sediment transport from uplands to streams include mean basin slope, reservoirs, physiography, and soil permeability. On average, 59% of upland suspended sediment generated is temporarily stored along large rivers draining the Coastal Plain or in reservoirs throughout the watershed. Applying erosion and sediment controls from agriculture and urban development in areas of the northern Piedmont close to the upper Bay, where the combined effects of watershed characteristics on sediment transport have the greatest influence may be most helpful in mitigating sedimentation in the bay and its tributaries. Stream restoration efforts addressing floodplain and bank stabilization and incision may be more effective in smaller, headwater streams outside of the Coastal Plain. ?? 2010 American Water Resources Association. No claim to original U.S. government works.

Clay mineralogy, strontium and neodymium isotope ratios in the sediments of two High Arctic catchments (Svalbard)

NASA Astrophysics Data System (ADS)

Hindshaw, Ruth S.; Tosca, Nicholas J.; Piotrowski, Alexander M.; Tipper, Edward T.

2018-03-01

The identification of sediment sources to the ocean is a prerequisite to using marine sediment cores to extract information on past climate and ocean circulation. Sr and Nd isotopes are classical tools with which to trace source provenance. Despite considerable interest in the Arctic Ocean, the circum-Arctic source regions are poorly characterised in terms of their Sr and Nd isotopic compositions. In this study we present Sr and Nd isotope data from the Paleogene Central Basin sediments of Svalbard, including the first published data of stream suspended sediments from Svalbard. The stream suspended sediments exhibit considerable isotopic variation (ɛNd = -20.6 to -13.4; 87Sr / 86Sr = 0.73421 to 0.74704) which can be related to the depositional history of the sedimentary formations from which they are derived. In combination with analysis of the clay mineralogy of catchment rocks and sediments, we suggest that the Central Basin sedimentary rocks were derived from two sources. One source is Proterozoic sediments derived from Greenlandic basement rocks which are rich in illite and have high 87Sr / 86Sr and low ɛNd values. The second source is Carboniferous to Jurassic sediments derived from Siberian basalts which are rich in smectite and have low 87Sr / 86Sr and high ɛNd values. Due to a change in depositional conditions throughout the Paleogene (from deep sea to continental) the relative proportions of these two sources vary in the Central Basin formations. The modern stream suspended sediment isotopic composition is then controlled by modern processes, in particular glaciation, which determines the present-day exposure of the formations and therefore the relative contribution of each formation to the stream suspended sediment load. This study demonstrates that the Nd isotopic composition of stream suspended sediments exhibits seasonal variation, which likely mirrors longer-term hydrological changes, with implications for source provenance studies based on fixed end-members through time.

Distribution and sources of organic matter in surface marine sediments across the North American Arctic margin

NASA Astrophysics Data System (ADS)

Goñi, Miguel A.; O'Connor, Alison E.; Kuzyk, Zou Zou; Yunker, Mark B.; Gobeil, Charles; Macdonald, Robie W.

2013-09-01

As part of the International Polar Year research program, we conducted a survey of surface marine sediments from box cores along a section extending from the Bering Sea to Davis Strait via the Canadian Archipelago. We used bulk elemental and isotopic compositions, together with biomarkers and principal components analysis, to elucidate the distribution of marine and terrestrial organic matter in different regions of the North American Arctic margin. Marked regional contrasts were observed in organic carbon loadings, with the highest values (≥1 mg C m-2 sediment) found in sites along Barrow Canyon and the Chukchi and Bering shelves, all of which were characterized by sediments with low oxygen exposure, as inferred from thin layers (<2 cm) of Mn oxihydroxides. We found strong regional differences in inorganic carbon concentrations, with sites from the Canadian Archipelago and Lancaster Sound displaying elevated values (2-7 wt %) and highly depleted 14C compositions consistent with inputs from bedrock carbonates. Organic carbon:nitrogen ratios, stable carbon isotopes, and terrigenous organic biomarkers (lignin phenols and cutin acids) all indicate marked regional differences in the proportions of marine and terrigenous organic matter present in surface sediments. Regions such as Barrow Canyon and the Mackenzie River shelf were characterized by the highest contributions of land-derived organic matter, with compositional characteristics that suggested distinct sources and provenance. In contrast, sediments from the Canadian Archipelago and Davis Strait had the smallest contributions of terrigenous organic matter and the lowest organic carbon loadings indicative of a high degree of post-depositional oxidation.

The influence of a semi-arid sub-catchment on suspended sediments in the Mara River, Kenya

PubMed Central

2018-01-01

The Mara River Basin in East Africa is a trans-boundary basin of international significance experiencing excessive levels of sediment loads. Sediment levels in this river are extremely high (turbidities as high as 6,000 NTU) and appear to be increasing over time. Large wildlife populations, unregulated livestock grazing, and agricultural land conversion are all potential factors increasing sediment loads in the semi-arid portion of the basin. The basin is well-known for its annual wildebeest (Connochaetes taurinus) migration of approximately 1.3 million individuals, but it also has a growing population of hippopotami (Hippopotamus amphibius), which reside within the river and may contribute to the flux of suspended sediments. We used in situ pressure transducers and turbidity sensors to quantify the sediment flux at two sites for the Mara River and investigate the origin of riverine suspended sediment. We found that the combined Middle Mara—Talek catchment, a relatively flat but semi-arid region with large populations of wildlife and domestic cattle, is responsible for 2/3 of the sediment flux. The sediment yield from the combined Middle Mara–Talek catchment is approximately the same as the headwaters, despite receiving less rainfall. There was high monthly variability in suspended sediment fluxes. Although hippopotamus pools are not a major source of suspended sediments under baseflow, they do contribute to short-term variability in suspended sediments. This research identified sources of suspended sediments in the Mara River and important regions of the catchment to target for conservation, and suggests hippopotami may influence riverine sediment dynamics. PMID:29420624

Fluvial-aeolian interactions in sediment routing and sedimentary signal buffering: an example from the Indus Basin and Thar Desert

USGS Publications Warehouse

East, Amy E.; Clift, Peter D.; Carter, Andrew; Alizai, Anwar; VanLaningham, Sam

2015-01-01

Sediment production and its subsequent preservation in the marine stratigraphic record offshore of large rivers are linked by complex sediment-transfer systems. To interpret the stratigraphic record it is critical to understand how environmental signals transfer from sedimentary source regions to depositional sinks, and in particular to understand the role of buffering in obscuring climatic or tectonic signals. In dryland regions, signal buffering can include sediment cycling through linked fluvial and eolian systems. We investigate sediment-routing connectivity between the Indus River and the Thar Desert, where fluvial and eolian systems exchanged sediment over large spatial scales (hundreds of kilometers). Summer monsoon winds recycle sediment from the lower Indus River and delta northeastward, i.e., downwind and upstream, into the desert. Far-field eolian recycling of Indus sediment is important enough to control sediment provenance at the downwind end of the desert substantially, although the proportion of Indus sediment of various ages varies regionally within the desert; dune sands in the northwestern Thar Desert resemble the Late Holocene–Recent Indus delta, requiring short transport and reworking times. On smaller spatial scales (1–10 m) along fluvial channels in the northern Thar Desert, there is also stratigraphic evidence of fluvial and eolian sediment reworking from local rivers. In terms of sediment volume, we estimate that the Thar Desert could be a more substantial sedimentary store than all other known buffer regions in the Indus basin combined. Thus, since the mid-Holocene, when the desert expanded as the summer monsoon rainfall decreased, fluvial-eolian recycling has been an important but little recognized process buffering sediment flux to the ocean. Similar fluvial-eolian connectivity likely also affects sediment routing and signal transfer in other dryland regions globally.

Heterocyclic Aromatics in Petroleum Coke, Snow, Lake Sediments, and Air Samples from the Athabasca Oil Sands Region.

PubMed

Manzano, Carlos A; Marvin, Chris; Muir, Derek; Harner, Tom; Martin, Jonathan; Zhang, Yifeng

2017-05-16

The aromatic fractions of snow, lake sediment, and air samples collected during 2011-2014 in the Athabasca oil sands region were analyzed using two-dimensional gas chromatography following a nontargeted approach. Commonly monitored aromatics (parent and alkylated-polycyclic aromatic hydrocarbons and dibenzothiophenes) were excluded from the analysis, focusing mainly on other heterocyclic aromatics. The unknowns detected were classified into isomeric groups and tentatively identified using mass spectral libraries. Relative concentrations of heterocyclic aromatics were estimated and were found to decrease with distance from a reference site near the center of the developments and with increasing depth of sediments. The same heterocyclic aromatics identified in snow, lake sediments, and air were observed in extracts of delayed petroleum coke, with similar distributions. This suggests that petroleum coke particles are a potential source of heterocyclic aromatics to the local environment, but other oil sands sources must also be considered. Although the signals of these heterocyclic aromatics diminished with distance, some were detected at large distances (>100 km) in snow and surface lake sediments, suggesting that the impact of industry can extend >50 km. The list of heterocyclic aromatics and the mass spectral library generated in this study can be used for future source apportionment studies.

Multi-scale constraints of sediment source to sink systems in frontier basins: a forward stratigraphic modeling case study of the Levant region

NASA Astrophysics Data System (ADS)

Hawie, Nicolas; Deschamps, Remy; Granjeon, Didier; Nader, Fadi-Henri; Gorini, Christian; Müller, Carla; Montadert, Lucien; Baudin, François

2015-04-01

Recent scientific work underlined the presence of a thick Cenozoic infill in the Levant Basin reaching up to 12 km. Interestingly; restricted sedimentation was observed along the Levant margin in the Cenozoic. Since the Late Eocene successive regional geodynamic events affecting Afro-Arabia and Eurasia (collision and strike slip deformation)induced fast marginal uplifts. The initiation of local and long-lived regional drainage systems in the Oligo-Miocene period (e.g. Lebanon versus Nile) provoked a change in the depositional pattern along the Levant margin and basin. A shift from carbonate dominated environments into clastic rich systems has been observed. Through this communication we explore the importance of multi-scale constraints (i.e.,seismic, well and field data) in the quantification of the subsidence history, sediment transport and deposition of a Middle-Upper Miocene "multi-source" to sink system along the northernLevant frontier region. We prove through a comprehensive forward stratigraphic modeling workflow that the contribution to the infill of the northern Levant Basin (offshore Lebanon) is split in between proximal and more distal clastic sources as well as in situ carbonate/hemipelagic deposition. In a wider perspective this work falls under the umbrella of multi-disciplinary source to sink studies that investigate the impact of geodynamic events on basin/margin architectural evolutions, consequent sedimentary infill and thus on petroleum systems assessment.

Distribution and region-specific sources of Dechlorane Plus in marine sediments from the coastal East China Sea.

PubMed

Wang, Guoguang; Peng, Jialin; Hao, Ting; Liu, Yao; Zhang, Dahai; Li, Xianguo

2016-12-15

Dechlorane Plus (DP) is a highly chlorinated flame retardant and found to be ubiquitously present in the environment. We reported here the first record of DP in sediments from the coastal East China Sea (ECS). DP was detected in most of the surface sediments, and the concentrations ranged from 14.8 to 198pg/g dry weight (dw) with a mean value of 64.4pg/g dw. Overall, DP levels exhibited a seaward decreasing trend from the inshore toward outer sea. The fractional abundance of anti-DP (f anti ) showed regional discrepancies, attributing to different environmental behaviors of DP isomers. Depth profiles of DP in a sediment core from estuarine environment showed distinct fluctuation, and the core in open sea had stable deposition environment with two peak values of DP in ~1978 and 2000. The f anti exhibited downward decreasing trend prior to mid-1950s, indicating a preferential degradation of anti-DP and/or a greater adsorption capacity of syn-DP after its burial. Lignin and lipid biomarkers (∑C 27 +C 29 +C 31 n-alkanes) of terrestrial organic matters were introduced to identify region-specific sources of DP, and the results showed that DP in the northern inner shelf, southern inner shelf of 29 °N and mud area southwest of Cheju Island was mainly come from Yangtze River (YR) input, surface runoffs after discharge of local sources close to the Taizhou-Wenzhou Region and the atmospheric deposition from the North China and East Asia, respectively. The coastal ECS was an important reservoir of DP in the world, with mass inventory of approximately 310.7kg in the surface sediments (0-5cm). Copyright © 2016 Elsevier B.V. All rights reserved.

Anthropogenic and natural variability in the composition of sedimentary organic matter of the urbanised coastal zone of Montevideo (Río de la Plata).

PubMed

Bueno, C; Brugnoli, E; Bergamino, L; Muniz, P; García-Rodríguez, F; Figueira, R

2018-01-01

This study is aimed to identify the different sources of sedimentary organic matter (SOM) within Montevideo coastal zone (MCZ). To this end δ 13 C, δ 15 N and C/N ratio were analysed in surface sediments and a sediment core. Sediment core analysis showed that until ~1950CE SOM was mainly marine, observing a shift towards lower δ 13 C in recent sediments, evidencing an estuarine composition. This trend was associated to the climatic variability, which exerted a major influence on the SOM composition, leading to an increased input of terrigenous material and associated anthropogenic contaminants. Surface sediments collected during different El Niño South Oscillation (ENSO) phases did not show inter-annual variability in SOM composition, which was mainly marine in both eastern and western region of MCZ and estuarine in Montevideo Bay. This spatial pattern provides new insights on the dynamics and factors affecting organic matter sources available for primary consumers along the study region. Copyright © 2017 Elsevier Ltd. All rights reserved.

Biomarkers in sedimentary sequences: Indicators to track sediment sources over decadal timescales

NASA Astrophysics Data System (ADS)

Chen, F. X.; Fang, N. F.; Wang, Y. X.; Tong, L. S.; Shi, Z. H.

2017-02-01

Long-term sedimentary sequence research can reveal how human activities and climate interact to affect catchment vegetation, flooding, soil erosion, and sediment sources. In this study, a biomarker sediment fingerprinting technique based on n-alkanes was used to identify long timescale (decadal) sediment sources in a small agricultural catchment. However, the highly saline carbonate environment and bacterial and algal activities elevated the levels of even-chain n-alkanes in the sediments, leading to an obvious even-over-odd predominance of short and middle components (C15-C26). Therefore, by analyzing three odd, long-chain n-alkanes (C27, C29 and C31) in 27 source samples from cropland, gully, and steep slope areas and one sediment sequence (one cultivated horizon and 47 flood couplets), a composite fingerprinting method and genetic algorithm optimization were applied to find the optimal source contributions to sediments. The biomarker fingerprinting results demonstrated that the primary sediment source is gullies, followed by cropland and steep slope areas. The average median source contributions associated with 47 flood couples collected from sediment core samples ranged from 0 ± 0.1% to 91.9 ± 0.4% with an average of 45.0% for gullies, 0 ± 0.4% to 95.6 ± 1.6% with an average of 38.2% for cropland, and 0 ± 2.1% to 60.7 ± 0.4% with an average of 16.8% for steep slopes. However, because farmers were highly motivated to manage the cropland after the 1980s, over half the sediments were derived from cropland in the 1980s. Biomarkers have significant advantages in the identification of sediments derived from different landscape units (e.g., gully and steep slope areas), and n-alkanes have considerable potential in high-resolution research of environmental change based on soil erosion in the hilly Loess Plateau region.

Lead isotope ratios in six lake sediment cores from Japan Archipelago: Historical record of trans-boundary pollution sources.

PubMed

Hosono, Takahiro; Alvarez, Kelly; Kuwae, Michinobu

2016-07-15

Sediment cores from six lakes situated from north to south on the Japanese Archipelago were collected during 2009-2010 to investigate the hypothesis that deposition of lead (Pb) was coming from East Asia (including China, South Korea and eastern part of Russia). Accumulation rates and ages of the lake sediment were estimated by the (210)Pb constant rate of supply model and (137)Cs inputs to reconstruct the historical trends of Pb accumulation. Cores from four lakes located in the north and central Japan, showed clear evidence of Pb pollution with a change in the (206)Pb/(207)Pb and (208)Pb/(207)Pb ratios in the recent sediment as compared to the deeper sediment. Among the six studied lakes, significant inputs of anthropogenic lead emissions were observed at Lake Mikazuki (north Hokkaido in north Japan), Lake Chokai (north of Honshu), and Lake Mikuriga (central part of Honshu). Pb isotopic comparison of collected core sediment and previously reported data for wet precipitation and aerosols from different Asian regions indicate that, before 1900, Pb accumulated in these three lakes was not affected by trans-boundary sources. Lake Mikazuki started to receive Pb emissions from Russia in early 1900s, and during the last two decades, this lake has been affected by trans-boundary Pb pollution from northern China. Lake Chokai has received Pb pollutant from northern China since early 1900s until 2009, whereas for the Lake Mikuriga the major Pb contaminant was transported from southern China during the past 100years. The results of our study demonstrate that Japan Archipelago has received trans-boundary Pb emissions from different parts of East Asian region depending on location, and the major source region has changed historically. Copyright © 2016 Elsevier B.V. All rights reserved.

Analysis of suspended-sediment concentrations and radioisotope levels in the Wild Rice River basin, northwestern Minnesota, 1973-98

USGS Publications Warehouse

Brigham, Mark E.; McCullough, Carolyn J.; Wilkinson, Philip M.

2001-01-01

We examined historical suspended-sediment data and activities of fallout radioisotopes (lead-210 [210Pb], cesium-137 [137Cs], and beryllium-7 [7Be]) associated with suspended sediments and source-area sediments (cultivated soils, bank material, and reference soils) in the Wild Rice River Basin, a tributary to the Red River of the North, to better understand sources of suspended sediment to streams in the region. Multiple linear regression analysis of suspended-sediment concentrations from the Wild Rice River at Twin Valley, Minnesota indicated significant relations between suspended-sediment concentrations and streamflow. Flow-adjusted sediment concentrations tended to be slightly higher in spring than summer-autumn. No temporal trends in concentration were observed during 1973-98. The fallout radioisotopes were nearly always detectable in suspended sediments during spring-summer 1998. Mean 210Pb and 7Be activities in suspended sediment and surficial, cultivated soils were similar, perhaps indicating little dilution of suspended sediment from low-isotopic-activity bank sediments. In contrast, mean 137Cs activities in suspended sediment indicated a mixture of sediment originating from eroded soils and from eroded bank material, with bank material being a somewhat more important source upstream of Twin Valley, Minnesota; and approximately equal fractions of bank material and surficial soils contributing to the suspended load downstream at Hendrum, Minnesota. This study indicates that, to be effective, efforts to reduce sediment loading to the Wild Rice River should include measures to control soil erosion from cultivated fields.

Tectonic isolation from regional sediment sourcing of the Paradox Basin

NASA Astrophysics Data System (ADS)

Smith, T. M.; Saylor, J.; Sundell, K. E.; Lapen, T. J.

2017-12-01

The Appalachian and Ouachita-Marathon mountain ranges were created by a series of tectonic collisions that occurred through the middle and late Paleozoic along North America's eastern and southern margins, respectively. Previous work employing detrital zircon U-Pb geochronology has demonstrated that fluvial and eolian systems transported Appalachian-derived sediment across the continent to North America's Paleozoic western margin. However, contemporaneous intraplate deformation of the Ancestral Rocky Mountains (ARM) compartmentalized much of the North American western interior and mid-continent. We employ lithofacies characterization, stratigraphic thickness, paleocurrent data, sandstone petrography, and detrital zircon U-Pb geochronology to evaluate source-sink relationships of the Paradox Basin, which is one of the most prominent ARM basins. Evaluation of provenance is conducted through quantitative comparison of detrital zircon U-Pb distributions from basin samples and potential sources via detrital zircon mixture modeling, and is augmented with sandstone petrography. Mixing model results provide a measure of individual source contributions to basin stratigraphy, and are combined with outcrop and subsurface data (e.g., stratigraphic thickness and facies distributions) to create tectonic isolation maps. These maps elucidate drainage networks and the degree to which local versus regional sources influence sediment character within a single basin, or multiple depocenters. Results show that despite the cross-continental ubiquity of Appalachian-derived sediment, fluvial and deltaic systems throughout much of the Paradox Basin do not record their influence. Instead, sediment sourcing from the Uncompahgre Uplift, which has been interpreted to drive tectonic subsidence and formation of the Paradox Basin, completely dominated its sedimentary record. Further, the strong degree of tectonic isolation experienced by the Paradox Basin appears to be an emerging, yet common feature among other intraplate, tectonically active basins.

Concentrations and sources of polycyclic aromatic hydrocarbons in surface coastal sediments of the northern Gulf of Mexico

PubMed Central

2014-01-01

Background Coastal sediments in the northern Gulf of Mexico have a high potential of being contaminated by petroleum hydrocarbons, such as polycyclic aromatic hydrocarbons (PAHs), due to extensive petroleum exploration and transportation activities. In this study we evaluated the spatial distribution and contamination sources of PAHs, as well as the bioavailable fraction in the bulk PAH pool, in surface marsh and shelf sediments (top 5 cm) of the northern Gulf of Mexico. Results PAH concentrations in this region ranged from 100 to 856 ng g−1, with the highest concentrations in Mississippi River mouth sediments followed by marsh sediments and then the lowest concentrations in shelf sediments. The PAH concentrations correlated positively with atomic C/N ratios of sedimentary organic matter (OM), suggesting that terrestrial OM preferentially sorbs PAHs relative to marine OM. PAHs with 2 rings were more abundant than those with 5–6 rings in continental shelf sediments, while the opposite was found in marsh sediments. This distribution pattern suggests different contamination sources between shelf and marsh sediments. Based on diagnostic ratios of PAH isomers and principal component analysis, shelf sediment PAHs were petrogenic and those from marsh sediments were pyrogenic. The proportions of bioavailable PAHs in total PAHs were low, ranging from 0.02% to 0.06%, with higher fractions found in marsh than shelf sediments. Conclusion PAH distribution and composition differences between marsh and shelf sediments were influenced by grain size, contamination sources, and the types of organic matter associated with PAHs. Concentrations of PAHs in the study area were below effects low-range, suggesting a low risk to organisms and limited transfer of PAHs into food web. From the source analysis, PAHs in shelf sediments mainly originated from direct petroleum contamination, while those in marsh sediments were from combustion of fossil fuels. PMID:24641695

Bridging the gap between small and large scale sediment budgets? - A scaling challenge in the Upper Rhone Basin, Switzerland

NASA Astrophysics Data System (ADS)

Schoch, Anna; Blöthe, Jan; Hoffmann, Thomas; Schrott, Lothar

2016-04-01

A large number of sediment budgets have been compiled on different temporal and spatial scales in alpine regions. Detailed sediment budgets based on the quantification of a number of sediment storages (e.g. talus cones, moraine deposits) exist only for a few small scale drainage basins (up to 10² km²). In contrast, large scale sediment budgets (> 10³ km²) consider only long term sediment sinks such as valley fills and lakes. Until now, these studies often neglect small scale sediment storages in the headwaters. However, the significance of these sediment storages have been reported. A quantitative verification whether headwaters function as sediment source regions is lacking. Despite substantial transport energy in mountain environments due to steep gradients and high relief, sediment flux in large river systems is frequently disconnected from alpine headwaters. This leads to significant storage of coarse-grained sediment along the flow path from rockwall source regions to large sedimentary sinks in major alpine valleys. To improve the knowledge on sediment budgets in large scale alpine catchments and to bridge the gap between small and large scale sediment budgets, we apply a multi-method approach comprising investigations on different spatial scales in the Upper Rhone Basin (URB). The URB is the largest inneralpine basin in the European Alps with a size of > 5400 km². It is a closed system with Lake Geneva acting as an ultimate sediment sink for suspended and clastic sediment. We examine the spatial pattern and volumes of sediment storages as well as the morphometry on the local and catchment-wide scale. We mapped sediment storages and bedrock in five sub-regions of the study area (Goms, Lötschen valley, Val d'Illiez, Vallée de la Liène, Turtmann valley) in the field and from high-resolution remote sensing imagery to investigate the spatial distribution of different sediment storage types (e.g. talus deposits, debris flow cones, alluvial fans). These sub-regions cover all three litho-tectonic units of the URB (Helvetic nappes, Penninic nappes, External massifs) and different catchment sizes to capture the inherent variability. Different parameters characterizing topography, surface characteristics, and vegetation cover are analyzed for each storage type. The data is then used in geostatistical models (PCA, stepwise logistic regression) to predict the spatial distribution of sediment storage for the whole URB. We further conduct morphometric analyses of the URB to gain information on the varying degree of glacial imprint and postglacial landscape evolution and their control on the spatial distribution of sediment storage in a large scale drainage basin. Geophysical methods (ground penetrating radar and electrical resistivity tomography) are applied on different sediment storage types on the local scale to estimate mean thicknesses. Additional data from published studies are used to complement our dataset. We integrate the local data in the statistical model on the spatial distribution of sediment storages for the whole URB. Hence, we can extrapolate the stored sediment volumes to the regional scale in order to bridge the gap between small and large scale studies.

Quantifying sediment source contributions in coastal catchments impacted by the Fukushima nuclear accident with carbon and nitrogen elemental concentrations and stable isotope ratios

NASA Astrophysics Data System (ADS)

Laceby, J. Patrick; Huon Huon, Sylvain; Onda, Yuichi; Evrard, Olivier

2016-04-01

The Fukushima Dai-ichi Nuclear Power Plant accidental release of radioactive contaminants resulted in the significant fallout of radiocesium over several coastal catchments in the Fukushima Prefecture. Radiocesium, considered to be the greatest risk to the short and long term health of the local community, is rapidly bound to fine soil particles and thus is mobilized and transported during soil erosion and runoff processes. As there has been a broad-scale decontamination of rice paddy fields and rural residential areas in the contaminated region, one important long term question is whether there is, or may be, a downstream transfer of radiocesium from forests that covered over 65% of the most contaminated region. Accordingly, carbon and nitrogen elemental concentrations and stable isotope ratios are used to determine the relative contributions of forests and rice paddies to transported sediment in three contaminated coastal catchments. Samples were taken from the three main identified sources: cultivated soils (rice paddies and fields, n=30), forest soils (n=45), and subsoils (channel bank and decontaminated soils, n = 25). Lag deposit sediment samples were obtained from five sampling campaigns that targeted the main hydrological events from October 2011 to October 2014. In total, 86 samples of deposited sediment were analyzed for particulate organic matter elemental concentrations and isotope ratios, 24 from the Mano catchment, 44 from the Niida catchment, and 18 from the Ota catchment. Mann-Whitney U-tests were used to examine the source discrimination potential of this tracing suite and select the appropriate tracers for modelling. The discriminant tracers were modelled with a concentration-dependent distribution mixing model. Preliminary results indicate that cultivated sources (predominantly rice paddies) contribute disproportionately more sediment per unit area than forested regions in these contaminated catchments. Future research will examine if there are areas in particular where forest sources have elevated concentrations and may require some attention in the decontamination and monitoring of potential radiocesium downstream transfers.

Quantifying postfire aeolian sediment transport using rare earth element tracers

USGS Publications Warehouse

Dukes, David; Gonzales, Howell B.; Ravi, Sujith; Grandstaff, David E.; Van Pelt, R. Scott; Li, Junran; Wang, Guan; Sankey, Joel B.

2018-01-01

Grasslands, which provide fundamental ecosystem services in many arid and semiarid regions of the world, are undergoing rapid increases in fire activity and are highly susceptible to postfire-accelerated soil erosion by wind. A quantitative assessment of physical processes that integrates fire-wind erosion feedbacks is therefore needed relative to vegetation change, soil biogeochemical cycling, air quality, and landscape evolution. We investigated the applicability of a novel tracer technique—the use of multiple rare earth elements (REE)—to quantify soil transport by wind and to identify sources and sinks of wind-blown sediments in both burned and unburned shrub-grass transition zone in the Chihuahuan Desert, NM, USA. Results indicate that the horizontal mass flux of wind-borne sediment increased approximately threefold following the fire. The REE tracer analysis of wind-borne sediments shows that the source of the horizontal mass flux in the unburned site was derived from bare microsites (88.5%), while in the burned site it was primarily sourced from shrub (42.3%) and bare (39.1%) microsites. Vegetated microsites which were predominantly sinks of aeolian sediments in the unburned areas became sediment sources following the fire. The burned areas showed a spatial homogenization of sediment tracers, highlighting a potential negative feedback on landscape heterogeneity induced by shrub encroachment into grasslands. Though fires are known to increase aeolian sediment transport, accompanying changes in the sources and sinks of wind-borne sediments may influence biogeochemical cycling and land degradation dynamics. Furthermore, our experiment demonstrated that REEs can be used as reliable tracers for field-scale aeolian studies.

Can rapid assessment protocols be used to judge sediment impairment in gravel-bed streams? A commentary

Treesearch

Thomas E. Lisle; John M. Buffington; Peter R. Wilcock; Kristin Bunte

2015-01-01

Land management agencies commonly use rapid assessments to evaluate the impairment of gravel-bed streams by sediment inputs from anthropogenic sources. We question whether rapid assessment can be used to reliably judge sediment impairment at a site or in a region. Beyond the challenges of repeatable and accurate sampling, we argue that a single metric or protocol is...

Surface-sediment grain-size distribution and sediment transport in the subaqueous Mekong Delta, Vietnam

NASA Astrophysics Data System (ADS)

Nguyen, T. T.; Stattegger, K.; Nittrouer, C.; Phung, P. V.; Liu, P.; DeMaster, D. J.; Bui, D. V.; Le, A. D.; Nguyen, T. N.

2016-02-01

Collected surface-sediment samples in coastal water around Mekong Delta (from distributary channels to Ca Mau Peninsula) were analyzed to determine surface-sediment grain-size distribution and sediment-transport trend in the subaqueous Mekong Delta. The grain-size data set of 238 samples was obtained by using the laser instrument Mastersizer 2000 and LS Particle Size Analyzer. Fourteen samples were selected for geochemical analysis (total-organic and carbonate content). These geochemical results were used to assist in interpreting variations of granulometricparamenters along the cross-shore transects. Nine transects were examined from CungHau river mouth to Ca Mau Peninsula and six thematic maps on the whole study area were made. The research results indicate that: (1) generally, the sediment becomes finer from the delta front downwards to prodelta and becomes coarser again and poorer sorted on the adjacent inner shelf due to different sources of sediment; (2) sediment-granulometry parameters vary among sedimentary sub-environments of the underwater part of Mekong Delta, the distance from sediment source and hydrodynamic regime controlling each region; (3) the net sediment transport is southwest toward the Ca Mau Peninsula.

Source-to-sink cycling of aeolian sediment in the north polar region of Mars

NASA Astrophysics Data System (ADS)

Ewing, R. C.; Kocurek, G.

2012-12-01

Aeolian sand dunes are prominent features on the landscapes of Earth, Mars, Venus and Titan and sedimentary deposits interpreted as aeolian in origin are found in the rock records of Earth and Mars. The widespread occurrence of aeolian dunes on the surface of these worlds and within their deep-time depositional records suggests that aeolian systems are and likely have been a default depositional environment for the Solar System. Within an aeolian source-to-sink context, we hypothesize that planet-specific boundary conditions strongly impact production, transport, accumulation and preservation of aeolian sediment, whereas dunes and dune-field patterns remain largely similar. This hypothesis is explored within the north polar region of Mars, which hosts the most extensive aeolian dune fields and aeolian sedimentary deposits yet recognized on Mars and appears to be a region of dynamic source-to-sink cycling of aeolian sediments. The Planum Boreum Cavi Unit rests beneath north polar ice cap of Mars and is composed of several hundred meters of niveo-aeolian dune cross-stratification. The overall architecture of the unit consists of sets of preserved dune topography with an upward increase in the abundance of ice. Dune sets are defined by stabilized, polygonally fractured bounding surfaces, erosional bounding surfaces and typical internal lee foresets made of sediment and ice. The accumulation of the Cavi Unit is interpreted as occurring through freezing and serves as an example of a cold temperature boundary condition on aeolian sediment accumulation. Preservation of the Cavi Unit arises because of deposition of the overlying ice cap and contrasts with preservation of aeolian sediment on Earth, which is largely driven by eustasy and tectonics. The Cavi Unit is thought to be one source of sediment for the north polar Olympia Undae Dune Field. The region of Olympia Undae near the Cavi Unit shows a reticulate dune field pattern composed of two sets of nearly orthogonal dune crestlines, with slipfaces on the primary crests, wind ripples, coarse-grained ripples and deflated interdune areas with exposed dune stratigraphy. Wind transport directions interpreted from wind ripple orientations show that the interaction between dune topography and wind flow on Mars are largely the same as on Earth giving rise to basic types of lee-slope processes - grain flow, grain fall and wind ripples. Using wind flow reconstruction and pattern analysis the pattern is interpreted as complex in which a younger pattern superposes a larger, older pattern. The younger pattern may have emerged with the development of the retreat of the Cavi reentrant into the Cavi Unit and ice cap, which acted to channel katabatic winds and inject a new sediment source into Olympia Undae. The similarity of the Olympia Undae dune-field pattern to dune-field patterns on other planets shows the robustness of pattern formation across different planetary boundary conditions and the applicability of pattern-analysis methods for paleoenvironmental reconstruction. The aeolian source-to-sink system of Mars' north polar region demonstrates how the stratigraphic and geomorphic principles of aeolian systems may differ because of different planetary boundary conditions and provides a framework for analysis of aeolian systems on other worlds.

Crustal Stretching Style and Lower Crust Flow of the South China Sea Northern Margin

NASA Astrophysics Data System (ADS)

Bai, Y.; Dong, D.; Runlin, D.

2017-12-01

There is a controversy about crustal stretching style of the South China Sea (SCS) northern margin mainly due to considerable uncertainty of stretching factor estimation, for example, as much as 40% of upper crust extension (Walsh et al., 1991) would be lost by seismic profiles due to poor resolution. To discover and understand crustal stretching style and lower crustal flow on the whole, we map the Moho and Conrad geometries based on gravity inversion constrained by deep seismic profiles, then according to the assumption of upper and lower crust initial thickness, upper and lower crust stretching factors are estimated. According to the comparison between upper and lower crust stretching factors, the SCS northern margin could be segmented into three parts, (1) sediment basins where upper crust is stretched more than lower crust, (2) COT regions where lower crust is stretched more than upper crust, (3) other regions where the two layers have similar stretching factors. Stretching factor map shows that lower crust flow happened in both of COT and sediment basin regions where upper crust decouples with lower crust due to high temperature. Pressure contrast by sediment loading in basins and erosion in sediment-source regions will lead to lower crust flow away from sediment sink to source. Decoupled and fractured upper crust is stretched further by sediment loading and the following compensation would result in relatively thick lower crust than upper crust. In COT regions with thin sediment coverage, low-viscosity lower crust is easier to thin in extensional environment, also the lower crust tends to flow away induced by magma upwelling. Therefore, continental crust on the margin is not stretching in a constant way but varies with the tectonic setting changes. This work is supported by National Natural Science Foundation of China (Grant No. 41506055, 41476042) and Fundamental Research Funds for the Central Universities China (No.17CX02003A).

Source and distribution of naturally occurring arsenic in groundwater from Alberta’s Southern Oil Sands Regions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moncur, Michael C.; Paktunc, Dogan; Jean Birks, S.

Arsenic (As) concentrations as high as 179 μg/L have been observed in shallow groundwater in the Alberta’s Southern Oil Sand Regions. The geology of this area of Alberta includes a thick cover (up to 200 m) of unconsolidated glacial deposits, with a number of regional interglacial sand and gravel aquifers, underlain by marine shale. Arsenic concentrations observed in 216 unconsolidated sediment samples ranged from 1 and 17 ppm. A survey of over 800 water wells sampled for As in the area found that 50% of the wells contained As concentrations exceeding drinking water guidelines of 10 μg/L. Higher As concentrationsmore » in groundwater were associated with reducing conditions. Measurements of As speciation from 175 groundwater samples indicate that As(III) was the dominant species in 74% of the wells. Speciation model calculations showed that the majority of groundwater samples were undersaturated with respect to ferrihydrite, suggesting that reductive dissolution of Fe-oxyhydroxides may be the source of some As in groundwater. Detailed mineralogical characterization of sediment samples collected from two formations revealed the presence of fresh framboidal pyrite in the deeper unoxidized sediments. Electron microprobe analysis employing wavelength dispersive spectrometry indicated that the framboidal pyrite had variable As content with an average As concentration of 530 ppm, reaching up to 1840 ppm. In contrast, the oxidized sediments did not contain framboidal pyrite, but exhibited spheroidal Fe-oxyhydroxide grains with elevated As concentrations. The habit and composition suggest that these Fe-oxyhydroxide grains in the oxidized sediment were an alteration product of former framboidal pyrite grains. X-ray absorption near edge spectroscopy (XANES) indicated that the oxidized sediments are dominated by As(V) species having spectral features similar to those of goethite or ferrihydrite with adsorbed As, suggesting that Fe-oxyhydroxides are the dominant As carriers. XANES spectra collected on unoxidized sediment samples, in contrast, indicated the presence of a reduced As species (As(-I)) characteristic of arsenopyrite and arsenian pyrite. The results of the mineralogical analyses indicate that the oxidation of framboidal pyrite during weathering may be the source of As released to shallow aquifers in this region.« less

Concentration distribution and assessment of several heavy metals in sediments of west-four Pearl River Estuary

NASA Astrophysics Data System (ADS)

Wang, Shanshan; Cao, Zhimin; Lan, Dongzhao; Zheng, Zhichang; Li, Guihai

2008-09-01

Grain size parameters, trace metals (Co, Cu, Ni, Pb, Cr, Zn, Ba, Zr and Sr) and total organic matter (TOM) of 38 surficial sediments and a sediment core of west-four Pearl River Estuary region were analyzed. The spacial distribution and the transportation procession of the chemical element in surficial sediments were studied mainly. Multivariate statistics are used to analyses the interrelationship of metal elements, TOM and the grain size parameters. The results demonstrated that terrigenous sediment taken by the rivers are main sources of the trace metal elements and TOM, and the lithology of parent material is a dominating factor controlling the trace metal composition in the surficial sediment. In addition, the hydrodynamic condition and landform are the dominating factors controlling the large-scale distribution, while the anthropogenic input in the coastal area alters the regional distribution of heavy metal elements Co, Cu, Ni, Pb, Cr and Zn. The enrichment factor (EF) analysis was used for the differentiation of the metal source between anthropogenic and naturally occurring, and for the assessment of the anthropogenic influence, the deeper layer content of heavy metals were calculated as the background values and Zr was chosen as the reference element for Co, Cu, Ni, Pb, Cr and Zn. The result indicate prevalent enrichment of Co, Cu, Ni, Pb and Cr, and the contamination of Pb is most obvious, further more, the peculiar high EF value sites of Zn and Pb probably suggest point source input.

Canada Basin revealed

USGS Publications Warehouse

Mosher, David C.; Shimeld, John; Hutchinson, Deborah R.; Chian, D; Lebedeva-Ivanova, Nina; Jackson, Ruth

2012-01-01

More than 15,000 line-km of new regional seismic reflection and refraction data in the western Arctic Ocean provide insights into the tectonic and sedimentologic history of Canada Basin, permitting development of new geologic understanding in one of Earth's last frontiers. These new data support a rotational opening model for southern Canada Basin. There is a central basement ridge possibly representing an extinct spreading center with oceanic crustal velocities and blocky basement morphology characteristic of spreading centre crust surrounding this ridge. Basement elevation is lower in the south, mostly due to sediment loading subsidence. The sedimentary succession is thickest in the southern Beaufort Sea region, reaching more than 15 km, and generally thins to the north and west. In the north, grabens and half-grabens are indicative of extension. Alpha-Mendeleev Ridge is a large igneous province in northern Amerasia Basin, presumably emplaced synchronously with basin formation. It overprints most of northern Canada Basin structure. The seafloor and sedimentary succession of Canada Basin is remarkably flat-lying in its central region, with little bathymetric change over most of its extent. Reflections that correlate over 100s of kms comprise most of the succession and on-lap bathymetric and basement highs. They are interpreted as representing deposits from unconfined turbidity current flows. Sediment distribution patterns reflect changing source directions during the basin’s history. Initially, probably late Cretaceous to Paleocene synrift sediments sourced from the Alaska and Mackenzie-Beaufort margins. This unit shows a progressive series of onlap unconformities with a younging trend towards Alpha and Northwind ridges, likely a response to contemporaneous subsidence. Sediment source direction appeared to shift to the Canadian Arctic Archipelago margin for the Eocene and Oligocene, likely due to uplift of Arctic islands during the Eurekan Orogeny. The final stage of sedimentation appears to be from the Mackenzie-Beaufort region for the Miocene and Pliocene when drainage patterns shifted in the Yukon and Alaska to the Mackenzie valley. Upturned reflections at onlap positions may indicate syn-depositional subsidence. There is little evidence, at least at a regional seismic data scale, of contemporaneous or post-depositional sediment reworking, suggesting little large-scale geostrophic or thermohaline-driven bottom current activity.

Water-quality assessment of the Kentucky River basin, Kentucky; nutrients, sediments, and pesticides in streams, 1987-90

USGS Publications Warehouse

Haag, K.H.; Porter, S.D.

1995-01-01

The U.S. Geological Survey investigated the water quality of the Kentucky River Basin in Kentucky as part of the National Water Quality Assessment program. Data collected during 1987-90 were used to describe the spatial and temporal variability of nutrients, suspended sediment, and pesticides in streams. Concentrations of phosphorus were signifi- cantly correlated with urban and agricultural land use. The high phosphorus content of Bluegrass Region soils was an important source of phosphorus in streams. At many sites in urban areas, all of the stream nitrogen load was attributable to wastewater- treatment-plant effluent. Tributary streams affected by agricultural sources of nutrients contained higher densities of phytoplankton than streams that drained forested areas. Data indicate that a consid- erable percentage of total nitrogen was transported as algal biomass during periods of low discharge. Average suspended-sediment concentrations for the study period were positively correlated with dis- charge. There was a downward trend in suspended- sediment concentrations downstream in the Kentucky River main stem during the study. Although a large amount of suspended sediment originates in the Eastern Coal Field Region, contributions of suspended sediment from the Red River and other tributary streams of the Knobs Region also are important. The most frequently detected herbicides in water samples were atrazine, 2,4-D, alachlor, metolachlor, and dicamba. Diazinon, malathion, and parathion were the most frequently detected organo- phosphate insecticides in water samples. Detectable concentrations of aldrin, chlordane, DDT, DDE, dieldrin, endrin, endosulfan, heptachlor, heptachlor epoxide, and lindane were found in streambed- sediment samples.

Holocene sediment distribution on the inner continental shelf of northeastern South Carolina: implications for the regional sediment budget and long-term shoreline response

USGS Publications Warehouse

Denny, Jane F.; Schwab, William C.; Baldwin, Wayne E.; Barnhardt, Walter A.; Gayes, Paul T.; Morton, R.A.; Warner, John C.; Driscoll, Neal W.; Voulgaris, George

2013-01-01

High-resolution geophysical and sediment sampling surveys were conducted offshore of the Grand Strand, South Carolina to define the shallow geologic framework of the inner shelf. Results are used to identify and map Holocene sediment deposits, infer sediment transport pathways, and discuss implications for the regional coastal sediment budget. The thickest deposits of Holocene sediment observed on the inner shelf form shoal complexes composed of moderately sorted fine sand, which are primarily located offshore of modern tidal inlets. These shoal deposits contain ~67 M m3 of sediment, approximately 96% of Holocene sediment stored on the inner shelf. Due to the lack of any significant modern fluvial input of sand to the region, the Holocene deposits are likely derived from reworking of relict Pleistocene and older inner-shelf deposits during the Holocene marine transgression. The Holocene sediments are concentrated in the southern part of the study area, due to a combination of ancestral drainage patterns, a regional shift in sediment supply from the northeast to the southwest in the late Pleistocene, and proximity to modern inlet systems. Where sediment is limited, only small, low relief ridges have formed and Pleistocene and older deposits are exposed on the seafloor. The low-relief ridges are likely the result of a thin, mobile veneer of sediment being transported across an irregular, erosional surface formed during the last transgression. Sediment textural trends and seafloor morphology indicate a long-term net transport of sediment to the southwest. This is supported by oceanographic studies that suggest the long-term sediment transport direction is controlled by the frequency and intensity of storms that pass through the region, where low pressure systems yield net along-shore flow to the southwest and a weak onshore component. Current sediment budget estimates for the Grand Strand yield a deficit for the region. Volume calculations of Holocene deposits on the inner shelf suggest that there is sufficient sediment to balance the sediment budget and provide a source of sediment to the shoreline. Although the processes controlling cross-shelf sediment transport are not fully understood, in sediment-limited environments such as the Grand Strand, erosion of the inner shelf likely contributes significant sediment to the beach system.

Historical record of lead accumulation and source in the tidal flat of Haizhou Bay, Yellow Sea: Insights from lead isotopes.

PubMed

Zhang, Rui; Guan, Minglei; Shu, Yujie; Shen, Liya; Chen, Xixi; Zhang, Fan; Li, Tiegang

2016-05-15

In order to investigate the historical records of lead contamination and source in coastal region of Haizhou Bay, Yellow Sea, a sediment core was collected from tidal flat, dated by (210)Pb and (137)Cs. Lead and its stable isotopic ratios were determined. The profiles of enrichment factor (EF) and Pb isotope ratios showed increasing trend upward throughout the core, correlating closely with the experience of a rapid economic and industrial development of the catchment. According to Pb isotopic ratios, coal combustion emission mainly contributed to the Pb burden in sediments. Based on end-member model, coal combustion emission dominated anthropogenic Pb sources in recent decades contributing from 48% to 67% in sediment. And the contribution of leaded gasoline was lower than 20%. A stable increase of coal combustion source was found in sediment core, while the contribution of leaded gasoline had declined recently, with the phase-out of leaded gasoline in China. Copyright © 2016 Elsevier Ltd. All rights reserved.

CHROMOPHORIC DISSOLVED ORGANIC MATTER (CDOM) SOURCE CHARACTERIZATION IN THE LOUISIANA BIGHT

EPA Science Inventory

Chromophoric dissolved organic matter (CDOM) in the Mississippi plume region may have several distinct sources: riverine (terrestrial soils), wetland (terrestrial plants), biological production (phytoplankton, zooplankton, microbial), and sediments. Complex mixing, photodegradati...

Distribution, input pathway and mass inventory of black carbon in sediments of the Gulf of Thailand, SE Asia

NASA Astrophysics Data System (ADS)

Hu, Limin; Shi, Xuefa; Bai, Yazhi; Fang, Yin; Chen, Yingjun; Qiao, Shuqing; Liu, Shengfa; Yang, Gang; Kornkanitnan, Narumol; Khokiattiwong, Somkiat

2016-03-01

The coastal margins around Southeast Asia (SE Asia) may serve as an ideal location to study the source-sink process of sedimentary black carbon (BC) because SE Asia has been identified as one of the major BC emission source regions in the world. This study provides an extensive picture of recent regional-scale sedimentary BC sequestration in the Gulf of Thailand (GOT), a tropical marine system in SE Asia. Generally, the sedimentary BC concentrations (0.07-3.99 mg/g) were in the low to moderate ranges of those obtained in other coastal sediments around the world. Regional variability of the BC and its correlation with the sediment grain size and total organic carbon (TOC) content indicated a general hydrodynamic constraint on BC occurrence in the lower Gulf in contrast to the upper Gulf with a more source dependence due to the direct land-based input. BC/TOC% values and the varied BC components (char and soot), as well as their correlations suggested that char was the predominant constituents of sedimentary BC both in the upper and lower Gulf, which could be mainly derived from biomass burning and entered into the nearshore region through direct fluvial transport and surface run-off. The estimated BC burial flux (∼212 μg/cm2/y) and mass inventory (∼200 Gg/y) in the GOT on the hundred-year timescale were of the same order of magnitude compared with other oceanic margins, and thus the tropical shelf sediments from SE Asia could serve as an important sink of land-emitted BC.

Clay mineralogy indicates the muddy sediment provenance in the estuarine-inner shelf of the East China Sea

NASA Astrophysics Data System (ADS)

Zhao, Yifei; Zou, Xinqing; Liu, Qing; Wang, Chenglong; Ge, Chendong; Xu, Min

2018-02-01

The estuarine-inner shelf mud regions of the East China Sea (ECS) are valuable for studying the source-to-sink processes of fluvial sediments deposited since the Holocene. In this study, we present evidence of the provenance and environmental evolution of two cores (S5-2 and JC07) from the estuarine-inner shelf regions of the ECS over the past 100 years based on 210Pb dating, high-resolution grain size measurements and clay mineral analyses. The results indicate that the clay mineral assemblages of cores S5-2 and JC07 are dominated by illite, followed by kaolinite and chlorite, and present scarce amounts of smectite. A comparison of these clay mineral assemblages with several major sources reveals that the fine sediments on the estuarine-inner shelf of the ECS represent a mixture of provenances associated with the Yangtze and Yellow Rivers, as well as smaller rivers. However, the contribution of each provenance has varied greatly over the past hundred years, as indicated by the down-core variability due to strong sediment reworking and transport on the inner shelf and the reduction of the sediment load from the Yangtze River basin. In the mud region of the Yangtze River estuary, the sediment from 1930 to 1956 was primarily derived from the Yangtze River, although the Yellow River was also an important influence. From 1956 to 2013, the Yellow River contribution decreased, whereas the Yangtze River contribution correspondingly increased. In the Zhe-Min mud region, the Yangtze River contributed more sediment than did other rivers from 1910 to 1950; however, the Yangtze River contribution gradually decreased from 1950 to 2013. Moreover, the other small rivers accounted for minor contributions, and the East Asian winter monsoon (EAWM) played an important role in the sediment transport process in the ECS. Our results indicate that the weakening/strengthening of the EAWM and a decrease in the sediment load of the Yangtze River influenced the transport and fate of sediment on the estuarine-inner shelf of the ECS.

A simple distributed sediment delivery approach for rural catchments

NASA Astrophysics Data System (ADS)

Reid, Lucas; Scherer, Ulrike

2014-05-01

The transfer of sediments from source areas to surface waters is a complex process. In process based erosion models sediment input is thus quantified by representing all relevant sub processes such as detachment, transport and deposition of sediment particles along the flow path to the river. A successful application of these models requires, however, a large amount of spatially highly resolved data on physical catchment characteristics, which is only available for a few, well examined small catchments. For the lack of appropriate models, the empirical Universal Soil Loss Equation (USLE) is widely applied to quantify the sediment production in meso to large scale basins. As the USLE provides long-term mean soil loss rates, it is often combined with spatially lumped models to estimate the sediment delivery ratio (SDR). In these models, the SDR is related to data on morphological characteristics of the catchment such as average local relief, drainage density, proportion of depressions or soil texture. Some approaches include the relative distance between sediment source areas and the river channels. However, several studies showed that spatially lumped parameters describing the morphological characteristics are only of limited value to represent the factors of influence on sediment transport at the catchment scale. Sediment delivery is controlled by the location of the sediment source areas in the catchment and the morphology along the flow path to the surface water bodies. This complex interaction of spatially varied physiographic characteristics cannot be adequately represented by lumped morphological parameters. The objective of this study is to develop a simple but spatially distributed approach to quantify the sediment delivery ratio by considering the characteristics of the flow paths in a catchment. We selected a small catchment located in in an intensively cultivated loess region in Southwest Germany as study area for the development of the SDR approach. The flow pathways were extracted in a geographic information system. Then the sediment delivery ratio for each source area was determined using an empirical approach considering the slope, morphology and land use properties along the flow path. As a benchmark for the calibration of the model parameters we used results of a detailed process based erosion model available for the study area. Afterwards the approach was tested in larger catchments located in the same loess region.

MERCURY IN METAL ORE DEPOSITS: AN UNRECOGNIZED, WIDESPREAD SOURCE TO LAKE SUPERIOR SEDIMENTS, CONTRIBUTION #1072

EPA Science Inventory

Mining operations have worked the rich mineral resources of the Lake Superior Basin for over 150 years, leaving industrially impacted regions with tailing piles and smelters. In Lake Superior sediments, mercury and copper inventories increase towards shorelines and are highly cor...

Sediment evidence of industrial leakage-induced asynchronous changes in polycyclic aromatic hydrocarbons and trace metals from a sub-trophic lake, southwest China.

PubMed

Wang, Lei; Chen, Guangjie; Kang, Wengang; Wang, Jiaoyuan; Liu, Yuanyuan; Chen, Li

2018-05-01

It has been well established that regional patterns of atmosphere-borne polycyclic aromatic hydrocarbons (PAHs) and trace metals were predominantly associated with the trajectory of socio-economic development; however, they could be potentially modulated by anthropogenic fingerprint of local sources such as industrial spill. Here, we established historical pollution data of both PAHs and trace metals from a well-dated sediment core from Yangzong Lake of Southwest China, which experienced a severe tailing leakage accident derived from a zinc concentrate smelting plant in 2007, aiming to evaluate the heterogeneity in their temporal trajectories and their sources of contamination in the context of regional deposition patterns. Sedimentary records show that the concentrations and fluxes of both PAHs and trace metals remained a consistently low level before the 1950s. An increasing trend and the synchronous changes of both PAHs and trace metals during ~ 1950-2002 were well consistent with the temporal pattern of socio-economic development in western China, with coal combustion and smelting industries as the main sources of contamination in this region. However, arsenic (As) and PAHs exhibited a concurrent spike for the period of ~ 2007-2013, contrasting strongly to the regional pattern of these contaminants. The modern concentrations of As revealed a 5- to 14-fold increase over the pre-1950 level, with the contemporary concentrations of PAHs rising by ~ 10-14 times. The sediment records reveal that local fingerprints of smelting activities in the catchment of Yangzong Lake have overridden the temporary pattern of regional atmosphere-borne As and PAHs over the last decade. This highlights the important role of local pollution sources in modulating or even overriding the regional pattern of anthropogenic contamination in highly impacted systems.

Character and provenance of aeolian sediments in northeast Thailand

NASA Astrophysics Data System (ADS)

Nichol, Janet E.; Nichol, Douglas W.

2015-12-01

Aeolian activity is not generally associated with the humid tropics, and although reports of loess-like soils in various locations in southeast Asia exist, these mainly lack the detailed analysis to set them in meaningful spatial or historical context. This paper examines the red and yellow sandy sediments of the Khorat Plateau in northeast Thailand which have been variously referred to as 'cover sands', 'loessial soils' or 'loess'. The sediments are referred to as having alluvial, biological as well as aeolian origin, and a date of 9-35 ka is reported. The study compares the Khorat sediments physically and geochemically with loess and aeolian sediments from other regions, as well as with other sites in southeast Asia which are reported here. The moderate degree of particle sorting and unimodal sizes of the sediments along with a sub-spherical sub-rounded form, supports previous diagnoses of an aeolian origin. Geochemical analysis of the Khorat sediments indicates severe depletion in both mobile and immobile elements, which are even more depleted than other southeast Asian loessic soils examined. This depletion, along with the only moderate particle sorting, suggests the source of the sediments to be the local weathered sandstones outcropping around the edge of the Khorat Plateau. The dissimilarity of the Khorat sediments from Upper Continental Crust (UCC) elemental values supports this, as homogenisation would occur if diverse source areas were involved. The study suggests that aeolian sediments of humid tropical regions warrant more attention as climate proxy markers, due to the dissimilarity between the present climate and conditions required for their formation.

From Source to Sink of Polycyclic Aromatic Hydrocarbons in Sediments in the East China Seas

NASA Astrophysics Data System (ADS)

Guo, Z.; Lin, T.; Hu, L.

2014-12-01

The East China Seas (ECSs), including Bohai Sea (77,000 km2), Yellow Sea (400,000 km2) and East China Sea (770,000 km2) have experienced a great variety of demographic and economic conditions which have a profound influence on the source composition of land-based polycyclic aromatic hydrocarbons (PAHs) in the sediments since ECSs's coasts support about 420 million peoples, provide more than half of the national GDP in China in 2007, and are major emission regions of PAHs in China. Furthermore, the ECSs are downwind of the Asian continental outflow in spring and winter driven by the East Asian monsoon. The sources of 16 USEPA priority PAHs in strategically selected surface sediment samples from the ECSs were apportioned using positive matrix factorization model, and the input pathways of PAHs were also revealed in the regions. Four sources were identified: petroleum residue, vehicular emissions, coal combustion and biomass burning. Petroleum residue was the dominant contributor of PAHs in the coast of the Bohai Bay probably due to Haihe River runoff, oil leakage from ships and offshore oil fields. The PAHs in sediments of the coastal East China Sea were mainly sourced from the Yangtze River discharge into the sea. The combined results of PMF, PCA and composition of PAHs suggest that the atmospheric deposition is the dominate input of PAHs for the open seas of Bohai Sea, East China Sea and Yellow Sea; while river input is the major pathway of PAHs in the estuarine and neighborhood coastal areas. The demographic and economic conditions around the ECSs have profound influence on the origins of the land-based PAHs in the sediments of the open seas.

Investigating the distribution and sources of organic matter in surface sediment of Coombabah Lake (Australia) using elemental, isotopic and fatty acid biomarkers

NASA Astrophysics Data System (ADS)

Dunn, R. J. K.; Welsh, D. T.; Teasdale, P. R.; Lee, S. Y.; Lemckert, C. J.; Meziane, T.

2008-10-01

Extensive physical and biological measurements were made of the surface sediments within the shallow, semi-urbanised Coombabah Lake in southern Moreton Bay, Australia. Sediment bulk parameters (C/N ratios, δ13C and δ15N) and fatty acid biomarkers were used to determine distributions and sources of organic matter in the intertidal sediments. The determination of organic matter sources within coastal and estuarine settings is important in understanding the roles of organic matter as energy and nutrient sources. Spatial variability of biomarker values within the sediments were interpreted by thematic maps employing the Krigging algorithm. Grain size analysis indicated the lake was dominated by mud (<63 μm) in the southern (landward) and sand (>63 μm) in the northern (seaward) lake regions, respectively. Surface sediment organic C and N values ranged from 0.12% to 1.76% and 0.01% to 0.12% dry weight, respectively, and C/N ratios averaged 16.3±3.19%. Sedimentary δ13C values ranged from -26.1‰ to -20.9‰, with an average value of -23.9±1.0‰. Sedimentary δ15N values ranged from +1.7‰ to +4.8‰, with an average value of +2.8±0.8‰. Bulk sediment parameters suggested that sedimentary organic matter is provided predominantly by allochthonous sources in the form of fringing mangroves. Thirty-nine individual fatty acids were identified using gas chromatography-mass spectrometry. The mean contributions of long chain fatty acids (LCFAs), polyunsaturated fatty acids (PUFAs), saturated fatty acids (SAFAs) and bacterial fatty acids (BAFAs) were, respectively, 13.9±11.4%, 7.6±4.1%, 53.6±8.6% and 18.2±4.6% of the identified fatty acid methyl esters (FAMEs), with BAFAs occurring in all sampled sediments. Fatty acid compositions varied throughout lake sediments, which indicated spatial differences in autochthonous and allochthonous organic matter sources, including terrestrial and planktonic (i.e. zooplankton, diatoms and other algal species) sources. The contribution of organic matter from shoreline mangroves was confirmed by the presence of LCFAs and 18:2 ω6 and 18:3 ω3, which are markers for mangroves in this ecosystem. BAFAs were identified in increased proportions in sediments adjacent to urban developments and dominated by mud. Grain size was identified as a dominant factor in the fatty acid compositions and contributing values to FAME pool. Spatial patterns of C/N ratios, δ13C and δ15N values, and fatty acid biomarker contributions illustrated that there is a greater contribution of autochthonous and labile organic matter to the sedimentary organic matter pool in the northern (marine entrance) sediments compared to the more allochthonous sourced organic matter of the southern region of the lake. This study details the distribution and sources of organic matter within Coombabah Lake and illustrates the usefulness of a multiple biomarker approach in discriminating organic matter sources within estuarine environments.

Mercury sedimentation in lakes in western Whatcom County, Washington, USA and its relation to local industrial and municipal atmospheric sources

USGS Publications Warehouse

Paulson, A.J.; Norton, D.

2008-01-01

Concentrations of mercury (Hg) were measured in six dated cores from four lakes in western Whatcom County, Washington, USA, that were at various bearings from a chlor-alkali plant, two municipal waste incinerators and a municipal sewage sludge incinerator. The importance of atmospheric emissions of Hg from these local municipal and industrial sources was evaluating by comparing the temporal trends in sedimentation of the lake cores with the emission history of each Hg species and by examining the geographical distribution of Hg sedimentation in relation to the region's primary wind pattern. Local municipal and industrial sources of atmospheric Hg were not responsible for the majority of the Hg in the upper layer of sediments of Whatcom County lakes because of (1) the significant enrichment of Hg in lake sediments prior to emissions of local industrial and municipal sources in 1964, (2) smaller increases in Hg concentrations occurred after 1964, (3) the similarity of maximum enrichments found in Whatcom County lakes to those in rural lakes around the world, (4) the inconsistency of the temporal trends in Hg sedimentation with the local emission history, and (5) the inconsistency of the geographic trends in Hg sedimentation with estimated deposition. Maximum enrichment ratios of Hg in lake sediments between 2 and 3 that are similar to rural areas in Alaska, Minnesota, and New England suggest that global sources of Hg were primarily responsible for increases of Hg in Whatcom County lakes beginning about 1900. ?? 2007 GovernmentEmployee: U.S. Government, Department of Interior, U.S. Geological Survey.

Detrital thermochronology of Rhine, Elbe and Meuse river sediment (Central Europe): implications for provenance, erosion and mineral fertility

NASA Astrophysics Data System (ADS)

Glotzbach, C.; Busschers, F. S.; Winsemann, J.

2018-03-01

Here we present detrital apatite fission track (AFT), zircon fission track (ZFT) and a few apatite (U-Th)/He (AHe) data of Middle Pleistocene to modern Rhine, Meuse and Elbe river sediments in order to resolve processes that control detrital age distributions (provenance, erosion and mineral fertility). We used a modelling approach to compare observed with theoretically predicted age distributions from an interpolated in situ AFT and ZFT age map. In situ cooling ages do show large differences in the Rhine drainage basin, facilitating the differentiation between different source regions. Inconsistencies between observed and theoretical age distributions of the Meuse and Elbe samples can be explained by mixing and reworking of sediments with different provenances (Meuse Middle Pleistocene terrace sediment) and a yet unexplored source region with old AFT ages (Elbe samples). Overall, the results show that detrital thermochronology is capable of identifying the provenance of Middle Pleistocene to modern sediments. The AFT age distributions of Rhine sediments are dominated ( 70%) by AFT ages representing the Alps. A possible explanation is higher erosion rates in the Alps as compared to areas outside the Alps. A Late Pleistocene sample from the Upper Rhine Graben contains apatite grains from the Molasse and Hegau volcanics, which we explain with a shift of the headwaters of the Rhine to the north as a result of intense Middle Pleistocene Riss glaciation. Contrary to the observed dominance of Alpine-derived AFT ages in Rhine sediments, the relative contribution of zircon ages with sources in the Alps is lower and significantly decreases downstream, suggesting a major source of zircons outside the Alps. This can be explained by increased zircon fertility of sediments derived from the Rhenish massif. Therefore, we conclude that erosion and mineral fertility are the main processes controlling detrital AFT and ZFT age distributions of the sampled river sediment. In case of the Rhine samples, AFT age distributions are mainly controlled by differences in erosion rates, whereas this impact is completely balanced by differences in mineral fertility for the ZFT data.

[Sources of Methane in the Boreal Region

NASA Technical Reports Server (NTRS)

1998-01-01

In determining the global methane budget the sources of methane must be balanced with the sinks and atmospheric inventory. The approximate contribution of the different methane sources to the budget has been establish showing the major terrestrial inputs as rice, wetlands, bogs, fens, and tundra. Measurements and modeling of production in these sources suggest that temperature, water table height and saturation along with substratum composition are important in controlling methane production and emission. The isotopic budget of 13 C and D/H in methane can be used as a tool to clarify the global budget. This approach has achieved success at constraining the inputs. Studies using the isotopic approach place constraints on global methane production from different sources. Also, the relation between the two biogenic production pathways, acetate fermentation and CO2 reduction, and the effect of substratum composition can be made using isotope measurements shows the relation between the different biogenic, thermogenic and anthropogenic sources of methane as a function of the carbon and hydrogen isotope values for each source and the atmosphere, tropospheric composition. Methane emissions from ponds and fens are a significant source in the methane budget of the boreal region. An initial study in 1993 and 1994 on the isotopic composition of this methane source and the isotopic composition in relation to oxidation of methane at the sediment surface of the ponds or fen was conducted as part of our BOREAS project. The isotopic composition of methane emitted by saturated anoxic sediment is dependent on the sediment composition and geochemistry, but will be influenced by in situ oxidation, in part, a function of rooted plant activity. The influence of oxidation mediated by rooted plant activities on the isotopic composition of methane is not well known and will depend on the plant type, sediment temperature, and numerous other variables. Information on this isotopic composition is important in both understanding the bio-geochemistry of the system and also in determining the regional and global inputs for the methane isotope budget. In determining the destruction of methane for balancing the atmospheric methane budget soil oxidation must be considered.

Mercury deposition and methylmercury formation in Narraguinnep Reservoir, southwestern Colorado, USA

USGS Publications Warehouse

Gray, John E.; Hines, Mark E.; Goldstein, Harland L.; Reynolds, Richard L.

2014-01-01

Narraguinnep Reservoir in southwestern Colorado is one of several water bodies in Colorado with a mercury (Hg) advisory as Hg in fish tissue exceed the 0.3 μg/g guideline to protect human health recommended by the State of Colorado. Concentrations of Hg and methyl-Hg were measured in reservoir bottom sediment and pore water extracted from this sediment. Rates of Hg methylation and methyl-Hg demethylation were also measured in reservoir bottom sediment. The objective of this study was to evaluate potential sources of Hg in the region and evaluate the potential of reservoir sediment to generate methyl-Hg, a human neurotoxin and the dominant form of Hg in fish. Concentrations of Hg (ranged from 1.1 to 5.8 ng/L, n = 15) and methyl-Hg (ranged from 0.05 to 0.14 ng/L, n = 15) in pore water generally were highest at the sediment/water interface, and overall, Hg correlated with methyl-Hg in pore water (R2 = 0.60, p = 0007, n = 15). Net Hg methylation flux in the top 3 cm of reservoir bottom sediment varied from 0.08 to 0.56 ng/m2/day (mean = 0.28 ng/m2/day, n = 5), which corresponded to an overall methyl-Hg production for the entire reservoir of 0.53 g/year. No significant point sources of Hg contamination are known to this reservoir or its supply waters, although several coal-fired power plants in the region emit Hg-bearing particulates. Narraguinnep Reservoir is located about 80 km downwind from two of the largest power plants, which together emit about 950 kg-Hg/year. Magnetic minerals separated from reservoir sediment contained spherical magnetite-bearing particles characteristic of coal-fired electric power plant fly ash. The presence of fly-ash magnetite in post-1970 sediment from Narraguinnep Reservoir indicates that the likely source of Hg to the catchment basin for this reservoir has been from airborne emissions from power plants, most of which began operation in the late-1960s and early 1970s in this region.

Metal pollution investigation of Goldman Park, Middletown Ohio: Evidence for steel and coal pollution in a high child use setting.

PubMed

Dietrich, Matthew; Huling, Justin; Krekeler, Mark P S

2018-03-15

A geochemical investigation of both ballfield sediment and street sediment in a park adjacent to a major steel manufacturing site in Middletown, Ohio revealed Pb, Cu, Cr and Zn exceeded background levels, but in heterogeneous ways and in varying levels of health concern. Pb, Sn, and Zn had geoaccumulation values>2 (moderate to heavy pollutants) in street sediment samples. Cr had a geoaccumulation value>1, while Ni, W, Fe and Mn had geoaccumulation values between 1 and 0 in street sediment. Street sediment contamination factors for respective elements are Zn (10.41), Sn (5.45), Pb (4.70), Sb (3.45), Cr (3.19), W (2.59), and Mn (2.43). The notable elements with the highest factors for ball fields are Zn (1.72), Pb (1.36), Cr (0.99), V (0.95), and Mn (1.00). High correlation coefficients of known constituents of steel, such as Fe and Mo, Ni and Cr, W and Co, W and V, as well as particulate steel and coal spherule fragments found by SEM suggest probable sourcing of some of the metals from the AK Steel facility directly adjacent to the park. However, overall extensive heterogeneity of metal pollutants in the area points to the difficulties in sourcing pollutant metals, with many outside sources likely contributing as well. This study demonstrates that different sediment media can be impacted by significantly different metal pollutants even when in very close proximity to a single source and points to unrecognized complexity in urban pollution processes in the region. This study pertains to large-scale regional importance, as Middletown, Ohio is indicative of a typical post-industrial Midwestern U.S. city where limited investigation has been conducted regarding urban pollution and sourcing of materials. Copyright © 2017 Elsevier B.V. All rights reserved.

n-Alkanes in sediments from the Yellow River Estuary, China: Occurrence, sources and historical sedimentary record.

PubMed

Wang, Shanshan; Liu, Guijian; Yuan, Zijiao; Da, Chunnian

2018-04-15

A total of 21 surface sediments from the Yellow River Estuary (YRE) and a sediment core from the abandoned Old Yellow River Estuary (OYRE) were analyzed for n-alkanes using gas chromatography-mass spectrometry (GC-MS). n-Alkanes in the range C 12 -C 33 and C 13 -C 34 were identified in the surface sediments and the core, respectively. The homologous series were mainly bimodal distribution pattern without odd/even predominance in the YRE and OYRE. The total n-alkanes concentrations in the surface sediments ranged from 0.356 to 0.572mg/kg, with a mean of 0.434mg/kg on dry wt. Evaluation of n-alkanes proxies indicated that the aliphatic hydrocarbons in the surface sediments were derived mainly from a petrogenic source with a relatively low contribution of submerged/floating macrophytes, terrestrial and emergent plants. The dated core covered the time period 1925-2012 and the mean sedimentation rate was ca. 0.5cm/yr. The total n-alkanes concentrations in the core ranged from 0.0394 to 0.941mg/kg, with a mean of 0.180mg/kg. The temporal evolution of n-alkanes reflected the historical input of aliphatic hydrocarbons and was consistent with local and regional anthropogenic activity. In general, the investigation on the sediment core revealed a trend of regional environmental change and the role of anthropogenic activity in environmental change. Copyright © 2017 Elsevier Inc. All rights reserved.

Geochemistry of polycyclic aromatic hydrocarbons in the bottom sediments of the eastern Arctic shelf

NASA Astrophysics Data System (ADS)

Petrova, V. I.; Batova, G. I.; Kursheva, A. V.; Litvinenko, I. V.; Savinov, V. M.; Savinova, T. N.

2008-04-01

Sources and pathways of supply of polycyclic aromatic hydrocarbons (PAH) in the surface sediments of the Laptev and East Siberian seas were identified based on an analysis of the lithological-geochemical characteristics and distribution of organic matter (OM). The distribution of organic carbon, humic acids, bitumoids, and hydrocarbons demonstrates the determining role of the riverine runoff in the formation of the recent sediments. The total average content of PAH in the sediments of this region approximates 37 ng/g, not exceeding 80 ng/g of dry sediment. The biogenic components of the PAH (alkylphenanthrenes, alkylchrysenes, perylene) dominate in the estuarine-shelf and coastal-shelf sediments enriched with plant detritus and significantly decrease in the pelagic zone. The anthropogenic influence is observed in sediments of the port of Tiksi, where the total content of PAH with dominant pyrogenic components is two orders of magnitude higher as compared with the background values in the study region.

Sources, Transport, and Storage of Sediment at Selected Sites in the Chesapeake Bay Watershed

USGS Publications Warehouse

Gellis, Allen C.; Hupp, Cliff R.; Pavich, Milan J.; Landwehr, Jurate M.; Banks, William S.L.; Hubbard, Bernard E.; Langland, Michael J.; Ritchie, Jerry C.; Reuter, Joanna M.

2009-01-01

The Chesapeake Bay Watershed covers 165,800 square kilometers and is supplied with water and sediment from five major physiographic provinces: Appalachian Plateau, Blue Ridge, Coastal Plain, Piedmont, and the Valley and Ridge. Suspended-sediment loads measured in the Chesapeake Bay Watershed showed that the Piedmont Physiographic Province has the highest rates of modern (20th Century) sediment yields, measured at U.S. Geological Survey streamflow-gaging stations, and the lowest rates of background or geologic rates of erosion (~10,000 years) measured with in situ beryllium-10. In the agricultural and urbanizing Little Conestoga Creek Watershed, a Piedmont watershed, sources of sediment using the 'sediment-fingerprinting' approach showed that streambanks were the most important source (63 percent), followed by cropland (37 percent). Cesium-137 inventories, which quantify erosion rates over a 40-year period, showed average cropland erosion of 19.39 megagrams per hectare per year in the Little Conestoga Creek Watershed. If this erosion rate is extrapolated to the 13 percent of the watershed that is in cropland, then cropland could contribute almost four times the measured suspended-sediment load transported out of the watershed (27,600 megagrams per hectare per year), indicating that much of the eroded sediment is being deposited in channel and upland storage. The Piedmont has had centuries of land-use change, from forest to agriculture, to suburban and urban areas, and in some areas, back to forest. These land-use changes mobilized a large percentage of sediment that was deposited in upland and channel storage, and behind thousands of mill dams. The effects of these land-use changes on erosion and sediment transport are still being observed today as stored sediment in streambanks is a source of sediment. Cropland is also an important source of sediment. The Coastal Plain Physiographic Province has had the lowest sediment yields in the 20th Century and with sandy soils, contributes little fine-grained sediment. In the agricultural Pocomoke River Watershed, a Coastal Plain watershed, cesium-137 mass-balance results indicate that erosion and deposition are both occurring on cropland fields. Sources of sediment using the sediment-fingerprinting approach for the Pocomoke River were distributed as follows: cropland (46 percent), ditch beds (34 percent), ditch banks and streambanks (7 percent), and forest (13 percent). Cropland was a source of sediment for the two largest peak flow events, which occurred during harvesting when the ground may have been bare. The Pocomoke River Watershed is heavily ditched and channelized, conditions that are favorable for ditch bed and bank erosion. In the mixed land use (forested, agricultural, and urbanizing) Mattawoman Creek Watershed, a Coastal Plain watershed, sources of sediment using the sediment-fingerprinting approach were distributed as follows: streambanks (30 percent), forest (29 percent), construction (25 percent), and cropland (17 percent). Mattawoman Creek Watershed drains a rapidly developing region with 182 hectares (approximately 1.26 percent of the watershed) under construction. Sediment from construction sites was also determined as a source of sediment in the Mattawoman Creek Watershed. The sediment-fingerprinting source results for the three watersheds analyzed, show that in all watersheds, both the stream corridor and agriculture were significant sources of sediment. Forest as a source of sediment in the Mattawoman Creek Watershed may indicate that these forests are being disturbed and forest soils are eroding. Bare ground can be an important sediment source. Spatial analysis of bare ground in the Little Conestoga Creek Watershed using satellite imagery between 2000 and 2005 showed that the majority of bare ground was classified as pasture. Bare ground was correlated to the growing season with the highest percentages occurring in the early spring (April, 34 percent) and a

Source to sink evaluation of sediment routing in the Gulf of Alaska and Southeast Alaska: A thermochronometric perspective

NASA Astrophysics Data System (ADS)

Dunn, Catherine A.; Enkelmann, Eva; Ridgway, Kenneth D.; Allen, Wai K.

2017-03-01

In this study, we present a source to sink evaluation of sediment routing at the glaciated convergent margin in Southeast Alaska. We investigate the efficacy of thermochronology to record spatial and temporal exhumation patterns in synorogenic sediment using Neogene strata drilled by Integrated Ocean Drilling Program Expedition 341 in the Gulf of Alaska. We present 1641 and 529 new detrital zircon and apatite fission track ages, respectively, from strata deposited on the continental shelf, slope, and deep-sea fans. These data are compared to results from the proposed source terrains, including the St. Elias Mountains and new data from the Alsek River. We find that the offshore Bagley-Bering sediment contains grains recording cooling ages much older (80-35 Ma) than those reported from the St. Elias syntaxis (3-2 Ma), indicating that extreme rapid exhumation does not extend west of the Seward-Bagley divide. Data from the sediment on the continental shelf, slope, and proximal deep sea all yield similar results, suggesting the same general source region since 1.2 Ma and limited sediment mixing along this glaciated margin. Data from sediment in the distal deep sea show that extreme, rapid, and deep-seated exhumation was ongoing at 11-8 Ma. Overall, this study demonstrates the strengths and limitations of using detrital fission track thermochronology to understand sediment routing on a glaciated convergent margin and to record changes in exhumation rates over geologic time scales.

A conceptual review of regional-scale controls on the composition of clastic sediment and the co-evolution of continental blocks and their sedimentary cover.

PubMed

Cox, R; Lowe, D R

1995-01-02

Both sediment recycling and first-cycle input influence the composition of clastic material in sedimentary systems. This paper examines conceptually the roles played by these processes in governing the composition of clastic sediment on a regional scale by outlining the expected effects on sediment composition of protracted sediment recycling and of continuous first-cycle input on a maturing continental block. Generally speaking, long-term recycling tends to enrich sediments in the most chemically and mechanically stable components: quartz in the sand and silt size fractions, and illite among the clay minerals. Sandstones trend towards pure quartz arenites, and mudrocks become more potassic and aluminous. The average grain size of clastic sediment decreases by a combination of progressive attrition of sand grains and ongoing breakdown of primary silicate minerals to finer-grained clay minerals and oxides. Sandstones derived by continuous first-cycle input from an evolving continental crustal source also become increasingly rich in quartz, but in addition become more feldspathic as the proportion of granitic material in the upper continental crust increases during crustal stabilization. Associated mudrocks also become richer in potassium and aluminum, but will have higher K2O/Al2O3 ratios than recycled muds. The average grain size of the sediment may increase with time as the proportion of sand-prone granitic source rocks increases at the expense of more mud-prone volcanic sources. In general, except in instances where chemical weathering is extreme, first-cycle sediments lack the compositional maturity of recycled detritus, and are characterized by the presence of a variety of primary silicate minerals. Sedimentary systems are not usually completely dominated by either recycling or first-cycle detritus. Generally, however, sedimentary systems associated with the earliest phases of formation and accretion of continental crust are characterized by first-cycle input from igneous and metamorphic rocks, whereas those associated with more mature cratons tend to be dominated by recycled sedimentary material.

Holocene and late glacial palaeoceanography and palaeolimnology of the Black Sea: Changing sediment provenance and basin hydrography over the past 20,000 years

USGS Publications Warehouse

Piper, David Z.; Calvert, S.E.

2011-01-01

The elemental geochemistry of Late Pleistocene and Holocene sediments of the Black Sea, recovered in box cores from the basin margins and a 5-m gravity core from the central abyssal region of the basin, identifies two terrigenous sediment sources over the last 20 kyrs. One source region includes Anatolia and the southern Caucasus; the second region is the area drained by rivers entering the Black Sea from Eastern Europe. Alkali metal:Al and heavy:light rare-earth element ratios reveal that the relative contribution of the two sources shifted abruptly every few thousand years during the late glacial and early Holocene lacustrine phase of the basin. The shifts in source were coeval with changes in the lake level as determined from the distribution of quartz and the heavy mineral-hosted trace elements Ti and Zr.The geochemistry of the abyssal sediments further recorded a sequence of changes to the geochemistry of the water column following the lacustrine phase, when high salinity Mediterranean water entered the basin beginning 9.3 kyrs BP. Bottom water that had been oxic throughout the lake phase became anoxic at approximately 8.4 kyrs BP, as recorded by the accumulation from the water column of several redox-sensitive trace metals (Mo, Re, U). The accumulation of organic carbon and several trace nutrients (Cd, Cu, Ni, Zn) increased sharply ca. 0.4 kyrs later, at 8.0 kyrs BP, reflecting an increase of primary productivity. Its increase was coeval with a shift in the dinoflagellate ecology from stenohaline to euryhaline assemblages. During this profound environmental change from the lacustrine to the marine phase, the accumulation rate of the lithogenous sediment fraction decreased as much as 10-fold in response to the rise of the water level in the basin from a low stand ca. 9.3 ka to its current level.

Holocene and late glacial palaeoceanography and palaeolimnology of the Black Sea: Changing sediment provenance and basin hydrography over the past 20,000 years

USGS Publications Warehouse

Piper, D.Z.; Calvert, S.E.

2011-01-01

The elemental geochemistry of Late Pleistocene and Holocene sediments of the Black Sea, recovered in box cores from the basin margins and a 5-m gravity core from the central abyssal region of the basin, identifies two terrigenous sediment sources over the last 20. kyrs. One source region includes Anatolia and the southern Caucasus; the second region is the area drained by rivers entering the Black Sea from Eastern Europe. Alkali metal:Al and heavy:light rare-earth element ratios reveal that the relative contribution of the two sources shifted abruptly every few thousand years during the late glacial and early Holocene lacustrine phase of the basin. The shifts in source were coeval with changes in the lake level as determined from the distribution of quartz and the heavy mineral-hosted trace elements Ti and Zr. The geochemistry of the abyssal sediments further recorded a sequence of changes to the geochemistry of the water column following the lacustrine phase, when high salinity Mediterranean water entered the basin beginning 9.3. kyrs BP. Bottom water that had been oxic throughout the lake phase became anoxic at approximately 8.4. kyrs BP, as recorded by the accumulation from the water column of several redox-sensitive trace metals (Mo, Re, U). The accumulation of organic carbon and several trace nutrients (Cd, Cu, Ni, Zn) increased sharply ca. 0.4. kyrs later, at 8.0. kyrs BP, reflecting an increase of primary productivity. Its increase was coeval with a shift in the dinoflagellate ecology from stenohaline to euryhaline assemblages. During this profound environmental change from the lacustrine to the marine phase, the accumulation rate of the lithogenous sediment fraction decreased as much as 10-fold in response to the rise of the water level in the basin from a low stand ca. 9.3. ka to its current level.

Sediments in Arctic sea ice: Implications for entrainment, transport and release

USGS Publications Warehouse

Nurnberg, D.; Wollenburg, I.; Dethleff, D.; Eicken, H.; Kassens, H.; Letzig, T.; Reimnitz, E.; Thiede, Jorn

1994-01-01

Despite the Arctic sea ice cover's recognized sensitivity to environmental change, the role of sediment inclusions in lowering ice albedo and affecting ice ablation is poorly understood. Sea ice sediment inclusions were studied in the central Arctic Ocean during the Arctic 91 expedition and in the Laptev Sea (East Siberian Arctic Region Expedition 1992). Results from these investigations are here combined with previous studies performed in major areas of ice ablation and the southern central Arctic Ocean. This study documents the regional distribution and composition of particle-laden ice, investigates and evaluates processes by which sediment is incorporated into the ice cover, and identifies transport paths and probable depositional centers for the released sediment. In April 1992, sea ice in the Laptev Sea was relatively clean. The sediment occasionally observed was distributed diffusely over the entire ice column, forming turbid ice. Observations indicate that frazil and anchor ice formation occurring in a large coastal polynya provide a main mechanism for sediment entrainment. In the central Arctic Ocean sediments are concentrated in layers within or at the surface of ice floes due to melting and refreezing processes. The surface sediment accumulation in central Arctic multi-year sea ice exceeds by far the amounts observed in first-year ice from the Laptev Sea in April 1992. Sea ice sediments are generally fine grained, although coarse sediments and stones up to 5 cm in diameter are observed. Component analysis indicates that quartz and clay minerals are the main terrigenous sediment particles. The biogenous components, namely shells of pelecypods and benthic foraminiferal tests, point to a shallow, benthic, marine source area. Apparently, sediment inclusions were resuspended from shelf areas before and incorporated into the sea ice by suspension freezing. Clay mineralogy of ice-rafted sediments provides information on potential source areas. A smectite maximum in sea ice sediment samples repeatedly occurred between 81??N and 83??N along the Arctic 91 transect, indicating a rather stable and narrow smectite rich ice drift stream of the Transpolar Drift. The smectite concentrations are comparable to those found in both Laptev Sea shelf sediments and anchor ice sediments, pointing to this sea as a potential source area for sea ice sediments. In the central Arctic Ocean sea ice clay mineralogy is significantly different from deep-sea clay mineral distribution patterns. The contribution of sea ice sediments to the deep sea is apparently diluted by sedimentary material provided by other transport mechanisms. ?? 1994.

[Accumulation, distribution and pollution assessment of heavy metals in surface sediment of Caohai plateau wetland, Guizhou province].

PubMed

Zhang, Qing-Hai; Lin, Chang-Hu; Tan, Hong; Lin, Shao-Xia; Yang, Hong-Bo

2013-03-01

The objective of this paper is to investigate the concentrations and distribution characteristics of heavy metals in surface sediments of different areas in the Caohai plateau wetland. 16 samples of surface sediments were collected and 7 heavy metals were analyzed. Heavy metal pollution in surface sediments of different areas in the Caohai plateau wetland was estimated by the Tomlinson Pollution Load Index (PLI) method. The analyzed results indicated that the average contents of Cd, Hg, As, Pb, Cr, Cu, Zn were 0.985, 0.345, 15.8, 38.9, 38.6, 22.8 and 384 mg x kg(-1), respectively. The heavy metal distributions varied with regional environment changes, the order of average contents of Cd and Hg in different regions was E (the eastern region) > S (the southern region) > N (the northern region), the order of the average content of Pb was N > E > S, and that of Zn was S > E > N. The results also suggested a medium heavy metal pollution level in the surface sediment of the Caohai plateau wetland with the PLI(zone) reaching 1.17. The order of pollution level in surface sediments of different regions was E > S > N. The results showed medium pollution levels in E and Hg which reached the extreme intensity pollution level were also the major polluted elements in surface sediments of the Caohai plateau wetland. And also, results showed medium pollution levels of Cd and Pb in surface sediments of Caohai plateau wetland. Cluster analysis results showed similar pollution sources of Cd, Zn, Pb and Hg, which should be attached great importance in terms of the prevention of the Caohai plateau wetland.

Identification of multiple mercury sources to stream sediments near Oak Ridge, TN, USA

DOE PAGES

Donovan, Patrick M.; Blum, Joel D.; Demers, Jason D.; ...

2014-03-03

In this paper, sediments were analyzed for total Hg concentration (THg) and isotopic composition from streams and rivers in the vicinity of the Y-12 National Security Complex (Y12) in Oak Ridge, TN (USA). In the stream directly draining Y12, where industrial releases of mercury (Hg) have been documented, high THg (3.26 to 60.1 μg/g) sediments had a distinct Hg isotopic composition (δ 202Hg of 0.02 ± 0.15‰ and Δ 199Hg of -0.07 ± 0.03‰; mean ± 1SD, n=12) compared to sediments from relatively uncontaminated streams in the region (δ 202Hg = -1.40 ± 0.06‰ and Δ 199Hg of –0.26 ±more » 0.03‰; mean ± 1SD, n=6). Additionally, several streams that are nearby but do not drain Y12 had sediments with intermediate THg (0.06 to 0.21 μg/g) and anomalous δ 202Hg (as low as -5.07‰). We suggest that the low δ 202Hg values in these sediments provide evidence for the contribution of an additional Hg source to sediments, possibly derived from atmospheric deposition. In sediments directly downstream of Y12 this third Hg source is not discernible and the Hg isotopic composition can be largely explained by the mixing of low THg sediments with high THg sediments contaminated by Y12 discharges.« less

Arctic Ocean sea ice drift origin derived from artificial radionuclides.

PubMed

Cámara-Mor, P; Masqué, P; Garcia-Orellana, J; Cochran, J K; Mas, J L; Chamizo, E; Hanfland, C

2010-07-15

Since the 1950s, nuclear weapon testing and releases from the nuclear industry have introduced anthropogenic radionuclides into the sea, and in many instances their ultimate fate are the bottom sediments. The Arctic Ocean is one of the most polluted in this respect, because, in addition to global fallout, it is impacted by regional fallout from nuclear weapon testing, and indirectly by releases from nuclear reprocessing facilities and nuclear accidents. Sea-ice formed in the shallow continental shelves incorporate sediments with variable concentrations of anthropogenic radionuclides that are transported through the Arctic Ocean and are finally released in the melting areas. In this work, we present the results of anthropogenic radionuclide analyses of sea-ice sediments (SIS) collected on five cruises from different Arctic regions and combine them with a database including prior measurements of these radionuclides in SIS. The distribution of (137)Cs and (239,240)Pu activities and the (240)Pu/(239)Pu atom ratio in SIS showed geographical differences, in agreement with the two main sea ice drift patterns derived from the mean field of sea-ice motion, the Transpolar Drift and Beaufort Gyre, with the Fram Strait as the main ablation area. A direct comparison of data measured in SIS samples against those reported for the potential source regions permits identification of the regions from which sea ice incorporates sediments. The (240)Pu/(239)Pu atom ratio in SIS may be used to discern the origin of sea ice from the Kara-Laptev Sea and the Alaskan shelf. However, if the (240)Pu/(239)Pu atom ratio is similar to global fallout, it does not provide a unique diagnostic indicator of the source area, and in such cases, the source of SIS can be constrained with a combination of the (137)Cs and (239,240)Pu activities. Therefore, these anthropogenic radionuclides can be used in many instances to determine the geographical source area of sea-ice. Copyright 2010 Elsevier B.V. All rights reserved.

Petrography and geochemistry characteristics of the lower Cretaceous Muling Formation from the Laoheishan Basin, Northeast China: implications for provenance and tectonic setting

NASA Astrophysics Data System (ADS)

Song, Yu; Liu, Zhaojun; Meng, Qingtao; Wang, Yimeng; Zheng, Guodong; Xu, Yinbo

2017-06-01

The petrography, mineralogy and geochemistry of sedimentary rocks from the lower Cretaceous Muling Formation (K1ml) in the Laoheishan basin, northeast (NE) China are studied to determine the weathering intensity, provenance and tectonic setting of the source region. Petrographic data indicate the average quartz-feldspar-lithic fragments (QFL) of the sandstone is Q = 63 %, F = 22 %, and L = 15 %. Lithic fragments mainly contain volcanic clasts that derived from surrounding basement. X-ray diffraction (XRD) data reveal abundant clay and detrital minerals (e.g. quartz), as well as minor calcite in the fine-grained sediments. The Hf contents and element concentration ratios such as Al2O3/TiO2, Co/Th, La/Sc, and La/Th are comparable to sediments derived from felsic and intermediate igneous rocks. The strong genetic relationship with the igneous rocks from the northwest and northeast areas provides evidence that the sediments of the Muling Formation (K1ml) in the Laoheishan basin have been derived from this area. The chemical index of alteration (CIA) and index of chemical variability (ICV) reveal an intensive weathering in the source region of the sediments. The multidimensional tectonic discrimination diagrams indicate that the source rocks of K1ml are mainly derived from the collision system. However, they may also comprise sediments derived from the continental rift system. The results are consistent with the geology of the study area.

Using rare earth elements to trace wind-driven dispersion of sediments from a point source

NASA Astrophysics Data System (ADS)

Van Pelt, R. Scott; Barnes, Melanie C. W.; Strack, John E.

2018-06-01

The entrainment and movement of aeolian sediments is determined by the direction and intensity of erosive winds. Although erosive winds may blow from all directions, in most regions there is a predominant direction. Dust emission causes the removal preferentially of soil nutrients and contaminants which may be transported tens to even thousands of kilometers from the source and deposited into other ecosystems. It would be beneficial to understand spatially and temporally how the soil source may be degraded and depositional zones enriched. A stable chemical tracer not found in the soil but applied to the surface of all particles in the surface soil would facilitate this endeavor. This study examined whether solution-applied rare earth elements (REEs) could be used to trace aeolian sediment movement from a point source through space and time at the field scale. We applied erbium nitrate solution to a 5 m2 area in the center of a 100 m diameter field 7854 m2 on the Southern High Plains of Texas. The solution application resulted in a soil-borne concentration three orders of magnitude greater than natively found in the field soil. We installed BSNE sampler masts in circular configurations and collected the trapped sediment weekly. We found that REE-tagged sediment was blown into every sampler mast during the course of the study but that there was a predominant direction of transport during the spring. This preliminary investigation suggests that the REEs provide a viable and incisive technique to study spatial and temporal variation of aeolian sediment movement from specific sources to identifiable locations of deposition or locations through which the sediments were transported as horizontal mass flux and the relative contribution of the specific source to the total mass flux.

Source apportionment of trace metals in river sediments: A comparison of three methods.

PubMed

Chen, Haiyang; Teng, Yanguo; Li, Jiao; Wu, Jin; Wang, Jinsheng

2016-04-01

Increasing trace metal pollution in river sediment poses a significant threat to watershed ecosystem health. Identifying potential sources of sediment metals and apportioning their contributions are of key importance for proposing prevention and control strategies of river pollution. In this study, three advanced multivariate receptor models, factor analysis with nonnegative constraints (FA-NNC), positive matrix factorization (PMF), and multivariate curve resolution weighted-alternating least-squares (MCR-WALS), were comparatively employed for source apportionment of trace metals in river sediments and applied to the Le'an River, a main tributary of Poyang Lake which is the largest freshwater lake in China. The pollution assessment with contamination factor and geoaccumulation index suggested that the river sediments in Le'an River were contaminated severely by trace metals due to human activities. With the three apportionment tools, similar source profiles of trace metals in sediments were extracted. Especially, the MCR-WALS and PMF models produced essentially the same results. Comparatively speaking, the weighted schemes might give better solutions than the unweighted FA-NNC because the uncertainty information of environmental data was considered by PMF and MCR-WALS. Anthropogenic sources were apportioned as the most important pollution sources influencing the sediment metals in Le'an River with contributions of about 90%. Among them, copper tailings occupied the largest contribution (38.4-42.2%), followed by mining wastewater (29.0-33.5%), and agricultural activities (18.2-18.7%). To protect the ecosystem of Le'an River and Poyang Lake, special attention should be paid to the discharges of mining wastewater and the leachates of copper tailing ponds in that region. Copyright © 2015 Elsevier Ltd. All rights reserved.

Challenges of ecosystem restoration in Louisiana - availability of sediment and its management

NASA Astrophysics Data System (ADS)

Khalil, S. M.; Freeman, A. M.

2015-03-01

Human intervention has impaired the Mississippi River's ability to deliver sediment to its delta wetlands, and as a consequence acute land loss in coastal Louisiana has resulted in an unprecedented ecocatastrophe. To mitigate this degradation, an unparalleled restoration effort is underway. For this effort to be successful and sustainable, various sediment input mechanisms must be integrated, including: building appropriate sediment-diversions; beneficially using the millions of cubic metres of sediment dredged annually from navigational channels; harvesting deposits of sand and suitable sediment from the river and offshore; and related sediment management activities that are compatible with other uses of the river. A comprehensive sediment management plan has been developed to identify and delineate potential sediment sources for restoration, and to provide a framework for managing sediment resources wisely, cost effectively, and in a systematic manner. The Louisiana Sediment Management Plan provides regional strategies for improved comprehensive management of Louisiana's limited sediment resources.

The distribution of sediments grain size along the depth in source of the Yangtze River, Tibetan Plateau, China

NASA Astrophysics Data System (ADS)

Zhou, Y.; Yao, S.; Zhou, S.; Liu, X.; Yan, X.; Lu, J.

2017-12-01

Sediment was the one result of river process, in alluvial rive, it can reflect the hydrodynamic characteristic, even the hydrology and climate. In the source region of the Yangtze River with few human activities, The Qumalai Reach of the Tongtianhe River was selected to research the distribution of sediments grain size along the depth. The vertical drilling tools were used to obtain 7 boreholes along the river cross section, and the sedimentary cores were made analysis of stratification and granularity. The results show: The sediments are dominated by sand and grail, the sediment transport capacity of river sources is strong; the grain size frequency distribution curve with 2 3 kurtosis, main peak is sharp, it is typical deposit sediment of the suspended load; The grain size coarsen from the stream terrace to the main channel, sediment transport capacity of main stream is bigger; There are several coarse and fine sediments layers in the sedimentary core of the terrace and flood plain, medium diameters of each layer are various from 0.4mm to 80mm, different layer with different grain size can reflect the different hydrodynamic characteristic of each historical period. This result can provide the original data and enlightenment to support the research for historical river process and hydrology so much as the climate change.

Comparison of estimated and measured sediment yield in the Gualala River

Treesearch

Matthew O’Connor; Jack Lewis; Robert Pennington

2012-01-01

This study compares quantitative erosion rate estimates developed at different spatial and temporal scales. It is motivated by the need to assess potential water quality impacts of a proposed vineyard development project in the Gualala River watershed. Previous erosion rate estimates were developed using sediment source assessment techniques by the North Coast Regional...

Tapping the deglacial secrets of Lake Oneida sediments: Establishing a connection between radiocarbon and paleomagnetics in Fish Creek sediments

NASA Astrophysics Data System (ADS)

Peck, D.; Rosenheim, B. E.; Ridge, J. C.

