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Sample records for permafrost sediment core

  1. Geochemical characteristics of organic compounds in a permafrost sediment core sample from northeast Siberia, Russia

    NASA Technical Reports Server (NTRS)

    Matsumoto, G. I.; Friedmann, E. I.; Gilichinsky, D. A.

    1995-01-01

    We studied total organic carbon (TOC), hydrocarbons and fatty acids in a permafrost sediment core sample (well 6-90, length 32.0 m, 1.5-2.5 Ma BP) from northeast Siberia (approximately 70 degrees N, 158 degrees E), Russia, to elucidate their geochemical features in relation to source organisms and paleoenvironmental conditions. Long-chain n-alkanes and n-alkanoic acids (>C19) were most predominant hydrocarbons and fatty acids, respectively, so organic matter in the sediment core was derived mainly from vascular plants and, to a much smaller extent, from bacteria. Low concentrations of unsaturated fatty acids revealed that organic matter in the sediment core was considerably degraded during and/or after sedimentation. The predominance of vascular plant components, the major ionic components of nonmarine sources, and geological data strongly implied that the sediment layers were formed in shallow lacustrine environments, such as swamp with large influences of tundra or forest-tundra vegetation. Also, no drastic changes in paleoenvironmental conditions for biological activity or geological events, such as sea transgressions or ice-sheet influences, occurred at the sampling site approximately 100 km from the coast of the East Siberian Sea during the late Pliocene an early Pleistocene periods.

  2. The permafrost carbon inventory on the Tibetan Plateau: a new evaluation using deep sediment cores.

    PubMed

    Ding, Jinzhi; Li, Fei; Yang, Guibiao; Chen, Leiyi; Zhang, Beibei; Liu, Li; Fang, Kai; Qin, Shuqi; Chen, Yongliang; Peng, Yunfeng; Ji, Chengjun; He, Honglin; Smith, Pete; Yang, Yuanhe

    2016-08-01

    The permafrost organic carbon (OC) stock is of global significance because of its large pool size and the potential positive feedback to climate warming. However, due to the lack of systematic field observations and appropriate upscaling methodologies, substantial uncertainties exist in the permafrost OC budget, which limits our understanding of the fate of frozen carbon in a warming world. In particular, the lack of comprehensive estimates of OC stocks across alpine permafrost means that current knowledge on this issue remains incomplete. Here, we evaluated the pool size and spatial variations of permafrost OC stock to 3 m depth on the Tibetan Plateau by combining systematic measurements from a substantial number of pedons (i.e. 342 three-metre-deep cores and 177 50-cm-deep pits) with a machine learning technique (i.e. support vector machine, SVM). We also quantified uncertainties in permafrost carbon budget by conducting Monte Carlo simulations. Our results revealed that the combination of systematic measurements with the SVM model allowed spatially explicit estimates to be made. The OC density (OC amount per unit area, OCD) exhibited a decreasing trend from the south-eastern to the north-western plateau, with the exception that OCD in the swamp meadow was substantially higher than that in surrounding regions. Our results also demonstrated that Tibetan permafrost stored a large amount of OC in the top 3 m, with the median OC pool size being 15.31 Pg C (interquartile range: 13.03-17.77 Pg C). 44% of OC occurred in deep layers (i.e. 100-300 cm), close to the proportion observed across the northern circumpolar permafrost region. The large carbon pool size together with significant permafrost thawing suggests a risk of carbon emissions and positive climate feedback across the Tibetan alpine permafrost region. PMID:26913840

  3. Aminostratigraphy of Organisms in Antarctic and Siberian Permafrost Cores

    NASA Technical Reports Server (NTRS)

    Brinton, K. L. F.; Tsapin, A. I.; McDonald, G. D.; Gilichinsky, D.

    1999-01-01

    Amino acid racemization dating (or aminostratigraphy) in Antarctic and Siberian permafrost core samples can be used to evaluate the age of organisms in frozen environments. The potential for subsurface permafrost on Mars makes terrestrial permafrost an important source of information regarding the preservation of both living organisms and their remains. Additional information is contained in the original extended abstract.

  4. Geomicrobial characterization of a 60 m long permafrost core from Svalbard

    NASA Astrophysics Data System (ADS)

    Fromreide, Siren; Tore Mørkved, Pål; Gilbert, Graham Lewis; Christiansen, Hanne H.; Reigstad, Laila

    2014-05-01

    In connection with a planned CO2 storage pilot project in the Arctic, a 60 m long permafrost core was drilled in Adventdalen, Svalbard. The on-shore drilling was performed through mainly marine and deltafront sediments, ending at the bedrock. The core has undergone detailed analyses of sedimentary stratigraphy, age, as well as the permafrost ice and carbon content at The University Centre in Svalbard (UNIS), and at the Center for Permafrost (CENPERM), Copenhagen. The main aim of the study presented here is to link the geochemical properties of the permafrost to the microbial community structure and its potential functions. As little is known about microbial life in permafrost at such depths this study will contribute to the understanding of these inaccessible ecosystems. A baseline geomicrobial description of 7 different depths in the 3 - 60 m interval of the permafrost core was done by culture independent methods such as 16S rRNA amplicon 454 pyrosequencing and functional and ribosomal gene quantifications. Additionally, geochemical analyses of the extracted pore water have been performed, as well as measurements of carbon content and major elements. The enumeration of the total prokaryotic community indicated similar numbers of bacteria and archaea down to approximately 50 m depth, while below this depth there was a dominance of archaeal cells. The bacterial 16S rRNA copy numbers ranged between 108 copies per gram sediment at 3 m depth to 104 copies per gram at the bedrock. Concerning the archaeal cells, the 16S rRNA copy numbers per gram sediment were in the range of 107 at the top of the core, ending at 105in the top of the bedrock. Detection and quantification of selected functional marker genes indicated high numbers of sulphate reducing bacteria at certain sediment depths, and a significant potential for microbial methanogenic activity throughout the core. Correlations studies between geochemical data and microbial community composition are currently ongoing.

  5. Contaminated Sediment Core Profiling

    EPA Science Inventory

    Evaluating the environmental risk of sites containing contaminated sediments often poses major challenges due in part to the absence of detailed information available for a given location. Sediment core profiling is often utilized during preliminary environmental investigations ...

  6. Methane in permafrost - Preliminary results from coring at Fairbanks, Alaska

    USGS Publications Warehouse

    Kvenvolden, K.A.; Lorenson, T.D.

    1993-01-01

    Permafrost has been suggested as a high-latitude source of methane (a greenhouse gas) during global warming. To begin to assess the magnitude of this source, we have examined the methane content of permafrost in samples from shallow cores (maximum depth, 9.5m) at three sites in Fairbanks, Alaska, where discontinuous permafrost is common. These cores sampled frozen loess, peat, and water (ice) below the active layer. Methane contents of permafrost range from <0.001 to 22.2mg/kg of sample. The highest methane content of 22.2mg/kg was found in association with peat at one site. Silty loess had high methane contents at each site of 6.56, 4.24, and 0.152mg/kg, respectively. Carbon isotopic compositions of the methane (??13C) ranged from -70.8 to -103.9 ???, and hydrogen isotopic compositions of the methane (??D) from -213 to -313 ???, indicating that the methane is microbial in origin. The methane concentrations were used in a one dimensional heat conduction model to predict the amount of methane that will be released from permafrost worldwide over the next 100 years, given two climate change scenarios. Our results indicate that at least 30 years will elapse before melting permafrost releases important amounts of methane; a maximum methane release rate will be about 25 to 30 Tg/yr, assuming that methane is generally distributed in shallow permafrost as observed in our samples.

  7. Challenges for coring deep permafrost on earth and mars

    SciTech Connect

    Pfiffner, Susan Marie; Onstott, Tullis; Ruskeeniemi, T; Talikka, M; Bakermans, Corien; McGown, Daniel; Chan, E.; Johnson, Adam; Phelps, Tommy Joe; Le Puil, M; Difurio, Sarah A; Pratt, L.M.; Stotler, R; Frape, S; Telling, J; Lollar, Barbara Sherwood; Neill, I; Zerbin, B

    2008-01-01

    A scientific drilling expedition to the High Lake region of Nunavut, Canada, was recently completed with the goals of collecting samples and delineating gradients in salinity, gas composition, pH, pe, and microbial abundance in a 400 m thick permafrost zone and accessing the underlying pristine subpermafrost brine. With a triple-barrel wireline tool and the use of stringent quality assurance and quality control (QA/QC) protocols, 200 m of frozen, Archean, mafic volcanic rock was collected from the lower boundary that separates the permafrost layer and subpermafrost saline water. Hot water was used to remove cuttings and prevent the drill rods from freezing in place. No cryopegs were detected during penetration through the permafrost. Coring stopped at the 535 m depth, and the drill water was bailed from the hole while saline water replaced it. Within 24 hours, the borehole iced closed at 125 m depth due to vapor condensation from atmospheric moisture and, initially, warm water leaking through the casing, which blocked further access. Preliminary data suggest that the recovered cores contain viable anaerobic microorganisms that are not contaminants even though isotopic analyses of the saline borehole water suggests that it is a residue of the drilling brine used to remove the ice from the upper, older portion of the borehole. Any proposed coring mission to Mars that seeks to access subpermafrost brine will not only require borehole stability but also a means by which to generate substantial heating along the borehole string to prevent closure of the borehole from condensation of water vapor generated by drilling.

  8. Challenges for coring deep permafrost on Earth and Mars.

    PubMed

    Pfiffner, S M; Onstott, T C; Ruskeeniemi, T; Talikka, M; Bakermans, C; McGown, D; Chan, E; Johnson, A; Phelps, T J; Le Puil, M; Difurio, S A; Pratt, L M; Stotler, R; Frape, S; Telling, J; Lollar, B Sherwood; Neill, I; Zerbin, B

    2008-06-01

    A scientific drilling expedition to the High Lake region of Nunavut, Canada, was recently completed with the goals of collecting samples and delineating gradients in salinity, gas composition, pH, pe, and microbial abundance in a 400 m thick permafrost zone and accessing the underlying pristine subpermafrost brine. With a triple-barrel wireline tool and the use of stringent quality assurance and quality control (QA/QC) protocols, 200 m of frozen, Archean, mafic volcanic rock was collected from the lower boundary that separates the permafrost layer and subpermafrost saline water. Hot water was used to remove cuttings and prevent the drill rods from freezing in place. No cryopegs were detected during penetration through the permafrost. Coring stopped at the 535 m depth, and the drill water was bailed from the hole while saline water replaced it. Within 24 hours, the borehole iced closed at 125 m depth due to vapor condensation from atmospheric moisture and, initially, warm water leaking through the casing, which blocked further access. Preliminary data suggest that the recovered cores contain viable anaerobic microorganisms that are not contaminants even though isotopic analyses of the saline borehole water suggests that it is a residue of the drilling brine used to remove the ice from the upper, older portion of the borehole. Any proposed coring mission to Mars that seeks to access subpermafrost brine will not only require borehole stability but also a means by which to generate substantial heating along the borehole string to prevent closure of the borehole from condensation of water vapor generated by drilling. PMID:18680412

  9. Diversity and community structure of fungi through a permafrost core profile from the Qinghai-Tibet Plateau of China.

    PubMed

    Hu, Weigang; Zhang, Qi; Li, Dingyao; Cheng, Gang; Mu, Jing; Wu, Qingbai; Niu, Fujun; An, Lizhe; Feng, Huyuan

    2014-12-01

    While a vast number of studies have addressed the prokaryotic diversity in permafrost, characterized by subzero temperatures, low water activity, and extremely low rates of nutrient and metabolite transfer, fungal patterns have received surprisingly limited attention. Here, the fungal diversity and community structure were investigated by culture-dependent technique combined with cloning-restriction fragment length polymorphism (RFLP) analysis of sediments in a 10-m-long permafrost core from the Qinghai-Tibet Plateau of China. A total of 62 fungal phylotypes related to 10 distinct classes representing three phyla were recovered from 5031 clones generated in 13 environmental gene libraries. A large proportion of the phylotypes (25/62) that were distantly related to described fungal species appeared to be novel diversity. Ascomycota was the predominant group of fungi, with respect to both clone and phylotype number. Our results suggested there was the existence of cosmopolitan psychrophilic or psychrotolerant fungi in permafrost sediments, the community composition of fungi varied with increasing depth, while these communities largely distributed according to core layers. PMID:24920339

  10. Permafrost

    USGS Publications Warehouse

    Ray, Louis L.

    1993-01-01

    In 1577, on his second voyage to the New World in search of the Northwest Passage, Sir Martin Frobisher reported finding ground in the far north that was frozen to depths of "four or five fathoms, even in summer," and that the frozen condition "so combineth the stones together that scarcely instruments with great force can unknit them." This permanently frozen ground, now termed permafrost, underlies perhaps a fifth of the Earth's land surface. It occurs in Antarctica but is most extensive in the Northern Hemisphere. In the lands surrounding the Arctic Ocean, its maximum thickness has been reported in thousands of feet as much as 5,000 feet in Siberia and 2,000 feet in northern Alaska.

  11. Metagenomics Reveals Microbial Community Composition And Function With Depth In Arctic Permafrost Cores

    NASA Astrophysics Data System (ADS)

    Jansson, J.; Tas, N.; Wu, Y.; Ulrich, C.; Kneafsey, T. J.; Torn, M. S.; Hubbard, S. S.; Chakraborty, R.; Graham, D. E.; Wullschleger, S. D.

    2013-12-01

    The Arctic is one of the most climatically sensitive regions on Earth and current surveys show that permafrost degradation is widespread in arctic soils. Biogeochemical feedbacks of permafrost thaw are expected to be dominated by the release of currently stored carbon back into the atmosphere as CO2 and CH4. Understanding the dynamics of C release from permafrost requires assessment of microbial functions from different soil compartments. To this end, as part of the Next Generation Ecosystem Experiment in the Arctic, we collected two replicate permafrost cores (1m and 3m deep) from a transitional polygon near Barrow, AK. At this location, permafrost starts from 0.5m in depth and is characterized by variable ice content and higher pH than surface soils. Prior to sectioning, the cores were CT-scanned to determine the physical heterogeneity throughout the cores. In addition to detailed geochemical characterization, we used Illumina MiSeq technology to sequence 16SrRNA genes throughout the depths of the cores at 1 cm intervals. Selected depths were also chosen for metagenome sequencing of total DNA (including phylogenetic and functional genes) using the Illumina HiSeq platform. The 16S rRNA gene sequence data revealed that the microbial community composition and diversity changed dramatically with depth. The microbial diversity decreased sharply below the first few centimeters of the permafrost and then gradually increased in deeper layers. Based on the metagenome sequence data, the permafrost microbial communities were found to contain members with a large metabolic potential for carbon processing, including pathways for fermentation and methanogenesis. The surface active layers had more representatives of Verrucomicrobia (potential methane oxidizers) whereas the deep permafrost layers were dominated by several different species of Actinobacteria. The latter are known to have a diverse metabolic capability and are able to adapt to stress by entering a dormant yet

  12. High permafrost ice contents in Holocene slope deposits as observed from shallow geophysics and a coring program in Pangnirtung, Nunavut, Canada

    NASA Astrophysics Data System (ADS)

    Carbonneau, A.; Allard, M.; L'Hérault, E.; LeBlanc, A.

    2011-12-01

    A study of permafrost conditions was undertaken in the Hamlet of Pangnirtung, Nunavut, by the Geological Survey of Canada (GSC) and Université Laval's Centre d'études nordiques (CEN) to support decision makers in their community planning work. The methods used for this project were based on geophysical and geomorphological approaches, including permafrost cores drilled in surficial deposits and ground penetrating radar surveys using a GPR Pulse EKKO 100 extending to the complete community area and to its projected expansion sector. Laboratory analysis allowed a detailed characterization of permafrost in terms of water contents, salinity and grain size. Cryostratigraphic analysis was done via CT-Scan imagery of frozen cores using medical imaging softwares such as Osiris. This non destructive method allows a 3D imaging of the entire core in order to locate the amount of the excess ice, determine the volumetric ice content and also interpret the ice-formation processes that took place during freezing of the permafrost. Our new map of the permafrost conditions in Pangnirtung illustrates that the dominant mapping unit consist of ice-rich colluvial deposits. Aggradationnal ice formed syngenitically with slope sedimentation. Buried soils were found imbedded in this colluvial layer and demonstrates that colluviation associated with overland-flow during snowmelt occurred almost continuously since 7080 cal. BP. In the eastern sector of town, the 1 to 4 meters thick colluviums cover till and a network of ice wedges that were revealed as spaced hyperbolic reflectors on GPR profiles. The colluviums also cover ice-rich marine silt and bedrock in the western sector of the hamlet; marine shells found in a permafrost core yielded a radiocarbon date of 9553 cal. BP which provides a revised age for the local deglaciation and also a revised marine submergence limit. Among the applied methods, shallow drilling in coarse grained permafrost, core recovery and CT-Scan allowed the

  13. Rates of landscape change in discontinuous permafrost terrain inferred from Goose Lake sediments, Scotty Creek Basin, Northwest Territories, Canada

    NASA Astrophysics Data System (ADS)

    Cockburn, J.; Baltzer, J.; Quinton, W. L.

    2012-12-01

    Changes to the Taiga Plain regions of the world due to recent permafrost thaw and a general warming trend has significant impacts on hydrology, ecology and carbon sequestration in these regions. Furthermore, the rates of these changes may prove to be positive feedbacks within the cryosphere. The recent sedimentary record from Goose Lake, NWT (61° 18' N, 121° 18' W) reveals changes in lake and adjacent landscape productivity, likely coincident with degrading permafrost through the late Holocene and noticeable shifts within the last half of the 20th century. Using short-cores retrieved in August 2012, this study presents preliminary models of late Holocene landscape changes. Shifts in the rates of change are due to recent thaw as evidenced by the sedimentary record and supported through process work completed in the region. Goose Lake is situated in the Taiga Plains, approximately 50 km south of Fort Simpson, in the lower Liard River basin. This small, lake (~2.5 m deep, 200 ha) in the Scotty Creek watershed headwaters is primarily fed through small fens. The Scotty Creek basin has had over a decade of permafrost and peatland hydrological monitoring (i.e., Quinton et al., 2009). As well, the Scotty Creek basin is the location of ongoing peatland ecological and hydrological monitoring programs. The monitoring work suggests that there is a cycle of bog - fen - plateau (ice-rich) landscape changes and that perhaps the rate of these cycles may be increasing as permafrost degradation increases. The lake sediment work aims to estimate the rates of these cycles through the late Holocene and potentially link to larger scale models of change within the Taiga Plains. A shift in cycling would have substantial impacts on carbon storage, ecosystem diversity and potentially change the overall hydrology of this peatland area. If Goose Lake is indicative of other small lakes in the Taiga Plains, combined with the hydrological and ecological observations, this system will be a

  14. Mid-Wisconsin to Holocene permafrost and landscape dynamics based on a drained lake basin core from the northern Seward Peninsula, northwest Alaska

    USGS Publications Warehouse

    Lenz, Josefine; Grosse, Guido; Jones, Benjamin M.; Anthony, Katey M. Walter; Bobrov, Anatoly; Wulf, Sabine; Wetterich, Sebastian

    2016-01-01

    Permafrost-related processes drive regional landscape dynamics in the Arctic terrestrial system. A better understanding of past periods indicative of permafrost degradation and aggradation is important for predicting the future response of Arctic landscapes to climate change. Here, we used a multi-proxy approach to analyse a ~ 4 m long sediment core from a drained thermokarst lake basin on the northern Seward Peninsula in western Arctic Alaska (USA). Sedimentological, biogeochemical, geochronological, micropalaeontological (ostracoda, testate amoebae) and tephra analyses were used to determine the long-term environmental Early-Wisconsin to Holocene history preserved in our core for central Beringia. Yedoma accumulation dominated throughout the Early to Late-Wisconsin but was interrupted by wetland formation from 44.5 to 41.5 ka BP. The latter was terminated by the deposition of 1 m of volcanic tephra, most likely originating from the South Killeak Maar eruption at about 42 ka BP. Yedoma deposition continued until 22.5 ka BP and was followed by a depositional hiatus in the sediment core between 22.5 and 0.23 ka BP. We interpret this hiatus as due to intense thermokarst activity in the areas surrounding the site, which served as a sediment source during the Late-Wisconsin to Holocene climate transition. The lake forming the modern basin on the upland initiated around 0.23 ka BP and drained catastrophically in spring 2005. The present study emphasises that Arctic lake systems and periglacial landscapes are highly dynamic and that permafrost formation as well as degradation in central Beringia was controlled by regional to global climate patterns as well as by local disturbances.

  15. Biogeochemical and suspended sediment responses to permafrost degradation in stream banks in Taylor Valley, Antarctica

    NASA Astrophysics Data System (ADS)

    Gooseff, M. N.; Van Horn, D.; Sudman, Z.; McKnight, D. M.; Welch, K. A.; Lyons, W. B.

    2015-09-01

    Stream channels in the McMurdo Dry Valleys are typically wide, incised, and stable. At typical flows, streams occupy a fraction of the oversized channels, providing habitat for algal mats. In January 2012, we discovered substantial channel erosion and subsurface thermomechanical erosion undercutting banks of Crescent Stream. We sampled stream water along the impacted reach and compared concentrations of solutes to the long-term data from this stream (~20 years of monitoring). Thermokarst-impacted stream water demonstrated higher electrical conductivity, and concentrations of chloride, sulfate, sodium, suspended sediments, and nitrate than the long-term medians. These results suggest that this mode of lateral permafrost degradation may substantially impact stream solute loads and potentially fertilize stream and lake ecosystems. The potential for sediment to scour or bury stream algal mats is yet to be determined, though it may offset impacts of associated increased nutrient loads to streams.

  16. Viable Species of Flamella (Amoebozoa: Variosea) Isolated from Ancient Arctic Permafrost Sediments.

    PubMed

    Shmakova, Lyubov; Bondarenko, Natalya; Smirnov, Alexey

    2016-02-01

    Six viable strains of amoebae belonging to the genus Flamella (Amoebozoa, Variosea) were isolated from permafrost sediments sampled in the Russian Arctic region. Two of them are from late Pleistocene permafrost in North-East Siberia, and four--from Holocene and late Pleistocene in North-West Siberia. Light- and electron-microscopic study and molecular phylogeny show that these isolates represent two new species belonging to the genus Flamella. Both species are cyst-forming. This is a remarkable case of high resistance of protozoan cysts, allowing them to survive and recover an amoebae population after a very long, geologically significant period of rest; a "snapshot" of evolution in time. This study directly shows for the first time that amoeba cysts can be conserved not only for years and decades but for many thousand years and then recover, contributing to the formation of an active microbial community. We propose to name the new species as Flamella pleistocenica n.sp. and Flamella beringiania n.sp. Phylogenetic analysis shows that the genus Flamella is a robust and potentially species-rich group of Variosea. PMID:26735346

  17. Stream biogeochemical and suspended sediment responses to permafrost degradation in stream banks in Taylor Valley, Antarctica

    NASA Astrophysics Data System (ADS)

    Gooseff, Michael N.; Van Horn, David; Sudman, Zachary; McKnight, Diane M.; Welch, Kathleene A.; Lyons, William B.

    2016-03-01

    Stream channels in the McMurdo Dry Valleys are characteristically wide, incised, and stable. At typical flows, streams occupy a fraction of the oversized channels, providing habitat for algal mats. In January 2012, we discovered substantial channel erosion and subsurface thermomechanical erosion undercutting banks of the Crescent Stream. We sampled stream water along the impacted reach and compared concentrations of solutes to the long-term data from this stream ( ˜ 20 years of monitoring). Thermokarst-impacted stream water demonstrated higher electrical conductivity, and concentrations of chloride, sulfate, sodium, and nitrate than the long-term medians. These results suggest that this mode of lateral permafrost degradation may substantially impact stream solute loads and potentially fertilize stream and lake ecosystems. The potential for sediment to scour or bury stream algal mats is yet to be determined, though it may offset impacts of associated increased nutrient loads to streams.

  18. Radiocarbon Age Offsets in Arctic Lake Sediments Describe the Vulnerability of Permafrost Carbon to Past Climate Warming

    NASA Astrophysics Data System (ADS)

    Gaglioti, B.; Mann, D. H.; Pohlman, J.; Kunz, M. L.; Jones, B. M.; Jones, M.; Wooller, M. J.

    2012-12-01

    A warming climate in the future could release permafrost carbon (C) as carbon dioxide and methane to the atmosphere, causing a positive feedback to climate warming. An effective approach to better understanding this problem is to observe how permafrost C dynamics responded to past warming events. Here we use the sediment record of a lake basin in northern Alaska as a long-term archive for past permafrost C release from the surrounding watershed. The age of deposition and burial for an arctic lake sediment horizon is often younger than the 14C age because of old, 14C-depleted C eroded or leached from peat, soil, and thawing permafrost in the watershed. Changes in the magnitude between the age of deposition ("true age") and the radiocarbon age of the bulk sediment from the same layer is the radiocarbon age-offset, which serves as a gauge for the relative amount of permafrost C released from the watershed. We analyzed the sediments of Lake of the Pleistocene (LOP), a partially-drained lake basin located in the northern flank of the Brooks Range that contains continuously deposited sediments spanning the last 14,500 calendar years. The LOP watershed is underlain by continuous permafrost and contains extensive, frozen peatlands. We were able to excavate a wide swath of the former lakebed and collect hundreds of willow twigs and sediment samples to construct a high-resolution age-offset chronology. We dated well-preserved willow twigs that are directly blown into the lake to obtain a "true" 14C age and the age of bulk lake-sediment organic matter from the same layer that records the age of both primary productivity from within the lake and of the old dissolved and particulate organic carbon reworked from the watershed. Today, the radiocarbon age of the surface sediments of LOP is 2,000 calendar years old, which is roughly the same as the age offset during the Younger Dryas cold interval. During the warmer than present Holocene Thermal Maximum (HTM; ~11,700-9,000 calendar

  19. Effect of Shallow Ponding on Warming and Thawing of Permafrost in Mineral-cored Palsas, Wolf Creek, Yukon, Canada

    NASA Astrophysics Data System (ADS)

    Lewkowicz, A. G.; Etzelmuller, B.; Smith, S.

    2011-12-01

    Few measurements exist of the effect of shallow water bodies on ground temperatures in the discontinuous permafrost zone. However, such ponds could become more common under climate warming and could affect rates of thaw of frozen ground and subsequent carbon release. To examine these effects, permafrost temperatures were monitored manually or continuously using temperature-loggers in six mineral-cored palsas (permafrost-cored mounds) located on a valley floor at treeline in the Wolf Creek basin near Whitehorse. The mounds were instrumented in 2004 in anticipation of water-level changes due to dam construction by beavers (Castor canadensis). Over this period beaver activity has raised water levels and created larger water bodies adjacent to all of the palsas, resulting in ground temperature increases and permafrost degradation. The ponds are shallow and some freeze to the bottom in winter, but their mean annual temperatures are higher than on adjacent exposed surfaces and they therefore warm the palsas laterally, eventually causing block collapse. A 7-year record of temperatures from a previously stable palsa, shows slight but progressive warming at the base of permafrost (at 7 m) since it was surrounded by water in 2009. Other palsas which were already degrading in 2001 are experiencing higher rates of warming and are rapidly settling beneath the water. Internal changes in unfrozen water contents within the palsas were revealed by differences between pairs of DC electrical resistivity profiles recorded in spring 2006 when most forms were stable, and repeated in spring 2011 when most were degrading. The rapidity of permafrost change when warmed by water illustrates the potential for drainage changes to dramatically increase heat flow through convection and hence to speed up rates of permafrost degradation.

  20. Dating sediment cores from Hudson River marshes

    SciTech Connect

    Robideau, R.; Bopp, R.F. . Dept. of Earth and Environmental Sciences)

    1993-03-01

    There are several methods for determining sediment accumulation rates in the Hudson River estuary. One involves the analysis of the concentration of certain radionuclides in sediment core sections. Radionuclides occur in the Hudson River as a result of: natural sources, fallout from nuclear weapons testing and low level aqueous releases from the Indian Point Nuclear Power Facility. The following radionuclides have been studied in the authors work: Cesium-137, which is derived from global fallout that started in the 1950's and has peaked in 1963. Beryllium-7, a natural radionuclide with a 53 day half-life and found associated with very recently deposited sediments. Another useful natural radionuclide is Lead-210 derived from the decay of Radon-222 in the atmosphere. Lead-210 has a half-life of 22 years and can be used to date sediments up to about 100 years old. In the Hudson River, Cobalt-60 is a marker for Indian Point Nuclear Reactor discharges. The author's research involved taking sediment core samples from four sites in the Hudson River Estuarine Research Reserve areas. These core samples were sectioned, dried, ground and analyzed for the presence of radionuclides by the method of gamma-ray spectroscopy. The strength of each current pulse is proportional to the energy level of the gamma ray absorbed. Since different radionuclides produce gamma rays of different energies, several radionuclides can be analyzed simultaneously in each of the samples. The data obtained from this research will be compared to earlier work to obtain a complete chronology of sediment deposition in these Reserve areas of the river. Core samples may then by analyzed for the presence of PCB's, heavy metals and other pollutants such as pesticides to construct a pollution history of the river.

  1. Impacts of Permafrost Degradation on Stream Geomorphology and Sediment Transport in Taylor Valley, Antarctica

    NASA Astrophysics Data System (ADS)

    Gooseff, M. N.; Sudman, Z. W.

    2015-12-01

    The McMurdo Dry Valleys (MDV) of Antarctica are a unique ice-free landscape that supports complex, microbially dominated ecosystems despite the harsh environment (<10 cm water equivalent/yr, -18°C mean air temperature). Recent observations suggest that this region is nearing a threshold of rapid landscape change. One such observation was the recent discovery of extensive thermokarst development (permafrost thaw features) along the banks of Crescent Stream in Taylor Valley. In 2012, a large stretch of the West Branch of Crescent Stream had significant bank failures, while the adjacent East Branch was unaffected. The objective of this study was to determine the rate of land surface change occurring on the stream bank, and the impacts of the sediment loading on the stream bed material. Three annually repeated terrestrial LiDAR scans were compared to determine the rates of ground surface change due to thermokarst degradation on the stream bank. The areal extent of the thermokarst was shown to be decreasing, however the average vertical erosion rate remained constant. Field measurements including, pebble counts, fine sediment counts, and sieve samples were collected and analyzed to determine the effects of the introduction of fine sediment on the stream bed material. The bed sediment of the thermokarst-impacted branch was consistently finer than the adjacent unaffected branch. The fine material introduced to the stream altered the bed material composition, which consequently increased the mobility of the of the bed material. These changes imposed on the stream have implications for stream morphology, endemic algal mat communities, and downstream aquatic systems.

  2. Ideas and perspectives: Holocene thermokarst sediments of the Yedoma permafrost region do not increase the northern peatland carbon pool

    NASA Astrophysics Data System (ADS)

    Hugelius, Gustaf; Kuhry, Peter; Tarnocai, Charles

    2016-04-01

    Permafrost deposits in the Beringian Yedoma region store large amounts of organic carbon (OC). Walter Anthony et al. (2014) describe a previously unrecognized pool of 159 Pg OC accumulated in Holocene thermokarst sediments deposited in Yedoma region alases (thermokarst depressions). They claim that these alas sediments increase the previously recognized circumpolar permafrost peat OC pool by 50 %. It is stated that previous integrated studies of the permafrost OC pool have failed to account for these deposits because the Northern Circumpolar Soil Carbon Database (NCSCD) is biased towards non-alas field sites and that the soil maps used in the NCSCD underestimate coverage of organic permafrost soils. Here we evaluate these statements against a brief literature review, existing data sets on Yedoma region soil OC storage and independent field-based and geospatial data sets of peat soil distribution in the Siberian Yedoma region. Our findings are summarized in three main points. Firstly, the sediments described by Walter Anthony et al. (2014) are primarily mineral lake sediments and do not match widely used international scientific definitions of peat or organic soils. They can therefore not be considered an addition to the circumpolar peat carbon pool. We also emphasize that a clear distinction between mineral and organic soil types is important since they show very different vulnerability trajectories under climate change. Secondly, independent field data and geospatial analyses show that the Siberian Yedoma region is dominated by mineral soils, not peatlands. Thus, there is no evidence to suggest any systematic bias in the NCSCD field data or maps. Thirdly, there is spatial overlap between these Holocene thermokarst sediments and previous estimates of permafrost soil and sediment OC stocks. These carbon stocks were already accounted for by previous studies and they do not significantly increase the known circumpolar OC pool. We suggest that these inaccurate

  3. Characterization of the prokaryotic diversity through a stratigraphic permafrost core profile from the Qinghai-Tibet Plateau.

    PubMed

    Hu, Weigang; Zhang, Qi; Tian, Tian; Li, Dingyao; Cheng, Gang; Mu, Jing; Wu, Qingbai; Niu, Fujun; An, Lizhe; Feng, Huyuan

    2016-05-01

    Permafrost on the Qinghai-Tibet Plateau is one of the most sensitive regions to climate warming, thus characterizing its microbial diversity and community composition may be important for understanding their potential responses to climate changes. Here, we investigated the prokaryotic diversity in a 10-m-long permafrost core from the Qinghai-Tibet Plateau by restriction fragment length polymorphism analysis targeting the 16S rRNA gene. We detected 191 and 17 bacterial and archaeal phylotypes representing 14 and 2 distinct phyla, respectively. Proteobacteria was the dominant bacterial phylum, while archaeal communities were characterized by a preponderance of Thaumarchaeota. Some of prokaryotic phylotypes were closely related to characterized species involved in carbon and nitrogen cycles, including nitrogen fixation, methane oxidation and nitrification. However, the majority of the phylotypes were only distantly related to known taxa at order or species level, suggesting the potential of novel diversity. Additionally, both bacterial α diversity and community composition changed significantly with sampling depth, where these communities mainly distributed according to core horizons. Arthrobacter-related phylotypes presented at high relative abundance in two active layer soils, while the deeper permafrost soils were dominated by Psychrobacter-related clones. Changes in bacterial community composition were correlated with most measured soil variables, such as carbon and nitrogen contents, pH, and conductivity. PMID:27033516

  4. Linking permafrost distribution, glacial retreat and colluvial sediment dynamics in the Saldur River basin, Eastern Italian Alps

    NASA Astrophysics Data System (ADS)

    Brardinoni, Francesco; Sosio, Rosanna; Scotti, Riccardo; Cavalli, Marco; Comiti, Francesco; Mair, Volkmar

    2014-05-01

    In the last three decades generalized atmospheric temperature rise has produced rapid glacial retreat and permafrost degradation in high mountain environments of the European Alps. While it is widely recognized that these changes can impart general instability to mountain slopes (i.e., several projects have documented single case studies of high magnitude-low frequency, catastrophic slope failures), to our knowledge, there appears to be little empirical data available for investigating the spatial distribution of mass-wasting intensity through time in high mountain areas in relation to permafrost degradation and deglaciation patterns. This is a critical shortcoming. Understanding and quantifying the influence of similar transient conditions on mass-wasting processes holds critical long-term implications on the overall sediment flux reshaping mountain landscapes (e.g., post-LGM landscape evolution), as well as more practical short-term applications on water quality issues, damage control/prevention to infrastructure, and reservoir siltation, to mention some. In this contribution we present an integrated approach that aims to: (i) document the spatial distribution of mass-wasting activity and sediment production in the Saldur River basin (97 km^2); (ii) detect causal linkages between mass-wasting intensity, the potential spatial distribution of discontinuous permafrost, and patterns of glacier retreat; and (iii) identify source-to-sink colluvial sedimentary pathways as modulated by the spatial organization of glacial and periglacial landforms. To these ends, we map rock glaciers, protalus ramparts and moraines, and compile a field- and air photo-based multi-temporal (1959-2012) inventory of colluvial sediment sources. We then combine these data with two historical datasets of debris flow and landslide events (both implemented and maintained by the Autonomous Province of Bolzano) and analyse mass-wasting spatial distribution and intensity in relation to proximity of

  5. ENANTIOMERIC RATIOS OF CHIRAL PCB ATROPISOMERS IN RADIODATED SEDIMENT CORES

    EPA Science Inventory

    Enantiomeric ratios (ERs)) of chiral polychlorinated biphenyl (PCB) atropisomers were quantified in radiodated sediment cores of Lake Hartwell SC, a reservoir heavily impacted by PCBS, to study spatial and temporal changes in chirality. A chiral analysis of cores showed accumulat...

  6. Infrared images of core sediments offshore southwestern Taiwan

    NASA Astrophysics Data System (ADS)

    Chiang, H. T.; Chuang, Y. H.

    2015-12-01

    The core sediments may retain the negative thermal anomaly caused by the gas hydrate dissociation on the way uploading from sea floor. To identify the signal of negative thermal anomaly, fifteen infrared images of core sediments with tens of meter in length have been analyzed the temperature distribution off southwestern Taiwan. This study results show that most of the core sediments were found lots of gaps with spiking pattern recognition of high temperature on the lower portions. The geochemistry study suggested that the gas in gaps and the sediments were mainly composed of methane which may be the indicators of gas hydrate dissociation in the higher temperature and lower pressure environment. The thermal gradients 0.044-0.114 ℃/m of core sediments are close to the observations in situ by the measurements of temperature probes that thermal gradient are 0.06-0.09 ℃/m. The temperature of all core sediments are greater than 20 ℃. It is obvious that the temperature of core sediments were increased tremendously by the heating of sea water. We found eight out of fifteen core sediments with significant negative thermal anomaly 0.4-1.0 ℃ in different depth between 2 and 10 meters below sea floor. Compare to the experiment in lab that the temperature could be decreased 1.1-1.5 ℃ due to the gas hydrate dissociation, the quantity of the negative thermal anomaly of the core sediments are possible related to the gas hydrate dissociation.

  7. /sup 137/Cs radioactive dating of Lake Ontario sediment cores

    SciTech Connect

    Ward, T.E.; Breeden, J.; Komisarcik, K.; Porter, R.; Czuczwa, J.; Kaminski, R.; McVeety, B.D.

    1987-12-01

    The distribution of /sup 137/Cs in sediment cores from Lake Ontario provides estimates of the sediment accumulation rates. Geochronology with /sup 210/Pb dating and distribution of Ambrosia (ragweed) pollen compare well with /sup 137/Cs dating. These methods can determine with precision, changes in sedimentation occurring over the past 100 years or so. Typical sedimentation rates of 0.18-0.36 cm/yr were measured. 16 refs., 3 figs., 2 tabs.

  8. Geochemistry of sediments in cores and sediment traps from Bear Lake, Utah and Idaho

    USGS Publications Warehouse

    Bischoff, James L.; Cummins, Kathleen; Shamp, Donald D.

    2005-01-01

    The present study of Bear Lake began in 1998. Initially, the study utilized sediments from three long cores (up to 5 m) previously collected in 1996 and short cores (up to 40 cm) collected in 1998. The short cores were specifically acquired to preserve the uppermost layers of sediment that may have been lost in the long cores. In addition, three arrays of sediment traps were deployed during the summer of 1998, and sediment from these traps was collected during the summers of 1999 and 2000 (see Dean and others, 2005, for core and sediment trap locations). The cores and sediment traps were sampled, and splits were distributed to various investigators for analyses of a wide variety of sediment parameters. The chemical composition of the acid-soluble component of the sediments is presented in this report. HCl or HNO3 treatment of the sediment quantitatively dissolves the authigenic component of the sediment, a component that includes carbonates, sulfates, and iron-mono sulfides. In the case of Bear Lake, CaCO3 is the major component of the sediment today and for most of the Holocene (Dean and others 2005). The chemical composition of the acid-soluble fraction gives important information on this component and, therefore, insight into the chemical conditions of the lake at the time of carbonate deposition.

  9. Historical records of organic pollutants in sediment cores.

    PubMed

    Bigus, Paulina; Tobiszewski, Marek; Namieśnik, Jacek

    2014-01-15

    Analyses of sediment core samples are primary sources of historical pollution trends in aquatic systems. Determining organic compounds, such as POPs, in the dated sediments enables the estimation of their temporal concentration changes and the identification of the contaminant origin in local regions. Wars, large-scale fires, economical transitions, and bans on certain chemicals are reflected in the sediment organic compound concentrations. The high POP concentrations in surficial sediments suggest that these chemicals, even after being banned, remain in the environment. Furthermore, vertical profiles can help in understanding the sedimentation process and in estimating effective countermeasures against pollution. Moreover, studies published during the period 1991-2013 on PAHs, PCBs, OCPs, dioxins and dioxin-like compound concentrations in sediment core samples are reviewed. PMID:24300286

  10. Geochemistry of drill core headspace gases and its significance in gas hydrate drilling in Qilian Mountain permafrost

    NASA Astrophysics Data System (ADS)

    Lu, Zhengquan; Rao, Zhu; He, Jiaxiong; Zhu, Youhai; Zhang, Yongqin; Liu, Hui; Wang, Ting; Xue, Xiaohua

    2015-02-01

    Headspace gases from cores are sampled in the gas hydrate drilling well DK-8 in the Qilian Mountain permafrost. Gas components and carbon isotopes of methane from headspace gas samples are analyzed. The geochemical features of the headspace gases along the well profile are compared with occurrences of gas hydrate, and with the distribution of faults or fractures. Their geochemical significance is finally pointed out in gas hydrate occurrences and hydrocarbon migration. Results show high levels of hydrocarbon concentrations in the headspace gases at depths of 149-167 m, 228-299 m, 321-337 m and 360-380 m. Visible gas hydrate and its associated anomalies occur at 149-167 m and 228-299 m; the occurrence of high gas concentrations in core headspace gases was correlated to gas hydrate occurrences and their associated anomalies, especially in the shallow layers. Gas compositions, gas ratios of C1/ΣC1-5, C1/(C2 + C3), iC4/nC4, and iC5/nC5, and carbon isotopic compositions of methane (δ13C1, PDB‰) indicate that the headspace gases are mainly thermogenic, partly mixed with biodegraded thermogenic sources with small amounts derived from microbial sources. Faults or fracture zones are identified at intervals of 149-167 m, 228-299 m, 321-337 m, and near 360-380 m; significantly higher gas concentrations and lower dryness ratio were found in the headspace gases within the fault or fracture zones compared with areas above these zones. In the shallow zones, low dryness ratios were observed in headspace gases in zones where gas hydrate and faults or fracture zones were found, suggesting that faults or fracture zones serve as migration paths for gases in the deep layers and provide accumulation space for gas hydrate in the shallow layers of the Qilian Mountain permafrost.

  11. Natural thorium isotopes in marine sediment core off Labuan port

    SciTech Connect

    Hafidz, B. Y.; Asnor, A. S.; Terence, R. C.; Mohamed, C. A. R.

    2014-02-12

    Sediment core was collected from Labuan port and analyzed to determine the radioactivity of thorium (Th) isotopes. The objectives of this study are to determine the possible sources of Th isotopes at Labuan port and estimates the sedimentation rate based on {sup 228}Th/{sup 232}Th model. The results suggest the {sup 230}Th and {sup 232}Th might be originated from terrestrial sedimentary rock while {sup 228}Th originated by authigenic origin. High ratio value of {sup 230}Th/{sup 232}Th detected at the top surface sediment indicates the increasing of {sup 230}Th at the recent years which might be contributed from the anthropogenic sources. The sedimentation rate of core sediment from Labuan Port was successfully estimated by using {sup 228}Th/{sup 232}Th model. The result show high sedimentation rate with 4.67 cm/year indicates rapid deposition occurred at this study area due to the high physical activity at the Labuan port. By assume the constant sedimentation rate at this area; we estimated the age of 142 cm core sediment obtained from Labuan port is 32 years started from 1981 to 2012. This chronology will be used in forthcoming research to investigate the historical profile of anthropogenic activities affecting the Labuan port.

  12. Methane production potentials in a thermokarst lake and its underlying permafrost

    NASA Astrophysics Data System (ADS)

    Heslop, J.; Walter Anthony, K. M.; Sepulveda-Jauregui, A.; Martinez-Cruz, K.

    2013-12-01

    Thermokarst lakes, formed in permafrost-thaw depressions, are known sources of atmospheric methane (CH4) and carbon dioxide (CO2) but the location of gas production in a thermokarst-lake environment is not well constrained. This study compares CH4 and CO2 production potentials of samples collected from various depths along a 5-m deep lake sediment core and an adjacent 40-m deep undisturbed permafrost profile, allowing for direct determination as to where CH4 and CO2 are originating within an active thermokarst-lake landscape. Vault Lake and Vault Creek Permafrost Tunnel are located approximately 40 km north of Fairbanks, Alaska in a region characterized by yedoma permafrost. The Vault Lake sediment core, collected in the center of a ~4000 m2 lake, captured the surface lake sediments, talik (thaw bulb), and the permafrost actively thawing beneath the lake for comparison to parallel permafrost soil samples from the Vault Creek Permafrost Tunnel. Samples were analyzed for bulk density, ice and water content, organic and inorganic carbon content, C:N ratios, and water-soluble organic C. Initial soil organic matter (SOM) composition was characterized using Fourier transform infrared (FTIR) spectroscopy and pyrolysis-gas chromatography/mass spectrometry (py-GC/MS). CH4 and CO2 production potentials and their stable carbon isotope values from 21 depths along the lake core and 17 depths along the permafrost tunnel were measured in anaerobic laboratory incubations. We incubated samples at four temperatures (0 C, 3 C, 10 C and 25 C) to test the potential response of methanogenesis to increasing temperature in scenarios of future climate warming. Preliminary results suggest methanogenesis is highest in the top 1 m of the Vault Lake core and at the base of the talik, which is the permafrost thaw front beneath the lake.

  13. Diffusimetry (diffusion constant estimation) on sediment cores by resistivity probe

    USGS Publications Warehouse

    Manheim, Frank T.; Waterman, Lee S.

    1974-01-01

    Measurement of formation factor (ratio of rock resistivity to interstitial water resistivity) from sediment cores provides an indirect measurment of the tortuosity of the fluid channels in the sediments. From these measurements one can estimate the diffusion coefficient of the sediment with depth. The F (formation factor) values for Indian Ocean sediments varied from 1.6 for a clayey diatom ooze having 87% porosity (70% water content) to 13.6 for a cemented limestone having 25% porosity (11% water content). These formation factors would yield diffusion coefficients for chloride ions in the corresponding sediments of 6.4 x 10-6 to 1.5 x 10-6 cm2/sec. In general, surficial sediments showed diffusion coefficients about one-half to one-third of those for free solution, values decreasing with depth and porosity.

  14. Relative Roles of Deterministic and Stochastic Processes in Driving the Vertical Distribution of Bacterial Communities in a Permafrost Core from the Qinghai-Tibet Plateau, China

    PubMed Central

    Tian, Tian; Li, Dingyao; Cheng, Gang; Mu, Jing; Wu, Qingbai; Niu, Fujun; Stegen, James C.; An, Lizhe; Feng, Huyuan

    2015-01-01

    Understanding the processes that influence the structure of biotic communities is one of the major ecological topics, and both stochastic and deterministic processes are expected to be at work simultaneously in most communities. Here, we investigated the vertical distribution patterns of bacterial communities in a 10-m-long soil core taken within permafrost of the Qinghai-Tibet Plateau. To get a better understanding of the forces that govern these patterns, we examined the diversity and structure of bacterial communities, and the change in community composition along the vertical distance (spatial turnover) from both taxonomic and phylogenetic perspectives. Measures of taxonomic and phylogenetic beta diversity revealed that bacterial community composition changed continuously along the soil core, and showed a vertical distance-decay relationship. Multiple stepwise regression analysis suggested that bacterial alpha diversity and phylogenetic structure were strongly correlated with soil conductivity and pH but weakly correlated with depth. There was evidence that deterministic and stochastic processes collectively drived bacterial vertically-structured pattern. Bacterial communities in five soil horizons (two originated from the active layer and three from permafrost) of the permafrost core were phylogenetically random, indicator of stochastic processes. However, we found a stronger effect of deterministic processes related to soil pH, conductivity, and organic carbon content that were structuring the bacterial communities. We therefore conclude that the vertical distribution of bacterial communities was governed primarily by deterministic ecological selection, although stochastic processes were also at work. Furthermore, the strong impact of environmental conditions (for example, soil physicochemical parameters and seasonal freeze-thaw cycles) on these communities underlines the sensitivity of permafrost microorganisms to climate change and potentially subsequent

  15. Relative Roles of Deterministic and Stochastic Processes in Driving the Vertical Distribution of Bacterial Communities in a Permafrost Core from the Qinghai-Tibet Plateau, China.

    PubMed

    Hu, Weigang; Zhang, Qi; Tian, Tian; Li, Dingyao; Cheng, Gang; Mu, Jing; Wu, Qingbai; Niu, Fujun; Stegen, James C; An, Lizhe; Feng, Huyuan

    2015-01-01

    Understanding the processes that influence the structure of biotic communities is one of the major ecological topics, and both stochastic and deterministic processes are expected to be at work simultaneously in most communities. Here, we investigated the vertical distribution patterns of bacterial communities in a 10-m-long soil core taken within permafrost of the Qinghai-Tibet Plateau. To get a better understanding of the forces that govern these patterns, we examined the diversity and structure of bacterial communities, and the change in community composition along the vertical distance (spatial turnover) from both taxonomic and phylogenetic perspectives. Measures of taxonomic and phylogenetic beta diversity revealed that bacterial community composition changed continuously along the soil core, and showed a vertical distance-decay relationship. Multiple stepwise regression analysis suggested that bacterial alpha diversity and phylogenetic structure were strongly correlated with soil conductivity and pH but weakly correlated with depth. There was evidence that deterministic and stochastic processes collectively drived bacterial vertically-structured pattern. Bacterial communities in five soil horizons (two originated from the active layer and three from permafrost) of the permafrost core were phylogenetically random, indicator of stochastic processes. However, we found a stronger effect of deterministic processes related to soil pH, conductivity, and organic carbon content that were structuring the bacterial communities. We therefore conclude that the vertical distribution of bacterial communities was governed primarily by deterministic ecological selection, although stochastic processes were also at work. Furthermore, the strong impact of environmental conditions (for example, soil physicochemical parameters and seasonal freeze-thaw cycles) on these communities underlines the sensitivity of permafrost microorganisms to climate change and potentially subsequent

  16. An inexpensive sampler for obtaining bulk sediment cores

    NASA Astrophysics Data System (ADS)

    Cooper, Charles M.; Schiebe, Frank R.; Ritchie, Jerry C.

    1991-09-01

    A large-volume core sampler for sediment—muck substrates is described. The sampler can acquire a discrete sediment core of 10 cm in diameter and up to 1.5 m long. Such samplers are needed to collect the volume necessary for analysis of sediments for contaminants, bulk density, or radioactive dating. The sampler consists of a 1- to 2-m length of PVC pipe mounted below a threaded metal pipe air exhaust—intake assembly. This assembly is quick-connected to standard threaded lengths (300 cm) of water pipe (2 cm diam) or electrical conduit so that bottom sediments in water depths of up to 10 m can be sampled. The core sampler is hand-operated and pushed into bottom sediments from a boat. It does not have to be triggered remotely because of the one-way modified check valve in the air exhaust—intake assembly. After the sampler is extracted from the sediment, the extension handle can be quickly removed for ease of sampler handling, and the core can be extruded from the PVC tube by air pressure.

  17. [Testaceans (Protozoa: Testacea) in quaternary permafrost sediments of Bykovsky Peninsula, arctic Yakutia].

    PubMed

    Bobrov, A A; Siegert, Ch; Schirrmeister, L; Andreev, A A

    2003-01-01

    The results of the first protozoological study in terms of paleoecology of long-term sediments and buried soils formed in the cryolite zone of northeastern Siberia are discussed. The data on testaceans (Protozoa: Testacea) inhabiting various sites of Bykovsky Peninsula, Laptev Sea coast near estuary of Lena, within the last 53,000 years (late Pleistocene and Holocene). PMID:12712585

  18. INNOVATIVE TECHNOLOGY EVALUATION REPORT, SEDIMENT SAMPLING TECHNOLOGY, ART'S MANUFACTURING, SPLIT CORE SAMPLER FOR SUBMERGED SEDIMENTS

    EPA Science Inventory


    The Split Core Sampler for Submerged Sediments (Split Core Sampler) designed and fabricated by Arts Manufacturing & Supply, Inc., was demonstrated under the U.S. Environmental Protection Agency (EPA) Superfund Innovative Technology Evaluation Program in April and May 1999 at ...

  19. Bioavailability of sediment-associated PAHs by Lumbriculus variegatus in sediment cores

    SciTech Connect

    Harkey, G.A.; VanHoof, P.L.; Landrum, P.F.

    1994-12-31

    Lumbriculus variegatus were exposed four weeks to sediment core sections. Sediment was taken from Lake George in northern Michigan and known to be historically contaminated with PAHs. Bioaccumulation was maximal at the 12--16 cm depth where sediment PAH concentrations were greatest. Accumulation was minimal in surficial and 44--48 cm sections. Accumulation peaked at about 96 h, then declined over the remainder of the study for some of the lower molecular weight PAHs. For most higher molecular weight compounds, accumulation peaked at 2 weeks, then slightly declined at 4 weeks. Uptake rate coefficients stayed relatively constant for specific PAH congeners over the range of sediment depths, suggesting constant bioavailability with sediment aging. Accumulation factors (AFs) of selected congeners were also consistent among sediment depths and were comparable to those calculated for other species reported in previous studies.

  20. Short Sediment Cores as Archives of Urban Pollution

    NASA Astrophysics Data System (ADS)

    Latimer, J. C.; McLennan, D. A.; Stone, J.; Memmer, E. D.; Foster, J. A.; Hardin, K. J.; Nickerson, Z.; Portwood, C. A.; Williams, T. M.

    2014-12-01

    Urban areas are host to numerous sources of environmental pollution, including industry, traffic, and past land uses. To document this pollution within Vigo County, Indiana, we collected several short cores from ponds and wetlands throughout the county, including cores from the old industrial park in Terre Haute, nature parks, a lake impacted by acid mine drainage, and a newly restored wetland to investigate heavy metal burial in these aquatic ecosystems. One core was collected from a holding pond that was constructed in the 1950's on the former International Paper (IP) site where corrugated packing products were produced for nearly a century. One of the nature parks (Dobbs Nature Park) was established in 1976, while the other sits on a former Brownfield site and was only recently opened to the public (Maple Avenue Nature Park). Scott Lake is adjacent to an abandoned coal mine, and continues to receive acidic drainage. Wabashiki Fish and Wildlife Area is flooded seasonally by the Wabash River. Prior land uses for the Wabashiki include agriculture and illegal dumping. All of these sites, except IP are designated fishing areas. Based on water chemistry and diatom assemblages, these ponds have acceptable water quality; however, some are becoming increasingly more eutrophic. Preliminary results from the IP and Maple Avenue Nature Park sediment cores indicate elevated heavy metal concentrations above background levels and at concentrations high enough to impact benthic organisms based on NOAA Sediment Quality Guidelines. Diatoms from the IP core suggest a transition from low productivity at the base to nutrient-rich conditions in more recent sediments, and several diatom specimens have observable deformities (typically an indicator of heavy metals). The base of the IP core also has metal concentrations that are 5 times greater than the top of the core. In many cases, sediments from the Maple Avenue Nature Park pond have metal concentrations higher than the surrounding

  1. Correlating Permafrost Organic Matter Composition and Characteristics with Methane Production Potentials in a First Generation Thermokarst Lake and Its Underlying Permafrost Near Fairbanks, Alaska, USA

    NASA Astrophysics Data System (ADS)

    Heslop, J.; Walter Anthony, K. M.; Sepulveda-Jauregui, A.; Martinez-Cruz, K. C.

    2014-12-01

    Thermokarst lakes, formed in permafrost-thaw depressions, are known sources of atmospheric methane (CH4) and carbon dioxide (CO2). The organic carbon (OC) utilized in the production of these greenhouse gases originates from microbial decomposition of aquatic and terrestrial organic matter (OM) sources, including soils of the lakes' watersheds and permafrost thaw beneath the lakes. OM derived from permafrost thaw is particularly important given the thickness of permafrost soils underlying some lakes (typically 10-30 m in yedoma permafrost); however, OM heterogeneity remains a significant uncertainty in estimating how microbial decomposition responds to permafrost thaw. This study correlates OM and water-extractable OC (WEOC) composition with CH4 production potentials determined from anaerobic laboratory incubations. Samples were collected from 21 depths along a 5.9-m deep thermokarst-lake sediment core and 17 depths along an adjacent 40-m deep undisturbed yedoma permafrost profile near Vault Creek, Alaska. The Vault Lake core, collected in the center of a 3230 m2 first generation thermokarst lake, includes surface lake sediments, the talik (thaw bulb), and permafrost actively thawing beneath the lake. Soil OM composition was characterized using pyrolysis-gas chromatography/mass spectrometry (py-GC/MS) and the most prevalent compounds were grouped into six indices based on their likely origin. WEOC was characterized using fluorescence spectrometry. Using stepwise multiple linear regression analyses, we found that CH4 production was negatively correlated with WEOC aromaticity (p = 0.018) and fulvic acids (p = 0.027). CH4 production was positively correlated with lipids and carboxylic acids (p < 0.001), polysaccharides (p = 0.036) and the degree of WEOC humification (p = 0.013). Results suggest OM and WEOC composition can be correlated with CH4 production, indicating potential for model building to better predict greenhouse gas release from permafrost thaw.

  2. Technologies for retrieving sediment cores in Antarctic subglacial settings.

    PubMed

    Hodgson, Dominic A; Bentley, Michael J; Smith, James A; Klepacki, Julian; Makinson, Keith; Smith, Andrew M; Saw, Kevin; Scherer, Reed; Powell, Ross; Tulaczyk, Slawek; Rose, Mike; Pearce, David; Mowlem, Matt; Keen, Peter; Siegert, Martin J

    2016-01-28

    Accumulations of sediment beneath the Antarctic Ice Sheet contain a range of physical and chemical proxies with the potential to document changes in ice sheet history and to identify and characterize life in subglacial settings. Retrieving subglacial sediments and sediment cores presents several unique challenges to existing technologies. This paper briefly reviews the history of sediment sampling in subglacial environments. It then outlines some of the technological challenges and constraints in developing the corers being used in sub-ice shelf settings (e.g. George VI Ice Shelf and Larsen Ice Shelf), under ice streams (e.g. Rutford Ice Stream), at or close to the grounding line (e.g. Whillans Ice Stream) and in subglacial lakes deep under the ice sheet (e.g. Lake Ellsworth). The key features of the corers designed to operate in each of these subglacial settings are described and illustrated together with comments on their deployment procedures. PMID:26667918

  3. A sampler for coring sediments in rivers and estuaries

    USGS Publications Warehouse

    Prych, Edmund A.; Hubbell, D.W.

    1966-01-01

    A portable sampler developed to core submerged unconsolidated sediments collects cores that are 180 cm long and 4.75cm in diameter. The sampler is used from a 12-m boat in water depths up to 20 m and in flow velocities up to 1.5m per second to sample river and estuarine deposits ranging from silty clay to medium sand. Even in sand that cannot be penetrated with conventional corers, the sampler achieves easy penetration through the combined application of vibration, suction, and axial force. A piston in the core barrel creates suction, and the suspension system is arranged so that tension on the support cable produces both a downward force on the core barrel and a lateral support against overturning. Samples are usually retained because of slight compaction in the driving head; as a precaution, however, the bottom of the core barrel is covered by a plate that closes after the barrel is withdrawn from the bed. Tests show that sample-retainers placed within the driving head restrict penetration and limit core lengths. Stratification within cores is disrupted little as a result of the sampling process.

  4. Diagenetic regimes in Arctic Ocean sediments: Implications for sediment geochemistry and core correlation

    NASA Astrophysics Data System (ADS)

    Meinhardt, A.-K.; März, C.; Schuth, S.; Lettmann, K. A.; Schnetger, B.; Wolff, J.-O.; Brumsack, H.-J.

    2016-09-01

    Dark brown sediment layers are a potential stratigraphic tool in Quaternary Arctic Ocean sediments. They are rich in Mn, Fe, and trace metals scavenged from the water column and were most likely deposited during interglacial intervals. In this study, we combine sediment and pore water data from sediment cores taken in different parts of the Arctic Ocean to investigate the influence of early diagenetic processes on sediment geochemistry. In most studied cores, Mn, Co, and Mo are released into the pore waters from Mn oxide dissolution in deeper (>1.5 m) sediment layers. The relationship between sedimentary Mn, Co, and Mo contents in excess of the lithogenic background (elementxs) shows that Coxs/Moxs values are a diagnostic tool to distinguish between layers with diagenetic metal addition from the pore waters (Coxs/Moxs < 1), layers affected by Mn oxide dissolution and metal release (Coxs/Moxs > 10), and unaffected layers (Coxs/Moxs from 1 to 10). Steady-state calculations based on current pore water profiles reveal that in the studied cores, the diagenetic addition of these metals from the pore water pool alone is not sufficient to produce the sedimentary metal enrichments. However, it seems evident that dissolution of Mn oxides in the Mn reduction zone can permanently alter the primary geochemical signature of the dark brown layers. Therefore, pore water data and Coxs/Moxs values should be considered before core correlation when this correlation is solely based on Mn contents and dark sediment color. In contrast to the mostly non-lithogenic origin of Mn in the dark brown layers, sedimentary Fe consists of a large lithogenic (80%) and a small non-lithogenic fraction (20%). Our pore water data show that diagenetic Fe remobilization is not currently occurring in the sediment. The dominant Fe sources are coastal erosion and river input. Budget calculations show that Fe seems to be trapped in the modern Arctic Ocean and accumulates in shelf and basin sediments. The Fe

  5. Reconstructed Sediment Mobilization Processes in a Large Reservoir Using Short Sediment Cores

    NASA Astrophysics Data System (ADS)

    Cockburn, J.; Feist, S.

    2014-12-01

    Williston Reservoir in northern British Columbia (56°10'31"N, 124°06'33") was formed when the W.A.C. Bennett Dam was created in the late 1960s, is the largest inland body of water in BC and facilitates hydroelectric power generation. Annually the reservoir level rises and lowers with the hydroelectric dam operation, and this combined with the inputs from several river systems (Upper Peace, Finlay, Parsnip, and several smaller creeks) renews suspended sediment sources. Several short-cores retrieved from shallow bays of the Finlay Basin reveal near-annual sedimentary units and distinct patterns related to both hydroclimate variability and the degree to which the reservoir lowered in a particular year. Thin section and sedimentology from short-cores collected in three bays are used to evaluate sediment mobilization processes. The primary sediment sources in each core location is linked to physical inputs from rivers draining into the bays, aeolian contributions, and reworked shoreline deposits as water levels fluctuate. Despite uniform water level lowering across the reservoir, sediment sequences differed at each site, reflecting the local stream inputs. However, distinct organic-rich units, facilitated correlation across the sites. Notable differences in particle size distributions from each core points to important aeolian derived sediment sources. Using these sedimentary records, we can evaluate the processes that contribute to sediment deposition in the basin. This work will contribute to decisions regarding reservoir water levels to reduce adverse impacts on health, economic activities and recreation in the communities along the shores of the reservoir.

  6. Exploring Viral Mediated Carbon Cycling in Thawing Permafrost Microbial Communities

    NASA Astrophysics Data System (ADS)

    Trubl, G. G.; Solonenko, N.; Moreno, M.; Sullivan, M. B.; Rich, V. I.

    2014-12-01

    Viruses are the most abundant biological entities on Earth and their impact on carbon cycling in permafrost habitats is poorly understood. Arctic C cycling is particularly important to interpret due to the rapid climate change occurring and the large amount of C stockpiled there (~1/3 of global soil C is stored in permafrost). Viruses of microbes (i.e. phages) play central roles in C cycling in the oceans, through cellular lysis (phage drive the largest ocean C flux about 150 Gt yr-1, dwarfing all others by >5-fold), production of associated DOC, as well as transport and expression during infection (1029 transduction events day-1). C cycling in thawing permafrost systems is critical in understanding the climate trajectory and phages may be as important for C cycling here as they are in the ocean. The thawed C may become a food source for microbes, producing CO2 and potentially CH4, both potent greenhouse gases. To address the potential role of phage in C cycling in these dynamic systems, we are examining phage from an arctic permafrost thaw gradient in northern Sweden. We have developed a protocol for successfully extracting phage from peat soils and are quantifying phage in 15 peat and 2 lake sediment cores, with the goal of sequencing viromes. Preliminary data suggest that phage are present at 109 g-1 across the permafrost thaw gradient (compared to the typical marine count ~105 ml-1), implying a potentially robust phage-host interaction web in these changing environments. We are examining phage from 11 depth intervals (covering the active and permafrost layer) in the cores to assess phage-host community dynamics. Phage morphology and abundance for each layer and environment are being determined using qTEM and EFM. Understanding the phage that infect bacteria and archaea in these rapidly changing habitats will provide insight into the controls on current and future CH4 and CO2 emissions in permafrost habitats.

  7. The Late Pliocene Eltanin Impact: Documentation From Sediment Core Analyses

    NASA Technical Reports Server (NTRS)

    Gersonde, R.; Kyte, F.; Flores, J. A.; Becquey, S.

    2002-01-01

    The expeditions ANT-XII/4 (1995) and ANT-XVIII/5a (2001) of the RV POLARSTERN collected extensive bathymetric and seismic data sets as well as sediment cores from an area in the Bellingshausen Sea (eastern Pacific Southern Ocean) that allow the first comprehensive geoscientific documentation of an asteroid impact into a deep ocean (approx. 5 km) basin, named the Eltanin impact. Impact deposits have now been recovered from a total of more than 20 sediment cores collected in an area covering about 80,000 km2. Combined biomagnetostratigraphic dating places the impact event into the earliest Matuyama Chron, a period of enhanced climate variability. Sediment texture analyses and studies of sediment composition including grain size and microfossil distribution reveal the pattern of impact- related sediment disturbance and the sedimentary processes immediately following the impact event. The pattern is complicated by the San Martin Seamounts (approx. 57.5 S, 91 W), a large topographic elevation that rises up to 3000 m above the surrounding abyssal plain in the area affected by the Eltanin impact. The impact ripped up sediments as old as Eocene and probably Paleocene that have been redeposited in a chaotic assemblage. This is followed by a sequence sedimented from a turbulent flow at the sea floor, overprinted by fall-out of airborne meteoritic ejecta that settled trough the water column. Grain size distribution reveals the timing and interaction of the different sedimentary processes. The gathered estimate of ejecta mass deposited over the studied area, composed of shock-melted asteroidal material and unmelted meteorites including fragments up to 2.5 cm in diameter, point to an Eltanin asteroid larger than the 1 km in diameter size originally suggested as a minimum based on the ANT-XII/4 results. This places the energy released by the impact at the threshold of those considered to cause environmental disturbance at a global scale and it makes the impact a likely transport

  8. The Late Pliocene Eltanin Impact - Documentation From Sediment Core Analyses

    NASA Astrophysics Data System (ADS)

    Gersonde, R.; Kuhn, G.; Kyte, F. T.; Flores, J.; Becquey, S.

    2002-12-01

    The expeditions ANT-XII/4 (1995) and ANT-XVIII/5a (2001) of the RV POLARSTERN collected extensive bathymetric and seismic data sets as well as sediment cores from an area in the Bellingshausen Sea (eastern Pacific Southern Ocean) that allow the first comprehensive geoscientific documentation of an asteroid impact into a deep ocean (~ 5 km) basin, named the Eltanin impact. Impact deposits have now been recovered from a total of more than 20 sediment cores collected in an area covering about 80,000 km2. Combined biomagnetostratigraphic dating places the impact event into the earliest Matuyama Chron, a period of enhanced climate variability. Sediment texture analyses and studies of sediment composition including grain size and microfossil distribution reveal the pattern of impact-related sediment disturbance and the sedimentary processes immediately following the impact event. The pattern is complicated by the San Martin Seamounts (~57.5 S, 91 W), a large topographic elevation that rises up to 3000 m above the surrounding abyssal plain in the area affected by the Eltanin impact. The impact ripped up sediments as old as Eocene and probably Paleocene that have been redeposited in a chaotic assemblage. This is followed by a sequence sedimented from a turbulent flow at the sea floor, overprinted by fall-out of airborne meteoritic ejecta that settled trough the water column. Grain size distribution reveals the timing and interaction of the different sedimentary processes. The gathered estimate of ejecta mass deposited over the studied area, composed of shock-melted asteroidal matrial and unmelted meteorites including fragments up to 2.5 cm in diameter, point to an Eltanin asteroid larger than the 1 km in diameter size originally suggested as a minimum based on the ANT-XII/4 results. This places the energy released by the impact at the threshold of those considered to cause environmental disturbance at a global scale and it makes the impact a likely transport mechanism

  9. LacCore: Support for the terrestrial sediment core research community

    NASA Astrophysics Data System (ADS)

    Brady, K. L.; Noren, A. J.; Myrbo, A.; Ito, E.

    2009-12-01

    LacCore, the National Lacustrine Core Facility, has been funded by the US National Science Foundation and the University of Minnesota for the past decade as a public facility to support the terrestrial sediment core research community. LacCore provides free or low-cost access to an array of expensive equipment and instrumentation in the field and lab, training for a variety of procedures, and core and data curation. The user base has increased from perhaps 20 users and a handful of projects in the first year to 621 users and 250 projects in 2008. The community served is diverse, with topics including invasive species, eutrophication, salinization, tectonics, geomicrobiology, evolutionary biology, isostatic rebound, stream bank erosion, glaciology, hydrogeology, atmospheric chemistry, carbon cycling, and rock magnetics, as well as paleoenvironment and paleoclimate. The changing needs of projects drive innovation in procedures and equipment, all of which become available to subsequent researchers. Among the newest additions to the lab is a benchtop scanning electron microscope with electron-dispersive x-ray spectrometry (SEM-EDX or -EDS) capability for sediment characterization. This instrument allows rapid imaging of sedimentary components and determination of their elemental composition without substantial sample preparation, lead time, or user training. These images and data augment the initial core description process, filling a void between existing smear slide and scanning micro XRF capabilities.

  10. Sediment core and glacial environment reconstruction - a method review

    NASA Astrophysics Data System (ADS)

    Bakke, Jostein; Paasche, Øyvind

    2010-05-01

    lakes. To retrieve these glacial sediments it is necessary to collect sediment cores from the lake bottom. Reading the glacial signal, as preserved in the lake sediments, now includes the application of various methods such as measuring the amount of minerogenic versus biologic matter (typically inferred from Loss-on-ignition (LOI)), grain size analysis (GSA), magnetic properties (MP), geochemical elements (GE), Rare-Earth Elements (REE), Bulk Sediment Density (BSD), but also other techniques such as XRF analyses. Moreover, detailed glacier reconstructions can also be used to assess denudation rates, chemical and physical weathering as well specific glaciological changes.

  11. Sediment magnetic, paleomagnetic, and geochemical data from Quaternary lacustrine sediment in a core from Grass Lake, Siskiyou County, California

    USGS Publications Warehouse

    Best, Patti J.; Reynolds, Richard L.; Rosenbaum, Joseph G.; Drexler, John W.; Adam, David P.

    1996-01-01

    Sediment magnetic and geochemical results have been obtained from the top 60 meters of lacustrine sediments recovered in two cores from Tule Lake in northern California. The sediment magnetic and geochemical data, presented here in tabular form, complement studies of diatoms and pollen in the cores that are the bases for published paleoclimatic interpretations. This report also documents the methods used to obtain the magnetic properties and geochemical data.

  12. Sediment magnetic and geochemical data from Quaternary lacustine sediment in two cores from Tule Lake, Siskiyou County, California

    USGS Publications Warehouse

    Best, Patti J.; Reynolds, Richard L.; Rosenbaum, Joseph G.; Dean, Walter E.; Honey, Jeannine; Drexler, John W.; Adam, David P.

    1996-01-01

    Sediment magnetic and geochemical results have been obtained from the top 60 meters of lacustrine sediments recovered in two cores from Tule Lake in northern California. The sediment magnetic and geochemical data, presented here in tabular form, complement studies of diatoms and pollen in the cores that are the bases for published paleoclimatic interpretations. This report also documents the methods used to obtain the magnetic properties and geochemical data.

  13. Arctic and subarctic environmental analyses utilizing ERTS-1 imagery. [permafrost sediment transport, snow cover, ice conditions, and water runoff in Alaska

    NASA Technical Reports Server (NTRS)

    Anderson, D. M.; Mckim, H. L.; Haugen, R. K.; Gatto, L. W.; Slaughter, C. W.; Marlar, T. L. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. Physiognomic landscape features were used as geologic and vegetative indicators in preparation of a surficial geology, vegetation, and permafrost map at a scale of 1:1 million using ERTS-1 band 7 imagery. The detail from this map compared favorably with USGS maps at 1:250,000 scale. Physical boundaries mapped from ERTS-1 imagery in combination with ground truth obtained from existing small maps and other sources resulted in improved and more detailed maps of permafrost terrain and vegetation for the same area. ERTS-1 imagery provides for the first time, a means of monitoring the following regional estuarine processes: daily and periodic surface water circulation patterns; changes in the relative sediment load of rivers discharging into the inlet; and, several local patterns not recognized before, such as a clockwise back eddy offshore from Clam Gulch and a counterclockwise current north of the Forelands. Comparison of ERTS-1 and Mariner imagery has revealed that the thermokarst depressions found on the Alaskan North Slope and polygonal patterns on the Yukon River Delta are possible analogs to some Martian terrain features.

  14. Evidence of fine-grained sediment transport and deposition in Sheboygan River, Wisconsin, based on sediment core chemical tracer profiles

    NASA Astrophysics Data System (ADS)

    Bzdusek, Philip A.; Lu, Jianhang; Christensen, Erik R.

    2005-04-01

    Fine-grained sediment transport and deposition is observed in nine dated sediment cores obtained from the Sheboygan River. The sediment cores were dated by 137Cs and 210Pb methods. Sediment dating was supported by a polychlorinated biphenyl (PCB) analysis and U.S. Army Corps of Engineers (USACE) hydrographic surveys from 1976 to 2002. Plots of 137Cs activity versus depth show distinct peaks related to peak Sheboygan River discharges in the years 1966, 1975, 1979, and 1989. These peaks result from the scouring of sediments during storm discharges and the increased deposition of the fine-grained fraction of particles, including colloidal clay particles (associated with 137Cs and, to some extent, PCBs), in place of the scoured sediments. Core SR1a, upstream of the Pennsylvania Avenue Bridge, and cores SR5-SR8, farther downstream, show continuous sedimentation (1.2-11.8 cm/yr) since the late 1950s, whereas net sediment accumulation virtually ceased after 1988 at the intermediate sites of cores SR1-SR4. The maximum PCB concentration (161 ppm) occurs in 1969 in core SR4.

  15. Permafrost as palaeo-environmental archive - potentials and limitations

    NASA Astrophysics Data System (ADS)

    Schirrmeister, L.; Wetterich, S.; Meyer, H.; Grosse, G.; Schwamborn, G.; Siegert, C.

    2009-04-01

    Since 1994, the Periglacial Research Group of the Alfred Wegener Institute is studying permafrost sequences of the Beringian landmass. The study sites in Siberia cover lake banks on Taymyr Peninsula, coastal sites at the Laptev and the East Siberian Seas, locations in the Lena Delta, at the lower Kolyma river, the middle Lena and the lower Aldan rivers, and the catchment area of the El'gygytgyn crater lake in Chukotka. In Alaska, permafrost tunnels near Fairbanks and Barrow, and coastal sites on the Seward Peninsula coast were studied. In addition, Canadian sites on Herschel Island in the Beaufort Sea and at the adjacent coast of the Yukon plain were studied. Subsurface exposures like tunnels and cellars provided the opportunity for three-dimensional studies of sedimentary and ground ice features, relatively ‘clean' field conditions for in-situ experiments, monitoring procedures, and detailed and repeatable sampling. Permafrost cores were drilled in order to study inaccessible sequences below the terrain surface and shelf sea floor. Cores were transported and stored frozen for further high-resolution analysis. Reference core sections were preserved for subsequent later studies. Terrestrial sediment cores are highly localized records, sometimes problematic in extrapolating horizons in inhomogeneous sediments like ground ice-deformed permafrost deposits, and drill campaigns are usually cost intensive and logistical challenging. Coastal permafrost cliffs often naturally expose large cross sections trough modern and ancient landscapes. Contrary to cores, they provide an opportunity to study the wider context of depositional environments and ground ice features. Due to the relative easy access to coasts and the recurring natural exposure of cliffs by thermo-abrasive wave action they are very convenient study objects for regional comparisons and correlation of past environmental conditions. Finally, palaeogeographical reconstructions are also guided by remote sensing

  16. The vertical variation of nutrients in a sediment core of Delong Lake reveals the anthropogenic effect.

    PubMed

    Guan, Ying; Zang, Shuying; Xiao, Haifeng

    2014-05-01

    Phosphorus content and its species were studied for the core sediments of Delong Lake, using the SMT sequential extraction method, and then were correlated to the contents of total nitrogen and organic matter. According to (210)Pb and (137)Cs dating, the historical profiles of 33 cm core sediments were generated. The objective of this study was to understand how nutrients of lake sediments evolved in order to get insights into the effect of human activities on their sedimentary history. The nutrients contents in the core sediments slowly increased after 1957, showing the human activity influence the natural deposition of the lake sediment. From 1978 to 1985, various nutrients in the lake sediment rapid increased, showing that the human activities strengthened. From 2003 to now, most of nutrients in the sediment rapidly increased and significantly modified the natural deposition of the lake sediment. PMID:24468926

  17. Geochemical assessment of metal pollution and ecotoxicology in sediment cores along Karachi Coast, Pakistan.

    PubMed

    Mashiatullah, Azhar; Chaudhary, Muhammad Zaman; Ahmad, Nasir; Ahmad, Nisar; Javed, Tariq; Ghaffar, Abdul

    2015-05-01

    This paper is an attempt to compare the pollution status in two sediment cores, one from a polluted site (Ghizri Creek) and another from a relatively unpolluted site (Sandspit). Sediment cores (45 cm in length) from coastal locations were characterized in terms of grain size, sediment composition, pH, organic matter, calcium carbonate, and metal element contents. Metal elements, including Al, Ca, Cr, Co Cu, Fe, K, Mg, Mn, Ni, Pb, V, Ti, and Zn, were determined using PIXE. Grain size analysis and sediment composition demonstrated a sandy nature of both cores. Acidic trend in sediment core I was predominant from bottom to top, whereas neutral pH was observed throughout core II. TOC values varied in the range of 1.23-2.68 and 1.14-2.60% in core I and core II, respectively; however, there was an increasing trend in TOC level from bottom to top. The values of enrichment factor for Zn, Cu, Co, Ni, Pb, and Cr were slightly higher in core I than core II. The average geo-accumulation index values for core I and core II showed that sediments were moderately Co- and Pb-polluted but not polluted with Mg, Al, Ca, K, Cr, Cu, Fe, Mn, Ni, Ti, V, and Zn. The degree of contamination was however considerably higher in core I relative to core II. The pollution load index values, although showing an increasing trend from bottom to top in both cores, overall rendered the marine sediment pollution free. The metal toxicology results demonstrated that heavy metal pollution, except Cr, may pose low to moderate risk to marine biota. The sum of toxic unit values however indicated that sediment core I was relatively more polluted than that of core II. PMID:25869090

  18. Historical trends in organochlorine compounds in river basins identified using sediment cores from reservoirs

    USGS Publications Warehouse

    Van Metre, P.C.; Callender, E.; Fuller, C.C.

