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Sample records for 210pb dated sediment

  1. 210Pb dating

    USGS Publications Warehouse

    Swarzenski, Peter W.

    2014-01-01

    Roughly fifty years ago, a small group of scientists from Belgium and the United States, trying to better constrain ice sheet accumulation rates, attempted to apply what was then know about environmental lead as a potential geochronometer. Thus Goldberg (1963) developed the first principles of the 210Pb dating method, which was soon followed by a paper by Crozaz et al. (1964), who examined accumulation history of Antarctic snow using 210Pb. Shortly thereafter, Koide et al. (1972, 1973) adapted this technique to unravel sediment deposition and accumulation records in deep-sea environments. Serendipitously, they chose to work in a deep basin off California, where an independent and robust age model had already been developed. Krishanswami et al. (1971) extended the use of this technique to lacustrine deposits to reconstruct depositional histories of lake sediment, and maybe more importantly, contaminant inputs and burial. Thus, the powerful tool for dating recent (up to about one century old) sediment deposits was established and soon widely adopted. Today almost all oceanographic or limnologic studies that address recent depositional reconstructions employ 210Pb as one of several possible geochronometers (Andrews et al., 2009; Gale, 2009; Baskaran, 2011; Persson and Helms, 2011). This paper presents a short overview of the principles of 210Pb dating and provides a few examples that illustrate the utility of this tracer in contrasting depositional systems. Potential caveats and uncertainties (Appleby et al., 1986; Binford, 1990; Binford et al., 1993; Smith, 2001; Hancock et al., 2002) inherent to the use and interpretation of 210Pb-derived age-models are also introduced. Recommendations as to best practices for most reliable uses and reporting are presented in the summary.

  2. Mercury contamination history of an estuarine floodplain reconstructed from a 210Pb-dated sediment core (Berg River, South Africa).

    PubMed

    Kading, T J; Mason, R P; Leaner, J J

    2009-01-01

    Mercury deposition histories have been scarcely documented in the southern hemisphere. A sediment core was collected from the ecologically important estuarine floodplain of the Berg River (South Africa). We establish the concentration of Hg in this (210)Pb-dated sediment core at <50 ng g(-1) Hg(T) throughout the core, but with 1.3 ng g(-1) methylmercury in surface sediments. The (210)Pb dating of the core provides a first record of mercury deposition to the site and reveals the onset of enhanced mercury deposition in 1970. The ratio of methylmercury to total mercury is relatively high in these sediments when compared to other wetlands.

  3. Influence of self-absorption corrections in the quantification of 210Pb and 241Am for sediment dating

    NASA Astrophysics Data System (ADS)

    González, J. Carrazana; Vargas, M. Jurado; Castillo, R. Gil

    2016-10-01

    The nuclides 210Pb and 241Am are used in geochronological studies. In this work, we examine the influence of the sediment chemical composition on the self-attenuation corrections needed for the accurate determination of specific activities for 210Pb and 241Am used for sediment dating. A theoretical exercise was carried out evaluating the relative bias obtained by four different analytical laboratories in the quantification of the 210Pb and 241Am activity concentration by gamma-ray spectrometry. The laboratories considered the same density for the sediment sample, but each one used a different chemical composition in the Monte Carlo calculations, and six different HPGe detectors (including n and p-types). An estimate of the impact that would have the relative biases found in the estimation of the 210Pb sediment ages, applying the Constant Rate of Supply (CRS) dating model, is also given. In addition, the performance scores that the laboratories would have obtained in a hypothetical IAEA proficiency test are also presented.

  4. Dating of sediments from four Swiss prealpine lakes with (210)Pb determined by gamma-spectrometry: progress and problems.

    PubMed

    Putyrskaya, V; Klemt, E; Röllin, S; Astner, M; Sahli, H

    2015-07-01

    In this paper the most important problems in dating lake sediments with unsupported (210)Pb are summarized and the progress in gamma-spectrometry of the unsupported (210)Pb is discussed. The main topics of these studies concern sediment samples preparation for gamma-spectrometry, measurement techniques and data analysis, as well as understanding of accumulation and sedimentation processes in lakes. The vertical distributions of artificial ((137)Cs, (241)Am, (239)Pu) and natural radionuclides ((40)K, (210,214)Pb, (214)Bi) as well as stable trace elements (Fe, Mn, Pb) in sediment cores from four Swiss lakes were used as examples for the interpretation, inter-comparison and validation of depth-age relations established by three (210)Pb-based models (CF-CSR, CRS and SIT). The identification of turbidite layers and the influence of the turbidity flows on the accuracy of sediment dating is demonstrated. Time-dependent mass sedimentation rates in lakes Brienz, Thun, Biel and Lucerne are discussed and compared with published data.

  5. 210Pb-dating of a lake sediment core from Lough Carra (Co. Mayo, western Ireland): use of paleolimnological data for chronology validation below the 210Pb dating horizon.

    PubMed

    O'Reilly, J; Vintró, L León; Mitchell, P I; Donohue, I; Leira, M; Hobbs, W; Irvine, K

    2011-05-01

    The chronologies and sediment accumulation rates for a lake sediment sequence from Lough Carra (Co. Mayo, western Ireland) were established by applying the constant initial concentration (CIC) and constant rate of supply (CRS) hypotheses to the measured (210)Pb(excess) profile. The resulting chronologies were validated using the artificial fallout radionuclides (137)Cs and (241)Am, which provide independent chronostratigraphic markers for the second half of the 20th century. The validity of extrapolating the derived CIC and CRS dates below the (210)Pb dating horizon using average sedimentation rates was investigated using supplementary paleolimnological information and historical data. Our data confirm that such an extrapolation is well justified at sites characterised by relatively stable sedimentation conditions.