2017-12-01

Postglacial varved and rhythmically-laminated clays deposited within the Ontario Basin are often associated with the retreat of the Laurentide Ice Sheet immediately preceding the onset of the Younger Dryas. The paleoclimatic significance of the Ontario Basin has made it a popularly studied region. To determine ages that correlate with ice sheet retreat, classical radiocarbon ages were generated. However low total organic carbon (TOC) values found in glaciolacustrine sediments make accuracy of data a concern. Using the magnetic orientation of sediments during deposition, paleomagnetism has presented reliable dates in similar regions across the northeastern United States. While useful, paleomagnetism also comes with limitations, which have left areas of unexplored research. Lake Oneida, last glaciated by the Ontario Lobe, is one of the deepest and most untapped reservoirs of sediment dating back to the retreat of the Laurentide Ice Sheet, due primarily to the difficulty it poses for classical methods. Using samples taken from exposed varved glaciolacustrine sediment exposed by the downcutting of Fish Creek, a fluvial system terminating in eastern Lake Oneida, we compare Ramped Pyrolysis 14C data with paleomagnetic data. Ramped PyrOx 14C data unmask the distribution of ages in the organic matter of these sediments, at least partially separating autochthonous sources of carbon from allochthonous sources that tend to be older in these settings. Our comparison will test whether Ramped PyrOx 14C data match paleomagnetic data well enough to be used as the sole chronometer in sediment cores taken from Lake Oneida cores for which paleomagnetic orientation becomes more difficult to ascertain.

Organic carbon burial in fjords: Terrestrial versus marine inputs

NASA Astrophysics Data System (ADS)

Cui, Xingqian; Bianchi, Thomas S.; Savage, Candida; Smith, Richard W.

2016-10-01

Fjords have been identified as sites of enhanced organic carbon (OC) burial and may play an important role in regulating climate change on glacial-interglacial timescales. Understanding sediment processes and sources of sedimentary OC are necessary to better constrain OC burial in fjords. In this study, we use Fiordland, New Zealand, as a case study and present data on surface sediments, sediment down-cores and terrestrial end-members to examine dynamics of sediments and the sources of OC in fjord sediments. Sediment cores showed evidence of multiple particle sources, frequent bioturbation and mass-wasting events. A multi-proxy approach (stable isotopes, lignin-phenols and fatty acids) allowed for separation of marine, soil and vascular plant OC in surface sediments. The relationship between mass accumulation rate (MAR) and OC contents in fjord surface sediments suggested that mineral dilution is important in controlling OC content on a global scale, but is less important for specific regions (e.g., New Zealand). The inconsistency of OC budgets calculated by using MAR weighted %OC and OC accumulation rates (AR; 6 vs 21-31 Tg OC yr-1) suggested that sediment flux in fjords was likely underestimated. By using end-member models, we propose that 55% to 62% of total OC buried in fjords is terrestrially derived, and accounts for 17 ± 12% of the OCterr buried in all marine sediments. The strong correlation between MAR and OC AR indicated that OC flux will likely decrease in fjords in the future with global warming due to decrease in sediment flux caused by glacier denudation.

Source-to-Sink Methods by Hyperspectral Imaging: a Case Study of the Laminated Sediments of Lake Linné (Svalbard).

NASA Astrophysics Data System (ADS)

Van Exem, A.; Debret, M.; Copard, Y.; Verpoorter, C.; Sorrel, P.; de Wet, G.; Werner, A.; Roof, S.; Laignel, B.; Retelle, M.

2016-12-01

Laminated sediments contained valuable information recorded on a micrometric scale. Information about sediments flux and origins require high-resolution source tracking analysis. Quick and non-destructive, hyperspectral imaging provides contiguous reflectance datasets into 2 dimensions with a spatial resolution of 0.02 mm. Located on the west of the Spitzbergen, Lake Linné is the largest lake in the region. Erosion is mainly driven by glacier fluctuations and three different bedrocks are potential sediment sources. Organic matter (coal) is only found in some carboniferous rocks. Four cores recovered from different parts of the lake contain millimeter scale laminae. Two approaches were compared: (i) measurement of statistical correlations between the sediments and source samples, (ii) extraction of extreme spectral signatures from the VNIR hyperspectral images. Total Organic Carbon (TOC) values of all samples were also given by bulk geochemistry (RE6 ® pyrolyzer). Consequently, the measured similarity between the hyperspectral image and the field samples illustrates the sources contribution within the core. Three sample clusters and three equivalent spectral signatures were found. TOC values from the archive show good correlation (r=0.86, p<0.001, n=73) with the hyperspectral signature relative to TOC content. A least-squares regression (r²=0.74) was used to extrapolate TOC values in order to represent their distribution at 0.02 mm resolution. This is the first source-to-sink study based on imaging spectroscopy. Our results indicate that hyperspectral imagery is a useful tool to (i) identify sediment sources, (ii) perform continuous paleo-environmental reconstruction at high resolution, and (iii) can provide quantitative results (TOC values) validated by destructive analyses.

Evaluation of simple geochemical indicators of aeolian sand provenance: Late Quaternary dune fields of North America revisited

USGS Publications Warehouse

Muhs, Daniel

2017-01-01

Dune fields of Quaternary age occupy large areas of the world's arid and semiarid regions. Despite this, there has been surprisingly little work done on understanding dune sediment provenance, in part because many techniques are time-consuming, prone to operator error, experimental, highly specialized, expensive, or require sophisticated instrumentation. Provenance of dune sand using K/Rb and K/Ba values in K-feldspar in aeolian sands of the arid and semiarid regions of North America is tested here. Results indicate that K/Rb and K/Ba can distinguish different river sands that are sediment sources for dunes and dune fields themselves have distinctive K/Rb and K/Ba compositions. Over the Basin and Range and Great Plains regions of North America, the hypothesized sediment sources of dune fields are reviewed and assessed using K/Rb and K/Ba values in dune sands and in hypothesized source sediments. In some cases, the origins of dunes assessed in this manner are consistent with previous studies and in others, dune fields are found to have a more complex origin than previously thought. Use of K/Rb and K/Ba for provenance studies is a robust method that is inexpensive, rapid, and highly reproducible. It exploits one of the most common minerals found in dune sand, K-feldspar. The method avoids the problem of using simple concentrations of key elements that may be subject to interpretative bias due to changes in mineralogical maturity of Quaternary dune fields that occur over time.

Modeling of depth to base of Last Glacial Maximum and seafloor sediment thickness for the California State Waters Map Series, eastern Santa Barbara Channel, California

USGS Publications Warehouse

Wong, Florence L.; Phillips, Eleyne L.; Johnson, Samuel Y.; Sliter, Ray W.

2012-01-01

Models of the depth to the base of Last Glacial Maximum and sediment thickness over the base of Last Glacial Maximum for the eastern Santa Barbara Channel are a key part of the maps of shallow subsurface geology and structure for offshore Refugio to Hueneme Canyon, California, in the California State Waters Map Series. A satisfactory interpolation of the two datasets that accounted for regional geologic structure was developed using geographic information systems modeling and graphics software tools. Regional sediment volumes were determined from the model. Source data files suitable for geographic information systems mapping applications are provided.

Speciation of phosphorus in the continental shelf sediments in the Eastern Arabian Sea

NASA Astrophysics Data System (ADS)

Acharya, Shiba Shankar; Panigrahi, Mruganka Kumar; Kurian, John; Gupta, Anil Kumar; Tripathy, Subhasish

2016-03-01

The distributions of various forms of phosphorus (P) and their relation with sediment geochemistry in two core sediments near Karwar and Mangalore offshore have been studied through the modified SEDEX procedure (Ruttenberg et al., 2009) and bulk chemical analysis. The present study provides the first quantitative analysis of complete phosphorus speciation in the core sediments of the Eastern Arabian shelf. The chemical index of alteration (CIA), chemical Index of Weathering (CIW) and Al-Ti-Zr ternary diagram suggest low to moderate source area weathering of granodioritic to tonalitic source rock composition, despite the intense orographic rainfall in the source area. Due to the presence of same source rock and identical oxic depositional environment, the studied sediments show the same range of variation of total phosphorus (24 to 83 μmol/g) with a down-depth depleting trend. Organic bound P and detrital P are the two major chemical forms followed by iron-bound P, exchangeable/loosely bound P and authigenic P. The authigenic P content in the sediments near Mangalore coast varies linearly with calcium (r=0.88) unlike that of Karwar coast. The different reactive-phosphorus pools exhibit identical depleting trend with depth. This indicates that the phosphorus released from the organic matter and Fe bound fractions are prevented from precipitating as authigenic phosphates in the deeper parts of the sediment column. The low concentration of total P, dominance of detrital non-reactive fraction of P and inhibition of formation of authigenic phosphate result in the absence of active phosphatization in the Eastern Arabian Shelf in the studied region. High sedimentation rate (35-58 cm/kyr) and absence of winnowing effect appear to be the dominant factor controlling the P-speciation in the studied sediments.

The dominant erosion processes supplying fine sediment to three major rivers in tropical Australia, the Daly (NT), Mitchell (Qld) and Flinders (Qld) Rivers

NASA Astrophysics Data System (ADS)

Caitcheon, Gary G.; Olley, Jon M.; Pantus, Francis; Hancock, Gary; Leslie, Christopher

2012-05-01

The tropics of northern Australia have received relatively little attention with regard to the impact of soil erosion on the many large river systems that are an important part of Australia's water resource, especially given the high potential for erosion when long dry seasons are followed by intense wet season rain. Here we use 137Cs concentrations to determine the erosion processes supplying sediment to two major northern Australian Rivers; the Daly River (Northern Territory), and the Mitchell River (Queensland). We also present data from five sediment samples collected from a 100 km reach of the Cloncurry River, a major tributary of the Flinders River (Queensland). Concentrations of 137Cs in the surface soil and subsurface (channel banks and gully) samples were used to derive 'best fit' probability density functions describing their distributions. These modelled distributions are then used to estimate the relative contribution of these two components to the river sediments. Our results are consistent with channel and gully erosion being the dominant source of sediment, with more than 90% of sediment transported along the main stem of these rivers originating from subsoil. We summarize the findings of similar studies on tropical Australian rivers and conclude that the primary source of sediment delivered to these systems is gully and channel bank erosion. Previously, as a result of catchment scale modelling, sheet-wash and rill erosion was considered to be the major sediment source in these rivers. Identifying the relative importance of sediment sources, as shown in this paper, will provide valuable information for land management planning in the region. This study also reinforces the importance of testing model predictions before they are used to target investment in remedial action.

Coupling distributed stormwater collection and managed aquifer recharge: Field application and implications.

PubMed

Beganskas, S; Fisher, A T

2017-09-15

Groundwater is increasingly important for satisfying California's growing fresh water demand. Strategies like managed aquifer recharge (MAR) can improve groundwater supplies, mitigating the negative consequences of persistent groundwater overdraft. Distributed stormwater collection (DSC)-MAR projects collect and infiltrate excess hillslope runoff before it reaches a stream, focusing on 40-400 ha drainage areas (100-1000 ac). We present results from six years of DSC-MAR operation-including high resolution analyses of precipitation, runoff generation, infiltration, and sediment transport-and discuss their implications for regional resource management. This project generated significant water supply benefit over six years, including an extended regional drought, collecting and infiltrating 5.3 × 10 5  m 3 (426 ac-ft). Runoff generation was highly sensitive to sub-daily storm frequency, duration, and intensity, and a single intense storm often accounted for a large fraction of annual runoff. Observed infiltration rates varied widely in space and time. The basin-average infiltration rate during storms was 1-3 m/d, with point-specific rates up to 8 m/d. Despite efforts to limit sediment load, 8.2 × 10 5  kg of fine-grained sediment accumulated in the infiltration basin over three years, likely reducing soil infiltration capacity. Periodic removal of accumulated material, better source control, and/or improved sediment detention could mitigate this effect in the future. Regional soil analyses can maximize DSC-MAR benefits by identifying high-infiltration capacity features and characterizing upland sediment sources. A regional network of DSC-MAR projects could increase groundwater supplies while contributing to improved groundwater quality, flood mitigation, and stakeholder engagement. Copyright © 2017 Elsevier Ltd. All rights reserved.

Oasis deposits in the southern margin of the Taklimakan Desert and abrupt environmental changes during the last 30 ka

NASA Astrophysics Data System (ADS)

Shu, P.; Li, B.; Wang, H.; Cheng, P.; An, Z.; Zhou, W.; Zhang, D. D.

2017-12-01

Taklimakan Desert, the largest arid landform in the Eurasia, is one of the most important dust sources in the world. Growing evidences shows that millennial-scale abrupt climate changes during the last glacial period in the region. However, records on millennial-scale climate and environmental changes remain poorly understood because dating eolian, lacustrine, and fluvial sediments and establishing the reliable environmental proxies from these records are always challenging. Here, we present 32 AMS 14C dates of bulk sediments, grain size, and Rb/Sr ratio parameters from the oasis sequence and dates of bulk loess and charcoal from the upstream source regions to examine the significance of oasis sediments on millennial-scale environmental changes in the Taklimakan Desert. We found that substantial reversal of radiocarbon dates on total organic carbon (TOC) was controlled by source region organic carbon input. Loess hills, alpine meadow north of the study region provided fluvial deposits along drainage system and deflation in the river valleys further provide eolain materials. We argue that early oasis deposits experienced deflation and re-deposition less severe than the younger oasis deposits. After refining radiocarbon age-depth relationships for an age model by Bacon package, proxy records show substantial abrupt fluctuations in climate and environments during the last glacial period, among which three wet intervals, two dry periods are identified. The wetter and warmer conditions during the Holocene facilitated human to occupy the oasis.

Contaminated Coastal Sediments in the Northeastern United States: Changing Sources Over Time

NASA Astrophysics Data System (ADS)

Buchholtz ten Brink, M. R.; Bothner, M. H.; Mecray, E. L.

2001-05-01

Regional studies of coastal sediments in the northeastern United States, conducted by the U.S. Geological Survey, show that trace metal contamination from land-based activities has occurred near all major urban centers. Concentrations of metals, such as Cu, Pb, Zn, Hg, and Ag, are 2-5 times background levels in sediments of Boston Harbor, Long Island Sound (LIS), offshore of Gulf of Maine coastal cities, and in the New York Bight (NYB). Contaminant accumulations are strongly influenced by sediment lithology and sediment transport properties in local areas, in addition to proximity to pollutant sources. Inventories are greatest in muddy depo-centers of the NYB, western LIS, and Boston Harbor. Based on sediment cores, the onset of metal contamination in the northeast occurs in the mid-1800s, with inputs increasing in the mid-1900s and decreasing (20-50%) from the 1970s to present. The increases correlate with local population growth and abundance of a bacterial sewage indicator, Clostridium perfringens. Increases of N and Corg in cores also reflect population growth and changing wastewater treatment practices. Corg values reach a high of 6% in buried sediments near the NYB disposal sites. Cores from western LIS have increasing values of C, N, and P in the most recently deposited sediments, in contrast to metal concentrations that have decreased in recent years. Cessation of sludge disposal and reduction of chemical discharges have been effective at reducing inputs; however, contaminated sediment deposits remain in rivers (e.g., the Charles), floodplains (e.g., the Housatonic), and coastal sediments. In the future, high concentrations of metal contaminants stored in buried sediments of marine and fluvial systems are likely to be a lingering and significant source of pollution to coastal environments. Until more effective source-reduction occurs, land-use and industrial practices associated with population growth in the northeast will remain dominant factors for nutrient loading. A multi-disciplinary approach, including predictive models that include changing sources and physical, chemical, and biological transport processes, is required to estimate the long-term fate and effect of pollutants currently in coastal sediments.

Mercury distribution in ancient and modern sediments of northeastern Bering Sea

USGS Publications Warehouse

Nelson, C. Hans; Pierce, D.E.; Leong, K.W.; Wang, F.F.

1972-01-01

A reconnaissance of surface and subsurface sediments to a maximum depth of 244 feet below the sea floor shows that natural mercury anomalies from 0.2 to 1.3 ppm have been present in northeastern Bering Sea since early Pliocene. The anomalies and mean values are highest in modern beach (maximum 1.3 and mean 0.22 ppm Hg) and nearshore subsurface gravels (maximum 0.6 and mean .06 ppm Hg) along the highly mineralized Seward Peninsula and in organic rich silt (maximum 0.16 and mean 0.10 ppm Hg) throughout the region; the mean values are lowest in offshore sands (0.03 ppm Hg) . Although gold mining may be partially responsible for high mercury levels in the beaches near Nome, Alaska, equally high or greater concentrations of mercury occur in ancient glacial sediments immediately offshore (0.6 ppm) and in modern unpolluted beach sediments at Bluff (0.45 - 1.3 ppm); this indicates that the contamination effects of mining may be no greater than natural concentration processes in the Seward Peninsula region. The background content of mercury (0.03) throughout the central area of northeastern Bering Sea is similar to that elsewhere in the world. The low mean values (0.04 ppm) even immediately offshore from mercury-rich beaches, suggests that in the surface sediments of northeastern Bering Sea, the highest concentrations are limited to the beaches near mercury sources; occasionally, however, low mercury anomalies occur offshore in glacial drift derived from mercury source regions of Chukotka and Seward Peninsula and reworked by Pleistocene shoreline processes. The minimal values offshore may be attributable to beach entrapment of heavy minerals containing mercury and/or dilution effects of modern sedimentation.

Hydrodynamic Controls on Archaeal Tetraether Lipid Compositions in Washington Margin Sediments: Insights From Compound-Specific Radiocarbon Measurements

NASA Astrophysics Data System (ADS)

Uchida, M.; Eglinton, T. I.; Montlucon, D. B.; Pearson, A.; Hayes, J. M.

2008-12-01

Continental margin sediments represent a large sink of organic carbon derived from marine and terrestrial sources. Archaeal glycerol dibiphytanyl glycerol tetraether lipids (GDGTs) are derived from both marine and terrestrial sources and have been used both for reconstruction of paleo sea surface temperatures and as an index of terrestrial carbon input to the marine sediments. However, the sources and modes of supply as well as the preservation of GDGTs in marginal sediments are poorly understood. The distribution and deposition of GDGTs is further complicated by hydrodynamic processes. We have analyzed a suite of surface sediment samples collected along a transect from the mouth of the Columbia River, across the Washington Margin, to the Cascadia Basin in the northeast Pacific Ocean. Sediments were separated according to their grain size and hydrodynamic properties, and the organic matter characterized in terms of its bulk elemental, isotopic, and molecular properties. Here we present radiocarbon measurements on individual GDGTs, alkenones, and fatty acids from size-fractionated sediments from shelf and slope sediments, and discuss the results in the context of previous studies of the molecular abundances and isotopic compositions of sedimentary organic matter for in this region. Systematic variations in elemental, isotopic and molecular-level composition are observed across the different particle classes. Moreover, these variations are manifested in the isotopic composition of different molecular markers of both marine and terrestrial sources organic matter. Both marine-derived lipids, including alkenones and marine archaeal tetraethers, and soil microbe-derived tetraether lipids show strong distributional and isotopic variations among the size-fractionated sediments. These variations in terrestrial and marine biomarker properties inform on the sources, particle dynamics, and transport history of organic matter buried on river-influenced continental margins. The implications of these findings for the application of molecular markers as proxies of organic matter input, and on the interpretation of past marine and continental environmental conditions from sedimentary records will also be discussed.

The clay mineral and Sr-Nd isotopic composition for fine-grained fraction of sediments from northwestern South China Sea: implications for sediment provenance

NASA Astrophysics Data System (ADS)

Cai, G.

2013-12-01

*Guanqiang Cai caiguanqiang@sina.com Guangzhou Marine Geological Survey, Guangzhou, 510760, P.R. China As the largest marginal sea in the western pacific, the South China Sea (SCS) receives large amount of terrigenous material annually through numerous rivers from surrounding continents and islands, which make it as the good place for the study of source to sink process. Yet few studies put emphasis on the northwestern continental shelf and slope in the SCS, even though most of the detrital materials derived from the Red River and Hainan Island are deposited in this area, and northwestern shelf plays a significant role in directly linking the South China, the Indochina and the South China Sea and thus controlling the source to sink process of terrestrial sediment. We presented the clay mineral and Sr-Nd isotopic composition of fine-grained fraction for sediments from northwestern SCS, in order to identify sediment source and transportation. The results show that the clay mineral of northwestern SCS sediments are mainly illite (30%~59%), smectite (20%~40%) and kaolinite (8%~35%), with minor chlorite. The illite chemical index varies between 0.19 and 0.75 with an average of 0.49, indicating an intensive hydrolysis in the source region. The 87Sr/86Sr ratios of sediments range from 0.716288 to 0.734416 (average of 0.724659), and ɛ Nd(0) values range from -10.31 to -11.62 (average of -10.93), which suggest that the source rocks of these sediments are derived from continental crust. The Hainan Island is an important source for sediments deposited in the nearshore and western shelf, especially for illite, kaolinite and smectite clay minerals. Furthermore, the relatively high contents of kaolinite and smectite in sediments from eastern shelf and southern slope of Hainan Island are also controlled by the supply of terrigenous materials from Hainan, which cannot be resulted from sedimentary differentiation of the Pearl and Red river sediments. And the correlation analysis between smectite and Sr-Nd isotopic ratios imply that the smectite in sediments mainly come from chemical weathering products of old continental crust, rather than volcanic rocks of Luzon island.

Estuarine bed-sediment-quality data collected in New Jersey and New York after Hurricane Sandy, 2013

USGS Publications Warehouse

Fischer, Jeffrey M.; Phillips, Patrick J.; Reilly, Timothy J.; Focazio, Michael J.; Loftin, Keith A.; Benzel, William M.; Jones, Daniel K.; Smalling, Kelly L.; Fisher, Shawn C.; Fisher, Irene J.; Iwanowicz, Luke R.; Romanok, Kristin M.; Jenkins, Darkus E.; Bowers, Luke; Boehlke, Adam; Foreman, William T.; Deetz, Anna C.; Carper, Lisa G.; Imbrigiotta, Thomas E.; Birdwell, Justin E.

2015-01-01

Bed-sediment samples were collected from June to October 2013 from 167 estuarine sites extending from Cape May, New Jersey, to the New York Harbor and the eastern end of Long Island. Each sampling location and study region was characterized by using geographic information to identify potential contaminant sources. Characterizations included land cover, locations and types of businesses (industrial, financial, and others), spills (sewage, chemical, and others), bulk storage facilities, effluent discharges within 2 kilometers of the sampling point, and discharges within inundated and non-inundated regions near the sampling location. Samples were analyzed for particle size, total organic carbon, metals and trace elements, semivolatile organic compounds, wastewater compounds, hormones, and sediment toxicity. Samples were also screened using x-ray fluorescence, Fourier transform infrared spectroscopy, and x-ray diffraction. In addition, bioassays for endocrine disruptors and protein phosphatase 2A inhibition were conducted. The study was designed to provide the data needed to understand the extent and sources of contamination resulting from Hurricane Sandy, to compare the chemistry and toxicity of estuarine bed sediments before and after the storm, and to evaluate the usefulness of rapid screening and bioassay approaches in disaster settings.

Identification of critical sediment source areas at regional level

NASA Astrophysics Data System (ADS)

Fargas, D.; Casasnovas, J. A. Martínez; Poch, R.

In order to identify critical sediment sources in large catchments, using easily available terrain information at regional scale, a methodology has been developed to obtain a qualitative assessment necessary for further studies. The main objective of the model is to use basic terrain data related to the erosive processes which contribute to the production, transport and accumulation of sediments through the main water paths in the watershed. The model is based on the selection of homogeneous zones regarding drainage density and lithology, achieved by joining the spatial basic units by a rating system. The values of drainage density are rated according to an erosion class (Bucko & Mazurova, 1958). The lithology is rated by erosion indexes, adapted from FAO (1977). The combination and reclassification of the results brings about five qualitative classes of sediment emission risk. This methodology has been tested an validated for the watershed of the Joaquín Costa reservoir (NE Spain), with a surface of 1500 km 2. The mapping scale was 1:100.000 and the model was implemented through a vector GIS (Arc/Info). The prediction was checked by means of photo-interpretation and field work, which gave a accuracy of 78.5%. The proposed methodology has been proved useful as an initial approach for erosion assessment and soil conservation planning at the regional level, and also to select priority areas where further analyses can be developed.

Low-maturity Kulthieth Formation coal: A possible source of polycyclic aromatic hydrocarbons in benthic sediment of the northern Gulf of Alaska

USGS Publications Warehouse

Van Kooten, G. K.; Short, J.W.; Kolak, J.J.

2002-01-01

The successful application of forensic geology to contamination studies involving natural systems requires identification of appropriate endmembers and an understanding of the geologic setting and processes affecting the systems. Studies attempting to delineate the background, or natural, source for hydrocarbon contamination in Gulf of Alaska (GOA) benthic sediments have invoked a number of potential sources, including seep oils, source rocks, and coal. Oil seeps have subsequently been questioned as significant sources of hydrocarbons present in benthic sediments of the GOA in part because the pattern of relative polycyclic aromatic hydrocarbon (PAH) abundance characteristic of benthic GOA sediments is inconsistent with patterns typical of weathered seep oils. Likewise, native coal has been dismissed in part because ratios of labile hydrocarbons to total organic carbon (e.g. PAH:TOC) for Bering River coal field (BRCF) sources are too low - i.e. the coals are over mature - to be consistent with GOA sediments. We present evidence here that native coal may have been prematurely dismissed, because BRCF coals do not adequately represent the geochemical signatures of coals elsewhere in the Kulthieth Formation. Contrary to previous thought, Kulthieth Formation coals east of the BRCF have much higher PAH: TOC ratios, and the patterns of labile hydrocarbons in these low thermal maturity coals suggest a possible genetic relationship between Kulthieth Formation coals and nearby oil seeps on the Sullivan anticline. Analyses of low-maturity Kulthieth Formation coal indicate the low maturity coal is a significant source of PAH. Source apportionment models that neglect this source will underestimate the contribution of native coals to the regional background hydrocarbon signature. ?? Published by Elsevier Science Ltd. on behalf of AEHS.

Sources and mass inventory of sedimentary polycyclic aromatic hydrocarbons in the Gulf of Thailand: Implications for pathways and energy structure in SE Asia.

PubMed

Hu, Limin; Shi, Xuefa; Qiao, Shuqing; Lin, Tian; Li, Yuanyuan; Bai, Yazhi; Wu, Bin; Liu, Shengfa; Kornkanitnan, Narumol; Khokiattiwong, Somkiat

2017-01-01

Surface sediments obtained from a matrix of 92 sample sites in the Gulf of Thailand (GOT) were analyzed for a comprehensive study of the distribution, sources, and mass inventory of polycyclic aromatic hydrocarbons (PAHs) to assess their input pathways and impacts of the regional land-based energy structure on the deposition of PAHs on the adjacent continental margins. The concentration of 16 PAHs in the GOT ranged from 2.6 to 78.1ng/g (dry weight), and the mean concentration was 19.4±15.1ng/g. The spatial distribution pattern of 16 PAH was generally consistent with that of sediment grain size, suggesting the influence of regional hydrodynamic conditions. Correlation and principal component analysis of the PAHs indicated that direct land-based inputs were dominantly responsible for the occurrence of PAHs in the upper GOT and the low molecular weight (LMW) PAHs in the coastal region could be from petrogenic sources. A positive matrix factorization (PMF) model apportioned five contributors: petroleum residues (~44%), biomass burning (~13%), vehicular emissions (~11%), coal combustion (~6%), and air-water exchange (~25%). Gas absorption may be a significant external input pathway for the volatile PAHs in the open GOT, which further implies that atmospheric loading could be important for the sink of PAHs in the open sea of the Southeast Asia (SE Asia). The different PAH source patterns obtained and a significant disparity of PAH mass inventory in the sediments along the East and Southeast Asia continental margins can be ascribed mainly to different land-based PAH emission features under the varied regional energy structure in addition to the depositional environment and climatic conditions. Copyright © 2016 Elsevier B.V. All rights reserved.

Sources of sediment to the coastal waters of the Southern California Bight

USGS Publications Warehouse

Warrick, J.A.; Farnsworth, K.L.

2009-01-01

The sources of sediment to the Southern California Bight were investigated with new calculations and published records of sediment fluxes, both natural and anthropogenic. We find that rivers are by far the largest source of sediment, producing over 10 ?? 106 t/yr on average, or over 80% of the sediment input to the Bight. This river flux is variable, however, over both space and time. The rivers draining the Transverse Ranges produce sediment at rates approximately an order of magnitude greater than the Peninsular Ranges (600-1500 t/km2/yr versus <90 t/km2/yr, respectively). Although the Transverse Range rivers represent only 23% of the total Southern California watershed drainage area, they are responsible for over 75% of the total sediment flux. River sediment flux is ephemeral and highly pulsed due to the semiarid climate and the influence of infrequent large storms. For more than 90% of the time, negligible amounts of sediment are discharged from the region's rivers, and over half of the post-1900 sediment load has been discharged during events with recurrence intervals greater than 10 yr. These rare, yet important, events are related to the El Ni??o-Southern Oscillation (ENSO), and the majority of sediment flux occurs during ENSO periods. Temporal trends in sediment discharge due to land-use changes and river damming are also observed. We estimate that there has been a 45% reduction in suspended-sediment flux due to the construction of dams. However, pre-dam sediment loads were likely artificially high due to the massive land-use changes of coastal California to rangeland during the nineteenth century. This increase in sediment production is observed in estuarine deposits throughout coastal California, which reveal that sedimentation rates were two to ten times higher during the nineteenth and twentieth centuries than during pre-European colonization. ?? 2009 The Geological Society of America.

Osmium isotopes demonstrate distal transport of contaminated sediments in Chesapeake Bay

USGS Publications Warehouse

Helz, G.R.; Adelson, J.M.; Miller, C.V.; Cornwell, J.C.; Hill, J.M.; Horan, M.; Walker, R.J.

2000-01-01

Because the isotopic composition of anthropogenic Os is normally distinctive in comparison to continental crust and is precisely measurable, this platinum-group element is attractive as a tracer of transport pathways for contaminated sediments in estuaries. Evidence herein and elsewhere suggest that biomedical research institutions are the chief source of anthropogenic Os. In the Chesapeake Bay region, uncontaminated sediments bear a crustal 187Os/188Os signature of 0.73 ?? 0.10. Slightly higher 187Os/188Os ratios occur in Re-rich Coastal Plain deposits due to post- Miocene 187Re decay. The upper Susquehanna Basin yields sediments also with higher 187Os/188Os. Beginning in the late 1970s, this signal was overprinted by a low 187Os/188Os (anthropogenic) source in the lower Susquehanna Basin. In the vicinity of Baltimore, which is a major center of heavy industry as well as biomedical research, anthropogenic Os has been found only in sediments impacted by the principal wastewater treatment plant. Surprisingly, a mid-Bay site distant from anthropogenic sources contains the strongest anthropogenic Os signal in the data set, having received anthropogenic Os sporadically since the mid-20th Century. Transport of particles to this site overrode the northward flowing bottom currents. Finding anthropogenic Os at this site cautions that other particle-borne substances, including hazardous ones, could be dispersed broadly in this estuary.Because the isotopic composition of anthropogenic Os is normally distinctive in comparison to continental crust and is precisely measurable, this platinum-group element is attractive as a tracer of transport pathways for contaminated sediments in estuaries. Evidence herein and elsewhere suggest that biomedical research institutions are the chief source of anthropogenic Os. In the Chesapeake Bay region, uncontaminated sediments bear a crustal 187Os/188Os signature of 0.73 ?? 0.10. Slightly higher 187Os/188Os ratios occur in Re-rich Coastal Plain deposits due to post-Miocene 187Re decay. The upper Susquehanna Basin yields sediments also with higher 187Os/188Os. Beginning in the late 1970s, this signal was overprinted by a low 187Os/188Os (anthropogenic) source in the lower Susquehanna Basin. In the vicinity of Baltimore, which is a major center of heavy industry as well as biomedical research, anthropogenic Os has been found only in sediments impacted by the principal wastewater treatment plant. Surprisingly, a mid-Bay site distant from anthropogenic sources contains the strongest anthropogenic Os signal in the data set, having received anthropogenic Os sporadically since the mid-20th Century. Transport of particles to this site overrode the northward flowing bottom currents. Finding anthropogenic Os at this site cautions that other particle-borne substances, including hazardous ones, could be dispersed broadly in this estuary.

Contribution of the upper river, the estuarine region, and the adjacent sea to the heavy metal pollution in the Yangtze Estuary.

PubMed

Yin, Su; Wu, Yuehan; Xu, Wei; Li, Yangyang; Shen, Zhenyao; Feng, Chenghong

2016-07-01

To determine whether the discharge control of heavy metals in the Yangtze River basin can significantly change the pollution level in the estuary, this study analyzed the sources (upper river, the estuarine region, and the adjacent sea) of ten heavy metals (As, Cd, Co, Cr, Cu, Hg, Ni, Pb, Sb, and Zn) in dissolved and particulate phases in the surface water of the estuary during wet, normal, and dry seasons. Metal sources inferred from section fluxes agree with those in statistical analysis methods. Heavy metal pollution in the surface water of Yangtze Estuary primarily depends on the sediment suspension and the wastewater discharge from estuary cities. Upper river only constitutes the main source of dissolved heavy metals during the wet season, while the estuarine region and the adjacent sea (especially the former) dominate the dissolved metal pollution in the normal and dry seasons. Particulate metals are mainly derived from sediment suspension in the estuary and the adjacent sea, and the contribution of the upper river can be neglected. Compared with the hydrologic seasons, flood-ebb tides exert a more obvious effect on the water flow directions in the estuary. Sediment suspension, not the upper river, significantly affects the suspended particulate matter concentration in the estuary. Copyright © 2016 Elsevier Ltd. All rights reserved.

Quantifying the seasonal variations in fluvial and eolian sources of terrigenous material to Cariaco Basin, Venezuela

NASA Astrophysics Data System (ADS)

Elmore, Aurora C.; Thunell, Robert C.; Styles, Richard; Black, David; Murray, Richard W.; Martinez, Nahysa; Astor, Yrene

2009-02-01

The varved sediments that accumulate in the Cariaco Basin provide a detailed archive of the region's climatic history, including a record of the quantity of fluvial and wind-transported material. In this study, we examine the sedimentological characteristics (clay mineralogy and grain size) of both surface sediments and sinking lithogenic material collected from sediment trap samples over a three-year period from 1997 to 2000. Data from biweekly sediment trap samples show a tri-modal particle size distribution, with prominent peaks at 2, 22 and 80 μm, indicating sediment contributions from both eolian and fluvial sources. The clay mineralogy of the water column samples collected from 1997 to 1999 also shows distinctive characteristics of eolian and fluvial material. An examination of surface sediment samples from the Cariaco Basin indicates that the Unare River is the main source of riverine sediments to the eastern sub-basin. By combining these sedimentological proxies, we estimate that ˜10% of the terrigenous material delivered to the Cariaco Basin is eolian, while ˜90% is fluvial. This represents an annual dust accumulation rate of ˜0.59 mg/cm 2/yr. Since aerosols are closely linked to climate variability, the ability to quantify paleo-dust fluxes using sedimentological characteristics will be a useful tool for future paleoclimate studies looking at sub-Saharan aridity and latitudinal migration of the Intertropical Convergence Zone.

A preliminary investigation of the environmental impact of a thermal power plant in relation to PCB contamination.

PubMed

Gedik, Kadir; Imamoglu, Ipek

2011-07-01

The most significant application of polychlorinated biphenyls (PCBs) is in transformers and capacitors. Therefore, power plants are important suspected sources for entry of PCBs into the environment. In this context, the levels and distribution of PCBs in sediment, soil, ash, and sludge samples were investigated around Seyitömer thermal power plant, Kütahya, Turkey. Moreover, identity and contribution of PCB mixtures were predicted using the chemical mass balance (CMB) receptor model. United States Environmental Protection Agency methods were applied during sample preparation, extraction (3540C), cleanup (3660B, 3665A, 3630C), and analysis (8082A). ΣPCB concentrations in the region ranged from not detected to 385 ng/g dry weight, with relatively higher contamination in sediments in comparison to soil, sludge, and ash samples collected from around the power plant. Congener profiles of the sediment and soil samples show penta-, hexa-, and hepta-chlorobiphenyls as the major homolog groups. The results from the CMB model indicate that PCB contamination is largely due to Clophen A60/A40 and Aroclor 1254/1254(late)/1260 release into the sediment and sludge samples around the thermal power plant. Since there are no other sources of PCBs in the region and the identity of PCB sources estimated by the CMB model mirrors PCB mixtures contained in transformers formerly used in the plant, the environmental contamination observed especially in sediments is attributed to the power plant. Release of PCBs over time, as indicated by the significant concentrations observed even in surface samples, emphasizes the importance of the need for better environmental management.

Sediment provenance in contractional orogens: The detrital zircon record from modern rivers in the Andean fold-thrust belt and foreland basin of western Argentina

NASA Astrophysics Data System (ADS)

Capaldi, Tomas N.; Horton, Brian K.; McKenzie, N. Ryan; Stockli, Daniel F.; Odlum, Margaret L.

2017-12-01

This study analyzes detrital zircon U-Pb age populations from Andean rivers to assess whether active synorogenic sedimentation accurately records proportional contributions from varied bedrock source units across different drainage areas. Samples of modern river sand were collected from west-central Argentina (28-33°S), where the Andes are characterized by active uplift and deposition in diverse contractional provinces, including (1) hinterland, (2) wedge-top, (3) proximal foreland, and (4) distal broken foreland basin settings. Potential controls on sediment provenance were evaluated by comparing river U-Pb age distributions with predicted age spectra generated by a sediment mixing model weighted by relative catchment exposure (outcrop) areas for different source units. Several statistical measures (similarity, likeness, and cross-correlation) are employed to compare how well the area-weighted model predicts modern river age populations. (1) Hinterland basin provenance is influenced by local relief generated along thrust-bounded ranges and high zircon fertility of exposed crystalline basement. (2) Wedge-top (piggyback) basin provenance is controlled by variable lithologic durability among thrust-belt bedrock sources and recycled basin sediments. (3) Proximal foreland (foredeep) basin provenance of rivers and fluvial megafans accurately reflect regional bedrock distributions, with limited effects of zircon fertility and lithologic durability in large (>20,000 km2) second-order drainage systems. (4) In distal broken segments of the foreland basin, regional provenance signatures from thrust-belt and hinterland areas are diluted by local contributions from foreland basement-cored uplifts.

Rare earth mineral potential in the southeastern U.S. Coastal Plain from integrated geophysical, geochemical, and geological approaches

USGS Publications Warehouse

Shah, Anjana K.; Bern, Carleton R.; Van Gosen, Bradley S.; Daniels, David L.; Benzel, William M.; Budahn, James R.; Ellefsen, Karl J.; Karst, Adam; Davis, Richard

2017-01-01

We combined geophysical, geochemical, mineralogical, and geological data to evaluate the regional presence of rare earth element (REE)−bearing minerals in heavy mineral sand deposits of the southeastern U.S. Coastal Plain. We also analyzed regional differences in these data to determine probable sedimentary provenance. Analyses of heavy mineral separates covering the region show strong correlations between thorium, monazite, and xenotime, suggesting that radiometric equivalent thorium (eTh) can be used as a geophysical proxy for those REE-bearing minerals. Airborne radiometric data collected during the National Uranium Resource Evaluation (NURE) program cover the southeastern United States with line spacing varying from ∼2 to 10 km. These data show eTh highs over Cretaceous and Tertiary Coastal Plain sediments from the Cape Fear arch in North Carolina to eastern Alabama; these highs decrease with distance from the Piedmont. Quaternary sediments along the modern coasts show weaker eTh anomalies, except near coast-parallel ridges from South Carolina to northern Florida. Prominent eTh anomalies are also observed over large riverbeds and their floodplains, even north of the Cape Fear arch where surrounding areas are relatively low. These variations were verified using ground geophysical measurements and sample analyses, indicating that radiometric methods are a useful exploration tool at varying scales. Further analyses of heavy mineral separates showed regional differences, not only in concentrations of monazite, but also of rutile and staurolite, and in magnetic susceptibility. The combined properties suggest the presence of subregions where heavy mineral sediments are primarily sourced from high-grade metamorphic, low-grade metamorphic, or igneous terrains, or where they represent a mixing of these sources. Comparisons between interpreted sources of heavy mineral sands near the Fall Line and igneous and metamorphic Piedmont and Blue Ridge units showed a strong correspondence with rocks closest to the Fall Line and poor correspondence with rocks farther inland. This strongly suggests that the primary source of those heavy minerals, especially monazite, is the rocks that formed the rocky coast that was present during opening of the Atlantic Ocean, which in turn indicates the importance of coastal processes in forming heavy mineral sand concentrations. Furthermore, narrow radiometric eTh and K anomalies are associated with major rivers, indicating limited spatial influence of fluvial processes. Later coastal plain sediment deposition appears to have involved reworking of sediments, providing an “inheritance” of the rocky coast composition that persists for some distance from the Fall Line. However, this inheritance is reduced with distance, and sediments within ∼100 km of the coast in Georgia and Florida exhibit properties indicative of mixing from multiple sources.

Identification and Classification of Mass Transport Complexes in Offshore Trinidad/Venezuela and Their Potential Anthropogenic Impact as Tsunamigenic Hazards

NASA Astrophysics Data System (ADS)

Moscardelli, L.; Wood, L. J.

2006-12-01

Several late Pleistocene-age seafloor destabilization events have been identified in the continental margin of eastern offshore Trinidad, of sufficient scale to produce tsunamigenic forces. This area, situated along the obliquely-converging-boundary of the Caribbean/South American plates and proximal to the Orinoco Delta, is characterized by catastrophic shelf-margin processes, intrusive-extrusive mobile shales, and active tectonism. A mega-merged, 10,000km2, 3D seismic survey reveals several mass transport complexes that range in area from 11.3km2 to 2017km2. Historical records indicate that this region has experienced submarine landslide- generated tsunamigenic events, including tsunamis that affected Venezuela during the 1700's-1900's. This work concentrates on defining those ancient deep marine mass transport complexes whose occurrence could potentially triggered tsunamis. Three types of failures are identified; 1) source-attached failures that are fed by shelf edge deltas whose sediment input is controlled by sea-level fluctuations and sedimentation rates, 2) source-detached systems, which occur when upper slope sediments catastrophically fail due to gas hydrate disruptions and/or earthquakes, and 3) locally sourced failures, formed when local instabilities in the sea floor trigger relatively smaller collapses. Such classification of the relationship between slope mass failures and the sourcing regions enables a better understanding of the nature of initiation, length of development history and petrography of such mass transport deposits. Source-detached systems, generated due to sudden sediment remobilizations, are more likely to disrupt the overlying water column causing a rise in tsunamigenic risk. Unlike 2D seismic, 3D seismic enables scientists to calculate more accurate deposit volumes, improve deposit imaging and thus increase the accuracy of physical and computer simulations of mass failure processes.

Sources and sinks of microplastics in Canadian Lake Ontario nearshore, tributary and beach sediments.

PubMed

Ballent, Anika; Corcoran, Patricia L; Madden, Odile; Helm, Paul A; Longstaffe, Fred J

2016-09-15

Microplastics contamination of Lake Ontario sediments is investigated with the aim of identifying distribution patterns and hotspots in nearshore, tributary and beach depositional environments. Microplastics are concentrated in nearshore sediments in the vicinity of urban and industrial regions. In Humber Bay and Toronto Harbour microplastic concentrations were consistently >500 particles per kg dry sediment. Maximum concentrations of ~28,000 particles per kg dry sediment were determined in Etobicoke Creek. The microplastic particles were primarily fibres and fragments <2mm in size. Both low- and high-density plastics were identified using Raman spectroscopy. We provide a baseline for future monitoring and discuss potential sources of microplastics in terms of how and where to implement preventative measures to reduce the contaminant influx. Although the impacts of microplastics contamination on ecosystem health and functioning is uncertain, understanding, monitoring and preventing further microplastics contamination in Lake Ontario and the other Great Lakes is crucial. Copyright © 2016 Elsevier Ltd. All rights reserved.

Polycyclic aromatic hydrocarbon contamination in stormwater detention pond sediments in coastal South Carolina.

PubMed

Weinstein, John E; Crawford, Kevin D; Garner, Thomas R

2010-03-01

The purpose of this study was to characterize the polycyclic aromatic hydrocarbon (PAH) contamination in the sediments of stormwater detention ponds in coastal South Carolina. Levels of the sum of PAH analytes were significantly higher in the sediments of commercial ponds compared to that of reference, golf course, low-density residential, and high-density residential ponds. Isomer ratio analysis suggested that the predominant source of PAHs were pyrogenic; however, many ponds had a PAH signature consistent with mixed uncombusted and combusted PAH sources. PAH levels in these sediments could be modeled using both pond drainage area and pond surface area. These results demonstrate that the sediment from most commercial ponds, and a few residential and golf course ponds, were moderately contaminated with PAHs. PAH levels in these contaminated ponds exceeded between 42% and 75% of the ecological screening values for individual PAH analytes established by US EPA Region IV, suggesting that they may pose a toxicological risk to wildlife.

Trace Metal Content of Sediments Close to Mine Sites in the Andean Region

PubMed Central

Yacoub, Cristina; Pérez-Foguet, Agustí; Miralles, Nuria

2012-01-01

This study is a preliminary examination of heavy metal pollution in sediments close to two mine sites in the upper part of the Jequetepeque River Basin, Peru. Sediment concentrations of Al, As, Cd, Cu, Cr, Fe, Hg, Ni, Pb, Sb, Sn, and Zn were analyzed. A comparative study of the trace metal content of sediments shows that the highest concentrations are found at the closest points to the mine sites in both cases. The sediment quality analysis was performed using the threshold effect level of the Canadian guidelines (TEL). The sediment samples analyzed show that potential ecological risk is caused frequently at both sites by As, Cd, Cu, Hg, Pb, and Zn. The long-term influence of sediment metals in the environment is also assessed by sequential extraction scheme analysis (SES). The availability of metals in sediments is assessed, and it is considered a significant threat to the environment for As, Cd, and Sb close to one mine site and Cr and Hg close to the other mine site. Statistical analysis of sediment samples provides a characterization of both subbasins, showing low concentrations of a specific set of metals and identifies the main characteristics of the different pollution sources. A tentative relationship between pollution sources and possible ecological risk is established. PMID:22606058

Provenance and depositional history of continental slope sediments in the Southwestern Gulf of Mexico unraveled by geochemical analysis

NASA Astrophysics Data System (ADS)

Armstrong-Altrin, John S.; Machain-Castillo, María Luisa; Rosales-Hoz, Leticia; Carranza-Edwards, Arturo; Sanchez-Cabeza, Joan-Albert; Ruíz-Fernández, Ana Carolina

2015-03-01

The aim of this work is to constrain the provenance and depositional history of continental slope sediments in the Southwestern Gulf of Mexico (~1089-1785 m water depth). To achieve this, 10 piston sediment cores (~5-5.5 m long) were studied for mineralogy, major, trace and rare earth element geochemistry. Samples were analyzed at three core sections, i.e. upper (0-1 cm), middle (30-31 cm) and lower (~300-391 cm). The textural study reveals that the core sediments are characterized by silt and clay fractions. Radiocarbon dating of sediments for the cores at different levels indicated a maximum of ~28,000 year BP. Sediments were classified as shale. The chemical index of alteration (CIA) values for the upper, middle, and lower sections revealed moderate weathering in the source region. The index of chemical maturity (ICV) and SiO2/Al2O3 ratio indicated low compositional maturity for the core sediments. A statistically significant correlation observed between total rare earth elements (∑REE) versus Al2O3 and Zr indicated that REE are mainly housed in detrital minerals. The North American Shale Composite (NASC) normalized REE patterns, trace element concentrations such as Cr, Ni and V, and the comparison of REE concentrations in sediments and source rocks indicated that the study area received sediments from rocks intermediate between felsic and mafic composition. The enrichment factor (EF) results indicated that the Cd and Zn contents of the upper section sediments were influenced by an anthropogenic source. The trace element ratios and authigenic U content of the core sediments indicated the existence of an oxic depositional environment.

Quantification of Gravel Rural Road Sediment Production

NASA Astrophysics Data System (ADS)

Silliman, B. A.; Myers Toman, E.

2014-12-01

Unbound rural roads are thought to be one of the largest anthropogenic sources of sediment reaching stream channels in small watersheds. This sediment deposition can reduce water quality in the streams negatively impacting aquatic habitat as well as impacting municipal drinking water sources. These roads are thought to see an increase in construction and use in southeast Ohio due to the expansion of shale gas development in the region. This study set out to quantify the amount of sediment these rural roads are able to produce. A controlled rain event of 12.7 millimeters of rain over a half hour period was used to drive sediment production over a 0.03 kilometer section of gravel rural road. These 8 segments varied in many characteristics and produced from 2.0 to 8.4 kilograms of sediment per 0.03 kilometers of road with the average production over the 8 segments being 5.5 kilograms of sediment. Sediment production was not strongly correlated with road segment slope but traffic was found to increase sediment production from 1.1 to 3.9 times as much sediment after traffic use. These results will help inform watershed scale sediment budgeting, and inform best management practices for road maintenance and construction. This study also adds to the understanding of the impacts of rural road use and construction associated with the changing land use from agricultural to natural gas extraction.

Accumulation and distribution of heavy metals in sediments and fish in the Kola Peninsula lakes under airborne contamination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dauvalter, V.A.; Kashulin, N.A.; Lukin, A.A.

1996-12-31

The copper-nickel smelter complexes of Kola Peninsula are powerful sources of atmospheric contamination by heavy metals (Ni, Cu, Co, Cd, etc.) and acidic oxides (SO{sub 2}) deposited in precipitation and caused negative effects on local freshwater ecosystems. The rise of background levels occurs over large areas in the region. The aim of the investigations is to assess effects of the air contamination on lake ecosystems at different distances (from 15 to 120 km) from one of the main heavy metal pollution sources of the Kola Peninsula - smelters of the Pechenganickel Company. Negative effects of air pollution by the smeltersmore » on the freshwater ecosystems were recorded. Lake sediments accumulate very intensively heavy metals. Heavy metal contamination factors calculated as the quotient of concentration from the uppermost (0-1 cm) sediment to the mean preindustrial background value (concentrations from 20-30 cm sediment layers) for the investigated region reach up 120 for Ni and 76 for Cu in the lakes within a distance of 40 km from the smelters. The lakes in this region have very high contamination degree according classification by Hakanson (1980). Concentrations of Ni in organs and tissues of all studied fishes (whitefish, pike, perch, arctic char, brown trout) were considerably higher in the investigated lakes than in remote unpolluted lakes. There is tight positive correlation between Ni concentrations in surficial sediment (0-1 cm) and fish kidney (r = +0.854), as well as between values of contamination degree and Ni content in fish (r = +0.871).« less

Water-quality assessment of the Kentucky River Basin, Kentucky; distribution of metals and other trace elements in sediment and water, 1987-90

USGS Publications Warehouse

Porter, Stephen D.; White, Kevin D.; Clark, J.R.

1995-01-01

The U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Program is designed to provide a nationally consistent description of the current status of water quality, to define water-quality trends, and to relate past and present water-quality conditions to natural features, uses of land and water, and other water-quality effects from human activities. The Kentucky River Basin is one of four NAWQA pilot projects that focused primarily on the quality of surface water. Water, sediment, and bedrock samples were collected in the Kentucky River Basin during 1987-90 for the purpose of (1) describing the spatial distribution, transport, and temporal variability of metals and other trace elements in streams of the basin; (2) estimating mean annual loads, yields, and trends of constituent concentrations and identifying potential causes (or sources) of spatial patterns; (3) providing baseline information for concentrations of metals in streambed and suspended sediments; (4) identifying stream reaches in the Kentucky River Basin with chronic water-quality problems; and (5) evaluating the merits of the NAWQA pilot study-approach for the assessment of metals and other trace elements in a river system. The spatial distribution of metals and other trace elements in streambed sediments of the Kentucky River Basin is associated with regional differences of geology, land use and cover, and the results of human activities. Median concentrations of constituents differed significantly among physiographic regions of the basin because of relations to bedrock geochemistry and land disturbance. Concentrations of potentially toxic metals were large in urban and industrial areas of the basin. Elevated concentrations of certain metals were also found in streambed sediments of the Knobs Region because of the presence of Devonian shale bedrock. Elevated concentrations of lead and zinc found in streambed sediments of the Bluegrass Region are likely associated with urban stormwater runoff, point-source discharges, and waste-management practices. Concentrations of cadmium, chromium, copper, mercury, and silver were elevated in streambed sediments downstream from wastewater-treatment plant discharges. Streambed-sediment concentrations of barium, chromium, and lithium were elevated in streams that receive brine discharges from oil production. Elevated concentrations of antimony, arsenic, molybdenum, selenium, strontium, uranium, and vanadium in streambed sediments of the Kentucky River Basin were generally associated with natural sources. Concentrations of metals and other trace elements in water samples from fixed stations (stations where water-quality samples were collected for 3.5 years) in the Kentucky River Basin were generally related to stream discharge and the concentration of suspended sediment, whereas constituent concentrations in the suspended-sediment matrix were indicative of natural and human sources. Estimated mean annual loads and yields for most metals and other trace elements were associated with the transport of suspended sediment. Land disturbance, such as surface mining and agriculture, contribute to increased transport of sediment in streams, thereby increasing concentrations of metals in water samples during periods of intense or prolonged rainfall and increased stream discharge. Concentrations of many metals and trace elements were reduced during low streamflow. Although total-recoverable and dissolved concentrations of certain metals and trace elements were large in streams affected by land disturbance, concentrations of constituents in the suspendedsediment matrix were commonly large in streams in the Knobs and Eastern Coal Field Regions (because of relations with bedrock geochemistry) and in streams that receive wastewater or oil-well-brine discharges. Concentrations and mean annual load estimates for aluminum, chromium, copper, iron, lead, manganese, and mercury were larger than those obtained from data collected by a State agency, probably because of differences in sample-collection methodology, the range of discharge associated with water-quality samples, and laboratory analytical procedures. However, concentrations, loads, and yields of arsenic, barium, and zinc were similar to those determined from the State data. Significant upward trends in the concentrations of aluminum, iron, magnesium, manganese, and zinc were indicated at one or more fixed stations in the Kentucky River Basin during the past 10 to 15 years. Upward trends for concentrations of aluminum, iron, and manganese were found at sites that receive drainage from coal mines in the upper Kentucky River Basin, whereas upward trends for zinc may be associated with urban sources. Water-quality criteria established by the U.S. Environmental Protection Agency (USEPA) or the State of Kentucky for concentrations of aluminum, beryllium, cadmium, chromium, copper, iron, manganese, nickel, silver, and zinc were exceeded at one or more fixed stations in the Kentucky River Basin. On a qualitative basis, dissolved concentrations of certain metals and trace elements were large during low streamflow at sites where (1) concentrations of these constituents in underlying streambed sediments were large, or (2) dissolvedoxygen concentrations were small. Concentrations of barium, lithium, and strontium were large during low streamflow, which indicates the influence of ground-water baseflows on the quality of surface water during low flow. The effects of point-source discharges, landfills, and other wastemanagement practices are somewhat localized in the Kentucky River Basin and are best indicated by the spatial distribution of metals and other trace elements in streambed sediments and in the suspended-sediment fraction of water samples at stream locations near the source. It was not possible to quantify the contribution of point sources to the total transport of metals and other trace elements at fixed stations because data were not available for wastewater effluents. Quantification of baseline concentrations of metals and other trace elements in streambed sediments provides a basis for the detection of water-quality changes that may result from improvements in wastewater treatment or the implementation of best-management practices for controlling contamination from nonpoint sources in the Kentucky River Basin.

Grain size dependent magnetic discrimination of Iceland and South Greenland terrestrial sediments in the northern North Atlantic sediment record

NASA Astrophysics Data System (ADS)

Hatfield, Robert G.; Stoner, Joseph S.; Reilly, Brendan T.; Tepley, Frank J.; Wheeler, Benjamin H.; Housen, Bernard A.

2017-09-01

We use isothermal and temperature dependent in-field and magnetic remanence methods together with electron microscopy to characterize different sieved size fractions from terrestrial sediments collected in Iceland and southern Greenland. The magnetic fraction of Greenland silts (3-63 μm) and sands (>63 μm) is primarily composed of near-stoichiometric magnetite that may be oxidized in the finer clay (<3 μm) fractions. In contrast, all Icelandic fractions dominantly contain titanomagnetite of a range of compositions. Ferrimagnetic minerals preferentially reside in the silt-size fraction and exist as fine single-domain (SD) and pseudo-single-domain (PSD) size inclusions in Iceland samples, in contrast to coarser PSD and multi-domain (MD) discrete magnetites from southern Greenland. We demonstrate the potential of using magnetic properties of the silt fraction for source unmixing by creating known endmember mixtures and by using naturally mixed marine sediments from the Eirik Ridge south of Greenland. We develop a novel approach to ferrimagnetic source unmixing by using low temperature magnetic susceptibility curves that are sensitive to the different crystallinity and cation substitution characteristics of the different source regions. Covariation of these properties with hysteresis parameters suggests sediment source changes have driven the magnetic mineral variations observed in Eirik Ridge sediments since the last glacial maximum. These observations assist the development of a routine method and interpretative framework to quantitatively determine provenance in a geologically realistic and meaningful way and assess how different processes combine to drive magnetic variation in the North Atlantic sediment record.

Characterization of heavy metal concentrations in the sediments of three freshwater rivers in Huludao City, Northeast China.

PubMed

Zheng, Na; Wang, Qichao; Liang, Zhongzhu; Zheng, Dongmei

2008-07-01

Wuli River, Cishan River, and Lianshan River are three freshwater rivers flowing through Huludao City, in a region of northeast China strongly affected by industrialization. Contamination assessment has never been conducted in a comprehensive way. For the first time, the contamination of three rivers impacted by different sources in the same city was compared. This work investigated the distribution and sources of Hg, Pb, Cd, Zn and Cu in the surface sediments of Wuli River, Cishan River, and Lianshan River, and assessed heavy metal toxicity risk with the application of two different sets of Sediment Quality Guideline (SQG) indices (effect range low/effect range median values, ERL/ERM; and threshold effect level/probable effect level, TEL/PEL). Furthermore, this study used a toxic unit approach to compare and gauge the individual and combined metal contamination for Hg, Pb, Cd, Zn and Cu. Results showed that Hg contamination in the sediments of Wuli River originated from previous sediment contamination of the chlor-alkali producing industry, and Pb, Cd, Zn and Cu contamination was mainly derived from atmospheric deposition and unknown small pollution sources. Heavy metal contamination to Cishan River sediments was mainly derived from Huludao Zinc Plant, while atmospheric deposition, sewage wastewater and unknown small pollution were the primary sources for Lianshan River. The potential acute toxicity in sediment of Wuli River may be primarily due to Hg contamination. Hg is the major toxicity contributor, accounting for 53.3-93.2%, 7.9-54.9% to total toxicity in Wuli River and Lianshan River, respectively, followed by Cd. In Cishan River, Cd is the major sediment toxicity contributor, however, accounting for 63.2-66.9% of total toxicity.

Using 15-minute acoustic data to analyze suspended-sediment dynamics in the Rio Grande in the Big Bend Region

USGS Publications Warehouse

Dean, David; Topping, David; Griffiths, Ronald; Sabol, Thomas; Schmidt, John C.; Bennett, Jeffery B.

2015-01-01

The Rio Grande in the Big Bend region is subject to rapid geomorphic change consisting of channel narrowing during years of low flow, and channel widening during rare, large, long duration floods. Since the 1940s, there have been large declines in mean and peak stream flow, and the channel has progressively narrowed. Large, channel widening floods are infrequent and have failed to widen the channel to widths measured prior to the onset of channel narrowing in the 1940s. Before the most recent channel-widening flood in September 2008, the Rio Grande in the Big Bend was more than 50 percent narrower than measured in the 1940s. Channel narrowing results in increased flood frequency and flood magnitude due to the loss of channel capacity and flood conveyance (Dean and Schmidt, 2011). Channel narrowing also results in the loss of important aquatic habitats such as backwaters and side-channels, because these habitats accumulate sediment and are converted to floodplains. Environmental managers are attempting to construct an environmental flow program for the purposes of minimizing channel narrowing during low flow years such that channel capacity, flood conveyance, and important aquatic habitats are maintained. Effective mitigation of channel narrowing processes requires an in-depth understanding of the predominant sediment source areas, the quantity of sediment input from those source areas, the parts of the flow regime responsible for the greatest sediment deposition, and the effect of managed flows in ameliorating the sediment loading that occurs within the channel. Here, we analyze data collected with acoustic instrumentation at high temporal resolution to quantify suspended-sediment transport during a variety of flood types. We also investigate the effect of long duration managed flows in promoting sediment export and minimizing channel narrowing.

High-Resolution Acoustic Imaging in the Agadir-Canyon Region, NW-Africa: Morphology, Processes and Geohazards

NASA Astrophysics Data System (ADS)

Krastel, S.; Wynn, R. B.; Feldens, P.; Unverricht, D.; Huehnerbach, V.; Stevenson, C.; Glogowski, S.; Schuerer, A.

2014-12-01

Agadir Canyon is one of the largest submarine canyons in the World, supplying giant submarine sediment gravity flows to the Agadir Basin and the wider Moroccan Turbidite System. While the Moroccan Turbidite System is extremely well investigated, almost no data from the source region, i.e. the Agadir Canyon, are available. Understanding why some submarine landslides remain as coherent blocks of sediment throughout their passage downslope, while others mix and disintegrate almost immediately after initial failure, is a major scientific challenge, which was addressed in the Agadir Canyon source region during Cruise MSM32. We collected ~ 1500 km of high-resolution seismic 2D-lines in combination with a dense net of hydroacoustic data. About 1000 km2 of sea floor were imaged during three deployments of TOBI (deep-towed sidescan sonar operated by the National Oceanography Centre Southampton). A total of 186 m of gravity cores and several giant box cores were recovered at more than 50 stations. The new data show that Agadir canyon is the source area of the world's largest submarine sediment flow, which occurred about 60,000 years ago. Up to 160 km3 of sediment was transported to the deep ocean in a single catastrophic event. For the first time, sediment flows of this scale have been tracked along their entire flow pathway. A major landslide area was identified south of Agadir Canyon. Landslide material enters Agadir canyon in about 2500 m water depth; the material is transported as debrite for at least another 200 km down the canyon. Initial data suggest that the last major slide from this source entered Agadir canyon at least 130,000 years ago. A large field of living deep-water corals was imaged north of Agadir canyon. To our knowledge, these are the first living cold water corals recovered off the coast of Morocco (except for the Gulf of Cadiz). They represent an important link between the known cold-water coral provinces off Mauritania and in the Gulf of Cádiz.

Regional-scale input of dispersed and discrete volcanic ash to the Izu-Bonin and Mariana subduction zones

NASA Astrophysics Data System (ADS)

Scudder, Rachel P.; Murray, Richard W.; Schindlbeck, Julie C.; Kutterolf, Steffen; Hauff, Folkmar; McKinley, Claire C.

2014-11-01

We have geochemically and statistically characterized bulk marine sediment and ash layers at Ocean Drilling Program Site 1149 (Izu-Bonin Arc) and Deep Sea Drilling Project Site 52 (Mariana Arc), and have quantified that multiple dispersed ash sources collectively comprise ˜30-35% of the hemipelagic sediment mass entering the Izu-Bonin-Mariana subduction system. Multivariate statistical analyses indicate that the bulk sediment at Site 1149 is a mixture of Chinese Loess, a second compositionally distinct eolian source, a dispersed mafic ash, and a dispersed felsic ash. We interpret the source of these ashes as, respectively, being basalt from the Izu-Bonin Front Arc (IBFA) and rhyolite from the Honshu Arc. Sr-, Nd-, and Pb isotopic analyses of the bulk sediment are consistent with the chemical/statistical-based interpretations. Comparison of the mass accumulation rate of the dispersed ash component to discrete ash layer parameters (thickness, sedimentation rate, and number of layers) suggests that eruption frequency, rather than eruption size, drives the dispersed ash record. At Site 52, the geochemistry and statistical modeling indicates that Chinese Loess, IBFA, dispersed BNN (boninite from Izu-Bonin), and a dispersed felsic ash of unknown origin are the sources. At Site 1149, the ash layers and the dispersed ash are compositionally coupled, whereas at Site 52 they are decoupled in that there are no boninite layers, yet boninite is dispersed within the sediment. Changes in the volcanic and eolian inputs through time indicate strong arc-related and climate-related controls.

Tracking Organic Carbon Transport From the Stordalen Mire to Glacial Lake Tornetrask, Abisko, Sweden

NASA Astrophysics Data System (ADS)

Beck, M. A.; Hamilton, B. T.; Spry, E.; Johnson, J. E.; Palace, M. W.; McCalley, C. K.; Varner, R. K.; Bothner, W. A.

2016-12-01

In subarctic regions, labile organic carbon from thawing permafrost and productivity of terrestrial and aquatic vegetation are sources of carbon to lake sediments. Methane is produced in lake sediments from the decomposition of organic carbon at rates affected by vegetation presence and type as well as sediment temperature. Recent research in the Stordalen Mire in northern Sweden has suggested that labile organic carbon sources in young, shallow lake sediments yield the highest in situ sediment methane concentrations. Ebullition (or bubbling) of this methane is predominantly controlled by seasonal warming. In this project we sampled stream, glacial and post-glacial lake sediments along a drainage transect through the Stordalen Mire into the large glacial Lake Torneträsk. Our results indicate that the highest methane and total organic carbon (TOC) concentrations were observed in lake and stream sediments in the upper 25 centimeters, consistent with previous studies. C/N ratios range from 8 to 32, and suggest that a mix of aquatic and terrestrial vegetation sources dominate the sedimentary record. Although water transport occurs throughout the mire, major depositional centers for sediments and organic carbon occur within the lakes and prohibit young, labile TOC from entering the larger glacial Lake Torneträsk. The lack of an observed sediment fan at the outlet of the Mire to the lake is consistent with this observation. Our results suggest that carbon produced in the mire stays in the mire, allowing methane production to be greater in the mire bound lakes and streams than in the larger adjacent glacial lake.

A smoothed particle hydrodynamics (SPH) study on polydisperse sediment from technical activities on seabed

NASA Astrophysics Data System (ADS)

Tran-Duc, Thien; Phan-Thien, Nhan; Khoo, Boo Cheong

2018-02-01

Technical activities to collect poly-metallic nodules on a seabed are likely to disturb the top-layer sediment and re-suspend it into the ambient ocean water. The transport of the re-suspended polydisperse-sized sediment is a process in which particles' size variation leads to a difference in their settling velocities; and thus the polydispersity in sizes of sediment has to be taken into account in the modeling process. The sediment transport within a window of 12 km is simulated and analyzed numerically in this study. The sediment characteristic and the ocean current data taken from the Peru Basin, Pacific Ocean, are used in the simulations. More than 50% of the re-suspended sediment are found to return to the bottom after 24 h. The sediment concentration in the ambient ocean water does not exceed 3.5 kg/m3 during the observed period. The deposition rate steadily increases and reaches 70% of the sediment re-suspension rate after 24 h. The sediment plume created by the activities comprises mainly very fine sediment particles (clays and silts), whereas coarser particles (sands) are found in abundance in the deposited sediment within 1 km from the source location. It is also found that the deposition process of the re-suspended sediment is changed remarkably as the current velocity increases from 0.05 m/s (medium current) to 0.1 m/s (strong current). The strong sediment deposition trend is also observed as the sediment source moves continuously over a region due to the sediment scattering effect.

Characterization of mercury contamination in the Androscoggin River, Coos County, New Hampshire

USGS Publications Warehouse

Chalmers, Ann; Marvin-DiPasquale, Mark C.; Degnan, James R.; Coles, James; Agee, Jennifer L.; Luce, Darryl

2013-01-01

Concentrations of total mercury (THg) and MeHg in sediment, pore water, and biota in the Androscoggin River were elevated downstream from the former chloralkali facility compared with those upstream from reference sites. Sequential extraction of surface sediment showed a distinct difference in Hg speciation upstream compared with downstream from the contamination site. An upstream site was dominated by potassium hydroxide-extractable forms (for example, organic-Hg or particle-bound Hg(II)), whereas sites downstream from the point source were dominated by more chemically recalcitrant forms (largely concentrated nitric acid-extractable), indicative of elemental mercury or mercurous chloride. At all sites, only a minor fraction (less than 0.1 percent) of THg existed in chemically labile forms (for example, water extractable or weak acid extractable). All metrics indicated that a greater percentage of mercury at an upstream site was available for Hg(II)-methylation compared with sites downstream from the point source, but the absolute concentration of bioavailable Hg(II) was greater downstream from the point source. In addition, the concentration of tin-reducible inorganic reactive mercury, a surrogate measure of bioavailable Hg(II) generally increased with distance downstream from the point source. Whereas concentrations of mercury species on a sediment-dry-weight basis generally reflected the relative location of the sample to the point source, river-reach integrated mercury-species inventories and MeHg production potential (MPP) rates reflected the amount of fine-grained sediment in a given reach. THg concentrations in biota were significantly higher downstream from the point source compared with upstream reference sites for smallmouth bass, white sucker, crayfish, oligochaetes, bat fur, nestling tree swallow blood and feathers, adult tree swallow blood, and tree swallow eggs. As with tin-reducible inorganic reactive mercury, THg in smallmouth bass also increased with distance downstream from the point source. Toxicity tests and invertebrate community assessments suggested that invertebrates were not impaired at the current (2009 and 2010) levels of mercury contamination downstream from the point source. Concentrations of THg and MeHg in most water and sediment samples from the Androscoggin River were below U.S. Environmental Protection Agency (USEPA), the Canadian Council of Ministers of the Environment, and probable effects level guidelines. Surface-water and sediment samples from the Androscoggin River had similar THg concentrations but lower MeHg concentrations compared with other rivers in the region. Concentrations of THg in fish tissue were all above regional and U.S. Environmental Protection Agency guidelines. Moreover, median THg concentrations in smallmouth bass from the Androscoggin River were significantly higher than those reported in regional surveys of river and streams nationwide and in the Northeastern United States and Canada. The higher concentrations of mercury in smallmouth bass suggest conditions may be more favorable for Hg(II)-methylation and bioaccumulation in the Androscoggin River compared with many other rivers in the United States and Canada.

Maastrichtian sedimentation and palaeoenvironments of the Saratov Volga region

NASA Astrophysics Data System (ADS)

Iakovishina, Elena; Blinova, Irina; Kopaevich, Ludmila; Vishnevskaya, Valentina; Bordunov, Sergey

2016-04-01

The Saratov Volga region was a shallow-marine epicontinental basin North-Eastern shelf zone of the Tethys Ocean in the Maastrichtian. The basis for the modeling conditions of sedimentation was the detection mineral composition of rocks, as well as the contents of various chemical elements in rocks in three reference sections: Lower Bannovka, quarries "Bolshevik" and "Kommunar". Rocks of quarries "Bolshevik" and "Kommunar" characterized by quartz-calcite mineral association. The main rock-forming mineral is calcite, small amounts in rocks contain quartz. Other mineral composition characterized section Lower Bannovka. At the base of the section in the rock marked the presence of the opal. The source of silica are radiolarians. Favorable conditions for the existence of which is cold deep water enriched with SiO2. Above the section marked authigenic glauconite, which are confined to zones of skip in sedimentation.Further up begins to dominate the accumulation of calcite with rich bentic foraminifera. Clay minerals in rocks of the section Lower Bannovka presented montmorillonite and illite. The relationship of chemical elements and their alkali modules allow to detail the conditions of sedimentation. The ratio of Fe/Mn in them varies from 44 to 5729. Higher values are characteristic of glauconite sandstones. Up the section marked decrease in the Ti/Zr, indicating that the increase in the distance from the source area to the place of deposition. The similarity values of the ratio Ti/Zr samples indicates a community source area. Sedimentation Model revealed the impact of the PreUral strait connecting Tethys and Paleoarktic. Through the Strait of deep cold water saturated with SiO2, penetrated into the of the Saratov Volga region, were accumulated clay. The closing of the PreUral Strait changed the conditions of sedimentation, the associated fall in sea levels due to global cooling reflected in the crisis of radiolarians, increase in the number of glauconite. Subsequent warming and warm-water transgression caused dominance of carbonates. The work was supported by grants 15-05-04990, 15-05-04700 Russian Foundation for Basic Research and IGCP project 609.

Quantifying the origin of different sediment types in a catchment of the Southern French Alps by combining hydro-sedimentary records and fingerprinting

NASA Astrophysics Data System (ADS)

Evrard, Olivier; Navratil, Oldrich; Ayrault, Sophie; Esteves, Michel; Legout, Cédric; Némery, Julien; Lefèvre, Irène; Bonté, Philippe

2013-04-01

Soil erosion and subsequent sediment supply to rivers are particularly massive and episodic in mountainous environments, such as in the Southern French Alps. Those processes typically lead to an increase in water turbidity and a rapid filling of reservoirs in downstream areas. This situation is particularly problematic in regions where reservoirs are used to provide clear water to hydroelectric power plants. Sediment source areas must first be delineated and sediment fluxes between hillslopes and the river system must be better understood to implement efficient sediment management. We therefore combined traditional monitoring techniques (i.e., installation of river gauges and sediment samplers in several subcatchments) and sediment fingerprinting using elemental geochemistry and fallout radionuclides as potential discriminant properties to quantify the supply of sediment provided by different lithological sources (i.e., black marls, marly limestones, conglomerates, Quaternary deposits) to the River Bléone (905 km²). Those analyses were conducted on different material types collected within the catchment (i.e. suspended and riverbed sediment), and at the catchment outlet (i.e. on a sequence of sections of a 3-m long sediment core). Sediment exports at the river catchment outlet (330±100 t km-2 yr-1) were mainly driven (80%) by the occurrence of widespread rainfall events (long duration, low intensities). In contrast, heavy, local and short duration storms generated high peak discharges and suspended sediment concentrations, but they were restricted to small upstream torrents. Our study (2007-2009) confirmed the important contribution of black marls (up to 70% at the flood scale) to sediment transported in rivers, although this substrate only occupies c. 10% of the total catchment surface. However, the contribution of other lithological sources varied at both intra- and inter-flood scales. Sediment exports generated by local convective storms were dominated by black marls/marly limestones. In contrast, widespread flood events that generate the bulk of annual sediment supply at the outlet were characterized by a more stable lithologic composition and by a larger contribution of limestones, Quaternary deposits and conglomerates, which corroborated the analysis of riverbed sediment. Finally, we found that black marls and marly limestone sources provided the main fraction of sediment analysed throughout the outlet core sequence (40 and 22 %, respectively, for the period 1962-2009). However, we also found evidence for the occurrence of major floods carrying large quantities of sediment originating from Quaternary deposits and conglomerates (25 and 16 %, respectively). The variability of sediment sources throughout the sequence may reflect the spatial variability of rainfall within the catchment, which in turn reflects its origin. This study emphasizes the importance of using archival data to validate the results of sediment fingerprinting studies conducted during short contemporary monitoring programmes.

Assessment of sediment quality in the Mediterranean Sea-Boughrara lagoon exchange areas (southeastern Tunisia): GIS approach-based chemometric methods.

PubMed

Kharroubi, Adel; Gargouri, Dorra; Baati, Houda; Azri, Chafai

2012-06-01

Concentrations of selected heavy metals (Cd, Pb, Zn, Cu, Mn, and Fe) in surface sediments from 66 sites in both northern and eastern Mediterranean Sea-Boughrara lagoon exchange areas (southeastern Tunisia) were studied in order to understand current metal contamination due to the urbanization and economic development of nearby several coastal regions of the Gulf of Gabès. Multiple approaches were applied for the sediment quality assessment. These approaches were based on GIS coupled with chemometric methods (enrichment factors, geoaccumulation index, principal component analysis, and cluster analysis). Enrichment factors and principal component analysis revealed two distinct groups of metals. The first group corresponded to Fe and Mn derived from natural sources, and the second group contained Cd, Pb, Zn, and Cu originated from man-made sources. For these latter metals, cluster analysis showed two distinct distributions in the selected areas. They were attributed to temporal and spatial variations of contaminant sources input. The geoaccumulation index (I (geo)) values explained that only Cd, Pb, and Cu can be considered as moderate to extreme pollutants in the studied sediments.

In-depth molecular characterization and biodegradability of water-extractable organic nitrogen in Erhai Lake sediment.

PubMed

Zhang, Li; Wang, Shengrui; Yang, Jiachun; Xu, Kechen

2018-05-08

Dissolved organic nitrogen (DON) constitutes a significant fraction of the total dissolved nitrogen content of most aquatic systems and is thus a major nitrogen source for bacteria and phytoplankton. The present work applied Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to a compound-level analysis of the depth-dependent molecular composition of water-extractable organic nitrogen (WEON) in lake sediment. The study focused on Erhai Lake, China. It was found that a large portion (from 16.33 ± 7.87 to 39.54 ± 5.77%) of the WEON in the lake sediment was reactive under cultivation by algal or bacteria. The WEON in the mid-region of Erhai sediment particularly exhibited a lower bioavailability, having been less affected by the basin environment. The FT-ICR MS results revealed the presence of thousands of compounds in the Erhai Lake sediment samples collected at different depths, with the N-containing compounds accounting for 28.3-34.4% of all the compounds. The WEON molecular weight was also observed to increase with increasing sediment depth. A van Krevelen diagram showed that the lignin-type components were dominant (~ 56.2%) in the sediment WEON, contributing to its stabilization and reducing the risk of sediment nutrient release. The FT-ICR MS results further revealed 204 overlapping formulas of WEON for each core sediment sample, attributable to the presence of refractory components. It was observed that 78.4% of the formulas were within the lignin-like region, suggesting unique allochthonous DON sources. The aliphatic component proportion of all the unique formulas was also found to increase with increasing sediment depth. This indicates that, with the development and evolution of the Erhai Basin, the more labile WEON components were transformed into more stable lignin-like substrates, with a positive effect on the Lake Erhai ecosystem. Graphical abstract ᅟ.

Dependable water supplies from valley alluvium in arid regions.

PubMed

Van Haveren, Bruce P

2004-12-01

Reliable sources of high-quality water for domestic use are much needed in arid regions. Valley alluvium, coarse sand and gravel deposited by streams and rivers, provides an ideal storage medium for water in many regions of the world. However, river sediments will not accumulate in a valley without a natural or artificial barrier to slow the water. Sediments will deposit upstream of a barrier dam and form an alluvial deposit of relatively well-sorted material. The alluvium then acts as both an underground water-supply reservoir and a water filter, yielding a constant flow of high-quality water. Trap dams that store water in alluvial sediments and slowly release the filtered water represent an appropriate and inexpensive technology for combating desertification and mitigating the effects of drought at the community level. Small trap dams may be built as a community project using local materials and local labor.

Shoreline erosion and decadal sediment accumulation in the Tar-Pamlico estuary, North Carolina, USA: A source-to-sink analysis

NASA Astrophysics Data System (ADS)

Eulie, Devon O.; Corbett, D. Reide; Walsh, J. P.

2018-03-01

Estuaries contain vital habitats and it is important to understand how these areas respond to human activities and natural processes such as sea-level rise and wave attack. As estuarine shorelines erode or become modified with hard structures, there is potential for significantly altering the availability of sediment and the filling of coastal systems. This study used a source-to-sink approach and quantified rates of shoreline erosion in the Tar-Pamlico sub-estuary, a tributary of the larger Albemarle-Pamlico Estuarine System (APES). The average shoreline change rate (SCR) determined using an end-point method was -0.5 ± 0.9 m yr-1 for the Tar-Pamlico. Incorporating bulk density estimates, this contributes 0.6 × 105 tons of fine sediment to the system annually, or after accounting for fluvial input, about 40% of the total sediment supply to the sub-estuary. The role of the Tar-Pamlico as a sink for these sediments was addressed using the radionuclide tracers 210Pb and 137Cs. Radionuclide activities and sediment accumulation rates identified several depositional regions, in particular in the middle of the estuary. Linear sediment accumulation rates ranged from 0.10 ± 0.02 to 0.38 ± 0.02 g cm-2 yr-1, and total storage of fine sediment in the system was 1.6 × 105 t yr-1. It was not possible to confidently discern a change in the rate of shoreline erosion or seabed accumulation. A preliminary budget for fine sediments (grain-size <63 μm) was then calculated to compare erosional sources with sedimentary sinks. Almost all (∼93.0%) of the fine sediment entering the system was accumulated and stored, while only about 7.0% was exported to Pamlico Sound.

An integrated suspended sediment budgeting of the agricultural Can Revull catchment (Mallorca, Spain)

NASA Astrophysics Data System (ADS)

Estrany, J.; Garcia, C.

2012-04-01

The Mediterranean region of Europe has a long history of human settlement and human impacts. The very high spatial and temporal variability of fluvial processes in the region also creates problems for measurement and monitoring and for assessment of effects. Extensive rainfed herbaceous crops are one of the most representative agricultural elements of this region, which should be one of the major factor affecting erosion processes. Although land use is commonly seen as resulting in increased sediment yields, the implementation of soil and water conservation practices can have the reverse effect. Sediment budgets offer a means to assess the sources, storage, rates of transport, yields, and efficiency of delivery of sediment for a range of catchment scales. Field measurements were conducted in Can Revull, a small agricultural catchment (1.03 km2) on the island of Mallorca. This study uses 137Cs measurements, sediment source fingerprinting and continuous turbidity records of four hydrological years (2004-2005 to 2007-2008) to quantify the individual components of the budget. A large proportion of the material mobilized from cultivated fields without conservation practices (gross erosion was 775 t yr-1; 1,270 t km-2 yr-1) was, however, subsequently deposited either within the field of origin (112 t yr-1; 180 t km-2 yr-1) or at intermediate locations between the source field and the channel network (field-to-channel conveyance loss was 591 t yr-1; 1,090 t km-2 yr-1). The estimates of sediment accumulation rates on the floodplain in the lower reaches of the catchment indicate that the mean sedimentation rate was 0.47 g cm-2 yr-1. This value was extrapolated to the total area of the floodplain to estimate a total annual conveyance loss or storage of 150 t yr-1. Monitoring at the catchment outlet over the study period indicated a mean annual suspended sediment yield of 7 t km-2 yr-1. The sum of the estimates of sediment yield and floodplain storage (157 t yr-1) was taken to represent the total annual input of suspended sediment to the channel system. This value was subsequently apportioned using the information provided by the fingerprinting investigation, to estimate the mass of sediment reaching the channel network from cultivated fields and from eroding channel banks. Thus the annual contribution from channel banks was estimated to be 84 t yr-1. In the case of the contributions from cultivated fields, the estimates obtained were, as expected, significantly less than the values of net soil loss from these zones provided by the 137Cs measurements due to conveyance losses associated to field-to-channel conveyance loss. The overall sediment delivery ratios (<1%) indicate that approximately 99% of the sediment mobilized by erosion within the Can Revull catchment is subsequently deposited before reaching the monitoring station. As such, the low sediment outputs from the study catchment should be seen as reflecting the importance of conveyance losses and storage rather than a lack of sediment mobilization from the catchment surface, although part of the catchment headwaters was modified historically by means of terraces and transverse walls to prevent erosion.

Baseline evaluation of sediment contamination in the shallow coastal areas of Saudi Arabian Red Sea.

PubMed

Ruiz-Compean, Pedro; Ellis, Joanne; Cúrdia, João; Payumo, Richard; Langner, Ute; Jones, Burton; Carvalho, Susana

2017-10-15

Despite the growing recognition of the importance of water and sediment quality there is still limited information on contamination levels in many regions globally including the Red Sea. This study provides a comprehensive assessment of three classes of contaminants (Polycyclic Aromatic Hydrocarbons - PAH; metals; plastics) in coastal sediments along the Saudi Arabian Red Sea mainly collected using grabs. Background concentrations are provided for metals in the region. Concentrations of metals and PAH were generally low in comparison to international guidelines. A clear relationship between the concentration of metals and anthropogenic sources was not always apparent and dust and vegetation may be relevant players in the region. Microplastic items (mainly polyethylene) were abundant (reaching up to 1gm -2 and 160piecesm -2 ) and in general associated with areas of high human activity. This study provides critical information for future monitoring and the development of national policies within the Red Sea region. Copyright © 2017 Elsevier Ltd. All rights reserved.

Geochemical Analyses of Rock, Sediment, and Water from the Region In and Around the Tuba City Landfill, Tuba City, Arizona

USGS Publications Warehouse

Johnson, Raymond H.; Wirt, Laurie

2009-01-01

The Tuba City Landfill (TCL) started as an unregulated waste disposal site in the 1940s and was administratively closed in 1997. Since the TCL closure, radionuclides have been detected in the shallow ground water. In 2006, the Bureau of Indian Affairs (BIA) contracted with the U.S. Geological Survey (USGS) to better understand the source of radionuclides in the ground water at the TCL compared to the surrounding region. This report summarizes those data and presents interpretations that focus on the geochemistry in the rocks and water from the Tuba City region. The TCL is sited on Navajo Sandstone above the contact with the Kayenta Formation. These formations are not rich in uranium but generally are below average crustal abundance values for uranium. Uranium ores in the area were mined nearby in the Chinle Formation and processed at the Rare Metals mill (RMM). Regional samples of rock, sediment, leachates, and water were collected in and around the TCL site and analyzed for major and minor elements, 18O, 2H, 3H, 13C, 14C,34S, 87Sr, and 234U/238U, as appropriate. Results of whole rock and sediment samples, along with leachates, suggest the Chinle Formation is a major source of uranium and other trace elements in the area. Regional water samples indicate that some of the wells within the TCL site have geochemical signatures that are different from the regional springs and surface water. The geochemistry from these TCL wells is most similar to leachates from the Chinle Formation rocks and sediments. Isotope samples do not uniquely identify TCL-derived waters, but they do provide a useful indicator for shallow compared to deep ground-water flow paths and general rock/water interaction times. Information in this report provides a comparison between the geochemistry within the TCL and in the region as a whole.

Distribution of metals and brominated flame retardants (BFRs) in sediments, soils and plants from an informal e-waste dismantling site, South China.

PubMed

Wang, Junxia; Liu, Lili; Wang, Jinfu; Pan, Bishu; Fu, Xiaoxu; Zhang, Gang; Zhang, Long; Lin, Kuangfei

2015-01-01

Brominated flame retardants (BFRs, including polybrominated diphenyl ethers (PBDEs) and tetrabromobisphenol-A (TBBPA)) and metals (Cu, Zn, Pb, Cd, Ni, Hg and As) in sediments, soils and herb plants from unregulated e-waste disposal sites were examined. The metal concentrations, ∑PBDE and TBBPA concentrations in all samples from the examined e-waste dismantling sites were relatively high in comparison with those of rural and urban areas around the world. The PBDE and TBBPA levels in soils significantly decreased with increasing distance from the e-waste dismantling sites, indicating that PBDEs and TBBPA had similar transport potential from the e-waste dismantling process as a point source to the surrounding region. BDE-209 and TBBPA predominated in all samples, which is consistent with the evidence that the deca-BDE and TBBPA commercial mixtures were extensively used in electronic products. Metals, PBDEs and TBBPA displayed significant positive correlations with TOC, whereas the correlations with pH were insignificant, indicating that TOC was a major factor governing the spatial distribution, transportation and fate in sediments and soils. A significant relationship between log-transformed metals and BFR concentrations indicated common pollution sources. Moreover, cluster analysis and principal component analysis further confirmed that the metals and BFRs had a common source, and penta- and deca-BDE commercial products may be two sources of PBDEs in this region.

Air-Seawater Exchange of Organochlorine Pesticides along the Sediment Plume of a Large Contaminated River.

PubMed

Lin, Tian; Guo, Zhigang; Li, Yuanyuan; Nizzetto, Luca; Ma, Chuanliang; Chen, Yingjun

2015-05-05

Gaseous exchange fluxes of organochlorine pesticides (OCPs) across the air-water interface of the coastal East China Sea were determined in order to assess whether the contaminated plume of the Yangtze River could be an important regional source of OCPs to the atmosphere. Hexachlorocyclohexanes (HCHs), chlordane compounds (CHLs), and dichlorodiphenyltrichloroethanes (DDTs) were the most frequently detected OCPs in air and water. Air-water exchange was mainly characterized by net volatilization for all measured OCPs. The net gaseous exchange flux ranged 10-240 ng/(m2·day) for γ-HCH, 60-370 ng/(m2·day) for trans-CHL, 97-410 ng/(m2·day) for cis-CHL, and ∼0 (e.g., equilibrium) to 490 ng/(m2·day) for p,p'-DDE. We found that the plume of the large contaminated river can serve as a significant regional secondary atmospheric source of legacy contaminants released in the catchment. In particular, the sediment plume represented the relevant source of DDT compounds (especially p,p'-DDE) sustaining net degassing when clean air masses from the open ocean reached the plume area. In contrast, a mass balance showed that, for HCHs, contaminated river discharge (water and sediment) plumes were capable of sustaining volatilization throughout the year. These results demonstrate the inconsistencies in the fate of HCHs and DDTs in this large estuarine system with declining primary sources.

Hydrocarbons in recent sediment of the Monterey Bay National Marine Sanctuary

USGS Publications Warehouse

Kvenvolden, K.A.; Hostettler, F.D.; Rosenbauer, R.W.; Lorenson, T.D.; Castle, W.T.; Sugarman, S.

2002-01-01

A complex mixture of hydrocarbons is present in the recent sediment of the Monterey Bay National Marine Sanctuary. Eighteen samples from the continental shelf between San Francisco and Monterey contain aliphatic and aromatic hydrocarbons showing biological contributions from both marine and terrigenous sources, with the terrigenous indicators more pronounced near Monterey. Of particular interest, however, is a low-level background of petroleum-related compounds, including 28,30-bisnorhopane and 18??+??(H)-oleanane, which are characteristic of many crude oils from the Monterey Formation of California. Thus, the sediments are overprinted by a regional chemical signature which may be derived from eroded Monterey Formation rocks and from onshore and offshore seeps releasing petroleum from Monterey Formation source rocks. ?? 2002 Elsevier Science B.V. All rights reserved.

Transverse Aeolian Ridges on Mars: Sediment sources, volumes, and ages.

NASA Astrophysics Data System (ADS)

Berman, D. C.; Balme, M. R.

2014-12-01

Transverse Aeolian Ridges (TARs) are aeolian bedforms that are morphologically and dimensionally distinct from Large Dark Dune (LDD) fields, being generally brighter than, or of similar albedo to, the surrounding terrain. These features are significantly smaller than the LDDs, appear to form normal to local winds, and tend to have simple, transverse, ripple-like morphologies. Whether these small martian bedforms represent large granule ripples, small transverse dunes, or something else entirely is currently under debate. The spatial distribution of TARs provides important information about where on Mars aeolian sediments are concentrated, and determining their volume can help us constrain the sediment transport regime on Mars. Also, if we can determine if TARs were active only in the past, or whether TARs are mobile under today's wind conditions, then we can begin to assess when and where TARs are/were active over Mars' recent geological history. Thus TARs have the potential for being indicators/records of climate change on Mars. In this work we build on previous work [1,2] and focus on the local/regional scale. We have identified six regional study areas, each 5° by 5°, to investigate the behavior of TARs in detail; one in the northern hemisphere, three in the equatorial band, and two in the southern hemisphere. We have systematically mapped TAR and LDD deposits in each study area to constrain sediment transport pathways and identify sediment sources. In general, TAR sediments appear to be tied to local sources such as LDDs or layered terrains. HiRISE DTMs were utilized to measure TAR heights, widths, wavelengths, and lengths to calculate sediment volumes and estimate volumes over entire study areas based on mapping. Crater count analyses on contiguous TAR fields in the equatorial regions, where the bedforms appear more lithified, reveal ages of several million years. Mid-latitude TAR fields do not show any superposed craters, suggesting much younger deposits. References: [1] Balme, M.R., D.C. Berman, M.C. Bourke, and J.R. Zimbelman, Transverse Aeolian Ridges (TARs) on Mars, Geomorphology, 101, 703-720, 2008. [2] Berman, D.C., M.R. Balme, S. Rafkin, and J.R. Zimbelman, Transverse Aeolian Ridges (TARs) on Mars II: Distributions, orientations, and ages, Icarus 213, 116-130, 2011

Mercury in Sediments From the Long Island Sound Region

NASA Astrophysics Data System (ADS)

Varekamp, J. C.; Lauriat, K.; Zierzow, T.; Buchholtz ten Brink, M.; Mecray, E.

2001-05-01

About 400 surface and core sediment samples from a sampling grid in Long Island Sound (LIS) were analyzed for mercury, Clostridium perfringens with many other chemical and physical parameters. About 16 cores from coastal salt marshes in Connecticut were analyzed as well. The Hg concentrations in LIS surface sediments vary between 30 and 650 ppb, with the highest values in the western end of LIS. The trend of increasing Hg to the west correlates with increasing abundances of fine-grained sediment and C-org. Normalization of the Hg data on mean grainsize or C-org contents still show an east-west trend. Data from the "12 mile sewage dump site" in the New York Bight area provide a linear relationship between C. perfringens and Hg. Using that relationship, we obtain that many LIS samples have 10-50 percent sewage-derived Hg, with values up to 70 percent in the extreme west. The remaining Hg is largely imported with fine-grained sediment from the surrounding watersheds, which is a focussed flux of the integrated regional atmospheric Hg deposition and point source mercury. The Housatonic River is an important source of mercury, with up to 5 ppm Hg in the river bed sediment. The Still River, a tributary of the Housatonic River, has sediments that carry up to 15 ppm Hg, and we surmise that the hatting industry of Danbury (CT) was an important Hg source. The in situ atmospheric deposition of Hg on LIS is only a small part of the overall LIS Hg sediment budget. Core data from LIS and surrounding marshes show contamination profiles with background values at 50-100 ppb Hg and peak values in the 200-500 range, with values up to 1200 ppb Hg at the mouth of the Housatonic River. Many cores show a decline in Hg concentrations in the upper 10-15 cm (last 40 years), whereas the C. perfringens concentrations increase exponentially towards the surface. The onset of Hg contamination coincides with the first elevated C. perfringens levels, indicating an anthropogenic origin for the Hg contamination.

Source Apportionment of Suspended Sediment Sources using 137Cs and 210Pbxs

NASA Astrophysics Data System (ADS)

Lamba, J.; Karthikeyan, K.; Thompson, A.

2017-12-01

A study was conducted in the Pleasant Valley Watershed (50 km 2) in South Central Wisconsin to better understand sediment transport processes using sediment fingerprinting technique. Previous studies conducted in this watershed showed that resuspension of fine sediment deposited on the stream bed is an important source of suspended sediment. To better understand the role of fine sediment deposited on the stream bed, fallout radionuclides,137Cs and 210Pbxs were used to determine relative contribution to suspended sediment from in-stream (stream bank and stream bed) and upland sediment sources. Suspended sediment samples were collected during the crop growing season. Potential sources of suspended sediment considered in this study included cropland, pasture and in-stream (stream bed and stream bank). Suspended sediment sources were determined at a subwatershed level. Results of this study showed that in-stream sediment sources are important sources of suspended sediment. Future research should be conducted to better understand the role of legacy sediment in watershed-level sediment transport processes.

Water-quality assessment of the Kentucky River basin, Kentucky; results of investigations of surface-water quality, 1987-90

USGS Publications Warehouse

Haag, K.H.; Garcia, Rene; Jarrett, G.L.; Porter, S.D.

1995-01-01

The U.S. Geological Survey investigated the water quality of the Kentucky River Basin in Kentucky as part of the National Water-Quality Assessment program. Data collected during 1987-90 were used to describe the spatial and temporal variability of water-quality constituents including metals and trace elements, nutrients, sediments, pesticides, dissolved oxygen, and fecal-coliform bacteria. Oil-production activities were the source of barium, bromide, chloride, magnesium, and sodium in several watersheds. High concentrations of aluminum, iron, and zinc were related to surface mining in the Eastern Coal Field Region. High concentrations of lead and zinc occurred in streambed sediments in urban areas, whereas concentrations of arsenic, strontium, and uranium were associated with natural geologic sources. Concentrations of phosphorus were significantly correlated with urban and agricultural land use. The high phosphorus content of Bluegrass Region soils was an important source of phosphorus in streams. At many sites in urban areas, most of the stream nitrogen load was attributable to wastewater-treatment-plant effluent. Average suspended-sediment concentrations were positively correlated with discharge. There was a downward trend in suspended-sediment concentrations downstream in the Kentucky River main stem during the study. The most frequently detected herbicides in water samples were atrazine, 2,4-D, alachlor, metolachlor, and dicamba. Diazinon, malathion, and parathion were the most frequently detected organophosphate insecticides in water samples. Detectable concentrations of aldrin, chlordane, DDT, DDE, dieldrin, endrin, endosulfan, heptachlor, and lindane were found in streambed-sediment samples. Dissolved-oxygen concentrations were sometimes below the minimum concentration needed to sustain aquatic life. At some sites, high concentrations of fecal-indicator bacteria were found and water samples did not meet sanitary water-quality criteria.