    1997-01-01

    This study used chemical analyses of dated sediment cores from reservoirs to define historical trends in water quality in the influent river basins. This work applies techniques from paleolimnology to reservoirs, and in the process, highlights differences between sediment-core interpretations for reservoirs and natural lakes. Sediment cores were collected from six reservoirs in the central and southeastern United States, sectioned, and analyzed for 137Cs and organochlorine compounds. 137Cs analyses were used to demonstrate limited post-depositional mixing, to indicate sediment deposition dates, and to estimate sediment focusing factors. Relative lack of mixing, high sedimentation rates, and high focusing factors distinguish reservoir sediment cores from cores collected in natural lakes. Temporal trends in concentrations of PCBs, total DDT (DDT + DDD + DDE), and chlordane reflect historical use and regulation of these compounds and differences in land use between reservoir drainages. PCB and total DDT core burdens, normalized for sediment focusing, greatly exceed reported cumulative regional atmospheric fallout of PCBs and total DDT estimated using cores from peat hogs and natural lakes, indicating the dominance of fluvial inputs of both groups of compounds to the reservoirs.This study used chemical analyses of dated sediment cores from reservoirs to define historical trends in water quality in the influent river basins. This work applies techniques from paleolimnology to reservoirs, and in the process, highlights differences between sediment-core interpretations for reservoirs and natural lakes. Sediment cores were collected from six reservoirs in the central and southeastern United States, sectioned, and analyzed for 137Cs and organochlorine compounds. 137Cs analyses were used to demonstrate limited post-depositional mixing, to indicate sediment deposition dates, and to estimate sediment focusing factors. Relative lack of mixing, high sedimentation rates, and high

  19. Distribution and partitioning of heavy metals in estuarine sediment cores and implications for the use of sediment quality standards

    NASA Astrophysics Data System (ADS)

    Spencer, K. L.; MacLeod, C. L.

    Total metal concentrations in surface sediments and historically contaminated sediments were determined in sediment cores collected from three estuaries (Thames, Medway and Blackwater) in south-east England. The partitioning behaviour of metals in these sediments was also determined using a sequential extraction scheme. These data were then compared with sediment quality values (SQVs) to determine the potential ecotoxicological risk to sediment dwelling organisms. When total metal concentrations in surface sediments are examined, no risk to biota in any of the estuaries is indicated. However, when historically contaminated sediments at depth are also considered, risks to biota are apparent and are greatest for the Thames, followed by the Medway and then the Blackwater. This suggests that regulatory authorities should examine vertical metal profiles, particularly in estuaries that are experiencing low sediment accumulation rates where historically contaminated sediments are in the shallow sub-surface zone and where erosion or dredging activities may take place. When metal partitioning characteristics are also considered, the risk to biota is comparable for the Medway and the Blackwater with the potentially bioavailable fraction presenting no ecotoxicological risk. Conversely, over 70% of metals are labile in the Thames Estuary sediments and toxic effects are probable. This suggests that the application of SQVs using total sediment metal concentrations may over- or under-estimate the risk to biota in geochemically dissimilar estuarine sediments.

  20. Airborne electromagnetic imaging of discontinuous permafrost

    USGS Publications Warehouse

    Minsley, B.J.; Abraham, J.D.; Smith, B.D.; Cannia, J.C.; Voss, C.I.; Jorgenson, M.T.; Walvoord, M.A.; Wylie, B.K.; Anderson, L.; Ball, L.B.; Deszcz-Pan, M.; Wellman, T.P.; Ager, T.A.

    2012-01-01

    The evolution of permafrost in cold regions is inextricably connected to hydrogeologic processes, climate, and ecosystems. Permafrost thawing has been linked to changes in wetland and lake areas, alteration of the groundwater contribution to streamflow, carbon release, and increased fire frequency. But detailed knowledge about the dynamic state of permafrost in relation to surface and groundwater systems remains an enigma. Here, we present the results of a pioneering ???1,800 line-kilometer airborne electromagnetic survey that shows sediments deposited over the past ???4 million years and the configuration of permafrost to depths of ???100 meters in the Yukon Flats area near Fort Yukon, Alaska. The Yukon Flats is near the boundary between continuous permafrost to the north and discontinuous permafrost to the south, making it an important location for examining permafrost dynamics. Our results not only provide a detailed snapshot of the present-day configuration of permafrost, but they also expose previously unseen details about potential surface-groundwater connections and the thermal legacy of surface water features that has been recorded in the permafrost over the past ???1,000 years. This work will be a critical baseline for future permafrost studies aimed at exploring the connections between hydrogeologic, climatic, and ecological processes, and has significant implications for the stewardship of Arctic environments. ?? 2012 by the American Geophysical Union.

  1. Permafrost as palaeo-environmental archive - potentials and limitations

    NASA Astrophysics Data System (ADS)

    Schirrmeister, L.; Wetterich, S.; Meyer, H.; Grosse, G.; Schwamborn, G.; Siegert, C.

    2009-04-01

    Since 1994, the Periglacial Research Group of the Alfred Wegener Institute is studying permafrost sequences of the Beringian landmass. The study sites in Siberia cover lake banks on Taymyr Peninsula, coastal sites at the Laptev and the East Siberian Seas, locations in the Lena Delta, at the lower Kolyma river, the middle Lena and the lower Aldan rivers, and the catchment area of the El'gygytgyn crater lake in Chukotka. In Alaska, permafrost tunnels near Fairbanks and Barrow, and coastal sites on the Seward Peninsula coast were studied. In addition, Canadian sites on Herschel Island in the Beaufort Sea and at the adjacent coast of the Yukon plain were studied. Subsurface exposures like tunnels and cellars provided the opportunity for three-dimensional studies of sedimentary and ground ice features, relatively ‘clean' field conditions for in-situ experiments, monitoring procedures, and detailed and repeatable sampling. Permafrost cores were drilled in order to study inaccessible sequences below the terrain surface and shelf sea floor. Cores were transported and stored frozen for further high-resolution analysis. Reference core sections were preserved for subsequent later studies. Terrestrial sediment cores are highly localized records, sometimes problematic in extrapolating horizons in inhomogeneous sediments like ground ice-deformed permafrost deposits, and drill campaigns are usually cost intensive and logistical challenging. Coastal permafrost cliffs often naturally expose large cross sections trough modern and ancient landscapes. Contrary to cores, they provide an opportunity to study the wider context of depositional environments and ground ice features. Due to the relative easy access to coasts and the recurring natural exposure of cliffs by thermo-abrasive wave action they are very convenient study objects for regional comparisons and correlation of past environmental conditions. Finally, palaeogeographical reconstructions are also guided by remote sensing

  2. Partitioning of Heavy Metals In Estuarine Sediments Cores and Implications For The Use of Sediment Quality Standards

    NASA Astrophysics Data System (ADS)

    Spencer, K.; MacLeod, C.

    Total metal concentrations and partitioning behaviour of metal contaminants in sedi- ment cores collected from three estuaries (Thames, Medway and Blackwater) in south east England were examined with respect to sediment quality guidelines (SQGs). Metal data from surface sediments were compared with historically contaminated sed- iments at depth to determine whether vertical contaminant profiles should be consid- ered when applying sediment quality guidelines. Initial investigations, based on total metal concentrations in surface sediments indicate that there is no risk to biota in any of the estuaries studied. However, in the Medway and Thames estuaries, which have received past industrial inputs, consideration of sediments at depth is also im- portant. Comparison of sediments at depth with SQGs suggests that local authorities should examine vertical metal profiles, particularly in estuaries that are experiencing low sediment accumulation rates, erosion or dredging activities. Total metal data indi- cate that the risk to biota is greatest in the Thames followed by the Medway and then the Blackwater. However, metal partitioning data indicate that the risk to biota is com- parable for the Medway and the Blackwater with the potentially bioavailable fraction presenting no risk to biota. Conversely, over 70% of metals are labile in the Thames Estuary sediments and toxic effects are probable. This suggests that the application of sediment quality guidelines using total sediment metal concentrations may over or under estimate the risk to biota in geochemically dissimilar estuarine sediments.

  3. Analysis of particulate matter collected by sediment traps and from sediment Cores

    NASA Astrophysics Data System (ADS)

    Collier, Bob; Dymond, Jack; Conard, Roberta; Robbins, Jim

    These contributions are primarily directed at elemental analyses for major and trace cations and silicon on particles collected by sediment traps and sediment cores; samples typically having at least several hundred milligrams available. The techniques outlined below and other wet chemical methods are reviewed in more detail in an OSU technical report by Robbins et al. [1984]. Typically, our group filters water samples for trace metal analyses immediately upon their arrival at the surface. The primary emphasis of these techniques focuses on the dissolved material. Since we have not had a full clean-lab available, we subsample the Niskins immediately using a semi-closed connection to large mouth bottles (LPE) which minimizes atmospheric exposure to contamination. The samples are then vacuum filtered within a portable laminar-flow hood (HEPA filtered) using plastic filtration "chimneys" (Millipore or Nuclepore) placed over a plastic vacuum chamber which contains the filtrate sample bottle. Filtration is carried out with 1 N HCl acid-leached Nuclepore or Poretics filters (0.4 μm) and the filtrate is collected directly into the final sample bottle. Both filtered and unfiltered subsamples are acidified to a pH<2 with 2 mL 6 N HCl L-1 sample using subboiling-distilled HCl, and the difference in concentration between the filtered and unfiltered sample is taken to represent an acid-labile particulate fraction.

  4. Perfluoroalkyl substances and extractable organic fluorine in surface sediments and cores from Lake Ontario.

    PubMed

    Yeung, Leo W Y; De Silva, Amila O; Loi, Eva I H; Marvin, Chris H; Taniyasu, Sachi; Yamashita, Nobuyoshi; Mabury, Scott A; Muir, Derek C G; Lam, Paul K S

    2013-09-01

    Fourteen perfluoroalkyl substances (PFASs) including short-chain perfluorocarboxylates (PFCAs, C4-C6) and perfluoroalkane sulfonates (PFSAs, C4 and C6) were measured in surface sediment samples from 26 stations collected in 2008 and sediment core samples from three stations (Niagara, Mississauga, and Rochester basins) collected in 2006 in Lake Ontario. Perfluorooctanesulfonate (PFOS), perfluorooctanoate (PFOA), perfluorononanoate (PFNA), perfluorodecanoate (PFDA), and perfluoroundecanoate (PFUnDA) were detected in all 26 surface sediment samples, whereas perfluorohexane sulfonate (PFHxS), perfluorooctane sulfonamide (FOSA), perfluorododecanoate (PFDoDA) and perfluorobutanoate (PFBA) were detected in over 70% of the surface sediment samples. PFOS was detected in all of the sediment core samples (range: 0.492-30.1ngg(-1) d.w.) over the period 1952-2005. The C8 to C11 PFCAs, FOSA, and PFBA increased in early 1970s. An overall increasing trend in sediment PFAS concentrations/fluxes from older to more recently deposited sediments was evident in the three sediment cores. The known PFCAs and PFSAs accounted for 2-44% of the anionic fraction of the extractable organic fluorine in surface sediment, suggesting that a large proportion of fluorine in this fraction remained unknown. Sediment core samples collected from Niagara basin showed an increase in unidentified organic fluorine in recent years (1995-2006). These results suggest that the use and manufacture of fluorinated organic compounds other than known PFCAs and PFSAs has diversified and increased. PMID:23911339

  5. Characterization and Modeling Of Microbial Carbon Metabolism In Thawing Permafrost

    NASA Astrophysics Data System (ADS)

    Graham, D. E.; Phelps, T. J.; Xu, X.; Carroll, S.; Jagadamma, S.; Shakya, M.; Thornton, P. E.; Elias, D. A.

    2012-12-01

    Increased annual temperatures in the Arctic are warming the surface and subsurface, resulting in thawing permafrost. Thawing exposes large pools of buried organic carbon to microbial degradation, increasing greenhouse gas generation and emission. Most global-scale land-surface models lack depth-dependent representations of carbon conversion and GHG transport; therefore they do not adequately describe permafrost thawing or microbial mineralization processes. The current work was performed to determine how permafrost thawing at moderately elevated temperatures and anoxic conditions would affect CO2 and CH4 generation, while parameterizing depth-dependent GHG production processes with respect to temperature and pH in biogeochemical models. These enhancements will improve the accuracy of GHG emission predictions and identify key biochemical and geochemical processes for further refinement. Three core samples were obtained from discontinuous permafrost terrain in Fairbanks, AK with a mean annual temperature of -3.3 °C. Each core was sectioned into surface/near surface (0-0.8 m), active layer (0.8-1.6 m), and permafrost (1.6-2.2 m) horizons, which were homogenized for physico-chemical characterization and microcosm construction. Surface samples had low pH values (6.0), low water content (18% by weight), low organic carbon (0.8%), and high C:N ratio (43). Active layer samples had higher pH values (6.4), higher water content (34%), more organic carbon (1.4%) and a lower C:N ratio (24). Permafrost samples had the highest pH (6.5), highest water content (46%), high organic carbon (2.5%) and the lowest C:N ratio (19). Most organic carbon was quantified as labile or intermediate pool versus stable pool in each sample, and all samples had low amounts of carbonate. Surface layer microcosms, containing 20 g sediment in septum-sealed vials, were incubated under oxic conditions, while similar active and permafrost layer samples were anoxic. These microcosms were incubated at -2

  6. User Friendly Processing of Sediment CT Data: Software and Application in High Resolution Non-Destructive Sediment Core Data Sets

    NASA Astrophysics Data System (ADS)

    Reilly, B. T.; Stoner, J. S.; Wiest, J.; Abbott, M. B.; Francus, P.; Lapointe, F.

    2015-12-01

    Computed Tomography (CT) of sediment cores allow for high resolution images, three dimensional volumes, and down core profiles, generated through the attenuation of X-rays as a function of density and atomic number. When using a medical CT-Scanner, these quantitative data are stored in pixels using the Hounsfield scale, which are relative to the attenuation of X-rays in water and air at standard temperature and pressure. Here we present MATLAB based software specifically designed for sedimentary applications with a user friendly graphical interface to process DICOM files and stitch overlapping CT scans. For visualization, the software allows easy generation of core slice images with grayscale and false color relative to a user defined Hounsfield number range. For comparison to other high resolution non-destructive methods, down core Hounsfield number profiles are extracted using a method robust to coring imperfections, like deformation, bowing, gaps, and gas expansion. We demonstrate the usefulness of this technique with lacustrine sediment cores from the Western United States and Canadian High Arctic, including Fish Lake, Oregon, and Sawtooth Lake, Ellesmere Island. These sites represent two different depositional environments and provide examples for a variety of common coring defects and lithologies. The Hounsfield profiles and images can be used in combination with other high resolution data sets, including sediment magnetic parameters, XRF core scans and many other types of data, to provide unique insights into how lithology influences paleoenvironmental and paleomagnetic records and their interpretations.

  7. Doppler Scanning of Sediment Cores: A Useful Method for Studying Sedimentary Structures and Defining the Cutting Angle for Half Cores

    NASA Astrophysics Data System (ADS)

    Acar, Dursun; Cagatay, Namik; Biltekin, Demet; Eris, Kadir; Albut, Gulum; Ogretmen, Nazik; Arslan, Tugce; Sari, Erol

    2014-05-01

    We tested the doppler ultrasound scanning of sediment cores in PVC liners using 8 megahertz ultrasonic waves for detection of angular laminations. The method was tested with artificially prepared cores as well as marine and lake sediment cores, and proven to be a useful and fast technique for imaging and determining the vertical angularity of sedimentary structures, such as laminations and beddings. Random cutting axes provide two angularities on X and Y dimensions. In this study, the main scientific problem is 'sequential angular disconformity'. Importance of detection of these anomalies on whole cores before dividing into half cores based on determining the right cutting axes. Successful imaging was obtained from top three centimeter depth of the sediments below the PVC liner, using a linear Doppler probe. Other Doppler probes (e.g., convex probe) did not work for core scanning because of their wave-form and reflection characteristics. Longitudinal and rotational scanning with gap filler and ultrasonic wave conductive gel material for keeping energy range of wave is necessary for detecting the variation in the dip of the bedding and laminae in the cores before separation. Another angular reasoned problem is about horizontal surface and can be easily solved with adjustable position of sensor or ray source placement. Border of sampling points between two different lithology must be stay with regard to neighbour sediment angles. Vertical angularity correction is not easy and its effect on signal propagation, detection biases and effectible to mixed samples contamination during physical sampling (particle size analyzing). Determining the attitude of angled bedding before core splitting is important for further core analyses such as elemental analysis and digital X-ray radiography. After Doppler scanning, the splitting direction (i.e., vertical to bedding and lamination) can be determined. The method is cheap, quick and non- hazardous to health, unlike the x

  8. Beryllium Isotope Dating of Sediment Cores From the Alpha Ridge, Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Sellen, E.; Jakobsson, M.; Kubik, P. W.; Frank, M.

    2007-12-01

    Poor preservation of biogenic calcium carbonate and biosilica in Arctic Ocean sediments has led to large problems regarding the establishment of a reliable chronostratigraphy. There are currently two differing sedimentation rate scenarios proposed for the Arctic Ocean. The first suggests sedimentation rates on the order of mm/ka and is based on cores from the Amerasian Basin, whereas the second suggests sedimentation rates on the order of cm/ka mainly derived from Eurasian Basin cores. Here we present dating results from cores HLY0503-09JPC and HLY0503-14JPC retrieved from the Alpha Ridge during the Healy-Oden Trans-Arctic Expedition 2005 (HOTRAX). These cores have been analyzed for seawater-derived beryllium (Be) isotopes in order to establish a chronostratigraphy. The isotopes 10Be and 9Be were extracted simultaneously from sample aliquots by using a leaching procedure. The decrease of 10Be concentration (half-life = 1.51 Million years) with depth in core provides first order sedimentation rates for the sampled cores. To eliminate the dilution effect of beryllium caused by short-term changes in sedimentation rate and grain size variability, the 10Be concentration was normalized to the stable isotope 9Be. The preliminary results show low downcore 10Be concentrations in both cores from the Alpha Ridge. Plotting 10Be against depth suggests an average sedimentation rate of ~2.9 mm/ka for core HLY0503-09JPC and ~2.3 mm/ka for HLY0503- 14JPC. The calculated 10Be/9Be ratios point to even lower average sedimentation rates of ~1.9 mm/ka for core HLY0503-09JPC and ~1.6 mm/ka for HLY0503-14JPC. However, core HLY0503-14JPC shows a pronounced variability of the 10Be concentration as well as for the 10Be/9Be ratio, which results in a large uncertainty of the calculated sedimentation rates. The 10Be concentrations for this core will be compared with the grain size record in order to reduce the scatter of the data. The preliminary beryllium isotope chronostratigraphy supports

  9. Chemical analysis of sediment cores from the East Waterway (Everett, Washington). Final report

    SciTech Connect

    Crecelius, E.A.; Bloom, N.S.; Gurtisen, J.M.

    1984-06-01

    Chemical data for two sediment cores from the East Waterway of Everett, Washington, indicate that 20 to 30 cm of contaminated sediments are accumulating per year. The concentrations of several heavy metals (Pb, Hg and Cu), polychlorinated biphenyls (PCBs) and petroleum hydrocarbons increase with depth in the sediments suggesting contamination of this waterway has varied by as much as a factor of 10 during the last 5 years. 7 references, 9 figures, 12 tables.

  10. Contaminant trends in reservoir sediment cores as records of influent stream quality

    USGS Publications Warehouse

    Van Metre, P.C.; Mahler, B.J.

    2004-01-01

    When reconstructing water-quality histories from lake and reservoir cores, it is sometimes assumed that the chemical signatures in the cores reflect historical water quality in the influent streams. To investigate this assumption, concentrations of metals, PAHs, and organochlorine compounds in sediment cores were compared to those associated with an influent-stream suspended sediment for three reservoirs in Fort Worth, TX, and two reservoirs in Boston, MA, U.S.A., and interpreted in light of land-use and regulation histories. In evaluating relations between suspended sediments and cores, three levels of preservation were indicated: (1) influent concentrations and historical trends are preserved in cores (metals at all sites; some organic contaminants at some sites); (2) some loss occurs during transport and initial deposition but relative historical trends are preserved in cores (some organic contaminants at some sites); and (3) neither stream concentrations nor relative historical trends are preserved (dieldrin and p,p???-DDT). The degree of preservation of influent concentration histories varied between lakes, particularly for PAHs. The results support the use of sediment cores to infer streamwater-quality histories for many contaminants but indicate that reservoir-bottom sediment samples might underestimate concentrations of organic contaminants in some streams.

  11. Anthropogenic Eutrophication of Narragansett Bay: Evidence from Dated Sediment Cores

    EPA Science Inventory

    The organic matter preserved in estuarine sediments provides a number of useful indicators, or "proxies" that can be used to infer paleoenvironmental changes One type of paleoenvironmental change is anthropogenic eutrophication. The human activity largely responsible for increasi...

  12. Identification of Water-Quality Trends Using Sediment Cores from Dillon Reservoir, Summit County, Colorado

    USGS Publications Warehouse

    Greve, Adrienne I.; Spahr, Norman E.; Van Metre, Peter C.; Wilson, Jennifer T.

    2001-01-01

    Since the construction of Dillon Reservoir, in Summit County, Colorado, in 1963, its drainage area has been the site of rapid urban development and the continued influence of historical mining. In an effort to assess changes in water quality within the drainage area, sediment cores were collected from Dillon Reservoir in 1997. The sediment cores were analyzed for pesticides, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and trace elements. Pesticides, PCBs, and PAHs were used to determine the effects of urban development, and trace elements were used to identify mining contributions. Water-quality and streambed-sediment samples, collected at the mouth of three streams that drain into Dillon Reservoir, were analyzed for trace elements. Of the 14 pesticides and 3 PCBs for which the sediment samples were analyzed, only 2 pesticides were detected. Low amounts of dichloro-diphenyldichloroethylene (DDE) and dichloro-diphenyldichloroethane (DDD), metabolites of dichlorodiphenyltrichloroethane (DDT), were found at core depths of 5 centimeters and below 15 centimeters in a core collected near the dam. The longest core, which was collected near the dam, spanned the entire sedimentation history of the reservoir. Concentrations of total combustion PAH and the ratio of fluoranthene to pyrene in the core sample decreased with core depth and increased over time. This relation is likely due to growth in residential and tourist populations in the region. Comparisons between core samples gathered in each arm of the reservoir showed the highest PAH concentrations were found in the Tenmile Creek arm, the only arm that has an urban area on its shores, the town of Frisco. All PAH concentrations, except the pyrene concentration in one segment in the core near the dam and acenaphthylene concentrations in the tops of three cores taken in the reservoir arms, were below Canadian interim freshwater sediment-quality guidelines. Concentrations of arsenic, cadmium

  13. Estimation of a Historic Mercury Load Function for Lake Michigan using Dated Sediment Cores

    EPA Science Inventory

    Box cores collected between 1994 and 1996 were used to estimate historic mercury loads to Lake Michigan. Based on a kriging spatial interpolation of 54 Pb-210 dated cores, 228 metric tons of mercury are stored in the lake’s sediments (excluding Green Bay). To estimate the time ...

  14. A method for estimation of historic contaminant loads using dated sediment cores

    EPA Science Inventory

    Dated sediment cores were used to assess the history of contaminant loads. The contaminant selected must be one that is not significantly remobilized by post depositional processes such as diagenesis. In addition, the core must be from an area with a high deposition rate and litt...

  15. Permafrost-ice-sheet interactions during the Quaternary

    NASA Astrophysics Data System (ADS)

    Willeit, Matteo; Ganopolski, Andrey

    2016-04-01

    Permafrost influences a number of processes which are relevant for local and global climate. For example, it is well known that permafrost plays an important role in global carbon and methane cycles. Less is known about the interaction between permafrost and ice sheets. We recently included a permafrost module in the Earth system model CLIMBER-2 to explore the coupled Northern Hemisphere (NH) permafrost-ice-sheet evolution during the Quaternary. The model has been shown to perform generally well at reproducing present-day permafrost extent and thickness. Modelled permafrost extent at the Last Glacial Maximum (LGM) agrees well with reconstructions and previous modeling estimates. In a previous study we showed that over the last glacial cycle permafrost has a relatively modest impact on simulated NH ice sheet volume except at LGM, when including permafrost increases ice volume by about 15 m sea level equivalent in our model. This is explained by a delayed melting of the ice base from below by the geothermal heat flux when the ice sheet sits on a porous sediment layer and permafrost has to be melted first. Permafrost affects ice sheet dynamics only when ice extends over areas covered by thick sediments, which is the case at LGM. In transient model simulations of the "40 kyr world" of the early Pleistocene we show that when all continents are covered by a thick sediment layer the response of ice volume to the obliquity component of orbital forcing is enhanced while the response to precession is dampened. We therefore argue that permafrost could have played a role for ice sheet evolution when all continents were covered by a thick sediment layer, as was likely the case in the early Pleistocene before the sediment layer was gradually eroded by expanding ice sheets over parts of northern Canada and Scandinavia.

  16. Uranium isotopes and dissolved organic carbon in loess permafrost: Modeling the age of ancient ice

    NASA Astrophysics Data System (ADS)

    Ewing, S. A.; Paces, J. B.; O'Donnell, J. A.; Jorgenson, M. T.; Kanevskiy, M. Z.; Aiken, G. R.; Shur, Y.; Harden, J. W.; Striegl, R.

    2015-03-01

    The residence time of ice in permafrost is an indicator of past climate history, and of the resilience and vulnerability of high-latitude ecosystems to global change. Development of geochemical indicators of ground-ice residence times in permafrost will advance understanding of the circumstances and evidence of permafrost formation, preservation, and thaw in response to climate warming and other disturbance. We used uranium isotopes to evaluate the residence time of segregated ground ice from ice-rich loess permafrost cores in central Alaska. Activity ratios of 234U vs. 238U (234U/238U) in water from thawed core sections ranged between 1.163 and 1.904 due to contact of ice and associated liquid water with mineral surfaces over time. Measured (234U/238U) values in ground ice showed an overall increase with depth in a series of five neighboring cores up to 21 m deep. This is consistent with increasing residence time of ice with depth as a result of accumulation of loess over time, as well as characteristic ice morphologies, high segregated ice content, and wedge ice, all of which support an interpretation of syngenetic permafrost formation associated with loess deposition. At the same time, stratigraphic evidence indicates some past sediment redistribution and possibly shallow thaw among cores, with local mixing of aged thaw waters. Using measures of surface area and a leaching experiment to determine U distribution, a geometric model of (234U/238U) evolution suggests mean ages of up to ∼200 ky BP in the deepest core, with estimated uncertainties of up to an order of magnitude. Evidence of secondary coatings on loess grains with elevated (234U/238U) values and U concentrations suggests that refinement of the geometric model to account for weathering processes is needed to reduce uncertainty. We suggest that in this area of deep ice-rich loess permafrost, ice bodies have been preserved from the last glacial period (10-100 ky BP), despite subsequent fluctuations in

  17. Uranium isotopes and dissolved organic carbon in loess permafrost: Modeling the age of ancient ice

    USGS Publications Warehouse

    Ewing, Stephanie A.; Paces, James B.; O'Donnell, J.A.; Jorgenson, M.T.; Kanevskiy, M.Z.; Aiken, George R.; Shur, Y.; Harden, Jennifer W.; Striegl, Rob

    2015-01-01

    The residence time of ice in permafrost is an indicator of past climate history, and of the resilience and vulnerability of high-latitude ecosystems to global change. Development of geochemical indicators of ground-ice residence times in permafrost will advance understanding of the circumstances and evidence of permafrost formation, preservation, and thaw in response to climate warming and other disturbance. We used uranium isotopes to evaluate the residence time of segregated ground ice from ice-rich loess permafrost cores in central Alaska. Activity ratios of 234U vs. 238U (234U/238U) in water from thawed core sections ranged between 1.163 and 1.904 due to contact of ice and associated liquid water with mineral surfaces over time. Measured (234U/238U) values in ground ice showed an overall increase with depth in a series of five neighboring cores up to 21 m deep. This is consistent with increasing residence time of ice with depth as a result of accumulation of loess over time, as well as characteristic ice morphologies, high segregated ice content, and wedge ice, all of which support an interpretation of syngenetic permafrost formation associated with loess deposition. At the same time, stratigraphic evidence indicates some past sediment redistribution and possibly shallow thaw among cores, with local mixing of aged thaw waters. Using measures of surface area and a leaching experiment to determine U distribution, a geometric model of (234U/238U) evolution suggests mean ages of up to ∼200 ky BP in the deepest core, with estimated uncertainties of up to an order of magnitude. Evidence of secondary coatings on loess grains with elevated (234U/238U) values and U concentrations suggests that refinement of the geometric model to account for weathering processes is needed to reduce uncertainty. We suggest that in this area of deep ice-rich loess permafrost, ice bodies have been preserved from the last glacial period (10–100 ky BP), despite subsequent

  18. Butyltin compounds in a sediment core from the old Tilbury basin, London, UK.

    PubMed

    Scrimshaw, M D; Wahlen, R; Catterick, T; Lester, J N

    2005-12-01

    Sections from a sediment core taken from the River Thames were analysed for butyltin species using gas chromatography with species-specific isotope dilution mass spectrometry. Results demonstrated that in most samples tributyltin concentrations of 20-60 ng/g accounted for <10% of the total butyltin species present, which is in agreement with data from other sediment samples which were historically contaminated with tributyltin. Vertical distribution of the organotin residues with depth throughout the core, with data on organochlorine compounds and heavy metals allowed for the construction of a consistent hypothesis on historical deposition of contaminated sediments. From this it was possible to infer that the concentrations of tributyltin in sediments deposited during the early 1960s were in the order of 400-600 microg/g by using degradation rate constants derived by other workers. Such values fall well within the range quoted for harbour sediments in the literature. PMID:16040058

  19. Seasonal variation of methylmercury in sediment cores from the Tagus Estuary (Portugal).

    PubMed

    Monteiro, Carlos Eduardo; Cesário, Rute; O'Driscoll, Nelson J; Nogueira, Marta; Válega, Mónica; Caetano, Miguel; Canário, João

    2016-03-15

    Seasonal and spatial variations of dissolved and particulate methylmercury were evaluated for the first time in sediment cores from the Tagus Estuary. Results showed the highest MeHg concentrations in summer months indicating that the "seasonally" methylation process occurs not only at the topmost layers of the sediments but also in the deeper layers of the sediment column. The proportion of MeHg (up to 92%) in some of our pore water samples was higher than values reported in the literature for other estuaries suggesting that the sedimentary environment in the Tagus tends to favour Hg methylation. This work points to the importance of seasonal variation of the MeHg production in sediment cores. In physically dominated estuaries this enhances seasonal MeHg production in deeper sediments that can have serious ecological impacts due to resuspension or advection processes under extreme events by the increase of MeHg transported to the water column. PMID:26851871

  20. Polychlorinated biphenyl congeners in sediment cores from the Upper Mississippi River.

    PubMed

    Martinez, Andres; Schnoebelen, Douglas J; Hornbuckle, Keri C

    2016-02-01

    We determined polychlorinated biphenyls (PCBs) and radionuclide (137)Cs in sediment cores from the Upper Mississippi River (UMR) and the Iowa River, Iowa, at their confluence. Vertical distribution of (137)Cs indicated negligible mixing in the UMR core, while the Iowa River core showed signs of mixing. A clear (137)Cs peak was found in the UMR core, which was correlated to 1963. The PCB vertical distribution in UMR core was similar to the historical trend in Aroclor production observed in Great Lakes cores, with a peak close to the (137)Cs peak, suggesting a date near 1960. In general, PCB congener profiles in both cores resembled the Iowa soil background signal. We concluded that despite evidence of mixing in the Iowa River core, both cores retain the PCB signature of historical and regional environmental exposure. Further, our results indicate that this iconic waterway has a long history of PCBs that reflects national production and use. PMID:26547030

  1. Influence of sampling on magnetic susceptibility anisotropy of soft sediments: comparison between gravity and piston cores

    NASA Astrophysics Data System (ADS)

    Shimono, Takaya; Yamazaki, Toshitsugu; Inoue, Seiko

    2014-12-01

    Anisotropy of magnetic susceptibility (AMS) has been used extensively for determining mineral orientatrections. In terms of the sample coordinate, K max declinations in the three gravity cores are oriented along the core-splitting surface, whereas K max declinations in the three piston cores are perpendicular to the splitting surface. We attribute the artificial AMS to the stress created by the deformation of core liners when being split. When interpreting AMS data from sediment cores, it is necessary to investigate the influence of sampling using the sample coordinates. In this paper, we also report over-sampling and under-sampling of piston cores from a comparison of down-core magnetic susceptibility variations between piston and gravity cores. It is noteworthy that under-sampling as well as over-sampling can occur in the uppermost few meters of piston cores.

  2. Rapid disturbances in Arctic permafrost regions (Invited)

    NASA Astrophysics Data System (ADS)

    Grosse, G.; Romanovsky, V. E.; Arp, C. D.; Jones, B. M.

    2013-12-01

    ponds have been forming indicate a broad range of possible biogeochemical feedbacks that require further study. Finally, thermokarst lake drainage observed in regions of continuous permafrost shows that local permafrost degradation, such as thermo-erosional gully formation, may increase permafrost extent in a region, in particular by new permafrost aggradation in freshly exposed, refreezing lake basin sediments. Thermokarst lake drainage across all types of permafrost extent increases habitat diversity, is important for regional biogeochemical cycling, and results in carbon sequestration. While all three disturbance types differ in spatial scale and current abundance, they also point at specific vulnerabilities of permafrost landscapes that are tied to local factors such as ground ice, highlight critical knowledge gaps for predictive ecosystem and biogeochemical models, and indicate the potential for rapid, substantial, and surprising changes in a future warmer Arctic.

  3. A record of hydrocarbon input to San Francisco Bay as traced by biomarker profiles in surface sediment and sediment cores

    USGS Publications Warehouse

    Hostettler, F.D.; Pereira, W.E.; Kvenvolden, K.A.; VanGeen, A.; Luoma, S.N.; Fuller, C.C.; Anima, R.

    1999-01-01

    San Francisco Bay is one of the world's largest urbanized estuarine systems. Its water and sediment receive organic input from a wide variety of sources; much of this organic material is anthropogenically derived. To document the spatial and historical record of the organic contaminant input, surficial sediment from 17 sites throughout San Francisco Bay and sediment cores from two locations Richardson Bay and San Pablo Bay were analyzed for biomarker constituents. Biomarkers, that is, 'molecular fossils', primarily hopanes, steranes, and n-alkanes, provide information on anthropogenic contamination, especially that related to petrogenic sources, as well as on recent input of biogenic material. The biomarker parameters from the surficial sediment and the upper horizons of the cores show a dominance of anthropogenic input, whereas the biomarker profiles at the lower horizons of the cores indicate primarily biogenic input. In the Richardson Bay core the gradual upcore transition from lower maturity background organics to a dominance of anthropogenic contamination occurred about 70-100 years ago and corresponds to the industrial development of the San Francisco Bay area. In San Pablo Bay, the transition was very abrupt, reflecting the complex depositional history of the area. This sharp transition, perhaps indicating a depositional hiatus or erosional period, dated at pre-1952, is clearly visible. Below, the hiatus the biomarker parameters are immature; above, they are mature and show an anthropogenic overlay. Higher concentrations of terrigenous n-alkanes in the upper horizons in this core are indicative of an increase in terrigenous organic matter input in San Pablo Bay, possibly a result of water diversion projects and changes in the fresh water flow into the Bay from the Delta. Alternatively, it could reflect a dilution of organic material in the lower core sections with hydraulic mining debris.

  4. Chemical composition of short sediment cores from Thermaikos Gulf (Eastern Mediterranean): Sediment accumulation rates, trawling and winnowing effects

    NASA Astrophysics Data System (ADS)

    Karageorgis, A. P.; Kaberi, H.; Price, N. B.; Muir, G. K. P.; Pates, J. M.; Lykousis, V.

    2005-12-01

    Four cores recovered within the framework of the INTERPOL Project have been analysed for their grain size and geochemistry; sediment accumulation rates (SARs) were also determined from 210Pb and 137Cs profiles. Two cores are representative of the Axios and Aliakmon Rivers depositional environment, whilst the third core represents the Pinios River province; the fourth core represents an environment of outer shelf relict sands. Apparent SARs ranged between 0.667 g cm -2 yr -1 (Axios and Aliakmon Rivers) and 0.414 g cm -2 yr -1 (Pinios River). Trawling activities and biomixing are critical processes that may be responsible for the mixing of the surface sediments, as observed from the excess 210Pb profiles. The thickness of the surface mixed layer was 4.5 cm in the vicinity of Axios and Aliakmon Rivers and in the area of Pinios River, 3.75 cm on the outer shelf and 1 cm in the area where no trawling was observed. Sediment accumulation appeared to be regulated by variations in the riverine discharge, shelf transport pathways and winnowing processes. Major element variations, such as Si, Al, Ti, V and Ni, were dominated by terrigenous supply as aluminosilicate minerals and quartz, whereas most Ca and Sr were biogenic. Si/Al and Ca/Al ratios have been used to express changes in sediment accumulation and winnowing. Redox processes were depicted by Mn, which showed an increase in the depth of its redoxcline, from ˜1 cm in inshore stations to ˜2 cm on the outer shelf. Si/Al ratios follow the Ca/Al ratios and can be used to assess percentage winnowing in the sediment. Increases in these ratios indicate a decrease in sediment input rates and are seen in the upper parts of most of the cores. Anthropogenic or 'excess' metal contents have been calculated from Zn/V and Pb/V ratios. Their distributions in the cores showed that by far the highest contamination is associated with the Axios River output, whilst sediments influenced by the Pinios River were relatively uncontaminated.

  5. Sediment Core Extrusion Method at Millimeter Resolution Using a Calibrated, Threaded-rod.

    PubMed

    Schwing, Patrick T; Romero, Isabel C; Larson, Rebekka A; O'Malley, Bryan J; Fridrik, Erika E; Goddard, Ethan A; Brooks, Gregg R; Hastings, David W; Rosenheim, Brad E; Hollander, David J; Grant, Guy; Mulhollan, Jim

    2016-01-01

    Aquatic sediment core subsampling is commonly performed at cm or half-cm resolution. Depending on the sedimentation rate and depositional environment, this resolution provides records at the annual to decadal scale, at best. An extrusion method, using a calibrated, threaded-rod is presented here, which allows for millimeter-scale subsampling of aquatic sediment cores of varying diameters. Millimeter scale subsampling allows for sub-annual to monthly analysis of the sedimentary record, an order of magnitude higher than typical sampling schemes. The extruder consists of a 2 m aluminum frame and base, two core tube clamps, a threaded-rod, and a 1 m piston. The sediment core is placed above the piston and clamped to the frame. An acrylic sampling collar is affixed to the upper 5 cm of the core tube and provides a platform from which to extract sub-samples. The piston is rotated around the threaded-rod at calibrated intervals and gently pushes the sediment out the top of the core tube. The sediment is then isolated into the sampling collar and placed into an appropriate sampling vessel (e.g., jar or bag). This method also preserves the unconsolidated samples (i.e., high pore water content) at the surface, providing a consistent sampling volume. This mm scale extrusion method was applied to cores collected in the northern Gulf of Mexico following the Deepwater Horizon submarine oil release. Evidence suggests that it is necessary to sample at the mm scale to fully characterize events that occur on the monthly time-scale for continental slope sediments. PMID:27585268

  6. The preglacial sediment record of Lake Ladoga, Russia - first results from a seismic survey and sediment coring in 2013

    NASA Astrophysics Data System (ADS)

    Melles, Martin; Krastel, Sebastian; Fedorov, Grigory; Subetto, Dmitry A.; Savelieva, Larisa A.; Andreev, Andrej; Wagner, Bernd

    2014-05-01

    The new German-Russian project PLOT (Paleolimnological Transect) aims at investigating the Late Quaternary climatic and environmental history along a more than 6000 km long longitudinal transect crossing northern Eurasia. Special emphasis is put on the preglacial history. For this purpose shallow and deep seismic surveys shall be carried out on five lakes, which potentially host preglacial sediment records, followed by sediment coring based on the results of the seismic campaigns. The well-studied Lake El'gygytgyn represents the eastern-most location of the transect and acts as reference site. Within the scope of a pilot phase for the PLOT project, funded by the German Federal Ministry of Education and Research, we were able to investigate Lake Ladoga, which is located close to St. Petersburg at the western end of the transect. Lake Ladoga is the largest lake in Europe, covering an area of almost 18.000 km2. The modern sedimentation as well as the late glacial and Holocene history of the lake were already studied in detail over the past decades. The older, preglacial lake history, however, is only rudimentary known from a core transect drilled in the southern lake in the 1930th. The cores of up to about 60 m length were only briefly described and are not existing any more. The results from these cores, known from unpublished reports only, suggest the existence of marine sediments of presumably Eemian age, representing a time when Lake Lagoga was part of a precursor of the Baltic Sea, which had a connection via Ladoga and Onega Lakes to the White Sea and further to the Arctic Ocean. In late August/early September 2013 we carried out a seismic survey on Lake Ladoga using a Mini-GI-Gun and a 32-channel seismic streamer. In total, 1500 km of seismic profiles were measured, covering most parts of the lake. The seismic lines typically show acoustically well stratified Holocene muds overlaying rather transparent postglacial varves. These sediment successions can reach

  7. The Fate of Organic Carbon Released by Permafrost Decay, Eastern Coast of Hudson Bay.

    NASA Astrophysics Data System (ADS)

    Jolivel, M.; Allard, M.

    2009-05-01

    Recent evaluations indicate that large amounts of organic carbon can be released in fluvial and costal systems because of permafrost degradation, with impacts on ecosystems. In order to obtain quantitative data on those transfers, we have installed instrumentation and have made first measurements in an intensive permafrost degradation area. The study area is located on the eastern coast of Hudson Bay, in the region of the Sheldrake river (drainage basin, river mouth and offshore area), near Umiujaq, in the discontinuous permafrost zone. Permafrost mounds (palsas, lithalsas) and plateaus are the most abundant permafrost landforms. This area contains one of the largest concentrations of frost heave landforms in the world. They developed principally in east-west oriented valleys in postglacial marine silts from the Tyrrell Sea which inundated low areas around Hudson Bay, following the receding ice front eastward and inland, about 8000 years BP. Palsas are covered by peat. Organic matter and clay released by thermokarst are transferred to the sea through the river system as suspended sediments, suspended organic matter and dissolved organic carbon. We postulate that continuing warming will further accelerate permafrost erosion, favour thermokarst and have an impact on carbon transfers. The adopted methodology should permit to quantify the release of clay and carbon through fluvial transport and deposition in coastal marine depocenters. Two leveloggers and two Optical Backscatter Sensors (OBS) have been installed during summer 2008, about 2km upstream from the Sheldrake river mouth in order to estimate transportation. Moreover, bathymetric surveys (eco-sounder coupled with sidescan sonar) have been made in a 20km2 area offshore the Sheldrake river mouth. We have located deeper basins (88m deep) in submerged valleys, which are likely efficient sediments traps for recent river inputs. Some sediment cores will be extracted in March 2009 from the ice pack in order to

  8. Geochemical assessment of metal concentrations in sediment core of Korangi Creek along Karachi Coast, Pakistan.

    PubMed

    Chaudhary, M Z; Ahmad, N; Mashiatullah, A; Ahmad, N; Ghaffar, A

    2013-08-01

    Sediment core from Korangi Creek, one of the polluted coastal locations along the Karachi Coast Pakistan, was collected to trace the history of marine pollution and to determine the impact of industrial activity in the area. Down core variation of metals such as Ca, K, Mg, Al, S, Ti, V, Cr, Mn, Fe, Ni, Cu and Zn was studied in the 72.0 cm core. Nuclear analytical techniques, proton induced X-rays emission (PIXE), was employed to ascertain the chemical composition in sediment core. Grain size analysis and sediment composition of cored samples indicated that Korangi creek sediments are clayey in nature. Correlation matrix revealed a strong association of Ni, Cu, Cr and Zn with Fe and Mn. To infer anthropogenic input, enrichment factor (EF), degree of contamination and pollution load index were calculated. EF showed severe enrichment in surface sediment for Ni, Cu, Cr and Zn, indicating increased industrial effluents discharge in recent years. The study suggests that heavy metal discharge in the area should be regulated. If the present trend of enrichment is allowed to continue unabated, it is most likely that the local food web complexes in the creek might be at highest risk. PMID:23279880

  9. Legacy Effects of Warming on Permafrost Carbon Release

    NASA Astrophysics Data System (ADS)

    Blok, D.; Faucherre, S.; Banyasz, I.; Michelsen, A.; Elberling, B.

    2015-12-01

    Warming in arctic tundra may thaw currently frozen upper permafrost layers, potentially releasing organic carbon (C) that was preserved by cold conditions for hundreds or thousands of years. Apart from the direct control of temperature on permafrost carbon dioxide (CO2) production, warming may alter permafrost CO2 production rates through changes in either permafrost C quality or changes in microbial communities. We incubated exogenous permafrost cores in four different warming experiments in NE-Greenland. The experiments were located in both Salix- and Cassiope-dominated sub-sites and were established in 2004 (old site) and 2007 (new site). Permafrost cores were buried as "open incubators" (free vertical water flow) at both 5-10cm depth (shallow) and 15-20cm depth (deep) in both non-manipulated (control) and warmed plots (warmed) and incubated for 2 years in the field. After retrieval from the field, permafrost cores were kept undisturbed in a lab fridge for three months, after which sub-samples were incubated at 5°C in glass vials. Permafrost CO2 production rates were subsequently measured after one week, four weeks and three months incubation in the lab. We measured the legacy effects of in situ conditions, including experimental warming in the field, on permafrost respiration under controlled laboratory conditions. We assessed the effects of plot type, vegetation type, experiment age, and incubation depth on permafrost CO2 production rates. After 3 months incubation in the lab, we measured a positive effect of warming on permafrost CO2 production rates for shallow-incubated cores, but not for deep-incubated cores. Production rates of CO2 were significantly higher for cores incubated in the old site compared to the new site. Our results suggest that warming may not only directly stimulate permafrost C release, but also indirectly through the effects of infiltrating water, nutrients and microbes from near-surface soil layers.

  10. Provenance of Apollo 15 deep drill core sediments

    NASA Technical Reports Server (NTRS)

    Basu, A.; Bower, J. F.

    1977-01-01

    Modal analysis and electron probe microanalysis were performed on polished thin sections prepared from Apollo 15 deep drill core soils in an effort to characterize their provenance. The particles were in the 0.25-1.00 mm size range. The particles were classified into mineral fragments, agglutinates, glasses, rock fragments, and breccias. The results show that highland and mare material occur in the core in an approximately 60:40 ratio, with mare component generally increasing from bottom to top in the core. Quartz-normative basalts are nearly twice as abundant as olivine basalts. Nonmare sources include KREEP basalt flow units from some depth in the crust, excavated by cratering events and supplied to the site as 'rays'.

  11. 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.

  12. Historical accumulation of organic contaminants in sediment cores from Massachusetts and Cape Cod Bays

    SciTech Connect

    Seavey, J.A.; Shea, D.; Weisbrod, A.V.; Hofelt, C.S.

    1995-12-31

    Trace level concentrations of over 50 polynuclear aromatic hydrocarbons (PAH) and linear alkyl benzenes (LAB), 16 chlorinated pesticides, and 20 polychlorinated biphenyls (PCB) were measured in sediment cores collected at ten sampling stations located in Massachusetts and Cape Cod Bays. The sediment cores were dated by using Pb-210. PAH and LAB values ranged from 36--30388 ng/g and < 1--181 ng/g (dry weight), respectively. Pesticide and PCB values ranged from 0.8--23 ng/g and 0.8--35 ng/g, respectively. As expected, the contaminant concentrations correlate with the amount of organic carbon in the sediment and generally decrease with increasing age of the sediment and increasing distance from Boston Harbor, the major historical source of many of these contaminants. Total inventories of contaminants in Massachusetts Bay were calculated and used to help construct a contaminant mass balance for the region. Down-core profiles were used to help reconstruct historical loading to the region. The relative distributions of contaminants in the sediment were used, along with source distributions (fingerprints), to calculate the contribution of each source to the measured sediment inventory. LABs were particularly useful in distinguishing the Boston Harbor sewage effluent from other sources. Implications to the long term fate and effects of contaminants in Massachusetts and Cape Cod Bays will be presented.

  13. (129)I record of nuclear activities in marine sediment core from Jiaozhou Bay in China.

    PubMed

    Fan, Yukun; Hou, Xiaolin; Zhou, Weijian; Liu, Guangshan

    2016-04-01

    Iodine-129 has been used as a powerful tool for environmental tracing of human nuclear activities. In this work, a sediment core collected from Jiaozhou Bay, the east coast of China, in 2002 was analyzed for (129)I to investigate the influence of human nuclear activities in this region. Significantly enhanced (129)I level was observed in upper 70 cm of the sediment core, with peak values in the layer corresponding to 1957, 1964, 1974, 1986, and after 1990. The sources of (129)I and corresponding transport processes in this region are discussed, including nuclear weapons testing at the Pacific Proving Grounds, global fallout from a large numbers of nuclear weapon tests in 1963, the climax of Chinese nuclear weapons testing in the early 1970s, the Chernobyl accident in 1986, and long-distance dispersion of European reprocessing derived (129)I. The very well (129)I records of different human nuclear activities in the sediment core illustrate the potential application of (129)I in constraining ages and sedimentation rates of the recent sediment. The releases of (129)I from the European nuclear fuel reprocessing plants at La Hague (France) and Sellafield (UK) were found to dominate the inventory of (129)I in the Chinese sediments after 1990, not only the directly atmospheric releases of these reprocessing plants, but also re-emission of marine discharged (129)I of these reprocessing plants in the highly contaminated European seas. PMID:26821329

  14. Selected data for sediment cores collected in Chesapeake Bay in 1996 and 1998

    USGS Publications Warehouse

    Baucom, P.C.; Bratton, J.F.; Colman, Steven M.; Moore, Johnnie N.; King, John W.; Seal, Chip; Seal, R.R., II

    2001-01-01

    As part of a study of recent history of the Chesapeake Bay ecosystem, one- to eight- meter long sediment cores were obtained from the mesohaline section of the Chesapeake Bay between the mouths of the Potomac and Rhode Rivers. The sediments consist of three lithofacies: coarse-grained channel deposits, restricted-estuary sands and muds, and open-estuary muds. Water content, biogenic silica, magnetic susceptibility, trace metals, and nutrients (carbon, nitrogen, and their isotopes) were measured in the cores. Biogenic silica, trace-metal, and nutrient data provide a strong basis for discussing past primary productivity and water-column anoxia in the bay.

  15. Non-destructive X-ray Computed Tomography (XCT) Analysis of Sediment Variance in Marine Cores

    NASA Astrophysics Data System (ADS)

    Oti, E.; Polyak, L. V.; Dipre, G.; Sawyer, D.; Cook, A.

    2015-12-01

    Benthic activity within marine sediments can alter the physical properties of the sediment as well as indicate nutrient flux and ocean temperatures. We examine burrowing features in sediment cores from the western Arctic Ocean collected during the 2005 Healy-Oden TransArctic Expedition (HOTRAX) and from the Gulf of Mexico Integrated Ocean Drilling Program (IODP) Expedition 308. While traditional methods for studying bioturbation require physical dissection of the cores, we assess burrowing using an X-ray computed tomography (XCT) scanner. XCT noninvasively images the sediment cores in three dimensions and produces density sensitive images suitable for quantitative analysis. XCT units are recorded as Hounsfield Units (HU), where -999 is air, 0 is water, and 4000-5000 would be a higher density mineral, such as pyrite. We rely on the fundamental assumption that sediments are deposited horizontally, and we analyze the variance over each flat-lying slice. The variance describes the spread of pixel values over a slice. When sediments are reworked, drawing higher and lower density matrix into a layer, the variance increases. Examples of this can be seen in two slices in core 19H-3A from Site U1324 of IODP Expedition 308. The first slice, located 165.6 meters below sea floor consists of relatively undisturbed sediment. Because of this, the majority of the sediment values fall between 1406 and 1497 HU, thus giving the slice a comparatively small variance of 819.7. The second slice, located 166.1 meters below sea floor, features a lower density sediment matrix disturbed by burrow tubes and the inclusion of a high density mineral. As a result, the Hounsfield Units have a larger variance of 1,197.5, which is a result of sediment matrix values that range from 1220 to 1260 HU, the high-density mineral value of 1920 HU and the burrow tubes that range from 1300 to 1410 HU. Analyzing this variance allows us to observe changes in the sediment matrix and more specifically capture

  16. Past freeze and thaw cycling in the margin of the El'gygytgyn Crater deduced from a 141 m long permafrost record

    NASA Astrophysics Data System (ADS)

    Schwamborn, G.; Meyer, H.; Schirrmeister, L.; Fedorov, G.

    2013-07-01

    Past permafrost thaw and freeze has destabilised the basin slopes of Lake El'gygytgyn in the northeastern Eurasian Arctic. This has probably promoted the release of mass movements from the lake edge to the deeper basin as known from frequently occurring turbidite layers in the lake sediment column. The continuous sediment record from the Arctic spans the last 3.6 Ma and for much of this time permafrost dynamics and lake level changes likely have played a crucial role for sediment delivery to the lake. Changes in the ground ice hydrochemical composition (pH, δ18O, δD, electrical conductivity, Na+, Mg2+, Ca2+, K+, HCO3-, Cl-, SO4-) of a 141 m long permafrost record from the western crater plain are examined to reconstruct repeated freeze and thaw cycles at the lake edge. Stable water isotope and major ion records of ground ice in the permafrost reflect both a synsedimentary palaeo-precipitation signal preserved in the near-surface permafrost (0.0 m to 9.1 m core depth) and a postdepositional record of talik thawing and refreezing in deeper layers of the core (9.1 to 141.0 m core depth). The lake marginal permafrost dynamics were controlled by lake level changes that episodically flooded the surfaces and induced thaw in the underlying frozen ground. At least three cycles of freeze and thaw during marine isotope stage (MIS) 7, possibly MIS 5, and the Allerød (AD) are identified and the hydrochemical data point to a vertical and horizontal talik refreezing through time.

  17. Past freeze and thaw cycling in the margin of the El'gygytgyn crater deduced from a 141 m long permafrost record

    NASA Astrophysics Data System (ADS)

    Schwamborn, G.; Meyer, H.; Schirrmeister, L.; Fedorov, G.

    2014-06-01

    The continuous sediment record from Lake El'gygytgyn in the northeastern Eurasian Arctic spans the last 3.6 Ma and for much of this time permafrost dynamics and lake level changes have likely played a crucial role for sediment delivery to the lake. Changes in the ground-ice hydrochemical composition (δ18O, δD, pH, electrical conductivity, Na+, Mg2+, Ca2+, K+, HCO3-, Cl-, SO4-) of a 141 m long permafrost record from the western crater plain are examined to reconstruct repeated periods of freeze and thaw at the lake edge. Stable water isotope and major ion records of ground ice in the permafrost reflect both a synsedimentary palaeo-precipitation signal preserved in the near-surface permafrost (0.0-9.1 m core depth) and a post-depositional record of thawing and refreezing in deeper layers of the core (9.1-141.0 m core depth). These lake marginal permafrost dynamics were controlled by lake level changes that episodically flooded the surfaces and induced thaw in the underlying frozen ground. During times of lake level fall these layers froze over again. At least three cycles of freeze and thaw are identified and the hydrochemical data point to a vertical and horizontal talik refreezing through time. Past permafrost thaw and freeze may have destabilised the basin slopes of Lake El'gygytgyn and this has probably promoted the release of mass movements from the lake edge to the deeper basin as known from frequently occurring turbidite layers in the lake sediment column.

  18. Slope Edge Deformation and Permafrost Dynamics Along the Arctic Shelf Edge, Beaufort Sea, Canada

    NASA Astrophysics Data System (ADS)

    Paull, C. K.; Dallimore, S.; Caress, D. W.; Gwiazda, R.; Lundsten, E. M.; Anderson, K.; Riedel, M.; Melling, H.

    2015-12-01

    The shelf of the Canadian Beaufort Sea is underlain by relict offshore permafrost that formed in the long intervals of terrestrial exposure during glacial periods. At the shelf edge the permafrost thins rapidly and also warms. This area has a very distinct morphology that we attribute to both the formation and degradation of ice bearing permafrost. Positive relief features include circular to oval shaped topographic mounds, up to 10 m high and ~50 m in diameter which occur at a density of ~6 per km2. Intermixed are circular topographic depressions up to 20 m deep. This topography was investigated using an autonomous underwater vehicle that provides 1 m horizontal resolution bathymetry and chirp profiles, a remotely operated vehicle to document seafloor textures, and sediment cores to sample pore waters. A consistent down-core freshening at rates of 14 to 96 mM Cl- per meter was found in these pore waters near the shelf edge. Downward extrapolation of these trends indicates water with ≤335 mM Cl- should occur at 2.3 to 22.4 m sub-seafloor depths within this shelf edge deformation band. Pore water with 335 mM Cl- or less freezes at -1.4°C. As bottom water temperatures in this area are persistently (<-1.4°C) cold and ground ice was observed in some core samples, we interpret the volume changes associated with mound formation are in part due to pore water freezing. Thermal models (Taylor et al., 2014) predict brackish water along the shelf edge may be sourced in relict permafrost melting under the adjacent continental shelf. Buoyant brackish water is hypothesized to migrate along the base of the relict permafrost, to emerge at the shelf edge and then refreeze when it encounters the colder seafloor. Expansion generated by the formation of ice-bearing permafrost generates the positive relief mounds and ridges. The associated negative relief features may be related to permafrost dynamics also. Permafrost dynamics may have geohazard implications that are unique to the

  19. Using sediment cores to establish targets for the remediation of aquatic environments.

    PubMed

    Lintern, Anna; Anderson, Marion; Leahy, Paul; Deletic, Ana; McCarthy, David

    2016-01-01

    When assigning site-specific restoration targets for deteriorating aquatic systems, it is necessary to have an understanding of the undisturbed or background state of the system. However, the site-specific characteristics of aquatic systems prior to disturbance are mostly unknown, due to the lack of historical water and sediment quality data. This study aims to introduce a method for filling this gap in our understanding, using dated sediment cores from the beds of aquatic environments. We used Bolin Billabong, a floodplain lake of the Yarra River (South-East Australia), as a case study to demonstrate the application of this method. We identified the concentrations of aluminium, cadmium, chromium, copper, iron, lead, manganese, nickel, tin and zinc at 8 cm intervals through the sediment core. This showed that aluminium, chromium, copper, iron, lead, nickel, tin and zinc concentrations in Bolin Billabong sediments significantly increased after European settlement in the river catchment in the mid-19th century. The differences between current Australian sediment quality guidelines trigger values and the background metal concentrations in Bolin Billabong sediments underscore the value of using locally relevant background toxicant concentrations when setting water and sediment quality targets. PMID:26877046

  20. Permeability of sediment cores from methane hydrate deposit in the Eastern Nankai Trough, Japan

    NASA Astrophysics Data System (ADS)

    Konno, Y.; Yoneda, J.; Egawa, K.; Ito, T.; Jin, Y.; Kida, M.; Suzuki, K.; Nakatsuka, Y.; Nagao, J.

    2013-12-01

    Effective and absolute permeability are key parameters for gas production from methane-hydrate-bearing sandy sediments. Effective and/or absolute permeability have been measured using methane-hydrate-bearing sandy cores and clayey and silty cores recovered from Daini Atsumi Knoll in the Eastern Nankai Trough during the 2012 JOGMEC/JAPEX Pressure coring operation. Liquid-nitrogen-immersed cores were prepared by rapid depressurization of pressure cores recovered by a pressure coring system referred to as the Hybrid PCS. Cores were shaped cylindrically on a lathe with spraying of liquid nitrogen to prevent hydrate dissociation. Permeability was measured by a flooding test or a pressure relaxation method under near in-situ pressure and temperature conditions. Measured effective permeability of hydrate-bearing sediments is less than tens of md, which are order of magnitude less than absolute permeability. Absolute permeability of clayey cores is approximately tens of μd, which would perform a sealing function as cap rocks. Permeability reduction due to a swelling effect was observed for a silty core during flooding test of pure water mimicking hydrate-dissociation-water. Swelling effect may cause production formation damage especially at a later stage of gas production from methane hydrate deposits. This study was financially supported by the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) that carries out Japan's Methane Hydrate R&D Program conducted by the Ministry of Economy, Trade and Industry (METI).

  1. Characterization of sediment cores containing methane hydrate recovered from the Eastern Nankai Trough

    NASA Astrophysics Data System (ADS)

    Nagao, J.; Jin, Y.; Konno, Y.; Yoneda, J.; Egawa, K.; Ito, T.; Kida, M.; Nakatsuka, Y.; Suzuki, K.; Fujii, T.; Yamamoto, K.

    2013-12-01

    On the March 2013, Japan Oil, Gas and Metals National Corporation (JOGMEC) has conducted the first gas production test from methane hydrate deposits in the Nankai Trough offshore Japan. In the Eastern Nankai Trough area off the Pacific coast of Japan, highly concentrated methane hydrate deposits were discovered in Pleistocene turbidite sediments.. Along with geological information, structure and physical properties of the sediments are essential information to understand the nature and origin of the deposits, and preserving those in-situ values in core samples for laboratory testing on surface is a quite important scientific challenge. To solve the problem, JOGMEC and JAMSTEC have developed a pressure coring device and utilized it on D/V Chikyu for our coring operation before the production test. In this operation, we obtained two types of cores; one is the dissociation preserved core by rapidly cooled by emerging into liquid nitrogen (LN2 core), the other is stored in special pressure vessels without depressurizing and kept under original pressure and temperature (pressure core). Here the summary of LN2 core sample analyses, such as X-ray CT, p-wave velocity, particle analysis, permeability, mechanical properties, and gas composition, is presented. Also future analysis plan for pressure core is explained. This work was supported by funding from the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) planned by METI.

  2. Paleoecological inferences of recent alluvial damming of a lake basin due to retrogressive permafrost thaw slumping

    NASA Astrophysics Data System (ADS)

    Quinlan, R.; Delaney, S.; Lamoureux, S. F.; Kokelj, S. V.; Pisaric, M. F.

    2014-12-01

    Expected climate impacts of future warming in the Arctic include thawing of permafrost landscapes in northern latitudes. Thawing permafrost is expected to have major consequences on hydrological dynamics, which will affect the limnological conditions of Arctic lakes and ponds. In this study we obtained a sediment core from a small lake (informally named "FM1") near Fort McPherson, Northwest Territories, Canada, with a large retrogressive thaw slump (nearly 1 kilometre in diameter) within its catchment. A radiocarbon date from the base of the FM1 sediment core suggests the lake formed between 990-1160 Cal AD. The analysis of aerial photographs indicate the thaw slump initiated between 1970-1990, and sediment geochemistry analysis indicated major changes in sediment content at 54-cm sediment core depth. Analyses of subfossil midge (Chironomidae) fossils inferred that, pre-slump, lake FM1 was shallow with a large bog or wetland environment, with midge assemblages dominated by taxa such as Limnophyes and Parametriocnemus. Post-thaw midge assemblages were dominated by subfamily Chironominae (Tribe Tanytarsini and Tribe Chironomini) taxa, and the appearance of deepwater-associated taxa such as Sergentia suggests that lake FM1 deepened, possibly as a result of alluvial damming from slump materials washing into the lake near its outlet. Most recent stratigraphic intervals infer a reversion back to shallower conditions, with a slight recovery of bog or wetland-associated midge taxa, possibly due to rapid basin infilling from increased deposition rates of catchment-derived materials. Results emphasize that there may be a variety of different outcomes to Arctic lake and pond ecosystems as a result of permafrost thawing, contingent on system-specific characteristics such as slump location relative to the lake basin, and relative inflow and outflow locations within the lake basin.

  3. Pressure Core Characterization

    NASA Astrophysics Data System (ADS)

    Santamarina, J. C.

    2014-12-01

    Natural gas hydrates form under high fluid pressure and low temperature, and are found in permafrost, deep lakes or ocean sediments. Hydrate dissociation by depressurization and/or heating is accompanied by a multifold hydrate volume expansion and host sediments with low permeability experience massive destructuration. Proper characterization requires coring, recovery, manipulation and testing under P-T conditions within the stability field. Pressure core technology allows for the reliable characterization of hydrate bearing sediments within the stability field in order to address scientific and engineering needs, including the measurement of parameters used in hydro-thermo-mechanical analyses, and the monitoring of hydrate dissociation under controlled pressure, temperature, effective stress and chemical conditions. Inherent sampling effects remain and need to be addressed in test protocols and data interpretation. Pressure core technology has been deployed to study hydrate bearing sediments at several locations around the world. In addition to pressure core testing, a comprehensive characterization program should include sediment analysis, testing of reconstituted specimens (with and without synthetic hydrate), and in situ testing. Pressure core characterization technology can be used to study other gas-charged formations such as deep sea sediments, coal bed methane and gas shales.

  4. Hexabromocyclododecanes in surface sediments and a sediment core from Rivers and Harbor in the northern Chinese city of Tianjin.

    PubMed

    Zhang, Yanwei; Ruan, Yuefei; Sun, Hongwen; Zhao, Lijie; Gan, Zhiwei

    2013-02-01

    In the present study, hexabromocyclododecanes (HBCDs) were investigated in the sediment from Haihe River (HR), Dagu Dainage Canal (DDC) and Tianjin Harbor (TH) at Bohai Bay using a total of 51 samples of surface sediments and a sediment core collected from May to September in 2010, and its diastereomer- and enantiomer-specific profiles were analyzed. The concentration of total HBCDs were generally high, with mean value and ranges of 31.0 and 1.35-634 ng g(-1)dw, respectively. The contamination followed the order of TH>DDC>HR. Higher levels (up to 634 ng g(-1)dw) occurred in the lower reach of HR and DDC located in an industrial area of Tianjin. This is the first time to report so high concentration of HBCDs in sediment in Southeast Asia. The γ-diastereomer dominated in most samples (44 out of 51), and this is in agreement with the diastereomer distribution pattern in industrial products, while α-HBCD was the dominant diastereomer in the other seven samples. However, only few samples exhibited γ-diastereomer ratio similar to that (75-89%) in technical products, indicating the inter-transformation and variable degradation of the different isomers. The high ratio of γ-diastereomer could be used as an indicator for fresh contamination input. Enantiomeric factors (EFs) of HBCD isomers in most of the samples were statistically different from technical products (p<0.05), showing a trend of more easily enrichment of the (-)-HBCD-enantiomer compared to the (+)-HBCD-enantiomer. The δ- and ε-diastereomers were frequently detected but at low level. The HBCDs in the sediment core showed several peaks, and the greatest value occurred in 2005, when a plastic manufacture plant using HBCD was set up nearby. PMID:23062943

  5. Chromium geochemistry of serpentinous sediment in the Willow core, Santa Clara County, California

    USGS Publications Warehouse

    Oze, Christopher J.; LaForce, Matthew J.; Wentworth, Carl M.; Hanson, Randall T.; Bird, Dennis K.; Coleman, Robert G.

    2003-01-01

    A preliminary investigation of Cr geochemistry in serpentinous sediment completed for a multiple-aquifer ground-water monitoring well (Willow core of Santa Clara County, CA) determined sediment at depths >225 meters contains Cr concentrations ranging from 195 to 1155 mg/kg. Serpentinous sediment from this site is a potential source of non-anthropogenic Cr contamination. Chromium-bearing minerals such as Cr-spinel appear to be the main source of Cr in the sediment; however, Cr-bearing silicates and clay minerals are additional Cr sources. Aqueous Cr concentrations in the sediment are <4.6 mg/L; however, the valence of Cr was not identified in the solutions or in the sediment. Although there is no indication of Cr(VI) contamination derived from the serpentinous sediment, elevated Cr concentrations in the sediment, the observed ‘dissolution’ textures of the Cr-bearing minerals, the estimated redox environment, and water chemistry indicate the formation of Cr(VI) is potentially favorable.

  6. DDTs and HCHs in sediment cores from the coastal East China Sea.

    PubMed

    Lin, Tian; Nizzetto, Luca; Guo, Zhigang; Li, Yuanyuan; Li, Jun; Zhang, Gan

    2016-01-01

    Four sediment cores were collected along the Yangtze-derived sediment transport pathway in the inner shelf of the East China Sea (ECS) for OCP analysis. The sediment records of HCHs and DDTs in estuarine environment reflected remobilization of chemicals from enhanced soil erosion associated to extreme flood events or large scale land use transformation. The sediment records in the open sea, instead, reflected long-term historical trends of OCP application in the source region. Unlike the so-called mud wedge distribution of sediment, inventories of HCHs and DDTs slightly increased from the mouth of Yangtze River alongshore toward south, suggesting the sediment deposition rate was one of factors on the exposure of chemicals within the inner shelf of the ECS. Re-suspension and transport of the Yangtze-derived sediment and consequent fractionation in grain size and TOC were also responsible for the spatial variation of inventories of catchment derived OCPs in a major repository area of the Yangtze suspended sediment. The total burdens of HCHs and DDTs in the inner shelf of the ECS were 35tons and 110tons, respectively. After 1983 (year of the official ban in China), those values were 13tons and 50tons, respectively. It appears that the Yangtze still delivers relatively high inputs of DDTs more than 30years after the official ban. High proportions of DDD+DDE and β-HCH suggested those OCPs mainly originated from historical usage in the catchment recent years. PMID:26372941

  7. Toxicity of sediment cores from Yangtze River estuary to zebrafish (Danio rerio) embryos.

    PubMed

    Wang, Peipei; Zhang, Lili; Liu, Li; Chen, Ling; Gao, Hongwen; Wu, Lingling

    2015-11-01

    Toxicity evaluation is an important segment in sediment quality monitoring in order to protect aquatic organisms and human health. The purpose of this study is to assess the toxicity of sediments from three sediment cores in Yangtze River Estuary, China, using the zebrafish (Danio rerio) embryo tests. Fertilized zebrafish eggs were exposed to both whole sediments and sediment organic extracts prepared from collected sediments, in order to provide a comprehensive and realistic insight into the bioavailable toxicity potential of the sediments. As end points, development parameters (mortality, hatching rate, and abnormality) in the developing embryos were recorded during the 96-h exposure. The results showed that some samples increased mortality, inhibited the hatching of embryos, and induced morphological abnormalities. The embryonic toxicities presented serrated changes and irregular distribution with depth, which may be related to hydrodynamic effect and unstable environmental input. However, lethal and sub-lethal effects were more significant at the sub-surface sediments (10∼40 cm), which indicated that the pollution is more serious in recent decades. PMID:25163567

  8. Bioavailability of polycyclic aromatic hydrocarbons from a historically contaminated sediment core

    SciTech Connect

    Harkey, G.A.; Van Hoof, P.L.; Landrum, P.F.

    1995-09-01

    To determine changes in bioavailability of selected polycyclic aromatic hydrocarbons (PAHs) with sediment aging, Lumbriculus variegatus were exposed for 4 weeks to sediment core sections taken from a contaminated lake. Core depths included surficial (0 to 4 cm), 4- to 8-, 12- to 16-, 28- to 32-, and 44- to 48-cm sections deposited for approximately 1899 to 1993, and were known to be historically contaminated with PAHs. Bioaccumulation was maximal at the 12- to 16-cm depth (circa 1967) where sediment PAH concentrations were greatest. Accumulation was generally below detection limits in the 0- to 4-cm depths, even though sediment concentrations of some compounds were comparable to those at the 12- to 16-cm depth where accumulation was great enough to generate accurate kinetics curves. Accumulation peaked at about 96 h, then declined over the remainder of the study for the lower-molecular-weight PAHs. For most higher-molecular-weight PAHs, accumulation peaked at about 2 weeks, then declined only slightly after 4 weeks. The differential bioavailability observed between surficial and at-depth core sections raises questions concerning the adequacy of results generated from toxicity and bioaccumulation tests routinely conducted surficial sediments.

  9. Historical PCDD inputs and their source implications from dated sediment cores in Queensland (Australia).

    PubMed

    Gaus, C; Brunskill, G J; Weber, R; Papke, O; Muller, J F

    2001-12-01

    Recent investigations have demonstrated the presence of an unidentified source of polychlorinated dibenzo-p-dioxins (PCDDs) in the coastal zone of Queensland (Australia). The present study provides new information on the possible PCDD sources and their temporal input to this environment. Two estuarine sediment cores were collected in northern Queensland for which radiochemical chronologies were established. Core sections from different depositional ages, up to three centuries, have been analyzed for 2,3,7,8-substituted PCDDs and polychlorinated dibenzofurans (PCDFs). Variations of PCDD concentrations in the sediment cores over several centuries of depositional history were relatively small, and elevated PCDD levels were still present in sediment slices from the early 17th century. PCDD/F isomer patterns and congener profiles in sediments deposited during the last 350 years were almost identical and correlated well to the characteristic profiles observed in surface sediments and soils from the entire Queensland coastline. Profiles were dominated by higher chlorinated PCDDs, in particular octachlorodibenzodioxin (OCDD), whereas PCDF concentrations were below or near the limit of detection. These results indicate the presence of a PCDD source prior to industrialization and production of commercial organochlorine products. Further, the present study demonstrates that PCDD input patterns have been similar along an extensive but localized area over at least several centuries, contributing relatively high concentrations of PCDDs to the coastal system of Queensland. PMID:11770761

  10. Thermal Properties of Bazhen fm. Sediments from Thermal Core Logging

    NASA Astrophysics Data System (ADS)

    Spasennykh, Mikhail; Popov, Evgeny; Popov, Yury; Chekhonin, Evgeny; Romushkevich, Raisa; Zagranovskaya, Dzhuliya; Belenkaya, Irina; Zhukov, Vladislav; Karpov, Igor; Saveliev, Egor; Gabova, Anastasia

    2016-04-01

    The Bazhen formation (B. fm.) is the hugest self-contained source-and-reservoir continuous petroleum system covering by more than 1 mln. km2 (West Siberia, Russia). High lithological differentiation in Bazhen deposits dominated by silicic shales and carbonates accompanied by extremely high total organic carbon values (of up to 35%), pyrite content and brittle mineralogical composition deteriorate standard thermal properties assessment for low permeable rocks. Reliable information of unconventional system thermal characteristics is the necessary part of works such as modelling of different processes in reservoir under thermal EOR for accessing their efficiency, developing and optimizing design of the oil recovery methods, interpretation of the well temperature logging data and for the basin petroleum modelling. A unique set of data including thermal conductivity, thermal diffusivity, volumetric heat capacity, thermal anisotropy for the B.fm. rocks was obtained from thermal core logging (high resolution continuous thermal profiling) on more than 4680 core samples (2000 of B.fm. samples are among) along seven wells for four oil fields. Some systematic peculiarities of the relation between thermal properties of the B.fm. rocks and their mineralogical composition, structural and texture properties were obtained. The high-resolution data are processed jointly with the standard petrophysical logging that allowed us to provide better separation of the formation. The research work was done with financial support of the Russian Ministry of Education and Science (unique identification number RFMEFI58114X0008).

  11. Correlations Between Physical and Hydraulic Properties and Uranium Desorption in Contaminated, Intact Sediment Cores

    NASA Astrophysics Data System (ADS)

    Rockhold, M. L.; Oostrom, M.; Wietsma, T. W.; Zachara, J. M.

    2010-12-01

    An unlined disposal pond in the 300 Area of the Hanford Site received uranium-bearing liquid effluents associated with nuclear reactor fuel rod processing from 1943 to 1975. Contaminated sediments from the base and sides of the former pond were excavated and removed from the site in the early 1990s, but a uranium plume has persisted in the groundwater at concentrations exceeding the drinking water standard. The former process pond is located adjacent to the Columbia River and seasonal fluctuations in the river stage and water table provide a mechanism for resupplying residual uranium from the vadose zone to the groundwater when the lower vadose zone is periodically rewetted. Intact cores were collected from the site for measurements of physical, hydraulic, and geochemical properties. Multistep outflow experiments were also performed on the intact cores to determine permeability-saturation-capillary pressure relations. Pore water displaced during these experiments for two of the vadose zone cores was also analyzed for uranium. For a core containing finer-textured sediment classified as muddy sandy gravel, and a core containing coarser-textured sediment classified as gravel, the relative aqueous uranium concentrations increased by factors of 8.3 and 1.5, respectively, as the cores were desaturated and progressively smaller pore-size classes were drained. Aqueous concentrations of uranium in the extracted pore waters were up to 115 times higher than the current drinking water standard of 30 ppb. These results confirm that there is a continuing source of uranium in the vadose zone at the site, and are consistent with a hypothesis that the persistence of the groundwater uranium plume is also associated, in part, with rate-limited mass transfer from finer-textured sediments. The data from these and several other intact cores from the site are evaluated to explore relationships between physical and hydraulic properties and uranium desorption characteristics.

  12. Shallow stratigraphy of the Skagit River Delta, Washington, derived from sediment cores

    USGS Publications Warehouse

    Grossman, Eric E.; George, Douglas A.; Lam, Angela

    2011-01-01

    Sedimentologic analyses of 21 sediment cores, ranging from 0.4 to 9.6 m in length, reveal that the shallow geologic framework of the Skagit River Delta, western Washington, United States, has changed significantly since 1850. The cores collected from elevations of 3.94 to -2.41 m (relative to mean lower low water) along four cross-shore transects between the emergent marsh and delta front show relatively similar environmental changes across an area spanning ~75 km2. Offshore of the present North Fork Skagit River and South Fork Skagit River mouths where river discharge is focused by diked channels through the delta, the entire 5–7-km-wide tidal flats are covered with 1–2 m of cross-bedded medium-to-coarse sands. The bottoms of cores, collected in these areas are composed of mud. A sharp transition from mud to a cross-bedded sand unit indicates that the tidal flats changed abruptly from a calm environment to an energetic one. This is in stark contrast to the Martha's Bay tidal flats north of the Skagit Bay jetty that was completed in the 1940s to protect the newly constructed Swinomish Channel from flooding and sedimentation. North of the jetty, mud ranging from 1 to 2 m thick drapes a previously silt- and sand-rich tidal flat. The silty sand is a sediment facies that would be expected there where North Fork Skagit River sedimentation occurred prior to jetty emplacement. This report describes the compositional and textural properties of the sediment cores by using geophysical, photographic, x-radiography, and standard sediment grain-size and carbon-analytical methods. The findings help to characterize benthic habitat structure and sediment transport processes and the environmental changes that have occurred across the nearshore of the Skagit River Delta. The findings will be useful for quantifying changes to nearshore marine resources, including impacts resulting from diking, river-delta channelization, shoreline development, and natural variations in fluvial-sediment

  13. Sediment Coring of the Proglacial Lake Donguz-Orun (northern Caucasus, Russia)

    NASA Astrophysics Data System (ADS)

    Alexandrin, Mikhail; Solomina, Olga; Kalugin, Ivan; Darin, Andrey; Nesje, Atle

    2014-05-01

    So far, no high-resolution reconstructions of climate and glacier variations based on lake sediment properties are available in Caucasus Mountains. In other presently glaciated regions this approach is proved to be very useful for this purpose (e.g. Nesje et al., 2001, 2011; Bakke, 2005, Nesje, 2009) In this paper we report the first results of the sediment coring of Donguz-Orun Lake (N 43°13'26", E 42°29'35") situated in the upper reaches of Donguz-Orun-Kyol, a tributary of Baksan river in the Elbrus region of Northern Caucasus, a typical proglacial lake dammed by a lateral moraine deposited by the Donguz-Orun Glacier. It is a drainage lake with several inflowing glacial streams and effluent river Donguz-Orun. The surface area is around 105 000 m2 with a water volume of 465 000m3. The average water depth is around 4.5 m, with a maximum water depth of 14 m. The deepest part is found close to the moraine dam in the narrow northern part of the lake. This is normally consistent with this type of glacial lake systems. An intensive gravitational drift of the moraine material towards the lake is observed. These non-rounded moraine boulders constitute a significant part of the lakebed. Lacustrine sediments are present though. The coring campaign from Institute of Geography, Russian Academy of Sciences (August 2012) used a modified piston corer with a 110 mm-diameter plastic tube (Nesje, 1992) mounted on the inflatable catamaran to obtain lake sediments from Lake Donguz-Orun. A 28-cm long core was retrieved from a water depth of around 7 m. The sediments consist of regularly laminated, fine beige clay, with several interlayers of sand. The coring process appeared to be challenging due to the stiffness of clay, which led to extreme bending of the sediment layers in the basal part of the core. The original thickness of the sediments was obviously higher than observed in the core. In order to clarify the recent history of the Donguz-Orun glacier, we used lichenometry and

  14. Depositional history of polychlorinated biphenyls in a dated sediment core from the northwestern Arabian Gulf.

    PubMed

    Gevao, Bondi; Aba, Abdul Aziz; Al-Ghadban, Abdul Nabi; Uddin, Saif

    2012-05-01

    The vertical distribution of polychlorinated biphenyls (PCBs) was measured in a dated sediment core from the northwestern Arabian Gulf to reconstruct their depositional history. The downcore profile showed an increase in concentrations from depth to a subsurface maximum of approximately 1,500 pg g(-1) in approximately 1991, followed by an exponential decrease to the sediment-water interface. Current concentrations of ΣPCBs are similar to levels predating the episodic input of PCBs in sediments dated coincident with the 1991 Arabian Gulf war. The spike in ΣPCB concentrations during the war may be related to the destruction of PCB-laden transformers during the conflict. The 15-fold decrease in ΣPCB concentrations from the period of maximum flux to prewar levels suggests that the factors delivering PCBs to sediments at present are similar to those that that existed before the war-related inputs. PMID:22218707

  15. Immunoassay screening of sediment cores for polychlorinated biphenyls, Devil's Swamp Lake near Baton Rouge, Louisiana, 2004

    USGS Publications Warehouse

    Van Metre, Peter C.; Wilson, Jennifer T.