  6. Dating of coastal marine sediments: 210Pb versus 137Cs signal on the Danube-influenced Black Sea shelf

    NASA Astrophysics Data System (ADS)

    Friedrich, Jana; Laptev, Gennady

    2010-05-01

    Coastal marine sediments represent a natural archive of pelagic processes, coastal erosion and river discharge of suspended matter. Correct dating of those sediments is a prerequisite for chronological reconstruction of the flux of pollutants and organic matter from the water column to the sediments and hence, the reconstruction of the pollution and eutrophication events. In the reconstruction of the sedimentation history during the pre-industrial and industrial periods, which usually spans the past 100 years, the natural occurring radionuclide 210Pb and the artificial radionuclides 137Cs and 241Am are widely applied tracers. 137Cs is used as an independent time marker for end the atmospheric bomb test fallout in 1963 and the Chernobyl accident in 1986. As the 137Cs signal is often weakened due to its mobility in sediments, 241Am, less mobile than 137Cs and derived from decay the bomb fallout of 241Pu, is used as a second time marker of the 1963 event. The northwestern shelf of the Black Sea has been seriously affected by eutrophication and pollution from the late 1960's to the mid-1990's, largely triggered by Danube River input of nutrients and pollutants. The aim of our study is ultimately to reconstruct the eutrophication history and recycling of nutrients following the deposition of organic matter. The ‘memory effect' of sediment recycling plays a critical role in maintaining eutrophic conditions in enclosed seas such as the Black Sea. Here we present results from sediment cores taken within the Danube River plume on the shallow northwestern shelf of the Black Sea. The cores have been dated in two laboratories to rule out artifacts. The sediment record is repeatedly interrupted by so-called turbidites that consist of stiff clay. The clay horizons display a drop in unsupported 210Pb and 137Cs and a higher signal of supported 210Pb than the non-clay horizons. Below the turbidite, the unsupported 210Pb and 137Cs increase again to values above the turbidite. This

  7. Dating sediment in a fast sedimentation reservoir using 137Cs and 210Pb

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Over 10,000 reservoirs have been constructed in agricultural watersheds in the United States since the 1940s to control floods and sediments. Reservoir sedimentation records provide a unique opportunity to retrospectively study the effects of land use changes and climate variations on sediment produ...

  8. Onset of industrial pollution recorded in Mumbai mudflat sediments, using integrated magnetic, chemical, 210Pb dating, and microscopic methods.

    PubMed

    Blaha, U; Basavaiah, N; Deenadayalan, K; Borole, D V; Mohite, R D

    2011-01-15

    The onset and rise of urban and industrial pollution in the Mumbai region was reconstructed from an anthropogenically contaminated mudflat sediment profile from the adjacent Thane creek using magnetic parameters, polycyclic aromatic hydrocarbon (PAH) data, metal contents, and the (210)Pb dating technique. The 1.8 m vertical section at Airoli (Navi Mumbai) reveals an increase of magnetic susceptibility (χ) from background values of (20-50) to (75-100) × 10(-8) [m(3) kg(-1)] in the anthropogenically affected zone above ∼93 cm. A sharp rise of χ from (75-100) to (130-215) × 10(-8) [m(3) kg(-1)] subdivides the anthropogenically affected zone at a depth of ∼63 cm. Characterization with rock magnetic parameters (SIRM, Soft IRM, and S-ratio) reveals a significant contribution of ferri(o)magnetic phases in the upper zone. Based on the magnetic classification sampling intervals for cost-intensive PAH and metal analyses were determined. Steadily increasing contents of PAH and metals of anthropogenic origin are observed above the boundary depth at ∼93 cm. A sediment accumulation rate of 1.2 ± 0.3 cm/yr provided by (210)Pb dating dates the ∼63 cm boundary to 1951. Increasing industrial activity, including the establishment of a coal-fired power plant in 1956, and refineries between 1955 and 1960, correlates well with the substantial increase of χ, PAH, and metal contents. Scanning electron microscopy (SEM) investigation on magnetic extracts from the contaminated zone reveals the presence of magnetic spherules derived from industrial high-temperature processes.

  9. Problems with the dating of sediment core using excess (210)Pb in a freshwater system impacted by large scale watershed changes.

    PubMed

    Baskaran, Mark; Nix, Joe; Kuyper, Clark; Karunakara, N

    2014-12-01

    Pb-210 dating of freshwater and coastal sediments have been extensively conducted over the past 40 years for historical pollution reconstruction studies, sediment focusing, sediment accumulation and mixing rate determination. In areas where there is large scale disturbance of sediments and the watershed, the vertical profiles of excess (210)Pb ((210)Pbxs) could provide erroneous or less reliable information on sediment accumulation rates. We analyzed one sediment core from Hendrix Lake in southwestern Arkansas for excess (210)Pb and (137)Cs. There is no decrease in excess (210)Pb activity with depth while the (137)Cs profile indicates sharp peak corresponding to 1963 and the (137)Cs penetration depth of (137)Cs corresponds to 1952. The historical data on the accelerated mercury mining during 1931-1944 resulted in large-scale Hg input to this watershed. Using the peak Hg activity as a time marker, the obtained sediment accumulation rates agree well with the (137)Cs-based rates. Four independent evidences (two-marker events based on (137)Cs and two marker events based on Hg mining activity) result in about the same sedimentation rates and thus, we endorse earlier suggestion that (210)Pb profile always needs to be validated with at least one another independent method. We also present a concise discussion on what important factors that can affect the vertical profiles of (210)Pbxs in relatively smaller lakes.

  10. {sup 210}Pb dating of sediments from the central and northern Adriatic Sea: deposition and preservation of sedimentary organic carbon

    SciTech Connect

    Hamilton, T. F., LLNL

    1998-04-01

    Lead-210 ({sup 21O}Pb) and organic C depth distribution profiles in sediments from the northern and central Adriatic Sea were measured as part of the EEC funded project on Eutrophic Limits of the Northern Adriatic (ELNA). {sup 210}Pb derived mass-accumulation rates decrease southward from between 0.15 and 0.2 g cm{sup -2}y{sup -1} close to the Po River outflow (> 24 m, water depth) to less than 0.04 g cm{sup -2}y{sup -1} in the Jabuka Pit (246 m, water depth) in the central Adriatic Sea. The mass- accumulation rates obtained in the Jabuka Pit correspond to mean sedimentation rates of about 0.03 cm y{sup -1} (ref. porosity = 0.5) and fall between 5 to 20 times lower than rates found for north Adriatic shelf cores. Estimated sedimentation rates are considered as upper limits because of the possible effects of bioturbation and physical disturbance on the {sup 21O}Pb sedimentary record but are consistent with data from previous work. Rates of sediment accumulation and carbon burial appear to be strongly influenced by the transport of fluvial materials from land and transport of fine-grained particles. First-order estimates of organic C burial rates into surface sediment ranged from 1 to 0.028 mMol cm{sup -2}y{sup -1} between the Po delta and the Jabuka Pit regions, respectively. We estimate that a maximum of 50% of organic C preserved in surface sediment may be derived from biological production in the overlying water column.