Oil pollution in soils and sediments from the Northern Peruvian Amazon.

PubMed

Rosell-Melé, Antoni; Moraleda-Cibrián, Núria; Cartró-Sabaté, Mar; Colomer-Ventura, Ferran; Mayor, Pedro; Orta-Martínez, Martí

2018-01-01

Oil has been extracted from the Northern Peruvian Amazon for over four decades. However, few scientific studies have assessed the impacts of such activities in the environment and health of indigenous communities in the region. We have investigated the occurrence of petrogenic hydrocarbon pollution in soils and sediments from areas favoured as hunting or fishing grounds by local indigenous inhabitants. The study was conducted in one of the most productive oil blocks in Peru, located in the headwaters of the Amazon river. Soils and river sediments, in the vicinity of oil extraction and processing infrastructure, contained an oil pollution signature as attested by the occurrence of hopanes and steranes. Given the lack of any other significant source of oil pollution in the region, the sources of hydrocarbons are likely to be the activities of the oil industry in the oil block, from voluntary discharges or accidental spills. Spillage of produced water was commonplace until 2009. Moreover, petrogenic compounds were absent in control samples in sites far removed from any oil infrastructure in the oil block. Our findings suggest that wildlife and indigenous populations in this region of the Amazon are exposed to the ingestion of oil polluted soils and sediments. The data obtained supports previous claims that the local spillage of oil and produced waters in the water courses in the Corrientes and Pastaza basins could have eventually reached the main water course of the Amazon. Copyright © 2017 Elsevier B.V. All rights reserved.

Petroleum hydrocarbon concentrations in eight mollusc species along Tamilnadu coast, Bay of Bengal, India.

PubMed

Veerasingam, S; Venkatachalapathy, R; Sudhakar, S; Raja, P; Rajeswari, V

2011-01-01

Eight mollusc species and sediment samples collected from three different stations along Tamilnadu coast, Bay of Bengal, India were analysed for the levels of petroleum hydrocarbons to elucidate the status of the petroleum residues in mollusc meant for human consumption. The concentrations of petroleum hydrocarbons in sediments along Tamilnadu coast varied from 5.04-25.5 microg/g dw (dry weight). High concentration of petroleum hydrocarbons in the sediment of Uppanar estuary (25.5 +/- 1.45 microg/g dw) was perhaps land and marine based anthropogenic sources of this region. The petroleum hydrocarbon residues in eight mollusc species collected from Uppanar, Vellar and Coleroon estuaries varied between 2.44-6.04 microg/g ww (wet weight). Although the concentration of petroleum hydrocarbons in sediment of the Uppanar region was markedly higher than the background, the petroleum hydrocarbon residues in mollusc collected from Uppanar estuary did not suggest bioaccumulation. The results signified that industrial growth has affected the aquatic environments and regular monitoring will help to adopt stringent pollution control measures for better management of the aquatic region.

Connecting source aggregating areas with distributive regions via Optimal Transportation theory.

NASA Astrophysics Data System (ADS)

Lanzoni, S.; Putti, M.

2016-12-01

We study the application of Optimal Transport (OT) theory to the transfer of water and sediments from a distributed aggregating source to a distributing area connected by a erodible hillslope. Starting from the Monge-Kantorovich equations, We derive a global energy functional that nonlinearly combines the cost of constructing the drainage network over the entire domain and the cost of water and sediment transportation through the network. It can be shown that the minimization of this functional is equivalent to the infinite time solution of a system of diffusion partial differential equations coupled with transient ordinary differential equations, that closely resemble the classical conservation laws of water and sediments mass and momentum. We present several numerical simulations applied to realstic test cases. For example, the solution of the proposed model forms network configurations that share strong similiratities with rill channels formed on an hillslope. At a larger scale, we obtain promising results in simulating the network patterns that ensure a progressive and continuous transition from a drainage drainage area to a distributive receiving region.

Reconstruction of atmospheric trace metals pollution in Southwest China using sediments from a large and deep alpine lake: Historical trends, sources and sediment focusing.

PubMed

Lin, Qi; Liu, Enfeng; Zhang, Enlou; Nath, Bibhash; Shen, Ji; Yuan, Hezhong; Wang, Rong

2018-02-01

Atmospheric pollution, one of the leading environmental problems in South and East Asia, and its impact on the terrestrial environmental quality remain poorly understood particularly in alpine areas where both historical and present-day mining and smelting operations might leave an imprint. Here, we reconstructed atmospheric trace metals pollution during the past century using core sediments from a large and deep alpine lake in Southwest China. The implication of in lake and/or in watershed sediment focusing in pollution quantification is discussed by analyzing 15 sediment cores. Factor analysis and enrichment factor indicated Cd, Pb and Sb as the typical pollutants. Distinct peaks of Pb and Sb pollution were observed around the 1920s, but little Pb pollution was detected in recent decades, different from other studies in similar regions. Cadmium pollution was observed until the mid-1980s synchronized with Sb. The distinctive variations in atmospheric trace metal pollution process in Southwest China highlight the regional and sub-regional sources of metal pollutants, which should be primarily attributed to non-ferrous metal smelting emissions. Both natural and anthropogenic metals showed wide concentration ranges though exhibited similar temporal trends in the 15 cores. Spatial variations of anthropogenic metals were influenced by the in-watershed pollutants remobilization, whereas, natural metals were regulated by the detrital materials in the sub-basin. In-lake sediment focusing had little influence on the spatial distributions of all metals, different from the traditional sediment focusing pattern observed in small lakes. Anthropogenic Cd accumulation in sediments ranged from 1.5 to 10.1mgm -2 in a specific core with an average of 6.5mgm -2 for the entire lake, highlighting that a reliable whole-lake pollutant budget requires an analysis of multiple cores. Our study suggests that the management of aquatic ecosystem health should take the remobilization of in-watershed stored pollutants into consideration especially under increasing human perturbation. Copyright © 2017 Elsevier B.V. All rights reserved.

Mercury distribution in ancient and modern sediment of northeastern Bering Sea

USGS Publications Warehouse

Nelson, C.H.; Pierce, D.E.; Leong, K.W.; Wang, F.F.H.

1975-01-01

Reconnaissance sampling of surface and subsurface sediment to a maximum depth of 80 m below the sea floor shows that typical values of 0.03 p.p.m. and anomalies of 0.2-1.3 p.p.m. mercury have been present in northeastern Bering Sea since Early Pliocene time. Values are highest in modern beach (maximum 1.3 and mean 0.22 p.p.m. Hg) and nearshore subsurface gravels (maximum 0.6 and mean 0.06 p.p.m. Hg) along the highly mineralized Seward Peninsula and in clayey silt rich in organic matter (maximum 0.16 and mean 0.10 p.p.m. Hg) throughout the region. Although gold mining may be partly responsible for high mercury levels in the modern beach near Nome, Alaska (maximum 0.45 p.p.m.), equally high or greater concentrations of mercury occur in buried Pleistocene sediments immediately offshore (maximum 0.6 p.p.m.) and in modern unpolluted beach sediments at Bluff (maximum 1.3 p.p.m.); this suggests that the contamination effects of mining may be no greater than natural concentration processes in the Seward Peninsula region. The mercury content of offshore surface sediment, even adjacent to mercury-rich beaches, corresponds to that of unpolluted marine and fresh-water sediment elsewhere. The normal values that prevail offshore may be attributable to entrapment of mercury-bearing heavy minerals on beaches near sources and/or dilution effects of offshore sedimentation. The few minor anomalies offshore occur in glacial drift derived from mercury source regions of Chukotka (Siberia) and Seward Peninsula; Pleistocene shoreline processes have reworked the drift to concentrate the heavy metals. The distribution pattern of mercury indicates that particulate mercury-bearing minerals have not been widely dispersed from onland deposits in quantities sufficient to increase mercury levels above normal in offshore sediments of Bering Sea; however, it shows that natural sedimentary processes can concentrate this mercury in beaches of the coastal zone where there already is concern because of potential pollution from man's activities.

Spatial variability in the abundance, composition, and age of organic matter in surficial sediments of the East China Sea

NASA Astrophysics Data System (ADS)

Wu, Ying; Eglinton, Timothy; Yang, Liyang; Deng, Bing; Montluçon, Daniel; Zhang, Jing

2013-12-01

the sources and fate of organic matter (OM) sequestered in continental margin sediments is of importance because the mode and efficiency of OM burial impact the carbon cycle and the regulation of atmospheric CO2 over long time scales. We carried out molecular (lignin-derived phenols from CuO oxidation), elemental, isotopic (δ13C, Δ14C), and sedimentological (grain size and mineral surface area) analyses in order to examine spatial variability in the abundance, source, age of surface sediments of the East China Sea. Higher terrigenous organic matter values were found in the main accumulating areas of fluvial sediments, including the Changjiang (Yangtze) Estuary and Zhejiang-Fujian coastal zone. Isotopic and biomarker data suggest that the sedimentary OM in the inner shelf region was dominated by aged (Δ14C = -423 ± 42‰) but relatively lignin-rich OM (Λ = 0.94 ± 0.57 mg/100 mg OC) associated with fine-grained sediments, suggesting important contributions from soils. In contrast, samples from the outer shelf, while of similar age (Δ14 C = -450 ± 99‰), are lignin poor (Λ = 0.25 ± 0.14 mg/100 mg OC) and associated with coarse-grained material. Regional variation of lignin phenols and OM ages indicates that OM content is fundamentally controlled by hydrodynamic sorting (especially, sediment redistribution and winnowing) and in situ primary production. Selective sorption of acid to aldehyde in clay fraction also modified the ratios of lignin phenols. The burial of lignin in East China Sea is estimated to be relatively efficient, possibly as a consequence of terrigenous OM recalcitrance and/or relatively high sedimentation rates in the Changjiang Estuary and the adjacent Zhejing-Fujian mud belt.

Contrasts in Sediment Delivery and Dispersal from River Mouth to Accumulation Zones in High Sediment Load Systems: Fly River, Papua New Guinea and Waipaoa River, New Zealand

NASA Astrophysics Data System (ADS)

Ogston, A. S.; Walsh, J. P.; Hale, R. P.

2011-12-01

The relationships between sediment-transport processes, short-term sedimentary deposition, subsequent burial, and long-term accumulation are critical to understanding the morphological development of the continental margin. This study focuses on processes involved in formation and evolution of the clinoform in the Gulf of Papua, Papua New Guinea in which much of the riverine sediment accumulates, and comparison to those processes active off the Waipaoa River, New Zealand that form mid-shelf deposits and export sediment to the slope. In tidally dominated deltas, sediment discharged from the river sources must transit through an estuarine region located within the distributary channels, where particle pathways can undergo significant transformations. Within the distributaries of the Fly River tidally dominated delta, near-bed fluid-mud concentrations were observed at the estuarine turbidity maximum and sediment delivery to the nearshore was controlled by the morphology and gradient of the distributary. El Niño results in anonymously low flow and sediment discharge conditions, which limits transport of sediment from the distributaries to the nearshore zone of temporary storage. Because the sediment stored nearshore feeds the prograding clinoform, this perturbation propagates throughout the dispersal system. In wave-dominated regions, transport mechanisms actively move sediment away from the river source, separating the site of deposition and accumulation from the river mouth. River-flood and storm-wave events each create discrete deposits on the Waipaoa River shelf and data has been collected to determine their form, distribution, and relationship to factors such as flood magnitude or wave energy. In this case, transport pathways appear to be influenced by structurally controlled shelf bathymetry. In both cases, the combined fluvial and marine processes can initiate and maintain gravity-driven density flows, and although their triggers and controls differ vastly, these flows play a significant role in the morpholigcal development of the continental margin. These sites, synthesized with examples from multiple other environments, provide a basis for understanding the interactions between physical processes responsible for the transport of sediment from river mouths to the sites of ultimate deposition.

Characterizing the impacts of the 2006 New Year's flood in the Laguna de Santa Rosa floodplain, Sonoma County, CA

NASA Astrophysics Data System (ADS)

Flint, L. E.; Curtis, J. A.; Flint, A. L.

2006-12-01

The Laguna de Santa Rosa (Laguna), the largest tributary to the Russian River located in Sonoma County, California, occupies a relatively flat low-lying area west of the Santa Rosa Plain. From December 12, 2005 to January 6, 2006 the Laguna experienced heavy flooding, with peak flows on New Year's Day of over 185 m3/s, at a location that experiences median flows of less than 14 m3/s. The objectives of this study were to (1) analyze precipitation intensities and amounts for the region to establish the conditions under which flooding occurred, (2) measure and map inundation areas and floodplain sediment deposition, and (3) compare field data with a GIS sediment deposition potential map. Spatial variations in intensities and total volumes of precipitation correlate well with evidence of local flooding throughout the region, particularly in the mountains to the east and southeast of Santa Rosa. Total precipitation for the month of December was 200 percent of normal, and maximum hourly intensities reached 20 mm/hour during the storm. High water marks and floodplain deposition sites were mapped using kinematic GPS surveying with post-processed differential correction, and sediment deposition was measured. The surveyed data were superimposed on an available two-foot-interval contour map to create an inundation map and a GIS point coverage of sediment deposition. Landscape attributes relevant to floodplain sedimentation were assessed and a sediment deposition potential map was created at the 30-m scale using a matrix of landscape characteristics that included: land use; roughness (influenced by vegetation type and density); channel and hillslope sediment sources (influenced by soils, geology, and cutbank erosion); slope and topography; and geomorphic terrain type. A calculation of sediment deposition potential was developed within a GIS that accounts for all contributing factors and illustrates that floodplain deposition is dominated by localized sedimentation, reflecting the importance of sediment point sources, rather than extensive sedimentation throughout the floodplain. The data collected in this study will be used to constrain model simulations of recurrence-interval floods and provide information on patterns of hydrology and sedimentation for extreme events that will help refine conceptual models of floodplain processes.

Chapter 34: Geology and petroleum potential of the rifted margins of the Canada Basin

USGS Publications Warehouse

Houseknecht, D.W.; Bird, K.J.

2011-01-01

Three sides of the Canada Basin are bordered by high-standing, conjugate rift shoulders of the Chukchi Borderland, Alaska and Canada. The Alaska and Canada margins are mantled with thick, growth-faulted sediment prisms, and the Chukchi Borderland contains only a thin veneer of sediment. The rift-margin strata of Alaska and Canada reflect the tectonics and sediment dispersal systems of adjacent continental regions whereas the Chukchi Borderland was tectonically isolated from these sediment dispersal systems. Along the eastern Alaska-southern Canada margin, termed herein the 'Canning-Mackenzie deformed margin', the rifted margin is deformed by ongoing Brooks Range tectonism. Additional contractional structures occur in a gravity fold belt that may be present along the entire Alaska and Canada margins of the Canada Basin. Source-rock data inboard of the rift shoulders and regional palaeogeographic reconstructions suggest three potential source-rock intervals: Lower Cretaceous (Hauterivian-Albian), Upper Cretaceous (mostly Turonian) and Lower Palaeogene. Burial history modelling indicates favourable timing for generation from all three intervals beneath the Alaska and Canada passive margins, and an active petroleum system has been documented in the Canning-Mackenzie deformed margin. Assessment of undiscovered petroleum resources indicates the greatest potential in the Canning-Mackenzie deformed margin and significant potential in the Canada and Alaska passive margins. ?? 2011 The Geological Society of London.

Cenozoic North American Drainage Basin Evolution, Sediment Yield, and Accumulation in the Gulf of Mexico Basin

NASA Astrophysics Data System (ADS)

Galloway, W.; Ganey-Curry, P. E.

2010-12-01

The Cenozoic fill of the Gulf of Mexico basin contains a continuous record of sediment supply from the North American continental interior for the past 65 million years. Regional mapping of unit thickness and paleogeography for 18 depositional episodes defines patterns of shifting entry points of continental fluvial systems and quantifies the total volume of sediment supplied during each episode. Eight fluvio-deltaic depocenters, named for geographic similarities to entry points and drainage basins of modern rivers, are present. From southwest to northeast, they are the Rio Bravo, Rio Grande, Guadalupe, Colorado, Houston-Brazos, Red, Mississippi, and Tennessee axes. Sediment volume was calculated from hand-contoured unit thickness maps compiled from basin-wide well and seismic control. Using a GIS algorithm to sum volumes within polygons bounding interpreted North American river contribution, the total extant volume was then calculated. General compaction factors were used to convert modern volume to quantitative approximations of total grain volume. Grain volume rate of supply for each depositional episode was then calculated. Values vary by more than an order of magnitude. Supply rate has commonly varied by two-fold or more between successive depositional episodes. Sediment supply is a significant, independent variable in development of stratigraphic sequences within the Gulf basin. Paleogeographic maps of the continental interior for eleven Cenozoic time intervals display the evolving and complex interplay of intracontinental tectonism, climate change, and drainage basin evolution. Five tectono-climatic eras are differentiated: Paleocene late Laramide era; early to middle Eocene terminal Laramide era; middle Cenozoic (Late Eocene—Early Miocene) dry, volcanogenic era; middle Neogene (Middle—Late Miocene) arid, extensional era; and late Neogene (Plio—Pleistocene) monsoonal, epeirogenic uplift era. Sediment supply to the GOM reflects the interplay of (1) areal extent of river drainage basins, (2) source area relief, (3) climate of the source areas and tributary systems, (4) source lithology, and (5) sediment storage within the upper drainage basin. Climate has played an important and complex role in modulating supply. In wet tropical to temperate climate regimes, abundant runoff efficiently removed entrained sediment. Arid climate limited runoff; resultant transport-limited tributaries and trunk streams deposited aggradational alluvial aprons, storing sediment in the drainage basin even in the absence of a structural depression. Eolian deposition commonly accompanied such alluvial aggradation. In contrast, seasonality and consequent runoff variability favored erosion and efficient sediment evacuation from the upper parts of drainage basins. Tectonism has played a prominent but equally complex role. Elevation of uplands by compression, crustal heating, or extrusive volcanism created primary loci of erosion and high sediment yield. At the same time, accompanying subsidence sometimes created long-lived sediment repositories that intercepted and sequestered sediment adjacent to sources. Regional patterns of uplift and subsidence relocated drainage divides and redirected trunk stream paths to the Gulf margin.

Observations of sediment transport on the Amazon subaqueous delta

USGS Publications Warehouse

Sternberg, R.W.; Cacchione, D.A.; Paulson, B.; Kineke, G.C.; Drake, D.E.

1996-01-01

A 19-day time series of fluid, flow, and suspended-sediment characteristics in the benthic boundary layer is analyzed to identify major sedimentary processes active over the prodelta region of the Amazon subaqueous delta. Measurements were made by the benthic tripod GEOPROBE placed on the seabed in 65 m depth near the base of the deltaic foreset beds from 11 February to 3 March 1990, during the time of rising water and maximum sediment discharge of the Amazon River; and the observations included: hourly measurements of velocity and suspended-sediment concentration at four levels above the seabed; waves and tides; and seabed elevation. Results of the first 14-day period of the time series record indicate that sediment resuspension occurred as a result of tidal currents (91% of the time) and surface gravity waves (46% of the time). Observations of suspended sediment indicated that particle flux in this region is 0.4-2% of the flux measured on the adjacent topset deposits and is directed to the north and landward relative to the Brazilian coast (268??T). Fortnightly variability is strong, with particle fluxes during spring tides five times greater than during neap tides. On the 15th day of the data record, a rapid sedimentation event was documented in which 44 cm of sediment was deposited at the study site over a 14-h period. Evaluation of various mechanisms of mass sediment movement suggests that this event represents downslope migration of fluid muds from the upper foreset beds that were set in motion by boundary shear stresses generated by waves and currents. This transport mechanism appears to occur episodically and may represent a major source of sediment to the lower foreset-bottomset region of the subaqueous delta.

Spatial variability of sediment erosion processes using GIS analysis within watersheds in a historically mined region, Patagonia Mountains, Arizona

USGS Publications Warehouse

Brady, Laura M.; Gray, Floyd; Wissler, Craig A.; Guertin, D. Phillip

2001-01-01

In this study, a geographic information system (GIS) is used to integrate and accurately map field studies, information from remotely sensed data, watershed models, and the dispersion of potentially toxic mine waste and tailings. The purpose of this study is to identify erosion rates and net sediment delivery of soil and mine waste/tailings to the drainage channel within several watershed regions to determine source areas of sediment delivery as a method of quantifying geo-environmental analysis of transport mechanisms in abandoned mine lands in arid climate conditions. Users of this study are the researchers interested in exploration of approaches to depicting historical activity in an area which has no baseline data records for environmental analysis of heavily mined terrain.

Mapping erodibility in dust source regions based on geomorphology, meteorology, and remote sensing

NASA Astrophysics Data System (ADS)

Parajuli, Sagar Prasad; Yang, Zong-Liang; Kocurek, Gary

2014-09-01

Mineral dust in the atmosphere has implications for Earth's radiation budget, biogeochemical cycles, hydrological cycles, human health, and visibility. Currently, the simulated vertical mass flux of dust differs greatly among the existing dust models. While most of the models utilize an erodibility factor to characterize dust sources, this factor is assumed to be static, without sufficient characterization of the highly heterogeneous and dynamic nature of dust source regions. We present a high-resolution land cover map of the Middle East and North Africa (MENA) in which the terrain is classified by visually examining satellite images obtained from Google Earth Professional and Environmental Systems Research Institute Basemap. We show that the correlation between surface wind speed and Moderate Resolution Imaging Spectroradiometer deep blue aerosol optical depth (AOD) can be used as a proxy for erodibility, which satisfactorily represents the spatiotemporal distribution of soil-derived dust sources. This method also identifies agricultural dust sources and eliminates the satellite-observed dust component that arises from long-range transport, pollution, and biomass burning. The erodible land cover of the MENA region is grouped into nine categories: (1) bedrock: with sediment, (2) sand deposit, (3) sand deposit: on bedrock, (4) sand deposit: stabilized, (5) agricultural and urban area, (6) fluvial system, (7) stony surface, (8) playa/sabkha, and (9) savanna/grassland. Our results indicate that erodibility is linked to the land cover type and has regional variation. An improved land cover map, which explicitly accounts for sediment supply, availability, and transport capacity, may be necessary to represent the highly dynamic nature of dust sources in climate models.

The Role of Source Material in Basin Sedimentation, as Illustrated within Eureka Valley, Death Valley National Park, CA.

NASA Astrophysics Data System (ADS)

Lawson, M. J.; Yin, A.; Rhodes, E. J.

2015-12-01

Steep landscapes are known to provide sediment to sink regions, but often petrological factors can dominate basin sedimentation. Within Eureka Valley, in northwestern Death Valley National Park, normal faulting has exposed a steep cliff face on the western margin of the Last Chance range with four kilometers of vertical relief from the valley floor and an angle of repose of nearly 38 degrees. The cliff face is composed of Cambrian limestone and dolomite, including the Bonanza King, Carrara and Wood Canyon formations. Interacting with local normal faulting, these units preferentially break off the cliff face in coherent blocks, which result in landslide deposits rather than as finer grained material found within the basin. The valley is well known for a large sand dune, which derives its sediment from distal sources to the north, instead of from the adjacent Last Chance Range cliff face. During the Holocene, sediment is sourced primary from the northerly Willow Wash and Cucomungo canyon, a relatively small drainage (less than 80 km2) within the Sylvan Mountains. Within this drainage, the Jurassic quartz monzonite of Beer Creek is heavily fractured due to motion of the Fish Valley Lake - Death Valley fault zone. Thus, the quartz monzonite is more easily eroded than the well-consolidated limestone and dolomite that forms the Last Change Range cliff face. As well, the resultant eroded material is smaller grained, and thus more easily transported than the limestone. Consequently, this work highlights an excellent example of the strong influence that source material can have on basin sedimentation.

Assessment and source identification of pollution risk for touristic ports: Heavy metals and polycyclic aromatic hydrocarbons in sediments of 4 marinas of the Apulia region (Italy).

PubMed

Mali, Matilda; Dell'Anna, Maria Michela; Mastrorilli, Piero; Damiani, Leonardo; Piccinni, Alberto Ferruccio

2017-01-30

The Apulia region in Italy has the longest Adriatic coastline; thus, maritime tourism is the driving force for its economic development. Pollution risk for four representative touristic ports of the region was assessed by determining the concentrations of 10 metals, 16 polycyclic aromatic hydrocarbons (PAHs) congeners, and the main nutrients. The cumulative mean Effects Range-Median quotient (mERMq) was used to assess the hazard degree, while the distribution patterns and content ratios of different PAH sediment concentrations were investigated to identify the pollution sources. Principal component analyses indicated an anomalous pollution trend for one of the small touristic ports assessed; this trend emerged from contamination by heavy metals and PAHs to a larger extent than expected, considering the main activity in this port, especially in its inner basin. The reason of this anomaly is thought to be the hydrodynamic and/or other stress factors. Copyright © 2016 Elsevier Ltd. All rights reserved.

Sources, dispersal, and fate of fine sediment supplied to coastal California

USGS Publications Warehouse

Farnsworth, Katherine L.; Warrick, Jonathan A.

2007-01-01

We have investigated the sources, dispersal, and fate of fine sediment supplied to California coastal waters in a partnership between the U.S. Geological Survey (USGS) and the California Sediment Management Workgroup (CSMW). The purpose of this study was to document the rates and characteristics of these processes so that the State can better manage its coastal resources, including sediment. In this study, we made the following observations: - Rivers dominate the supply of fine sediment to the California coastal waters, with an average annual flux of 34 megatonnes (Mt). - Cliff and bluff erosion in central and southern California is a source of fine sediment, with a delivery rate of approximately 10 percent of river loads. In the southern most part of the State, however, where river-sediment loads are low, cliff and bluff erosion represent approximately 40 percent of the total fine-sediment flux. - Temporal variation in the sources of fine sediment is high. River floods and bluff erosion are episodic and dominated by winter storms, which supply most sediment flux to the coast. The magnitude of winter storms is generally related to the El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) climate cycles. - The three rivers that dominate fine-sediment flux to the California coast are the Eel, Salinas, and Santa Clara Rivers. Because the sediment delivery from these and all other California coastal watersheds is episodic, individual rivers discharge most of their annual loads over the course of only a few days per year. - Spatial variation in river-sediment discharge is high and generally related to such watershed characteristics as geology, precipitation, and drainage area. For example, the Transverse Range of southern California represents only 9 percent of the watershed-drainage area but 18 percent of the fine-sediment flux, a function of the young sedimentary bedrock and active tectonics of this region. The urban rivers of southern California were observed to discharge sediment at rates consistent with those of the surrounding Transverse Range rivers, which share the same geologic setting. - Direct observations of fine-sediment dispersal have been limited to the river-mouth settings of the Eel and Santa Clara Rivers, where sediment has been observed to settle quickly from buoyant plumes and be transported along the seabed during periods of storm waves. - After heavy loading of fine sediment onto the continental shelf during river floods, there is increasing evidence that fluid-mud gravity flows occur within a layer 10 to 50 cm above the seabed and efficiently transport fine sediment offshore. - All along the California coast, the timing of river discharge and coastal winds and waves from storm events are strongly coherent; however, of large wave events with the potential for resuspending and transporting fine sediment occur during periods without significant rainfall and therefore no significant river discharge. - Although fine sediment dominates the midshelf mud belts offshore of California river mouths, these mud belts are not the dominant sink of fine sediment, much of which is deposited across the entire continental shelf, including the inner shelf, and offshelf into deeper water depths. - Accumulation rates of fine sediment, which can exceed several millimeters per year, are generally highest near river sources of sediment and along the inner shelf and midshelf. - Sediment-accumulation rates, as summarized from both long-term and recent investigations of continental-shelf geochronology, are generally consistent across California except in southern California, where recently the sediment-accumulation rate has been tenfold greater than the long-term rate, possibly as a result of increased river discharge, wastewater outfall inputs, or other anthropogenic sources. Thus, fine sediment is a natural and dynamic element of the California coastal system because of large, natural sediment sources and dynamic transport processes.

Organic sedimentation in modern lacustrine systems: A case study from Lake Malawi, East Africa

USGS Publications Warehouse

Ellis, Geoffrey S.; Barry J. Katz,; Christopher A. Scholz,; Peter K. Swart,

2015-01-01

This study examines the relationship between depositional environment and sedimentary organic geochemistry in Lake Malawi, East Africa, and evaluates the relative significance of the various processes that control sedimentary organic matter (OM) in lacustrine systems. Total organic carbon (TOC) concentrations in recent sediments from Lake Malawi range from 0.01 to 8.80 wt% and average 2.83 wt% for surface sediments and 2.35 wt% for shallow core sediments. Hydrogen index (HI) values as determined by Rock-Eval pyrolysis range from 0 to 756 mg HC g−1 TOC and average 205 mg HC g−1 TOC for surface sediments and 228 mg HC g−1 TOC for shallow core samples. On average, variations in primary productivity throughout the lake may account for ~33% of the TOC content in Lake Malawi sediments (as much as 1 wt% TOC), and have little or no impact on sedimentary HI values. Similarly, ~33% to 66% of the variation in TOC content in Lake Malawi sediments appears to be controlled by anoxic preservation of OM (~1–2 wt% TOC), although some component of the water depth–TOC relationship may be due to physical sediment transport processes. Furthermore, anoxic preservation has a minimal effect on HI values in Lake Malawi sediments. Dilution of OM by inorganic sediment may account for ~16% of variability in TOC content in Lake Malawi sediments (~0.5 wt% TOC). The effect of inputs of terrestrial sediment on the organic character of surface sediments in these lakes is highly variable, and appears to be more closely related to the local depositional environment than the regional flux of terrestrial OM. Total nitrogen and TOC content in surface sediments collected throughout the lake are found to be highly correlated (r2 = 0.95), indicating a well-homogenized source of OM to the lake bottom. The recurring suspension and deposition of terrestrial sediment may account for significant amounts of OM deposited in offshore regions of the lake. This process effectively separates denser inorganic sediment from less dense OM and allows terrestrial OM to preferentially be transported farther offshore. The conclusion is that for the organic carbon content in these regions to be elevated a mixed terrestrial-lacustrine origin is required. The hydrodynamic separation of mineral and organic constituents is most pronounced in regions with shallow bathymetric gradients, consistent with previous findings from Lake Tanganyika.

Clay mineralogy and source-to-sink transport processes of Changjiang River sediments in the estuarine and inner shelf areas of the East China Sea

NASA Astrophysics Data System (ADS)

Zhao, Yifei; Zou, Xinqing; Gao, Jianhua; Wang, Chenglong; Li, Yali; Yao, Yulong; Zhao, Wancang; Xu, Min

2018-02-01

We examined the source-to-sink sediment transport processes from the Changjiang River to the estuarine coastal shelf area by analyzing the clay mineral assemblages in suspended sediment samples from the Changjiang River catchment and surface samples from the estuarine coastal shelf area following the impoundment of the Three Gorges Dam (TGD) in 2003. The results indicate that the clay mineral compositions throughout the study area are dominated by illite, with less abundant kaolinite and chlorite and scarce smectite. The clay minerals display distinct differences in the tributaries and exhibit obvious changes in the trunk stream compared with the periods before 2003, and the source of sediment has largely shifted to the mid- to lower reaches of the river after 2003. Spatially, the clay mineral assemblages in the estuarine area define two compositionally distinct provinces. Province I covers the mud area of the Changjiang River estuary and the Zhe-Min coastal region, where sediment is primarily supplied by the Changjiang River. Province II includes part of the Changjiang River estuary and the southeastern portion of the study area, where the sediment is composed of terrestrial material from the Changjiang River and re-suspended material from the Huanghe River carried by the Jiangsu coastal current. Moreover, the other smaller rivers in China (including the Oujiang and Minjiang rivers of mainland China and the rivers of West Taiwan) also contribut sediments to the estuarine and inner shelf areas. In general, the clay mineral assemblages in the Changjiang River estuarine area are have mainly been controlled by sediment supplied from upstream of the Changjiang River tributaries. However, since the completion of the TGD in 2003, the mid- to downstream tributaries have become the main source of sediments from the Changjiang catchment into the East China Sea. These analyses further demonstrate that the coastal currents and the decrease in the sediment load of the river have the greatest impacts on the distribution and transport of clay minerals assemblages in the sediments.

Distribution and sources of carbon, nitrogen, phosphorus and biogenic silica in the sediments of Chilika lagoon

NASA Astrophysics Data System (ADS)

Nazneen, Sadaf; Raju, N. Janardhana

2017-02-01

The present study investigated the spatial and vertical distribution of organic carbon (OC), total nitrogen (TN), total phosphorus (TP) and biogenic silica (BSi) in the sedimentary environments of Asia's largest brackish water lagoon. Surface and core sediments were collected from various locations of the Chilika lagoon and were analysed for grain-size distribution and major elements in order to understand their distribution and sources. Sand is the dominant fraction followed by silt + clay. Primary production within the lagoon, terrestrial input from river discharge and anthropogenic activities in the vicinity of the lagoon control the distribution of OC, TN, TP and BSi in the surface as well as in the core sediments. Low C/N ratios in the surface sediments (3.49-3.41) and cores (4-11.86) suggest that phytoplankton and macroalgae may be major contributors of organic matter (OM) in the lagoon. BSi is mainly associated with the mud fraction. Core C5 from Balugaon region shows the highest concentration of OC ranging from 0.58-2.34%, especially in the upper 30 cm, due to direct discharge of large amounts of untreated sewage into the lagoon. The study highlights that Chilika is a dynamic ecosystem with a large contribution of OM by autochthonous sources with some input from anthropogenic sources as well.

Urban rivers as conveyors of hydrocarbons to sediments of estuarine areas: source characterization, flow rates and mass accumulation.

PubMed

Mauad, Cristiane R; Wagener, Angela de L R; Massone, Carlos G; Aniceto, Mayara da S; Lazzari, Letícia; Carreira, Renato S; Farias, Cássia de O

2015-02-15

Aliphatic (n-C12-n-C40, unresolved complex mixture, resolved peaks) and aromatic hydrocarbons (46 PAH) were investigated in suspended particulate matter (SPM) sampled over eleven months in six of the major rivers and two channels of the Guanabara Bay Basin. PAH flow rates of the most contaminated rivers, the contribution to the PAH sediment load of the receiving bay, and the main sources of hydrocarbons were determined. PAH (38) ranged from 28 ng L(-1) to 11,514 ng L(-1). Hydrocarbon typology and statistical evaluation demonstrated contribution of distinct sources in different regions and allowed quantification of these contributions. Total flow rate for the five major rivers amounts to 3 t year(-1) and responds for 30% of the total PAH annual input into the northern area of the Guanabara Bay. For the first time PAH mass deposited in the bay sediments has been estimated and shall serve as base for decision making and source abatement. Copyright © 2014 Elsevier B.V. All rights reserved.

Application of the positive matrix factorization approach to identify heavy metal sources in sediments. A case study on the Mexican Pacific Coast.

PubMed

González-Macías, C; Sánchez-Reyna, G; Salazar-Coria, L; Schifter, I

2014-01-01

During the last two decades, sediments collected in different sources of water bodies of the Tehuantepec Basin, located in the southeast of the Mexican Pacific Coast, showed that concentrations of heavy metals may pose a risk to the environment and human health. The extractable organic matter, geoaccumulation index, and enrichment factors were quantified for arsenic, cadmium, copper, chromium, nickel, lead, vanadium, zinc, and the fine-grained sediment fraction. The non-parametric SiZer method was applied to assess the statistical significance of the reconstructed metal variation along time. This inference method appears to be particularly natural and well suited to temperature and other environmental reconstructions. In this approach, a collection of smooth of the reconstructed metal concentrations is considered simultaneously, and inferences about the significance of the metal trends can be made with respect to time. Hence, the database represents a consolidated set of available and validated water and sediment data of an urban industrialized area, which is very useful as case study site. The positive matrix factorization approach was used in identification and source apportionment of the anthropogenic heavy metals in the sediments. Regionally, metals and organic matter are depleted relative to crustal abundance in a range of 45-55 %, while there is an inorganic enrichment from lithogenous/anthropogenic sources of around 40 %. Only extractable organic matter, Pb, As, and Cd can be related with non-crustal sources, suggesting that additional input cannot be explained by local runoff or erosion processes.

Geochemical indications and Detrital Zircon U-Pb ages of net-like laterite from Youjiang terrace, Bose Basin, southwestern China: new evidence of proximal provenance for laterite sediments

NASA Astrophysics Data System (ADS)

Cheng, F.; Hong, H.; Li, C.; Ye, H.; Yang, H.

2015-12-01

The net-like laterite sediments is widely spread over the terraces and high lands of the river valley in southern China during mid-Pleistocene, although whose origin is still debated. The Xiaomei laterite sediments on the terraces of Youjiang River, Guangxi Zhuang Autonomous Region, southern China, was dominated by the intermittently uplift of the Tibetan Plateau for the mechanism during the Quaternary times. Compared to the loess-paleosol deposits in Chinese Loess Plateau (CLP), the upper continental crust (UCC) and the post-Archean Australian average shale (PAAS), the sediments show notable depletion of the relative mobile compositions like CaO, MgO, Na2O, K2O, Sr, Ba and the accumulation of TiO2, Al2O3, Fe2O3(t), Zr, but similar with other laterite sediments (the Xuancheng and Jiujiang laterite profiles) in the middle to lower reaches of Yangtze River, southern China. The relatively uniform La/Th ratio, U/Pb vs. Th/Pb ratio and chondrite-normalized REE distribution pattern of Xiaomei samples are similar with the loess-paleosol deposits and UCC values, which suggesting the sediments have experienced well-mixing prior to deposition and intense superficial weathering. The low ɛNd(t) values and uniform 147Sm/144Nd ratios with the 87Sr/86Sr vs. Rb/Sr ratios show the notable differences with loess-paleosol deposits and the recycling function of the old fluvial sediments which are similar with the Pearl River sediments. The stable zircon age distribution pattern with three age groups of 240-300Ma, 420-480Ma and 900-1000Ma for Xiaomei laterite samples are different with the loess-paleosol deposits and its source regions. The zircons are mainly derived from a source of the Upper Permian to Middle Triassic clastic rocks in Youjiang Basin, superordinate tectonic unit of Bose Basin, and their potential source areas like the Emeishan Large Igneous Province (Emeishan LIP) and the southeastern area of south China Craton (SCC). For the basis of these data, we suggest that that the aeolian dusts may have not started to accumulate in southern China during these times, and the laterite sediments in southern China may dominate by the proximal supplementation.

Quality of Tourist Beaches in Huatulco, SW of Mexico: Multiproxy Studies

NASA Astrophysics Data System (ADS)

Retama, I.; Jonathan, M. P.; Rodriguez-Espinosa, P. F.

2014-12-01

40 beach water and sediment samples were collected from the inter-tidal zones of tourist beaches of Huatulco in the State of Oaxaca, South Western part of Mexico. The samples were collected in an aim to know the concentration pattern of metals (Cu, Cd, Cr, Ni, Pb, Zn, Co, Mn, Fe, As, Hg) in sediments and microplastics. Physico-chemical parameters like temperature, pH, dissolved oxygen, conductivity and total dissolved solids, salinity and redox potential. Collection of samples was done during the peak season in April 2013. Our results from water samples indicate that the physico-chemical conditions of the beach water have been altered due to human activities in large numbers. The bioavailable metal concentrations indicate that enrichment of Pb, Cd, Cr and As and it is also supported by the higher values observed from the calculation of enrichment factor and geoaccumulation index. The higher values in the sediments is either due to natural sources like chemical weathering of rocks and external sources, which points to high tourism, agricultural activities in the region. Identification of micro-plastics was done through SEM photographs, indicating the type of plastic wastes deposited into the beach regions which can indicate the density, durability and the persistence level in the sediments. Eventhough the enrichment of metals and modification of beach water quality is observed, care need to be taken to avoid further damage to the coastal ecosystem. Keywords: Tourism, Beach sediments, Beach water, Micro plastics, Trace metals, Contamination indices, Huatulco, Mexico.

Characterization of land-based sources of pollution in Jobos Bay, Puerto Rico: status of heavy metal concentration in bed sediment.

PubMed

Apeti, Dennis A; Whitall, David R; Pait, Anthony S; Dieppa, Angel; Zitello, Adam G; Lauenstein, Gunnar G

2012-01-01

As part of an assessment of land-based sources of pollution in Jobos Bay, Puerto Rico, sediment samples were collected at 43 sites to characterize concentrations of a suite of pollutants, including metals. Fifteen major and trace metals (Ag, Al, As, Cd, Cr, Cu, Fe, Hg, Mn Ni, Pb, Sb, Se, Sn, and Zn) were measured along with total organic carbon and grain size in surficial sediments. For most metals, maximum concentrations were seen in the eastern bay; however, values were still within concentration ranges found in other estuarine systems. In contrast, silver was higher in the western region. In general, metal distribution in the bay was positively correlated with grain size. Additionally, correlations between Al and other metals suggest natural sources for metals. The data presented here suggest that, although the Jobos Bay watershed contains both urban centers along with industrial and agricultural developments, anthropogenic inputs of metals may be negligible.

Effect of nutrient enrichment on the source and composition of sediment organic carbon in tropical seagrass beds in the South China Sea.

PubMed

Liu, Songlin; Jiang, Zhijian; Zhang, Jingping; Wu, Yunchao; Lian, Zhonglian; Huang, Xiaoping

2016-09-15

To assess the effect of nutrient enrichment on the source and composition of sediment organic carbon (SOC) beneath Thalassia hemprichii and Enhalus acoroides in tropical seagrass beds, Xincun Bay, South China Sea, intertidal sediment, primary producers, and seawater samples were collected. No significant differences on sediment δ(13)C, SOC, and microbial biomass carbon (MBC) were observed between T. hemprichii and E. acoroides. SOC was mainly of autochthonous origin, while the contribution of seagrass to SOC was less than that of suspended particulate organic matter, macroalgae and epiphytes. High nutrient concentrations contributed substantially to SOC of seagrass, macroalgae, and epiphytes. The SOC, MBC, and MBC/SOC ratio in the nearest transect to fish farming were the highest. This suggested a more labile composition of SOC and shorter turnover times in higher nutrient regions. Therefore, the research indicates that nutrient enrichment could enhance plant-derived contributions to SOC and microbial use efficiency. Copyright © 2016 Elsevier Ltd. All rights reserved.

Estimation of mercury background values in sediment and biota of the Bijagós archipelago, Guinea-Bissau.

PubMed

Coelho, J P; Monteiro, R J R; Catry, T; Lourenço, P M; Catry, P; Regalla, A; Catry, I; Figueira, P; Pereira, E; Vale, C; P Granadeiro, José

2016-10-15

This work evaluates the mercury (Hg) contamination status (sediments and biota) of the Bijagós archipelago, off the coast of Guinea-Bissau. Sediments exhibited very low concentrations (<1-12ngg(-1)), pointing to negligible sources of anthropogenic Hg in the region. Nevertheless, Hg is well correlated to the fine fraction, aluminium, and loss on ignition, indicating the effect of grain size and organic matter content on the presence of Hg in sediments. Mercury in the bivalves Tagelus adansoni and Senilia senilis did not vary considerably among sites, ranging within narrow intervals (0.09-0.12 and 0.12-0.14μgg(-1) (dry weight), respectively). Divergent substrate preferences/feeding tactics may justify slight differences between species. The value 11ngg(-1) is proposed as the sediment background concentration for this West-African coastal region, and concentrations within the interval 8-10ngg(-1) (wet weight) may be considered as reference range for S. senilis and T. adansoni in future monitoring studies. Copyright © 2016 Elsevier Ltd. All rights reserved.

The system controlling the composition of clastic sediments

USGS Publications Warehouse

Johnsson, Mark J.

1993-01-01

The composition of clastic sediments and rocks is controlled by a complex suite of parameters operating during pedogenesis, erosion, transport, deposition, and burial. The principal first-order parameters include source rock composition, modification by chemical weathering, mechanical disaggregation and abrasion, authigenic inputs, hydrodynamic sorting, and diagenesis. Each of these first-order parameters is influenced to varying degrees by such factors as the tectonic settings of the source region, transportational system and depositional environment, climate, vegetation, relief, slope, and the nature and energy of transportational and depositional systems. These factors are not independent; rather a complicated web of interrelationships and feedback mechanisms causes many factors to be modulated by others. Accordingly, processes controlling the composition of clastic sediments are best viewed as constituting a system, and in evaluating compositional information the dynamics of the system must be considered as whole.

Hawaii Regional Sediment Management (RSM): Regional Sediment Budget for the West Maui Region

DTIC Science & Technology

2016-06-01

Increased sedimentation associated with loss of forest land, historical agriculture practices, stream channelization , and rapid development has...ER D C/ CH L TR -1 6- 5 Regional Sediment Management (RSM) Program Hawaii Regional Sediment Management (RSM): Regional Sediment Budget...acwc.sdp.sirsi.net/client/default. Regional Sediment Management (RSM) Program ERDC/CHL TR-16-5 June 2016 Hawaii Regional Sediment Management

Effects of Chinese Deforestation and Reforestation Policies on Sediment Sourcing in Yunnan, China

NASA Astrophysics Data System (ADS)

Henck Schmidt, A. C.; Bierman, P. R.; Sosa-Gonzalez, V.; Neilson, T. B.; Singleton, A.; Qiu, Y.; Bower, J.; Rood, D. H.

2015-12-01

Widespread deforestation from the 1960s through 1980s, blamed for catastrophic flooding in the lower Yangtze in 1998, prompted bans on logging and agriculture on steep slopes in western China. However, despite reports of extensive erosion resulting from the deforestation, sediment yield data show no corresponding increase during this time. Prior work suggested that if the deforestation increased erosion, the sediment is stored in floodplains, terraces, and alluvial fans throughout the region. In order to test this hypothesis, we sampled in-channel and overbank sediments at 38 locations, 19 of which are co-located with Chinese hydrology stations with at least five years of daily sediment yield data. Sediments were analyzed for meteoric and in situ 10-Be, unsupported 210-Pb, and 137-Cs. Unsupported 210-Pb activity is uniformly low throughout the study area and 137-Cs was found only in a few high-altitude, low-relief watersheds. Modern sediment yields, determined from Chinese data, are higher than long term in situ 10-Be-derived erosion rates in all but four watersheds, where we hypothesize sediment is being stored in alluvial features and agricultural terraces or that stochastic events such as landslides were not captured in the sediment yield data. Overall there is no relationship between topographic or climatic metrics, including slope, relief, or mean annual rainfall for any of the four isotopes except for a weak but statistically significant negative relationship between in situ 10-Be derived erosion rate and rainfall. Although paired in-channel and overbank samples are statistically indistinguishable for meteoric and in situ 10-Be, the overbank samples have lower unsupported 210-Pb activity, suggesting deeper sediment sourcing during the monsoon. In summary, in addition to suggesting differences between wet- and dry-season sediment sources, preliminary results support previous hypotheses regarding increased contemporary erosion and low hillslope-channel connectivity.

Holocene Depositional History of the Southern New Jersey Barrier and Backbarrier Regions

DTIC Science & Technology

1990-02-01

1954) that the continental shelf is a source for beach sediment. 25. Biederman (1962) and Charlesworth (1968) compared sediments along- shore and...perpendicular to the coast in a number of barrier and backbarrier environments. Biederman (1962) found that mean grain size decreased from north to south...Geology and Stratigraphic Preser- vation Potential and Evolution of Delaware’s Barrier Systems," Marine Geology. Vol 63, pp 235-262. Biederman , E. W

Radioactive fallout reconstruction from contemporary measurements of reservoir sediments.

PubMed

Krey, P W; Heit, M; Miller, K M

1990-11-01

The temporal history of atmospheric deposition to a watershed area can be preserved in the sediment of a lake or reservoir that is supplied by the watershed. The 137Cs and isotopic Pu concentrations with depth were determined in the sediments of two reservoirs, Enterprise and Deer Creek, which are located in widely separated regions of the state of Utah. Our data not only reconstruct the history of the total radioactive fallout in the area, but also permit estimating the contributions from global sources and from the Nevada Test Site detonations in the 1950s.

Geoacoustic Characterization of the Mud Drape at the New England Mud Patch

NASA Astrophysics Data System (ADS)

Reed, A. H.

2016-02-01

The New England Mud Patch is an extensive deposit of fine-grained sediments that extends from an area south of Cape Cod, MA to south of Montauk Point Long Island, NY out on the continental shelf in water depths of 60 to 90 meters. The mud patch has a remarkable accumulation of up to a 13 meter thick sequence of mud that overlays a transgressive surface of Pleistocene Age and then thins out on the periphery where surficial sediments convert from mud to sand and sand/gravel. The deposit likely accumulated in this region due to the coalescing of shelf currents that had oppositional flow. This work focuses on a section of the mud patch that is centered over the thickest portion of mud and extends east-west for 30 km and north south for 10 km. Gravity cores were collected throughout this region and the cores penetrated the upper 2-4 m of mud at 28 different sites with multiple cores collected in several locations. The mud thickness in these regions exceeded the core barrel length, therefore the cores did not penetrate into the basal sand sediment layer, a relict transgressional horizon, which displays prominently in the acoustic data for this selected region. These cores were evaluated for compressional sound speed (averaging 1480 m/s) and density (1580 kg/m3) and found to be largely homogeneous and similar throughout the study area. The largest source of inhomogeneity was due to dispersed shell hash and disarticulated bivalves, but these inclusions represent minor components in the total sediment volume. The overlying sediment that characterizes the New England Mud Patch can be readily classified as mud, silty mud, or sandy-silty mud. This fine-grained sediment deposit reflects upon the low-energy nature of the hydrodynamics within this region.

A sediment-dispersal model for the South Texas continental shelf, northwest Gulf of Mexico

USGS Publications Warehouse

Shideler, G.L.

1978-01-01

Textural-distribution patterns of sea-floor sediments on the South Texas continental shelf between Matagorda Bay and the U.S.-Mexico international boundary were evaluated as part of a regional environmental-studies program. Sediment textural gradients support a conceptual model for the regional sediment-dispersal system, which is characterized by both net offshore transport and net south-trending coastwise transport components on a wind-dominated shelf. Coastwise transport results in the net southward migration of both palimpsest sandy mud composing the ancestral Brazos-Colorado delta flank in the northern sector, and modern mud composing the central sector; these migrating sediments are encroaching southward onto immobile relict muddy sands composing the ancestral Rio Grande delta in the southern sector. In the proposed model, the suspension transport of modern silt-enriched mud derived mainly from coastal sources is the dominant dispersal mechanism. Net offshore transport is attributed both to diffusion, and to the advective ebb-tide discharge of turbid lagoonal-estuarine waters from coastal inlets. Net southward transport is attributed mainly to advection by seasonally residual coastwise drift currents reflecting a winter-dominated hydraulic regime. Frequent winter storms characterized by relatively high-speed northerly winds that accompany the passage of cold fronts appear to be dominant regional dispersal agents. ?? 1978.

Mercury and methylmercury in water and sediment of the Sacramento River Basin, California

USGS Publications Warehouse

Domagalski, Joseph L.

2001-01-01

Mercury (Hg) and methylmercury (CH3Hg+) concentrations in streambed sediment and water were determined at 27 locations throughout the Sacramento River Basin, CA. Mercury in sediment was elevated at locations downstream of either Hg mining or Au mining activities where Hg was used in the recovery of Au. Methylmercury in sediment was highest (2.84 ng/g) at a location with the greatest wetland land cover, in spite of lower total Hg at that site relative to other river sites. Mercury in unfiltered water was measured at 4 locations on the Sacramento River and at tributaries draining the mining regions, as well as agricultural regions. The highest levels of Hg in unfiltered water (2248 ng/l) were measured at a site downstream of a historic Hg mining area, and the highest levels at all sites were measured in samples collected during high streamflow when the levels of suspended sediment were also elevated. Mercury in unfiltered water exceeded the current federal and state recommended criterion for protection of aquatic life (50 ng/l as total Hg in unfiltered water) only during high streamflow conditions. The highest loading of Hg to the San Francisco Bay system was attributed to sources within the Cache Creek watershed, which are downstream of historic Hg mines, and to an unknown source or sources to the mainstem of the Sacramento River upstream of historic Au mining regions. That unknown source is possibly associated with a volcanic deposit. Methylmercury concentrations also were dependent on season and hydrologic conditions. The highest levels (1.98 ng/l) in the Sacramento River, during the period of study, were measured during a major flood event. The reactivity of Hg in unfiltered water was assessed by measuring the amount available for reaction by a strong reducing agent. Although most Hg was found to be nonreactive, the highest reactivity (7.8% of the total Hg in water) was measured in the sample collected from the same site with high CH3Hg+ in sediment, and during the time of year when that site was under continual flooded conditions. Although Hg concentrations in water downstream of the Hg mining operations were measured as high as 2248 ng/l during stormwater runoff events, the transported Hg was found to have a low potential for geochemical transformations, as indicated by the low reactivity to the reducing agent (0.0001% of the total), probably because most of the Hg in the unfiltered water sample was in the mercury sulfide form.

Distribution of biologic, anthropogenic, and volcanic constituents as a proxy for sediment transport in the San Francisco Bay Coastal System

USGS Publications Warehouse

McGann, Mary; Erikson, Li H.; Wan, Elmira; Powell, Charles; Maddocks, Rosalie F.; Barnard, P.L.; Jaffee, B.E.; Schoellhamer, D.H.

2013-01-01

Although conventional sediment parameters (mean grain size, sorting, and skewness) and provenance have typically been used to infer sediment transport pathways, most freshwater, brackish, and marine environments are also characterized by abundant sediment constituents of biological, and possibly anthropogenic and volcanic, origin that can provide additional insight into local sedimentary processes. The biota will be spatially distributed according to its response to environmental parameters such as water temperature, salinity, dissolved oxygen, organic carbon content, grain size, and intensity of currents and tidal flow, whereas the presence of anthropogenic and volcanic constituents will reflect proximity to source areas and whether they are fluvially- or aerially-transported. Because each of these constituents have a unique environmental signature, they are a more precise proxy for that source area than the conventional sedimentary process indicators. This San Francisco Bay Coastal System study demonstrates that by applying a multi-proxy approach, the primary sites of sediment transport can be identified. Many of these sites are far from where the constituents originated, showing that sediment transport is widespread in the region. Although not often used, identifying and interpreting the distribution of naturally-occurring and allochthonous biologic, anthropogenic, and volcanic sediment constituents is a powerful tool to aid in the investigation of sediment transport pathways in other coastal systems.

Quantifying Post-Fire Aeolian Sediment Transport Using Rare Earth Element Tracers.

NASA Astrophysics Data System (ADS)

Dukes, D.; Ravi, S.; Grandstaff, D. E.; Gonzales, H. B.; Li, J. J.; Sankey, J. B.; Wang, G.; Van Pelt, R. S.

2016-12-01

Grasslands and rangelands in arid and semi-arid regions of the world, which provide fundamental ecosystem services, are undergoing rapid increases in fire activity and are highly susceptible to post-fire accelerated soil erosion by wind. A quantitative assessment that integrates fire-wind erosion feedbacks is therefore critically needed in understanding vegetation change, soil biogeochemical cycling, air quality, and landscape evolution. We investigated the applicability of a novel tracer technique - the use of rare earth element (REE) tracers - to quantify soil erosion by wind and to identify sources and sinks of wind-blown sediments in both a burned and unburned shrub-grass transition zone within the Chihuahuan desert (New Mexico, USA). At the beginning of the windy season, March 2016, silt and sand sized particles in shrub, grass, and bare microsites were each tagged with a unique REE oxide, Ho, Eu, and Yb respectively. Samples were then taken directly after application prior to a prescribed fire and again at the end of the windy season in June 2016. All REE tracers showed signs of depletion and mixing, with the depletion in the burned site up to 20% greater than the unburned. REE concentration comparisons between the burned and unburned plots reveal a shift in the source and sink dynamics of sediment post fire. In unburned plots, changes in microsite REE concentrations indicate that sediment moved from the bare to vegetated microsites, whereas the opposite occurred in burned plots. However, burned plot grass microsites acted as a sink for sediment from shrub microsites, whereas unburned plot grass microsites exhibited no enrichment from shrub microsite-sourced sediment. Though fires are known to immediately increase aeolian sediment transport, accompanying changes in the sources and sinks of wind borne sediment may influence biogeochemical cycling and vegetation shifts possibly providing a feedback mechanism for land degradation in dryland ecosystems.

New Zealand as a Potential Source of Mineral Dust to the Atmosphere and Ocean during Glacial Periods

NASA Astrophysics Data System (ADS)

Koffman, B. G.; Goldstein, S. L.; Winckler, G.; Kaplan, M. R.; Bolge, L.; Cai, Y.; Recasens, C.; Koffman, T. N. B.

2017-12-01

The geochemical composition of sediments and dust can be used to trace their provenance, thereby providing insights into a range of Earth surface processes. During past glacial climates, much of the South Island of New Zealand (NZ) was blanketed by temperate erosive glacier systems, which significantly would have enhanced sediment production, including from associated active outwash plains. Such glacially-derived mineral dust from NZ may have impacted climate and ecological systems. In addition, dust and sediment can be used to trace downstream aeolian and oceanic transport. To this end, we systematically characterized the geochemical compositions of likely sediment- and dust-producing regions from the NZ South Island. We observe a strong relationship between sediment geochemical composition and geologic setting. Specifically, sediments from the central South Island, including the Canterbury Plains and Mackenzie Basin, where glaciers eroded mainly the Torlesse Greywacke, have a relatively homogenous isotopic composition, with 87Sr/86Sr = 0.7095-0.7165, ɛNd = -6.5 to -4.0, 206Pb/204Pb = 18.75-19.04, 207Pb/204Pb = 15.65-15.68, 208Pb/204Pb = 38.68-38.93. Southern South Island sediment sources, including southern Otago and Southland, show younger crust formation ages and more variable Sr and Nd isotopic compositions, reflecting the presence of Paleozoic volcanic complexes. Here 87Sr/86Sr = 0.7041-0.7140, ɛNd = -4.0 to +5.3, 206Pb/204Pb = 18.71-18.92, 207Pb/204Pb = 15.62-15.65, 208Pb/204Pb = 38.44-38.87. During the Last Glacial Maximum (LGM), glacial outwash and associated fluvial systems downstream were greatly expanded relative to present day, which could have provided regions for dust deflation - especially given a sea level lowering of 130 m. Due to processes linked to glaciations and lower sea levels, we suggest that the NZ South Island, though limited in extent compared to larger southern landmasses, may still have served as an important source of detritus during ice age climates.

Impact of Increased Thermokarst Activity on Polycyclic Aromatic Compound (PAC) Accumulation in Sediment of Lakes in the Hydrocarbon-Rich Uplands Adjacent to the Mackenzie Delta, NT, Canada

NASA Astrophysics Data System (ADS)

Eickmeyer, D.; Thienpont, J. R.; Blais, J. M.

2017-12-01

In ecologically sensitive, hydrocarbon-rich regions like the western Canadian Arctic, environmental monitoring of oil and gas development often focuses on both direct and unintentional consequences of increased exploration and extraction of hydrocarbon resources. However, proper assessments of impact from these activities could be confounded by natural petrogenic sources in permafrost-rich regions where increased thermokarst activity results in permafrost exposure and erosion of hydrocarbon-rich deposits. Using a paired-lake design in the tundra uplands adjacent to the Mackenzie Delta, NT, we examined 4 lakes with retrogressive thaw slump scars along their shores, and 4 nearby undisturbed reference lakes, focusing on polycyclic aromatic compound (PAC) deposition and composition in the sediment. Total organic carbon (TOC)-normalized concentrations for parent and alkylated PACs were higher in surface sediments of slump-affected lakes than the reference lakes. This followed the pattern previously observed for persistent organic pollutants in these lakes where presence of thaw slumps on the lake shore was associated with lower TOC content in the water column, resulting in a smaller pool of available organic carbon, leading to higher PAC concentrations. Diagnostic ratios of specific PACs also suggested the sediment of slump-affected lakes had greater influence from petroleum-based PAC sources than their reference counterparts. This interpretation was corroborated by a principle components analysis of the metal content in the sediment. Slump-affected lakes were enriched in metals related to shale-based, Quaternary deposits of the Mackenzie Basin (e.g. Ca, Sr, Mg) when compared to reference lakes where these surficial materials were not exposed by thermokarst activity. Higher PAC concentrations and composition indicative of petrogenic sources observed in sediment of slump-affected lakes were best explained as a combination of low TOC availability and increased inputs of previously bound hydrocarbons from the catchment due to permafrost erosion. These findings demonstrate that, to avoid misinterpreting the scale and nature of the impact of hydrocarbon development in northern landscapes, monitoring of sediment PACs must be assessed in the proper framework of these dynamic freshwater systems.

Direct atmospheric deposition of 210Pb to rivers determined through 210Pb (210Po) disequilibrium and implications to sediment source apportionment

NASA Astrophysics Data System (ADS)

Blumentritt, D. J.; Shottler, S.; Engstrom, D. R.

2011-12-01

Atmospheric radioisotopes such as 210Pb can be an effective tool for determining sediment source types in rivers and streams. Pb-210 is ubiquitous in deposition from atmospheric washout and is highly particle reactive, so sediments derived from a surface with prolonged exposure to rainfall, such as farm fields, are enriched in atmospheric 210Pb. Conversely, sediment sources that are not readily exposed to rainfall (i.e. streambanks) are absent of any appreciable 210Pb. Many sediment source apportionment studies have used 210Pb to quantify the proportion of sediment loads from the two source types, field and non-field. These studies, however, primarily take place in smaller watersheds where 210Pb that falls directly onto the surface of the water is assumed negligible. Lake Pepin is a riverine lake located in southeastern Minnesota with a 122,000 km2 watershed composed of three major rivers, the Minnesota, headwaters Mississippi, and St. Croix. The sediment load in Lake Pepin has increased by an order of magnitude since Euro-American settlement in the region. Most of the sediment (>80%) is transported to Lake Pepin from the highly agricultural Minnesota River basin. Extensive sediment fingerprinting work has been done on Lake Pepin sediments, but a source of significant uncertainty still exists: How much of the 210Pb measured in Lake Pepin is directly deposited to the surface of the contributing water bodies and did not enter on eroded particles? To answer this important question, we have developed a method to quantify the amount of directly deposited 210Pb. Alpha spectrometry is used to measure 210Po, a daughter product of 210Pb decay. Because 210Po has a short half-life (138 days), it takes approximately one year to reach equilibrium with 210Pb on sediment particles. If deposition of 210Pb directly from the atmosphere to the water surface is significant, there will be disequilibrium between the two radioisotopes and the activity of 210Po will increase as an inverse exponential function, with respect to time, following sample collection. The magnitude of this increase is the amount of directly deposited 210Pb. Samples were collected at four locations, corresponding to gauging stations, on the Minnesota/Mississippi River system above Lake Pepin. Three measurements were made on each sample over the course of a year after collection. Based on those three measurements, the activity of 210Po was modeled for time zero and for the equilibrium concentration, revealing the amount of 210Pb from direct atmospheric deposition. These estimates were flow-weighted over the course of the year, providing a critical correction to the source apportionment model.

Distribution and source analysis of heavy metal pollutants in sediments of a rapid developing urban river system.

PubMed

Xia, Fang; Qu, Liyin; Wang, Ting; Luo, Lili; Chen, Han; Dahlgren, Randy A; Zhang, Minghua; Mei, Kun; Huang, Hong

2018-09-01

Heavy metal pollution of aquatic environments in rapidly developing industrial regions is of considerable global concern due to its potential to cause serious harm to aquatic ecosystems and human health. This study assessed heavy metal contamination of sediments in a highly industrialized urban watershed of eastern China containing several historically unregulated manufacturing enterprises. Total concentrations and solid-phase fractionation of Cu, Zn, Pb, Cr and Cd were investigated for 39 river sediments using multivariate statistical analysis and geographically weighted regression (GWR) methods to quantitatively examine the relationship between land use and heavy metal pollution at the watershed scale. Results showed distinct spatial patterns of heavy metal contamination within the watershed, such as higher concentrations of Zn, Pb and Cd in the southwest and higher Cu concentration in the east, indicating links to specific pollution sources within the watershed. Correlation and PCA analyses revealed that Zn, Pb and Cd were dominantly contributed by anthropogenic activities; Cu originated from both industrial and agricultural sources; and Cr has been altered by recent pollution control strategies. The GWR model indicated that several heavy metal fractions were strongly correlated with industrial land proportion and this correlation varied with the level of industrialization as demonstrated by variations in local GWR R 2 values. This study provides important information for assessing heavy metal contaminated areas, identifying heavy metal pollutant sources, and developing regional-scale remediation strategies. Copyright © 2018 Elsevier Ltd. All rights reserved.

Turbulent Suspension Mechanics in Sediment-Laden Boundary Layers

NASA Astrophysics Data System (ADS)

Kiger, K.

2013-05-01

Accurate prediction of benthic sediment transport is a challenging problem due the two-phase nature of the flow near the mobile bed, as well as the large difference in scales between the meso-scale flow and smaller-scale structures interacting with the sediment bed. Of particular importance is the parameterization of the physics at the bottom boundary. This requires estimation of key quantities such as effective bed stress and sediment flux based on the on the outer regional-scale velocity field. An appropriate turbulence/sediment parameterization is needed to specify the correct bottom momentum and sediment flux. Prior work has shown the shortcoming of standard models to properly predict such behavior, which is speculated to result from the dominant role played by large-scale coherent structures in the generation of the bed morphology, suspension of particulates, and important particle-fluid coupling effects. The goal of the current work is to elucidate such relationships through a combination of direct simulation and laboratory-scale experiment, the latter of which will be the primary focus of this paper. Specifically, two-phase PIV is used to provide a novel quantitative description of both phases, allowing for a detailed examination of the flow behavior and particle-turbulence coupling. Experiments were conducted in both a steady, fully-developed turbulent channel flow and an oscillatory boundary layer in order to examine the fundamental behaviour of the suspension and particle coupling mechanisms. The turbulent channel flow measurements indicated an increase in the effective wall stress due to the presence of the sediment on the order of 7%. The sediment suspension was directly correlated with the ejection dynamics of prototypical hairpin structures, but were found to settle back towards the bed in a manner uncorrelated with the fluid structure. In contrast, the measurements of the oscillatory flow reveal it to be dominated by alternating streaming motions and the ejection of a large-scale vortex at flow reversal. The vortex formation is initiated by the separation from the lee side of the dune during the relaxation of the favourable pressure gradient approaching the peak velocity. Through the deceleration phase, the recirculation region strengthens and grows, detaching into a free vortex as flow reversal is approached. Examining the fluctuating component of Reynolds stress show the vortex to be the dominant source of turbulent transport into the outer flow, which gradually decays as it is transported over the dunes. This vortex is also seen to be the major source of sediment transport into the outer flow region, with the time-averaged sediment flux streaming in a recirculating pattern emanating from the dune crests. The recirculation region is continually populated by particles scoured from the high-shear region on the upstream stoss slope, and upon flow reversal are ejected into the outer flow. Comparison of particle a fluid velocity shows significant slip in the vortex/particle cloud, with the particles settling relative to the fluid at close to 2 cm/s. In other regions of the flow, the mean slip magnitude is generally small, but negative, as one might expect owing to the net settling influence exerted by gravity.

Giant landslides and turbidity currents in the Agadir Canyon Region, NW-Africa

NASA Astrophysics Data System (ADS)

Krastel, Sebastian; Wynn, Russell B.; Stevenson, Christopher; Feldens, Peter; Mehringer, Lisa; Schürer, Anke

2017-04-01

Coring and drilling of the Moroccan Turbidite System off NW-Africa revealed a long sequence of turbidites, mostly sourced from the Moroccan continental margin and the volcanic Canary Islands. The largest individual flow deposits in the Moroccan Turbidite System contain sediment volumes >100 km3, although these large-scale events are relatively infrequent with a recurrence interval of 10,000 years (over the last 200,000 years). The largest siliciclastic flow in the last 200,000 years was the 'Bed 5 event', which transported 160 km3 of sediment up to 2000 km from the Agadir Canyon region to the southwest Madeira Abyssal Plain. While the Moroccan Turbidite System is extremely well investigated, almost no data from the source region, i.e. the Agadir Canyon, are available. Understanding why some submarine landslides remain as coherent blocks of sediment throughout their passage downslope, while others mix and disintegrate almost immediately after initial failure, is a major scientific challenge, which was addressed in the Agadir Canyon source region during RV Maria S. Merian Cruise MSM32 in late 2013. A major landslide area was identified 200 km south of the Agadir Canyon. A landslide was traced from this failure area to the Agadir Canyon. This landslide entered the canyon in about 2500 m water depth. Despite a significant increase in slope angle, the landslide did not disintegrate into a turbidity current when entering the canyon but moved on as landslide for at least another 200 km down the canyon. The age of the landslide ( 145 ka) does not correspond to any major turbidte deposit in the Moroccan Turbidite System, further supporting the fact that the landslide did not disintegrate into a major turbidity current. A core taken about 350 m above the thalweg in the head region of Agadir Canyon shows a single coarse-grained turbidite, which resembles the composition of the Bed 5 event in the Madeira Abyssal Plain. Hence, the Bed 5 turbidite originated as a failure in the head region of the Agadir Canyon. Interestingly, this failure did not leave a major landslide scarp behind suggesting a small initial failure despite the large-volume deposits in the Madeira Abyssal Plain. The turbidity current must have eroded and incorporated huge amounts of sediments while traveling through the canyon.

Natural and Human Impacts on the Coastal Environment of Taiwan Recorded in Marine Sediments During the last century

NASA Astrophysics Data System (ADS)

Li, H.; Chen, Z.; Huh, C.; Chen, K.; Lin, Y.; Hsu, F.

2012-12-01

Located at tropical-to-subtropical region on the Pacific rim, Taiwan has very high erosion rate due to steep topography and heavy rainfall especially typhoons. The high sedimentation rates in Taiwan Strait allow us to retrieve high-resolution marine records which reveal natural changes and human impacts on the coastal environment of Taiwan over the past 100 years. Five gravity and box cores well dated by 210Pb and 137Cs methods were analyzed for elemental concentrations in the acid-leachable phase, total organic carbon (TOC), δ13CTOC, δ13C and δ18O of carbonates. The results show that: (1) Positive correlation between TOC and typhoon rainfall since 1940 indicate that decline of vegetation coverage resulted in intensification of soil erosion. The δ13CTOC values illustrate that the organic carbon in the sediments was originated mainly from land input. (2) The δ18O difference between foraminiferal shells and carbonate grains can be used for rainfall reconstruction. (3) The Ca concentrations mainly from carbonates in the sediments were decreased since AD 1940, reflecting changes in sedimentary source and ocean acidfication. As development of the land use, more and more soil erosion caused depletion of authigenic marine sediments in the coast region. Ocean acidification led to less carbonate formation in seawater. (4) Since 1920, Pb concentration rapidly increased and peaked at ~1970 as Pb input from gasoline usage. Pb concentration dropped from 1970 to 1975 perhaps due to unleaded gasoline replacement. (5) In the nearshore environment, heavy metals such as Mn, Cu and Pb in the acid-leachable phase of the sediments strongly increased from 1950 to 1965 then kept relatively high level, reflecting heavy metal contamination from industrial source. The human impact on the coastal region of Taiwan not only caused changes in marine sediments and ocean water, but also disturbed the marine ecosystem. This study has been funded by NSC-100-3113-E-002-009: Study of CO2 capture, conversion, storage and reuse through the coastal ocean of Taiwan: The biological pump.

Forest access roads: design, maintenance, and soil loss

Treesearch

Lloyd W. Swift

1988-01-01

The Regional Guide for,the South (United States Department of Agriculture 1984b) recognizes that roads and skid trails are the major sources of sediment from forestry-related activities. The overall environmental impact statement for Region 8 (United States Department of Agriculture 1984a) estimates an existing national forest road network of 56,300 km (3 1,000 miles)...

Vertical profile, source apportionment, and toxicity of PAHs in sediment cores of a wharf near the coal-based steel refining industrial zone in Kaohsiung, Taiwan.

PubMed

Chen, Chih-Feng; Chen, Chiu-Wen; Ju, Yun-Ru; Dong, Cheng-Di

2016-03-01

Three sediment cores were collected from a wharf near a coal-based steel refining industrial zone in Kaohsiung, Taiwan. Analyses for 16 polycyclic aromatic hydrocarbons (PAHs) of the US Environmental Protection Agency priority list in the core sediment samples were conducted using gas chromatography-mass spectrometry. The vertical profiles of PAHs in the core sediments were assessed, possible sources and apportionment were identified, and the toxicity risk of the core sediments was determined. The results from the sediment analyses showed that total concentrations of the 16 PAHs varied from 11774 ± 4244 to 16755 ± 4593 ng/g dry weight (dw). Generally, the vertical profiles of the PAHs in the sediment cores exhibited a decreasing trend from the top to the lower levels of the S1 core and an increasing trend of PAHs from the top to the lower levels of the S2 and S3 cores. Among the core sediment samples, the five- and six-ring PAHs were predominantly in the S1 core, ranging from 42 to 54 %, whereas the composition of the PAHs in the S2 and S3 cores were distributed equally across three groups: two- and three-ring, four-ring, and five- and six-ring PAHs. The results indicated that PAH contamination at the site of the S1 core had a different source. The molecular indices and principal component analyses with multivariate linear regression were used to determine the source contributions, with the results showing that the contributions of coal, oil-related, and vehicle sources were 38.6, 35.9, and 25.5 %, respectively. A PAH toxicity assessment using the mean effect range-median quotient (m-ERM-q, 0.59-0.79), benzo[a]pyrene toxicity equivalent (TEQ(carc), 1466-1954 ng TEQ/g dw), and dioxin toxicity equivalent (TEQ(fish), 3036-4174 pg TEQ/g dw) identified the wharf as the most affected area. The results can be used for regular monitoring, and future pollution prevention and management should target the coal-based industries in this region for pollution reduction.

Determining the sources of fine-grained sediment using the Sediment Source Assessment Tool (Sed_SAT)

USGS Publications Warehouse

Gorman Sanisaca, Lillian E.; Gellis, Allen C.; Lorenz, David L.

2017-07-27

A sound understanding of sources contributing to instream sediment flux in a watershed is important when developing total maximum daily load (TMDL) management strategies designed to reduce suspended sediment in streams. Sediment fingerprinting and sediment budget approaches are two techniques that, when used jointly, can qualify and quantify the major sources of sediment in a given watershed. The sediment fingerprinting approach uses trace element concentrations from samples in known potential source areas to determine a clear signature of each potential source. A mixing model is then used to determine the relative source contribution to the target suspended sediment samples.The computational steps required to apportion sediment for each target sample are quite involved and time intensive, a problem the Sediment Source Assessment Tool (Sed_SAT) addresses. Sed_SAT is a user-friendly statistical model that guides the user through the necessary steps in order to quantify the relative contributions of sediment sources in a given watershed. The model is written using the statistical software R (R Core Team, 2016b) and utilizes Microsoft Access® as a user interface but requires no prior knowledge of R or Microsoft Access® to successfully run the model successfully. Sed_SAT identifies outliers, corrects for differences in size and organic content in the source samples relative to the target samples, evaluates the conservative behavior of tracers used in fingerprinting by applying a “Bracket Test,” identifies tracers with the highest discriminatory power, and provides robust error analysis through a Monte Carlo simulation following the mixing model. Quantifying sediment source contributions using the sediment fingerprinting approach provides local, State, and Federal land management agencies with important information needed to implement effective strategies to reduce sediment. Sed_SAT is designed to assist these agencies in applying the sediment fingerprinting approach to quantify sediment sources in the sediment TMDL framework.

Verifying Sediment Fingerprinting Results with Known Mixtures

NASA Astrophysics Data System (ADS)

Gellis, A.; Gorman-Sanisaca, L.; Cashman, M. J.

2017-12-01

Sediment fingerprinting is a widely used approach to determine the specific sources of fluvial sediment within a watershed. It relies on the principle that potential sediment sources can be identified using a set of chemical tracers (or fingerprints), and comparison of these source fingerprints with fluvial (target) sediment allows for source apportionment of the fluvial sediment. There are numerous source classifications, fingerprints, and statistical approaches used in the literature to apportion sources of sediment. However, few of these studies have sought to test the method by creating controls on the ratio of sources in the target sediment. Without a controlled environment for inputs and outputs, such verification of results is ambiguous. Here, we generated artificial mixtures of source sediment from an agricultural/forested watershed in Virginia, USA (Smith Creek, 246 km2) to verify the apportionment results. Target samples were established from known mixtures of the four major sediment sources in the watershed (forest, pasture, cropland, and streambanks). The target samples were sieved to less than 63 microns and analyzed for elemental and isotopic chemistry. The target samples and source samples were run through the Sediment Source Assessment Tool (Sed_SAT) to verify if the statistical operations provided the correct apportionment. Sed_SAT uses a multivariate parametric approach to identify the minimum suite of fingerprints that discriminate the source areas and applies these fingerprints through an unmixng model to apportion sediment. The results of this sediment fingerprinting verification experiment will be presented in this session.

Tidal and flood signatures of settling particles in the Gaoping submarine canyon (SW Taiwan) revealed from radionuclide and flow measurements

USGS Publications Warehouse

Huh, C.-A.; Liu, J.T.; Lin, H.-L.; Xu, J. P.

2009-01-01

Sediment transport and sedimentation processes in the Gaoping submarine canyon were studied using sediment trap and current meter moorings deployed at a location during the winter (January-March) and the summer (July-September) months in 2008. At the end of each deployment, sediment cores were also collected from the canyon floor at the mooring site. Samples from sediment traps and sediment cores were analyzed for 210Pb and 234Th by gamma spectrometry. In conjunction with particle size and flow measurements, the datasets suggest that sediment transport in the canyon is tidally-modulated in the drier winter season and flood (river)-dominated in the wetter summer season. From the magnitude and temporal variation of sediment flux in the canyon with respect to the burial flux and sediment budget on the open shelf and slope region, we reaffirm that, on annual or longer timescales, the Gaoping submarine canyon is an effective conduit transporting sediments from the Gaoping River's drainage basin (the source) to the deep South China Sea (the ultimate sink). ?? 2009 Elsevier B.V.

Paleoclimatic and Paleoceanographic Holocene Sedimentary Records in the Gulf of California - Eastern Pacific Ocean Interhemispheric Connections

NASA Astrophysics Data System (ADS)

Perez-Cruz, L.; Urrutia-Fucugauchi, J.

2009-05-01

Initial results of a study on the distribution, thickness and stratigraphy of the sedimentary sequences in the Gulf of California are presented. The Gulf is an elongated narrow young oceanic basin bordered by the Baja California peninsula and mainland Mexico. The Gulf extends over 1200 km across the Tropic of Cancer from the tropical to the temperate zones, surrounded by arid and semi-arid regions, including the Sonora-Mojave Desert. Paleoceanographic conditions are dominated by water exchange at the Gulf mouth and water masses changes along the Gulf. Tectonic basins reach down in excess of 3000 m depths and get shallower to the north. Here we focus on the Holocene sediment sequences in the southern sector, which contains several marginal and central anoxic basins that constitute rich archives of paleoclimatic and paleoenvironmental evolution for the past 3.6 Ma. In the mouth area, main sources of sediments are silicic volcanic and intrusive rocks in the Baja peninsula and mainland, including Los Cabos and Puerto Vallarta batholiths. Fine-grained eolian dusts, pluvial and biogenic sediments are present in the sediment cores in the Gulf basins such as La Paz, Alfonso, Carmen, Pescadero and Guaymas basins. Turbiditic currents and tephra deposits also occur in the cores. Paleoclimatic records show the influences of regional processes, including the ENSO and PDO signals marked by drought and increased precipitation phases. Relative distribution and thickness of sediments at the mouth of the Gulf correlate with bathymetry and location with respect to spreading center, transform faults and margins of the peninsula and mainland Mexico. Rock magnetic core scans and mineralogy at few locations are available, which allow inferences on sediment sources, transport and deposition processes, diagenesis, paleoceanographic and paleoclimatic evolution for the Holocene.

From deposition to erosion: Spatial and temporal variability of sediment sources, storage, and transport in a small agricultural watershed

USGS Publications Warehouse

Florsheim, J.L.; Pellerin, B.A.; Oh, N.H.; Ohara, N.; Bachand, P.A.M.; Bachand, Sandra M.; Bergamaschi, B.A.; Hernes, P.J.; Kavvas, M.L.

2011-01-01

The spatial and temporal variability of sediment sources, storage, and transport were investigated in a small agricultural watershed draining the Coast Ranges and Sacramento Valley in central California. Results of field, laboratory, and historical data analysis in the Willow Slough fluvial system document changes that transformed a transport-limited depositional system to an effective erosion and transport system, despite a large sediment supply. These changes were caused by a combination of factors: (i) an increase in transport capacity, and (ii) hydrologic alteration. Alteration of the riparian zone and drainage network pattern during the past ~ 150 years included a twofold increase in straightened channel segments along with a baselevel change from excavation that increased slope, and increased sediment transport capacity by ~ 7%. Hydrologic alteration from irrigation water contributions also increased transport capacity, by extending the period with potential for sediment transport and erosion by ~ 6 months/year. Field measurements document Quaternary Alluvium as a modern source of fine sediment with grain size distributions characterized by 5 to 40% fine material. About 60% of an upland and 30% of a lowland study reach incised into this deposit exhibit bank erosion. During this study, the wet 2006 and relatively dry 2007 water years exhibited a range of total annual suspended sediment load spanning two orders of magnitude: ~ 108,500 kg/km2/year during 2006 and 5,950 kg/km2/year during 2007, only 5% of that during the previous year. Regional implications of this work are illustrated by the potential for a small tributary such as Willow Slough to contribute sediment – whereas large dams limit sediment supply from larger tributaries – to the Sacramento River and San Francisco Bay Delta and Estuary. This work is relevant to lowland agricultural river–floodplain systems globally in efforts to restore aquatic and riparian functions and where water quality management includes reducing fine sediment contributions that can couple with other pollutants.

Inferring tidal wetland stability from channel sediment fluxes: observations and a conceptual model

USGS Publications Warehouse

Ganju, Neil K.; Nidzieko, Nicholas J.; Kirwan, Matthew L.

2013-01-01

Anthropogenic and climatic forces have modified the geomorphology of tidal wetlands over a range of timescales. Changes in land use, sediment supply, river flow, storminess, and sea level alter the layout of tidal channels, intertidal flats, and marsh plains; these elements define wetland complexes. Diagnostically, measurements of net sediment fluxes through tidal channels are high-temporal resolution, spatially integrated quantities that indicate (1) whether a complex is stable over seasonal timescales and (2) what mechanisms are leading to that state. We estimated sediment fluxes through tidal channels draining wetland complexes on the Blackwater and Transquaking Rivers, Maryland, USA. While the Blackwater complex has experienced decades of degradation and been largely converted to open water, the Transquaking complex has persisted as an expansive, vegetated marsh. The measured net export at the Blackwater complex (1.0 kg/s or 0.56 kg/m2/yr over the landward marsh area) was caused by northwesterly winds, which exported water and sediment on the subtidal timescale; tidally forced net fluxes were weak and precluded landward transport of suspended sediment from potential seaward sources. Though wind forcing also exported sediment at the Transquaking complex, strong tidal forcing and proximity to a turbidity maximum led to an import of sediment (0.031 kg/s or 0.70 kg/m2/yr). This resulted in a spatially averaged accretion of 3.9 mm/yr, equaling the regional relative sea level rise. Our results suggest that in areas where seaward sediment supply is dominant, seaward wetlands may be more capable of withstanding sea level rise over the short term than landward wetlands. We propose a conceptual model to determine a complex's tendency toward stability or instability based on sediment source, wetland channel location, and transport mechanisms. Wetlands with a reliable portfolio of sources and transport mechanisms appear better suited to offset natural and anthropogenic loss.

Contaminant distribution and accumulation in the surface sediments of Long Island Sound

USGS Publications Warehouse

Mecray, E.L.; Buchholtz ten Brink, Marilyn R.

2000-01-01

The distribution of contaminants in surface sediments has been measured and mapped as part of a U.S. Geological Survey study of the sediment quality and dynamics of Long Island Sound. Surface samples from 219 stations were analyzed for trace (Ag, Ba, Cd, Cr, Cu, Hg, Ni, Pb, V, Zn and Zr) and major (Al, Fe, Mn, Ca, and Ti) elements, grain size, and Clostridium perfringens spores. Principal Components Analysis was used to identify metals that may covary as a function of common sources or geochemistry. The metallic elements generally have higher concentrations in fine-grained deposits, and their transport and depositional patterns mimic those of small particles. Fine-grained particles are remobilized and transported from areas of high bottom energy and deposited in less dynamic regions of the Sound. Metal concentrations in bottom sediments are high in the western part of the Sound and low in the bottom-scoured regions of the eastern Sound. The sediment chemistry was compared to model results (Signell et al., 1998) and maps of sedimentary environments (Knebel et al., 1999) to better understand the processes responsible for contaminant distribution across the Sound. Metal concentrations were normalized to grain-size and the resulting ratios are uniform in the depositional basins of the Sound and show residual signals in the eastern end as well as in some local areas. The preferential transport of fine-grained material from regions of high bottom stress is probably the dominant factor controlling the metal concentrations in different regions of Long Island Sound. This physical redistribution has implications for environmental management in the region.

Governing change: land-use change and the prevention of nonpoint source pollution in the north coastal basin of California.

PubMed

Short, Anne G

2013-01-01

Many rural areas in the United States and throughout much of the postindustrial world are undergoing significant ecological, socioeconomic, and political transformations. The migration of urban and suburban dwellers into rural areas has led to the subdivision of large tracts of land into smaller parcels, which can complicate efforts to govern human-environmental problems. Non-point source (NPS) pollution from private rural lands is a particularly pressing human-environmental challenge that may be aggravated by changing land tenure. In this article, I report on a study of the governance and management of sediment (a common NPS pollutant) in the North Coastal basin of California, a region undergoing a transition from traditional extractive and agricultural land uses to rural residential and other alternative land uses. I focus on the differences in the governance and management across private timber, ranch, residential, vacation, and other lands in the region. I find that (1) the stringency and strength of sediment regulations differ by land use, (2) nonregulatory programs tend to target working landscapes, and (3) rural residential landowners have less knowledge of sediment control and report using fewer sediment-control techniques than landowners using their land for timber production or ranching. I conclude with an exploration of the consequences of these differences on an evolving rural landscape.

Governing Change: Land-Use Change and the Prevention of Nonpoint Source Pollution in the North Coastal Basin of California

NASA Astrophysics Data System (ADS)

Short, Anne G.

2013-01-01

Many rural areas in the United States and throughout much of the postindustrial world are undergoing significant ecological, socioeconomic, and political transformations. The migration of urban and suburban dwellers into rural areas has led to the subdivision of large tracts of land into smaller parcels, which can complicate efforts to govern human-environmental problems. Non-point source (NPS) pollution from private rural lands is a particularly pressing human-environmental challenge that may be aggravated by changing land tenure. In this article, I report on a study of the governance and management of sediment (a common NPS pollutant) in the North Coastal basin of California, a region undergoing a transition from traditional extractive and agricultural land uses to rural residential and other alternative land uses. I focus on the differences in the governance and management across private timber, ranch, residential, vacation, and other lands in the region. I find that (1) the stringency and strength of sediment regulations differ by land use, (2) nonregulatory programs tend to target working landscapes, and (3) rural residential landowners have less knowledge of sediment control and report using fewer sediment-control techniques than landowners using their land for timber production or ranching. I conclude with an exploration of the consequences of these differences on an evolving rural landscape.

Quantifying relief on alluvial fans using airborne lidar to reveal patterns of sediment accumulation

NASA Astrophysics Data System (ADS)

Morelan, A. E., III; Oskin, M. E.

2017-12-01

We present a method of quantifying detailed surface relief on alluvial fans from high-resolution topography. Average slope and curvature of the fan are used together to empirically derive an idealized, radially symmetric fan surface, from which we compute residual topography. Maps produced using this technique highlight spatial patterns of fan deposition and avulsion. Regions of high residual topography reveal active and abandoned sediment lobes accumulated from recent depositional events, often with well-defined channels at their apex. Preliminary observations suggest that surface relief is uniform across a collection of fans in a given region and source lithology. Alluvial fans with granitic catchment lithologies in eastern California (n=12), each with varying source catchment size and mean fan slope, all show relief of around 4 meters. A collection of fans from the Carrizo Plain in central California (n=12), with source catchments set within Miocene marine and nonmarine sedimentary rocks, show significantly lower relief values around 2 meters. We hypothesize that particle grain size determines this contrasting relief through its control on the thickness of fan-building debris flows. In both settings we find that sediment lobes tend to extend toward the fan toe. This pattern supports a process, observed in analog experiments, of fan deposition dominated by back-filling and overtopping of distributary channels by debris-flows.

Assessment of heavy metals contamination in sediments from three adjacent regions of the Yellow River using metal chemical fractions and multivariate analysis techniques.

PubMed

Ma, Xiaoling; Zuo, Hang; Tian, Mengjing; Zhang, Liyang; Meng, Jia; Zhou, Xuening; Min, Na; Chang, Xinyuan; Liu, Ying

2016-02-01

Metal chemical fractions obtained by optimized BCR three-stage extraction procedure and multivariate analysis techniques were exploited for assessing 7 heavy metals (Cr, Pb, Cd, Co, Cu, Zn and Ni) in sediments from Gansu province, Ningxia and Inner Mongolia Autonomous Regions of the Yellow River in Northern China. The results indicated that higher susceptibility and bioavailability of Cr and Cd with a strong anthropogenic source were due to their higher availability in the exchangeable fraction. A portion of Pb, Cd, Co, Zn, and Ni in reducible fraction may be due to the fact that they can form stable complexes with Fe and Mn oxides. Substantial amount of Pb, Co, Ni and Cu was observed as oxidizable fraction because of their strong affinity to the organic matters so that they can complex with humic substances in sediments. The high geo-accumulation indexes (I(geo)) for Cr and Cd showed their higher environmental risk to the aquatic biota. Principal component analysis (PCA) revealed that high toxic Cr and Cd in polluted sites (Cd in S10, S11 and Cr in S13) may be contributed to anthropogenic sources, it was consistent with the results of dual hierarchical clustering analysis (DHCA), which could give more details about contributing sources. Copyright © 2015 Elsevier Ltd. All rights reserved.

Constraining Modern and Historic Mercury Emissions From Gold Mining

NASA Astrophysics Data System (ADS)

Strode, S. A.; Jaeglé, L.; Selin, N. E.; Sunderland, E.

2007-12-01

Mercury emissions from both historic gold and silver mining and modern small-scale gold mining are highly uncertain. Historic mercury emissions can affect the modern atmosphere through reemission from land and ocean, and quantifying mercury emissions from historic gold and silver mining can help constrain modern mining sources. While estimates of mercury emissions during historic gold rushes exceed modern anthropogenic mercury emissions in North America, sediment records in many regions do not show a strong gold rush signal. We use the GEOS-Chem chemical transport model to determine the spatial footprint of mercury emissions from mining and compare model runs from gold rush periods to sediment and ice core records of historic mercury deposition. Based on records of gold and silver production, we include mercury emissions from North and South American mining of 1900 Mg/year in 1880, compared to modern global anthropogenic emissions of 3400 Mg/year. Including this large mining source in GEOS-Chem leads to an overestimate of the modeled 1880 to preindustrial enhancement ratio compared to the sediment core record. We conduct sensitivity studies to constrain the level of mercury emissions from modern and historic mining that is consistent with the deposition records for different regions.

Aeolian process of the dried-up riverbeds of the Hexi Corridor, China: a wind tunnel experiment.

PubMed

Zhang, Caixia; Wang, Xunming; Dong, Zhibao; Hua, Ting

2017-08-01

Wind tunnel studies, which remain limited, are an important tool to understand the aeolian processes of dried-up riverbeds. The particle size, chemical composition, and the mineral contents of sediments arising from the dried river beds are poorly understood. Dried-up riverbeds cover a wide area in the Hexi Corridor, China, and comprise a complex synthesis of different land surfaces, including aeolian deposits, pavement surfaces, and Takyr crust. The results of the present wind tunnel experiment suggest that aeolian transport from the dried-up riverbeds of the Hexi Corridor ranges from 0 to 177.04 g/m 2 /min and that dry riverbeds could be one of the main sources of dust emissions in this region. As soon as the wind velocity reaches 16 m/s and assuming that there are abundant source materials available, aeolian transport intensity increases rapidly. The dried-up riverbed sediment and the associated aeolian transported material were composed mainly of fine and medium sands. However, the transported samples were coarser than the bed samples, because of the sorting effect of the aeolian processes on the sediment. The aeolian processes also led to regional elemental migration and mineral composition variations.

Contribution of phytoplankton and benthic microalgae to inner shelf sediments of the north-central Gulf of Mexico

NASA Astrophysics Data System (ADS)

Grippo, M. A.; Fleeger, J. W.; Rabalais, N. N.; Condrey, R.; Carman, K. R.

2010-03-01

Marine sediment may contain both settled phytoplankton and benthic microalgae (BMA). In river-dominated, shallow continental shelf systems, spatial, and temporal heterogeneity in sediment type and water-column characteristics (e.g., turbidity and primary productivity) may promote spatial variation in the relative contribution of these two sources to the sediment organic matter pool available to benthic consumers. Here we use photosynthetic pigment analysis and microscopic examination of sediment microalgae to investigate how the biomass, composition, and degradation state of sediment-associated microalgae vary along the Louisiana (USA) inner shelf, a region strongly influenced by the Mississippi River. Three sandy shoals and surrounding muddy sediments with depths ranging from 4 to 20 m were sampled in April, August, and October 2007. Pigment composition suggested that sediment microalgae were primarily diatoms at all locations. We found no significant differences in sediment chlorophyll a concentrations (8-77 mg m -2) at the shoal and off-shoal stations. Epipelic pennate diatoms (considered indicative of BMA) made up a significantly greater proportion of sediment diatoms at sandy (50-98%) compared to more silty off-shoal stations (16-56%). The percentage of centric diatoms (indicators of settled phytoplankton) in the sediment was highest in August. Sediment total pheopigment concentrations on sandy stations (<20 mg m -2) were significantly lower than concentrations at nearby muddy stations (>40 mg m -2), suggesting differences in sediment microalgal degradation state. These observations suggest that BMA predominate in shallow sandy sediments and that phytodetritus predominates at muddy stations. Our results also suggest that the relative proportion of phytodetritus in the benthos was highest where phytoplankton biomass in the overlying water was greatest, independent of sediment type. The high biomass of BMA found on shoals suggests that benthic primary production on sandy sediments represents a potentially significant local source of sediment microalgal carbon that may be utilized by benthic consumers in continental shelf food webs.

Superfund record of decision (EPA Region 6): Southern Shipbuilding Corp., Slidell, LA, July 20, 1995

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1996-03-01

This decision document presents the selected remedial action for the source control operable unit of the Southern Shipbuilding Corporation (SSC) site in Slidell, Louisiana. This remedy represents the source control operable unit which addresses remediation of highly contaminated sludge and soil, the marginally contaminated soil, and the graving dock sediments at the Southern Shipbuilding Corporation site.

Source identification and ecological impact evaluation of PAHs in urban river sediments: A case study in Taiwan.

PubMed

Tu, Y T; Ou, J H; Tsang, D C W; Dong, C D; Chen, C W; Kao, C M

2018-03-01

The Love River and Ho-Jin River, two major urban rivers in Kaohsiung City, Taiwan, are moderately to heavily polluted because different types of improperly treated wastewaters are discharged into the rivers. In this study, sediment and river water samples were collected from two rivers to investigate the river water quality and accumulation of polycyclic aromatic hydrocarbons (PAHs) in sediments. The spatial distribution, composition, and source appointment of PAHs of the sediments were examined. The impacts of PAHs on ecological system were assessed using toxic equivalence quotient (TEQ) of potentially carcinogenic PAHs (TEQ carc ) and sediment quality guidelines. The average PAHs concentrations ranged from 2161 ng/g in Love River sediment to 160 ng/g in Ho-Jin River sediment. This could be due to the fact that Love River Basin had much higher population density and pyrolytic activities. High-ring PAHs (4-6 rings) contributed to 59-90% of the total PAHs concentrations. Benzo(a)pyrene (BaP) had the highest toxic equivalence quotient (up to 188 ng TEQ/g). Moreover, the downstream sediments contained higher TEQ of total TPHs than midstream and upstream sediment samples. The PAHs were adsorbed onto the fine particles with high organic content. Results from diagnostic ratio analyses indicate that the PAHs in two urban river sediments might originate from oil/coal combustion, traffic-related emissions, and waste combustion (pyrogenic activities). Future pollution prevention and management should target the various industries, incinerators, and transportation emission in this region to reduce the PAHs pollution. Copyright © 2017 Elsevier Ltd. All rights reserved.