    2004-01-01

    Devil?s Swamp Lake near Baton Rouge, Louisiana, constructed by dredging in 1973 in Devil?s Swamp along the Mississippi River, is contaminated with polychlorinated biphenyls (PCBs). This study investigated the possible historical contribution of PCBs from a hazardous-chemical disposal facility by way of a wastewater drainage ditch that operated from 1971 to 1993. Six sediment cores from the lake and three bottom-material samples from the drainage ditch were collected on October 5, 2004, and analyzed for PCBs using an immunoassay screening method. The results were used to evaluate qualitatively the historical input record of PCBs to the lake. Deposition dates in three of the cores were estimated by assuming that penetration of the push corer was stopped by firmer, pre-lake materials that mark the 1973 subsurface level of dredging. Sixty-one samples from five of the six cores and three bottom-material samples from the drainage ditch were analyzed. PCBs were at higher concentrations in ditch bottom material (about 1.1 to 2.2 milligrams per kilogram) than in cores from sites near where the ditch enters the lake (about 0.1 to 1.0 milligrams per kilogram). The highest concentrations of PCBs (maximum about 15 milligrams per kilogram) were detected in lake-bottom sediment about 350 meters west of where the drainage ditch enters the lake. Detection rates and median PCB concentrations were higher in all of the dated core sediments deposited before about 1990 than after 1990.

  16. Marine permafrost detection using galvanic electrical resistivity methods

    SciTech Connect

    Corwin, R.F.

    1983-05-01

    Because of the high electrical resistivity contrast between ice-bonded sediments (permafrost) and the same sediments in an unfrozen state, galvanic (direct-current) electrical resistivity measurements are capable of determining the depth below the sea floor of marine permafrost layers. Unlike the seismic refraction method usually used for offshore permafrost surveying, resistivity measurements can determine the thickness as well as the depth of a permafrost layer. Also, the resistivity method is usable in acoustic anomaly areas where seismic data cannot be obtained and in shallow water where air gun sources are not effective. Marine resistivity measurements may be made through the sea ice in the winter or from a stationary or moving boat in the summer. The results of field trials conducted in the Prudhoe Bay area indicated that marine permafrost depths and thicknesses determined from resistivity measurements agreed well with those obtained from borehole data.

  17. Climatic fluctuations during the Holocene based on eastern Mediterranean continental shelf sediment cores

    NASA Astrophysics Data System (ADS)

    Mor-Federman, Tsofit; Bookman, Revital; Almogi-Labin, Ahuva; Herut, Barak

    2013-04-01

    Sediments deposited on the south eastern Mediterranean continental shelf are sensitive recorders of climatic and oceanographic variability affected by the north Atlantic and indirectly by monsoonal systems. In order to reconstruct the influence of these climatic systems two cores were taken off shore the southern and central Israeli coast at water depths of ~35 m. The sediments were characterized by majors and traces elements, and the sediment provenance was determined using 87Sr/86Sr ratios. Detrital input from the Nile and local environment was studied using grain size distribution and sedimentation rates. Water column productivity was inferred by TOC and δ13Corg. The cores, dated to 7,630 and 8,440 14C years BP, show two distinct sedimentation regimes. The early Holocene is characterized by high sedimentation rates (190-140 cm/ka) that decrease in the last 5,500 years (50-60 cm/ka) in both north and central cores. Coarse grain size is dominant in the early Holocene, with a decreasing trend in the northern core. This distribution is probably connected to eustatic sea level rise and recycling of coarse sediments from the flooded shallow Nile cone. In the late Holocene, as sea level stabilized, grain size is finer in the south; while to the north, cycles of ~1,500 years in coarse grain size characterize the period. Carbonate and organic carbon further present the change along the period. Decrease in carbonate content and increase in δ13Corg during the late Holocene indicate decrease in water column productivity. In contradiction, organic carbon is relatively high in the late Holocene. This is explained by the coarse sediment texture in the early Holocene leading to better oxidation of buried organic matter. Strontium isotopes show changes in sediment provenance. In the early Holocene high 87Sr/86Sr values of ~0.71 reflect a dominant signature of the White Nile and the Yellow Nile and in part the local streams. During the last 5,500 years lower values of ~0

  18. Climate Change and the Permafrost Carbon Feedback

    NASA Astrophysics Data System (ADS)

    Schuur, E. A. G.; McGuire, A. D.; Grosse, G.; Harden, J. W.; Hayes, D. J.; Hugelius, G.; Koven, C. D.; Kuhry, P.; Lawrence, D. M.; Natali, S.; Olefeldt, D.; Romanovsky, V. E.; Schaedel, C.; Schaefer, K. M.; Turetsky, M. R.; Treat, C. C.; Vonk, J.

    2014-12-01

    Approximately twice as much soil carbon is stored in the northern circumpolar permafrost zone than is currently contained in the atmosphere. Permafrost thaw, and the microbial decomposition of previously frozen organic carbon, is considered one of the most likely positive feedbacks from terrestrial ecosystems to the atmosphere in a warmer world. Yet, the rate and form of release is highly uncertain but crucial for predicting the strength and timing of this carbon cycle feedback this century and beyond. New insight brought together under a multi-year synthesis effort by the Permafrost Carbon Network helps constrain current understanding of the permafrost carbon feedback to climate, and provides a framework for newly developing research initiatives in this region. A newly enlarged soil carbon database continues to verify the widespread pattern of large quantities of carbon accumulated deep in permafrost soils. The known pool of permafrost carbon is now estimated to be 1330-1580 Pg C, with the potential for ~400 Pg C in deep permafrost sediments that remain largely unquantified. Laboratory incubations of these permafrost soils reveal that a significant fraction of this material can be mineralized by microbes and converted to CO2 and CH4 on time scales of years to decades, with decade-long average losses from aerobic incubations ranging from 6-34% of initial carbon. Variation in loss rates is depended on the carbon to nitrogen ratio, with higher values leading to more proportional loss. Model scenarios show potential C release from the permafrost zone ranging from 37-174 Pg C by 2100 under the current climate warming trajectory (RCP 8.5), with an average across models of 92±17 Pg C. Furthermore, thawing permafrost C is forecasted to impact global climate for centuries, with models, on average, estimating 59% of total C emissions after 2100. Taken together, greenhouse gas emissions from warming permafrost appear likely to occur at a magnitude similar to other

  19. [Character and sources identification of heavy metals contamination in sediment from the core sediment in Nanshan Lake, the Zhalong wetland].

    PubMed

    Su, Dan; Zang, Shu-Ying; Ye, Hua-Xiang; Sun, Li; Jia, Xiao-Dan; Li, Miao

    2012-06-01

    NSH2 sediment core from Nanshan Lake in the south of Zhalong wetland was studied, which was a typical lake for both empolder and aquaculture. The vertical distributions of heavy metals (Hg, Cd, Pb, Cr, As, Mn, Ag, Cu, Co, Fe and Zn) were investigated. The method of principal component analysis (PCA) was adopted to apportion the sources of heavy metals, and particle size, combined with 210Pb(ex) dating data were used to indicate characteristics, sources and polluted history of heavy metals in lake sediments since 1829. The results showed that: 1) the trend of changes in accumulation in the sedimentation was rather slow in the earlier stage, then was fast in the middle stage, and finally slowed down again in the later stage. The history of elements pollution is correspondent with the production of human activities and policies of soil and water conservation of Nanshan Lake; 2) the contents of all elements varied smoothly before 1957, and which fluctuated slightly from 1957 to 1985. The contents of Hg, Cd and Ag increased obviously since 1985. The sources of heavy metals determined were mainly from sewage, the loss of fertilizers, and combustion of fuel such as coal and gasoline; 3) natural sources of the degradation of organic matter, rock weathering and erosion, as well as the source of industrial emissions, with the contributions of 50.14%, 19.90% and 10.32%, respectively. High potential risk of heavy metals existed in NSH2 sediment core. Hence, enough attention must be paid to the pollution control of lakes. Therefore, this study can provide basic data for help wetland ecological environment improvement in Zhalong wetland. PMID:22946160

  20. Inorganic nitrogen transformations in the bed of the Shingobee River, Minnesota: Integrating hydrologic and biological processes using sediment perfusion cores

    USGS Publications Warehouse

    Sheibley, R.W.; Duff, J.H.; Jackman, A.P.; Triska, F.J.

    2003-01-01

    Inorganic N transformations were examined in streambed sediments from the Shingobee River using sediment perfusion cores. The experimental design simulated groundwater-stream water mixing within sediment cores, which provided a well-defined one-dimensional representation of in situ hydrologic conditions. Two distinct hydrologic and chemical settings were preserved in the sediment cores: the lowermost sediments, perfused with groundwater, remained anaerobic during the incubations, whereas the uppermost sediments, perfused with oxic water pumped from the overlying water column, simulated stream water penetration into the bed. The maintenance of oxic and anoxic zones formed a biologically active aerobic-anaerobic interface. Ammonium (NH4+) dissolved in groundwater was transported conservatively through the lower core zone but was removed as it mixed with aerated recycle water. Concurrently, a small quantity of nitrate (NO3-) equaling ???25% of the NH4+ loss was produced in the upper sediments. The NH4+ and NO3- profiles in the uppermost sediments resulted from coupled nitrification-denitrification, because assimilation and sorption were negligible. We hypothesize that anaerobic microsites within the aerated upper sediments supported denitrification. Rates of nitrification and denitrification in the perfusion cores ranged 42-209 and 53-160 mg N m-2 day-1, respectively. The use of modified perfusion cores permitted the identification and quantification of N transformations and verified process control by surface water exchange into the shallow hyporheic zone of the Shingobee River.

  1. A Direct-Push Sample-Freezing Drive Shoe for Collecting Sediment Cores with Intact Pore Fluid, Microbial, and Sediment Distributions

    NASA Astrophysics Data System (ADS)

    Bekins, B. A.; Trost, J.; Christy, T. M.; Mason, B.

    2015-12-01

    Abiotic and biological reactions in shallow groundwater and bottom sediments are central to understanding groundwater contaminant attenuation and biogeochemical cycles. The laminar flow regime in unconsolidated surficial aquifers creates narrow reaction zones. Studying these reaction zones requires fine-scale sampling of water together with adjacent sediment in a manner that preserves in situ redox conditions. Collecting representative samples of these narrow zones with traditional subsurface sampling equipment is challenging. For example, use of a basket type core catcher for saturated, non-cohesive sediments results in loss of fluid and sediments during retrieval. A sample-freezing drive shoe designed for a wire line piston core sampler allowed collection of cores with intact sediment, microbial, and pore fluid distributions and has been the basis for studies documenting centimeter-scale variations in aquifer microbial populations (Murphy and Herkelrath, 1996). However, this freezing drive shoe design is not compatible with modern-day direct push sampling rigs. A re-designed sample-freezing drive shoe compatible with a direct-push dual-tube coring system was developed and field-tested. The freezing drive shoe retained sediment and fluid distributions in saturated sediment core samples by freezing a 10 centimeter plug below the core sample with liquid CO­2. Core samples collected across the smear zone at a crude oil spill site near Bemidji, Minnesota, were successfully extracted without loss of fluid or sediment. Multiple core sections from different depths in the aquifer were retrieved from a single hole. This new design makes a highly effective sampling technology available on modern-day direct push sampling equipment to inform myriad questions about subsurface biogeochemistry processes. The re-design of the freezing drive shoe was supported by the USGS Innovation Center for Earth Sciences. References: Murphy, Fred, and W. N. Herkelrath. "A sample

  2. Analysis of the microbial community and geochemistry of a sediment core from Great Slave Lake, Canada.

    PubMed

    Lim, Jesmine; Woodward, John; Tulaczyk, Slawek; Christoffersen, Poul; Cummings, Stephen P

    2011-02-01

    Sediment cores taken from Great Slave Lake, Canada, were analysed to investigate their metabolically active microbial populations and geochemistry. The amplification of cDNA detected metabolically active bacterial (50 separate bands) and archaeal (49 separate band) communities. The bacterial communities were further resolved indicating active actinobacterial and γ-proteobacterial communities (36 and 43 individual bands respectively). Redundancy discriminate analysis and Monte Carlo permutation testing demonstrated the significant impact of geochemical parameters on microbial community structures. Geochemical analyses suggest that the upper 0.4 m represents soil weathering and erosion in the lake catchment. An increase in organic carbon in the lower core suggests either more primary productivity, indicating warmer climate conditions, associated with Holocene Climatic Optimum conditions pre 5,000 years BP or change from a reducing environment in the lower core to an oxidizing environment during more recent deposition. Drivers for bacterial, archaeal and actinobacterial community structures were sediment particle size, and its mineral composition. Depth also significantly affected γ- proteobacterial community structure. In contrast the organic carbon content did not significantly shape the microbial community structures within the sediment. This study indicates that geochemical parameters significantly contribute to microbial community structure in these sediments. PMID:20803250

  3. Analytical approaches for determination of bromine in sediment core samples by X-ray fluorescence spectrometry.

    PubMed

    Pashkova, Galina V; Aisueva, Tatyana S; Finkelshtein, Alexander L; Ivanov, Egor V; Shchetnikov, Alexander A

    2016-11-01

    Bromine has been recognized as a valuable indicator for paleoclimatic studies. Wavelength dispersive X-ray fluorescence (WDXRF) and total reflection X-ray fluorescence (TXRF) methods were applied to study the bromine distributions in lake sediment cores. Conventional WDXRF technique usually requires relatively large mass of a sediment sample and a set of calibration samples. Some analytical approaches were developed to apply WDXRF to small sediment core samples in the absence of adequate calibration samples with a known Br content. The mass of a sample to be analyzed was reduced up to 200-300mg and the internal standard method with correction using fundamental parameters was developed for Br quantification. TXRF technique based on the direct analysis of a solid suspension using 20mg of sediment sample by internal standard method was additionally tested. The accuracy of the WDXRF and TXRF techniques was assessed by the comparative analysis of reference materials of sediments, soil and biological samples. In general, good agreement was achieved between the reference values and the measured values. The detection limits of Br were 1mg/kg and 0.4mg/kg for WDXRF and TXRF respectively. The results of the Br determination obtained with different XRF techniques were comparable to each other and used for paleoclimatic reconstructions. PMID:27591627

  4. Profile of trace metals accumulation in core sediment from Seine river estuary (docks basin).

    PubMed

    Hamzeh, Mariam; Ouddane, Baghdad; El-Daye, Mirna; Halwani, Jalal

    2013-01-01

    The Seine is one of the most polluted rivers in Europe with respect to potentially harmful elements. It receives effluents from the upstream Paris urban and industrial area, and also local inputs from the heavily industrialized Rouen and Le Havre regions. The present study deals with this environmental topic and the concentrations of Cd, Ni, Pb, Hg, Zn and Cu were determined in sediment cores collected in the docks basin of Rouen harbour in 2008. The intensity of metal pollution during recent decades was evaluated using an enrichment factor (EF) and a geoaccumulation index (Igeo). The results of vertical distribution showed that the metal pollution in the past is much higher than in the surface sediment. Mercury was found to be the heaviest pollutant (with Igeo and EF exceeding 4 and 20, respectively), and Cd and Pb were the second most important pollutants. A slight contamination in Ni was observed with very low Igeo values. To estimate the sediment toxicity, simultaneously extracted metals/acid volatile sulfides ratio (SEM/AVS) was calculated. Low values of the toxicity index SEM/AVS were observed in the core sediments indicating the inexistence of metal potential toxicity. Also the concentrations of these trace metals were lower than the probable effect concentration values reported as consensus-based sediment quality guidelines for fresh water ecosystems. PMID:24191442

  5. [Study on trace elements of lake sediments by ICP-AES and XRF core scanning].

    PubMed

    Cheng, Ai-Ying; Yu, Jun-Qing; Gao, Chun-Liang; Zhang, Li-Sha; He, Xian-Hu

    2013-07-01

    It is the first time to study sediment of Toson lake in Qaidam Basin. Trace elements including Cd, Cr, Cu, Zn and Pb in lake sediment were measured by ICP-AES method, studied and optimized from different resolution methods respectively, and finally determined a optimum pretreatment system for sediment of Toson lake, namely, HCl-HNO3-HF-HClO4-H2O2 system in the proportions of 5 : 5 : 5 : 1 : 1 was determined. At the same time, the data measured by XRF core scanning were compared, the use of moisture content correction method was analyzed, and the influence of the moisture content on the scanning method was discussed. The results showed that, compared to the background value, the contents of Cd and Zn were a little higher, the content of Cr, Cu and Pb was within the background value limits. XRF core scanning was controlled by sediment elements as well as water content in sediment to some extent. The results by the two methods showed a significant positive correlation, with the correlation coefficient up to 0.673-0.925, and they have a great comparability. PMID:24059207

  6. Dispersion of the Geomagnetic Field Caused by Secular Variation: Constraints From Sediment Cores From Around Antarctica

    NASA Astrophysics Data System (ADS)

    Acton, G.; Jovane, L.; Verosub, K. L.; Sagnotti, L.; Ohneiser, C.; Strada, E.; Florindo, F.; Wilson, G. S.

    2010-12-01

    The angular dispersion of the virtual geomagnetic pole (VGP) measured over time and at many sites around the globe provides a measure of spatial variability in geodynamo processes. For example, longitudinal and latitudinal variations in dispersion may imply lateral differences in the boundary conditions at the core-mantle interface. Latitudinal variations in dispersion may also provide constraints on the size of dipole wobble and zonal non-dipole components. Furthermore, changes in dispersion across high latitudes may be indicative of changes in outer core flow regimes across the tangent cylinder. The spatial variation of dispersion, particularly the latitudinal variation, thus has the potential to be a powerful constraint on geodynamo models. Currently, estimates of the latitudinal variation in dispersion are based on volcanic data sets that give ambiguous results, with some studies finding an increase in dispersion with latitude and others finding virtually no change with latitude. The ambiguity arises mainly from the sparseness of data from high latitudes and from the difficulty in dealing with excursional VGPs in volcanic data sets. To improve the dispersion estimates at high latitudes, we use paleomagnetic data obtained from sedimentary ocean drill cores from several sites from around Antarctica, including ODP Leg 178 Sites 1095, 1096, and 1098 cored off the Antarctic Peninsula, and ANDRILL Site AND-2A and Eltanin Core 27-21 from the Ross Sea. Unlike volcanic units, sedimentary sections can provide continuous paleomagnetic records that capture both short and long term geomagnetic field variability. This allows us to examine not only the size of dispersion but changes in dispersion that occur over time. Such records also make it possible to investigate the amount of time it takes to average paleosecular variation and to use that information to estimate the duration of sedimentation at other sites. As with volcanics, a variety of issues, including sedimentation

  7. Paleomagnetic chronology of Arctic Ocean sediment cores; reversals and excursions the conundrum

    NASA Astrophysics Data System (ADS)

    Løvlie, R.; Jakobsson, M.; Backman, J.

    2003-04-01

    Chronologies of Arctic Ocean sediment cores are mainly based on interpretation of paleomagnetic inclination records. The first paleomagnetic chronology assigned zones with negative inclinations to polarity reversals (Steuerwald et al, 1968) because geomagnetic excursions at that time were a novel observation and had only been reported from lavas. Arctic Ocean sedimentation rates were thus established to be in the mm/ka-range. A general recognition of excursions as real features of the geomagnetic field emerged more than three decades later, and presently there is still no consensus regarding the number (or name), duration and age of global synchronous excursions within the Brunhes Chron. Assigning inclination records to polarity reversals or excursions is an ambiguous exercise without independent age information. Based on independently derived time frames, 11 negative inclination intervals in core 96/12-1pc from the Lomonosov Ridge were assigned to reported excursions resulting in cm/ka deposition rates (Jakobsson et al, 2000). However, the detail of the "excursional stratigraphy" in this core is problematic. The absence of two (three?) excursions in the upper 2 m of core (base MIS5) was tentatively suggested to reflect pDRM-erasing in this sandy part of the core, while the short extent of the inferred pre-Brunhes Matyuama Chron remains unaccounted for. We have recently retrieved a relative paleointensity record from a parallel core (96/B6-1pc) for alternative dating control and assessment of stratigraphic completeness and uniformity of deposition. This study indicated the presence of a hiatus of the order of 200 ka (Løvlie et al 2002). We present a paleointensity record from core 96/12-1pc and will address identification of depositional hiatuses and their significance in understanding the paleomagnetic record in Arctic Ocean cores. Steuerwald B.A., Clark D.L. and Andrew J.A., 1968. Magnetic stratigraphy and faunal patterns in Arctic Ocean sediments. Earth and

  8. Chlorinated hydrocarbon pesticides and polychlorinated biphenyls in sediment cores from San Francisco Bay

    USGS Publications Warehouse

    Venkatesan, M.I.; De Leon, R. P.; VanGeen, A.; Luoma, S.N.

    1999-01-01

    Sediment cores of known chronology from Richardson and San Pablo Bays in San Francisco Bay, CA, were analyzed for a suite of chlorinated hydrocarbon pesticides and polychlorinated biphenyls to reconstruct a historic record of inputs. Total DDTs (DDT = 2,4'- and 4,4'-dichlorodiphenyltrichloroethane and the metabolites, 2,4'- and 4,4'-DDE, -DDD) range in concentration from 4-21 ng/g and constitute a major fraction (> 84%) of the total pesticides in the top 70 cm of Richardson Bay sediment. A subsurface maximum corresponds to a peak deposition date of 1969-1974. The first measurable DDT levels are found in sediment deposited in the late 1930's. The higher DDT inventory in the San Pablo relative to the Richardson Bay core probably reflects the greater proximity of San Pablo Bay to agricultural activities in the watershed of the Sacramento and San Joaquin rivers. Total polychlorinated biphenyls (PCBs) occur at comparable levels in the two Bays (< 1-34 ng/g). PCBs are first detected in sediment deposited during the 1930's in Richardson Bay, about a decade earlier than the onset of detectable levels of DDTs. PCB inventories in San Pablo Bay are about a factor of four higher in the last four decades than in Richardson Bay, suggesting a distribution of inputs not as strongly weighed towards the upper reaches of the estuary as DDTs. The shallower subsurface maximum in PCBs compared to DDT in the San Pablo Bay core is consistent with the imposition of drastic source control measures four these constituents in 1970 and 1977 respectively. The observed decline in DDT and PCB levels towards the surface of both cores is consistent with a dramatic drop in the input of these pollutants once the effect of sediment resuspension and mixing is taken into account.

  9. Amino acid epimerization implies rapid sedimentation rates in Arctic Ocean cores

    USGS Publications Warehouse

    Sejrup, H.P.; Miller, G.H.; Brigham-Grette, J.; Lovlie, R.; Hopkins, D.

    1984-01-01

    The palaeooceanography of the Arctic Ocean is less well known than any other ocean basin, due to difficulties in obtaining cores and in providing a secure chronological framework for those cores that have been raised. Most recent investigators have suggested that low sedimentation rates (0.05-0.1 cm kyr-1) have characterized the deep basins over the past 5 Myr (refs 1,2) despite the glacial-marine character of the sediment and proximity to major centres of shelf glaciation. These calculations have been primarily based on the down-core pattern in the inclination of magnetic minerals, supported by uranium-series, 14C and micropalaeontological evidence. Here we analyse amino acid diagnesis in foraminifera from two gravity cores raised from the floor of the Arctic Ocean, our results suggest that these cores span <200 kyr., conflicting with the earlier estimate of 3 Myr based on palaeomagnetic data. The chronology of other Arctic Ocean cores and previous palaeoenvironmental interpretations need re-evaluation. ?? 1984 Nature Publishing Group.

  10. Geochemical studies of backfill aggregates, lake sediment cores and the Hueco Bolson Aquifer

    NASA Astrophysics Data System (ADS)

    Thapalia, Anita

    This dissertation comprises of three different researches that focuses on the application of geochemistry from aggregates, lake sediment cores and Hueco Bolson Aquifer. Each study is independent and presented in the publication format. The first chapter is already published and the second chapter is in revision phase. Overall, three studies measure the large scale (field) as well as bench scale (lab) water-rock interactions influenced by the climatic and anthropogenic factors spans from the field of environmental geology to civil engineering. The first chapter of this dissertation addresses the chemical evaluation of coarse aggregates from six different quarries in Texas. The goal of this work is to find out the best geochemical methods for assessing the corrosion potential of coarse aggregates prior to their use in mechanically stabilized earth walls. Electrochemical parameters help to define the corrosion potential of aggregates following two different leaching protocols. Testing the coarse and fine aggregates demonstrate the chemical difference due to size-related kinetic leaching effects. Field fines also show different chemistry than the bulk rock indicating the weathering impact on carbonate rocks. The second chapter investigates zinc (Zn) isotopic signatures from eight lake sediment cores collected both from pristine lakes and those impacted by urban anthropogenic contamination. Zinc from the natural weathering of rocks and anthropogenic atmospheric pollutants are transported to these lakes and the signatures are recorded in the sediments. Isotopic analysis of core samples provides the signature of anthropogenic contamination sources. Dated sediment core and isotopic analysis can identify Zn inputs that are correlated to the landuse and population change of the watersheds. Comparison of isotopic data from both pristine and urban lake sediment core also serves as an analog in other lake sediment cores in the world. The third chapter studies on Hueco Bolson

  11. Historical trends of PBDEs and HBCDs in sediment cores from Sydney estuary, Australia.

    PubMed

    Drage, D; Mueller, J F; Birch, G; Eaglesham, G; Hearn, L K; Harrad, S

    2015-04-15

    This paper presents the first historical data on the occurrence of polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCDs) in estuarine sediment from Australia. Sediment cores and surficial sediment samples were collected from four locations within Sydney estuary, Australia. Large increases in concentrations were observed for all compounds between 1980 and 2014, especially for BDE-209 (representative usage of Deca-BDE commercial mixture), which was found in surficial sediment at an average concentration of 42 ng/g dry wt (21-65 ng/g dry wt). PBDE congeners representative of both the Penta- and Octa-BDE commercial mixtures (∑6PBDEs) were also found in their highest concentrations in surficial sediments (average: 1.3 ng/g dry wt; range: 0.65-2.5 ng/g dry wt). PBDE concentrations in surficial sediments were relatively high when compared with those presented in the available literature. This suggests that their input into the Sydney estuary has not decreased since their bans almost a decade earlier. After a sharp increase in the 1990s, HBCD concentrations peaked at an average of 3.5 ng/g dry wt (1.8-5.3 ng/g dry wt) in surficial samples. With global legislation on HBCDs allowing its usage for the next 10 years, it is expected that its input into the estuary is likely to continue. PMID:25617997

  12. Rare earth element compositions of core sediments from the shelf of the South Sea, Korea: Their controls and origins

    NASA Astrophysics Data System (ADS)

    Jung, Hoi-Soo; Lim, Dhongil; Choi, Jin-Yong; Yoo, Hae-Soo; Rho, Kyung-Chan; Lee, Hyun-Bok

    2012-10-01

    Rare earth elements (REEs) of bulk sediments and heavy mineral samples of core sediments from the South Sea shelf, Korea, were analyzed to determine the constraints on REE concentrations and distribution patterns as well as to investigate their potential applicability for discriminating sediment provenance. Bulk sediment REEs showed large variation in concentrations and distribution patterns primarily due to grain size and carbonate dilution effects, as well as due to an abundance of heavy minerals. In the fine sandy sediments (cores EZ02-15 and 19), in particular, heavy minerals (primarily monazite and titanite/sphene) largely influenced REE compositions. Upper continental crust-normalized REE patterns of these sand-dominated sediments are characterized by enriched light REEs (LREEs), because of inclusion of heavy minerals with very high concentrations in LREEs. Notably, such a strong LREE enrichment is also observed in Korean river sediments. So, a great care must be taken when using the REE concentrations and distribution patterns of sandy and coarse silty shelf sediments as a proxy for discriminating sediment provenance. In the fine-grained muddy sediments with low heavy mineral abundance, in contrast, REE fractionation ratios and their UCC-normalized patterns seem to be reliable proxies for assessing sediment provenance. The resultant sediment origin suggested a long lateral transportation of some fine-grained Chinese river sediments (probably the Changjiang River) to the South Sea of Korea across the shelf of the northern East China Sea.

  13. Relationship between microbial diversity and chemical contamination along a 50-year-old sediment core

    NASA Astrophysics Data System (ADS)

    Berthe, T.; Petit, F.; Boust, D.; Lesueur, P.; Roose-Amsaleg, C.; Cécillon, S.; Kaci-Benaicha, A.

    2013-12-01

    The purpose of this study was to evaluate the potential use of sediment microbial diversity (community structure) as an indicator of the impact of anthropogenic activities within an estuarine ecosystem. The diversity of microbial communities was investigated along a 5-m-long sediment core collected in an anthropized European estuary (Seine, France), giving an evolution of trace metal, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) concentrations over the last 50 years. An increase of trace metal and PCB concentrations are observed with depth, with an enrichment of these contaminants in the 1970s. The concentration profiles of light, intermediate and heavy PAHs showed distinct peaks, but the highest total PAH concentration was also detected in the sediment from the 1970s. We first investigated the bacterial community resistant to cobalt, zinc and cadmium by analyzing the diversity of the czcA gene encoding an RND efflux pump (Heavy Metal Efflux-RND) in 5-year and 33-year-old sediment samples displaying contrasted concentrations in these trace metals. The diversity of the czcA gene was reduced in the 33-year-old and more contaminated sediments suggesting a selection of resistant bacterial species. A molecular fingerprinting method (DGGE) was used to study the evolution of total microbial (Bacteria and Archaea) community structures for samples selected along the sediment core. A correlation is observed between the bacterial community structures, the sediment age, the trace metal and PAH concentrations. The metabolically active and total microbial communities were further characterized by a microarray approach (Phylochips) in sediment samples selected according to the DGGE results. Bacterial diversity was found dominated by Proteobacteria, Actinobacteria, and Firmicutes in all analyzed samples. Diversity of phylotypes corresponds to changes in PAH and trace metal concentrations in sediment, suggesting that chemical contaminants have

  14. The Record of Geomagnetic Excursions from a ~150 m Sediment Core: Clear Lake, Northern California

    NASA Astrophysics Data System (ADS)

    Levin, E.; Byrne, R.; Looy, C. V.; Wahl, D.; Noren, A. J.; Verosub, K. L.

    2015-12-01

    We are studying the paleomagnetic properties of a new ~150 meter drill core from Clear Lake, CA. Step-wise demagnetization of the natural remanent magnetism (NRM) yields stable directions after 20 mT, implying that the sediments are reliable recorders of geomagnetic field behavior. Several intervals of low relative paleointensity (RPI) from the core appear to be correlated with known geomagnetic excursions. At about 46 m depth, and ~33 ka according to an age model based on radiocarbon dates obtained from pollen and the Olema ash bed, a low RPI zone seems to agree with the age and duration of the Mono Lake Excursion, previously identified between 32 and 35 ka. Slightly lower in the core, at about 50 m depth and ~40 ka, noticeably low RPI values seem to be coeval with the Laschamp excursion, which has been dated at ~41 ka. A volcanic ash near the bottom of the core (141 mblf) is near the same depth as an ash identified in 1988 by Andrei Sarna-Wojcicki and others as the Loleta ash bed in a previous Clear Lake core. If the basal ash in the new core is indeed the, Loleta ash bed, then the core may date back to about 270-300 ka. Depending on the age of the lowest ash, a sequence of low RPI intervals could correlate with the Blake (120 ka), Iceland Basin (188 ka), Jamaica/Pringle Falls (211 ka), and CR0 (260 ka) excursions. Correlation of the low RPI intervals to these geomagnetic excursions will help in the development of a higher resolution chronostratigraphy for the core, resolve a long-standing controversy about a possible hiatus in the Clear Lake record, and provide information about climatically-driven changes in sedimentation.

  15. Sediment core fossils in ancient Lake Ohrid: testing for faunal change since the Last Interglacial

    NASA Astrophysics Data System (ADS)

    Albrecht, C.; Vogel, H.; Hauffe, T.; Wilke, T.

    2010-11-01

    Ancient Lake Ohrid is probably of early Pleistocene or Pliocene origin and amongst the few lakes in the world harbouring an outstanding degree of endemic biodiversity. Although there is a long history of evolutionary research in Lake Ohrid, particularly on molluscs, a mollusc fossil record has been missing up to date. For the first time, gastropod and bivalve fossils are reported from the basal, calcareous part of a 2.6 m long sediment succession (core Co1200) from the north-eastern part of Lake Ohrid. Electron spin resonance (ESR) dating of mollusc shells from the same stratigraphic level yielded an age of 130 ± 28 ka. Lithofacies III sediments, i.e. a stratigraphic subdivision comprising the basal succession of core Co1200 between 181.5-263 cm, appeared solid, greyish-white, and consisted almost entirely of silt-sized endogenic calcite (CaCO3>70%) and intact and broken mollusc shells. Here we compare the faunal composition of the thanatocoenosis with recent mollusc associations in Lake Ohrid. A total of 13 mollusc species (9 gastropod and 4 bivalve species) could be identified within Lithofacies III sediments. The value of sediment core fossils for reconstructing palaeoenvironmental settings was evaluated and the agreement between sediment and palaeontological proxies was tested. The study also aims at investigating major faunal changes since the Last Interglacial and searching for signs of extinction events. The combined findings of the ecological study and the sediment characteristics suggest deposition in a shallow water environment during the Last Interglacial. The fossil fauna exclusively included species also found in the present fauna, i.e. no extinction events are evident for this site since the Last Interglacial. The thanatocoenosis showed the highest similarity with recent Intermediate Layer (5-25 m water depth) mollusc assemblages. The demonstrated existence of a mollusc fossil record in Lake Ohrid sediment cores also has great significance for future

  16. Antarctic Sediment and Rock Cores: Decoding the Geologic History of Antarctica

    NASA Astrophysics Data System (ADS)

    Huffman, L.; Rack, F. R.

    2007-12-01

    Sediment and rock cores are like a history book waiting to be read, and ANDRILL (ANtarctic geologic DRILLing) scientists have developed techniques for decoding the messages locked in the stratigraphic record. Educators accompany the multinational, interdisciplinary science team to Antarctica through their participation in a program known as ARISE (ANDRILL Research Immersion for Science Educators). Capitalizing on the excitement and interest surrounding polar research during the IPY (International Polar Year), the ARISE team collaborates with scientists to develop activities and lessons to transfer the technology of sediment and rock core drilling, and the science involved in decoding the information about past climates stored within them, to non-technical audiences. This talk will present information about a successful model of education and outreach that includes examples of geoscience activities developed for grades 5-12, and discuss methods of teacher training through immersion in scientific research.

  17. Nondestructive X-Ray Computed Tomography Analysis of Sediment Cores: A Case Study from the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Oti, E.; Polyak, L. V.; Cook, A.; Dipre, G.

    2014-12-01

    Investigation of marine sediment records can help elucidate recent changes in the Arctic Ocean circulation and sea ice conditions. We examine sediment cores from the western Arctic Ocean, representing Late to Early Quaternary age (potentially up to 1 Ma). Previous studies of Arctic sediment cores indicate that interglacial/interstadial periods with relatively high sea levels and reduced ice cover are characterized by vigorous bioturbation, while glacial intervals have little to no bioturbation. Traditional methods for studying bioturbation require physical dissection of the cores, effectively destroying them. To treat this limitation, we evaluate archival sections of the cores using an X-ray Computed Tomography (XCT) scanner, which noninvasively images the sediment cores in three dimensions. The scanner produces density sensitive images suitable for quantitative analysis and for identification of bioturbation based on size, shape, and orientation. We use image processing software to isolate burrows from surrounding sediment, reconstruct them three-dimensionally, and then calculate their surface areas, volumes, and densities. Preliminary analysis of a core extending to the early Quaternary shows that bioturbation ranges from 0 to approximately 20% of the core's volume. In future research, we will quantitatively define the relationship between bioturbation activity and glacial regimes. XCT examination of bioturbation and other sedimentary features has the potential to shed light on paleoceanographic conditions such as sedimentation patterns and food flux. XCT is an alternative, underexplored investigation method that bears implications not only for illustrating paleoclimate variations but also for preserving cores for future, more advanced technologies.

  18. Microscale Deformation of (Post) Perovskite-Dominated Sediment in the Uppermost Outer Core

    NASA Astrophysics Data System (ADS)

    Petford, N.; Yuen, D.; Rushmer, T.

    2005-05-01

    Seismic and nutational data hint strongly at a layer comprised of silicate sediments several km thick confined to the top of the liquid outer core, directly beneath the core-mantle boundary and equating with observed ultra low velocity zones (ULVZs)1. Its origin is thought to be due to high pressure chemical reactions that take place between Fe-rich silicate in the lower mantle and liquid iron in the underlying outer core. We speculate that the Fe silicate is dominated by the newly discovered post-perovskite phase (ppv). Initial numerical investigations show that viscous compaction in the sediment layer will act to expel interstitial core metal liquid and reduce an initial 50% porosity to a residual value of < 0.1 on timescales of the order 80-100 Ma1. Using a modified form of Biot's equations2, we show that deformation of a poro-viscoelastic sediment pile will respond by drawing up Fe liquid metal into the layer from below at a rate proportional to the shear stress rate. Instead of a static, isolated residual porosity distribution in the most compacted upper regions of sediment, we envisage a more dynamic environment where fresh core liquid is emplaced periodically into the slowly accumulating pile. Estimates of the potential magnitude of the instability, including pressure changes, local fluid flow rates and timescales compare favourably with fluid motions in the convecting outer core. A key difference between both models, which are in fact complementary, relates to the rheology and microscale deformation behaviour of the assumed ppv-dominated sediment. The small grain size of the suspension is close to the limit of dilatant behaviour (c. 10-6 m) in granular materials. More information is required on the chemical and physical behaviour of the post-perovskite phase at lengthscales characteristic of geophysically interesting colloidal suspensions under high P-T conditions. 1.Buffet, BA., Garnero, EJ & Jeanloz, R. 2000. Science, 290, 1338-1342. 2.Koenders, MA

  19. Effects of Local Farming and Deforestation on Sediment Discharge Inferred From Sediment Accumulation Rates and Patterns in Lake Core Records From Coastal Lake Tanganyika, East Africa

    NASA Astrophysics Data System (ADS)

    Strickler, M. L.; Lezzar, K. E.; Soreghan, M.; Cohen, A. S.; Swarzenski, P. W.; Berke, M.; McHeni, M.; Gunderson, K.; Allen, K.; Palke, A.; Modesta, M.; Nkotagu, H.

    2006-12-01

    Lake Tanganyika is the oldest and largest of the East African rift lakes and vital to the economy of the surrounding villages and countries. Deforestation around the lake causes many negative effects from an increased sediment flux and has changed dramatically as a function of population. Increases in inorganic sediment flux from deforested watersheds and an associated decrease in organic sediment flux may negatively impact the viability of littoral habitats in the lake. This study examines the interrelationship between deforestation on streams that feed into Lake Tanganyika and sedimentation offshore. We mapped stream morphology of two distinct streams: Kalande (Gombe Stream National Park), and Ngelwa (deforested). An offshore core was collected from the lake bottom just offshore of the deforested Ngelwa stream at a water depth of 106m and dated using 14C and 210Pb geochronologic methods. In addition, multiple laboratory analyses were performed on the core and within the streams to help constrain sedimentation and deforestation effects. Three distinct units within the core correlate to reflect changes in sedimentation (higher rates as deforestation continues) in addition to a shift from dry, low lake level conditions to wet, high lake levels as evidenced by shifts in core lithologies, diatom taxonomy and content, magnetic susceptibility, and clastic particle size. Streambed and suspended sediment analyses reflect high levels of erosion in deforested watersheds coupled with changes in dissolved nutrients in the water (silica, orthophosphate), which may suggest an overall diminished level of ecosystem function in deforested and heavily farmed watersheds.

  20. Magnetostratigraphy of a long Quaternary sediment core in the South Yellow Sea

    NASA Astrophysics Data System (ADS)

    Liu, Jianxing; Liu, Qingsong; Zhang, Xunhua; Liu, Jian; Wu, Zhiqiang; Mei, Xi; Shi, Xuefa; Zhao, Quanhong

    2016-07-01

    Continental shelves serve as a bridge between the continent and ocean and sediments in this region are sensitive to land-sea interaction, sea-level variation and local subsidence. In this study, we present a comprehensive magnetic study of the longest sediment core (CSDP-1, 300.1 m) recovered from the South Yellow Sea. The major magnetic minerals in the studied sediments are magnetite, hematite and greigite. Greigite records a chemical remanent magnetization, which can be removed effectively by thermal demagnetization. The magnetostratigraphy defined in this study contains the Matuyama-Brunhes boundary (M/B, 781 ka) at ∼73.68 m, which is consistent with results from adjacent cores. The base of the Quaternary (∼2.6 Ma) in the Yellow Sea is recovered for the first time at a depth of 227.16 m. The basal age of the core is estimated to be ∼3.50 Ma. It indicates that the first transgression of the Yellow Sea occurred no later than ∼1.7 Ma. Succeeding large amplitude regressions occurred in some cold periods such as during MIS 20, MIS 18, and MIS 10. Our results provide the first chronology that brackets the entire Quaternary and we reconstruct the sedimentary evolution of the Yellow Sea with robust age constraints, which provides an important framework for further paleoenvironmental and tectonic studies.

  1. Sediment Core Sectioning and Extraction of Pore Waters under Anoxic Conditions.

    PubMed

    Keimowitz, Alison R; Zheng, Yan; Lee, Ming-Kuo; Natter, Michael; Keevan, Jeffrey

    2016-01-01

    We demonstrate a method for sectioning sediment cores and extracting pore waters while maintaining oxygen-free conditions. A simple, inexpensive system is built and can be transported to a temporary work space close to field sampling site(s) to facilitate rapid analysis. Cores are extruded into a portable glove bag, where they are sectioned and each 1-3 cm thick section (depending on core diameter) is sealed into 50 ml centrifuge tubes. Pore waters are separated with centrifugation outside of the glove bag and then returned to the glove bag for separation from the sediment. These extracted pore water samples can be analyzed immediately. Immediate analyses of redox sensitive species, such as sulfide, iron speciation, and arsenic speciation indicate that oxidation of pore waters is minimal; some samples show approximately 100% of the reduced species, e.g. 100% Fe(II) with no detectable Fe(III). Both sediment and pore water samples can be preserved to maintain chemical species for further analysis upon return to the laboratory. PMID:27023267

  2. Relationship between catchment events (earthquake and heavy rain) and sediment core analysis result in Taiwan.

    NASA Astrophysics Data System (ADS)

    Chen, Hsin-Ying; Lin, Jiun-Chuan

    2015-04-01

    Lake sediments contains material from the catchment. In those sediments, there are some features which can indicate characteristic or status of the catchment. These features were formed by different mechanisms, including some events like earthquakes or heavy rain, which are very common in Taiwan. By analyzing and discussing features of sediments there is a chance to identify historical events and rebuild catchment history. In this study, we compare features of sediment core ( including density, mineral grain size, whole grain size, and biogenic silica content) and earthquake, precipitation records. Sediment cores are collected from Emerald peak lake (24.514980, 121.605844; 77.5, 77.2, 64cm depth), Liyutan lake (23.959878, 120.996585; 43.2, 78.1 cm depth), Sun Moon Lake (23.847043, 120.909869; 181 cm depth), and Dongyuan lake (22.205742, 120.854984; 45.1, 44.2cm depth) in 2014. We assume that there are regular material and organic output in catchments. And rain will provide impetus to move material into lakes. The greater the rain is the larger the material can move. So, if there is a heavy rainfall event, grain size of lake sediment may increase. However, when earthquakes happen, it will produce more material which have lower organic composition than ordinary. So we suggest that after earthquakes there will be more material stored in catchment than often. And rainfall event provides power to move material into lakes, cause more sediment and mineral content higher than usual. Comparing with earthquake record(from 1949, by USGS) and precipitation record(from1940, by Central Weather Bureau,Taiwan), there were few earthquakes which happened near lakes and scale were more than 7 ML. There were 28 rainfall events near Emerald peak lake; 32 near Liyutan lake and Sun Moon Lake; 58 near Dongyuan lake ( rainfall event: >250 mm/day ). In sediment analytical results, ratio of whole and mineral grain size indeed have similar trends with earthquake record. However, rainfall

  3. Is it possible to use "twin cores" as a unique sedimentary record? An experimental design based on sediment color

    NASA Astrophysics Data System (ADS)

    Veiga-Pires, C.; Mestre, N. C.

    2009-01-01

    Sedimentary cores are widely used for studying Quaternary records. However, the amount of sediment that is available is proportional to the diameter of the core, which is rarely bigger than 15 cm. One way to obtain more sediment is to use two cores retrieved from almost the same location and use them as if they represent a unique sedimentary record. In the present work, an experimental design has been applied to verify if "twin cores" from an estuary can be considered as representing the same sedimentary record with twice the amount of sediment to study. Because sediment can be characterized based on its color, the variables used as replicates in the experimental design are the three Lab CIE colors acquired with a X-Rite Colortron spectrophotometer. Sediment cores were retrieved from the upper saltmarsh of Gilão River's estuary, southern Portugal. Twin cores, with in between distances of 50 cm, 100 cm and 200 cm, from two different sites were analysed. Results from a nested ANOVA show that even for the closest twin cores (50 cm apart) there is at least one color variable that shows significant variations between the profiles of both cores. These results clearly show that "twin cores" cannot be used as a unique sedimentary record without any previous testing, at least in such transitional regions.

  4. Ground Ice in the New Crrel Permafrost Tunnel

    NASA Astrophysics Data System (ADS)

    Kanevskiy, M. Z.; Shur, Y.; Beget, J. E.; Bigelow, N. H.; Bjella, K.; Cysewski, M.; Jorgenson, T.; Sturm, M.

    2014-12-01

    Permafrost in the new CRREL tunnel was described based on mapping of massive-ice bodies and other permafrost features exposed in the tunnel as well as studying frozen sediment cores from numerous boreholes drilled around and above the tunnel and from its floor. The mapping covers 48-m long and 4-m high walls and the ceiling of the tunnel. A general cryostratigraphic map of the entire tunnel and more detailed maps of several parts of the tunnel were compiled, and ground-ice content was estimated. The tunnel presents features typical of ice-rich syngenetic permafrost (yedoma): ice wedges with a vertical extent of more than 10 m, the prevalence of micro-cryostructures, and the occurrence of large amount of almost undecomposed organic matter. The isotope composition of the Late Pleistocene ice wedges ranges between -28.7‰ and -25.5‰ for δ18O (mean value -27.3‰, n=18), while for the Holocene wedges the range is between -26.5‰ and -21.9‰ (mean value -24.3‰, n=26). Numerous bodies of thermokarst-cave ice and several layers of segregated ice (both of the Late Pleistocene age) were also sampled: δ18O values for thermokarst-cave ice vary from -25.5‰ to -19.3‰ (mean value -23.0‰, n=23), and for layers of segregated ice (ice "belts") - from -23.4‰ to -21.0‰ (mean value -21.7‰, n=9). Five main cryostratigraphic units include (described from the top): (1) active layer, 0.6 to 0.8-m thick; (2) intermediate layer (ice-rich silt, up to 0.6-m thick); (3) yedoma silts reworked by thermokarst and thermal erosion during the Holocene, 3 to 5-m thick, generally ice-poor, with thin ice wedges; (4) Late Pleistocene ice-rich yedoma silts with large ice wedges, 10 to 14-m thick; (5) ice-poor alluvial gravels. Occurrence of the ice-poor deposits in the upper permafrost protects ice-rich yedoma deposits from thermokarst development. These studies revealed significant differences in the cryostratigraphy of the new and old CRREL tunnels: permafrost in the new tunnel has

  5. Sediment cores as archives of historical changes in floodplain lake hydrology.

    PubMed

    Lintern, Anna; Leahy, Paul J; Zawadzki, Atun; Gadd, Patricia; Heijnis, Henk; Jacobsen, Geraldine; Connor, Simon; Deletic, Ana; McCarthy, David T

    2016-02-15

    Anthropogenic activities are contributing to the changing hydrology of rivers, often resulting in their degradation. Understanding the drivers and nature of these changes is critical for the design and implementation of effective mitigation strategies for these systems. However, this can be hindered by gaps in historical measured flow data. This study therefore aims to use sediment cores to identify historical hydrological changes within a river catchment. Sediment cores from two floodplain lakes (billabongs) in the urbanised Yarra River catchment (Melbourne, South-East Australia) were collected and high resolution images, trends in magnetic susceptibility and trends in elemental composition through the sedimentary records were obtained. These were used to infer historical changes in river hydrology to determine both average trends in hydrology (i.e., coarse temporal resolution) as well as discrete flood layers in the sediment cores (i.e., fine temporal resolution). Through the 20th century, both billabongs became increasingly disconnected from the river, as demonstrated by the decreasing trends in magnetic susceptibility, particle size and inorganic matter in the cores. Additionally the number of discrete flood layers decreased up the cores. These reconstructed trends correlate with measured flow records of the river through the 20th century, which validates the methodology that has been used in this study. Not only does this study provide evidence on how natural catchments can be affected by land-use intensification and urbanisation, but it also introduces a general analytical framework that could be applied to other river systems to assist in the design of hydrological management strategies. PMID:26779954

  6. Permafrost in the Fox Permafrost Tunnel

    NASA Astrophysics Data System (ADS)

    Shur, Y.; Bray, M. T.; Anderson, D. A.

    2002-12-01

    Geology, engineering geology, and paleo-geography of the Fox permafrost tunnel have been thoroughly studied (Sellmann, 1967, 1972; Hamilton and others, 1988, Huang, 1985, Johansen and others 1981, 1982,). Permafrost specific information from previous studies is very limited and controversial. We applied 3D mapping and a cryo-facial analysis to identify genesis and structure of permafrost and distinguish between original syngenetic permafrost and later alternations of soil and massive ice. By mapping the tunnel in a 3D framework, features which occur on both walls of the tunnel and at its ceiling can be connected. For example, ice wedge continuity can be seen along with the nature of their disruption patterns. Mapping is particularly useful for determining the history of syngenetic ice-wedges modification, which show most visually the timing patterns and nature of the events that transpired in modification of the original permafrost conditions. Main principals of the cryo-facial analysis (Katasonov, 1960) are based on dependence of shape and size of ice inclusions in permafrost on facial type of soil and consequently on morphological conditions in which soil was deposited and frozen such floodplain, slope, etc. Quaternary permafrost deposits have different ice content depending on its genesis and facial type. We analyzed the permafrost cryogenic structure and soil water content to distinguish between original syngetetic permafrost and soil altered later. In previous studies two layers of silt with a sub-horizontal thermal unconformity between them and two types of massive ice (ice-wedges and buried ice) have been identified. Our study contradicts to such descriptions. Ice, which was described previously as buried pond or aufeis, we identified as thermokarst-cave ice, which was formed inside permafrost in channels made by running water. Such thermokarst caves occur mainly in ice-wedges and seldom in ice-rich soil. Both situations take place in the Fox permafrost

  7. Undiscovered Arctic gas hydrates: permafrost relationship and resource evaluation.

    NASA Astrophysics Data System (ADS)

    Cherkashov, G. A.; Matveeva, T.

    2011-12-01

    Though ice-core studies show that multidecadal-scale methane variability is only weakly correlated with reconstructed temperature variations (Mitchell et al., 2010) methane emission to the atmosphere still consider as the most significant contributions to the global warming processes. Pockmarks, seeps, mud volcanoes and other features associated with methane fluxes from the seabed have been widely reported, particularly during the last three decades. On continental margins, seepage of hydrocarbon gases from shallow sedimentary layers is a common phenomenon, resulting either from in situ formation of gases (mainly methane) by bacterial decomposition of organic matter within rapidly accumulated upper sediments or from upward migration of gases formed at greater depths. Furthermore, processes associated with seabed fluid flow have been shown to affect benthic ecology and to supply methane to the hydrosphere and the atmosphere (Judd, 2003; Hovland and Judd, 2007). The most recent investigations testified that revaluation of the role of gas seeps and related gas hydrate formation processes in the Arctic environment is necessary for the understanding of global methane balance and global climate changes (Westbrook et al., 2009; Shahova and Semiletov, 2010). With respect to gas hydrate formation, due to the presence of relict permafrost the Arctic submarine environment holds a specific place that is distinct from the rest of the Ocean. Submarine gas hydrates in the Arctic may be confined to (1) relict permafrost occurrences on the shelf; (2) concentrated methane infiltration toward the seafloor (shallow-seated gas hydrates); (3) dissipated methane infiltration from great depths (deep-seated gas hydrates). Permafrost-related or cryogenic gas hydrates form due to exogenous cooling of sediment (intra- and sub-permafrost gas hydrates). It is also suggested that some parts of hydrates may be preserved owing to a self-preservation effect above the gas hydrate stability zone

  8. The peculiarities of relict gas hydrate forms existence within permafrost layers

    NASA Astrophysics Data System (ADS)

    Chuvilin, E.

    2005-12-01

    It's well known that permafrost zone of the Earth is favorable for formation and existence of such ice-like compounds as gas (mainly methane) hydrates. Currently methane hydrate accumulations have identified either by direct evidences (hydrate-containing core sample) or indirect evidences in various permafrost regions of the world (Arctic coast of Canada, Alaska, the North of Siberia etc.). The special interest excites the fact that gas hydrate-shows (indirect evidences) are documented for shallow depths (down to 200-300 m) above the gas hydrate stability zone (GHSZ). The north-west part of Yamal ( West Siberia) is one of such areas (Chuvilin et al.,1998, Yakushev and Chuvilin, 2000). Special research, which included analysis of monitoring wells in cryolithozone, as well research of permafrost cores recovered during drilling, can be assumed that at least a part of gas in similar intrapermafrost accumulations exist in the form of metastable (relict) gas hydrates. They were formed in the past and exist now to the self-preservation effect. Some models of gas hydrate formation in shallow depths in permafrost are possible. They can associate with sea transgression, regional ice cover formation, freezing of gas saturated talik zones, permafrost sediments formation etc. After pressure reduction, hydrate passed through the self-preservation stage remained metastable for a long time. However, according to the shallow depth and metastable condition self reserved gas hydrate have tendency to dissociate due to the global climate warming, as well as to different technogenic effects such drilling and mining. Possibilities of formation metastable gas hydrate in permafrost confirm the special experimental investigation of gas hydrate accumulation in freezing sediments (Chuvilin and Kozlova, 2004). The experimental data shows, that the cooling of gas hydrate saturated sediments to negative temperature induced ice formation. Enclosing hydrate ice would originate from the remaining

  9. Colloid mobilization in an undisturbed sediment core under semiarid recharge rates

    NASA Astrophysics Data System (ADS)

    Liu, Ziru; Flury, Markus; Harsh, James B.; Mathison, Jon B.; Vogs, Carolina

    2013-08-01

    The semiarid US Department of Energy Hanford site has a deep vadose zone with low recharge rates. Contaminants originating from nuclear waste processing are expected to move slowly through the vadose zone. The movement of certain contaminants can be facilitated by colloids. We hypothesized that the low recharge rates and low water contents in semiarid regions, however, tend to inhibit movement of colloidal particles, thereby reducing the risk for colloid-facilitated contaminant transport. The goal of this study was to investigate whether in situ natural colloids can be mobilized and transported in undisturbed, deep vadose zone sediments at the Hanford site under typical, semiarid recharge rates. We sampled an undisturbed sediment core (i.d. 50 cm, 59.5 cm height) from a depth of 17 m below ground at the Hanford 200 Area. The core was set up as a laboratory lysimeter and exposed to an infiltration rate of 18 mm/yr by applying simulated pore water onto the surface. Particle concentrations were quantified in the column outflow, and selected samples were examined microscopically and for elemental composition (transmission electron microscopy and energy dispersive X-ray). Measured water contents and potentials were used to calibrate a numerical model (HYDRUS-1D), which was then applied to simulate colloid mobilization from the sediment core. During 5.3 years of monitoring, natural colloids like silicates, aluminosilicates, and Fe-oxides were observed in the core outflow, indicating the continuous mobilization of in situ colloids. The total amount of particles mobilized during 5.3 years corresponded to 1.1% of the total dispersible colloids inside the core. Comparison of the amounts of colloids released with weathering rates suggests that mineral weathering can be a major source of the mobilized colloids. The fitted colloid release rate coefficient was 6 to 7 orders of magnitude smaller than coefficients reported from previous studies, where disturbed Hanford sediments

  10. ESA Data User Element PERMAFROST: a spaceborne permafrost monitoring and information system

    NASA Astrophysics Data System (ADS)

    Bartsch, A.; Heim, B.; Boike, J.; Elger, K.; Muster, S.; Langer, M.; Westermann, S.; Sobiech, J.

    2010-12-01

    Permafrost is a subsurface phenomenon whose ground thermal regime is mainly influenced by air temperature, land cover, soil and rock properties and snow parameters. Many spaceborne applications are potentially indicative for the thermal state of Permafrost, such as ‘land surface temperature’, ‘surface moisture’, ‘freeze/thaw’, ‘terrain’, ‘vegetation’ and ‘changes of surface waters’. The major task of the ESA Data User Element Permafrost project is to develop circumarctic/-boreal Earth Observation services of these parameters with extensive involvement of the permafrost research community The DUE PERMAFROST datasets will be processed in the EO-PERMAFROST Information System and provided via a WebGIS-interface. Further information is available at www.ipf.tuwien.ac.at/ permafrost. In order to set up the required validation tasks and information services, a target area approach with specified case study regions is used. Most of the foreseen DUE PERMAFROST remote sensing applications are well established and can optimally become operational. The goal of DUE PERMAFROST is to lend confidence in their scientific utility for high-latitude permafrost landscapes. Therefore, a major component is the evaluation of the DUE PERMAFROST products. Ground measurements in the high-latitude landscapes involve challenging logistics and are networked on multidisciplinary and circum-arctic level by the Permafrost community. The International Permafrost Association (IPA) has built up the Global Terrestrial Network for Permafrost (GTN-P) that is a network of the Circumpolar Active Layer Monitoring (CALM) and the Thermal State of Permafrost (TSP) projects. A major part of the DUE PERMAFROST core User group is contributing to GTN-P. Additional members of these programs and circum-arctic networks have also been involved in the consulting process and ground data providing process. Match-up data sets of ground data and remote sensing products coincident in time and

  11. Detection of Tephra Layers in Antarctic Sediment Cores with Hyperspectral Imaging.

    PubMed

    Aymerich, Ismael F; Oliva, Marc; Giralt, Santiago; Martín-Herrero, Julio

    2016-01-01

    Tephrochronology uses recognizable volcanic ash layers (from airborne pyroclastic deposits, or tephras) in geological strata to set unique time references for paleoenvironmental events across wide geographic areas. This involves the detection of tephra layers which sometimes are not evident to the naked eye, including the so-called cryptotephras. Tests that are expensive, time-consuming, and/or destructive are often required. Destructive testing for tephra layers of cores from difficult regions, such as Antarctica, which are useful sources of other kinds of information beyond tephras, is always undesirable. Here we propose hyperspectral imaging of cores, Self-Organizing Map (SOM) clustering of the preprocessed spectral signatures, and spatial analysis of the classified images as a convenient, fast, non-destructive method for tephra detection. We test the method in five sediment cores from three Antarctic lakes, and show its potential for detection of tephras and cryptotephras. PMID:26815202

  12. Detection of Tephra Layers in Antarctic Sediment Cores with Hyperspectral Imaging

    PubMed Central

    Aymerich, Ismael F.; Oliva, Marc; Giralt, Santiago; Martín-Herrero, Julio

    2016-01-01

    Tephrochronology uses recognizable volcanic ash layers (from airborne pyroclastic deposits, or tephras) in geological strata to set unique time references for paleoenvironmental events across wide geographic areas. This involves the detection of tephra layers which sometimes are not evident to the naked eye, including the so-called cryptotephras. Tests that are expensive, time-consuming, and/or destructive are often required. Destructive testing for tephra layers of cores from difficult regions, such as Antarctica, which are useful sources of other kinds of information beyond tephras, is always undesirable. Here we propose hyperspectral imaging of cores, Self-Organizing Map (SOM) clustering of the preprocessed spectral signatures, and spatial analysis of the classified images as a convenient, fast, non-destructive method for tephra detection. We test the method in five sediment cores from three Antarctic lakes, and show its potential for detection of tephras and cryptotephras. PMID:26815202

  13. Results of submerged sediment core sampling and analysis on Par Pond, Pond C, and L Lake: July 1995

    SciTech Connect

    Koch, J.W. II; Martin, F.D.; Friday, G.P.

    1996-06-01

    Sediment cores from shallow and deep water locations in Par Pond, Pond C, and L Lake were collected and analyzed in 1995 for radioactive and nonradioactive constituents. This core analysis was conducted to develop a defensible characterization of contaminants found in the sediments of Par Pond, Pond C, and L Lake. Mercury was the only nonradiological constituent with a nonestimated quantity that was detected above the U.S Environmental Protection Agency Region IV potential contaminants of concern screening criteria. It was detected at a depth of 0.3--0.6 meters (1.0--2.0 feet) at one location in L Lake. Cesium-137, promethium-146, plutonium-238, and zirconium-95 had significantly higher concentrations in Par Pond sediments than in sediments from the reference sites. Cobalt-60, cesium-137, plutonium-238, plutonium-239/240, and strontium-90 had significantly higher concentrations in L-Lake sediments than sediments from the reference sites.

  14. Meiofauna Analyses of Sediment Cores to Investigate the Influence of Sea Level Rise on Saltmarsh Development

    NASA Astrophysics Data System (ADS)

    Radl, Michaela; Hughes, Rob G.; Horne, David J.

    2013-04-01

    The text-book explanation for the development of coastal saltmarshes is through increase in sediment elevation (with respect to sea level), mainly facilitated by plants leading to seaward progradation and succession from the lowest plant species to higher ones. An alternative hypothesis is that saltmarshes develop mainly by sea level rise leading to landward migration, where succession will be from the higher to lower species. These competing hypotheses are tested by comparing the assemblages of foraminifera in sediment cores with surface samples, in saltmarshes on isostatically rising (NW Scotland) and sinking coasts (SE England and Wales). The surface meiofauna assemblages differ with saltmarsh vertical zones and between saltmarshes. Ostracod abundance decreased with elevation at both sites and none were found in the high marsh (among sea couch grass Elytrigia atherica), limiting their use in some succession studies. The ratio of agglutinated foraminifera (e.g. Jadammina macrescens) to calcified species (e.g. Quinqueloculina spp.) increases with elevation. Geographical differences also occur which may be related to different sediment characteristics, particularly grain size, water content and plant species or grazing effects. For example, the domination of the mid-low saltmarsh by Cornuspira involuens on the sandier west coast in Wales and Quinqueloculina spp. in a muddier saltmarsh in SE England. Foraminifera assemblages throughout a 2.5 meter core in Tollesbury (SE England) were dominated by agglutinated species, indicating high marsh. The absence of lower marsh assemblages supports the hypothesis for the importance of sea level rise in saltmarsh development. In Loch Riddon (W Scotland) too there is no evidence of low marsh assemblages in the sediment strata (1 meter core). While there is no evidence of facilitation succession in this saltmarsh, sea level rise is unlikely to be responsible for its formation and development as it is on a rising coast.

  15. Time trends of polybrominated diphenyl ethers in sediment cores from the Pearl River Estuary, South China.

    PubMed

    Chen, She-Jun; Luo, Xiao-Jun; Lin, Zhen; Luo, Yong; Li, Ke-Chang; Peng, Xian-Zhi; Mai, Bi-Xian; Ran, Yong; Zeng, Eddy Y

    2007-08-15

    The present study provides information on the time trend of PBDEs in three sediment cores from the Pearl River Estuary (PRE), South China, using 210Pb dating technique. The sigmaPBDEs (except for BDE 209) concentrations in all sediment cores increased gradually from the bottom (mid-1970s) to the middle layer (later 1980s and early 1990s) followed by different temporal trends in different locations to the surface sediments, reflecting the variations in the consumption of commercial penta-BDEs mixture in different regions of the Pearl River Delta. The BDE 209 concentrations remained constant until 1990 and thereafter increased exponentially to the present, with doubling times of 2.6 +/- 0.5-6.4 +/- 1.6 years, suggesting the increasing market demands for deca-BDE mixture after 1990 in China. The inventories of sigmaPBDEs and BDE 209 in sediments of the PRE were 56.0 and 368.2 ng cm(-2), respectively, and the total burden of PBDEs in the PRE were estimated at 8.6 metric tons. The current sigmaPBDEs and BDE 209 fluxes to the PRE were 2.1 and 29.7 ng cm(-2) yr(-1), respectively. The concurrent increase of BDE 209 fluxes and the annual gross industrial output values of electronics manufacturing revealed that the rapid growth of electronics manufacturing in this region since the early 1990s was responsible for the sharp rise of BDE 209 fluxes in the past decade. The PBDE congener compositions of the cores indicated the various input pathways for PBDEs transport to different locations of the estuary. PMID:17874760

  16. Paleomagnetic Study of Marine Sediment Core OR715-21 from Eastern Offshore of Taiwan

    NASA Astrophysics Data System (ADS)

    Lee, T.; Wei, K.; Huh, C.

    2009-12-01

    This study presents paleomagnetic secular variation results of a marine sediment core, named as OR715-21, taken from eastern offshore of Taiwan (121.5°E, 22.7°N, water depth 760 m). The total recovered length is 1.87 meters. Sediments in the core mainly consist of gray clay and silt. Planktonic foraminiferal shells (>250 μm, >6 mg, Globigerinoides spp. and Orbulina universa) were picked from six levels of the core and subjected to AMS 14C dating for constructing the age model. The results indicated that this core could support the information for the last 7000 years. The averaged sedimentation rate is estimated to be of about 26.5 cm/kyr. Psuedo-single domain (PSD) magnetite is identified as the most important magnetic carrier. Alternating field (AF) demagnetization was applied to treat the u-channel samples of the core. The median destructive field of the samples distributed between 15~25 mT. The characteristic remanent magnetization could be resolved after 20 mT cleaning. The paleo-declinations of the samples varied about ±200 around their mean and their paleo-inclinations varied between 300 and 500 . The variation pattern of the paleo-declination is somehow similar to the pattern compiled by Hyoto et al. (1993) based on the lake and marine sediment records from Japan except the varied amplitude is less between 4000 and 5000 yrB.P. Using NRM/ARM after 20 mT cleaning to simulate the paleo-intensity secular variation, our record shows that an increased trend began from 6500 yrB.P. to 3000 yrB.P., but decreased after. Magnetic proxies of this core indicate that 4 stages of environmental changes has happened in the area studied: (1) high magnetite abundance with relative low oxidized magnetic mineral contents occurred during ~6900 to 6200 yrB.P.; (2) a relative low abundance of magnetite with relative high oxidized magnetic minerals during ~6200 to ~5400 yrB.P.; (3) an abnormal low HIRM with relative higher ARM/SIRM could be found during the time period of ~5400

  17. Anthropogenic stressors and changes in the Clear Lake ecosystem as recorded in sediment cores.

    PubMed

    Richerson, Peter J; Suchanek, Thomas H; Zierenberg, Robert A; Osleger, David A; Heyvaert, Alan C; Slotton, Darell G; Eagles-Smith, Collin A; Vaughn, Charles E

    2008-12-01

    Sediment cores were collected to investigate multiple stresses on Clear Lake, California, USA, through the period of European occupation to the present day. Earlier workers suggested the hypothesis that the use of mechanized earthmoving equipment, starting in the 1920s and 1930s, was responsible for erosion, mercury (Hg) contamination, and habitat loss stresses. Cores (approximately 2.5 m in depth) were collected in 1996 and 2000 from each of the three arms of the lake. Carbon-14 dating suggests that these cores represent as much as 3000 years of the lake's history, beginning long before European settlement. Total mercury (TotHg) and methylmercury (MeHg), dry matter, water, carbon, nitrogen, phosphorus, sulfur, and the stable isotopes 13C and 15N were measured at 5-cm intervals. Nearly all parameters show major changes at depths of 58-135 cm, beginning at ca. 1927 (dated with 210Pb). Accepting this date for concomitant major changes in seven cores yields an estimated 8.6 mm/yr average sedimentation rate after 1927. Pre-1927 sedimentation rates were approximately 1 mm/yr. Total mercury and MeHg, dry matter, phosphorus, and 15N increase significantly, whereas nitrogen, sulfur, carbon, and water content decrease significantly above the 1927 horizon. Both TotHg and MeHg show extremely large increases (roughly 10-fold) above the 1927 horizon. A peak in inorganic deposition rate and minimum values for percentage of water is present at depths corresponding to ca. 1970. Interestingly, the first 75 years of European settlement in the Clear Lake basin (including the most productive years of the Sulphur Bank Mercury Mine) appeared to have had undetectable effects on lake cores. Changes since 1927 were dramatic. The large increase in Hg beginning about 1927 corresponds to the use of heavy equipment to exploit the ore deposit at the mine using open-pit methods. Increases in sediment deposition from increased earthmoving in the basin and sulfate loading from the mine are the

  18. Identifying water-quality trends in the Trinity River, Texas, USA, 1969-1992, using sediment cores from Lake Livingston

    USGS Publications Warehouse

    Van Metre, P.C.; Callender, E.

    1996-01-01

    Chemical analyses were done on cores of bottom sediment from three locations in Lake Livingston, a reservoir on the Trinity River in east Texas to identify trends in water quality in the Trinity River using the chemical record preserved in bottom sediments trapped by the reservoir. Sediment cores spanned the period from 1969, when the reservoir was impounded, to 1992, when the cores were collected. Chemical concentrations in reservoir sediment samples were compared to concentrations for 14 streambed sediment samples from the Trinity River Basin and to reported concentrations for soils in the eastern United States and shale. These comparisons indicate that sediments deposited in Lake Livingston are representative of the environmental setting of Lake Livingston within the Trinity River Basin. Vertical changes in concentrations within sediment cores indicate temporal trends of decreasing concentrations of lead, sodium, barium, and total DDT (DDT plus its metabolites DDD and DDE) in the Trinity River. Possible increasing temporal trends are indicated for chlordane and dieldrin. Each sediment-derived trend is related to trends in water quality in the Trinity River or known changes in environmental factors in its drainage basin or both.

  19. Geochemical proxies for weathering and provenance of Late Quaternary alluvial core-sediments from NW India

    NASA Astrophysics Data System (ADS)

    Singh, Ajit; Amir, Mohd; Paul, Debajyoti; Sinha, Rajiv

    2014-05-01

    The Indo-Gangetic alluvial plains are formed by sediment deposition in the foreland basin as a result of upliftment and subsequent erosion of the Himalaya. Earlier study (Sinha et al., 2013) has shown the subsurface existence of buried channel bodies beneath the Ghaggar plains in NW Indo-Gangetic plains. The mapped sand bodies follow trace of a paleochannel that begins at the mountain front near the exit of river Sutlej and extends to the northern margin of the Thar desert, suggesting existence of a large Himalayan-sourced river (Singh et al., 2011) in the past. The buried sand bodies hold potential records of erosion history over the Himalaya that could be used to assess climate-controlled erosion over the Himalaya. Geochemical variations in the sediments from two (~45m long) cores drilled below the trace of the paleochannel (upstream) near Sirhind, Punjab and two cores (GS-10 & 11) from downstream near Kalibangan, Rajasthan, are used in this study to understand the erosional pattern over the Himalaya during Late Quaternary. Down-core variations in chemical index of alteration (CIA=51-79) along with K2O/Na2O and Al2O3/(CaO+Na2O) ratios are consistent with the trends of SW summer monsoonal fluctuations during the Glacial-Interglacial periods indicating climate controlled weathering at the source; higher values during Interglacial and lower during Glacial periods with maximum value during the Holocene. Sr-Nd isotopic compositions of drill-cores sediments, 87Sr/86Sr (0.7314-0.7946), ɛNd (-23.2 to -14) are within the range of silicate rocks from the Higher and Lesser Himalaya. Significant down-core variations in 87Sr/86Sr and ɛNd are observed that reflect the mixing of varying proportions of the Higher and Lesser Himalayan sediments, the two dominant sources to the core sites. Sediments deposited during MIS-2 and MIS-4, cold and dry Glacial periods, show high 87Sr/86Sr and low ɛNd suggesting an enhanced contribution from the Lesser Himalayan rocks that are

  20. Mono Lake Excursion in Cored Sediment from the Eastern Tyrrhenian Sea

    NASA Astrophysics Data System (ADS)

    Liddicoat, Joseph; Iorio, Marina; Sagnotti, Leonardo; Incoronato, Alberto

    2013-04-01

    A search for the Laschamp and Mono Lake excursions in cored marine and lacustrine sediment younger than 50,000 years resulted in the discovery of both excursions in the Greenland Sea (73.3˚ N, 351.0˚ E, Nowaczyk and Antanow, 1997), in the North Atlantic Ocean (62.7˚ N, 222.5˚ E, Channell, 2006), in Pyramid Lake in the Lahontan Basin, NV, USA (40.1˚ N, 240.2˚ E, Benson et al., 2008), and in the Black Sea (43.2˚ N, 36.5˚ E, Nowaczyk et al., 2012). The inclination, declination, and relative field intensity during the Mono Lake Excursion (MLE) in the Black Sea sediment matches well the behaviour of the excursion in the Mono Basin, CA, in that a reduction in inclination during westerly declination is soon followed by steep positive inclination when declination is easterly, and relative field intensity increases after a low at the commencement of the excursion (Liddicoat and Coe, 1979). A large clockwise loop of Virtual Geomagnetic Poles (VGPs) at the Black Sea when followed from old to young patterns very well the VGP loop formed by the older portion of the MLE in the Mono Basin (Liddicoat and Coe, 1979). We also searched for the MLE in cored sediment from the eastern Tyrrhenian Sea (40.1˚ N, 14.7˚ E) where the age of the sediment is believed to be about 32,000 years when comparing the susceptibility in the core with the susceptibility in a nearby one that is dated by palaeomagnetic secular variation records, Carbon-14, and numerous tephra layers in the Tyrrhenian Sea sediment (Iorio et al., 2011). In the Tyrrhenian Sea core, called C1067, closely spaced samples demagnetized in an alternating field to100 mT record a shallowing of positive inclination to 48˚ that is followed by steep positive inclination of 82˚ when declination moves rapidly to the southeast. The old to young path of the VGPs in C1067 forms a narrow counter-clockwise loop that reaches 30.3˚ N, 30.8˚ E and that is centered at about 55˚ N, 15˚ E. Although descending to a latitude that is

  1. Rare earth elements in core marine sediments of coastal East Malaysia by instrumental neutron activation analysis.

    PubMed

    Ashraf, Ahmadreza; Saion, Elias; Gharibshahi, Elham; Kamari, Halimah Mohamed; Kong, Yap Chee; Hamzah, Mohd Suhaimi; Elias, Md Suhaimi

    2016-01-01

    A study was carried out on the concentration of REEs (Dy, Sm, Eu,Yb, Lu, La and Ce) that are present in the core marine sediments of East Malaysia from three locations at South China Sea and one location each at Sulu Sea and Sulawesi Sea. The sediment samples were collected at a depth of between 49 and 109 m, dried, and crushed to powdery form. The entire core sediments prepared for Instrumental Neutron Activation Analysis (INAA) were weighted approximately 0.0500 g to 0.1000 g for short irradiation and 0.1500 g to 0.2000 g for long irradiation. The samples were irradiated with a thermal neutron flux of 4.0×10(12) cm(-2) s(-1) in a TRIGA Mark II research reactor operated at 750 kW. Blank samples and standard reference materials SL-1 were also irradiated for calibration and quality control purposes. It was found that the concentration of REEs varies in the range from 0.11 to 36.84 mg/kg. The chondrite-normalized REEs for different stations suggest that all the REEs are from similar origins. There was no significant REEs contamination as the enrichment factors normalized for Fe fall in the range of 0.42-2.82. PMID:26405840

  2. Atmospheric Mercury Depositional Chronology Reconstructed from Lake Sediments and Ice Core in the Himalayas and Tibetan Plateau.

    PubMed

    Kang, Shichang; Huang, Jie; Wang, Feiyue; Zhang, Qianggong; Zhang, Yulan; Li, Chaoliu; Wang, Long; Chen, Pengfei; Sharma, Chhatra Mani; Li, Qing; Sillanpää, Mika; Hou, Juzhi; Xu, Baiqing; Guo, Junming

    2016-03-15

    Alpine lake sediments and glacier ice cores retrieved from high mountain regions can provide long-term records of atmospheric deposition of anthropogenic contaminants such as mercury (Hg). In this study, eight lake sediment cores and one glacier ice core were collected from high elevations across the Himalaya-Tibet region to investigate the chronology of atmospheric Hg deposition. Consistent with modeling results, the sediment core records showed higher Hg accumulation rates in the southern slopes of the Himalayas than those in the northern slopes in the recent decades (post-World War II). Despite much lower Hg accumulation rates obtained from the glacier ice core, the temporal trend in the Hg accumulation rates matched very well with that observed from the sediment cores. The combination of the lake sediments and glacier ice core allowed us to reconstruct the longest, high-resolution atmospheric Hg deposition chronology in High Asia. The chronology showed that the Hg deposition rate was low between the 1500s and early 1800, rising at the onset of the Industrial Revolution, followed by a dramatic increase after World War II. The increasing trend continues to the present-day in most of the records, reflecting the continuous increase in anthropogenic Hg emissions from South Asia. PMID:26878654

  3. Geochemical data for core and bottom-sediment samples collected in 2007 from Grand Lake O' the Cherokees, northeast Oklahoma

    USGS Publications Warehouse

    Fey, David L.; Becker, Mark F.; and Smith, Kathleen S.