  11. Implications of excess 210Pb and 137Cs in sediment cores from Mikawa Bay, Japan.

    PubMed

    Lu, Xueqiang; Matsumoto, Eiji

    2009-01-01

    Four sediment cores were collected from Mikawa Bay, Japan, and excess 210Pb and 137Cs were measured by gamma spectrometry. Sedimentation rates for the four cores were determined by 210Pb method. The sedimentation rate range is 0.10-0.70 g/(cm2 x year). The bio-mixing depth for each core is less than 7.0 cm, and was determined by the excess 210Pb profiles as well. Therefore, the bioturbation is slight. The 210Pb-derived dates coincided with the results from 137Cs geochronology. Acceleration in sedimentation rate due to environmental alteration has been found in cores A2.5 and 05AS8, representing two depocenters due to their topography. Evidence of the Tokai Flood in 2000 was found in core 05AS8 according to the profiles of both radioisotopes and trace metals.

  12. 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.

  13. {sup 210}Pb dating of sediments from the central and the northern Adriatic Sea: The deposition and preservation of sedimentary organic carbon

    SciTech Connect

    Hamilton, T.; Fowler, S.; Miquel, J.C.; La Rosa, J.

    1996-04-01

    A central goal of the ELNA project is to assess the carbon assimilation capacity of the Northern Adriatic Sea. This requires fundamental quantitative information on budgets and sinks of organic carbon. Any change in carbon production in the water column should be reflected in the underlying sediments. Moreover, the fraction of particulate organic carbon reaching the sea floor which is subsequently preserved in the sediment will be strongly coupled to sediment accumulation and mixing. In this study a series of box cores were collected in order to characterize a hypothetical eutrophication gradient extending from the Po River outflow region in the north down to the shallow meso-Adriatic depression (Jabuka Pit). The main tasks assigned to IAEA-MEL were to provide {sup 210}Pb derived sedimentation and dry-mass accumulation rates and to examine the possible correlations between sedimentary processes, the deposition and preservation of sedimentary organic carbon and pelagic primary productivity.

  14. Sedimentation rates in the Sea of Marmara: a comparison of results based on organic carbon—primary productivity and 210Pb dating

    NASA Astrophysics Data System (ADS)

    Ergi˙n, Mustafa; Bodur, Mehmet N.; Yildi˙z, Mehmet; Edi˙ger, Di˙lek; Edi˙ger, Vedat; Yemeniciog˛lu, S.; Yücesoy, Fulya

    1994-10-01

    A large number of surficial sediment samples (75 grab samples, one boomerang core, four ☐ cores) as well as primary productivity measurements have been used to estimate the rates of sediment accumulation in the Sea of Marmara; using an empirical expression for the relationship between surface productivity and organic carbon content of the sediment ( MüLLER-SUESS formula). It was found that calculated low sedimentation rates occurred on the inner southern Marmara shelf (ave. 8 cm 1000 y -1) where the primary production was relatively high (ave. 161 gC m -2 y -1); and vice versa, high sedimentation rates were calculated for the southwestern shelf (123 cm 1000 y -1), an area with very low primary productivity (64 gCm -2 y -1). This discrepancy among the values, is probably due to the combined effects of the distinctive and peculiar oceanography of the Sea of Marmara (well stratified flow, strong horizontal transport, and varying conditions for mineralization of organic matter etc.). Utilizing the 210Pb method, sediment accumulation rates have been determined of approximately 190 cm 1000 y -1 on the northeastern shelf, 120 cm 1000 y -1 in the eastern depression, 260 cm 1000 y -1 in the central depression, 100 cm 1000 y -1 in the western depression and 280 cm 1000 y -1 on the southwestern shelf of this sea. These generally high rates of sedimentation using this method further support the conclusion that the amount of primary produced organic carbon preserved in the recent bottom deposits of the Sea of Marmara seems not to be universally related to the rate of sedimentation.

  15. 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.

  16. Natural radioisotope210Pb as an indicator of origin of fine-grained sediment

    USGS Publications Warehouse

    Holmes, C.W.

    1984-01-01

    Distribution of210Pb in sediments on the South Texas Continental Shelf is related to dynamics of the sedimentary transport processes. This radioisotope, whose concentration is time-dependent, defines three depocenters on the shelf. In addition, the variation of210Pb activity at the sediment/water interface delineates areas of terrigenous sedimentation from hemipelagic sedimentation. ?? 1985 Springer-Verlag New York Inc.

  17. Relationship between (210)Pb(ex) activity and sedimentary organic carbon in sediments of 3 Chinese lakes.

    PubMed

    Xu, Libin; Wu, Fengchang; Wan, Guojiang; Liao, Haiqing; Zhao, Xiaoli; Xing, Baoshan

    2011-12-01

    This report demonstrates that organic matter was an important factor in lake sediment (210)Pb(ex) dating. Sediment cores from lakes in central and western China with different-trophic levels were collected, and the (210)Pb(ex) activity and total organic carbon (TOC) were measured. The Rock-Eval pyrolysis technique was used to deconvolute TOC into free hydrocarbons (S1), thermally less-stable macromolecular organic matter (S2a), kerogen (S2b), and residual carbon (RC). The results show significant correlations between TOC and (210)Pb(ex), particularly between S2a and (210)Pb(ex), in all the sediment cores. This indicated that the algal-derived organic component S2a may play the most important role in controlling the distribution of (210)Pb(ex). Scavenging by algal-derived organic matter may be the main mechanism. As chronology is the key to the understanding of pollution reconstruction and early diagenesis in sediments, more attention should be paid to the influence of organic matter on (210)Pb(ex).

  18. Geochronology of recent sediments from the Cariaco Trench (Venezuela) by Alpha Spectrometry of {sup 210}Pb ({sup 210}Po)

    SciTech Connect

    Arriojas, A.; Barros, H.; Palacios, D.; Sajo-Bohus, L.; Hurtado, S.; Villa, M.; Perez, K.; Alfonso, J.

    2010-08-04

    210Pb concentration in marine sediments of the Cariaco Trench (North-East of Venezuela) was measured through the analysis of 210Po alpha emissions, which can be assumed to be in secular equilibrium with 210Pb. The analysed sediment core has a length of 1.9 m. The results allowed to apply the CF:CS dating model (Constant Flux and Constant Supply). The sedimentation rate was estimated to be 0.25 cm/y. As far as we know this is the first {alpha}- dating carried out in the country, performed with an alpha spectrometer recently funded by the IAEA.