Sources and pathways of polycyclic aromatic and saturated hydrocarbons in the Arkona Basin (Southern Baltic Sea, Central Europe)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schulz, H.M.

The Baltic Sea (Central Europe) is surrounded by coastal regions with long histories of industrialization. The heavy metal profiles in the sediments in the center of the Arkona Basin, one of the depressions of the southern Baltic Sea area, clearly reflect the historical anthropogenic influence. The Arkona Basin-is the final sink for materials derived from the Oder river which drains a highly polluted industrial area of Eastern Europe. Surficial muddy sediments from a close-meshed field of sampling-points were analyzed for distribution patterns of aliphatics and quantities and ratios of selected polycyclic aromatic hydrocarbons (PAH). These compounds are thought to reflectmore » anthropogenic pollution related to emissions from traffic, heating, etc. We use these marker substances to test if the basin sediments reflect riverine input, and if additional sources can be identified.« less

Historical polycyclic aromatic and petrogenic hydrocarbon loading in Northern Central Gulf of Mexico shelf sediments.

PubMed

Overton, E B; Ashton, B M; Miles, M S

2004-10-01

The distribution of selected hydrocarbons within ten dated sediment cores taken from the Mississippi River Bight off coastal Louisiana suggests a chronic contaminant loading from several sources including the river itself, oil and gas exploration in the central Gulf of Mexico (GOM) shelf area, and natural geologic hydrocarbon seeps. Data were grouped as either total polycyclic aromatic hydrocarbons (PAH's), which were indicative of pyrogenic PAH's; or estimated total hopanes (indicative of petrogenic hydrocarbons). The total PAH concentrations and estimated total hopanes begin increasing above background levels (approximately 200 ng g(-1)) after the 1950s. The distribution of these hydrocarbons and hopanes within the dated sediment cores suggests that the Mississippi River is a regional source of pyrogenic PAH's, and that the hopanes are from natural geologic hydrocarbon seeps, oil and gas exploration in the GOM, or both.

Sediment‐associated organic matter sources and sediment oxygen demand in a Special Area of Conservation (SAC): A case study of the River Axe, UK

PubMed Central

Zhang, Y.; McMillan, S.; Dixon, E. R.; Stringfellow, A.; Bateman, S.; Sear, D. A.

2017-01-01

Abstract Oxygen demand in river substrates providing important habitats for the early life stages of aquatic ecology, including lithophilous fish, can arise due to the oxidation of sediment‐associated organic matter. Oxygen depletion associated with this component of river biogeochemical cycling, will, in part, depend on the sources of such material. A reconnaissance survey was therefore undertaken to assess the relative contributions from bed sediment‐associated organic matter sources potentially impacting on the River Axe Special Area of Conservation (SAC), in SW England. Source fingerprinting, including Monte Carlo uncertainty analysis, suggested that the relative frequency‐weighted average median source contributions ranged between 19% (uncertainty range 0–82%) and 64% (uncertainty range 0–99%) for farmyard manures or slurries, 4% (uncertainty range 0–49%) and 35% (uncertainty range 0–100%) for damaged road verges, 2% (uncertainty range 0–100%) and 68% (uncertainty range 0–100%) for decaying instream vegetation, and 2% (full uncertainty range 0–15%) and 6% (uncertainty range 0–48%) for human septic waste. A reconnaissance survey of sediment oxygen demand (SOD) along the channel designated as a SAC yielded a mean SOD5 of 4 mg O2 g−1 dry sediment and a corresponding SOD20 of 7 mg O2 g−1 dry sediment, compared with respective ranges of 1–15 and 2–30 mg O2 g−1 dry sediment, measured by the authors for a range of river types across the UK. The findings of the reconnaissance survey were used in an agency (SW region) catchment appraisal exercise for informing targeted management to help protect the SAC. PMID:29527135

The potential of carbon and nitrogen isotopes to conservatively discriminate between subsoil sediment sources

NASA Astrophysics Data System (ADS)

Laceby, J. Patrick; Olley, Jon

2013-04-01

Moreton Bay, in South East Queensland, Australia, is a Ramsar wetland of international significance. A decline of the bay's ecosystem health has been primarily attributed to sediments and nutrients from catchment sources. Sediment budgets for three catchments indicated gully erosion dominates the supply of sediment in Knapp Creek and the Upper Bremer River whereas erosion from cultivated soils is the primary sediment source in Blackfellow Creek. Sediment tracing with fallout-radionuclides confirmed subsoil erosion processes dominate the supply of sediment in Knapp Creek and the Upper Bremer River whereas in Blackfellow Creek cultivated and subsoil sources contribute >90% of sediments. Other sediment properties are required to determine the relative sediment contributions of channel bank, gully and cultivated sources in these catchments. The potential of total organic carbon (TOC), total nitrogen (TN), and carbon and nitrogen stable isotopes (δ13C, δ15N) to conservatively discriminate between subsoil sediment sources is presented. The conservativeness of these sediment properties was examined through evaluating particle size variations in depth core soil samples and investigating whether they remain constant in source soils over two sampling occasions. Varying conservative behavior and source discrimination was observed. TN in the

A reassessment of the sources and importance of land-derived organic matter in surface sediments from the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Goñi, Miguel A.; Ruttenberg, Kathleen C.; Eglinton, Timothy I.

1998-09-01

Organic matter in surface sediments from two onshore-offshore transects in the northwestern Gulf of Mexico was characterized by a variety of techniques, including elemental, stable carbon, radiocarbon, and molecular-level analyses. In spite of the importance of the Mississippi River as a sediment source, there is little evidence for a significant terrigenous input based on the low carbon:nitrogen ratios (8-5) and the enriched δ 13C values of bulk sedimentary organic carbon (-19.7‰ to -21.7‰). Radiocarbon analyses, on the other hand, yield depleted Δ 14C values (-277‰ to -572‰) which indicate that a significant fraction of the sedimentary organic carbon (OC) in all these surface sediments must be relatively old and most likely of allochthonous origin. CuO oxidations yield relatively low quantities of lignin products (0.4-1.4 mg/100 mg OC) along with compounds derived from proteins, polysaccharides, and lipids. Syringyl:vanillyl and cinnamyl:vanillyl ratios (averaging 1.6 and 0.5, respectively) and acid:aldehyde ratios for both vanillyl and syringyl phenols (averaging 0.8 and 1.2, respectively) indicate that the lignin present in sediments originates from nonwoody angiosperm sources and is highly degraded. The δ 13C values of lignin phenols in shelf sediments are relatively depleted in 13C (averaging -26.3‰) but are increasingly enriched in 13C at the slope sites (averaging -17.5‰ for the two deepest stations). We interpret these molecular and isotopic compositions to indicate that a significant fraction (≥50%) of the lignin and, by inference, the land-derived organic carbon in northwestern Gulf of Mexico sediments ultimately originated from C 4 plants. The source of this material is likely to be soil organic matter eroded from the extensive grasslands of the Mississippi River drainage basin. Notably, the mixed C 4 and C 3 source and the highly degraded state of this material hampers its recognition and quantification in shelf and slope sediments. Our data are consistent with higher than previously estimated inputs of land-derived organic carbon to regions of the ocean, such as the Gulf of Mexico, with significant sources of terrigenous C 4-derived organic matter.

The South Carolina Coastal Erosion Study: Numerical modeling of circulation and sediment transport in Long Bay, SC

NASA Astrophysics Data System (ADS)

Warner, J. C.; Sullivan, C.; Voulgaris, G.; Work, P.; Haas, K.; Hanes, D. M.

2004-12-01

Long Bay, South Carolina, is a heavily populated coastal region that supports a large tourism industry. Sand resources are important for both recreation and coastal habitat. Earlier geological framework studies have identified a large sand deposit oblique to the shoreline, oriented clockwise in the offshore direction. This sand feature is ~ 10 km long, 2 km wide, and in excess of 3m thick, possibly providing a source for beach nourishment material. Objectives of this study are to describe the physical processes that control the transport of sediment in Long Bay, specifically off the coast of Myrtle Beach, South Carolina. Specifically we seek to 1) measure and model the oceanographic circulation in the region, 2) identify the processes that maintain the presence of the offshore sand feature, 3) quantify the control that the shoal exerts on the nearshore through changes in wave energy propagation, and 4) identify consequences of removal of the offshore sand feature. Both observational and numerical experiments are used to study the oceanographic circulation and transport of sediment. The observational study is described in an accompanying poster and consists of eight sites that measured tides, surface waves, currents, salinity, temperature, suspended sediment concentrations, and bed forms from October 2003 to April 2004. Numerical modeling for circulation and sediment transport in the study region uses a new version of ROMS (v2.1) that now includes transport of multiple grain sizes, coupling of sediment transport to wave bottom boundary layer models, and evolution of the bottom morphology. The SWAN model is used to compute wave propagation. Results indicate that currents in the study area are strongly influenced by both tidal motion and wind driven setup / setdown. The presence of the offshore sand feature alters the residual flows in the region. Sediment transport is more significant during periods of sustained strong winds that generate local waves. Wind direction plays a key role in determining the direction and magnitude of sediment transport.

Biogeochemical transformation of Fe minerals in a petroleum-contaminated aquifer

USGS Publications Warehouse

Zachara, John M.; Kukkadapu, Ravi K.; Glassman, Paul L.; Dohnalkova, Alice; Fredrickson, Jim K.; Anderson, Todd

2004-01-01

The Bemidji aquifer in Minnesota, USA is a well-studied site of subsurface petroleum contamination. The site contains an anoxic groundwater plume where soluble petroleum constituents serve as an energy source for a region of methanogenesis near the source and bacterial Fe(III) reduction further down gradient. Methanogenesis apparently begins when bioavailable Fe(III) is exhausted within the sediment. Past studies indicate that Geobacter species and Geothrix fermentens-like organisms are the primary dissimilatory Fe-reducing bacteria at this site. The Fe mineralogy of the pristine aquifer sediments and samples from the methanogenic (source) and Fe(III) reducing zones were characterized in this study to identify microbiologic changes to Fe valence and mineral distribution, and to identify whether new biogenic mineral phases had formed. Methods applied included X-ray diffraction; X-ray fluorescence (XRF); and chemical extraction; optical, transmission, and scanning electron microscopy; and Mössbauer spectroscopy.All of the sediments were low in total Fe content (≈ 1%) and exhibited complex Fe-mineralogy. The bulk pristine sediment and its sand, silt, and clay-sized fractions were studied in detail. The pristine sediments contained Fe(II) and Fe(III) mineral phases. Ferrous iron represented approximately 50% of FeTOT. The relative Fe(II) concentration increased in the sand fraction, and its primary mineralogic residence was clinochlore with minor concentrations found as a ferroan calcite grain cement in carbonate lithic fragments. Fe(III) existed in silicates (epidote, clinochlore, muscovite) and Fe(III) oxides of detrital and authigenic origin. The detrital Fe(III) oxides included hematite and goethite in the form of mm-sized nodular concretions and smaller-sized dispersed crystallites, and euhedral magnetite grains. Authigenic Fe(III) oxides increased in concentration with decreasing particle size through the silt and clay fraction. Chemical extraction and Mössbauer analysis indicated that this was a ferrihydrite like-phase. Quantitative mineralogic and Fe(II/III) ratio comparisons between the pristine and contaminated sediments were not possible because of textural differences. However, comparisons between the texturally-similar source (where bioavailable Fe(III) had been exhausted) and Fe(III) reducing zone sediments (where bioavailable Fe(III) remained) indicated that dispersed detrital, crystalline Fe(III) oxides and a portion of the authigenic, poorly crystalline Fe(III) oxide fraction had been depleted from the source zone sediment by microbiologic activity. Little or no effect of microbiologic activity was observed on silicate Fe(III). The presence of residual “ferrihydrite” in the most bioreduced, anoxic plume sediment (source) implied that a portion of the authigenic Fe(III) oxides were biologically inaccessible in weathered, lithic fragment interiors. Little evidence was found for the modern biogenesis of authigenic ferrous-containing mineral phases, perhaps with the exception of thin siderite or ferroan calcite surface precipitates on carbonate lithic fragments within source zone sediments.

Drastic shift of lava geochemistry between pre- and post- Japan Sea opening in NE Japan subduction zone: constraints on source composition and slab surface melting processes

NASA Astrophysics Data System (ADS)

Okamura, S.; Inaba, M.; Igarashi, S.; Aizawa, M.; Shinjo, R.

2017-12-01

Isotopic and trace element data imply a temporal change in magma sources and thermal conditions beneath the northern Fossa Magna, NE Japan arc from the Oligocene to the Pleistocene. Less radiogenic 176Hf/177Hf and 143Nd/144Nd, and high Zr/Hf characterize the Oligocene - Early Miocene volcanism in the northern Fossa Magna region. The mantle wedge in the Oligocene - Early Miocene consisted of enriched mantle source. We propose that during the onset of subduction, influx of hot asthenospheric mantle provided sufficient heat to partially melt newly subducting sediment. Geochemical modeling results suggest breakdown of zircon in the slab surface sediments for the Oligocene - Early Miocene lavas in the northern Fossa Magna region. In the Middle Miocene, the injection of hot and depleted asthenospheric material replaced the mantle beneath the northern Fossa Magna region of NE Japan. The Middle Miocene lavas characterized by most radiogenic Hf and Nd isotope ratios, have high Zr/Hf. An appropriate working petrogenetic model is that the Middle Miocene lavas were derived from asthenospheric depleted mantle, slightly (<1%) contaminated by slab melt accompanied by full dissolution of zircon. All the Late Miocene - Pleistocene samples are characterized by distinctly more radiogenic 176Hf/177Hf and 143Nd/144Nd, and are displaced toward lower Zr/Hf, which requires mixing between depleted mantle and a partial melt of subducted metasediment saturated with trace quantity of zircon. The Oligocene - Early Miocene volcanism in the northern Fossa Magna region may represent the early stage of continental margin magmatism associated with a back-arc rift. Here volcanism is dominated by sediment melts. Perhaps asthenospheric injection, triggering Japan Sea opening, allowed higher temperatures and more melting at the slab-mantle interface. The mantle wedge was gradually cooled during the Middle Miocene to the Pleistocene with back-arc opening ending in the Late Miocene. Slab surface temperatures were still high enough for sediments to melt but not too high (< 780 °C) to lose zircon as a residual phase.

Distribution of Cr, Pb, Cd, Zn, Fe and Mn in Lake Victoria sediments, East Africa

DOE Office of Scientific and Technical Information (OSTI.GOV)

Onyari, J.M.; Wandiga, S.O.

1989-06-01

The presence of many metals at trace or ultra-trace levels in the human environment has received increased global attention. Sediments as a sink for pollutants are widely recognized pollution sources and diagenesis and biochemical transformations within the sediment may mobilize pollutants posing a threat to a wider biological community. The natural (background) concentrations of heavy metals in lake sediments can be estimated either by analysis of surface sediments in non-polluted regions or by analysis of core samples antedating modern pollution. The distribution pattern of heavy metals in tropical freshwater systems has been little studied. The authors found increased concentrations ofmore » lead and other trace metals in Lake Victoria. Thus this study was initiated in order to further investigate the distribution patterns of lead and other metals in Lake Victoria.« less

Temporal variability in sediment PAHs accumulation in the northern Gulf of Mexico Shelf

NASA Astrophysics Data System (ADS)

Bam, W.; Maiti, K.; Adhikari, P. L.

2017-12-01

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous group of organic pollutants, some of which are known to be toxic, and/or carcinogenic to humans. The major source of these PAHs into the northern Gulf of Mexico (NGOM) are Mississippi River discharge, coastal erosion, atmospheric deposition, and numerous natural oil seeps and spills. In addition to these background source of PAHs, the Deepwater Horizon (DWH) oil spill in 2010 added 21,000 tons of PAHs into the NGOM water. In this study, we measured PAHs distribution and accumulation rates in coastal sediments near the Mississippi River mouth in 2011 and 2015 to understand the effect of DWH oil spill in PAHs accumulation in coastal sediments. Sediment cores were collected and sliced at 1 cm interval to measure PAHs concentration, and to estimate 210Pb-based sedimentation and the PAHs' accumulation rates. The results showed that the sediment deposition rates in this region varied between 0.5 to 0.9 cm/yr. The results also showed that the concentration of total PAHs (ΣPAH43) and their accumulation rates vary between 68 - 100 ng g-1 and 7 - 160 ng cm-2 yr-1, respectively. While the PAHs accumulation rate in coastal sediment varied over the years, there is no significant variation in PAHs accumulation rate before and after the DWH oil spill.

Atmospheric mercury deposition during the last 270 years--A glacial ice core record of natural and anthropogenic sources

USGS Publications Warehouse

Schuster, Paul F.; Krabbenhoft, David P.; Naftz, David L.; Cecil, L. DeWayne; Olson, Mark L.; DeWild, John F.; Susong, David D.; Green, Jaromy R.; Abbott, Michael L.

2002-01-01

Mercury (Hg) contamination of aquatic ecosystems and subsequent methylmercury bioaccumulation are significant environmental problems of global extent. At regional to global scales, the primary mechanism of Hg contamination is atmospheric Hg transport. Thus, a better understanding of the long-term history of atmospheric Hg cycling and quantification of the sources is critical for assessing the regional and global impact of anthropogenic Hg emissions. Ice cores collected from the Upper Fremont Glacier (UFG), Wyoming, contain a high-resolution record of total atmospheric Hg deposition (ca. 1720−1993). Total Hg in 97 ice-core samples was determined with trace-metal clean handling methods and low-level analytical procedures to reconstruct the first and most comprehensive atmospheric Hg deposition record of its kind yet available from North America. The record indicates major atmospheric releases of both natural and anthropogenic Hg from regional and global sources. Integrated over the past 270-year ice-core history, anthropogenic inputs contributed 52%, volcanic events 6%, and background sources 42%. More significantly, during the last 100 years, anthropogenic sources contributed 70% of the total Hg input. Unlike the 2−7-fold increase observed from preindustrial times (before 1840) to the mid-1980s in sediment-core records, the UFG record indicates a 20-fold increase for the same period. The sediment-core records, however, are in agreement with the last 10 years of this ice-core record, indicating declines in atmospheric Hg deposition.

Sedimentation and provenance of the Antofagasta region of the southern Puna Plateau, central Andes

NASA Astrophysics Data System (ADS)

Zhou, Renjie; Schoenbohm, Lindsay M.; Sobel, Edward R.; Carrapa, Barbara; Davis, Donald W.

2014-05-01

Stratigraphic and provenance studies of Cenozoic non-marine sedimentary basins in the Central Andean Puna Plateau provide insight into the regional development and dynamics. The southern plateau hosts several poorly exposed intramontane basins bounded by basement-involved ~N-S striking thrust faults; their origin is explained differently by contrasting geodynamic models. This study focuses on the Antofagasta region (NW Argentina). The top of the studied basin was over-thrust by basement rocks along a west-dipping thrust fault, which was likely active during exhumation of the Calalaste range to the west (25-29 Ma, Carrapa et al., 2005). We studied three sections SW of Antofagasta de la Sierra. S3 (552 m) is the lowest section and is composed of mud playa to sandflat sediments, with at least two paleosol horizons. Lower S2 (1,263 m) contains ~300 meters of proximal alluvial fan sediments. Upper S2 is composed of fluvial to shallow lacustrine sediments. The separation between the top of S2 and the bottom of S1 (1,062 m) is ~540 m. The lower ~600 m of S1 is composed of thick, distal alluvial fan and braided river sediments. In the upper S1, the depositional environment changes to fluvial-alluvial, with a paleosol developed at the top of S1. Imbricated pebbles suggest prevailing eastward paleoflow. Modal compositions of 18 sandstones plot in the mixed zone on a Qm-F-Lt plot, and the transitional continental and recycled orogenic zones on a Qt-F-L plot (Dickinson, 1985). Their compositions cluster and do not show any evolutionary trends, despite being sampled from a ~3000 m-thick sedimentary column. However, when combined with data from the Quinoas Formation (Late Eocene to Late Oligocene) and the Chacras Formation (Late Oligocene to Early Miocene), outcropped west of the study site (Carrapa et al., 2005), the Antofagasta samples mark the beginning of an evolving trend towards the dissected arc and transitional arc zones. We analyzed U-Pb ages of detrital zircons from eight samples. Four young grains from three samples near the top of S2 yield ages of 38-39.5 Ma. If these grains were derived from air-fall volcanics, they indicate a late Eocene depositional age for the studied strata, but otherwise they give a maximum age estimate. We tentatively favour the former interpretation. For all samples, detrital zircon U-Pb age spectra show significant late Cambrian to early Ordovician and Precambrian (~1000-1400 Ma, ~1700-1900 Ma) sources. The ~1000-1400 Ma cluster is well matched with ages from the Sierra de Maz, to the west. A minor Permian-Triassic source (~240-290 Ma) is also present which could reflect limited exposures of plutonic rocks west of the study site. Our work suggests that the ~3000 meter thick unit in the Antofagasta basin is time-equivalent of the Quinoas Formation and accumulated with a high sedimentation rate. The sediments were sourced primarily from the west, with little input from volcanics. The consistent western source regions and the rapid subsidence lead us to favour a foreland-type origin for the late Eocene Antofagasta Basin.

Suspended-sediment sources in an urban watershed, Northeast Branch Anacostia River, Maryland

USGS Publications Warehouse

Devereux, Olivia H.; Prestegaard, Karen L.; Needelman, Brian A.; Gellis, Allen C.

2010-01-01

Fine sediment sources were characterized by chemical composition in an urban watershed, the Northeast Branch Anacostia River, which drains to the Chesapeake Bay. Concentrations of 63 elements and two radionuclides were measured in possible land-based sediment sources and suspended sediment collected from the water column at the watershed outlet during storm events. These tracer concentrations were used to determine the relative quantity of suspended sediment contributed by each source. Although this is an urbanized watershed, there was not a distinct urban signature that can be evaluated except for the contributions from road surfaces. We identified the sources of fine sediment by both physiographic province (Piedmont and Coastal Plain) and source locale (streambanks, upland and street residue) by using different sets of elemental tracers. The Piedmont contributed the majority of the fine sediment for seven of the eight measured storms. The streambanks contributed the greatest quantity of fine sediment when evaluated by source locale. Street residue contributed 13% of the total suspended sediment on average and was the source most concentrated in anthropogenically enriched elements. Combining results from the source locale and physiographic province analyses, most fine sediment in the Northeast Branch watershed is derived from streambanks that contain sediment eroded from the Piedmont physiographic province of the watershed. Sediment fingerprinting analyses are most useful when longer term evaluations of sediment erosion and storage are also available from streambank-erosion measurements, sediment budget and other methods.

Origin and processing of terrestrial organic carbon in the Amazon system: lignin phenols in river, shelf, and fan sediments

NASA Astrophysics Data System (ADS)

Sun, Shuwen; Schefuß, Enno; Mulitza, Stefan; Chiessi, Cristiano M.; Sawakuchi, André O.; Zabel, Matthias; Baker, Paul A.; Hefter, Jens; Mollenhauer, Gesine

2017-05-01

The Amazon River transports large amounts of terrestrial organic carbon (OCterr) from the Andean and Amazon neotropical forests to the Atlantic Ocean. In order to compare the biogeochemical characteristics of OCterr in the fluvial sediments from the Amazon drainage basin and in the adjacent marine sediments, we analysed riverbed sediments from the Amazon mainstream and its main tributaries as well as marine surface sediments from the Amazon shelf and fan for total organic carbon (TOC) content, organic carbon isotopic composition (δ13CTOC), and lignin phenol compositions. TOC and lignin content exhibit positive correlations with Al / Si ratios (indicative of the sediment grain size) implying that the grain size of sediment discharged by the Amazon River plays an important role in the preservation of TOC and leads to preferential preservation of lignin phenols in fine particles. Depleted δ13CTOC values (-26.1 to -29.9 ‰) in the main tributaries consistently correspond with the dominance of C3 vegetation. Ratios of syringyl to vanillyl (S / V) and cinnamyl to vanillyl (C / V) lignin phenols suggest that non-woody angiosperm tissues are the dominant source of lignin in the Amazon basin. Although the Amazon basin hosts a rich diversity of vascular plant types, distinct regional lignin compositions are not observed. In the marine sediments, the distribution of δ13CTOC and Λ8 (sum of eight lignin phenols in organic carbon (OC), expressed as mg/100 mg OC) values implies that OCterr discharged by the Amazon River is transported north-westward by the North Brazil Current and mostly deposited on the inner shelf. The lignin compositions in offshore sediments under the influence of the Amazon plume are consistent with the riverbed samples suggesting that processing of OCterr during offshore transport does not change the encoded source information. Therefore, the lignin compositions preserved in these offshore sediments can reliably reflect the vegetation in the Amazon River catchment. In sediments from the Amazon fan, low lignin content, relatively depleted δ13CTOC values and high (Ad / Al)V ratios indicating highly degraded lignin imply that a significant fraction of the deposited OCterr is derived from petrogenic (sourced from ancient rocks) sources.

Footwall degradation styles and associated sedimentary facies distribution in SE Crete: Insights into tilt-block extensional basins on continental margins

NASA Astrophysics Data System (ADS)

Alves, Tiago M.; Cupkovic, Tomas

2018-05-01

Depositional facies resulting from footwall degradation in extensional basins of SE Crete are studied based on detailed geological maps, regional transects, lithological columns and outcrop photos. During an extensional episode affecting Crete in the late Miocene-early Pliocene, depocentres trending N20°E and N70°E were filled with fan deltas, submarine mass-wasting deposits, sandy turbidites and fine-grained hemipelagites sourced from both nearby and distal sediment sources. Deposition of proximal continental and shallow-marine units, and relatively deep (marine) turbidites and mass-transport deposits, occurred within a complex mosaic of tectonically controlled depocentres. The new geological maps and transects in this work reveal that depositional facies in SE Crete were controlled by: a) their relative proximity to active faults and uplifting footwall blocks, b) the relative position (depth and relative height above sea level) of hanging-wall basins, and c) the nature of the basement units eroded from adjacent footwall blocks. Distal sediment sources supplied background siliciclastic sediment ('hemipelagites'), which differ markedly from strata sourced from local footwalls. In parallel, mass-transport of sediment was ubiquitous on tectonically active slopes, and so was the presence of coarse-grained sediment with sizes varying from large blocks > 50 m-wide to heterolithic mass-transport deposits and silty-sandy turbidites. We expect similar tectono-sedimentary settings to have predominated in tectonically active Miocene basins of the eastern Mediterranean, in which hydrocarbon exploration is occurring at present, and on rifted continental margins across the world.

Clostridium perfringens in Long Island Sound sediments: An urban sedimentary record

USGS Publications Warehouse

Buchholtz ten Brink, Marilyn R.; Mecray, E.L.; Galvin, E.L.

2000-01-01

Clostridium perfringens is a conservative tracer and an indicator of sewage-derived pollution in the marine environment. The distribution of Clostridium perfringens spores was measured in sediments from Long Island Sound, USA, as part of a regional study designed to: (1) map the distribution of contaminated sediments; (2) determine transport and dispersal paths; (3) identify the locations of sediment and contaminant focusing; and (4) constrain predictive models. In 1996, sediment cores were collected at 58 stations, and surface sediments were collected at 219 locations throughout the Sound. Elevated concentrations of Clostridium perfringens in the sediments indicate that sewage pollution is present throughout Long Island Sound and has persisted for more than a century. Concentrations range from undetectable amounts to 15,000 spores/g dry sediment and are above background levels in the upper 30 cm at nearly all core locations. Sediment focusing strongly impacts the accumulation of Clostridium perfringens spores. Inventories in the cores range from 28 to 70,000 spores/cm2, and elevated concentrations can extend to depths of 50 cm. The steep gradients in Clostridium perfringens profiles in muddier cores contrast with concentrations that are generally constant with depth in sandier cores. Clostridium perfringens concentrations rarely decrease in the uppermost sediment, unlike those reported for metal contaminants. Concentrations in surface sediments are highest in the western end of the Sound, very low in the eastern region, and intermediate in the central part. This pattern reflects winnowing and focusing of Clostridium perfringens spores and fine-grained sediment by the hydrodynamic regime; however, the proximity of sewage sources to the westernmost Sound locally enhances the Clostridium perfringens signals.

The Border Environmental Health Initiative-investigating the transboundary Santa Cruz watershed

USGS Publications Warehouse

Norman, Laura M.; Callegary, James; van Riper, Charles; Gray, Floyd

2010-01-01

In 2004 the U.S. Geological Survey (USGS) launched the Border Environmental Health Initiative (BEHI), a major project encompassing the entire U.S.-Mexico border region. In 2009, a study of the Santa Cruz River Watershed (SCW), located in the border region of Arizona and Sonora, Mexico, was initiated as part of the BEHI. In this borderland region of the desert Southwest, human health and the ecosystems on which humans rely depend critically on limited water resources. Surface water is scarce during much of the year, and groundwater is the primary source for industrial, agricultural, and domestic use. In order to identify risks to water resources in the SCW, and the potential consequences to riparian ecosystems and ultimately human health, the USGS is using an interdisciplinary and integrative approach that incorporates the expertise of geographers, hydrologists, biologists, and geologists to track organic and inorganic contaminants and their effects from sources to sinks in sediment, water, plants, and animals. Existing groundwater and surface-water models are being used and modified to assess contaminant and sediment transport.

Levels and distribution of dissolved hydrophobic organic contaminants in the Morava river in Zlín district, Czech Republic as derived from their accumulation in silicone rubber passive samplers.

PubMed

Prokeš, Roman; Vrana, Branislav; Klánová, Jana

2012-07-01

Dissolved waterborne polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were assessed over a period of one year at five sampling sites in a model industrial region in the Czech Republic using silicone rubber passive samplers. The spatial variability of POPs in the studied region in water was small and diffusive pollution sources predominate. Concentrations of the most volatile PAHs decreased with increasing water temperature in the whole region, which reflects the seasonality in atmospheric deposition. The dissolved concentrations of more hydrophobic PAHs, PCBs and OCPs in and downstream the industrial zone are related to desorption from suspended particles. Upstream the industrial area, a positive correlation of dissolved and particle-bound contamination was observed only for DDT metabolites and hexachlorobenzene. Calculated fugacities in water and bottom sediment indicated a fair degree of equilibrium between these compartments for OCPs and PCBs, whereas sediment represented a potential source of PAHs. Copyright © 2012 Elsevier Ltd. All rights reserved.

Plastic litter in aquatic environments of Maremma Regional Park (Tyrrhenian Sea, Italy): Contribution by the Ombrone river and levels in marine sediments.

PubMed

Guerranti, Cristiana; Cannas, Susanna; Scopetani, Costanza; Fastelli, Paolo; Cincinelli, Alessandra; Renzi, Monia

2017-04-15

During two surveys in 2015 and 2016, sediments samples were collected along the Ombrone river (Maremma Regional Park, province of Grosseto, Italy), in particular at its mouth and in the marine area in front of it, in order to quantify, identify and categorize plastic items (macro, meso and micro-plastics and colour, material etc.) and evaluate their potential sources. The Albegna and Osa rivers were identified as external areas of comparison. The results of the analysis showed different situations, especially as regards fluvial inputs, in addition to evidencing local provisions of plastic material derived from agricultural activities. The microplastics values per kg of sediment and the prevailing type of items found largely varied between the investigated sites (45-1069items/kg dry sample). Copyright © 2017 Elsevier Ltd. All rights reserved.

Linking mercury, carbon, and nitrogen stable isotopes in Tibetan biota: Implications for using mercury stable isotopes as source tracers

PubMed Central

Xu, Xiaoyu; Zhang, Qianggong; Wang, Wen-Xiong

2016-01-01

Tibetan Plateau is located at a mountain region isolated from direct anthropogenic sources. Mercury concentrations and stable isotopes of carbon, nitrogen, and mercury were analyzed in sediment and biota for Nam Co and Yamdrok Lake. Biotic mercury concentrations and high food web magnification factors suggested that Tibetan Plateau is no longer a pristine site. The primary source of methylmercury was microbial production in local sediment despite the lack of direct methylmercury input. Strong ultraviolet intensity led to extensive photochemical reactions and up to 65% of methylmercury in water was photo-demethylated before entering the food webs. Biota displayed very high Δ199Hg signatures, with some highest value (8.6%) ever in living organisms. The δ202Hg and Δ199Hg in sediment and biotic samples increased with trophic positions (δ15N) and %methylmercury. Fish total length closely correlated to δ13C and Δ199Hg values due to dissimilar carbon sources and methylmercury pools in different living waters. This is the first mercury isotope study on high altitude lake ecosystems that demonstrated specific isotope fractionations of mercury under extreme environmental conditions. PMID:27151563

Assessment of sediment toxicity and chemical concentrations in the San Diego Bay region, California, USA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fairey, R.; Roberts, C.; Jacobi, M.

1998-08-01

Sediment quality within San Diego Bay, Mission Bay, and the Tijuana River Estuary of California was investigated as part of an ongoing statewide monitoring effort (Bay Protection and Toxic Cleanup Program). Study objectives were to determine the incidence, spatial patterns, and spatial extent of toxicity in sediments and porewater; the concentration and distribution of potentially toxic anthropogenic chemicals; and the relationships between toxicity and chemical concentrations. Rhepoxynius abronius survival bioassays, grain size, and total organic carbon analyses were performed on 350 sediment samples. Strongylocentrotus purpuratus development bioassays were performed on 164 pore-water samples. Toxicity was demonstrated throughout the San Diegomore » Bay region, with increased incidence and concordance occurring in areas of industrial and shipping activity. Trace metal and trace synthetic organic analyses were performed on 229 samples. Copper, zinc, mercury, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and chlordane were found to exceed ERM (effects range median) or PEL (probable effects level) sediment quality guidelines and were considered the six major chemicals or chemical groups of concern. Statistical analysis of the relationships between amphipod toxicity, bulk phase sediment chemistry, and physical parameters demonstrated few significant linear relationships. Significant differences in chemical levels were found between toxic and nontoxic responses using multivariate and univariate statistics. Potential sources of anthropogenic chemicals were discussed.« less

Sources and fate of microplastics in marine and beach sediments of the Southern Baltic Sea-a preliminary study.

PubMed

Graca, Bożena; Szewc, Karolina; Zakrzewska, Danuta; Dołęga, Anna; Szczerbowska-Boruchowska, Magdalena

2017-03-01

Microplastics' (particles size ≤5 mm) sources and fate in marine bottom and beach sediments of the brackish are strongly polluted Baltic Sea have been investigated. Microplastics were extracted using sodium chloride (1.2 g cm -3 ). Their qualitative identification was conducted using micro-Fourier-transform infrared spectroscopy (μFT-IR). Concentration of microplastics varied from 25 particles kg -1 d.w. at the open sea beach to 53 particles kg -1  d.w. at beaches of strongly urbanized bay. In bottom sediments, microplastics concentration was visibly lower compared to beach sediments (0-27 particles kg -1  d.w.) and decreased from the shore to the open, deep-sea regions. The most frequent microplastics dimensions ranged from 0.1 to 2.0 mm, and transparent fibers were predominant. Polyester, which is a popular fabrics component, was the most common type of microplastic in both marine bottom (50%) and beach sediments (27%). Additionally, poly(vinyl acetate) used in shipbuilding as well as poly(ethylene-propylene) used for packaging were numerous in marine bottom (25% of all polymers) and beach sediments (18% of all polymers). Polymer density seems to be an important factor influencing microplastics circulation. Low density plastic debris probably recirculates between beach sediments and seawater in a greater extent than higher density debris. Therefore, their deposition is potentially limited and physical degradation is favored. Consequently, low density microplastics concentration may be underestimated using current methods due to too small size of the debris. This influences also the findings of qualitative research of microplastics which provide the basis for conclusions about the sources of microplastics in the marine environment.

Impacts of shore expansion and catchment characteristics on lacustrine thermokarst records in permafrost lowlands, Alaska Arctic Coastal Plain

USGS Publications Warehouse

Lenz, Josefine; Jones, Benjamin M.; Wetterich, Sebastian; Tjallingii, Rik; Fritz, Michael; Arp, Christopher D.; Rudaya, Natalia; Grosse, Guido

2016-01-01

Arctic lowland landscapes have been modified by thermokarst lake processes throughout the Holocene. Thermokarst lakes form as a result of ice-rich permafrost degradation, and they may expand over time through thermal and mechanical shoreline erosion. We studied proximal and distal sedimentary records from a thermokarst lake located on the Arctic Coastal Plain of northern Alaska to reconstruct the impact of catchment dynamics and morphology on the lacustrine depositional environment and to quantify carbon accumulation in thermokarst lake sediments. Short cores were collected for analysis of pollen, sedimentological, and geochemical proxies. Radiocarbon and 210Pb/137Cs dating, as well as extrapolation of measured historic lake expansion rates, were applied to estimate a minimum lake age of ~1400 calendar years BP. The pollen record is in agreement with the young lake age as it does not include evidence of the “alder high” that occurred in the region ~4000 cal yr BP. The lake most likely initiated from a remnant pond in a drained thermokarst lake basin (DTLB) and deepened rapidly as evidenced by accumulation of laminated sediments. Increasing oxygenation of the water column as shown by higher Fe/Ti and Fe/S ratios in the sediment indicate shifts in ice regime with increasing water depth. More recently, the sediment source changed as the thermokarst lake expanded through lateral permafrost degradation, alternating from redeposited DTLB sediments, to increased amounts of sediment from eroding, older upland deposits, followed by a more balanced combination of both DTLB and upland sources. The characterizing shifts in sediment sources and depositional regimes in expanding thermokarst lakes were, therefore, archived in the thermokarst lake sedimentary record. This study also highlights the potential for Arctic lakes to recycle old carbon from thawing permafrost and thermokarst processes.

Straight from the source's mouth; a quantitative study of grain-size export for an entire active rift, the Corinth Rift, central Greece

NASA Astrophysics Data System (ADS)

Watkins, Stephen E.; Whittaker, Alexander C.; Bell, Rebecca E.; Brooke, Sam A. S.; McNeill, Lisa C.; Gawthorpe, Robert L.

2017-04-01

The volumes, grain sizes and characteristics of sediment supplied from source catchments fundamentally controls basin stratigraphy. However, to date, few studies have constrained sediment budgets, including grain size, released into an active rift basin at a regional scale. The Gulf of Corinth, central Greece, is one of the most rapidly extending rifts in the world, with geodetic measurements of 5 mm/yr in the East to 15 mm/yr in the West. It has well-constrained climatic and tectonic boundary conditions and bedrock lithologies are well-characterised. It is therefore an ideal natural laboratory to study the grain-size export for a rift. In the field, we visited the river mouths of 49 catchments draining into the Corinth Gulf, which in total drain 83% of the rift. At each site, hydraulic geometries, surface grain-size of channel bars and full-weighted grain-size distributions of river sediment were obtained. The surface grain-size was measured using the Wolman point count method and the full-weighted grain-size distribution of the bedload by in-situ sieving. In total, approximately 17,000 point counts and 3 tonnes of sediment were processed. The grain-size distributions show an overall increase from East to West on the southern coast of the gulf, with largest grain-sizes exported from the Western rift catchments. D84 ranges from 20 to 110 mm, however 50% of D84 grain-sizes are less than 40 mm. Subsequently, we derived the full Holocene sediment budget for the Corinth Gulf by combining our grain size data with catchment sediment fluxes, constrained using the BQART model and calibrated to known Holocene sediment volumes in the basin from seismic data (c.f. Watkins et al., in review). This is the first time such a budget has been derived for the Corinth Rift. Finally, our estimates of sediment budgets and grain sizes were compared to regional uplift constraints, fault distributions, slip rates and lithology to identify the relative importance of these controls on sediment supply to the basin.

Sources and characteristics of organochlorine pesticides in the soil and sediment along the Kaidu-Peacock River, Northwest of China

NASA Astrophysics Data System (ADS)

Chen, Wei; Qi, Shihua; Peng, Fei; Qu, Chengkai; Zhang, Yuan; Xing, Xinli; Zhang, Jiaquan

2016-04-01

Organochlorine pesticides (OCPs) are a sub-group of persistent organic pollutants (POPs), which have raised the concerns from researchers all around the world for several decades. But very little research has been conducted on POPs in the arid zone of Northwest China. More than 100 soil and sediment samples were collected from Kaidu-Peacock River of Xinjiang, Northwest of China, to investigate the organochlorine pesticides (OCPs) in this region analysed by the gas chromatograph equipped with a mass selective detector (GC-MSD). Our pre-study in 2006 (Chen et al. 2011) in the same region, showed that OCPs except o,p'-DDT were detected in sediments from the Peacock River. Similar results were found in the whole river catchment in this investigation. DDTs, HCHs, chlordanes and endosulfans were the dominant OCPs residual in the soil and sediments. This study confirmed that POPs, such as OCPs in this region were contributed to by both local emissions and long-term atmospheric transport and may pose risks to human health and the ecosystem. Chen, W., Jing, M., Bu, J., Ellis Burnet, J., Qi, S., Song, Q., Ke, Y., Miao, J., Liu, M. & Yang, C. (2011) Organochlorine pesticides in the surface water and sediments from the Peacock River Drainage Basin in Xinjiang, China: a study of an arid zone in Central Asia. Environmental Monitoring and Assessment, 177, 1-21.

The Saguenay Fjord, Quebec, Canada: Integrating marine geotechnical and geophysical data for spatial seismic slope stability and hazard assessment

USGS Publications Warehouse

Urgeles, R.; Locat, J.; Lee, H.J.; Martin, F.

2002-01-01

In 1996 a major flood occurred in the Saguenay region, Quebec, Canada, delivering several km3 of sediment to the Saguenay Fjord. Such sediments covered large areas of the, until then, largely contaminated fjord bottom, thus providing a natural capping layer. Recent swath bathymetry data have also shown that sediment landslides are widely present in the upper section of the Saguenay Fjord, and therefore, should a new event occur, it would probably expose the old contaminated sediments. Landslides in the Upper Saguenay Fjord are most probably due to earthquakes given its proximity to the Charlevoix seismic region and to that of the 1988 Saguenay earthquake. In consequence, this study tries to characterize the permanent ground deformations induced by different earthquake scenarios from which shallow sediment landslides could be triggered. The study follows a Newmark analysis in which, firstly, the seismic slope performance is assessed, secondly, the seismic hazard analyzed, and finally an evaluation of the seismic landslide hazard is made. The study is based on slope gradients obtained from EM1000 multibeam bathymetry data as well as water content and undrained shear strength measurements made in box and gravity cores. Ground motions integrating local site conditions were simulated using synthetic time histories. The study assumes the region of the 1988 Saguenay earthquake as the most likely source area for earthquakes capable of inducing large ground motions in the Upper Saguenay region. Accordingly, we have analyzed several shaking intensities to deduce that generalized sediment displacements will begin to occur when moment magnitudes exceed 6. Major displacements, failure, and subsequent landslides could occur only from earthquake moment magnitudes exceeding 6.75. ?? 2002 Elsevier Science B.V. All rights reserved.

Lead concentration and isotope chronology in two coastal environments in Western and South East Asia

NASA Astrophysics Data System (ADS)

Carrasco, G. G.; Chen, M.; Boyle, E. A.; Zhao, N.; Nurhati, I. S.; Gevao, B.; al Ghadban, A.; Switzer, A.; Lee, J. M.

2014-12-01

Lead is a trace metal that is closely related to anthropogenic activity, mainly via leaded gasoline and coal combustion. The study of lead concentrations and isotopes in seawater, sediments, corals and aerosols allows for a systematic look at its sources and their time evolution in a natural environment. We will discuss results from two projects in Western and South East Asia, regions that have seen dramatic socio-economical changes over the past half-century that may have left environmental signals. These results highlight the usefulness of the method, indicate the degree of complexity of these systems, and point to the need for a continuous monitoring of anthropogenic trace metals in the small-medium coastal scale to be able to asses the larger scale effects of human activity. On the one hand, coastal Kuwait is heavily influenced by the Shat al-Arab river and shows a clear anthropogenic signature from Kuwait city. A mix of two sources can be tracked through the coral and sediment chronological records, with Pb206/Pb207 ratios (1.202 and 1.151) that approach the suspected source values (1.21 and 1.12) and eliminate the possibility of other sources. Through a wide sediment geographic distribution, the strength of the anthropogenic signature is modulated. On the other hand, Singapore offers a more complex system, where an apparent mix of two sources (extreme isotope ratios 1.215 and ~1.14) occurs also, but where either an unresolved potentially important third source (isotope ratio ~1.18), or an isotope exchange process should be invoked. The sediment and coral records allows us to track the changes through time; however, there seems to be incongruence with the aerosol isotope record. Further potential sources are being explored currently and will be discussed.

Development of a time-stepping sediment budget model for assessing land use impacts in large river basins.

PubMed

Wilkinson, S N; Dougall, C; Kinsey-Henderson, A E; Searle, R D; Ellis, R J; Bartley, R

2014-01-15

The use of river basin modelling to guide mitigation of non-point source pollution of wetlands, estuaries and coastal waters has become widespread. To assess and simulate the impacts of alternate land use or climate scenarios on river washload requires modelling techniques that represent sediment sources and transport at the time scales of system response. Building on the mean-annual SedNet model, we propose a new D-SedNet model which constructs daily budgets of fine sediment sources, transport and deposition for each link in a river network. Erosion rates (hillslope, gully and streambank erosion) and fine sediment sinks (floodplains and reservoirs) are disaggregated from mean annual rates based on daily rainfall and runoff. The model is evaluated in the Burdekin basin in tropical Australia, where policy targets have been set for reducing sediment and nutrient loads to the Great Barrier Reef (GBR) lagoon from grazing and cropping land. D-SedNet predicted annual loads with similar performance to that of a sediment rating curve calibrated to monitored suspended sediment concentrations. Relative to a 22-year reference load time series at the basin outlet derived from a dynamic general additive model based on monitoring data, D-SedNet had a median absolute error of 68% compared with 112% for the rating curve. RMS error was slightly higher for D-SedNet than for the rating curve due to large relative errors on small loads in several drought years. This accuracy is similar to existing agricultural system models used in arable or humid environments. Predicted river loads were sensitive to ground vegetation cover. We conclude that the river network sediment budget model provides some capacity for predicting load time-series independent of monitoring data in ungauged basins, and for evaluating the impact of land management on river sediment load time-series, which is challenging across large regions in data-poor environments. © 2013. Published by Elsevier B.V. All rights reserved.

Alkane and polycyclic aromatic hydrocarbons in sediments and benthic invertebrates of the northern Chukchi Sea

NASA Astrophysics Data System (ADS)

Harvey, H. Rodger; Taylor, Karen A.

2017-10-01

The Hanna Shoal region represents an important northern gateway for transport and deposition in the Chukchi Sea. This study determined the concentration and distribution of organic contaminants (aliphatic hydrocarbon and polycyclic aromatic hydrocarbons, PAHs) in surface sediments from 34 sites across Hanna Shoal. Up to 31 total PAHs, including parent and alkyl homologues were detected with total concentrations ranging from a low of 168 ng g-1 the western flank of Hanna Shoal (station H34) to 1147 ng g-1 at station in Barrow Canyon (station BarC5). Alkyl PAHs were more abundant than parent structures and accounted for 53-64% of the summed concentrations suggesting overall at background levels (< 1600 ng g-1) in sediments. Alkane (C15-C33) hydrocarbons ranged from 4.3 μg g-1 on the southern flank of Hanna shoal to 31 μg g-1 at a northern station. Sediments were often dominated by short chain (C15-C22) alkanes with overall terrestrial aquatic ratios (TAR) for the region averaging 0.20. Based on the ratio of Fl/(Fl+ Py) and BaF/(Baf+BeP) verses (BA/BA+Ch) in sediments, PAHs are largely derived from petrogenic sources with minor amounts of mixed combustion sources. A diversity of PAHs were detected in the northern whelk Neptunea heros foot muscle with total concentrations ranging from 0.14 to 1.5 μg g-1 dry tissue wt. Larger (and presumably older) animals showed higher levels of PAH per unit muscle tissue, suggesting that animals may bioaccumulate PAHs over time, with low but increasing concentrations also present in internal and external eggs. Alkane hydrocarbons were also higher in whelks with distributions similar to that seen in sediments. The mussel Muscularus discors collected in Barrow Canyon showed constrained distributions and substantially lower concentrations of both PAHs and alkanes than the surrounding surface sediments.

Downslope transport does not explain higher 230Th inventories in the Panama Basin

NASA Astrophysics Data System (ADS)

Singh, A. K.; Marcantonio, F.; Lyle, M. W.

2009-12-01

Mass accumulation rates (burial fluxes) in the Panama Basin calculated using oxygen isotope age models differ from those calculated using the 230Th normalized flux method. During the Holocene and the last glacial, the 230Th-derived MARs are consistently lower than age-model-derived MARs. Most importantly, using both methods, glacial MARs are always significantly higher than Holocene MARs. The discrepancy in the calculated MARs may be due to deep-ocean sediment redistribution processes, specifically downslope transport of sediments from nearby topographic highs [1]. We test this hypothesis by analyzing sediment from shallower sites throughout the Panama basin (from 712-2870 meters) and, specifically, from the tops of ridges surrounding the basin (e.g., Carnegie and Cocos Ridges). Based on 230Th methodology we determine ridge-top focusing factors (FF) that are as high as, or higher than those in the deeper parts of the basin, as determined by us or others [1]. The excess inventories of 230Th are also proportionally higher during the glacial versus Holocene in all but one of the nine new sites we have analyzed. If the source of the higher-than-predicted inventory of 230Th is topographic highs in the region, one would expect to see a correlation between 230Th and depth. We find no such correlation. Although our data suggest that within-basin topographic highs are not the source of higher 230Th inventories in the region, extrabasinal sources cannot be ruled out. In addition, there is the possibility that MARs can be underestimated using the 230Th method in Panama Basin sediments. [1] Kienast et al. 2007, Paleoceanography 22, 2213.

Linking hysteresis patterns and variations in suspended sediment sources in a highly urbanized river: a case of the River Aire, UK

NASA Astrophysics Data System (ADS)

Vercruysse, Kim; Grabowski, Robert

2017-04-01

The natural sediment balance of rivers is often disturbed as a result of increased fine sediment influx from soil erosion and/or modifications to the river channel and floodplains, causing numerous problems related to ecology, water quality, flood risk and infrastructure. It is of great importance to understand fine sediment dynamics in rivers in order to manage the problems appropriately. However, despite decades of research, our understanding of fine sediment transport is not yet sufficient to fully explain the spatial and temporal variability in sediment concentrations in rivers. To this end, the study aims to investigate the importance of sediment source variations to explain hysteresis patterns in suspended sediment transport. A sediment fingerprinting technique based on infrared spectrometry was applied in the highly urbanized River Aire catchment in northern England to identify the dominant sources of suspended sediment. Three types of potential sediment source samples were collected: soil samples from pasture in three lithological areas (limestone, millstone grit and coal measures), eroding riverbanks and urban street dust. All source samples were analyzed with Diffuse Reflectance Infrared Fourier Transform spectrometry (DRIFTS). Discriminant analysis demonstrated that the source materials could be discriminated based on their respective infrared spectra. Infrared spectra of experimental mixtures were then used to develop statistical models to estimate relative source contributions from suspended sediment samples. Suspended sediment samples were collected during a set of high flow events between 2015 and 2016, showing different hysteresis patterns between suspended sediment concentration and discharge. The fingerprinting results suggest that pasture from the limestone area is the dominant source of fine sediment. However, significant variations in source contributions during and between events are present. Small events, in terms of discharge, are marked by relatively high contributions of urban street dust, while high stream flows correspond with higher sediment contributions from riverbanks and pasture. Seasonal variations in the dominant sources are also present. The results emphasize the importance of capturing sediment source variations to gain better insights into the drivers of fine sediment transport over various timescales.

Toxic heavy metals in sediments, seawater, and molluscs in the eastern and western coastal waters of Guangdong Province, South China.

PubMed

Zhang, Ling; Shi, Zhen; Zhang, Jingping; Jiang, Zhijian; Wang, Fei; Huang, Xiaoping

2016-05-01

Heavy metal concentrations and distribution were studied in sediments, seawater, and molluscs, and the possible heavy metal sources in the coastal waters of Guangdong Province, South China were discussed. The results showed that the concentrations of Cu, Pb, Zn, and Cr in sediments in eastern coastal waters were generally higher than those in the western coastal waters. However, concentrations of most metals in seawater and molluscs in western waters were higher than in the eastern waters, which was tightly related to the local economics and urbanization development, especially, the different industrial structure in two regions. The main heavy metal sources were attributed to the industrial and agricultural effluent, domestic sewage, and even waste gas. Furthermore, heavy metal contamination assessment indicated that high contamination levels of Cd, Zn, and Pb occurred in sediments in local areas, especially in the bays and harbors. The metal accumulation levels by molluscs ranked following the order of Cd > Cu > As > Zn > Pb > Cr, and the ecological risks introduced by heavy metals in different areas were in the order of Zhanjiang > Yangmao > Shantou > Shanhui.

Source identification, spatio-temporal distribution and ecological risk of persistent organic pollutants in sediments from the upper Danube catchment.

PubMed

Kukučka, Petr; Audy, Ondřej; Kohoutek, Jiří; Holt, Eva; Kalábová, Tereza; Holoubek, Ivan; Klánová, Jana

2015-11-01

Riverine sediments, collected on a monthly basis during a period of one year, from five sites in a mixed land use region of the Czech Republic were analysed for chlorinated and brominated persistent organic pollutants (POPs). The region is located in the upper catchment of the Danube River. The POPs concentrations were as follows: 11-930 pg g(-1) polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/Fs), 170-980 pg g(-1) dioxin-like polychlorinated biphenyls (dl-PCBs), 34-13,700 pg g(-1) polychlorinated naphthalenes (PCNs), 5.7-29,200 pg g(-1) polybrominated diphenylethers (PBDEs) and 0.21-351 ng g(-1) hexabromocyclododecanes (HBCDs). Concentrations expressed as toxic equivalents (TEQs), for PCDD/F+dl-PCB+PCN (TEQPCDD/F+dl-PCB+PCN) ranged from 0.37 to 19 pg g(-1). The results revealed a clear spatial separation between sites based on concentration and congener profile. There were also some obvious temporal patterns of selected POPs, which were related to river flow (seasonality) and organic carbon (TOC) of the sediment. Potential sources of POPs include local municipalities (flame retardants), some diffuse sources (PCNs and PCDDs/Fs) and potential point sources (PBDEs). Risk assessment based on risk quotients (RQ) revealed limited to medium ecological risk from PBDEs. TEQPCDD/F+dl-PCB+PCN were low relative to other European rivers, hence the risk to aquatic organisms was considered to be low. PCNs contributed significantly to overall TEQ in several cases. Copyright © 2015 Elsevier Ltd. All rights reserved.

Boron desorption and fractionation in Subduction Zone Fore Arcs: Implications for the sources and transport of deep fluids

NASA Astrophysics Data System (ADS)

Saffer, Demian M.; Kopf, Achim J.

2016-12-01

At many subduction zones, pore water geochemical anomalies at seafloor seeps and in shallow boreholes indicate fluid flow and chemical transport from depths of several kilometers. Identifying the source regions for these fluids is essential toward quantifying flow pathways and volatile fluxes through fore arcs, and in understanding their connection to the loci of excess pore pressure at depth. Here we develop a model to track the coupled effects of boron desorption, smectite dehydration, and progressive consolidation within sediment at the top of the subducting slab, where such deep fluid signals likely originate. Our analysis demonstrates that the relative timing of heating and consolidation is a dominant control on pore water composition. For cold slabs, pore water freshening is maximized because dehydration releases bound water into low porosity sediment, whereas boron concentrations and isotopic signatures are modest because desorption is strongly sensitive to temperature and is only partially complete. For warmer slabs, freshening is smaller, because dehydration occurs earlier and into larger porosities, but the boron signatures are larger. The former scenario is typical of nonaccretionary margins where insulating sediment on the subducting plate is commonly thin. This result provides a quantitative explanation for the global observation that signatures of deeply sourced fluids are generally strongest at nonaccretionary margins. Application of our multitracer approach to the Costa Rica, N. Japan, N. Barbados, and Mediterranean Ridge subduction zones illustrates that desorption and dehydration are viable explanations for observed geochemical signals, and suggest updip fluid migration from these source regions over tens of km.

Sediment heavy metals and benthic diversities in Hun-Tai River, northeast of China.

PubMed

Qu, Xiaodong; Ren, Ze; Zhang, Min; Liu, Xiaobo; Peng, Wenqi

2017-04-01

In aquatic ecosystems, metal contamination in sediments has become a ubiquitous environmental problem, causing serious issues. Hun-Tai River, located in northeast of China, flows through an important heavy industry region and metropolitan area. This study examined the heavy metals (Cd, Cr, Cu, Fe, Mn, Pb, Ni, and Zn) of sediments and diversities (taxa richness, Shannon diversity, and evenness) of benthic assemblages (benthic algae and macroinvertebrate) in Hun-Tai River. The results clearly described the spatial patterns of metal contamination in terms of geo-accumulation index and contamination factor, as well as the spatial patterns of benthic diversities in terms of taxa richness, Shannon index, and evenness by kriging interpolation. The sediments were largely contaminated by Cd, followed by Cu, Fe, Zn, Mn, and Ni. Cd and Zn had similar spatial patterns and similar sources. Cu, Fe, Mn, and Ni showed similar spatial patterns and similar sources. The surface sediments were unpolluted by Cr and Pb. The metal mines and the heavy industry in the major cities were the potential pollution sources. Benthic algae and macroinvertebrate responded similarly to the heterogeneous environment and metal contamination, with high taxa richness and Shannon index in middle-upper reaches of Hun-Tai River. Evenness showed complex spatial patterns. Under low contamination, both taxa richness, Shannon diversity, and evenness had a large variation range. However, under the moderate and high contamination, the taxa richness and Shannon diversity kept to a low level but the evenness had a high level. This study provided insights into the sediment heavy metal contamination in Hun-Tai River.

Background Radioactivity in River and Reservoir Sediments near Los Alamos, New Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

S.G.McLin; D.W. Lyons

2002-05-05

As part of its continuing Environmental Surveillance Program, regional river and lake-bottom sediments have been collected annually by Los Alamos National Laboratory (the Laboratory) since 1974 and 1979, respectively. These background samples are collected from three drainage basins at ten different river stations and five reservoirs located throughout northern New Mexico and southern Colorado. Radiochemical analyses for these sediments include tritium, strontium-90, cesium-137, total uranium, plutonium-238, plutonium-239,-240, americium-241, gross alpha, gross beta, and gross gamma radioactivity. Detection-limit radioactivity originates as worldwide fallout from aboveground nuclear weapons testing and satellite reentry into Earth's atmosphere. Spatial and temporal variations in individual analytemore » levels originate from atmospheric point-source introductions and natural rate differences in airborne deposition and soil erosion. Background radioactivity values on sediments reflect this variability, and grouped river and reservoir sediment samples show a range of statistical distributions that appear to be analyte dependent. Traditionally, both river and reservoir analyte data were blended together to establish background levels. In this report, however, we group background sediment data according to two criteria. These include sediment source (either river or reservoir sediments) and station location relative to the Laboratory (either upstream or downstream). These grouped data are statistically evaluated through 1997, and background radioactivity values are established for individual analytes in upstream river and reservoir sediments. This information may be used to establish the existence and areal extent of trace-level environmental contamination resulting from historical Laboratory research activities since the early 1940s.« less

Assessment of the Distribution, Sources and Potential Ecological Risk of Heavy Metals in the Dry Surface Sediment of Aibi Lake in Northwest China

PubMed Central

Abuduwaili, Jilili; Zhang, Zhao yong; Jiang, Feng qing

2015-01-01

The distribution, sources and potential ecological risk of heavy metals in the sediment of lakes in eastern China and other areas of the world that have undergone rapid economic development have been widely researched by scholars. However, this is not true for heavy metals in the sediment of rump lakes in the arid regions of China and world-wide. Because of this, we chose Aibi Lake to serve as a typical rump lake in an oasis in an arid area in northwest China for our study. Sediment samples were collected from the lake and then the quantities of the heavy metals Pb, Ni, Cd, Cu, Zn, Hg and Cr were measured. Then using a variety of statistical methods, we analyzed the distribution, sources, pollution status and the potential ecological risk of these metals. The results show that: (1) The amounts of the seven heavy metals all fell within the Second Soil National Standard, but the average and maximum values were all higher than the background values of Xinjiang in northwest China. (2) Multivariate statistical analysis determined that the Cd, Pb, Hg and Zn in the sediment were mainly derived from man-sources, and Cu, Ni, and Cr were mainly from the natural geological background. (3) Enrichment factor analysis and the geo-accumulation index evaluation method show that Cd, Hg and Pb in the surface sediment of the Aibi Lake were at low and partial pollution levels, while Zn, Cr, Ni and Cu were at no and low pollution levels. (4) Calculation of the potential ecological hazards index found that, among the seven tested heavy metals, Cd, Hg and Pb were the main potential ecological risk factors, and the contribution of each was 42.6%, 28.6%, and 24.0%, respectively. Cd is the main potential ecological risk factor, followed by Hg and Pb. This work revealed that recent economic development of the Aibi Lake Basin has negatively influenced the accumulation of heavy metals in the sediments of the lake, and, therefore, we should pay increasing attention to this problem and take effective measures to protect the ecology of the Aibi Lake Basin. This work can provide a scientific basis for an early warning of heavy metal pollution and for protection of the environment. Furthermore, it can serve as a reference when creating policies for the economic development in Aibi Lake Basin and environmental protection of rump lakes in arid regions of northwest China and other areas of the world. PMID:25781032

Seafloor environments within the Boston Harbor- Massachusetts Bay sedimentary system: A regional synthesis

USGS Publications Warehouse

Knebel, H.J.; Circe, R.C.

1995-01-01

Modern seafloor sedimentary environments within the glaciated, topographically complex Boston Harbor and Massachusetts Bay area have been interpreted and mapped from an extensive collection of sidescan sonar records and supplemental marine geologic data. Three categories of environments are present that reflect the dominant long-term processes of erosion or nondeposition, deposition, and sediment reworking. (1) Environments of erosion or nondeposition comprise exposures of bedrock, glacial drift, coarse lag deposits, and possibly coastal plain rocks that contain sediments (where present) ranging from boulder fields to gravelly sands and occur in areas of relatively strong currents. (2) Environments of deposition contain fine-grained sediments ranging from muddy sands to muds that have accumulated in areas of predominantly weak bottom currents. (3) Environments of sediment reworking contain patches with textures ranging from sandy gravels to muds that have been produced by a combination of erosion and deposition in areas with variable bottom currents. The distribution of sedimentary environments across the Boston Harbor-Massachusetts Bay area is extremely patchy. Locally, this patchiness is due either to modifications of bottom-current strength (caused by the irregular topography and differences in water depth) or to small-scale changes in the supply of fine-grained sediments. Regional patchiness, however, reflects differences in geologic and oceanographic conditions among the estuarine, inner shelf, and basinal parts of the sedimentary system. The estuarine part of the system (Boston Harbor) is a depositional trap for fine-grained sediments because it is protected from large waves, has generally weak and variable tidal currents, and receives a large supply of fine grained detritus from natural and anthropogenic sources. The inner shelf, on the other hand, is largely an area of erosion or nondeposition due to sediment removal and redistribution during past sea-level changes, to sediment resuspension and winnowing by modern waves and currents, and to an inadequate supply of fine-grained sediments. The basinal part of the system (Stellwagen Basin) is mainly a tranquil depositional environment in which fine-grained sediments from several potential sources settle through the water column and accumulate under weak bottom currents. This study indicates areas within the Boston Harbor-Massachusetts Bay sedimentary system where fine-grained sediments and associated contaminants are likely to be either moved or deposited. It also provides a guide to the locations and variability of benthic habitats.

A manual to identify sources of fluvial sediment

USGS Publications Warehouse

Gellis, Allen C.; Fitzpatrick, Faith A.; Schubauer-Berigan, Joseph

2016-01-01

Sediment is an important pollutant of concern that can degrade and alter aquatic habitat. A sediment budget is an accounting of the sources, storage, and export of sediment over a defined spatial and temporal scale. This manual focuses on field approaches to estimate a sediment budget. We also highlight the sediment fingerprinting approach to attribute sediment to different watershed sources. Determining the sources and sinks of sediment is important in developing strategies to reduce sediment loads to water bodies impaired by sediment. Therefore, this manual can be used when developing a sediment TMDL requiring identification of sediment sources.The manual takes the user through the seven necessary steps to construct a sediment budget:Decision-making for watershed scale and time period of interestFamiliarization with the watershed by conducting a literature review, compiling background information and maps relevant to study questions, conducting a reconnaissance of the watershedDeveloping partnerships with landowners and jurisdictionsCharacterization of watershed geomorphic settingDevelopment of a sediment budget designData collectionInterpretation and construction of the sediment budgetGenerating products (maps, reports, and presentations) to communicate findings.Sediment budget construction begins with examining the question(s) being asked and whether a sediment budget is necessary to answer these question(s). If undertaking a sediment budget analysis is a viable option, the next step is to define the spatial scale of the watershed and the time scale needed to answer the question(s). Of course, we understand that monetary constraints play a big role in any decision.Early in the sediment budget development process, we suggest getting to know your watershed by conducting a reconnaissance and meeting with local stakeholders. The reconnaissance aids in understanding the geomorphic setting of the watershed and potential sources of sediment. Identifying the potential sediment sources early in the design of the sediment budget will help later in deciding which tools are necessary to monitor erosion and/or deposition at these sources. Tools can range from rapid inventories to estimate the sediment budget or quantifying sediment erosion, deposition, and export through more rigorous field monitoring. In either approach, data are gathered and erosion and deposition calculations are determined and compared to the sediment export with a description of the error uncertainty. Findings are presented to local stakeholders and management officials.Sediment fingerprinting is a technique that apportions the sources of fine-grained sediment in a watershed using tracers or fingerprints. Due to different geologic and anthropogenic histories, the chemical and physical properties of sediment in a watershed may vary and often represent a unique signature (or fingerprint) for each source within the watershed. Fluvial sediment samples (the target sediment) are also collected and exhibit a composite of the source properties that can be apportioned through various statistical techniques. Using an unmixing-model and error analysis, the final apportioned sediment is determined.

Spatial and temporal dynamics of sediment in contrasted mountainous watersheds (Mexican transvolcanic belt and French Southern Alps) combining river gauging, elemental geochemistry and fallout radionuclides

NASA Astrophysics Data System (ADS)

Evrard, O.; Navratil, O.; Gratiot, N.; Némery, J.; Duvert, C.; Ayrault, S.; Lefèvre, I.; Legout, C.; Bonté, P.; Esteves, M.

2009-12-01

In mountainous environments, an excessive fine sediment supply to the rivers typically leads to an increase in water turbidity, contaminant transport and a rapid filling of reservoirs. This situation is particularly problematic in regions where water reservoirs are used to provide drinking water to large cities (e.g. in central Mexico) or where stream water is used to run hydroelectric power plants (e.g. in the French Southern Alps). In such areas, sediment source areas first need to be delineated and sediment fluxes between hillslopes and the river system must be better understood before implementing efficient erosion control measures. In this context, the STREAMS (« Sediment Transport and Erosion Across MountainS ») project funded by the French National Research Agency (ANR) aims at understanding the spatial and temporal dynamics of sediment at the scale of mountainous watersheds (between 500 - 1000 km2) located in contrasted environments. This 3-years study is carried out simultaneously in a volcanic watershed located in the Mexican transvolcanic belt undergoing a subhumid tropical climate, as well as in a sedimentary watershed of the French Southern Alps undergoing a transitional climate with Mediterranean and continental influences. One of the main specificities of this project consists in combining traditional monitoring techniques (i.e. installation of river gauges, turbidimeters and sediment samplers in several sub-catchments) and sediment fingerprinting using elemental geochemistry (measured by Instrumental Neutron Activation Analysis - INAA - and Inductively Coupled Plasma - Mass Spectrometry - ICP-MS) and fallout radionuclides (measured by gamma spectrometry). In the French watershed, geochemical analysis allows outlining different sediment sources (e.g. the contribution of calcareous vs. marl-covered sub-watersheds). Radionuclide ratios (e.g.Be-7/Cs-137) allow identifying the dominant erosion processes occurring within the watershed. Areas mostly affected by gully erosion, rill or sheet erosion have been delineated. Furthermore, the measurement of radionuclide content in suspended sediment after the snowmelt suggests that most of this sediment consists in resuspended material rather than on newly eroded soil. In the Mexican watershed, a different contribution of andisols and acrisols to erosion is suspected. Overall, the bulk of erosion is generated by rather small areas within the watershed. In this region characterised by a succession of wet and dry seasons, the Be-7 content in rainfall and sediment has been measured at the scale of a 2.5 km2 sub-watershed in order to better understand the erosion transfer between hillslopes and rivers during the rainy season. This outlines the contribution of individual storms to seasonal erosion. Overall, this study brings important insights about sediment sources and fluxes within these watersheds located in contrasted environments. A further step consists in comparing experimental results with model outputs, and to evaluate the impact of on-going erosion mitigation measures.

Polybrominated diphenyl ethers (PBDEs) and alternative brominated flame retardants (aBFRs) in sediments from four bays of the Yellow Sea, North China.

PubMed

Zhen, Xiaomei; Tang, Jianhui; Xie, Zhiyong; Wang, Runmei; Huang, Guopei; Zheng, Qian; Zhang, Kai; Sun, Yongge; Tian, Chongguo; Pan, Xiaohui; Li, Jun; Zhang, Gan

2016-06-01

The distribution characteristics and potential sources of polybrominated diphenyl ethers (PBDEs) and alternative brominated flame retardants (aBFRs) were investigated in 54 surface sediment samples from four bays (Taozi Bay, Sishili Bay, Dalian Bay, and Jiaozhou Bay) of North China's Yellow Sea. Of the 54 samples studied, 51 were collected from within the four bays and 3 were from rivers emptying into Jiaozhou Bay. Decabromodiphenylethane (DBDPE) was the predominant flame retardant found, and concentration ranged from 0.16 to 39.7 ng g(-1) dw and 1.13-49.9 ng g(-1) dw in coastal and riverine sediments, respectively; these levels were followed by those of BDE 209, and its concentrations ranged from n.d. to 10.2 ng g(-1) dw and 0.05-7.82 ng g(-1) dw in coastal and riverine sediments, respectively. The levels of DBDPE exceeded those of decabromodiphenyl ether (BDE 209) in most of the samples in the study region, whereas the ratio of DBDPE/BDE 209 varied among the four bays. This is indicative of different usage patterns of brominated flame retardants (BFRs) and also different hydrodynamic conditions among these bay areas. The spatial distribution and composition profile analysis indicated that BFRs in Jiaozhou Bay and Dalian Bay were mainly from local sources, whereas transport from Laizhou Bay by coastal currents was the major source of BFRs in Taozi Bay and Sishili Bay. Both the ∑PBDEs and ∑aBFRs (sum of pentabromotoluene (PBT), 2,3-diphenylpropyl-2,4,6-tribromophenyl ether (DPTE), pentabromoethylbenzene (PBEB), and hexabromobenzene (HBB)) were at low concentrations in all the sediments. This is probably attributable to a combination of factors such as low regional usage of these products, atmospheric deposition patterns, coastal currents transportation patterns, and degradation processes for higher BDE congeners. This paper is the first study that has investigated the levels of DBDPE in the coastal sediments of China's Yellow Sea. Copyright © 2016 Elsevier Ltd. All rights reserved.

Source tracing of fluvial suspended sediments by magnetic and geochemical particle characterization: example of the Canche watershed (Nord-Pas-de-Calais, France)

NASA Astrophysics Data System (ADS)

Patault, Edouard; Alary, Claire; Franke, Christine; Gauthier, Arnaud; Abriak, Nor-Edine

2016-04-01

In France, erosion by water run-off is estimated to 1.5 t ha-1yr-1 and can exceed 10 t ha-1yr-1 in large growing areas, such as the North of France (Nord-Pas-de-Calais). In this region, the Canche watershed (1294 km2) sustains heavy loss of fertile soils. The land use is mainly dominated by arable lands (80%) and in 2013, 104 kt of suspended sediment transited to the estuary. As demonstrated in literature, agricultural soil erosion leads to the gradual disappearance and depletion of fertile soil, which constitute a non-renewable resource at human time scale. Additionally, water erosion can significantly damage the aquatic habitat and can be responsible for the input of nutrients, bacteria, pesticides, heavy metals and radionuclides into surface waters. Conscious of these effects, many programs have emerged in the Nord-Pas-de-Calais to reduce erosion. This study presents a combination of environmental magnetic proxy parameters and geochemical analyses on sediments and suspended particulate matter. The aim is to develop effective tools to trace erosion by water run-off and quantify this process. In order to identify the respective sediment sources in the Canche watershed, sediment trap samples of suspended particulate matter were recovered at key positions along the Canche watershed. The preliminary results show that magnetic concentration (Mrs) shows typical values for the agricultural soils in the region, but these variations in magnetic concentrations and total irons concentrations are not always correlated, which may be explained by the iron speciation. In calculating the so-called S-ratio for each sample we can distinguish changes in magneto-mineralogy (and thus iron speciation) from magnetite-dominated assemblages in the mainstream Canche (naturel background signal) to high-coercivity-dominated assemblages in the tributaries, typical for soil erosion material rich in hematite/goethite. In combination with the element concentrations from ICP analyses, this proxy parameter may give valuable insight into the tracing of the suspended sediment sources. In perspective, the seasonal variability and the discharge in the Canche watershed have to be taken into account.

Sediment discharge into a subsiding Louisiana deltaic estuary through a Mississippi River diversion

USGS Publications Warehouse

Snedden, G.A.; Cable, J.E.; Swarzenski, C.; Swenson, E.

2007-01-01

Wetlands of the Mississippi River deltaic plain in southeast Louisiana have been hydrologically isolated from the Mississippi River by containment levees for nearly a century. The ensuing lack of fluvial sediment inputs, combined with natural submergence processes, has contributed to high coastal land loss rates. Controlled river diversions have since been constructed to reconnect the marshes of the deltaic plain with the river. This study examines the impact of a pulsed diversion management plan on sediment discharge into the Breton Sound estuary, in which duplicate 185 m3 s-1-diversions lasting two weeks each were conducted in the spring of 2002 and 2003. Sediment delivery during each pulse was highly variable (11,300-43,800 metric tons), and was greatest during rising limbs of Mississippi River flood events. Overland flow, a necessary transport mechanism for river sediments to reach the subsiding backmarsh regions, was induced only when diversion discharge exceeded 100 m3 s-1. These results indicate that timing and magnitude of diversion events are both important factors governing marsh sediment deposition in the receiving basins of river diversions. Though the diversion serves as the primary source of river sediments to the estuary, the inputs observed here were several orders of magnitude less than historical sediment discharge through crevasses and uncontrolled diversions in the region, and are insufficient to offset present rates of relative sea level rise. ?? 2006 Elsevier Ltd. All rights reserved.

Deconvolving the Fate of Carbon in Coastal Sediments

NASA Astrophysics Data System (ADS)

Van der Voort, Tessa S.; Mannu, Utsav; Blattmann, Thomas M.; Bao, Rui; Zhao, Meixun; Eglinton, Timothy I.

2018-05-01

Coastal oceans play a crucial role in the global carbon cycle, and are increasingly affected by anthropogenic forcing. Understanding carbon cycling in coastal environments is hindered by convoluted sources and myriad processes that vary over a range of spatial and temporal scales. In this study, we deconvolve the complex mosaic of organic carbon manifested in Chinese Marginal Sea (CMS) sediments using a novel numerical clustering algorithm based on 14C and total OC content. Results reveal five regions that encompass geographically distinct depositional settings. Complementary statistical analyses reveal contrasting region-dependent controls on carbon dynamics and composition. Overall, clustering is shown to be highly effective in demarcating areas of distinct organic facies by disentangling intertwined organic geochemical patterns resulting from superimposed effects of OC provenance, reworking and deposition on a shelf region exhibiting pronounced spatial heterogeneity. This information will aid in constraining region-specific budgets of carbon burial and carbon cycle processes.

Mercury in waters, soils, and sediments of the New Jersey Coastal Plain: A comparison of regional distribution and mobility with the mercury contamination at the William J. Hughes Technical Center, Atlantic County, New Jersey

USGS Publications Warehouse

Barringer, Julia L.; Szabo, Zoltan; Reilly, Pamela A.

2012-01-01

Mercury in soils, surface water, and groundwater at the William J. Hughes Technical Center , Atlantic County, New Jersey, has been found at levels that exceed established background concentrations in Coastal Plain waters, and, in some cases, New Jersey State standards for mercury in various media. As of 2012, it is not known whether this mercury is part of regional mercury contamination or whether it is related to former military activities. Regionally, groundwater supplying about 700 domestic wells in the New Jersey Coastal Plain is contaminated with mercury that appears to be derived from anthropogenic inputs, such as agricultural pesticide use and atmospheric deposition. High levels of mercury occasionally are found in Coastal Plain soils, but disturbance during residential development on former agricultural land is thought to have mobilized any mercury applied during farming, a hypothesis borne out by experiments leaching mercury from soils. In the unsewered residential areas with mercury-contaminated groundwater, septic-system effluent is believed to create reducing conditions in which mercury sorbed to subsoils is mobilized to groundwater. In comparing the levels of mercury found in soils, sediments, streamwater, and groundwater at the William J. Hughes Technical Center site with those found regionally, mercury concentrations in groundwater in the region are, in some cases, substantially higher than those found in groundwater at the William J. Hughes Technical Center site. Nevertheless, concentrations of mercury in streamwater at the site are, in some instances, higher than most found regionally. The mercury contents in soils and sediment at the William J. Hughes Technical Center site are substantially higher than those found to date (2012) in the region, indicating that a source other than regional sources may be present at the site.

Distribution pattern and mass budget of sedimentary polycyclic aromatic hydrocarbons in shelf areas of the Eastern China Marginal Seas

NASA Astrophysics Data System (ADS)

Wang, C. L.; Zou, X. Q.; Zhao, Y. F.; Li, Y. L.; Song, Q. C.; Wang, T.; Yu, W. W.

2017-06-01

This study conducted the first extensive and comprehensive investigation of the regional-scale sedimentary polycyclic aromatic hydrocarbons (PAHs) concentration, flux, and budget in the continental shelves of the Eastern China Marginal Seas (ECMSs). Surface sediment samples from multiple sites were collected and assessed, and the latest data from current research were assessed. The spatial distribution pattern of PAHs in the ECMSs was significantly influenced by the regional hydrodynamics, sediment properties (grain-size, total organic carbon [TOC] content, and sedimentation rate), and anthropogenic impacts. Relatively higher PAHs concentrations occurred in areas with fine-grained sediment. Results of source apportionment found that the relative proportions of PAHs showed significant regional variation, mainly influenced by socioeconomic differences between north and south China. The PAHs burial flux in the study area ranged from 11.2 to 1308 ng cm-2 yr-1 with an average value of 101 ± 104 ng cm-2 yr-1. The area-integrated sedimentary PAHs burial flux across the ECMSs was 494 t yr-1. A mass budget calculation revealed that riverine input and atmospheric deposition were the most significant sources contributing, 28.4% and 71.6%, respectively. The study demonstrated that net PAHs transportation occurs between the Bohai Sea (BS) and Yellow Sea (YS), with a flux of approximately 10.2 t yr-1. PAHs were also transported from YS to the East China Sea (ECS), due to water exchange between the YS and ECS. Additionally, substantial amounts of PAHs in the inner shelf of the ECS were transported out of the shelf area due to cross-shelf plume.

Late Pleistocene aeolian dust provenances and wind direction changes reconstructed by heavy mineral analysis of the sediments of the Dehner dry maar (Eifel, Germany)

NASA Astrophysics Data System (ADS)

Römer, Wolfgang; Lehmkuhl, Frank; Sirocko, Frank

2016-12-01

The study presents the results of a heavy mineral analysis from a 38 m long record of lacustrine Eifel maar sediments from a core section of the Dehner dry maar. The record encompasses the period from 29,000 to about 12,500 b2k. Statistical analyses enabled the distinction of local and regional source areas of aeolian material and revealed pronounced changes in the amounts of different heavy mineral species and corresponding changes in the grain size Index (GSI and CSI). The results indicate that during the early stages of MIS2 (39 to 30 m depth) aeolian sediments were supplied mostly from local sources. This period is characterized by low GSI and CSI ratios resulting from a reduced mobility of material due to a vegetation cover. The period between 23,000 and 12,900 b2k is characterized by a higher supply of heavy minerals from regional and more distant sources. Changes in the provenance areas are indicated in inverse relationships between zircon, rutile, tourmaline (ZRT) and carbonate particles. Shifts in the wind direction are documented in pronounced peaks of carbonate particles indicating easterly winds that have crossed the limestone basins in the Eifeler North South Zone. ZRT-group minerals on the other hand suggest a westerly source area from Palaeozoic clastic sedimentary rocks. The heavy mineral assemblage of the LGM section at 23,000 to 15,000 b2k displays a close correspondence with the stratigraphic relationships that have been obtained for the Landscape Evolution Zone 4 of the ELSA-Vegetation Stack of Sirocko et al. (2016). From the Heinrich 2 event onwards the analyses indicate an increasing degree of mixing of heavy minerals from various provinces. This suggests the existence of a presumably incomplete, thin cover of deflated loess-like sediments that has been repeatedly reworked on the elevated surfaces of the Eifel.

Mercury Sources and Fate in the Gulf of Maine

PubMed Central

Sunderland, Elsie M.; Amirbahman, Aria; Burgess, Neil M.; Dalziel, John; Harding, Gareth; Jones, Stephen H.; Kamai, Elizabeth; Karagas, Margaret R.; Shi, Xun; Chen, Celia Y.

2012-01-01

Most human exposure to mercury (Hg) in the United States is from consuming marine fish and shellfish. The Gulf of Maine is a complex marine ecosystem comprised of twelve physioregions, including the Bay of Fundy, coastal shelf areas and deeper basins that contain highly productive fishing grounds. Here we review available data on spatial and temporal Hg trends to better understand the drivers of human and biological exposures. Atmospheric Hg deposition from U.S. and Canadian sources has declined since the mid-1990s in concert with emissions reductions but deposition from global sources has increased. Oceanographic circulation is the dominant source of total Hg inputs to the entire Gulf of Maine region (59%), followed by atmospheric deposition (28%), wastewater/industrial sources (8%), and rivers (5%). Resuspension of sediments increases MeHg inputs to overlying waters raising concerns about benthic trawling activities in shelf regions. In the near coastal areas, elevated sediment and mussel Hg levels are co-located in urban embayments and near large historical point sources. Temporal patterns in sentinel species (mussels and birds) have in some cases declined in response to localized point source mercury reductions but overall Hg trends do not show consistent declines. For example, levels of Hg have either declined or remained stable in eggs from four seabird species collected in the Bay of Fundy since 1972. Quantitatively linking Hg exposures from fish harvested from the Gulf of Maine to human health risks is challenging at this time because no data are available on the geographic origin of seafood consumed by coastal residents. In addition, there is virtually no information on Hg levels in commercial species for offshore regions of the Gulf of Maine where some of the most productive fisheries are located. Both of these data gaps should be priorities for future research. PMID:22572623

Calibration of an estuarine sediment transport model to sediment fluxes as an intermediate step for simulation of geomorphic evolution

USGS Publications Warehouse

Ganju, N.K.; Schoellhamer, D.H.

2009-01-01

Modeling geomorphic evolution in estuaries is necessary to model the fate of legacy contaminants in the bed sediment and the effect of climate change, watershed alterations, sea level rise, construction projects, and restoration efforts. Coupled hydrodynamic and sediment transport models used for this purpose typically are calibrated to water level, currents, and/or suspended-sediment concentrations. However, small errors in these tidal-timescale models can accumulate to cause major errors in geomorphic evolution, which may not be obvious. Here we present an intermediate step towards simulating decadal-timescale geomorphic change: calibration to estimated sediment fluxes (mass/time) at two cross-sections within an estuary. Accurate representation of sediment fluxes gives confidence in representation of sediment supply to and from the estuary during those periods. Several years of sediment flux data are available for the landward and seaward boundaries of Suisun Bay, California, the landward-most embayment of San Francisco Bay. Sediment flux observations suggest that episodic freshwater flows export sediment from Suisun Bay, while gravitational circulation during the dry season imports sediment from seaward sources. The Regional Oceanic Modeling System (ROMS), a three-dimensional coupled hydrodynamic/sediment transport model, was adapted for Suisun Bay, for the purposes of hindcasting 19th and 20th century bathymetric change, and simulating geomorphic response to sea level rise and climatic variability in the 21st century. The sediment transport parameters were calibrated using the sediment flux data from 1997 (a relatively wet year) and 2004 (a relatively dry year). The remaining years of data (1998, 2002, 2003) were used for validation. The model represents the inter-annual and annual sediment flux variability, while net sediment import/export is accurately modeled for three of the five years. The use of sediment flux data for calibrating an estuarine geomorphic model guarantees that modeled geomorphic evolution will not exceed the actual supply of sediment from the watershed and seaward sources during the calibration period. Decadal trends in sediment supply (and therefore fluxes) can accumulate to alter decadal geomorphic change. Therefore, simulations of future geomorphic evolution are bolstered by this intermediate calibration step.

The significance of 24-norcholestanes, triaromatic steroids and dinosteroids in oils and Cambrian-Ordovician source rocks from the cratonic region of the Tarim Basin, NW China

USGS Publications Warehouse

Li, Meijun; Wang, T.-G.; Lillis, Paul G.; Wang, Chunjiang; Shi, Shengbao

2012-01-01

Two oil families in Ordovician reservoirs from the cratonic region of the Tarim Basin are distinguished by the distribution of regular steranes, triaromatic steroids, norcholestanes and dinosteroids. Oils with relatively lower contents of C28 regular steranes, C26 20S, C26 20R + C27 20S and C27 20R regular triaromatic steroids, dinosteranes, 24-norcholestanes and triaromatic dinosteroids originated from Middle–Upper Ordovician source rocks. In contrast, oils with abnormally high abundances of the above compounds are derived from Cambrian and Lower Ordovician source rocks. Only a few oils have previously been reported to be of Cambrian and Lower Ordovician origin, especially in the east region of the Tarim Basin. This study further reports the discovery of oil accumulations of Cambrian and Lower Ordovician origin in the Tabei and Tazhong Uplifts, which indicates a potential for further discoveries involving Cambrian and Lower Ordovician sourced oils in the Tarim Basin. Dinosteroids in petroleum and ancient sediments are generally thought to be biomarkers for dinoflagellates and 24-norcholestanes for dinoflagellates and diatoms. Therefore, the abnormally high abundance of these compounds in extracts from the organic-rich sediments in the Cambrian and Lower Ordovician and related oils in the cratonic region of the Tarim Basin suggests that phytoplankton algae related to dinoflagellates have appeared and might have flourished in the Tarim Basin during the Cambrian Period. Steroids with less common structural configurations are underutilized and can expand understanding of the early development history of organisms, as well as define petroleum systems.

Rock-Bound Arsenic Influences Ground Water and Sediment Chemistry Throughout New England

USGS Publications Warehouse

Robinson, Gilpin R.; Ayotte, Joseph D.

2007-01-01

The information in this report was presented at the Northeastern Region Geological Society of America meeting held March 11-14, 2007, in Durham, New Hampshire. In the New England crystalline bedrock aquifer, concentrations of arsenic that exceed the drinking water standard of 10 ?g/L occur most frequently in ground water from wells sited in specific metamorphic and igneous rock units. Geochemical investigations indicate that these geologic units typically have moderately elevated whole-rock concentrations of arsenic compared to other rocks in the region. The distribution of ground water wells with As > 5 ?g/L has a strong spatial correlation with specific bedrock units where average whole-rock concentrations of arsenic exceed 1.1 mg/kg and where geologic and geochemical factors produce high pH ground water. Arsenic concentrations in stream sediments collected from small drainages reflect the regional distribution of this natural arsenic source and have a strong correlation with both rock chemistry and the distribution of bedrock units with elevated arsenic chemistry. The distribution of ground water wells with As > 5 ?g/L has a strong spatial correlation with the distribution of stream sediments where concentrations of arsenic exceed 6 mg/kg. Stream sediment chemistry also has a weak correlation with the distribution of agricultural lands where arsenical pesticides were used on apple, blueberry, and potato crops. Elevated arsenic concentrations in bedrock wells, however, do not correlate with agricultural areas where arsenical pesticides were used. These results indicate that both stream sediment chemistry and the solubility and mobility of arsenic in ground water in bedrock are influenced by host-rock arsenic concentrations. Stream sediment chemistry and the distribution of geologic units have been found to be useful parameters to predict the areas of greatest concern for elevated arsenic in ground water and to estimate the likely levels of human exposure to elevated arsenic in drinking water in New England. However, the extreme local variability of arsenic concentrations in ground water from these rock sources indicate that arsenic concentrations in ground water are affected by other factors in addition to arsenic concentrations in rock.

Trace metals in sediments of two estuarine lagoons from Puerto Rico.

PubMed

Acevedo-Figueroa, D; Jiménez, B D; Rodríguez-Sierra, C J

2006-05-01

Concentrations of As, Cd, Cu, Fe, Hg, Pb and Zn were evaluated in surface sediments of two estuaries from Puerto Rico, known as San José Lagoon (SJL) and Joyuda Lagoon. Significantly higher concentrations in microg/g dw of Cd (1.8 vs. 0.1), Cu (105 vs. 22), Hg (1.9 vs. 0.17), Pb (219 vs. 8), and Zn (531 vs. 52) were found in sediment samples from SJL when compared to Joyuda Lagoon. Average concentrations of Hg, Pb, and Zn in some sediment samples from SJL were above the effect range median (ERM) that predict toxic effects to aquatic organisms. Enrichments factors using Fe as a normalizer, and correlation matrices showed that metal pollution in SJL was the product of anthropogenic sources, while the metal content in Joyuda Lagoon was of natural origins. Sediment metal concentrations found in SJL were comparable to aquatic systems classified as contaminated from other regions of the world.

Provenance of the lower Miocene of the Gulf of Mexico from detrital zircon double dating

NASA Astrophysics Data System (ADS)

xu, J.

2013-12-01

The lower Miocene interval of the Gulf of Mexico (GOM) has recently gained increasing attention from oil and gas industry due to its hydrocarbon potential below the salt canopy. However, it has been less well studied than both the underlying Oligocene and overlying middle Miocene strata. The lower Miocene worldwide is a transitional period of tectonic, climatic, and oceanographic change. In particular, it is a period of major tectonic reorganization in the western interior of North America (Rocky Mountains), involving a shift from the Oligocene thermal phase, with abundant volcanic activity recorded in the thick Frio/Vicksburg succession of the GOM, to the Miocene Basin-Range extensional phase. Climatic conditions also changed from a relatively arid Oligocene to wetter Miocene, resulting in increased sediment yields from exhumed tectonic structures. Previous provenance studies used proportions of quartz, feldspar and lithic fragments and consideration of likely river courses through known paleogeomorphological elements. Only limited detrital zircon (DZ) U-Pb studies on Paleocene strata have been undertaken and there has been no previous U-Pb and (U-Th)/He double dating in the GOM. In this study we apply the latest analytical approaches, such as DZ U-Pb dating to gain robust source terranes ages and more fully elucidate the complex sediment provenance and dispersal history of GOM. We also employ DZ (U-Th)/He (ZHe) dating, combined with DZ U-Pb, to not only define sedimentary provenance but also the exhumation histories of detrital source regions. Samples of lower Miocene outcrop exposures in Texas and Louisiana have been collected to discriminate the varied tectonic and drainage system changes across the basin in lateral. In addition, samples from the Eocene, Oligocene and middle Miocene have been obtained to reveal vertical shift of source terranes contributions. Our initial age data show detrital zircons of lower Miocene sediments come from a wide range of source terranes including a large populations from the western interior of North America (Rocky Mountains), Grenville, Mid-Continent, and Yavapai-Mazatzal provinces, with smaller populations from the Appalachian-Ouachita, Wyoming or Superior regions. Based on U-Pb dating results, we will carry out (U-Th)/He dating on selected zircons to reveal the detailed exhumation histories of the sediment source regions. Using the dual criteria of DZ crystallization age (U-Pb) and cooling age (U-Th/He) to constrain provenance will enable us to generate rigorous reconstructions of the lower Miocene depositional systems from source terrane to deep-water sink for this key transitional period in geologic history.

Estimation of sediment sources using selected chemical tracers in the Perry lake basin, Kansas, USA

USGS Publications Warehouse

Juracek, K.E.; Ziegler, A.C.

2009-01-01

The ability to achieve meaningful decreases in sediment loads to reservoirs requires a determination of the relative importance of sediment sources within the contributing basins. In an investigation of sources of fine-grained sediment (clay and silt) within the Perry Lake Basin in northeast Kansas, representative samples of channel-bank sources, surface-soil sources (cropland and grassland), and reservoir bottom sediment were collected, chemically analyzed, and compared. The samples were sieved to isolate the <63 ?? m fraction and analyzed for selected nutrients (total nitrogen and total phosphorus), organic and total carbon, 25 trace elements, and the radionuclide cesium-137 (137Cs). On the basis of substantial and consistent compositional differences among the source types, total nitrogen (TN), total phosphorus (TP), total organic carbon (TOC), and 137Cs were selected for use in the estimation of sediment sources. To further account for differences in particle-size composition between the sources and the reservoir bottom sediment, constituent ratio and clay-normalization techniques were used. Computed ratios included TOC to TN, TOC to TP, and TN to TP. Constituent concentrations (TN, TP, TOC) and activities (137Cs) were normalized by dividing by the percentage of clay. Thus, the sediment-source estimations involved the use of seven sediment-source indicators. Within the Perry Lake Basin, the consensus of the seven indicators was that both channel-bank and surface-soil sources were important in the Atchison County Lake and Banner Creek Reservoir subbasins, whereas channel-bank sources were dominant in the Mission Lake subbasin. On the sole basis of 137Cs activity, surface-soil sources contributed the most fine-grained sediment to Atchison County Lake, and channel-bank sources contributed the most fine-grained sediment to Banner Creek Reservoir and Mission Lake. Both the seven-indicator consensus and 137Cs indicated that channel-bank sources were dominant for Perry Lake and that channel-bank sources increased in importance with distance downstream in the basin. ?? 2009 International Research and Training Centre on Erosion and Sedimentation and the World Association for Sedimentation and Erosion Research.

Watershed sediment source fingerprinting: a view under the hood

NASA Astrophysics Data System (ADS)

Smith, H.

2015-12-01

Sediment source fingerprinting procedures involve the discrimination of sediment sources based on physical and chemical properties and estimation of the contributions from those sources to mixtures of fine-grained sediment transported within watersheds. Sources of sediment widely considered include agricultural land uses, channel banks and geological zones. There has been a tendency in the literature for sediment fingerprinting to be presented as a technique that can deliver accurate and precise information on source contributions to sediment across a range of environments. However, recent research indicates that such a view of sediment fingerprinting cannot presently be supported. Furthermore, many past papers lack transparency in data processing and presentation that prevents the critical assessment of results and hinders wider uptake of the technique. Therefore, this contribution aims to delve 'under the hood' of sediment fingerprinting to promote further discussion and debate over future research needs and method limitations. It draws on important developments from the last two years concerning the effect of (i) tracer selection, (ii) tracer behaviour during transport, (iii) corrections to tracer datasets and (iv) the choice of mixing model on predictions of sediment source contributions. Sediment fingerprinting has the potential to make a very significant contribution to the measurement of contemporary sediment sources in watersheds, but cannot be viewed as an 'off-the-shelf' technique for widespread application until important challenges have been addressed.

Clay Mineralogy of AN Alluvial Aquifer in a Mountainous, Semiarid Terrain, AN Example from Rifle, Colorado

NASA Astrophysics Data System (ADS)

Elliott, W. C.; Lim, D.; Zaunbrecher, L. K.; Pickering, R. A.; Williams, K. H.; Navarre-Sitchler, A.; Long, P. E.; Noel, V.; Bargar, J.; Qafoku, N. P.