    2010-01-01

    Grand Lake O' the Cherokees is a large reservoir in northeast Oklahoma, below the confluence of the Neosho and Spring Rivers, both of which drain the Tri-State Mining District to the north. The Tri-State district covers an area of 1,200 mi2 (3,100 km2) and comprises Mississippi Valley-type lead-zinc deposits. A result of 120 years of mining activity is an estimated 75 million tons of processed mine tailings (chat) remaining in the district. Concerns of sediment quality and the possibility of human exposure to cadmium and lead through eating fish have led to several studies of the sediments in the Tri-State district. In order to record the transport and deposition of metals from the Tri-State district by the Spring and Neosho Rivers into Grand Lake O' the Cherokees, the U.S. Geological Survey collected 11 sediment cores and 15 bottom-sediment samples in September 2007. Subsamples from five selected cores and the bottom-sediment samples were analyzed for major and trace elements and forms of carbon. The sediment samples collected from the sediment-water interface had larger average concentrations of zinc, cadmium, and lead than local background. The core collected from the Spring River had the largest concentrations of mining-related elements. A core collected just south of Twin Bridges State Park, at the confluence of the Spring and Neosho Rivers, showed a mixing zone with more mining-related elements coming from the Spring River side. The element zinc showed the most definitive patterns in graphs depicting concentration-versus-depth profiles. A core collected from the main body of the reservoir showed affected sediment down to a depth of 85 cm (33 in). This core and two others appear to have penetrated to below mining-affected sediment.

  4. Distribution, provenance and early diagenesis of major and trace metals in sediment cores from the Mandovi estuary, western India

    NASA Astrophysics Data System (ADS)

    Prajith, A.; Rao, V. Purnachandra; Chakraborty, P.

    2016-03-01

    Major elements and trace metals were analyzed in four sediment cores recovered along a transect in the Mandovi estuary for their distribution, provenance and early diagenesis. The sediments were clayey silts in cores from the upper/lower estuary and sand-dominated in cores from the middle estuary/bay. Organic carbon (OC) content varied from 0.5 to 4%, with higher values in fine-grained sediments. The mean Fe and Mn contents of sediments from the upper/middle estuary were 3-5 times and 8-13 times, respectively higher than the reference sediment (RS) from the same estuary. The mean Fe and Mn contents of sediments from the lower estuary/bay were close to the RS. Strong inter-metal correlation among Ti, V, Cr and Zr in all the cores indicated their contribution from a common source, probably the laterites from hinterland. Trace metals were more enriched in fine-grained sediments than in sand-dominated sediments. Early diagenetic control on the redistribution of metal is evident in core sediments from the middle estuary to Bay. The distribution of Mo, U and Pb followed that of Fe and Mn in the upper estuary and OC in the lower estuary/bay. Our results indicated strong anthropogenic contribution of metals from ore deposits in the upper/middle estuary. The Mn and Cr contents of sediment in the upper/middle estuary and Fe in the middle estuary were highly enriched suggestive of 'significant pollution signal'. More trace metals from the middle estuary were moderately enriched. Speciation studies showed Mn and Pb occurred abundantly in non-residual phases. High Mn content and its high percentage in exchangeable and reductive phases indicate that it was susceptible to be mobilized. However, Fe, Cu and Ni occurred abundantly in residual phases and less percentage of them were expected to be bio-available.

  5. Physical processes in Subglacial Lake Whillans, West Antarctica: Inferences from sediment cores

    NASA Astrophysics Data System (ADS)

    Hodson, T. O.; Powell, R. D.; Brachfeld, S. A.; Tulaczyk, S.; Scherer, R. P.

    2016-06-01

    The hydrologic system beneath the Antarctic Ice Sheet is thought to influence both the dynamics and distribution of fast flowing ice streams, which discharge most of the ice lost by the ice sheet. Despite considerable interest in understanding this subglacial network and its affect on ice flow, in situ observations from the ice sheet bed are exceedingly rare. Here we describe the first sediment cores recovered from an active subglacial lake. The lake, known as Subglacial Lake Whillans, is part of a broader, dynamic hydrologic network beneath the Whillans Ice Stream in West Antarctica. Even though "floods" pass through the lake, the lake floor shows no evidence of erosion or deposition by flowing water. By inference, these floods must have insufficient energy to erode or transport significant volumes of sediment coarser than silt. Consequently, water flow beneath the region is probably incapable of incising continuous channels into the bed and instead follows preexisting subglacial topography and surface slope. Sediment on the lake floor consists of till deposited during intermittent grounding of the ice stream following flood events. The fabrics within the till are weaker than those thought to develop in thick deforming beds suggesting subglacial sediment fluxes across the ice plain are currently low and unlikely to have a large stabilizing effect on the ice stream's grounding zone.

  6. Sediment cores and chemistry for the Kootenai River White Sturgeon Habitat Restoration Project, Boundary County, Idaho

    USGS Publications Warehouse

    Barton, Gary J.; Weakland, Rhonda J.; Fosness, Ryan L.; Cox, Stephen E.; Williams, Marshall L.

    2012-01-01

    The Kootenai Tribe of Idaho, in cooperation with local, State, Federal, and Canadian agency co-managers and scientists, is assessing the feasibility of a Kootenai River habitat restoration project in Boundary County, Idaho. This project is oriented toward recovery of the endangered Kootenai River white sturgeon (Acipenser transmontanus) population, and simultaneously targets habitat-based recovery of other native river biota. Projects currently (2010) under consideration include modifying the channel and flood plain, installing in-stream structures, and creating wetlands to improve the physical and biological functions of the ecosystem. River restoration is a complex undertaking that requires a thorough understanding of the river. To assist in evaluating the feasibility of this endeavor, the U.S. Geological Survey collected and analyzed the physical and chemical nature of sediment cores collected at 24 locations in the river. Core depths ranged from 4.6 to 15.2 meters; 21 cores reached a depth of 15.2 meters. The sediment was screened for the presence of chemical constituents that could have harmful effects if released during restoration activities. The analysis shows that concentrations of harmful chemical constituents do not exceed guideline limits that were published by the U.S. Army Corps of Engineers in 2006.

  7. Rapid Permafrost Carbon Degradation at the Land-Ocean Interface

    NASA Astrophysics Data System (ADS)

    Tanski, G.

    2015-12-01

    Climate change has a strong impact on permafrost coasts in the Arctic. With increasing air and water temperatures, the ice-rich unlithified permafrost coasts will thaw and erode at a greater pace. Organic carbon that has been stored for thousands of years is mobilized and degrades on its way to the ocean. The objective of this study is to investigate to what extent permafrost carbon degrades after thawing before it enters the ocean in a retrogressive thaw slump. A slump located on Herschel Island (Yukon Territory, Canada) was sampled systematically along transects from the permafrost headwall to the coastline. Concentrations of particulate and dissolved organic carbon (POC and DOC) as well as its stable carbon isotopes (δ13C-POC and δ13C-DOC) were measured and compared in frozen deposits and in thawed sediments. Ammonium, nitrite and nitrate were also analyzed in order to identify and understand the carbon metabolization mechanisms taking place during slump activity. Our results show that major portions of permafrost carbon are metabolized right after thawing. Ammonium concentrations are highest in areas where thawed permafrost material directly accumulates. We suggest that before entering the nearshore zone permafrost organic carbon and nitrogen is subject to major degradation and metabolization. This makes permafrost coasts and retrogressive thaw slumps degradation hotspots at the land-ocean-interface.

  8. Biogenic silica in Lake Baikal sediments: results from 1990-1992 American cores

    USGS Publications Warehouse

    Carter, Susan J.; Colman, Steven M.

    1994-01-01

    The Lake Baikal Paleoclimate Project is a joint Russian-American program established to study the paleoclimate of Central Asia. During three summer field seasons, duplicate Russian and American cores were taken at a number of sites in different sedimentary environments in the lake. Eight cores returned to the U.S. were quantitatively analyzed for biogenic silica using a single-step 5-hour alkaline leach, followed by dissolved silicon analysis by inductively-coupled-plasma atomic-emission spectroscopy. Sediments of Holocene age in these cores have biogenic silica maxima that range from about 15 to 80 percent. An underlying zone in each core with low biogenic-silica concentrations (0 to 5 percent) dates from the last glacial maximum. The transition from the last glaciation to the present interglaciation, recorded by biogenic silica, began about 13,000 years ago. Biogenic silica profiles from these cores appear to be a good measure of past diatom productivity and a useful basis for paleoclimatic interpretations.

  9. Cryopegs as destabilization factor of intra-permafrost gas hydrates

    NASA Astrophysics Data System (ADS)

    Chuvilin, Evgeny; Bukhanov, Boris; Istomin, Vladimir

    2016-04-01

    A characteristic feature of permafrost soils in the Arctic is widespread intra-permafrost unfrozen brine lenses - cryopegs. They are often found in permafrost horizons in the north part of Western Siberia, in particular, on the Yamal Peninsula. Cryopegs depths in permafrost zone can be tens and hundreds of meters from the top of frozen strata. The chemical composition of natural cryopegs is close to sea waters, but is characterized by high mineralization. They have a sodium-chloride primary composition with a minor amount of sulphate. Mineralization of cryopegs brine is often hundreds of grams per liter, and the temperature is around -6…-8 °C. The formation of cryopegs in permafrost is associated with processes of long-term freezing of sediments and cryogenic concentration of salts and salt solutions in local areas. The cryopegs' formation can take place in the course of permafrost evolution at the sea transgressions and regressions during freezing of saline sea sediments. Very important feature of cryopegs in permafrost is their transformation in the process of changing temperature and pressure conditions. As a result, the salinity and chemical composition are changed and in addition the cryopegs' location can be changed during their migration. The cryopegs migration violates the thermodynamic conditions of existence intra-permafrost gas hydrate formations, especially the relic gas hydrates deposits, which are situated in the shallow permafrost up to 100 meters depth in a metastable state [1]. The interaction cryopegs with gas hydrates accumulations can cause decomposition of intra-permafrost hydrates. Moreover, the increasing of salt and unfrozen water content in sedimentary rocks sharply reduce the efficiency of gas hydrates self-preservation in frozen soils. It is confirmed by experimental investigations of interaction of frozen gas hydrate bearing sediments with salt solutions [2]. So, horizons with elevated pressure can appear, as a result of gas hydrate

  10. Surface (sea floor) and near-surface (box cores) sediment mineralogy in Baffin Bay as a key to sediment provenance and ice sheet variations

    USGS Publications Warehouse

    Andrews, John T.; Eberl, D.D.

    2011-01-01

    To better understand the glacial history of the ice sheets surrounding Baffin Bay and to provide information on sediment pathways, samples from 82 seafloor grabs and core tops, and from seven box cores were subjected to quantitative X-ray diffraction weight percent (wt.%) analysis of the 2000 m) all show an abrupt drop in calcite wt.% (post-5 cal ka BP?) following a major peak in detrital carbonate (mainly dolomite). This dolomite-rich detrital carbonate (DC) event in JR175BC06 is possibly coeval with the Younger Dryas cold event. Four possible glacial-sourced end members were employed in a compositional unmixing algorithm to gain insight into down core changes in sediment provenance at the deep central basin. Estimates of the rates of sediment accumulation in the central basin are only in the range of 2 to 4 cm/cal ka, surprisingly low given the glaciated nature of the surrounding land.

  11. Structure of Syngenetic Permafrost: New Data from the CRREL Permafrost Tunnel, Fox, Alaska

    NASA Astrophysics Data System (ADS)

    Kanevskiy, M.; Fortier, D.; Cysewski, M.; Shur, Y.; Jorgenson, T.

    2006-12-01

    Syngenetic permafrost formation is a complex process related to sedimentation in cold conditions when the base of the active layer rises up step by step in phase with the accumulation of deposits of various origin (alluvial, slope, aeolian, lacustrine, etc.) at the surface. Syngenetically frozen sediments usually have high silt particles content (up to 70-80%); slightly decomposed rootlets and buried organic-rich horizons; high ice content; ice wedges with big vertical length; rhythmically organized cryogenic structure specific for syngenetic permafrost. The well-known CRREL Permafrost Tunnel near Fairbanks Alaska offers excellent exposures of syngenetic permafrost. The section of Late Pleistocene deposits in the Tunnel is comprised mostly of syngenetically frozen aeolian and fluvial silts with sand lenses, partly reworked by thermal erosion which proceeded mainly along the large ice wedges. Gullies and underground channels cut in the Late Pleistocene permafrost were filled with ice and soils of different origins and cryogenic structures. The Permafrost Tunnel consists of a main shaft and an inclined winze. The former has been extensively studied during the last 40 years. However the permafrost in the winze has not been studied thoroughly even though the Late Wisconsinian syngenetic permafrost is better preserved there than in the main shaft. The main objective of our work was to map the cryostratigraphy (scale 1:20) of the winze. The results show the prevalence of syngenetic permafrost with a micro-lenticular cryostructure. The gravimetric moisture content of such sediments is very high and varies from 100 to 240%. The sediments which were formed in the tunnels cut in the permafrost and in the filled gullies are mostly stratified silts with lenses of sands and (sometimes) gravel. The gravimetric moisture content of these sediments varies from 70 to100% which is smaller than the water content of the Late Wisconsinian syngenetic permafrost. In the upper part of the

  12. Dissolved methane profiles in marine sediments observed in situ differ greatly from analyses of recovered cores

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Brewer, P. G.; Hester, K.; Ussler, W.; Walz, P. M.; Peltzer, E. T.; Ripmeester, J.

    2009-12-01

    The flux of dissolved methane through continental margin sediments is of importance in marine geochemistry due to its role in massive hydrate formation with enigmatic climate consequences, and for the huge and complex microbial assemblage it supports. Yet the actual dissolved methane concentration driving this flux is poorly known since strong degassing during sample recovery from depth is commonplace. Thus, pore water analyses from high CH4 environments typically show values clustered around the one-atmosphere equilibrium value of 1-2 mM, erasing the original pore water profile and frustrating model calculations. We show that accurate measurement of pore water profiles of dissolved CH4, SO4, and H2S can be made rapidly in situ using a Raman-based probe. While Raman spectra were formerly believed to yield only qualitative data we show that by using a peak area ratio technique to known H2O bands and a form of Beer’s Law quantitative data may be readily obtained. Results from Hydrate Ridge, Oregon clearly show coherent profiles of all three species in this high flux environment, and while in situ Raman and conventional analyses of SO4 in recovered cores agree well, very large differences in CH4 are found. The in situ CH4 results show up to 35 mM in the upper 30cm of seafloor sediments and are inversely correlated with SO4. This is below the methane hydrate saturation value, yet disturbing the sediments clearly released hydrate fragments suggesting that true saturation values may exist only in the hydrate molecular boundary layer, and that lower values may typically characterize the bulk pore fluid of hydrate-hosting sediments. The in situ Raman measurement protocols developed take only a few minutes. Profiles obtained in situ showed minimal fluorescence while pore water samples from recovered cores quickly developed strong fluorescence making laboratory analyses using Raman spectroscopy challenging and raising questions over the reaction sequence responsible for

  13. Source determination of benzotriazoles in sediment cores from two urban estuaries on the Atlantic Coast of the United States.

    PubMed

    Cantwell, Mark G; Sullivan, Julia C; Katz, David R; Burgess, Robert M; Bradford Hubeny, J; King, John

    2015-12-15

    Benzotriazoles (BZTs) are used in a broad range of commercial and industrial products, particularly as metal corrosion inhibitors and as ultraviolet (UV) light stabilizer additives in plastics and polymers. In this study, dated sediment cores from two east coast estuaries were analyzed for commonly used BZTs. In Narragansett Bay, UV stabilizing BZTs (UV-BZTs) were present at high levels from 1961 on, reflecting their patent date, local production and long-term preservation in sediment. In Salem Sound, UV-BZTs were present at concentrations consistent with other coastal marine locations not influenced by BZT production. Anticorrosive BZTs (AC-BZTs) were found in both cores, with the highest levels reported to date present in Narragansett Bay, indicating sorption to, and preservation in, sediments. This study revealed that both classes of BZTs have remained structurally intact over time in coastal sediment cores, demonstrating their resistance to degradation and persistence in environmental compartments. PMID:26561444

  14. Preliminary Results of a Multi-Proxy Lake Sediment Core Study in East-Central France

    NASA Astrophysics Data System (ADS)

    Misner, T.; Meyers, S.; Rosenmeier, M.; Strano, S.; Straffin, E.

    2008-12-01

    This paper presents the preliminary results of a multi-proxy study of natural and human-induced changes in the Burgundian environment, as recorded in the sediment geochemistry of three small freshwater basins within the Arroux River Valley, east-central France. Accelerator mass spectrometry radiocarbon dates constrain the age of core material collected from the basins, and indicate that these mill and farm ponds were constructed by at least 1200 A.D. The pond sediments are predominantly massive, organic-rich muds that contain discrete sand and gravel lenses likely related to episodic flooding and/or basin drainage. In this study, continuous X-ray fluorescence (XRF) scanning is used to quantify bulk geochemical variability throughout the lake sediment cores, and to investigate specific elemental proxies for paleoenvironmental change (detrital flux, biogenic flux, and redox state). The high-resolution XRF data are supplemented by sediment magnetic susceptibility measurements, and organic matter concentration as determined by loss on ignition. These records demonstrate a general increase in detrital sediment input from 1200 to 1300 A.D., during a period of known regional agricultural expansion. We infer these changes to be the consequence of increased catchment soil erosion and material flux to the water bodies. The data also suggest changes in mill and farm pond primary productivity, also related to soil erosion and changing transport of soil nutrients to the basins. Near the onset of the Little Ice Age (ca. 1500 A.D.) pond productivity reductions are apparent, likely indicating colder climates. These mill and farm pond sedimentary archives, in conjunction with historic records, can be used to better understand past land management strategies. Furthermore, historically documented landscape changes can be examined within the context of prevailing climatic conditions over the last ~800 years in an effort to establish future best management practices and the most

  15. Tracking the Transformation and Preservation of Organic Biomarkers in a Varved Sediment-Core Series

    NASA Astrophysics Data System (ADS)

    Tolu, J.; Bigler, C.; Bindler, R.

    2014-12-01

    An important premise for reconstructing environmental changes using sediment records is to understand which environmental information reaches the lake bottom and how diagenetic processes may affect the proxies, such as terrestrial and aquatic organic biomarkers. We can tackle this question using a unique series of varved sediment cores collected from the lake Nylandssjön (northern Sweden). In addition to limnological and sediment trap sampling since 2001, we have a collection of freeze cores taken in late winter and stored since 1979, which allows us to track individual varve years (e.g., 1978) over time (~30 years). A previous study using this collection showed that 23 % of C and 35 % of N were lost during the first 25 years with a C:N ratio increase of ≈21, suggesting important implications for diagenetic effects on organic biomarkers. To assess the preservation/transformation of organic biomarkers, we developed a new Pyrolysis-Gas Chromatography/Mass Spectrometry method that allows the rapid determination of biomarkers from the common OM classes (e.g., plant waxes, microbial lipids, lignins) using sub-mg sample sizes and thus applicable to high-resolution sampling of the varved sediment (Tolu et al., under review). Our results show that the different biomarkers exhibit a broad spectrum of reactivities over ~30 years -% change determined by ([Peak area at t] - [Peak area at t=0])/ [peak area at t=0] x 100-. For example: 67-80 % of the algal chlorophyll-derived product 'phytene' is lost depending which single varve year is followed over time (e.g., 1979). Only 12-32 % of "pristene", the degraded form of algal chlorophyll, is lost. The guaiacyl and syringyl lignin units are affected by a smaller loss, i.e. 5-15 %, and the S/G ratio, indicative of angiosperm/gymnosperm plant input remains stable, which is contrary to previous work on non-varved lake sediments. Considering all biomarkers, the degradation/production plateaued after ~15 years, which indicates that

  16. Sediment cores from kettle holes in NE Germany reveal recent impacts of agriculture.

    PubMed

    Kleeberg, Andreas; Neyen, Marielle; Schkade, Uwe-Karsten; Kalettka, Thomas; Lischeid, Gunnar

    2016-04-01

    Glacial kettle holes in young moraine regions receive abundant terrigenous material from their closed catchments. Core chronology and sediment accumulation were determined for two semi-permanent kettle holes, designated RG and KR, on arable land close to the villages of Rittgarten and Kraatz, respectively, in Uckermark, NE Germany. Core dating ((210)Pb, (137)Cs) revealed variable sediment accretion rates through time (RG 0.4-23.1 mm a(-1); KR 0.2-35.5 mm a(-1)), with periods of high accumulation corresponding to periods of intensive agricultural activity and consequent erosional inputs from catchments. Sediment composition (C, N, P, S, K, Ca, Fe, Mn, Zn, Cu, Mo, Pb, Cd, Zr) was used to determine sediment source and input processes. At RG, annual P input increased from 0.65 kg ha(-1) in the early nineteenth century to 1.67 kg ha(-1) by 2013. At KR, P input increased from 0.6 to 4.1 kg ha(-1) over the last century. There was a concurrent increase in Fe input in both water bodies. Thus, Fe/P ratios showed no temporal trend and did not differ between RG (18.5) and KR (18.4), indicating similar P mobility. At RG, the S/Fe ratio increased from 0.4 to 2.3, indicating more iron sulphides and thus higher P availability, coinciding with high coverage of duckweed (Spirodela polyrhiza (L.)) and soft hornwort (Ceratophyllum submersum L.). At KR, however, this ratio remained low and relatively unchanged (0.3 ± 0.4), indicating more efficient Fe-P binding and lower hydrophyte productivity. Trends in sediment composition indicate a shift towards eutrophication in both kettle holes, but with differences in timing and magnitude. Other morphologically similar kettle holes in NE Germany that are prone to erosion could have been similarly impacted but may differ in the extent of sediment infilling and degradation of their ecological functions. PMID:26695416

  17. Quality and Distribution of Frozen Organic Matter (Old, Deep, Fossil Carbon) in Siberian Permafrost

    NASA Astrophysics Data System (ADS)

    Schirrmeister, Lutz; Strauss, Jens; Wetterich, Sebastian; Grosse, Guido; Overduin, Pier Paul

    2013-04-01

    Permafrost deposits constitute a large organic carbon (OC) pool vulnerable to degradation and potential carbon release due to global warming. Permafrost sections along coastal and river bank exposures and subsea cores in northeastern Siberia were studied for organic matter (OM) characteristics and ice content. OM stored in Quaternary permafrost grew, accumulated, froze, partly decomposed, and refroze under different periglacial environments, reflected in specific biogeochemical and cryolithological features. For the studied individual strata (Saalian ice-rich deposits, Pre-Eemian floodplain, Eemian lake deposits, Early to Middle Weichselian fluvial deposits, Middle Weichselian Yedoma, Late Weichselian Yedoma , Taberites, Holocene cover, Holocene thermokarst, Holocene thermoerosional valley and submerged lagoon and fluvial deposits) OM accumulation, preservation, and distribution are strongly linked to a broad variety of paleoenvironmental factors and specific surface and subsurface conditions before inclusion of OM into the permafrost. OM in permafrost includes twigs, leaves, peat, grass roots, plant detritus, and particulate and dissolved OM. The vertical distribution of total OC (TOC) in exposures varies from 0.1 wt % of the dry sediment in fluvial deposits to 45 wt % in Holocene peats. High TOC, high C/N, and low d13C reflect less decomposed OM accumulated under wet, anaerobic soil conditions characteristic of interglacial and interstadial periods. Glacial and stadial periods are characterized by less variable, low TOC, low C/N, and high d13C values indicating stable environments with reduced bioproductivity and stronger OM decomposition under dryer, aerobic soil conditions. Based on TOC data and updated information on bulk densities, we estimate average OC inventories for different stratigraphic units in northeastern Siberia, ranging from 7 kg C/m³ for Early Weichselian fluvial deposits, to 33 kg C/m³ for Middle Weichselian Yedoma deposits, to 75 kg C/m³ for

  18. Geophysical characterization of permafrost terrain at Iqaluit International Airport, Nunavut

    NASA Astrophysics Data System (ADS)

    Oldenborger, Greg A.; LeBlanc, Anne-Marie

    2015-12-01

    Iqaluit International Airport presently suffers from instabilities and subsidence along its runway, taxiways and apron. In particular, asphalt surfaces are significantly impacted by settlement and cracking. These instabilities may be related to permafrost, permafrost degradation and associated drainage conditions. Low induction number electromagnetic measurements along with galvanic and capacitive electrical resistivity surveys were performed over selected areas within the airport boundary and in the near vicinity to assist with permafrost characterization and to investigate active permafrost processes. Electrical resistivity images suggest distinct electrical signatures for different terrain units and sediment types, and for ice-rich material including ice wedges. Anomalous regions are identified that are coincident with localized settlement problems. Repeated resistivity maps reveal seasonal changes indicative of high unfrozen water content and freeze/thaw of groundwater beneath airport infrastructure in distinct regions related to surficial geology. Even with continuous permafrost and cold permafrost temperatures, the resistivity models reveal anomalously conductive material at depth that is not obviously correlated to mapped surficial sediments and that may represent thaw susceptible sediments or significant unfrozen water content.

  19. Permafrost aggradation in recently deglaciated alpine environments

    NASA Astrophysics Data System (ADS)

    Leopold, Matthias; Dusik, Jana; Stocker-Waldhuber, Martin; Völkel, Jörg; Becht, Michael

    2015-04-01

    Permafrost degradation is of major interest in the present discussion about alpine climate change and natural hazard prevention. Glacial retreat since the Little Ice Age (LIA) is followed by destabilisation of the surrounding mountains due to melting permafrost in bedrock and sediments. Glacial retreat also exposes huge areas of lateral and ground moraines. Areas of formerly temperate glaciers experience colder temperatures only since their ice cover has melted and basal meltwater no longer heats the ground. With a huge pore volume in the sediment body, water supply during the melt season and large daily temperature variations in high mountains, distinct freeze and thaw processes start and generate periglacial forms like patterned ground in the direct glacier forefield. Those geomorphic features are precursors for possible permafrost aggradation in proglacial areas. The work presented is part of the joint project PROSA (High-resolution measurements of morphodynamics in rapidly changing PROglacial Systems of the Alps) that aims in the quantification of a sediment budget for the upper Kaunertal valley, Austrian Central Alps. In this sense and to find out about erosion causing prerequisites and processes, permafrost and ground ice occurrence, as well as sediment thickness is measured by i.a. application of geophysical measurements, multitemporal airborne and terrestrial LiDAR, as well as aerial photographs. In this case study we examine the spatial and temporal settings for permafrost aggradation in a recently deglaciated cirque, belonging to the catchment area of the Gepatschferner glacier using electric resistivity tomography (ERT) and basal temperature of the winterly snowcover (BTS) measurements to detect the state of the permafrost, multitemporal aerial photographs dating back to 1953 to reproduce recent deglaciation of the cirque and multitemporal airborne LiDAR data to gain information about surface elevation changes. The northeast facing cirque is situated in

  20. Effects of permafrost aggradation on peat properties as determined from a pan-Arctic synthesis of plant macrofossils

    NASA Astrophysics Data System (ADS)

    Treat, C. C.; Jones, M. C.; Camill, P.; Gallego-Sala, A.; Garneau, M.; Harden, J. W.; Hugelius, G.; Klein, E. S.; Kokfelt, U.; Kuhry, P.; Loisel, J.; Mathijssen, P. J. H.; O'Donnell, J. A.; Oksanen, P. O.; Ronkainen, T. M.; Sannel, A. B. K.; Talbot, J.; Tarnocai, C.; Väliranta, M.

    2016-01-01

    Permafrost dynamics play an important role in high-latitude peatland carbon balance and are key to understanding the future response of soil carbon stocks. Permafrost aggradation can control the magnitude of the carbon feedback in peatlands through effects on peat properties. We compiled peatland plant macrofossil records for the northern permafrost zone (515 cores from 280 sites) and classified samples by vegetation type and environmental class (fen, bog, tundra and boreal permafrost, and thawed permafrost). We examined differences in peat properties (bulk density, carbon (C), nitrogen (N) and organic matter content, and C/N ratio) and C accumulation rates among vegetation types and environmental classes. Consequences of permafrost aggradation differed between boreal and tundra biomes, including differences in vegetation composition, C/N ratios, and N content. The vegetation composition of tundra permafrost peatlands was similar to permafrost-free fens, while boreal permafrost peatlands more closely resembled permafrost-free bogs. Nitrogen content in boreal permafrost and thawed permafrost peatlands was significantly lower than in permafrost-free bogs despite similar vegetation types (0.9% versus 1.5% N). Median long-term C accumulation rates were higher in fens (23 g C m-2 yr-1) than in permafrost-free bogs (18 g C m-2 yr-1) and were lowest in boreal permafrost peatlands (14 g C m-2 yr-1). The plant macrofossil record demonstrated transitions from fens to bogs to permafrost peatlands, bogs to fens, permafrost aggradation within fens, and permafrost thaw and reaggradation. Using data synthesis, we have identified predominant peatland successional pathways, changes in vegetation type, peat properties, and C accumulation rates associated with permafrost aggradation.

  1. Effects of permafrost aggradation on peat properties as determined from a pan-Arctic synthesis of plant macrofossils

    USGS Publications Warehouse

    Treat, C.C.; Jones, Miriam C.; Camill, P.; Gallego-Sala, A.; Garneau, M.; Harden, Jennifer W.; Hugelius, G.; Klein, E.S.; Kokfelt, U.; Kuhry, P.; Loisel, J.; Mathijssen, J.H.; O'Donnell, J.A.; Oksanen, P.O.; Ronkainen, T.M.; Sannel, A.B.K.; Talbot, J. J.; Tarnocal, C.M.; Valiranta, M.

    2016-01-01

    Permafrost dynamics play an important role in high-latitude peatland carbon balance and are key to understanding the future response of soil carbon stocks. Permafrost aggradation can control the magnitude of the carbon feedback in peatlands through effects on peat properties. We compiled peatland plant macrofossil records for the northern permafrost zone (515 cores from 280 sites) and classified samples by vegetation type and environmental class (fen, bog, tundra and boreal permafrost, and thawed permafrost). We examined differences in peat properties (bulk density, carbon (C), nitrogen (N) and organic matter content, and C/N ratio) and C accumulation rates among vegetation types and environmental classes. Consequences of permafrost aggradation differed between boreal and tundra biomes, including differences in vegetation composition, C/N ratios, and N content. The vegetation composition of tundra permafrost peatlands was similar to permafrost-free fens, while boreal permafrost peatlands more closely resembled permafrost-free bogs. Nitrogen content in boreal permafrost and thawed permafrost peatlands was significantly lower than in permafrost-free bogs despite similar vegetation types (0.9% versus 1.5% N). Median long-term C accumulation rates were higher in fens (23 g C m−2 yr−1) than in permafrost-free bogs (18 g C m−2 yr−1) and were lowest in boreal permafrost peatlands (14 g C m−2 yr−1). The plant macrofossil record demonstrated transitions from fens to bogs to permafrost peatlands, bogs to fens, permafrost aggradation within fens, and permafrost thaw and reaggradation. Using data synthesis, we have identified predominant peatland successional pathways, changes in vegetation type, peat properties, and C accumulation rates associated with permafrost aggradation.

  2. An Ocean Sediment Core-Top Calibration of Foraminiferal (Cibicides) Stable Carbon Isotope Ratios

    NASA Astrophysics Data System (ADS)

    Schmittner, A.; Mix, A. C.; Lisiecki, L. E.; Peterson, C.; Mackensen, A.; Cartapanis, O. A.

    2015-12-01

    Stable carbon isotope ratios (δ13C) measured on calcium carbonate shells of benthic foraminifera (cibicides) from late Holocene sediments (δ13CCib) are compiled and compared with newly updated datasets of contemporary water-column δ13C observations of dissolved inorganic carbon (δ13CDIC) as the initial core-top calibration of the international Ocean Circulation and CarbonCycling (OC3) project. Using selection criteria based on the spatial distance between samples we find high correlation between δ13CCib and natural (pre-industrial) δ13CDIC, confirming earlier work. However, our analysis reveals systematic differences such as higher (lower) δ13CCib values in the Atlantic (Indian and Pacific) oceans. Regression analyses are impacted by anthropogenic carbon and suggest significant carbonate ion, temperature, and pressure effects, consistent with lab experiments with planktonic foraminifera and theory. The estimated standard error of core-top sediment data is generally σ ~= 0.25 ‰, whereas modern foram data from the South Atlantic indicate larger errors (σ ~= 0.4 ‰).

  3. Phosphorus in foraminiferal sediments from North Atlantic Ridge cores and in pure limestones

    NASA Technical Reports Server (NTRS)

    Sherwood, B. A.; Sager, S. L.; Holland, H. D.

    1987-01-01

    Samples of foraminiferal ooze from two North Atlantic cores were cleaned and progressively dissolved. Most of the P, Fe, and Mn was released during the first of two reductive cleaning steps. Most of the remainder of these elements and most of the Ca were released during the final acid dissolution step. The P in these samples is present largely in Fe- and Mn-rich coatings, not as a constituent of the foraminiferal shells themselves. Our results are consistent with those of earlier studies. The concentration of P in carbonate oozes in which it is clearly associated with coatings is similar to that of modern calcareous sediments in general, and with that of reasonably pure limestones of all ages. Phosphorus is apparently associated with (Fe, Mn)-oxide coatings in many carbonate sediments. The rate of removal of P from the oceans as a constituent of such sediments depends on the rate of formation of (Fe, Mn) coatings, not on the rate of incorporation of P into calcium carbonate.

  4. Vertical distribution and indications of lipids biomarkers in the sediment core from East China Sea

    NASA Astrophysics Data System (ADS)

    Wang, Rui; Wang, Jiangtao; Li, Feng; Yang, Shu; Tan, Liju

    2016-07-01

    To study the distribution and indications of lipids biomarkers in the mud areas of the East China Sea shelf, a sediment core was collected. Lipids were determined to find the origination of different organic matter (fatty acids and sterols) inputs. The results demonstrated that the distribution of fatty acids and sterols indicated the organic matter derived from the mixed allochthonous and autochthonous sources, but mainly autochthonous. The total fatty acids concentrations ranged from 29.08 μg g-1 to 303.92 μg g-1 and exhibited unimodal distribution with the predominance of C16-fatty acid. Neutral lipid concentrations ranged from 1.77 μg g-1 to 4.65 μg g-1. Furthermore, the distribution patterns of sterols varied with depth, and were dominated by C27-sterol and C29-sterol in the top and bottom sediments respectively. Although bacterial lipids were recruited during diagenesis, the refractory terrestrial lipids were usually preferentially preserved. This records dated from the 1980s suggested that the phytoplankton community was mainly influenced by eutrophication in the East China Sea and this variation may be recorded by lipid biomarkers deposited in the sediment.

  5. Promise and Pitfalls of Using Grain Size Analysis to Identify Glacial Sediments in Alpine Lake Cores.

    NASA Astrophysics Data System (ADS)

    Clark, D. H.

    2011-12-01

    Lakes fed by glacier outwash should have a clastic particle-size record distinct from non-glacial lakes in the same area, but do they? The unique turquoise color of alpine glacial lakes reflects the flux of suspended clastic glacial rock flour to those lakes; conversely, lakes not fed by outwash are generally clear with sediments dominated by organics or slope-wash from nearby hillslopes. This contrast in sediment types and sources should produce a distinct and measureable different in grain sizes between the two settings. Results from a variety of lakes suggest the actual situation is often more subtle and complex. I compare grain size results to other proxies to assess the value of grain size analysis for paleoglacier studies. Over the past 10 years, my colleagues and I have collected and analyzed sediment cores from a wide variety of lakes below small alpine glaciers in an attempt to constrain the timing and magnitude of alpine glaciation in those basins. The basic concept is that these lakes act as continuous catchments for any rock flour produced upstream by glacier abrasion; as a glacier grows, the flux of rock flour to the lake will also increase. If the glacier disappears entirely, rock flour deposition will also cease in short order. We have focused our research in basins with simple sedimentologic settings: mostly small, high-altitude, stripped granitic or metamorphic cirques in which the cirque glaciers are the primary source of clastic sediments. In most cases, the lakes are fed by meltwater from a modern glacier, but were ice free during the earlier Holocene. In such cases, the lake cores should record formation of and changes in activity of the glacier upstream. We used a Malvern Mastersizer 2000 laser particle size analyzer for our grain size analyses, as well as recording magnetic susceptibility, color, and organics for the same cores. The results indicate that although lakes often experience increases in silt and clay-size (<0.63 mm) clastic

  6. Submerged terrestrial landscapes in the Baltic Sea: Evidence from multiproxy analyses of sediment cores from Fehmarnbelt

    NASA Astrophysics Data System (ADS)

    Enters, Dirk; Wolters, Steffen; Blume, Katharina; Segschneider, Martin; Lücke, Andreas; Theuerkauf, Martin; Hübener, Thomas

    2016-04-01

    Five sediment cores were taken from the southern part of the Fehmarn Belt (Baltic Sea) in the context of an environmental impact study for the intended fixed traverse between Germany and Denmark. The lithologies of the 8m long cores reveal dramatic changes in sedimentary environments which reflect the early Holocene history of the southern Baltic Sea. A succession of terrestrial, semiterrestrial and limnic facies from glacial sediments to peat, lacustrine/estuarine deposits and finally marine sediments document the interplay of eustatic sea level rise and isostatic rebound, which finally lead to the establishment of marine conditions during the Littorina transgression. An age control of the observed changes was established by dating over 50 C-14 samples of different fractions. During the Lateglacial minerogenic varves with thicknesses of several centimeters verify the existence of a proglacial lake in the Fehmarnbelt. Peat development started around 11.250 cal. BP and terminated ca. 10.600 cal. BP which is roughly contemporaneous with the end of the Yoldia Phase in the central Baltic Sea. The oldest peat layers consist of undecomposed sedges and reed. Woody remains of willows appear not before 10.700 cal BP and indicate a stagnant or slowly decreasing water table. This semi-terrestrial phase is followed by a shallow inland lake which existed until the Littorina transgression around 8.300 cal. BP. Initially the lacustrine sediments exhibit high C/N ratios, low low δ13Corg values and contain numerous wood fragments as well as other botanical macro remains. This indicates shallow conditions close to the lake shore. Later, the occurrence of planktonic diatom species such as Aulacoseira ambigua suggest greater water depths. We did not find any indications of the often postulated catastrophic outburst of the Ancylus Lake via Fehmarnbelt and the Great Belt into the North Sea. Likewise, XRF scanning does not show conspicuous peaks in Ti or K which would have been

  7. Disequilibrium between [sup 226]Ra and supported [sup 210]Pb in a sediment core from a shallow Florida lake

    SciTech Connect

    Brenner, M.; Peplov, A.J.; Schelske, C.L. )

    1994-07-01

    [sup 210]Pb dating can be used to assign ages in lake sediment cores, calculate rates of sediment accumulation, and determine the timing of recent changes in lake-watershed ecosystems. We used low-background gamma counting to measure [sup 226]Ra and total [sup 210]Pb activity in a core from Lake Rowell, Florida. [sup 226]Ra activity was high and strongly variable throughout the core, even exceeding total [sup 210]Pb activity in recently deposited sediments. We traced one source of Ra-rich sediments to the only inflow, Alligator Creek, where stream-bottom deposits display disequilibrium between [sup 226]Ra and supported [sup 210]Pb. High and variable [sup 226]Ra activity in the Lake Rowell profile argues for direct estimates of in situ Ra in lake sediment cores from disturbed watersheds that have Ra-bearing bedrock. Isotopic disequilibrium between [sup 226]Ra and supported [sup 210]Pb makes it difficult to distinguish between supported and unsupported [sup 210]Pb activity throughout the Lake Rowell core and would require special assumptions and nonconventional dating models to establish age-depth relationships. 78 refs., 3 figs., 1 tab.

  8. Age and spatial distribution of Holocene permafrost in Norway - model results and implications for glacier-permafrost interaction

    NASA Astrophysics Data System (ADS)

    Lilleoren, K. S.; Etzelmuller, B.; Gisnås, K.; Humlum, O.

    2011-12-01

    Following the last glaciation, cryogenic processes related to valley and cirque glaciers, permafrost and seasonal frost have dominated the Norwegian landscape development in high-mountain environments. This is evident by different landscape and landform features, like rock glaciers, block fields, palsas, ice-wedge polygons and ice-cored moraines. For Scandinavia the present regional distribution of mountain permafrost is reasonably well known, both through ground temperature measurements in boreholes, geophysical soundings and spatial modelling exercises. An important question in this context is the dynamics of permafrost during the Holocene, as a major factor for landscape development and geomorphological processes in high mountain areas of Scandinavia. In the present study mean annual air temperature deviation curves through Holocene have been compiled to drive a 1D heat flow model over the last 10 ka period for several mountain sites in Norway. At each site temperature-monitored boreholes were used to calibrate the model. Both an annual run and a seasonal run including monthly temperature variations were performed for each site. In addition the spatial distribution of permafrost during selected time periods of the Holocene were addressed using an equilibrium permafrost model on a 1*1 km resolution. The results of this study indicate an altitudinal zonation of relative permafrost age in Norway, where permafrost has existed continuously since the deglaciation in the highest areas, while large areas that is underlain by permafrost today were degraded during the Holocene Thermal Maximum (HTM). In all boreholes the deepest simulated permafrost occurred during the Little Ice Age (LIA), and also the largest areal distribution of Holocene permafrost in Norway is connected to the LIA. In addition, there exist a clear connection between the distribution of permafrost and presence of blockfields. These findings have several implications, such as for the subglacial

  9. Intra-permafrost water and hydrological chronology; a case study of aufeis and spring hydrology in continuous permafrost regions

    NASA Astrophysics Data System (ADS)

    Yoshikawa, K.; Romanovsky, V.; Hinzman, L.; Zheleznyak, M.; Romanovsky, N.; Buldovich, S.

    2006-12-01

    The purpose of this study is to identify and characterize groundwater infiltration and discharge processes in continuous permafrost regions between the Lena River in Siberia and the Mackenzie River in Canada. The source and heat content of the intra-, or sub- permafrost groundwater is being studied. Intra permafrost (30- 40m below ground surface) taliks, which serve as groundwater reservoirs, are widely observed in the cold continuous permafrost regions of Siberia, Alaska and Canada. These talik formations are often located at favorable sites in glacial outwash or sandy flood plains. The areas have densely-distributed closed system pingos and/or alas formations, which are useful to understand the subsurface talik environments. Stable isotope results from these alas lakes provide indications of aquifer connections to the intra-, or sub- permafrost groundwater. Radio active isotopes (36Cl, 14C, 3H, and 129I), stable isotopes (18O, 2H, 13C, 87/86Sr), chemical compositions and discharge measurements were used to detect areas of infiltration of surface water, residence time and bedrock interactions. The residence time of the groundwater was determined to be several months to several decades depending on study site. The same infiltration process was observed for the last 20 years in the headwaters of the Mackenzie River. The preliminary results show a large amount of the groundwater could be held in storage in the intra permafrost talik layers. Talik permeability is an important parameter for an existing aquifer system in cold permafrost. Conclusions from this study were that the perennial intra permafrost groundwater has four different types of flow: 1) sub-alas talik network flow in sandy sediments, 2) relict stream talik flow, 3) relict aquifer flow systems in glaciated areas, and 4) limestone related bedrock controlled flow systems. Each of these flow paths plays a critical role in aufeis and spring formations in permafrost-dominated watersheds. This study presents

  10. Response of Benthic Foraminiferal Size to Oxygen Concentration in Antarctic Sediment Cores

    NASA Astrophysics Data System (ADS)

    Guo, D.; Keating-Bitonti, C.; Payne, J.

    2014-12-01

    Oxygen availability is important for biological reactions and the demand of oxygen is determined by the size of the organism. Few marine organisms can tolerate low oxygen conditions, but benthic foraminifera, a group of amoeboid protists that are highly sensitive to environmental factors, are known to live in these conditions. Benthic foraminifera may be able to live in oxygen stressed environments by changing the size and shape of their test. Low oxygen concentrations should favor smaller, thinner-shelled, flattened test morphologies. We hypothesize that the volume-to-surface area ratio of benthic foraminifera will decrease with decreasing dissolved oxygen concentrations. To test this hypothesis, we picked two calcareous species (Epistominella exigua and Cassulinoides porrectus) and one agglutinated species (Portatrochammina antarctica) from three sediment cores collected from Explorer's Cove, Antarctica. Starting at the sediment-water interface, each core spans approximately 5-8 cm of depth. Profiles of dissolved oxygen concentrations were measured at the time of collection. At specific depths within the cores, we measured the three dimensions of picked foraminiferal tests using NIS-Elements. We calculated the volume and surface area of the tests assuming the shape of the foraminifers was an ellipsoid. The size trends of E. exigua confirm our hypothesis that the test volume-to-surface area ratios correlate positively with dissolved oxygen concentrations (p-value < 0.001). However, the size trends of the other species refute our hypothesis: P. antarctica shows no correlation and C. porrectus shows a negative correlation (p-value < 0.001) to dissolved oxygen concentrations. Thus, our results show that the change in size in response to variations in dissolved oxygen concentrations is species dependent. Moreover, we find that calcareous species are more sensitive to oxygen fluctuations than agglutinated species.

  11. Possible Recording of the Hilina Pali Excursion in Cored Tyrrhenian Sea Sediment

    NASA Astrophysics Data System (ADS)

    Iorio, Marina; Liddicoat, Joseph; Sagnotti, Leonardo; Incoronato, Alberto; de Anteriis, Giovanni; Insinga, Donatella; Angelino, Antimo

    2013-04-01

    First encountered in marine sediment cored from the Gulf of Mexico (19.5˚ N, 267.0˚ E)(Clark and Kennett, 1973), the Hilina Pali Excursion (HPE) is named for a locality in Hawaii (19.5˚ N, 205.0˚ E) where inclination of about negative 40˚ is documented in cored basalt (Teanby et al., 2002). Prior to naming the excursion, Coe et al. (1978) also found shallow inclination in basalt from Kilauea Volcano (19.2˚ N, 204.7˚ E) that is dated at about 18,000 yrs B.P. (uncorrected Carbon-14, Rubin and Berthold, 1961) - the age now assigned to the HPE - and was erupted when the field intensity was reduced to nearly half the present intensity. More recently, the HPE was located at Changbaishan Volcano in northeastern China (40.2˚ N, 128.0˚ E) where the age is established by Ar40/Ar39 dates (Singer et al., 2011). In exposed lake sediments in the Mono Basin, CA (38.0˚ N, 240.8˚ E), shallow positive inclination at about 18,000 yrs B.P. might also be the HPE. In the Mono Basin, normalized (NRM/ARM) intensity is reduced at that time (Zimmerman et al., 2006), and the Virtual Geomagnetic Poles (VGPs) during the reduced intensity form a clockwise trending loop when followed from old to young that descends to 53.8˚ N, 22.7˚ E (n = 6, Alpha-95 = 2.3˚) and is centered at about 50˚ N, 30˚ E (Coe and Liddicoat, 2012). There is a possible excursion of the palaeomagnetic field recorded in marine sediment at a locality in the Tyrrhenian Sea about 25 km south of Ischia (40.5˚ N, 13.7˚ E). The excursion is in sediment from two core segments that span about 22,000-18,000 yrs B.P. (de Alteriis et al., 2010) and occurs as reduced positive inclination (about 50˚) at about 20,000 yrs B.P. that increases to about 80˚ at about 18,000 yrs B.P. when declination changes from west to east. This pattern of field behaviour is similar to the behaviour of the possible HPE in the Mono Basin (Coe and Liddicoat, 2012) and in sediment cored from Lac du Bouchet, FR (44.9˚ N, 3.8˚ E) that is

  12. Elevated dissolved organic carbon biodegradability from thawing and collapsing permafrost

    NASA Astrophysics Data System (ADS)

    Abbott, Benjamin W.; Larouche, Julia R.; Jones, Jeremy B.; Bowden, William B.; Balser, Andrew W.

    2014-10-01

    As high latitudes warm, a portion of the large organic carbon pool stored in permafrost will become available for transport to aquatic ecosystems as dissolved organic carbon (DOC). If permafrost DOC is biodegradable, much will be mineralized to the atmosphere in freshwater systems before reaching the ocean, accelerating carbon transfer from permafrost to the atmosphere, whereas if recalcitrant, it will reach marine ecosystems where it may persist over long time periods. We measured biodegradable DOC (BDOC) in water flowing from collapsing permafrost (thermokarst) on the North Slope of Alaska and tested the role of DOC chemical composition and nutrient concentration in determining biodegradability. DOC from collapsing permafrost was some of the most biodegradable reported in natural systems. However, elevated BDOC only persisted during active permafrost degradation, with a return to predisturbance levels once thermokarst features stabilized. Biodegradability was correlated with background nutrient concentration, but nutrient addition did not increase overall BDOC, suggesting that chemical composition may be a more important control on DOC processing. Despite its high biodegradability, permafrost DOC showed evidence of substantial previous microbial processing, and we present four hypotheses explaining this incongruity. Because thermokarst features form preferentially on river banks and lake shores and can remain active for decades, thermokarst may be the dominant short-term mechanism delivering sediment, nutrients, and biodegradable organic matter to aquatic systems as the Arctic warms.

  13. Iron Fertilization in the Southern Ocean Deduced From Environmental Magnetism of Sediment Cores

    NASA Astrophysics Data System (ADS)

    Yamazaki, T.; Ikehara, M.

    2012-12-01

    With rock-magnetic technique, biogenic magnetites in sediments can be detected utilizing the characteristics of almost no magnetostatic interactions and narrow coercivity distribution, reflecting occurrence of single-domain magnetites in a chain (e.g., Egli et al., 2010; Roberts et al., 2011). Magnetic mineral assemblages in pelagic sediments of Pacific and Indian Oceans often have two distinctive constituents; the first is characterized by non-interacting on first-order reversal curve (FORC) diagrams and low-coercivity (~40 mT) with small dispersion on isothermal remanent magnetization (IRM) component analyses, and the second is characterized by interacting and middle-coercivity (~100 mT). The former is interpreted as biogenic magnetites and the latter is terrigenous maghemites (Yamazaki, 2009; 2012). The ratio of anhysteretic remanent magnetization susceptibility to saturation IRM reflects relative abundance of the biogenic and terrigenous components. In the Southern Ocean, magnetic mineral concentration increases in glacial periods. The variation pattern closely resembles eolian dust flux records from Antarctic ice cores, but the cause of the linkage was unclear, as the dust flux is too small for the source of terrigenous materials in the Southern Ocean. Our environmental magnetic study of late Pleistocene sediments from the south Indian Ocean revealed that biogenic magnetites are a dominant constituent of the magnetic minerals. In glacials, the abundance of both biogenic and terrigenous components increased with increased proportions of the latter. Increased ocean productivity in glacials is suggested from increased proportions of biogenic magnetites with elongated morphologies, indicative of less-oxic conditions, and increased sedimentation rates. These observations suggest that the increased magnetic concentration in glacials in the Southern Ocean may be explained by iron fertilization; the production of biogenic magnetites was enhanced associated with

  14. Microbial population, activity, and phylogenetic diversity in the subseafloor core sediment from the Sea of Okhotsk

    NASA Astrophysics Data System (ADS)

    Inagaki, F.; Suzuki, M.; Takai, K.; Nealson, K. H.; Horikoshi, K.

    2002-12-01

    Subseafloor environments has already been recognized as the largest biosphere on the planet Earth, however, the microbial diversity and activity has been still poorly understood, even in their impacts on biogeochemical processes, tectonic settings, and paleoenvironmental events. We demonstrate here the evaluation of microbial community structure and active habitats in deeply buried cold marine sediments collected from the Sea of Okhotsk by a combined use of molecular ecological surveys and culturing assays. The piston core sediment (MD01-2412) was collected by IMAGES (International Marine Global Change Study) Project from the southeastern Okhotsk Sea, June 2001. The total recovered length was about 58m. The lithology of the core sediment was mainly constructed from pelagic clay (PC) and volcanic ash layers (Ash). We collected aseptically the most inside core parts from 16 sections at different depths for microbiological study. The direct count of DAPI-stained cells revealed that the cells in Ash samples were present 1.2 to 2.2 times higher than in PC samples. The quantitative-PCR of 16S rDNA between bacterial and archaeal rDNA suggested that the increased population density in Ash layers was caused by the bacterial components. We studied approximately 650 and 550 sequences from bacterial and archaeal rDNA clone libraries, respectively. The similarity and phylogenetic analyses revealed that the microbial community structures were apparently different between in Ash layers and PC samples. From bacterial rDNA clone libraries, the members within gamma-Proteobacteria such as genera Halomonas, Shewanella, Psychromonas and Methylosinus were predominantly detected in Ash layers whereas the Dehalococcoides group and delta-Proteobacteria were major bacterial components in PC samples. From archaeal libraries, the sequences from Ash and PC samples were affiliated into the clusters represented by the environmental sequences obtained from terrestrial and deep-sea environments

  15. Permafrost: An International Approach to 21th Century Challenges

    NASA Astrophysics Data System (ADS)

    Brown, J.

    2003-12-01

    Whereas glaciers are easily discernible to the human eye and satellites, permafrost terrains and their physical components are not easily detected from the surface without supplemental knowledge and measurements. In the Northern Hemisphere, approximately 17 million km2 of exposed land contains some extent of permafrost or ground that remains frozen for more than two years. The vast majority, or 11 million km2, of permafrost terrain has temperatures of 5° C or below, with perennially frozen ground underlying essentially all ground surfaces to considerable depths. Permafrost in the remaining regions, including mid-latitude mountains, is both warmer and is spatially variable (discontinuous). As climate warms the uppermost permafrost is subjected to increase thaw with resulting ground subsidence, accelerated erosion, and related biogeochemical modifications. The challenging questions to geocryologists, modelers and the public relate to the rate of change and the spatial variability of the projected thaw, particularly in the warmer zones where actual areal and subareal distribution of permafrost is poorly known. An international network of active layer measurements and borehole sites now exists under the Global Climate Observing System (GCOS), but requires additional sites for representative coverage. This Global Terrestrial Network for Permafrost (GTN-P) is coordinated by the 24-member, International Permafrost Association. At the Eighth International Conference on Permafrost (ICOP) in Zurich in July 2003, the IPA Council agreed on the scope of new activities for the next five years, many of which will be undertaken in cooperation with other international organizations (e.g. WCRP/CliC; ICSI, IASC, SCAR, IGU, IUGS). Examples of the activities of the IPA Working Groups are: 1. Antarctic Permafrost and Periglacial Environments (active layer processes, maps, database). 2. Coastal and Offshore Permafrost (sediment and organic transfers, subsea permafrost dynamics). 3

  16. GlobPermafrost - how space supports understanding of permafrost?

    NASA Astrophysics Data System (ADS)

    Bartsch, Annett; Grosse, Guido; Kääb, Andreas; Westermann, Sebastian; Strozzi, Tazio; Wiesmann, Andreas; Duguay, Claude; Seifert, Frank Martin

    2016-04-01

    The GlobPermafrost project (2016-2019) develops, validates and implements information products to support the research communities and related international organisations like IPA and CliC in their work on understanding permafrost better by integration of EO data. Permafrost cannot be directly detected from space, but many surface features of permafrost terrains and typical periglacial landforms are observable with a variety of EO sensors ranging from very high to medium resolution in various wavelengths. Prototype cases will cover different aspects of permafrost by integrating in situ measurements of subsurface permafrost properties (active layer depth, active layer and permafrost temperatures, organic layer thickness, liquid water content in the active layer and permafrost), surface properties (vegetation cover, snow depth)and modelling to provide a better understanding of permafrost today. The techniques will extend point source process and permafrost monitoring to a broader spatial domain, to support permafrost distribution modelling and mapping techniques implemented in a GIS framework and will complement active layer and thermal observing networks. Initial user requirements have been gathered at the DUE-IPA-GTNP-CliC workshop in Frascati in February 2014, which have been further consolidated within the Permafrost community during 2014 in request of the WMO Polar Space Task Group. A subset of these requirements will be demonstrated within GlobPermafrost and assessed by user organisations: -Circumpolar permafrost extend -Permafrost dedicated land cover class prototype -Local investigations around long term monitoring sites -Regional transects for "hot spot" identification -Mountain permafrost areas The initial observation scenario is presented, discussing challenges in methods as well as data availability.

  17. The International Permafrost Association: current initiatives for cryospheric research

    NASA Astrophysics Data System (ADS)

    Schollaen, Karina; Lewkowicz, Antoni G.; Christiansen, Hanne H.; Romanovsky, Vladimir E.; Lantuit, Hugues; Schrott, Lothar; Sergeev, Dimitry; Wei, Ma

    2015-04-01

    The International Permafrost Association (IPA), founded in 1983, has as its objectives to foster the dissemination of knowledge concerning permafrost and to promote cooperation among persons and national or international organizations engaged in scientific investigation and engineering work on permafrost. The IPA's primary responsibilities are convening International Permafrost Conferences, undertaking special projects such as preparing databases, maps, bibliographies, and glossaries, and coordinating international field programs and networks. Membership is through adhering national or multinational organizations or as individuals in countries where no Adhering Body exists. The IPA is governed by its Executive Committee and a Council consisting of representatives from 26 Adhering Bodies having interests in some aspect of theoretical, basic and applied frozen ground research, including permafrost, seasonal frost, artificial freezing and periglacial phenomena. This presentation details the IPA core products, achievements and activities as well as current projects in cryospheric research. One of the most important core products is the circumpolar permafrost map. The IPA also fosters and supports the activities of the Global Terrestrial Network on Permafrost (GTN-P) sponsored by the Global Terrestrial Observing System, GTOS, and the Global Climate Observing System, GCOS, whose long-term goal is to obtain a comprehensive view of the spatial structure, trends, and variability of changes in the active layer thickness and permafrost temperature. A further important initiative of the IPA are the biannually competitively-funded Action Groups which work towards the production of well-defined products over a period of two years. Current IPA Action Groups are working on highly topical and interdisciplinary issues, such as the development of a regional Palaeo-map of Permafrost in Eurasia, the integration of multidisciplinary knowledge about the use of thermokarst and permafrost

  18. Possible recording of the Mono Lake Excursion in cored sediment from Clear Lake, California

    NASA Astrophysics Data System (ADS)

    Liddicoat, Joseph; Verosub, Kenneth

    2010-05-01

    We report the possible recording of the Mono Lake Excursion (MLE) in cored sediment from Clear Lake, CA. The locality (39.0˚N, 237.3˚E) is about 120 km north of San Francisco, CA, and 320 km northwest of the Mono Basin, CA, where the MLE first was discovered in North America (Denham and Cox, 1971). The field behaviour at Clear Lake that might be the MLE is recorded in clay and peaty clay about 50 cm below the top of the lowermost 80-cm core slug of a 21.6-m core. The coring was done by the wire-line method (Sims and Rymer, 1975) and the samples (rectangular solids 21 mm on a side and 15 mm high) were measured in a cryogenic magnetometer after demagnetization in an alternating field to 35 milliTesla (Verosub, 1977). The continuously-spaced samples record negative inclination of nearly 20˚ and northerly declination when unnormalized relative field intensity was reduced by an order of magnitude from the mean value. Those palaeomagnetic directions are followed immediately by positive inclination to about 50˚ and easterly declination of about 60˚ when the field intensity is at a relative high. That pattern of behaviour is recorded at three localities (Wilson Creek, Mill Creek, and Warm Springs) in the Mono Basin at the MLE (Liddicoat and Coe, 1979; Liddicoat, 1992). A path of the Virtual Geomagnetic Poles (VGPs) at Clear Lake form a clockwise-trending loop that is centered at 65˚N, 20˚E in the hemisphere away from the locality. The VGP that is farthest from the North Geographic Pole is at 29.3˚N, 337.1˚E, which is close to the path formed by the VGPs in the older portion of the MLE (Liddicoat and Coe, 1979; Liddicoat, 1992). The age of the sediment recording the anomalous palaeomagnetic directions in Clear Lake is about 30,000 years B.P. (Verosub, 1977). That age was determined from six (uncalibrated) radiocarbon dates, three of which are from near the base of the core (Sims and Rymer, 1975) where there are the anomalous palaeomagnetic directions, and linear

  19. Diagenetic effects on magnetic minerals in a Holocene lacustrine sediment core from Huguangyan maar lake, southeast China

    NASA Astrophysics Data System (ADS)

    Wu, Xudong; Wang, Yong; Bian, Liu; Shen, Ji

    2016-06-01

    Post-depositional reductive diagenesis usually results in partial or entire cleansing of the pristine palaeomagnetic signal, therefore, its intensity is important to be assessed for sediments that are in the purpose of retrieving palaeomagnetic information. Grain size, rock magnetic and geochemical studies on the entire core, along with scanning electron microscope (SEM) observations and X-ray diffraction (XRD) analyses for representative samples were carried out on a Holocene sediment core retrieved from the deep water part of Huguangyan maar lake (HGY), southeast China. The pristine magnetic mineral assemblage of the studied core is domianted by superparamagnetic (SP) and stable single domain (SSD) titanomagnetite, and high coercivity minerals are not detectable. Based on down-core variations of the average grain size (MZ), total organic carbon (TOC), detrital elements (Al, Ti, Fe and Mn), and the concentration and mineralogy of magnetic minerals, the studied core could be divided into three subsections. The uppermost subsection is the least affected by diagenesis, with detrital titanomagnetite as the dominant magnetic mineral. This is owing to low TOC contents, but high detrital input generated by weak Asian summer monsoon intensity during the late Holocene. The intermediate subsection shows down-core progressively enhanced dissolution of detrital titanomagnetite, and concomitant formation of authigenic pyrite and siderite, which indicates down-core progressively enhanced diagenesis generated by down-core progressive increasing TOC content, but decreasing detrital input as the result of down-core progressively strengthened Asian summer monsoon intensity. The pristine magnetic mineral assemblage has been profoundly modified in the lowermost subsection. At certain positions of the lowermost subsection, detrital titanomagnetite has been even completely dissolved via diagenesis, giving place to authigenic pyrite and siderite. High TOC content, but low detrital input

  20. Estimation of sources and inflow of dioxins and polycyclic aromatic hydrocarbons from the sediment core of Lake Suwa, Japan.

    PubMed

    Ikenaka, Yoshinori; Eun, Heesoo; Watanabe, Eiki; Kumon, Fujio; Miyabara, Yuichi

    2005-12-01

    To elucidate the historical changes in polychlorinated dibenzo-p-dioxin (PCDD), polychlorinated dibenzofuran (PCDF), coplanar polychlorinated biphenyl (co-PCB), and polycyclic aromatic hydrocarbon (PAH) inflows in Lake Suwa, their concentrations in the sediment core were analyzed in 5 cm interval. The maximum concentrations (depth cm) of PCDDs/DFs, co-PCBs, and PAHs were 25.2 ng/g dry (30-35 cm), 19.0 ng/g dry (30-35 cm), and 738, 795 ng/g dry (50-55 cm, 30-35 cm), respectively. Age and sedimentation rate of the sediment were estimated from the vertical changes in apparent density. Deposition rate of dioxins and PAHs were calculated from the concentration and sedimentation rate of the sediment. The results indicate that large amounts of dioxins and PAHs flowed into the lake in flood stage compared to normal stage. PMID:15964115

  1. Landforms indicative of former glaciations and permafrost along continental margin of the Chukchi and East Siberian seas

    NASA Astrophysics Data System (ADS)

    Niessen, F.; Matthiessen, J. J.; Stein, R. H.; Jensen, L.; Jokat, W.; Nam, S. I.

    2015-12-01

    In the western Arctic Ocean glacial landforms are interpreted as a complex pattern of Pleistocene glaciations along the continental margin of the East Siberian Sea and the Chukchi borderland. These landforms include moraines, drumlinized features, glacigenic debris flows, till wedges, mega-scale glacial lineations (MSGL), and iceberg plough marks. Orientations of some of the landforms suggest the presence of former ice sheets on the Chukchi Borderland and the East Siberian shelf. In seismic and sub-bottom profiles as well as sediment cores, there is evidence that glaciations have occurred repeatedly. Typically, several generations of glacial wedges intercalate with well-stratified (interglacial) sediments in ice-distal locations. MSGL of former ice grounding in present water depths of more than 1200 m suggests that some ice sheets developed significant thickness and size. The extent of glacial features and deposits into the Arctic Ocean decreased with time. We interpret this as indication that ice sheets in the western Arctic Ocean were thicker and larger during earlier times of the Pleistocene and became restricted to the Chukchi Borderland during the most recent glaciation (Last Glacial Maximum, LGM). Finally, icebergs intensively ploughed the sediments along the Chukchi and East Siberian margin in a range from 350m to 80m present water depth. In water depth shallower than 80m, sub-bottom profiles in the East Siberian Sea exhibit acoustic facies more typical for submarine permafrost. Discontinuous (permafrost) reflectors mask sub-bottom strata beneath an unfrozen 10m thick top sediment layer. In places, unfrozen sediment-filled depressions (taliks) are visible to about 20m below the seafloor, which may be related to former thermokarst and/or channels. We suggest that only during the LGM permafrost formed in the exposed area of the entire East Siberian Sea, whereas some areas have been largely covered by ice sheets during previous glacial periods.

  2. Concentration of Antifouling Biocides and Metals in Sediment Core Samples in the Northern Part of Hiroshima Bay

    PubMed Central

    Tsunemasa, Noritaka; Yamazaki, Hideo

    2014-01-01

    Accumulation of Ot alternative antifoulants in sediment is the focus of this research. Much research had been done on surface sediment, but in this report, the accumulation in the sediment core was studied. The Ot alternative antifoulants, Diuron, Sea-Nine211, and Irgarol 1051, and the latter’s degradation product, M1, were investigated in five samples from the northern part of Hiroshima Bay. Ot compounds (tributyltin (TBT) and triphenyltin (TPT)) were also investigated for comparison. In addition, metal (Pb, Cu, Zn, Fe and Mn) levels and chronology were measured to better understand what happens after accumulation on the sea floor. It was discovered that Ot alternative antifoulant accumulation characteristics in sediment were like Ot compounds, with the concentration in the sediment core being much higher than surface sediment. The concentration in sediment seems to have been affected by the regulation of Ot compounds in 1990, due to the concentration of Ot alternative antifoulants and Ot compounds at the survey point in front of the dock, showing an increase from almost the same layer after the regulation. PMID:24901529

  3. Paleomagnetic inclination errors in sediments cored from a Gulf of Mexico salt dome - An indicator of ancient sea level

    SciTech Connect

    Sager, W.W.; Singleton, S.W. )

    1989-08-01

    A paleomagnetic study of piston-cored sediments was done in conjunction with a high-resolution seismic reflection study of a salt dome on the upper continental slope in the northern Gulf of Mexico. Seismic data showed that late Pleistocene sediment layers are exposed around the bank and tilted up to 8{degree} by the diapiric uplift. Cores were taken on the flanks of the bank to test the use of paleomagnetism in measuring the tectonic tilt of the sediments. After structural corrections, results from six cores agreed with the geocentric axial dipole inclination for the site, but four other cores displayed significantly shallowed inclinations. Moreover, several cores showed linear trends of inclination shallowing, increasing downcore. The anomalous results are from the summit of the bank and suggest a relation to subaerial exposure during a sea-level lowstand. The authors think that the shallow inclinations were caused by compaction, but that the linear trends resulted from rehydration of the sediments after exposure by erosion.

  4. Historical tide gauge data and sediment cores put Hurricane Sandy in context

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2012-11-01

    Historical tide gauge data and sediment cores put Hurricane Sandy in context Several studies that put the recent devastating Hurricane Sandy in context were reported on 5 November at the annual meeting of the Geological Society of America in Charlotte, N. C. Stefan Talke of Portland State University explained that old tide gauge data that he and colleagues have been digitizing show that Sandy was the largest hurricane to hit New York in more than 100 years. Compared to the 1893 storm that was the largest in their records, "Hurricane Sandy was much larger, probably about twice as large, in terms of storm surge," he said. Their study is part of an effort to determine whether sea level rise is accelerating.

  5. Characterization of organic matter in a sediment Core near the Mataripe refinery, Bahia-Brazil.

    PubMed

    Costa, Alexandre Barreto; de Souza, José Roberto Bispo; Zucchi, Maria do Rosário; de Azevedo, Antonio Expedito Gomes; de Argollo, Roberto Max

    2016-04-15

    A sediment core was taken from the Todos os Santos Bay, near the Mataripe Bahia-Brazil refinery. The results of dating, (210)Pb and (137)Cs methods, combined with organic indicators, Polycyclic aromatic hydrocarbons (PAHs), n-alkanes and total organic carbon (TOC), showed significant change with the start of production of the oil fields of Aratu, Itaparica and Dom João (1939-1947) and the construction of the Mataripe refinery (1949-1950). This event was marked by a series of significant changes, including an abrupt increase in TOC and the growth of PAH concentrations and the presence Unresolved/Resolved ratio (UR/R)>4 in n-alkanes fraction, which indicated that the contamination was of petrogenic origin. The δ(13)C of specific n-alkanes compounds showed gradual deplete with the depth. PMID:26920428

  6. Well cementing in permafrost

    SciTech Connect

    Wilson, W.N.

    1980-01-01

    A process for cementing a string of pipe in the permafrost region of a borehole of a well wherein aqueous drilling fluid actually used in drilling the wellbore in the permafrost region of a wellbore is employed. The drilling fluid contains or is adjusted to contain from about 2 to about 16 volume percent solids. Mixing with the drilling fluid (1) an additive selected from the group consisting of ligno-sulfonate, lignite, tannin, and mixtures thereof, (2) sufficient base to raise the pH of the drilling fluid into the range of from about 9 to about 12, and (3) cementitious material which will harden in from about 30 to about 40 hours at 40/sup 0/F. The resulting mixture is pumped into the permafrost region of a wellbore to be cemented and allowed to harden in the wellbore. There is also provided a process for treating an aqueous drilling fluid after it has been used in drilling the wellbore in permafrost, and a cementitious composition for cementing in a permafrost region of a wellbore.

  7. Natural uranium and thorium isotopes in sediment cores off Malaysian ports

    NASA Astrophysics Data System (ADS)

    Yusoff, Abdul Hafidz; Sabuti, Asnor Azrin; Mohamed, Che Abd Rahim

    2015-06-01

    Sediment cores collected from three Malaysian marine ports, namely, Kota Kinabalu, Labuan and Klang were analyzed to determine the radioactivities of 234U, 238U, 230Th, 232Th and total organic carbon (TOC) content. The objectives of this study were to determine the factors that control the activity of uranium isotopes and identify the possible origin of uranium and thorium in these areas. The activities of 234U and 238U show high positive correlation with TOC at the middle of sediment core from Kota Kinabalu port. This result suggests that activity of uranium at Kota Kinabalu port was influenced by organic carbon. The 234U/238U value at the upper layer of Kota Kinabalu port was ≥1.14 while the ratio value at Labuan and Klang port was ≤ 1.14. These results suggest a reduction process occurred at Kota Kinabalu port where mobile U(VI) was converted to immobile U(IV) by organic carbon. Therefore, it can be concluded that the major input of uranium at Kota Kinabalu port is by sorptive uptake of authigenic uranium from the water column whereas the major inputs of uranium to Labuan and Klang port are of detrital origin. The ratio of 230Th/232Th was used to estimate the origin of thorium. Low ratio value (lt; 1.5) at Labuan and Klang ports support the suggestion that thorium from both areas were come from detrital input while the high ratio (> 1.5) of 230Th/232Th at Kota Kinabalu port suggest the anthropogenic input of 230Th to this area. The source of 230Th is probably from phosphate fertilizers used in the oil-palm cultivation in Kota Kinabalu that is adjacent to the Kota Kinabalu port.

  8. Physical and chemical characteristics of the Subglacial Lake Whillans sediment cores, Whillans Ice Stream, West Antarctica

    NASA Astrophysics Data System (ADS)

    Hodson, T. O.; Powell, R. D.

    2013-12-01

    Sediment recovered from Subglacial Lake Whillans (SLW) is well-homogenized, structureless diamict; typical subglacial till. Based on theoretical estimates, the basal ice above SLW should be below the pressure melting point preventing melt-out of debris from basal ice. Therefore, the lake floor diamict likely formed through deformation while the ice stream was grounded at the drill site. Using satellite altimetry, Fricker, et al. (2007) inferred that SLW experiences short (~7 month) discharge events, lowering the ice surface and lake water level by between 1 and 4 m. The lake 'lowstands' are separated by longer periods of gradual recharge, but over the period of a lowstand the ice stream is suspected to touch down and couple with the lake floor, potentially shearing new till into the lake. The lack of sorted sediment or erosional lags indicates water flow during discharge/recharge events has had a low current velocity with quiescent conditions in the lake. The most notable variability in the cores is a uniformly weak, critical porosity horizon extending to ~50 cm depth above more consolidated till. We interpret the weak upper horizon as the product of shear deformation and decreasing effective pressure experienced during the final stages of grounding prior to a lake recharge event (see generally, the undrained plastic bed model of Tulaczyk et al. (2000)). The presence of this weak layer illustrates the importance of hydrology in modulating till rheology and is an example of how subglacial sediments can preserve archives of hydrologic conditions at the glacial bed. Fricker, H.A., T. Scambos, R. Bindschadler and L. Padman. 2007. An active subglacial water system in West Antarctica mapped from space. Science, 315(5818), 1544-1548. Tulaczyk S, Kamb WB, Engelhardt HF. 2000. Basal mechanics of Ice Stream B, West Antarctica. 2. Undrained plastic bed model. J. Geophys. Res. 105:483-94.

  9. Major and trace elements in 35 lake and reservoir sediment cores from across the United States, 1994-2001

    USGS Publications Warehouse

    Van Metre, Peter C.; Mahler, Barbara J.; Wilson, Jennifer T.; Callender, Edward

    2006-01-01

    This report presents data on major and trace element concentrations in sediment cores collected from 35 lakes and reservoirs during 1994-2001. The lakes and reservoirs are located in or near 18 major urban areas across the United States and provide a geographically diverse coverage of urban land use for the country as well as some reference settings. Vertical intervals of the cores were analyzed for eight major elements and eight trace elements.

  10. Influence of permafrost thaw on carbon cycling and vegetation communities in a northern discontinuous permafrost peatland complex at Scotty Creek, Northwest Territories

    NASA Astrophysics Data System (ADS)

    Pelletier, N.; Olefeldt, D.; Turetsky, M. R.; Quinton, W. L.; Sonnentag, O.; Talbot, J.

    2013-12-01

    Globally, peatlands comprise an important proportion of the total belowground carbon pool. Peatlands in permafrost regions are usually considered as particularly important carbon sinks since their decomposition rate is slowed by the effects of low temperatures causing the ground to be frozen year-round. Discontinuous permafrost regions are particularly sensitive to contemporary climate changes causing rapid permafrost degradation with associated changes in land cover from forested permafrost peat plateaus to treeless, permafrost-free bogs. However, only little is known about the impact of these fundamental changes in land cover on peatland carbon cycling. Here we present an analysis based on peat cores collected in the late-winter of 2012 and summer 2013 in a discontinuous permafrost boreal forest-peatland complex located in the Northwest Territories, Canada. This site is known to show signs of rapid permafrost degradation over the last 40 years. Our results suggest that the hydrological changes that follow permafrost thaw might have a beneficial effect on carbon storage via changes in plant functional types. Pollen analyses performed on the same cores provide a comprehensive insight of the regional vegetation and fire dynamics over the Holocene period. Testate Amoebae analyses provide information in regards to local past hydrological conditions. Together, our results allow for a better understanding of the ways hydrology, vegetation and fire affect carbon cycling in a discontinuous permafrost peatland.

  11. Grain Size Analyses of Neogene-Quaternary Sediments from the Arctic Coring Expedition

    NASA Astrophysics Data System (ADS)

    Moran, K.; Lado-Insua, T.; O'Regan, M.

    2013-12-01

    The Arctic Coring Expedition (ACEX) recovered the first Cenozoic sediment sequence from the central Arctic Ocean. Results from this expedition indicate that perennial sea ice may have formed in the Arctic at or before the early mid-Miocene. Sea ice formation is an important process in the global climate system, affecting directly the Earth's albedo and indirectly the Meridional Overturning Circulation. The deep Arctic Ocean receives sediment primarily from ice-rafted debris and turbidity currents. Suspension freezing on the shallow continental shelves of the Arctic has generally been considered the major process trapping sediment within sea ice. Sea ice motion is largely driven by wind. The anticyclonic Beaufort Gyre transports sea ice over the Amerasia Basin, while the Transpolar Drift transports it across the Eurasian Basin. The Transpolar Drift is divided into a Siberian and Polar branch, both branches cross the position of the ACEX drilling sites on the Lomonosov Ridge. Grain size analyses of ACEX sediments were obtained with a Malvern Mastersizer 2000 laser diffraction particle sizing system. Preliminary analyses indicate pulses with a higher percentage of sand between 3.64 Ma ago until the end of the Gelasian (1.8 Ma). The percent sand remained relatively low during the Cenozoic with the exception of two major increases of sand occurring ~6.2 and 9.2 Ma ago and a smaller peak ~8.2 Ma ago. These intervals also show less sorting and lower values for skewness and kurtosis. Increases in the percentage of sand and less sorting at this latitude relate to ice rafted debris, indicating an increase in sea-ice melting during these periods. A Principal Components Analysis and a Maximum Correlation Factor Analysis agree on a correlation between different grain sizes that would divide the grain size in two major distributions (<19 μm and 19 μm to 2 mm) based on the sedimentation and transport mechanism. These two classes do not agree with the major divisions of sand (63

  12. The Effectiveness of L*a*b* Color Analysis in Determining the Elemental and Mineralogical Composition of Lake Sediment Cores

    NASA Astrophysics Data System (ADS)

    Dawson, S.; Lascu, I.; Myrbo, A.; Wittkop, C.

    2006-12-01

    High-resolution L*a*b color and x-ray fluorescence (XRF) elemental profiles were compared for a set of Midwestern U.S. lake sediment cores held in the National Lacustrine Core Repository. The cores all display centi- to decimeter scale light-dark banding (nicknamed "raccoon-tail banding"), determined by variations in carbonate versus organic matter content. Carbonate minerals are evidently depleted in the organic-rich strata due to carbonate dissolution in the hypolimnion and sediment column, which is the result of both external (i.e., climatic) and internal factors. XRF was performed at a resolution comparable to the L*a*b* image analysis of the core sections, which allowed the investigation of the relationship between sediment color and composition within a core. The "a" component in this image analysis is correlated with elemental iron abundance, and the "b" and "L" components are related to calcium (calcite) and organic carbon content. Overall, this study has determined that L*a*b* color analysis of high-resolution digital images is an easy and fast way to obtain preliminary information about the composition of core material. When used in conjunction with scanning XRF data, color analysis can replace lower-resolution geochemical analyses to produce sub-annual scale records of lake dynamics and responses to climate change.

  13. A carbon, nitrogen, and sulfur elemental and isotopic study in dated sediment cores from the Louisiana Shelf

    USGS Publications Warehouse

    Rosenbauer, R.J.; Swarzenski, P.W.; Kendall, C.; Orem, W.H.; Hostettler, F.D.; Rollog, M.E.