  19. Recent changes in Red Lake (Romania) sedimentation rate determined from depth profiles of 210Pb and 137Cs radioisotopes.

    PubMed

    Begy, R; Cosma, C; Timar, A

    2009-08-01

    This work presents a first estimation of the sedimentation rate for the Red Lake (Romania). The sediment accumulation rates were determined by two well-known methods for recent sediment dating: (210)Pb and (137)Cs methods. Both techniques implied used the gamma emission of the above-mentioned radionuclides. The (210)Pb and (137)Cs concentrations in the sediment were measured using a gamma spectrometer with a HpGe detector, Gamma-X type. Activities ranging from 41+/-7 to 135+/-34Bq/kg were found for (210)Pb and from 3+/-0.5 to 1054+/-150Bq/kg for (137)Cs. The sediment profile indicates acceleration in sedimentation rate in the last 18 years. Thus, the sedimentation process for the Red Lake can be divided in two periods, the last 18 years, and respectively, the period before that. Using the Constant Rate of (210)Pb Supply method values between 0.18+/-0.04 and 1.85+/-0.5g/cm(2) year (0.32+/-0.08 and 2.83+/-0.7cm/year) were obtained. Considering both periods, an average sedimentation rate of 0.87+/-0.17g/cm(2) year (1.17cm/year) was calculated. Considering an average depth of 5.41m for the lake and the sedimentation rate estimated for the last 18 years, it could be estimated that the lake will disappear in 195 years.

  20. Role of surface vegetation in 210Pb-dating of peat cores.

    PubMed

    Olid, Carolina; Garcia-Orellana, Jordi; Martínez-Cortizas, Antonio; Masqué, Pere; Peiteado, Eva; Sanchez-Cabeza, Joan-Albert

    2008-12-01

    210Pb-dated ombrotrophic peat cores have been widely used to reconstructthe atmospheric fluxes of heavy metals forthe past century. Many of these studies rarely include the overlying vegetation compartment (i.e., the aerial part of vegetation and decayed plant remains) in the analysis although it represents the first layer capturing atmospheric deposition. The aim of this study was to evaluate the radionuclide and Pb content of this biologically active layer in bogs and to assess its implications on the total inventories and the 210Pb-derived chronology. We analyzed two short ombrotrophic peat cores from the same bog (Chao de Lamoso, Galicia, Spain) for 210Pb, artificial radionuclides (137Cs and 241Am), and Pb. The total Pb inventory was underestimated by about 12% when the plant material was not included in the record. The atmospheric origin of 210Pb and the uptake of 137Cs by roots led to significant activities of these radionuclides in the upper layers. Therefore, removing them from the peat record would imply even larger underestimations of the total inventories, ranging from 25% to 36% for 137Cs and from 39% to 49% for 210Pb. In contrast to the chronologies inferred from the constant rate of supply (CRS) model when only peat layers are considered, the 210Pb chronology agreed well with artificial radionuclide dating when surface vegetation was included. These results suggest that an accurate peat chronology requires an initial evaluation of the relevance of plant inventories and emphasizes the need of considering the biologically active layer when atmospheric fluxes of heavy metals and other pollutants are reconstructed.

  1. Mixing and cycling of uranium, thorium and 210Pb in Puget Sound sediments

    NASA Astrophysics Data System (ADS)

    Carpenter, R.; Peterson, M. L.; Bennett, J. T.; Somayajulu, B. L. K.

    1984-10-01

    Activity profiles of excess 234Th, excess 210Pb, 232Th, 230Th, 234U and 238U, and 228/232Th ratios determined in eight box cores of sediment from six sites in central Puget Sound provide new insights into the dynamic nature of solid phase mixing in surface sediments, the exchange of 228Ra and other soluble species across the sediment-water interface, and the cycling of U, Th and 210Pb in this coastal zone. Comparison of excess 234Th inventories in sediments with its production rate in the overlying water column indicates a mean residence time of at most 14 days for particles in the central Puget Sound water column. Surface sediment horizons with excess 234Th have no excess 228Th which might be used to ascertain sediment accumulation rates over the past decade. Instead, deficiencies of 228Th due to loss of soluble 228Ra from pore water to the overlying water persist to 20-30 cm, revealing that exchange of soluble chemicals between pore and overlying waters reaches these depths in the extensively bioturbated sediments of Puget Sound. Solid phase U isotope concentrations tend to increase by up to a factor of two with depth in sediments, as a result of dissolved U being biologically pumped down into sediments where it is partially removed when conditions become mildly reducing. 232Th and 230Th activities and 230/232Th ratios are constant with depth in sediments, indicating constant detrital phase compositions and essentially no authigenic 230Th. Steady state 210Pb depositional activities in and fluxes to Puget Sound sediments average only about onehalf those for sediments of the open Washington coast north of the Columbia River mouth, primarily because of a much lower supply of dissolved 210Pb in sea waters adverting into Puget Sound. Excess 234Th profiles in sediments reveal much more detail about the depth dependency, dynamic nature and recent history of solid phase mixing processes than excess 210Pb profiles. At least six of eight 234Th profiles show that mixing

  2. Trace element fluxes and natural potential risks from 210Pb-dated sediment cores in lacustrine environments at the Central Mexican Plateau.

    PubMed

    Ontiveros-Cuadras, J F; Ruiz-Fernández, A C; Sanchez-Cabeza, J A; Pérez-Bernal, L H; Sericano, J L; Preda, M; Wee Kwong, L Liong; Páez-Osuna, F

    2014-01-15

    The accumulation, enrichment and provenance of selected trace metals (Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, V and Zn) were studied in sediment cores collected from three lakes located in the Central Mexican Plateau, selected on the basis of their contrasting degree of urbanization: Santa Elena Lake, in a rural and remote area; El Tule Lake, in a rural and slightly urbanized area; and Chapala Lake, in a highly urbanized area. Grain size, magnetic susceptibility and sedimentary constituents such as organic carbon, calcium carbonate, as well as major (Al, Fe, Mn) and minor (Ca, Li, Rb, Sr, Th) elements were analyzed to explain the concentration trends of trace metals. Factor analysis (FA) was used to assess the provenance of the trace elements. The highest metal enrichment factor (EF) above natural concentration levels was found at Chapala Lake for Ag (EF = 3.9), although other trace element EF in all lakes was <2.0, indicating slight contamination. However, the concentration levels of Cr and Ni in all lakes, Hg and Zn in Chapala Lake, Cu in El Tule Lake and As in Santa Elena Lake were above international benchmarks for which adverse effects are expected to occur frequently, even for those metals only slightly enriched (e.g. As, Cr). Through FA, the terrigenous contribution was identified as the most important source of trace metals to the three lakes, most likely related to deforestation and erosion of the surrounding areas, followed by atmospheric transport of volcanic ashes, rather than to direct sources.