2015-12-01

Alluvial sediments deposited along the Colorado River corridor in the semi-arid regions of central to western Colorado can be important hosts for legacy contamination including U, V, As and Se. These alluvial sediments host aquifers which are thought to provide important "hot spots" and "hot moments" for microbiological activity controlling organic carbon processing and fluxes in the subsurface. Relatively little is known about the clay mineralogy of these alluvial aquifers and the parent alluvial sediments in spite of the fact that they commonly include lenses of silt-clay materials. These lenses are typically more reduced than coarser grained materials, but zones of reduced and more oxidized materials are present in these alluvial aquifer sediments. The clay mineralogy of the non-reduced parent alluvial sediments of the alluvial aquifer located in Rifle, CO (USA) is composed of chlorite, smectite, illite, kaolinite and quartz. The clay mineralogy of non-reduced fine-grained materials at Rifle are composed of the same suite of minerals found in the sediments plus a vermiculite-smectite intergrade that occurs near the bottom of the aquifer near the top of the Wasatch Formation. The clay mineral assemblages of the system reflect the mineralogically immature character of the source sediments. These assemblages are consistent with sediments and soils that formed in a moderately low rainfall climate and suggestive of minimal transport of the alluvial sediments from their source areas. Chlorite, smectite, smectite-vermiculite intergrade, and illite are the likely phases involved in the sorption of organic carbon and related microbial redox transformations of metals in these sediments. Both the occurrence and abundance of chlorite, smectite-vermiculite, illite and smectite can therefore exert an important control on the contaminant fluxes and are important determinants of biogeofacies in mountainous, semiarid terrains.

Contamination of nonylphenolic compounds in creek water, wastewater treatment plant effluents, and sediments from Lake Shihwa and vicinity, Korea: Comparison with fecal pollution

USGS Publications Warehouse

Choi, Minkyu; Furlong, Edward T.; Moon, Hyo-Bang; Yu, Jun; Choi, Hee-Gu

2011-01-01

Nonylphenolic compounds (NPs), coprostanol (COP), and cholestanol, major contaminants in industrial and domestic wastewaters, were analyzed in creek water, wastewater treatment plant (WWTP) effluent, and sediment samples from artificial Lake Shihwa and its vicinity, one of the most industrialized regions in Korea. We also determined mass discharge of NPs and COP, a fecal sterol, into the lake, to understand the linkage between discharge and sediment contamination. Total NP (the sum of nonylphenol, and nonylphenol mono- and di-ethoxylates) were 0.32–875 μg L-1 in creeks, 0.61–87.0 μg L-1 in WWTP effluents, and 29.3–230 μg g-1 TOC in sediments. Concentrations of COP were 0.09–19.0 μg L-1 in creeks, 0.11–44.0 μg L-1 in WWTP effluents, and 2.51–438 μg g-1 TOC in sediments. The spatial distributions of NPs in creeks and sediments from the inshore region were different from those of COP, suggesting that Lake Shihwa contamination patterns from industrial effluents differ from those from domestic effluents. The mass discharge from the combined outfall of the WWTPs, located in the offshore region, was 2.27 kg d-1 for NPs and 1.00 kg d-1 for COP, accounting for 91% and 95% of the total discharge into Lake Shihwa, respectively. The highest concentrations of NPs and COP in sediments were found in samples at sites near the submarine outfall of the WWTPs, indicating that the submarine outfall is an important point source of wastewater pollution in Lake Shihwa.

Recent paleorecords document rising mercury contamination in Lake Tanganyika

USGS Publications Warehouse

Conaway, C.H.; Swarzenski, P.W.; Cohen, A.S.

2012-01-01

Recent Lake Tanganyika Hg deposition records were derived using 14C and excess 210Pb geochronometers in sediment cores collected from two contrasting depositional environments: the Kalya Platform, located mid-lake and more removed from watershed impacts, and the Nyasanga/Kahama River delta region, located close to the lake's shoreline north of Kigoma. At the Kalya Platform area, pre-industrial Hg concentrations are 23??0.2ng/g, increasing to 74ng/g in modern surface sediment, and the Hg accumulation rate has increased from 1.0 to 7.2??g/m 2/a from pre-industrial to present, which overall represents a 6-fold increase in Hg concentration and accumulation. At the Nyasanga/Kahama delta region, pre-industrial Hg concentrations are 20??3ng/g, increasing to 46ng/g in surface sediment. Mercury accumulation rate has increased from 30 to 70??g/m 2/a at this site, representing a 2-3-fold increase in Hg concentration and accumulation. There is a lack of correlation between charcoal abundance and Hg accumulation rate in the sediment cores, demonstrating that local biomass burning has little relationship with the observed Hg concentration or Hg accumulation rates. Examined using a sediment focusing-corrected mass accumulation rate approach, the cores have similar anthropogenic atmospheric Hg deposition profiles, suggesting that after accounting for background sediment concentrations the source of accumulating Hg is predominantly atmospheric in origin. In summary, the data document an increase of Hg flux to the Lake Tanganyika ecosystem that is consistent with increasing watershed sediment delivery with background-level Hg contamination, and regional as well as global increases in atmospheric Hg deposition. ?? 2011.

Geochemical evidence for the provenance of aeolian deposits in the Qaidam Basin, Tibetan Plateau

NASA Astrophysics Data System (ADS)

Du, Shisong; Wu, Yongqiu; Tan, Lihua

2018-06-01

The main purpose of this study is to analyse the material source of different grain-size components of dune sand in the Qaidam Basin. We determined the trace and rare earth element (REE) compositions and Sr-Nd isotopic compositions of the coarse (75-500 μm) and fine (<75 μm) fractions of surface sediment samples. The comparison of the immobile trace element and REE compositions, Sr-Nd isotopic compositions and multidimensional scaling (MDS) results of the dune sands with those of different types of sediments in potential source areas revealed the following information. (1) The fine- and coarse-grained fractions of dune sands in the Qaidam Basin exhibit distinctly different elemental concentrations, elemental patterns and characteristic parameters of REE. Moreover, Sr-Nd isotopic differences also exist between different grain-size fractions of aeolian sand, which means that different grain-size fractions of these dune sands have different source areas. (2) The geochemical characteristics of the coarse particles of dune sand exhibit obvious regional heterogeneity and generally record a local origin derived from local fluvial sediments and alluvial/proluvial sediments. The coarse- and fine-grained dune sand in the southern Qaidam Basin mainly came from Kunlun Mountains, whereas the coarse- and fine-grained dune sand in the northeastern Qaidam Basin mainly came from Qilian Mountains. (3) The fine-grained fractions of sediments throughout the entire Qaidam Basin may have been affected by the input of foreign materials from the Tarim Basin.

A Manual to Identify Sources of Fluvial Sediment | Science ...

EPA Pesticide Factsheets

Sedimentation is one of the main causes of stream/river aquatic life use impairments in R3. Currently states lack standard guidance on appropriate tools available to quantify sediment sources and develop sediment budgets in TMDL Development. Methods for distinguishing sediment types for TMDL development will focus stream restoration and soil conservation efforts in strategic locations in a watershed and may better target appropriate BMPs to achieve sediment load reductions. Properly identifying sediment sources in a TMDL will also help focus NPDES permitting, stream restoration activities and other TMDL implementation efforts. This project will focus on developing a framework that will be published as a guidance document that outlines steps and approaches to identify the significant sources of fine-grained sediment in 303D listed watersheds. In this framework, the sediment-fingerprinting and sediment budget approaches will be emphasized. This project will focus on developing a framework that will be published as a guidance document that outlines steps and approaches to identify the significant sources of fine-grained sediment in 303D listed watersheds. In this framework, the sediment-fingerprinting and sediment budget approaches will be emphasized.

Sediment Loading from Crab Creek and Other Sources to Moses Lake, Washington, 2007 and 2008

USGS Publications Warehouse

Magirl, Christopher S.; Cox, Stephen E.; Mastin, Mark C.; Huffman, Raegan L.

2010-01-01

The average sediment-accumulation rate on the bed of Moses Lake since 1980, based on the identification of Mount St. Helens ash in lakebed cores, was 0.24 inches per year. Summed over the lake surface area, the average sediment-accumulation rate on the lakebed is 190,000 tons per year. Based on USGS stream-gaging station data, the average annual sediment load to Moses Lake from Crab Creek was 32,000 tons per year between 1943 and 2008; the post Mount St. Helens eruption annual load from Crab Creek was calculated to be 13,000 tons per year. The total mass input from Crab Creek and other fluvially derived sediment sources since 1980 has been about 20,000 tons per year. Eolian sediment loading to Moses Lake was about 50,000 tons per year before irrigation and land-use development largely stabilized the Moses Lake dune field. Currently, eolian input to the lake is less than 2,000 tons per year. Considering all sediment sources to the lake, most (from 80 to 90 percent) of post-1980 lakebed-sediment accumulation is from autochthonous, or locally formed, mineral matter, including diatom frustuals and carbonate shells, derived from biogenic production in phytoplankton and zooplankton. Suspended-sediment samples collected from Crab Creek and similar nearby waterways in 2007 and 2008 combined with other USGS data from the region indicated that a proposed Bureau of Reclamation supplemental feed of as much as 650 cubic feet per second through Crab Creek might initially contain a sediment load of as much as 1,500 tons per day. With time, however, this sediment load would decrease to about 10 tons per day in the sediment-supply-limited creek as available sediment in the channel is depleted. Sediment loads in the supplemental feed ultimately would be similar to loads in other bypass canals near Moses Lake. Considering the hydrology and geomorphology of the creek over multiple years, there is little evidence that the proposed supplemental feed would substantially increase the overall sediment load from Crab Creek to Moses Lake relative to natural, background conditions. Because Moses Lake is relatively shallow and subject to significant wind-driven circulation currents, mixing also would redistribute some of the fluvial sediment load deposited from Crab Creek throughout Parker Horn and the rest of Moses Lake, further mitigating the local effect of Crab Creek sedimentation near the City of Moses Lake.

Concentrations and isotope ratios of mercury in sediments from shelf and continental slope at Campos Basin near Rio de Janeiro, Brazil.

PubMed

Araujo, Beatriz Ferreira; Hintelmann, Holger; Dimock, Brian; Almeida, Marcelo Gomes; Rezende, Carlos Eduardo

2017-07-01

Mercury (Hg) may originate from both anthropogenic and natural sources. The measurement of spatial and temporal variations of Hg isotope ratios in sediments may enable source identification and tracking of environmental processes. In this study we establish the distribution of mercury concentrations and mercury isotope ratios in surface sediments of three transects along the continental shelf and slope in Campos Basin-RJ-Brazil. The shelf showed on average lower total Hg concentrations (9.2 ± 5.3 ng g -1 ) than the slope (24.6 ± 8.8 ng g -1 ). MMHg average concentrations of shelf 0.15 ± 0.12 ng g -1 and slope 0.13 ± 0.06 ng g -1 were not significantly different. Distinct differences in Hg isotope ratio signatures were observed, suggesting that the two regions were impacted by different sources of Hg. The shelf showed more negative δ 202 Hg and Δ 199 Hg values ranging from -0.59 to -2.19‰ and from -0.76 to 0.08‰, respectively. In contrast, the slope exhibited δ 202 Hg values from -0.29 to -1.82‰ and Δ 199 Hg values from -0.23 to 0.09‰. Mercury found on the shelf, especially along the "D" and "I" transects, is depleted in heavy isotopes resulting in more negative δ 202 Hg compared to the slope. Isotope ratios observed in the "D" and "I" shelf region are similar to Hg ratios commonly associated with plants and vegetation and very comparable to those detected in the estuary and adjoining mangrove forest, which suggests that Hg exported from rivers may be the dominating source of Hg in near coastal regions along the northern part of the shelf. Copyright © 2017 Elsevier Ltd. All rights reserved.

Identifying sources of acidity and spatial distribution of acid sulfate soils in the Anglesea River catchment, southern Australia

NASA Astrophysics Data System (ADS)

Wong, Vanessa; Yau, Chin; Kennedy, David

2015-04-01

Globally, coastal and estuarine floodplains are frequently underlain by sulfidic sediments. When exposed to oxygen, sulfidic sediments oxidise to form acid sulfate soils, adversely impacting on floodplain health and adjacent aquatic ecoystems. In eastern Australia, our understanding of the formation of these coastal and estuarine floodplains, and hence, spatial distribution of acid sulfate soils, is relatively well established. These soils have largely formed as a result of sedimentation of coastal river valleys approximately 6000 years BP when sea levels were one to two metres higher. However, our understanding of the evolution of estuarine systems and acid sulfate soil formation, and hence, distribution, in southern Australia remains limited. The Anglesea River, in southern Australia, is subjected to frequent episodes of poor water quality and low pH resulting in closure of the river and, in extreme cases, large fish kill events. This region is heavily reliant on tourism and host to a number of iconic features, including the Great Ocean Road and Twelve Apostles. Poor water quality has been linked to acid leakage from mining activities and Tertiary-aged coal seams, peat swamps and acid sulfate soils in the region. However, our understanding of the sources of acidity and distribution of acid sulfate soils in this region remains poor. In this study, four sites on the Anglesea River floodplain were sampled, representative of the main vegetation communities. Peat swamps and intertidal marshes were both significant sources of acidity on the floodplain in the lower catchment. However, acid neutralising capacity provided by carbonate sands suggests that there are additional sources of acidity higher in the catchment. This pilot study has highlighted the complexity in the links between the floodplain, upper catchment and waterways with further research required to understand these links for targeted acid management strategies.

Floodplains as a source of fine sediment in grazed landscapes: tracing the source of suspended sediment in the headwaters of an intensively managed agricultural landscape

NASA Astrophysics Data System (ADS)

Yu, M.; Rhoads, B. L.; Stumpf, A.

2017-12-01

The flux of fine sediment within agricultural watersheds is an important factor determining the environmental quality of streams and rivers. Despite this importance, the contributions of sediment sources to suspended sediment loads within intensively managed agricultural watersheds remain poorly understood. This study assesses the provenance of fine suspended sediment in the headwater portion of a river flowing through an agricultural landscape in Illinois. Sediment source samples were collected from five potential sources: streambanks, forested floodplain, grassland, and grazed floodplains. Event-based and aggregated suspended sediment samples were collected from the stream at the watershed outlet. Quantitative geochemical fingerprinting techniques and a mixing model were employed to estimate the relative contributions of sediment from five potential sources to the suspended sediment loads. Organic matter content, trace elements, and fallout radionuclides were used as potential tracers. Principal Component analysis was employed to complement the results and Monte Carlo random sampling routine was used to test the uncertainty in estimated contributions of sources to in-stream sediment loads. Results indicate that the majority of suspended sediment is derived from streambanks and grazed floodplains. Erosion of the floodplain both by surface runoff and by streambank erosion from lateral channel migration contributes to the production of fine sediment within the stream system. These results suggest that human activities, in this case grazing, have converted portions of floodplains, normally net depositional environments, into sources of fine sediments. Efforts to reduce fluxes of fine sediment in this intensively managed landscape should focus on degraded floodplain surfaces and eroding channel banks within heavily grazed reaches of the stream.

Lead contamination and source in Shanghai in the past century using dated sediment cores from urban park lakes.

PubMed

Li, H B; Yu, S; Li, G L; Deng, H

2012-08-01

Lead contamination becomes of importance to urban resident health worldwide, especially for child health and growth. Undisturbed lake sediment cores are increasingly employed as a useful tool to backdate environmental contamination history. Five intact sediment cores collected from lakes in five urban parks were dated using (210)Pb and analyzed for total Pb content and isotope ratio to reconstruct the Pb contamination history over the last century in Shanghai, China. Total Pb content in the sediment cores increased by about 2- to 3-fold since 1900s. The profile of Pb flux in each sediment core revealed a remarkable increase of Pb contamination in Shanghai over the past century, especially in the latest three decades when China was experiencing a rapid economic and industrial development. Significant correlations were found between Pb fluxes in sediment cores and Pb emission from coal combustion in Shanghai. Coal combustion emission dominated anthropogenic Pb sources during the past century contributing from 52% to 69% of total Pb in cores, estimated by a three-end member model of Pb isotope ratios. Leaded gasoline emission generally contributed <30% of total Pb, which was banned by 1997 in the Shanghai region. Our results implicate that coal combustion-based energy consumption should be replaced, or at least partially replaced, to reduce health risks of Pb contamination in Shanghai. Copyright © 2012 Elsevier Ltd. All rights reserved.

Analysis of heavy metals from water, sediment, and tissues of Labeo angra (Hamilton, 1822), from an Ox-box lake- an wetland site from Assam, India.

PubMed

Das, Suchismita; Choudhury, Shamim Sultana

2016-01-01

The aim of this study was to assess the regional impacts of heavy metals (Mn, Fe, Mg, Ca, Cu, Zn, Cd, Cr, Pb and Ni) on water, sediment and a native, teleost fish species, Labeo angra, inhabiting a flood plain wetland of Barak River in Assam, India. Heavy metal concentrations in the water, sediments and fish were measured; bioaccumulation factor, metal pollution index as well as condition indices were calculated, to assess the pollution load and health status of the fish. Multivariate statistical analysis was used on wetland water and sediment heavy metals to ascertain the possible sources and seasonal variations of the pollutants. Results showed that most heavy metals in the wetland water and sediments exceeded the water (drinking and irrigation) and sediment quality guidelines, respectively. Seasonal variations were observed for geogenic heavy metals, Mn, Fe, Mg and Ca while no seasonal variations were observed for anthropogenic heavy metals, Cu, Cd, Cr, Pb and Ni. Multivariate statistical analysis showed that there was strong correlation between geogenic and anthropogenic heavy metals in water and sediment, both originating from the common anthropogenic sources. Accumulation of most of the metals in all the tissues was above the safe limits as recommended by the Food and Agriculture Organization. High bioaccumulation factors and metal pollution index for these metals in the different tissues revealed that metals were extensively bio-accumulated and bioconcentrated. Condition indices in fish from the wetland suggested metabolic abnormalities.

Level, source identification, and risk analysis of heavy metal in surface sediments from river-lake ecosystems in the Poyang Lake, China.

PubMed

Zhang, Hua; Jiang, Yinghui; Ding, Mingjun; Xie, Zhenglei

2017-09-01

The concentrations, sources, and risks of heavy metals (Fe, Al, Mn, Cr, Co, Ni, Cu, Zn, As, Cd, W, Pb, and Tl) in sediments in five river-lake ecosystems in the Poyang Lake region were studied. The concentrations of the heavy metals varied spatially, with most of the highest concentrations in the Raohe river-lake ecosystem (RH). All heavy metals except As, Cd, W, and Tl were enriched in sediments possessing high total organic carbon contents or in finer sediments. Based on enrichment factors and statistical methods, it was found that Cd in sediments in the Xiushui (XS), Ganjiang (GJ), Xinjiang (XJ) river-lake ecosystems, and RH; Mn in the XS, GJ, and RH; and W in the XS and GJ were greatly affected by anthropogenic inputs. Moreover, the origins of Cu, Zn, and As require more attention due to the high concentrations found. The high enrichment factor of Cd in the sediments indicated that this metal might cause significant pollution in the environment. The results of the modified potential ecological risk index revealed that the XS, GJ, RH, and XJ were at considerable ecological risk, while the sediments in the Fuhe river-lake ecosystem (FH) were at moderate ecological risk, with Cd contributing the highest proportion of risk. The hazard score fundamentally validated the modified potential ecological risk analysis and revealed a mean toxicity of 57.80% to the benthic organisms in the RH.

Using sediment particle size distribution to evaluate sediment sources in the Tobacco Creek Watershed

NASA Astrophysics Data System (ADS)

Liu, Cenwei; Lobb, David; Li, Sheng; Owens, Philip; Kuzyk, ZouZou

2014-05-01

Lake Winnipeg has recently brought attention to the deteriorated water quality due to in part to nutrient and sediment input from agricultural land. Improving water quality in Lake Winnipeg requires the knowledge of the sediment sources within this ecosystem. There are a variety of environmental fingerprinting techniques have been successfully used in the assessment of sediment sources. In this study, we used particle size distribution to evaluate spatial and temporal variations of suspended sediment and potential sediment sources collected in the Tobacco Creek Watershed in Manitoba, Canada. The particle size distribution of suspended sediment can reflect the origin of sediment and processes during sediment transport, deposition and remobilization within the watershed. The objectives of this study were to quantify visually observed spatial and temporal changes in sediment particles, and to assess the sediment source using a rapid and cost-effective fingerprinting technique based on particle size distribution. The suspended sediment was collected by sediment traps twice a year during rainfall and snowmelt periods from 2009 to 2012. The potential sediment sources included the top soil of cultivated field, riparian area and entire profile from stream banks. Suspended sediment and soil samples were pre-wet with RO water and sieved through 600 μm sieve before analyzing. Particle size distribution of all samples was determined using a Malvern Mastersizer 2000S laser diffraction with the measurement range up to 600μm. Comparison of the results for different fractions of sediment showed significant difference in particle size distribution of suspended sediment between snowmelt and rainfall events. An important difference of particle size distribution also found between the cultivated soil and forest soil. This difference can be explained by different land uses which provided a distinct fingerprint of sediment. An overall improvement in water quality can be achieved by managing sediment according to the identified sediment sources in the watershed.

A 400-ka tephrochronological framework for Central America from Lake Petén Itzá (Guatemala) sediments

NASA Astrophysics Data System (ADS)

Kutterolf, S.; Schindlbeck, J. C.; Anselmetti, F. S.; Ariztegui, D.; Brenner, M.; Curtis, J.; Schmid, D.; Hodell, D. A.; Mueller, A.; Pérez, L.; Pérez, W.; Schwalb, A.; Frische, M.; Wang, K.-L.

2016-10-01

Lake Petén Itzá, northern Guatemala, lies within a hydrologically closed basin in the south-central area of the Yucatán Peninsula, and was drilled under the auspices of the International Continental Scientific Drilling Program (ICDP) in 2006. At 16°55‧N latitude, the lake is ideally located for study of past climate and environmental conditions in the Neotropical lowlands. Because of its great depth (>160 m), Lake Petén Itzá has a record of continuous sediment accumulation that extends well into the late Pleistocene. A key obstacle to obtaining long climate records from the region is the difficulty of establishing a robust chronology beyond ∼40 ka, the limit of 14C dating. Tephra layers within the Lake Petén Itzá sediments, however, enable development of age/depth relations beyond 40 ka. Ash beds from large-magnitude, Pleistocene-to-Holocene silicic eruptions of caldera volcanoes along the Central American Volcanic Arc (CAVA) were found throughout drill cores collected from Lake Petén Itzá. These ash beds were used to establish a robust chronology extending back 400 ka. We used major- and trace-element glass composition to establish 12 well-constrained correlations between the lacustrine tephra layers in Lake Petén Itzá sediments and dated deposits at the CAVA source volcanoes, and with their marine equivalents in eastern Pacific Ocean sediments. The data also enabled revision of eight previous determinations of erupted volumes and masses, and initial estimates for another four eruptions, as well as the designation of source areas for 14 previously unknown eruptions. The new and revised sedimentation rates for the older sediment successions identify the interglacial of MIS5a between 84 and 72 ka, followed by a stadial between 72 and 59 ka that corresponds to MIS4. We modified the age models for the Lake Petén Itzá sediment sequences, extended the paleoclimate and paleoecological record for this Neotropical region to ∼400 ka, and determined the magnitude and timing of CAVA eruptions.

Biogeochemistry of Arsenic in Groundwater Flow Systems: The Case of Southern Louisiana

NASA Astrophysics Data System (ADS)

Johannesson, K. H.; Yang, N.; Datta, S.

2017-12-01

Arsenic (As) is a highly toxic and carcinogenic metalloid that can cause serious health effects, including increased risk of cancers, infant mortality, and reduced intellectual and motor function in children to populations chronically exposed to As. Recent estimates suggest that more than 140 million people worldwide are drinking As-contaminated groundwater (i.e., As ≥ 10 µg kg-1), and the most severely affected region is the Ganges-Brahmaputra-Meghna delta in Bangladesh and India (i.e., Bengal Basin). Arsenic appears to be mobilized to Bengal Basin groundwaters by reductive dissolution of Fe oxides in aquifer sediments with the source of the labile organic matter occurring in the aquifer sediments. Studies within the lower Mississippi River delta of southern Louisiana (USA) also reveal high As concentrations (up to 640 µg kg-1) in shallow groundwaters. It is not known what affects, if any, the elevated groundwater As has had on local communities. The regional extent of high As shallow groundwaters is controlled, in part, by the distribution of Holocene sediments, deltaic deposits, and organic-rich sediments, similar to the Bengal Basin. Field and laboratory studies suggest that As is largely of geogenic origin, and further that microbial reduction of Fe(III)/Mn(IV) oxides/oxyhydroxides within the sediments contributes the bulk of the As to the groundwaters. Incubation studies are supported by biogeochemical reactive transport modeling, which also indicates reductive dissolution of metal oxides/oxyhydroxides as the likely source of As to these groundwaters. Finally, reactive transport modeling of As in shallow groundwaters suggests that sorption to aquifer mineral surfaces limits the transport of As after mobilization, which may explain, in part, the heterogeneous distribution of As in groundwaters of southern Louisiana and, perhaps, the Bengal Basin.

Improvements in Quantifying Bank Erosion for Sediment Budgets within the Chesapeake Bay Watershed by Integrating Structure-From-Motion Photogrammetry

NASA Astrophysics Data System (ADS)

Bell, J. M.; Cashman, M. J.; Nibert, L.; Jackson, S.

2017-12-01

Fine sediment is a major source of pollution due to its ability to attenuate light, smother habitat, and sorb and transport nutrients, such as phosphorus and nitrogen. Piedmont streams in the Mid-Atlantic region of the United States are frequently characterized as incised with steep, highly erodible banks of legacy sediment that can contribute to high sediment loads. Multiple sediment fingerprinting studies in this region have demonstrated that stream banks can contribute a large proportion of the total sediment load, but stream banks are frequently overlooked in sediment delivery models and Total Maximum Daily Load allocations. The direct quantification of bank erosion is therefore essential to producing accurate sediment budgets, which are needed to inform the targeted mitigation and remediation of degraded fluvial systems. This study contrasts the use of traditional bank pin measurements, structure-from-motion photogrammetric techniques, and aerial LIDAR at sites within Maryland, USA. Bank pin measurements, representing only single points in space, were found to be highly variable with subjective initial placement often missing nearby, large-scale bank failures. In contrast, photogrammetric techniques, using structure-from-motion, were able to capture a more spatially-complete streambank profile. Using a Nikon D810 camera, bank scans were able to reconstruct banks with a RMSE as low as 0.1mm and repeat scan alignment resolution of <2mm. However, during summer months, photogrammetry exhibited some coverage gaps in areas of high vegetation density. Difference-maps rendered from multiple UAV structure-from-motion scans provided an ability to rapidly assess changes to river channel morphology during leaf-off conditions. Additionally, UAV-derived scans were georeferenced over historical LIDAR data to evaluate historical bank-erosion over multi-year timescales. Future work will include difference mapping channel features at watershed scales. This photogrammetric approach of quantifying geomorphic change, when coupled with bank-sediment bulk density, has promise to accurately quantify volumetric change as well as sediment loads originating from bank erosion, and may provide valuable data of the quantification of bank erosion for incorporation into regional sediment models.

Distribution, speciation, environmental risk, and source identification of heavy metals in surface sediments from the karst aquatic environment of the Lijiang River, Southwest China.

PubMed

Xu, Daoquan; Wang, Yinghui; Zhang, Ruijie; Guo, Jing; Zhang, Wei; Yu, Kefu

2016-05-01

The distribution and speciation of several heavy metals, i.e., As, Cd, Cr, Cu, Hg, Pb, and Zn, in surface sediments from the karst aquatic environment of the Lijiang River, Southwest China, were studied comparatively. The mean contents of Cd, Cu, Hg, Pb, and Zn were 1.72, 38.07, 0.18, 51.54, and 142.16 mg/kg, respectively, which were about 1.5-6 times higher than their corresponding regional sediment background values. Metal speciation obtained by the optimized BCR protocol highlighted the bioavailable threats of Cd, Cu, and Zn, which were highly associated with the exchangeable fraction (the labile phase). Hierarchical cluster analysis indicated that in sediments, As and Cr were mainly derived from natural and industrial sources, whereas fertilizer application might lead to the elevated level of Cd. Besides, Cu, Hg, Pb, and Zn were related to traffic activities. The effects-based sediment quality guidelines (SQGs) showed that Hg, Pb, and Zn could pose occasional adverse effects on sediment-dwelling organisms. However, based on the potential ecological risk assessment (PER) and risk assessment code (RAC), Cd was the most outstanding pollutant and posed the highest ecological hazard and bioavailable risk among the selected metals. Moreover, the metal partitioning between water and sediments was quantified through the calculation of the pseudo-partitioning coefficient (K P), and result implied that the sediments in this karst aquatic environment cannot be used as stable repositories for the metal pollutants.

Can sediments at hydrocarbon seep sites represent a source for marine bioavailable iron? — A case study from the South China Sea

NASA Astrophysics Data System (ADS)

Li, N.; Feng, D.; Chen, D.

2017-12-01

Niu Li1, Dong Feng1,2, and Duofu Chen2,31CAS Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China. 2Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, China. 3Hadal Science and Technology Research Center, College of Marine Sciences, Shanghai Ocean University, Shanghai 201306, China. Iron is an essential micronutrient and commonly considered to be one of the key-limiting factors for biological productivity in many ocean regions. Seafloor Fe supply should be most efficient in suboxic conditions. Recent studies shown that widely spread anoxic environments can develop in hydrocarbon seep sediment and local bottom water, owing to the occurrence of aerobic and/or anaerobic methane oxidation. Under this condition, the iron in sediment can be reduced to dissolved Fe2+ in the ocean. However, questions remain about whether the hydrocarbon seep sediment can represent a source for bioavailable iron to the ocean, and the control factor for the transformation of iron in the sediment remains largely unexplored. For a number of hydrocarbon seeps from the northern and southern South China Sea, the iron speciation, pyrite sulfur isotope, and iron isotope, as well as the major and trace elements are used to constrain the intensity of cold seep, and its impact on transformation of iron in sediment. Samples from both areas show sediment iron lost during the high methane flux conditions, owing to the suboxic conditions cause by aerobic methane oxidation. On the other hand, high sediment iron content accompanied by high sulfur content can be seen during the conditions of high methane flux without the occurrence of aerobic methane oxidation, which is possible ascribed to the anaerobic methane oxidation and the release of iron through seep activity. This study reveals the transformation of iron in the sediment is closely related to the methane flux and the hydrocarbon seep sediment can represent a source for bioavailable iron to the ocean. Acknowledgments: Funding was provided by the NSF of China (Grants: 41422602 and 41373085).

A new method for fingerprinting sediments source contributions using distances from discriminant function analysis

USDA-ARS?s Scientific Manuscript database

Mixing models have been used to predict sediment source contributions. The inherent problem of the mixing models limited the number of sediment sources. The objective of this study is to develop and evaluate a new method using Discriminant Function Analysis (DFA) to fingerprint sediment source contr...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cregg, A.K.

Kenya basins have evolved primarily through extension related to episodic continental rifting. In eastern Kenya, thick accumulations of sediments formed within grabens during the prerift phase (Precambrian to Carboniferous) of the Gondwana breakup. Synrift sedimentation (Late Carboniferous to Middle Jurassic) occurred within a north-south rift system, which included the Mandera basin, South Anza basin, and Lamu embayment. During the Early Jurassic, a marine transgression invaded the margins of the eastern Kenya rift basins, resulting in the deposition of platform carbonates and shales. A Callovian-aged salt basin formed in the offshore regions of the Lamu embayment. Intermittent tectonic activity and eustaticmore » sea-level changes controlled sedimentation, which produced marine shales, carbonates or evaporites, and fluvio-deltaic to lacustrine sandstones. From the Early Cretaceous to recent, continental sediments were deposited within the North Anza and Turkana basins. These fluvial-lacustrine sediments are similar to the Lower Cretaceous sequences that have produced oil in the Mesozoic Sudanese Abu Gabra rift. Although exploration activities began in the early 1950s, significant occurrences of potential reservoir, source, and seal lithologies as well as trapping configurations remain in many areas. Favorable structures and sequences of reservoir sandstones and carbonates overlain by potentially sealing lacustrine or marine shales, evaporites, or volcanics have been noted. Potential source beds are believed to be present within shales of the lacustrine or marine depositional environments.« less

A deep oxic ecosystem in the subseafloor South Pacific Gyre

NASA Astrophysics Data System (ADS)

D'Hondt, S. L.; Inagaki, F.; Alvarez Zarikian, C. A.; Integrated Ocean Drilling Program Expedition 329 Shipboard Scientific Party

2011-12-01

Scientific ocean drilling has demonstrated the occurrence of rich microbial communities, abundant active cells and diverse anaerobic activities in anoxic subseafloor sediment. Buried organic matter from the surface photosynthetic world sustains anaerobic heterotrophs in anoxic sediment as deeply buried as 1.6 km below the seafloor. However, these studies have been mostly restricted to the organic-rich sediment of continental margins and biologically productive regions. IODP Expedition 329 discovered that subseafloor habitat and life are fundamentally different in the vast expanse of organic-poor sediment that underlies Earth's largest oceanic province, the South Pacific Gyre (SPG). Dissolved O2 and dissolved major nutrients (C, N, P) are present throughout the entire sediment sequence and the upper basaltic basement of the SPG. The drilled sediment is up to 75 m thick. Although heterotrophic O2 reduction (aerobic respiration) persists for millions of years in SPG sediment (which accumulates very slowly), it falls below minimum detection just a few meters to tens of meters beneath the SPG seafloor. Cell concentrations approach minimum detection at similar depths, but are intermittently detectable throughout the entire sediment sequence. In situ radiolysis of water may be a significant source of energy for the microbes that inhabit the deepest (oldest) sediment.

Estimation of Sediment Sources Using Selected Chemical Tracers in the Perry Lake and Lake Wabaunsee Basins, Northeast Kansas

USGS Publications Warehouse

Juracek, Kyle E.; Ziegler, Andrew C.

2007-01-01

In Kansas and nationally, stream and lake sediment is a primary concern as related to several important issues including water quality and reservoir water-storage capacity. The ability to achieve meaningful decreases in sediment loads to reservoirs requires a determination of the relative importance of sediment sources within the contributing basins. To investigate sources of sediment within the Perry Lake and Lake Wabaunsee Basins of northeast Kansas, representative samples of channel-bank sources, surface-soil sources (cropland and grassland), and reservoir bottom sediment were collected, analyzed, and compared. Subbasins sampled within the Perry Lake Basin included Atchison County Lake, Banner Creek Reservoir, Gregg Creek, Mission Lake, and Walnut Creek. The samples were sieved to isolate the less than 63-micron fraction (that is, the silt and clay) and analyzed for selected nutrients (total nitrogen and total phosphorus), organic and total carbon, 25 trace elements, and the radionuclide cesium-137 (137Cs). To determine which of the 30 constituents provided the best ability to discriminate between channel-bank and surface-soil sources in the two basins, four selection criteria were used. To be selected, it was required that the candidate constituent (1) was detectable, (2) had concentrations or activities that varied substantially and consistently between the sources, (3) had concentration or activity ranges that did not overlap between the sources, and (4) had concentration or activity differences between the sources that were statistically significant. On the basis of the four selection criteria, total nitrogen (TN), total phosphorus (TP), total organic carbon (TOC), and 137Cs were selected. Of the four selected constituents, 137Cs likely is the most reliable indicator of sediment source because it is known to be conservative in the environment. Trace elements were not selected because concentrations in the channel-bank and surface-soil sources generally were similar or did not vary in a consistent manner. To further account for differences in particle-size composition between the sources and the reservoir bottom sediment prior to the sediment-source estimations, constituent ratio and clay-normalization techniques were used. Computed ratios included the ratio of TOC to TN, TOC to TP, and TN to TP. Constituent concentrations (TN, TP, TOC) and activities (137Cs) were normalized by dividing by the percentage of clay. Thus, the sediment-source estimations involved the use of seven sediment-source indicators (that is, three constituent ratios and the clay-normalized concentration or activity for four constituents). Sediment-source estimation for each reservoir was based on a comparison between the reservoir bottom sediment and the end member channel-bank and surface-soil sources. Within the Perry Lake Basin, the seven-indicator consensus indicated that both channel-bank and surface-soil sources were important contributors of the sediment deposited in Atchison County Lake and Banner Creek Reservoir, whereas channel-bank sources were the dominant source of sediment for Mission Lake. On the sole basis of 137Cs activity, surface-soil sources contributed the most sediment to Atchison County Lake, and channel-bank sources contributed the most sediment to Banner Creek Reservoir and Mission Lake. For Perry Lake, both the seven-indicator consensus and 137Cs indicated that channel-bank sources were dominant and that channel-bank sources increased in importance with distance downstream in the Perry Lake Basin. For Lake Wabaunsee, the seven-indicator consensus and 137Cs indicated that both channel-bank and surface-soil sources were important. Given that the relative contribution of sediment from channel-bank and surface-soil sources can vary within and between basins and over time, basin-specific strategies for sediment management and monitoring are appropriate.

Eco-environmental implications of elemental and carbon isotope distributions in ornithogenic sediments from the Ross Sea region, Antarctica

NASA Astrophysics Data System (ADS)

Liu, Xiaodong; Nie, Yaguang; Sun, Liguang; Emslie, Steven D.

2013-09-01

Seabirds have substantial influence on geochemical circulation of elements, serving as a link for substance exchange between their foraging area and colonies. In this study, we investigated the elemental and carbon isotopic composition of five penguin-affected sediment profiles excavated from Ross Island and Beaufort Island in the Ross Sea region, Antarctica. Among the three main constituents of the sediments (including weathered bedrock, guano and algae), guano was the main source of organic matter and nutrients, causing selective enrichment of several elements in each of the sediment profiles. In the 22 measured elements, As, Cd, Cu, P, S, Se and Zn were identified as penguin bio-elements in the Ross Sea region through statistical analysis and comparison with local end-member environmental media such as weathered bedrock, fresh guano and fresh algae. Carbon isotopic composition in the ornithogenic sediments showed a mixing feature of guano and algae. Using a two-member isotope mixing equation, we were able to reconstruct the historical change of guano input and algal bio-mass. Compared with research in other parts of Antarctic, Arctic, and South China Sea, we found apparent overlap of avian bio-elements including As, Cd, Cu, P, Se, and Zn. Information on the composition and behavior of bio-elements in seabird guano on a global scale, and the role that bio-vectors play in the geochemical circulation between land and sea, will facilitate future research on avian ecology and paleoclimatic reconstruction.

Biomass production in the Lower Mississippi River Basin: Mitigating associated nutrient and sediment discharge to the Gulf of Mexico.

PubMed

Ha, Miae; Zhang, Zhonglong; Wu, May

2018-04-24

A watershed model was developed using the Soil and Water Assessment Tool (SWAT) that simulates nitrogen, phosphorus, and sediment loadings in the Lower Mississippi River Basin (LMRB). The LMRB SWAT model was calibrated and validated using 21 years of observed flow, sediment, and water-quality data. The baseline model results indicate that agricultural lands within the Lower Mississippi River Basin (LMRB) are the dominant sources of nitrogen and phosphorus discharging into the Gulf of Mexico. The model was further used to evaluate the impact of biomass production, in the presence of riparian buffers in the LMRB, on suspended-sediment and nutrient loading discharge from the Mississippi River into the Gulf of Mexico. The interplay among land use, riparian buffers, crop type, land slope, water quality, and hydrology were anlyzed at various scales. Implementing a riparian buffer in the dominant agricultural region within the LMRB could reduce suspended sediment, nitrogen, and phosphorus loadings at the regional scale by up to 65%, 38%, and 39%, respectively. Implementation of this land management practice can reduce the suspended-sediment content and improve the water quality of the discharge from the LMRB into the Gulf of Mexico and support the potential production of bioenergy and bio-products within the Mississippi River Basin. Copyright © 2017 Elsevier B.V. All rights reserved.

Surface Sediment Geochemistry in and around the Hudson Shelf Valley Offshore of New York

NASA Astrophysics Data System (ADS)

Mecray, E. L.; ten Brink, M. B.; Butman, B.; Denny, J.; Murray, R. W.

2001-05-01

The Hudson Shelf Valley, an ancient submerged portion of the Hudson River, extends across the continental shelf offshore of New York and New Jersey. Between 1959 and 1987, the area near the head of the valley was used for disposal of approximately 1.20 x 108 m3 of dredged material and sewage sludge. The distribution of metal concentrations and sediment characteristics were used to investigate the transport and fate of the sediments and their associated contaminants. Surface (0-2cm) sediments collected at 440 stations throughout the New York Bight between 1993 and 1998 were used to establish the regional distribution of pollutant metals, grain size, organic carbon, and Clostridium perfringens spores. Sediments in the New York Bight are generally sandy, however fine-grained sediments are found in the axis of the Valley. Statistical methods identified common sources and chemical mobility within groups of anthropogenic and naturally-occurring elements. High metal concentrations, fine-grained sediments, and higher organic carbon concentrations co-occur in depo-centers within the Valley. Normalization of the metal concentrations to these factors shows higher metal concentrations on the fine-grained particles in sandy areas of the Bight, particularly along the southern shore of Long Island. These distributions have implications for evaluating the impact of the mass distribution for contaminated metals in different habitats and areas. Decreasing concentrations of pollutants with time are observed, reflecting reduced contaminant loading in the upper region of the Valley; however, concentrations are still above natural background levels.

Holocene Climate Change in Sub-Alpine Southwestern Alberta: Evidence from Oxygen and Carbon Isotope values of Hogarth Lake Marl.

NASA Astrophysics Data System (ADS)

Matkowski, D.; Patterson, W. P.; Timsic, S.

2017-12-01

A 3.6-meter lake sediment core was recovered from Upper Hogarth Lake, providing proxy evidence for climate variability over the last 11,500 years. The core was sampled at millimeter scale for high-resolution oxygen and carbon isotope values. Large variations (up to 6‰) in the carbon isotope values are attributed to the increasingly dominant role of terrestrial-sourced organic matter over bedrock-sourced DIC during initial lake formation and subsequent changes in regional humidity. Variations (up to 4‰) in oxygen isotope values of the marl are interpreted as representing changes in meteoric water source and regional temperature. The hydrologically-open, fresh-water lake is hosted in Devonian-Carboniferous carbonates, recharged via groundwater, surface flow and precipitation. Marl sediment is generated by the green algae Chara sp., with marl deposition beginning approximately 11,500 cal yBP. Our age model was constructed using tephrochronology and radiocarbon dating of 8 terrestrial plant samples, then calibrated using the University of Minnesota's "Bacon" software. The presence of an ash layer in the core was associated with the Mazama ash layer dated 7,627 ±150 yBP, and was used to support the 14C age model. Sediment deposition is characterized by 3 stages: from the recent, dating back to 11,500 cal yBP, the core is marl dominated, comprising 70% of the 3.6m core. Prior to marl deposition there is a 500-year depositional period of carbonate and allochthonous clastic material. Below 2.65 meters, the sediment consists of fine sand and mud; sourced from the weathering of surrounding bedrock. Isotope data are characterized by 5 distinct periods. 7,800 cal yBP to the end Younger Dryas ( 11,500 cal yBP) exhibits irregular, and generally decreasing, δ13C and δ18O values, with a positive excursion in δ18O values occurring around 9,000 cal yBP. Climate was stable, cool and dry from 5,000-7,000 cal yBP, evidenced by relatively invariant δ13C and δ18O values. The period from 3,000-5,000 cal yBP exhibits decreasing δ13C values and increasing δ18O values, suggesting regional climate warming, possibly accompanied by an increase in humidity. From 3,000 cal yBP to the present, δ13C and δ18O values coincidently decrease, suggesting an increase in regional humidity along with a general cooling trend.

Tracing suspended sediment sources in the Upper Sangamon River Basin using conservative and non-conservative tracers

NASA Astrophysics Data System (ADS)

Yu, M.; Rhoads, B. L.; Stumpf, A.

2015-12-01

As the awareness of water pollution, eutrophication and other water related environmental concerns grows, the significance of sediment in the transport of nutrients and contaminants from agricultural areas to streams has received increasing attention. Both the physical and geochemical properties of suspended sediment are strongly controlled by sediment sources. Thus, tracing sources of suspended sediment in watersheds is important for the design of management practices to reduce sediment loads and contributions of sediment-adsorbed nutrients from agricultural areas to streams. However, the contributions of different sediment sources to suspended sediment loads within intensively managed watersheds in the Midwest still remain insufficiently explored. This study aims to assess the provenance of suspended sediment and the relation between channel morphology and production of suspended sediment in the Upper Sangamon River Basin, Illinois, USA. The 3,690-km2 Upper Sangamon River Basin is characterized by low-relief, agricultural lands dominated by row-crop agriculture. Sediment source samples were collected in the Saybrook from five potential sources: farmland, forests, floodplains, river banks, and grasslands. Event-based and accumulated suspended sediment samples were collected by ISCO automatic pump samplers and in situ suspended sediment samplers and from the stream at watershed outlet. A quantitative geochemical fingerprinting technique, combining statistically verified multicomponent signatures and an un-mixing model, was employed to estimate the relative contributions of sediment from five potential sources to the suspended sediment loads. Organic matter content, trace elements, and radionuclides from soil samples were used as potential tracers. Our preliminary results indicate that the majority of suspended sediment is derived from floodplains in the downstream portions of the watersheds, while only minor amounts of suspended sediment are derived from upland areas and banks. These results suggest that floodplain erosion during high flow events contributes to the suspended sediment.

Neutral carbohydrate geochemistry of particulate material in the central equatorial Pacific

NASA Astrophysics Data System (ADS)

Hernes, Peter J.; Hedges, John I.; Peterson, Michael L.; Wakeham, Stuart G.; Lee, Cindy

Neutral carbohydrate compositions were determined for particulate samples from plankton net tows, shallow floating sediment traps, mid-depth and deep moored sediment traps, and sediment cores collected along a north-south transect in the central equatorial Pacific Ocean during the U.S. JGOFS EqPac program. Total neutral carbohydrate depth profiles and patterns along the transect follow essentially the same trends as bulk and organic carbon (OC) fluxes—attenuating with depth, high near the equator and decreasing poleward. OC-normalized total aldose (TCH 2,O) yields along the transect and with depth do not show any consitent patterns. Relative to a planktonic source, neutral carbohydrate compositions in sediment trap and sediment core samples reflect preferential loss of ribose and storage carbohydrates rich in glucose, and preferential preservation of structural carbohydrates rich in rhamnose, xylose, fucose, and mannose. There is also evidence for an intermediately labile component rich in galactose. It appears that compositional signatures of neutral carbohydrates in sediments are more dependent upon their planktonic source than on any particular diagenetic pathway. Relative to other types of organic matter, neutral carbohydrates are better preserved in calcareous oozes from 12°S to 5°N than in red clays at 9°N based on OC-normalized TCH 2O yields, due to either differing sources or sorption characteristics. Weight per cent glucose generally decreases with increased degradation of organic material in the central equatorial Pacific region. Based on weight per cent glucose, comparisons of samples between Survey I (El Niõn) and Survey II (non-El Niño) indicate that during Survey I, organic material in the epipelagic zone in the northern hemisphere may have undergone more degradation than organic material in the southern hemisphere.

The potential for gamma-emitting radionuclides to contribute to an understanding of erosion processes in South Africa

NASA Astrophysics Data System (ADS)

Foster, Ian D. L.; Boardman, John; Collins, Adrian L.; Copeland-Phillips, Ruth; Kuhn, Nikolaus J.; Mighall, Tim M.; Pulley, Simon; Rowntree, Kate M.

2017-03-01

Several research projects undertaken by the authors and others over the last 14 years have used fallout and geogenic radionuclides for understanding erosion processes and sediment yield dynamics in South Africa over the last 100-200 years as European settlers colonised the interior plains and plateaux of the country and imported new livestock and farming techniques to the region. These projects have used two fallout radionuclides (210Pb and 137Cs) to date sediments accumulating in reservoirs, farm dams, wetlands, alluvial fans and floodouts and have used other fallout nuclides (7Be) and long-lived geogenic radionuclides (e.g. 40K, 235U) as part of a composite fingerprint exploring contemporary sediment sources and changes to sources through time. While successful in many parts of the world, applying these techniques in Southern Africa has posed a number of challenges often not encountered elsewhere. Here we explore some of the benefits and challenges in using gamma-emitting radionuclides, especially 137Cs, in these landscapes. Benefits include the potential for discriminating gully sidewall from topsoil sources, which has helped to identify contemporary gully systems as sediment conduits, rather than sources, and for providing a time-synchronous marker horizon in a range of sedimentary environments that has helped to develop robust chronologies. Challenges include the spatial variability in soil cover on steep rocky hillslopes, which is likely to challenge assumptions about the uniformity of initial fallout nuclide distribution, the paucity of stable (non-eroding) sites in order to estimate atmospheric fallout inventories, and the limited success of 210Pb dating in some rapidly accumulating high altitude catchments where sediments often comprise significant amounts of sand and gravel. Despite these challenges we present evidence suggesting that the use of gamma-emitting radionuclides can make a significant contribution to our understanding of erosion processes and sediment yield dynamics. Future research highlighted in the conclusion will try to address current challenges and outline new projects established to address them more fully.

Heavy metals in the surface sediments of the northern portion of the South China Sea shelf: distribution, contamination, and sources.

PubMed

Xu, Fangjian; Tian, Xu; Yin, Feng; Zhao, Yongfang; Yin, Xuebo

2016-05-01

The concentrations of seven heavy metals (Cr, Ni, Cu, Zn, As, Cd, and Pb) in the surface sediments of the northern portion of the South China Sea (SCS) shelf collected between 2012 and 2014 were measured to assess the potential contamination levels and determine the environmental risks that are associated with heavy metals in the area. The measured concentrations in the sediments were 12.4-72.5 mg kg(-1) for Cr, 4.4-29.2 mg kg(-1) for Ni, 7.1-38.1 mg kg(-1) for Cu, 19.3-92.5 mg kg(-1) for Zn, 1.3-12.1 mg kg(-1) for As, 0.03-0.24 mg kg(-1) for Cd, and 8.5-24.4 mg kg(-1) for Pb. These results indicate that the heavy metal concentrations in the sediments generally meet the China Marine Sediment Quality criteria and suggest that the overall sediment quality of the northern portion of the SCS shelf has not been significantly impacted by heavy metal pollution. However, the enrichment factor (EF) and geoaccumulation index (I geo) clearly show that elevated concentrations of Cd occur in the region. A Pearson's correlation analysis was performed, and the results suggest that Cr, Ni, Cu, and Zn have a natural origin; Cd is primarily sourced from anthropogenic activities, with partial lithogenic components, and As and Pb may be affected by factors such as varying input sources or pathways (i.e., coal burning activities and aerosol precipitation). Heavy metal contamination mostly occurred to the east of Hainan Island, mainly because of the rapid economic and social developments in the Hainan Island. The results of this study will be useful for marine environment managers for the remediation of pollution sources.

Mineralogical and geochemical features of alluvial sediments from the Lobo watershed (Southern Cameroon): Implications for rutile exploration

NASA Astrophysics Data System (ADS)

Nyobe, Jules Mbanga; Sababa, Elisé; Bayiga, Elie Constantin; Ndjigui, Paul-Désiré

2018-03-01

This paper is focused on the morphological, mineralogical, and geochemical features of alluvial sediments from the Neoproterozoic Pan-African belt to explore rutile. The fine-grained sediments, which contain a large proportion of rutile, are made up of quartz, rutile, zircon, brookite, tourmaline, andalusite, and kyanite. The high SiO2 and TiO2 contents highlight the predominance of silica minerals in the alluvia from the humid tropical zone. La/Sc, La/Co, Th/Sc and Zr/Cr ratios reflect the contribution of felsic and mafic sources. The highest Ti contents, which occur at the outlet of the Lobo watershed, indicate the resistance of rutile. The REE distribution could be linked to the heavy mineral sorting. The low (La/Yb)N ratios and high Zr contents are attributed to the high proportion of zircon. Chondrite-normalized REE patterns indicate high felsic sources, which are the regional rocks. Ultimately, the Yaoundé Group constitutes a favorable potential target for further rutile exploration.

Spatial distribution and contamination assessment of heavy metals in marine sediments of the southern coast of Sfax, Gabes Gulf, Tunisia.

PubMed

Naifar, Ikram; Pereira, Fernando; Zmemla, Raja; Bouaziz, Moncef; Elleuch, Boubaker; Garcia, Daniel

2018-06-01

In order to investigate the current distribution of metal concentrations in surface marine sediments of the southern coast of Sfax (Tunisia), thirty-nine samples were collected in the vicinity of a mixed industrial and domestic wastewater effluent discharge. In comparison with the threshold effect level and probable effect level, the majority of metals had high ecological and biological risks. Enrichment factor and geoaccumulation Index showed that the majority of sediments are unpolluted by As, Ni and Pb, moderately polluted by Cr and Cu and moderately to strongly polluted by P, Y, Zn. Besides, all sites are extremely polluted by Cd. Principal component analysis indicates that As, Cu and Ni were mainly from lithogenic sources, whereas Cd, Cr, F, P, Pb, Y and Zn were mainly derived from anthropogenic source. Findings of this research can be used as suitable reference for future studies and environmental management plans in the region. Copyright © 2018 Elsevier Ltd. All rights reserved.

A field survey-Staroe lake suffering from atmospheric deposition in the region north of the Arctic Circle.

PubMed

Kikuchi, Ryunosuke; Gorbacheva, Tamara T

2009-06-01

The Arctic holds large stores of minerals, and extracted materials are provided to the world's economy; in this sense, the Arctic issue associated with mining is not local but global. In a part of the Arctic region (the Kola Peninsula, 66-70 degrees N and 28-41 degrees E), metal levels are generally elevated in the lake sediment. There is a question as to what results in elevated metal levels-a natural process (naturally abundant minerals) or an anthropogenic process (mining and metallurgy). In terms of solving this question, Staroe lake located on the Kola Peninsula was researched as a case study. The following parameters were determined in relation with Staroe lake: (1) the current quality of the lake's water-each 1,000-ml sample was collected at a surface point and a deep point (near the bottom layer), and the collected samples were directly analyzed after filtration; (2) atmospheric bulk deposition-bulk deposition was collected using a set of three rainwater samplers near the lake. In addition, bulk deposition was collected in a background site (250 km to the southwest of the smelter complex) as a reference; and (3) sediment profile (plus principal component analysis)-lake-bottom sediment was collected by an open-gravimetric column sampler equipped with an automatic diaphragm. After collection, the sample columns were cut at a 1-cm interval for analysis. Eigenvalues and variances by factor were calculated from the correlation coefficients. The obtained data show that (1) naturally poor elements (Cu, Ni, Si, and SO(4) (2-)) dominantly influence the lake's water quality; (2) they are transported from the anthropogenic sources to the study lake through the atmospheric pathway; (3) mainly the contents of Cu, Ni, Sr, and Ca have influenced the sediment quality since the 1950s, corresponding to the industrial movement; and (4) Cu, Ni, and Sr originate from an anthropogenic source (smelter), and Ca originates from both natural and anthropogenic sources. As compared with the Russian standard (San Pin 2.1.980-00), the contents of NO(3) (-) (50.3 +/- 0.1 mg l(-1)) and particulates (2.3 +/- 0.2 mg l(-1)) exceeded the standard levels (0.7 mg l(-1) NO(3) (-) and 45 mg l(-1) particulates); Staroe lake may be slightly contaminated. However, the contamination factor (comparison with the background data) implies that Staroe lake is considerably contaminated. There is a strong possibility that fine overburden detritus (<0.1 mm diameter) may be transported from an open pit to the study lake by natural forces such as wind. Although it is difficult to suppose that one factor dominantly affects the sediment quality, it follows from a factor analysis that factors 1 and 2 account for about 70% of the total variance: Factor 1 is the most dominant, and factor 2 is the second most dominant in the variability of sediment quality. It is considered that Cu, Sr, and Ni in factor 1 originate from anthropogenic sources because they are poor in sediment rocks. The field survey conducted in Staroe lake can give the following answers to the key objectives: (1) The present water quality is affected by Cu, Ni, Si, and SO(4) (2-) in light of the contamination factor, and these elements originate from anthropogenic sources (the smelter and the open pit) and are transported to the lake through the atmospheric pathway; (2) the sediment profile and statistic analysis show that the lake quality has been influenced by deposition of metals since the 1950s; and (3) Cu, Ni, Sr, and Ca have influenced the sediment quality in light of the most dominant factor-Cu, Ni, and Sr originate from an anthropogenic source, whereas Ca comes from both natural and anthropogenic sources. The presented lake survey shows that the dispersion of human-related pollutants via the atmospheric pathway takes place in the Arctic region. If the current pollution continues without countermeasures, the high-latitude environment may lose its original characteristics; hence, this subject is important when considering how to implement a wide range of environmental protection measures in the Arctic.

Bank-derived material dominates fluvial sediment in a suburban Chesapeake Bay watershed

NASA Astrophysics Data System (ADS)

Cashman, M. J.; Gellis, A.; Gorman-Sanisaca, L.; Noe, G. B.; Cogliandro, V.; Baker, A.

2017-12-01

Excess fine sediment is a leading cause of ecological degradation within the Chesapeake Bay watershed. The Piedmont physiographic province, which includes parts of the Washington, D.C. metro area, has the highest sediment yields in the Chesapeake Bay. In order to effectively employ sediment mitigation measures, it is necessary to identify and quantify the contributions of sediments sources within rapidly urbanizing areas in the Piedmont. This sediment fingerprinting study examines the inputs of various sediment sources to Upper Difficult Run (14.2 km2; 22.6% impervious surface), an urbanized watershed in Fairfax County, Virginia. A source sediment library was constructed from collections of stream bank material, forest soils, and road dust from across the watershed. Target fluvial sediments were collected from fine channel margin deposits and from suspended sediment using an autosampler during 16 storm events from 2008 - 2012. Apportionment of the target samples to the source sediments was performed using Sed_SAT, a publically available toolkit for sediment fingerprinting. Bed sediment was found to be dominated by stream bank sources (mean: 96%), with minor contributions from forest (4%) and no detectable contribution from roads (0%). Suspended fine sediments were also found to predominantly originate from stream bank sources (SSC-weighted mean: 91%), with minor contributions from roads (8%), and negligible contributions from forests (1%). Stream bank sources dominated at all discharges, with the greatest contributions from overland sources found only at low discharges. On the rising limb of the hydrograph and at peak flow, sediment concentrations increased due to increasing contributions of bank material rather than surface erosion caused by overland flow. Results demonstrate that stream bank erosion is responsible for the vast majority of fine sediment occurring in this suburban basin of the Chesapeake Bay watershed. This is likely a consequence of storm-water energy characteristics in urbanized watersheds resulting in channel widening and bank failure. Thus, bank stabilization, channel restoration, and/or storm water management to attenuate stream energy may improve the ecological condition of these waterbodies.

A spatially explicit suspended-sediment load model for western Oregon

USGS Publications Warehouse

Wise, Daniel R.; O'Connor, Jim

2016-06-27

Knowledge of the regionally important patterns and factors in suspended-sediment sources and transport could support broad-scale, water-quality management objectives and priorities. Because of biases and limitations of this model, however, these results are most applicable for general comparisons and for broad areas such as large watersheds. For example, despite having similar area, precipitation, and land-use, the Umpqua River Basin generates 68 percent more suspended sediment than the Rogue River Basin, chiefly because of the large area of Coast Range sedimentary province in the Umpqua River Basin. By contrast, the Rogue River Basin contains a much larger area of Klamath terrane rocks, which produce significantly less suspended load, although recent fire disturbance (in 2002) has apparently elevated suspended sediment yields in the tributary Illinois River watershed. Fine-scaled analysis, however, will require more intensive, locally focused measurements.

Branched GDGT distributions in lakes from Mexico and Central America

NASA Astrophysics Data System (ADS)

Lei, A.; Werne, J. P.; Correa-Metrio, A.; Pérez, L.; Caballero, M.

2017-12-01

The potential to use bacterial derived branched glycerol dialkyl glycerol tetraethers (brGDGTs) to reconstruct mean annual air temperatures from soils sparked significant interest in the terrestrial paleoclimate community, where a high-fidelity paleotemperature proxy is desperately needed. While the source of brGDGTs remains unknown (but are potentially attributed to the highly diverse phylum Acidobacteria), much evidence points to the potential for these bacteria to live not only in the terrestrial environment but also in lake water and sediments as well. Though the application of brGDGTs to lacustrine reconstructions is promising, the initial applications of soil-based MBT/CBT proxy to lacustrine sediments typically resulted in lower temperatures than were reasonable, likely due to additions from lacustrine bacterial brGDGTs. Here, we present data from a suite of >100 lakes in Mexico and Central America, producing a regional core-top calibration different from those developed in other regions. Results indicate a significant role for regional differences in controlling the brGDGTs distribution, likely due to different brGDGT-producing microbial communities thriving under varying environmental conditions. Rigorous development of brGDGT based proxies will improve our understanding of the source and applicability of these biomarkers, and increase confidence in the accuracy of paleotemperature reconstructions to numerous lacustrine records in the region.

PAHs and PCBs deposited in surficial sediments along a rural to urban transect in a mid-Atlantic coastal river basin (USA).

PubMed

Foster, Gregory D; Cui, Vickie

2008-10-01

PAHs and PCBs were measured in river sediments along a 226 km longitudinal transect that spanned rural to urban land use settings through Valley and Ridge, Piedmont Plateau and Coastal Plain physiographic provinces in the Potomac River basin (mid-Atlantic USA). A gradient in PAH concentrations was found in river bed sediments along the upstream transect in the Potomac and Shenandoah Rivers that correlated with population densities in the nearby sub-basins. Sediment PAH concentrations halved per each approximately 40 km of transect distance upstream (i.e., the half-concentration distance) from the urban center (Washington, DC) of the Potomac River basin in direct proportion to population density. The PAH molecular composition was consistent across all geologic provinces, revealing a dominant pyrogenic source. Fluoranthene to perylene ratios served as useful markers for urban inputs, with a ratio > 2.4 observed in sediments near urban structures such as roadways, bridges and sewer outfalls. PCBs in sediments were not well correlated with population densities along the river basin transect, but the highest concentrations were found in the urban Coastal Plain region near Washington, DC and in the Shenandoah River near a known industrial Superfund site. PAHs were moderately correlated with sediment total organic carbon (TOC) in the Shenandoah River and Coastal Plain Potomac River regions, but TOC was poorly correlated with PCB concentrations throughout the entire basin. Although both PAHs and PCBs are widely recognized as urban-derived contaminants, their concentration profiles and geochemistry in river sediments were uniquely different throughout the upper Potomac River basin.

Tracking sediment through the Holocene: Determining anthropogenic contributions to a sediment-rich agricultural system, north-central USA

NASA Astrophysics Data System (ADS)

Gran, Karen; Belmont, Patrick; Finnegan, Noah

2013-04-01

Management and restoration of sediment-impaired streams requires quantification of sediment sources and pathways of transport. Addressing the role of humans in altering the magnitude and sources of sediment supplied to a catchment is notoriously challenging. Here, we explore how humans have amplified erosion in geomorphically-sensitive portions of the predominantly-agricultural Minnesota River basin in north-central USA. In the Minnesota River basin, the primary sources of sediment are classified generally as upland agricultural field vs. near-channel sources, with near-channel sources including stream banks, bluffs, and ravines. Using aerial lidar data, repeat terrestrial lidar scans of bluffs, ravine monitoring, historic air photo analyses, and sediment fingerprinting, we have developed a sediment budget to determine the relative importance of each source in a tributary to the Minnesota River, the Le Sueur River. We then investigate how these sources have changed through time, from changes evident over the past few decades to changes associated with valley evolution over the past 13,400 years. The Minnesota River valley was carved ~13,400 years ago through catastrophic drainage of glacial Lake Agassiz. As the Minnesota River valley incised, knickpoints have migrated upstream into tributaries, carving out deep valleys where the most actively eroding near-channel sediment sources occur. The modern sediment budget, closed for the time period 2000 to 2010, shows that the majority of the fine sediment load in the Le Sueur River comes from bluffs and other near-channel sources in the deeply-incised knick zone. Numerical modeling of valley evolution constrained by mapped and dated strath terraces cut into the glacial till presents an opportunity to compare the modern sediment budget to that of the river prior to anthropogenic modification. This comparison reveals a natural background or "pre-agriculture" rate of erosion from near-channel sources to be 3-5 times lower than modern near-channel erosion rates. Notably, depositional records from a naturally-dammed lake downstream on the upper Mississippi River show a more dramatic 10-fold increase in deposition rates from pre-agricultural times to the present. Sediment fingerprinting shows that pre-agriculture sediment loads were dominated by near-channel sediment sources. As deposition rates rose in the late 1800s and early 1900s, the sources shifted increasingly to agricultural soil erosion. In the past few decades, deposition rates have remained high, but sediment fingerprinting indicates yet another significant shift back to near-channel sources. On-going changes in basin hydrology, from both installation of agricultural drainage systems and on-going climate change have put more water in the rivers, increasing rates of near-channel bank and bluff erosion. This most recent shift in sediment sources has significant implications for turbidity management in the Minnesota River basin.

Trace metal occurrence and distribution in sediments and mangroves, Pumicestone region, southeast Queensland, Australia.

PubMed

Preda, Micaela; Cox, Malcolm E

2002-11-01

The Pumicestone region is a unique catchment in northern Moreton Bay, southeast Queensland. The region supports a wide range of land-use activities as well as attractions such as nature conservation areas. One environmental aspect that has not previously been addressed in this area is the occurrence of minor and trace metals in estuarine sediments associated with the main estuaries of the region. The trace metals included in this investigation are: vanadium, chromium, molybdenum, cobalt, nickel, copper, zinc, cadmium, lead and arsenic. To determine and evaluate the occurrence and distribution of metals in the area, several components have been analysed: bedrock material, pre-industrial settings, recent estuarine sediments, soils of estuarine origin and mangrove pneumatophores. The 40 sites chosen for sediment and soil samples cover a variety of estuarine settings and represent a range of natural conditions in terms of channel and bank morphology, tidal energy, vegetation cover, relationship to bedrock, water salinity and land disturbance. The chemical, mineralogical and statistical analyses employed in this study enabled (a) establishment of background values for the area, (b) determination of relationships between metals and (c) identification of sites with anomalous metal concentrations. All the metals found in the sediments of the area are sourced from the geological bedrock. The dominant trace elements identified in sediments are Zn, V and Cr. The remaining metals are highly variable spatially. All trace metals are controlled by the presence of Fe and Mn oxides, and by the grainsize of the sediment. Typically, fine-grained Fe-rich materials tend to adsorb more trace metals than sandy sediments. In soils that have developed from estuarine muds, some metals such as Cr, Mo, Pb and As tend to be in larger quantities than in the estuarine counterparts. Some of the elements, which occur in significant amounts in the sediment, have been detected in mangrove tissue (Avicenniamarina) such as V, Cr, Zn, Fe and Mn. Of particular note is Cu, which is present in mangrove tissue in quantities many times exceeding the sediment concentration. The comparative analysis of pre-industrial settings and recent sediments and soils highlighted some areas of metal enrichment such as acid-affected sites where oxidation of pyrite has mobilised metals from sediments; these metals are then redistributed in Fe-rich surficial layers. Disturbed banks within the estuaries are also likely to have low levels of metal enrichment due to boating activities.

Investigating the sources of sediment in a Canadian agricultural watershed using a colour-based fingerprinting technique

NASA Astrophysics Data System (ADS)

Barthod, Louise; Lobb, David; Owens, Philip; Martinez-Carreras, Nuria; Koiter, Alexander; Petticrew, Ellen; McCullough, Gregory

2014-05-01

The development of beneficial management practises to minimize adverse impacts of agriculture on soil and water quality requires information on the sources of sediment at the watershed scale. Sediment fingerprinting allows for the determination of sediment sources and apportionment of their contribution within a watershed, using unique physical, radiochemical or biogeochemical properties, or fingerprints, of the potential sediment sources. The use of sediment colour as a fingerprint is an emerging technique that can provide a rapid and inexpensive means of investigating sediment sources. This technique is currently being utilized to determine sediment sources within the South Tobacco Creek Watershed, an agricultural watershed located in the Canadian prairies (south-central Manitoba). Suspended sediment and potential source (topsoil, channel bank and shale bedrock material) samples were collected between 2009 and 2011 at six locations along the main stem of the creek. Sample colour was quantified from diffuse reflectance spectrometry measurements over the visible wavelength range using a spectroradiometer (ASD Field Spec Pro, 400-2500 nm). Sixteen colour coefficients were derived from several colour space models (CIE XYZ, CIE xyY, CIE Lab, CIE Luv, CIE Lch, Landsat RGB, Redness Index). The individual discrimination power of the colour coefficients, after passing several prerequisite tests (e.g., linearly additive behaviour), was assessed using discriminant function analysis. A stepwise discriminant analysis, based on the Wilk's lambda criterion, was then performed in order to determine the best-suited colour coefficient fingerprints which maximized the discrimination between the potential sources. The selected fingerprints classified the source samples in the correct category 86% of the time. The misclassification is due to intra-source variability and source overlap which can lead to higher uncertainty in sediment source apportionment. The selected fingerprints were then included in a Bayesian mixing model using Monte-Carlo simulation (Stable Isotope Analysis in R, SIAR) in order to apportion the contribution of the different sources to the sediment collected at each location. A switch in the dominant sediment source between the headwaters and the outlet of the watershed is observed. Sediment is enriched with shale bedrock and depleted of topsoil sources as the stream crosses and down-cuts through the Manitoba Escarpment. The switch in sources highlights the importance of the sampling location in relation to the scale and geomorphic connectivity of the watershed. Although the results include considerable uncertainty, they are consistent with the findings from a classical fingerprinting approach undertaken in the same watershed (i.e., geochemical and radionuclide fingerprints), and confirm the potential of sediment colour parameters as suitable fingerprints.

Use of sediment source fingerprinting to assess the role of subsurface erosion in the supply of fine sediment in a degraded catchment in the Eastern Cape, South Africa.

PubMed

Manjoro, Munyaradzi; Rowntree, Kate; Kakembo, Vincent; Foster, Ian; Collins, Adrian L

2017-06-01

Sediment source fingerprinting has been successfully deployed to provide information on the surface and subsurface sources of sediment in many catchments around the world. However, there is still scope to re-examine some of the major assumptions of the technique with reference to the number of fingerprint properties used in the model, the number of model iterations and the potential uncertainties of using more than one sediment core collected from the same floodplain sink. We investigated the role of subsurface erosion in the supply of fine sediment to two sediment cores collected from a floodplain in a small degraded catchment in the Eastern Cape, South Africa. The results showed that increasing the number of individual fingerprint properties in the composite signature did not improve the model goodness-of-fit. This is still a much debated issue in sediment source fingerprinting. To test the goodness-of-fit further, the number of model repeat iterations was increased from 5000 to 30,000. However, this did not reduce uncertainty ranges in modelled source proportions nor improve the model goodness-of-fit. The estimated sediment source contributions were not consistent with the available published data on erosion processes in the study catchment. The temporal pattern of sediment source contributions predicted for the two sediment cores was very different despite the cores being collected in close proximity from the same floodplain. This highlights some of the potential limitations associated with using floodplain cores to reconstruct catchment erosion processes and associated sediment source contributions. For the source tracing approach in general, the findings here suggest the need for further investigations into uncertainties related to the number of fingerprint properties included in un-mixing models. The findings support the current widespread use of ≤5000 model repeat iterations for estimating the key sources of sediment samples. Copyright © 2016 Elsevier Ltd. All rights reserved.

A shift of thermokarst lakes from carbon sources to sinks during the Holocene epoch

USGS Publications Warehouse

Walter Anthony, K. M.; Zimov, S. A.; Grosse, G.; Jones, Miriam C.; Anthony, P.; Chapin, F. S.; Finlay, J. C.; Mack, M. C.; Davydov, S.; Frenzel, P.F.; Frolking, S.

2014-01-01

Thermokarst lakes formed across vast regions of Siberia and Alaska during the last deglaciation and are thought to be a net source of atmospheric methane and carbon dioxide during the Holocene epoch1,2,3,4. However, the same thermokarst lakes can also sequester carbon5, and it remains uncertain whether carbon uptake by thermokarst lakes can offset their greenhouse gas emissions. Here we use field observations of Siberian permafrost exposures, radiocarbon dating and spatial analyses to quantify Holocene carbon stocks and fluxes in lake sediments overlying thawed Pleistocene-aged permafrost. We find that carbon accumulation in deep thermokarst-lake sediments since the last deglaciation is about 1.6 times larger than the mass of Pleistocene-aged permafrost carbon released as greenhouse gases when the lakes first formed. Although methane and carbon dioxide emissions following thaw lead to immediate radiative warming, carbon uptake in peat-rich sediments occurs over millennial timescales. We assess thermokarst-lake carbon feedbacks to climate with an atmospheric perturbation model and find that thermokarst basins switched from a net radiative warming to a net cooling climate effect about 5,000 years ago. High rates of Holocene carbon accumulation in 20 lake sediments (47±10 grams of carbon per square metre per year; mean±standard error) were driven by thermokarst erosion and deposition of terrestrial organic matter, by nutrient release from thawing permafrost that stimulated lake productivity and by slow decomposition in cold, anoxic lake bottoms. When lakes eventually drained, permafrost formation rapidly sequestered sediment carbon. Our estimate of about 160petagrams of Holocene organic carbon in deep lake basins of Siberia and Alaska increases the circumpolar peat carbon pool estimate for permafrost regions by over 50 per cent (ref. 6). The carbon in perennially frozen drained lake sediments may become vulnerable to mineralization as permafrost disappears7,8,9, potentially negating the climate stabilization provided by thermokarst lakes during the late Holocene.

[Assessment of the impacts of soil erosion on water environment based on the integration of soil erosion process and landscape pattern].

PubMed

Liu, Yu; Wu, Bing-Fang; Zeng, Yuan; Zhang, Lei

2013-09-01

The integration of the effects of landscape pattern to the assessment of the impacts of soil erosion on eco-environmental is of practical significance in methodological prospect, being able to provide an approach for identifying water body's sediment source area, assessing the potential risks of sediment export of on-site soil erosion to the target water body, and evaluating the capacity of regional landscape pattern in preventing soil loss. In this paper, the RUSLE model was applied to simulate the on-site soil erosion rate. With the consideration of the soil retention potential of vegetation cover and topography, a quantitative assessment was conducted on the impacts of soil erosion in the water source region of the middle route for South-to-North Water Transfer Project on rivers and reservoirs by delineating landscape pattern at point (or cell) scale and sub-watershed level. At point (or grid cell) scale, the index of soil erosion impact intensity (I) was developed as an indicator of the potential risk of sediment export to the water bodies. At sub-watershed level, the landscape leakiness index (LI) was employed to indicate the sediment retention capacity of a given landscape pattern. The results revealed that integrating the information of landscape pattern and the indices of soil erosion process could spatially effectively reflect the impact intensity of in situ soil erosion on water bodies. The LI was significantly exponentially correlated to the mean sediment retention capacity of landscape and the mean vegetation coverage of watershed, and the sediment yield at sub-watershed scale was significantly correlated to the LI in an exponential regression. It could be concluded that the approach of delineating landscape pattern based on soil erosion process and the integration of the information of landscape pattern with its soil retention potential could provide a new approach for the risk evaluation of soil erosion.

Distribution of long-lived radioactive iodine isotope (I-129) in pore waters from the gas hydrate fields on the continental margins: Indication for methane source of gas hydrate deposits

NASA Astrophysics Data System (ADS)

Tomaru, H.; Lu, Z.; Fehn, U.

2011-12-01

Because iodine has a strong association with organic matters in marine environments, pore waters in high methane potential region, in particular gas hydrate occurrences on the continental margins, are enriched significantly in iodine compared with seawater. Natural iodine system is composed of stable and radioactive species, I-129 (half-life of 15.7 Myr) has been used for estimating the age of source formations both for methane and iodine, because iodine can be liberated into pore water during the degradation of organic matter to methane in deep sediments. Here we present I-129 age data in pore waters collected from variety of gas hydrate occurrences on the continental margins. The I-129 ages in pore waters from these locations are significantly older than those of host sediments, indicating long-term transport and accumulation from deep/old sediments. The I-129 ages in the Japan Sea and Okhotsk Sea along the plate boundary between the North American and Amurian Plates correspond to the ages of initial spreading of these marginal seas, pointing to the massive deposition of organic matter for methane generation in deep sediments within limited periods. On the Pacific side of these areas, organic matter-rich back stop is responsible for methane in deep-seated gas hydrate deposits along the Nankai Trough. Deep coaly sequences responsible for deep conventional natural gas deposits are also responsible for overlying gas hydrate deposits off Shimokita Peninsula, NE Japan. Those in the Gulf of Mexico are correlative to the ages of sediments where the top of salt diapirs intrude. Marine sediments on the Pacific Plate subducting beneath the Australian Plate are likely responsible for the methane and iodine in the Hikurangi Trough, New Zealand. These ages reflect well the regional geological settings responsible for generation, transport, and accumulation of methane, I-129 is a key to understand the geological history of gas hydrate deposition.

Bed turbulent kinetic energy boundary conditions for trapping efficiency and spatial distribution of sediments in basins.

PubMed

Isenmann, Gilles; Dufresne, Matthieu; Vazquez, José; Mose, Robert

2017-10-01

The purpose of this study is to develop and validate a numerical tool for evaluating the performance of a settling basin regarding the trapping of suspended matter. The Euler-Lagrange approach was chosen to model the flow and sediment transport. The numerical model developed relies on the open source library OpenFOAM ® , enhanced with new particle/wall interaction conditions to limit sediment deposition in zones with favourable hydrodynamic conditions (shear stress, turbulent kinetic energy). In particular, a new relation is proposed for calculating the turbulent kinetic energy threshold as a function of the properties of each particle (diameter and density). The numerical model is compared to three experimental datasets taken from the literature and collected for scale models of basins. The comparison of the numerical and experimental results permits concluding on the model's capacity to predict the trapping of particles in a settling basin with an absolute error in the region of 5% when the sediment depositions occur over the entire bed. In the case of sediment depositions localised in preferential zones, their distribution is reproduced well by the model and trapping efficiency is evaluated with an absolute error in the region of 10% (excluding cases of particles with very low density).

Floodplains as a source of fine sediment in grazed landscapes: Tracing the source of suspended sediment in the headwaters of an intensively managed agricultural landscape

NASA Astrophysics Data System (ADS)

Yu, Mingjing; Rhoads, Bruce L.

2018-05-01

The flux of fine sediment within agricultural watersheds is an important factor determining the environmental quality of streams and rivers. Despite this importance, the contributions of sediment sources to suspended sediment loads within intensively managed agricultural watersheds remain poorly understood. This study assesses the provenance of fine suspended sediment in the headwater portion of a river flowing through an agricultural landscape in Illinois. Sediment source samples were collected from five sources: croplands, forested floodplains, grasslands, upper grazed floodplains, and lower grazed floodplains. Event-based and aggregated suspended sediment samples were collected from the stream at the watershed outlet. Quantitative geochemical fingerprinting techniques and a mixing model were employed to estimate the relative contributions of sediment from the five sources to the suspended sediment loads. To account for possible effects of small sample sizes, the analysis was repeated with only two sources: grazed floodplains and croplands/grasslands/forested floodplains. Results based on mean values of tracers indicate that the vast majority of suspended sediment within the stream (>95%) is derived from erosion of channel banks and the soil surface within areas of grazed floodplains. Uncertainty analysis based on Monte Carlo simulations indicates that mean values of tracer properties, which do not account for sampling variability in these properties, probably overestimate contributions from the two major sources. Nevertheless, this analysis still supports the conclusion that floodplain erosion accounts for the largest percentage of instream sediment (≈55-75%). Although grazing occurs over only a small portion of the total watershed area, grazed floodplains, which lie in close proximity to the stream channel, are an important source of sediment in this headwater steam system. Efforts to reduce fluxes of fine sediment in this intensively managed landscape should focus on eroding floodplain surfaces and channel banks within heavily grazed reaches of the stream.

Ascribing soil erosion of hillslope components to river sediment yield.

PubMed

Nosrati, Kazem

2017-06-01

In recent decades, soil erosion has increased in catchments of Iran. It is, therefore, necessary to understand soil erosion processes and sources in order to mitigate this problem. Geomorphic landforms play an important role in influencing water erosion. Therefore, ascribing hillslope components soil erosion to river sediment yield could be useful for soil and sediment management in order to decrease the off-site effects related to downstream sedimentation areas. The main objectives of this study were to apply radionuclide tracers and soil organic carbon to determine relative contributions of hillslope component sediment sources in two land use types (forest and crop field) by using a Bayesian-mixing model, as well as to estimate the uncertainty in sediment fingerprinting in a mountainous catchment of western Iran. In this analysis, 137 Cs, 40 K, 238 U, 226 Ra, 232 Th and soil organic carbon tracers were measured in 32 different sampling sites from four hillslope component sediment sources (summit, shoulder, backslope, and toeslope) in forested and crop fields along with six bed sediment samples at the downstream reach of the catchment. To quantify the sediment source proportions, the Bayesian mixing model was based on (1) primary sediment sources and (2) combined primary and secondary sediment sources. The results of both approaches indicated that erosion from crop field shoulder dominated the sources of river sediments. The estimated contribution of crop field shoulder for all river samples was 63.7% (32.4-79.8%) for primary sediment sources approach, and 67% (15.3%-81.7%) for the combined primary and secondary sources approach. The Bayesian mixing model, based on an optimum set of tracers, estimated that the highest contribution of soil erosion in crop field land use and shoulder-component landforms constituted the most important land-use factor. This technique could, therefore, be a useful tool for soil and sediment control management strategies. Copyright © 2016 Elsevier Ltd. All rights reserved.

Sources of suspended sediment in the Lower Roanoke River, NC

NASA Astrophysics Data System (ADS)

Jalowska, A. M.; McKee, B. A.; Rodriguez, A. B.; Laceby, J. P.

2015-12-01

The Lower Roanoke River, NC, extends 220 km from the fall line to the bayhead delta front in the Albemarle Sound. The Lower Roanoke is almost completely disconnected from the upper reaches by a series of dams, with the furthest downstream dam located at the fall line. The dams effectively restrict the suspended sediment delivery from headwaters, making soils and sediments from the Lower Roanoke River basin, the sole source of suspended sediment. In flow-regulated rivers, bank erosion, especially mass wasting, is the major contributor to the suspended matter. Additional sources of the suspended sediment considered in this study are river channel, surface soils, floodplain surface sediments, and erosion of the delta front and prodelta. Here, we examine spatial and temporal variations in those sources. This study combined the use of flow and grain size data with a sediment fingerprinting method, to examine the contribution of surface and subsurface sediments to the observed suspended sediment load along the Lower Roanoke River. The fingerprinting method utilized radionuclide tracers 210Pb (natural atmospheric fallout), and 137Cs (produced by thermonuclear bomb testing). The contributions of surface and subsurface sources to the suspended sediment were calculated with 95% confidence intervals using a Monte-Carlo numerical mixing model. Our results show that with decreasing river slope and changing hydrography along the river, the contribution of surface sediments increases and becomes a main source of sediments in the Roanoke bayhead delta. At the river mouth, the surface sediment contribution decreases and is replaced by sediments eroded from the delta front and prodelta. The area of high surface sediment contribution is within the middle and upper parts of the delta, which are considered net depositional. Our study demonstrates that floodplains, often regarded to be a sediment sink, are also a sediment source, and they should be factored into sediment, carbon and nutrient budgets.

An Isotopic Map of Dust Source Areas in the McMurdo Sound Sector of Antarctica

NASA Astrophysics Data System (ADS)

Blakowski, M. A.; Aciego, S.; Delmonte, B.; Baroni, C.; Salvatore, M. C.

2014-12-01

The McMurdo Sound sector of Antarctica features a unique, polar desert ecosystem characterized by low temperatures, hyper-aridity, and high-speed winds. These climatic conditions result in limited water sources, sparse vegetation, underdeveloped soils, and abundant unconsolidated sediment easily influenced by wind-driven transport. Radiogenic isotopes (87Sr/86Sr, 143Nd/144Nd) provide constant signatures of dust from source- to sink-areas. Accordingly, aeolian dust derived from arid regions has been recognized in many studies as an important tracer of atmospheric circulation, as well as a tool for deciphering past climatic conditions in dust source regions. However, while major global dust sources (e.g. from South America, Africa, and Asia) are well studied and easily identifiable via distinct isotopic signatures when encountered in different depositional environments (e.g. Antarctic ice cores), local material from sources in and around the ice-free Dry Valleys and surrounding areas have remained in need of further documentation. We analyzed 40 samples of silt, sand, glacial drift, and weathered regolith material in both fine (<5μm) and coarse fractions collected from Victoria Land and the McMurdo Sound sector, including Cape Royds, Cape Bird, and the McMurdo Ice Shelf. Here we present an ArcGIS-generated, high-precision geochemical map of Antarctic PSAs synthesized from our data and combined with geomorphological and stratigraphic information on the studied sites. We believe that our expanded isotopic catalogue and map can be used to enhance and/or prompt regional studies in a variety of disciplines, such as by providing greater constraints on models of regional dust variability and transport pathways and of the melting history of the Antarctic ice sheet, and by determining the provenance of dust archived in ice cores, lake sediment, soil records, and impurities in Antarctic sea-ice.

Chemical and carbon isotopic composition of dissolved organic carbon in a regional confined methanogenic aquifer

USGS Publications Warehouse

Aravena, R.; Wassenaar, L.I.; Spiker, E. C.

2004-01-01

This study demonstrates the advantage of a combined use of chemical and isotopic tools to understand the dissolved organic carbon (DOC) cycle in a regional confined methanogenic aquifer. DOC concentration and carbon isotopic data demonstrate that the soil zone is a primary carbon source of groundwater DOC in areas close to recharge zones. An in-situ DOC source linked to organic rich sediments present in the aquifer matrix is controlling the DOC pool in the central part of the groundwater flow system. DOC fractions, 13C-NMR on fulvic acids and 14C data on DOC and CH4 support the hypothesis that the in-situ DOC source is a terrestrial organic matter and discard the Ordovician bedrock as a source of DOC. ?? 2004 Taylor and Francis Ltd.

[Pollution distribution and potential ecological risk assessment of heavy metals in sediments from the different eastern dredging regions of Lake Taihu].

PubMed

Mao, Zhi-Gang; Gu, Xiao-Hong; Lu, Xiao-Ming; Zeng, Qing-Fei; Gu, Xian-Kun; Li, Xu-Guang

2014-01-01

In order to investigate the distribution characteristics of nutrients and heavy metals in sediments from different eastern dredging regions of Lake Taihu, the surface and core sediment samples at 5 sites (in East Taihu Lake and Xukou Bay) were collected in 2012. Contents of nutrients (TOC, TN and TP) and heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) in the sediments were measured and the pollution degrees of heavy metals were evaluated with the potential ecological risk method. The results showed that the heavy metal contents in Xukou Bay were generally higher than those in East Taihu Lake, whereas the nutrients contents showed the reverse trend. There were significant differences between the phytoplankton-dominated and culture lake regions. The concentrations of both nutrients and heavy metals decreased with increasing profile depth. Moreover, the contents of nutrients and heavy metals in the sediments of all dredged areas were lower than those in the un-dredged areas, suggesting that dredging may be a useful approach for decreasing nutrients and heavy metals loading in sediments, but its effectiveness decreased with time. Significant positive correlations were found among different heavy metals and nutrients, indicating that they were from the same pollution source. The Hakanson potential ecological risk index was applied for assessing the status of sediment heavy metal enrichment and the result indicated that sediment dredging could reduce the extent of potential ecological risk. The risk index in different sites followed the order: X1 > D1 > D3 > X2 > D2, while the risk index in site X1 of Xukou Bay was higher than that in site D1 of East Taihu Lake. And the comprehensive ecological risk grades in sites X1 and D1 were in the moderate range, while the sites D2, D3 and X2 were low.

The Effect of DEM Source and Grid Size on the Index of Connectivity in Savanna Catchments

NASA Astrophysics Data System (ADS)

Jarihani, Ben; Sidle, Roy; Bartley, Rebecca; Roth, Christian

2017-04-01

The term "hydrological connectivity" is increasingly used instead of sediment delivery ratio to describe the linkage between the sources of water and sediment within a catchment to the catchment outlet. Sediment delivery ratio is an empirical parameter that is highly site-specific and tends to lump all processes, whilst hydrological connectivity focuses on the spatially-explicit hydrologic drivers of surficial processes. Detailed topographic information plays a fundamental role in geomorphological interpretations as well as quantitative modelling of sediment fluxes and connectivity. Geomorphometric analysis permits a detailed characterization of drainage area and drainage pattern together with the possibility of characterizing surface roughness. High resolution topographic data (i.e., LiDAR) are not available for all areas; however, remotely sensed topographic data from multiple sources with different grid sizes are used to undertake geomorphologic analysis in data-sparse regions. The Index of Connectivity (IC), a geomorphometric model based only on DEM data, is applied in two small savanna catchments in Queensland, Australia. The influence of the scale of the topographic data is explored by using DEMs from LiDAR ( 1 m), WorldDEM ( 10 m), raw SRTM and hydrologically corrected SRTM derived data ( 30 m) to calculate the index of connectivity. The effect of the grid size is also investigated by resampling the high resolution LiDAR DEM to multiple grid sizes (e.g. 5, 10, 20 m) and comparing the extracted IC.

The Importance of Actualistic Source-to-Sink Sand Provenance Studies in Illuminating the Nature of Ancient Fluvial Systems From the Deep-Marine Clastic Successions They Sourced

NASA Astrophysics Data System (ADS)

Marsaglia, K. M.; Parra, J. G.; Dawson, S.

2006-12-01

Successions of gravity-flow deposits in deep-marine fan systems have the potential to record the evolution of their fluvial source region as well as specific tectonic, climatic, eustatic and anthropogenic events. Deciphering these signals involves the description and quantification of key sediment attributes such as fan volume, the rate of sediment accumulation, the frequency of depositional events, sediment texture, and sediment composition. Sediment composition/provenance provides insight into the nature of the fluvial source, including drainage basin geology and drainage development. For example, Marsaglia et al. (1995) demonstrated a connection between source river lengthening owing to eustatic change and sand composition in Quaternary turbidite successions of the Santa Barbara Basin at Ocean Drilling Program (ODP) Site 893. In contrast, longer-term compositional trends recognized in the Mesozoic to Cenozoic rift-to-drift successions cored by various ODP legs on the North Atlantic margins are more likely associated with continental margin drainage development and fluvial system evolution (Marsaglia et al., in press). These two connections between sink and source were made possible by well-documented petrologic data sets for both modern onshore fluvial systems and older offshore deep-marine successions, but in each case different workers collected the onshore and offshore data sets. In the Waipaoa River Sedimentary System of North Island, New Zealand we have taken a different, more holistic approach, with a limited and linked group of researchers and sample data base covering the complete system. The study area is an active forearc margin characterized by uplifted and deformed sedimentary successions and periodic input of arc-derived ash. Recently, the modern onshore system has been thoroughly documented via studies of the petrology of outcropping Mesozoic to Cenozoic units, fluvial terrace deposits, and modern fluvial sediments (e.g., James et al., in press). Now we are building on that data set and moving from source-to-sink to trace sandy sediment through the system out onto the shelf and slope where it has been encountered in shallow cores. Lessons learned onshore, such as a distinct compositional dependence on grain size and the relationships of bedrock geology to certain sand grain types, also apply to these offshore core samples. Many of the sandy intervals are largely composed of reworked tephra from Taupo eruptions, whereas quartz and feldspar dominate finer sand samples. Lithic-dominated sands are less common and coarser grained. Isolated greywacke gravel clasts indicate that at some point coarse sediment "leaked" into the basin from the south. The volumetric importance of this extrabasinal input can be assessed by looking at the types and proportions of lithic fragments within the finer sand fraction.

Oils and hydrocarbon source rocks of the Baltic syneclise

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kanev, S.; Margulis, L.; Bojesen-Koefoed, J.A.

Prolific source rock horizons of varying thickness, having considerable areal extent, occur over the Baltic syneclise. These source sediments are rich and have excellent petroleum generation potential. Their state of thermal maturity varies form immature in the northeastern part of the syneclise to peak generation maturity in the southwestern part of the region-the main kitchen area. These maturity variations are manifest in petroleum composition in the region. Hence, mature oils occur in the Polish and Kaliningrad areas, immature oils in small accumulations in Latvian and central Lithuanian onshore areas, and intermediate oils in areas between these extremes. The oil accumulationsmore » probably result from pooling of petroleum generated from a number of different source rocks at varying levels of thermal maturity. Hence, no single source for petroleum occurrences in the Baltic syneclise may be identified. The paper describes the baltic syneclise, source rocks, thermal maturity and oils and extracts.« less

Historical records of polycyclic aromatic hydrocarbon deposition in a shallow eutrophic lake: Impacts of sources and sedimentological conditions.

PubMed

Li, Chaocan; Huo, Shouliang; Yu, Zhiqiang; Guo, Wei; Xi, Beidou; He, Zhuoshi; Zeng, Xiangying; Wu, Fengchang

2016-03-01

Sediment core samples collected from Lake Chaohu were analyzed for 15 priority polycyclic aromatic hydrocarbons (PAHs) to assess the spatial and temporal distributions of the PAHs during lacustrine sedimentary processes and regional economic development. Assessing the PAH sedimentary records over an approximately 100-year time span, we identified two stages in the PAH inputs and sources (before the 1970s and after the 1970s) in the eastern lake region near a village, whereas three stages (before the 1950s, 1950s-1990s and after the 1990s) were identified in the western lake region near urban and industrial areas. Rapid increases in the PAH depositional fluxes occurred during the second stage due to increased human activities in the Lake Chaohu basin. The composition and isomeric ratios of the PAHs revealed that pyrolysis is the main source of PAHs in this lake. Strong positive relationships between PAH concentration and the total organic carbon concentration, sediment grain size (<4μm), as well as the local population and Gross Domestic Product indicated that the sedimentary conditions impact the depositional characteristics of the PAHs; simultaneously, socioeconomic activities, such as energy consumption and the levels of urban industrialization and civilization, affect both the composition and abundance of the PAHs. Copyright © 2015. Published by Elsevier B.V.

Biomarkers reveal the effects of hydrography on the sources and fate of marine and terrestrial organic matter in the western Irish Sea

NASA Astrophysics Data System (ADS)

O'Reilly, Shane S.; Szpak, Michal T.; Flanagan, Paul V.; Monteys, Xavier; Murphy, Brian T.; Jordan, Sean F.; Allen, Christopher C. R.; Simpson, Andre J.; Mulligan, Stephen M.; Sandron, Sara; Kelleher, Brian P.

2014-01-01

A suite of lipid biomarkers were investigated from surface sediments and particulate matter across hydrographically distinct zones associated with the western Irish Sea gyre and the seasonal bloom. The aim was to assess the variation of organic matter (OM) composition, production, distribution and fate associated with coastal and southern mixed regions and also the summer stratified region. Based on the distribution of a suite of diagnostic biomarkers, including phospholipid fatty acids, source-specific sterols, wax esters and C25 highly branched isoprenoids, diatoms, dinoflagellates and green algae were identified as major contributors of marine organic matter (MOM) in this setting. The distribution of cholesterol, wax esters and C20 and C22 polyunsaturated fatty acids indicate that copepod grazing represents an important process for mineralising this primary production. Net tow data from 2010 revealed much greater phytoplankton and zooplankton biomass in well-mixed waters compared to stratified waters. This appears to be largely reflected in MOM input to surface sediments. Terrestrial organic matter (TOM), derived from higher plants, was identified as a major source of OM regionally, but was concentrated in proximity to major riverine input at the Boyne Estuary and Dundalk Bay. Near-bottom residual circulation and the seasonal gyre also likely play a role in the fate of TOM in the western Irish Sea.

Distribution of branched GDGTs in surface sediments from the Colville River, Alaska: Implications for the MBT'/CBT paleothermometer in Arctic marine sediments

NASA Astrophysics Data System (ADS)

Hanna, Andrea J. M.; Shanahan, Timothy M.; Allison, Mead A.

2016-07-01

Significant climate fluctuations in the Arctic over the recent past, and additional predicted future temperature changes, highlight the need for high-resolution Arctic paleoclimate records. Arctic coastal environments supplied with terrigenous sediment from Arctic rivers have the potential to provide annual to subdecadal resolution records of climate variability over the last few millennia. A potential tool for paleotemperature reconstructions in these marine sediments is the revised methylation index of branched tetraethers (MBT')/cyclization ratio of branched tetraethers (CBT) proxy based on branched glycerol dialkyl glycerol tetraethers (brGDGTs). In this study, we examine the source of brGDGTs in the Colville River, Alaska, and the adjacent Simpson Lagoon and reconstruct temperatures from Simpson Lagoon sediments to evaluate the applicability of this proxy in Arctic estuarine environments. The Colville catchment soils, fluvial sediments, and estuarine sediments contain statistically similar brGDGT distributions, indicating that the brGDGTs throughout the system are soil derived with little alteration from in situ brGDGT production in the river or coastal waters. Temperatures reconstructed from the MBT'/CBT indices for surface samples show good agreement with regional summer (June through September) temperatures, suggesting a seasonal bias in Arctic temperature reconstructions from the Colville system. In addition, we reconstruct paleotemperatures from an estuarine sediment core that spans the last 75 years, revealing an overall warming trend in the twentieth century that is consistent with trends observed in regional instrumental records. These results support the application of this brGDGT-based paleotemperature proxy for subdecadal-scale summer temperature reconstructions in Arctic estuaries containing organic material derived from sediment-laden, episodic rivers.