    2009-01-01

    Three sediment cores were collected off the Mississippi River delta on the Louisiana Shelf at sites that are variably influenced by recurring, summer-time water-column hypoxia and fluvial loadings. The cores, with established chronology, were analyzed for their respective carbon, nitrogen, and sulfur elemental and isotopic composition to examine variable organic matter inputs, and to assess the sediment record for possible evidence of hypoxic events. Sediment from site MRJ03-3, which is located close to the Mississippi Canyon and generally not influenced by summer-time hypoxia, is typical of marine sediment in that it contains mostly marine algae and fine-grained material from the erosion of terrestrial C4 plants. Sediment from site MRJ03-2, located closer to the mouth of the Mississippi River and at the periphery of the hypoxic zone (annual recurrence of summer-time hypoxia >50%), is similar in composition to core MRJ03-3, but exhibits more isotopic and elemental variability down-core, suggesting that this site is more directly influenced by river discharge. Site MRJ03-5 is located in an area of recurring hypoxia (annual recurrence >75%), and is isotopically and elementally distinct from the other two cores. The carbon and nitrogen isotopic composition of this core prior to 1960 is similar to average particulate organic matter from the lower Mississippi River, and approaches the composition of C3 plants. This site likely receives a greater input of local terrestrial organic matter to the sediment. After 1960 and to the present, a gradual shift to higher values of ??13C and ??15N and lower C:N ratios suggests that algal input to these shelf sediments increased as a result of increased productivity and hypoxia. The values of C:S and ??34S reflect site-specific processes that may be influenced by the higher likelihood of recurring seasonal hypoxia. In particular, the temporal variations in the C:S and ??34S down-core are likely caused by changes in the rate of

  14. Methane release from pingo-like features across the South Kara Sea shelf, an area of thawing offshore permafrost

    NASA Astrophysics Data System (ADS)

    Serov, Pavel; Portnov, Alexey; Mienert, Jurgen; Semenov, Peter; Ilatovskaya, Polina

    2015-08-01

    The Holocene marine transgression starting at ~19 ka flooded the Arctic shelves driving extensive thawing of terrestrial permafrost. It thereby promoted methanogenesis within sediments, the dissociation of gas hydrates, and the release of formerly trapped gas, with the accumulation in pressure of released methane eventually triggering blowouts through weakened zones in the overlying and thinned permafrost. Here we present a range of geophysical and chemical scenarios for the formation of pingo-like formations (PLFs) leading to potential blowouts. Specifically, we report on methane anomalies from the South Kara Sea shelf focusing on two PLFs imaged from high-resolution seismic records. A variety of geochemical methods are applied to study concentrations and types of gas, its character, and genesis. PLF 1 demonstrates ubiquitously low-methane concentrations (14.2-55.3 ppm) that are likely due to partly unfrozen sediments with an ice-saturated internal core reaching close to the seafloor. In contrast, PLF 2 reveals anomalously high-methane concentrations of >120,000 ppm where frozen sediments are completely absent. The methane in all recovered samples is of microbial and not of thermogenic origin from deep hydrocarbon sources. However, the relatively low organic matter content (0.52-1.69%) of seafloor sediments restricts extensive in situ methane production. As a consequence, we hypothesize that the high-methane concentrations at PLF 2 are due to microbial methane production and migration from a deeper source.

  15. 3D Porosity Estimation of the Nankai Trough Sediments from Core-log-seismic Integration

    NASA Astrophysics Data System (ADS)

    Park, J. O.

    2015-12-01

    The Nankai Trough off southwest Japan is one of the best subduction-zone to study megathrust earthquake fault. Historic, great megathrust earthquakes with a recurrence interval of 100-200 yr have generated strong motion and large tsunamis along the Nankai Trough subduction zone. At the Nankai Trough margin, the Philippine Sea Plate (PSP) is being subducted beneath the Eurasian Plate to the northwest at a convergence rate ~4 cm/yr. The Shikoku Basin, the northern part of the PSP, is estimated to have opened between 25 and 15 Ma by backarc spreading of the Izu-Bonin arc. The >100-km-wide Nankai accretionary wedge, which has developed landward of the trench since the Miocene, mainly consists of offscraped and underplated materials from the trough-fill turbidites and the Shikoku Basin hemipelagic sediments. Particularly, physical properties of the incoming hemipelagic sediments may be critical for seismogenic behavior of the megathrust fault. We have carried out core-log-seismic integration (CLSI) to estimate 3D acoustic impedance and porosity for the incoming sediments in the Nankai Trough. For the CLSI, we used 3D seismic reflection data, P-wave velocity and density data obtained during IODP (Integrated Ocean Drilling Program) Expeditions 322 and 333. We computed acoustic impedance depth profiles for the IODP drilling sites from P-wave velocity and density data. We constructed seismic convolution models with the acoustic impedance profiles and a source wavelet which is extracted from the seismic data, adjusting the seismic models to observed seismic traces with inversion method. As a result, we obtained 3D acoustic impedance volume and then converted it to 3D porosity volume. In general, the 3D porosities show decrease with depth. We found a porosity anomaly zone with alteration of high and low porosities seaward of the trough axis. In this talk, we will show detailed 3D porosity of the incoming sediments, and present implications of the porosity anomaly zone for the

  16. Historical trends in Chesapeake Bay dissolved oxygen based on benthic foraminifera from sediment cores

    USGS Publications Warehouse

    Karlsen, A.W.; Cronin, T. M.; Ishmans, S.E.; Willard, D.A.; Kerhin, R.; Holmes, C.W.; Marot, M.

    2000-01-01

    Environmentally sensitive benthic foraminifera (protists) from Chesapeake Bay were used as bioindicators to estimate the timing and degree of changes in dissolved oxygen (DO) over the past five centuries. Living foraminifers from 19 surface samples and fossil assemblages from 11 sediment cores dated by 210Pb, 137Cs, 14C, and pollen stratigraphy were analyzed from the tidal portions of the Patuxent, Potomac, and Choptank Rivers and the main channel of the Chesapeake Bay. Ammonia parkinsoniana, a facultative anaerobe tolerant of periodic anoxic conditions, comprises an average of 74% of modern Chesapeake foraminiferal assemblages (DO = 0.47 and 1.72 ml l-1) compared to 0% to 15% of assemblages collected in the 1960s. Paleoecological analyses show that A. parkinsoniana was absent prior to the late 17th century, increased to 10-25% relative frequency between approximately 1670-1720 and 1810-1900, and became the dominant (60-90%) benthic foraminiferal species in channel environments beginning in the early 1970s. Since the 1970s, deformed tests of A. parkinsoniana occur in all cores (10-20% of Ammonia), suggesting unprecedented stressful benthic conditions. These cores indicate that prior to the late 17th century, there was limited oxygen depletion. During the past 200 years, decadal scale variability in oxygen depletion has occurred, as dysoxic (DO = 0.1-1.0 ml l-1), perhaps short-term anoxic (DO < 0.1 ml l-1) conditions developed. The most extensive (spatially and temporally) anoxlc conditions were reached during the 1970s. Over decadal timescales, DO variability seems to be linked closely to climatological factors influencing river discharge; the unprecedented anoxia since the early 1970s is attributed mainly to high freshwater flow and to an increase in nutrient concentrations from the watershed.

  17. Assessment of PCDD/F source contributions in Baltic Sea sediment core records.

    PubMed

    Assefa, Anteneh T; Tysklind, Mats; Sobek, Anna; Sundqvist, Kristina L; Geladi, Paul; Wiberg, Karin

    2014-08-19

    Spatial and temporal trends of sources of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the Baltic Sea were evaluated by positive matrix factorization (PMF) and principal component analysis (PCA). Sediment cores were sampled at eight coastal, one coastal reference, and six offshore sites covering the northern to the southern Baltic Sea. The cores, which covered the period 1919-2010, were sliced into 2-3 cm disks among which 8-11 disks per core (in total 141 disks) were analyzed for all tetra- through octa-CDD/Fs. Identification and apportionment of PCDD/F sources was carried out using PMF. Five stable model PCDD/F congener patterns were identified, which could be associated with six historically important source types: (i) atmospheric background deposition (ABD), (ii) use and production of penta-chlorophenol (PCP), (iii) use and production of tetra-chlorophenol (TeCP), (iv) high temperature processes (Thermal), (v) hexa-CDD-related sources (HxCDD), and (vi) chlorine-related sources (Chl), all of which were still represented in the surface layers. Overall, the last four decades of the period 1920-2010 have had a substantial influence on the Baltic Sea PCDD/F pollution, with 88 ± 7% of the total amount accumulated during this time. The 1990s was the peak decade for all source types except TeCP, which peaked in the 1980s in the northern Baltic Sea and has still not peaked in the southern part. The combined impact of atmospheric-related emissions (ABD and Thermal) was dominant in the open sea system throughout the study period (1919-2010) and showed a decreasing south to north trend (always >80% in the south and >50% in the north). Accordingly, to further reduce levels of PCDD/Fs in the open Baltic Sea ecosystem, future actions should focus on reducing atmospheric emissions. PMID:25103626

  18. RECONSTRUCTION OF CONTAMINANT TRENDS IN A SALT WEDGE ESTUARY WITH SEDIMENT CORES DATED USING A MULTIPLE PROXY APPROACH

    EPA Science Inventory

    The Taunton River is a partially mixed tidal estuary in southeastern Massachusetts (USA) which has received significant contaminant inputs, yet little information exists on the history of discharge and the subsequent fate of these contaminants. Three sediment cores taken along a...

  19. 210Pb-derived chronology in sediment cores evidencing the anthropogenic occupation history at Corumbataí River basin, Brazil

    NASA Astrophysics Data System (ADS)

    Bonotto, D. M.; de Lima, J. L. N.

    2006-07-01

    Activity profiles of excess 210Pb combined with chemical data determined in two sediment cores from Corumbataí River basin, São Paulo State, Brazil, provided new insights into the reconstruction of historical inputs of anthropogenic constituents, contributing to improving management strategies of the hydrological resources in the basin since most of the municipalities extensively utilize the waters of Corumbataí River and tributaries for drinking purposes, among other uses. Excellent significant relationships between loss on ignition (LOI) and organic matter were found for sediments of both analyzed profiles. Silica was found to be inversely related to organic matter at both analyzed profiles: its decrease accompanied an increase in the specific surface of the sediments. This relationship was confirmed by a great number of inverse significant correlations among silica and oxides Na2O, K2O, CaO, MgO, Al2O3, P2O5, Fe2O3, MnO, and TiO2. It was possible to identify the role of organic matter on adsorption of several oxides/elements in the core sediments profiles. Apparent sediment mass accumulation rates corresponding to 224 and 802 mg cm-2 year-1 were obtained, and are compatible with field evidence, indicating a higher value associated with sand mining activities interfering with the natural/normal sedimentation process, due to modifications of the channel drainage.

  20. Impact of Climate and Fires on Abrupt Permafrost Thaw in Alaskan Tundra

    NASA Astrophysics Data System (ADS)

    Chipman, M. L.; Reents, C.; Greenberg, J. A.; Hu, F.

    2015-12-01

    Thermo-erosion from abrupt permafrost thaw is a key pulse disturbance in the Arctic that may impact the global carbon cycle. Abrupt thaw can occur when the permafrost active layer expands in response to climate warming and/or increased wildfire activity. Understanding these drivers of thermo-erosion is necessary to anticipate feedbacks in the Arctic, where summer temperature and fire frequency are predicted to increase. We examine modern and late-Holocene thermo-erosion in high-fire (Noatak) and low-fire (North Slope) tundra ecoregions of Alaska using a combination of remote-sensing and paleo-records. Lakes with active thaw features were identified through Landsat-7 image classification and time-series analysis based on observed 0.52-0.60 μm reflectance peaks following slump formation. We identified 1067 and 1705 lakes with active features between CE 2000-2012 in the Noatak and North Slope ecoregions, respectively. The density of features was higher in the highly flammable Noatak (0.04 versus 0.01 features km-2, respectively), suggesting that warmer climate and/or fires likely promote high thermo-erosional activity at present. To assess modern signals of thermo-erosion and identify past events, we analyzed soil profiles and lake-sediment cores from both ecoregions using X-ray fluorescence. The ratios of Ca:K and Ca:Sr increased with depth in permafrost soils, were higher in soils from younger versus older slump surfaces, and were significantly correlated with the ratio of carbonate to feldspar and clay minerals in lake sediments (r=0.96 and 0.93, P<0.0001, n=15). We interpret past increases in Ca:K, Ca:Sr, and δ13C as enhanced weathering of carbonate-rich permafrost soils associated with thermo-erosion. At the North Slope site, we identified ten episodes of thermoerosion over the past 6000 years and found strong correspondence to summer temperature trends. Events were more frequent at the Noatak site, where 15 thermo-erosional episodes and 26 fires occurred over

  1. Urban Landscapes on Permafrost: Oganer Case Study

    NASA Astrophysics Data System (ADS)

    Streletskiy, D. A.; Grebenets, V. I.

    2013-12-01

    Norilsk with a population of 205,000 is by far the biggest city ever built on permafrost. Oganer, located near Norilsk is the latest administrative unit of the city with a population of about 7,000 people. It was originally designed as a satellite city for about 50-80 thousand workers and their families. Idea of a satellite city became apparent in mid-80th, when Norilsk was unable to grow to extent needed to accommodate large workforce. Located in a valley, the city was already surrounded by two metallurgy plants and steep mountains slopes. The only direction of city limit extension was east, but the area was previously occupied by garages and barracks resulting in deterioration of cold permafrost and decrease in high bearing capacity of the ground required for construction of large residential houses. Oganer was built 8 km east from the Norilsk, where initial geologic survey shown close location of bedrock to the surface making possible construction of large structures on permafrost. First houses were built in 1986 according to the passive principle of construction on permafrost. Additional geologic surveys in Oganer revealed that original bedrock extent is quite small and subsequent construction had to deal with ice-reach (40-60%) permafrost in fine-grained sediments (silt and clay). The change in economic direction in the beginning of 1990s resulted in population outmigration from Norilsk, so Oganer originally planned as a large 5-district city was never complete. Presently, it is represented by only one district, with several 9-storey tall buildings which were never complete. Despite that mean annual temperature is -9.7 C, permafrost temperature is relatively warm -1..-3 C. High permafrost temperature, presence of ground ice and large bodies of tabular ground ice in the area made construction quite challenging. In the paper we demonstrate how climateand various construction practices and designs used in the city modified natural landscapes, and how periglacial

  2. Subsea Permafrost Mapped Across the U.S. Beaufort Sea Using Multichannel Seismic Data

    NASA Astrophysics Data System (ADS)

    Brothers, L.; Hart, P. E.; Ruppel, C. D.

    2011-12-01

    Circum-Arctic continental shelves at water depths less than ~100 m were subaerial permafrost prior to the onset of sea-level rise starting in the late Pleistocene. Rapid transgression and the resulting temperature increase at the sediment surface have led to thawing of the inundated permafrost, landward retreat of the leading edge of the permafrost, and dissociation of permafrost-associated gas hydrates. Past numerical modeling has shown that gas hydrate dissociation is particularly pronounced at the permafrost-to-no permafrost transition offshore. On the U.S. Beaufort margin, subsea permafrost has never been systematically mapped, and the best insights about permafrost and associated gas hydrate have been based on a limited number of offshore boreholes and numerical studies, with sometimes contrasting predictions of the permafrost's seaward extent. We bring together 5370 km of multichannel seismic (MCS) data acquired during various proprietary exploration industry and public domain government surveys between 1977 and 1992 to map a velocity anomaly diagnostic of submerged permafrost along 500 km of the US Beaufort coastline. These high-velocity (>~2.8 km/s) refractions (HVR), which are evident in prestack MCS shot records, reveal laterally continuous layers of shallow, ice-bonded, coarse-grained sediments beneath the inner continental shelf. The HVR occur in less than 5% of the tracklines, and calculated HVR depths range from 60 to 350 m below seafloor. The velocity anomaly is not observed seaward of the 20 m isobath, and is only found within 30 km of the current shoreline. These results can be used to: 1) create a map of the minimum distribution of remaining US Beaufort shelf subsea permafrost; 2) reconcile discrepancies between model-predicted and borehole-verified offshore permafrost distribution; and 3) constrain where to expect hydrate dissociation.

  3. Application of 2-D geoelectrical resistivity tomography for mountain permafrost detection in sporadic permafrost environments: Experiences from Eastern Austria

    NASA Astrophysics Data System (ADS)

    Kellerer-Pirklbauer, Andreas

    2015-04-01

    Mountain permafrost covers some 2000 km² of the Austrian Alps which is less than 2.5% of the national territory. Delineating the altitudinal lower limit of permafrost in the mountains of Austria is difficult due the complex topography, the rather sparseness of field verification data and the lack of long-term permafrost monitoring data. Such monitoring data should cover different slope aspects, different elevations, different substrates and different mountain regions of Austria. In this study it was attempted to delineate the lower limit of permafrost at two study sites in the Tauern Range, Austria, applying two-dimensional geoelectrical resistivity tomography (ERT). In addition, multi-annual ground temperature data collected by miniature temperature datalogger (MDT) were used to validate the results. At the study site Hochreichart (maximum elevation 2416 m asl), located in the Seckauer Tauern Range, 14 ERT profiles (lengths 48-196 m; electrode spacing 2, 2.5 or 4 m) were measured at elevations between 1805 and 2416 m asl. Measurements were carried out at two cirques (Reichart, Schöneben) and at the summit plateau of Hochreichart. Results at this site indicate that permafrost lenses are detectable at elevations down to c.1900 m asl at radiation-sheltered sites. Furthermore, at the summit plateau permafrost only occurs as rather small lenses. The ERT-based permafrost pattern is generally confirmed by the MTD data with negative mean annual ground temperature values at only a few monitoring sites. However, the possibility of air-filled cavities causing higher resistive zones faking permafrost existence cannot be excluded because coarse-grained sediments (i.e. relict rock glaciers and autochthonous block fields) are widespread at this study site. At the second study site Kögele Cirque (maximum elevation 3030 m asl) located in the Schober Mountains 12 ERT profiles (lengths 48 m; electrode spacing 2 m) were measured at elevations between 2631 and 2740 m asl. Spatially

  4. Correction of interstitial water changes in calibration methods applied to XRF core-scanning major elements in long sediment cores: Case study from the South China Sea

    NASA Astrophysics Data System (ADS)

    Chen, Quan; Kissel, Catherine; Govin, Aline; Liu, Zhifei; Xie, Xin

    2016-05-01

    Fast and nondestructive X-ray fluorescence (XRF) core scanning provides high-resolution element data that are widely used in paleoclimate studies. However, various matrix and specimen effects prevent the use of semiquantitative raw XRF core-scanning intensities for robust paleoenvironmental interpretations. We present here a case study of a 50.8 m-long piston Core MD12-3432 retrieved from the northern South China Sea. The absorption effect of interstitial water is identified as the major source of deviations between XRF core-scanning intensities and measured element concentrations. The existing two calibration methods, i.e., normalized median-scaled calibration (NMS) and multivariate log-ratio calibration (MLC), are tested with this sequence after the application of water absorption correction. The results indicate that an improvement is still required to appropriately correct the influence of downcore changes in interstitial water content in the long sediment core. Consequently, we implement a new polynomial water content correction in NMS and MLC methods, referred as NPS and P_MLC calibrations. Results calibrated by these two improved methods indicate that the influence of downcore water content changes is now appropriately corrected. We therefore recommend either of the two methods to be applied for robust paleoenvironmental interpretations of major elements measured by XRF-scanning in long sediment sequences with significant downcore interstitial water content changes.

  5. Permafrost soils and carbon cycling

    DOE PAGESBeta

    Ping, C. L.; Jastrow, J. D.; Jorgenson, M. T.; Michaelson, G. J.; Shur, Y. L.

    2015-02-05

    Knowledge of soils in the permafrost region has advanced immensely in recent decades, despite the remoteness and inaccessibility of most of the region and the sampling limitations posed by the severe environment. These efforts significantly increased estimates of the amount of organic carbon stored in permafrost-region soils and improved understanding of how pedogenic processes unique to permafrost environments built enormous organic carbon stocks during the Quaternary. This knowledge has also called attention to the importance of permafrost-affected soils to the global carbon cycle and the potential vulnerability of the region's soil organic carbon (SOC) stocks to changing climatic conditions. Inmore » this review, we briefly introduce the permafrost characteristics, ice structures, and cryopedogenic processes that shape the development of permafrost-affected soils, and discuss their effects on soil structures and on organic matter distributions within the soil profile. We then examine the quantity of organic carbon stored in permafrost-region soils, as well as the characteristics, intrinsic decomposability, and potential vulnerability of this organic carbon to permafrost thaw under a warming climate. Overall, frozen conditions and cryopedogenic processes, such as cryoturbation, have slowed decomposition and enhanced the sequestration of organic carbon in permafrost-affected soils over millennial timescales. Due to the low temperatures, the organic matter in permafrost soils is often less humified than in more temperate soils, making some portion of this stored organic carbon relatively vulnerable to mineralization upon thawing of permafrost.« less

  6. Benchscale Assessment of the Efficacy of a Reactive Core Mat to Isolate PAH-spiked Aquatic Sediments

    PubMed Central

    Meric, Dogus; Barbuto, Sara; Sheahan, Thomas C.; Shine, James P.; Alshawabkeh, Akram N.

    2013-01-01

    This paper describes the results of a benchscale testing program to assess the efficacy of a reactive core mat (RCM) for short term isolation and partial remediation of contaminated, subaqueous sediments. The 1.25 cm thick RCM (with a core reactive material such as organoclay with filtering layers on top and bottom) is placed on the sediment, and approximately 7.5 – 10 cm of overlying soil is placed on the RCM for stability and protection. A set of experiments were conducted to measure the sorption characteristics of the mat core (organoclay) and sediment used in the experiments, and to determine the fate of semi-volatile organic contaminants and non-reactive tracers through the sediment and reactive mat. The experimental study was conducted on naphthalene-spiked Neponset River (Milton, MA) sediment. The results show nonlinear sorption behavior for organoclay, with sorption capacity increasing with increasing naphthalene concentration. Neponset River sediment showed a notably high sorption capacity, likely due to the relatively high organic carbon fraction (14%). The fate and transport experiments demonstrated the short term efficiency of the reactive mat to capture the contamination that is associated with the post-capping period during which the highest consolidation-induced advective flux occurs, driving solid particles, pore fluid and soluble contaminants toward the reactive mat. The goal of the mat placement is to provide a physical filtering and chemically reactive layer to isolate contamination from the overlying water column. An important finding is that because of the high sorption capacity of the Neponset River sediment, the physical filtering capability of the mat is as critical as its chemical reactive capacity. PMID:24367237

  7. Initial Results on the Extraterrestrial Component of New Sediment Cores Containing Deposits of the Eltanin Impact Event

    NASA Technical Reports Server (NTRS)

    Kyte, Frank T.; Gersonde, Rainer

    2003-01-01

    Background The impact of the Eltanin asteroid into the Bellingshausen Sea (2.15 Ma) is the only known impact in a deep-ocean (approx. 5 km) basin. In 1995, Polarstern expedition ANT XII/4 made the first geological survey of the suspected impact region. Three sediment cores sampled around the San Martin seamounts (approx. 57.5 S, 91 W) contained well-preserved impact deposits. Sediments of Eocene age and younger were ripped up and redeposited by the impact. The depositional sequence produced by the impact has three units: a chaotic assemblage of sediment fragments up to 50 cm, followed by laminated sands deposited as a turbulent flow, and finally silts and clays that accumulated from dispersed sediments in the water column. The meteoritic impact ejecta, which is composed of shock-melted asteroidal materials and unmelted meteorites, settled through the water column and concentrated near the top of the laminated sands.

  8. Winter sea surface temperature reflected by the TEX86 proxy in core sediments from the coastal northern South China Sea

    NASA Astrophysics Data System (ADS)

    Wei, Y.; Wang, P.; Zhao, M.; Zhang, C.

    2013-12-01

    Although TEX86 is widely used as a sea surface temperature proxy for the open ocean, the validity of TEX86 in the coastal seas has yet to be tested. In this study, three sediment cores from the coastal northwestern South China Sea (SCS) (water depth 33 m for core A9, 73 m for core, and 102 m for core A9, respectively) were analyzed using lipid biomarker approaches. The distribution of archaeal core lipids varied in core A9 and A7 but remained constant in A5. TEX86-based temperature according to Kim et al. (2010) averaged 17.2 × 0.4 οC (n=30), 20.9 × 0.3 οC (n=19) and 23.0 × 0.3 οC(n=16) in core A9, A7 and A5, respectively. These results show that temperature changed little with sediment depth at each location and increased by about 3 οC between the two adjacent locations. These are lower than the annual SST (24.5-25.7 οC) and much lower than the summer SST (>28 οC), indicating that organisms producing the TEX86-related compounds mostly lived in the winter season.

  9. The multiproxy analysis of a lacustrine-palustrine sediment core from Lebanon reveals four climate cycles

    NASA Astrophysics Data System (ADS)

    Gasse, F. A.; van Campo, E.; Demory, F.; Develle, A.; Tachikawa, K.; Buchet, N.; Sonzogni, C.; Thouveny, N.; Bard, E. G.; Vidal, L.

    2013-12-01

    The study of a sediment core retrieved from the small Yammouneh basin (34.06°N-34.09°N, 36.0°E-36.03°E, 1360 m a.s.l.), Lebanon, provides for the first time a nearly continuous record spanning approximately 360 ka in northern Levant. The basin, located on the eastern flank of Mount Lebanon, is mainly supplied by karstic springs which discharge snowmelt water infiltrated through the western highlands. Part of its water inputs is lost by seepage through its faulted bottom. The core, 73 m long, consists of four whitish carbonated intervals rich in lacustrine organism remains, interrupting a thick accumulation of colored silty clays almost devoid of shells but for ostracods. We analyzed sediment features (mineralogical and elemental composition, light microscopy and SEM observations, grain size), magnetic properties, pollen and calcite oxygen isotopes (δc) derived from ostracod shell composition. The chronological framework is based on 14C ages of wood fragments, U/Th dating, and a high resolution reconstruction of relative paleointensity variations correlated with regional (Portuguese margin) and global (Sint-800) master curves down to about 360 ka. Although the chronology still needs improvement, the 3 upper carbonated intervals undoubtedly fit Interglacials MIS 1, MIS 5.5 and MIS 7, respectively. The deepest one (49-60 m) is assigned to MIS 9 by its proxy analogies with dated Interglacials. The sequence covers a large part of MIS 10. Relationships between individual indicators are explored, in addition to visual comparisons of individual records, from the multiproxy matrix after resampling at a common depth scale of 25 cm. We compute simple linear coefficients between 20 variables, perform Principal Component Analyses based on all variables, on terrestrial pollen biomes, on all sedimentological proxies, and cross-correlations between them and δc. During Interglacial maxima, high local and regional efficient moisture is evidenced by dense arboreal vegetation of

  10. Distribution and sources of lipid compound series in sediment cores of the southern South China Sea.

    PubMed

    Tahir, N Mohd; Pang, S Y; Simoneit, B R T

    2015-05-01

    Three short sediment cores from inner continental shelf of the southern South China Sea (5-50 km) off Terengganu were analyzed for lipid contents (i.e., homologous aliphatic compounds and sterols) using gas chromatography-mass spectrometry. The concentrations of the total aliphatic hydrocarbons (TAHs) ranged from 0.152 to 6.91 μg/g dry weight. The n-alkane distribution was from nC₁₃ to nC₃₆, with a carbon preference index (CPI₁₃₋₃₅) from 1.08 to 4.28 and a carbon number maximum (Cmax), depending on a sample, at 31 or 18. In addition, a strong odd-to-even carbon number predominance was observed in nC₂₅-nC₃₅ range. The distribution of the n-alkanoic acids and n-alkanols in all samples exhibited an even-to-odd carbon number predominance and ranged from C₁₀ to C₂₆ and from C₁₂ to C₃₄, respectively. The n-alkanols were dominated by the long-chain homologs with Cmax at 22; on the other hand, the n-alkanoic acid distributions showed a predominance of short-chain homologs with a Cmax at 16. The total sterol concentrations ranged from 0.41 to 3.57 μg/g dry weight. Cholesterol was most abundant at the offshore stations, whereas sitosterol was dominant at near-shore station. Pentacyclic triterpenoids such as friedelin and taraxerol α- and β-amyrins, which are known biomarkers for higher plants, were detected at all stations with a dilution trend offshore. In conclusion, the marine sediments off southern Terengganu can still be considered uncontaminated, where the compound sources are biogenic from terrestrial plants superimposed with a marine productivity input. PMID:25752627

  11. Investigation of mechanisms of gas hydrates accumulation in permafrost environments

    NASA Astrophysics Data System (ADS)

    Chuvilin, E. M.

    2012-12-01

    The feature of permafrost sediments is capability to accumulate a quantity of natural gases foremost methane with low admixture of carbon dioxide. In consequence of natural and climatic changes, formation of favorable thermobaric conditions for transformation of intra-permafrost gas accumulations from free state into gas hydrate is possible. In consideration of high gas-saturation of frozen sediments, the active processes of hydrate formation in permafrost during the transgression of arctic seas or under continental glaciations can be expected. A special experimental technique was elaborated to perform physical modeling of hydrate formation conditions in cryogenic ice-containing sediments. The experiments were carried out under constant negative temperatures in interval from -2 oC to -9 oC. Methane (99.98%) was used as hydrate-former gas. During the experiments the kinetics of gas consumption in porous media was investigated and also part of porous water turned into hydrate and hydrate- saturation of sediment samples were estimated. Experiments show that hydrate formation in gas saturated sediments occurs actively not only in freezing sediments (above 0 oC) but also in frozen sediments (below 0 oC). Intensity of hydrate formation in frozen sediments depends on such factors as ice-saturation, thermobaric conditions and gas composition. Experimental data shows that after attenuation of hydrate formation in frozen sediments the considerable activization of hydrate accumulation processes during the increasing of temperature above 0 oC can occur. That leads to the thawing of porous ice, which does not turn into hydrate, and attendant this process structural-textural changes result in appearance of new gas-water contacts. As a result there is second hydrate formation on background of thawing of ice. Based on analysis of geological data and experimental researches possible geological models of gas hydrates formation in shallow permafrost under the sea transgression and

  12. Paleomagnetism and environmental magnetism of GLAD800 sediment cores from Bear Lake, Utah and Idaho

    USGS Publications Warehouse

    Heil, C.W., Jr.; King, J.W.; Rosenbaum, J.G.; Reynolds, R.L.; Colman, Steven M.

    2009-01-01

    A ???220,000-year record recovered in a 120-m-long sediment core from Bear Lake, Utah and Idaho, provides an opportunity to reconstruct climate change in the Great Basin and compare it with global climate records. Paleomagnetic data exhibit a geomagnetic feature that possibly occurred during the Laschamp excursion (ca. 40 ka). Although the feature does not exhibit excursional behavior (???40?? departure from the expected value), it might provide an additional age constraint for the sequence. Temporal changes in salinity, which are likely related to changes in freshwater input (mainly through the Bear River) or evaporation, are indicated by variations in mineral magnetic properties. These changes are represented by intervals with preserved detrital Fe-oxide minerals and with varying degrees of diagenetic alteration, including sulfidization. On the basis of these changes, the Bear Lake sequence is divided into seven mineral magnetic zones. The differing magnetic mineralogies among these zones reflect changes in deposition, preservation, and formation of magnetic phases related to factors such as lake level, river input, and water chemistry. The occurrence of greigite and pyrite in the lake sediments corresponds to periods of higher salinity. Pyrite is most abundant in intervals of highest salinity, suggesting that the extent of sulfidization is limited by the availability of SO42-. During MIS 2 (zone II), Bear Lake transgressed to capture the Bear River, resulting in deposition of glacially derived hematite-rich detritus from the Uinta Mountains. Millennial-scale variations in the hematite content of Bear Lake sediments during the last glacial maximum (zone II) resemble Dansgaard-Oeschger (D-O) oscillations and Heinrich events (within dating uncertainties), suggesting that the influence of millennial-scale climate oscillations can extend beyond the North Atlantic and influence climate of the Great Basin. The magnetic mineralogy of zones IV-VII (MIS 5, 6, and 7

  13. Permafrost and Climate Change

    NASA Astrophysics Data System (ADS)

    Basnet, S.; Shahroudi, N.

    2012-12-01

    This paper examines the effects of climate change on Permafrost. Climate change has been shown to have a global correlation with decreased snow cover in high latitudes. In the current research station and satellite data were used to detect the location of permafrost. Permafrost is dependent on the temperature of the ground surface. Air temperature and snow cover from Integrated Surface Database (ISD) downloaded from National Climatic Data Center (NCDC) were observed for six consecutive years (1999-2004). The research was carried out over the entire globe to study the trend between fluctuating temperature and snow cover. Number of days with temperature below zero (freezing) and above zero (melting) was counted over a 6-year period. It was observed that each year the area of ice cover decreased by 0.3% in the Northern Hemisphere; a 1% increase in air temperature was also observed. Furthermore, the results from station data for snow cover and air temperature were compared with the snow cover and skin temperature from the satellite data. The skin temperature was retrieved from infrared (IR) radiance at International Satellite Cloud Climatology Project (ISCCP) and the snow cover is derived from visible satellite data at The National Environmental Satellite, Data, and Information Service (NESDIS), part of the National Oceanic and Atmospheric Administration (NOAA). Both dataset projected that the higher latitudes had the highest number of days with temperature below zero degree Celsius and these locations will be able to house permafrost. In order to improve the data quality as well as for more accurate results, in the future ISD data and satellite skin temperature will be analyzed for longer period of time (1979-2011) and (1983-2007) respectively also, two additional station data will be studied. The two datasets for future studies are Integrated Global Radiosonde Archive (IGRA) and International Comprehensive Ocean-Atmosphere Data Set (ICOADS). The results outputted by

  14. Temporal trends of triclosan contamination in dated sediment cores from four urbanized estuaries: evidence of preservation and accumulation.

    PubMed

    Cantwell, Mark G; Wilson, Brittan A; Zhu, Jun; Wallace, Gordon T; King, John W; Olsen, Curtis R; Burgess, Robert M; Smith, Joseph P

    2010-01-01

    Triclosan is an antimicrobial agent added to a wide array of consumer goods and personal care products. Through its use, it is introduced into municipal sewer systems where it is only partially removed during wastewater treatment. In this study, triclosan was measured in dated sediment cores from four urbanized estuaries in order to reconstruct temporal and spatial trends of accumulation. Measurable concentrations of triclosan first appeared in each of the sediment cores near 1964, which corresponds with the US patent issuance date of triclosan. The presence of triclosan at each of the study sites at or near the patent date indicates that long-term preservation is occurring in estuarine sediments. Temporal trends of triclosan at each location are unique, reflecting between site variability. Concentrations at one site climbed to as high as 400ngg(-1), due in part, to local commercial production of triclosan. At two locations, levels of triclosan rise towards the surface of each core, suggesting increasing usage in recent years. One location adjacent to a major combined sewer overflow had high sediment concentrations of triclosan, confirming their potential as a source of triclosan to estuaries. PMID:20006371

  15. Depth Depending Pattern Recognition (DDPR) - a tool for visualization of spatial and temporal similarities of properties in sediment cores

    NASA Astrophysics Data System (ADS)

    Büttner, Olaf; Baborowski, Martina

    2013-04-01

    Depth Depending Pattern Recognition (DDPR) is a new simple tool for the visualization of spatial and temporal similarities of measured parameters in a set of sediment cores. It was developed to support the multivariate analysis of data of sediment cores taken in a still water area of the River Elbe [1]. The idea behind is the assumption that correlations in spatial or temporal distributions of environmental parameters can be visualized by different ways and that a distance between two patterns can be defined with mathematical methods. So the similarity of two patterns can be quantified and assessed by a catalog of subjective rules. Generally, defining one reference pattern, the computation of a distance matrix for different parameter distributions is easily possible. Consequently, the three main steps of the algorithm are a) the creation of the pattern from the measurements, b) the definition of the distance calculation and c) the interpretation and assessment of the distance matrix. The method can be used in addition to classical uni- or multivariate statistical methods like regression analysis, principal component analysis, correlation analysis etc. DDPR supports hypothesis testing and explanation of relationships. In the poster DDPR is explained and the method is presented for two examples, an artificial one and one with data from sediment cores. Reference [1] Baborowski M., Büttner O., Morgenstern P., Jancke T., Westrich B. (2012) Spatial variability of metal pollution in groyne fields of the Middle Elbe - Implications for sediment monitoring, Environmental Pollution, 167,115-123

  16. Tracing metal sources in core sediments of the artificial lake An-Dong, Korea: Concentration and metal association.

    PubMed

    Choi, Mansik; Park, Jongkyu; Cho, Dongjin; Jang, Dongjun; Kim, Miseon; Choi, Jongwoo

    2015-09-15

    The concentration and source of trace metals in the artificial lake An-Dong, which has widespread abandoned mines and a Zn smelter upstream of the drainage basin, were investigated. Soils (18ea), stream waters (15ea) and sediments (15ea) in the main channel and five tributaries downstream of the Zn smelter towards the lake (~ 50 km downstream) were collected. And two core sediments were also taken from the middle of the lake. All samples were analyzed for trace metals in bulk and in a 1N HCl-leached fraction. Although the soil and stream sediments consisted mostly of sand-sized grains, concentrations of metals (Cu, Zn, Cd and Pb) were very high in all samples, including soils, stream waters and sediments at sites near the Zn smelter. However the metal concentrations decreased rapidly downstream, suggesting that the area of impact of the smelter lies within 5 km. Highly enriched metal concentrations were also found in dated core sediments from the lake; while the highest concentrations of Co, Ni, As, Cu, Zn, Cd and Pb were detected in the bottom of the sediment core (dated 1980) they decreased towards 2000, and only Cu, Zn and Cd concentrations increased again in present-day samples. Since the temporal variation in metal concentrations appeared consistent with historical variation in ore mining and Zn smelter production rates, a model combining the production rates of each was developed, which estimated 3%, 12% and 7% contributions from Zn smelter compared to ore mining production rate to levels of Cu, Cd and Zn, respectively, suggesting the different pathways by different sources. In addition, analysis of Cd/Zn and Cu/Zn ratios showed that contamination from ore mining decreased from 1980 to 2000, and smelting processes were most likely responsible for metal enrichment (Cu, Cd and Zn) from 2000 to the present. PMID:25981937

  17. Iridium Concentrations and Abundances of Meteoritic Ejecta from the Eltanin Impact in Sediment Cores from Polarstern Expedition ANT XII/4

    NASA Technical Reports Server (NTRS)

    Kyte, Frank T.

    2002-01-01

    The abundances of meteoritic ejecta from the Eltanin asteroid impact have been examined in several sediment cores recovered by the FS Polarstern during expedition ANT XII/4 using elemental concentrations of iridium and weights of coarse ejecta debris. Three cores with well-preserved impact deposits, PS204-1, PS2708-1, and PS2709-1, each contain Ir and ejecta fluences similar to those found in USNS Eltanin core E13-4. Small Ir anomalies and traces of ejecta were found in cores PS2706-1 and PS2710-1, but since these cores lack well-defined deposits, these are considered to be reworked and not representative of the fallout. No evidence of ejecta was found in cores PS2802-1 and PS2705-1. These results confirm earlier speculation that the Eltanin impact resulted in deposits of ejecta with up to 1 gram/sq centimeter of depris over a wide area of the ocean floor. However, there are sill large uncertainties over the actual regional or global extent of this unique sediment deposit.

  18. Quantitative mineralogy of surface sediments of the Iceland shelf, and application to down-core studies of holocene ice-rafted sediments

    USGS Publications Warehouse

    Andrews, John T.; Eberl, D.D.

    2007-01-01

    Quantitative X-ray diffraction analyses on the < 2 mm sediment fraction from the Iceland shelves are reported for subglacial diamictons, seafloor surface sediments, and the last 2000 cal yr BP from two cores. The overall goal of the paper is to characterize the spatial variability of the mineralogy of the present-day surface sediments (18 non-clay minerals and 7 clay minerals), compare that with largely in situ erosional products typified by the composition of subglacial diamictons, and finally examine the late Holocene temporal variability in mineral composition using multi-mineral compositions. The subglacial diamictons are dominated in the non-clay-mineral fraction by the plagioclase feldspars and pyroxene with 36.7 ?? 6.1 and 17.9 ?? 3.5 wt % respectively, with smectites being the dominant clay minerals. The surface seafloor sediments have similar compositions although there are substantial amounts of calcite, plus there is a distinct band of sites from NW to N-central Iceland that contain 1-6 wt% of quartz. This latter distribution mimics the modern and historic pattern of drift ice in Iceland waters. Principal component analysis of the transformed wt% (log-ratio) non-clay minerals is used to compare the subglacial, surface, and down-core mineral compositions. Fifty-eight percent of the variance is explained by the first two axes, with dolomite, microcline, and quartz being important "foreign" species. These analyses indicate that today the NW-N-central Iceland shelf is affected by the import of exotic minerals, which are transported and released from drift ice. The down-core mineralogy indicates that this is a process that has varied over the last 2000 cal yr BP. Copyright ?? 2007, SEPM (Society for Sedimentary Geology).

  19. Microorganisms from Permafrost Viable and Detectable by 16SRNA Analysis: A Model for Mars

    NASA Technical Reports Server (NTRS)

    Tsapin, A. I.; McDonald, G. D.; Andrews, M.; Bhartia, R.; Douglas, S.; Gilichinsky, D.

    1999-01-01

    Preliminary studies of Arctic and Antarctic permafrost have shown that this environment harbors microorganisms which can be isolated in pure culture, and that these organisms can survive for a long period of time (up to 20 Ma) in permafrost. It is believed that the permanent subzero temperatures in permafrost and ice environments are the main parameters ensuring the longevity of microbes. In this project we studied permafrost cores from different areas of the Siberian Arctic and Antarctic, with ages from several thousand years up to several millions years (Ma). In general, Antarctic permafrost has a higher sand content, while Siberian permafrost has a texture more characteristic of clay or normal soil. Additional information is contained in the original extended abstract.

  20. Compositional classification and sedimentological interpretation of the laminated lacustrine sediments at Baumkrichen (Western Austria) using XRF core scanning data

    NASA Astrophysics Data System (ADS)

    Barrett, Samuel; Tjallingii, Rik; Bloemsma, Menno; Brauer, Achim; Starnberger, Reinhard; Spötl, Christoph; Dulski, Peter

    2015-04-01

    The outcrop at Baumkirchen (Austria) encloses part of a unique sequence of laminated lacustrine sediments deposited during the last glacial cycle. A ~250m long composite sediment record recovered at this location now continuously covers the periods ~33 to ~45 ka BP (MIS 3) and ~59 to ~73 ka BP (MIS 4), which are separated by a hiatus. The well-laminated (mm-cm scale) and almost entirely clastic sediments reveal alternations of clayey silt and medium silt to very-fine sand layers. Although radiocarbon and optically stimulated luminescence (OSL) dating provide a robust chronology, accurate dating of the sediment laminations appears to be problematic due to very high sedimentation rates (3-8 cm/yr). X-ray fluorescence (XRF) core scanning provided a detailed ~150m long record of compositional changes of the sediments at Baumkirchen. Changes in the sediments are subtle and classification into different facies based on individual elements is therefore subjective. We applied a statistically robust clustering analysis to provide an objective compositional classification without prior knowledge, based on XRF measurements for 15 analysed elements (all those with an acceptable signal-noise ratio: Zr, Sr, Ca, Mn, Cu, Zn, Rb, Ni, Fe, K, Cr, V, Si, Ba, T). The clustering analysis indicates a distinct compositional change between sediments deposited below and above the stratigraphic hiatus, but also differentiates between individual different laminae. Preliminary results suggest variations in the sequence are largely controlled by the relative occurrence of different kinds of sediment represented by different clusters. Three clusters identify well-laminated sediments, visually similar in appearance, each dominated by an anti-correlation between Ca and one or more of the detrital elements K, Zr, Ti, Si and Fe. Two of these clusters occur throughout the entire sequence, one frequently and the other restricted to short sections, while the third occurs almost exclusively below the

  1. History and geochemistry of a metalliferous sediment core from the Mid-Atlantic Ridge at 26 degree N

    SciTech Connect

    Metz, S.; Trefry, J.H. ); Nelsen, T.A. )

    1988-10-01

    Fourteen thousand years of hydrothermal deposition are recorded in a metalliferous sediment core recovered from the Trans-Atlantic Geotraverse (TAG) Hydrothermal Field on the Mid-Atlantic Ridge at 26{degree}N. An estimated 26 to > 96% of the sediment at this core site is hydrothermally derived as determined from the CaCO{sub 3}, Al and Fe data. Layers of essentially pure vent precipitates contain < 3% CaCO{sub 3} and < 0.5% Al, with high concentrations of Fe (43%), Cu (4.1%), Zn (1.2%), Mn (1.1%), V (480 ppm), Pb (175 ppm), Cd (32 ppm) and Hg (3.8 ppm). Sediment accumulation rates vary from {approximately}1 to > 30 g/cm{sup 2}/1,000 y throughout the core, a function of the intensity of hydrothermal inputs. Distinct hydrothermal events are recorded at 6,000 and 8,500 y B.P. in layers containing > 90% vent-derived material. Vertical metal profiles and interelement relationships in the core result from variable deposition of oxides and sulfides, oxidation and dissolution of sulfide phases and scavenging of metals from seawater.

  2. Are Your Paleoecological Indicators Telling the Truth? Diatoms in Great Lakes Sediment Cores As an Example

    NASA Astrophysics Data System (ADS)

    Reavie, E. D.; Heathcote, A.

    2014-12-01

    Many existing models to infer paleoecological conditions from species assemblages are based on weak species-environmental relationships that are confounded by secondary variables, resulting in poor predictive power. We evaluated diatoms from Laurentian Great Lakes phytoplankton samples in the development of a total phosphorus (TP) transfer function based on weighted-average species abundance. Several tests were applied to validate our new indicator. Of the 118 common diatom taxa 76% had non-monotonous responses along the Great Lakes TP gradient. However, there was substantial autocorrelation among samples, justifying the need for further validation. A randomization procedure indicated that the actual transfer function consistently performed better than simulated functions. Further, TP was minimally confounded by other environmental variables. We then hindcasted TP using fossil diatom assemblages in a Lake Superior sediment core. Passive, multivariate analysis of the fossil samples against the training set data indicated that TP was a major determinant of historical diatoms, verifying that the function was well suited to reconstruct past TP. Collectively, these results show that diatom coefficients for water quality are robust indicators of Great Lakes condition. We recommend use in management when retrospective data are needed for tracking long-term degradation, remediation and trajectories.

  3. USE OF SEDIMENT CORE PROFILING IN ASSESSING EFFECTIVENESS OF MONITORED NATURAL RECOVERY

    EPA Science Inventory

    The Sediment Issue summarizes two studies conducted by the National Risk Management Research Laboratory of U.S. EPA to evaluate the natural recovery of surface sediments contaminated with polycyclic aromatic hydrocarbons (PAHs) an polychlorinated biphenyls (PCBs). Natural recove...

  4. Magnetic and Sedimentological Analyses of Sediment Cores from Otsego Lake Reveal Climate and Possible Delta Dynamics Throughout the Holocene

    NASA Astrophysics Data System (ADS)

    Geiss, C. E.; Hasbargen, L. E.

    2015-12-01

    Otsego Lake (42°43'N, -74°54'W) is a large oligotrophic, monomictic lake in upstate New York that occupies a narrow, N-S trending basin (approx. 13 km length, 2 km width) and has a maximum water depth of approx. 50 m. We collected two sediment cores from a shallow (4 m water depth) bench near the SW shore of the lake. The cores were collected approximately 200 m off-shore from a small stream delta. Age control was established through five 14C AMS-dates obtained from terrestrial plant macrofossils. We analyzed sediments for their magnetic properties (magnetic susceptibility, anhysteretic- and isothermal remanent magnetization, hysteresis properties and coercivity distributions) and performed loss-on-ignition and X-ray analyses to determine the relative abundance of organic matter, quartz and calcite. The watershed of Otsego Lake rests in glacial debris and Devonian shale and limestone. The base of the core (> 9 ka) consists mostly of silt-sized, massive to weakly laminated siliceous and strongly magnetic sediments. Between 8-9 ka the climate warmed sufficiently to allow for the formation of calcareous sediments. Between 8 - 6 ka magnetic minerals are characterized by low abundance and small grainsize, while organic and inorganic carbon increase. Sedimentation rates decrease significantly between 6-2 ka (from ~100 cm/ka to 12-15 cm/ka). During this time interval the relative abundance of quartz increases, sediment becomes slightly more magnetic, and the magnetic grain-size increases as well. We interpret this time period as a low-stand, when lower lake levels allow for the redeposition and possible loss of sediment into the deeper part of the lake, as well as increased terrigenous input from the nearby lakeshore. This lowstand is clearly identified as a strong, continuous reflector in GPR profiles. Sediments younger than 2 ka are characterized by variable abundances of magnetic minerals, with magnetic remanence peaks appearing semi-periodically approximately every

  5. Permafrost Monitoring Sonnblick

    NASA Astrophysics Data System (ADS)

    Reisenhofer, Stefan; Riedl, Claudia

    2014-05-01

    Within the project 'Permafrost Monitoring Sonnblick' (PERSON) the spatial distribution of permafrost is investigated by the 'Zentralanstalt für Meteorologie und Geodynamik' (ZAMG) in the Sonnblick area, in the Hohe Tauern in Austria. The aim of PERSON is to identify parameters affecting permafrost (geological, geomorphological, orographical and climatic factors), to determine its spatio-temporal behaviour under present day climate conditions and to estimate its possible future extension under a climate change scenario. PERSON makes use of a permafrost monitoring network that was installed 2005 in the Sonnblick area and is made up by four study sites: On the one hand the spatial extension of permafrost was focused at the ice-dammed lake Pilatus and the rock glacier Zirmsee. On the other hand, at two sites, namely Goldbergspitze and Wintergasse measurements of 'Ground-Surface Temperature' (GST) and 'Bottom Temperatures of the Snow cover' (BTS) are measured. In order to record temperatures in the uppermost layer of the ground and avoid heating by direct solar radiation loggers were buried a few centimetres into the ground or installed in boreholes at depths between 2 and 140 cm. Each of the 'Near Surface Temperature' (NST) borehole mouths is closed up with insulating foam to protect the measurements from atmospheric influence. In addition to these measurements, continuous temperature records from three 20 m deep boreholes located at the southern slope of Hoher Sonnblick are available since 2007, which represent the longest series of its kind in Austria. Furthermore, data from seismic and geoelectric measurements, temperature sensors readings at the surface and extensive meteorological observations from the Sonnblick Observatory are available. Already collected and evaluated data indicate that the thickness of the debris layer around the boreholes reaches a depth of 2 m but no more. The active layer thickness measured in the borehole next to the glacier ranges between

  6. Chronological constraints on Cordilleran Ice Sheet glaciomarine sedimentation from core MD02-2496 off Vancouver Island (western Canada)

    NASA Astrophysics Data System (ADS)

    Cosma, T. N.; Hendy, I. L.; Chang, A. S.

    2008-05-01

    Chronology based on 46 radiocarbon dates has been generated for MD02-2496, western Vancouver Island, Canada. Subsequent correlation between glaciomarine sedimentary sequences within the core and the terrestrial stratigraphy of the Cordilleran Ice Sheet for the last 50 ka provide new insight into Cordilleran Ice Sheet processes. Glaciomarine sedimentation associated with the most recent advance (Fraser Glaciation) of the Cordilleran Ice Sheet began at 30.5 cal kyr BP (˜25 14C kyr BP). Extremely high sedimentation rates indicate the ice sheet became proximal to the site at ˜19.5 cal kyr BP (16 14C kyr BP). Deposition of ice rafted detritus (IRD) began at ˜17 cal kyr BP (14 14C kyr BP), and abruptly terminated at ˜16.2 cal kyr BP (13.5 14C kyr BP) indicating rapid regional ice sheet retreat. A minor IRD event followed at ˜14.7 cal kyr BP (12.5 14C kyr BP). Glaciomarine sediment deposition abruptly ended at 10.2 cal kyr BP (˜8.8 14C kyr BP) with the resumption of biogenic sedimentation. The Olympia Interstade is represented by an interval of hemipelagic sedimentation between ˜43 and 31.5 ka. Prior to ˜45 ka sediment deposition is controlled by glaciomarine processes with evidence for a significant IRD event at ˜47 cal kyr BP (>41±1.06 14C kyr BP).

  7. Chronologies of marine sediment cores during the Last Interglacial: strengths and limitations of commonly used climato-stratigraphic alignments

    NASA Astrophysics Data System (ADS)

    Govin, Aline; Capron, Emilie

    2015-04-01

    The Last Interglacial (LIG, ~129-116 thousand of years, ka) is relatively well documented in marine sediment cores retrieved across the globe. However, these records exhibit very few absolute age markers such as magnetic events and dated tephra layers, which limits the definition of independent and precise LIG age models. As a result, age models of marine sediments are defined using various methods based on the (i) synchronisation or (ii) climato-stratigraphic alignment of marine records to dated "reference" records, assuming simultaneous regional changes for a given climate variable (e.g. foraminiferal δ18O, temperature). The use of different "reference" chronologies (e.g. LR04, speleothem or ice core chronologies) also limits a precise investigation of climatic sequences across the LIG. Here, we evaluate the underlying hypotheses, strengths and limitations, and age uncertainties of methods commonly used in marine sediments during the LIG: i.e. benthic δ18O alignment to the LR04 benthic δ18O stack, temperature alignment to ice core or to speleothem records. We compare the resulting age models using examples from the North Atlantic core MD95-2042 and the Southern Ocean core MD02-2488. We show a lack of remarkable tie-points within the LIG, which limits the study of the sub-millennial-scale climate variability. We also report age offsets up to 4 ka when different reference chronologies (e.g. ice cores vs. speleothems) or different types of aligned records (e.g. SST vs. planktonic δ18O) are used. These results highlight the need for careful estimates of age uncertainties when defining age models in marine sediments. They also emphasize the fact that LIG chronologies should be considered with care. A clear statement on the reference chronology, the method of alignment and the type of tracers that are used should be given when investigating the LIG sequence of climatic events from various sediment cores or when comparing LIG marine records and climate model

  8. Vegetation history of central Chukotka deduced from permafrost paleoenvironmental records of the El'gygytgyn Impact Crater

    NASA Astrophysics Data System (ADS)

    Andreev, A. A.; Morozova, E.; Fedorov, G.; Schirrmeister, L.; Bobrov, A. A.; Kienast, F.; Schwamborn, G.

    2012-08-01

    Frozen sediments from three cores bored in the permafrost surrounding the El'gygytgyn Impact Crater Lake have been studied for pollen, non-pollen palynomorphs, plant macrofossils and rhizopods. The palynological study of these cores contributes to a higher resolution of time intervals presented in a poor temporal resolution in the lacustrine sediments; namely the Allerød and succeeding periods. Moreover, the permafrost records better reflect local environmental changes, allowing a more reliable reconstruction of the local paleoenvironments. The new data confirm that shrub tundra with dwarf birch, shrub alder and willow dominated the lake surroundings during the Allerød warming. Younger Dryas pollen assemblages reflect abrupt changes to grass-sedge-herb dominated environments reflecting significantly drier and cooler climate. Low shrub tundra with dwarf birch and willow dominate the lake vicinity at the onset of the Holocene. The find of larch seeds indicate its local presence around 11 000 cal yr BP and, thus a northward shift of treeline by about 100 km during the early Holocene thermal optimum. Forest tundra with larch and shrub alder stands grew in the area during the early Holocene. After ca. 3500 cal yr BP similar-to-modern plant communities became common in the lake vicinity.

  9. Vegetation history of Central Chukotka deduced from permafrost paleoenvironmental records of the El'gygytgyn Impact Crater

    NASA Astrophysics Data System (ADS)

    Andreev, A. A.; Morozova, E.; Fedorov, G.; Schirrmeister, L.; Bobrov, A. A.; Kienast, F.; Schwamborn, G.

    2012-04-01

    Frozen sediments from three cores bored in permafrost surrounding of the El'gygytgyn Impact Crater Lake have been studied for pollen, non-pollen palynomorphs, plant macrofossils, and rhizopods. The palynological study of the cores contributes to a higher resolution of time intervals presented in a poor temporal resolution in the lacustrine sediments; namely the Allerød and succeeding periods. Moreover, permafrost records better reflect local environmental changes, thus, allowing more reliable reconstruction of the local paleoenvironments. The new data confirm that shrub tundra with dwarf birch, shrub alder and willow dominated in the lake surroundings during the Allerød warming. Younger Dryas pollen assemblages reflect abrupt changes to grass-sedge-herb dominated environments reflecting significant climate deterioration. Low shrub tundra with dwarf birch and willow dominate the lake vicinity at the onset of the Holocene. The founds of larch seeds indicate its local presence around 11 000 cal. yr BP and, thus a northward shift of treeline by about 100 km during the early Holocene thermal optimum. Forest tundra with larch and shrub alder stands grew in the area during the early Holocene. After ca. 3500 cal. yr BP similar-to-modern plant communities became common in the lake vicinity.

  10. Tool for Sampling Permafrost on a Remote Planet

    NASA Technical Reports Server (NTRS)

    Peters, Gregory

    2006-01-01

    A report discusses the robotic arm tool for rapidly acquiring permafrost (RATRAP), which is being developed for acquiring samples of permafrost on Mars or another remote planet and immediately delivering the samples to adjacent instruments for analysis. The prototype RATRAP includes a rasp that protrudes through a hole in the bottom of a container that is placed in contact with the permafrost surface. Moving at high speed, the rasp cuts into the surface and loads many of the resulting small particles of permafrost through the hole into the container. The prototype RATRAP has been shown to be capable of acquiring many grams of permafrost simulants in times of the order of seconds. In contrast, a current permafrost sampling system that the RATRAP is intended to supplant works by scraping with tines followed by picking up the scrapings in a scoop, sometimes taking hours to acquire a few grams. Also, because the RATRAP inherently pulverizes the sampled material, it is an attractive alternative to other sampling apparatuses that generate core or chunk samples that must be further processed by a crushing apparatus to make the sample particles small enough for analysis by some instruments.

  11. ADAPT: building conceptual models of the physical and biological processes across permafrost landscapes

    NASA Astrophysics Data System (ADS)

    Allard, M.; Vincent, W. F.; Lemay, M.

    2012-12-01

    Fundamental and applied permafrost research is called upon in Canada in support of environmental protection, economic development and for contributing to the international efforts in understanding climatic and ecological feedbacks of permafrost thawing under a warming climate. The five year "Arctic Development and Adaptation to Permafrost in Transition" program (ADAPT) funded by NSERC brings together 14 scientists from 10 Canadian universities and involves numerous collaborators from academia, territorial and provincial governments, Inuit communities and industry. The geographical coverage of the program encompasses all of the permafrost regions of Canada. Field research at a series of sites across the country is being coordinated. A common protocol for measuring ground thermal and moisture regime, characterizing terrain conditions (vegetation, topography, surface water regime and soil organic matter contents) is being applied in order to provide inputs for designing a general model to provide an understanding of transfers of energy and matter in permafrost terrain, and the implications for biological and human systems. The ADAPT mission is to produce an 'Integrated Permafrost Systems Science' framework that will be used to help generate sustainable development and adaptation strategies for the North in the context of rapid socio-economic and climate change. ADAPT has three major objectives: to examine how changing precipitation and warming temperatures affect permafrost geosystems and ecosystems, specifically by testing hypotheses concerning the influence of the snowpack, the effects of water as a conveyor of heat, sediments, and carbon in warming permafrost terrain and the processes of permafrost decay; to interact directly with Inuit communities, the public sector and the private sector for development and adaptation to changes in permafrost environments; and to train the new generation of experts and scientists in this critical domain of research in Canada

  12. Historical profiles of PCB in dated sediment cores suggest recent lake contamination through the "halo effect".

    PubMed

    Naffrechoux, Emmanuel; Cottin, Nathalie; Pignol, Cécile; Arnaud, Fabien; Jenny, Jean-Philippe; Perga, Marie-Elodie

    2015-02-01

    We investigated the major sources of polychlorinated biphenyls (PCB) and interpreted the environmental fate processes of these persistent organic pollutants in the past and current PCB contamination of three large, urbanized, French peri-alpine lakes. Dated sediment cores were analyzed in order to reconstruct and compare the historical contamination in all three lakes. Stratigraphic changes of PCB contents and fluxes were considered as revealing the temporal dynamics of PCB deposition to the lakes and the distribution of the seven indicator congeners (further referred to as PCBi) as an indicator of the main contamination origin and pathway. Although located within a single PCB industrial production region, concentration profiles for the three lakes differed in timing, peak concentration magnitudes, and in the PCBi congeners compositions. PCBi fluxes to the sediment and the magnitude of the temporal changes were generally much lower in Lake Annecy (0.05-2 ng·cm(-2)·yr(-1)) as compared to Lakes Geneva (0.05-5 ng·cm(-2)·yr(-1)) and Bourget (5-290 ng·cm(-2)·yr(-1)). For all three lakes, the paramount contamination occurred in the early 1970s. In Lakes Annecy and Bourget, PCB fluxes have declined and plateaued at 0.5 and 8 ng·cm(-2)·yr(-1), respectively, since the early 1990s. In Lake Geneva, PCB fluxes have further decreased by the end of the XX(th) century and are now very low. For the most contaminated lake (Lake Bourget), the high PCBi flux (5-290 ng·cm(-2)·yr(-1)) and the predominance of heavy congeners for most of the time period are consistent with a huge local input to the lake. This still high rate of Lake Bourget is explained by transport of suspended solids from one of its affluents, polluted by an industrial point source. Intermediate historical levels and PCBi distribution over time for Lake Geneva suggest a mixed contamination (urban point sources and distant atmospheric transport), while atmospheric deposition to Lake Annecy explains its lowest

  13. Tephrostratigraphic studies on a sediment core from Lake Prespa in the Balkans

    NASA Astrophysics Data System (ADS)

    Damaschke, M.; Sulpizio, R.; Zanchetta, G.; Wagner, B.; Böhm, A.; Nowaczyk, N.; Rethemeyer, J.; Hilgers, A.

    2013-01-01

    A detailed tephrostratigraphic record, which dates back to Marine Isotope Stage (MIS) 5b (ca. 91 kyr), has been established from a 17.76 m long core (Co1215) from Lake Prespa (Macedonia, Albania and Greece). A total of eleven tephra and cryptotephra layers (PT0915-1 to PT0915-11) were identified, using XRF scanning, magnetic susceptibility measurements, and macro- and microscopic inspection of the sediments. The major element composition of glass shards and/or micro-pumice fragments indicates that the tephras and cryptotephras originate from the explosive volcanism of Italy. Eight tephra and cryptotephra layers were correlated with specific volcanic eruptions: the AD 512 eruption of Somma-Vesuvius (1438 cal yr BP), the Mercato eruption of Somma-Vesuvius (8890 ± 90 cal yr BP), the Tufi Biancastri/LN1-LN2 eruption of the Campi Flegrei (14 749 ± 523 cal yr BP and 15 551 ± 621 cal yr BP), the SMP1-e/Y-3 eruption of the Campi Flegrei (30 000-31 000 cal yr BP), the Campanian Ignimbrite/Y-5 eruption of the Campi Flegrei (39 280 ± 110 cal yr BP), the SMP1-a event of Ischia Island (around 44 000 cal yr BP) and the Green Tuff/Y-6 eruption of Pantelleria Island (around 45 000 cal yr BP). One tephra could be attributed to the volcanic activity of Mount Etna, but probably represents an unknown eruption at ca. 60 000 cal yr BP. Cryptotephras PT0915-6 and PT0915-10 remain unclassified so far, but according to the presented age-depth model these would have been deposited around 35 000 and 48 500 cal yr BP, respectively. Some of the tephras and cryptotephras are recognised for the first time in the Balkan region. The tephrostratigraphic work provides important information about ash dispersal and explosion patterns of source volcanoes and can be used to correlate and date geographically distant paleoenvironmental and archaeological archives in the central Mediterranean region. Moreover, the tephrostratigraphic work in combination with radiocarbon and electron spin resonance (ESR

  14. Numerical modeling of coupled nitrification-denitrification in sediment perfusion cores from the hyporheic zone of the Shingobee River, MN

    USGS Publications Warehouse

    Sheibley, R.W.; Jackman, A.P.; Duff, J.H.; Triska, F.J.

    2003-01-01

    Nitrification and denitrification kinetics in sediment perfusion cores were numerically modeled and compared to experiments on cores from the Shingobee River MN, USA. The experimental design incorporated mixing groundwater discharge with stream water penetration into the cores, which provided a well-defined, one-dimensional simulation of in situ hydrologic conditions. Ammonium (NH+4) and nitrate (NO-3) concentration gradients suggested the upper region of the cores supported coupled nitrification-denitrification, where groundwater-derived NH+4 was first oxidized to NO-3 then subsequently reduced via denitrification to N2. Nitrification and denitrification were modeled using a Crank-Nicolson finite difference approximation to a one-dimensional advection-dispersion equation. Both processes were modeled using first-order reaction kinetics because substrate concentrations (NH+4 and NO-3) were much smaller than published Michaelis constants. Rate coefficients for nitrification and denitrification ranged from 0.2 to 15.8 h-1 and 0.02 to 8.0 h-1, respectively. The rate constants followed an Arrhenius relationship between 7.5 and 22 ??C. Activation energies for nitrification and denitrification were 162 and 97.3 kJ/mol, respectively. Seasonal NH+4 concentration patterns in the Shingobee River were accurately simulated from the relationship between perfusion core temperature and NH+4 flux to the overlying water. The simulations suggest that NH+4 in groundwater discharge is controlled by sediment nitrification that, consistent with its activation energy, is strongly temperature dependent. ?? 2003 Elsevier Ltd. All rights reserved.

  15. Sediment core fossils in ancient Lake Ohrid: testing for faunal change in molluscs since the Last Interglacial period

    NASA Astrophysics Data System (ADS)

    Albrecht, C.; Vogel, H.; Hauffe, T.; Wilke, T.

    2010-05-01

    Ancient Lake Ohrid is probably of early Pleistocene or Pliocene origin and amongst the few lakes in the world harboring an outstanding degree of endemic biodiversity. Although there is a long history of evolutionary research in Lake Ohrid, particularly on molluscs, a mollusc fossil record has been missing up to date. For the first time, gastropod and bivalve fossils are reported from the basal, calcareous part of a 2.6 m long sediment succession (core Co1200) from the north-eastern part of Lake Ohrid. Electron spin resonance (ESR) dating of mollusc shells from the same stratigraphic level yielded an age of 130±28 ka. Lithofacies III sediments, i.e. a subdivision of the stratigraphic unit comprising the basal succession of core Co1200 between 181.5-263 cm appeared solid, grayish-white, and consisted almost entirely of silt-sized endogenic calcite (CaCO3>70%) and intact and broken mollusc shells. Here we compare the faunal composition of the thanatocoenosis with recent mollusc associations in Lake Ohrid. A total of 13 mollusc species (9 gastropod and 4 bivalve species) could be identified within Lithofacies III sediments. The value of sediment core fossils for reconstructing palaeoenvironmental settings was evaluated. The agreement between sediment and palaeontological proxies was tested. The combined findings of the ecological study and the sediment characteristics suggest deposition in a shallow water environment during the Last Interglacial period. We tested for major faunal changes since the Last Interglacial period and searched for signs of extinction events. The fossil fauna exclusively included species also found in the present fauna, i.e. no extinction events are evident for this site since the Last Interglacial. The thanatocoenosis showed the highest similarity with recent Intermediate Layer (5-25 m) mollusc assemblages. The demonstrated existence of a mollusc fossil record in Lake Ohrid sediment cores also has great significance for future deep drilling

  16. The extent and historical trend of metal pollution recorded in core sediments from the artificial Lake Shihwa, Korea.

    PubMed

    Ra, Kongtae; Bang, Jae-Hyun; Lee, Jung-Moo; Kim, Kyung-Tae; Kim, Eun-Soo

    2011-08-01

    The vertical distribution of trace metals in sediment cores was investigated to evaluate the extent and the historical record of metal pollution over 30 years in the artificial Lake Shihwa in Korea. A marked increase of trace metals after 1980 was observed due to the operation of two large industrial complexes and dike construction for a reclamation project. There was a decreasing trend of metal concentrations with the distance from the pollution source. The enrichment factor and pollution load index of the metals indicated that the metal pollution was mainly derived from Cu, Zn and Cd loads due to anthropogenic activities. The concentrations of Cr, Ni, Cu, Zn, As and Pb in the upper part of all core sediments exceeded the ERL criteria of NOAA. Our results indicate that inadequate planning and management of industrialization and a large reclamation project accomplished by dike construction have continued to strongly accelerate metal pollution in Lake Shihwa. PMID:21658731

  17. Beaded streams of Arctic permafrost landscapes

    NASA Astrophysics Data System (ADS)

    Arp, C. D.; Whitman, M. S.; Jones, B. M.; Grosse, G.; Gaglioti, B. V.; Heim, K. C.

    2014-07-01

    Beaded streams are widespread in permafrost regions and are considered a common thermokarst landform. However, little is known about their distribution, how and under what conditions they form, and how their intriguing morphology translates to ecosystem functions and habitat. Here we report on a Circum-Arctic inventory of beaded streams and a watershed-scale analysis in northern Alaska using remote sensing and field studies. We mapped over 400 channel networks with beaded morphology throughout the continuous permafrost zone of northern Alaska, Canada, and Russia and found the highest abundance associated with medium- to high-ice content permafrost in moderately sloping terrain. In the Fish Creek watershed, beaded streams accounted for half of the drainage density, occurring primarily as low-order channels initiating from lakes and drained lake basins. Beaded streams predictably transition to alluvial channels with increasing drainage area and decreasing channel slope, although this transition is modified by local controls on water and sediment delivery. Comparison of one beaded channel using repeat photography between 1948 and 2013 indicate relatively stable form and 14C dating of basal sediments suggest channel formation may be as early as the Pleistocene-Holocene transition. Contemporary processes, such as deep snow accumulation in stream gulches effectively insulates river ice and allows for perennial liquid water below most beaded stream pools. Because of this, mean annual temperatures in pool beds are greater than 2 °C, leading to the development of perennial thaw bulbs or taliks underlying these thermokarst features. In the summer, some pools stratify thermally, which reduces permafrost thaw and maintains coldwater habitats. Snowmelt generated peak-flows decrease rapidly by two or more orders of magnitude to summer low flows with slow reach-scale velocity distributions ranging from 0.1 to 0.01 m s-1, yet channel runs still move water rapidly between pools

  18. Relationship of polycyclic aromatic hydrocarbons with algae-derived organic matter in sediment cores from a subtropical region

    NASA Astrophysics Data System (ADS)

    Duan, Dandan; Huang, Youda; Cheng, Hefa; Ran, Yong

    2015-11-01

    The influence of algae-derived organic matter (AOM) and climate warming on the historical record of polycyclic aromatic hydrocarbons (PAHs) in the subtropical reservoir sediments was investigated. The profiles of PAH concentrations and AOM contents at the eutrophic and meso-eutrophic reservoirs are significantly elevated and show good correlations with increasing mean air temperature during the past 60 years, suggesting that increasing temperature plays a significant role in increase of algal productivity and PAH deposition. Temperature-mediated AOM is suggested to enhance the deposition and accumulation of pyrogenic PAHs in the sediment cores, also implying an inaccurate estimation on the historical record for atmospheric deposition of PAHs in eutrophic and meso-eutrophic reservoirs. For an oligotrophic reservoir, PAHs decrease as the sediment depth decreases and are less significantly related to AOM. As the oligotrophic reservoir is phosphorus limited and its AOM is significantly oxidized, the effect of increasing temperature on AOM and PAHs is insignificant.

  19. 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. PMID:27058126

  20. [Concentrations and Distribution of Metals in the Core Sediments from Estuary and City Section of Liaohe River].

    PubMed

    Wang, Wei-jie; Zhou, Jun-li; Pei, Shu-wei; Liu, Zheng-tao

    2016-01-15

    The particle size, total organic carbon (TOC), total nitrogen (TN), C/N ratio and metal concentrations as well as activities of 210Pb were determined in Liaohe River estuary area (LN-2) and Shenyang area (LN-5), and the organic matter resources were discussed in two core sediments. Also the index of geoaccumulation (Igeo) and enrichment factors (EFs) methods were applied to evaluate the state of heavy metal contamination in the studied sties. The study showed that both sediment cores LN-2 and LN-5 were dominated by silts, and the vertical variations of grain-size composition and organic matter were well distributed in LN- 2 while fluctuated in LN-5. According to the organic matter source analysis through C/N ratio, C/N ratio varied in the scale of 5. 24-7.93 in LN-2 which was dominated by river source, and 9.94-14.21 in LN-5 which was dominated by terrestrial input. Al, Ca, Fe, Mn, Ni, Cu, Zn, Cd, Pb and Cr in two sediment cores had different vertical changing rules, Ni and Zn in LN-2 as well as Pb and Zn in LN-5 were affected by both natural and human factors, other elements had similar distributions to those of organic matters, which showed that these elements were mainly affected by the natural activities. Based on Igeo and EFs, both sediment cores were more severely polluted with Ni, Zn and Pb than other metals. The effects of human activities on the environment were also discussed in this study, combined with the economical development of Liaoning Province and the studied sites in the past 20 years. PMID:27078953

  1. Historical contamination of PAHs, PCBs, DDTs, and heavy metals in Mississippi River Delta, Galveston Bay and Tampa Bay sediment cores.

    PubMed

    Santschi, P H; Presley, B J; Wade, T L; Garcia-Romero, B; Baskaran, M

    2001-07-01

    Profiles of trace contaminant concentrations in sediment columns can be a natural archive from which pollutant inputs into coastal areas can be reconstructed. Reconstruction of historical inputs of anthropogenic chemicals is important for improving management strategies and evaluating the success of recent pollution controls measures. Here we report a reconstruction of historical contamination into three coastal sites along the US Gulf Coast: Mississippi River Delta, Galveston Bay and Tampa Bay. Within the watersheds of these areas are extensive agricultural lands as well as more than 50% of the chemical and refinery capacity of the USA. Despite this pollution potential, relatively low concentrations of trace metals and trace organic contaminants were found in one core from each of the three sites. Concentrations and fluxes of most trace metals found in surface sediments at these three sites, when normalized to Al, are typical for uncontaminated Gulf Coast sediments. Hydrophobic trace organic contaminants that are anthropogenic (polycyclic aromatic hydrocarbons, DDTs, and polychlorinated biphenyls) are found in sediments from all locations. The presence in surface sediments from the Mississippi River Delta of low level trace contaminants such as DDTs, which were banned in the early 1970's, indicate that they are still washed out from cultivated soils. It appears that the DDTs profile in that sediment core was produced by a combination of erosion processes of riverine and other sedimentary deposits during floods. Most of the pollutant profiles indicate that present-day conditions have improved from the more contaminated conditions in the 1950-1970's, before the advent of the Clean Water Act. PMID:11488356

  2. Effects of Temperature and Substrate Availability on Methanotrophy in Arctic Permafrost Landscapes

    NASA Astrophysics Data System (ADS)

    Roy Chowdhury, T.; Graham, D. E.; Wullschleger, S. D.

    2014-12-01

    Arctic permafrost ecosystems store ~ 50 % of global belowground carbon (C) and are a considerable source of atmospheric methane (CH4). Current estimates report that nearly 10 - 40 Tg yr-1 of CH4 is released from permafrost environments. In particular, topographic depressions on the landscape are predominantly anoxic and conducive to active methanogenesis. At the sediment-water interfaces of the water-saturated polygonal units, namely low- and flat-centered polygons, CH4 and oxygen gradients overlap and bacterial CH4 oxidation is an important process contributing to CH4 consumption. Methanotrophic bacteria represent the major terrestrial sinks for CH4 and can reduce CH4 emissions by ~70 %. Therefore, determining how the activity and abundance of methanotrophic communities respond to warming temperature conditions is critical to predicting effects of permafrost thaw and active layer warming on CH4 emissions. As ground temperature increases in the Arctic landscape, a major impact of permafrost thaw could be draining of the active layer with resultant subsidence leading to the formation of elevated and relatively oxic high-centered polygons. These changes can impact both methanogen and methanotroph communities and affect net CH4 fluxes. To understand the controls of temperature and substrate availability on CH4 oxidation, we examined process rates and temporal dynamics of methanotroph biomass in contrasting landscape gradients. We investigated the active layer and Cryoturbated permafrost organic soilsd from replicate soil cores collected from high-centered and flat-centered polygonal units in the Barrow Environmental Observatory, Barrow, AK. We used quantitative PCR to quantify methanogen (mcrA) and methanotroph (pmoA) population size by functional gene analysis. We present potential methane oxidation activity in response to three incubation temperatures (-2 oC, 4 oC, and 10 oC) that represent thaw-season ground temperatures. Our objectives were to estimate the rates

  3. Final report on the sampling and analysis of sediment cores from the L-Area oil and chemical basin

    SciTech Connect

    Not Available

    1985-08-01

    Nine vibracores were collected in the L-Area oil and chemical basin (904-83G) during late March and early April 1985. These cores were collected for analysis of the sludge on the basin floor and the underlying sediment. Several different field and laboratory analyses were performed on each three inch segment of all the cores. These included: (1) Sediment characterization; (2) Percent moisture; (3) Dry weight; (4) Spectral gamma analysis; (5) Gross alpha and beta analysis. Detailed chemical analysis were measured on selected intervals of 2 cores (LBC-5 and 6) for complete chemical characterization of the sediments. This sampling program was conducted to provide information so that a closure plan for the basin could be developed. This report describes the methods employed during the project and provide a hard copy of the analytical results from the sample analyses. Included in the appendices are copies of all field and laboratory notes taken during the project and copies of the gas chromatograms for the petroleum hydrocarbon analysis. All chemical results were also submitted on a 5-inch floppy disk.

  4. The stabilisation of wet sediment cores by means of a polyethylene glycol/freeze-drying treatment for display and permanent storage

    NASA Astrophysics Data System (ADS)

    Hoffmann, Per; Pätzold, Jürgen

    2001-12-01

    A reversible method is presented to transform waterlogged sediment cores into dry and stable specimens which can go on exhibition or into permanent storage, needing no special precautions. Wet sediment core segments are bath-impregnated with polyethylene glycol of molecular weight 3,350 (PEG 3,350) dissolved in water. The samples are then subjected to a freeze-drying process, during which the PEG forms a stabilising and bonding porous network structure in the capillary system of the sediment. Standard sediment cores at least 1 m long become strong enough to stand upright. Sediment types ranging from muddy deep-sea sediments to very coarse littoral Halimeda sand were successfully stabilised. For standard cores of 10-cm diameters split length-wise, impregnation times vary from 2 weeks for coarse sand to 6-10 weeks for more compacted sediments. With regard to the stability of the samples and the visual clarity of detail, best results were obtained by impregnation with 25 to 60% solutions of PEG 3,350, coarse sediments needing more PEG than finer ones. Colour changes are systematic - the processed samples are lighter in appearance and the contrasts are enhanced, but there is no serious shift in colour tones. The PEG can easily be re-dissolved and washed out of the sediments. Display specimens can thus be made available for research again.