  3. Dating human skeletal remains using 90Sr and 210Pb: case studies.

    PubMed

    Schrag, Bettina; Uldin, Tanya; Mangin, Patrice; Bochud, François; Froidevaux, Pascal

    2014-01-01

    In legal medicine, the post mortem interval (PMI) of interest covers the last 50 years. When only human skeletal remains are found, determining the PMI currently relies mostly on the experience of the forensic anthropologist, with few techniques available to help. Recently, several radiometric methods have been proposed to reveal PMI. For instance, (14)C and (90)Sr bomb pulse dating covers the last 60 years and give reliable PMI when teeth or bones are available. (232)Th series dating has also been proposed but requires a large amount of bones. In addition, (210)Pb dating is promising but is submitted to diagenesis and individual habits like smoking that must be handled carefully. Here we determine PMI on 29 cases of forensic interest using (90)Sr bomb pulse. In 12 cases, (210)Pb dating was added to narrow the PMI interval. In addition, anthropological investigations were carried out on 15 cases to confront anthropological expertise to the radiometric method. Results show that 10 of the 29 cases can be discarded as having no forensic interest (PMI>50 years) based only on the (90)Sr bomb pulse dating. For 10 other cases, the additional (210)Pb dating restricts the PMI uncertainty to a few years. In 15 cases, anthropological investigations corroborate the radiometric PMI. This study also shows that diagenesis and inter-individual difference in radionuclide uptake represent the main sources of uncertainty in the PMI determination using radiometric methods.

  4. Measurements of210Pb,137Cs, organic carbon and trace elements in sediments of the Illinois and Mississippi rivers

    USGS Publications Warehouse

    Cahill, R.A.; Autrey, A.D.

    1987-01-01

    Radiometric dating of sediment accumulations by137Cs and210Pb has been successfully initiated in the Illinois and Mississippi Rivers. Sedimentation rates measured at 13 locations range from 0.7 to 3.6 cm/y. Chemical analysis has been completed for up to 45 major and trace elements in core samples. The upper Illinois River contains higher metal levels than the Mississippi River. The amount of carbon (energy) lost to sediments in large floodplain rivers is estimated between 370 and 4000 g/m2/y. ?? 1987 Akade??miai Kiado??.

  5. Dilution of /sup 210/Pb by organic sedimentation in lakes of different trophic states, and application to studies of sediment-water interactions

    SciTech Connect

    Binford, M.W.; Brenner, M.

    1986-05-01

    Lake sediments reflect conditions in the water column and can be used for rapid, integrative measurements of limnological variables. Examination of /sup 210/Pb-dated cores from 12 Florida lakes of widely differing trophic state (expressed as Carlson's trophic state index: TSI) shows that net accumulation rate of organic matter is related to primary productivity in the water column. In 26 other lakes the activity of unsupported /sup 210/Pb g/sup -1/ organic matter in surficial sediments is inversely related to trophic state and, therefore, to organic accumulation rate. From this observation, the authors develop a new method that uses fallout /sup 210/Pb as a dilution tracer to calculate net sedimentary accumulation rates of any material in surface mud. They demonstrate strong relationships between net loss rate of biologically important materials (C, N, P, and pigments) and their respective water concentrations (expressed as TSI). Multiple regression models incorporating net sediment accumulation rates of all four variables explain up to 70% of the lake-to-lake variation of TSI. The /sup 210/Pb-dilution method has application for studies for material cycling, paleolimnology, and sediment accumulation processes.

  6. Transport and sediment accumulation of sup 210 Pb and sup 137 Cs in two southeast Alaskan fjords

    SciTech Connect

    Sugai, S.F. )

    1991-05-01

    Sediment profiles of {sup 210}Pb and {sup 137}Cs in cores collected at increasing distances form the heads of Smeaton Bay and Boca de Quadra fjords indicate that watersheds influence the inventories of radioisotopes present and that the steep topographies of the fjords enhance sediment redistribution. Episodic deposition of terrestrially derived sediment was responsible for roughly 50% of the {sup 137}Cs and 45% of the {sup 210}Pb inventories in shallower (less than 180 m) locations in Wilson and Bakewell arms of Smeaton Bay. {sup 210}Pb sedimentation rates at shallower sites when corrected for episodic deposition were less than sedimentation rates obtained in the deep basins of the fjords where sediment focusing and increased primary productivity in the overlaying water column occur. Higher fluxes of dissolved Mn from surficial sediments and subsequent reoxidation in the overlying water may have enhanced scavenging of {sup 210}Pb in basin locatons resulting in higher inventories. Episodic events have occured frequently in Smeaton Bay and Boca de Quadra suggesting that steady-state conditions with respect to sedimenting particles can be achieved only when averaged over long time periods approaching the time over which {sup 137}Cs and {sup 210}Pb are useful.

  7. 210Pb method for estimating the rate of carbonate sand sedimentation

    USGS Publications Warehouse

    Holmes, Charles W.

    1981-01-01

    The plot of 210Pb activity against depth in carbonate sands on the Virgin Island Bank is a negative asymmetric hyperbolic curve. As depth increases, an initial rapid decrease in 210Pb activity caused by the decay of unsupported 210Pb and 226Ra is followed by increasing activity as a result of 210Pb achieving equilibrium with in growing 230Th. As this curve is time dependent, an estimate of the relative ages in carbonate sequences and the rates of net carbonate accumulation can be made. The ease of 210Pb activity determinations makes this procedure an attractive method in obtaining carbonate sand accumulation rates.