Heavy metals in sediments, soils, and aquatic plants from a secondary anabranch of the three gorges reservoir region, China.

PubMed

Gao, Jun-Min; Sun, Xiu-Qian; Jiang, Wen-Chao; Wei, Yun-Mei; Guo, Jin-Song; Liu, Yuan-Yuan; Zhang, Ke

2016-06-01

We investigated the occurrence of cadmium (Cd), copper (Cu), chromium (Cr), nickel (Ni), lead (Pb), Znic (Zn), iron (Fe), manganese (Mn), and magnesium (Mg) in sediments, as well as in related soils and aquatic plants in the Liangtan River, a typical secondary anabranch of the Yangtze River in the Three Gorges Reservoir Region (TGRR) of China. We found that sediments accumulated more metals than soils and aquatic plants. Concentrations of the nine metals in sediments and soils followed the same sequence, while their concentrations in aquatic plants followed a different sequence. Potential adverse effects of contaminated sediments on benthic fauna were evaluated, and the results showed that the toxic effect on benthic organisms followed the sequence Zn > Ni > Cr > Cu > Cd > Pb. The potential ecological risk index analysis indicated that Cd in sediments had considerable ecological risk, whereas Cr, Cu, Zn, Ni, and Pb had low ecological risk. The potential ecological risk index (RI) of the heavy metals in sediments of the Liangtan River was 174.9, indicating moderate ecological risk. The transfer factor trend of metals for aquatic plants showed that Cd and Ni had the most and least accumulation, respectively. For Cu, Cd, Mg, Pb, and Cr, a significant positive correlation of the metal concentrations was observed between sediments and soils, but no correlations (excluding Cr) were detected between sediments and aquatic plants. Our study indicated that anthropogenic input may be the primary source of metal contamination in the Liangtan River, and that Zn and Cd pollution in the Liangtan River should be further explored.

Response and recovery of streams to an intense regional flooding event

NASA Astrophysics Data System (ADS)

Dethier, E.; Magilligan, F. J.; Renshaw, C. E.; Kantack, K. M.

2015-12-01

Determining the relative roles of frequent and infrequent events on landscape form and material transport has implications for understanding landscape development, and informs planning and infrastructure decisions. Flooding due to Tropical Storm Irene in 2011 provides a unique opportunity to examine the effects of a rare, major disturbance across a broad area (14,000 km2). Intense flooding caused variable but widespread channel and riparian reconfiguration, including 995 channel-adjacent mass-wasting events, collectively referred to here as landslides, that mostly occurred in glacial deposits. Of these, about half involved reactivation of existing scars. Landslides were generally small, ranging from 60 - 26,000 m2 in planform, and covered less than 0.01 % of land in the region, yet sediment input from landslides alone (131 mm/kyr when integrated over the study area) exceeded inferred local background erosion rates by 60 times. If Irene inputs are included in a thirty-year erosion record, the estimated erosion rate, 7.2 mm/kyr, aligns closely with long-term regional rates of 5-10 mm/kyr. Landslides also input trees to streams, increasing large wood influence on those reaches. Combined wood and sediment inputs contributed to channel changes downstream of landslides. In four years since Irene, terrestrial lidar and suspended sediment sampling has documented continued large wood and sediment input. Erosion occurred on each of seventeen monitored landslides during snowmelt, but is otherwise limited except during intense precipitation and/or flood events. Repeat lidar models have recorded erosion of up to 5,000 m3 on a single slide in one year, including as much as 4000 m3 during a single event. Tree fall on scarps during erosion events creates sediment traps at the base of landslides, contributing to an observed return to equilibrium slopes. Despite trapping, substantial sediment continues to enter streams. Ninety-five suspended sediment samples from forty sites show that landslides remain important sediment sources. Across a range of flows, 2014 - 2015 sediment flux for a given discharge is an order of magnitude higher than pre-Irene flux. Though landslide slope relaxation suggests incipient recovery from Irene, persistent rapid erosion of large wood and sediment indicates that recovery is still on-going.

Spatial distribution of pollen grains and spores in surface sediments of Guanabara Bay, Rio de Janeiro, Brazil.

PubMed

Barreto, Cintia F; Vilela, Claudia G; Baptista-Neto, José A; Barth, Ortrud M

2012-09-01

Aiming to investigate the deposition of pollen grains and spores in Guanabara Bay, Rio de Janeiro State, 61 surface sediment samples were analyzed. The results showed that the current deposition of palynomorphs in surface sediments of Guanabara Bay represents the regional vegetation of this hydrographic basin. The differential distribution of palynomorphs followed a pattern influenced by bathymetry, tidal currents speed, discharge of numerous rivers, and by human activity. The dominance of representatives of Field Vegetation reflects the changes of the original flora caused by intense human activities in the region. The continued presence and richness of pollen types of rain forest in the samples indicates that their source area might be the vegetation from riparian border of rivers in the western sector of the Bay, where the mangrove vegetation is being preserved. The large amount of damaged palynomorphs may be related to abrasion that occurs during river transport, indicating removal or reworking from their areas of origin.

Structural mapping of Chikotra River basin in the Deccan Volcanic Province of Maharashtra, India from ground magnetic data

NASA Astrophysics Data System (ADS)

Anand, S. P.; Erram, Vinit C.; Patil, J. D.; Pawar, N. J.; Gupta, Gautam; Suryavanshi, R. A.

2016-03-01

Ground magnetic data collected over Chikotra River in the peripheral region of Deccan Volcanic Province (DVP) of Maharashtra located in Kolhapur district was analysed to throw light on the structural pattern and distribution of magnetic sources within the basin. In order to isolate the magnetic anomalies showing varying trend and amplitude, several transformation operations including wavelength filtering, and upward continuation has been carried out on the reduced to pole anomaly map. Qualitative interpretation of these products help identify the distribution of magnetic sources, viz., the Deccan basalts, dolerite intrusives and older greenstone and schist belts in the subsurface. Present study suggests that the Chikotra basin is composed of three structural units; a NE-SW unit superposed on deeper NW-SE unit with randomly distributed trap flows on the surface. One of the major outcome of the present study is the delineation of almost 900-m thick Proterozoic Kaladgi sediments below the Deccan trap flows. The NE-SW magnetic sources may probably represent intrusives into the Kaladgi sediments, while the deeper NW-SE trends are interpreted as the northward extension of the Dharwars, underneath the Deccan lava flows, that forms the basement for the deposition of Kaladgi sediments.

The application of microtextural and heavy mineral analysis to discriminate between storm and tsunami deposits

USGS Publications Warehouse

Costa, Pedro J.M.; Gelfenbaum, Guy R.; Dawson, Sue; La selle, Seanpaul; Milne, F; Cascalho, J.; Ponte Lira, C.; Andrade, C.; Freitas, M. C.; Jaffe, Bruce E.

2017-01-01

Recent work has applied microtextural and heavy mineral analyses to sandy storm and tsunami deposits from Portugal, Scotland, Indonesia and the USA. We looked at the interpretation of microtextural imagery (scanning electron microscopy) of quartz grains and heavy mineral compositions. We consider inundation events of different chronologies and sources (the AD 1755 Lisbon and 2004 Indian Ocean tsunamis, the Great Storm of 11 January 2005 in Scotland, and Hurricane Sandy in 2012) that affected contrasting coastal and hinterland settings with different regional oceanographic conditions. Storm and tsunami deposits were examined along with potential source sediments (alluvial, beach, dune and nearshore sediments) to determine provenance.Results suggest that tsunami deposits typically exhibit a significant spatial variation in grain sizes, microtextures and heavy minerals. Storm deposits show less variability, especially in vertical profiles. Tsunami and storm quartz grains had more percussion marks and fresh surfaces compared to potential source material. Moreover, in the studied cases, tsunami samples had fewer fresh surfaces than storm deposits.Heavy mineral assemblages are typically site-specific. The concentration of heavy minerals decreases upwards in tsunamigenic units, whereas storm sediments show cyclic concentrations of heavy minerals, reflected in the laminations observed macroscopically in the deposits.

Contamination history of lead and other trace metals reconstructed from an urban winter pond in the Eastern Mediterranean coast (Israel).

PubMed

Zohar, I; Bookman, R; Levin, N; de Stigter, H; Teutsch, N

2014-12-02

Pollution history of Pb and other trace metals was reconstructed for the first time for the Eastern Mediterranean, from a small urban winter pond (Dora, Netanya), located at the densely populated coastal plain of Israel. An integrated approach including geochemical, sedimentological, and historical analyses was employed to study sediments from the center of the pond. Profiles of metal concentrations (Pb, Zn, V, Ni, Cu, Cr, Co, Cd, and Hg) and Pb isotopic composition denote two main eras of pre- and post-19th century. The deeper sediment is characterized by low concentrations and relatively constant 206Pb/207Pb (around 1.20), similar to natural Pb sources, with slight indications of ancient anthropogenic activity. The upper sediment displays an upward increase in trace metal concentrations, with the highest enrichment factor for Pb (18.4). Lead fluxes and isotopic composition point to national/regional petrol-Pb emissions as the major contributor to Pb contamination, overwhelming other potential local and transboundary sources. Traffic-related metals are correlated with Pb, emphasizing the polluting inputs of traffic. The Hg profile, however, implies global pollution rather than local sources.

Changing Dust Provenance to the South Atlantic Since the Last Glacial Maximum and Implications for the Southern Hemisphere Wind Belts

NASA Astrophysics Data System (ADS)

Franzese, A. M.; Goldstein, S. L.; Hemming, S. R.

2017-12-01

The Southern Hemisphere Westerly Winds are known to be important for climate due to their effects on the global carbon cycle and on the global thermohaline circulation (THC). Numerous proxy records have been interpreted to indicate significant glacial to interglacial changes in the SHWW. There is no clear consensus regarding their strength and position during the Last Glacial Maximum (LGM), though most observations are consistent with an equatorward displacement of the glacial wind belts. We test this hypothesis using geochemical provenance measurements of deep-sea sediments deposited along the Mid-Atlantic Ridge between 24°S and 37°S. In the central South Atlantic, dust can be delivered from South America via the Westerlies, or from Africa via the Trade Winds. The dust sources on South America and Africa have very different geochemical signatures, making it possible to distinguish between eolian transport via the Westerlies vs. the Trade Winds. Any northward shift in the Southern Hemisphere Westerlies should increase the northward extent of a South American provenance in sediments dominated by eolian sources. We measured major and trace element concentrations, and radiogenic isotopes of Ar, Sr, Nd, and Pb on the <5 μm lithogenic sediments from a latitudinal transect of cores along the flanks of the Mid-Atlantic Ridge. In general, the data point to an older continental provenance for the northernmost sites, and a much younger provenance for the southernmost sites, consistent with western Africa as the primary source of sediment in the north, and South American sediments being delivered to the south. Glacial sediments display a clear compositional boundary near 30°S, which likely reflects the boundary between the Westerlies and the Trade Winds. The data are therefore not consistent with northward shifted wind belts at the LGM. The observed variations in terrigenous sediment composition at these sites may, however, be consistent with an equatorward displacement of the SHWW through the deglaciation. The results may also point to changes in the continental source regions supplying dust to the atmosphere as the glaciers retreated.

A century-long sedimentary record of pesticide use in the Küçükçekmece Lagoon region, Turkey

NASA Astrophysics Data System (ADS)

Unlu, Selma; Alpar, Bedri

2017-04-01

Organochlorine pesticides (OCPs), extensively used for pest and disease control since the 1940s, can be bioaccumulated through food chains and cause adverse impacts on the environment and human health. Their use and manufacture have been banned or restricted in the 1980s in most countries. OCPs have a strong affinity to suspended particles, so they subsequently settle down into sediment. Sediments in aquatic systems could also become another source of OCPs, due to water turbulence, dredging and bioturbation. Piston coring recoveries in the Küçükçekmece Lagoon, a coastal wetland protected from the sea by a narrow strip of sandbar in the western part of Istanbul, indicated mostly homogeneous and seasonally layered lithological textures throughout the cores. The sediment profiles seem to be not subjected serious physical rearrangements, so that there is the opportunity for deposit preservation. The core 5 was analysed to delineate the vertical variations of selected organochlorine pesticide (OCPs) residues using gas chromatography (GC-ECD/MS) and dated using 210Pb and 137Cs dating methods. The total OCP residues ranged from 3.0 to 498.7 ng/g-dw, with the median concentration of 64 ng/g-dw, while α-HCH and p,p'-DDT were dominant OCPs, with maximum concentrations of 469.3 and 71.0 ng/g dw, respectively. Dated concentration-depth profiles suggest that highest inputs occurred in the first half of last century and followed by significant decreases. Despite the restriction in use, the prevalent nature of OCPs in the core sediment reflects the persistent nature and the lipophilic character of these contaminants. The major sources of the HCHs were from the use of technical HCHs. Sources DDTs identified by specific molecular ratios indicated that DDT residues were mainly originated from technical DDTs from both historical usage and recent input. The organochlorine pesticide residues did demonstrate markedly different distributions reflecting different agricultural and domestic usage in the region. Even though the risk of sediment toxicity was not so high according to the sediment quality guidelines, the bioaccumulation and the amplification of toxic organic pollutants may have major implications. Therefore, this study on the residual levels of the OCPs, their temporal distributions and the source analysis will not only contribute to understanding the environmental behaviour but also provide the necessary theoretical basis for persistent toxic pollution prevention and lake environmental management. This research was supported by the Scientific and Technological Council of Turkey (112Y104) and the Research Funds of Istanbul University (byp-22247).

Detrital and volcanic zircon U-Pb ages from southern Mendoza (Argentina): An insight on the source regions in the northern part of the Neuquén Basin

NASA Astrophysics Data System (ADS)

Naipauer, Maximiliano; Tapia, Felipe; Mescua, José; Farías, Marcelo; Pimentel, Marcio M.; Ramos, Victor A.

2015-12-01

The infill of the Neuquén Basin recorded the Meso-Cenozoic geological and tectonic evolution of the southern Central Andes being an excellent site to investigate how the pattern of detrital zircon ages varies trough time. In this work we analyze the U-Pb (LA-MC-ICP-MS) zircon ages from sedimentary and volcanic rocks related to synrift and retroarc stages of the northern part of the Neuquén Basin. These data define the crystallization age of the synrift volcanism at 223 ± 2 Ma (Cerro Negro Andesite) and the maximum depositional age of the original synrift sediments at ca. 204 Ma (El Freno Formation). Two different pulses of rifting could be recognized according to the absolute ages, the oldest developed during the Norian and the younger during the Rhaetian-Sinemurian. The source regions of the El Freno Formation show that the Choiyoi magmatic province was the main source rock of sediment supply. An important amount of detrital zircons with Triassic ages was identified and interpreted as a source area related to the synrift magmatism. The maximum depositional age calculated for the Tordillo Formation in the Atuel-La Valenciana depocenter is at ca. 149 Ma; as well as in other places of the Neuquén Basin, the U-Pb ages calculated in the Late Jurassic Tordillo Formation do not agree with the absolute age of the Kimmeridgian-Tithonian boundary (ca. 152 Ma). The main source region of sediment in the Tordillo Formation was the Andean magmatic arc. Basement regions were also present with age peaks at the Carboniferous, Neoproterozoic, and Mesoproterozoic; these regions were probably located to the east in the San Rafael Block. The pattern of zircon ages summarized for the Late Jurassic Tordillo and Lagunillas formations were interpreted as a record of the magmatic activity during the Triassic and Jurassic in the southern Central Andes. A waning of the magmatism is inferred to have happened during the Triassic. The evident lack of ages observed around ca. 200 Ma suggests cessation of the synrift magmatism. The later increase in magmatic activity during the Early Jurassic is attributed to the onset of Andean subduction, with maximum peaks at ca. 191 and 179 Ma. The trough at ca. 165 Ma and the later increase in the Late Jurassic could be explained by changes in the relative convergence rate in the Andean subduction regime, or by the shift to a more mafic composition of the magmatism with minor zircon fertility.

Stream Sediment Sources in Midwest Agricultural Basins with Land Retirement along Channel.

PubMed

Williamson, T N; Christensen, V G; Richardson, W B; Frey, J W; Gellis, A C; Kieta, K A; Fitzpatrick, F A

2014-09-01

Documenting the effects of agricultural land retirement on stream-sediment sources is critical to identifying management practices that improve water quality and aquatic habitat. Particularly difficult to quantify are the effects from conservation easements that commonly are discontinuous along channelized streams and ditches throughout the agricultural midwestern United States. Our hypotheses were that sediment from cropland, retired land, stream banks, and roads would be discernible using isotopic and elemental concentrations and that source contributions would vary with land retirement distribution along tributaries of West Fork Beaver Creek in Minnesota. Channel-bed and suspended sediment were sampled at nine locations and compared with local source samples by using linear discriminant analysis and a four-source mixing model that evaluated seven tracers: In, P, total C, Be, Tl, Th, and Ti. The proportion of sediment sources differed significantly between suspended and channel-bed sediment. Retired land contributed to channel-bed sediment but was not discernible as a source of suspended sediment, suggesting that retired-land material was not mobilized during high-flow conditions. Stream banks were a large contributor to suspended sediment; however, the percentage of stream-bank sediment in the channel bed was lower in basins with more continuous retired land along the riparian corridor. Cropland sediments had the highest P concentrations; basins with the highest cropland-sediment contributions also had the highest P concentrations. Along stream reaches with retired land, there was a lower proportion of cropland material in suspended sediment relative to sites that had almost no land retirement, indicating less movement of nutrients and sediment from cropland to the channel as a result of land retirement. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Stream sediment sources in midwest agricultural basins with land retirement along channel

USGS Publications Warehouse

Williamson, Tanja N.; Christensen, Victoria G.; Richardson, William B.; Frey, Jeffrey W.; Gellis, Allen C.; Kieta, K. A.; Fitzpatrick, Faith A.

2014-01-01

Documenting the effects of agricultural land retirement on stream-sediment sources is critical to identifying management practices that improve water quality and aquatic habitat. Particularly difficult to quantify are the effects from conservation easements that commonly are discontinuous along channelized streams and ditches throughout the agricultural midwestern United States. Our hypotheses were that sediment from cropland, retired land, stream banks, and roads would be discernible using isotopic and elemental concentrations and that source contributions would vary with land retirement distribution along tributaries of West Fork Beaver Creek in Minnesota. Channel-bed and suspended sediment were sampled at nine locations and compared with local source samples by using linear discriminant analysis and a four-source mixing model that evaluated seven tracers: In, P, total C, Be, Tl, Th, and Ti. The proportion of sediment sources differed significantly between suspended and channel-bed sediment. Retired land contributed to channel-bed sediment but was not discernible as a source of suspended sediment, suggesting that retired-land material was not mobilized during high-flow conditions. Stream banks were a large contributor to suspended sediment; however, the percentage of stream-bank sediment in the channel bed was lower in basins with more continuous retired land along the riparian corridor. Cropland sediments had the highest P concentrations; basins with the highest cropland-sediment contributions also had the highest P concentrations. Along stream reaches with retired land, there was a lower proportion of cropland material in suspended sediment relative to sites that had almost no land retirement, indicating less movement of nutrients and sediment from cropland to the channel as a result of land retirement.

Andean stratigraphic record of the transition from backarc extension to orogenic shortening: A case study from the northern Neuquén Basin, Argentina

NASA Astrophysics Data System (ADS)

Horton, Brian K.; Fuentes, Facundo; Boll, Andrés; Starck, Daniel; Ramirez, Sebastian G.; Stockli, Daniel F.

2016-11-01

The temporal transition from backarc extension to retroarc shortening is a fundamental process in the evolution of many Andean-type convergent margins. This switch in tectonic regime is preserved in the 5-7 km thick Mesozoic-Cenozoic stratigraphic record of west-central Argentina at 34-36°S, where the northern Neuquén Basin and succeeding Cenozoic foreland succession chronicle a long history of fluctuating depositional systems and diverse sediment source regions during Andean orogenesis. New findings from sediment provenance and facies analyses are integrated with detrital zircon U-Pb geochronological results from 16 samples of Jurassic through Miocene clastic deposits to delineate the progressive exhumation of the evolving Andean magmatic arc, retroarc fold-thrust belt, and foreland province. Abrupt changes in provenance and depositional conditions can be reconciled with a complex Mesozoic-Cenozoic history of extension, postextensional thermal subsidence, punctuated tectonic inversion, thick- and thin-skinned shortening, overlapping igneous activity, and alternating phases of basin accumulation, sediment bypass, and erosion. U-Pb age distributions constrain the depositional ages of Cenozoic units and reveal a prolonged late middle Eocene to earliest Miocene (roughly 40-20 Ma) hiatus in the retroarc foreland basin. This stratigraphic gap is expressed as a regional disconformity that marks a pronounced shift in depositional conditions and sediment sources, from (i) slow Paleocene-middle Eocene accumulation of distal fluviolacustrine sediments (Pircala and Coihueco Formations) contributed from far western magmatic arc sources (Cretaceous-Paleogene volcanic rocks) and subordinate eastern basement rocks (Permian-Triassic Choiyoi igneous complex) to (ii) rapid Miocene-Quaternary accumulation of proximal fluvial to megafan sediments (Agua de la Piedra, Loma Fiera, and Tristeza Formations) recycled from emerging western thrust-belt sources of Mesozoic basin fill originally derived from basement and magmatic arc sources. The mid-Cenozoic stratigraphic gap signified ∼20 Myr of nondeposition, potentially during passage of a flexural forebulge or during neutral to extensional conditions driven by mechanical decoupling and a possible retreating-slab configuration along the Nazca-South America plate boundary. Neogene eastward propagation of the Malargüe fold-thrust belt involved basement inversion with geometrically and kinematically linked thin-skinned shortening at shallow foreland levels, including late Miocene deposition of accurately dated 10.5-7.5 Ma growth strata and ensuing displacement along the frontal emergent and blind thrust structures. Subsequent partitioning and exhumation of Cenozoic clastic fill of the Malargüe foreland basin has been driven by inboard advance of arc magmatism and Pliocene-Quaternary uplift of the San Rafael basement block farther east.

Sources of mercury to San Francisco Bay surface sediment as revealed by mercury stable isotopes

USGS Publications Warehouse

Gehrke, Gretchen E.; Blum, Joel D.; Marvin-DePasquale, Mark

2011-01-01

Mercury (Hg) concentrations and isotopic compositions were examined in shallow-water surface sediment (0–2 cm) from San Francisco (SF) Bay to determine the extent to which historic Hg mining contributes to current Hg contamination in SF Bay, and to assess the use of Hg isotopes to trace sources of contamination in estuaries. Inter-tidal and wetland sediment had total Hg (HgT) concentrations ranging from 161 to 1529 ng/g with no simple gradients of spatial variation. In contrast, inter-tidal and wetland sediment displayed a geographic gradient of δ202Hg values, ranging from -0.30% in the southern-most part of SF Bay (draining the New Almaden Hg District) to -0.99% in the northern-most part of SF Bay near the Sacramento–San Joaquin River Delta. Similar to SF Bay inter-tidal sediment, surface sediment from the Alviso Slough channel draining into South SF Bay had a δ202Hg value of -0.29%, while surface sediment from the Cosumnes River and Sacramento–San Joaquin River Delta draining into north SF Bay had lower average δ202Hg values of -0.90% and -0.75%, respectively. This isotopic trend suggests that Hg-contaminated sediment from the New Almaden Hg District mixes with Hg-contaminated sediment from a low δ202Hg source north of SF Bay. Tailings and thermally decomposed ore (calcine) from the New Idria Hg mine in the California Coast Range had average δ202Hg values of -0.37 and +0.03%, respectively, showing that Hg calcination fractionates Hg isotopes resulting in Hg contamination from Hg(II) mine waste products with higher δ202Hg values than metallic Hg(0) produced from Hg mines. Thus, there is evidence for at least two distinct isotopic signals for Hg contamination in SF Bay: Hg associated with calcine waste materials at Hg mines in the Coast Range, such as New Almaden and New Idria; and Hg(0) produced from these mines and used in placer gold mines and/or in other industrial processes in the Sierra Nevada region and SF Bay area.

Discriminating sediment archives and sedimentary processes in the arid endorheic Ejina Basin, NW China using a robust geochemical approach

NASA Astrophysics Data System (ADS)

Yu, Kaifeng; Hartmann, Kai; Nottebaum, Veit; Stauch, Georg; Lu, Huayu; Zeeden, Christian; Yi, Shuangwen; Wünnemann, Bernd; Lehmkuhl, Frank

2016-04-01

Geochemical characteristics have been intensively used to assign sediment properties to paleoclimate and provenance. Nonetheless, in particular concerning the arid context, bulk geochemistry of different sediment archives and corresponding process interpretations are hitherto elusive. The Ejina Basin, with its suite of different sediment archives, is known as one of the main sources for the loess accumulation on the Chinese Loess Plateau. In order to understand mechanisms along this supra-regional sediment cascade, it is crucial to decipher the archive characteristics and formation processes. To address these issues, five profiles in different geomorphological contexts were selected. Analyses of X-ray fluorescence and diffraction, grain size, optically stimulated luminescence and radiocarbon dating were performed. Robust factor analysis was applied to reduce the attribute space to the process space of sedimentation history. Five sediment archives from three lithologic units exhibit geochemical characteristics as follows: (i) aeolian sands have high contents of Zr and Hf, whereas only Hf can be regarded as a valuable indicator to discriminate the coarse sand proportion; (ii) sandy loess has high Ca and Sr contents which both exhibit broad correlations with the medium to coarse silt proportions; (iii) lacustrine clays have high contents of felsic, ferromagnesian and mica source elements e.g., K, Fe, Ti, V, and Ni; (iv) fluvial sands have high contents of Mg, Cl and Na which may be enriched in evaporite minerals; (v) alluvial gravels have high contents of Cr which may originate from nearby Cr-rich bedrock. Temporal variations can be illustrated by four robust factors: weathering intensity, silicate-bearing mineral abundance, saline/alkaline magnitude and quasi-constant aeolian input. In summary, the bulk-composition of the late Quaternary sediments in this arid context is governed by the nature of the source terrain, weak chemical weathering, authigenic minerals, aeolian sand input, whereas pedogenesis and diagenesis exert only limited influences. Hence, this study demonstrates a practical geochemical strategy supplemented by grain size and mineralogical data, to discriminate sediment archives and thereafter enhance our ability to offer more intriguing information about the sedimentary processes in the arid central Asia.

REGIONAL MAGNETOTELLURIC SURVEYS IN HYDROCARBON EXPLORATION, PARANA BASIN, BRAZIL.

USGS Publications Warehouse

Stanley, William D.; Saad, Antonio; Ohofugi, Walter

1985-01-01

The mangetotelluric geophysical method has been used effectively as a hydrocarbon exploration tool in the intracratonic Parana basin of South America. The 1-2 km thick surface basalts and buried diabase sills pose no problem for the magnetotelluric method because the natural electromagnetic fields used as the energy source pass easily through the basalt. Data for the regional study were taken on six profiles with sounding spaced 8 to 15 km apart. The magnetotelluric sounding data outline a linear uplift known as the Ponta Grossa arch. This major structural feature cuts across the northeast-trending intracratonic basin almost perpendicularly, and is injected with numerous diabase dikes. Significant electrical contrasts occur between the Permian sediments and older units, so that magnetotelluric measurements can give an indication of the regional thickness of the Permian and younger sediments to aid in interpreting hydrocarbon migration patterns and possible trap areas. Refs.

Sources and Fate of Chiral Organochlorine Pesticides in Western U.S. National Park Ecosystems

PubMed Central

Genualdi, Susan A.; Hageman, Kimberly J.; Ackerman, Luke K.; Usenko, Sascha; Simonich, Staci L. Massey

2011-01-01

The enantiomer fractions (EFs) of alpha-hexachlorocyclohexane (α-HCH), cis-, trans-, and oxychlordane, and heptachlor epoxide were measured in 73 snow, fish, and sediment samples collected from remote lake catchments, over a wide range of latitudes, in seven western U.S. National Parks/Preserves in order to investigate their sources, fate, accumulation and biotransformation in these ecosystems. The present study is novel because these lakes had no inflow or outflow and the measurement of chiral organochlorine pesticides (OCPs) EFs in snowpack from these lake catchments provided a better understanding of the OCP sources in the Western U.S., while their measurement in fish and sediment provided a better understanding of their biotic transformations within the lake catchments. Non-racemic α-HCH was measured in seasonal snowpack collected from continental U.S. National Parks, while racemic α-HCH was measured in seasonal snowpack collected from the Alaskan parks, suggesting the influence of regional sources to the continental U.S. parks and long-range sources to the Alaskan parks. The α-HCH EFs measured in trout collected from the lake catchments were similar to the α-HCH EFs measured in seasonal snowpack collected from the same lake catchments, suggesting that these fish did not biotransform α-HCH enantioselectively. Racemic cis-chlordane was measured in seasonal snowpack and sediment collected from Sequoia, indicating that it had not undergone significant enantioselective biotransformation in urban soils since its use as a termiticide in the surrounding urban areas. However, non-racemic cis-chlordane was measured in seasonal snowpack and sediments from Rocky Mountain, suggesting cis-chlordane does undergo enantioselective biotransformation in agricultural soils. The trout from these lakes showed preferential biotransformation of the (+)-enantiomer of cis-chlordane and the (−)-enantiomer of trans-chlordane. PMID:21462235

Source apportionment and distribution of polycyclic aromatic hydrocarbons, risk considerations, and management implications for urban stormwater pond sediments in Minnesota, USA.

PubMed

Crane, Judy L

2014-02-01

High concentrations of polycyclic aromatic hydrocarbons (PAHs) are accumulating in many urban stormwater ponds in Minnesota, resulting in either expensive disposal of the excavated sediment or deferred maintenance by economically challenged municipalities. Fifteen stormwater ponds in the Minneapolis-St. Paul, MN, metropolitan area were studied to determine sources of PAHs to bed sediments through the application of several environmental forensic techniques, including a contaminant mass balance receptor model. The model results were quite robust and indicated that coal tar-based sealant (CT-sealant) particulate washoff and dust sources were the most important sources of PAHs (67.1%), followed by vehicle-related sources (29.5%), and pine wood combustion particles (3.4%). The distribution of 34 parent and alkylated PAHs was also evaluated regarding ancillary measurements of black carbon, total organic carbon, and particle size classes. None of these parameters were significantly different based on major land-use classifications (i.e., residential, commercial, and industrial) for pond watersheds. PAH contamination in three stormwater ponds was high enough to present a risk to benthic invertebrates, whereas nine ponds exceeded human health risk-based benchmarks that would prompt more expensive disposal of dredged sediment. The State of Minnesota has been addressing the broader issue of PAH-contaminated stormwater ponds by encouraging local municipalities to ban CT-sealants (29 in all) and to promote pollution prevention alternatives to businesses and homeowners, such as switching to asphalt-based sealants. A statewide CT-sealant ban was recently enacted. Other local and regional jurisdictions may benefit from using Minnesota's approach where CT-sealants are still used.

Sources and seasonal variation of PAHs in the sediments of drinking water reservoirs in Hong Kong and the Dongjiang River (China).

PubMed

Liang, Yan; Fung, Pui Ka; Tse, Man Fung; Hong, Hua Chang; Wong, Ming Hung

2008-11-01

The main objective of this study was to investigate occurrence of polycyclic aromatic hydrocarbons (PAHs) in the sources of the drinking water supply of Hong Kong. The main emphasis was on the Dongjiang River in mainland China which is the major source, supplying 80% of the total consumption in Hong Kong (the remaining 20% is obtained from rain water). Sediments were collected from four sites along the Dongjiang River and four reservoirs in Hong Kong during both the dry and wet weather seasons. The concentrations of total PAHs in the sediments ranged between 36 and 539 microg/kg dry wt. The lower levels were detected at the upstream site on the Dongjiang River and at the reservoirs in Hong Kong (44-85 microg/kg dry wt), while the mid- and downstream sites on the Dongjiang River were more polluted (588-658 microg/kg dry wt). Examination of the PAH profiles revealed that the mid- and downstream sections of the Dongjiang River contained high percentages of 4,5,6-ring PAHs, similar to the amounts of atmospheric particulate matter and road dust collected during the dry weather season from the Pearl River Delta region as reported in the literature. Seasonal changes were revealed in the reservoirs of Hong Kong, with higher PAH levels in the wet weather season than in the dry weather season. For those reservoirs in Hong Kong that store water from the Dongjiang River, a distinct seasonal pattern was also observed, namely, that under dry weather season conditions the PAHs found in the sediments were primarily from petrogenic source, while under wet weather season conditions they were from pyrolytic sources. No such pattern was detected in the reservoirs which stored only rain water.

Lead isotopic compositions of common arsenical pesticides used in New England

USGS Publications Warehouse

Ayuso, Robert; Foley, Nora; Robinson, Gilpin; Wandless, Gregory; Dillingham, Jeremy

2004-01-01

The three most important arsenical pesticides and herbicides that were extensively used on apple, blueberry, and potato crops in New England from mid-1800s to recent times are lead arsenate, calcium arsenate, and sodium arsenate. Lead arsenate was probably the most heavily used of the arsenical pesticides until it was banned in 1988. Other metal-arsenic pesticides were also used but in lesser amounts. A recent report identified areas in New England where arsenical pesticides were used extensively (Robinson and Ayuso, 2004). On the basis of factor analysis of metal concentrations in stream sediment samples, a positive correlation with pesticide use was shown in regions having stream sediment sample populations that contained concentrations of high arsenic and lead. Lead isotope compositions of stream sediments from areas with heavy use of the pesticides could not be entirely explained by lead originating from rock sulfides and their weathering products. An industrial lead contribution (mostly from atmospheric deposition of lead) was suggested in general to explain the lead isotopic distributions of the stream sediments that could not be accounted for by the natural lead in the environment. We concluded that when agricultural land previously contaminated with arsenical pesticides is urbanized, pesticide residues in the soils and stream sediments could be released into the groundwater. No lead isotopic data characterizing the compositions of pesticides were available for comparison. We have determined the lead isotopic compositions of commonly used pesticides in New England, such as lead arsenate, sodium metaarsenite, and calcium arsenate, in order to assist in future isotopic comparisons and to better establish anthropogenic sources of Pb and As. New data are also presented for copper acetoarsenite (or Paris green), methyl arsonic acid and methane arsonic acid, as well as for arsanilic acid, all of which are used as feed additives to promote swine and poultry growth. The new data characterize these anthropogenic sources. The data show that the arsenical pesticides have similar compositions: 208Pb/207Pb = 2.3839-2.4721, 206Pb/207Pb = 1.1035-1.2010, and 206Pb/204Pb = 17.070-18.759 and, more importantly, that the pesticides overlap the composition of the stream sediments that represent the areas with the most extensive agricultural use. Copper acetoarsenite (Paris green), arsenic oxide, methyl arsonic acid, methane arsonic acid, and arsanilic acid were also analyzed and have lead isotope compositions that range widely. An important source of arsenic and metals to most of the stream sediment samples in New England appears to be weathering products from rocks and industrial lead, but the extensive use of arsenical pesticides and herbicides up to about the 1960s can also be a significant anthropogenic source in agricultural regions.

Acoustic measurement of sediment dynamics in the coastal zones using wireless sensor networks

NASA Astrophysics Data System (ADS)

Sudhakaran, A., II; Paramasivam, A.; Seshachalam, S.; A, C.

2014-12-01

Analyzing of the impact of constructive or low energy waves and deconstructive or high energy waves in the ocean are very much significant since they deform the geometry of seashore. The deformation may lead to productive result and also to the end of deteriorate damage. Constructive waves results deposition of sediment which widens the beach where as deconstructive waves results erosion which narrows the beach. Validation of historic sediment transportation and prediction of the direction of movement of seashore is essential to prevent unrecoverable damages by incorporating precautionary measurements to identify the factors that influence sediment transportation if feasible. The objective of this study is to propose a more reliable and energy efficient Information and communication system to model the Coastal Sediment Dynamics. Various factors influencing the sediment drift at a particular region is identified. Consequence of source depth and frequency dependencies of spread pattern in the presence of sediments is modeled. Property of source depth and frequency on sensitivity to values of model parameters are determined. Fundamental physical reasons for these sediment interaction effects are given. Shallow to deep water and internal and external wave model of ocean is obtained intended to get acoustic data assimilation (ADA). Signal processing algorithms are used over the observed data to form a full field acoustic propagation model and construct sound speed profile (SSP). The inversions of data due to uncertainties at various depths are compared. The impact of sediment drift over acoustic data is identified. An energy efficient multipath routing scheme Wireless sensor networks (WSN) is deployed for the well-organized communication of data. The WSN is designed considering increased life time, decreased power consumption, free of threats and attacks. The practical data obtained from the efficient system to model the ocean sediment dynamics are evaluated with remote sensing data and the reasons of deviations and uncertainties are unbiased. The probability of changes and impact of sediment drift over ocean dynamic model over the long running of years is estimated.

Sediment source fingerprinting as an aid to catchment management: A review of the current state of knowledge and a methodological decision-tree for end-users

USGS Publications Warehouse

Collins, A.L; Pulley, S.; Foster, I.D.L; Gellis, Allen; Porto, P.; Horowitz, A.J.

2017-01-01

The growing awareness of the environmental significance of fine-grained sediment fluxes through catchment systems continues to underscore the need for reliable information on the principal sources of this material. Source estimates are difficult to obtain using traditional monitoring techniques, but sediment source fingerprinting or tracing procedures, have emerged as a potentially valuable alternative. Despite the rapidly increasing numbers of studies reporting the use of sediment source fingerprinting, several key challenges and uncertainties continue to hamper consensus among the international scientific community on key components of the existing methodological procedures. Accordingly, this contribution reviews and presents recent developments for several key aspects of fingerprinting, namely: sediment source classification, catchment source and target sediment sampling, tracer selection, grain size issues, tracer conservatism, source apportionment modelling, and assessment of source predictions using artificial mixtures. Finally, a decision-tree representing the current state of knowledge is presented, to guide end-users in applying the fingerprinting approach.

Using multiple composite fingerprints to quantify fine sediment source contributions: A new direction

USDA-ARS?s Scientific Manuscript database

Sediment source fingerprinting provides a vital means for estimating sediment source contributions, which are needed not only for soil conservation planning but also for erosion model evaluation. A single optimum composite fingerprint has been widely used in the literature to estimate sediment prov...

A model for Cryogenian iron formation

NASA Astrophysics Data System (ADS)

Cox, Grant M.; Halverson, Galen P.; Poirier, André; Le Heron, Daniel; Strauss, Justin V.; Stevenson, Ross

2016-01-01

The Neoproterozoic Tatonduk (Alaska) and Holowilena (South Australia) iron formations share many characteristics including their broadly coeval (Sturtian) ages, intimate association with glaciogenic sediments, and mineralogy. We show that these shared characteristics extend to their neodymium (εNd) and iron isotope (δ56Fe) systematics. In both regions δ56Fe values display a distinct up-section trend to isotopically heavier values, while εNd values are primitive and similar to non-ferruginous mudstones within these successions. The δ56Fe profiles are consistent with oxidation of ferruginous waters during marine transgression, and the εNd values imply that much of this iron was sourced from the leaching of continental margin sediments largely derived from continental flood basalts. Rare earth element data indicate a secondary hydrothermal source for this iron.

Application of quantitative composite fingerprinting technique to identify the main sediment sources in two small catchments of Iran

NASA Astrophysics Data System (ADS)

Kouhpeima, A.; Feiznia, S.; Ahmadi, H.; Hashemi, S. A.; Zareiee, A. R.

2010-09-01

The targeting of sediment management strategies is a key requirement in developing countries including Iran because of the limited resources available. These targeting is, however hampered by the lack of reliable information on catchment sediment sources. This paper reports the results of using a quantitative composite fingerprinting technique to estimate the relative importance of the primary potential sources within the Amrovan and Royan catchments in Semnan Province, Iran. Fifteen tracers were first selected for tracing and samples were analyzed in the laboratory for these parameters. Statistical methods were applied to the data including nonparametric Kruskal-Wallis test and Differentiation Function Analysis (DFA). For Amrovan catchment three parameters (N, Cr and Co) were found to be not significant in making the discrimination. The optimum fingerprint, comprising Oc, PH, Kaolinite and K was able to distinguish correctly 100% of the source material samples. For the Royan catchment, all of the 15 properties were able to distinguish between the six source types and the optimum fingerprint provided by stepwise DFA (Cholorite, XFD, N and C) correctly classifies 92.9% of the source material samples. The mean contributions from each sediment source obtained by multivariate mixing model varied at two catchments. For Amrovan catchment Upper Red formation is the main sediment sources as this sediment source approximately supplies 36% of the reservoir sediment whereas the dominant sediment source for the Royan catchment is from Karaj formation that supplies 33% of the reservoir sediments. Results indicate that the source fingerprinting approach appears to work well in the study catchments and to generate reliable results.

Maps showing gas-hydrate distribution off the east coast of the United States

USGS Publications Warehouse

Dillon, William P.; Fehlhaber, Kristen L.; Coleman, Dwight F.; Lee, Myung W.; Hutchinson, Deborah R.

1995-01-01

These maps present the inferred distribution of natural-gas hydrate within the sediments of the eastern United States continental margin (Exclusive Economic Zone) in the offshore region from Georgia to New Jersey (fig. 1). The maps, which were created on the basis of seismic interpretations, represent the first attempt to map volume estimates for gas hydrate. Gas hydrate forms a large reservoir for methane in oceanic sediments. Therefore it potentially may represent a future source of energy and it may influence climate change because methane is a very effective greenhouse gas. Hydrate breakdown probably is a controlling factor for sea-floor landslides, and its presence has significant effect on the acoustic velocity of sea-floor sediments.

Quantifying the main sediment sources in agricultural landscapes of Southern Brazil cultivated with conventional and conservation practices

NASA Astrophysics Data System (ADS)

Evrard, Olivier; Le Gall, Marion; Tiecher, Tales; Gomes Minella, Jean Paolo; Laceby, J. Patrick; Ayrault, Sophie

2017-04-01

Agricultural expansion that occurred in the 1960s in Southern Brazil significantly increased soil erosion and sediment supply to the river networks. To limit the deleterious impacts of soil erosion, conservation practices were progressively implemented in the 1990s, including the direct sowing of crops on a soil densely covered with plant residues, contour farming, the installation of ponds to trap sediment in the landscape and the use of crop rotations. However, there remains a lack of observational data to investigate the impact of these conservation practices on soil erosion and sediment supply. This data is crucial to protect soil resources and maintain the sustainability of food production systems in this region of the world characterized by a rapidly increasing population. Accordingly, sediment sources were investigated in the Guaporé catchment (2,032 km2) representative of the cultivated environments found in this part of the world. In the upper catchment, the landscape is characterized by gentle slopes and deep soils (Ferralsols, Nitisols) corresponding to the edge of the basaltic plateau. Soybean, corn and wheat under direct sowing are the main crops in this area. In contrast, steep and shallow soils (Luvisols, Acrisols, Leptosols) highly connected to the rivers are found in the lower catchment, where tobacco and corn fields are cultivated with conventional ploughing. These soil types were characterized by elemental geochemistry and 87Sr/86Sr ratios. Sediment sources were then modelled using the optimal suite of properties (87Sr/86Sr ratios, K, Ti, Co, As, Ba, and Pb). The results demonstrate that sediment collected at the catchment outlet during two hydrological years (2012-2014) mainly originated from downstream soils (Luvisols, Acrisols, Leptosols; 92±3%), with this proportion remaining stable throughout the monitoring period. This research indicates that conservation practices implemented in the upper catchment are effective and that similar methods should be applied to downstream soils in order to conserve soil resources and limit the degradation of freshwater environments.

Eruptive and environmental processes recorded by diatoms in volcanically-dispersed lake sediments from the Taupo Volcanic Zone, New Zealand

USGS Publications Warehouse

Harper, Margaret A.; Pledger, Shirley A.; Smith, Euan G. C.; Van Eaton, Alexa; Wilson, Colin J. N.

2015-01-01

Late Pleistocene diatomaceous sediment was widely dispersed along with volcanic ash (tephra) across and beyond New Zealand by the 25.4 ka Oruanui supereruption from Taupo volcano. We present a detailed analysis of the diatom populations in the Oruanui tephra and the newly discovered floras in two other eruptions from the same volcano: the 28.6 ka Okaia and 1.8 ka Taupo eruptions. For comparison, the diatoms were also examined in Late Pleistocene and Holocene lake sediments from the Taupo Volcanic Zone (TVZ). Our study demonstrates how these microfossils provide insights into the lake history of the TVZ since the Last Glacial Maximum. Morphometric analysis of Aulacoseira valve dimensions provides a useful quantitative tool to distinguish environmental and eruptive processes within and between individual tephras. The Oruanui and Okaia diatom species and valve dimensions are highly consistent with a shared volcanic source, paleolake and eruption style (involving large-scale magma-water interaction). They are distinct from lacustrine sediments sourced elsewhere in the TVZ. Correspondence analysis shows that small, intact samples of erupted lake sediment (i.e., lithic clasts in ignimbrite) contain heterogeneous diatom populations, reflecting local variability in species composition of the paleolake and its shallowly-buried sediments. Our analysis also shows a dramatic post-Oruanui supereruption decline in Cyclostephanos novaezelandiae, which likely reflects a combination of (1) reorganisation of the watershed in the aftermath of the eruption, and (2) overall climate warming following the Last Glacial Maximum. This decline is reflected in substantially lower proportions of C. novaezelandiae in the 1.8 ka Taupo eruption deposits, and even fewer in post-1.8 ka sediments from modern (Holocene) Lake Taupo. Our analysis highlights how the excellent preservation of siliceous microfossils in volcanic tephra may fingerprint the volcanic source region and retain a valuable record of volcanically-influenced environmental change.

Polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides in water columns from the Pearl River and the Macao harbor in the Pearl River Delta in South China.

PubMed

Luo, Xiaojun; Mai, Bixian; Yang, Qingshu; Fu, Jiamo; Sheng, Guoying; Wang, Zhishi

2004-06-01

Polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) were measured in suspended particles and dissolved phase from the Baiertang water column and the Macao water column samples as collected from the Guangzhou channel of the Pearl River and the Macao harbor, where the sediments were heavily contaminated with organic pollutants. Total OCPs concentration varies from 23.4 to 61.7 ng/l in Baiertang water column and from 25.2 to 67.8 ng/l in Macao column, while total PAHs concentration varies from 987.1 to 2878.5 ng/l in the Baiertang water column and from 944.0 to 6654.6 ng/l in the Macao column. The vertical distribution profiles of pollutants and the partition of pollutants between particles and dissolved phases indicate that the sediments in Baiertang act as an important source of selected pollutants, and the pollutants in water of this region were mainly originated from the release and re-suspension of contaminants residing in the sediments. The sediments in Macao harbor act as a reservoir for organochlorine pesticides, such as DDTs mainly introduced by river inflow from Xijiang and PAHs input by brackish water from the Lingdingyang estuary. Combustion of fossil fuels and petroleum input are the main sources of PAHs in the Macao water column, while combustion of fossil fuels and coal is responsible for the PAHs in the Baiertang water column. The ratios of DDT/(DDD+DDE) for the Macao water column samples demonstrate that such chemicals were input into this region in recent times.

Cyclic Sediment Trading Between Channel and River Bed Sediments

NASA Astrophysics Data System (ADS)

Haddadchi, A.

2015-12-01

Much of the previous work on sediment tracing has focused on determining either the initial sources of the sediment (soils derive from a particular rock type) or the erosion processes generating the sediment. However, alluvial stores can be both a source and sink for sediment transported by streams. Here geochemical and fallout radionuclide tracing of river-bed and alluvial sediments are used to determine the role of secondary sources, sediment stores, as potential sources of sediment leaving Emu Creek catchment, southeastern Queensland, Australia. Activity concentrations of 137Cs on the river sediments are consistent with channel erosion being the dominant source at all sites sampled along the river. To characterise the deposition and remobilisation cycles in the catchment, a novel geochemical tracing approach was used. Successive pockets of alluvium were treated as discrete sink terms within geochemical mixing models and their source contributions compared with those of river bed sediments collected adjacent to each alluvial pocket. Three different size fractions were examined; silts and clays (<10 μm), silts (10-63 μm), and fine sands (63-212 μm). The contribution of the initial soil/rock type sources to river bed and alluvial sediments at each sampling site was identical for all three different size fractions, but varied along the stream. Combining these findings it is concluded that proximal alluvial stores dominated the supply of sediment to the river at each location, with this being particularly evident at the catchment outlet. Identical contribution of rock type sources to both river bed and alluvial pockets together with the dominant erosion being from channel banks indicates a high degree of 'trading' between the fluvial space and the alluvial space. Hence, management works aimed at primarily reducing the supply of sediments to the outlet of Emu Creek should focus on rehabilitation of channel banks in the lower catchment.

Suspended sediments from upstream tributaries as the source of downstream river sites

NASA Astrophysics Data System (ADS)

Haddadchi, Arman; Olley, Jon

2014-05-01

Understanding the efficiency with which sediment eroded from different sources is transported to the catchment outlet is a key knowledge gap that is critical to our ability to accurately target and prioritise management actions to reduce sediment delivery. Sediment fingerprinting has proven to be an efficient approach to determine the sources of sediment. This study examines the suspended sediment sources from Emu Creek catchment, south eastern Queensland, Australia. In addition to collect suspended sediments from different sites of the streams after the confluence of tributaries and outlet of the catchment, time integrated suspended samples from upper tributaries were used as the source of sediment, instead of using hillslope and channel bank samples. Totally, 35 time-integrated samplers were used to compute the contribution of suspended sediments from different upstream waterways to the downstream sediment sites. Three size fractions of materials including fine sand (63-210 μm), silt (10-63 μm) and fine silt and clay (<10 μm) were used to find the effect of particle size on the contribution of upper sediments as the sources of sediment after river confluences. And then samples were analysed by ICP-MS and -OES to find 41 sediment fingerprints. According to the results of Student's T-distribution mixing model, small creeks in the middle and lower part of the catchment were major source in different size fractions, especially in silt (10-63 μm) samples. Gowrie Creek as covers southern-upstream part of the catchment was a major contributor at the outlet of the catchment in finest size fraction (<10 μm) Large differences between the contributions of suspended sediments from upper tributaries in different size fractions necessitate the selection of appropriate size fraction on sediment tracing in the catchment and also major effect of particle size on the movement and deposition of sediments.

Quantitative sediment source attribution with compound-specific isotope analysis in a C3 plant-dominated catchment (central Switzerland)

NASA Astrophysics Data System (ADS)

Alewell, Christine; Birkholz, Axel; Meusburger, Katrin; Schindler Wildhaber, Yael; Mabit, Lionel

2016-03-01

As sediment loads impact freshwater systems and infrastructure, their origin in complex landscape systems is of crucial importance for sustainable management of agricultural catchments. We differentiated the sediment source contribution to a lowland river in central Switzerland by using compound-specific isotope analysis (CSIA). We found a clear distinction of sediment sources originating from forest and agricultural land use. Our results demonstrate that it is possible to reduce the uncertainty of sediment source attribution in: (i) using compound content (in our case, long-chain fatty acids; FAs) rather than soil organic matter content to transfer δ13C signal of FAs to soil contribution and (ii) restricting the investigation to the long-chain FAs (> C22 : 0) not to introduce errors due to aquatic contributions from algae and microorganisms. Results showed unambiguously that during base flow, agricultural land contributed up to 65 % of the suspended sediments, while forest was the dominant sediment source during high flow. This indicates that connectivity of sediment source areas within the river changes between base and high flow conditions. Uncertainty, which might occur in complex, large-scale studies due to undetected source attribution and/or CSSI signature degradation, is low because of limited data complexity in our study (i.e., two-three sources and two tracers). Our findings are the first published results highlighting (i) significant differences in compound-specific stable isotope (CSSI) signature of sediment sources from land uses dominated by C3 plant cultivation and (ii) the use of these differences to quantify sediment contribution to a small river.

Application of modified export coefficient method on the load estimation of non-point source nitrogen and phosphorus pollution of soil and water loss in semiarid regions.

PubMed

Wu, Lei; Gao, Jian-en; Ma, Xiao-yi; Li, Dan

2015-07-01

Chinese Loess Plateau is considered as one of the most serious soil loss regions in the world, its annual sediment output accounts for 90 % of the total sediment loads of the Yellow River, and most of the Loess Plateau has a very typical characteristic of "soil and water flow together", and water flow in this area performs with a high sand content. Serious soil loss results in nitrogen and phosphorus loss of soil. Special processes of water and soil in the Loess Plateau lead to the loss mechanisms of water, sediment, nitrogen, and phosphorus are different from each other, which are greatly different from other areas of China. In this study, the modified export coefficient method considering the rainfall erosivity factor was proposed to simulate and evaluate non-point source (NPS) nitrogen and phosphorus loss load caused by soil and water loss in the Yanhe River basin of the hilly and gully area, Loess Plateau. The results indicate that (1) compared with the traditional export coefficient method, annual differences of NPS total nitrogen (TN) and total phosphorus (TP) load after considering the rainfall erosivity factor are obvious; it is more in line with the general law of NPS pollution formation in a watershed, and it can reflect the annual variability of NPS pollution more accurately. (2) Under the traditional and modified conditions, annual changes of NPS TN and TP load in four counties (districts) took on the similar trends from 1999 to 2008; the load emission intensity not only is closely related to rainfall intensity but also to the regional distribution of land use and other pollution sources. (3) The output structure, source composition, and contribution rate of NPS pollution load under the modified method are basically the same with the traditional method. The average output structure of TN from land use and rural life is about 66.5 and 17.1 %, the TP is about 53.8 and 32.7 %; the maximum source composition of TN (59 %) is farmland; the maximum source composition of TP (38.1 %) is rural life; the maximum contribution rates of TN and TP in Baota district are 36.26 and 39.26 %, respectively. Results may provide data support for NPS pollution prevention and control in the loess hilly and gully region and also provide scientific reference for the protection of ecological environment of the Loess Plateau in northern Shaanxi.

Diagenesis in tephra-rich sediments from the Lesser Antilles Volcanic Arc: Pore fluid constraints

NASA Astrophysics Data System (ADS)

Murray, Natalie A.; McManus, James; Palmer, Martin R.; Haley, Brian; Manners, Hayley

2018-05-01

We present sediment pore fluid and sediment solid phase results obtained during IODP Expedition 340 from seven sites located within the Grenada Basin of the southern Lesser Antilles Volcanic Arc region. These sites are generally characterized as being low in organic carbon content and rich in calcium carbonate and volcanogenic material. In addition to the typical reactions related to organic matter diagenesis, pore fluid chemistry indicates that the diagenetic reactions fall within two broad categories; (1) reactions related to chemical exchange with volcanogenic material and (2) reactions related to carbonate dissolution, precipitation, or recrystallization. For locations dominated by reaction with volcanogenic material, these sites exhibit increases in dissolved Ca with coeval decreases in Mg. We interpret this behavior as being driven by sediment-water exchange reactions from the alteration of volcanic material that is dispersed throughout the sediment package, which likely result in formation of Mg-rich secondary authigenic clays. In contrast to this behavior, sediment sequences that exhibit decreases in Ca, Mg, Mn, and Sr with depth suggest that carbonate precipitation is an active diagenetic process affecting solute distributions. The distributions of pore fluid 87Sr/86Sr reflect these competitive diagenetic reactions between volcanic material and carbonate, which are inferred by the major cation distributions. From one site where we have solid phase 87Sr/86Sr (site U1396), the carbonate fraction is found to be generally consistent with the contemporaneous seawater isotope values. However, the 87Sr/86Sr of the non-carbonate fraction ranges from 0.7074 to 0.7052, and these values likely represent a mixture of local arc volcanic sources and trans-Atlantic eolian sources. Even at this site where there is clear evidence for diagenesis of volcanogenic material, carbonate diagenesis appears to buffer pore fluid 87Sr/86Sr from the larger changes that might be expected given the high abundance of tephra in these sediments. Part of this carbonate buffering, at this site as well as throughout the region, derives from the fact that the Sr concentration in the non-carbonate fraction is generally low (<200 ppm), whereas the carbonate fraction has Sr concentrations approaching ∼1000 ppm.

Characterisation of organic matter source and sediment distribution in Ashtamudi Estuary, southern India

NASA Astrophysics Data System (ADS)

Kumar, Prem; Ankit, Yadav; Mishra, Praveen K.; Jha, Deepak Kumar; Anoop, Ambili

2017-04-01

In the present study we have focussed on the surface sediments of Ashtamudi Estuary (southern India) to understand (i) the fate and sources of organic matter by investigating lipid biomarker (n-alkanes) distribution in modern sediments and vegetation samples and (ii) the processes controlling the sediment distribution into the lake basin using end-member modelling approach. The sediment n-alkanes from the Ashtamudi Estuary exhibit a pronounced odd over even predominance with maxima at C29 and C31 chain length indicative of a dominant terrestrial contribution. A number of n-alkane indices have been calculated to illustrate the variability in space by considering separately the river dominated northern reaches and tidal influenced southern part of Ashtamudi Estuary. The highest terrigenous organic contents were found in sediments from the river and upper bay sites, with smaller contributions to the lower parts of the estuary. The Paq and TAR (terrigenous/aquatic ratio) indices demonstrate maximum aquatic productivity (plankton growth and submerged macrophytes) in the tidal dominated region of the Ashtamudi Estuary. The carbon preference index (CPI) and average chain length (ACL) provide evidence for high petrogenic organic inputs in the tidal zone, whereas dominant biogenic contribution have been observed in the riverine zone. In addition, the end member modeling of the grain size distribution of the surface sediment samples enabled us to decipher significant sedimentological processes affecting the sediment distribution in the estuarine settings. The end-member distribution showing highest loading with the coarser fraction is maximum where estuary debouches into the sea. However, the samples near the mouth of the river shows finer fraction of the end-member.

Testing Models of Modern Glacial Erosion of the St. Elias Mountains, Alaska Using Marine Sediment Provenance

NASA Astrophysics Data System (ADS)

Penkrot, M. L.; Jaeger, J. M.; Loss, D. P.; Bruand, E.

2015-12-01

The glaciated coastal St. Elias Range in Alaska is a primary site to examine climate-tectonic interactions. Work has primarily focused on the Bering-Bagley and Malaspina-Seward ice fields, utilizing detrital and bedrock zircon and apatite geochronology to examine local exhumation and glacial erosion (Berger et al., 2008; Enkelmann et al., 2009; Headly et al., 2013). These studies argue for specific regions of tectonically focused or climatically widespread glacial erosion. Analyzed zircon and apatite grains are sand size, however glacial erosion favors the production of finer-grained sediments. This study focuses on the geochemical provenance of the silt-size fraction (15-63μm) of surface sediments collected throughout the Gulf of Alaska (GOA) seaward of the Bering and Malaspina glaciers to test if the exhumation patterns observed in zircon and apatites are also applicable for the silt size fraction. Onshore bedrock Al-normalized elemental data were used to delineate sediment sources, and a subset of provenance-applicable elements was chosen. Detrital thermochronologic data suggest that sediment produced by the Bagley/Bering system is derived from bedrock on the windward side with input from the Chugach Metamorphic Complex (CMC) underlying the Bagley only during glacial surge events (Headly et al., 2013). Geochemical observations of GOA silt deposited during the 1994-95 surge event confirm input of CMC sediment (elevated in Cr, Ni, Sc, Sr, depleted in Hf, Pb and Rb relative to Kultieth and Poul Creek formations). We also observe a windward-side sediment source (Kultieth and Poul Creek). It is hypothesized that the sediment carried by the Malaspina is primarily from CMC rock underlying the Seward ice field mixed with Yakataga formation rock that underlies the Seward throat (Headly et al., 2013). Geochemical observations of GOA silt support this hypothesis.

Origin of increased terrigenous supply to the NE South American continental margin during Heinrich Stadial 1 and the Younger Dryas

NASA Astrophysics Data System (ADS)

Zhang, Yancheng; Chiessi, Cristiano M.; Mulitza, Stefan; Zabel, Matthias; Trindade, Ricardo I. F.; Hollanda, Maria Helena B. M.; Dantas, Elton L.; Govin, Aline; Tiedemann, Ralf; Wefer, Gerold

2015-12-01

We investigate the redistribution of terrigenous materials in the northeastern (NE) South American continental margin during slowdown events of the Atlantic Meridional Overturning Circulation (AMOC). The compilation of stratigraphic data from 108 marine sediment cores collected across the western tropical Atlantic shows an extreme rise in sedimentation rates off the Parnaíba River mouth (about 2°S) during Heinrich Stadial 1 (HS1, 18-15 ka). Sediment core GeoB16206-1, raised offshore the Parnaíba River mouth, documents relatively constant 143Nd/144Nd values (expressed as εNd(0)) throughout the last 30 ka. Whereas the homogeneous εNd(0) data support the input of fluvial sediments by the Parnaíba River from the same source area directly onshore, the increases in Fe/Ca, Al/Si and Rb/Sr during HS1 indicate a marked intensification of fluvial erosion in the Parnaíba River drainage basin. In contrast, the εNd(0) values from sediment core GeoB16224-1 collected off French Guiana (about 7°N) suggest Amazon-sourced materials within the last 30 ka. We attribute the extremely high volume of terrigenous sediments deposited offshore the Parnaíba River mouth during HS1 to (i) an enhanced precipitation in the catchment region and (ii) a reduced North Brazil Current, which are both associated with a weakened AMOC.

Stochastic Geomorphology: A Framework for Creating General Principles on Erosion and Sedimentation in River Basins (Invited)

NASA Astrophysics Data System (ADS)

Benda, L. E.

2009-12-01

Stochastic geomorphology refers to the interaction of the stochastic field of sediment supply with hierarchically branching river networks where erosion, sediment flux and sediment storage are described by their probability densities. There are a number of general principles (hypotheses) that stem from this conceptual and numerical framework that may inform the science of erosion and sedimentation in river basins. Rainstorms and other perturbations, characterized by probability distributions of event frequency and magnitude, stochastically drive sediment influx to channel networks. The frequency-magnitude distribution of sediment supply that is typically skewed reflects strong interactions among climate, topography, vegetation, and geotechnical controls that vary between regions; the distribution varies systematically with basin area and the spatial pattern of erosion sources. Probability densities of sediment flux and storage evolve from more to less skewed forms downstream in river networks due to the convolution of the population of sediment sources in a watershed that should vary with climate, network patterns, topography, spatial scale, and degree of erosion asynchrony. The sediment flux and storage distributions are also transformed downstream due to diffusion, storage, interference, and attrition. In stochastic systems, the characteristically pulsed sediment supply and transport can create translational or stationary-diffusive valley and channel depositional landforms, the geometries of which are governed by sediment flux-network interactions. Episodic releases of sediment to the network can also drive a system memory reflected in a Hurst Effect in sediment yields and thus in sedimentological records. Similarly, discreet events of punctuated erosion on hillslopes can lead to altered surface and subsurface properties of a population of erosion source areas that can echo through time and affect subsequent erosion and sediment flux rates. Spatial patterns of probability densities have implications for the frequency and magnitude of sediment transport and storage and thus for the formation of alluvial and colluvial landforms throughout watersheds. For instance, the combination and interference of probability densities of sediment flux at confluences creates patterns of riverine heterogeneity, including standing waves of sediment with associated age distributions of deposits that can vary from younger to older depending on network geometry and position. Although the watershed world of probability densities is rarified and typically confined to research endeavors, it has real world implications for the day-to-day work on hillslopes and in fluvial systems, including measuring erosion, sediment transport, mapping channel morphology and aquatic habitats, interpreting deposit stratigraphy, conducting channel restoration, and applying environmental regulations. A question for the geomorphology community is whether the stochastic framework is useful for advancing our understanding of erosion and sedimentation and whether it should stimulate research to further develop, refine and test these and other principles. For example, a changing climate should lead to shifts in probability densities of erosion, sediment flux, storage, and associated habitats and thus provide a useful index of climate change in earth science forecast models.

Integration of bed characteristics, geochemical tracers, current measurements, and numerical modeling for assessing the provenance of beach sand in the San Francisco Bay Coastal System

USGS Publications Warehouse

Barnard, Patrick L.; Foxgrover, Amy C.; Elias, Edwin P.L.; Erikson, Li H.; Hein, James; McGann, Mary; Mizell, Kira; Rosenbauer, Robert J.; Swarzenski, Peter W.; Takesue, Renee K.; Wong, Florence L.; Woodrow, Don

2013-01-01

Over 150 million m3 of sand-sized sediment has disappeared from the central region of the San Francisco Bay Coastal System during the last half century. This enormous loss may reflect numerous anthropogenic influences, such as watershed damming, bay-fill development, aggregate mining, and dredging. The reduction in Bay sediment also appears to be linked to a reduction in sediment supply and recent widespread erosion of adjacent beaches, wetlands, and submarine environments. A unique, multi-faceted provenance study was performed to definitively establish the primary sources, sinks, and transport pathways of beach-sized sand in the region, thereby identifying the activities and processes that directly limit supply to the outer coast. This integrative program is based on comprehensive surficial sediment sampling of the San Francisco Bay Coastal System, including the seabed, Bay floor, area beaches, adjacent rock units, and major drainages. Analyses of sample morphometrics and biological composition (e.g., Foraminifera) were then integrated with a suite of tracers including 87Sr/86Sr and 143Nd/144Nd isotopes, rare earth elements, semi-quantitative X-ray diffraction mineralogy, and heavy minerals, and with process-based numerical modeling, in situ current measurements, and bedform asymmetry to robustly determine the provenance of beach-sized sand in the region.

Small river plumes off the northeastern coast of the Black Sea under average climatic and flooding discharge conditions

NASA Astrophysics Data System (ADS)

Osadchiev, Alexander; Korshenko, Evgeniya

2017-06-01

This study focuses on the impact of discharges of small rivers on the delivery and fate of fluvial water and suspended matter at the northeastern part of the Black Sea under different local precipitation conditions. Several dozens of mountainous rivers flow into the sea at the study region, and most of them, except for several of the largest, have little annual runoff and affect adjacent coastal waters to a limited extent under average climatic conditions. However, the discharges of these small rivers are characterized by a quick response to precipitation events and can significantly increase during and shortly after heavy rains, which are frequent in the considered area. The delivery and fate of fluvial water and terrigenous sediments at the study region, under average climatic and rain-induced flooding conditions, were explored and compared using in situ data, satellite imagery, and numerical modeling. It was shown that the point-source spread of continental discharge dominated by several large rivers under average climatic conditions can change to the line-source discharge from numerous small rivers situated along the coast in response to heavy rains. The intense line-source runoff of water and suspended sediments forms a geostrophic alongshore current of turbid and freshened water, which induces the intense transport of suspended and dissolved constituents discharged with river waters in a northwestern direction. This process significantly influences water quality and causes active sediment load at large segments of the narrow shelf at the northeastern part of the Black Sea compared to average climatic discharge conditions.

Small river plumes near the north-eastern coast of the Black Sea under climatic mean and flooding discharge conditions

NASA Astrophysics Data System (ADS)

Osadchiev, Alexander; Korshenko, Evgeniya

2017-04-01

The study is focused on the impact of discharge from small rivers on propagation and final location of fluvial waters and suspended matter at the north-eastern part of the Black Sea under different local precipitation conditions. Several dozens of mountainous rivers inflow into the sea at the studied region and most of them, except the several largest of them, have small annual runoff and limitedly affect adjacent coastal waters under climatic mean conditions. However, discharges of these small rivers are characterized by quick response to precipitation events and can dramatically increase during and shortly after heavy rains, which are frequent in the area under consideration. Propagation and final location of fluvial waters and terrigenous sediments at the studied region under climatic mean and rain-induced flooding conditions were explored and compared using in situ data, satellite imagery and numerical modelling. It was shown that the point-source spread of continental discharge dominated by several large rivers during climatic mean conditions can change to the line-source discharge from numerous small rivers situated along the coast in response to heavy rains. Intense line-source runoff of water and suspended sediments form a geostrophic alongshore current of turbid and freshened water, which induces intense transport of suspended and dissolved constituents discharged with river waters in a north-western direction. This process significantly influences water quality and causes active sediment load at large segments of narrow shelf at the north-eastern part of the Black Sea as compared to climatic mean discharge conditions.

Heavy mineral analyses as a powerful tool in fluvial geomorphology

NASA Astrophysics Data System (ADS)

von Suchodoletz, Hans; Gärtner, Andreas; Faust, Dominik

2014-05-01

The Marneuli depression is a tectonic sub-basin of the Transcaucasian depression in eastern Georgia, filled with several decametres of fluvial, lacustrine and aeolian Quaternary sediments. In order to reconstruct past landscape evolution of the region we studied Late Quaternary fluvial sediments found along several rivers that flow through that depression. Whereas Holocene river sediments could generally easily be assigned to corresponding rivers, this was not always the case for older fluvial sediments. For this reason, we studied the heavy mineral contents of five recent rivers and of four sedimentary deposits of potential precursors. A total of 4088 analysed heavy mineral grains enabled us to set up the characteristic heavy mineral distribution pattern for each sample. Using these data, we were able to reconstruct the most likely source areas of the Late Pleistocene fluvial sediments and to link them with the catchment areas of recent rivers. This allowed us to identify and to substantiate significant Late Quaternary river diversions that could at least partly be assigned to ongoing tectonic processes.

Hydrogeochemical and stream sediment reconnaissance basic data report for Williams NTMS quadrangle, Arizona

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wagoner, J.L.

Wet and dry sediments were collected throughout the 18,500-km/sup 2/arid-to-semiarid region and water samples at available streams, springs, and wells. Samples were collected between August 1977 and January 1978. Results of neutron activation analyses of uranium and trace elements and other field and laboratory analyses are presented in tabular hardcopy and microfiche format. The report includes six full-size overlays for use with the Williams NTMS 1:250,000 quadrangle. Sediment samples are divided into five general groups according to the source rock from which the sediment was derived. Background uranium concentrations for the quadrangle are relatively low, ranging from 1.91 to 2.40more » ppM, with the highest associated with the Precambrian igneous and metamorphic complexes of the Basin and Range province. Uranium correlates best with the rare-earth elements and iron, scandium, titanium, and manganese. Known uranium occurrences are not readily identified by the stream sediment data.« less

The effect of Hurricane Lili on the distribution of organic matter along the inner Louisiana shelf (Gulf of Mexico, USA)

NASA Astrophysics Data System (ADS)

Goñi, Miguel A.; Gordon, Elizabeth S.; Monacci, Natalie M.; Clinton, Rebecca; Gisewhite, Rachel; Allison, Mead A.; Kineke, Gail

2006-11-01

On October 3, 2002 Hurricane Lili made landfall on a previously studied region of the inner Louisiana shelf as a Category 2 storm with winds over 160 km/h. A week after the hurricane, major impacts of the storm were not evident in the water column except for the lower than expected inshore salinities (˜12 psu) for this time of year, which was characterized by low river discharge. Turbidity profiles were typical of those measured during previous investigations with suspended sediment concentrations >75 mg/L at inshore stations and <50 mg/L in surface waters and offshore. The implication is that the sediments resuspended during the hurricane settled soon after the storm passage. Water column particulate organic carbon (POC) concentrations ranged from 0.1 to over 2.0 mg/L, with the highest concentrations measured near the seabed and in the inshore portions of the study area. Suspended particles were characterized by low organic matter content (%POC of 0.5-2 wt%), low chlorophyll:POC ratios (Chl:POC<4 mg/g) and moderately elevated POC:particulate nitrogen ratios (POC:PN of 10-14 mol/mol), all suggesting their source was locally resuspended seabed sediment rather than from algal biomass or land-derived vascular plant detritus. Post hurricane sediment deposition throughout the study area resulted in a storm layer that ranged from <0.5 to 20 cm in thickness. In most locations sediment accumulation ranged from 3 to 10 cm. The storm deposits were generally composed of silty clays with a coarser, somewhat sandy 1-2 cm basal layer. Surface sediments from the storm layer were characterized by relatively high mineral surface areas (SA of 30-50 m 2/g) and elevated OC contents (%OC of 1.0-2.0%). The dispersal of fine sediments following the hurricane resulted in marked changes in the SA and %OC values of surface sediments from offshore locations, which prior to the storm contained coarser, organic-poor particles (SA of 5-15 m 2/g and %OC of 0.2-0.6%). The OC:SA and OC:N ratios of storm layer sediments ranged from 0.4 to 0.6 mg OC/m 2 and from 10 to 12 mol/mol, respectively, and were comparable to those measured in surface sediments prior to the hurricane. Such similarities in the composition of the organic matter reinforce the idea that the source of the storm deposits was the finer fraction of resuspended seabed sediments, with little evidence for inputs from local land-derived sources or autochthonous algal production. Overall, the magnitude of sediment and organic matter deposition on the seabed after the storm greatly exceeded the annual inputs from the Atchafalaya River and coastal primary production. The combined effects of hurricane-driven erosion and post-storm deposition represent a major perturbation to the benthic community of the region, which is already subject to these types of disturbances due to the combined effects of peaks in river discharge and the passage of storm fronts.

A Manual to Identify Sources of Fluvial Sediment

EPA Science Inventory

Sedimentation is one of the main causes of stream/river aquatic life use impairments in R3. Currently states lack standard guidance on appropriate tools available to quantify sediment sources and develop sediment budgets in TMDL Development. Methods for distinguishing sediment t...

Linkages between the spatial toxicity of sediments and sediment dynamics in the Yangtze River Estuary and neighboring East China Sea.

PubMed

Gao, Jinjuan; Shi, Huahong; Dai, Zhijun; Mei, Xuefei; Zong, Haibo; Yang, Hongwei; Hu, Lingling; Li, Shushi

2018-02-01

Anthropogenic activities are driving an increase in sediment contamination in coastal areas. This poses significant challenges for the management of estuarine ecosystems and their adjacent seas worldwide. However, few studies have been conducted on how dynamic mechanisms affect the sediment toxicity in the estuarine environment. This study was designed to investigate the linkages between sediment toxicity and hydrodynamics in the Yangtze River Estuary (YRE) area. High sediment toxicity was found in the Yangtze River mouth (Region I), the depocenter of the Yangtze River Delta (Region II), and the southeastern area of the adjacent sea (Region III), while low sediment toxicity was found in the northeastern offshore region (Region IV). A spatial comparison analysis and regression model indicated that the distributed pattern of sediment toxicity was likely related to hydrodynamics and circumfluence in the East China Sea (ECS) shelf. Specifically, high sediment toxicity in Region I may be affected by the Yangtze River Pump (YRP) and the low hydrodynamics there, and high toxicity in Region II can be influenced by the low sediment dynamics and fine sediment in the depocenter. The high sediment toxicity in Region III might be related to the combination of the YRP and Taiwan Warm Current, while the low toxicity in Region IV may be influenced by the local coarse-grained relict sand with strong sediment dynamics there. The present research results further suggest that it is necessary to link hydrodynamics and the spatial behavior of sediment and sediment-derived pollutants when assessing the pollution status of estuarine environments, especially for those mega-estuaries and their neighboring ocean environments with complex waves, tides and ocean currents. Copyright © 2017 Elsevier Ltd. All rights reserved.

Integrated observation and modelling of runoff and sediments across different compartments of semi-arid catchments and channel networks

NASA Astrophysics Data System (ADS)

Bronstert, Axel; Ramon, Batalla; Araújo José C., De; da Costa Alexandre, Cunha; Till, Francke; Andreas, Güntner; Jose, Lopez-Tarazon; George, Mamede; Müller Eva, N.

2010-05-01

About one-third of the global population currently lives in countries which experience conditions of water stress. Such regions, often located within dryland ecosystems, are exposed to the hazard that the available freshwater resources fail to meet the water demand in domestic, agricultural and industrial sectors. Water availability often relies on the retention of river runoff in artificial lakes and reservoirs. However, the water storage in reservoirs is often adversely affected by sedimentation as a result of soil erosion. Erosion of the land surface due to natural or anthropogenic reasons and deposition of the eroded material in reservoirs threatens the reliability of reservoirs as a source of water supply. To sustain future water supply, a quantification of the sediment export from large dryland catchments becomes indispensable. A comprehensive modelling framework for water and sediment transport at the meso-scale, with a particular focus on dryland regions, has been developed from a German, Catalonian and Brazilian team during the last decade. It includes novel components for erosion from erosion-prone hillslopes, sediment transfer, retention and re-mobilization through the river system and sediment distribution, trapping and transfer through a reservoir. The parameterisation for pilot catchments is based on field monitoring campaigns of water and sediment fluxes, the analysis of land-use patterns, and the identification of the sediment hot spots through remotely sensed data. We present results of erosion-prone landscape units, the role of sediment transport in the river system, and the sedimentation processes in reservoirs. The modelling studies demonstrate the wide range of environmental problems where the model may be employed to develop sustainable management strategies for land and water resources. Evaluation of scenarios (land use, climate change) combined with an integrated assessment of options in reservoir management opens the opportunity to address relevant questions of water management including problems of water yield, reservoir capacity and economical comparison of on-/ offsite sediment management.

Radionuclide contamination of sediment deposits in the Ob and Yenisey estuaries and areas of the Kara Sea.

PubMed

Standring, W J F; Stepanets, O; Brown, J E; Dowdall, M; Borisov, A; Nikitin, A

2008-04-01

The Ob and Yenisey rivers are major contributors to total riverine discharge to the Arctic Ocean. Several large nuclear facilities discharge into these rivers, which could affect actual and potential discharges of radionuclides to the Arctic region. This article presents new radionuclide concentration and grain-size data resulting from analyses of several sediment samples collected during research cruises in the Ob and Yenisey estuaries and adjacent areas during 2000 and 2001. Results indicate that discharges from the main nuclear facilities do not constitute a major contribution to the level of radioactive contamination in the marine areas studied, though Co-60 was detected at low concentrations in some sediment horizons. However, the aggregate contamination from different sources is not radioecologically significant in sediments within the study area, maximum Cs-137 levels being approximately 80 Bq kg(-1) dry weight.

Distribution of radionuclides in the guano sediments of Xisha Islands, South China Sea and its implication.

PubMed

Xu, L Q; Liu, X D; Sun, L G; Yan, H; Liu, Y; Luo, Y H; Huang, J; Wang, Y H

2010-05-01

Several natural and anthropogenic radionuclides ((210)Pb, (226)Ra and (137)Cs) in guano-phosphatic coral sediments and pure guano particles collected from Ganquan, Guangjin, Jinqing and Jinyin Islands of the Xisha archipelago, South China Sea, were analyzed. The Constant Initial Concentration (CIC) model and the Constant Rate of Supply (CRS) model were applied for age calculation. The average supply rate of (210)Pb was 126 Bq m(-2) a(-1), very close to the flux of northern hemisphere average (125 Bq m(-2) a(-1)). The activities of anthropogenic radionuclides in the sediments were very low, indicating that human nuclear tests did not notably impact this region. The main source of radionuclides in the sediments was from atmospheric precipitation, and the organic matter derived from plant and produced by nutrient-rich guano could further enhance them. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

The mountain-lowland debate: deforestation and sediment transport in the upper Ganga catchment.

PubMed

Wasson, R J; Juyal, N; Jaiswal, M; McCulloch, M; Sarin, M M; Jain, V; Srivastava, P; Singhvi, A K

2008-07-01

The Himalaya-Gangetic Plain region is the iconic example of the debate about the impact on lowlands of upland land-use change. Some of the scientific aspects of this debate are revisited by using new techniques to examine the role of deforestation in erosion and river sediment transport. The approach is whole-of-catchment, combining a history of deforestation with a history of sediment sources from well before deforestation. It is shown that deforestation had some effect on one very large erosional event in 1970, in the Alaknanda subcatchment of the Upper Ganga catchment, but that both deforestation and its effects on erosion and sediment transport are far from uniform in the Himalaya. Large magnitude erosional events occur for purely natural reasons. The impact on the Gangetic Plain of erosion caused by natural events and land cover change remains uncertain.

Sedimentology and geochemistry of mud volcanoes in the Anaximander Mountain Region from the Eastern Mediterranean Sea.

PubMed

Talas, Ezgi; Duman, Muhammet; Küçüksezgin, Filiz; Brennan, Michael L; Raineault, Nicole A

2015-06-15

Investigations carried out on surface sediments collected from the Anaximander mud volcanoes in the Eastern Mediterranean Sea to determine sedimentary and geochemical properties. The sediment grain size distribution and geochemical contents were determined by grain size analysis, organic carbon, carbonate contents and element analysis. The results of element contents were compared to background levels of Earth's crust. The factors that affect element distribution in sediments were calculated by the nine push core samples taken from the surface of mud volcanoes by the E/V Nautilus. The grain size of the samples varies from sand to sandy silt. Enrichment and Contamination factor analysis showed that these analyses can also be used to evaluate of deep sea environmental and source parameters. It is concluded that the biological and cold seep effects are the main drivers of surface sediment characteristics from the Anaximander mud volcanoes. Copyright © 2015 Elsevier Ltd. All rights reserved.

Sediment Sources, Depositional Environment, and Diagenetic Alteration of the Marcellus Shale, Appalachian Basin, USA: Nd, Sr, Li and U Isotopic Constraints

NASA Astrophysics Data System (ADS)

Phan, T. T.; Capo, R. C.; Gardiner, J. B.; Stewart, B. W.

2017-12-01

The organic-rich Middle Devonian Marcellus Shale in the Appalachian Basin, eastern USA, is a major target of natural gas exploration. Constraints on local and regional sediment sources, depositional environments, and post-depositional processes are essential for understanding the evolution of the basin. In this study, multiple proxies, including trace metals, rare earth elements (REE), the Sm-Nd and Rb-Sr isotope systems, and U and Li isotopes were applied to bulk rocks and authigenic fractions of the Marcellus Shale and adjacent limestone/sandstone units from two locations separated by 400 km. The range of ɛNd values (-7.8 to -6.4 at 390 Ma) is consistent with a clastic sedimentary component derived from a well-mixed source of fluvial and eolian material of the Grenville orogenic belt. The Sm-Nd isotope system and bulk REE distributions appear to have been minimally affected by post-depositional processes, while the Rb-Sr isotope system shows evidence of limited post-depositional redistribution. While REE are primarily associated with silicate minerals (80-95%), REE patterns of sequentially extracted fractions reflect post-depositional alteration at the intergranular scale. Although the chemical index of alteration (CIA = 54 to 60) suggests the sediment source was not heavily weathered, Li isotope data are consistent with progressively increasing weathering of the source region during Marcellus Shale deposition. δ238U values in bulk shale and reduced phases (oxidizable fraction) are higher than those of modern seawater and upper crust. The isotopically heavy U accumulated in these authigenic phases can be explained by the precipitation of insoluble U in anoxic/euxinic bottom water. Unlike carbonate cement within the shale, the similarity between δ238U values and REE patterns of the limestone units and those of modern seawater indicates that the limestone formed under open ocean (oxic) conditions.

Interpreting stream sediment fingerprints against primary and secondary source signatures in agricultural catchments

NASA Astrophysics Data System (ADS)

Blake, Will H.; Haley, Steve; Smith, Hugh G.; Taylor, Alex; Goddard, Rupert; Lewin, Sean; Fraser, David

2013-04-01

Many sediment fingerprinting studies adopt a black box approach to source apportionment whereby the properties of downstream sediment are compared quantitatively to the geochemical fingerprints of potential catchment sources without consideration of potential signature development or modification during transit. Working within a source-pathway-receptor framework, this study aimed to undertake sediment source apportionment within 6 subcatchments of an agricultural river basin with specific attention to the potential role of contaminants (vehicle emissions and mine waste) in development of stream sediment signatures. Fallout radionuclide (FRN) and geochemical fingerprinting methods were adopted independently to establish source signatures for primary sediment sources of surface and subsurface soil materials under various land uses plus reworked mine and 'secondary' soil material deposited, in transit, along road networks. FRN data demonstrated expected variability between surface soil (137Cs = 14 ± 3 Bq kg-1; 210Pbxs = 40 ± 7 Bq kg-1) and channel bank materials (137Cs = 3 ± 1 Bq kg-1; 210Pbxs = 24 ± 5 Bq kg-1) but road transported soil material was considerably elevated in 210Pbxs (up to 673 ± 51 Bq kg-1) due to sediment interaction with pluvial surface water within the road network. Geochemical discrimination between surface and subsurface soil materials was dominated by alkaline earth and alkali metals e.g. Ba, Rb, Ca, K, Mg which are sensitive to weathering processes in soil. Magnetic susceptibility and heavy metals were important discriminators of road transported material which demonstrated transformation of the signatures of material transported via the road network. Numerical unmixing of stream sediment indicated that alongside channel bank erosion, road transported material was an important component in some systems in accord with FRN evidence. While mining spoil also ranked as a significant source in an affected catchment, perhaps related to legacy sediment, the potential role of dissolved metal leaching and subsequent sediment-water interaction within the channel on signature modification remained unclear. Consideration of sediment signature modification en route from primary source to stream elucidated important information regarding sediment transfer pathways and dynamics relevant to sediment management decisions. Further work on sediment-water interactions and potential for signature transformation in the channel environment is required.

Fingerprinting Sources of Suspended Sediment in a Canadian Agricultural Watershed Using the MixSIAR Bayesian Unmixing Model

NASA Astrophysics Data System (ADS)

Smith, J. P.; Owens, P. N.; Gaspar, L.; Lobb, D. A.; Petticrew, E. L.

2015-12-01

An understanding of sediment redistribution processes and the main sediment sources within a watershed is needed to support watershed management strategies. The fingerprinting technique is increasingly being recognized as a method for establishing the source of the sediment transported within watersheds. However, the different behaviour of the various fingerprinting properties has been recognized as a major limitation of the technique, and the uncertainty associated with tracer selection needs to be addressed. There are also questions associated with which modelling approach (frequentist or Bayesian) is the best to unmix complex environmental mixtures, such as river sediment. This study aims to compare and evaluate the differences between fingerprinting predictions provided by a Bayesian unmixing model (MixSIAR) using different groups of tracer properties for use in sediment source identification. We used fallout radionuclides (e.g. 137Cs) and geochemical elements (e.g. As) as conventional fingerprinting properties, and colour parameters as emerging properties; both alone and in combination. These fingerprinting properties are being used (i.e. Koiter et al., 2013; Barthod et al., 2015) to determine the proportional contributions of fine sediment in the South Tobacco Creek Watershed, an agricultural watershed located in Manitoba, Canada. We show that the unmixing model using a combination of fallout radionuclides and geochemical tracers gave similar results to the model based on colour parameters. Furthermore, we show that a model that combines all tracers (i.e. radionuclide/geochemical and colour) gave similar results, showing that sediment sources change from predominantly topsoil in the upper reaches of the watershed to channel bank and bedrock outcrop material in the lower reaches. Barthod LRM et al. (2015). Selecting color-based tracers and classifying sediment sources in the assessment of sediment dynamics using sediment source fingerprinting. J Environ Qual. Doi:10.2134/jeq2015.01.0043 Koiter AJ et al. (2013). Investigating the role of connectivity and scale in assessing the sources of sediment in an agricultural watershed in the Canadian prairies using sediment source fingerprinting. J Soils Sediments, 13, 1676-1691.

40Ar- 39Ar dating of detrital muscovite in provenance investigations: a case study from the Adelaide Rift Complex, South Australia

NASA Astrophysics Data System (ADS)

Haines, Peter W.; Turner, Simon P.; Kelley, Simon P.; Wartho, Jo-Anne; Sherlock, Sarah C.

2004-11-01

Detrital zircon ages are commonly used to investigate sediment provenance and supply routes. Here, we explore the advantages of employing multiple, complimentary techniques via a case study of the Neoproterozoic and Cambrian of the Adelaide Rift Complex, South Australia. Detrital muscovite Ar-Ar ages are presented from stratigraphic units, or equivalents, that have previously been the subject of U-Pb detrital zircon dating, and, in some cases, whole-rock Sm-Nd isotope studies. The zircon age ranges and whole-rock Sm-Nd isotope data suggest that early Neoproterozoic sediments from near the base of the Adelaide Rift Complex comprise a mixture of detritus derived from the adjacent Gawler Craton (Palaeoproterozoic to earliest Mesoproterozoic) and overlying Gairdner flood basalts. In contrast, detrital muscovites from this level have a broad scatter of Mesoproterozoic infrared (IR) laser total fusion Ar-Ar ages, while UV laser traverses indicate that the age spread reflects partial resetting by multiple heating events, rather than a mixture of sources. Younger Neoproterozoic sediments document replacement of the Gawler Craton by the more distant Musgrave and/or Albany-Fraser Orogens as the main provenance. The Cambrian Kanmantoo Group marks an abrupt change in depositional style and a new sediment source. The Kanmantoo Group have older Nd model ages than underlying strata, yet are dominated by near to deposition-aged (˜500-650 Ma) detrital zircons and muscovites, suggesting rapid cooling and exhumation of a tectonically active provenance region. Although this source remains uncertain, evidence points towards the distant Pan-African orogenic belts. Deposition in the Adelaide Rift Complex was terminated in the late Early Cambrian by the Delamerian Orogeny, and the results of previous detrital mineral dating studies from the Lachlan Fold Belt to the east are consistent with at least partial derivation of these sediments from reworked upper Adelaide Rift Complex (Kanmantoo Group), rather than a continuation of sediment supply from the Kanmantoo Group sediment source. More broadly, the data suggest a close link between basin formation and orogen exhumation, and we also speculate that mantle plumes have played a significant role in crustal evolution at this Palaeo-Pacific margin of Gondwanaland, challenging the notion that subduction zones are the principle sites of crustal growth and sediment provenance.

Observed salinity changes in the Alappuzha mud bank, southwest coast of India and its implication to hypothesis of mudbank formation

NASA Astrophysics Data System (ADS)

Muraleedharan, K. R.; Dinesh Kumar, P. K.; Prasanna Kumar, S.; Srijith, B.; John, Sebin; Naveen Kumar, K. R.

2017-04-01

Alappuzha mud bank draws special attention among the twenty-mud bank locations reported along the Kerala coast by its remoteness from riverine sources. Among several hypotheses proposed for the formation of mud bank, the subterranean hypothesis was most accepted because of the occurrence of low salinity in the bottom layers. The present study provides evidence to show that occurrence of low salinity waters near the bottom in the mud bank region is an artifact of measuring technique employed for the measurement of salinity. The usual technique of conductivity based salinity determination completely fails in the presence of water laden with high amount of suspended sediment. Laboratory experiments were conducted to determine the response of electrode and conductivity cell sensor types to determine the salinity using a range of suspended sediment in the water column. Actual sediment samples from the mud bank region were utilized for the above studies. Based on field observations and experiments, we conclude that the low salinity was the manifestation of the presence highly turbid fluid mud formation in the mud bank region rather than the influence of fresh water.

Element distribution patterns in the ordovician Galena group, Southeastern Minnesota: Indicators of fluid flow and provenance of terrigenous material

USGS Publications Warehouse

Lively, R.S.; Morey, G.B.; Mossler, J.H.

1997-01-01

As part of a regional geochemical investigation of lower Paleozoic strata in the Hollandale embayment of southeastern Minnesota, elemental concentrations in acid-insoluble residues were determined for carbonate rock in the Middle Ordovician Galena Group. Elemental distribution patterns within the insoluble residues, particularly those of Ti, Al, and Zr, show that the Wisconsin dome and the Wisconsin arch, which contributed sediment to the embayment prior to Galena time, continued as weak sources of sediment during this period. In contrast, trace metals commonly associated with Mississippi Valley-type lead-zinc mineralization, including Pb, Zn, Cu, Ag, Ni, Co, As, and Mo, show dispersal patterns that are independent of those associated with primary depositional phenomena. These trace metals are concentrated in southern Minnesota in carbonate rocks near the interface between limestone- and dolostone-dominated strata. Dispersal patterns imply that the metals were carried by a north-flowing regional ground-water system. The results show that the geochemical attributes of insoluble residues can be used to distinguish provenance and transport directions of primary sediments within a depositional basin from effects of subsequent regional ground-water flow systems.

Mineralogy of the Pahrump Hills Region, Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Rampe, E. B.; Ming, D. W.; Vaniman, D. T.; Blake, D. F.; Chipera, S. J.; Morris, R. V.; Bish, D. L.; Cavanagh, P. D.; Achilles, C. N.; Bristow, T. F.;

Risk assessment of trace metal-polluted coastal sediments on Hainan Island: A full-scale set of 474 geographical locations covering the entire island.

PubMed

Li, Feng; Lin, Ze-Feng; Wen, Jia-Sheng; Wei, Yan-Sha; Gan, Hua-Yang; He, Hai-Jun; Lin, Jin-Qin; Xia, Zhen; Chen, Bi-Shuang; Guo, Wen-Jie; Tan, Cha-Sheng; Cai, Hua-Yang

2017-12-15

Hainan Island is the second largest island and one of the most famous tourist destinations in China, but sediment contamination by trace metals in coastal areas is a major issue. However, full-scale risk assessments of trace metal-polluted coastal sediments are lacking. In this study, coastal surface sediments from 474 geographical locations covering almost the entire island were collected to identify risk-related variables. Controlling factors and possible sources of trace metals were identified, and the toxicity effects were carefully evaluated. Our results suggest that trace-metal pollution in coastal sediments, which was mainly caused by Pb, Zn and Cu emissions, has primarily resulted from industrial sewage and shipping activities and has threatened the offshore ecosystem of Hainan Island and warrants extensive consideration. This is the first study that has systematically investigated trace metal-polluted coastal sediments throughout the entirety of Hainan Island and provides solid evidence for sustainable marine management in the region. Copyright © 2017 Elsevier Ltd. All rights reserved.

Characterization of sediment sources, sediment budget estimations, consequences and implications for populations in the Jatún Mayu watershed (Cochabamba, Bolivia)

NASA Astrophysics Data System (ADS)

Vuignier, Jean-Marie; Penna, Ivanna; Jaboyedoff, Michel; Sudmeier-Rieux, Karen

2015-04-01

Natural and human-induced erosive processes shape landscape by transferring masses from the mountain to downstream areas. They also impact population both located in the source areas of sediments as well as urban areas settle on the depositional area. Mountain areas in Bolivia present high surface dynamics and high rates of rural migrations, causing e.g. a significant increase of population in Cochabamba city in the last 20 years. This work aims to estimate the sediment production on the Jatún Mayu (Pankuruma) watershed in Cochabamba department taking into account the different origins of sediments. The population of this region is predominantly rural and quechua speaking. The region of study consists in a mountain area situated in the Andes with altitudes ranging from 2500 to 4600m. Field work on July 2014 and high resolution satellite image interpretation (2004 & 2009) allowed us to map and measure landslides and gullies. Almost a hundred of landslides are recorded mostly around the river channel in the middle and the lower part of the valley and provide a moving surface estimated at 3,15km2. Most of the gullies are situated in the upper part of the valley where the vegetation is less abundant on low-sloping agricultural lands. Photogrammetric reconstructions using camera and drone were the main method used to characterise some strategic points along the river in order to get dimensions of landslides, gullies, as well as the riverbed roughness, as the final goal was to model the flooding prone area at the mouth of the watershed, were migrants have been settling for the last years. A total of 9 points of interests along the river bed were surveyed and for each of them a square surface equal to 25m2 was analysed. Approximately 250 pictures by area were needed to estimate roughness along the channel. A flood model has been performed, by using the Riverflo-2D software, to produce a susceptibility map of the downstream region.

Links between sediment consolidation and Cascadia megathrust slip behaviour

NASA Astrophysics Data System (ADS)

Han, Shuoshuo; Bangs, Nathan L.; Carbotte, Suzanne M.; Saffer, Demian M.; Gibson, James C.

2017-12-01

At sediment-rich subduction zones, megathrust slip behaviour and forearc deformation are tightly linked to the physical properties and in situ stresses within underthrust and accreted sediments. Yet the role of sediment consolidation at the onset of subduction in controlling the downdip evolution and along-strike variation in megathrust fault properties and accretionary wedge structure is poorly known. Here we use controlled-source seismic data combined with ocean drilling data to constrain the sediment consolidation and in situ stress state near the deformation front of the Cascadia subduction zone. Offshore Washington where the megathrust is inferred to be strongly locked, we find over-consolidated sediments near the deformation front that are incorporated into a strong outer wedge, with little sediment subducted. These conditions are favourable for strain accumulation on the megathrust and potential earthquake rupture close to the trench. In contrast, offshore Central Oregon, a thick under-consolidated sediment sequence is subducting, and is probably associated with elevated pore fluid pressures on the megathrust in a region where reduced locking is inferred. Our results suggest that the consolidation state of the sediments near the deformation front is a key factor contributing to megathrust slip behaviour and its along-strike variation, and it may also have a significant role in the deformation style of the accretionary wedge.