  5. Tephra in marine sediment cores offshore southern Iceland: A 68,000 year record of explosive volcanism

    NASA Astrophysics Data System (ADS)

    Bonanati, Christina; Wehrmann, Heidi; Portnyagin, Maxim; Hoernle, Kaj; Mirzaloo, Maryam; Nürnberg, Dirk

    2016-04-01

    Explosive volcanic eruptions on Iceland, even of intermediate magnitude have far-reaching impacts. Their far-distal deposits have been found up to Northern Continental Europe and Greenland. On Iceland, the harsh environment and strongly erosive conditions limit the preservation of volcanic deposits and their accessibility on land. The area offshore southern Iceland preserves information about the depositional fans at medial distance from the volcanic source. Here we use this sedimentary archive to reconstruct the Icelandic eruption record in greater detail. This high resolution geological record allows us to infer eruption frequencies and explosiveness in great detail and contributes to the assessment of Icelandic volcanic hazards, volcano-climate interaction, stratigraphy and palaeoceanographic reconstructions. Eight gravity cores were obtained during RV Poseidon Cruise 457, at 260 to 1,600 m water depths and distances of 130 to 400 km west to southeast of Iceland. The ˜4 to 10 m long sediment cores reach back to the Late Pleistocene (˜68 ka BP; dated by 14C and sedimentation rates), mostly excluding the Holocene. Potential tephra layers were identified by visual inspection and color scans. Volcanic glass shards were analyzed for their major element composition by electron microprobe and assigned to their eruptive source by geochemical fingerprinting. More than 50 primary tephra layers and nearly as many reworked layers were identified, several of which were correlated across the cores. The mostly basaltic tephra shards are derived from the Katla, Grímsvötn-Lakagígar, Bárðarbunga-Veiðivötn, and Hekla volcanic systems. Primary and mixed layers with particles of unique bimodal composition identical to the ˜12 ka BP Vedde-Tephra from the Katla Volcanic System, including rhyolitic particles, were identified in nearly all cores and used as time marker and for inter-core correlation. Tephra layers of unique unknown composition were also identified and

  6. Dating of pollen samples from the sediment core of Lake St Anne in the East Carpathian Mountains, Romania

    NASA Astrophysics Data System (ADS)

    Hubay, Katalin; Katalin Magyari, Enikö; Braun, Mihály; Schabitz, Frank; Molnár, Mihály

    2016-04-01

    Lake St Anne (950 m a.s.l.) is situated in the Ciomadul volcano crater, the youngest volcano in the Carpathians. Aims driving forward the studies there are twofold, one is dating the latest eruption of the Ciomadul volcano and the other is the multi-proxy palaeoenvironmental reconstruction of this region. The sediment of Lake St Anne was sampled several times already, but never reached the bottom of the lake before. During the winter of 2013 at a new core location drilling started at 600 cm water depth and finally reached the bottom of the lake sediment at approximately 2300 cm including water depth. As for all multi-proxy studies essential requirement was to build a reliable chronology. Sediments were dated by radiocarbon method. Previous radiocarbon dates were measured on plant macrofossils, charcoal, Cladocera eggs, chironomid head capsules and bulk lake sediments. Lake St Anne has volcanic origin and there is intensive upwelling of CO2it is important to study and take into consideration, whether there is any local reservoir effect at the case of samples where it could be problematic. Furthermore the late part of the sediment section (between 15,000 and 30,000 cal. yr BP) has low organic matter content (less than 2-4%) with scarcity of datable plant macrofossil material. In this review a different fraction of pollen samples with terrestrial origin was tested and studied as a novel sample type for the radiocarbon dating. Pollen samples were extracted from the lake sediment cores. This type of organic material could be an ideal candidate for radiocarbon based chronological studies as it has terrestrial source and is present in the whole core in contrast with the terrestrial macrofossils. Although the pollen remains were present in the whole core, in many cases their amount give a challenge even for the AMS technic. Samples were measured with EnvironMICADAS AMS and its gas ion source in the HEKAL laboratory (Debrecen, Hungary). We examine the reliability the

  7. Vertical and lateral flux on the continental slope off Pakistan: correlation of sediment core and trap results

    NASA Astrophysics Data System (ADS)

    Schulz, H.; von Rad, U.

    2014-06-01

    Due to the lack of bioturbation, the varve-laminated muds from the oxygen minimum zone (OMZ) off Pakistan provide a unique opportunity to precisely determine the vertical and lateral sediment fluxes in the nearshore part of the northeastern Arabian Sea. West of Karachi (Hab area), the results of two sediment trap stations (EPT and WPT) were correlated with 16 short sediment cores on a depth transect crossing the OMZ. The top of a distinct, either reddish- or light-gray silt layer, 210Pb-dated as AD 1905 ± 10, was used as an isochronous stratigraphic marker bed to calculate sediment accumulation rates. In one core, the red and gray layer were separated by a few (5-10) thin laminae. According to our varve model, this contributes < 10 years to the dating uncertainty, assuming that the different layers are almost synchronous. We directly compared the accumulation rates with the flux rates from the sediment traps that collected the settling material within the water column above. All traps on the steep Makran continental slope show exceptionally high, pulsed winter fluxes of up to 5000 mg m-2 d-1. Based on core results, the flux at the seafloor amounts to 4000 mg m-2 d-1 and agrees remarkably well with the bulk winter flux of material, as well as with the flux of the individual bulk components of organic carbon, calcium carbonate and opal. However, due to the extreme mass of remobilized matter, the high winter flux events exceeded the capacity of the shallow traps. Based on our comparisons, we argue that high-flux events must occur regularly during winter within the upper OMZ off Pakistan to explain the high accumulations rates. These show distribution patterns that are a negative function of water depth and distance from the shelf. Some of the sediment fractions show marked shifts in accumulation rates near the lower boundary of the OMZ. For instance, the flux of benthic foraminifera is lowered but stable below ~1200-1300 m. However, flux and sedimentation in the

  8. Seismically induced soft-sediment deformation structures revealed by X-ray computed tomography of boring cores

    NASA Astrophysics Data System (ADS)

    Nakashima, Yoshito; Komatsubara, Junko

    2016-06-01

    X-ray computed tomography (CT) allows us to visualize three-dimensional structures hidden in boring cores nondestructively. We applied medical X-ray CT to cores containing seismically induced soft-sediment deformation structures (SSDSs) obtained from the Kanto region of Japan, where the 2011 off the Pacific coast of Tohoku Earthquake occurred. The CT images obtained clearly revealed various types of the seismically induced SSDSs embedded in the cores: a propagating sand dyke bent complexly by the preexisting geological structure, deformed laminations of fluidized sandy layers, and two types of downward mass movement (ductile downward folding and brittle normal faulting) as compensation for upward sand transport through sand dykes. Two advanced image analysis techniques were applied to the sand dyke CT images for the first time. The GrowCut algorithm, a specific digital image segmentation technique that uses cellular automata, was used successfully to extract the three-dimensional complex sand dyke structures embedded in the sandy sediments, which would have been difficult to achieve using a conventional image processing technique. Local autocorrelation image analysis was performed to detect the flow pattern aligned along the sand dykes objectively. The results demonstrate that X-ray CT coupled with advanced digital image analysis techniques is a promising approach to studying the seismically induced SSDSs in boring cores.

  9. A pervasive link between Antarctic ice core and subarctic Pacific sediment records over the past 800 kyrs

    NASA Astrophysics Data System (ADS)

    Jaccard, S. L.; Galbraith, E. D.; Sigman, D. M.; Haug, G. H.

    2010-01-01

    Recently developed XRF core-scanning methods permit paleoceanographic reconstructions on timescales similar to those of ice-core records. We have investigated the distribution of biogenic barium (Ba/Al), opal and carbonate (Ca/Al) in a sediment core retrieved from the abyssal subarctic Pacific (ODP 882, 50°N, 167°E, 3244 m) over an interval that spans the full length of the EPICA Dome C (EDC) ice-core record. Ba/Al and biogenic opal show a strong resemblance to the EDC δD and CO 2, with generally high concentrations during interglacials and lower values during ice ages of the past 800 kyrs. The sedimentary Ba/Al and biogenic opal are most easily interpreted as indicating a reduced sinking flux of organic matter from the surface ocean during cold periods. The Ba/Al maxima during peak interglacials are accompanied by transient Ca/Al peaks in these otherwise carbonate-devoid sediments, which are best explained by a deepening of the calcite lysocline, presumably due to reduced storage of respired CO 2 in the deep North Pacific. For most of the "luke-warm" interglacials noted between 420 and 750 ka in EDC, the Ba/Al peaks in ODP 882 are also lower, further strengthening the evidence for a simple physical link between global climate and the biogeochemistry of the subarctic Pacific.

  10. Impacts of permafrost change on landscape stability and water quality

    NASA Astrophysics Data System (ADS)

    Lamoureux, S. F.; Lafreniere, M. J.

    2015-12-01

    Communities and northern development depend on knowledge to support safe infrastructure design and to define appropriate environmental targets. Projected climate change is expected to have substantial impacts on permafrost through increased seasonal thaw. These changes will likely result in changing hydrological processes that will alter surface and subsurface water flow and quality. Similarly, in settings with ice-rich surficial materials, changing active layer depth and hydrological conditions can contribute to permafrost degradation and land instability. Predicting these impacts is an important need for sustainable development in permafrost regions. We have investigated these processes through a long term integrated watershed program at the Cape Bounty Arctic Watershed Observatory (CBAWO) in the Canadian Arctic. Surface water discharge and quality has been assessed since 2005 and in particular, through a period of record summer temperatures that resulted in substantial active layer perturbation and resulted in widespread localized disturbance. Research has documented the impact and recovery from these permafrost changes and demonstrate several key linkages between changing hydrological conditions, quality, and landscape sensitivity to disturbance. Deeper active layer thaw appears to alter subsurface flow paths, resulting sustained changes to water quality through increased solute fluxes and changes to nutrients. These effects are widespread across the landscape, while physical disturbance due to permafrost slope failures are dispersed and generate impacts ranging from minimal to locally-significant increases in downstream sediment and solute transport. We note that this strong spatial contrast between "thermal" and "physical" perturbation of the shallow permafrost system represents a key impact in these settings. Further, subsurface water pressurization appears to be localized but linked to physical disturbance. Hence, results indicate the benefit of an

  11. Permafrost soils and carbon cycling

    DOE PAGESBeta

    Ping, C. L.; Jastrow, J. D.; Jorgenson, M. T.; Michaelson, G. J.; Shur, Y. L.

    2014-10-30

    Knowledge of soils in the permafrost region has advanced immensely in recent decades, despite the remoteness and inaccessibility of most of the region and the sampling limitations posed by the severe environment. These efforts significantly increased estimates of the amount of organic carbon (OC) stored in permafrost-region soils and improved understanding of how pedogenic processes unique to permafrost environments built enormous OC stocks during the Quaternary. This knowledge has also called attention to the importance of permafrost-affected soils to the global C cycle and the potential vulnerability of the region's soil OC stocks to changing climatic conditions. In this review,more » we briefly introduce the permafrost characteristics, ice structures, and cryopedogenic processes that shape the development of permafrost-affected soils and discuss their effects on soil structures and on organic matter distributions within the soil profile. We then examine the quantity of OC stored in permafrost-region soils, as well as the characteristics, intrinsic decomposability, and potential vulnerability of this OC to permafrost thaw under a warming climate.« less

  12. Initial Results on the Meteoritic Component of new Sediment Cores Containing Deposits of the Eltanin Impact Event

    NASA Technical Reports Server (NTRS)

    Kyte, Frank T.; Gersonde, Rainer; Kuhn, Gerhard

    2002-01-01

    The late Pliocene impact of the Eltanin asteroid is the only known asteroid impact in a deep- ocean (-5 km) basin . This was first discovered in 1981 as an Ir anomaly in sediment cores collected by the USNS Eltanin in 1965. In 1995, Polarstern expedition ANT XII/4 made the first geological survey of the suspected impact region. Three sediment cores sampled around the San Martin seamounts (approx. 57.5 S, 91 W) contained well-preserved impact deposits that include disturbed ocean sediments and meteoritic impact ejecta. The latter is composed of shock-melted asteroidal materials and unmelted meteorites. In 2001, the FS Polarstern returned to the impact area during expedition ANT XVIIU5a. At least 16 cores were recovered that contain ejecta deposits. These cores and geophysical data from the expedition can be used to map the effects of the impact over a region of about 80,000 square km. To date we have measured Ir concentrations in sediments from seven of the new cores and preliminary data should be available for a few more by the time of the meeting. Our initial interpretation of these data is that there is a region in the vicinity of the San Martin Seamounts comprising at least 20,000 square km in which the average amount of meteoritic material deposited was more than 1 g per square cm. This alone is enough material to support a 500 m asteroid. Beyond this is a region of about 60,000 square km, mostly to the north and west, where the amount of ejecta probably averages about 0.2 g per square cm. Another 400 km to the east, USNS Eltanin core E10-2 has about 0.05 g per square cm, so we know that ejecta probably occurs across more than a million square km of ocean floor. A key to future exploration of this impact is to find evidence of the ejecta at more sites distant from the seamounts. We currently have almost no data from regions to the west or south of the San Martin seamounts.

  13. Sediment core record of global fallout and Bikini close-in fallout Pu in Sagami Bay, Western Northwest Pacific margin.

    PubMed

    Zheng, Jian; Yamada, Masatoshi

    2004-07-01

    The total 239-240Pu activity and 240Pu/239Pu atom ratio in the sediments in Sagami Bay of the western Northwest Pacific margin were investigated using ICP-MS with a shield torch system. 239+240Pu inventories in the examined sediment cores were found to be much higher than those predicted from atmospheric global fallout (42 MBq/km2) at the same latitude. In addition, elevated 240Pu/239Pu atom ratios ranging from 0.22 to 0.28 were observed in the sediment samples. On the basis of the vertical profiles of 239+240Pu and characterized 240Pu/239Pu atom ratios in a sediment core collected in the center of Sagami Bay, we identified two distinct sources of fallout Pu in the bay: the global stratospheric fallout with characteristic 240Pu/239Pu ratio of 0.18 and the transported close-in fallout derived from Bikini and Enewetak surface nuclear weapon test series in the 1950s. We propose that the Pu transportation was mainly due to oceanic processes (for example, through the North Equatorial Current and the Kuroshio Current). Using a two fallout end-member model, we find that the contribution of Bikini close-in fallout Pu ranged from 44 to 59% in Sagami Bay sediments. To the best of our knowledge, this is the first report that Pu contamination, which originated from Bikini and Enewetak nuclear weapon test series in the 1950s, has extended westwards as far as the Japanese coast. PMID:15296298

  14. Climatic Impact on Major and Trace Elements in Deltaic Core Sediments: Evidence from Muthupet Lagoon, South East Coast of India

    NASA Astrophysics Data System (ADS)

    Jayaprakash, M.; Velmurugan, P. M.; Giridharan, L.; Urban, B.

    2013-05-01

    Geochemistry of lagoon deposits provides a continuous record of climatic changes, and such core sediments at successive deeper and older layers have long been utilized for sedimentologic, and organic geochemical studies. These ecosystems provide a mechanism for trapping sediment and can act as a recorder of climatic changes via geochemical imprints. The aim of the present study is to evaluate the climatic and depositional controls in the Muthupet lagoon, Southeast coast of India, situated at the southern most end of the Cauvery delta. The down core variations of geochemical parameters and their ratios were employed to reveal the characteristics of Holocene climate and associated paleoenvironmental implications of the study area. Moderate values of the Chemical Index of Alteration (CIA) suggest intensive chemical weathering of the source rock under tropical to subtropical climatic conditions. Index of Composition Variability (ICV) values indicate low proportion of nonclay silicate minerals in these sediments. V/Cr ratio has been used as a paleo-oxygenation indicator and in the present study, the ratio V/Cr was found to be < 2 indicating oxic-depositional conditions prevailing in this lagoon. Ni/Co, Ni/V and (Cu+Mg)/Zn ratios of the sediments are evaluated and the variations are interpreted to reflect the changes in the input from the marine environment. Fe/Ti and Fe/Al ratios yields valuable information on the impact of climate changes on the sedimentation of the study areas. Na and S, indicators of paleosalinity and marine flooding have been evaluated. The increase in the concentration of Na at various depths was identified and the marine incursions were characterized.

  15. Aliphatic hydrocarbons in sediment cores from the southern basin of Lake Michigan

    SciTech Connect

    Doskey, P.V.; Andren, A.W.

    1991-10-01

    Aliphatic hydrocarbons in sediments of the southern basin of Lake Michigan have planktonic, terrigenous, and petroleum residue origins. Surficial sediments collected near the eastern shore in 60-80 m of water contained more petroleum residue and planktonic hydrocarbons and exhibited less terrigenous character than sediments collected from the deepest location in the basin. Petroleum residue inputs have increased since 1900 as evidenced by a change in the flux of an unresolved complex mixture (UCM) of hydrocarbons from 6 ng/cm{sup 2}{center_dot}yr to a flux of approximately 100 ng/cm{sup 2}{center_dot}yr in 1980. Sediment profiles of the UCM exhibited subsurface concentration maxima that may be due to reduced inputs of combustion products or feeding by oligochaetes. Profiles of n-C{sub l7} and pristane indicated that planktonic n-alkanes undergo degradation in the aerobic, mixed zone of the sediments.

  16. Permafrost Hazards and Linear Infrastructure

    NASA Astrophysics Data System (ADS)

    Stanilovskaya, Julia; Sergeev, Dmitry

    2014-05-01

    The international experience of linear infrastructure planning, construction and exploitation in permafrost zone is being directly tied to the permafrost hazard assessment. That procedure should also consider the factors of climate impact and infrastructure protection. The current global climate change hotspots are currently polar and mountain areas. Temperature rise, precipitation and land ice conditions change, early springs occur more often. The big linear infrastructure objects cross the territories with different permafrost conditions which are sensitive to the changes in air temperature, hydrology, and snow accumulation which are connected to climatic dynamics. One of the most extensive linear structures built on permafrost worldwide are Trans Alaskan Pipeline (USA), Alaska Highway (Canada), Qinghai-Xizang Railway (China) and Eastern Siberia - Pacific Ocean Oil Pipeline (Russia). Those are currently being influenced by the regional climate change and permafrost impact which may act differently from place to place. Thermokarst is deemed to be the most dangerous process for linear engineering structures. Its formation and development depend on the linear structure type: road or pipeline, elevated or buried one. Zonal climate and geocryological conditions are also of the determining importance here. All the projects are of the different age and some of them were implemented under different climatic conditions. The effects of permafrost thawing have been recorded every year since then. The exploration and transportation companies from different countries maintain the linear infrastructure from permafrost degradation in different ways. The highways in Alaska are in a good condition due to governmental expenses on annual reconstructions. The Chara-China Railroad in Russia is under non-standard condition due to intensive permafrost response. Standards for engineering and construction should be reviewed and updated to account for permafrost hazards caused by the

  17. Using Cyclic Variations Of Early Pliocene Diatom Assemblages To Determine Sediment Accumulation Rates In The ANDRILL AND-1B Core

    NASA Astrophysics Data System (ADS)

    Konfirst, M. A.; Scherer, R. P.; Monien, D.; Kuhn, G.; Winter, D.; Sjunneskog, C. M.

    2009-12-01

    In the 2006-2007 Antarctic field season, the ANDRILL MIS project recovered a 1,285m record of Miocene through Plio-Pleistocene sediments near Ross Island in the Ross Sea region of Antarctica. Diatom biostratigraphy, radiometric dating and magnetostratigraphy were used in conjunction with the evaluation of glacial surfaces of erosion (GSEs) to produce a well-constrained age model for the core. However, within the Plio-Pleistocene interval (the upper ~620m), the ANDRILL record also included 13 discrete intervals composed of nearly pure diatomite, the longest of which is over 80m thick. The lack of GSEs during periods of high diatom accumulation has created limitations in assigning ages to specific core depths within the diatomite intervals. In this study, data were collected on abundance of key diatom species present within 290 samples from the long Early Pliocene diatomite unit (DU XI- 363.37-459.24 mbsf) as well as ~15m of diatom-rich mudstone immediately overlying it. We analyzed diatom records at high resolution (as high as ca. 600 year sample interval, according to the chronostratigraphic correlations established by this study). This approximately 100m section was then subdivided into five units based on major diatom assemblage shifts and changes in both geochemical properties and clast abundance counts (Pompilio et al., 2007). Cyclic changes in relative diatom abundance were identified within each unit using characteristic species and matched to variations in the oxygen isotope record (Lisiecki & Raymo, 2005) using the chronostratigraphic framework established by Naish et al. (2007), which included the assignment of an oxygen isotope age to specific core depths. Additionally, the core ages provided by the correlation of diatom abundance with the isotope record allowed the calculation of sediment accumulation rates through the interval. The results presented here provide a further refinement to the ANDRILL age model and allow interpretation of the interaction

  18. A chronology of Late-Pleistocene permafrost events in southern New Jersey, eastern USA

    USGS Publications Warehouse

    French, H.M.; Demitroff, M.; Forman, S.L.; Newell, W.L.

    2007-01-01

    Frost fissures, filled with wind-abraded sand and mineral soil, and numerous small-scale non-diastrophic deformations, occur in the near-surface sediments of the Pine Barrens of southern New Jersey. The fissures are the result of thermal-contraction cracking and indicate the previous existence of either permafrost or seasonally-frozen ground. The deformations reflect thermokarst activity that occurred when permafrost degraded, icy layers melted and density-controlled mass displacements occurred in water-saturated sediments. Slopes and surficial materials of the area reflect these cold-climate conditions. Optically-stimulated luminescence permits construction of a tentative Late-Pleistocene permafrost chronology. This indicates Illinoian, Early-Wisconsinan and Late-Wisconsinan episodes of permafrost and/or deep seasonal frost and a Middle-Wisconsinan thermokarst event. Copyright ?? 2007 John Wiley & Sons, Ltd.

  19. [The possible contribution of late pleistocene biota to biodiversity in present permafrost zone].

    PubMed

    Gubin, S V; Maksimovich, S V; Davydov, S P; Gilichinskiĭ, D A; Shatilovich, A V; Spirina, E V; Iashina, S G

    2003-01-01

    During the last decade a wide range of biological objects, which have preserved their viability for tens and hundreds of thousands of years, was found in the samples of permafrost sediments from North-East Eurasia. Among them are bacteria, fungi, algae, moss spores, seeds of higher plants, protists. Along with physiological mechanisms of cryoconservation and constant low temperature of great importance for long-term preservation of biological objects in permafrost layers are ways of burying the organisms and conditions that prevail before the transition of sediments to the permafrost state. The analysis of viability showed by preserved biological objects gives reasons to suppose that some representatives of Pleistocene biota buried in permafrost thickness may contribute to the biodiversity of present cryolite zone. PMID:12723372

  20. Microbes in thawing permafrost: the unknown variable in the climate change equation

    SciTech Connect

    Graham, David E; Wallenstein, Matthew D; Vishnivetskaya, T.; Waldrop, Mark P.; Phelps, Tommy Joe; Pfiffner, Susan M.; Onstott, T. C.; Whyte, Lyle; Rivkina, Elizaveta; Gilichinsky, David A; Elias, Dwayne A; Mackelprang, Rachel; Verberkmoes, Nathan C; Hettich, Robert {Bob} L; Wagner, Dirk; Wullschleger, Stan D; Jansson, Janet

    2012-01-01

    Considering that 25% of Earth s terrestrial surface is underlain by permafrost (ground that has been continuously frozen for at least 2 years), our understanding of the diversity of microbial life in this extreme habitat is surprisingly limited. Taking into account the total mass of perennially frozen sediment (up to several hundred meters deep), permafrost contains a huge amount of buried, ancient organic carbon (Tarnocai et al., 2009). In addition, permafrost is warming rapidly in response to global climate change (Romanovsky et al., 2010), potentially leading to widespread thaw and a larger, seasonally thawed soil active layer. This concern has prompted the question: will permafrost thawing lead to the release of massive amounts of carbon dioxide (CO2) and methane (CH4) into the atmosphere? This question can only be answered by understanding how the microbes residing in permafrost will respond to thaw, through processes such as respiration, fermentation, methanogenesis and CH4 oxidation (Schuur et al., 2009). Predicting future carbon fluxes is complicated by the diversity of permafrost environments, ranging from high mountains, southern boreal forests, frozen peatlands and Pleistocene ice complexes (yedoma) up to several hundred meters deep, which vary widely in soil composition, soil organic matter (SOM) quality, hydrology and thermal regimes (Figure 1). Permafrost degradation can occur in many forms: thaw can progress downward from seasonally-thawed active layer soils in warming climates or laterally because of changes in surface or groundwater flow paths (Grosse et al., 2011). Permafrost degradation can sometimes lead to dramatic changes in ecosystem structure and function

  1. On the connection of permafrost and debris flow activity in Austria

    NASA Astrophysics Data System (ADS)

    Huber, Thomas; Kaitna, Roland

    2016-04-01

    Debris flows represent a severe hazard in alpine regions and typically result from a critical combination of relief energy, water, and sediment. Hence, besides water-related trigger conditions, the availability of abundant sediment is a major control on debris flows activity in alpine regions. Increasing temperatures due to global warming are expected to affect periglacial regions and by that the distribution of alpine permafrost and the depth of the active layer, which in turn might lead to increased debris flow activity and increased interference with human interests. In this contribution we assess the importance of permafrost on documented debris flows in the past by connecting the modeled permafrost distribution with a large database of historic debris flows in Austria. The permafrost distribution is estimated based on a published model approach and mainly depends of altitude, relief, and exposition. The database of debris flows includes more than 4000 debris flow events in around 1900 watersheds. We find that 27 % of watersheds experiencing debris flow activity have a modeled permafrost area smaller than 5 % of total area. Around 7 % of the debris flow prone watersheds have an area larger than 5 %. Interestingly, our first results indicate that watersheds without permafrost experience significantly less, but more intense debris flow events than watersheds with modeled permafrost occurrence. Our study aims to contribute to a better understanding of geomorphic activity and the impact of climate change in alpine environments.

  2. Sulfate reduction controlled by organic matter availability in deep sediment cores from the saline, alkaline Lake Van (Eastern Anatolia, Turkey)

    PubMed Central

    Glombitza, Clemens; Stockhecke, Mona; Schubert, Carsten J.; Vetter, Alexandra; Kallmeyer, Jens

    2013-01-01

    As part of the International Continental Drilling Program deep lake drilling project PaleoVan, we investigated sulfate reduction (SR) in deep sediment cores of the saline, alkaline (salinity 21.4‰, alkalinity 155 m mEq-1, pH 9.81) Lake Van, Turkey. The cores were retrieved in the Northern Basin (NB) and at Ahlat Ridge (AR) and reached a maximum depth of 220 m. Additionally, 65–75 cm long gravity cores were taken at both sites. SR rates (SRR) were low (≤22 nmol cm-3 day-1) compared to lakes with higher salinity and alkalinity, indicating that salinity and alkalinity are not limiting SR in Lake Van. Both sites differ significantly in rates and depth distribution of SR. In NB, SRR are up to 10 times higher than at AR. SR could be detected down to 19 mblf (meters below lake floor) at NB and down to 13 mblf at AR. Although SRR were lower at AR than at NB, organic matter (OM) concentrations were higher. In contrast, dissolved OM in the pore water at AR contained more macromolecular OM and less low molecular weight OM. We thus suggest, that OM content alone cannot be used to infer microbial activity at Lake Van but that quality of OM has an important impact as well. These differences suggest that biogeochemical processes in lacustrine sediments are reacting very sensitively to small variations in geological, physical, or chemical parameters over relatively short distances. PMID:23908647

  3. Sulfate reduction controlled by organic matter availability in deep sediment cores from the saline, alkaline Lake Van (Eastern Anatolia, Turkey).

    PubMed

    Glombitza, Clemens; Stockhecke, Mona; Schubert, Carsten J; Vetter, Alexandra; Kallmeyer, Jens

    2013-01-01

    As part of the International Continental Drilling Program deep lake drilling project PaleoVan, we investigated sulfate reduction (SR) in deep sediment cores of the saline, alkaline (salinity 21.4‰, alkalinity 155 m mEq(-1), pH 9.81) Lake Van, Turkey. The cores were retrieved in the Northern Basin (NB) and at Ahlat Ridge (AR) and reached a maximum depth of 220 m. Additionally, 65-75 cm long gravity cores were taken at both sites. SR rates (SRR) were low (≤22 nmol cm(-3) day(-1)) compared to lakes with higher salinity and alkalinity, indicating that salinity and alkalinity are not limiting SR in Lake Van. Both sites differ significantly in rates and depth distribution of SR. In NB, SRR are up to 10 times higher than at AR. SR could be detected down to 19 mblf (meters below lake floor) at NB and down to 13 mblf at AR. Although SRR were lower at AR than at NB, organic matter (OM) concentrations were higher. In contrast, dissolved OM in the pore water at AR contained more macromolecular OM and less low molecular weight OM. We thus suggest, that OM content alone cannot be used to infer microbial activity at Lake Van but that quality of OM has an important impact as well. These differences suggest that biogeochemical processes in lacustrine sediments are reacting very sensitively to small variations in geological, physical, or chemical parameters over relatively short distances. PMID:23908647

  4. Determination of Sediment Oxygen Demand in the Ziya River Watershed, China: Based on Laboratory Core Incubation and Microelectrode Measurements

    PubMed Central

    Rong, Nan; Shan, Baoqing; Wang, Chao

    2016-01-01

    A study coupling sedimentcore incubation and microelectrode measurementwas performed to explore the sediment oxygen demand (SOD) at 16 stations in the Ziya River Watershed, a severely polluted and anoxic river system in the north of China. Total oxygen flux values in the range 0.19–1.41 g/(m2·d) with an average of 0.62 g/(m2·d) were obtained by core incubations, and diffusive oxygen flux values in the range 0.15–1.38 g/(m2·d) with an average of 0.51 g/(m2·d) were determined by microelectrodes. Total oxygen flux obviously correlated with diffusive oxygen flux (R2 = 0.842). The microelectrode method produced smaller results than the incubation method in 15 of 16 sites, and the diffusive oxygen flux was smaller than the total oxygen flux. Although the two sets of SOD values had significant difference accepted by the two methods via the Wilcoxon signed-rank test (p < 0.05), the microelectrode method was shown to produce results that were similar to those from the core incubation method. The microelectrode method, therefore, could be used as an alternative method for traditional core incubation method, or as a method to verify SOD rates measured by other methods. We consider that high potential sediment oxygen demand would occur in the Ziya River Watershed when the dissolved oxygen (DO) recovered in the overlying water. PMID:26907307

  5. Determination of Sediment Oxygen Demand in the Ziya River Watershed, China: Based on Laboratory Core Incubation and Microelectrode Measurements.

    PubMed

    Rong, Nan; Shan, Baoqing; Wang, Chao

    2016-02-01

    A study coupling sedimentcore incubation and microelectrode measurement was performed to explore the sediment oxygen demand (SOD) at 16 stations in the Ziya River Watershed, a severely polluted and anoxic river system in the north of China. Total oxygen flux values in the range 0.19-1.41 g/(m²·d) with an average of 0.62 g/(m²·d) were obtained by core incubations, and diffusive oxygen flux values in the range 0.15-1.38 g/(m²·d) with an average of 0.51 g/(m²·d) were determined by microelectrodes. Total oxygen flux obviously correlated with diffusive oxygen flux (R² = 0.842). The microelectrode method produced smaller results than the incubation method in 15 of 16 sites, and the diffusive oxygen flux was smaller than the total oxygen flux. Although the two sets of SOD values had significant difference accepted by the two methods via the Wilcoxon signed-rank test (p < 0.05), the microelectrode method was shown to produce results that were similar to those from the core incubation method. The microelectrode method, therefore, could be used as an alternative method for traditional core incubation method, or as a method to verify SOD rates measured by other methods. We consider that high potential sediment oxygen demand would occur in the Ziya River Watershed when the dissolved oxygen (DO) recovered in the overlying water. PMID:26907307

  6. The Inter-Tropical Convergence Zone: A causal mechanism for Pb isotope cyclicity in Tropical Atlantic sediment cores

    NASA Astrophysics Data System (ADS)

    Abouchami, W.; Zabel, M.

    2003-04-01

    Lead isotopic compositions of bulk sediment cores from the Tropical Atlantic can be used to infer variations in the provenance of terrigenous input to the Tropical Atlantic during Pleistocene climate cycles. Pb isotope data were obtained using the triple spike method (Galer, 1999) on bulk sediments cores and cover the last six Marine Isotope Stages. The 200-ka high precision (2σ ˜100 ppm) Pb isotope records of the Ceará Rise (Western Atlantic, core GeoB1523-1, 3^o49'N, 41^o37'W, 3292 m) and Sierra Leone Rise (Eastern Atlantic, core GeoB2910-1, 4^o50'N, 21^o03'W, 2703 m) cores show a clear glacial-interglacial cyclicity, reflected by alternating unradiogenic Pb and radiogenic Pb. Changes in the relative proportions of the glacial (unradiogenic) and interglacial (radiogenic) Pb source(s) can be explained by changes in the erosional regime (chemical vs. physical) as a function of prevailing climate, combined with different mechanisms of Pb transport to the oceans (predominantly eolian in the Eastern Atlantic vs. riverine in the Western Atlantic). We interpret these regional changes as reflecting shifts in the mean latitude of the Inter-Tropical Convergence Zone that affects the hydrological cycle over South America and the wind systems over Africa. Our results strongly favor an increase in winter wind transport (rather than glacial hyper aridity) as the cause of enhanced glacial terrigenous fluxes observed in the Tropical Atlantic (Ruddiman, 1997). The two Atlantic Pb isotopic records exhibit strong correlations with Pleistocene sea level fluctuations, providing evidence for global teleconnection between tropical records and high latitude climate. Galer, S.J.G. (1999). Optimal double and triple spiking for high precision lead isotopic measurements. Chem. Geol. 154, 255-274. Ruddiman, W. F. (1997). Tropical Atlantic terrigenous fluxes since 25,000 yrs B.P., Mar. Geol., 136, 189-207.

  7. Chemical quality of sediment cores from the Laguna Madre, Laguna Atascosa and Arroyo Colorado, Texas

    USGS Publications Warehouse

    Van Metre, Peter C.

    1999-01-01

    Many contaminants introduced into the environment by human activities are hydrophobic, meaning they are relatively insoluble in water and, thus, are associated primarily with sediments. These contaminants include the organochlorine pesticides DOT and chlordane, polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) from industrial facilities and urban areas, and heavy metals such as arsenic, lead, mercury, and zinc. Understanding the occurrence of these contaminants in the environment requires sampling the sediments where the contaminants might be detected.

  8. Microbes in Thawing Permafrost: The Unknown Variable in the Climate Change Equation

    SciTech Connect

    Graham, David E; Wallenstein, Matthew D; Vishnivetskaya, T.; Waldrop, Mark P.; Phelps, Tommy Joe; Pfiffner, Susan M.; Onstott, T. C.; Whyte, Lyle; Rivkina, Elizaveta; Gilichinsky, David A; Elias, Dwayne A; Mackelprang, Rachel; Verberkmoes, Nathan C; Hettich, Robert {Bob} L; Wagner, Dirk; Wullschleger, Stan D; Jansson, Janet

    2012-01-01

    Considering that 25% of Earth's terrestrial surface is underlain by permafrost (ground that has been continuously frozen for at least 2 years), our understanding of the diversity of microbial life in this extreme habitat is surprisingly limited. Taking into account the total mass of perennially frozen sediment (up to several hundred meters deep), permafrost contains a huge amount of buried, ancient organic carbon (Tarnocai et al., 2009).

  9. Polarization study on solid core photonic crystal fibers partially sedimented with polyethylene micro-spheres and carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Pérez-Chimal, R. Janette; Mata-Chávez, Ruth I.; Estudillo-Ayala, J. M.; Vargas-Rodríguez, E.; Alvarado-Méndez, E.; Rojas-Laguna, R.

    2010-10-01

    We present an experimental study of light polarization on solid core microstructured optical fibers type (Large Mode Area) LMA-16, LMA-20 and LMA-25. These fibers were partially filled with one micron diameter polyethylene spheres or carbon nanotubes diluted in distilled H2O by capillarity. Polarization characterization was realized on these Photonic Crystal fibers with air filled holes and partially particle filled holes using a He-Ne 633nm central wavelength laser at 10mW. The achieved results were compared using graphical data of every test collected at different exposition dates where the fiber was exposed to particle sedimentation. Results depicted that short time sedimentation of these particles does not change the light polarization leaving from the fiber except for the phase of the beam. On the other hand, longer time particle exposition visibly changes the light phase measured at the end of the photonic crystal fiber with repeatable results.

  10. Magnetic fingerprint in marine sediments: clues from cultivated Magnetovibrio blakemorei and recent cores from Brazilian Coast

    NASA Astrophysics Data System (ADS)

    Jovane, L.; Florindo, F.; Bazylinski, D. A.; Pellizari, V. H.; Brandini, F. P.; de Almeida, L. A.; Carneiro, F. R.; Braga, E. D.; Lins, U.

    2013-12-01

    The magnetic properties (first order reversal curves, ferromagnetic resonance and decomposition of saturation remanent magnetization acquisition) of Magnetovibrio blakemorei strain MV-1, a marine magnetotactic bacterium, differ from those of other magnetotactic species from sediments deposited in lakes and marine habitats previously studied. This finding suggests that magnetite produced by some magnetotactic bacteria retains magnetic properties in relation to the crystallographic structure of the magnetic phase produced and thus might represent a 'magnetic fingerprint' for a specific magnetotactic bacterium. The technique used to determine this fingerprint is a non-destructive, new technology that might allow for the identification and presence of specific species or types of magnetotactic bacteria in certain environments such as sediment. We also show some preliminary results on the biogeochemical factors that control magnetotactic bacterial populations, documenting the environment and the preservation of bacterial magnetite, which dominates the palaeomagnetic signal throughout recent sediments from Brazilian Coast. We searched for magnetotactic bacteria in order to understand the ecosystems and environmental change related to their presence in sediments. We focused on studying the environmental conditions that allow for the presence of magnetotactic bacteria and magnetosomes in sediments including determining magnetotactic bacterial populations in marine settings, measuring crucial nutrient availability in the water column and in sediments, and examining particulate delivery to the seafloor.

  11. Structural identification of long-chain polyamines associated with diatom biosilica in a Southern Ocean sediment core

    NASA Astrophysics Data System (ADS)

    Bridoux, Maxime C.; Ingalls, Anitra E.

    2010-07-01

    Long-chain polyamines (LCPAs) constitute a new family of natural organic compounds that have recently been isolated and characterized from the biosilicified cell walls of diatom cultures. To date, diatom-specific polyamines have not been investigated from the marine environment and their fate in the environment is entirely unknown. Here, we report a series of LCPAs in a diatom frustule-rich sediment core (TNO57-13 PC4), originating from the Atlantic sector of the Southern Ocean and spanning from the Holocene to the Last Glacial Maximum (LGM). Liquid chromatography with electrospray ionization mass spectrometry (LC-ESI-MS) revealed a complex mixture of linear polyamines with at least 28 individual molecular species. Ion trap mass fragmentation studies, combined with high resolution Time of Flight (TOF) mass spectrometry showed that the polyamine pool consisted of a series of N-methylated propylamine compounds attached to a putrescine moiety, with individual LCPAs varying in chain length and degree of methylation. The structural similarity between LCPAs extracted from the diatom-rich sediment core and those extracted from the frustules of cultured diatoms suggests that sedimentary LCPAs are derived from diatom frustules. We hypothesize that these intrinsically labile organic molecular fossils are protected from diagenesis by encapsulation within the frustule. These compounds constitute a new class of biomarkers that could potentially be indicators of diatom species distribution. Isotopic analysis of LCPAs could be used to improve age models for sediment cores that lack calcium carbonate and to improve current interpretations of diatom-based paleoproxies, including diatom-bound nitrogen isotopes.

  12. Increased precipitation drives mega slump development and destabilization of ice-rich permafrost terrain, northwestern Canada

    NASA Astrophysics Data System (ADS)

    Kokelj, S. V.; Tunnicliffe, J.; Lacelle, D.; Lantz, T. C.; Chin, K. S.; Fraser, R.

    2015-06-01

    It is anticipated that an increase in rainfall will have significant impacts on the geomorphology of permafrost landscapes. Field observations, remote sensing and historical climate data were used to investigate the drivers, processes and feedbacks that perpetuate the growth of large retrogressive thaw slumps. These "mega slumps" (5-40 ha) are now common in formerly glaciated, fluvially incised, ice-cored terrain of the Peel Plateau, NW Canada. Individual thaw slumps can persist for decades and their enlargement due to ground ice thaw can displace up to 106 m3 of materials from slopes to valley bottoms reconfiguring slope morphology and drainage networks. Analysis of Landsat images (1985-2011) indicate that the number and size of active slumps and debris tongue deposits has increased significantly with the recent intensification of rainfall. The analyses of high resolution climatic and photographic time-series for summers 2010 and 2012 shows strong linkages amongst temperature, precipitation and the downslope sediment flux from active slumps. Ground ice thaw supplies meltwater and sediments to the slump scar zone and drives diurnal pulses of surficial flow. Coherence in the timing of down valley debris tongue deposition and fine-scaled observations of sediment flux indicate that heavy rainfall stimulates major mass flow events. Evacuation of sediments from the slump scar zone can help to maintain a headwall of exposed ground ice, perpetuating slump growth and leading to larger disturbances. The development of debris tongue deposits divert streams and increase thermoerosion to initiate adjacent slumps. We conclude that higher rainfall can intensify thaw slump activity and rapidly alter the slope-sediment cascade in regions of ice-cored glaciogenic deposits.

  13. Continuous recording of seismic signals in Alpine permafrost

    NASA Astrophysics Data System (ADS)

    Hausmann, H.; Krainer, K.; Staudinger, M.; Brückl, E.

    2009-04-01

    Over the past years various geophysical methods were applied to study the internal structure and the temporal variation of permafrost whereof seismic is of importance. For most seismic investigations in Alpine permafrost 24-channel equipment in combination with long data and trigger cables is used. Due to the harsh environment source and geophone layouts are often limited to 2D profiles. With prospect for future 3D-layouts we introduce an alternative of seismic equipment that can be used for several applications in Alpine permafrost. This study is focussed on controlled and natural source seismic experiments in Alpine permafrost using continuous data recording. With recent data from an ongoing project ("Permafrost in Austria") we will highlight the potential of the used seismic equipment for three applications: (a) seismic permafrost mapping of unconsolidated sediments, (b) seismic tomography in rock mass, and (c) passive seismic monitoring of rock falls. Single recording units (REFTEK 130, 6 channels) are used to continuously record the waveforms of both the seismic signals and a trigger signal. The combination of a small number of recording units with different types of geophones or a trigger allow numerous applications in Alpine permafrost with regard to a high efficiency and flexible seismic layouts (2D, 3D, 4D). The efficiency of the light and robust seismic equipment is achieved by the simple acquisition and the flexible and fast deployment of the (omni-directional) geophones. Further advantages are short (data and trigger) cables and the prevention of trigger errors. The processing of the data is aided by 'Seismon' which is an open source software project based on Matlab® and MySQL (see SM1.0). For active-source experiments automatic stacking of the seismic signals is implemented. For passive data a program for automatic detection of events (e.g. rock falls) is available which allows event localization. In summer 2008 the seismic equipment was used for the

  14. Holocene paleoclimate history of Fallen Leaf Lake, CA., from geochemistry and sedimentology of well-dated sediment cores

    NASA Astrophysics Data System (ADS)

    Noble, Paula J.; Ball, G. Ian; Zimmerman, Susan H.; Maloney, Jillian; Smith, Shane B.; Kent, Graham; Adams, Kenneth D.; Karlin, Robert E.; Driscoll, Neal

    2016-01-01

    Millennial-scale shifts in aridity patterns have been documented during the Holocene in the western United States, yet the precise timing, severity, and regional extent of these shifts prompts further study. We present lake sediment core data from Fallen Leaf Lake, a subalpine system at the southern end of the Lake Tahoe basin for which 80% of the contemporary inflow is derived from snowpack delivered by Pacific frontal storm systems. A high quality age model has been constructed using 14C ages on plant macrofossils, 210Pb, and the Tsoyowata tephra datum (7.74-7.95 cal kyr BP). One core captures the transition from the Late Tioga-younger Dryas glaciolacustrine package to laminated opaline clay at 11.48 cal kyr BP. Early Holocene sedimentation rates are relatively high (∼1.9 mm/year) and cooler winter temperatures are inferred by the presence of pebbles interpreted to be transported out into the lake via shore ice. There is a geochemically distinct interval from ∼4.71 to 3.65 cal kyr BP that is interpreted as a late Holocene neopluvial, characterized by depleted δ13C and lower C:N that point to reduced runoff of terrigenous organic matter, increased winter precipitation, and increased algal productivity. The largest Holocene signal in the cores occurs at the end of the neopluvial, at 3.65 cal kyr BP, and marks a shift into a climate state with variable precipitation, yet is overall more arid than the neopluvial. This new climate state persists for ∼3 ka, until the Little Ice Age. Low sedimentation rates (0.5 mm/year), the homogeneous opaline sediment, and steadily increasing contributions of terrestrial vs. algal organic matter in these cores suggest that the lowstand state of Fallen Leaf Lake may have been the norm from 3.65 to 0.55 cal kyr BP, punctuated by short term high precipitation years or multi-year intervals capable of rapid short duration lake level rise. Fallen Leaf Lake is strongly influenced by changes in winter precipitation and temperature

  15. Abundances, depositional fluxes, and homologue patterns of polychlorinated biphenyls in dated sediment cores from the Pearl River Delta, China.

    PubMed

    Mai, Bixian; Zeng, Eddy Y; Luo, Xiaojun; Yang, Qingshu; Zhang, Gan; Li, Xiangdong; Sheng, Guoying; Fu, Jiamo

    2005-01-01

    Despite the recent efforts to investigate the distribution and fate of persistent organic pollutants in the tropical and subtropical regions of Asia, very little was known about the temporal change of polychlorinated biphenyls (PCBs) in the environmental ecosystem of China. In this study, three dated sediment cores collected from the Pearl River Delta of southern China were analyzed for a large suite of PCB congeners, from which the temporal profiles of PCB abundances, fluxes, and homologue patterns were constructed. The sedimentary inventories of total PCBs at the sampling sites ranged from 480 to 1310 ng/cm2, at the low end of the worldwide figures. Although production and use of PCBs have been banned or highly restricted in China since the early 1980s, the fluxes of total PCBs continued to increase in the Pearl River Delta sediments. There was a concurrent increase of PCB fluxes and gross domestic product per capita in the region from 1980 to 1997, and a decline of agricultural land use was evident at the same time. Apparently, large-scale land transform since the early 1980s as well as emissions from the PCB-containing electrical equipments were responsible for the sharp rise of PCB fluxes in the recent sediments. The difference in the PCB homologue patterns from 1940 to the mid-1970s was probably indicative of the different timelines of PCB usage in Macao/Hong Kong and mainland China and the differenttypes of technical PCBs commercially used. PCBs were detectable in sediments deposited well before the time frame when production of PCBs began (before 1930) and were relatively enriched in the less chlorinated homologue groups (3Cl and 4Cl PCBs), suggesting the downward mobility of lightly chlorinated PCB congeners in the sediment column. PMID:15667074

  16. Historical trends of organochlorine pesticides in a sediment core from the Gulf of Batabanó, Cuba.

    PubMed

    Alonso-Hernández, C M; Tolosa, I; Mesa-Albernas, M; Díaz-Asencio, M; Corcho-Alvarado, J A; Sánchez-Cabeza, J A

    2015-10-01

    Sediments can be natural archives to reconstruct the history of pollutant inputs into coastal areas. This is important to improve management strategies and evaluate the success of pollution control measurements. In this work, the vertical distribution of organochlorine pesticides (DDTs, Lindane, HCB, Heptachlor, Aldrin and Mirex) was determined in a sediment core collected from the Gulf of Batabanó, Cuba, which was dated by using the (210)Pb dating method and validated with the (239,240)Pu fallout peak. Results showed significant changes in sediment accumulation during the last 40 years: recent mass accumulation rates (0.321 g cm(-2) yr(-1)) double those estimated before 1970 (0.15 g cm(-2) yr(-1)). This change matches closely land use change in the region (intense deforestation and regulation of the Colon River in the late 1970s). Among pesticides, only DDTs isomers, Lindane and HCB were detected, and ranged from 0.029 to 0.374 ng g(-1) dw for DDTs, from<0.006 to 0.05 ng g(-1) dw for Lindane and from<0.04 to 0.134 ng g(-1) dw for HCB. Heptachlor, Aldrin and Mirex were below the detection limits (∼0.003 ng g(-1)), indicating that these compounds had a limited application in the Coloma watershed. Pesticide contamination was evident since the 1970s. DDTs and HCB records showed that management strategies, namely the banning the use of organochlorine contaminants, led to a concentration decline. However, Lindane, which was restricted in 1990, can still be found in the watershed. According to NOAA guidelines, pesticides concentrations encountered in these sediments are low and probably not having an adverse effect on sediment dwelling organisms. PMID:26051863

  17. Microorganisms Trapped Within Permafrost Ice In The Fox Permafrost Tunnel, Alaska

    NASA Astrophysics Data System (ADS)

    Katayama, T.; Tanaka, M.; Douglas, T. A.; Cai, Y.; Tomita, F.; Asano, K.; Fukuda, M.

    2008-12-01

    Several different types of massive ice are common in permafrost. Ice wedges are easily recognized by their shape and foliated structure. They grow syngenetically or epigenetically as a result of repeated cycles of frost cracking followed by the infiltration of snow, melt water, soil or other material into the open frost cracks. Material incorporated into ice wedges becomes frozen and preserved. Pool ice, another massive ice type, is formed by the freezing of water resting on top of frozen thermokarst sediment or melting wedges and is not foliated. The Fox Permafrost Tunnel in Fairbanks was excavated within the discontinuous permafrost zone of central Alaska and it contains permafrost, ice wedges, and pool ice preserved at roughly -3°C. We collected samples from five ice wedges and three pool ice structures in the Fox Permafrost Tunnel. If the microorganisms were incorporated into the ice during its formation, a community analysis of the microorganisms could elucidate the environment in which the ice was formed. Organic material from sediments in the tunnel was radiocarbon-dated between 14,000 and 30,000 years BP. However, it is still not clear when the ice wedges were formed or subsequently deformed because they are only partially exposed and their upper surfaces are above the tunnel walls. The objectives of our study were to determine the biogeochemical conditions during massive ice formation and to analyze the microbial community within the ices by incubation-based and DNA-based analyses. The geochemical profile and the PCR-DGGE band patterns of bacteria among five ice wedge and 3 portions of pool ice samples were markedly different. The DGGE band patterns of fungi were simple with a few bands of fungi or yeast. The dominant bands of ice wedge and pool ice samples were affiliated with the genus Geomyces and Doratomyces, respectively. Phylogenetic analysis using rRNA gene ITS regions indicated isolates of Geomyces spp. from different ice wedges were affiliated

  18. Magnetotactic bacteria in marine sediments: clues from recent cores from Brazilian Coast

    NASA Astrophysics Data System (ADS)

    Jovane, L.; Pellizari, V. H.; Brandini, F. P.; Braga, E. D. S.; Freitas, G. R.; Benites, M.; Rodelli, D.; Giorgioni, M.; Iacoviello, F.; Ruffato, D. G.; Lins, U.

    2014-12-01

    The magnetic properties (first order reversal curves, ferromagnetic resonance and decomposition of saturation remanent magnetization acquisition) of marine magnetotactic bacteria, in conjunction with geophysical, geochemical and oceanographic data from the Brazilian Coast, provide interesting insights regarding the primary productivity distribution in oceans. This finding suggests that magnetite produced by some magnetotactic bacteria retains magnetic properties in relation to the crystallographic structure of the magnetic phase produced and thus might represent a "magnetic fingerprint" for the presence of magnetotactic bacteria. The use of those magnetic properties is a non-destructive, new technology that might allow for the identification and presence of specific species or types of magnetotactic bacteria in certain environments such as sediment. We will also show some preliminary results on the biogeochemical factors that control magnetotactic bacterial populations, documenting the environment and the preservation of bacterial magnetite, which dominates the palaeomagnetic signal throughout recent sediments from Brazilian Coast. We searched for magnetotactic bacteria in order to understand the ecosystems and environmental change related to their presence in sediments. We studied magnetotactic bacterial concentration and geophysical, geochemical and oceanographic results in marine settings measuring crucially nutrients availability in the water column and in sediments, on particulate delivery to the seafloor, to understand the environmental condition that allow the presence of magnetotactic bacteria and magnetosomes in sediments.

  19. Degrading permafrost and gas hydrate under the Beaufort Shelf and marine gas hydrate on the adjacent continental slope

    NASA Astrophysics Data System (ADS)

    Paull, C. K.; Dallimore, S. R.; Hughes Clarke, J. E.; Blasco, S.; Melling, H.; Lundsten, E.; Vagle, S.; Collett, T. S.

    2011-12-01

    The sub-seafloor under the Arctic Shelf is arguably the part of the Earth that is undergoing the most dramatic warming. In the southern Beaufort Sea, the shelf area was terrestrially exposed during much of the Quaternary period when sea level was ~120m lower than present. As a consequence, many areas are underlain by >600m of ice-bonded permafrost that conditions the geothermal regime such that the base of the methane hydrate stability can be >1000m deep. Marine transgression has imposed a change in mean annual surface temperature from -15°C or lower during periods of terrestrial exposure, to mean annual sea bottom temperatures near 0°C. The thermal disturbance caused by transgression is still influencing the upper km of subsurface sediments. Decomposition of gas hydrate is inferred to be occurring at the base and the top of the gas hydrate stability zone. As gas hydrate and permafrost intervals degrade, a range of processes occur that are somewhat unique to this setting. Decomposition of gas hydrate at depth can cause sediment weakening, generate excess pore water pressure, and form free gas. Similarly, thawing permafrost can cause thaw consolidation, liberate trapped gas bubbles in ice bonded permafrost. Understanding the connection between deep subsurface processes generated by transgression, surficial sediment processes near the seafloor, and gas flux into the ocean and atmosphere is important to assessing geohazard and environmental conditions in this setting. In contrast, conditions for marine gas hydrate formation occur on the adjacent continental slope below ~270m water depths. In this paper, we present field observations of gas venting from three geologically distinct environments in the Canadian Beaufort Sea, two on the shelf and one on the slope. A complimentary paper by Dallimore et al reviews the geothermal changes conditioning this environment. Vigorous methane venting is occurring over Pingo-Like-Features (PLF) on the mid-shelf. Diffuse venting of

  20. The Comparative Study of Paleoenvironmental Proxies from 3 Sediment Cores Sampled from Lake Erie at 1988, 1991 and 2003

    NASA Astrophysics Data System (ADS)

    Lu, Y.; Meyers, P. A.; Brian, E. J.; Robbins, J. A.

    2006-05-01

    The oxygen isotopic composition of calcium carbonate in hardwater lakes reflect the impacts from meteorological factors whereas the carbon and nitrogen isotopes indicate the changes of biological productivity in the lake. However, the fidelity of these proxies in recording paleoenvironment information can be biased by the post-deposition diagenesis. We have compared the isotopic contents and the mass accumulation rates of organic carbon and calcium carbonate in sediment cores collected in 1988, 1991, and 2003 from the same location in Lake Erie to each other and to meteorological records beginning in 1895. Eutrophication accelerated calcite dissolution, but isotopic proxies are preserved. The comparison of paleoenvironmental histories concurrently interpreted from the there cores has provided interesting insights into early diagenesis, carbon dynamics and past depositional environments in Lake Erie. The geochemical proxies also reflect significant impacts from twentieth century urbanization.

  1. Holocene climate change in Newfoundland reconstructed using oxygen isotope analysis of lake sediment cores

    NASA Astrophysics Data System (ADS)

    Finkenbinder, Matthew S.; Abbott, Mark B.; Steinman, Byron A.

    2016-08-01

    Carbonate minerals that precipitate from open-basin lakes can provide archives of past variations in the oxygen isotopic composition of precipitation (δ18Oppt). Holocene δ18Oppt records from the circum- North Atlantic region exhibit large fluctuations during times of rapid ice sheet deglaciation, followed by more stable conditions when interglacial boundary conditions were achieved. However, the timing, magnitude, and climatic controls on century to millennial-scale variations in δ18Oppt in northeastern North America are unclear principally because of a dearth of paleo-proxy data. Here we present a lacustrine sediment oxygen isotope (δ18O) record spanning 10,200 to 1200 calendar years before present (cal yr BP) from Cheeseman Lake, a small, alkaline, hydrologically open lake basin located in west-central Newfoundland, Canada. Stable isotope data from regional lakes, rivers, and precipitation indicate that Cheeseman Lake water δ18O values are consistent with the isotopic composition of inflowing meteoric water. In light of the open-basin hydrology and relatively short water residence time of the lake, we interpret down-core variations in calcite oxygen isotope (δ18Ocal) values to primarily reflect changes in δ18Oppt and atmospheric temperature, although other factors such as changes in the seasonality of precipitation may be a minor influence. We conducted a series of climate sensitivity simulations with a lake hydrologic and isotope mass balance model to investigate theoretical lake water δ18O responses to climate change. Results from these experiments suggest that Cheeseman Lake δ18O values are primarily controlled by temperature and to a much lesser extent, the seasonality of precipitation. Increasing and more positive δ18Ocal values between 10,200 and 8000 cal yr BP are interpreted to reflect the waning influence of the Laurentide Ice Sheet on atmospheric circulation, warming temperatures, and rapidly changing surface ocean δ18O from the input of

  2. Spatial Variations in Archaeal Lipids of Surface Water and Core-Top Sediments in the South China Sea and Their Implications for Paleoclimate Studies▿†

    PubMed Central

    Wei, Yuli; Wang, Jinxiang; Liu, Jie; Dong, Liang; Li, Li; Wang, Hui; Wang, Peng; Zhao, Meixun; Zhang, Chuanlun L.

    2011-01-01

    The South China Sea (SCS) is the largest marginal sea of the western Pacific Ocean, yet little is known about archaeal distributions and TEX86-based temperatures in this unique oceanic setting. Here we report findings of abundances in both core lipids (CL) and intact polar lipids (IPL) of Archaea from surface water (CL only) and core-top sediments from different regions of the SCS. TEX86-derived temperatures were also calculated for these samples. The surface water had extremely low abundances of CL (average of 0.05 ± 0.13 ng/liter; n = 75), with higher values present in regions where upwelling is known to occur. The core-top sediments had CL values of 0.1 to 0.9 μg/g, which are on the low end of CL concentrations reported for other marine sediments and may reflect the oligotrophic nature of the open SCS. The IPL of Archaea accounted for 6 to 36.4% of total lipids (CL plus IPL), indicating that the majority of archaeal lipids in core-top sediments were derived from nonliving cells. The TEX86-based temperatures of surface water were overall lower than satellite-based sea surface temperatures or CTD-measured in situ temperatures. The core-top sediment samples, however, had TEX86 temperatures very close to the mean annual sea surface temperatures, except for samples with water depths of less than 100 m. Our results demonstrated low and heterogeneous distributions of archaeal lipids in surface water and core-top sediments of the SCS, which may reflect local or regional differences in productivity of Archaea. While TEX86-based temperatures for core-top marine sediments at deep water depths (>100 m) generally reflected mean annual sea surface temperatures, TEX86 temperatures in surface water varied basin wide and underestimated sea surface temperatures in most locations for the season when surface water samples were collected. PMID:21890672

  3. Spatial Variations in Archaeal Lipids of Surface Water and Core-Top Sediments in the South China Sea: Implications for Paleoclimate Studies

    NASA Astrophysics Data System (ADS)

    Wei, Y.; Wang, J.; Liu, J.; Dong, L.; Li, L.; Wang, H.; Wang, P.; Zhao, M.; Zhang, C.

    2011-12-01

    The South China Sea (SCS) is the largest marginal sea of the western Pacific Ocean; yet, little is known about archaeal distributions and TEX86-based temperatures in this unique oceanic setting. Here we report findings of abundances in both core lipids (CL) and intact polar lipids (IPL) of Archaea from surface water (CL only) and core-top sediments from different regions of the SCS. TEX86-derived temperatures were also calculated for these samples. The surface water had extremely low abundances of CL (average 0.05±0.13 ng/L; n = 75) with higher values present in regions where upwelling is known to occur. The core-top sediments had CL values of 0.1 to 0.9 g/g, which are in the low end of CL concentrations reported for other marine sediments and may reflect the oligotrophic nature of the open SCS. The IPL of Archaea accounted for 6-36.4% of total lipids (CL+IPL), indicating that the majority of archaeal lipids in core-top sediments were derived from nonliving cells. The TEX86-based temperatures of surface water were overall lower than satellite-based sea surface temperatures or CTD-measured in situ temperatures. The core-top sediment samples, however, had TEX86 temperatures very close to the mean annual sea surface temperatures except for samples with water depth shallower than 100 m. Our results demonstrated low and heterogeneous distributions of archaeal lipids in surface water and core-top sediments of the SCS, which may reflect the local or regional differences in productivity of Archaea. While TEX86-based temperatures for core-top marine sediments at deep water depths (>100 m) generally reflected mean annual sea surface temperatures, TEX86 temperatures in surface water varied basin wide and underestimated sea surface temperatures in most locations for the season when surface water samples were collected.

  4. Development of a Geocryologic Model of Permafrost From 2D Inversion of IP Profiling

    NASA Astrophysics Data System (ADS)

    Fortier, R.; Leblanc, A.

    2004-05-01

    Non-invasive investigation of permafrost along a planned route of pipeline, road or airstrip in cold regions involves the use of effective methods for detecting, characterizing, mapping and monitoring permafrost conditions on various spatial and temporal scales. Among the available near-surface geophysical methods, the electrical resistivity imaging is probably the most suitable method since the resistivity contrast between unfrozen and frozen ground can be one or two orders of magnitude. Induced polarization (IP) profiling was carried out to study the spatial distribution of ground ice in two permafrost mounds near Umiujaq in Nunavik, Canada. A dipole-dipole array was used to perform the IP profiling. Pseudo-sections of electrical resistivity and chargeability giving a misrepresented cross-section of the sub-surface were first draw. The inversion of IP profiling was also performed using DCIP2D developed by UBC-GIF for estimating the spatial distribution of electrical properties in the ground to create realistic models of sub-surface resistivity and chargeability cross-section. The inverse models show clearly the presence of ice-rich core in the permafrost mounds. The ice-rich cores are underlined by high resistivity values while the unfrozen zones show low resistivity values. The localisation of the permafrost table is highlighted by a strong contrast of resistivity while the permafrost base is marked by a transitional change in resistivity. In the hollow between the permafrost mounds, the models show low resistivity values characteristic of unfrozen zone. A synthetic resistivity sounding built from the most acceptable inverse model correlates well with electrical resistivity logging carried out in the permafrost mound during cone penetration tests. The inversion of IP profiling is fundamental for defining realistic models of sub-surface resistivity and chargeability. Electrical resistivity imaging is a appropriate near-surface geophysical method for permafrost

  5. Approximation methods for the solution of inverse problems in lake and sea sediment core analysis

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Rosen, I. G.

    1985-01-01

    A theoretical model employing one-dimensional (depth) transport equations to describe vertical redistribution of ocean-floor and lake-floor sediment (particulates, volcanic ash, microtektites, or radioactive tracers) by episodic and nonepisodic events including bioturbation is developed analytically and demonstrated. The principles underlying the model are explained; the model equations are derived; the inverse problem of identifying the depth-dependent bioturbation coefficient is addressed; two approximation theorems are presented; and numerical results for two sample problems are presented graphically. It is suggested that compatification, porosity effects, and depth-dependent sedimentation be taken into account when formulating future models.

  6. Mapping permafrost with airborne electromagnetics

    NASA Astrophysics Data System (ADS)

    Minsley, B. J.; Ball, L. B.; Bloss, B. R.; Kass, A.; Pastick, N.; Smith, B. D.; Voss, C. I.; Walsh, D. O.; Walvoord, M. A.; Wylie, B. K.

    2014-12-01

    Permafrost is a key characteristic of cold region landscapes, yet detailed assessments of how the subsurface distribution of permafrost impacts the environment, hydrologic systems, and infrastructure are lacking. Data acquired from several airborne electromagnetic (AEM) surveys in Alaska provide significant new insight into the spatial extent of permafrost over larger areas (hundreds to thousands of square kilometers) than can be mapped using ground-based geophysical methods or through drilling. We compare several AEM datasets from different areas of interior Alaska, and explore the capacity of these data to infer geologic structure, permafrost extent, and related hydrologic processes. We also assess the impact of fires on permafrost by comparing data from different burn years within similar geological environments. Ultimately, interpretations rely on understanding the relationship between electrical resistivity measured by AEM surveys and the physical properties of interest such as geology, permafrost, and unfrozen water content in the subsurface. These relationships are often ambiguous and non-unique, so additional information is useful for reducing uncertainty. Shallow (upper ~1m) permafrost and soil characteristics identified from remotely sensed imagery and field observations help to constrain and aerially extend near-surface AEM interpretations, where correlations between the AEM and remote sensing data are identified using empirical multivariate analyses. Surface nuclear magnetic resonance (sNMR) measurements quantify the contribution of unfrozen water at depth to the AEM-derived electrical resistivity models at several locations within one survey area. AEM surveys fill a critical data gap in the subsurface characterization of permafrost environments and will be valuable in future mapping and monitoring programs in cold regions.

  7. Holocene environmental changes of the Godavari Delta, east coast of India, inferred from sediment core analyses and AMS 14C dating

    NASA Astrophysics Data System (ADS)

    Nageswara Rao, Kakani; Saito, Yoshiki; Nagakumar, K. Ch. V.; Demudu, G.; Basavaiah, N.; Rajawat, A. S.; Tokanai, Fuyuki; Kato, Kazuhiro; Nakashima, Rei

    2012-11-01

    The Godavari delta in India is a major wave dominated delta of a tropical monsoon-fed river with one of the largest sediment deliveries in the world. While several earlier studies revealed the nature of landforms and progradation style of the delta plain during the Holocene, the present study attempts to reconstruct the depositional environment of the Godavari delta through the analysis of core sediment and accelerator mass spectrometry (AMS) 14C dating from three locations. The sediment core obtained from a 27.06 m deep borehole at Vilasavilli (VV) supported by 13 14C dates revealed the complete succession of the Holocene deposits unconformably overlying Pleistocene sediments. Textural analysis indicates the lower upward-fining and upper upward-coarsening units in the Holocene succession. Total organic carbon (TOC)/total nitrogen (TN) ratios of > 20; high content of TOC around 1.5-2.5%; and black to very dark colored sediment throughout the muddy part of the Holocene succession indicated a predominance of terrigenous material. The VV core and two other cores (DRP and SDG) with 14 14C dates indicated the thickness of the Holocene sediments in the Godavari delta plain is in the order of ~ 20-50 m, unconformably resting on a seaward sloping Pleistocene basement. Sediment facies and sediment accumulation of the three cores show the evolution of the Godavari delta. A transgressive phase is recognized as an upward-fining succession in the VV core, 8.4-8.0 cal ky BP, followed by a low accumulation period, 8.0-6.3 cal ky BP including the Holocene maximum transgression in the Godavari delta. After 6.3 cal ky BP, areas of high accumulation rates have changed laterally between the central part (VV site) and southwestern part (DRP and SDG sites), may be controlled by the location of river-mouths. Further analysis coupled with 11 more 14C dates compiled from earlier works indicated that the strandplain of the Godavari delta prograded seaward in three stages, and that the rate

  8. Collaboration in Education: International Field Class on Permafrost

    NASA Astrophysics Data System (ADS)

    Streletskiy, D. A.; Shiklomanov, N. I.; Grebenets, V. I.

    2011-12-01

    from the position of technogenic impact which required knowledge of historical, political and socio-economic aspects of development. Students learned how to conduct meteorological observations; describe vegetation, soil and permafrost conditions, and cryogenic processes, such as ice-wedges, solifluction, pingoes, thermokarst etc; and use temperature logging and core drilling devices. In urbanized areas, students learned how to apply different construction methods and foundation designs in permafrost regions; use techniques of permafrost temperature monitoring under building and structures; and apply mitigation strategies to prevent permafrost from warming under different types of technogenic pressure. The experience gained by students in the field cannot be adequately replaced by any classroom demonstrations, which is why it is critically important to conduct such classes in the future. We thank administration of Igarka, Igarka Geocryological Station, Norilsk Nickel, Norilsk Geologiya, and Funamentproekt Norilsk for help in the organization of this class.

  9. International Field School on Permafrost, Polar Urals, 2012

    NASA Astrophysics Data System (ADS)

    Streletskiy, D. A.; Grebenets, V.; Ivanov, M.; Sheinkman, V.; Shiklomanov, N. I.; Shmelev, D.

    2012-12-01

    The international field school on permafrost was held in the Polar Urals region from June, 30 to July 9, 2012 right after the Tenth International Conference on Permafrost which was held in Salekhard, Russia. The travel and accommodation support generously provided by government of Yamal-Nenets Autonomous Region allowed participation of 150 permafrost young research scientists, out of which 35 students from seven countries participated in the field school. The field school was organized under umbrella of International Permafrost Association and Permafrost Young Research Network. The students represented diverse educational backgrounds including hydrologists, engineers, geologists, soil scientists, geocryologists, glaciologists and geomorphologists. The base school camp was located near the Harp settlement in the vicinity of Polar Urals foothills. This unique location presented an opportunity to study a diversity of cryogenic processes and permafrost conditions characteristic for mountain and plain regions as well as transition between glacial and periglacial environments. A series of excursions was organized according to the following topics: structural geology of the Polar Urals and West Siberian Plain (Chromite mine "Centralnaya" and Core Storage in Labitnangy city); quaternary geomorphology (investigation of moraine complexes and glacial conditions of Ronamantikov and Topographov glaciers); principles of construction and maintains of structures built on permafrost (Labitnangy city and Obskaya-Bovanenkovo Railroad); methods of temperature and active-layer monitoring in tundra and forest-tundra; cryosols and soil formation in diverse landscape condition; periglacial geomorphology; types of ground ice, etc. Every evening students and professors gave a series of presentations on climate, vegetation, hydrology, soil conditions, permafrost and cryogenic processes of the region as well as on history, economic development, endogenous population of the Siberia and the

  10. Paleomagnetic record of a marine sediment core from eastern offshore of Taiwan over the past 7,500 years

    NASA Astrophysics Data System (ADS)

    Huang, Y.; Lee, T.

    2013-12-01

    To study the Holocene geomagnetic field behavior, we performed a series of paleomagnetic experiments, including measurements of magnetic susceptibility (χ), natural remanent magnetization (NRM), anhysteretic remanent magnetization (ARM), and isothermal remanent magnetization (IRM), to a marine sediment core OR1-715-21 obtained from eastern offshore of Taiwan during the OR1-715 cruise. The analyzed magnetic properties show that the remanent magnetization (RM) carriers of the core are uniformly dominated by single-domain (SD) and pseudo-single-domain (PSD) magnetite, suggesting a suitable material for relative paleointensity (RPI) determination. Also the stable and well defined characteristic remanent magnetization (ChRM) indicates the reliable determination of the paleomagnetic direction (inclination and declination). Virtual dipole moment (VDM) is further calculated based on these reliable RPI and paleo direction data. The VDM variability of the study compares well to the CALS10K model (a continuous model of archaeomagnetic and lake sediment data for the past 10,000 years). Outcomes of the study imply the domination of the magnetic dipole field in Taiwan area over the past 7,500 years.

  11. Hexabromocyclododecanes, polybrominated diphenyl ethers, and polychlorinated biphenyls in radiometrically dated sediment cores from English lakes, ~1950-present.

    PubMed

    Yang, Congqiao; Rose, Neil L; Turner, Simon D; Yang, Handong; Goldsmith, Ben; Losada, Sara; Barber, Jonathan L; Harrad, Stuart

    2016-01-15

    This paper reports input fluxes between ~1950 and present, of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and hexabromocyclododecanes (HBCDs) in radiometrically-dated sediment cores from 7 English lakes. Fluxes of PCBs at all but one location prone to significant sediment resuspension peaked in the late-1960s/early-1990s, before declining thereafter. Input fluxes of HBCDs at all sites increased from first emergence in the mid-1960s. Thereafter, fluxes peaked in the late-1980s/early-2000s, before declining through to the present, except at the most urban site where HBCD fluxes are still increasing. Trends of PBDEs predominant in the Penta-BDE and Octa-BDE formulations vary between sites. While at some locations, fluxes peaked in the late-1990s/early-2000s; at others, fluxes are still increasing. This suggests the full impact of EU restrictions on these formulations has yet to be felt. Fluxes of BDE-209 have yet to peak at all except one location, suggesting little discernible environmental response to recent EU restrictions on the Deca-BDE product. Strikingly, fluxes of BDE-209 in the most recent core slices either exceed or approach peak fluxes of ΣPCBs, implying substantial UK use of Deca-BDE. Excepting HBCDs, inventories of our target contaminants correlated significantly with local population density, implying substantial urban sources. PMID:26433331

  12. Accumulation and partitioning of seven trace metals in mangroves and sediment cores from three estuarine wetlands of Hainan Island, China.

    PubMed

    Qiu, Yao-Wen; Yu, Ke-Fu; Zhang, Gan; Wang, Wen-Xiong

    2011-06-15

    Trace metals in mangrove tissues (leaf, branch, root and fruit) of nine species and sediments of ten cores collected in 2008 from Dongzhai Harbor, Sanya Bay and Yalong Bay, Hainan Island, were analyzed. The average concentrations of Cu, Pb, Zn, Cd, Cr, Hg and As in surface sediments were 14.8, 24.1, 57.9, 0.17, 29.6, 0.08 and 9.7 μg g(-1), whereas those in mangrove tissues were 2.8, 1.4, 8.7, 0.03, 1.1, 0.03, and 0.2 μg g(-1), respectively. Compared to those from other typical mangrove wetlands of the world, the metal levels in Hainan were at low- to median-levels, which is consistent with the fact that Hainan Island is still in low exploitation and its mangroves suffer little impact from human activities. Metal concentrations among different tissues of mangroves were different. In general, Zn and Cu were enriched in fruit, Hg was enriched in leaf, Pb, Cd and Cr were enriched in branch, and As was enriched in root. The cycle of trace metals in mangrove species were estimated. The biota-sediment accumulation factors (BSAFs) followed the sequence of Hg (0.43)>Cu (0.27)>Cd (0.22)>Zn (0.17)>Pb (0.07)>Cr (0.06)>As (0.02). PMID:21501926

  13. Origin and vertical variation of the bound fatty acids in core sediments of Lake Dianchi in Southwest China.

    PubMed

    Wang, Lifang; Wu, Fengchang; Xiong, Yongqiang; Fang, Jidun

    2013-04-01

    Based on the molecular distribution of bound fatty acid (BFA) compound classes in core sediments of Lake Dianchi combined with the compound-specific δ(13)C values of the straight-chain BFAs, origin and vertical changes of organic matters in the sediments were investigated. The results indicated a significant change of BFA sources over the past 700 years. Contrast to the low concentrations of the terrestrial BFAs, the abundance of BFAs derived from the plankton/bacteria in the top sections (1944-recent) was more than 80%. The increasing proportions of the branched and unsaturated BFAs in total fatty acids were closely correlated with the heavy eutrophication and the frequent algal blooms in the decades. Furthermore, the positive shift of δ (13)C of C16 and C18 (~2‰) in the upper section might be an indicator of the excess phytoplankton productivity. However, it was found that the plankton/bacteria-derived BFAs were more easily degraded during the early diagenetic process. The special compound carbon isotopic compositions of the long straight-chain BFAs (C24 and C26) in the sediments showed a depletion of heavier δ (13)C values (ca. -30‰) in the midsections (1559-1787), reflecting a relatively growing contribution of C3 plants to C4 plants or that C4 plant growth was inhibited in cold and arid climates during the period. PMID:22903813

  14. Historical lead isotope record of a sediment core from the Derwent River (Tasmania, Australia): a multiple source environment.

    PubMed

    Townsend, Ashley T; Seen, Andrew J

    2012-05-01

    A 105 cm sediment core from the Derwent River (Tasmania, Australia) was collected in 2004 and was characterised considering both physical (loss on ignition at 550 °C and grain size) and chemical (Fe, Cu, Zn, Cd and Pb concentrations, Pb isotope ratios and (210)Pb dating) properties. The core was analysed to (i) investigate the historical profiles of some important elements associated with the Risdon zinc refinery adjacent to the Derwent River, (ii) determine Pb isotopic signatures of sediment samples, and (iii) assess the veracity of Pb isotope ratios as indicators of contaminant Pb input. Extractable metal concentrations were (all values as mgkg(-1), non-normalised for grain size) Fe: 20,000-35,000, Zn: 42-4500, Pb: 5-1090, Cu: 13-141, and Cd: 1-31; with a close correlation between Cu, Zn, Cd and Pb. Metal enrichment factors (normalised to Al) were Pb: 0.9-144, Zn: 0.8-93, Cd: 0.8-30, Cu: 0.8-8.9 and Fe: 0.9-1.3, confirming anthropogenic contributions of Cu, Zn, Pb and Cd to the sediments. The onset of metal contamination above background levels occurred at a depth between 43 and 49 cm, with maximum concentrations noted near 20 cm for Cu, Zn, Cd and Pb. Lead isotope ratios were determined in sediments using sector field ICP-MS, and were found to be 36.5-38.8, 16.5-18.7 and 1.07-1.20 for (208)Pb/(204)Pb, (206)Pb/(204)Pb and (206)Pb/(207)Pb ratios, respectively. Major Australian ores processed at the refinery over the previous ~90 years include those from Broken Hill, Rosebery, Mt Isa, Elura, Hellyer and Century deposits. Anthropogenic impact by Pb with Broken Hill type isotopic ratio was initially evident in the core at 43-49 cm. The introduction of Rosebery and Elura ores to the refinery was also clearly noted. Pb isotope ratios further highlight that the Derwent River has been exposed to a greater impact by anthropogenic Pb in comparison to other major Tasmanian rivers, namely the Huon and Tamar. PMID:22444061

  15. Paleoenvironmental records from newly recovered sediment cores at the southeast margin of the Salar de Atacama, Chile

    NASA Astrophysics Data System (ADS)

    Boutt, D. F.; Munk, L. A.; Hynek, S. A.; Corenthal, L.; Huff, H. A.

    2014-12-01

    A suite of new cores recovered from recent boreholes in the southeastern margin of the Salar de Atacama, Chile span a modern environmental gradient from distal alluvial fans, groundwater discharge marshes, sulfate-rich playas, saline lagoons, and the halite nucleus of the salar. These same environments are preserved as stratigraphic records of environmental change in the cores. Cores from the salar nucleus are dominated by halite, and similarly alluvial cores provide a poor paleoenvironmental record. However, the cores from the transition zone between the salar margin and the halite nucleus document alluvial, lagoonal, and evaporite environments. Cores near the halite nucleus record inter-bedded carbonate, gypsum, and halite. Finely laminated carbonates inter-bedded with cm-thick halite beds are a target for U-series geochronology. Cores near modern lagoons contain 2-6 m thick diatomites in addition to microbially-mediated carbonate, organic-rich mud, and minor alluvium. The uppermost 20 cm of diatomite deposits are commonly rooted with vascular plant material which is being processed for 14C geochronology. Ignimbrite and tephra deposits are also encountered and will provide important chronological control. The presence and absence of the 3.5-4.0 Ma Tucucaro ignimbrite in various cores documents a complex pattern of subsidence near the salar margin, some areas have accumulated little sediment since its deposition while in other areas the cores likely record only late Pleistocene deposition. Preliminary interpretations of the stratigraphic records within a paleohydrologic context are tenable. The specific control on this paleohydrologic record is likely to be a combination of increased inflow due to wetter climates and migration of the freshwater/brine interface which underlies the margins of the Salar de Atacama. Stratigraphic variations in the lithium content of evaporite minerals is being explored as a potential indicator of water balance. Lithium concentrations

  16. Distribution and possible source of trace elements in the sediment cores of a tropical macrotidal estuary and their ecotoxicological significance.