  8. River-plume sedimentation and 210Pb/7Be seabed delivery on the Mississippi River delta front

    NASA Astrophysics Data System (ADS)

    Keller, Gregory; Bentley, Samuel J.; Georgiou, Ioannis Y.; Maloney, Jillian; Miner, Michael D.; Xu, Kehui

    2016-10-01

    To constrain the timing and processes of sediment delivery and submarine mass-wasting events spanning the last few decades on the Mississippi River delta front, multi-cores and gravity cores (0.5 and <3 m length respectively) were collected seaward of the Mississippi River Southwest Pass in 25-75 m water depth in 2014. The cores were analyzed for radionuclide activity (7Be, 210Pb, 137Cs), grain size, bulk density, and fabric (X-radiography). Core sediments are faintly bedded, sparsely bioturbated, and composed mostly of clay and fine silt. Short-term sedimentation rates (from 7Be) are 0.25-1.5 mm/day during river flooding, while longer-term accumulation rates (from 210Pb) are 1.3-7.9 cm/year. In most cores, 210Pb activity displays undulatory profiles with overall declining activity versus depth. Undulations are not associated with grain size variations, and are interpreted to represent variations in oceanic 210Pb scavenging by river-plume sediments. The 210Pb profile of one gravity core from a mudflow gully displays uniform basal excess activity over a zone of low and uniform bulk density, interpreted to be a mass-failure event that occurred 9-18 years before core collection. Spatial trends in sediment deposition (from 7Be) and accumulation (from 210Pb) indicate that proximity to the river mouth has stronger influence than local facies (mudflow gully, depositional lobe, prodelta) over the timeframe and seabed depth represented by the cores (<40 years, <3 m length). This may be explained by rapid proximal sediment deposition from river plumes coupled with infrequent tropical cyclone activity near the delta in the last 7 years (2006-2013), and by the location of most sediment failure surfaces (from mass flows indicated by parallel geophysical studies) deeper than the core-sampling depths of the present study.

  9. Distribution of (226)Ra-(210)Pb-(210)Po in marine biota and surface sediments of the Red Sea, Sudan.

    PubMed

    Sirelkhatim, D A; Sam, A K; Hassona, R K

    2008-12-01

    Activity concentration levels and ratios of (226)Ra, (210)Pb and (210)Po are presented in multicellular marine algae, molluscs, coral as well as in surface marine sediments collected from the shallower waters of the fringing reefs area extending towards north and south (Flamingo bay) of PortSudan harbour, Sudan. The analyses were performed adopting alpha-spectrometry, liquid scintillation and Cerenkov counting techniques. Surface sediments from this coastal region are poor in their radioactivity content in contrast to similar data reported from different coastal areas around the globe. There is surface enrichment of (210)Pb and (210)Po with respect to their progenitor (226)Ra as it is evident from the activity ratios of (210)Pb/(226)Ra (3.03+/-1.79) and (210)Po/(226)Ra (2.23+/-1.56). Among marine plants and animals investigated, the green algae species, Halimeda, and coral species, Favites, show substantial concentration of radium at 8.2Bq/kg and 21.9Bq/kg dry weight, respectively. Similarly, the highest concentration of (210)Po was met in Favites at 38.7Bq/kg followed by brown algae, Cystoseria sp., at 32.6Bq/kg. There is no variation seen among algal species for (210)Pb uptake, however, converse to radium and polonium, Favites (coral) was found to contain the minimum concentration of lead (3.88Bq/kg). In most species there is preferential accumulation of polonium over its parent radium as indicated by (210)Po:(226)Ra activity ratio with Cystoseria (brown algae) showing the highest value at 8.81. On the other hand, (210)Po:(210)Pb activity concentration ratio revealed that coral species Favites (9.97) and the brown algae Sargassum (1.85) have a greater tendency to accumulate (210)Po over (210)Pb, while in the rest of species; this ratio is less than unity.

  10. 210Pb chronology and trace metal geochemistry in the intertidal sediment of Qinjiang River estuary, China

    NASA Astrophysics Data System (ADS)

    Xia, Peng; Meng, Xianwei; Feng, Aiping; Yin, Ping; Wang, Xiangqin; Zhang, Jun

    2012-06-01

    Historical records of metal inputs were studied by using a sediment core collected from a sand-rich mudflat in the Qinjiang River estuary, China. 210Pb chronology was used to reconstruct the fluxes of Hg, Cu, Pb, Zn, Cd, Cr and As to the core site during the last 86 years. Based on the constant initial concentration model, the sedimentation rates are 1.18 cm year-1 in the top 30 cm sandy layer and 0.92 cm year-1 in the muddy bottom layer. To compensate for grain-size and mineralogy effects on metal concentrations, aluminum was used as the normalizing element. The enrichment factors ( EF) indicate that the natural inputs had prevailed up to the early 1980s. After this period, the intensity of human activities has resulted in continual increasing trend of metals towards the surface. Recent sediment samples from the Qinjiang River estuary are found moderately enriched by Cd ( EF>1.5) and slightly enriched by other metals ( EF<1.5). Considering that the drainage area of the Qinjiang River is mostly agricultural land, the increased Cd may be due to the usage of fertilizers and pesticides in agricultural activities and the combustion of fossil fuels.

  11. Examining (239+240)Pu, (210)Pb and historical events to determine carbon, nitrogen and phosphorus burial in mangrove sediments of Moreton Bay, Australia.

    PubMed

    Sanders, Christian J; Santos, Isaac R; Maher, Damien T; Breithaupt, Joshua L; Smoak, Joseph M; Ketterer, Michael; Call, Mitchell; Sanders, Luciana; Eyre, Bradley D

    2016-01-01

    Two sediment cores were collected in a mangrove forest to construct geochronologies for the previous century using natural and anthropogenic radionuclide tracers. Both sediment cores were dated using (239+240)Pu global fallout signatures as well as (210)Pb, applying both the Constant Initial Concentration (CIC) and the Constant Rate of Supply (CRS) models. The (239+240)Pu and CIC model are interpreted as having comparable sediment accretion rates (SAR) below an apparent mixed region in the upper ∼5 to 10 cm. In contrast, the CRS dating method shows high sediment accretion rates in the uppermost intervals, which is substantially reduced over the lower intervals of the 100-year record. A local anthropogenic nutrient signal is reflected in the high total phosphorus (TP) concentration in younger sediments. The carbon/nitrogen molar ratios and δ(15)N values further support a local anthropogenic nutrient enrichment signal. The origin of these signals is likely the treated sewage discharge to Moreton Bay which began in the early 1970s. While the (239+240)Pu and CIC models can only produce rates averaged over the intervals of interest within the profile, the (210)Pb CRS model identifies elevated rates of sediment accretion, organic carbon (OC), nitrogen (N), and TP burial from 2000 to 2013. From 1920 to 2000, the three dating methods provide similar OC, N and TP burial rates, ∼150, 10 and 2 g m(-2) year(-1), respectively, which are comparable to global averages.