Variations in sediment texture on the northern Monterey Bay National Marine Sanctuary continental shelf

USGS Publications Warehouse

Edwards, B.D.

2002-01-01

The storm-protected continental shelf of Monterey Bay, part of the Monterey Bay National Marine Sanctuary, north-central California, is subject to abundant, episodic sediment input from fluvial sources. North of Monterey Bay, conditions of reduced sediment supply combined with the exposed nature of the shelf provide an effective laboratory for studying the contrasting effects of storm- versus fluvial-dominated conditions on modern sedimentation. Textural analyses performed on surface sediment samples collected from more than 380 box cores and MultiCores??? document the existence of a clearly defined mud belt occupying the mid-shelf throughout the region. Inshore sands combined with these mid-shelf muds represent deposits from modern sedimentation processes. In Monterey Bay, where episodic fluvial input from winter storms dominates sedimentation, the mid-shelf mud belt extends across the shelf to the shelf break. North of Monterey Bay, where sediment loads are reduced and both oceanographic and storm processes dominate, the mid-shelf mud belt is bordered by relict sediments occupying the outer shelf. In the study area, mass accumulation rates established by radiochemical studies support the contention that storm-induced along-shelf processes result in northward transport of sediment within the mud belt. The continuity of transport, however, is interrupted by topographic highs which are barriers or inhibitors to sediment transport created by wrench-style tectonics associated with the San Andreas fault system.

Spatial variations in geochemical characteristics of the modern Mackenzie Delta sedimentary system

NASA Astrophysics Data System (ADS)

Vonk, Jorien E.; Giosan, Liviu; Blusztajn, Jerzy; Montlucon, Daniel; Graf Pannatier, Elisabeth; McIntyre, Cameron; Wacker, Lukas; Macdonald, Robie W.; Yunker, Mark B.; Eglinton, Timothy I.

2015-12-01

The Mackenzie River in Canada is by far the largest riverine source of sediment and organic carbon (OC) to the Arctic Ocean. Therefore the transport, degradation and burial of OC along the land-to-ocean continuum for this riverine system is important to study both regionally and as a dominant representative of Arctic rivers. Here, we apply sedimentological (grain size, mineral surface area), and organic and inorganic geochemical techniques (%OC, δ13C-OC and Δ14C-OC, 143Nd/144Nd, δ2H and δ18O, major and trace elements) on particulate, bank, channel and lake surface sediments from the Mackenzie Delta, as well as on surface sediments from the Mackenzie shelf in the Beaufort Sea. Our data show a hydrodynamic sorting effect resulting in the accumulation of finer-grained sediments in lake and shelf deposits. A general decrease in organic carbon (OC) to mineral surface area ratios from river-to-sea furthermore suggests a loss of mineral-bound terrestrial OC during transport through the delta and deposition on the shelf. The net isotopic value of the terrestrial OC that is lost en route, derived from relationships between δ13C, OC and surface area, is -28.5‰ for δ13C and -417‰ for Δ14C. We calculated that OC burial efficiencies are around 55%, which are higher (∼20%) than other large river systems such as the Amazon. Old sedimentary OC ages, up to 12 14C-ky, suggest the delivery of both a petrogenic OC source (with an estimated contribution of 19 ± 9%) as well as a pre-aged terrestrial OC source. We calculated the 14C-age of this pre-aged, biogenic, component to be about 6100 yrs, or -501‰, which illustrates that terrestrial OC in the watershed can reside for millennia in soils before being released into the river. Surface sediments in lakes across the delta (n = 20) showed large variability in %OC (0.92-5.7%) and δ13C (-30.7‰ to -23.5‰). High-closure lakes, flooding only at exceptionally high water levels, hold high sedimentary OC contents (>2.5%) and young biogenic OC with a terrestrial or an autochthonous source whereas no-closure lakes, permanently connected to a river channel, hold sediments with pre-aged, terrestrial OC. The intermediate low-closure lakes, flooding every year during peak discharge, display the largest variability in OC content, age and source, likely reflecting variability in for example the length of river-lake connections, the distance to sediment source and the number of intermediate settling basins. Bank, channel and suspended sediment show variable 143Nd/144Nd values, yet there is a gradual but distinct spatial transition in 143Nd/144Nd (nearly three ε units; from -11.4 to -13.9) in the detrital fraction of lake surface sediments from the western to the eastern delta. This reflects the input of younger Peel River catchment material in the west and input of older geological source material in the east, and suggests that lake sediments can be used to assess variability in source watershed patterns across the delta.

Inverse modelling of fluvial sediment connectivity identifies characteristics and spatial distribution of sediment sources in a large river network.

NASA Astrophysics Data System (ADS)

Schmitt, R. J. P.; Bizzi, S.; Kondolf, G. M.; Rubin, Z.; Castelletti, A.

2016-12-01

Field and laboratory evidence indicates that the spatial distribution of transport in both alluvial and bedrock rivers is an adaptation to sediment supply. Sediment supply, in turn, depends on spatial distribution and properties (e.g., grain sizes and supply rates) of individual sediment sources. Analyzing the distribution of transport capacity in a river network could hence clarify the spatial distribution and properties of sediment sources. Yet, challenges include a) identifying magnitude and spatial distribution of transport capacity for each of multiple grain sizes being simultaneously transported, and b) estimating source grain sizes and supply rates, both at network scales. Herein, we approach the problem of identifying the spatial distribution of sediment sources and the resulting network sediment fluxes in a major, poorly monitored tributary (80,000 km2) of the Mekong. Therefore, we apply the CASCADE modeling framework (Schmitt et al. (2016)). CASCADE calculates transport capacities and sediment fluxes for multiple grainsizes on the network scale based on remotely-sensed morphology and modelled hydrology. CASCADE is run in an inverse Monte Carlo approach for 7500 random initializations of source grain sizes. In all runs, supply of each source is inferred from the minimum downstream transport capacity for the source grain size. Results for each realization are compared to sparse available sedimentary records. Only 1 % of initializations reproduced the sedimentary record. Results for these realizations revealed a spatial pattern in source supply rates, grain sizes, and network sediment fluxes that correlated well with map-derived patterns in lithology and river-morphology. Hence, we propose that observable river hydro-morphology contains information on upstream source properties that can be back-calculated using an inverse modeling approach. Such an approach could be coupled to more detailed models of hillslope processes in future to derive integrated models of hillslope production and fluvial transport processes, which is particularly useful to identify sediment provenance in poorly monitored river basins.

U-Pb Detrital Zircon Ages from Sarawak: Changes in Provenance Reflecting the Tectonic Evolution of Southeast Asia

NASA Astrophysics Data System (ADS)

Breitfeld, H. T.; Galin, T.; Hall, R.

2014-12-01

Sarawak is located on the northern edge of Sundaland in NW Borneo. Five sedimentary basins are distinguished with ages from Triassic to Cenozoic. New light mineral, heavy mineral and U-Pb detrital zircon ages show differences in provenance reflecting the tectonic evolution of the region. The oldest clastic sediments are Triassic of the Sadong-Kuching Basin and were sourced by a Carnian to Norian volcanic arc and erosion of Cathaysian rocks containing zircons of Paleoproterozoic age. Sandstones of the Upper Jurassic to Cretaceous Bau-Pedawan Basin have distinctive zircon populations indicating a major change of tectonic setting, including initiation of subduction below present-day West Sarawak in the Late Jurassic. A wide range of inherited zircon ages indicates various Cathaysian fragments as major source areas and the arrival of the SW Borneo Block following subduction beneath the Schwaner Mountains in the early Late Cretaceous. After collision of the SW Borneo Block and the microcontinental fragments with Sundaland in the early Late Cretaceous, deep marine sedimentation (Pedawan Formation) ceased, and there was uplift forming the regional Pedawan-Kayan unconformity. Two episodes of extension were responsible for basin development on land from the latest Cretaceous onwards, probably in a strike-slip setting. The first episode formed the Kayan Basin in the Latest Cretaceous (Maastrichtian) to Early Paleocene, and the second formed the Ketungau Basin and the Penrissen Sandstone in the Middle to Late Eocene. Zircons indicate nearby volcanic activity throughout the Early Cenozoic in NW Borneo. Inherited zircon ages indicate an alternation between Borneo and Tin Belt source rocks. A large deep marine basin, the Rajang Basin, formed north of the Lupar Line fault. Zircons from sediments of the Rajang Basin indicate they are of similar age and provenance as the contemporaneous terrestrial sediments to the south suggesting a narrow steep continental Sundaland margin at the position of the Lupar Line.

Eolian sand transport pathways in the southwestern United States: Importance of the Colorado River and local sources

USGS Publications Warehouse

Muhs, D.R.; Reynolds, R.L.; Been, J.; Skipp, G.

2003-01-01

Geomorphologists have long recognized that eolian sand transport pathways extend over long distances in desert regions. Along such pathways, sediment transport by wind can surmount topographic obstacles and cross major drainages. Recent studies have suggested that three distinct eolian sand transport pathways exist (or once existed) in the Mojave and Sonoran Desert regions of the southwestern United States. One hypothesized pathway is colian sand transport from the eastern Mojave Desert of California into western Arizona, near Parker, and would require sand movement across what must have been at least a seasonally dry Colorado River valley. We tested this hypothesis by mineralogical, geochemical and magnetic analyses of eolian sands on both sides of the Colorado River, as well as sediment from the river itself. Results indicate that dunes on opposite sides of the Colorado River are mineralogically distinct: eastern California dunes are feldspar-rich whereas western Arizona dunes are quartz-rich, derived from quartz-rich Colorado River sediments. Because of historic vegetation changes, little new sediment from the Colorado River is presently available to supply the Parker dunes. Based on this study and previous work, the Colorado River is now known to be the source of sand for at least three of the major dune fields of the Sonoran Desert of western Arizona and northern Mexico. On the other hand, locally derived alluvium appears to be a more important source of dune fields in the Mojave Desert of California. Although many geomorphologists have stressed the importance of large fluvial systems in the origin of desert dune fields, few empirical data actually exist to support this theory. The results presented here demonstrate that a major river system in the southwestern United States is a barrier to the migration of some dune fields, but essential to the origin of others. Published by Elsevier Science Ltd.

Distribution and mobility of mercury in soils of a gold mining region, Cuyuni river basin, Venezuela.

PubMed

Santos-Francés, F; García-Sánchez, A; Alonso-Rojo, P; Contreras, F; Adams, M

2011-04-01

An extensive and remote gold mining region located in the East of Venezuela has been studied with the aim of assessing the distribution and mobility of mercury in soil and the level of Hg pollution at artisanal gold mining sites. To do so, soils and pond sediments were sampled at sites not subject to anthropological influence, as well as in areas affected by gold mining activities. Total Hg in regionally distributed soils ranged between 0.02 mg kg(-1) and 0.40 mg kg(-1), with a median value of 0.11 mg kg(-1), which is slightly higher than soil Hg worldwide, possibly indicating long-term atmospheric input or more recent local atmospheric input, in addition to minor lithogenic sources. A reference Hg concentration of 0.33 mg kg(-1) is proposed for the detection of mining affected soils in this region. Critical total Hg concentrations were found in the surrounding soils of pollutant sources, such as milling-amalgamation sites, where soil Hg contents ranged from 0.16 mg kg(-1) to 542 mg kg(-1) with an average of 26.89 mg kg(-1), which also showed high levels of elemental Hg, but quite low soluble+exchangeable Hg fraction (0.02-4.90 mg kg(-1)), suggesting low Hg soil mobility and bioavailability, as confirmed by soil column leaching tests. The vertical distribution of Hg through the soil profiles, as well as variations in soil Hg contents with distance from the pollution source, and Hg in pond mining sediments were also analysed. Copyright © 2010 Elsevier Ltd. All rights reserved.

Use of reservoir deposits to reconstruct the recent changes in sediment yields from a small granite catchment in the Yimeng Mountain region, China

NASA Astrophysics Data System (ADS)

Zhang, Yunqi; Long, Yi; Li, Bao; Xu, Shujian; Wang, Xiaoli; Liao, Jia

2017-09-01

Information on recent changes in sediment yields from small catchments provides a better understanding of temporal trends in soil loss from certain physical and human-influenced landscapes that have been subjected to recent environmental changes, and will help bridge the current knowledge gap that exists between hillslope erosion and sediment transport in rivers. The Yimeng Mountain region, characterized by alternating granite and limestone, is one of the most susceptible regions to soil erosion in northern China, and has been subjected to intensive anthropogenic activity in recent years. Soil loss from areas underlain by granite is particularly obvious, and is the main sediment source for the Yihe River. In this study, we used reservoir deposits to estimate the changes in sediment yields over the past 50 years from a small catchment underlain by granite, namely the Jiangzhuang catchment in the Yimeng Mountain region. Three cores were collected from the Jiangzhuang Reservoir in the catchment. The activities of 137Cs and 210Pbex at different depths, clay (grain size < 5 μm) contents, and sedimentary organic carbon (SOC) contents in the cores were analysed with reference to human activity and environmental change in the catchment. The chronologies of the cores were established by 137Cs and 210Pbex dating. The area-specific sediment yield (SSY) for different time periods since dam construction was estimated from each core by referring to the original capacity curve of the reservoir. The results indicate that the depth profiles of 137Cs, 210Pbex, clay, and SOC contents in cores from the Jiangzhuang Reservoir reflect the general history of human disturbances on the catchment over the past 50 years. The estimated SSY value from each core for each period ranged from 7.2 ± 2.7 to 23.7 ± 8.3 t ha- 1 y- 1, with a mean of 12.5 ± 4.6 t ha- 1 y- 1. SSY decreased during 1954-1972, and then showed a general tendency to increase. The temporal pattern of the sediment yield largely reflects the history of environmental change influenced by human activity in the catchment.

Sediment source fingerprinting as an aid to catchment management: A review of the current state of knowledge and a methodological decision-tree for end-users.

PubMed

Collins, A L; Pulley, S; Foster, I D L; Gellis, A; Porto, P; Horowitz, A J

2017-06-01

The growing awareness of the environmental significance of fine-grained sediment fluxes through catchment systems continues to underscore the need for reliable information on the principal sources of this material. Source estimates are difficult to obtain using traditional monitoring techniques, but sediment source fingerprinting or tracing procedures, have emerged as a potentially valuable alternative. Despite the rapidly increasing numbers of studies reporting the use of sediment source fingerprinting, several key challenges and uncertainties continue to hamper consensus among the international scientific community on key components of the existing methodological procedures. Accordingly, this contribution reviews and presents recent developments for several key aspects of fingerprinting, namely: sediment source classification, catchment source and target sediment sampling, tracer selection, grain size issues, tracer conservatism, source apportionment modelling, and assessment of source predictions using artificial mixtures. Finally, a decision-tree representing the current state of knowledge is presented, to guide end-users in applying the fingerprinting approach. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Depositional environments, provenance and paleoclimatic implications of Ordovician siliciclastic rocks of the Thango Formation, Spiti Valley, Tethys Himalaya, northern India

NASA Astrophysics Data System (ADS)

Rashid, Shaik A.; Ganai, Javid A.

2018-05-01

Recently published findings indicate that the Ordovician period has been much more dynamic than previously anticipated thus making this period significant in geological time. The Ordovician of India can best be studied in the Spiti region because the Spiti basin records the complete uninterrupted history of excellent marine sedimentary rocks starting from Cambrian to Paleogene which were deposited along the northern margin of India. Due to these reasons the geochemical data on the Ordovician rocks from the Spiti region is uncommon. The present geochemical study on the Ordovician Thango Formation (Sanugba Group) is mainly aimed to understand the provenance and the paleoclimatic conditions. The sandstones are the dominant lithology of the Thango Formation with intercalations of minor amount of shales. Detailed petrographic and sedimentological analysis of these rocks suggest that three major depositional environments, viz., fluvial, transitional and marine prevailed in the basin representing transgressive and regressive phases. The major and trace element ratios such as SiO2/Al2O3, K2O/Na2O and La-Th- Sc discrimination diagram suggest that these rocks were deposited in passive margin tectonic settings. Various geochemical discriminants and elemental ratios such as K2O/Na2O, Al2O3/TiO2, La/Sc, Th/Sc, Cr/Th, Zr/Sc, (Gd/Yb)N and pronounced negative Eu anomalies indicate the rocks to be the product of weathering of post-Archean granites. The striking similarities of the multi-elemental spider diagrams of the studied sediments and the Himalayan granitoids indicate that sediments are sourced from the Proterozoic orogenic belts of the Himalayan region. Chemical index of alteration (CIA) values of the studied sediments (55-72) suggest that the source rocks underwent low to moderate degree of chemical weathering. The span of the CIA values (55-72) recorded in the sediments from the Spiti region may have resulted from varying degrees of weathering conditions in the source area. This, in turn, reflects variable climatic conditions prevailing during the Ordovician period, which is consistent with the global studies. The high CIA values observed by numerous studies on siliciclastic sediments may imply warm paleoclimate attributed to an increase in atmospheric carbon dioxide and/or methane levels inducing an acidic weathering environment and enhanced silicate weathering. While the low CIA values indicates prevalence of arid-glacial conditions where negligible chemical alteration is possible. This study documents the noteworthy events like fluctuating (rise and fall) atmospheric CO2 and sea levels during the Ordovician period, a conclusion which is consistent with the other such studies on the Phanerozoic glaciation (or mass extinction) events on Gondwana supercontinent.

Coastal erosion vs riverline sediment discharge in the Arctic shelfx seas

USGS Publications Warehouse

Rachold, V.; Grigoriev, M.N.; Are, F.E.; Solomon, Sean C.; Reimnitz, E.; Kassens, H.; Antonow, M.

2000-01-01

This article presents a comparison of sediment input by rivers and by coastal erosion into both the Laptev Sea and the Canadian Beaufort Sea (CBS). New data on coastal erosion in the Laptev Sea, which are based on field measurements and remote sensing information and existing data on coastal erosion in the CBS as well as riverine sediment discharge into both the Laptev Sea and the CBS are included. Strong regional differences in the percentages of coastal ero- sion and riverine sediment supply are observed. The CBS is dominated by the riverine sediment discharge (64.45x106 t a-1) mainly of the Mackenzie River. which is the largest single source of sediments in the Arctic. Riverine sediment discharge into the Laptev Sea amounts to 24.10x106 t a-1, more than 70% of which are related to the Lena River. In comparison with the CBS. the Laptev Sea coast on average delivers approximately twice as much sediment mass per kilometer, a result of higher erosion rates due to higher cliffs and seasonal ice melting. In the Laptev Sea sediment input by coastal erosion (58.4x106 t a-1) is therefore more important than in the CBS and the ratio between riverine and coastal sediment input amounts to 0.4. Coastal erosion supplying 5.6x106 t a-1 is less significant for the sediment budget of the CBS where riverine sediment discharge exceeds coastal sediment input by a factor of ca. 10.

Tracing subducted sediment inputs to the Ryukyu arc-Okinawa Trough system: Evidence from thallium isotopes

NASA Astrophysics Data System (ADS)

Shu, Yunchao; Nielsen, Sune G.; Zeng, Zhigang; Shinjo, Ryuichi; Blusztajn, Jerzy; Wang, Xiaoyuan; Chen, Shuai

2017-11-01

Sediments are actively subducted in virtually every arc worldwide. However, quantifying their contributions to arc lavas and thereby establishing budgets of how sediments participate in slab-mantle interaction is challenging. In this contribution we use thallium (Tl) abundances and isotopic compositions of lavas from the Ryukyu arc (including south Kyushu) and its back-arc basin, Okinawa Trough, to investigate the influence of sediments from arc to back-arc. We also present extensive geochemical data for sediments and altered oceanic crust (AOC) outboard of the northern (DSDP Sites 296, 442B, 443 and 444) and central (DSDP Sites 294 and 295) part of the Ryukyu arc. The Tl isotopic compositions of sediments change systematically from lighter outboard of northern Ryukyu arc to heavier outboard of central Ryukyu arc. The feature reflects the dominance of terrigenous material and pelagic sedimentation outboard of the northern and central Ryukyu arc, respectively. Central and northern sections of Ryukyu arc and Okinawa Trough display larger range of Tl isotopic variation than southern section, which is consistent with more pelagic provenance for sediments outboard of central and northern Ryukyu arcs than that of expected sediments outboard of southern Ryukyu arc. Identical Tl, Sr, Nd and Pb isotope variations are found when comparing arc and back arc lavas, which indicates that sediments fluxes also account for the Tl isotopic variations in the Okinawa Trough lavas. Two-end-member mixing models of Tl with Pb, Sr and Nd isotopes require sediment inputs of< 1%, 0.1-1% and 0.3-2% by weight to the depleted mantle source to account for all these isotopic compositions of lavas from northern, central and southern portion of the Ryukyu arc and Okinawa Trough. Bulk mixing between mantle and sediment end members predict very similar sediment fluxes when using Tl, Sr, Nd and Pb isotopes, which indicates that fractionation of these elements must have happened after mixing between mantle and sediments. This conclusion is corroborated by model calculations of mixing between sediment melts with fractionated Sr/Nd ratios and mantle wedge, which show that no arc lava plot on such mixing lines. Thus bulk sediment mixing, rather than sediment melt, is required for the generation of the lavas from the Ryukyu arc and Okinawa Trough. The requirement of bulk sediment mixing occurring before trace element fractionation in the sub-arc mantle is consistent with models where mélange layers form at the top of the slab and are the principle source material for arc lavas. In addition, the fact that sediment components observed in the Ryukyu arc and Okinawa Trough lavas are similar, suggests that transport of mélange material to the source regions of the arc and back arc is equally efficient. This feature is most readily explained if mélange material is transported from the slab as diapirs.

Predicting fire effects on water quality: a perspective and future needs

NASA Astrophysics Data System (ADS)

Smith, Hugh; Sheridan, Gary; Nyman, Petter; Langhans, Christoph; Noske, Philip; Lane, Patrick

2017-04-01

Forest environments are a globally significant source of drinking water. Fire presents a credible threat to the supply of high quality water in many forested regions. The post-fire risk to water supplies depends on storm event characteristics, vegetation cover and fire-related changes in soil infiltration and erodibility modulated by landscape position. The resulting magnitude of runoff generation, erosion and constituent flux to streams and reservoirs determines the severity of water quality impacts in combination with the physical and chemical composition of the entrained material. Research to date suggests that most post-fire water quality impacts are due to large increases in the supply of particulates (fine-grained sediment and ash) and particle-associated chemical constituents. The largest water quality impacts result from high magnitude erosion events, including debris flow processes, which typically occur in response to short duration, high intensity storm events during the recovery period. Most research to date focuses on impacts on water quality after fire. However, information on potential water quality impacts is required prior to fire events for risk planning. Moreover, changes in climate and forest management (e.g. prescribed burning) that affect fire regimes may alter water quality risks. Therefore, prediction requires spatial-temporal representation of fire and rainfall regimes coupled with information on fire-related changes to soil hydrologic parameters. Recent work has applied such an approach by combining a fire spread model with historic fire weather data in a Monte Carlo simulation to quantify probabilities associated with fire and storm events generating debris flows and fine sediment influx to a reservoir located in Victoria, Australia. Prediction of fire effects on water quality would benefit from further research in several areas. First, more work on regional-scale stochastic modelling of intersecting fire and storm events with landscape zones of erosion vulnerability is required to support quantitative evaluation of water quality risk and the effect of future changes in climate and land management. Second, we underscore previous calls for characterisation of landscape-scale domains to support regionalisation of parameter sets derived from empirical studies. Recent examples include work identifying aridity as a control of hydro-geomorphic response to fire and the use of spectral-based indices to predict spatial heterogeneity in ash loadings. Third, information on post-fire erosion from colluvial or alluvial stores is needed to determine their significance as both sediment-contaminant sinks and sources. Such sediment stores may require explicit spatial representation in risk models for some environments and sediment tracing can be used to determine their relative importance as secondary sources. Fourth, increased dating of sediment archives could provide regional datasets of fire-related erosion event frequency. Presently, the lack of such data hinders evaluation of risk models linking fire and storm events to erosion and water quality impacts.

Identifying sediment sources in the sediment TMDL process

USGS Publications Warehouse

Gellis, Allen C.; Fitzpatrick, Faith A.; Schubauer-Berigan, Joseph P.; Landy, R.B.; Gorman Sanisaca, Lillian E.

2015-01-01

Sediment is an important pollutant contributing to aquatic-habitat degradation in many waterways of the United States. This paper discusses the application of sediment budgets in conjunction with sediment fingerprinting as tools to determine the sources of sediment in impaired waterways. These approaches complement monitoring, assessment, and modeling of sediment erosion, transport, and storage in watersheds. Combining the sediment fingerprinting and sediment budget approaches can help determine specific adaptive management plans and techniques applied to targeting hot spots or areas of high erosion.

Distribution and flux estimates of soluble, colloidal, and leachable particulate trace metals in dynamic and oxygen depleted Mauritanian shelf waters

NASA Astrophysics Data System (ADS)

Rapp, I.; Schlosser, C.; Gledhill, M.; Achterberg, E. P.

2016-02-01

Fe availability in surface waters determines primary production, N2 fixation and microbial community structure and thus plays an important role in ocean carbon and nitrogen cycles. Eastern boundary upwelling areas with oxygen minimum zones, such as the Mauritanian shelf region, are typically associated with elevated Fe concentrations with shelf sediments as key source of Fe to bottom and surface waters. The magnitude of vertical and horizontal Fe fluxes from shelf sediments to onshore and offshore surface waters are not well constrained and there are still large uncertainties concerning the stabilisation of Fe once released from sediments into suboxic and oxic waters. Supportive data of other trace metals can be used as an indicator of sediment release, scavenging processes and biological utilisation. Here we present soluble (<0.02 µm), dissolved (<0.2 µm) and total dissolvable (unfiltered) trace metal data collected at 10 stations on a 90 nautical mile transect across the Mauritanian shelf region in June 2014 (cruise Meteor 107). The samples were pre-concentrated using an automated off-line pre-concentration device and analysed simultaneously for Cd, Pb, Fe, Ni, Cu, Zn, Mn and Co using a high resolution inductively coupled plasma mass spectrometer (HR-ICP-MS). First results indicate the importance of benthic sources to the overall Fe budget in this region. Both dissolved Fe and Mn showed enhanced concentrations close to the shelf at depths between 40 and 180 m corresponding with low oxygen concentrations (<50 µmol L-1). Elevated soluble, dissolved, and total dissolvable Fe and Mn concentrations at an offshore station coincided with the location of a cyclonic Eddie that was characterised by an oxygen depleted water body. To further assess the accuracy of vertical and horizontal fluxes of Fe and other trace metals, we compare diffusivity estimates determined by a microstructure profiler and the scale length method (de Jong et al. 2012) with observed isotopic Ra data.

Multivariate analysis of heavy metal contamination using river sediment cores of Nankan River, northern Taiwan

NASA Astrophysics Data System (ADS)

Lee, An-Sheng; Lu, Wei-Li; Huang, Jyh-Jaan; Chang, Queenie; Wei, Kuo-Yen; Lin, Chin-Jung; Liou, Sofia Ya Hsuan

2016-04-01

Through the geology and climate characteristic in Taiwan, generally rivers carry a lot of suspended particles. After these particles settled, they become sediments which are good sorbent for heavy metals in river system. Consequently, sediments can be found recording contamination footprint at low flow energy region, such as estuary. Seven sediment cores were collected along Nankan River, northern Taiwan, which is seriously contaminated by factory, household and agriculture input. Physico-chemical properties of these cores were derived from Itrax-XRF Core Scanner and grain size analysis. In order to interpret these complex data matrices, the multivariate statistical techniques (cluster analysis, factor analysis and discriminant analysis) were introduced to this study. Through the statistical determination, the result indicates four types of sediment. One of them represents contamination event which shows high concentration of Cu, Zn, Pb, Ni and Fe, and low concentration of Si and Zr. Furthermore, three possible contamination sources of this type of sediment were revealed by Factor Analysis. The combination of sediment analysis and multivariate statistical techniques used provides new insights into the contamination depositional history of Nankan River and could be similarly applied to other river systems to determine the scale of anthropogenic contamination.

Use of stable isotopes of carbon and nitrogen to identify sources of organic matter to bed sediments of the Tualatin River, Oregon

USGS Publications Warehouse

Bonn, Bernadine A.; Rounds, Stewart A.

2010-01-01

The potential sources of organic matter to bed sediment of the Tualatin River in northwestern Oregon were investigated by comparing the isotopic fractionation of carbon and nitrogen and the carbon/nitrogen ratios of potential sources and bed sediments. Samples of bed sediment, suspended sediment, and seston, as well as potential source materials, such as soil, plant litter, duckweed, and wastewater treatment facility effluent particulate were collected in 1998-2000. Based on the isotopic data, terrestrial plants and soils were determined to be the most likely sources of organic material to Tualatin River bed sediments. The delta 13C fractionation matched well, and although the delta 15N and carbon/nitrogen ratio of fresh plant litter did not match those of bed sediments, the changes expected with decomposition would result in a good match. The fact that the isotopic composition of decomposed terrestrial plant material closely resembled that of soils and bed sediments supports this conclusion. Phytoplankton probably was not a major source of organic matter to bed sediments. Compared to the values for bed sediments, the delta 13C values and carbon/nitrogen ratios of phytoplankton were too low and the delta 15N values were too high. Decomposition would only exacerbate these differences. Although phytoplankton cannot be considered a major source of organic material to bed sediment, a few bed sediment samples in the lower reach of the river showed a small influence from phytoplankton as evidenced by lower delta 13C values than in other bed sediment samples. Isotopic data and carbon/nitrogen ratios for bed sediments generally were similar throughout the basin, supporting the idea of a widespread source such as terrestrial material. The delta 15N was slightly lower in tributaries and in the upper reaches of the river. Higher rates of sediment oxygen demand have been measured in the tributaries in previous studies and coupled with the isotopic data may indicate the presence of more labile organic matter in these areas. Results from this study indicate that strategies to improve oxygen conditions in the Tualatin River are likely to be more successful if they target sources of soil, leaf litter, and other terrestrially derived organic materials to the river rather than the instream growth of algae.

Pollution Characteristics and Possible Sources of Seldom Monitored Trace Elements in Surface Sediments Collected from Three Gorges Reservoir, China

PubMed Central

Gao, Bo; Wei, Xin; Zhou, Huaidong; Lu, Jin; Hao, Hong; Wan, Xiaohong

2014-01-01

A geochemical study of Three Gorges Reservoir (TGR) sediments was carried out to analyze the concentrations, distribution, accumulation, and potential sources of the seldom monitored trace elements (SMTEs). The mean concentrations of Li, B, Be, Bi, V, Co, Ga, Sn, Sb, and Tl were 47.08, 2.47, 59.15, 0.50, 119.20, 17.83, 30.31, 3.25, 4.14, and 0.58 mg/kg, respectively. The concentrations of total SMTEs, together with their spatial distribution, showed that the SMTEs were mainly due to anthropogenic inputs in the region of TGR. The assessment by Geoaccumulation Index indicates that Tl, Be, V, Co, and Fe are at the unpolluted level; Bi, Li, Ga, and Sn were at the “uncontaminated to moderately contaminated” level. However, B was classified as “moderately contaminated” level and Sb was ranked as “strongly contaminated” level. The pollution level of the SMTEs is Sb > B > Bi > Li > Ga > Sn > Tl > Be > V > Co > Fe. The results of Correlation Analysis and Principal Component Analysis indicated Be, V, Co, Ga, Sn, Tl, Bi, and Fe in sediments have a natural source. B and Li were positively correlated with each other and mainly attributed into similar anthropogenic input. In addition, Sb has less relationship with other SMTEs, indicating that Sb has another kind of anthropogenic source. PMID:25136647

Core-Log-Seismic investigations of the Surveyor Fan and Channel system during the Pleistocene; IODP Exp. 341

NASA Astrophysics Data System (ADS)

Somchat, K.; Reece, R.; Gulick, S. P. S.

2017-12-01

The Chugach-St. Elias mountain range is the product of the ongoing subduction and collision of the Yakutat microplate with the North America Plate. The presence of this high topography close to the shoreline creates a unique source-to-sink system in which glacial eroded sediment is transported directly to the sea and preserved offshore in a deep sea fan without intervening storage. Surveyor Fan and Channel system is the product of this system. In this study we will focus on the four tributary channels that form at the head of the Surveyor Channel complex and merge into the main channel trunk 200 km from the shelf edge. We integrated drill core and 2D seismic reflection data to study the evolution of these tributaries in order to decipher glacial history along the southern Alaskan margin since the mid-Pleistocene (1.2 Ma). An age model from Integrated Ocean Drilling Program Expedition 341 Site U1418 provides a higher resolution chronology of sediment delivery to the Surveyor Fan than previous studies. We regionally mapped the seismic subunits previously identified by Exp. 341 scientists starting from Site U1418 and analyzed regional patterns of sediment deposition. Channel migrations are observable between 1.2-0.5 Ma which could be the result of increasing glacial ice volume onshore due to onset of the MPT. Two-way travel time (isopach) maps of the three subunits show that sediment depocenter began to move eastward since 1.2 Ma with a trend of overall sediment flux increase in all tributary channels. Changes in sediment flux in each system represent the changes in volume of glacial ice over successive glacial intervals. Additionally, seismic analysis of channel geomorphology shows that each system contains distinct geomorphological evolutions that respond to the glacially eroded sediment flux at different times. Since glacial erosional processes is the driver of this source-to-sink system, a history of glacial ice onshore since the Pleistocene can be inferred from deep-sea sedimentary processes. This study shows an interaction between a climate driver and deep sea fan sediment deposition and has implications for how glacial ice at high latitude margins can shape continental margins on a 100 kyr timescale.

IDENTIFICATION OF SEDIMENT SOURCE AREAS WITHIN A WATERSHED

EPA Science Inventory

Identification of sediment source areas is crucial for designing proper abatement strategies that reduce sediment and associated contaminant loading to receiving water downstream. In this study, two methodologies were developed to identify the source areas and their relative stre...

Early Miocene sequence development across the New Jersey margin

USGS Publications Warehouse

Monteverde, D.H.; Mountain, Gregory S.; Miller, K.G.

2008-01-01

Sequence stratigraphy provides an understanding of the interplay between eustasy, sediment supply and accommodation in the sedimentary construction of passive margins. We used this approach to follow the early to middle Miocene growth of the New Jersey margin and analyse the connection between relative changes of sea level and variable sediment supply. Eleven candidate sequence boundaries were traced in high-resolution multi-channel seismic profiles across the inner margin and matched to geophysical log signatures and lithologic changes in ODP Leg 150X onshore coreholes. Chronologies at these drill sites were then used to assign ages to the intervening seismic sequences. We conclude that the regional and global correlation of early Miocene sequences suggests a dominant role of global sea-level change but margin progradation was controlled by localized sediment contribution and that local conditions played a large role in sequence formation and preservation. Lowstand deposits were regionally restricted and their locations point to both single and multiple sediment sources. The distribution of highstand deposits, by contrast, documents redistribution by along shelf currents. We find no evidence that sea level fell below the elevation of the clinoform rollover, and the existence of extensive lowstand deposits seaward of this inflection point indicates efficient cross-shelf sediment transport mechanisms despite the apparent lack of well-developed fluvial drainage. ?? 2008 The Authors. Journal compilation ?? 2008 Blackwell Publishing.

Spatiotemporal patterns of mercury accumulation in lake sediments of western North America

USGS Publications Warehouse

Drevnick, Paul; Cooke, Colin A.; Barraza, Daniella; Blais, Jules M.; Coale, Kenneth; Cumming, Brian F.; Curtis, Chris; Das, Biplob; Donahue, William F.; Eagles-Smith, Collin A.; Engstrom, Daniel R.; Fitzgerald, William F.; Furl, Chad V.; Gray, John R.; Hall, Roland I.; Jackson, Togwell A.; Laird, Kathleen R.; Lockhart, W. Lyle; Macdonald, Robie W.; Mast, M. Alisa; Mathieu, Callie; Muir, Derek C.G.; Outridge, Peter; Reinemann, Scott; Rothenberg, Sarah E.; Ruiz-Fernandex, Ana Carolina; St. Louis, V.L.; Sanders, Rhea; Sanei, Hamed; Skierszkan, Elliott; Van Metre, Peter C.; Veverica, Timothy; Wiklund, Johan A.; Wolfe, Brent B.

2016-01-01

For the Western North America Mercury Synthesis, we compiled mercury records from 165 dated sediment cores from 138 natural lakes across western North America. Lake sediments are accepted as faithful recorders of historical mercury accumulation rates, and regional and sub-regional temporal and spatial trends were analyzed with descriptive and inferential statistics. Mercury accumulation rates in sediments have increased, on average, four times (4×) from 1850 to 2000 and continue to increase by approximately 0.2 μg/m2 per year. Lakes with the greatest increases were influenced by the Flin Flon smelter, followed by lakes directly affected by mining and wastewater discharges. Of lakes not directly affected by point sources, there is a clear separation in mercury accumulation rates between lakes with no/little watershed development and lakes with extensive watershed development for agricultural and/or residential purposes. Lakes in the latter group exhibited a sharp increase in mercury accumulation rates with human settlement, stabilizing after 1950 at five times (5×) 1850 rates. Mercury accumulation rates in lakes with no/little watershed development were controlled primarily by relative watershed size prior to 1850, and since have exhibited modest increases (in absolute terms and compared to that described above) associated with (regional and global) industrialization. A sub-regional analysis highlighted that in the ecoregion Northwestern Forest Mountains, <1% of mercury deposited to watersheds is delivered to lakes. Research is warranted to understand whether mountainous watersheds act as permanent sinks for mercury or if export of “legacy” mercury (deposited in years past) will delay recovery when/if emissions reductions are achieved.

Dust fluxes linked to intensification of Prevailing Westerlies and Trade Winds stimulated Ethmodiscus rex giant diatom blooms in the southern Mariana Trench, western tropical Pacific at onset of the Last Glacial Maximum

NASA Astrophysics Data System (ADS)

Chen, D.; Luo, M.; Algeo, T. J.; Chen, L.

2017-12-01

The strontium (Sr) and neodymium (Nd) isotope compositions and clay-mineral assemblages of the detrital fraction of sediments in the southern Mariana Trench together with major- and trace-elements concentrations of bulk sediments have been determined to trace the sediment provenance and investigate the relationship between Asian dust input and blooms of the giant diatom Ethmodiscus rex. Enrichment of barium (Ba) in relative to upper continental crust (UCC) and low average Rb/K ratios in all study cores point to both hydrothermal and volcaniclastic inputs to the sediments. Both the Sr-Nd isotope compositions and the clay-mineral assemblages of the detrital fraction reflect a two-component mixing system consisting of Mariana arc volcaniclastics and eolian Asian dust. A decrease in smectite content and an increase in illite content just before formation of laminated diatom mats (LDMs) suggest a change in the source of the eolian dust from eastern Asian deserts (EADs) to central Asian deserts (CADs) at the onset of the Last Glacial Maximum (LGM). This observation suggests a causal linkage between atmospheric circulation patterns, the sources of eolian Asian dust, and marine productivity in the western Pacific region. We postulate that the shift to CAD-sourced dust may have played a greater role in promoting biological productivity in the oligotrophic western Pacific Ocean during the LGM than previously realized.

Sediment sources and their contribution along northern coast of the South China Sea: Evidence from clay minerals of surface sediments

NASA Astrophysics Data System (ADS)

Liu, Jianguo; Yan, Wen; Chen, Zhong; Lu, Jun

2012-09-01

Clay minerals of surface sediment samples from nine bays/harbors along northern coast of the South China Sea (SCS) are used for sediment sources and contribution estimation in the study areas. Results reveal that sediments in the study bays/harbors seem to be a mixture of sediments from the Pearl, Hanjiang River and local islands/rivers, but their clay mineral assemblage is distinct from that of Luzon and Taiwan sediments, indicating that sediments are derived mainly from the neighboring sources through riverine input and partly from localized sediments. Due to input of local sediments in the northern SCS, sediments from both east of the Leizhou Peninsula (Area IV) and next to the Pearl River estuary (PRE, Area II) have high smectite percent. Affected by riverine input of the Pearl and Hanjiang Rivers, sediments in west of the PRE (Area III) and east of the PRE (Area I) have high illite (average 47%) and kaolinite (54%) percents, respectively. Sediment contributions of various major sources to the study areas are estimated as the following: (1) the Hanjiang River provide 95% and 84% sediments in Areas I and II, respectively, (2) the Pearl River supply 79% and 29% sediments in Areas III and IV, respectively and (3) local sediments contribute the rest and reach the maximum (˜71%) in Area IV.

Controls on sediment production in two U.S. deserts

NASA Astrophysics Data System (ADS)

Belnap, Jayne; Walker, Beau J.; Munson, Seth M.; Gill, Richard A.

2014-09-01

Much of the world’s airborne sediment originates from dryland regions. Soil surface disturbances in these regions are ever-increasing due to human activities such as energy and mineral exploration and development, recreation, suburbanization, livestock grazing and cropping. Sediment production can have significant impacts to human health with particles potentially carrying viruses such as Valley Fever or causing asthma or other respiratory diseases. Dust storms can cause decreased visibility at the ground level, resulting in highway accidents, and reduced visual quality in park and wildland airsheds. Sediment production and deposition is also detrimental to ecosystem health, as production reduces soil fertility at its source and can bury plants and other organisms where it is deposited. Therefore, it is important to understand how we can predict what areas are prone to producing sediment emissions both before and after soil surface disturbance. We visited 87 sites in two deserts of the western U.S. that represented a range of soil texture and surface cover types. We used a portable wind tunnel to estimate the threshold friction velocity (TFV) required to initiate sediment transport and the amount of sediment produced by the tunnel at a set wind speed. Wind tunnel runs were done before and after soil surface disturbance with a four-wheel drive vehicle. Results show that most undisturbed desert soils are very stable, especially if covered by rocks or well-developed biological soil crusts, which make them virtually wind-erosion proof. Particles at disturbed sites, in contrast, moved at relatively low wind speeds and produced high amounts of sediment. Silt was an important predictor of TFV and sediment production across all sites, whereas the influence of rock cover and biological soil crusts was site-dependent. Understanding the vulnerability of a site after disturbance is important information for land managers as they plan land use activities and attempt to mitigate the harmful effects that sediment production can have on both human and ecosystem health.

Controls on sediment production in two U.S. deserts

USGS Publications Warehouse

Belnap, Jayne; Walker, Beau J.; Munson, Seth M.; Gill, Richard A.

2014-01-01

Much of the world’s airborne sediment originates from dryland regions. Soil surface disturbances in these regions are ever-increasing due to human activities such as energy and mineral exploration and development, recreation, suburbanization, livestock grazing and cropping. Sediment production can have significant impacts to human health with particles potentially carrying viruses such as Valley Fever or causing asthma or other respiratory diseases. Dust storms can cause decreased visibility at the ground level, resulting in highway accidents, and reduced visual quality in park and wildland airsheds. Sediment production and deposition is also detrimental to ecosystem health, as production reduces soil fertility at its source and can bury plants and other organisms where it is deposited. Therefore, it is important to understand how we can predict what areas are prone to producing sediment emissions both before and after soil surface disturbance. We visited 87 sites in two deserts of the western U.S. that represented a range of soil texture and surface cover types. We used a portable wind tunnel to estimate the threshold friction velocity (TFV) required to initiate sediment transport and the amount of sediment produced by the tunnel at a set wind speed. Wind tunnel runs were done before and after soil surface disturbance with a four-wheel drive vehicle. Results show that most undisturbed desert soils are very stable, especially if covered by rocks or well-developed biological soil crusts, which make them virtually wind-erosion proof. Particles at disturbed sites, in contrast, moved at relatively low wind speeds and produced high amounts of sediment. Silt was an important predictor of TFV and sediment production across all sites, whereas the influence of rock cover and biological soil crusts was site-dependent. Understanding the vulnerability of a site after disturbance is important information for land managers as they plan land use activities and attempt to mitigate the harmful effects that sediment production can have on both human and ecosystem health.

Characterization and quantification of suspended sediment sources to the Manawatu River, New Zealand.

PubMed

Vale, S S; Fuller, I C; Procter, J N; Basher, L R; Smith, I E

2016-02-01

Knowledge of sediment movement throughout a catchment environment is essential due to its influence on the character and form of our landscape relating to agricultural productivity and ecological health. Sediment fingerprinting is a well-used tool for evaluating sediment sources within a fluvial catchment but still faces areas of uncertainty for applications to large catchments that have a complex arrangement of sources. Sediment fingerprinting was applied to the Manawatu River Catchment to differentiate 8 geological and geomorphological sources. The source categories were Mudstone, Hill Subsurface, Hill Surface, Channel Bank, Mountain Range, Gravel Terrace, Loess and Limestone. Geochemical analysis was conducted using XRF and LA-ICP-MS. Geochemical concentrations were analysed using Discriminant Function Analysis and sediment un-mixing models. Two mixing models were used in conjunction with GRG non-linear and Evolutionary optimization methods for comparison. Discriminant Function Analysis required 16 variables to correctly classify 92.6% of sediment sources. Geological explanations were achieved for some of the variables selected, although there is a need for mineralogical information to confirm causes for the geochemical signatures. Consistent source estimates were achieved between models with optimization techniques providing globally optimal solutions for sediment quantification. Sediment sources was attributed primarily to Mudstone, ≈38-46%; followed by the Mountain Range, ≈15-18%; Hill Surface, ≈12-16%; Hill Subsurface, ≈9-11%; Loess, ≈9-15%; Gravel Terrace, ≈0-4%; Channel Bank, ≈0-5%; and Limestone, ≈0%. Sediment source apportionment fits with the conceptual understanding of the catchment which has recognized soft sedimentary mudstone to be highly susceptible to erosion. Inference of the processes responsible for sediment generation can be made for processes where there is a clear relationship with the geomorphology, but is problematic for processes which occur within multiple terrains. Copyright © 2015 Elsevier B.V. All rights reserved.

Hydrothermal sediments are a source of water column Fe and Mn in the Bransfield Strait, Antarctica

NASA Astrophysics Data System (ADS)

Aquilina, Alfred; Homoky, William B.; Hawkes, Jeffrey A.; Lyons, Timothy W.; Mills, Rachel A.

2014-07-01

Short sediment cores were collected from ∼1100 m water depth at the top of Hook Ridge, a submarine volcanic edifice in the Central Basin of the Bransfield Strait, Antarctica, to assess Fe and Mn supply to the water column. Low-temperature hydrothermal fluids advect through these sediments and, in places, subsurface H2S is present at high enough concentrations to support abundant Sclerolinum sp., an infaunal tubeworm that hosts symbiotic thiotrophic bacteria. The water column is fully oxic, and oxygen penetration depths at all sites are 2-5 cmbsf. Pore water Fe and Mn content is high within the subsurface ferruginous zone (max. 565 μmol Fe L-1, >3-7 cmbsf)-14-18 times higher than values measured at a nearby, background site of equivalent water depth. Diffusion and advection of pore waters supply significant Fe and Mn to the surface sediment. Sequential extraction of the sediment demonstrates that there is a significant enrichment in a suite of reactive, authigenic Fe minerals in the upper 0-5 cm of sediment at one site characterised by weathered crusts at the seafloor. At a site with only minor authigenic mineral surface enrichment we infer that leakage of pore water Fe and Mn from the sediment leads to enriched total dissolvable Fe and Mn in bottom waters. An Eh sensor mounted on a towed package mapped a distinct Eh signature above this coring site which is dispersed over several km at the depth of Hook Ridge. We hypothesise that the main mechanism for Fe and Mn efflux from the sediment is breach of the surface oxic layer by the abundant Sclerolinum sp., along with episodic enhancements by physical mixing and resuspension of sediment in this dynamic volcanic environment. We propose that Hook Ridge sediments are an important source of Fe and Mn to the deep waters of the Central Basin in the Bransfield Strait, where concentrations are sustained by the benthic flux, and Fe is stabilised in the water column as either colloidal phases or ligand-bound dissolved species. Entrainment of this water mass into the Drake Passage and thereby the Antarctic Circumpolar Current could provide a significant metal source to this HNLC region of the Southern Ocean if mixing and upwelling occurs before removal of this metal pool to underlying sediments. Sediment-covered volcanic ridges are common within rifted margins and may play a previously overlooked role in the global Fe cycle.

Temperature, productivity and sediment characteristics as drivers of seasonal and spatial variations of dissolved methane in the near-shore coastal areas (Belgian coastal zone, North Sea)

NASA Astrophysics Data System (ADS)

Borges, Alberto V.; Speeckaert, Gaëlle; Champenois, Willy; Scranton, Mary I.; Gypens, Nathalie

2017-04-01

The open ocean is a modest source of CH4 to the atmosphere compared to other natural and anthropogenic CH4 emissions. Coastal regions are more intense sources of CH4 to the atmosphere than open oceanic waters, in particular estuarine zones. The CH4 emission to the atmosphere from coastal areas is sustained by riverine inputs and methanogenesis in the sediments due to high organic matter (OM) deposition. Additionally, natural gas seeps are sources of CH4 to bottom waters leading to high dissolved CH4 concentrations in bottom waters (from tenths of nmol L-1 up to several µmol L-1). We report a data set of dissolved CH4 concentrations obtained at nine fixed stations in the Belgian coastal zone (Southern North Sea), during one yearly cycle, with a bi-monthly frequency in spring, and a monthly frequency during the rest of the year. This is a coastal area with multiple possible sources of CH4 such as from rivers and gassy sediments, and where intense phytoplankton blooms are dominated by the high dimethylsulfoniopropionate (DMSP) producing micro-algae Phaeocystis globosa, leading to DMSP and dimethylsulfide (DMS) concentrations. Furthermore, the BCZ is a site of important OM sedimentation and accumulation unlike the rest of the North Sea. Spatial variations of dissolved CH4 concentrations were very marked with a minimum yearly average of 9 nmol L-1 in one of the most off-shore stations and maximum yearly average of 139 nmol L-1 at one of the most near-shore stations. The spatial variations of dissolved CH4 concentrations were related to the organic matter (OM) content of sediments, although the highest concentrations seemed to also be related to inputs of CH4 from gassy sediments associated to submerged peat. In the near-shore stations with fine sand or muddy sediments with a high OM content, the seasonal cycle of dissolved CH4 concentration closely followed the seasonal cycle of water temperature, suggesting the control of methanogenesis by temperature in these OM replete sediments. In the off-shore stations with permeable sediments with a low OM content, the seasonal cycle of dissolved CH4 concentration showed a yearly peak following the chlorophyll-a spring peak. This suggests that in these OM poor sediments, methanogenesis depended on the delivery to the sediments of freshly produced OM. In both types of sediments, the seasonal cycle of dissolved CH4 concentrations was unrelated the seasonal cycles of DMS, and DMSP, despite the fact that these quantities were very high during the spring Phaeocystis globosa bloom. This suggests that in this shallow coastal environment CH4 production is overwhelmingly related to benthic processes and unrelated to DMS(P) transformations in the water column as recently suggested in several open ocean regions. The annual average CH4 emission was 41 mmol m-2 yr-1 in the most near-shore stations ( 4 km from the coast) and 10 mmol m-2 yr-1 in the most off-shore stations ( 23 km from the coast), 410-100 times higher than the average value in the open ocean (0.1 mmol m-2 yr-1). The strong control of CH4 concentrations by sediment OM content and by temperature suggests that marine coastal CH4 emissions, in particular shallow coastal areas, should respond in future to eutrophication and warming of climate. This is confirmed by the comparison of CH4 concentrations at five stations obtained in March in years 1990 and 2016, showing a decreasing trend consistent with alleviation of eutrophication in the area.

Determining the sources of suspended sediment in a Mediterranean groundwater-dominated river: the Na Borges basin (Mallorca, Spain).

NASA Astrophysics Data System (ADS)

Estrany, Joan; Martinez-Carreras, Nuria

2013-04-01

Tracers have been acknowledged as a useful tool to identify sediment sources, based upon a variety of techniques and chemical and physical sediment properties. Sediment fingerprinting supports the notion that changes in sedimentation rates are not just related to increased/reduced erosion and transport in the same areas, but also to the establishment of different pathways increasing sediment connectivity. The Na Borges is a Mediterranean lowland agricultural river basin (319 km2) where traditional soil and water conservation practices have been applied over millennia to provide effective protection of cultivated land. During the twentieth century, industrialisation and pressure from tourism activities have increased urbanised surfaces, which have impacts on the processes that control streamflow. Within this context, source material sampling was focused in Na Borges on obtaining representative samples from potential sediment sources (comprised topsoil; i.e., 0-2 cm) susceptible to mobilisation by water and subsequent routing to the river channel network, while those representing channel bank sources were collected from actively eroding channel margins and ditches. Samples of road dust and of solids from sewage treatment plants were also collected. During two hydrological years (2004-2006), representative suspended sediment samples for use in source fingerprinting studies were collected at four flow gauging stations and at eight secondary sampling points using time-integrating sampling samplers. Likewise, representative bed-channel sediment samples were obtained using the resuspension approach at eight sampling points in the main stem of the Na Borges River. These deposits represent the fine sediment temporarily stored in the bed-channel and were also used for tracing source contributions. A total of 102 individual time-integrated sediment samples, 40 bulk samples and 48 bed-sediment samples were collected. Upon return to the laboratory, source material samples were oven-dried at 40° C, disaggregated using a pestle and mortar, and dry sieved to

Targeted versus statistical approaches to selecting parameters for modelling sediment provenance

NASA Astrophysics Data System (ADS)

Laceby, J. Patrick

2017-04-01

One effective field-based approach to modelling sediment provenance is the source fingerprinting technique. Arguably, one of the most important steps for this approach is selecting the appropriate suite of parameters or fingerprints used to model source contributions. Accordingly, approaches to selecting parameters for sediment source fingerprinting will be reviewed. Thereafter, opportunities and limitations of these approaches and some future research directions will be presented. For properties to be effective tracers of sediment, they must discriminate between sources whilst behaving conservatively. Conservative behavior is characterized by constancy in sediment properties, where the properties of sediment sources remain constant, or at the very least, any variation in these properties should occur in a predictable and measurable way. Therefore, properties selected for sediment source fingerprinting should remain constant through sediment detachment, transportation and deposition processes, or vary in a predictable and measurable way. One approach to select conservative properties for sediment source fingerprinting is to identify targeted tracers, such as caesium-137, that provide specific source information (e.g. surface versus subsurface origins). A second approach is to use statistical tests to select an optimal suite of conservative properties capable of modelling sediment provenance. In general, statistical approaches use a combination of a discrimination (e.g. Kruskal Wallis H-test, Mann-Whitney U-test) and parameter selection statistics (e.g. Discriminant Function Analysis or Principle Component Analysis). The challenge is that modelling sediment provenance is often not straightforward and there is increasing debate in the literature surrounding the most appropriate approach to selecting elements for modelling. Moving forward, it would be beneficial if researchers test their results with multiple modelling approaches, artificial mixtures, and multiple lines of evidence to provide secondary support to their initial modelling results. Indeed, element selection can greatly impact modelling results and having multiple lines of evidence will help provide confidence when modelling sediment provenance.

Martian outflow channels: How did their source aquifers form, and why did they drain so rapidly?

PubMed

Rodriguez, J Alexis P; Kargel, Jeffrey S; Baker, Victor R; Gulick, Virginia C; Berman, Daniel C; Fairén, Alberto G; Linares, Rogelio; Zarroca, Mario; Yan, Jianguo; Miyamoto, Hideaki; Glines, Natalie

2015-09-08

Catastrophic floods generated ~3.2 Ga by rapid groundwater evacuation scoured the Solar System's most voluminous channels, the southern circum-Chryse outflow channels. Based on Viking Orbiter data analysis, it was hypothesized that these outflows emanated from a global Hesperian cryosphere-confined aquifer that was infused by south polar meltwater infiltration into the planet's upper crust. In this model, the outflow channels formed along zones of superlithostatic pressure generated by pronounced elevation differences around the Highland-Lowland Dichotomy Boundary. However, the restricted geographic location of the channels indicates that these conditions were not uniform. Furthermore, some outflow channel sources are too high to have been fed by south polar basal melting. Using more recent mission data, we argue that during the Late Noachian fluvial and glacial sediments were deposited into a clastic wedge within a paleo-basin located in the southern circum-Chryse region, which at the time was completely submerged under a primordial northern plains ocean [corrected]. Subsequent Late Hesperian outflow channels were sourced from within these geologic materials and formed by gigantic groundwater outbursts driven by an elevated hydraulic head from the Valles Marineris region. Thus, our findings link the formation of the southern circum-Chryse outflow channels to ancient marine, glacial, and fluvial erosion and sedimentation.

Martian outflow channels: How did their source aquifers form, and why did they drain so rapidly?

PubMed Central

Rodriguez, J. Alexis P.; Kargel, Jeffrey S.; Baker, Victor R.; Gulick, Virginia C.; Berman, Daniel C.; Fairén, Alberto G.; Linares, Rogelio; Zarroca, Mario; Yan, Jianguo; Miyamoto, Hideaki; Glines, Natalie

2015-01-01

Catastrophic floods generated ~3.2 Ga by rapid groundwater evacuation scoured the Solar System’s most voluminous channels, the southern circum-Chryse outflow channels. Based on Viking Orbiter data analysis, it was hypothesized that these outflows emanated from a global Hesperian cryosphere-confined aquifer that was infused by south polar meltwater infiltration into the planet’s upper crust. In this model, the outflow channels formed along zones of superlithostatic pressure generated by pronounced elevation differences around the Highland-Lowland Dichotomy Boundary. However, the restricted geographic location of the channels indicates that these conditions were not uniform Boundary. Furthermore, some outflow channel sources are too high to have been fed by south polar basal melting. Using more recent mission data, we argue that during the Late Noachian fluvial and glacial sediments were deposited into a clastic wedge within a paleo-basin located in the southern circum-Chryse region, which was then completely submerged under a primordial northern plains ocean. Subsequent Late Hesperian outflow channels were sourced from within these geologic materials and formed by gigantic groundwater outbursts driven by an elevated hydraulic head from the Valles Marineris region. Thus, our findings link the formation of the southern circum-Chryse outflow channels to ancient marine, glacial, and fluvial erosion and sedimentation. PMID:26346067

Occurrence, source analysis and risk assessment of androgens, glucocorticoids and progestagens in the Hailing Bay region, South China Sea.

PubMed

Liu, Shan; Chen, Hui; Zhou, Guang-Jie; Liu, Shuang-Shuang; Yue, Wei-Zhong; Yu, Shen; Sun, Kai-Feng; Cheng, Hefa; Ying, Guang-Guo; Xu, Xiang-Rong

2015-12-01

The occurrence and spatial distribution of 40 steroids in the environmental matrices of the Hailing Bay region, South China Sea, were investigated by rapid resolution liquid chromatography-tandem mass spectrometry (RRLC-MS/MS). Seventeen, 14 and 11 of 40 steroids were detected with the concentrations ranging from 0.04 (testosterone) to 40.00 ng/L (prednisolone), 1.33 (4-hydroxy-androst-4-ene-17-dione) to 1855 ng/L (androsta-1,4-diene-3,17-dione) and <0.19 (androsta-1,4-diene-3,17-dione) to 2.37 ng/g (progesterone) in the seawater, the municipal sewage discharged effluent and the sediment samples, respectively. The concentrations and risk quotients (RQs) of the steroids detected in the water samples decreased in the order of municipal sewage discharge site>wharves~aquaculture zones~tourism areas>offshore areas. The distribution of steroids in the marine environment was significantly correlated with the levels of chemical oxygen demand (COD) and ammonium nitrogen (NH4-N). Source analysis indicated that untreated municipal sewage was the main source of steroids in the marine environment. Furthermore, progesterone was found to be a reliable chemical indicator to surrogate different steroids in both the water and sediment phases based on the correlation analysis. Copyright © 2015 Elsevier B.V. All rights reserved.

Multi-faceted monitoring of estuarine turbidity and particulate matter provenance: Case study from Salem Harbor, USA.

PubMed

Hubeny, J Bradford; Kenney, Melanie; Warren, Barbara; Louisos, Jeremy

2017-01-01

Turbidity is a water quality parameter that is known to adversely affect aquatic systems, however the causes of turbid water are often elusive. We present results of a study designed to constrain the source of particulate matter in a coastal embayment that has suffered from increased turbidity over past decades. Our approach utilized monitoring buoys to quantify turbidity at high temporal resolution complemented by geochemical isotope analysis of suspended sediment samples and meteorological data. Results reveal a complex system in which multiple sources are associated with particulate matter. Weight of evidence demonstrates that phytoplankton productivity in the water column, however, is the dominant source of particulate matter associated with elevated turbidity in Salem Harbor, Massachusetts. Allochthonous matter from the watershed was observed to mix into the pool of suspended particulate matter near river mouths, especially in spring and summer. Resuspension of harbor surface sediments likely provides additional particulates in the regions of boat moorings, especially during summer when recreational boats are attached to moorings. Our approach allows us to constrain the causes of turbidity events in this embayment, is helping with conservation efforts of environmental quality in the region, and can be used as a template for other locations. Copyright © 2016 Elsevier B.V. All rights reserved.

The Border Environmental Health Initiative: Investigation of the Transboundary Santa Cruz Watershed

NASA Astrophysics Data System (ADS)

Norman, L. M.; Callegary, J. B.; van Riper, C.; Gray, F.; Paretti, N.; Villarreal, M.

2009-12-01

In the borderland region of the desert southwest, human health and the ecosystems upon which humans rely largely depend on the quality, quantity, and distribution of water resources. In the Santa Cruz River Watershed (SCW), located in the Arizona and Sonora, Mexico border region, surface water is scarce and unreliable, and, during much of the year, is composed of effluent from the local wastewater treatment plant. This makes groundwater the preferred and, consequently, primary source for industrial, agricultural, and domestic use. USGS scientists are using an integrative approach, incorporating the expertise of the Geography, Water, Biology, and Geology disciplines to identify risks to water resources in the SCW, and the potential for impacts to riparian ecosystems and ultimately, human health. This includes tracking organic and inorganic contaminants and their effects from sources to sinks in sediment, water, plants, and animals. Existing ground- and surface-water models will be used and modified to assess contaminant and sediment transport. Water quality, sediment, aquatic macro invertebrates, aquatic plants (macrophytes), algae, riparian grasses, fish, and birds will be sampled at five locations along the Santa Cruz River. Field sampling data will be obtained at sites that coincide with historical sampling programs. Site locations include (i.) the Santa Cruz River headwaters (which should be unaffected by downstream contaminant sources), (ii.) a tributary routed through an abandoned mining district, (iii.) a binational tributary that flows though highly urbanized areas, (iv.) effluent from the local wastewater treatment plant, and (v.) the downstream confluence of the first four sources. The Soil and Water Assessment Tool (SWAT) model will be used in combination with field data to identify key sources of contaminants, contributing areas, and transport modes to track their movement to surface waters. These data will be used together to test relationships between sediment and hydrologic parameters, for the purpose of determining functional links. Further, it is planned that estimates of runoff and evapotranspiration resulting from the SWAT model simulations will be used to modify boundary conditions in the groundwater flow model to improve understanding of the effects of human activities on aquifer dynamics and contaminant transport. The SWAT model will then be used to identify critical sub-watersheds where implementing management practices could be most effective to abate pollution. An overview of our study design and preliminary results will be presented.

Combining sediment fingerprinting and a conceptual model for erosion and sediment transfer to explore sediment sources in an Alpine catchment

NASA Astrophysics Data System (ADS)

Costa, A.; Stutenbecker, L.; Anghileri, D.; Bakker, M.; Lane, S. N.; Molnar, P.; Schlunegger, F.

2017-12-01

In Alpine basins, sediment production and transfer is increasingly affected by climate change and human activities, specifically hydropower exploitation. Changes in sediment sources and pathways significantly influence basin management, biodiversity and landscape evolution. We explore the dynamics of sediment sources in a partially glaciated and highly regulated Alpine basin, the Borgne basin, by combining geochemical fingerprinting with the modelling of erosion and sediment transfer. The Borgne basin in southwest Switzerland is composed of three main litho-tectonic units, which we characterised following a tributary-sampling approach from lithologically characteristic sub-basins. We analysed bulk geochemistry using lithium borate fusion coupled with ICP-ES, and we used it to discriminate the three lithologic sources using statistical methods. Finally, we applied a mixing model to estimate the relative contributions of the three sources to the sediment sampled at the outlet. We combine results of the sediment fingerprinting with simulations of a spatially distributed conceptual model for erosion and transport of fine sediment. The model expresses sediment erosion by differentiating the contributions of erosional processes driven by erosive rainfall, snowmelt, and icemelt. Soil erodibility is accounted for as function of land-use and sediment fluxes are linearly convoluted to the outlet by sediment transfer rates for hillslope and river cells, which are a function of sediment connectivity. Sediment connectivity is estimated on the basis of topographic-hydraulic connectivity, flow duration associated with hydropower flow abstraction and permanent storage in hydropower reservoirs. Sediment fingerprinting at the outlet of the Borgne shows a consistent dominance (68-89%) of material derived from the uppermost, highly glaciated reaches, while contributions of the lower part (10-25%) and middle part (1-16%), where rainfall erosion is predominant, are minor. This result is confirmed by the model simulation which shows that, despite the large flow abstraction (about 90%), the upstream reaches contribute the most of the sediments. This study shows how combining geochemical techniques and sediment erosion models provides insight in the dynamics of sediment sources.

Community managed forests dominate the catchment sediment cascade in the mid-hills of Nepal: A compound-specific stable isotope analysis.

PubMed

Upadhayay, Hari Ram; Smith, Hugh G; Griepentrog, Marco; Bodé, Samuel; Bajracharya, Roshan Man; Blake, William; Cornelis, Wim; Boeckx, Pascal

2018-05-08

Soil erosion by water is critical for soil, lake and reservoir degradation in the mid-hills of Nepal. Identification of the nature and relative contribution of sediment sources in rivers is important to mitigate water erosion within catchments and siltation problems in lakes and reservoirs. We estimated the relative contribution of land uses (i.e. sources) to suspended and streambed sediments in the Chitlang catchment using stable carbon isotope signature (δ 13 C) of long-chain fatty acids as a tracer input for MixSIAR, a Bayesian mixing model used to apportion sediment sources. Our findings reveal that the relative contribution of land uses varied between suspended and streambed sediment, but did not change over the monsoon period. Significant over- or under-prediction of source contributions could occur due to overlapping source tracer values, if source groups are classified on a catchment-wide basis. Therefore, we applied a novel deconvolutional framework of MixSIAR (D-MixSIAR) to improve source apportionment of suspended sediment collected at tributary confluences (i.e. sub-catchment level) and at the outlet of the entire catchment. The results indicated that the mixed forest was the dominant (41 ± 13%) contributor of sediment followed by broadleaf forest (15 ± 8%) at the catchment outlet during the pre-wet season, suggesting that forest disturbance as well as high rainfall and steep slopes interact for high sediment generation within the study catchment. Unpaved rural road tracks located on flat and steep slopes (11 ± 8 and 9 ± 7% respectively) almost equally contributed to the sediment. Importantly, agricultural terraces (upland and lowland) had minimal contribution (each <7%) confirming that proper terrace management and traditional irrigation systems played an important role in mitigating sediment generation and delivery. Source contributions had a small temporal, but large spatial, variation in the sediment cascade of Chitlang stream. D-MixSIAR provided significant improvement regarding spatially explicit sediment source apportionment within the entire catchment system. This information is essential to prioritize implementation measures to control erosion in community managed forests to reduce sediment loadings to Kulekhani hydropower reservoir. In conclusion, using compound-specific stable isotope (CSSI) tracers for sediment fingerprinting in combination with a deconvolutional Bayesian mixing model offers a versatile approach to deal with the large tracer variability within catchment land uses and thus to successfully apportion multiple sediment sources. Copyright © 2018. Published by Elsevier B.V.

Sediment supply versus local hydraulic controls on sediment transport and storage in a river with large sediment loads

USGS Publications Warehouse

Dean, David; Topping, David; Schmidt, John C.; Griffiths, Ronald; Sabol, Thomas

2016-01-01

The Rio Grande in the Big Bend region of Texas, USA, and Chihuahua and Coahuila, Mexico, undergoes rapid geomorphic changes as a result of its large sediment supply and variable hydrology; thus, it is a useful natural laboratory to investigate the relative importance of flow strength and sediment supply in controlling alluvial channel change. We analyzed a suite of sediment transport and geomorphic data to determine the cumulative influence of different flood types on changing channel form. In this study, physically based analyses suggest that channel change in the Rio Grande is controlled by both changes in flow strength and sediment supply over different spatial and temporal scales. Channel narrowing is primarily caused by substantial deposition of sediment supplied to the Rio Grande during tributary-sourced flash floods. Tributary floods have large suspended-sediment concentrations, occur for short durations, and attenuate rapidly downstream in the Rio Grande, depositing much of their sediment in downstream reaches. Long-duration floods on the mainstem have the capacity to enlarge the Rio Grande, and these floods, released from upstream dams, can either erode or deposit sediment in the Rio Grande depending upon the antecedent in-channel sediment supply and the magnitude and duration of the flood. Geomorphic and sediment transport analyses show that the locations and rates of sand erosion and deposition during long-duration floods are most strongly controlled by spatial changes in flow strength, largely through changes in channel slope. However, spatial differences in the in-channel sediment supply regulate sediment evacuation or accumulation over time in long reaches (greater than a kilometer).

Improvement of suspended sediment concentration estimation for the Yarlung Zangbo river

NASA Astrophysics Data System (ADS)

Zeng, C.; Zhang, F.

2017-12-01

Suspended sediment load of a river represents integrated results of soil erosion, ecosystem variation and landform change occurring within basin over a specified period. Accurate estimation of suspended sediment concentration is important for calculating suspended sediment load, therefore is helpful for evaluating the impact of natural and anthropogenic factors on earth system processes under the background of global climate change. However, long-term observation of suspended sediment concentration usually very difficult in harsh condition areas e.g. rivers on the Tibet Plateau. This study proposed two sediment rating curve subdivision methods, the flood rank method and suspended sediment concentration stages method, to improve the estimations of daily suspended sediment concentration of the Yarlung Zangbo river during 2007 to 2009. The flood rank method, hypothesized that the higher water flow with larger erosive power can mobilize sediment sources not available during lower flows, suitable for application where sediments were mainly transported by first few flood events. The suspended sediment concentration stages method, assumed that precipitation is the dominating driving force of sediment erosion and transport processes during the flooding periods, suitable for application where soil erosion was closely related to precipitation events. Compared to traditional sediment rating curve and subdivision methods, results showed that the proposed methods can improve suspended sediment concentration and subsequent suspended sediment load estimations in the middle reach of the Yarlung Zangbo river with higher coefficients of determination (R2) and Nash-Sutcliffe efficiency coefficients (NSE), and yielded smaller bias (BIAS) and root-mean-square errors (RMSE). This study can provide guidelines for regional ecological and environmental management.

The End of Monterey Submarine Canyon Incision and Potential River Source Areas-Os, Nd, and Pb Isotope Constraints from Hydrogenetic Fe-Mn Crusts

NASA Astrophysics Data System (ADS)

Conrad, T. A.; Nielsen, S.; Ehrenbrink, B. P. E.; Blusztajn, J.; Hein, J. R.; Paytan, A.

2015-12-01

The Monterey Canyon off central California is the largest submarine canyon off North America and is comparable in scale to the Grand Canyon. The age and history of the Monterey Canyon are poorly constrained due to thick sediment cover and sediment disruption from turbidity currents. To address this deficit we analyzed isotopic proxies (Os, Pb, Nd) from hydrogenetic ferromanganese (Fe-Mn) crusts, which grow over millions of years on elevated rock surfaces by precipitation of metals from seawater. Fe-Mn crusts were studied from Davidson Seamount near the base of the Monterey submarine fan, the Taney Seamount Chain, and from Hoss Seamount, which serves as a regional control (Fig.). Fe-Mn crusts were dated using Os isotope ratios compared to those that define the Cenozoic Os isotope seawater curve. Four Fe-Mn crust samples from Davidson and Taney Seamounts deviate from the Os isotopic seawater curve towards radiogenic values after 4.5±1 Ma. Osmium is well mixed in the global ocean and is not subject to significant diffusive reequilibration in Fe-Mn crusts. We therefore attribute deviations from the Os isotope seawater curve to large-scale terrestrial input that ended about 4.5±1 Ma. The two Davidson samples also show more radiogenic Nd isotope values from about 4.5±1 Ma. Lead isotopes in one Davidson Seamount crust, measured by LA-ICPMS, deviate from regional values after 4.5±1 Ma for about 500 ka towards terrestrial sources. The Taney Seamount Fe-Mn crust does not deviate from regional Nd nor Pb isotope values due to its greater distance from Monterey Canyon and the shorter marine residence times of Nd and Pb. Isotope plots of our crust data and compiled data for potential source rocks indicate that the river that carved Monterey Canyon carried sediment with values closer to the Sierra Nevada than to a Colorado Plateau source, with cessation of major riverine input occurring approximately 4.5±1 Ma, an age that we interpret as the end of the Monterey Canyon incision.

Potential urban runoff impacts and contaminant distributions in shoreline and reservoir environments of Lake Havasu, southwestern United States.

PubMed

Wilson, Doyle C

2018-04-15

Heavy metal, nutrient, and hydrocarbon levels in and adjacent to Lake Havasu, a regionally significant water supply reservoir with a highly controlled, dynamic flow regime, are assessed in relation to possible stormwater runoff impacts from an arid urban center. Shallow groundwater and sediment analyses from ephemeral drainage (wash) mouths that convey stormwater runoff from Lake Havasu City, Arizona to the reservoir, provided contaminant control points and correlation ties with the reservoir environment. Fine-grain sediments tend to contain higher heavy metal concentrations whereas nutrients are more evenly distributed, except low total organic carbon levels from young wash mouth surfaces devoid of vegetation. Heavy metal and total phosphate sediment concentrations in transects from wash mouths into the reservoir have mixed and decreasing trends, respectively. Both series may indicate chemical depositional influences from urban runoff, yet no statistically significant concentration differences occur between specific wash mouths and corresponding offshore transects. Heavy metal pollution indices of all sediments indicate no discernible to minor contamination, indicating that runoff impacts are minimal. Nevertheless, several heavy metal concentrations from mid-reservoir sediment sites increase southward through the length of the reservoir. Continual significant water flow through the reservoir may help to disperse locally derived runoff particulates, which could mix and settle down gradient with chemical loads from upriver sources and local atmospheric deposition. Incorporating the shoreline environment with the reservoir investigation provides spatial continuity in assessing contaminant sources and distribution patterns. This is particularly acute in the investigation of energetic, flow-through reservoirs in which sources may be overlooked if solely analyzing the reservoir environment. Copyright © 2017 Elsevier B.V. All rights reserved.

Sources, transport and deposition of terrestrial organic material: A case study from southwestern Africa

NASA Astrophysics Data System (ADS)

Herrmann, Nicole; Boom, Arnoud; Carr, Andrew S.; Chase, Brian M.; Granger, Robyn; Hahn, Annette; Zabel, Matthias; Schefuß, Enno

2016-10-01

Southwestern Africa's coastal marine mudbelt, a prominent Holocene sediment package, provides a valuable archive for reconstructing terrestrial palaeoclimates on the adjacent continent. While the origin of terrestrial inorganic material has been intensively studied, the sources of terrigenous organic material deposited in the mudbelt are yet unclear. In this study, plant wax derived n-alkanes and their compound-specific δ13C in soils, flood deposits and suspension loads from regional fluvial systems and marine sediments are analysed to characterize the origin of terrestrial organic material in the southwest African mudbelt. Soils from different biomes in the catchments of the Orange River and small west coast rivers show on average distinct n-alkane distributions and compound-specific δ13C values reflecting biome-specific vegetation types, most notably the winter rainfall associated Fynbos Biome of the southwestern Cape. In the fluvial sediment samples from the Orange River, changes in the n-alkane distributions and compound-specific δ13C compositions reveal an overprint by local vegetation along the river's course. The smaller west coast rivers show distinct signals, reflecting their small catchment areas and particular vegetation communities. Marine surface sediments spanning a transect from the northern mudbelt (29°S) to St. Helena Bay (33°S) reveal subtle, but spatially coherent, changes in n-alkane distributions and compound-specific δ13C, indicating the influence of Orange River sediments in the northern mudbelt, the increasing importance of terrigenous input from the adjacent western coastal biomes in the central mudbelt, and contributions from the Fynbos Biome to the southern mudbelt. These findings indicate the different sources of terrestrial organic material deposited in the mudbelt, and highlight the potential the mudbelt has to preserve evidence of environmental change from the adjacent continent.

Organic-rich source beds and hydrocarbon production in Gulf Coast region

DOE Office of Scientific and Technical Information (OSTI.GOV)

Williams, D.F.; Lerche, I.

1988-09-01

Two models (I and II) are presented that relate the production of hydrocarbons in the Gulf Coast region to organic-rich source beds of ancient intraslope basins. Model I is empirical, based on present-day depositional environments like the anoxic Orca basin of the northern Gulf of Mexico and the Bannock basin of the eastern Mediterranean Sea. Model I proposed that low oxygen levels in intraslope basins of the northwestern Gulf of Mexico (GOM) have been a common mechanism for the accumulation of sediments with significantly increased amounts of marine organic carbon. In Model I progradation of the shelf-slope and regional saltmore » tectonics control the occurrence and stratigraphic distribution of source beds throughout the Tertiary of the GOM. In turn, the maturation history of these organic-rich sediments is influenced by the high thermal conductivity of the underlying salt structures. Model II is statistical; it uses random number theory to suggest that the occurrence of organic-rich black muds in intraslope basins of the northwestern GOM had sufficient capacity to account for a dynamic range estimate of 30 to 500 billion bbl oil total and 30 to 300 bcf/million years per ephemeral basin of gas. These estimates, while approximate, clearly indicate the enormous hydrocarbon potential for generating oil and gas reserves in the Gulf Coast geosyncline. Such estimates underscore the need for a better understanding of intraslope basins of the northwestern GOM.« less

Downstream mixing of sediment and tracers in agricultural catchments: Evidence of changing sediment sources and fluvial processes?

NASA Astrophysics Data System (ADS)

Ralph, Timothy; Wethered, Adam; Smith, Hugh; Heijnis, Henk

2014-05-01

Land clearance, soil tillage and grazing in agricultural catchments have liberated sediment and altered hydrological connectivity between hillslopes and channels, leading to increased sediment availability, mobilisation and delivery to rivers. The type and amount of sediment supplied to rivers is critical for fluvial geomorphology and aquatic ecosystem health. Contemporary sediment dynamics are routinely investigated using environmental radionuclides such as caesium-137 (Cs-137) and excess lead-210 (Pb-210ex), which can provide information regarding sediment source types and fluvial processes if sediment sources can be distinguished from one another and mixing models applied to representative samples. However, downstream transport, mixing and dilution of radionuclide-labelled sediment (especially from sources with low initial concentrations) can obliterate the tracer signal; sometimes before anything of geomorphological importance happens in the catchment. Can these findings be used as evidence of sediment source variations and fluvial processes when the limits of detection (of Cs-137 in particular) are being exceeded so rapidly downstream? Sediment sources and downstream sediment dynamics were investigated in Coolbaggie Creek, a major supplier of sediment to the Macquarie River in an agricultural catchment with temperate to semi-arid climate in Australia. Radionuclides were used to discriminate between the <63 micron fraction of sediment sources including forested topsoils (Cs-137 11.28 +/- 0.75 Bq/kg; Pb-210ex 181.87 +/- 20.00 Bq/kg), agricultural topsoils (Cs-137 3.21 +/- 0.26 Bq/kg; Pb-210ex 29.59 +/- 10.94 Bq/kg) and sub-soils from channel banks and gullies (Cs-137 1.45 +/- 0.47 Bq/kg; Pb-210ex 4.67 +/- 1.93 Bq/kg). Within the trunk stream, suspended sediment, organic matter and Cs-137 and Pb-210ex concentrations declined downstream. Results from a mixing model suggest that agricultural topsoils account for 95% of fine sediment entering the channel in the upper reach (<10 km long), while sub-soils account for 90 to 100% of sediment entering and being transported in the remaining ~50 km of the system. This shift in dominant sediment source material coincided with a large increase in channel cross sectional area (~20 to >200 m2) downstream, with channel expansion and gullies contributing fine sediment to the system. A lack of topsoil being supplied to the channel suggests minimal lateral connectivity between the catchment and the trunk stream in all areas apart from the upper catchment. The enlargement and entrenchment of the channel downstream has also resulted in lateral disconnection between the channel and floodplain. In this case, a rapid reduction in radionuclide concentrations downstream does coincide with hydrogeomorphic changes, supporting their use for studying short-term sediment dynamics. These findings highlight the importance of understanding hydrogeomorphic processes and connectivity when interpreting sediment source and tracer data.

A method for the concentration of fine-grained rutile (TiO2) from sediment and sedimentary rocks by chemical leaching

USGS Publications Warehouse

Commeau, Judith A.; Valentine, Page C.

1991-01-01

Most of the sample analyzed by the method described were marine muds collected from the Gulf of Maine (Valentine and Commeau, 1990). The silt and clay fraction (up to 99 wt% of the sediment) is composed of clay minerals (chiefly illite-mica and chlorite), silt-size quartz and feldspar, and small crystals (2-12 um) of rutile and hematite. The bulk sediment samples contained an average of 2 to 3 wt percent CaCO3. Tiher samples analyzed include red and gray Carboniferous and Triassic sandstones and siltstones exposed around the Bay of Fundy region and Paleozoic sandstones, siltstones, and shales from northern Maine and New Brunswick. These rocks are probable sources for the fine-grained rutile found in the Gulf of Maine.

Metal concentrations in surface sediments of Boston Harbor: Changes with time

USGS Publications Warehouse

Bothner, Michael H.; Buchholtz ten Brink, Marilyn R.; Manheim, F.T.

1998-01-01

The concentrations of metals in surface sediments of Boston Harbor have decreased during the period 1977–1993. This conclusion is supported by analysis of: (1) surface sediments collected at monitoring stations in the outer harbor between 1977 and 1993; (2) metal concentration profiles in sediment cores from depositional areas of the harbor; and (3) historical data from a contaminated-sediment database, which includes information on metal and organic contaminants and sediment texture. The background and matrix-corrected concentrations of lead (Pb) measured in the surficial layer (0–2 cm) of cores decreased by an average of 46%±12% among four locations in the outer harbor during the 16 y period. Chromium (Cr), copper (Cu), mercury (Hg), silver (Ag), and zinc (Zn) exhibited similar trends. Results from our sediment sampling are supported by historical data that were compiled from diverse sources into a regional sediment database. This sediment database contains approximately 3000 samples; of these, about 460 samples were collected and analyzed for Cu, Hg, or Zn and many other sediment parameters in Boston Harbor surface sediments between 1971–1993. The database indicates that the concentrations of these three metals also decreased with time in Boston’s Inner Harbor. The decreases in metal concentrations that are observed in more recent years parallel a general decrease in the flux of metals to the harbor, implemented by: (1) ending the sewage sludge discharge to the Harbor in December, 1991; (2) greater source reduction (e.g. recovery of silver from photographic processing) and closing or moving of industries; (3) improvements in wastewater handling and sewage treatment; and (4) diminishing use of lead in gasoline beginning about 1973. Despite the general decrease in metal concentrations in Boston Harbor surface sediments, the concentrations of Ag and Hg measured at some outer harbor stations in 1993 were still at, or above, the level associated with frequent adverse effects to marine organisms (guidelines are: Ag 3.7 μg g−1, Hg 1.17 μg g−1, from Long et al., 1995). Concentrations of the other metals listed were in the range considered to occasionally induce adverse biological effects.

Source identification of hydrocarbon contaminants and their transportation over the Zonguldak shelf, Turkish Black Sea

NASA Astrophysics Data System (ADS)

Unlu, S.; Alpar, B.

2009-04-01

Under great anthropogenic pressure due to the substantial freshwater input from the surrounding industrial and agricultural areas, especially central and middle-Eastern Europe, the Black Sea basin is ranked among the most ecologically threatened water bodies of the world. Oil levels are unacceptable in many coastal areas perilously close to polluted harbors and many river mouths; the places presenting the highest levels of bio-diversity and having a high socio-economic importance due to human use of coastal resources. There are about sixty sources of pollution which resulted in "hot spots" having disastrous impacts on sensitive marine and coastal areas and needing immediate priorities for action. Beyond such land-based sources, trans-boundary pollution sources from Black Sea riparian countries, heavy maritime traffic, particularly involving petroleum transports and fishing boats, and the improper disposal of ballast and bilge waters and solid waste are also important marine sources of pollution. Found in fossil fuels such as Polycyclic Aromatic Hydrocarbons are generated by incomplete combustion of organic matter. In order to estimate their distribution in sediment and their sources, they were monitored from the bottom samples offshore the Zonguldak industry region, one of the most polluted spots in the Turkish Black Sea. There the budget of pollutants via rivers is not precisely known due to an evident lack of data on chemical and granulometric composition of the river runoff and their fluxes. Therefore the marine sediments, essential components of marine ecosystems, are very important in our estimating the degree of the damage given to the ecosystem by such inputs. Realization of the sources and transport of these contaminants will be a critical tool for future management of the Zonguldak industry region and its watershed. The sea bottom in study area is composed of mainly sand and silt mixtures with small amount of clay. Geochemical analyses have shown that oil contamination was dominated in near-shore sediments. Their spatial distributions over the shelf area make an estimation of possible pollution sources and their transportation routes possible. Sea port activities, industrial inputs and partly maritime petroleum transport are the main sources of pollutants. They are under the control of the longshore currents supplied with river alluvium and coastal abrasion material.

The contribution of chemical fluxes across the sediment-water interface to carbon cycling in estuarine regions: A case study at the Rhône River mouth (NW Mediterranean)

NASA Astrophysics Data System (ADS)

Rassmann, Jens; Eitel, Eryn; Bombled, Bruno; Lansard, Bruno; Taillefert, Martial; Rabouille, Christophe

2016-04-01

Despite their small surface compared to the global oceans, continental shelf regions play a significant role in the global carbon cycle. Whereas shelf regions are seen as a sink for atmospheric CO2, estuarine regions are seen as a source. These regions are caracterized by the export of allochthonous terrigenous organic matter (OM) and the production of autochthonous marine organic carbon. An important fraction of this OM is mineralized in the sediments close to the river mouth. As a result, high exchange fluxes of dissolved inorganic carbon (DIC), total alkalinity (TA), oxygen and nutriments cross the sediment-water interface (SWI) and cause acidification of the bottom waters. Potentially, primary production in the water column is enhanced by these fluxes. Therefore, OM mineralisation in estuarine regions plays a key role in the carbon cycle as a direct producer of DIC and as a potential control factor for primary production. This work aims to quantify chemical fluxes through the SWI at the prodelta of the Rhone River (Mediterranen). In September 2015, a benthic chamber has been deployed at several stations in the prodelta to measure directly (in situ) fluxes of DIC, TA, ammonium and dissolved calcium at the SWI. At the same stations, in situ microprofiles of oxygen and pH have been recorded and sediment cores were taken for pore water extraction and analysis (DIC, TA, NH4+ and Ca2+). The results show a strong decrease of the fluxes in offshore direction indicating a strong variation of respiration rates in this direction. From pore water profiles, diffusive fluxes have been calculated and compared with the fluxes measured by the benthic chamber. This comparison enables us to include pore water profiles from previous investigations to calculate a carbon mass budget of this region.

First post-fire flush in a Mediterranean temporary stream: source ascription in bed sediments

NASA Astrophysics Data System (ADS)

Estrany Bertos, Joan; García-Comendador, Julián; Fortesa, Josep; Calsamiglia, Aleix; Garcias, Francesca

2017-04-01

First flushes can be of great importance for suspended-sediment transport in fluvial systems of drylands, being temporary streams a characteristic feature of Mediterranean basins. After a wildfire, storm flows may enhance runoff delivery to channels and then increasing the first-flush effect. 137Cs and 210Pbex were used as tracers for recognizing the first post-fire flush effect in the source ascription of bed sediments temporarily stored in a Mediterranean temporary stream severely affected by a wildfire. Thirty potential sediment source samples were collected along the main stem of a catchment located in Mallorca (Spain) during a field campaign developed some weeks after the wildfire. The sample collection was designed considering the wildfire affection, and also distinguishing between soil surface and channel bank. To quantify the relative source contribution to the bed sediment temporarily stored, five sediment samples -deposited during the first storm occurred three months after the wildfire- were collected into the bed stream of the main channel. The 137Cs and 210Pbex concentrations were measured by gamma spectrometry. Then, a linear mixing model was used to establish the relative contribution of each source type to the bed sediments discerning between the most upstream and the downstream parts of the catchment. Post-fire first-flush effect was generated by a torrential event with a suspended-sediment concentration peak ca. 33,618 mg L-1, although transmission losses under a very low runoff coefficient (1%) promoted sediment deposition. Significant differences were observed in fallout radionuclide concentrations between burned surface soil and channel bank samples (p < 0.05), as well as between burned and unburned sources at the downstream part of the catchment (p < 0.01). The radioactivity concentrations in bed sediments samples were statistically similar (p > 0.05). Source ascription in bed sediments in the middle stream shows that 67% was generated in burned hillslopes, reaching 75% in the downstream part because downstream propagation of the sediment derived from the burned area. Bed sediments were mostly generated in burned hillslopes because of the fire effects on soils and sediment availability, high intensity rainfall and limited contribution of channel banks that are fixed by dry-stone walls. This hydro-sedimentary response indicates an association between driven sediment transport factors and sediment availability, generating an effective slope-to-channel sediment connectivity. Long-term sediment sources monitoring will elucidate if the most effective period of the window of disturbance at catchment scale is further extended (i.e., ≈5 years).

Molecular characterization of lake sediment WEON by Fourier transform ion cyclotron resonance mass spectrometry and its environmental implications.

PubMed

Zhang, Li; Wang, Shengrui; Xu, Yisheng; Shi, Quan; Zhao, Haichao; Jiang, Bin; Yang, Jiachun

2016-12-01

The compositional properties of water-extractable organic nitrogen (WEON) affect its behavior in lake ecosystems. This work is the first comprehensive study using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) for the characterization of the molecular composition of WEON in lake sediment. In sediments of Erhai Lake in China, this study found complex WEON species, with N-containing compounds in the northern, central, and southern regions contributing 34.47%, 42.44%, and 40.6%, respectively, of total compounds. Additionally, a van Krevelen diagram revealed that lignin components were dominant in sediment WEON structures (68% of the total), suggesting terrestrial sources. Furthermore, this study applied ESI-FT-ICR-MS to the examination of the environmental processes of lake sediment WEON on a molecular level. The results indicated that sediment depth impacted WEON composition and geochemical processes. Compared with other ecosystems, the double bond equivalent (DBE) value was apparently lower in Erhai sediment, indicating the presence of relatively fewer and smaller aromatic compounds. In addition, the presence of a large number of N-containing species and abundant oxidized nitrogen functional compounds that were likely to biodegrade may have further increased the potential releasing risk of WEON from Erhai sediment under certain environmental conditions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Characterization of heavy-metal-contaminated sediment by using unsupervised multivariate techniques and health risk assessment.

PubMed

Wang, Yeuh-Bin; Liu, Chen-Wuing; Wang, Sheng-Wei

2015-03-01

This study characterized the sediment quality of the severely contaminated Erjen River in Taiwan by using multivariate analysis methods-including factor analysis (FA), self-organizing maps (SOMs), and positive matrix factorization (PMF)-and health risk assessment. The SOMs classified the dataset with similar heavy-metal-contaminated sediment into five groups. FA extracted three major factors-traditional electroplating and metal-surface processing factor, nontraditional heavy-metal-industry factor, and natural geological factor-which accounted for 80.8% of the variance. The SOMs and FA revealed the heavy-metal-contaminated-sediment hotspots in the middle and upper reaches of the major tributary in the dry season. The hazardous index value for health risk via ingestion was 0.302. PMF further qualified the source apportionment, indicating that traditional electroplating and metal-surface-processing industries comprised 47% of the health risk posed by heavy-metal-contaminated sediment. Contaminants discharged from traditional electroplating and metal-surface-processing industries in the middle and upper reaches of the major tributary must be eliminated first to improve the sediment quality in Erjen River. The proposed assessment framework for heavy-metal-contaminated sediment can be applied to contaminated-sediment river sites in other regions. Copyright © 2014 Elsevier Inc. All rights reserved.

Long-range transport of pollutants to the Falkland Islands and Antarctica: evidence from lake sediment fly ash particle records.

PubMed

Rose, Neil L; Jones, Vivienne J; Noon, Philippa E; Hodgson, Dominic A; Flower, Roger J; Appleby, Peter G

2012-09-18

(210)Pb-dated sediment cores taken from lakes on the Falkland Islands, the South Orkney Islands, and the Larsemann Hills in Antarctica were analyzed for fly ash particles to assess the temporal record of contamination from high temperature fossil-fuel combustion sources. Very low, but detectable, levels were observed in the Antarctic lakes. In the Falkland Island lakes, the record of fly ash extended back to the late-19th century and the scale of contamination was considerably higher. These data, in combination with meteorological, modeling, and fossil-fuel consumption data, indicate most likely sources are in South America, probably Chile and Brazil. Other southern hemisphere sources, notably from Australia, contribute to a background contamination and were more important historically. Comparing southern polar data with the equivalent from the northern hemisphere emphasizes the difference in contamination of the two circumpolar regions, with the Falkland Island sites only having a level of contamination similar to that of northern Svalbard.

Microbial Communities Associated with Phosphorite-bearing Sediments

NASA Astrophysics Data System (ADS)

Zoss, R.; Bailey, J.; Flood, B.; Jones, D. S.

2016-12-01

Phosphorus is a limiting nutrient in the environment and is an important component of many biological molecules. Calcium phosphate mineral deposits known as phosphorites, are also the primary source of P for agriculture. Understanding phosphorite formation may improve management of P resources. However, the processes that mediate calcium phosphate mineral precipitation in certain marine pore waters remain poorly understood. Phosphogenesis occurs in sediments beneath some oceanic upwelling zones that harbor polyphosphate-accumulating giant sulfur bacteria (GSB). These bacteria may concentrate phosphate in sediment pore waters - creating supersaturated conditions with respect to apatite. However, the relationship between microbes and phosphogenesis is not fully resolved. To further study this relationship, we examined microbial communities from two sources: sediment cores recovered from the shelf of the Benguela region, and DNA extracted from washed phosphorites recovered from those same sediments. We used itag and clone library sequencing of the 16S rRNA gene to examine the microbial communities and their relationship with the environment. We found that many of our sediments shared large numbers of phylotypes with one another, and that the same metabolic guilds were represented at localities across the shelf. Sulfur-reducing bacteria and sulfur-oxidizing bacteria were abundant in our datasets. Phylotypes that are known to carry out nitrification and/or anammox (anaerobic ammonia oxidation) were also well-represented. Our phosphorite extraction, however, contained a distinct microbial community from those observed in the modern sediments. We observed both an enrichment of certain common microbial classes and a complete absence of others. These results could represent an ancient microbial assemblage that was present when the apatite precipitated. While these taxa may or may not have contributed to apatite precipitation, several groups represented in the phosphorite dataset have the genetic potential, as determined through the analysis of published genomes, to synthesize, and perhaps accumulate, polyphosphate.

Storm Event Suspended Sediment-Discharge Hysteresis and Controls in Agricultural Watersheds: Implications for Watershed Scale Sediment Management.

PubMed

Sherriff, Sophie C; Rowan, John S; Fenton, Owen; Jordan, Philip; Melland, Alice R; Mellander, Per-Erik; hUallacháin, Daire Ó

2016-02-16

Within agricultural watersheds suspended sediment-discharge hysteresis during storm events is commonly used to indicate dominant sediment sources and pathways. However, availability of high-resolution data, qualitative metrics, longevity of records, and simultaneous multiwatershed analyses has limited the efficacy of hysteresis as a sediment management tool. This two year study utilizes a quantitative hysteresis index from high-resolution suspended sediment and discharge data to assess fluctuations in sediment source location, delivery mechanisms and export efficiency in three intensively farmed watersheds during events over time. Flow-weighted event sediment export was further considered using multivariate techniques to delineate rainfall, stream hydrology, and antecedent moisture controls on sediment origins. Watersheds with low permeability (moderately- or poorly drained soils) with good surface hydrological connectivity, therefore, had contrasting hysteresis due to source location (hillslope versus channel bank). The well-drained watershed with reduced connectivity exported less sediment but, when watershed connectivity was established, the largest event sediment load of all watersheds occurred. Event sediment export was elevated in arable watersheds when low groundcover was coupled with high connectivity, whereas in the grassland watershed, export was attributed to wetter weather only. Hysteresis analysis successfully indicated contrasting seasonality, connectivity and source availability and is a useful tool to identify watershed specific sediment management practices.