    PubMed

    Chatterjee, M; Silva Filho, E V; Sarkar, S K; Sella, S M; Bhattacharya, A; Satpathy, K K; Prasad, M V R; Chakraborty, S; Bhattacharya, B D

    2007-04-01

    The paper presents the first document regarding concentration, distribution and possible sources of selected trace elements (Cu, Fe, Mn, Zn, Cr, Co, Ni, Pb, Al, B and Ba) in core sediments (<63 micro particle size) from the lower stretch of Hugli (Ganges) estuary, northeast coast of Bay of Bengal by ICP-AES and EDXRF to evaluate geochemical processes influencing their distribution and possible environmental consequences. The levels of elements showed a wide range of variations in different core depths, in upper and lower intertidal zones as well as among three sampling stations. The most interesting feature of the study is the downward increase of concentrations of majority of the elements reaching overall maximum values at a depth of 20-28 cm in upper littoral zone of the site located in the extreme downstream stretch of the estuary. Values of organic carbon showed very strong positive correlations with most of the elements as revealed by correlation matrix (r) values. The interelemental relationship revealed the identical behavior of element during its transport in the estuarine environment. The overall variation in concentration can be attributed to differential discharge of untreated effluents originating from industrial, agricultural, and aquacultural sources as well as from domestic sewage along with the fishing and boating activities. The resulting compositional dataset was tested by principal component analyses and cluster analyses. Pollution load index (PLI) and index of Geoaccumulation (Igeo) revealed overall low values but the enrichment factors (EFs) for Pb were typically high for all the stations. The mean concentrations of Zn and to some extent Cu exceeded the Effects Range-Low (ER-L) values in the majority of the cases indicating that there may be some ecotoxicological risk to organisms living in sediments. The concentration of the trace elements reported in this work is useful as baselines for comparison in future sediment quality studies. PMID

  17. Effect of Submarine Groundwater Discharge on Relict Arctic Submarine Permafrost and Gas Hydrate

    NASA Astrophysics Data System (ADS)

    Frederick, J. M.; Buffett, B. A.

    2014-12-01

    Permafrost-associated gas hydrate deposits exist at shallow depths within the sediments of the circum-Arctic continental shelves. Degradation of this shallow water reservoir has the potential to release large quantities of methane gas directly to the atmosphere. Gas hydrate stability and the permeability of the shelf sediments to gas migration is closely linked with submarine permafrost. Submarine permafrost extent depends on several factors, such as the lithology, sea level variations, mean annual air temperature, ocean bottom water temperature, geothermal heat flux, and the salinity of the pore water. The salinity of the pore water is especially relevant because it partially controls the freezing point for both ice and gas hydrate. Measurements of deep pore water salinity are few and far between, but show that deep off-shore sediments are fresh. Deep freshening has been attributed to large-scale topographically-driven submarine groundwater discharge, which introduces fresh terrestrial groundwater into deep marine sediments. We investigate the role of submarine ground water discharge on the salinity field and its effects on the seaward extent of relict submarine permafrost and gas hydrate stability on the Arctic shelf with a 2D shelf-scale model based on the finite volume method. The model tracks the evolution of the temperature, salinity, and pressure fields given imposed boundary conditions, with latent heat of water ice and hydrate formation included. The permeability structure of the sediments is coupled to changes in permafrost. Results show that pore fluid is strongly influenced by the permeability variations imposed by the overlying permafrost layer. Groundwater discharge tends to travel horizontally off-shore beneath the permafrost layer and the freshwater-saltwater interface location displays long timescale transient behavior that is dependent on the groundwater discharge strength. The seaward permafrost extent is in turn strongly influenced by the

  18. Climatic Impact on Major and Trace Elements in Deltaic Core Sediments: Evidence from Muthupet Lagoon, se Coast of India

    NASA Astrophysics Data System (ADS)

    Jayaprakash, M.; Urban, B.; Murugan, P. M. V.; Dharan, L.; Seshachalam, S.; Jonathan, M.

    2013-12-01

    Geochemistry of lagoon deposits provides a continuous record of climatic changes, and such core sediments at successive deeper and older layers have long been utilized for sedimentologic and organic geochemical studies. These ecosystems present a mechanism for trapping sediment and therefore record climatic changes in the form of geochemical imprints. The aim of the present study is to evaluate the climatic and depositional controls in the Muthupet lagoon, situated at the southern most end of the Cauvery delta, south east India. The variations of geochemical parameters with depth and their ratios were employed to reveal the characteristics of Holocene climate and associated paleoenvironmental implications of this region. Moderate values of the Chemical Index of Alteration (CIA) suggest intermediate chemical weathering of the source rock under tropical to subtropical climatic conditions. Index of Composition Variability (ICV) values indicate low proportion of non clay silicate minerals in these sediments. V/Cr ratio has been used as a paleo-oxygenation indicator and in the present study, the ratio V/Cr was found to be < 2 indicating oxic-depositional conditions prevailing in this lagoon. Fe/Ti and Fe/Al ratios reveal valuable information on the impact of climate changes on the sedimentation in the study area. Na and S, indicators of paleosalinity and marine flooding were evaluated. The increase in concentration of Na at various depths was identified and marine incursions characterized. Abrupt changes in the values at certain depths were directly related to major climatic events using the available rainfall and 210Pb data. Key words: Climate change, Weathering Pattern, Muthupet Mangroves, SE coast of India. Location map of the study area

  19. Magnetostratigraphy of a greigite-bearing core from the South Yellow Sea: Implications for remagnetization and sedimentation

    NASA Astrophysics Data System (ADS)

    Liu, Jianxing; Shi, Xuefa; Liu, Qingsong; Ge, Shulan; Liu, Yanguang; Yao, Zhengquan; Zhao, Quanhong; Jin, Chunsheng; Jiang, Zhaoxia; Liu, Shengfa; Qiao, Shuqing; Li, Xiaoyan; Li, Chuanshun; Wang, Chunjuan

    2014-10-01

    Sediments from the continental shelf are sensitive to sea level, climatic changes, and local tectonic history. In this study, we carried out a high-resolution magnetostratigraphic investigation on the longest core (NHH01, 125.64 m) recovered from the South Yellow Sea (SYS). An abnormal interval dominated by negative inclinations was discovered by applying alternating field demagnetization (AFD) on samples from a greigite-bearing layer (44.90-51.80 m). In contrast, the inclinations of most greigite-bearing samples changed from negative to positive when heated to ~360°C. This strongly indicates that this inclination anomaly revealed by the AFD alone is not a true negative subchron. After neglecting the effects of greigite-bearing layers, the straightforward correlation of the interpreted magnetostratigraphy defines the Matuyama-Brunhes boundary (781 ka) and the Jaramillo top (990 ka) at 68.64 m and 101.54 m, respectively. The linearly extrapolated basal age of the core is ~1.10 Ma. In addition, several short-lived inclination anomalies can be tentatively assigned to magnetic excursions, which indicates that the sedimentation could be continuous even at the millennial time scale at depth intervals bracketing these fast geomagnetic events. Moreover, the excellent correspondence between clay content variations of the core and the marine oxygen isotope record indicates the potential of clay content as a paleoclimatic proxy in the studied region in the past ~1 Ma. In brief, our study provides not only a robust age model in the SYS but also a methodological guide for paleomagnetic studies in continental shelf region.

  20. 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

  1. Determining the controls on δ13C of sedimentary organic matter in Lake Tiefer See (NE Germany) - an integration of sediment cores and monitoring data

    NASA Astrophysics Data System (ADS)

    Dräger, Nadine; Kienel, Ulrike; Groß-Schmölders, Miriam; Plessen, Birgit; Brauer, Achim

    2016-04-01

    The carbon isotopic composition of sedimentary organic matter (δ13Corg) is widely used in paleoenvironmental studies and commonly considered as proxy for lake productivity. In order to better understand the δ13Corg record of the partly annually laminated (varved) sediment profile of Lake Tiefer See, we complemented measurements from a long sediment core with analyses of short cores from different water depths and sediment trap data. The δ13Corg signature was determined (i) at 2 cm resolution from a 7.7 m-long continuous sediment record covering the last ˜6100 years retrieved from the deepest part of the lake (62 m), (ii) at 1 cm resolution from four short cores (0.5 to 0.9 m long) located at different water depths (20 -- 62 m) and covering at least the last 200 years and (iii) at bi-weekly to monthly resolution from sediment trap material collected at three water depths (5, 12 and 45 m) since march 2012. We observed that δ13Corg fluctuations are paralleled by changes in varve preservation, as well-varved sections show more negative δ13Corg values compared to non-varved intervals (1 -- 4‰ difference; analytical precision ±0.2‰). In short cores the negative shift of δ13Corg always appears at the most recent transition from non-varved to well-varved sediments. Depending on the water depth the onset of varve preservation occurred at different times (e.g. AD 1924 in 62 m water depth; AD 1981 in 20 m water depth). Since sediment trap data exhibit similar δ13Corg values of -30‰ to -31‰ in the entire water column and in the uppermost varved parts of the sediment cores, it is unlikely that the shift in δ13Corg was caused by processes in the water column because this should be seen in all cores at the same time. Therefore, we suggest that the δ13Corg record of the long sediment core of Lake Tiefer See does not reflect processes in the water column (i.e. productivity), but different early diagenetic processes in varved and non-varved sediment. In this study

  2. Polycyclic aromatic hydrocarbons in Holocene-Pleistocene sediments of the Laptev Sea

    NASA Astrophysics Data System (ADS)

    Drozdova, A. N.; Vetrov, A. A.; Romankevich, E. A.; Prokuda, N. A.; Sukhoverkhov, S. V.; Bratskaya, S. Yu.; Sergienko, V. I.; Semiletov, I. P.; Ulyantsev, A. S.

    2016-05-01

    The distribution and genesis of polycyclic aromatic hydrocarbons (PAHs) were studied in a 40-m core from a lagoon of the Laptev Sea that appeared during the Holocene resulting from the flooding of seawater into a freshwater lake in the area of the Buor-Khaya Gulf. The bulk of the core is constituted of permafrost rocks, thawed partially in their upper layers and covered with recent sediments (mainly by the products of intense thermoabrasion). The ratio of petrogenic and pyrogenic PAHs was evaluated.

  3. Estimation of Mercury Storage in Permafrost and Potential Release to the Environment by Thaw

    NASA Astrophysics Data System (ADS)

    Schuster, P. F.; Kamark, B. L.; Striegl, R. G.; Aiken, G.

    2011-12-01

    Changing climatic conditions in northern regions are causing perennially frozen soils (permafrost) to thaw. This thawing may have major implications for the cycling of carbon and metals, particularly mercury (Hg) in arctic and subarctic ecosystems. Hg is a ubiquitous pollutant that can impact aquatic resources and pose serious threat to human health. Northern regions of the world have the potential to contribute substantially to the global Hg cycling pool due to 1) enhanced deposition as a result of arctic springtime Hg depletion events, 2) increasing atmospheric Hg sources from rapidly expanding Asian industrialization, and perhaps most significantly, 3) the release of Hg historically sequestered in permafrost due to recent and potential future thawing. Total Hg concentrations (THg) were measured in three permafrost cores collected within the Yukon River basin of Alaska. Core 1, averaging 38 percent organic matter, was collected in a low-lying region of black spruce underlain by continuous permafrost; Core 2, a mineral-rich core averaging 8 percent organic matter, was collected in an upland region on a north facing slope of white spruce underlain by discontinuous permafrost; Core 3, also an organic-rich core, was collected in a low-lying collapsed bog region of discontinuous permafrost. All three cores were subsampled for THg at 1-2 cm intervals and represent a large range of permafrost soil conditions extending back about 10,000 years. Preliminary results show THg concentrations were highly variable ranging from 67 to 207 ng per g of soil (dry weight, n=94). Core 1 exhibited elevated Hg concentrations (50% above the mean) spanning several thousand years. Core 2 contained a lens of lightly-colored material (likely volcanic ash known as the White River Tephra based on XRD analysis) coincident with the some of the highest Hg concentrations in all three cores. Studies have shown that volcanic ash may have elevated concentrations of Hg. Preliminary estimates for the

  4. Pleistocene meteoric pore water in dated marine sediment cores off Callao, Peru

    NASA Astrophysics Data System (ADS)

    Kriete, Cornelia; Suckow, Axel; Harazim, Bodo

    2004-03-01

    During cruise SO 147 of the German research vessel SONNE, a large decrease in salinity with depth was found in the pore water at a site about 10 sea miles off Callao, Lima, Peru. The origin of this freshening was investigated in a multidisciplinary approach using geochemical, geochronological and isotope hydrological methods. The methodology applied is a possible strategy to deal with anomalous pore water freshenings and if necessary to put them into the general framework of submarine groundwater discharge. Concentrations of the major and conservative elements (e.g., Na, K, Cl, B, Br) decrease at the same ratios. Deuterium ( δD) and oxygen-18 ( δ18O) data reveal the meteoric origin of the fresh water end member, indicating a mixture of 30% seawater and 70% fresh water at a depth in sediment of about 10 m. 210Pb and 137Cs sedimentation rates determined by gamma spectrometry range between 2 and 4.5 mm/y for the last century whereas values derived from AMS 14C for the last millennia give mean rates smaller than 1 mm/y. This indicates strongly varying sedimentation conditions. Nevertheless, from the geochronological data it can be concluded that the origin of the fresh water end member is situated in sediments of Pleistocene age. Literature data of the isotope signature of modern water in the nearby Lima aquifer are clearly different from the calculated values for the fresh water end member in the pore waters. On the basis of the isotopic altitude effect described in the literature, the isotopic signature of the fresh pore water end member can be explained as rain water directly infiltrated into the Lima aquifer. In contrast, this infiltration is negligible there under present-day arid climatic conditions. Theoretical considerations on pore water advective and diffusive transport give further indications that the fresh pore water end member is entrapped paleowater of Pleistocene origin. The observed pore water freshening and the geochemical and geochronological data

  5. Zn and Cu isotopes as tracers of anthropogenic contamination in a sediment core from an Urban Lake

    USGS Publications Warehouse

    Thapalia, A.; Borrok, D.M.; Van Metre, P.C.; Musgrove, M.; Landa, E.R.

    2010-01-01

    In this work, we use stable Zn and Cu isotopes to identify the sources and timing of the deposition of these metals in a sediment core from Lake Ballinger near Seattle, Washington, USA. The base of the Lake Ballinger core predates settlement in the region, while the upper sections record the effects of atmospheric emissions from a nearby smelter and rapid urbanization of the watershed. ??66Zn and ??65Cu varied by 0.50% and 0.29%, respectively, over the 500 year core record. Isotopic changes were correlated with the presmelter period (~1450 to 1900 with ??66Zn = +0.39% ?? 0.09% and ??65Cu = +0.77% ?? 0.06%), period of smelter operation (1900 to 1985 with ??66Zn = +0.14 ?? 0.06% and ??65Cu = +0.94 ?? 0.10%), and postsmelting/stable urban land use period (post 1985 with ??66Zn = 0.00 ?? 0.10% and ??65Cu = +0.82% ?? 0.12%). Rapid early urbanization during the post World War II era increased metal loading to the lake but did not significantly alter the ??66Zn and ??65Cu, suggesting that increased metal loads during this time were derived mainly from mobilization of historically contaminated soils. Urban sources of Cu and Zn were dominant since the smelter closed in the 1980s, and the (??66Zn measured in tire samples suggests tire wear is a likely source of Zn. ?? 2010 American Chemical Society.

  6. Noble Gas and Mineralogical Tracers of Interplanetary Dust Particles and Impact Debris in a Central Pacific Sediment Core

    NASA Astrophysics Data System (ADS)

    Darrah, T. H.; Poreda, R. J.

    2005-12-01

    Thirty-five deep ocean sediment samples from the Central Pacific sediment core LL-44 GPC-3 were examined for their noble gas composition and mineralogy. The samples spanned from 30 to 71 Ma in age, including the Cretaceous/Tertiary (K/T), Paleocene/Eocene (P/E), and Eocene/Oligocene (E/O) boundaries. From each bulk sediment sample, magnetic grains (5-200 μg/g; 1-20 μm diameter) were isolated and analyzed. Noble gas measurements determined the helium and neon isotopic compositions and the abundance of extra-terrestrial (ET) noble gases for the bulk and magnetic fractions. 3He/4He ratios of 3.1x10-4 and 20Ne/22Ne ratios of 9.96-12.62 are consistent with the SEP (solar energetic particle) signature seen in both zero-age magnetic grains (Z-MAG) from the central Pacific sediments and stratospheric interplanetary dust particles (IDPs). The isolated magnetic fraction typically consisted of less than 1% of the bulk sample while accounting for 3 to 10% of the bulk sediment 3He with a maximum of 40% at K/T boundary. The magnetic isolates revealed no significant differences of 3He/4He, 20Ne/22Ne, or (3He/20Ne)solar from the bulk GPC-3 sediments or Z-MAG grains. No temporal variation in He or Ne or anomalous gas signatures associated with the boundaries present within this time interval was observed. Scanning electron microscope analysis was utilized to determine the mineralogy of the magnetic isolates in an effort to distinguish between the continuous flux of interplanetary dust particles and the flux associated with major impact events. This information may also assist in determining the carrier phase of ET noble gases. Anomalously high Ni, Mg, Al, and Cr compositions combined with low or nonexistent abundances of titanium can distinguish extraterrestrial spinel grains from terrestrial spinel. The SEM analysis revealed stark contrasts in composition and morphology in the samples associated with the boundaries included in this study. A survey of ``background'' samples

  7. Results of a detailed infill lake-sediment survey in the Snow Lake area: Evaluation and comparison of grab sample and short core data

    USGS Publications Warehouse

    Friske, P.W.B.

    1996-01-01

    As part of the Exploration Science and Technology Initiative (EXTECH) program a detailed infill lake-sediment and water survey was undertaken in the Snow Lake area during the fall of 1991. This involved the collection of 346 lake sediment grab samples and concomitant waters. In 1993, additional work was undertaken involving the collection of 23 short cores from selected grab sample sites. The primary objectives of the infill survey and short core work were to: 1) evaluate the effectiveness of lake sediment geochemistry in detecting known mineralization in the Snow Lake area; 2) evaluate and develop new approaches in the use of lake sediment geochemistry; and, 3) define, if possible, new exploration targets. At most sites, data from the cores verify the original grab sample results. However, at a few sites the original anomalous grab sample results are interpreted as being related to contamination as opposed to naturally elevated levels. An unusually thick sequence of contaminated surface sediments with extremely high concentrations of trace metals is a likely contributing factor, a condition which is restricted to lakes in the immediate vicinity of local anthropogenic activity. Collection of lake cores provides a useful new approach to the follow-up of grab sample data and to the application of lake sediment geochemistry, particularly in areas with significant local contamination. Much of the known mineralization in the area is clearly reflected by the lake sediment data. Character of the anomalies mirror the composition of the nearby mineralization. The lake sediment data also identify a number of areas that warrant further investigation, several of which are discussed.

  8. Permafrost, heat flow, and the geothermal regime at Prudhoe Bay, Alaska.

    USGS Publications Warehouse

    Lachenbruch, A.H.; Sass, J.H.; Marshall, B.V.; Moses, T.H., Jr.

    1982-01-01

    Temperature measurements through permafrost in the oil field at Prudhoe Bay, Alaska, combined with laboratory measurements of the thermal conductivity of drill cutting permit an evaluation of in situ thermal properties and an understanding of the general factors that control the geothermal regime. A sharp contrast in temperatire gradient at c600m represents a contrast in thermal conductivity caused by the downward change from interstitial ice to interstitial water at the base of permafrost under near steady state conditions. These results yield a heat flow of c1.3HFU, which is similar to other values on the Alaskan Arctic Coast: the anomalously deep permafrost is a result of the anomalously high conductivity of the siliceous ice-rich sediments. With confirmation of the permafrost configuration by offshore drilling, heat conduction models can yield reliable new information on the chronology of arctic shoreline. -from Authors

  9. Detecting environmental change in estuaries: Nutrient and heavy metal distributions in sediment cores in estuaries from the Gulf of Finland, Baltic Sea

    NASA Astrophysics Data System (ADS)

    Vaalgamaa, S.; Conley, D. J.

    2008-01-01

    Historical sediment nutrient concentrations and heavy metal distributions were studied in four estuaries in the Gulf of Finland, Baltic Sea to examine the response of these estuaries to temporal changes in human activities. Cores were collected using a 1-m Mackereth corer and dated using 210Pb and 137Cs. The cores were analyzed for total carbon (TC), total nitrogen (TN), total phosphorus (TP), organic phosphorus (OP), inorganic phosphorus (IP), biogenic silica (BSi), loss-on-ignition (LOI), Cu, Zn, Al, Fe, Mn, K, Ca, Mg and Na. Principal component analysis (PCA) was used to summarize the trends in the chemical variables and to compare the trends at the different sites. Applying the 1986 137Cs date as a reference point, 210Pb chronologies were constructed for the sites using either the CRS model or a composite model (using both CIC and CRS). Significant increases were observed in sedimentation rates, TP and TN concentrations in all of the cores. Copper showed clear increases from 1850 towards present at all sites. Furthermore, redundancy analysis (RDA) was used to correlate environmental variables (catchment land use, catchment size, estuary surface area, depth and lake percentage) to sediment geochemistry. Based on redundancy analysis (RDA), the percentage of agriculture in the catchment was the most important factor affecting the sediment accumulation rate. Urban land-use types and industry correlate well with sediment Cu and Ca concentrations. Forest areas were related to high sediment BSi concentrations. Catchment land use was the most significant factor affecting sediment geochemical composition and sediment accumulation rates in these coastal embayments. Our results demonstrate that the coastal estuaries of the Gulf of Finland respond to the increased nutrient loading with the increased sedimentation and nutrient accumulation rates.

  10. High-resolution OSL chronology of a sediment core from Lake Nam Co on the southern Tibetan Plateau: Comparison with radiocarbon dating

    NASA Astrophysics Data System (ADS)

    Long, Hao; Shen, Ji; Haberzettl, Torsten; Fuchs, Markus; Frechen, Manfred; Wang, Junbo

    2013-04-01

    Numerous studies on lake sediment cores from the Tibetan Plateau aimed to reconstruct spatial and temporal changes of the late Glacial and Holocene monsoon variations, which are characterized by fluctuations in precipitation and expansion of monsoonal air masses across the Plateau. Accurate and reliable dating of lacustrine deposits is of crucial importance in both the reconstruction of palaeolake and palaeoclimate evolution and the understanding of the mechanisms for climate changes, especially abrupt changes of regional-hemispheric hydrological circulation. Radiocarbon dating is the most commonly used method for establishing chronologies of lake sediments. However, 14C dating of such sediments could be problematic due to the lack of organic matter or a reservoir effect, which appears common in radiocarbon dating of lacustrine sediments from the Tibetan Plateau. In this study, ca. 10.5 m long core (NC core) was retrieved from the water depth of 93 m at Nam Co Lake, which is the second largest saline lake in China, located on the southern Tibetan Plateau. For this core, high-resolution samples (23 samples) were obtained for optically stimulated luminescence (OSL) dating. Quartz of fine-grain (4-11 μm) fraction were extracted from this samples for OSL dating, which is compared with the 14C chronology of NC core based on accelerator mass spectrometry (AMS) dating of bulk organic matter of 22 samples. The sample from the top of NC core was dated to approximate zero age, indicating the sediments bleached well before deposition. Luminescence behaviors of the study samples further confirmed the robustness of OSL ages. Comparison between OSL and 14C ages suggested that: (1) two kinds of ages are in agreement within error from top to 1.8 m, (2) from 1.8 m to the base of NC core, the 14C ages show a general trend to ca. 4 ka higher ages than the OSL ages. Although 14C dating overestimate the ages from 1.8 m to base, they still show the general trend in sedimentation rate

  11. Hg Deposition to Lakes in Northern New England Inferred at Multiple Scales From 210Pb-Dated Sediment Cores

    NASA Astrophysics Data System (ADS)

    Kamman, N. C.; Engstrom, D.

    2004-05-01

    Mercury (Hg) contamination of aquatic systems is recognized to be a problem of global consequence, and Hg bioaccumulation poses significant risks to piscivorous animals and humans who consume gamefish. In order to quantify historical and current Hg deposition to the northern New England landscape, we dated and performed Hg analyses on sediments cores from various lakes at local and regional scales. In this presentation, we contrast results of three studies: a regional assessment of Hg deposition to the VT-NH landscape (10 lakes); a localized study of deposition to the Lye Brook Wilderness of southern VT (four lakes); and the first-ever dated assessment of sediment Hg deposition history for Lake Champlain (three sites + one adjacent inland lake). At the VT-NH scale, total Hg (HgT) fluxes to sediments ranged from 5 to 17 μ g.m-2.yr-1 during pre-industrial times, and from 21 to 83 μ g.m-2.yr-1 presently. Present-day HgT fluxes are between 2.1 to 6.9 times greater than pre-1850 fluxes, and atmospheric Hg deposition to the VT-NH region was estimated at 21 μ g.m-2.yr-1. This agrees well with measured HgT deposition, when re-evasion of Hg is accounted for. Hg fluxes to lake sediments have declined in recent decades, owing to reductions in atmospheric Hg deposition to the lake surfaces. In the high-elevation Lye Brook Wilderness landscape, baseline, peak, and present accumulations were higher than those estimated from the VT-NH dataset, a finding that highlights the roles of elevation, watershed size, and dissolved organic carbon export in mediating Hg transport. Available data from the Lake Champlain Basin show the influence of historical and current watershed sediment delivery due to land cultivation, and more recently to land-use conversion. These studies jointly indicate that watershed export of legacy Hg continues despite declines in present-day deposition rates, contributing to the impression that Hg retention by watershed soils has declined.

  12. Overview on Hydrate Coring, Handling and Analysis

    SciTech Connect

    Jon Burger; Deepak Gupta; Patrick Jacobs; John Shillinglaw

    2003-06-30

    Gas hydrates are crystalline, ice-like compounds of gas and water molecules that are formed under certain thermodynamic conditions. Hydrate deposits occur naturally within ocean sediments just below the sea floor at temperatures and pressures existing below about 500 meters water depth. Gas hydrate is also stable in conjunction with the permafrost in the Arctic. Most marine gas hydrate is formed of microbially generated gas. It binds huge amounts of methane into the sediments. Worldwide, gas hydrate is estimated to hold about 1016 kg of organic carbon in the form of methane (Kvenvolden et al., 1993). Gas hydrate is one of the fossil fuel resources that is yet untapped, but may play a major role in meeting the energy challenge of this century. In June 2002, Westport Technology Center was requested by the Department of Energy (DOE) to prepare a ''Best Practices Manual on Gas Hydrate Coring, Handling and Analysis'' under Award No. DE-FC26-02NT41327. The scope of the task was specifically targeted for coring sediments with hydrates in Alaska, the Gulf of Mexico (GOM) and from the present Ocean Drilling Program (ODP) drillship. The specific subjects under this scope were defined in 3 stages as follows: Stage 1: Collect information on coring sediments with hydrates, core handling, core preservation, sample transportation, analysis of the core, and long term preservation. Stage 2: Provide copies of the first draft to a list of experts and stakeholders designated by DOE. Stage 3: Produce a second draft of the manual with benefit of input from external review for delivery. The manual provides an overview of existing information available in the published literature and reports on coring, analysis, preservation and transport of gas hydrates for laboratory analysis as of June 2003. The manual was delivered as draft version 3 to the DOE Project Manager for distribution in July 2003. This Final Report is provided for records purposes.

  13. High risk of permafrost thaw

    SciTech Connect

    Schuur, E.A.G.; Abbott, B.; Koven, C.D,; Riley, W.J.; Subin, Z.M.; al, et

    2011-11-01

    In the Arctic, temperatures are rising fast, and permafrost is thawing. Carbon released to the atmosphere from permafrost soils could accelerate climate change, but the likely magnitude of this effect is still highly uncertain. A collective estimate made by a group of permafrost experts, including myself, is that carbon could be released more quickly than models currently suggest, and at levels that are cause for serious concern. While our models of carbon emission from permafrost thaw are lacking, experts intimately familiar with these landscapes and processes have accumulated knowledge about what they expect to happen, based on both quantitative data and qualitative understanding of these systems. We (the authors of this piece) attempted to quantify this expertise through a survey developed over several years, starting in 2009. Our survey asked experts what percentage of surface permafrost they thought was likely to thaw, how much carbon would be released, and how much of that would be methane, for three time periods and under four warming scenarios that are part of the new IPCC Fifth Assessment Report.

  14. The use of vintage surficial sediment data and sedimentary cores to determine past and future trends in estuarine metal contamination (Sydney estuary, Australia).

    PubMed

    Birch, G F; Chang, C-H; Lee, J-H; Churchill, L J

    2013-06-01

    The objectives of the present investigation were to determine past trends in sediment contamination and possibly predict future trends. Multiple vintages of surficial sediment metal data, from a quasi-decadal 'Status and Trends' programme, were used to provide large-scale spatial information on current status and temporal change. This information was augmented by sediment cores, specifically located to verify surface sediment data and to determine trends at major points of stormwater discharge. The data obtained indicate that surficial sediment metal concentrations have declined, since about the early 1990s, in extensive parts of the upper and central estuaries and have increased slightly in the lower estuary, due mainly to a down-estuary shift in industry and urbanisation. Declining surficial sediment metal concentrations is due to a movement of industry out of the catchment, especially from foreshore areas and the introduction of regulation, which prevent pollutants being discharged directly to the estuary. The major present-day source of metals is stormwater, with minor inputs from the main estuary channel into embayments and runoff from previously contaminated mainland sites. Modelled relaxation rates are optimistic as high metal concentrations in stormwater will slow predicted rates. Stormwater remediation should be the main managerial focus for this estuary. Multiple vintages of surficial sediment metal data covering the past 30 years, supplemented by sedimentary core data, have allowed past and future contamination trends to be determined. This type of science-based information provides an important tool for strategic management of this iconic waterway. PMID:23570910

  15. Integrated sequence stratigraphy of the postimpact sediments from the Eyreville core holes, Chesapeake Bay impact structure inner basin

    USGS Publications Warehouse

    Browning, J.V.; Miller, K.G.; McLaughlin, P.P., Jr.; Edwards, L.E.; Kulpecz, A.A.; Powars, D.S.; Wade, B.S.; Feigenson, M.D.; Wright, J.D.

    2009-01-01

    The Eyreville core holes provide the first continuously cored record of postimpact sequences from within the deepest part of the central Chesapeake Bay impact crater. We analyzed the upper Eocene to Pliocene postimpact sediments from the Eyreville A and C core holes for lithology (semiquantitative measurements of grain size and composition), sequence stratigraphy, and chronostratigraphy. Age is based primarily on Sr isotope stratigraphy supplemented by biostratigraphy (dinocysts, nannofossils, and planktonic foraminifers); age resolution is approximately ??0.5 Ma for early Miocene sequences and approximately ??1.0 Ma for younger and older sequences. Eocene-lower Miocene sequences are subtle, upper middle to lower upper Miocene sequences are more clearly distinguished, and upper Miocene- Pliocene sequences display a distinct facies pattern within sequences. We recognize two upper Eocene, two Oligocene, nine Miocene, three Pliocene, and one Pleistocene sequence and correlate them with those in New Jersey and Delaware. The upper Eocene through Pleistocene strata at Eyreville record changes from: (1) rapidly deposited, extremely fi ne-grained Eocene strata that probably represent two sequences deposited in a deep (>200 m) basin; to (2) highly dissected Oligocene (two very thin sequences) to lower Miocene (three thin sequences) with a long hiatus; to (3) a thick, rapidly deposited (43-73 m/Ma), very fi ne-grained, biosiliceous middle Miocene (16.5-14 Ma) section divided into three sequences (V5-V3) deposited in middle neritic paleoenvironments; to (4) a 4.5-Ma-long hiatus (12.8-8.3 Ma); to (5) sandy, shelly upper Miocene to Pliocene strata (8.3-2.0 Ma) divided into six sequences deposited in shelf and shoreface environments; and, last, to (6) a sandy middle Pleistocene paralic sequence (~400 ka). The Eyreville cores thus record the fi lling of a deep impact-generated basin where the timing of sequence boundaries is heavily infl uenced by eustasy. ?? 2009 The Geological

  16. Historical records of mercury, lead, and polycyclic aromatic hydrocarbons depositions in a dated sediment core from the Eastern Mediterranean.

    PubMed

    Azoury, S; Tronczyński, J; Chiffoleau, J-F; Cossa, D; Nakhlé, K; Schmidt, S; Khalaf, G

    2013-07-01

    Depth profiles of mercury, lead and its stable isotopes, and polycyclic aromatic hydrocarbons were determined in a dated sediment core from the Levantine basin. Sedimentary records show that preindustrial fluxes and levels of Hg, Pb, and PAHs remained generally constant in the region before 1850. An almost concurrent uniform increase of both metals and PAHs deposition occurring at the beginning of the Industrial Revolution suggests coal combustion as a main source of these contaminants in the Levantine basin after the 1850s. However, none of the contaminant profiles indicates a decline after 1950-60, the characteristic period of coal use reduction. The modern fluxes of Hg and Pb reveal a 3- to 5-fold increase over preindustrial loads, while the contemporaneous flux of PAHs rises by 4-7 times. On the whole, records in the Eastern Mediterranean suggest atmospheric inputs from relatively distant sources, likely from Central and Eastern Europe. PMID:23725373

  17. Temporal trends of hydrocarbons in sediment cores from the Pearl River Estuary and the northern South China Sea.

    PubMed

    Peng, Xianzhi; Wang, Zhendi; Yu, Yiyi; Tang, Caiming; Lu, Hong; Xu, Shiping; Chen, Fanrong; Mai, Bixian; Chen, Shejun; Li, Kechang; Yang, Chun

    2008-11-01

    Concentrations and fluxes of unresolved complex mixture of hydrocarbons (UCM) and polycyclic aromatic hydrocarbons (PAHs) were analyzed for two (210)Pb dated sediment cores from the Pearl River Estuary (PRE) and the adjacent northern South China Sea (NSCS). Compound-specific stable carbon isotopic compositions of individual n-alkanes were also measured for identification of the hydrocarbon sources. The historical records of PAHs in the NSCS reflected the economic development in the Pearl River Delta during the 20th century. PAHs in the NSCS predominantly derive from combustion of coal and biomass, whereas PAHs in the PRE are a mixture of petrogenic and pyrogenic in origins. The isotopic profiles reveal that the petrogenic hydrocarbons in the PRE originate predominantly from local spillage/leakage of lube oil and crude oils. The accumulation rates of pyrogenic PAHs have significantly increased, whereas UCM accumulation has slightly declined in the NSCS in the recent three decades. PMID:18339464

  18. Further Paleogene and Cretaceous sediment cores from the Kilwa area of coastal Tanzania: Tanzania Drilling Project Sites 6 10

    NASA Astrophysics Data System (ADS)

    Pearson, Paul N.; Nicholas, Christopher J.; Singano, Joyce M.; Bown, Paul R.; Coxall, Helen K.; van Dongen, Bart E.; Huber, Brian T.; Karega, Amina; Lees, Jackie A.; MacLeod, Kenneth; McMillan, Ian K.; Pancost, Richard D.; Pearson, Marion; Msaky, Emma

    2006-07-01

    Initial results from scientific drilling in southern coastal Tanzania are described. In a field season in 2003, a total of five sites was drilled (mostly using continuous coring) by the Tanzania Drilling Project for paleoclimate studies. The sediments are predominantly marine clays and claystones deposited in an outer shelf or slope environment and often contain excellently preserved microfossils suitable for geochemical analysis. The studies reported here include summaries of the lithostratigraphy, biostratigraphy (planktonic foraminifers, calcareous nannofossils, benthic foraminifers, and palynology) and organic geochemistry. TDP Site 6 was drilled near Kilwa Masoko (UTM 37L 555752, 9014922), 350 m to the south-east of a previous site, TDP Site 1. The top 59.58 m, which was mostly drilled without coring, consists of an Oligocene clay formation belonging to nannofossil Zone NP23. The rest of the hole, to a total depth of 61.25 m, consists of a fault zone in which the Oligocene sediments are intermixed with middle Eocene clays of planktonic foraminifer Zone E9 and nannofossil Subzone NP15b. TDP Site 7 consists of two holes (Hole TDP7A: UTM 37L 547126, 9030142; Hole TDP7B: UTM 37L 0547130, 9030140) drilled just 5 m apart at Kwamatola, a creek to the south of Kilwa Kivinje. Underneath approximately 20 m of unconsolidated sands and gravels, claystones and siltstones were recovered to a total depth of 128.00 m. The site spans lower Eocene planktonic foraminifer Zones E1, E2 and E3 and nannofossil Subzones NP 9b and NP10. The bottom of Hole TDP7B approaches the Paleocene-Eocene boundary but no unambiguously Paleocene sediments were recovered. TDP Site 8 was drilled to the south-east of Singino Hill (UTM 37L 548033, 9025811). Below a covering of surface gravels, it yielded predominantly dark greenish-grey claystones to a total depth of 22.95 m. The sediments are from the lower Eocene and span the boundary between planktonic foraminifer Zones E3 and E4 and fall within

  19. Characterization of Vadose Zone Sediment: Uncontaminated RCRA Borehole Core Samples and Composite Samples

    SciTech Connect

    Serne, R. Jeffrey; Bjornstad, Bruce N.; Schaef, Herbert T.; Williams, Bruce A.; Lanigan, David C.; Horton, Duane G.; Clayton, Ray E.; Mitroshkov, Alexandre V.; Legore, Virginia L.; O'Hara, Matthew J.; Brown, Christopher F.; Parker, Kent E.; Kutnyakov, Igor V.; Serne, Jennifer N.; Last, George V.; Smith, Steven C.; Lindenmeier, Clark W.; Zachara, John M.; Burke, Deborah S.

    2008-09-11

    This report was revised in September 2008 to remove acid-extractable sodium data from Tables 4.14, 4.16, 5.20, 5.22, 5.43, and 5.45. The sodium data was removed due to potential contamination introduced during the acid extraction process. The rest of the text remains unchanged from the original report issued in February 2002. The overall goal of the of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., is to define risks from past and future single-shell tank farm activities. To meet this goal, CH2M HILL Hanford Group, Inc. asked scientists from Pacific Northwest National Laboratory to perform detailed analyses on vadose zone sediment from within the S-SX Waste Management Area. This report is one in a series of four reports to present the results of these analyses. Specifically, this report contains all the geologic, geochemical, and selected physical characterization data collected on vadose zone sediment recovered from Resource Conservation and Recovery Act (RCRA) borehole bore samples and composite samples.

  20. Ice core measurements of 14CH4 show no evidence of methane release from methane hydrates or old permafrost carbon during a large warming event 11,600 years ago

    NASA Astrophysics Data System (ADS)

    Petrenko, Vasilii; Severinghaus, Jeffrey; Smith, Andrew; Riedel, Katja; Brook, Edward; Schaefer, Hinrich; Baggenstos, Daniel; Harth, Christina; Hua, Quan; Buizert, Christo; Schilt, Adrian; Fain, Xavier; Mitchell, Logan; Bauska, Thomas; Orsi, Anais

    2015-04-01

    Thawing permafrost and marine methane hydrate destabilization in the Arctic and elsewhere have been proposed as large sources of methane to the atmosphere in the future warming world. To evaluate this hypothesis it is useful to ask whether such methane releases happened during past warming events. The two major abrupt warming events of the last deglaciation, Oldest Dryas - Bølling (OD-B, ≈ 14,500 years ago) and Younger Dryas - Preboreal (YD-PB; ≈11,600 years ago), were associated with large (up to 50%) increases in atmospheric methane (CH4) concentrations. The sources of these large warming-driven CH4 increases remain incompletely understood, with possible contributions from tropical and boreal wetlands, thawing permafrost as well as marine CH4 hydrates. We present new measurements of 14C of paleoatmospheric CH4 over the YD-PB transition from ancient ice outcropping at Taylor Glacier, Antarctica. 14C can unambiguously identify CH4 emissions from "old carbon" sources, such as permafrost and CH4 hydrates. The only prior study of paleoatmospheric 14CH4 (from Greenland ice) suggested that wetlands were the main driver of the YD-PB CH4 increase, but the results were weakened by an unexpected and poorly understood 14CH4 component from in situ cosmogenic production directly in near-surface ice. In this new study, we have been able to accurately characterize and correct for the cosmogenic 14CH4 component. All samples from before, during and after the abrupt warming and associated CH4 increase yielded 14CH4 values that are consistent with 14C of atmospheric CO2 at that time, indicating a purely contemporaneous methane source. These new measurements rule out the possibility of large CH4 releases to the atmosphere from methane hydrates or old permafrost carbon in response to the large and rapid YD-PB warming. To the extent that the characteristics of the YD-PB warming are comparable to those of the current anthropogenic warming, our measurements suggest that large future

  1. Periglacial Landscape Stabilization Following Rapid Permafrost Degradation by Thermo-erosion, Bylot Island, Nunavut, Canadian Arctic Archipelago

    NASA Astrophysics Data System (ADS)

    Fortier, D.; Godin, E.; Perreault, N.; Levesque, E.

    2010-12-01

    The Byam Martin Mountains that run southeast-northwest across Bylot Island are covered by an ice cap which is flowing towards the lowlands into valleys. The bottom of these valleys is filled with sediments shaped into various periglacial landforms that developed during the Holocene such as ice-wedge polygons, pingos, and thermokarst lakes (Fortier and Allard, 2004). At the study site (N 73° 09’ - W 79° 53’), snow-melt run-off driven processes of thermo-erosion have recently drastically modified the periglacial landscape by creating extensive network of gullies in ice-wedge polygons. In the valley of glacier C-79, thirty five gullies, hundreds of meters to kilometers long, were identified and studied in the field. The formation of these gullies has changed the local hydrographic network by connecting the valley walls to a proglacial river flowing in the valley. The gully heads were characterized by active thermo-erosion processes operating underground and at the surface for a number of years (Fortier et al. 2007). Downstream, the gully walls were affected by various permafrost degradation processes such as active-layer detachment, retrogressive thaw slumping, drainage of the active layer of the polygons into the gully channel and differential thaw settlement of the surface (Godin and Fortier, 2010). It was observed that after a few years the downstream parts of the gully systems were stabilized and the gully walls partially colonized by vegetation. Drilling and coring operations into stabilized areas revealed the presence of ground ice a few decimeters below the surface with cryostructures indicative of permafrost aggradation. On stabilized gully walls, the sediments were aligned parallel to the slope and showed ice-rich reticulate to suspended cryostructures. Down to about one meter, the sediments were separated by centimeters-thick ice lenses which contained air bubbles aligned perpendicular to the slope. We propose that drainage of the soils on the slope

  2. Metal binding in soil cores and sediments in the vicinity of a dammed agricultural and industrial watershed.

    PubMed

    Kanbar, Hussein Jaafar; Hanna, Nour; El Samrani, Antoine G; Kazpard, Véronique; Kobaissi, Ahmad; Harb, Nafez; Amacha, Nabil

    2014-12-01

    The environment is witnessing a downgrade caused by the amelioration of the industrial and agricultural sectors, namely, soil and sediment compartments. For those reasons, a comparative study was done between soil cores and sediments taken from two locations in the Qaraaoun reservoir, Lebanon. The soil cores were partitioned into several layers. Each layer was analyzed for several physicochemical parameters, such as functional groups, particle size distribution, ζ-potential, texture, pH, electric conductivity, total dissolved solids, organic matter, cation exchange capacity, active and total calcareous, available sodium and potassium, and metal content (cadmium, copper, and lead). The metal content of each site was linked to soil composition and characteristics. The two sites showed distinguishable characteristics for features such as organic matter, pH, mineral fraction, calcareous, and metal content. The samples taken toward the south site (Q1), though contain lower organic matter than the other but are more calcareous, showed higher metal content in comparison to the other site (Q2) (average metal content of Q1 > Q2; for Cd 3.8 > 1.8 mg/kg, Cu 28.6 > 21.9 mg/kg, Pb 26.7 > 19 mg/kg). However, the metal content in this study did not correlate as much to the organic matter; rather, it was influenced by the location of the samples with respect to the dam, the reservoir's hydrodynamics, the calcareous nature of the soil, and the variation of the industrial and agricultural influence on each site. PMID:25228528

  3. Historical Associations of Molecular Measurements of Escherichia coli and Enterococci to Anthropogenic Activities and Climate Variables in Freshwater Sediment Cores.

    PubMed

    Brooks, Yolanda M; Baustian, Melissa M; Baskaran, Mark; Ostrom, Nathaniel E; Rose, Joan B

    2016-07-01

    This study investigated the long-term associations of anthropogenic (sedimentary P, C, and N concentrations, and human population in the watershed), and climatic variables (air temperature, and river discharge) with Escherichia coli uidA and enterococci 23S rRNA concentrations in sediment cores from Anchor Bay (AB) in Lake St. Clair, and near the mouth of the Clinton River (CR), Michigan. Calendar year was estimated from vertical abundances of (137)Cs. The AB and CR cores spanned c.1760-2012 and c.1895-2012, respectively. There were steady state concentrations of enterococci in AB during c.1760-c.1860 and c.1910-c.2003 at ∼0.1 × 10(5) and ∼2.0 × 10(5) cell equivalents (CE) per g-dry wt, respectively. Enterococci concentrations in CR increased toward present day, and ranged from ∼0.03 × 10(5) to 9.9 × 10(5) CE/g-dry wt. The E. coli concentrations in CR and AB increased toward present day, and ranged from 0.14 × 10(7) to 1.7 × 10(7) CE/g-dry wt, and 1.8 × 10(6) to 8.5 × 10(6) CE/g-dry wt, respectively. Enterococci was associated with population and river discharge, while E. coli was associated with population, air temperature, and N and C concentrations (p < 0.05). Sediments retain records of the abundance of fecal indicator bacteria, and offer a way to evaluate responses to increased population, nutrient loading, and environmental policies. PMID:27322138

  4. Shallow-marine sediment cores record climate variability and earthquake activity off Lisbon (Portugal) for the last 2000 years

    NASA Astrophysics Data System (ADS)

    Abrantes, F.; Lebreiro, S.; Rodrigues, T.; Gil, I.; Bartels-Jónsdóttir, H.; Oliveira, P.; Kissel, C.; Grimalt, J. O.

    2005-12-01

    Sea Surface Temperature (SST), river discharge and biological productivity have been reconstructed from a multi-proxy study of a high-temporal-resolution sedimentary sequence recovered from the Tagus deposition center off Lisbon (Portugal) for the last 2000 years. SST shows 2 °C variability on a century scale that allows the identification of the Medieval Warm Period (MWP) and the Little Ice Age (LIA). High Iron (Fe) and fine-sediment deposition accompanied by high n-alkane concentrations and presence of freshwater diatoms during the LIA (1300-1900 AD) (Science 292 (2001) 662) suggest augmented river discharge, whereas higher total-alkenone concentrations point to increased river-induced productivity. During the MWP (550-1300 AD) (Science 292 (2001) 662) larger mean-grain size and low values of magnetic susceptibility, and concentrations of Fe, n-alkanes, and n-alcohols are interpreted to reflect decreased runoff. At the same time, increased benthic and planktonic foraminifera abundances and presence of upwelling related diatoms point to increased oceanic productivity. On the basis of the excellent match found between the negative phases of the North Atlantic Oscillation (NAO) index and the intensified Tagus River discharge observed for the last century, it is hypothesized that the increased influx of terrigenous material during the LIA reflects a negative NAO-like state or the occurrence of frequent extreme NAO minima. During the milder few centuries of the MWP, stronger coastal upwelling conditions are attributed to a persistent, positive NAO-like state or the frequent occurrence of extreme NAO maxima. The peak in magnetic susceptibility, centered at 90 cm composite core depth (ccd), is interpreted as the result of the well-known 1755 AD Lisbon earthquake. The Lisbon earthquake and accompanying tsunami are estimated to have caused the loss of 39 cm of sediment (355 years of record—most of the LIA) and the instantaneous deposition of a 19-cm sediment bed.

  5. Anthropogenic impact on the Swartvlei lake system in the Wilderness area (South Africa) as reflected in a sediment core

    NASA Astrophysics Data System (ADS)

    Haberzettl, Torsten; Kirsten, Kelly; Franz, Sarah; Reinwarth, Bastian; Baade, Jussi; Daut, Gerhard; Kasper, Thomas; Meadows, Michael; Su, Youliang; Mäusbacher, Roland

    2016-04-01

    Swartvlei is one of the most thoroughly investigated lacustrine coastal systems in South Africa. However, studies focussing on anthropogenic impacts on sediment deposition in the most recent past (i.e., the last 30-40 years) are rare. A 96 cm long sediment core, covering the past two centuries, provides evidence for intense changes over the last few decades probably related to anthropogenic activities, such as farming, water abstraction etc. A decrease in marine influence is observed starting somewhat earlier but was potentially supported by human management activities. The development of the age-depth model turned out to be a serious issue, as old marine carbon affected samples impacted the robustness of the chronology, hence further investigations are required in most coastal geoarchives from South Africa. A multi-dating approach using several methods is suggested as errors in the chronology distinctly impact paleoenvironmental reconstructions (timing, flux rates etc.). In this context initial paleomagnetic secular variation data are presented, which needs further exploration and inclusion in the future.

  6. Collection, analysis, and age-dating of sediment cores from 56 U.S. lakes and reservoirs sampled by the U.S. Geological Survey, 1992-2001

    USGS Publications Warehouse

    Van Metre, Peter; Wilson, Jennifer T.; Fuller, Christopher C.; Callender, Edward; Mahler, Barbara J.

    2004-01-01

    The U.S. Geological Survey Reconstructed Trends National Synthesis study collected sediment cores from 56 lakes and reservoirs between 1992 and 2001 across the United States. Most of the sampling was conducted as part of the National Water-Quality Assessment (NAWQA) Program. The primary objective of the study was to determine trends in particle-associated contaminants in response to urbanization; 47 of the 56 lakes are in or near one of 20 U.S. cities. Sampling was done with gravity, piston, and box corers from boats and push cores from boats or by wading, depending on the depth of water and thickness of sediment being sampled. Chemical analyses included major and trace elements, organochlorine pesticides, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, cesium-137, and lead-210. Age-dating of the cores was done on the basis of radionuclide analyses and the position of the pre-reservoir land surface in the reservoir and, in a few cases, other chemical or lithologic depth-date markers. Dates were assigned in many cores on the basis of assumed constant mass accumulation between known depth-date markers. Dates assigned were supported using a variety of other date markers including first occurrence and peak concentrations of DDT and polychlorinated biphenyls and peak concentration of lead. A qualitative rating was assigned to each core on the basis of professional judgment to indicate the reliability of age assignments. A total of 122 cores were collected from the 56 lakes and age dates were assigned to 113 of them, representing 54 of the 56 lakes. Seventy-four of the 122 cores (61 percent) received a good rating for the assigned age dates, 28 cores (23 percent) a fair rating, and 11 cores (9 percent) a poor rating; nine cores (7 percent) had no dates assigned. An analysis of the influence of environmental factors on the apparent quality of age-dating of the cores concluded that the most important factor was the mass accumulation rate (MAR) of sediment: the

  7. Extensive lake sediment coring survey on Sub-Antarctic Indian Ocean Kerguelen Archipelago (French Austral and Antarctic Lands)

    NASA Astrophysics Data System (ADS)

    Arnaud, Fabien; Fanget, Bernard; Malet, Emmanuel; Poulenard, Jérôme; Støren, Eivind; Leloup, Anouk; Bakke, Jostein; Sabatier, Pierre

    2016-04-01

    Recent paleo-studies revealed climatic southern high latitude climate evolution patterns that are crucial to understand the global climate evolution(1,2). Among others the strength and north-south shifts of westerlies wind appeared to be a key parameter(3). However, virtually no lands are located south of the 45th South parallel between Southern Georgia (60°W) and New Zealand (170°E) precluding the establishment of paleoclimate records of past westerlies dynamics. Located around 50°S and 70°E, lost in the middle of the sub-Antarctic Indian Ocean, Kerguelen archipelago is a major, geomorphologically complex, land-mass that is covered by hundreds lakes of various sizes. It hence offers a unique opportunity to reconstruct past climate and environment dynamics in a region where virtually nothing is known about it, except the remarkable recent reconstructions based on a Lateglacial peatbog sequence(4). During the 2014-2015 austral summer, a French-Norwegian team led the very first extensive lake sediment coring survey on Kerguelen Archipelago under the umbrella of the PALAS program supported by the French Polar Institute (IPEV). Two main areas were investigated: i) the southwest of the mainland, so-called Golfe du Morbihan, where glaciers are currently absent and ii) the northernmost Kerguelen mainland peninsula so-called Loranchet, where cirque glaciers are still present. This double-target strategy aims at reconstructing various independent indirect records of precipitation (glacier advance, flood dynamics) and wind speed (marine spray chemical species, wind-borne terrigenous input) to tackle the Holocene climate variability. Despite particularly harsh climate conditions and difficult logistics matters, we were able to core 6 lake sediment sites: 5 in Golfe du Morbihan and one in Loranchet peninsula. Among them two sequences taken in the 4km-long Lake Armor using a UWITEC re-entry piston coring system by 20 and 100m water-depth (6 and 7m-long, respectively). One

  8. Lake Chad sedimentation and environments during the late Miocene and Pliocene: New evidence from mineralogy and chemistry of the Bol core sediments

    NASA Astrophysics Data System (ADS)

    Moussa, Abderamane; Novello, Alice; Lebatard, Anne-Elisabeth; Decarreau, Alain; Fontaine, Claude; Barboni, Doris; Sylvestre, Florence; Bourlès, Didier L.; Paillès, Christine; Buchet, Guillaume; Duringer, Philippe; Ghienne, Jean-François; Maley, Jean; Mazur, Jean-Charles; Roquin, Claude; Schuster, Mathieu; Vignaud, Patrick; Brunet, Michel

    2016-06-01

    This study presents mineralogical and geochemical data from a borehole drilled near the locality of Bol (13°27‧N, 14°44‧E), in the eastern archipelago of the modern Lake Chad (Chad). Samples were taken from a ∼200 m long core section forming a unique sub-continuous record for Central Africa. Among these samples, 25 are dated between 6.4 and 2.4 Ma. Dominant minerals are clays (66% average) mixed with varying amounts of silt and diatomite. The clay fraction consists of Fe-beidellite (87% average), kaolinite, and traces of illite. Clay minerals originate from the erosion of the vertisols that surrounded the paleolake Chad. Sedimentological data indicate that a permanent lake (or recurrent lakes) existed from 6.7 until 2.4 Ma in the vicinity of Bol. By comparison with modern latitudinal distribution of vertisols in Africa the climate was Sudanian-like. Changes in the sedimentation rate suggest a succession of wetter and dryer periods during at least six million years in the region during the critical time period covering the Miocene-Pliocene transition.

  9. Factors Affecting the Sensitivity of Permafrost to Climate Change

    NASA Astrophysics Data System (ADS)

    Jorgenson, T.; Romanovsky, V.; Harden, J.; Shur, Y.; Hinzman, L.; Marchenko, S.; Bolton, R.; O'Donnell, J.

    2009-05-01

    degradation when water is impounded in sinking depressions. Thus, the amount of ground ice and potential thaw settlement greatly affects permafrost sensitivity. Water bodies (lakes, ponds, rivers) have a warming effect on permafrost and often create thawing zones for which their geometry is defined by water depth, sediment texture, and climate. Convective heat transfer associated with groundwater movement can create an unfrozen zone on top or within permafrost. Surface and groundwater flow, and surface impoundment, in turn are affected by topography and soil texture. Because permafrost is greatly affected by these ecological components, permafrost properties evolve along with the successional patterns of ecosystem development, which in turn affects the sensitivity of permafrost to degradation. We explore the relative effects of these factors through modeling and comparison of field measurements. Because there is no single model available that can include all these disparate factors, we evaluate factors separately and use differences in mean annual ground temperatures at the surface and at 2-m depth to compare the magnitude of each effect.

  10. Thermal regime of permafrost at Prudhoe Bay, Alaska

    USGS Publications Warehouse

    Lachenbruch, A.H.; Sass, J.H.; Marshall, B.V.; Moses, T.H., Jr.

    1982-01-01

    Temperature measurements through permafrost in the oil field at Prudhoe Bay, Alaska, combined with laboratory measurements of the thermal conductivity of drill cuttings permit an evaluation of in situ thermal properties and an understanding of the general factors that control the geothermal regime. A sharp contrast in temperature gradient at ~600 m represents a contrast in thermal conductivity caused by the downward change from interstitial ice to interstitial water at the base of permafrost under near steady-state conditions. Interpretation of the gradient contrast in terms of a simple model for the conductivity of an aggregate yields the mean ice content and thermal conductivities for the frozen and thawed sections (8.1 and 4.7 mcal/cm sec ?C, respectively). These results yield a heat flow of ~1.3 HFU which is similar to other values on the Alaskan Arctic Coast; the anomalously deep permafrost is a result of the anomalously high conductivity of the siliceous ice-rich sediments. Curvature in the upper 160 m of the temperature profiles represents a warming of ~1.8?C of the mean surface temperature, and a net accumulation of 5-6 kcal/cm 2 by the solid earth surface during the last 100 years or so. Rising sea level and thawing sea cliffs probably caused the shoreline to advance tens of kilometers in the last 20,000 years, inundating a portion of the continental shelf that is presently the target of intensive oil exploration. A simple conduction model suggests that this recently inundated region is underlain by near-melting ice-rich permafrost to depths of 300-500 m; its presence is important to seismic interpretations in oil exploration and to engineering considerations in oil production. With confirmation of the permafrost configuration by offshore drilling, heat-conduction models can yield reliable new information on the chronology of arctic shorelines.

  11. Past climate changes and permafrost depth at the Lake El'gygytgyn site: implications from data and thermal modelling

    NASA Astrophysics Data System (ADS)

    Mottaghy, D.; Schwamborn, G.; Rath, V.

    2012-07-01

    We present results of numerical simulations of the temperature field of the subsurface around and beneath the crater Lake El'gygytgyn in NE Russia, which is subject of an interdisciplinary drilling campaign within the International Continental Drilling Program (ICDP). This study focuses on determining the permafrost depth and the transition between talik and permafrost regimes, both, under steady-state and transient conditions of past climate changes. Thermal properties of the subsurface are deduced from measurements on three representative core samples taken from the quaternary sediments and the underlying impact rock. Further information is derived from the available geophysical logs and literature data. The temperature data from the lake borehole ICDP site 5011-1 down to 400 m depth below lake bottom are dominated by thermal perturbations related to the drilling process, and thus only give reliable values for the lowermost value in the borehole. Undisturbed temperature data recorded over more than two years in the 140 m deep land-based borehole ICDP site 5011-3 allow to determine the mean annual ground surface temperature (GST), as well as its history (GSTH) to a certain extent. Although the borehole's depth is by far not sufficient for a complete reconstruction of past temperatures back to the last glacial maximum (LGM), the temperature data and our modelling results show that there is still an influence of the LGM on the thermal regime, and thus on the permafrost depth. Whereas the latter result is obtained from the deeper part of the temperature profile, the rather strong curvature of the temperature data in shallower depths around 30 m can be explained by a comparatively large amplitude of the Little Ice Age (LIA), with a subsequently persistent cool period. Other mechanisms like varying porosity may also have an influence on the temperature profile, however, our modelling studies imply a major contribution from recent climate changes.

  12. Late Quaternary accretion and decline of syngenetic ice-rich permafrost

    NASA Astrophysics Data System (ADS)

    Wetterich, Sebastian; Strauss, Jens; Fuchs, Margret C.; Schirrmeister, Lutz

    2016-04-01

    The region of perennially frozen ground constitutes one quarter of the northern hemisphere landmass. Negative annual mean air temperatures and ground freezing periods exceeding ground thaw periods are the prerequisites for downward freezing of loose deposits and bedrock in non-glaciated regions. Hence, permafrost distribution and thickness on Earth are closely related to late Quaternary climate variations and ecosystem modifications. Generally, glacial stages are expected to promote permafrost accretion and ground ice formation in accumulating sediments, whereas interglacial stages lead to intense permafrost thaw and ground-ice melt. Deep freezing synchronous with ongoing sedimentation is termed as syngenetic while epigenetic freezing occurs in pre-existing deposits. Typical landforms of syngenetic permafrost are ice-wedge polygons of past tundra environments. Ice-rich silty and/or peaty deposits intersected by large ice wedges (up to several decameters in height and meters in with) build-up unique Ice Complex (IC) strata, which are aligned to mid- and late Pleistocene stadial and interstadial stages. The most prominent example for such formations is the Yedoma IC of MIS 3 interstadial age. Increasing air and ground temperatures during warm stages disturbed the thermal equilibrium at the upper permafrost boundary and subsequently led to permafrost thaw, ground-ice melt and surface subsidence. Typical permafrost degradation processes are thermokarst and thermo-erosion that result in large lake-filled basins (up to kilometers in diameter) and valley structures, respectively. The modern periglacial surface in Alaskan and East Siberian lowlands preserves Yedoma IC remnants in uplands and hills next to widely-distributed thermokarst basins since lateglacial and Holocene warming affected up to 70% of the original IC distribution on an area of more than 1,000,000 km2. The overarching climate-driven pattern of cold-stage IC permafrost accretion and warm-stage IC permafrost

  13. Controls on the distribution and fractionation of yttrium and rare earth elements in core sediments from the Mandovi estuary, western India

    NASA Astrophysics Data System (ADS)

    Prajith, A.; Rao, V. Purnachandra; Kessarkar, Pratima M.

    2015-01-01

    Mineralogy, major elements (Fe, Mn and Al), rare earths and yttrium (REY) of bulk sediments were analyzed in four gravity cores recovered along the main channel of the Mandovi estuary, western India, to determine the sources and controls on REY distribution. The accelerator mass spectrometer (AMS) ages of total organic carbon indicated modern age for the sediments of the upper estuary and, maximum mean ages of 1588 years AD and 539 years AD for the bottom sediments of the cores in the lower estuary and bay, respectively. The sediments of the upper/middle estuary showed abundant hematite, magnetite and goethite and high Fe, Mn, total-REE (ΣREE) and Y, while those in the lower estuary/bay showed abundant silicate minerals and relatively low Fe, Mn, ΣREE and Y. ΣREE showed significant correlation with clay and silt fractions and Y, Al and organic carbon (OC) content of the sediments. The light to heavy REE ratios (LREE/HREE) of sediments were lower than in Post-Archean Australian Shale (PAAS). The PAAS-normalized rare earths and yttrium (REY; Y inserted between Dy and Ho) patterns of sediments showed middle REE (MREE)- and HREE-enrichment with positive Eu anomaly (Eu/Eu*) and variable Ce anomaly (Ce/Ce*). The REY of sediments is primarily controlled by its texture and REE of source sediment, which is ore material-dominated in the upper/middle estuary and silicate material-dominated in the lower estuary/bay. Low LREE/HREE ratios suggest that very fine-grained sediments were carried away from the estuary because of high-energy conditions. Fractionations of REY (Y/Ho, Sm/Nd, Ce/Ce* and Eu/Eu*) are controlled by different mechanisms. High Y/Ho ratios in clayey silts are due to redistribution of Y and Ho by adsorption onto organic-rich, clays. Variations in Sm/Nd ratios are similar to that of Eu/Eu* in cores from the lower estuary/bay and are controlled by mineral constituents of the sediments. Positive Ce and Eu anomalies are inherited from ore material, and ore

  14. Spatial and Temporal Variations in the Geomagnetic Field Determined From the Paleomagnetism of Sediment Cores From Scientific Ocean Drilling

    NASA Astrophysics Data System (ADS)

    Acton, G.

    2014-12-01

    Quantifying the spatial and temporal variations of the main geomagnetic field at Earth's surface is important for understanding underlying geodynamo processes and conditions near the core-mantle boundary. Much of the geomagnetic variability, known as secular variation, occurs on timescales of tens of years to many thousands of years, requiring the use of paleomagnetic observations to derive continuous records of the ancient field, referred to as paleosecular variation (PSV) records. Marine depositional systems where thick sedimentary sections accumulate at high sedimentation rates provide some of the best locations for obtaining long continuous PSV records that can reveal both the short- and long-term changes in the field. Scientific ocean drilling has been successful at recovering many such sections and the paleomagnetic records from these reveal how the amplitude of PSV differs between sites and through time. In this study, several such records cored during Ocean Drilling Program (ODP), Integrated Ocean Drilling Program (IODP), and other cruises from high, mid, and low latitudes will be used to quantify time intervals of low and high PSV, to examine time-average properties of the field, to map spatial variations in the angular dispersion of the virtual geomagnetic pole (VGP), and to assess whether the spatial variation in angular dispersion changes with time.

  15. Apollo 11 drive-tube core samples: an initial physical analysis of lunar surface sediment.

    PubMed

    Fryxell, R; Anderson, D; Carrier, D; Greenwood, W; Heiken, G

    1970-01-30

    Two drive-tube core samples were obtained at Tranquillity Base. Fines include much glass, are unweathered, medium gray, loose, nonstructured, very weakly coherent, and demonstrate both accumulation and mixing in a waterless vacuum environment. In contrast to chemical weathering characteristic on the earth, lunar alteration processes are primarily mechanical. We infer that environmental processes of the lunar surface may be expressed as follows: R (regolith) = f(cl, p, r, t, b, a, . . .), in which climate (cl) is constant and the time (t)-de-pendent processes of bombardment (b) and accumulation (a) assume significance unparalleled on the earth because of their effects on parent material (p) and relief (r). PMID:17781569

  16. Carbon Stocks in Permafrost-Affected Soils of the Lena River Delta

    NASA Astrophysics Data System (ADS)

    Zubrzycki, S.; Kutzbach, L.; Grosse, G.; Desyatkin, A.; Pfeiffer, E.

    2012-12-01

    The soil organic carbon stock (SSOC) of soils in arctic permafrost regions is known to be significant but is insufficiently investigated so far. Previous SSOC studies report mainly the gravimetric carbon (C) contents and are limited to the active layer depth at the time of sampling. Since C deposits in permafrost regions are likely to become a future C source, more detailed investigations of the presently frozen likely carbon-rich sediment and soil layers are of importance. Our investigations were performed on Samoylov Island in the southern-central part of the Lena River Delta (32,000 km2) which is the largest arctic delta and the fifth largest delta worldwide. Samoylov Island is representative for the Lena River Delta's first terrace and the active floodplains. Within this study a new portable Snow-Ice-Permafrost-Research-Establishment (SIPRE) auger was used during a spring field session to obtain 1 m deep frozen soil cores (n = 29) distributed over all known soil and vegetation units. These cores are analyzed for bulk contents of nitrogen (N) and C, ice content and bulk density (BD) and to determine the SSOC including the rarely investigated currently permanently frozen layers up to 1 m depth on Samoylov Island. Our study provides evidence for high SSOC for a depth of 1 m for the investigated area ranging between 7 kg m-2 and 48 kg m-2. Considering the spatial extent of different soil units on the two geomorphological units of Samoylov Island, the area-weighted average SSOC were 29 kg m-2 (n = 22) for the first terrace and 14 kg m-2 (n = 7) for the active floodplain. For the correspondent soil units of Turbels and Orthels in circumpolar permafrost regions a mean SSOC of 27 kg m-2 (min: 0.1 kg m-2, max: 126 kg m-2) for a depth of 1 m was reported [1]. For up-scaling solely over the soil-covered areas of the Lena River Delta, we excluded all water bodies >3,600 m2 from the geomorphological units studied (first river terrace and the active floodplains) and

  17. Using lead isotopes and trace element records from two contrasting Lake Tanganyika sediment cores to assess watershed – Lake exchange

    USGS Publications Warehouse

    Odigie, Kingsley; Cohen, A.D.; Swarzenski, Peter W.; Flegal, R

    2014-01-01

    Lead isotopic and trace element records of two contrasting sediment cores were examined to reconstruct historic, industrial contaminant inputs to Lake Tanganyika, Africa. Observed fluxes of Co, Cu, Mn, Ni, Pb, and Zn in age-dated sediments collected from the lake varied both spatially and temporally over the past two to four centuries. The fluxes of trace elements were lower (up to 10-fold) at a mid-lake site (MC1) than at a nearshore site (LT-98-58), which is directly downstream from the Kahama and Nyasanga River watersheds and adjacent to the relatively pristine Gombe Stream National Park. Trace element fluxes at that nearshore site did not measurably change over the last two centuries (1815–1998), while the distal, mid-lake site exhibited substantial changes in the fluxes of trace elements – likely caused by changes in land use – over that period. For example, the flux of Pb increased by ∼300% from 1871 to 1991. That apparent accelerated weathering and detrital mobilization of lithogenic trace elements was further evidenced by (i) positive correlations (r = 0.77–0.99, p < 0.05) between the fluxes of Co, Cu, Mn, Ni, Pb, and Zn and those of iron (Fe) at both sites, (ii) positive correlations (r = 0.82–0.98, p < 0.01, n = 9) between the fluxes of elements (Al, Co, Cu, Fe, Mn, Ni, Pb, and Zn) and the mass accumulation rates at the offshore site, (iii) the low enrichment factors (EF < 5) of those trace elements, and (iv) the temporal consistencies of the isotopic composition of Pb in the sediment. These measurements indicate that accelerated weathering, rather than industrialization, accounts for most of the increases in trace element fluxes to Lake Tanganyika in spite of the development of mining and smelting operations within the lake’s watershed over the past century. The data also indicate that the mid-lake site is a much more sensitive and useful recorder of environmental changes than the nearshore site. Furthermore, the lead isotopic compositions

  18. Permafrost on Mars: distribution, formation, and geological role

    NASA Technical Reports Server (NTRS)

    Nummedal, D.

    1984-01-01

    The morphology of channels, valleys, chaotic and fretted terrains and many smaller features on Mars is consistent with the hypothesis that localized deterioration of thick layers of ice-rich permafrost was a dominant geologic process on the Martian surface. Such ground ice deterioration gave rise to large-scale mass movement, including sliding, slumping and sediment gravity flowage, perhaps also catastropic floods. In contrast to Earth, such mass movement processes on Mars lack effective competition from erosion by surface runoff. Therefore, Martian features due to mass movement grew to reach immense size without being greatly modified by secondary erosional processes. The Viking Mission to Mars in 1976 provided adequate measurements of the relevant physical parameters to constrain models for Martian permafrost.

  19. The Deep Permafrost Carbon Pool of Siberia and Alaska (Invited)

    NASA Astrophysics Data System (ADS)

    Strauss, J.; Schirrmeister, L.; Grosse, G.; Ulrich, M.; Wetterich, S.; Herzschuh, U.; Hubberten, H. W.

    2013-12-01

    Estimating the amount of organic carbon stored in Arctic permafrost and its biogeochemical characteristics are important topics in today's permafrost research. While the uppermost cryosoil horizons are reasonably studied and recorded in the Northern Circumpolar Soil Carbon Database (NCSCD), there are large uncertainties concerning the quantity and distribution of permafrost deep organic carbon. We studied the organic carbon content of the Yedoma region of unglaciated Siberia and Alaska. This region is unique because of its long-term accumulation of organic carbon, which was deeply incorporated into permafrost during the late Quaternary. Inclusion of labile organic matter into permafrost halted decomposition and resulted in a deep long-term carbon sink. Organic carbon in the Yedoma region occurs mainly as peat inclusions, twigs and root fragments, other solid and fine detrital plant remains, fossil remains of mammals, insects, aquatic plankton and soil microorganisms, and finally their decompositional and metabolic products in terms of particulate and dissolved organic matter. With our study we show that two major sub-reservoirs compose the Yedoma region deep frozen organic carbon; Yedoma deposits (late Pleistocene ice- and organic-rich silty sediments) and deposits formed in thaw-lake basins (generalised as thermokarst deposits). Thaw-lake basins result when lake formation degrades Yedoma deposits, then the lakes drain and deposits refreeze. Therefore, the deep Yedoma region organic carbon pool is far from homogeneous and strongly linked to depositional and permafrost dynamics as well as the ecological and climatic history. Using of approximately 1000 frozen samples from 23 Siberian and Alaskan study sites and a new approach for upscaling, we find significant differences to former estimates of the Yedoma coverage area, thickness of the relevant frozen deposits, ground ice content and finally in organic carbon content that lead to a reassessment of the deep

  20. Zn and Cu Isotopes as Tracers of Anthropogenic Contamination in a Sediment Core from an Urban Lake

    USGS Publications Warehouse

    Thapalia, Anita; Borrok, David M.; Van Metre, Peter C.; Musgrove, MaryLynn; Landa, Edward R.

    2010-01-01

    In this work, we use stable Zn and Cu isotopes to identify the sources and timing of the deposition of these metals in a sediment core from Lake Ballinger near Seattle, Washington, USA. The base of the Lake Ballinger core predates settlement in the region, while the upper sections record the effects of atmospheric emissions from a nearby smelter and rapid urbanization of the watershed. δ66Zn and δ65Cu varied by 0.50%o and 0.29%o, respectively, over the 500 year core record. Isotopic changes were correlated with the presmelter period (~1450 to 1900 with δ66Zn = +0.39%o ± 0.09%o and δ65Cu = +0.77%o ± 0.06%o), period of smelter operation (1900 to 1985 with δ66Zn = +0.14 ± 0.06%o and δ65Cu = +0.94 ± 0.10%o), and postsmelting/stable urban land use period (post 1985 with δ66Zn = 0.00 ± 0.10%o and δ65Cu = +0.82%o ± 0.12%o). Rapid early urbanization during the post World War II era increased metal loading to the lake but did not significantly alter the δ66Zn and δ65Cu, suggesting that increased metal loads during this time were derived mainly from mobilization of historically contaminated soils. Urban sources of Cu and Zn were dominant since the smelter closed in the 1980s, and the δ66Zn measured in tire samples suggests tire wear is a likely source of Zn.

  1. Mercury accumulation in sediment cores from three Washington state lakes: evidence for local deposition from a coal-fired power plant.

    PubMed

    Furl, Chad V; Meredith, Callie A

    2011-01-01

    Mercury accumulation rates measured in age-dated sediment cores were compared at three Washington state lakes. Offutt Lake and Lake St. Clair are located immediately downwind (18 and 28 km, respectively) of a coal-fired power plant and Lake Sammamish is located outside of the immediate area of the plant (110 km). The sites immediately downwind of the power plant were expected to receive increased mercury deposition from particulate and reactive mercury not deposited at Lake Sammamish. Mercury accumulation in cores was corrected for variable sedimentation, background, and sediment focusing to estimate the anthropogenic contribution (Hg(A,F)). Results indicated lakes immediately downwind of the power plant contained elevated Hg(A,F) levels with respect to the reference lake. Estimated fluxes to Lake Sammamish were compared to measured values from a nearby mercury wet deposition collector to gauge the efficacy of the core deconstruction techniques. Total deposition calculated through the sediment core (20.7 μg/m²/year) fell just outside of the upper estimate (18.9 μg/m²/year) of total deposition approximated from the wet deposition collector. PMID:20437040

  2. Simultaneous determination of mercury and organic carbon using a direct mercury analyzer: Mercury profiles in sediment cores from oxbow lakes in the Mississippi Delta

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sediment cores from seasonal wetland and open water areas from six oxbow lakes in the Mississippi River alluvial flood plain were analyzed for total-mercury (Hg) using a direct mercury analyzer (DMA). In the process we evaluated the feasibility of simultaneously determining organic matter content by...

  3. RECENT DECLINES IN PAH, PCB, AND TOXAPHENE LEVELS IN THE NORTHERN GREAT LAKES AS DETERMINED FROM HIGH RESOLUTION SEDIMENT CORES. (R825151)

    EPA Science Inventory

    Sediment cores were collected from two sites in Grand Traverse Bay, Lake
    Michigan in May 1998, dated using 210Pb geochronology, and analyzed
    for polychlorinated biphenyl (PCB) congeners, polycyclic aromatic hydrocarbons
    (PAHs), and toxaphene. The extraor...

  4. Distribution of REEs in box-core sediments offshore an industrial area in SE Sicily, Ionian Sea: evidence of anomalous sedimentary inputs.

    PubMed

    Di Leonardo, Rossella; Bellanca, Adriana; Neri, Rodolfo; Tranchida, Giorgio; Mazzola, Salvo

    2009-10-01

    The distribution of rare earth elements and yttrium (REEs+Y) has been investigated in box-core sediments recovered from four stations in the Sicilian coastal zone seawards of Augusta, one of the most industrialized and contaminated areas in the Mediterranean region. Shale-like REE patterns and low Y/Ho ratios (close to the chondritic ratio) suggest a dominant terrigenous (geogenic) source for REE. Slight enrichment of LREE over the HREE is interpreted as due to preferential adsorptive transfer of LREE from seawater to sediment particles. Samples from offshore cores exhibit slightly positive Gd and negative Ce anomalies. It is here hypothesized that main drivers of anthropogenic Gd flux towards the offshore are dredged contaminated materials that, recovered from the Augusta Bay, have been repeatedly discharged offshore. Consistent with the redox-chemistry of Ce, these anomalous sedimentary inputs induce a decrease of O(2) concentration in the sediment, which in turn triggers Ce regeneration. PMID:19735932

  5. The rare earth element geochemistry on surface sediments, shallow cores and lithological units of Lake Acıgöl basin, Denizli, Turkey

    NASA Astrophysics Data System (ADS)

    Budakoglu, Murat; Abdelnasser, Amr; Karaman, Muhittin; Kumral, Mustafa

    2015-11-01

    The sediments in Lake Acıgöl, located in SW Anatolia, Turkey, were formed under tectono-sedimentary events. REE geochemical investigations of the Lake Acıgöl sediments, from surface and shallow core sediments at different depths (0-10 cm, 10-20 cm and 20-30 cm) are presented to clarify the characteristics of REE and the nature of source rocks in the lake sediments' and to deduce their paleoenvironmental proxies. The chondrite-normalized REE patterns of these sediments are shown as light enrichment in LREE and flat HREE with a negative Eu anomaly that is close to the continental collision basin (CCB) in its profile; this is not comparable with PAAS and UCC. Inorganic detrital materials control the REE characteristics of the Lake Acıgöl sediments and these sediments were accumulated in oxic and dysoxic depositional conditions and/or at passive margins derived from oceanic island arc rocks. They were affected by low chemical weathering, either at the original source or during transport, before deposition under arid or subtropical humid climatic conditions. In addition, we used GIS techniques (such as Inverse Distance Weighted (IDW) and Geographically Weighted Regression (GWR)) to investigate the spatial interpolation and spatial correlation of the REEs from the lake surface sediments in Lake Acıgöl and its surrounding lithological units. GIS techniques showed that the lithological units (e.g., Hayrettin Formation) north of Lake Acıgöl have high REE contents; however, Eu/Eu∗ values were higher in some lake surface sediments than in lithological units, and that refers to a negative Eu-anomaly. Therefore, Lake Acıgöl sediments are derived from the weathered products, mainly from local, highly basic bedrock around the lake from the Archean crust. The chronology of Lake Acıgöl sediment was conducted using the Constant Rate of Supply (CRS) model. Using the CRS methods for the calculation of sedimentation rate, we obtained a 0.012 g/cm2/year value which is an

  6. Paleoclimatic record of the late Quaternary from a gravity core sediment of Lake Hovsgol in northern Mongolia

    NASA Astrophysics Data System (ADS)

    Cheong, D.; Kim, B.