  12. Dating human skeletal remains using a radiometric method: biogenic versus diagenetic 90Sr and 210Pb in vertebrae.

    PubMed

    Schrag, Bettina; Uldin, Tanya; Mangin, Patrice; Froidevaux, Pascal

    2012-07-10

    In forensic science, there is a strong interest in determining the post-mortem interval (PMI) of human skeletal remains up to 50 years after death. Currently, there are no reliable methods to resolve PMI, the determination of which relies almost exclusively on the experience of the investigating expert. Here we measured (90)Sr and (210)Pb ((210)Po) incorporated into bones through a biogenic process as indicators of the time elapsed since death. We hypothesised that the activity of radionuclides incorporated into trabecular bone will more accurately match the activity in the environment and the food chain at the time of death than the activity in cortical bone because of a higher remodelling rate. We found that determining (90)Sr can yield reliable PMI estimates as long as a calibration curve exists for (90)Sr covering the studied area and the last 50 years. We also found that adding the activity of (210)Po, a proxy for naturally occurring (210)Pb incorporated through ingestion, to the (90)Sr dating increases the reliability of the PMI value. Our results also show that trabecular bone is subject to both (90)Sr and (210)Po diagenesis. Accordingly, we used a solubility profile method to determine the biogenic radionuclide only, and we are proposing a new method of bone decontamination to be used prior to (90)Sr and (210)Pb dating.

  13. The sediment budget of an urban coastal lagoon (Jamaica Bay, NY) determined using 234Th and 210Pb

    NASA Astrophysics Data System (ADS)

    Renfro, Alisha A.; Cochran, J. Kirk; Hirschberg, David J.; Bokuniewicz, Henry J.; Goodbred, Steven L.

    2016-10-01

    The sediment budget of Jamaica Bay (New York, USA) has been determined using the natural particle-reactive radionuclides 234Th and 210Pb. Inventories of excess thorium-234 (234Thxs, half-life = 24.1 d) were measured in bottom sediments of the Bay during four cruises from September 2004 to July 2006. The mean bay-wide inventory for the four sampling periods ranged from 3.5 to 5.0 dpm cm-2, four to six times that expected from 234Th production in the overlying water column. The presence of dissolved 234Th and a high specific activity of 234Thxs on particles at the bay inlet (∼30 dpm g-1) indicated that both dissolved and particulate 234Th could be imported into the bay from the ocean. Based on these observations, a mass balance of 234Th yields an annual input of ∼39 ± 14 × 1010 g sediment into the bay. Mass accumulation rates determined from profiles of excess 210Pb (half-life = 22.3 y) in sediment cores require annual sediment import of 7.4 ± 4.5 × 1010 g. Both radionuclides indicate that there is considerable marine-derived sediment import to Jamaica Bay, consistent with earlier work using 210Pb. Such sediment input may be important in sustaining longer-term accretion rates of salt marshes in the bay.

  14. Pu, 137Cs and excess 210Pb in Russian Arctic sediments

    NASA Astrophysics Data System (ADS)

    Baskaran, M.; Asbill, Shaunna; Santschi, Peter; Brooks, James; Champ, Michael; Adkinson, Dan; Colmer, Matthew R.; Makeyev, Vyacheslav

    1996-05-01

    The activity ratios of Pu and radiocesium isotopes have been used to delineate the major sources (such as global and close-in (debris) fallout, nuclear fuel reprocessing and fabrication plant effluents) in the environment. We have measured 238Pu, 239,240Pu, 137Cs, and excess 210Pb concentrations in 107 surficial sediments as well as in 5 sediment cores collected in the summer months of 1993 and 1994 from the Ob and Yenisey Rivers (Russia) and the Kara sea. A comparison of the sediment core inventories of 239,240Pu and 137Cs, along with the 238Pu/ 239,240Pu activity ratios, with those expected from global fallout allows us to estimate the relative amounts, if any, of reactor-derived 238Pu and 239,240Pu from the dumped reactor sites in the study area. In surficial sediment samples collected in 1993 and 1994, the 239,240Pu concentrations varied between 4.2 and 856 mBq kg -1, with a mean of 239 mBq kg -1. In samples with a measurable 238Pu, the 238Pu/ 239,240Pu activity ratios varied between 0.010 and 0.069, with an average value of 0.035 ± 0.014. This range can be compared to the average 238Pu/ 239,240Pu activity ratio of 0.030 for the year 1993 from nuclear weapons testing and SNAP fallout obtained from soil studies, indicating very little (≤ 5%) additional sources of 238Pu to the sediments in the study area. The inventories of Pu in the 5 sediment cores from the study area varied between 2.67 ± 0.67 and 24.5 ± 2.2 Bq m -2 with a mean value of 8.83 Bq m -2. The 137Cs concentrations in the upper 3 cm of the sediments varied between below detection limit to 71.4 Bq kg -1, with a mean of 14.9 Bq kg -1. The 137Cs inventories in the 5 sediment cores varied between 156.7 ± 28.3 and 1600 ± 153.3 Bq m -2, with a mean value of 583.3 Bq m -2. The mean ratio of inventories of Pu to that of 137Cs, 0.015, is comparable to the values in other places in the Arctic region. There is a significant correlation between total organic carbon and concentrations of 137Cs, 239,240Pu

  15. Bioturbation depths, rates and processes in Massachusetts Bay sediments inferred from modeling of 210Pb and 239 + 240Pu profiles

    USGS Publications Warehouse

    Crusius, John; Bothner, Michael H.; Sommerfield, Christopher K.

    2004-01-01

    Profiles of 210Pb and 239 + Pu from sediment cores collected throughout Massachusetts Bay (water depths of 36-192 m) are interpreted with the aid of a numerical sediment-mixing model to infer bioturbation depths, rates and processes. The nuclide data suggest extensive bioturbation to depths of 25-35 cm. Roughly half the cores have 210Pb and 239 + 240Pu profiles that decrease monotonically from the surface and are consistent with biodiffusive mixing. Bioturbation rates are reasonably well constrained by these profiles and vary from ~0.7 to ~40 cm2 yr-1. As a result of this extensive reworking, however, sediment ages cannot be accurately determined from these radionuclides and only upper limits on sedimentation rates (of ~0.3 cm yr-1) can be inferred. The other half of the radionuclide profiles are characterized by subsurface maxima in each nuclide, which cannot be reproduced by biodiffusive mixing models. A numerical model is used to demonstrate that mixing caused by organisms that feed at the sediment surface and defecate below the surface can cause the subsurface maxima, as suggested by previous work. The deep penetration depths of excess 210Pb and 239 + 240Pu suggest either that the organisms release material over a range of >15 cm depth or that biodiffusive mixing mediated by other organisms is occurring at depth. Additional constraints from surficial sediment 234Th data suggest that in this half of the cores, the vast majority of the present-day flux of recent, nuclide-bearing material to these core sites is transported over a timescale of a month or more to a depth of a few centimeters below the sediment surface. As a consequence of the complex mixing processes, surface sediments include material spanning a range of ages and will not accurately record recent changes in contaminant deposition.