Occurrence of fecal-indicator bacteria and protocols for identification of fecal-contamination sources in selected reaches of the West Branch Brandywine Creek, Chester County, Pennsylvania

USGS Publications Warehouse

Cinotto, Peter J.

2005-01-01

The presence of fecal-indicator bacteria indicates the potential presence of pathogens originating from the fecal matter of warm-blooded animals. These pathogens are responsible for numerous human diseases ranging from common diarrhea to meningitis and polio. The detection of fecal-indicator bacteria and interpretation of the resultant data are, therefore, of great importance to water-resource managers. Current (2005) techniques used to assess fecal contamination within the fluvial environment primarily assess samples collected from the water column, either as grab samples or as depth- and (or) width-integrated samples. However, current research indicates approximately 99 percent of all bacteria within nature exist as attached, or sessile, bacteria. Because of this condition, most current techniques for the detection of fecal contamination, which utilize bacteria, assess only about 1 percent of the total bacteria within the fluvial system and are, therefore, problematic. Evaluation of the environmental factors affecting the occurrence and distribution of bacteria within the fluvial system, as well as the evaluation and modification of alternative approaches that effectively quantify the larger population of sessile bacteria within fluvial sediments, will present water-resource managers with more effective tools to assess, prevent, and (or) eliminate sources of fecal contamination within pristine and impaired watersheds. Two stream reaches on the West Branch Brandywine Creek in the Coatesville, Pa., region were studied between September 2002 and August 2003. The effects of sediment particle size, climatic conditions, aquatic growth, environmental chemistry, impervious surfaces, sediment and soil filtration, and dams on observed bacteria concentrations were evaluated. Alternative approaches were assessed to better detect geographic sources of fecal contamination including the use of turbidity as a surrogate for bacteria, the modification and implementation of sandbag bacteria samplers, and the use of optical brighteners. For the purposes of this report, sources of bacteria were defined as geographic locations where elevated concentrations of bacteria are observed within, or expected to enter, the main branch of the West Branch Brandywine Creek. Biologic sources (for example, waterfowl) were noted where applicable; however, no specific study of biologic sources (such as bacterial source tracking) was conducted. Data indicated that specific bacterial populations within fluvial sediments could be related to specific particle-size ranges. This relation is likely the result of the reduced porosity and permeability associated with finer sediments and the ability of specific bacteria to tolerate particular environments. Escherichia coli (E. coli) showed a higher median concentration (2,160 colonies per gram of saturated sediment) in the 0.125 to 0.5-millimeter size range of natural sediments than in other ranges, and enterococcus bacteria showed a higher median concentration (61,830 colonies per gram of saturated sediment) in the 0.062 to 0.25-millimeter size range of natural sediments than in other ranges. There were insufficient data to assess the particle-size relation to fecal coliform bacteria and (or) fecal streptococcus bacteria. Climatic conditions were shown to affect bacteria concentrations in both the water column and fluvial sediments. Drought conditions in 2002 resulted in lower overall bacteria concentrations than the more typically wet year of 2003. E. coli concentrations in fluvial sediment along the Coatesville study reach in 2002 had a median concentration of 92 colonies per gram of saturated sediment; in 2003, the median concentration had risen to 4,752 colonies per gram of saturated sediment. Symbiotic relations between bacteria and aquatic growth were likely responsible for increased bacteria concentrations observed within an impoundment area on the Coatesville study reach. This reach showed evidence of

Contribution of sediment fluxes and transformations to the summer nitrogen budget of an Upper Mississippi River backwater system

USGS Publications Warehouse

James, W.F.; Richardson, W.B.; Soballe, D.M.

2008-01-01

Routing nitrate through backwaters of regulated floodplain rivers to increase retention could decrease loading to nitrogen (N)-sensitive coastal regions. Sediment core determinations of N flux were combined with inflow-outflow fluxes to develop mass balance approximations of N uptake and transformations in a flow-controlled backwater of the Upper Mississippi River (USA). Inflow was the dominant nitrate source (>95%) versus nitrification and varied as a function of source water concentration since flow was constant. Nitrate uptake length increased linearly, while uptake velocity decreased linearly, with increasing inflow concentration to 2 mg l-1, indicating limitation of N uptake by loading. N saturation at higher inflow concentration coincided with maximum uptake capacity, 40% uptake efficiency, and an uptake length 2 times greater than the length of the backwater. Nitrate diffusion and denitrification in sediment accounted for 27% of the backwater nitrate retention, indicating that assimilation by other biota or denitrification on other substrates were the dominant uptake mechanisms. Ammonium export from the backwater was driven by diffusive efflux from the sediment. Ammonium increased from near zero at the inflow to a maximum mid-lake, then declined slightly toward the outflow due to uptake during transport. Ammonium export was small compared to nitrate retention. ?? 2007 Springer Science+Business Media B.V.

Lake sedimentary DNA accurately records 20th Century introductions of exotic conifers in Scotland.

PubMed

Sjögren, Per; Edwards, Mary E; Gielly, Ludovic; Langdon, Catherine T; Croudace, Ian W; Merkel, Marie Kristine Føreid; Fonville, Thierry; Alsos, Inger Greve

2017-01-01

Sedimentary DNA (sedDNA) has recently emerged as a new proxy for reconstructing past vegetation, but its taphonomy, source area and representation biases need better assessment. We investigated how sedDNA in recent sediments of two small Scottish lakes reflects a major vegetation change, using well-documented 20 th Century plantations of exotic conifers as an experimental system. We used next-generation sequencing to barcode sedDNA retrieved from subrecent lake sediments. For comparison, pollen was analysed from the same samples. The sedDNA record contains 73 taxa (mainly genus or species), all but one of which are present in the study area. Pollen and sedDNA shared 35% of taxa, which partly reflects a difference in source area. More aquatic taxa were recorded in sedDNA, whereas taxa assumed to be of regional rather than local origin were recorded only as pollen. The chronology of the sediments and planting records are well aligned, and sedDNA of exotic conifers appears in high quantities with the establishment of plantations around the lakes. SedDNA recorded other changes in local vegetation that accompanied afforestation. There were no signs of DNA leaching in the sediments or DNA originating from pollen. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Geochemical constraints on possible subduction components in lavas of Mayon and Taal Volcanoes, Southern Luzon, Philippines

USGS Publications Warehouse

Castillo, P.R.; Newhall, C.G.

2004-01-01

Mayon is the most active volcano along the east margin of southern Luzon, Philippines. Petrographic and major element data indicate that Mayon has produced a basaltic to andesitic lava series by fractional crystallization and magma mixing. Trace element data indicate that the parental basalts came from a heterogeneous mantle source. The unmodified composition of the mantle wedge is similar to that beneath the Indian Ocean. To this mantle was added a subduction component consisting of melt from subducted pelagic sediment and aqueous fluid dehydrated from the subducted basaltic crust. Lavas from the highly active Taal Volcano on the west margin of southern Luzon are compositionally more variable than Mayon lavas. Taal lavas also originated from a mantle wedge metasomatized by aqueous fluid dehydrated from the subducted basaltic crust and melt plus fluid derived from the subducted terrigenous sediment. More sediment is involved in the generation of Taal lavas. Lead isotopes argue against crustal contamination. Some heterogeneity of the unmodified mantle wedge and differences in whether the sediment signature is transferred into the lava source through an aqueous fluid or melt phase are needed to explain the regional compositional variation of Philippine arc lavas. ?? Oxford University Press 2004; all rights reserved.

Occurrence and potential sources of pyrethroid insecticides in stream sediments from seven U.S. metropolitan areas

USGS Publications Warehouse

Kuivila, Kathryn; Hladik, Michelle; Ingersoll, Christopher G.; Kemble, Nile E.; Moran, Patrick W.; Calhoun, Daniel L.; Nowell, Lisa H.; Gilliom, Robert J.

2012-01-01

A nationally consistent approach was used to assess the occurrence and potential sources of pyrethroid insecticides in stream bed sediments from seven metropolitan areas across the United States. One or more pyrethroids were detected in almost half of the samples, with bifenthrin detected the most frequently (41%) and in each metropolitan area. Cyhalothrin, cypermethrin, permethrin, and resmethrin were detected much less frequently. Pyrethroid concentrations and Hyalella azteca mortality in 28-d tests were lower than in most urban stream studies. Log-transformed total pyrethroid toxic units (TUs) were significantly correlated with survival and bifenthrin was likely responsible for the majority of the observed toxicity. Sampling sites spanned a wide range of urbanization and log-transformed total pyrethroid concentrations were significantly correlated with urban land use. Dallas/Fort Worth had the highest pyrethroid detection frequency (89%), the greatest number of pyrethroids (4), and some of the highest concentrations. Salt Lake City had a similar percentage of detections but only bifenthrin was detected and at lower concentrations. The variation in pyrethroid concentrations among metropolitan areas suggests regional differences in pyrethroid use and transport processes. This study shows that pyrethroids commonly occur in urban stream sediments and may be contributing to sediment toxicity across the country.

Sources and Distribution of Organic Matter in Sediments of the Louisiana Continental Shelf

EPA Science Inventory

Both riverine and marine sources of organic matter (OM) contribute to sediment organic pools, and either source can contribute significantly to sediment accumulation, burial, and remineralization rates on river dominated continental shelf systems. For the Louisiana continental sh...

Subjective Mapping of Dust-Emission Sources by Using MODIS Imagery

DTIC Science & Technology

2017-05-01

within the inset of Panel A. Panel A is a True Color image that depicts white clouds against a brown landscape; a bird’s eye representation of Earth...shows the location of the Hamun dry lakes, which are an important dust source in the region. The enlarged image box in the top right depicts the...Bacon and McDonald 2016). For example, dry lakebeds filled with unconsolidated ERDC/CRREL TR-17-8 4 fine-grained sediments are commonly

Quantifying ratios of suspended sediment sources in forested headwater streams following timber-harvesting operations

NASA Astrophysics Data System (ADS)

Rachels, A. A.; Bladon, K. D.; Bywater-Reyes, S.

2017-12-01

Historically, timber-harvesting has increased fine sediment inputs to streams due to increased hillslope and streambank erosion and mass wasting along roads. However, under modern best management practices, the relative importance and variability of these sources is poorly understood. We present preliminary results from an ongoing study investigating the primary sources of suspended sediment in Oregon Coast Range streams influenced by timber harvesting. We instrumented two catchments, Enos Creek (harvested 2016) and Scheele Creek (reference) in fall 2016. Phillips samplers (5-6 per catchment) have been deployed longitudinally down the streams to enable robust characterization of suspended sediments—the collected samples integrate the chemical signatures of upstream sediment exports. We will collect samples monthly over 2 wet seasons and return to the laboratory to analyze the sediment using source fingerprinting approaches. The fingerprinting technique compares the chemical properties of stream sediment samples with the chemical properties of potential source areas, including 1) roads, 2) stream banks, and 3) hillslopes. To design a robust model for sediment-source identification, different types of chemical data are required—we will analyze sediment samples using a combination of: a) stable isotopes and C/N ratios (i.e., δ15N, δ13C, and C/N), b) geochemistry (Fe, K, and Ca), and c) radiogenic isotopes (137Cs and 210Pb). At the harvested site, the C/N ratios of the streambanks (17.9 ± 3.8) and the hillslopes (26.4 ± 4.8) are significantly different from one another (p = .016). C/N ratios of the suspended sediment (20.5 ± 2.0) are intermediate values between potential endmembers and behave conservatively with transport. The C/N ratios of the suspended sediment appear unaffected by roads (18.9 ± 8.7) along specific sections of the stream, suggesting that roads are not a primary sediment contributor. Under this assumption, the suspended sediment is, on average, comprised of 69.5% streambank sediments and 30.5% hillslope sediments. Additional analyses are required (and in progress) to support these implications and to further interpret the importance and variability of suspended sediment sources through both space (from head to outlet) and time.

Heavy Minerals in Palaeotsunami Deposits: Assemblages, Spatial Distribution and Microtextural Imprints

NASA Astrophysics Data System (ADS)

Costa, P. J.; Andrade, C.; Cascalho, J.; Dawson, A. G.; Freitas, M. C.; Dawson, S.; Mahaney, W. C.

2013-12-01

The sedimentological record provides a database useful to characterize and evaluate recurrence of tsunamis, which contributes to assessing the vulnerability of any coastal area to this natural hazard. Thus, the enhancement of our ability to recognize signatures specific of tsunami activity imprinted in coastal sediments is of unquestionable interest. The aim of this study is to discuss and further contribute to the improvement of the characterization of (palaeo)tsunami deposits, and of their source materials. With that purpose the vertical and horizontal distribution of heavy mineral (HM) assemblages in sand-sized tsunamigenic deposits from six locations exhibiting a varied suite of coastal contexts and corresponding to three inundation events -(8200yrs BP - Scotland, 1500yrs BP - Scotland, AD 1755 - Portugal) were studied. In general, results from paleotsunami sediments show that site-specific effects prevent 'blind' extrapolations; instead, the bulk of the HM assemblages reflect local specificities related with the regional geology. In the Portuguese sediments (Martinhal, Boca do Rio and Salgados) ca. 90% of the non-opaque HM population consists of tourmaline, andalusite and staurolite, whereas amphiboles are dominant (> 90% of the assemblage) in the Scottish sediments (Scasta Voe, Basta Voe and Whale Firth). Principal Components Analyses revealed that the first 2 components explain more than 2/3 of the total variance found in each site. Horizontal and vertical variations in the HM were observed and especially in the heavier mineral species. Although, in some of the studied cases, the deposit was macroscopically massive, data on HM allowed the distinction of backwash layer(s), related with incorporation of inland materials. In what concerns sources, results indicate that palaeotsunami sediments share fewer compositional similarities with present-day inshore and offshore materials and more resemblances with dune and beach sediment, thus indicating these as the more likely source areas. In addition, preliminary results of SEM analysis of microtextural features imprinted in the surface of heavy minerals indicate an increase in the number of mechanical marks in the surface of palaeotsunami grains when compared with potential source materials (beach, dune, inshore and offshore samples). This work further reveals the potential to use heavy minerals as a complementary sedimentological tool in the study of palaeotsunami deposits.

Can land use intensification in the Mallee, Australia increase the supply of soluble iron to the Southern Ocean?

PubMed Central

Bhattachan, Abinash; D'Odorico, Paolo

2014-01-01

The supply of soluble iron through atmospheric dust deposition limits the productivity of the Southern Ocean. In comparison to the Northern Hemisphere, the Southern Hemisphere exhibits low levels of dust activity. However, given their proximity to the Southern Ocean, dust emissions from continental sources in the Southern Hemisphere could have disproportionate impact on ocean productivity. Australia is the largest source of dust in the Southern Hemisphere and aeolian transport of dust has major ecological, economic and health implications. In the Mallee, agriculture is a major driver of dust emissions and dust storms that affect Southeastern Australia. In this study, we assess the dust generating potential of the sediment from the Mallee, analyze the sediment for soluble iron content and determine the likely depositional region of the emitted dust. Our results suggest that the Mallee sediments have comparable dust generating potential to other currently active dust sources in the Southern Hemisphere and the dust-sized fraction is rich in soluble iron. Forward trajectory analyses show that this dust will impact the Tasman Sea and the Australian section of the Southern Ocean. This iron-rich dust could stimulate ocean productivity in future as more areas are reactivated as a result of land-use and droughts. PMID:25109703

Predicting geomorphically-induced flood risk for the Nepalese Terai communities

NASA Astrophysics Data System (ADS)

Dingle, Elizabeth; Creed, Maggie; Attal, Mikael; Sinclair, Hugh; Mudd, Simon; Borthwick, Alistair; Dugar, Sumit; Brown, Sarah

2017-04-01

Rivers sourced from the Himalaya irrigate the Indo-Gangetic Plain via major river networks that support 10% of the global population. However, many of these rivers are also the source of devastating floods. During the 2014 Karnali River floods in west Nepal, the Karnali rose to around 16 m at Chisapani (where it enters the Indo-Gangetic Plain), 1 m higher than the previous record in 1983; the return interval for this event was estimated to be 1000 years. Flood risk may currently be underestimated in this region, primarily because changes to the channel bed are not included when identifying areas at risk of flooding from events of varying recurrence intervals. Our observations in the field, corroborated by satellite imagery, show that river beds are highly mobile and constantly evolve through each monsoon. Increased bed levels due to sediment aggradation decreases the capacity of the river, increasing significantly the risk of devastating flood events; we refer to these as 'geomorphically-induced floods'. Major, short-lived episodes of sediment accumulation in channels are caused by stochastic variability in sediment flux generated by storms, earthquakes and glacial outburst floods from upstream parts of the catchment. Here, we generate a field-calibrated, geomorphic flood risk model for varying upstream scenarios, and predict changing flood risk for the Karnali River. A numerical model is used to carry out a sensitivity analysis of changes in channel geometry (particularly aggradation or degradation) based on realistic flood scenarios. In these scenarios, water and sediment discharge are varied within a range of plausible values, up to extreme sediment and water fluxes caused by widespread landsliding and/or intense monsoon precipitation based on existing records. The results of this sensitivity analysis will be used to inform flood hazard maps of the Karnali River floodplain and assess the vulnerability of the populations in the region.

Widespread legacy brine contamination from oil production reduces survival of chorus frog larvae

USGS Publications Warehouse

Hossack, Blake R.; Puglis, Holly J.; Battaglin, William A.; Anderson, Chauncey; Honeycutt, Richard; Smalling, Kelly

2017-01-01

Advances in drilling techniques have facilitated a rapid increase in hydrocarbon extraction from energy shales, including the Williston Basin in central North America. This area overlaps with the Prairie Pothole Region, a region densely populated with wetlands that provide numerous ecosystem services. Historical (legacy) disposal practices often released saline co-produced waters (brines) with high chloride concentrations, affecting wetland water quality directly or persisting in sediments. Despite the potential threat of brine contamination to aquatic habitats, there has been little research into its ecological effects. We capitalized on a gradient of legacy brine-contaminated wetlands in northeast Montana to conduct laboratory experiments to assess variation in survival of larval Boreal Chorus Frogs (Pseudacris maculata) reared on sediments from 3 local wetlands and a control source. To help provide environmental context for the experiment, we also measured chloride concentrations in 6 brine-contaminated wetlands in our study area, including the 2 contaminated sites used for sediment exposures. Survival of frog larvae during 46- and 55-day experiments differed by up to 88% among sediment sources (Site Model) and was negatively correlated with potential chloride exposure (Chloride Model). Five of the 6 contaminated wetlands exceeded the U.S. EPA acute benchmark for chloride in freshwater (860 mg/L) and all exceeded the chronic benchmark (230 mg/L). However, the Wetland Site model explained more variation in survival than the Chloride Model, suggesting that chloride concentration alone does not fully reflect the threat of contamination to aquatic species. Because the profiles of brine-contaminated sediments are complex, further surveys and experiments are needed across a broad range of conditions, especially where restoration or remediation actions have reduced brine-contamination. Information provided by this study can help quantify potential ecological threats and help land managers prioritize conservation strategies as part of responsible and sustainable energy development.

Provenance Analysis of Upper Cretaceous - Paleogene Sandstones in the Foreland Basin System of the Tansen Unit, Central Nepal

NASA Astrophysics Data System (ADS)

Neupane, B.; Ju, Y.; Allen, C.

2016-12-01

The continental deposits foreland basin of Central Nepal, Amile Formation, Bhainskati Formation and Dumri Formation (Tansen unit) are the key region for provenance analysis, preserved almost complete sedimentation history of tectonic collision of Indian and Asian plates. Samples from two field traverses are examined petrographically and through zircon U-Pb dating, one traverse through the Tansen Group, and another through its potential source rocks, the Higher and Tethys Himalaya. The Tansen Group ages are well known through fossil assemblages. We examine sandstone-bearing units of the Tansen Group, the upper 3 of 5 Formations. The optical petrography data and resulting classify Tansen sediments as "recycled orogenic" and "Quartzose recycled", indicating that Indian cratonal sediments as the likely source of sediments for the Amile Formations, and the Tethyan Himalaya as the source for the Bhainskati Formation, and both the Tethys and Higher Himalaya as the major sources for the Dumri Formation. The Cretaceous to Paleocene pre-collisional Amile Formation is dominated by a broad 1830 Ma age peak with neither Paleozoic nor Neoproterozic zircons, but hosts a significant proportion (23%) of syndepositional Cretaceous zircons (121 to 105 Ma) indicative of nearby Cretaceous volcanism at that time. Therefore, the rare volcanic fragments in detritus of Amile Formation were derived from the Rajmahal Volcanic Province defining the middle to late Cretaceous depositional age. The other Formations of the Tansen Group are more similar to Tethys units than to Higher Himalaya. Further, the 23+/-1 Ma zircons in two of the crystalline Higher Himalaya units suggest that they could not have been exposed until at or after this time.

Priority substances in sediments of the "Carska Bara" special nature reserve, a natural scientific research area on the UNESCO list.

PubMed

Grba, Nenad; Krčmar, Dejan; Isakovski, Marijana Kragulj; Jazić, Jelena Molnar; Maletić, Snežana; Pešić, Vesna; Dalmacija, Božo

2016-11-01

Surface sediments were subject to systematic long-term monitoring (2002-2014) in the Republic of Serbia (Province of Vojvodina). Eight heavy metals (Ni, Zn, Cd, Cr, Cu, Pb, As and Hg), mineral oils (total petroleum hydrocarbons), 16 EPA PAHs, selected pesticides and polychlorinated biphenyls (PCB) were monitored. As part of this research, this paper presents a sediment contamination spatial and temporal trend study of diverse pollution sources and the ecological risk status of the alluvial sediments of Carska Bara at three representative sampling sites (S1S3), in order to establish the status of contamination and recommend substances of interest for more widespread future monitoring. Multivariate statistical methods including factor analysis of principal component analysis (PCA/FA), Pearson correlation and several synthetic indicators were used to evaluate the extent and origin of contamination (anthropogenic or natural, geogenic sources) and potential ecological risks. Hg, Cd, As, mineral oils and PAHs (dominated by dibenzo(a,h)anthracene and benzo(a)pyrene, contributing 85.7% of the total) are derived from several anthropogenic sources, whereas Ni, Cu, Cr and Zn are convincingly of geogenic origin, and exhibit dual origins. Cd and Hg significantly raise the levels of potential ecological risk for all sampling locations, demonstrating the effect of long-term bioaccumulation and biomagnification. Pb is isolated from the other parameters, implying unique sources. This research suggests four heavy metals (Zn, Cr, Cu and As) and dibenzo(a,h)anthracene be added to the list of priority pollutants within the context of the application of the European Water Framework Directive (WFD), in accordance with significant national and similar environmental data from countries in the region. Copyright © 2016 Elsevier Ltd. All rights reserved.

A record of Appalachian denudation in postrift Mesozoic and Cenozoic sedimentary deposits of the U.S. Middle Atlantic continental margin

USGS Publications Warehouse

Poag, C.W.; Sevon, W.D.

1989-01-01

The complex interplay between source-terrain uplift, basin subsidence, paleoclimatic shifts, and sea-level change, left an extensive sedimentary record in the contiguous offshore basins of the U.S. middle Atlantic margin (Salisbury Embayment, Baltimore Canyon Trough, and Hatteras Basin). Isopach maps of 23 postrift (Lower Jurassic to Quaternary) a allostratigraphic units, coupled with a revised stratigraphic framework, reveal that tectonism, by regulating sediment supply (accumulation rate), dominated the interplay of forcing mechanisms. Tectonic pulses are evidenced by abruptly accelerated sediment accumulation, marked latitudinal shifts in the location of depocenters, and regional changes in lithofacies. Relatively rapid tectonic subsidence during the Early and Middle Jurassic history of the basins may have enhanced sediment accumulation rates. Beginning in the Late Jurassic, however, subsidence rates decreased significantly, though occasional short pulses of subsidence may have effected relative sea-level rises. Sea-level change heavily influenced the distribution and redistribution of sediments one they reached the basins, and paleoclimate regulated the relative abundance of carbonates and evaporites in the basins. We conclude that source terrains of the central Appalachian Highlands were tectonically uplifted, intensely weathered, and rapidly eroded three times since the Late Triassic: (1) Early to Middle Jurassic (Aalenian to Callovian); (2) mid-Early Cretaceous (Barremian); and (3) Late Cenozoic (Middle Miocene). Intervals of tectonic quiescence following these three tectonic pulses provided conditions suitable for the formation of regional erosion surfaces, geomorphic features commonly reported to characterize the central Appalachian Highlands. This series of three, irregularly spaced, tectonic/quiescent cycles does not, however, match the traditional four-cycle concept of post-Triassic Appalachian "peneplanation". ?? 1989.

Eutrophication and carbon sources in Chesapeake Bay over the last 2700 yr: Human impacts in context

USGS Publications Warehouse

Bratton, J.F.; Colman, Steven M.; Seal, R.R.

2003-01-01

To compare natural variability and trends in a developed estuary with human-influenced patterns, stable isotope ratios (δ13C and δ15N) were measured in sediments from five piston cores collected in Chesapeake Bay. Mixing of terrestrial and algal carbon sources primarily controls patterns of δ13Corg profiles, so this proxy shows changes in estuary productivity and in delivery of terrestrial carbon to the bay. Analyses of δ15N show periods when oxygen depletion allowed intense denitrification and nutrient recycling to develop in the seasonally stratified water column, in addition to recycling taking place in surficial sediments. These conditions produced 15N-enriched (heavy) nitrogen in algal biomass, and ultimately in sediment. A pronounced increasing trend in δ15N of +4‰ started in about A.D. 1750 to 1800 at all core sites, indicating greater eutrophication in the bay and summer oxygen depletion since that time. The timing of the change correlates with the advent of widespread land clearing and tillage in the watershed, and associated increases in erosion and sedimentation. Isotope data show that the region has experienced up to 13 wet-dry cycles in the last 2700 yr. Relative sea-level rise and basin infilling have produced a net freshening trend overprinted with cyclic climatic variability. Isotope data also constrain the relative position of the spring productivity maximum in Chesapeake Bay and distinguish local anomalies from sustained changes impacting large regions of the bay. This approach to reconstructing environmental history should be generally applicable to studies of other estuaries and coastal embayments impacted by watershed development.

Persistence of deeply sourced iron in the Pacific Ocean

PubMed Central

Horner, Tristan J.; Williams, Helen M.; Hein, James R.; Saito, Mak A.; Burton, Kevin W.; Halliday, Alex N.; Nielsen, Sune G.

2015-01-01

Biological carbon fixation is limited by the supply of Fe in vast regions of the global ocean. Dissolved Fe in seawater is primarily sourced from continental mineral dust, submarine hydrothermalism, and sediment dissolution along continental margins. However, the relative contributions of these three sources to the Fe budget of the open ocean remains contentious. By exploiting the Fe stable isotopic fingerprints of these sources, it is possible to trace distinct Fe pools through marine environments, and through time using sedimentary records. We present a reconstruction of deep-sea Fe isotopic compositions from a Pacific Fe−Mn crust spanning the past 76 My. We find that there have been large and systematic changes in the Fe isotopic composition of seawater over the Cenozoic that reflect the influence of several, distinct Fe sources to the central Pacific Ocean. Given that deeply sourced Fe from hydrothermalism and marginal sediment dissolution exhibit the largest Fe isotopic variations in modern oceanic settings, the record requires that these deep Fe sources have exerted a major control over the Fe inventory of the Pacific for the past 76 My. The persistence of deeply sourced Fe in the Pacific Ocean illustrates that multiple sources contribute to the total Fe budget of the ocean and highlights the importance of oceanic circulation in determining if deeply sourced Fe is ever ventilated at the surface. PMID:25605900

Persistence of deeply sourced iron in the Pacific Ocean.

PubMed

Horner, Tristan J; Williams, Helen M; Hein, James R; Saito, Mak A; Burton, Kevin W; Halliday, Alex N; Nielsen, Sune G

2015-02-03

Biological carbon fixation is limited by the supply of Fe in vast regions of the global ocean. Dissolved Fe in seawater is primarily sourced from continental mineral dust, submarine hydrothermalism, and sediment dissolution along continental margins. However, the relative contributions of these three sources to the Fe budget of the open ocean remains contentious. By exploiting the Fe stable isotopic fingerprints of these sources, it is possible to trace distinct Fe pools through marine environments, and through time using sedimentary records. We present a reconstruction of deep-sea Fe isotopic compositions from a Pacific Fe-Mn crust spanning the past 76 My. We find that there have been large and systematic changes in the Fe isotopic composition of seawater over the Cenozoic that reflect the influence of several, distinct Fe sources to the central Pacific Ocean. Given that deeply sourced Fe from hydrothermalism and marginal sediment dissolution exhibit the largest Fe isotopic variations in modern oceanic settings, the record requires that these deep Fe sources have exerted a major control over the Fe inventory of the Pacific for the past 76 My. The persistence of deeply sourced Fe in the Pacific Ocean illustrates that multiple sources contribute to the total Fe budget of the ocean and highlights the importance of oceanic circulation in determining if deeply sourced Fe is ever ventilated at the surface.

Standard operating procedures for collection of soil and sediment samples for the Sediment-bound Contaminant Resiliency and Response (SCoRR) strategy pilot study

USGS Publications Warehouse

Fisher, Shawn C.; Reilly, Timothy J.; Jones, Daniel K.; Benzel, William M.; Griffin, Dale W.; Loftin, Keith A.; Iwanowicz, Luke R.; Cohl, Jonathan A.

2015-12-17

An understanding of the effects on human and ecological health brought by major coastal storms or flooding events is typically limited because of a lack of regionally consistent baseline and trends data in locations proximal to potential contaminant sources and mitigation activities, sensitive ecosystems, and recreational facilities where exposures are probable. In an attempt to close this gap, the U.S. Geological Survey (USGS) has implemented the Sediment-bound Contaminant Resiliency and Response (SCoRR) strategy pilot study to collect regional sediment-quality data prior to and in response to future coastal storms. The standard operating procedure (SOP) detailed in this document serves as the sample-collection protocol for the SCoRR strategy by providing step-by-step instructions for site preparation, sample collection and processing, and shipping of soil and surficial sediment (for example, bed sediment, marsh sediment, or beach material). The objectives of the SCoRR strategy pilot study are (1) to create a baseline of soil-, sand-, marsh sediment-, and bed-sediment-quality data from sites located in the coastal counties from Maine to Virginia based on their potential risk of being contaminated in the event of a major coastal storm or flooding (defined as Resiliency mode); and (2) respond to major coastal storms and flooding by reoccupying select baseline sites and sampling within days of the event (defined as Response mode). For both modes, samples are collected in a consistent manner to minimize bias and maximize quality control by ensuring that all sampling personnel across the region collect, document, and process soil and sediment samples following the procedures outlined in this SOP. Samples are analyzed using four USGS-developed screening methods—inorganic geochemistry, organic geochemistry, pathogens, and biological assays—which are also outlined in this SOP. Because the SCoRR strategy employs a multi-metric approach for sample analyses, this protocol expands upon and reconciles differences in the sample collection protocols outlined in the USGS “National Field Manual for the Collection of Water-Quality Data,” which should be used in conjunction with this SOP. A new data entry and sample tracking system also is presented to ensure all relevant data and metadata are gathered at the sample locations and in the laboratories.

Seafloor environments in Cape Cod Bay, a large coastal embayment

USGS Publications Warehouse

Knebel, H.J.; Rendigs, R. R.; List, J.H.; Signell, R.P.

1996-01-01

Cape Cod Bay is a glacial, semi-enclosed embayment that has a patchy distribution of modern seafloor sedimentary environments of erosion or nondeposition, deposition, and sediment reworking. Sidescan-sonar records and supplemental bathymetric, sedimentary, subbottom, and physical- oceanographic data indicate that the characteristics and distribution of these three categories of bottom environments are controlled by a combination of geologic and oceanographic processes that range from episodic to long-term and from regional to local. (1) Environments of erosion or nondeposition comprise exposares of bedrock, glacial drift, and coarse lag deposits that contain sediments (where present) ranging from boulder fields to gravelly coarse-to-medium sands. These environments are dominant on the shallow margins of the bay (water depths <30 m) where they reflect sediment resuspension, winnowing, and transport during modern northerly storms. (2) Environments of deposition are blanketed by fine-grained sediments ranging from muds to muddy fine sands. These environments are dominant across the floor of the central basin (water depths= 30-60 m) where fine- grained sediments (derived from regional and local sources and emplaced primarily during episodic wind- and density-driven flow) settle through the water column and accumulate under weak bottom currents during nonstorm conditions. (3) Environments of sediment reworking contain patches with diverse textures ranging from gravelly sands to muds. These environments occupy much of the transitional slopes between the margins and the basin floor and reflect a combination of erosion and deposition. The patchy distribution of sedimentary environments within the bay reflects not only regional changes in processes between the margins and the basin but local changes within each part of the bay as well. Small-scale patchiness is caused by local changes in the strengths of wave- and wind-driven currents and (on the margins) by local variations in the supply of fine-grained sediments. This study indicates areas within Cape Cod Bay where fine-grained sediments and associated contaminants are likely to be either moved or deposited. It also provides a guide to the locations and variability of benthic habitats.

Seafloor environments in Cape Cod Bay, a large coastal embayment

USGS Publications Warehouse

Knebel, H.J.; Rendigs, R. R.; List, J.H.; Signell, Richard P.

1996-01-01

Cape Cod Bay is a glacial, semi-enclosed embayment that has a patchy distribution of modern seafloor sedimentary environments of erosion or nondeposition, deposition, and sediment reworking. Sidescan-sonar records and supplemental bathymetric, sedimentary, subbottom, and physical-oceanographic data indicate that the characteristics and distribution of these three categories of bottom environments are controlled by a combination of geologic and oceanographic processes that range from episodic to long-term and from regional to local. (1) Environments of erosion or nondeposition comprise exposures of bedrock, glacial drift, and coarse lag deposits that contain sediments (where present) ranging from boulder fields to gravelly coarse-to-medium sands. These environments are dominant on the shallow margins of the bay (water depths < 30 m) where they reflect sediment resuspension, winnowing, and transport during modern northerly storms. (2) Environments of deposition are blanketed by fine-grained sediments ranging from muds to muddy fine sands. These environments are dominant across the floor of the central basin (water depths = 30–60 m) where fine-grained sediments (derived from regional and local sources and emplaced primarily during episodic wind- and density-driven flow) settle through the water column and accumulate under weak bottom currents during nonstorm conditions. (3) Environments of sediment reworking contain patches with diverse textures ranging from gravelly sands to muds. These environments occupy much of the transitional slopes between the margins and the basin floor and reflect a combination of erosion and deposition.The patchy distribution of sedimentary environments within the bay reflects not only regional changes in processes between the margins and the basin but local changes within each part of the bay as well. Small-scale patchiness is caused by local changes in the strengths of wave- and wind-driven currents and (on the margins) by local variations in the supply of fine-grained sediments.This study indicates areas within Cape Cod Bay where fine-grained sediments and associated contaminants are likely to be either moved or deposited. It also provides a guide to the locations and variability of benthic habitats.

Coal-tar-based sealcoated pavement: a major PAH source to urban stream sediments.

PubMed

Witter, Amy E; Nguyen, Minh H; Baidar, Sunil; Sak, Peter B

2014-02-01

We used land-use analysis, PAH concentrations and assemblages, and multivariate statistics to identify sediment PAH sources in a small (~1303 km(2)) urbanizing watershed located in South-Central, Pennsylvania, USA. A geographic information system (GIS) was employed to quantify land-use features that may serve as PAH sources. Urban PAH concentrations were three times higher than rural levels, and were significantly and highly correlated with combined residential/commercial/industrial land use. Principal components analysis (PCA) was used to group sediments with similar PAH assemblages, and correlation analysis compared PAH sediment assemblages to common PAH sources. The strongest correlations were observed between rural sediments (n = 7) and coke-oven emissions sources (r = 0.69-0.78, n = 5), and between urban sediments (n = 22) and coal-tar-based sealcoat dust (r = 0.94, n = 47) suggesting that coal-tar-based sealcoat is an important urban PAH source in this watershed linked to residential and commercial/industrial land use. Copyright © 2013 Elsevier Ltd. All rights reserved.

The response of source-bordering aeolian dunefields to sediment-supply changes 1: Effects of wind variability and river-valley morphodynamics

USGS Publications Warehouse

Sankey, Joel B.; Kasprak, Alan; Caster, Joshua; East, Amy; Fairley, Helen C.

2018-01-01

Source-bordering dunefields (SBDs), which are primarily built and maintained with river-derived sediment, are found in many large river valleys and are currently impacted by changes in sediment supply due to climate change, land use changes, and river regulation. Despite their importance, a physically based, applied approach for quantifying the response of SBDs to changes in sediment supply does not exist. To address this knowledge gap, here we develop an approach for quantifying the geomorphic responses to sediment-supply alteration based on the interpretation of dunefield morphodynamics from geomorphic change detection and wind characteristics. We use the approach to test hypotheses about the response of individual dunefields to variability in sediment supply at three SBDs along the Colorado River in Grand Canyon, Arizona, USA during the 11 years between 2002 and 2013 when several river floods rebuilt some river sandbars and channel margin deposits that serve as sediment source areas for the SBDs. We demonstrate that resupply of fluvially sourced aeolian sediment occurred at one of the SBDs, but not at the other two, and attribute this differential response to site-specific variability in geomorphology, wind, and sediment source areas. The approach we present is applied in a companion study to shorter time periods with high-resolution topographic data that bracket individual floods in order to infer the resupply of fluvially sourced aeolian sediment to SBDs by managed river flows. Such an applied methodology could also be useful for measuring sediment connectivity and anthropogenic alterations of connectivity in other coupled fluvial-aeolian environments.

The response of source-bordering aeolian dunefields to sediment-supply changes 1: Effects of wind variability and river-valley morphodynamics

NASA Astrophysics Data System (ADS)

Sankey, Joel B.; Kasprak, Alan; Caster, Joshua; East, Amy E.; Fairley, Helen C.

2018-06-01

Source-bordering dunefields (SBDs), which are primarily built and maintained with river-derived sediment, are found in many large river valleys and are currently impacted by changes in sediment supply due to climate change, land use changes, and river regulation. Despite their importance, a physically based, applied approach for quantifying the response of SBDs to changes in sediment supply does not exist. To address this knowledge gap, here we develop an approach for quantifying the geomorphic responses to sediment-supply alteration based on the interpretation of dunefield morphodynamics from geomorphic change detection and wind characteristics. We use the approach to test hypotheses about the response of individual dunefields to variability in sediment supply at three SBDs along the Colorado River in Grand Canyon, Arizona, USA during the 11 years between 2002 and 2013 when several river floods rebuilt some river sandbars and channel margin deposits that serve as sediment source areas for the SBDs. We demonstrate that resupply of fluvially sourced aeolian sediment occurred at one of the SBDs, but not at the other two, and attribute this differential response to site-specific variability in geomorphology, wind, and sediment source areas. The approach we present is applied in a companion study to shorter time periods with high-resolution topographic data that bracket individual floods in order to infer the resupply of fluvially sourced aeolian sediment to SBDs by managed river flows. Such an applied methodology could also be useful for measuring sediment connectivity and anthropogenic alterations of connectivity in other coupled fluvial-aeolian environments.

Lead isotopes tracing the life cycle of a catchment: From source rock via weathering to human impact

NASA Astrophysics Data System (ADS)

Negrel, P. J.; Petelet-Giraud, E.; Guerrot, C.; Millot, R.

2015-12-01

Chemical weathering of rocks involves consumption of CO2, a greenhouse gas with a strong influence on climate. Among rocks exposed to weathering, basalt plays a major role in the carbon cycle as it is more easily weathered than other crystalline silicate rocks. This means that basalt weathering acts as a major atmospheric CO2 sink. The present study investigated the lead isotopes in rock, soil and sediment for constraining the life cycle of a catchment, covering source rocks, erosion processes and products, and anthropogenic activities. For this, we investigated the Allanche river drainage basin in the Massif Central, the largest volcanic areas in France, that offers opportunities for selected geochemical studies since it drains a single type of virtually unpolluted volcanic rock, with agricultural activity increasing downstream. Soil and sediment are derived exclusively from basalt weathering, and their chemistry, coupled to isotope tracing, should shed light on the behavior of chemical species during weathering from parental bedrock. Bedrock samples of the basin, compared to regional bedrock of the volcanic province, resulted from a complex history and multiple mantle reservoir sources and mixing. Regarding soils and sediments, comparison of Pb and Zr normalized to mobile K shows a linear evolution of weathering processes, whereby lead enrichment from atmospheric deposition is the other major contributor. Lead-isotope ratios showed that most of the lead budget in sediment and soil results from bedrock weathering with an influence of past mining and mineral processing of ores in the Massif Central, and deposition of lead-rich particles from gasoline combustion, but no lead input from agricultural activity. A classic box model was used to investigate the dynamics of sediment transfer at the catchment scale, the lead behavior in the continuum bedrock-soil-sediment and the historical evolution of anthropogenic aerosol emissions.

Hydrogen isotope fractionation in leaf waxes in the Alaskan Arctic tundra

NASA Astrophysics Data System (ADS)

Daniels, William C.; Russell, James M.; Giblin, Anne E.; Welker, Jeffrey M.; Klein, Eric S.; Huang, Yongsong

2017-09-01

Leaf wax hydrogen isotopes (δDwax) are increasingly utilized in terrestrial paleoclimate research. Applications of this proxy must be grounded by studies of the modern controls on δDwax, including the ecophysiological controls on isotope fractionation at both the plant and landscape scales. Several calibration studies suggest a considerably smaller apparent fractionation between source water and waxes (εapp) at high latitudes relative to temperate or tropical locations, with major implications for paleoclimatic interpretations of sedimentary δDwax. Here we investigate apparent fractionation in the Arctic by tracing the isotopic composition of leaf waxes from production in modern plants to deposition in lake sediments using isotopic observations of precipitation, soil and plant waters, living leaf waxes, and waxes in sediment traps in the Brooks Range foothills of northern Alaska. We also analyze a lake surface sediment transect to compare present-day vegetation assemblages to εapp at the watershed scale. Source water and εapp were determined for live specimens of Eriophorum vaginatum (cottongrass) and Betula nana (dwarf birch), two dominant tundra plants in the Brooks Range foothills. The δD of these plants' xylem water closely tracks that of surface soil water, and reflects a summer-biased precipitation source. Leaf water is enriched by 23 ± 15‰ relative to xylem water for E. vaginatum and by 41 ± 19‰ for B. nana. Evapotranspiration modeling indicates that this leaf water enrichment is consistent with the evaporative enrichment expected under the climate conditions of northern Alaska, and that 24-h photosynthesis does not cause excessive leaf water isotope enrichment. The εapp determined for our study species average -89 ± 14‰ and -106 ± 16‰ for B. nana n-alkanes and n-acids, respectively, and -182 ± 10‰ and -154 ± 26‰ for E. vaginatum n-alkanes and n-acids, which are similar to the εapp of related species in temperate and tropical regions, indicating that apparent fractionation is similar in Arctic relative to other regions, and there is no reduced fractionation in the Arctic. Sediment trap data suggest that waxes are primarily transported into lakes from local (watershed-scale) sources by overland flow during the spring freshet, and so δDwax within lakes depends on watershed-scale differences in water isotope compositions and in plant ecophysiology. As such, the large difference between our study species suggests that the relative abundance of graminoids and shrubs is potentially an important control on δDwax in lake sediments. These inferences are supported by δDwax data from surface sediments of 24 lakes where εapp, relative to δDxylem, averages -128 ± 13‰ and -130 ± 8‰ for n-acids and n-alkanes, respectively, and co-varies with vegetation type across watersheds. These new determinations of plant source water seasonality and εapp for the Arctic will improve the δDwax paleoclimate proxy at high latitudes.

Sediment source fingerprinting to quantify fine sediment sources in forested catchments, Chile.

NASA Astrophysics Data System (ADS)

Schuller, P.; Walling, D. E.; Iroume, A.; Castillo, A.; Quilodran, C.

2012-04-01

A study to improve the understanding of the primary sediment sources and transfer pathways in catchments disturbed following forest plantation harvesting is being undertaken in South-Central Chile. The study focuses on two sets of paired experimental catchments (treatment and control), located about 400 km apart, with similar soil type but contrasting mean annual rainfall: Nacimiento (1,200 mm year-1) and Los Ulmos (2,500 mm year-1). Sediment source fingerprinting techniques are being used to document the primary fine sediment sources. In each catchment, three potential sediment sources were defined: clearcut slopes (Z1), forest roads (Z2) and the stream channel (Z3). In each catchment, multiple representative composite samples of the different potential source materials were collected before harvest operations from the upper 1 cm layer in Z1, Z2, and from the channel bank and bed for Z3. A time-integrating trap sampler installed in the discharge monitoring station constructed at the outlet of each catchment has been used to collect samples of the suspended sediment and these have been supplemented by sediment collected from the weir pools. Total suspended sediment load is been quantified in the monitoring stations using discharge records and integrated water sampling. Caesium-137 (137Cs), excess lead-210 (210Pbex) and other sediment properties are being used as fingerprints. After air-drying, oven-drying at 40°C and disaggregation, both the source material samples and the sediment samples collected in the discharge monitoring stations were sieved through a 63-μm sieve and the <63-μm fractions were used for subsequent analyses. For radionuclide assay, the samples were sealed in Petri dishes and after 4 weeks the mass activity density (activity concentration) of 137Cs and 210Pbex was determined by gamma analysis, using an ORTEC extended range Ge detector of 53% relative efficiency. The 137Cs and 210Pbex activity and organic carbon (Corg) concentration associated with potential source materials and the target sediment show that the two radionuclides used in combination with the Corg property provide effective source fingerprints. Additional work using a mixing model taking account of particle size effects is required to establish the relative contributions of the three sources to the fine sediment loads of the study catchments. This research is supported by the Chilean Government through FONDECYT Project 1090574 and by the IAEA through CRP D1.20.11 (Contract CHI-15531 and Technical Contract 15478) and the RLA 05/051 Project.

Verifying mapping, monitoring and modeling of fine sediment pollution sources in West Maui, Hawai'i, USA

NASA Astrophysics Data System (ADS)

Cerovski-Darriau, C.; Stock, J. D.

2017-12-01

Coral reef ecosystems, and the fishing and tourism industries they support, depend on clean waters. Fine sediment pollution from nearshore watersheds threatens these enterprises in West Maui, Hawai'i. To effectively mitigate sediment pollution, we first have to know where the sediment is coming from, and how fast it erodes. In West Maui, we know that nearshore sediment plumes originate from erosion of fine sand- to silt-sized air fall deposits where they are exposed by grazing, agriculture, or other disturbances. We identified and located these sediment sources by mapping watershed geomorphological processes using field traverses, historic air photos, and modern orthophotos. We estimated bank lowering rates using erosion pins, and other surface erosion rates were extrapolated from data collected elsewhere on the Hawaiian Islands. These measurements and mapping led to a reconnaissance sediment budget which showed that annual loads are dominated by bank erosion of legacy terraces. Field observations during small storms confirm that nearshore sediment plumes are sourced from bank erosion of in-stream, legacy agricultural deposits. To further verify this sediment budget, we used geochemical fingerprinting to uniquely identify each potential source (e.g. stream banks, agricultural fields, roads, other human modified soils, and hillslopes) from the Wahikuli watershed (10 km2) and analyzed the fine fraction using ICP-MS for elemental geochemistry. We propose to apply this the fingerprinting results to nearshore suspended sediment samples taken during storms to identify the proportion of sediment coming from each source. By combining traditional geomorphic mapping, monitoring and geochemistry, we hope to provide a powerful tool to verify the primary source of sediment reaching the nearshore.

Sediment sources in a small agricultural catchment: A composite fingerprinting approach based on the selection of potential sources

NASA Astrophysics Data System (ADS)

Zhou, Huiping; Chang, Weina; Zhang, Longjiang

2016-08-01

Fingerprinting techniques have been widely used as a reasonable and reliable means for investigating sediment sources, especially in relatively large catchments in which there are significant differences in surface materials. However, the discrimination power of fingerprint properties for small catchments, in which the surface materials are relatively homogeneous and human interference is marked, may be affected by fragmentary or confused source information. Using fingerprinting techniques can be difficult, and there is still a need for further studies to verify the effectiveness of such techniques in these small catchments. A composite fingerprinting approach was used in this study to investigate the main sources of sediment output, as well as their relative contributions, from a small catchment (30 km2) with high levels of farming and mining activities. The impact of the selection of different potential sediment sources on the derivation of composite fingerprints and its discrimination power were also investigated by comparing the results from different combinations of potential source types. The initial source types and several samples that could cause confusion were adjusted. These adjustments improved the discrimination power of the composite fingerprints. The results showed that the composite fingerprinting approach used in this study had a discriminatory efficiency of 89.2% for different sediment sources and that the model had a mean goodness of fit of 0.90. Cultivated lands were the main sediment source. The sediment contribution of the studied cultivated lands ranged from 39.9% to 87.8%, with a mean of 76.6%, for multiple deposited sediment samples. The mean contribution of woodlands was 21.7%. Overall, the sediment contribution from mining and road areas was relatively low. The selection of potential sources is an important factor in the application of fingerprinting techniques and warrants more attention in future studies, as is the case with other uncertainty factors.

Sediment features at the grounding zone and beneath Ekström Ice Shelf, East Antarctica, imaged using on-ice vibroseis.

NASA Astrophysics Data System (ADS)

Smith, Emma C.; Eisen, Olaf; Hofstede, Coen; Lambrecht, Astrid; Mayer, Christoph

2017-04-01

The grounding zone, where an ice sheet becomes a floating ice shelf, is known to be a key threshold region for ice flow and stability. A better understanding of ice dynamics and sediment transport across such zones will improve knowledge about contemporary and palaeo ice flow, as well as past ice extent. Here we present a set of seismic reflection profiles crossing the grounding zone and continuing to the shelf edge of Ekström Ice Shelf, East Antarctica. Using an on-ice vibroseis source combined with a snowstreamer we have imaged a range of sub-glacial and sub-shelf sedimentary and geomorphological features; from layered sediment deposits to elongated flow features. The acoustic properties of the features as well as their morphology allow us to draw conclusions as to their material properties and origin. These results will eventually be integrated with numerical models of ice dynamics to quantify past and present interactions between ice and the solid Earth in East Antarctica; leading to a better understanding of future contributions of this region to sea-level rise.

A centennial record of anthropogenic impacts and extreme weather events in southwestern Taiwan: evidence from sedimentary molecular markers in coastal margin.

PubMed

Kuo, Li-Jung; Lee, Chon-Lin; Louchouarn, Patrick; Huh, Chih-An; Liu, James T; Chen, Jian-Cheng; Lee, Kun-Je

2014-09-15

A 100-year history of human and natural disturbances in southwestern Taiwan was reconstructed using a suite of molecular markers in four dated sediment cores from the upper slope region off the Gaoping River mouth. Trends in polycyclic aromatic hydrocarbons (PAHs) tracked Taiwan's industrialization/urbanization starting in the 1970s, and the enactment of environmental regulatory policies thereafter. The predominant pyrogenic sources include vehicular, smelter, and coal combustion but spatial differences are observed among sub-regions of the shelf. Profiles of lignin oxidation products (LOPs) point to a significant increase in terrestrial organic matter inputs driven by land development after the 1970s. Low lignin diagenetic signature ratios [(Ad/Al)v] in all sediments suggest quick transport of fresh plant material from land to sea via mountainous rivers. Shifts in PAHs, LOPs, and radionuclides in recent sediments reveal the deposition of turbidites resulting from typhoon-induced floods. Multiproxy analysis illustrates the interplay between anthropogenic activities and natural processes. Copyright © 2014 Elsevier Ltd. All rights reserved.

A COMPREHENSIVE NONPOINT SOURCE FIELD STUDY FOR SEDIMENT, NUTRIENTS AND PATHOGENS IN THE SOUTH FORK BROAD RIVER WATERSHED, GEORGIA

EPA Science Inventory

There is an urgent need for EPA to develop protocols for establishing Total Maximum Daily Loads (TMDLs) in streams, lakes and estuaries. A cooperative TMDL field data collection project between ORD and Region 4 is ongoing in the South Fork Broad River Watershed (SFBR), a 245.18 ...

Analytical method for determining rill detachment of purple soil as compared with that of loess soil

USDA-ARS?s Scientific Manuscript database

Rills are commonly found on sloping farmlands in both the loess and purple soil regions of China. Rill erosion is an important component of slope water erosion, and primary sediment sources in small catchments in the areas. A comparative study on rill erosion on loess and purple soils is important t...

Meteorological Situations Favouring the Development of Dust Plumes over Iceland

NASA Astrophysics Data System (ADS)

Schepanski, K.; Szodry, K.

2017-12-01

The knowledge on mineral dust emitted at high latitudes is limited, but its impact on the polar environments is divers. Within a warming climate, dust emitted from regions in cold climates is expected to increase due to the retreat of the ice sheet and increasing melting rates. Therefore, and for its extensive impacts on different aspects of the climate system, a better understanding of the atmospheric dust life-cycle at high latitudes/cold climates in general, and the spatio-temporal distribution of dust sources in particular, are essential. At high-latitudes, glacio-fluvial sediments as found on river flood plains e.g. supplied by glaciers are prone to wind erosion when dry and bare. In case of the occurrence of strong winds, sediments are blown out and dust plumes develop. As dust uplift is controlled by soil surface characteristics, the availability of suitable sediments, and atmospheric conditions, an interannual variability in dust source activity is expected. We investigated atmospheric circulation patterns that favour the development of dust plumes over Iceland, which presents a well-known dust source at high latitudes. Using the atmosphere model COSMO (COnsortium for Small-scale MOdeling), we analysed the wind speed distribution over the Iceland region for identified and documented dust cases. As one outcome of the study, the position of the Icelandic low, the anticyclones located over Northern Europe, and the resulting pressure gradients are of particular relevance. The interaction of the synoptic-scale winds with the Icelandic orography may locally enhance the wind speeds and thus foster local dust emission. Results from this study suggest that the atmospheric circulation determined by the pressure pattern is of particular relevance for the formation of dust plumes entering the North Atlantic.

Increasing trends in rainfall-runoff erosivity in the Source Region of the Three Rivers, 1961-2012.

PubMed

Wang, Yousheng; Cheng, Congcong; Xie, Yun; Liu, Baoyuan; Yin, Shuiqing; Liu, Yingna; Hao, Yanfang

2017-08-15

As the head source of the two longest rivers in China and the longest river in Southeast Asia, the East Qinghai-Tibetan Plateau (QTP) is experiencing increasing thaw snowmelt and more heavy precipitation events under global warming, which might lead to soil erosion risk. To understand the potential driving force of soil erosion and its relationship with precipitation in the context of climate change, this study analyzed long-term variations in annual rainfall-runoff erosivity, a climatic index of soil erosion, by using the Mann-Kendall statistical test and Theil and Sen's approach in the Source Region of the Three Rivers during 1961-2012. The results showed the followings: (i) increasing annual rainfall-runoff erosivity was observed over the past 52years, with a mean relative trend index (RT 1 ) value of 12.1%. The increasing trend was more obvious for the latest two decades: RT 1 was nearly three times larger than that over the entire period; (ii) more precipitation events and a higher precipitation amount were the major forces for the increasing rainfall-runoff erosivity; (iii) similar rising trends in sediment yields, which corresponded to rainfall-runoff erosivity under slightly increasing vegetation coverage in the study area, implied a large contribution of rainfall-runoff erosivity to the increasing sediment yields; and (iv) high warming rates increased the risk of soil destruction, soil erosion and sediment yields. Conservation measures, such as enclosing grassland, returning grazing land to grassland and rotation grazing since the 1980s, have maintained vegetation coverage and should be continued and strengthened. Copyright © 2017 Elsevier B.V. All rights reserved.

Verification Modal Summation Technique for Synthetic and Observation Seismogram for Pidie Jaya Earthquake M6.5

NASA Astrophysics Data System (ADS)

Irwandi, Irwandi; Fashbir; Daryono

2018-04-01

Neo-Deterministic Seismic Hazard Assessment (NDSHA) method is a seismic hazard assessment method that has an advantage on realistic physical simulation of the source, propagation, and geological-geophysical structure. This simulation is capable on generating the synthetics seismograms at the sites that being observed. At the regional NDSHA scale, calculation of the strong ground motion is based on 1D modal summation technique because it is more efficient in computation. In this article, we verify the result of synthetic seismogram calculations with the result of field observations when Pidie Jaya earthquake on 7 December 2016 occurred with the moment magnitude of M6.5. Those data were recorded by broadband seismometers installed by BMKG (Indonesian Agency for Meteorology, Climatology and Geophysics). The result of the synthetic seismogram calculations verifies that some stations well show the suitability with observation while some other stations show the discrepancies with observation results. Based on the results of the observation of some stations, evidently 1D modal summation technique method has been well verified for thin sediment region (near the pre-tertiary basement), but less suitable for thick sediment region. The reason is that the 1D modal summation technique excludes the amplification effect of seismic wave occurring within thick sediment region. So, another approach is needed, e.g., 2D finite difference hybrid method, which is a part of local scale NDSHA method.

Data on fluoride concentration in drinking water resources in Iran: A case study of Fars province; Larestan region.

PubMed

Dehghani, Mohammad Hadi; Haghighat, Gholam Ali; Yousefi, Mahmood

2018-08-01

Fluoride is a natural element among minerals, geochemical sediments and natural water systems which is entered to body chain by drinking water. Groundwater is the main and the best source of drinking water in southern areas of Iran especially in the cities of Lar and Gerash (Fars province). So due to the health significance fluoride including dental and skeletal fluorosis, fertility, abortion and thyroid diseases, etc., measuring has high importance in the water resources of this region of Iran. Fluoride concentration was 0.35-3.46 mg/L and 78.26% drinking water sources contains fluoride concentration above the WHO guideline.

Increasing rates of atmospheric mercury deposition in midcontinental North America

USGS Publications Warehouse

Swain, Edward B.; Engstrom, Daniel R.; Brigham, Mark E.; Henning, Thomas A.; Brezonik, P.L.

1992-01-01

Mercury contamination of remote lakes has been attributed to increasing deposition of atmospheric mercury, yet historic deposition rates and inputs from terrestrial sources are essentially unknown. Sediments of seven headwater lakes in Minnesota and Wisconsin were used to reconstruct regional modern and preindustrial deposition rates of mercury. Whole-basin mercury fluxes, determined from lake-wide arrays of dated cores, indicate that the annual deposition of atmospheric mercury has increased from 3.7 to 12.5 micrograms per square meter since 1850 and that 25 percent of atmospheric mercury deposition to the terrestrial catchment is exported to the lake. The deposition increase is similar among sites, implying regional or global sources for the mercury entering these lakes.

An assessment of injury to sediments and sediment-dwelling organisms in the Grand Calumet River and Indiana Harbor Area of Concern, USA.

PubMed

MacDonald, D D; Ingersoll, C G; Smorong, D E; Lindskoog, R A; Sparks, D W; Smith, J R; Simon, T P; Hanacek, M A

2002-08-01

This article is the first in a series of three that describe the results of a Natural Resource Damage Assessment (NRDA) conducted in the Grand Calumet River and Indiana Harbor Area of Concern (IHAOC). The assessment area is located in northwest Indiana and was divided into nine reaches to facilitate the assessment. This component of the NRDA was undertaken to determine if sediments and sediment-dwelling organisms have been injured due to exposure to contaminants that have accumulated in sediments as a result of discharges of oil or releases of other hazardous substances from industrial, municipal, and nonpoint sources. To support this assessment, information was compiled on the chemical composition of sediment and pore water; on the toxicity of whole sediments, pore water, and elutriates; and on the status of benthic invertebrate communities. The data on each of these indicators were compared to regionally relevant benchmarks to assess the presence and extent of injury to surface water resources ( i.e., sediments) or biological resources ( i.e., sediment-dwelling organisms). The results of this assessment indicate that sediment injury has occurred throughout the assessment area, with up to four distinct lines of evidence demonstrating injury within the various reaches. The primary contaminants of concern ( i.e., those substances that are present at concentrations that are sufficient to cause or substantially contribute to sediment injury) include metals, polycyclic aromatic hydrocarbons, and total polychlorinated biphenyls.

Sediment focusing in the Panama Basin, Eastern Equatorial Pacific Ocean

NASA Astrophysics Data System (ADS)

Singh, Ajay K.; Marcantonio, Franco; Lyle, Mitchell

2011-09-01

Age-model derived sediment mass accumulation rates (MARs) are consistently higher than 230Th-normalized MARs in the Equatorial Pacific Ocean during the past 25 ka. The offset, being highest in the Panama Basin, suggests a significant role for deep-sea sediment redistribution (i.e., sediment focusing) in this region. Here, we test the hypothesis that downslope transport of sediments from topographically high regions that surround the Panama Basin is the cause of higher-than-expected xs 230Th inventories over the past 25 ka in the deeper parts of the basin. We find little difference in xs 230Th inventories between the highest and lowest reaches of the basin. Furthermore, there is no correlation between xs 230Th-derived sediment focusing factors and water depth which suggests that the topographic highs do not serve as a source of xs 230Th. A spatial analysis suggests that there may be an enhanced scavenging effect on xs 230Th concentrations in sediment closest to the equator where productivity is the highest, although further data is necessary to corroborate this. At the equator xs 230Th-derived focusing factors are high and range from about 1 to 5 during the Holocene and about 1 to 11 during the last glacial. In contrast, non-equatorial cores show a smaller range in variability from about 0.7 to 2.8 during the Holocene and from 0.7 to 3.6 during the last glacial. Based on 232Th flux measurements, we hypothesize that the location at which eolian detrital fluxes surpass the riverine detrital fluxes is approximately 300 km from the margin. While riverine fluxes from coastal margins were higher during the Holocene, eolian fluxes were higher during the last glacial.

Role of land use change in landslide-related sediment fluxes in tropical mountain regions

NASA Astrophysics Data System (ADS)

Guns, M.; Vanacker, V.; Demoulin, A.

2012-04-01

Tropical mountain regions are characterised by high denudation rates. Landslides are known to be recurrent phenomena in active mountain belts, but their contribution to the overall sedimentary fluxes is not yet well known. Previous studies on sedimentary cascades have mostly focused on natural environments, without considering the impact of human and/or anthropogenic disturbances on sedimentary budgets. In our work, we hypothesise that human-induced land use change might alter the sediment cascade through shifts in the landslide magnitude-frequency relationship. We have tested this assumption in the Virgen Yacu catchment (approximately 11km2), in the Ecuadorian Cordillera Occidental. Landslide inventories and land use maps were established based on a series of sequential aerial photos (1963, 1977, 1984 and 1989), a HR Landsat image (2001) and a VHR WorldView2 image (2010). Aerial photographs were ortho-rectified, and coregistred with the WorldView2 satellite image. Field campaigns were realised in 2010 and 2011 to collect field-based data on landslide type and geometry (depth, width and length). This allowed us to establish an empirical relationship between landslide area and volume, which was then applied to the landslide inventories to estimate landslide-related sediment production rates for various time periods. The contribution of landslides to the overall sediment flux of the catchment was estimated by comparing the landslide-related sediment production to the total sediment yield. The empirical landslide area-volume relationship established here for the Ecuadorian Andes is similar to that derived for the Himalayas. It suggests that landslides are the main source of sediment in this mountainous catchment. First calculations indicate that human-induced land use change alters the magnitude-frequency relationship through strong increase of small landslides.

Sediment source detection by stable isotope analysis, carbon and nitrogen content and CSSI in a small river of the Swiss Plateau

NASA Astrophysics Data System (ADS)

SchindlerWildhaber, Yael; Alewell, Christine; Birkholz, Axel

2014-05-01

Suspended sediment (SS) and organic matter in rivers can harm the fauna by affecting health and fitness of free swimming fish and by causing siltation of the riverbed. The temporal and spatial dynamics of sediment, carbon (C) and nitrogen (N) during the brown trout spawning season in a small river of the Swiss Plateau were assessed and C isotopes as well as the C/N atomic ratio were used to distinguish autochthonous and allochthonous sources of organic matter in SS loads. The visual basic program IsoSource with 13Ctot and 15N as input isotopes was used to quantify the temporal and spatial sources of SS. We determined compound specific stable carbon isotopes (CSSI) in fatty acids of possible sediment source areas to the stream in addition and compared them to SS from selected high flow and low flow events. Organic matter concentrations in the infiltrated and suspended sediment were highest during low flow periods with small sediment loads and lowest during high flow periods with high sediment loads. Peak values in nitrate and dissolved organic C were measured during high flow and high rainfall, probably due to leaching from pasture and arable land. The organic matter was of allochthonous sources as indicated by the C/N atomic ratio and δ13Corg. Organic matter in SS increased from up- to downstream due to an increase in sediment delivery from pasture and arable land downstream of the river. While the major sources of SS are pasture and arable land during base flow conditions, SS from forest soils increased during heavy rain events and warmer winter periods most likely due to snow melt which triggered erosion. Preliminary results of CSSI analysis of sediment source areas and comparison to SS of selected events indicate that differences in d13C values of individual fatty acids are too small to differentiate unambiguously between sediment sources.

Discharge modulates stream metabolism dependence on fine particulate organic carbon in a Mediterranean WWTP-influenced stream

NASA Astrophysics Data System (ADS)

Drummond, J. D.; Bernal, S.; Meredith, W.; Schumer, R.; Martí Roca, E.

2017-12-01

Waste water treatment plant (WWTP) effluents constitute point source inputs of fine sediment, nutrients, carbon, and microbes to stream ecosystems. A range of responses to these inputs may be observed in recipient streams, including increases in respiration rates, which augment CO2 emissions to the atmosphere. Yet, little is known about which fractions of organic carbon (OC) contribute the most to stream metabolism in WWTP-influenced streams. Fine particulate OC (POC) represents ca. 40% of the total mass of OC in river networks, and is generally more labile than dissolved OC. Therefore, POC inputs from WWTPs could contribute disproportionately to higher rates of heterotrophic metabolism by stream microbial communities. The aim of this study was to investigate the influence of POC inputs from a WWTP effluent on the metabolism of a Mediterranean stream over a wide range of hydrologic conditions. We hypothesized that POC inputs would have a positive effect on respiration rates, and that the response to POC availability would be larger during low flows when the dilution capacity of the recipient stream is negligible. We focused on the easily resuspended fine sediment near the sediment-water interface (top 3 cm), as this region is a known hot spot for biogeochemical processes. For one year, samples of resuspended sediment were collected bimonthly at 7 sites from 0 to 800 m downstream of the WWTP point source. We measured total POC, organic matter (OM) content (%), and the associated metabolic activity of the resuspended sediment using the resazurin-resorufin smart tracer system as a proxy for aerobic ecosystem respiration. Resuspended sediment showed no difference in total POC over the year, while the OM content increased with decreasing discharge. This result together with the decreasing trend of total POC observed downstream of the point source during autumn after a long dry period, suggests that the WWTP effluent was the main contributor to stream POC. Furthermore, there was a positive relationship between aerobic ecosystem respiration and OM content in resuspended sediments. Our results suggest that WWTP effluents can be important sources of POC to recipient streams, and that the increased availability of POC enhances aerobic ecosystem respiration, especially when the dilution capacity of the recipient streams is low.

Development of recent chronologies and evaluation of temporal variations in Pb fluxes and sources in lake sediment and peat cores in a remote, highly radiogenic environment, Cairngorm Mountains, Scottish Highlands

NASA Astrophysics Data System (ADS)

Farmer, John G.; MacKenzie, Angus B.; Graham, Margaret C.; Macgregor, Kenneth; Kirika, Alexander

2015-05-01

The use of stable Pb isotope analyses in conjunction with recent (210Pb and anthropogenic radionuclide) chronologies has become a well-established method for evaluating historical trends in depositional fluxes and sources of atmospherically deposited Pb using archival records in lake sediment or peat cores. Such studies rely upon (i) simple radioactive disequilibrium between unsupported 210Pb and longer-lived members of the 238U decay series and (ii) well-defined values for the isotopic composition of contaminant Pb and indigenous Pb in the study area. However, areas of high natural radioactivity can present challenging environments for such studies, with potential complications arising from more complex disequilibria in the 238U decay series and the occurrence, at local or regional level, of anomalous, ill-defined stable isotope ratios due to the presence of elevated levels of radiogenic Pb. Results are presented here for a study of a sediment core from a freshwater lake, Loch Einich, in the high natural radioactivity area of the Cairngorm Mountains of Scotland. 238U decay series disequilibria revealed recent diagenetic re-deposition of both U and 226Ra, the latter resulting in a requirement to use a modified calculation to derive a 210Pb chronology for the core. Confidence in the chronology was provided by good agreement with the independent 241Am chronology, but the 137Cs distribution was affected by significant post-depositional mobility in the organic-rich sediment. The systematics of variations in 230Th, 232Th and stable Pb isotope ratio distributions were used to establish the indigenous Pb characteristics of the sediment. The relatively high radiogenic content of the indigenous Pb resulted in complications in source apportionment, in particular during the 20th century, with multiple natural and anthropogenic sources precluding the use of a simple binary mixing model. Consequently, 206Pb/207Pb ratios in Scottish moss samples from an archive collection were used to provide the input term for atmospheric deposition in order to establish historical trends in indigenous and anthropogenic Pb fluxes. A test of the accuracy of the derived Pb fluxes was provided by analysis of a core from a nearby blanket peat deposit, Great Moss. Independent atmospheric and basal inputs gave a complex distribution of 210Pb in the peat, but this did not affect calculation of a 210Pb chronology. Once again, the 210Pb chronology was supported by the 241Am distribution. Temporal trends in anthropogenic Pb deposition derived for the Loch Einich sediment core were in generally good agreement with those for the Great Moss peat core, other peat cores and some other lake sediment cores from northern Scotland, providing confidence in the use of the archive moss data to characterise atmospheric deposition. However, sustained input of Pb to Loch Einich sediment at relatively high levels in the late 20th century, after the regional decline in atmospheric Pb deposition, suggested that catchment-derived Pb is now a significant component of the depositional flux for Loch Einich.

Origin and effect factors of sedimentary organic carbon in a karst groundwater-fed reservoir, South China.

PubMed

Huang, Siyu; Pu, Junbing; Cao, Jianhua; Li, Jianhong; Zhang, Tao; Jiang, Feng; Li, Li; Wu, Feihong; Pan, Moucheng; Bai, Bing

2018-03-01

Reservoirs are commonly recharged by groundwater that is rich in bicarbonate ions in karst regions of South China, and the recharge of this groundwater to the reservoir can affect the biogeochemical processes of carbon sedimentation at the reservoir bottom. In this study, Dalongdong Reservoir, which is mainly recharged by two subterranean streams, was investigated based on a 42-cm-thick sedimentary core and the 210 Pb/ 137 Cs dating technique and isotope analyses to understand the sedimentary history and identify the carbon sources. The 210 Pb/ 137 Cs age model showed that the sediments were accumulated over the last 60 years. The annual increase precipitation and temperature showed no obvious change compared with trends of δ 13 C in total organic carbon (δ 13 C org ), δ 15 N values in total nitrogen, and the carbon and nitrogen ratio (C/N). This shows that climate was not the main control of the variation in sediment factors. Based on δ 13 C org , δ 15 N, C/N, and isotopic mixing modeling, sources of organic carbon in the sediments were derived from plankton (60.84%), soil (22.93%), waste water (14.56%), and terrestrial plants (1.67%). From 1958 to 1978, reservoir establishment and leakage affected the contribution of the four sources. The contribution of the plankton source increased from 1978 to 2015, resulting from change of water level and continued input of external nitrogen. However, because of the revegetation supplied by an economic aid project the contribution of soil showed a considerable decreasing trend from 1978 to 2002. After 2002, For "Grain for Green" project, the contribution from soil further decreased. After reservoir construction, the contribution of waste water stabilized. The contribution of terrestrial plants started increased rapidly after 2002. Karst groundwater, which contains more dissolved inorganic carbon containing lower δ 13 C DIC than the water sources of other lakes or reservoirs, makes the δ 13 C org value of sediment more negative by phytoplankton photosynthesis in the reservoir.

A new approach of using multiple composite fingerprints to apportion sediment sources

USDA-ARS?s Scientific Manuscript database

Sediment source fingerprinting provides an essential means for estimating sediment source contributions, which are needed not only for soil conservation planning but also for erosion model evaluation and refinement. A single optimum composite fingerprint has been widely used in the literature to es...

Distribution, Source, and Ecological Risk Assessment of Polycyclic Aromatic Hydrocarbons in Surface Sediment of Liaodong Bay, Northeast China

NASA Astrophysics Data System (ADS)

Xu, Shuang; Tao, Ping; Li, Yuxia; Guo, Qi; Zhang, Yan; Wang, Man; Jia, Hongliang; Shao, Mihua

2018-01-01

Sixteen polycyclic aromatic hydrocarbons (PAHs) were determined in surface sediments from Liaodong Bay, northeast China. The concentration levels of total PAHs (Σ16PAHs) in sediment were 11.0˜249.6 ng·g-1 dry weight (dw), with a mean value of 89.9 ng·g-1 dry weight (dw). From the point of the spatial distribution, high PAHs levels were found in the western areas of Liaodong Bay. In the paper, sources of PAHs were investigated by diagnostic ratios, which indicated that pyrogenic sources were the main sources of PAHs in the sediment of Liaodong Bay. Therefore, selected PAH levels in sediments were compared with Sediments Quality Guidelines (ERM-ERL indexes) for evaluation probable toxic effects on marine organism.

Historical changes in organic matter input to the muddy sediments along the Zhejiang-Fujian Coast, China over the past 160 years

USGS Publications Warehouse

Chen, Li-lei; Liu, Jian; Xing, Lei; Krauss, Ken W.; Wang, Jia-sheng; Xu, Gang; Li, Li

2017-01-01

The burial of sedimentary organic matter (SOM) in the large river-influenced estuarine-coastal regions is affected by hydrodynamic sorting, diagenesis and human activities. Typically, the inner shelf region of the East China Sea is a major carbon sink of the Yangtze River-derived fine-grained sediments. Most of the previous work concentrated on the studies of surface sediments or used a single-proxy in this region. In this study, two cores from the Zhejiang-Fujian Coast were analyzed using bulk (TOC, TN and δ13CTOC) and molecular biomarker (n-alkane, brassicasterol, dinosterol and glycerol dialkyl glycerol tetraether lipids) techniques to clarify the sources, spatiotemporal distribution and fate of SOM in the Yangtze River Estuary and adjacent shelf. Results from this study indicated that the effects of diagenesis and diffusion on different sedimentary biomarkers resulted in overestimation of the relative contribution of terrestrial organic matter (%OMterr), compared with those based on δ13CTOC. The amounts of terrestrial plant organic matter (OMplant) and%OMterr in sediments decreased offshore. In contrast, the amounts of marine organic matter (OMmarine) increased offshore, but closer to the Yangtze River mouth, the amounts of soil organic matter (OMsoil) increased. Moreover, the amounts of TOC, OMplant and OMmarine biomarkers increased, but OMsoil and%OMterrdecreased over time in recent decades. Our study suggests that spatial organic matter distribution patterns in marine shelf sediments were controlled primarily by hydrodynamic sorting and nutrient concentrations, and temporally diverse patterns were controlled predominantly by anthropogenic influence (e.g., dam construction and soil conservation, reclamation and agricultural plantations, anthropogenic nutrient input, dust storms, eutrophication, etc) and climate events (e.g., interdecadal climatic jump and heavy rain events) in the geological period.

On modeling heterogeneous coastal sediment transport - A numerical study using multiphase Eulerian and Euler-Lagrangian approaches

NASA Astrophysics Data System (ADS)

Cheng, Z.; Yu, X.; Hsu, T. J.; Calantoni, J.; Chauchat, J.

2016-02-01

Regional scale coastal evolution models do not explicitly resolve wave-driven sediment transport and must rely on bedload/suspended modules that utilize empirical assumptions. Under extreme wave events or in regions of high sediment heterogeneity, these empirical bedload/suspended load modules may need to be reevaluated with detailed observation and more sophisticated small-scale models. In the past decade, significant research efforts have been devoted to modeling sediment transport using multiphase Eulerian or Euler-Lagrangian approaches. Recently, an open-source multi-dimensional Reynolds-averaged two-phase sediment transport model, SedFOAM is developed by the authors and it has been adopted by many researchers to study momentary bed failure, granular rheology in sheet flow and scour around structures. In this abstract, we further report our recent progress made in extending the model with 3D turbulence-resolving capability and to model the sediment phase with the Discrete Element method (DEM). Adopting the large-eddy simulation methodology, we validate the 3D model with measured fine sediment transport is oscillatory sheet flow and demonstrate that the model is able to resolve sediment burst events during flow reversals. To better resolve the intergranular interactions and to model heterogeneous properties of sediment (e.g., mixed grain sizes and grain shape), we use an Euler-Lagrangian solver called CFDEM, which couples OpenFOAM for the fluid phase and LIGGGHTS for the particle phase. We improve the model by better enforcing conservation of mass in the pressure solver. The modified CFDEM solver is validated with measured oscillatory sheet flow data for coarse sand and we demonstrated that the model can reproduce the well-known armoring effects. We show that under Stokes second-order wave forcing, the armoring effect is more significant during the energetic positive peak, and hence the net onshore transport is reduced. Preliminary results modeling the shape effects using composite particles will be presented. This research is supported by Office of Naval Research and National Science Foundation.

Benthic Community Structure and Sediment Geochemical Properties at Hydrocarbon Seeps Along the Continental Slope of the Western North Atlantic

NASA Astrophysics Data System (ADS)

Demopoulos, A. W.; Bourque, J. R.; Brooke, S.

2015-12-01

Hydrocarbon seeps support distinct benthic communities capable of utilizing reduced chemical compounds for nutrition. In recent years, methane seepage has been increasingly documented along the continental slope of the U.S. Atlantic margin. In 2012 and 2013, two seeps were investigated in this region: a shallow site near Baltimore Canyon (410-450 m) and a deep site near Norfolk Canyon (1600 m). Both sites contain extensive mussel beds and microbial mats. Sediment cores and grab samples were collected to quantify the abundance, diversity, and community structure of benthic macrofauna (>300 mm) in relationship to the associated sediment environment (organic carbon and nitrogen, stable isotopes 13C and 15N, grain size, and depth) of mussel beds, mats, and slope habitats. Macrofaunal densities in microbial mats were four times greater than those present in mussel beds and slope sediments. Macrofaunal communities were distinctly different both between depths and among habitat types. Specifically, microbial mat sediments were dominated by the annelid families Dorvilleidae, Capitellidae, and Tubificidae, while mussel habitats had higher proportions of crustaceans. Diversity was lower in Baltimore microbial mat habitats, but higher in mussel and slope sediments compared to Norfolk seep habitats found at deeper depths. Multivariate statistical analysis identified sediment carbon:nitrogen (C:N) ratios and 13C values as important variables for structuring the macrofaunal communities. Higher C:N ratios were present within microbial mat habitats and depleted 13C values occurred in sediments adjacent to mussel beds found in Norfolk Canyon seeps. Differences in the quality and source of organic matter present in the seep habitats are known to be important drivers in macrofaunal community structure and associated food webs. The multivariate analysis provides new insight into the relative importance of the seep sediment quality in supporting dense macrofaunal communities compared to other seeps found throughout the region.

Recent sediment transport and deposition in the Cap-Ferret Canyon, South-East margin of Bay of Biscay

NASA Astrophysics Data System (ADS)

Schmidt, Sabine; Howa, Hélène; Diallo, Amy; Martín, Jacobo; Cremer, Michel; Duros, Pauline; Fontanier, Christophe; Deflandre, Bruno; Metzger, Edouard; Mulder, Thierry

2014-06-01

The Cap-Ferret Canyon (CFC), a major morphologic feature of the eastern margin of the Bay of Biscay, occupies a deep structural depression that opens about 60 km southwest of the Gironde Estuary. Detailed depth profiles of the particle-reactive radionuclides 234Th and 210Pb in interface sediments were used to characterise the present sedimentation (bioturbation, sediment mass accumulation, and focusing) in the CFC region. Two bathymetric transects were sampled along the CFC axis and the southern adjacent margin. Particle fluxes were recorded from the nearby Landes Plateau by means of sediment traps in 2006 and 2007. This dataset provides a new and comprehensive view of particulate matter transfer in the Cap-Ferret Canyon region, through a direct comparison of the canyon with the adjacent southern margin. Radionuclide profiles (234Th and 210Pb) and mass fluxes demonstrate that significant particle dynamics occur on the SE Aquitanian margin in comparison with nearby margins. The results also suggest show three distinct areas in terms of sedimentary activity. In the upper canyon (<500 m), there is little net sediment accumulation, suggesting a by-pass area. Sediment focusing is apparent at the middle canyon (500-1500 m), that therefore acts as a depocenter for particles from the shelf and the upper canyon. The lower canyon (>2000 m) can be considered inactive at annual or decadal scales. In contrast with the slow and continuous accumulation of relatively fresh material that characterises the middle canyon, the lower canyon receives pulses of sediment via gravity flows on longer time scales. At decadal scale, the CFC can be considered as a relatively quiescent canyon. The disconnection of the CFC from major sources of sediment delivery seems to limit its efficiency in particle transfer from coastal areas to the adjacent ocean basin.

Texture, mineralogy and geochemistry of the continental slope sediments in front of Los Tuxtlas, Gulf of Mexico, Mexico: implications on weathering, origin and depositional environments

NASA Astrophysics Data System (ADS)

Marca-Castillo, M. E.; Armstrong-Altrin, J.

2017-12-01

The textural analysis, mineralogy and geochemistry of two sediment cores recovered from the deep water zone of the southwestern part of the Gulf of Mexico ( 1666 and 1672 m water depth) were studied to infer the provenance and depositional behavior. The textural analysis revealed that both cores are dominated by silt, which occupy more than 50% in both samples and the clay occupy 40%. The petrographic analysis revealed remains of biogenic origin sediments and lithic fragments with an angular shape and low sphericity, indicating a low energy environment and therefore a low level of weathering in the sediment, which suggests that the sediments were not affected by transport and derived from a nearby source rock. In both cores quartz fragments were identified; also volcanic lithic and pyroxenes fragments, which are rocks of intermediate composition and are generally associated with the volcanic activity of the continental margins. SEM-EDS studies showed that the analysed samples have concentrations of minerals such as barite, gibbsite, kaolinite, grossular, magnetite, plagioclase and chlorite, which are probably derived from the mainland to the deep sea zone. In the trace element analysis it was observed a low Sc content, while Co, Ni, V and Cu are slightly enriched with respect to the upper continental crust; this enrichment is related to sediments from intermediate sources. The sediments are classified as shale in the log (SiO2 / Al2O3) - log (Fe2O / K2O) diagram. The fine particles of the shale indicate that a deposit occurred as a result of the gradual sedimentation due to relatively non-turbulent currents, which is consistent with the petrographic analysis. The geochemical features of major and trace elements suggest sediments were derived largely from the natural andesite erosion of coastal regions along the Gulf of Mexico. High values of Fe2O3 and MnO are observed in the upper intervals, reflecting the influence of volcanic sediments. The major element discriminant function diagrams indicate the provenance of sediments from a passive margin, which is consistent with the geology of the Gulf of Mexico.

Estimating sedimentation rates and sources in a partially urbanized catchment using caesium-137

NASA Astrophysics Data System (ADS)

Ormerod, L. M.

1998-06-01

While there has been increased interest in determining sedimentation rates and sources in agricultural and forested catchments in recent years, there have been few studies dealing with urbanized catchments. A study of sedimentation rates and sources within channel and floodplain deposits of a partially urbanized catchment has been undertaken using the 137Cs technique. Results for sedimentation rates showed no particular downstream pattern. This may be partially explained by underestimation of sedimentation rates at some sites by failure to sample the full 137Cs profile, floodplain erosion and deliberate removal of sediment. Evidence of lateral increases in net sedimentation rates with distance from the channel may be explained by increased floodplain erosion at sites closer to the channel and floodplain formation by lateral deposition. Potential sediment sources for the catchment were considered to be forest topsoil, subsurface material and sediments derived from urban areas, which were found to be predominantly subsurface material. Tracing techniques showed an increase in subsurface material for downstream sites, confirming expectations that subsurface material would increase in the downstream direction in response to the direct and indirect effects of urbanization.

Targeting sediment management strategies using sediment quantification and fingerprinting methods

NASA Astrophysics Data System (ADS)

Sherriff, Sophie; Rowan, John; Fenton, Owen; Jordan, Phil; hUallacháin, Daire Ó.

2016-04-01

Cost-effective sediment management is required to reduce excessive delivery of fine sediment due to intensive land uses such as agriculture, resulting in the degradation of aquatic ecosystems. Prioritising measures to mitigate dominant sediment sources is, however, challenging, as sediment loss risk is spatially and temporally variable between and within catchments. Fluctuations in sediment supply from potential sources result from variations in land uses resulting in increased erodibility where ground cover is low (e.g., cultivated, poached and compacted soils), and physical catchment characteristics controlling hydrological connectivity and transport pathways (surface and/or sub-surface). Sediment fingerprinting is an evidence-based management tool to identify sources of in-stream sediments at the catchment scale. Potential sediment sources are related to a river sediment sample, comprising a mixture of source sediments, using natural physico-chemical characteristics (or 'tracers'), and contributions are statistically un-mixed. Suspended sediment data were collected over two years at the outlet of three intensive agricultural catchments (approximately 10 km2) in Ireland. Dominant catchment characteristics were grassland on poorly-drained soils, arable on well-drained soils and arable on moderately-drained soils. High-resolution (10-min) calibrated turbidity-based suspended sediment and discharge data were combined to quantify yield. In-stream sediment samples (for fingerprinting analysis) were collected at six to twelve week intervals, using time-integrated sediment samplers. Potential sources, including stream channel banks, ditches, arable and grassland field topsoils, damaged road verges and tracks were sampled, oven-dried (<40oC) and sieved (125 microns). Soil and sediment samples were analysed for mineral magnetics, geochemistry and radionuclide tracers, particle size distribution and soil organic carbon. Tracer data were corrected to account for particle size and organic matter selectivity processes. Contributions from potential sources type groups (channel - ditches and stream banks, roads - road verges and tracks, fields - grassland and arable topsoils) were statistically un-mixed using FR2000, an uncertainty-inclusive algorithm, and combined with sediment yield data. Results showed sediment contributions from channel, field and road groups were 70%, 25% and 5% in the poorly-drained catchment, 59%, 22% and 19% in the well-drained catchment, and 17%, 74% and 9% in the moderately-drained catchment. Higher channel contributions in the poorly-drained catchment were attributed to bank erosion accelerated by the rapid diversion of surface runoff into channels, facilitated by surface and sub-surface artificial drainage networks, and bank seepage from lateral pressure gradients due to confined groundwater. Despite the greatest proportion of arable soils in the well-drained catchment, this source was frequently hydrologically disconnected as well-drained soils largely infiltrated rainfall and prevented surface soil erosion. Periods of high and intense rainfall were associated with greater proportions of field losses in the well-drained catchment likely due to infiltration exceeding the saturated hydraulic conductivity of soils and establishment of surface hydrological connectivity. Losses from field topsoils dominated in the moderately-drained catchment as antecedent soil wetness maintained surface flow pathways and coincided with low groundcover on arable soils. For cost-effective management of sediment pressures to aquatic ecosystems, catchment specific variations in sediment sources must be considered.

Baltic Sea Blue Carbon: Role of environmental factors influencing the carbon sink capacity of eelgrass (Zostera marina) meadows.

NASA Astrophysics Data System (ADS)

Röhr, E.; Holmer, M.; Boström, C.

2016-02-01

Although the global seagrass coverage area is less than 0.2 % of the worlds ocean floor, the carbon sink capacity of seagrasses may account up to 18 % of oceanic carbon burial and thus play a critical structural and functional role in many coastal ecosystems. Recent studies have shown considerable variation in the global estimates for seagrass meadow Corg accumulation rates and stocks, and indicate lack of understanding the factors influencing this variability. We sampled 20 eelgrass (Zostera marina) meadows in Finland and Denmark to study the variation in Corg accumulation rates and stocks within the Baltic Sea area. The study sites in both regions spanned a gradient from sheltered to exposed locations. The estimates for Corg accumulation rates at the Finnish eelgrass meadows were two orders of magnitude lower than the estimates for the Danish sites. The Corg stock integrated over the top 25 cm of sediment showed similar pattern, suggesting that the Finnish eelgrass meadows are carbon sources rather than carbon sinks, and the produced Corg is exported from the meadows. In contrast, at the Danish sites both Corg accumulation rates and areal Corg stock was more varying suggesting, that in this region the meadows function both as carbon sinks and sources. Our analysis further showed that a large percentage (> 55 %) of the variation in the Corg stocks was explained by sediment characteristics (density, fraction of silt and grain size distribution). In addition, the contribution of Zostera marina detritus to the sediment Corg pool explained >14 % of the variation in the Corg stocks. In order to get more reliable regional and global estimates of the role of seagrass meadows in the ocean carbon cycle, more studies accounting for the full range of environmental and species characteristics are urgently needed.

The Growing Season, but Not the Farming System, Is a Food Safety Risk Determinant for Leafy Greens in the Mid-Atlantic Region of the United States

PubMed Central

Marine, Sasha C.; Pagadala, Sivaranjani; Wang, Fei; Pahl, Donna M.; Melendez, Meredith V.; Kline, Wesley L.; Oni, Ruth A.; Walsh, Christopher S.; Everts, Kathryne L.; Buchanan, Robert L.

2015-01-01

Small- and medium-size farms in the mid-Atlantic region of the United States use varied agricultural practices to produce leafy greens during spring and fall, but the impact of preharvest practices on food safety risk remains unclear. To assess farm-level risk factors, bacterial indicators, Salmonella enterica, and Shiga toxin-producing Escherichia coli (STEC) from 32 organic and conventional farms were analyzed. A total of 577 leafy greens, irrigation water, compost, field soil, and pond sediment samples were collected. Salmonella was recovered from 2.2% of leafy greens (n = 369) and 7.7% of sediment (n = 13) samples. There was an association between Salmonella recovery and growing season (fall versus spring) (P = 0.006) but not farming system (organic or conventional) (P = 0.920) or region (P = 0.991). No STEC was isolated. In all, 10% of samples were positive for E. coli: 6% of leafy greens, 18% of irrigation water, 10% of soil, 38% of sediment, and 27% of compost samples. Farming system was not a significant factor for levels of E. coli or aerobic mesophiles on leafy greens but was a significant factor for total coliforms (TC) (P < 0.001), with higher counts from organic farm samples. Growing season was a factor for aerobic mesophiles on leafy greens (P = 0.004), with higher levels in fall than in spring. Water source was a factor for all indicator bacteria (P < 0.001), and end-of-line groundwater had marginally higher TC counts than source samples (P = 0.059). Overall, the data suggest that seasonal events, weather conditions, and proximity of compost piles might be important factors contributing to microbial contamination on farms growing leafy greens. PMID:25616798

Sediment geochemistry of Corte Madera Marsh, San Francisco Bay, California: have local inputs changed, 1830-2010?

USGS Publications Warehouse

Takesue, Renee K.; Jaffe, Bruce E.

2013-01-01

Large perturbations since the mid-1800s to the supply and source of sediment entering San Francisco Bay have disturbed natural processes for more than 150 years. Only recently have sediment inputs through the Sacramento-San Joaquin Delta (the Delta) decreased to what might be considered pre-disturbance levels. Declining sediment inputs to San Francisco Bay raise concern about continued tidal marsh accretion, particularly if sea level rise accelerates in the future. The aim of this study is to explore whether the relative amount of local-watershed sediment accumulating in a tidal marsh has changed as sediment supply from the Sacramento-San Joaquin Rivers has decreased. To address this question, sediment geochemical indicators, or signatures, in the fine fraction (silt and clay) of Sacramento River, San Joaquin River, San Francisco Bay, and Corte Madera Creek sediment were identified and applied in sediment recovered from Corte Madera Marsh, one of the few remaining natural marshes in San Francisco Bay. Total major, minor, trace, and rare earth element (REE) contents of fine sediment were determined by inductively coupled plasma mass and atomic emission spectroscopy. Fine sediment from potential source areas had the following geochemical signatures: Sacramento River sediment downstream of the confluence of the American River was characterized by enrichments in chromium, zirconium, and heavy REE; San Joaquin River sediment at Vernalis and Lathrop was characterized by enrichments in thorium and total REE content; Corte Madera Creek sediment had elevated nickel contents; and the composition of San Francisco Bay mud proximal to Corte Madera Marsh was intermediate between these sources. Most sediment geochemical signatures were relatively invariant for more than 150 years, suggesting that the composition of fine sediment in Corte Madera Marsh is not very sensitive to changes in the magnitude, timing, or source of sediment entering San Francisco Bay through the Delta. Nor does there appear to be a ubiquitous increase in the proportion of fine sediment from Corte Madera watershed accumulating in the marsh during the last 20 years when sediment inflows through the Delta have decreased to pre-disturbance levels. We conclude that a large, well-mixed reservoir, such as the transportable fine sediment pool in San Francisco Bay, is the primary source of sediment to Corte Madera Marsh, and this source buffers the marsh against changes in sediment supply from the Delta and local watersheds. This study also found that Corte Madera Marsh sediment between about 10-30 centimeters depth is highly contaminated with lead, likely a legacy of lead smelter operations near Carquinez Strait and leaded gasoline use.

Analysis of the typical small watershed of warping dams in the sand properties

NASA Astrophysics Data System (ADS)

Li, Li; Yang, Ji Shan; Sun, Wei Ying; Shen, Sha Sha

2018-06-01

Coarse sediment with a particle size greater than 0.05mm is the main deposit of riverbed in the lower Yellow River, the Loess Plateau is one of the concentrated source of coarse sediment, warping dam is one of the important engineering measures for gully control. Jiuyuangou basin is a typical small basin in the first sub region of hilly-gullied loess region, twenty warping dams in Jiuyuangou basin was selected as research object, samples of sediment along the main line of dam from upper, middle to lower reaches of dam fields and samples of undisturbed soil in slope of dam control basin were taken to carry out particle gradation analysis, in the hope of clearing reducing capacity on coarse sediment of different types of warping dam through the experimental data. The results show that the undisturbed soil in slope of dam control basin has characteristics of standard loess, the particle size are mainly distributed in 0.025 0.05mm, and the 0.05mm particle size of Jiuyuangou basinof loess is an obvious boundary; Particle size of sediment in 15 warping dam of Jiuyuangou basin are mainly distributed in 0.031 0.05mm with the dam tail is greater than dam front in general. The separation effect of horizontal pipe drainage is better than shaft drainage for which particle size greater than 0.05mm, notch dam is for particle size between 0.025 0.1 mm, and fill dam is for particle size between 0.016 0.1 mm, they all have a certain function in the sediment sorting.

Controls on hillslope stability in a mountain river catchment

NASA Astrophysics Data System (ADS)

Golly, Antonius; Turowski, Jens; Hovius, Niels; Badoux, Alexandre

2015-04-01

Sediment transport in fluvial systems accounts for a large fraction of natural hazard damage costs in mountainous regions and is an important factor for risk mitigation, engineering and ecology. Although sediment transport in high-gradient channels gathered research interest over the last decades, sediment dynamics in steep streams are generally not well understood. For instance, the sourcing of the sediment and when and how it is actually mobilized is largely undescribed. In the Erlenbach, a mountain torrent in the Swiss Prealps, we study the mechanistic relations between in-channel hydrology, channel morphology, external climatic controls and the surrounding sediment sources to identify relevant process domains for sediment input and their characteristic scales. Here, we analyze the motion of a slow-moving landslide complex that was permanently monitored by time-lapse cameras over a period of 70 days at a 30 minutes interval. In addition, data sets for stream discharge, air temperature and precipitation rates are available. Apparent changes in the channel morphology, e.g. the destruction of channel-spanning bed forms, were manually determined from the time-lapse images and were treated as event marks in the time series. We identify five relevant types of sediment displacement processes emerging during the hillslope motion: concentrated mud flows, deep seated hillslope failure, catastrophic cavity failure, hillslope bank erosion and individual grain loss. Generally, sediment displacement occurs on a large range of temporal and spatial scales and sediment dynamics in steep streams not only depend on large floods with long recurrence intervals. We find that each type of displacement acts in a specific temporal and spatial domain with their characteristic scales. Different external climatic forcing (e.g. high-intensity vs. long-lasting precipitation events) promote different displacement processes. Stream morphology and the presence of boulders have a large effect on sediment input through deep seated failures and cavity failures while they have only minor impact on the other process types. In addition to large floods, which are generally recognized to produce huge amounts of sediment, we identify two relevant climatic regimes that play an important role for the sediment dynamics: a) long-lasting but low-intensity rainfall that explicitly trigger specific sediment displacement processes on the hillslopes and b) smaller discharge events with recurrence intervals of approximately one year that mobilize sediments from the hillslope's toes along the channel.