    2007-12-01

    Gravity core sediment (HS 7) from Lake Hovsgol(Mongolia) is divided into three sedimentary units on the basis of sediments texture, water contents, occurrence of fossils and sediment color. Unit 1(27¢¦128§¯) is generally massive and is crudely stratified. Ostracods are well preserved over the all interval of Unit1, but diatoms are not well preserved. At Unit2(9¢¦27§¯), mud content is slightly low and lamination is well developed. It is dark greenish gray in the upper part, and dark greenish gray is alternating with light brownish gray in the lower part. Diatom contents increase towards the top and ostracods fragments disappear at the top of Unit 2. Unit3(0¢¦9§¯) is laminated mud in olive gray color. Diatom contents are high but ostracods are not observed in this unit. According to 14C age dating results, we assumed that Unit1 is Pleistocene sediment, Unit2 is sediment of a transitional stage and Unit 3 is Holocene sediment. Chemical composition of trace elements from ostracods show variations through Unit1, especially showing a distinct change at 95¢¦100§¯ interval. It matches to the distribution of ostracod at this interval. Contents of ostracod decrease at the interval and contents of Cytherissa lacustris decrease, but Limnocythere inopinata increase. It was interpreted that warm air was supplied to Lake Hovsgol after LGM(Last Glacial Maximum), causing ice melting. Consequently the bottom environment of Lake Hovsgol experienced some changes as the lake level increased little bit. At the top of Unit 1 appear a lots of pyrite which are arranged in line, and diatoms occure but ostracods are not observed toward the top of Unit 2, and lamination is developed in Unit 2. It means the bottom environment of Lake Hovsgol changed to anoxic condition. At that time, plenty of water was supplied into the lake, resulting in water stratification and cutting off oxygen supply to the bottom of Lake Hovsgol. It made the lake level rise higher, so that the bottom

  7. Hydrothermal energy transfer and contribution to autotrophic CO2 fixation down sediment core in Central Indian Basin

    NASA Astrophysics Data System (ADS)

    Das, Anindita; LokaBharathi P., A.

    2014-05-01

    Hydrothermal Energy Transfer is not only restricted to active vents sites but also to the passive ones. These passive sources could include the sub-seafloor hydrothermal fluid flux derived from distant sources like erupting vents or from deep-mantle. The contribution from such fluxes in stimulating autotrophic carbon fixation could be measurable. In this paper an attempt is made to measure the autotrophic CO2 fixation down a siliceous sediment core (Core 20, 75?30'E, 12?S) adjoining Trace of Rodrigues Triple Junction in the Central Indian Basin (CIB) with a fluid flux influence at 15-20 cms bsf (below sea-floor) which is quite distinct from the pelagic influence on the overlying 0-15 cms bsf. This work assumes that NH4+and S2- are major e-donors/reductants to fuel C-Fixation. The down-core carbon fixation varied from 0.032-0.122μmol C g-1day-1 with the larger peak at 15-20 cms bsf. This coincides with the dips in pore-water concentrations of NH4+ and S2-. Therefore the corresponding standard free energy change (ΔG?') down-core varied from -97 at 4-6 cms bsf to -375 J μmol-1 C fixed m-3 day-1 at 12-14 cms bsf in case of NH4+. In case of S2- the values varied from -42 at 4-6 cms bsf to -162 J μmol-1 m-3 day-1at 12-14 cms bsf. Integrated down-core estimate of ΔG?' is calculated to be -26.97 J μmol-1 C fixation m-2 day-1 during CO2 fixation using NH4+ and -11.7 J μmol-1 C fixation m-2 day-1 using S2-. This fluid-flow influenced layer appears physically as a brown-green transition zone in the core at a depth of 15-20 cm bsf. Interestingly similar observations have been made in >15 such cores around the present test core. These observations suggest that this spreading bed at this depth could be due to the upward fluid flow that then spreads laterally. This spread could perhaps be more than the area that the current observations permit. So the Hydrothermal Energy Transfer is equivalent to -11.70 to -26.97 J μmol-1 C fixation m-2 day-1and corresponds to 88 μmol of

  8. Late Quaternary sediment deposition of core MA01 in the Mendeleev Ridge, the western Arctic Ocean: Preliminary results

    NASA Astrophysics Data System (ADS)

    Park, Kwang-Kyu; Kim, Sunghan; Khim, Boo-Keun; Xiao, Wenshen; Wang, Rujian

    2014-05-01

    Late Quaternary deep marine sediments in the Arctic Ocean are characterized by brown layers intercalated with yellowish to olive gray layers (Poore et al., 1999; Polyak et al., 2004). Previous studies reported that the brown and gray layers were deposited during interglacial (or interstadial) and glacial (or stadial) periods, respectively. A 5.5-m long gravity core MA01 was obtained from the Mendeleev Ridge in the western Arctic Ocean by R/V Xue Long during scientific cruise CHINARE-V. Age (~450 ka) of core MA01 was tentatively estimated by correlation of brown layers with an adjacent core HLY0503-8JPC (Adler et al., 2009). A total of 22 brown layers characterized by low L* and b*, high Mn concentration, and abundant foraminifera were identified. Corresponding gray layers are characterized by high L* and b*, low Mn concentration, and few foraminiferal tests. Foraminifera abundance peaks are not well correlated to CaCO3 peaks which occurred with the coarse-grained (>0.063 mm) fractions (i.e., IRD) both in brown and gray layers. IRDs are transported presumably by sea ice for the deposition of brown layers and by iceberg for the deposition of gray layers (Polyak et al., 2004). A strong correlation coefficient (r2=0.89) between TOC content and C/N ratio indicates that the major source of organic matter is terrestrial. The good correlations of CaCO3 content to TOC (r2=0.56) and C/N ratio (r2=0.69) imply that IRDs contain detrital CaCO3 which mainly originated from the Canadian Arctic Archipelago. In addition, high kaolinite/chlorite (K/C) ratios mostly correspond to CaCO3 peaks, which suggests that the fine-grained particles in the Mendeleev Ridge are transported from the north coast Alaska and Canada where Mesozoic and Cenozoic strata are widely distributed. Thus, the Beaufort Gyre, the predominant surface current in the western Arctic Ocean, played an important role in the sediment delivery to the Mendeleev Ridge. It is worthy of note that the TOC and CaCO3 peaks are

  9. Dynamics of metallic contaminants at a basin scale--Spatial and temporal reconstruction from four sediment cores (Loire fluvial system, France).

    PubMed

    Dhivert, E; Grosbois, C; Courtin-Nomade, A; Bourrain, X; Desmet, M

    2016-01-15

    From the 19th century, the Loire basin (France) presents potentially pollutant activities such as mining and heavy industries. This paper shows spatio-temporal distribution of trace elements in sediments at a basin-scale, based on a comparison of archived temporal signals recorded in four sedimentary cores. Anthropogenic sources contributing to sediment contamination are also characterized, using geochemical signatures recorded in river bank sediments of the most industrialized tributaries. This study highlights upstream-downstream differences concerning recorded contamination phases in terms of spatial influence and temporality of archiving processes. Such differences were related to (i) various spatial influences of contamination sources and (ii) polluted sediments dispersion controlled by transport capacity of metal-carrier phases and hydrosedimentary dynamics. PMID:26490530

  10. Analysis of the La:P ratio in lake sediments - Vertical and spatial distribution assessed by a multiple-core survey.

    PubMed

    Yasseri, Said; Epe, Tim S

    2016-06-15

    In recent years, lanthanum modified bentonite has been increasingly applied to eutrophic lakes with the aim of converting potentially bio-available forms of phosphorus in sediments into biologically unavailable forms. In many of these applications, however, no attempts have been made to assess the efficiency and efficacy of the measure in terms of its effect on the sediment. In this study, we collected sediment cores from a heavily eutrophied lake that has previously been treated with lanthanum modified clay. This restoration method is based on the strong ionic bond formed between lanthanum and phosphate which results in the formation of LaPO4 (Rhabdophane) in the sediment. In order to determine the changes that had occurred in the sediments as a result of the addition of the clay, we measured the vertical distribution of lanthanum in the collected cores, calculated La:P ratios of the different sediment layers and used the ratios to determine whether or not the applied dosage was sufficient. By means of the geostatistical method of kriging these values were transferred into maps of different depth intervals to visualize the results. The results indicate that the La:P ratio may be a useful tool which allows lake managers to measure the vertical distribution of lanthanum in sediments following treatments and determine whether or not dosages are sufficient to permanently render sediment phosphorus biologically unavailable. The method may also provide a basis on which to decide whether or not smaller reapplications are needed and can be used to control the dispersion of the material. PMID:26250755

  11. Hominin Sites and Paleolakes Drilling Project. Chew Bahir, southern Ethiopia: How to get from three tonnes of sediment core to > 500 ka of continuous climate history?

    NASA Astrophysics Data System (ADS)

    Foerster, Verena; Asrat, Asfawossen; Cohen, Andrew S.; Gromig, Raphael; Günter, Christina; Junginger, Annett; Lamb, Henry F.; Schaebitz, Frank; Trauth, Martin H.

    2016-04-01

    In search of the environmental context of the evolution and dispersal of Homo sapiens and our close relatives within and beyond the African continent, the ICDP-funded Hominin Sites and Paleolakes Drilling Project (HSPDP) has recently cored five fluvio-lacustrine archives of climate change in East Africa. The sediment cores collected in Ethiopia and Kenya are expected to provide valuable insights into East African environmental variability during the last ~3.5 Ma. The tectonically-bound Chew Bahir basin in the southern Ethiopian rift is one of the five sites within HSPDP, located in close proximity to the Lower Omo River valley, the site of the oldest known fossils of anatomically modern humans. In late 2014, the two cores (279 and 266 m long respectively, HSPDP-CHB14-2A and 2B) were recovered, summing up to nearly three tonnes of mostly calcareous clays and silts. Deciphering an environmental record from multiple records, from the source region of modern humans could eventually allow us to reconstruct the pronounced variations of moisture availability during the transition into Middle Stone Age, and its implications for the origin and dispersal of Homo sapiens. Here we present the first results of our analysis of the Chew Bahir cores. Following the HSPDP protocols, the two parallel Chew Bahir sediment cores have been merged into one single, 280 m long and nearly continuous (>90%) composite core on the basis of a high resolution MSCL data set (e.g., magnetic susceptibility, gamma ray density, color intensity transects, core photographs). Based on the obvious cyclicities in the MSCL, correlated with orbital cycles, the time interval covered by our sediment archive of climate change is inferred to span the last 500-600 kyrs. Combining our first results from the long cores with the results from the accomplished pre-study of short cores taken in 2009/10 along a NW-SE transect across the basin (Foerster et al., 2012, Trauth et al., 2015), we have developed a hypothesis

  12. Ultra-high-resolution paleoenvironmental records via direct laser-based analysis of lipid biomarkers in sediment core samples

    PubMed Central

    Wörmer, Lars; Elvert, Marcus; Fuchser, Jens; Lipp, Julius Sebastian; Buttigieg, Pier Luigi; Zabel, Matthias; Hinrichs, Kai-Uwe

    2014-01-01

    Marine microorganisms adapt to their habitat by structural modification of their membrane lipids. This concept is the basis of numerous molecular proxies used for paleoenvironmental reconstruction. Archaeal tetraether lipids from ubiquitous marine planktonic archaea are particularly abundant, well preserved in the sedimentary record and used in several molecular proxies. We here introduce the direct, extraction-free analysis of these compounds in intact sediment core sections using laser desorption ionization (LDI) coupled to Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). LDI FTICR-MS can detect the target lipids in single submillimeter-sized spots on sediment sections, equivalent to a sample mass in the nanogram range, and could thus pave the way for biomarker-based reconstruction of past environments and ecosystems at subannual to decadal resolution. We demonstrate that ratios of selected archaeal tetraethers acquired by LDI FTICR-MS are highly correlated with values obtained by conventional liquid chromatography/MS protocols. The ratio of the major archaeal lipids, caldarchaeol and crenarchaeol, analyzed in a 6.2-cm intact section of Mediterranean sapropel S1 at 250-µm resolution (∼4-y temporal resolution), provides an unprecedented view of the fine-scale patchiness of sedimentary biomarker distributions and the processes involved in proxy signal formation. Temporal variations of this lipid ratio indicate a strong influence of the ∼200-y de Vries solar cycle on reconstructed sea surface temperatures with possible amplitudes of several degrees, and suggest signal amplification by a complex interplay of ecological and environmental factors. Laser-based biomarker analysis of geological samples has the potential to revolutionize molecular stratigraphic studies of paleoenvironments. PMID:25331871

  13. Thin Film XRF measurements (Wet and dry) of Black Sea Sediment Samples And Their Elemental Comparisons With Same Core U Channel Sample.

    NASA Astrophysics Data System (ADS)

    Acar, Dursun; Eris, Kadir; Sarı, Erol; Genc, S. Can

    2015-04-01

    This paper presents the XRF data from about 0.3mm thin film sediment core. We prepared 3 different model from same sediment core. The main aim is the finding for elemental changing of spectra variety and their comparison with physical changes of samples about mass and water content. Our XRF measurements were carried out by ITRAX (Cox System), and we have documented the some useful and more precision tricks; a) the first point is that the wet or dry nature of the core, b) the second is the use of U channel sample or thin film sample. For base referencing for the selected elements, we prepared normal wet U channel sample with the thickness of 1.5 cm. We used thin material (film) for keeping the humidty of every core sample's surface. Because humidity loss very high on thin film core sample and very effective to get bad results related to changing of topography and beam emission related to loss of pore water. Our XRF measurements have revealed that the Zn, Ti, Si, V,S, Cr, Mn, Ba, K and Ca elements were measured more precisely and accurate using by the dry thin film sample than those of wet U channel and wet thin sediment sample experiments. Beside this, Y, Zr, Nb, Rb, Sr, Ir, Fe,Co, Ni and Al elements were measured from the wet U channeled core more reliable with respect to the former. Lead (Pb) and Cd elements have behaved constantly during the three types of measurements. Keywords: Thin film XRF, U channel, Elements, Sediment, Measurement

  14. Clay Mineralogy of Shallow Core Sediments of Lake Acigöl, Denizli, Turkey

    NASA Astrophysics Data System (ADS)

    Budakoglu, Murat; Karaman, Muhittin; Geredeli, Serpil; Unal, Hatice; Abdelnasser, Amr; Kiran Yildirim, Demet

    2014-05-01

    Lake Acıgöl is a hypersaline and active industrial salt production lake located in Denizli, Turkey. Lake Acıgöl has been investigated to elucidate the distribution clay minerals under the saline conditions of the lake and carbonate and ophiolitic rocks controlled lake basin. The lake is very shallow and generally characterized by an un-stratified and whole oxygenated water table. Determination clay minerals in the bulk samples via XRD method was not possible due to the their small amount. Therefore, the sequential clay enrichment procedure applied to the bulk samples such as sample dispersion, removal of soluble salts and ions, and particle-size fractionation. The XRD analyses of normal, glycolated and heat-treated shallow core samples show that the dominant clay minerals in the samples to be illite, including the swelling montmorillonite and kaolinite minerals are encountered less frequently. Glauberite, Blodite, Dansite and Nickelblodite have been also identified as soda minerals by XRD studies.

  15. Hg Isotope Ratios of a Sediment Core from Plastic Lake, Ontario: Implications for Hg Cycle in Aquatic Environment

    NASA Astrophysics Data System (ADS)

    Xie, Q.; Dillon, P.; Evans, D.; Lu, S.

    2004-12-01

    Hg isotope ratios in a sediment core obtained in Plastic Lake, Ontario, Canada, have been measured by coupling a gold trap with an MC-ICP-MS. The core is about 30 cm in depth and corresponds to a time period of about 250 years, based on 210Pb dating. The samples were combusted at high temperature and the Hg collected onto a gold trap. The gold trap was subsequently heated to release Hg directly into the MC-ICP-MS. An in-house sample introduction system was employed to extend Hg signal duration in order to obtain high precision in isotope ratio measurement. The instrumental mass bias was corrected using Tl introduced simultaneously via an Aridus membrane desolvation nebulizer. Based on long term measurement of a NIST-2225 elemental Hg standard (over 120 measurements since Oct. 2002), the external reproducibility ranges from 45 ppm for 201Hg/202Hg to 100 ppm for 199Hg/202Hg (2 sigma relative standard error). Hg in the sediments shows an increase in light isotope enrichment at about 10 cm depth. The total Hg also displays an increase at the same depth. The depth corresponds to approximately the 1920s, a time period when there was a major increase in coal-burning power generation. Limited Hg isotope data for other terrestrial samples appears to indicate that Hg bound to organic carbon is enriched in light isotopes relative to elemental Hg. For example, the DOLT-3, a dogfish liver standard reference material with half of its Hg as MeHg, has the lightest Hg isotope composition among measured terrestrial samples. It is not clear at this stage whether the increase in total Hg and light Hg isotope enrichment in recent years represent a change in methylation rate of the lake, or an increase in atmospheric deposition of Hg combined with a change in source. Discussions based on available Hg isotope data of terrestrial samples together with other chemical data for the lake will be presented.

  16. Offshore Extent of the Iceland Ice Cap During the Last Glacial Maximum Inferred from Multibeam Bathymetric Data and Sediment Cores.

    NASA Astrophysics Data System (ADS)

    Helgadottir, G.; Brandsdottir, B.; Geirsdottir, A.; Björnsson, H.

    2005-12-01

    The insular margin of Iceland is incised by several major troughs, which mark the pathways of outlet glaciers during the last glaciations. Multibeam bathymetric data have revealed features of glacial erosion and sedimentation pertinent to the extent of the Iceland ice cap during the Last Glacial Maximum. Marginal moraines have been identified at the southern, western and northwestern edge of the insular margin. Furthermore, glacial erosion and sedimentation along the Kolbeinsey Ridge, North Iceland, indicates that the Iceland ice cap extended beyond 67°30'N. The ridge axis is made up of various types of seamounts, crater rows and hummocky ridges whereas older seamounts have been sculptured into roche moutonnées by glacial erosion. The far extent of the ice cap to the north is also supported by sediment studies on cores that have been retrieved from the troughs on the northern and northwestern part of the insular margin. Numerous smaller moraines exist closer to land marking stepwise retreat of the ice cap during deglacial times. Such moraines have been identified at 400-500 m depth within a 3-6 km wide, U-shaped valley along the western margin of the Kolbeinsey ridge (at 66°55'N) and within many of the costal fjords. Many of the offshore features resemble those known from land, such as streamlined bedrock features elongated in the regional direction of ice flow, eskers and subglacial meltwater channels together with erosional channels possibly formed by jökulhlaups. Extensive number of ice plough marks are revealed on bank areas and landslides on the marginal slope. Fluted surfaces and subglacially formed meltwater channels suggest formation underneath fast flowing, warm-based ice streams. These newly identified glacial features reveal new information on the spatial extent, dynamics and retreat of the Iceland ice cap during the last glaciation and deglaciation. Eustatic and isostatic contributions can be predicted from models of ice sheets and mantle rheology

  17. Application of ground-penetrating radar imagery for three-dimensional visualisation of near-surface structures in ice-rich permafrost, Barrow, Alaska

    USGS Publications Warehouse

    Munroe, J.S.; Doolittle, J.A.; Kanevskiy, M.Z.; Hinkel, Kenneth M.; Nelson, F.E.; Jones, Benjamin M.; Shur, Y.; Kimble, J.M.

    2007-01-01

    Three-dimensional ground-penetrating radar (3D GPR) was used to investigate the subsurface structure of ice-wedge polygons and other features of the frozen active layer and near-surface permafrost near Barrow, Alaska. Surveys were conducted at three sites located on landscapes of different geomorphic age. At each site, sediment cores were collected and characterised to aid interpretation of GPR data. At two sites, 3D GPR was able to delineate subsurface ice-wedge networks with high fidelity. Three-dimensional GPR data also revealed a fundamental difference in ice-wedge morphology between these two sites that is consistent with differences in landscape age. At a third site, the combination of two-dimensional and 3D GPR revealed the location of an active frost boil with ataxitic cryostructure. When supplemented by analysis of soil cores, 3D GPR offers considerable potential for imaging, interpreting and 3D mapping of near-surface soil and ice structures in permafrost environments.

  18. Depth and temperature of permafrost on the Alaskan Arctic Slope; preliminary results

    USGS Publications Warehouse

    Lachenbruch, Arthur H.; Sass, J.H.; Lawver, L.A.; Brewer, M.C.; Moses, T.H.

    1982-01-01

    As permafrost is defined by its temperature, the only way to determine its depth is to monitor the return to equilibrium of temperatures in boreholes that penetrate permafrost. Such measurements are under way in 25 wells on the Alaskan Arctic Slope; 21 are in Naval Petroleum Reserve Alaska (NPRA), and 4 are in the foothills to the east. Near-equilibrium results indicate that permafrost thickness in NPRA generally ranges between 200 and 400 m (compared to 600+ m at Prudhoe Bay); there are large local variations and no conspicuous regional trends. By contrast the long-term mean temperature of the ground surface (one factor determining permafrost depth) varies systematically from north to south in a pattern modified by the regional topography. The observed variation in permafrost temperature and depth cannot result primarily from effects of surface bodies of water or regional variations in heat flow; they are consistent, however, with expectable variations in the thermal conductivity of the sediments. It remains to be determined (with conductivity measurements) whether certain sites with anomalously high local gradients have anomalously high heat flow; if they do, they might indicate upwelling of interstitial fluids in the underlying basin sediments.

  19. CSciBox: An Intelligent Assistant for Dating Ice and Sediment Cores

    NASA Astrophysics Data System (ADS)

    Finlinson, K.; Bradley, E.; White, J. W. C.; Anderson, K. A.; Marchitto, T. M., Jr.; de Vesine, L. R.; Jones, T. R.; Lindsay, C. M.; Israelsen, B.

    2015-12-01

    CSciBox is an integrated software system for the construction and evaluation of age models of paleo-environmental archives. It incorporates a number of data-processing and visualization facilities, ranging from simple interpolation to reservoir-age correction and 14C calibration via the Calib algorithm, as well as a number of firn and ice-flow models. It employs modern database technology to store paleoclimate proxy data and analysis results in an easily accessible and searchable form, and offers the user access to those data and computational elements via a modern graphical user interface (GUI). In the case of truly large data or computations, CSciBox is parallelizable across modern multi-core processors, or clusters, or even the cloud. The code is open source and freely available on github, as are one-click installers for various versions of Windows and Mac OSX. The system's architecture allows users to incorporate their own software in the form of computational components that can be built smoothly into CSciBox workflows, taking advantage of CSciBox's GUI, data importing facilities, and plotting capabilities. To date, BACON and StratiCounter have been integrated into CSciBox as embedded components. The user can manipulate and compose all of these tools and facilities as she sees fit. Alternatively, she can employ CSciBox's automated reasoning engine, which uses artificial intelligence techniques to explore the gamut of age models and cross-dating scenarios automatically. The automated reasoning engine captures the knowledge of expert geoscientists, and can output a description of its reasoning.

  20. Chemical gradients in sediment cores from an EPA reference site off the Farallon Islands - Assessing chemical indicators of dredged material disposal in the deep sea

    USGS Publications Warehouse

    Bothner, Michael H.; Gill, P.W.; Boothman, W.S.; Taylor, B.B.; Karl, Herman A.

    1998-01-01

    Heavy metal and organic contaminants have been determined in undisturbed sediment cores from the US Environmental Protection Agency reference site for dredged material on the continental slope off San Francisco. As expected, the concentrations are significantly lower than toxic effects guidelines, but concentrations of PCBs, PAHs, Hg, Pb, and Clostridium perfringens (a bacterium spore found in sewage) were nearly two or more times greater in the surface sediments than in intervals deeper in the cores. These observations indicate the usefulness of measuring concentration gradients in sediments at the San Francisco deep ocean disposal site (SF-DODS) where a thin (0.5 cm thick) layer of dredged material has been observed beyond the boundary. This thin layer has not been chemically characterized by the common practice of homogenizing over the top 10 cm. An estimated 300 million cubic yards of dredged material from San Francisco Bay are expected to be discharged at the SF-DODS site during the next 50 years. Detailed depth analysis of sediment cores would add significant new information about the fate and effects of dredged material in the deep sea.

  1. Mercury enrichments in core sediments in Hugli-Matla-Bidyadhari estuarine complex, north-eastern part of the Bay of Bengal and their ecotoxicological significance

    NASA Astrophysics Data System (ADS)

    Chatterjee, M.; Canário, J.; Sarkar, S. K.; Branco, V.; Bhattacharya, A. K.; Satpathy, K. K.

    2009-05-01

    Mercury concentrations (HgT) in fine-grained fraction (<63 μm) of core sediments of the Hugli-Matla-Bidyadhari estuarine complex, India were analyzed. Results revealed a wide range of spatial variations (<4-93 ng g-1 dry weight) with a definite enhancement level at the lower stretch of the estuarine complex infested with mangrove plants, which might act as a sink to HgT. An elevated concentration of Hg was encountered in surface/subsurface layer of the core in majority of the cases resulting from physical, biogenic and postdepositional diagenetic processes that remobilized and resuspended the metal from deeper sediments. A strong positive correlation was observed between the Hg and clay fraction content of the sediments, while the correlations of Hg with Al, Fe and Mn were poor. Based on the index of geoaccumulation ( I geo) and effects range-low (ER-L) value, it is considered that the sediments are less polluted and thus there is less chance of ecotoxicological risk to organisms living in sediments.

  2. Preliminary Results of the Permafrost Carbon Study in the Lower Kolyma Lowland (Eastern Siberia) Based on Drilling Record

    NASA Astrophysics Data System (ADS)

    Spektor, V. V.; Kholodov, A. L.; Bulygina, E. B.; Andreeva, V.; Broderick, D.; Spawn, S.; Natali, S.; Davydova, A.

    2012-12-01

    In 2012, the Polaris Project (thepolarisproject.org, Director R.M. Holmes) has conducted the permafrost drilling on the Kolyma Lowland for a complex study of permafrost carbon as a potential source for microbial decomposition. In July 2012, the first two boreholes, 15.1 and 13.4 m in depth, were drilled. The first borehole (BH 12/1) was drilled in the stratum of ice complex (yedoma) on the local watershed near the Schuch'e lake in the vicinity of the town Chersky (N68°44.7' E161°23'). The depth of active layer is 45 cm. The permafrost to the depth of 15.1 m represents grey and brown silts with predominant homogeneous structure. Silts contain numerous thread-like roots, scarce plant macrofossils, and in places are colored with unclear spots of ferrugination. Cryostructure is mainly pore ice or thin lense-like ice layers. Wedge ice is observed in the interval 12.5-12.9 m. The moisture volumetric percentage of silts varies along the stratum, mainly, between 40-50%. The organic content, defined in every 20 cm of the core as a loss on ignition, varies between 2-4%. The second borehole (BH 12/2), located in the Pleistocene Park (N68°30.8' E161°30') was drilled through modern floodplain sediments (0-0.6 m) of the Kolyma River with polygonal network at the surface, underlain by peat (0.6-1.3 m), silt deposits of thermokarst lake (1.3-12.0 m), and river grey sands (12.0-13.4 m). The active layer thickness is 65 cm. The cryostructure is predominantly lattice-like. Silts contain modern wedge ice at the depth of 2.5-2.7 m. Mollusk shells and large amount of plant macrofossils are observed in the interval 5.7-8.0 m. The organic content in the thermokarst deposits varies in average within 2-3 %, but is about 1% in the underlying river sands. To investigate permafrost carbon, samples for microbial and enzyme activities, as well as samples of trapped gases were collected from different horizons of frozen cores. Samples for palynological, diatom, and lithological analyses, as

  3. Geologic columns for the ICDP-USGS Eyreville A and B cores, Chesapeake Bay impact structure: Sediment-clast breccias, 1096 to 444 m depth

    USGS Publications Warehouse

    Edwards, L.E.; Powars, D.S.; Gohn, G.S.; Dypvik, H.

    2009-01-01

    The Eyreville A and B cores, recovered from the "moat" of the Chesapeake Bay impact structure, provide a thick section of sediment-clast breccias and minor stratified sediments from 1095.74 to 443.90 m. This paper discusses the components of these breccias, presents a geologic column and descriptive lithologic framework for them, and formalizes the Exmore Formation. From 1095.74 to ??867 m, the cores consist of nonmarine sediment boulders and sand (rare blocks up to 15.3 m intersected diameter). A sharp contact in both cores at ??867 m marks the lowest clayey, silty, glauconitic quartz sand that constitutes the base of the Exmore Formation and its lower diamicton member. Here, material derived from the upper sediment target layers, as well as some impact ejecta, occurs. The block-dominated member of the Exmore Formation, from ??855-618.23 m, consists of nonmarine sediment blocks and boulders (up to 45.5 m) that are juxtaposed complexly. Blocks of oxidized clay are an important component. Above 618.23 m, which is the base of the informal upper diamicton member of the Exmore Formation, the glauconitic matrix is a consistent component in diamicton layers between nonmarine sediment clasts that decrease in size upward in the section. Crystalline-rock clasts are not randomly distributed but rather form local concentrations. The upper part of the Exmore Formation consists of crudely fining-upward sandy packages capped by laminated silt and clay. The overlap interval of Eyreville A and B (940-??760 m) allows recognition of local similarities and differences in the breccias. ?? 2009 The Geological Society of America.

  4. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    SciTech Connect

    Richard Sigal; Kent Newsham; Thomas Williams; Barry Freifeld; Timothy Kneafsey; Carl Sondergeld; Shandra Rai; Jonathan Kwan; Stephen Kirby; Robert Kleinberg; Doug Griffin

    2005-02-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. The work scope drilled and cored a well The Hot Ice No. 1 on Anadarko leases beginning in FY 2003 and completed in 2004. An on-site core analysis laboratory was built and utilized for determining the physical characteristics of the hydrates and surrounding rock. The well was drilled from a new Anadarko Arctic Platform that has a minimal footprint and environmental impact. The final efforts of the project are to correlate geology, geophysics, logs, and drilling and production data and provide this information to scientists developing reservoir models. No gas hydrates were encountered in this well; however, a wealth of information was generated and is contained in this report. The Hot Ice No. 1 well was drilled from the surface to a measured depth of 2300 ft. There was almost 100% core recovery from the bottom of surface casing at 107 ft to total depth. Based on the best estimate of the bottom of the methane hydrate stability zone (which used new data obtained from Hot Ice No. 1 and new analysis of data from adjacent wells), core was recovered over its complete range. Approximately 580 ft of porous, mostly frozen, sandstone and 155 of conglomerate were recovered in the Ugnu Formation and approximately 215 ft of porous sandstone were recovered in the West Sak Formation. There were gas shows in the bottom

  5. Climate-sensitive subsea permafrost and related gas expulsions on the South Kara Sea shelf. Field studies and modeling results.

    NASA Astrophysics Data System (ADS)

    Portnov, Alexey; Mienert, Jurgen; Serov, Pavel

    2015-04-01

    Thawing subsea permafrost controls methane release bearing a considerable impact on the climate-sensitive Arctic environment. Significant expulsion of methane into shallow Russian shelf areas may continue to rise into the atmosphere on the Arctic shelves in response to intense degradation of relict subsea permafrost. The release of formerly trapped gas, essentially methane, is linked to the permafrost evolution. Modeling of the permafrost at the West Yamal shelf allowed describing its evolution from the Late Pleistocene to Holocene. During the previous work we detected extensive emissions of free gas into the water column at the boundary between today's shallow water permafrost and deeper water non-permafrost areas. These gas expulsions formed seismic and hydro-acoustic anomalies on the high-resolution seismic records. We supposed that in the water depths <20m continuous ice-bearing permafrost plays a role of a seal through which gas can not migrate. We integrate 1D modeling results of relict permafrost distributions with these field data from the South Kara Sea. Modeling results suggest a highly-dynamic permafrost system that directly responds to even minor variations of lower and upper boundary conditions, e.g. heat flux from below and/or bottom water temperature changes from above. We present several scenarios of permafrost evolution and show that potentially minimal modern extent of the permafrost at the West Yamal shelf is limited by ~17 m isobaths, whereas maximal probable extent coincides with ~100 m isobaths. The model also predicts seaward tapering of relict permafrost with its maximal thickness 275-390 m near the shore line. We also present sensitivity analysis which define the wider range of modeling results depending on the changing input parameters (e.g. geothermal heat flux, bottom water temperature, porosity of the sediments). The model adapts well to corresponding field data, providing crucial information about the modern permafrost conditions

  6. Linking Sediment Microbial Communities to Carbon Cycling in High-Latitude Lakes

    NASA Astrophysics Data System (ADS)

    Emerson, J. B.; Varner, R. K.; Johnson, J. E.; Owusu-Dommey, A.; Binder, M.; Woodcroft, B. J.; Wik, M.; Freitas, N. L.; Boyd, J. A.; Crill, P. M.; Saleska, S. R.; Tyson, G. W.; Rich, V. I.

    2015-12-01

    It is well recognized that thawing permafrost peatlands are likely to provide a positive feedback to climate change via CH4 and CO2 emissions. High-latitude lakes in these landscapes have also been identified as sources of CH4 and CO2 loss to the atmosphere. To investigate microbial contributions to carbon loss from high-latitude lakes, we characterized sediment geochemistry and microbiota via cores collected from deep and shallow regions of two lakes (Inre Harrsjön and Mellersta Harrsjön) in Arctic Sweden in July, 2012. These lakes are within the Stordalen Mire long-term ecological area, a focal site for investigating the impacts of climate change-related permafrost thaw, and the lakes in this area are responsible for ~55% of the CH4 loss from this hydrologically interconnected system. Across 40 samples from 4 to 40 cm deep within four sediment cores, Illumina 16S rRNA gene sequencing revealed that the sedimentary microbiota was dominated by candidate phyla OP9 and OP8 (Atribacteria and Aminicenantes, respectively, including putative fermenters and anaerobic respirers), predicted methanotrophic Gammaproteobacteria, and predicted methanogenic archaea from the Thermoplasmata Group E2 clade. We observed some overlap in community structure with nearby peatlands, which tend to be dominated by methanogens and Acidobacteria. Sediment microbial communities differed significantly between lakes, by overlying lake depth (shallow vs. deep), and by depth within a core, with each trend corresponding to parallel differences in biogeochemical measurements. Overall, our results support the potential for significant microbial controls on carbon cycling in high-latitude lakes associated with thawing permafrost, and ongoing metagenomic analyses of focal samples will yield further insight into the functional potential of these microbial communities and their dominant members.

  7. Distribution and hosts of arsenic in a sediment core from the Chianan Plain in SW Taiwan: Implications on arsenic primary source and release mechanisms.

    PubMed

    Yang, Huai-Jen; Lee, Chi-Yu; Chiang, Yu-Ju; Jean, Jiin-Shuh; Shau, Yen-Hong; Takazawa, Eiichi; Jiang, Wei-Teh

    2016-11-01

    High arsenic abundance of 50-700μg/L in the groundwater from the Chianan Plain in southwestern Taiwan is a well-known environmental hazard. The groundwater-associated sediments, however, have not been geochemically characterized, thus hindering a comprehensive understanding of arsenic cycling in this region. In this study, samples collected from a 250m sediment core at the centre of the Chianan Plain were analyzed for arsenic and TOC concentrations (N=158), constituent minerals (N=25), major element abundances (N=105), and sequential arsenic extraction (N=23). The arsenic data show a prevalence of >10mg/kg with higher concentrations of 20-50mg/kg concentrated at 60-80 and 195-210m. Arsenic was extracted mainly as an adsorbate on clay minerals, as a co-precipitate in amorphous iron oxyhydroxide, and as a structural component in clay minerals. Since the sediments consist mainly of quartz, chlorite, and illite, the correlations between arsenic concentration and abundances of K2O and MgO pinpoint illite and chlorite as the major arsenic hosts. The arsenic-total iron correlation reflects the role of chlorite along with the contribution from amorphous iron oxyhydroxide as indicated by arsenic extraction data. Organic matter is not the dominant arsenic host for low TOC content, low arsenic abundance extracted from it, and a relatively low R(2) of the arsenic-TOC correlation. The major constituent minerals in the sediments are the same as those of the upriver metapelites, establishing a sink-source relationship. Composition data from two deep groundwater samples near the sediment core show Eh values and As(V)/As(III) ratios of reducing environments and high arsenic, K, Mg, and Fe contents necessary for deriving arsenic from sediments by desorption from clay and dissolution of iron oxyhydroxide. Therefore, groundwater arsenic was mainly derived from groundwater-associated sediments with limited contributions from other sources, such as mud volcanoes. PMID:27343940

  8. Mid-Pleistocene Orbital and Millennial Scale Climate Change in a 200 ky lacustrine sediment core from SW North America

    NASA Astrophysics Data System (ADS)

    Fawcett, P. J.; Werne, J. P.; Anderson, R. S.; Heikoop, J. M.; Brown, E. T.; Berke, M. A.; Smith, S.; Goff, F. E.; Hurley, L. L.; Cisneros Dozal, L. M.; Schouten, S.; Sinninghe Damsté, J. S.; Huang, Y.; Toney, J. L.; Fessenden, J. E.; Woldegabriel, G. W.; Geissman, J. W.; Allen, C. D.

    2009-12-01

    How anthropogenic climate change will affect hydroclimate of the arid regions of SW North America over the next century is a concern. Model projections suggest permanent “dust bowl-like” conditions; however, any anthropogenic change will be superimposed on long-term natural climate variability. We use the paleoclimatic record from an 82-m deep lacustrine sediment core (VC-3) from the Valles Caldera, New Mexico to examine continental climate variations spanning two glacial cycles through the middle Pleistocene from MIS 14 to MIS 10 (552 ka to ~360 ka). Both orbital and millennial-scale variations are evident in multiple proxies, and a strong relationship occurs between the warmest temperatures in the record and periods of extended aridity. We suggest that these periods of aridity are characterized by decreased winter as well as summer precipitation amounts. A new group of organic geochemical proxies (MBT and CBT) allow us to reconstruct the annual mean air temperature (MAT) of the Valles Caldera watershed as well as the watershed soil pH down the length of the core. We compare these proxies to climatically sensitive pollen taxa and other core properties. The MAT record of VC-3 shows considerable glacial-interglacial variation and significant variability within individual glacial and interglacial periods. The warmest interglacial MATs (5 to 7°C) compare favorably with modern MATs of ~5°C in the Valle Grande. MIS 11 has three warm substages, based on MAT estimates (2°C warmer than the cool substages), warm (Juniperus, Quercus, Rosaceae) vs. cool (Abies, Picea, Artemisia) pollen taxa and variation in aquatic productivity proxies (TOC, Si:Ti). The three warm substages of MIS 11 appear to correspond to the three precessional peaks that occur during this interval. Glacial MATs range from -5 to +2°C, with multiple millennial-scale temperature oscillations evident. Several of the interstadials show a distinct pattern of relatively slower temperature increases and

  9. Water-quality trends in White Rock Creek Basin from 1912-1994 identified using sediment cores from White Rock Lake Reservoir, Dallas, Texas

    USGS Publications Warehouse

    Van Metre, P.C.; Callender, E.

    1997-01-01

    Historical trends in selected water-quality variables from 1912 to 1994 in White Rock Creek Basin were identified by dated sediment cores from White Rock Lake. White Rock Lake is a 4.4-km2 reservoir filled in 1912 and located on the north side of Dallas, Texas, with a drainage area of 259 km2. Agriculture dominated land use in White Rock Creek Basin before about 1950. By 1990, 72% of the basin was urban. Sediment cores were dated using cesium-137 and core lithology. Major element concentrations changed, and sedimentation rates and percentage of clay-sized particles in sediments decreased beginning in about 1952 in response to the change in land use. Lead concentrations, normalized with respect to aluminum, were six times larger in sediment deposited in about 1978 than in pre-1952 sediment. Following the introduction of unleaded gasoline in the 1970s, normalized lead concentrations in sediment declined and stabilized at about two and one-half times the pre-1952 level. Normalized zinc and arsenic concentrations increased 66 and 76%, respectively, from before 1952 to 1994. No organochlorine compounds were detected in sediments deposited prior to about 1940. Concentrations of polychlorinated biphenyls (PCB) and DDE (a metabolite of DDT) increased rapidly beginning in the 1940s and peaked in the 1960s at 21 and 20 ??g kg-1, respectively, which is coincident with their peak use in the United States. Concentrations of both declined about an order of magnitude from the 1960s to the 1990s to 3.0 and 2.0 ??g kg-1, respectively. Chlordane and dieldrin concentrations increased during the 1970s and 1980s. The largest chlordane concentration was 8.0 ??g kg-1 and occurred in a sediment sample deposited in about 1990. The largest dieldrin concentration was 0.7 ??g kg-1 and occurred in the most recent sample deposited in the early 1990s. Agricultural use of chlordane and dieldrin was restricted in the 1970s; however, both were used as termiticides, and urban use of chlordane

  10. A semi-quantitative method to estimate organic matter content of lake sediments using ITRAX micro-XRF core scanner data

    NASA Astrophysics Data System (ADS)

    Avşar, Ulaş; Hubert-Ferrari, Aurélia; Jónsson, Sigurjón; De Batist, Marc; Fagel, Nathalie; Geirsdóttir, Áslaug; Miller, Gifford H.

    2014-05-01

    Organic matter (OM) content of lake sediments may provide valuable information about the past depositional processes and environments. It is most commonly obtained by loss-on-ignition (LOI550) method, which is based on burning the OM in sediments at 550 °C for 4 hours. In addition to LOI550, OM content of sediments can be determined by total organic carbon (TOC) measurements by elemental analyzers. LOI550 is a simple and inexpensive method by which upto 50 samples can be measured per day. However, it is not reliable for sediments containing OM less than 8-10%. TOC measurements, on the other hand, can be reliable for sediments containing minor amounts of OM, ~1% or even less. However, TOC measurements are more expensive and require more pre-treatments such as carbonate removal and grinding etc. For both methods, it is unlikely to achieve measurement resolution more than 5 mm. ITRAX micro-XRF core scanner, which can provide variations of 15-20 elements along sediment cores, can reach measurement increments as fine as 0.2 mm. Even though ITRAX can produce high-resolution data in relatively short times with minor labour, the produced data suffers from a major weakness. OM content, particle size-distribution, mineralogical and density variations may significantly affect the results. This study illustrates how this weakness can be used to estimate OM content of sediments at resolutions that cannot be achieved by conventional LOI550 and TOC methods. A total of 19 m-long sediment cores from four lakes in Turkey and one lake in Iceland were scanned by ITRAX at 0.5-2.0 mm resolution. OM content of the sediments was quantified by 970 LOI550 and 490 TOC measurements at 1-2 cm increments. Multiple regression analysis was utilized to generate formulas specific to each lake in order to estimate the measured OM content values by ITRAX data. Accordingly, the generated formulas successfully provided estimations with correlation coefficient values (r2) around 0.95. Even if the

  11. Permafrost Meta-Omics and Climate Change

    NASA Astrophysics Data System (ADS)

    Mackelprang, Rachel; Saleska, Scott R.; Jacobsen, Carsten Suhr; Jansson, Janet K.; Taş, Neslihan

    2016-06-01

    Permanently frozen soil, or permafrost, covers a large portion of the Earth's terrestrial surface and represents a unique environment for cold-adapted microorganisms. As permafrost thaws, previously protected organic matter becomes available for microbial degradation. Microbes that decompose soil carbon produce carbon dioxide and other greenhouse gases, contributing substantially to climate change. Next-generation sequencing and other -omics technologies offer opportunities to discover the mechanisms by which microbial communities regulate the loss of carbon and the emission of greenhouse gases from thawing permafrost regions. Analysis of nucleic acids and proteins taken directly from permafrost-associated soils has provided new insights into microbial communities and their functions in Arctic environments that are increasingly impacted by climate change. In this article we review current information from various molecular -omics studies on permafrost microbial ecology and explore the relevance of these insights to our current understanding of the dynamics of permafrost loss due to climate change.

  12. Spatial heterogeneity of dechlorinating bacteria and limiting factors for in situ trichloroethene dechlorination revealed by analyses of sediment cores from a polluted field site.

    PubMed

    Dowideit, Kerstin; Scholz-Muramatsu, Heidrun; Miethling-Graff, Rona; Vigelahn, Lothar; Freygang, Martina; Dohrmann, Anja B; Tebbe, Christoph C

    2010-03-01

    Microbiological analyses of sediment samples were conducted to explore potentials and limitations for bioremediation of field sites polluted with chlorinated ethenes. Intact sediment cores, collected by direct push probing from a 35-ha contaminated area, were analyzed in horizontal layers. Cultivation-independent PCR revealed Dehalococcoides to be the most abundant 16S rRNA gene phylotype with a suspected potential for reductive dechlorination of the major contaminant trichloroethene (TCE). In declining abundances, Desulfitobacterium, Desulfuromonas and Dehalobacter were also detected. In TCE-amended sediment slurry incubations, 66% of 121 sediment samples were dechlorinating, among them one-third completely and the rest incompletely (end product cis-1,2-dichloroethene; cDCE). Both PCR and slurry analyses revealed highly heterogeneous horizontal and vertical distributions of the dechlorination potentials in the sediments. Complete reductive TCE dechlorination correlated with the presence of Dehalococcoides, accompanied by Acetobacterium and a relative of Trichococcus pasteurii. Sediment incubations under close to in situ conditions showed that a low TCE dechlorination activity could be stimulated by 7 mg L(-1) dissolved carbon for cDCE formation and by an additional 36 mg carbon (lactate) L(-1) for further dechlorination. The study demonstrates that the highly heterogeneous distribution of TCE degraders and their specific requirements for carbon and electrons are key issues for TCE degradation in contaminated sites. PMID:20041951

  13. The evolution of a thermokarst-lake landscape: Late Quaternary permafrost degradation and stabilization in interior Alaska

    NASA Astrophysics Data System (ADS)

    Edwards, Mary; Grosse, Guido; Jones, Benjamin M.; McDowell, Patricia

    2016-07-01

    Thermokarst processes characterize a variety of ice-rich permafrost terrains and often lead to lake formation. The long-term evolution of thermokarst landscapes and the stability and longevity of lakes depend upon climate, vegetation and ground conditions, including the volume of excess ground ice and its distribution. The current lake status of thermokarst-lake landscapes and their future trajectories under climate warming are better understood in the light of their long-term development. We studied the lake-rich southern marginal upland of the Yukon Flats (northern interior Alaska) using dated lake-sediment cores, observations of river-cut exposures, and remotely-sensed data. The region features thick (up to 40 m) Quaternary deposits (mainly loess) that contain massive ground ice. Two of three studied lakes formed ~ 11,000-12,000 cal yr BP through inferred thermokarst processes, and fire may have played a role in initiating thermokarst development. From ~ 9000 cal yr BP, all lakes exhibited steady sedimentation, and pollen stratigraphies are consistent with regional patterns. The current lake expansion rates are low (0 to < 7 cm yr- 1 shoreline retreat) compared with other regions (~ 30 cm yr- 1 or more). This thermokarst lake-rich region does not show evidence of extensive landscape lowering by lake drainage, nor of multiple lake generations within a basin. However, LiDAR images reveal linear "corrugations" (> 5 m amplitude), deep thermo-erosional gullies, and features resembling lake drainage channels, suggesting that highly dynamic surface processes have previously shaped the landscape. Evidently, widespread early Holocene permafrost degradation and thermokarst lake initiation were followed by lake longevity and landscape stabilization, the latter possibly related to establishment of dense forest cover. Partial or complete drainage of three lakes in 2013 reveals that there is some contemporary landscape dynamism. Holocene landscape evolution in the study area

  14. Volcanic time-markers for Marine Isotopic Stages 6 and 5 in Southern Ocean sediments and Antarctic ice cores: implications for tephra correlations between palaeoclimatic records

    NASA Astrophysics Data System (ADS)

    Hillenbrand, C.-D.; Moreton, S. G.; Caburlotto, A.; Pudsey, C. J.; Lucchi, R. G.; Smellie, J. L.; Benetti, S.; Grobe, H.; Hunt, J. B.; Larter, R. D.

    2008-03-01

    Three megascopic and disseminated tephra layers (which we refer to as layers A, B, and C) occur in late Quaternary glaciomarine sediments deposited on the West Antarctic continental margin. The stratigraphical positions of the distal tephra layers in 28 of the 32 studied sediment cores suggest their deposition during latest Marine Isotopic Stage (MIS) 6 and MIS 5. One prominent tephra layer (layer B), which was deposited subsequent to the penultimate deglaciation (Termination II), is present in almost all of the cores. Geochemical analyses carried out on the glass shards of the layers reveal a uniform trachytic composition and indicate Marie Byrd Land (MBL), West Antarctica, as the common volcanic source. The geochemical composition of the marine tephra is compared to that of ash layers of similar age described from Mount Moulton and Mount Takahe in MBL and from ice cores drilled at Dome Fuji, Vostok and EPICA Dome C in East Antarctica. The three tephra layers in the marine sediments are chemically indistinguishable. Also five englacial ash layers from Mt. Moulton, which originated from highly explosive Plinian eruptions of the Mt. Berlin volcano in MBL between 142 and 92 ka ago, are chemically very similar, as are two tephra layers erupted from Mt. Takahe at ca 102 ka and ca 93 ka. Statistical analysis of the chemical composition of the glass shards indicates that the youngest tephra (layer A) in the marine cores matches the ash layer that erupted from Mt. Berlin at 92 ka, which was previously correlated with tephra layers in the EPICA Dome C and the Dome Fuji ice cores. A tephra erupted from Mt. Berlin at 136 ka seems to correspond to a tephra layer deposited at 1733 m in the EPICA Dome C ice core. Additionally, the oldest tephra (layer C) in the marine sediments resembles an ash layer deposited at Vostok around 142 ka, but statistical evidence for the validity of this correlation is inconclusive. Although our results underscore the potential of

  15. δ 18Osw estimate for Globigerinoides ruber from core-top sediments in the East China Sea

    NASA Astrophysics Data System (ADS)

    Horikawa, Keiji; Kodaira, Tomohiro; Zhang, Jing; Murayama, Masafumi

    2015-12-01

    The paired analyses of the Mg/Ca ratio and oxygen isotopic composition ( δ 18Oc) of surface-dwelling planktonic foraminifera have become a widely used method for reconstructing the oxygen isotopic composition of ambient seawater ( δ 18Osw) as a robust proxy for surface salinity. Globigerinoides ruber ( G. ruber) is a mixed-layer dweller, and its fossil shell is an ideal archive for recording past sea surface water conditions, such as those caused by variability in the East Asian summer monsoon (EASM). Here, we investigate the validity of shell-derived δ 18Osw estimates for G. ruber using core-top sediments from the East China Sea (ECS). First, we determined a local δ 18Osw-salinity equation for the eastern part of the ECS in July [ δ 18Osw = -7.74 + 0.23 × salinity]. Then, we calculated δ 18Osw from core-top δ 18Oc and Mg/Ca values in G. ruber using the δ 18Oc-temperature equation of Bemis et al. (Paleoceanography 13(2):150-160, 1998) and the Mg/Ca-temperature equation of Hastings et al. (EOS 82:PP12B-10, 2001). The core-top δ 18Osw and salinity were estimated to be in the ranges of -0.2 to +0.39 ‰ and 33.7 to 34.5, respectively, which fall close to the local δ 18Osw-salinity regression line. The core-top data showed that the Mg/Ca-temperature calibration by Hastings et al. (EOS 82:PP12B-10, 2001) and the δ 18Oc-temperature equation by Bemis et al. (Paleoceanography 13(2):150-160, 1998) are appropriate for calculating δ 18Osw in the ECS. Furthermore, we measured core-top Ba/Ca ratios of G. ruber (Ba/Ca G. ruber ), which ranged from 0.66 to 2.82 μmol mol-1. There was not a significant relationship between the salinity and Ba/Ca G. ruber ratios due to the highly variable Ba/Ca G. ruber data. Given the seawater Ba/Ca data and the published partition coefficient for Ba ( D Ba = 0.15-0.22), pristine Ba/Ca G. ruber ratios at northern Okinawa Trough sites should be less than 0.84 μmol mol-1. Anomalously high Ba/Ca G. ruber ratios (>0.84 μmol mol-1) might

  16. A new sediment core from the early Aptian OAE1a: the Cau section (Prebetic Zone, Spain)

    NASA Astrophysics Data System (ADS)

    Alejandro Ruiz-Ortiz, Pedro; Castro, José Manuel; de Gea, Ginés A.; Jarvis, Ian; Loeser, Hannes; Molina, José Miguel; Nieto, Luis Miguel; Pancost, Richard; Quijano, María Luisa; Reolid, Matías; Skelton, Peter; Weissert, Helmut

    2016-04-01

    The occurrence of time intervals of enhanced deposition of organic matter (OM) during the Cretaceous, defined as Oceanic Anoxic Events (OAE), reflect abrupt changes in global carbon cycling. The exemplary Aptian OAE1a (120 Ma), is recorded in all the main ocean basins and associated with massive burial of OM in marine sediments [1]. OAE1a is concomitant with the 'nannoconid crisis', which represents a major biotic turnover [2], and also with widespread demise of carbonate platforms [1]. Much research has been done on the OAE1a from different sections in the world over the last decades, since the definition of the C-isotope stratigraphy of the event [3]. Notwithstanding, high-resolution studies across the entire event will be crucial to elucidate the precise timing and rates of the different environmental and biotic changes involved. In order to perform high-resolution studies, drill-cores can represent the best option. Previous cores with successful scientific results has been performed in two reference sections, the Cismon Apti-core [4], and more recently in La Bédoule [5]. Here we present a new drill-core from southern Spain, the Cau section core, drilled in the last quarter of 2015. The Cau section is located in the easternmost part of the Prebetic Zone (Betic Cordillera), which represents the platform deposits of the Southern Iberian Palaeomargin. The lower Aptian of the Cau section is represented by an hemipelagic unit (Almadich Formation, ca. 200 m thick), deposited in a highly subsiding sector of a tilted block, located in the distal parts of the Prebetic Platform. Previous studies of the early Aptian of the Cau section have focused on the stratigraphy, bioevents, C-isotope stratigraphy, and organic and elemental geochemistry [6], [7], among others. A recent study on the Cau section based on biomarkers has presented a detailed record of the PCO2, [8]. All these studies reveal that the Cau section represents an excellent site to investigate the OAE1a, based

  17. Percussive Force Magnitude in Permafrost

    NASA Technical Reports Server (NTRS)

    Eustes, A. W., III; Bridgford, E.; Tischler, A.; Wilcox, B. H.

    2000-01-01

    An in-depth look at percussive drilling shows that the transmission efficiency is very important; however, data for percussive drilling in hard rock or permafrost is rarely available or the existing data are very old. Transmission efficiency can be used as a measurement of the transmission of the energy in the piston to the drill steel or bit and from the bit to the rock. Having a plane and centralized impact of the piston on the drill steel can optimize the transmission efficiency from the piston to the drill steel. A transmission efficiency of near 100% between piston and drill steel is possible. The transmission efficiency between bit and rock is dependent upon the interaction within the entire system. The main factors influencing this transmission efficiency are the contact area between cutting structure and surrounding rock (energy loss due to friction heat), damping characteristics of the surrounding rock (energy dampening), and cuttings transport. Some of these parameters are not controllable. To solve the existing void regarding available drilling data, an experiment for gathering energy data in permafrost for percussive drilling was designed. Fifteen artificial permafrost samples were prepared. The samples differed in the grain size distribution to observe a possible influence of the grain size distribution on the drilling performance. The samples were then manually penetrated (with a sledge-hammer) with two different spikes.

  18. Early Miocene Antarctic glacial history: new insights from heavy mineral analysis from ANDRILL AND-2A drill core sediments

    NASA Astrophysics Data System (ADS)

    Iacoviello, Francesco; Giorgetti, Giovanna; Turbanti Memmi, Isabella; Passchier, Sandra

    2015-04-01

    The present study deals with heavy mineral analysis of late Early Miocene marine sediments recovered in the McMurdo Sound region (Ross Sea, Antarctica) during the ANDRILL—SMS Project in 2007. The main objective is to investigate how heavy mineral assemblages reflect different source rocks and hence different provenance areas. These data contribute to a better understanding of East Antarctica ice dynamics in the Ross Sea sector during the Early Miocene (17.6-20.2 Ma), a time of long-term global warming and sea level rise. The AND-2A drill core recovered several stratigraphic intervals that span from Early Miocene to Pleistocene and it collected a variety of terrigenous lithologies. The heavy mineral assemblages of the lower 650-m-thick sedimentary succession were analyzed through SEM observations and SEM-EDS microanalyses on heavy mineral grains. The heavy mineral analysis shows that the sediments are a mix of detritus dominated by McMurdo Volcanic Group sources most likely located in the present-day Mount Morning area (Proto-Mount Morning) with minor contribution from Transantarctic Mountains source rocks located west of the drill site. The heavy mineral assemblages in Interval 1 indicate that between 20.2 and 20.1 Ma, the grounding line of the ice sheet advanced to a position near the present-day Mount Morning volcanic center. During deposition of Interval 2 (20.1-19.3 Ma), the ice sheet most likely experienced a dynamic behavior with interval of ice advance alternating with periods of ice retreat, while Interval 3 (19.3-18.7 Ma) records further retreat to open water conditions. A dynamic behavior is noted in Interval 4 (18.7-17.6 Ma) with a decreasing contribution of materials derived from the basalts of the Mount Morning volcanic center located to the south of the drill site and a consequent increasing contribution of materials derived from the Transantarctic Mountains to the west of the drill site.

  19. Anisotropy of magnetic susceptibility as a tool for recognizing core deformation: reevaluation of the paleomagnetic record of Pleistocene sediments from drill hole OL-92, Owens Lake, California

    USGS Publications Warehouse

    Rosenbaum, Joseph; Reynolds, Richard T.; Smoot, Joseph; Meyer, Robert

    2000-01-01

    At Owens Lake, California, paleomagnetic data document the Matuyama/Brunhes polarity boundary near the bottom of a 323-m core (OL-92) and display numerous directional fluctuations throughout the Brunhes chron. Many of the intervals of high directional dispersion were previously interpreted to record magnetic excursions. For the upper ~120 m, these interpretations were tested using the anisotropy of magnetic susceptibility (AMS), which typically defines a subhorizontal planar fabric for sediments deposited in quiet water. AMS data from intervals of deformed core, determined from detailed analysis of sedimentary structures, were compared to a reference AMS fabric derived from undisturbed sediment. This comparison shows that changes in the AMS fabric provide a means of screening core samples for deformation and the associated paleomagnetic record for the adverse effects of distortion. For that portion of core OL-92 studied here (about the upper 120 m), the combined analyses of sedimentary structures and AMS data demonstrate that most of the paleomagnetic features, previously interpreted as geomagnetic excursions, are likely the result of core deformation.

  20. Use of strontium isotopes to constrain the timing and mode of dolomitization of upper Cenozoic sediments in a core from San Salvador, Bahamas

    USGS Publications Warehouse

    Swart, Peter K.; Ruiz, Joaquin; Holmes, Charles W.

    1985-01-01

    The 87Sr/86Sr ratios and the activity ratios of 234U/238U and 230Th/238U have been measured in dolomites from a 168-m-deep core taken on the island of San Salvador, Bahamas. These data suggest two periods of dolomitization. The first episode dolomitized Miocene age sediments during the latest Miocene, and the second dolomitized the Pliocene portion of the core and was still active as recently as 150 ka. The late timing of the second episode argues against penecontemporaneous models of dolomitization for the Pliocene sediments. Instead, dolomitization is favored either as a result of mixing-zone development during the large Pleistocene sea-level changes or by movement of seawater through the platform.

  1. Effects of urbanization and long-term rainfall on the occurrence of organic compounds and trace elements in reservoir sediment cores, streambed sediment, and fish tissue from the Santa Ana River basin, California, 1998

    USGS Publications Warehouse

    Burton, Carmen A.

    2002-01-01

    Organcochlorine compounds, semivolatile-organic compounds (SVOC), and trace elements were analyzed in reservoir sediment cores, streambed sediment, and fish tissue in the Santa Ana River Basin as part of the U.S. Geological Survey's National Water-Quality Assessment Program. Three reservoirs were sampled in areas that have different degrees of urbanization. Streambed sediment and fish tissue collected at 12 sites were divided into two groups, urban and nonurban. More organochlorine compounds were detected in reservoir sediment cores, streambed sediment and fish tissue, and at higher concentrations at urban sites than at nonurban sites. At all sites, except West Street Basin, concentrations of organochlorine compounds were lower than the probable-effect concentration (PEC). At the highly urbanized West Street Basin, chlordane and p,p'-DDE exceeded the PEC throughout the historical record. The less stringent threshold-effect concentration (TEC) was exceeded for six compounds at eight sites. Most of the organochlorine compounds detected in streambed sediment and fish tissue were at urban sites on the Santa Ana River as opposed to its tributaries, suggesting accumulation and persistence in the river. More SVOCs were detected in reservoir sediment cores and streambed sediment, and at higher concentrations, at urban sites than at nonurban sites. At all the sites, except West Street Basin, concentrations of SVOCs were lower than the PEC. At West Street Basin, chrysene, pyrene, and total polycyclic-aromatic hydrocarbons exceeded the PEC throughout the historical record. The TEC was exceeded for 10 compounds at 3 sites. Most of the SVOCs were detected in streambed sediment at urban sites on tributaries to the Santa Ana River rather than the mainstem itself. The less frequent occurrence and lower concentrations in the Santa Ana River suggest that SVOCs are less persistent than organochlorine compounds, possibly as a result of volatization, gradation, or dilution. Most trace

  2. Deception island, Antarctica: a terrestrial analogue for the study and understanding of the martian permafrost and subsurface glaciers

    NASA Astrophysics Data System (ADS)

    Hernandez de Pablo, M. A.; Ramos, M.; Vieira, G.; Gilichinsky, D.; Gómez, F.; Molina, A.; Segovia, R.

    2009-04-01

    , the objectives of our Antarcti research program in this island include some activities focused on drill shallow and depth (about 25 m) boreholes to extract ice-rich permafrost cores that will be analyzed to study the habitability on the permafrost. Results of these analyses could also used in astrobiological studies of the martian permafrost. In this work we show the most important characteristics of glaciers and permafrost in Deception Island, and some possible analogues from Mars.

  3. Paleomagnetism of a 150 m Sediment Core from the Co-Seismic Subsidence Depocenter of the 2009 Mw=6.1 L'Aquila Earthquake (Italy)

    NASA Astrophysics Data System (ADS)

    Macri', P.; Porreca, M.; Sagnotti, L.; Smedile, A.; Speranza, F.

    2014-12-01

    The 150 m deep borehole LAQUI-CORE was drilled in the co-seismic subsidence depocenter, shown by INSAR images in the middle Aterno continental basin, after the 2009 Mw=6.1 earthquake that struck the historical city of L'Aquila (Italy). The drill site was located where geological, seismological and geophysical surveys indicated a continuous record with a maximum thickness of fine-grained sediments. The aim was to investigate stratigraphic and geometrical architecture of the middle Aterno basin, in order to define its relationship with the local active fault system. The core consists of continental Holocene and Pleistocene sediments subdivided into two main sequences separated by an erosional discontinuity. The upper sequence consists of 41 m thick fluvial-alluvial deposits of silt and sand interbedded with metric intervals of rounded gravel. The lower sequence consists of palustrine sediments of clays and sands interrupted in the middle by a 30 m thick coarse gravel deposit. Biostratigraphic and radiometric measurements on the core are still in progress, while high-resolution paleomagnetic and rock magnetic measurements were performed on u-channel samples. Natural remanent magnetization (NRM), anhysteretic remanent magnetization (ARM), magnetic susceptibility (k) were measured at 1-cm spacing using a 2G Cryogenic magnetometer. The sediments carry a well-defined characteristic remanent magnetization (ChRM), isolated between 15 and 40 mT AF steps. The ChRM is of normal polarity down to ca. 83 m depth, with paleomagnetic inclination values oscillating around 57°. The main magnetic carrier in this interval is magnetite, below ca. 115 m depth the data show frequent apparent polarity changes due to the additional widespread occurrence of greigite. This interval has to be anyway older than the Brunhes-Matuyama transition. Relative paleointensity (RPI) curves were obtained by normalising the NRM20mT with k and ARM20mT and may be useful to improve the dating of the core.

  4. Latitudinal trends in fluxes and congener patterns of PCBs inferred from lake sediment cores from mid-latitude and Arctic Lakes

    SciTech Connect

    Muir, D.; Omelchenko, A.; Grift, N.; Lockhart, L.; Wilkinson, P.; Brunskill, G.; Robbins, J.A.

    1995-12-31

    Sediment cores collected from 9 remote lakes in central and Arctic Canada (49{degree}N to 82{degree}N and from 71{degree} to 136{degree}W) were analyzed for PCBs with the objective of examining latitudinal and temporal trends in deposition. Core slices (1--1.3 cm) were dated with {sup 210}Pb and {sup 137}Cs using the Robbins rapid steady-state mixing model and sediment focusing factors were determined with the aid of soil cores or predictions of historical radionuclide deposition. Slices were freeze-dried, Soxhlet extracted with DCM and chromatographed on Florisil, then analyzed by high resolution GC-ECD with confirmation by GC-HRMS. {Sigma}PCB concentrations in surface sediments were low ranging from 8 to 40 ng{center_dot}g{sup {minus}1} (dry wt) in southern mid-continental sites (49--63{degree}N) to 2 ng{center_dot}g{sup {minus}1} in Lake Hazen, the most northerly location (82{degree}N). Highest concentrations were found in the most recent slices (1980s) of cores from high Arctic lakes (at 75 and 82{degree}N) whereas peak concentrations were reached earlier (in the 1970s) at more southerly locations. Principal components analysis revealed that sediments from high Arctic lakes could be distinguished by greater proportions of lower chlorinated PCBs in comparison with published results for Lakes Ontario and Superior. Focus corrected {Sigma}PCBs fluxes ranged from 305 to 920 ng{center_dot}m{sup 2}{center_dot}yr{sup {minus}1} in the 9 lakes and were negatively correlated with latitude (r{sup 2} = 0.53). Fluxes of Cl{sup 8} CBs had a strong negative correlation with latitude (r2 = 0.88) while Cl{sup 3} CBs showed no latitudinal trend. The results generally support several of the predictions of the cold condensation hypothesis.

  5. Diversity of active microbial communities subjected to long-term exposure to chemical contaminants along a 40-year-old sediment core.

    PubMed

    Kaci, Assia; Petit, Fabienne; Fournier, Matthieu; Cécillon, Sébastien; Boust, Dominique; Lesueur, Patrick; Berthe, Thierry

    2016-03-01

    In estuarine ecosystems, metallic and organic contaminants are mainly associated with fine grain sediments which settle on mudflats. Over time, the layers of sediment accumulate and are then transformed by diagenetic processes mainly controlled by microbial activity, recording the history of the estuary's chemical contamination. In an environment of this specific type, we investigated the evolution of the chemical contamination and the structure of both total and active microbial communities, based on PhyloChip analysis of a 4.6-m core corresponding to a 40-year sedimentary record. While the archaeal abundance remained constant along the core, a decrease by one order of magnitude in the bacterial abundance was observed with depth. Both total and active microbial communities were dominated by Proteobacteria, Actinobacteria, and Firmicutes in all sediment samples. Among Proteobacteria, alpha-Proteobacteria dominated both total (from 37 to 60 %) and metabolically active (from 19.7 to 34.6 %) communities, including the Rhizobiales, Rhodobacter, Caulobacterales, and Sphingomonadales orders. Co-inertia analysis revealed a relationship between polycyclic aromatic hydrocarbons, zinc and some polychlorobiphenyls concentrations, and the structure of total and active microbial communities in the oldest and most contaminated sediments (from 1970 to 1975), suggesting that long-term exposure to chemicals shaped the structure of the microbial community. PMID:25934230

  6. Glacial and Holocene terrestrial temperature variability in subtropical east Australia as inferred from branched GDGT distributions in a sediment core from Lake McKenzie

    NASA Astrophysics Data System (ADS)

    Woltering, Martijn; Atahan, Pia; Grice, Kliti; Heijnis, Henk; Taffs, Kathryn; Dodson, John

    2014-07-01

    Branched glycerol dialkyl glycerol tetraether (GDGT) distributions observed in a sediment core from Lake McKenzie were utilized to quantitatively reconstruct the pattern of mean annual air temperature (MAAT) from coastal subtropical eastern Australia between 37 and 18.3 cal ka BP and 14.0 cal ka BP to present. Both the reconstructed trend and amplitude of MAAT changes from the top of the sediment core were nearly identical to a local instrumental MAAT record from Fraser Island, providing confidence that in this sediment core branched GDGTs could be used to produce a quantitative record of past MAAT. The reconstructed trend of MAAT during 37 to 18.3 cal ka BP and timing of the Last Glacial Maximum (LGM) in the Lake McKenzie record were in agreement with previously published nearby marine climate records. The amplitude of lower-than-present MAAT during the LGM potentially provides information on the latitude of separation of the Tasman Front from the East Australian current in the subtropical western Pacific. The Lake McKenzie record shows an earlier onset of near modern day warm temperatures in the early Holocene compared to marine records and the presence of a warmer than present day period during the mid-Holocene.

  7. Biogeochemistry of sulfur in a sediment core from the west-central Baltic Sea: Evidence from stable isotopes and pyrite textures

    NASA Astrophysics Data System (ADS)

    Böttcher, Michael E.; Lepland, Aivo

    2000-07-01

    The biogeochemistry of the sulfur cycle in a ca. 5-m-long sediment core from the eastern slope (221 m water depth) of the Landsort Deep in the west-central Baltic Sea was investigated by analyzing the solid phase records of sulfur isotopes and pyrite textures, besides selected main and minor elements. The sediments were deposited during post-glacial history of the Baltic Sea when the basin experienced alteration of brackish (Yoldia Sea, Littorina Sea) and freshwater (Baltic Ice Lake, Ancylus Lake) conditions. The stable isotopic composition of total sulfur was analyzed as a function of depth. In selected samples pyrite (FeS 2), greigite (Fe 3S 4), and barite (BaSO 4) fractions were separated for isotope analyses. Pyrite textures were analyzed by SEM and optical microscopy. Microbial reactions associated with the oxidation of organic matter resulted in assemblages of authigenic sulfide minerals which for the post-Ancylus Lake brackish water environment are dominated by pyrite and for freshwater environments by Fe-monosulfides. The sulfur isotopic composition of the brackish water Littorina Sea sediments ( δ34S between -40 and -27‰ vs. V-CDT) is believed to be determined by cellular sulfate reduction rates and reactions involving intermediate sulfur species. The availability of reactive iron and decomposable organic matter as well as sedimentation rate and the chemocline position are important variables upon the δ34S values of sulfides in brackish water environment. The syn-depositional abundance of sulfur and organic matter, and transport of dissolved sulfur species vs. rates of microbial reactions determine δ34S in the freshwater sediments. The upper part of the Ancylus Lake sediments is sulfidized by downward diffusing H 2S and/or sulfate from overlying brackish water sediments. Minor concretionary barite formation in the freshwater sediments is most likely due to the reaction of pore water sulfate diffusing downward from brackish water sediments with barium

  8. Geochemical investigation of a sediment core from the Trajan basin at Portus, the harbor of ancient Rome

    NASA Astrophysics Data System (ADS)

    Delile, H.; Mazzini, I.; Blichert-Toft, J.; Goiran, J. P.; Arnaud-Godet, F.; Salomon, F.; Albarède, F.

    2014-03-01

    From the 1st century AD and for the duration of the Roman Empire, the Portus complex was the main harbor of Rome. Its location on the Tiber delta next to the Tyrrhenian Sea produced rapid environmental changes that, together with historical vicissitudes, largely determined the fate of the harbor. We have assembled data on the mineralogy, sedimentology, geochemistry, and ostracod populations of a sediment core drilled in the access channel of the hexagonal basin of Trajan, with the expectation that such a combined data set will shed new light on how the connections of the inland Trajan basin with the Tiber river, the earlier Claudius harbor on the nearby shoreline, and the sea evolved through the centuries. The data define four distinct periods which geochemistry characterizes by different conditions of salinity and oxygenation. These in turn can be related to historical periods and events by means of 14C data. The early Imperial Period was dominated by input of well-oxygenated freshwater from the Tiber. During the Late Empire, harbor water became relatively more influenced by seawater and increasingly oxygen deficient, which attests to a decommissioning of the Canale Trasverso connecting the harbor to the Tiber. The strong anthropogenic signal, which is visible very clearly in geochemical parameters, attests to the human occupation of the harbor area up to the Early Middle Ages, when human activity was brought to an abrupt end. The simultaneous use in this study of multiple complementary tracers has allowed for the sedimentary sources of the different classes of particles in the harbor basin to be identified and assigned to either the freshwater supply from the Canale Trasverso or the seawater of the Claudius harbor.

  9. Peatland carbon cycling and the implications of permafrost thaw; a chronosequence study.

    NASA Astrophysics Data System (ADS)

    Olefeldt, D.; Pelletier, N.; Talbot, J.; Blodau, C.; Turetsky, M. R.

    2015-12-01

    Peatlands in the Mackenzie River valley initiated ~9000 years ago and have built up vast soil carbon stores since. Peatland development history in this region is characterized by several distinct stages, varying in nutrient status and permafrost conditions. Widespread permafrost thaw has recently occurred in response to warming, thus making large soil C stores available for microbial processes and mineralization. A crucial question to answer is whether these peatland become net sinks or sources of C following thaw. The net response to thaw will either be dominated by new peat C accumulation at the surface or by mineralization of old peat C released from permafrost. In order to address this question we cored peat plateaus and nearby thermokarst bogs near Fort Simpson, Northwest Territories, representing 4 chronosequences. The cores were analyzed for C content, radiocarbon dates, macrofossils, testate amoebas, peat humification degree, elemental analysis, and microbial lability through an incubation experiment. Together, these approaches reveal peatland development histories, both before and following permafrost thaw. It is clear from our findings that C cycling following permafrost thaw will be intrinsically dependent on the developmental history of the peatland.

  10. Coastal dynamics and submarine permafrost in shallow water of the central Laptev Sea, East Siberia

    NASA Astrophysics Data System (ADS)

    Overduin, P.; Wetterich, S.; Günther, F.; Grigoriev, M. N.; Grosse, G.; Schirrmeister, L.; Hubberten, H.-W.; Makarov, A.

    2015-07-01

    Coastal erosion and relative sea-level rise transform terrestrial landscapes into marine environments. In the Arctic, these processes inundate terrestrial permafrost with seawater and create submarine permafrost. Permafrost begins to warm under marine conditions, which can destabilize the sea floor and may release greenhouse gases. We report on the transition of terrestrial to submarine permafrost at a site where the timing of inundation can be inferred from the rate of coastline retreat. On Muostakh Island in the central Laptev Sea, East Siberia, changes in annual coastline position have been measured for decades and vary highly spatially. We hypothesize that these rates are inversely related to the inclination of the upper surface of submarine ice-bonded permafrost (IBP) based on the consequent duration of inundation with increasing distance from the shoreline. We compared rapidly eroding and stable coastal sections of Muostakh Island and find permafrost-table inclinations, determined using direct current resistivity, of 1 and 5 %, respectively. Determinations of submarine IBP depth from a drilling transect in the early 1980s were compared to resistivity profiles from 2011. Based on boreholes drilled in 1982-1983, the thickness of unfrozen sediment overlying the IBP increased from 0 up to 14 m below sea level with increasing distance from the shoreline. The geoelectrical profiles showed thickening of the unfrozen sediment overlying ice-bonded permafrost over the 28 years since drilling took place. Parts of our geoelectrical profiles trace permafrost flooded, and showed that IBP degradation rates decreased from over 0.6 m a-1 following inundation to around 0.1 m a-1 as the duration of inundation increased to 250 years. We discuss that long-term rates are expected to be less than these values, as the depth to the IBP increases and thermal and pore water solute concentration gradients over depth decrease. For this region, it can be summarized that recent increases

  11. Coastal dynamics and submarine permafrost in shallow water of the central Laptev Sea, East Siberia

    NASA Astrophysics Data System (ADS)

    Overduin, Pier Paul; Wetterich, Sebastian; Günther, Frank; Grigoriev, Mikhail N.; Grosse, Guido; Schirrmeister, Lutz; Hubberten, Hans-Wolfgang; Makarov, Aleksandr

    2016-07-01

    Coastal erosion and flooding transform terrestrial landscapes into marine environments. In the Arctic, these processes inundate terrestrial permafrost with seawater and create submarine permafrost. Permafrost begins to warm under marine conditions, which can destabilize the sea floor and may release greenhouse gases. We report on the transition of terrestrial to submarine permafrost at a site where the timing of inundation can be inferred from the rate of coastline retreat. On Muostakh Island in the central Laptev Sea, East Siberia, changes in annual coastline position have been measured for decades and vary highly spatially. We hypothesize that these rates are inversely related to the inclination of the upper surface of submarine ice-bonded permafrost (IBP) based on the consequent duration of inundation with increasing distance from the shoreline. We compared rapidly eroding and stable coastal sections of Muostakh Island and find permafrost-table inclinations, determined using direct current resistivity, of 1 and 5 %, respectively. Determinations of submarine IBP depth from a drilling transect in the early 1980s were compared to resistivity profiles from 2011. Based on borehole observations, the thickness of unfrozen sediment overlying the IBP increased from 0 to 14 m below sea level with increasing distance from the shoreline. The geoelectrical profiles showed thickening of the unfrozen sediment overlying ice-bonded permafrost over the 28 years since drilling took place. We use geoelectrical estimates of IBP depth to estimate permafrost degradation rates since inundation. Degradation rates decreased from over 0.4 m a-1 following inundation to around 0.1 m a-1 at the latest after 60 to 110 years and remained constant at this level as the duration of inundation increased to 250 years. We suggest that long-term rates are lower than these values, as the depth to the IBP increases and thermal and porewater solute concentration gradients over depth decrease. For the

  12. Use Of Amino Acid Racemization To Investigate The Metabolic Activity Of ?Dormant? Microorganisms In Siberian Permafrost

    NASA Astrophysics Data System (ADS)

    Tsapin, A.; McDonald, G.

    2002-12-01

    search for extraterrestrial life or its remnants is based on studying the most probable environments in which life (extant or extinct) may be found, and determining the maximum period of time over which such life could be preserved. The terrestrial permafrost, inhabited by cold adapted microbes, can be considered as an extraterrestrial analog environment. The cells and their metabolic end-products in Earth's permafrost can be used in the search for possible ecosystems and potential inhabitants on extraterrestrial cryogenic bodies. The study of microorganisms (or their remnants) that were buried for a few million years in permafrost provides us with a unique opportunity to determine the long-term viability of (micro)organisms. We have analyzed the degree of racemization of aspartic acid in permafrost samples from Northern Siberia (Brinton et al. 2002, Astrobiology 2, 77), an area from which microorganisms of apparent ages up to a few million years have previously been isolated and cultured. We find that the extent of aspartic acid racemization in permafrost cores increases very slowly up to an age of approximately 25,000 years (around 5 m depth). The apparent temperature of racemization over the age range 0-25,000 years, determined using measured aspartic acid racemization rate constants, is ?19 C. This apparent racemization temperature is significantly lower than the measured environmental temperature (?11 to ?13 C), and suggests active recycling of D-aspartic acid in Siberian permafrost up to an age of around 25,000 years. This indicates that permafrost organisms are capable of repairing some molecular damage incurred while they are in a ?dormant? state over geologic time.

  13. Insecticides in sediment cores from a rural and a suburban area in South China: A reflection of shift in application patterns.