  16. Why would we use the Sediment Isotope Tomography (SIT) model to establish a 210Pb-based chronology in recent-sediment cores?

    PubMed

    Abril Hernández, José-María

    2015-05-01

    After half a century, the use of unsupported (210)Pb ((210)Pbexc) is still far off from being a well established dating tool for recent sediments with widespread applicability. Recent results from the statistical analysis of time series of fluxes, mass sediment accumulation rates (SAR), and initial activities, derived from varved sediments, place serious constraints to the assumption of constant fluxes, which is widely used in dating models. The Sediment Isotope Tomography (SIT) model, under the assumption of non post-depositional redistribution, is used for dating recent sediments in scenarios in that fluxes and SAR are uncorrelated and both vary with time. By using a simple graphical analysis, this paper shows that under the above assumptions, any given (210)Pbexc profile, even with the restriction of a discrete set of reference points, is compatible with an infinite number of chronological lines, and thus generating an infinite number of mathematically exact solutions for histories of initial activity concentrations, SAR and fluxes onto the SWI, with these two last ranging from zero up to infinity. Particularly, SIT results, without additional assumptions, cannot contain any statistically significant difference with respect to the exact solutions consisting in intervals of constant SAR or constant fluxes (both being consistent with the reference points). Therefore, there is not any benefit in its use as a dating tool without the explicit introduction of additional restrictive assumptions about fluxes, SAR and/or their interrelationship.

  17. (210)Pb as a tracer of soil erosion, sediment source area identification and particle transport in the terrestrial environment.

    PubMed

    Matisoff, Gerald

    2014-12-01

    Although (137)Cs has been used extensively to study soil erosion and particle transport in the terrestrial environment, there has been much less work using excess or unsupported (210)Pb ((210)Pbxs) to study the same processes. Furthermore, since (137)Cs activities in soils are decreasing because of radioactive decay, some locations have an added complication due to the addition of Chernobyl-derived (137)Cs, and the activities of (137)Cs in the southern hemisphere are low, there is a need to develop techniques that use (210)Pbxs to provide estimates of rates of soil erosion and particle transport. This paper reviews the current status of (210)Pbxs methods to quantify soil erosion rates, to identify and partition suspended sediment source areas, and to determine the transport rates of particles in the terrestrial landscape. Soil erosion rates determined using (210)Pbxs are based on the unsupported (210)Pb ((210)Pbxs) inventory in the soil, the depth distribution of (210)Pbxs, and a mass balance calibration ('conversion model') that relates the soil inventory to the erosion rate using a 'reference site' at which neither soil erosion nor soil deposition has occurred. In this paper several different models are presented to illustrate the effects of different model assumptions such as the timing, depth and rates of the surface soil mixing on the calculated erosion rates. The suitability of model assumptions, including estimates of the depositional flux of (210)Pbxs to the soil surface and the post-depositional mobility of (210)Pb are also discussed. (210)Pb can be used as one tracer to permit sediment source area identification. This sediment 'fingerprinting' has been extended far beyond using (210)Pb as a single radioisotope to include numerous radioactive and stable tracers and has been applied to identifying the source areas of suspended sediment based on underlying rock type, land use (roads, stream banks, channel beds, cultivated or uncultivated lands, pasture lands

  18. Use of 210Pb/ 226Ra disequilibria in the dating of deep-sea whale falls

    NASA Astrophysics Data System (ADS)

    Schuller, Daniel; Kadko, David; Smith, Craig R.

    2004-02-01

    Deep-sea whale falls, in particular the skeletal remains of whales that have sunk to the seafloor, are remarkable temporary reducing habitats. Reduced chemical species created by anaerobic microbial decay of lipid and organic compounds within the whale bone matrix fuel chemosynthetic-based communities, including bacteria, mussels, limpets, snails, and clams. Many of these species exhibit taxonomic affinities to other chemosynthetic deep-sea organisms colonizing hydrothermal vents and cold seeps. Knowledge of the timescales of whale fall community succession and persistence of these assemblages is needed to reliably estimate the abundance of whale fall habitats and to understand the dynamics of the whale fall communities and their potential roles as stepping stones for sulfophilic species. We have developed a radiochemical method based on 210Pb/ 226Ra disequilibria for estimating the ages of seafloor whale bone communities. Measurements of 210Pb/ 226Ra performed on known age bone samples yielded radioisotope ages in good agreement with the known ages. Our results indicate that this technique is valid for bones 10-85 years old (time since cetacean death). This technique, applied to multiple bones of unknown age whale falls taken from Monterey Canyon, Santa Catalina Basin, and San Nicholas Basin, constrained the upper limit ages of these systems (in 2002) to 6.3±1.0 years, 44.0±7.0 to 53.4±8.3 years, and 66.4±9.6 to 82.6±11 years, respectively. These ages were in reasonable agreement with faunal and/or skeletal observations. In addition, a preliminary lipid degradation rate was calculated for the Santa Catalina Basin whale fall using an independent time series and calibrated to the radiochemically determined age. Both radiochemical and lipid degradation evidence suggest that the whale fall microhabitat is able to support life for many decades.

  19. Bayesian integration of radioisotope dating (210Pb, 137Cs, 241Am, 14C) and an 18-20th century mining history of Brotherswater, English Lake District

    NASA Astrophysics Data System (ADS)

    Schillereff, Daniel; Chiverrell, Richard; Macdonald, Neil; Hooke, Janet; Welsh, Katharine; Piliposyan, Gayane; Appleby, Peter

    2014-05-01

    Lake sediment records are often a useful tool for investigating landscape evolution as geomorphic changes in the catchment are reflected by altered sediment properties in the material transported through the watershed and deposited at the lake bed. Recent research at Brotherswater, an upland waterbody in the Lake District, northwest England, has focused on reconstructing historical floods from their sedimentary signatures and calculating long-term sediment and carbon budgets from fourteen sediment cores extracted from across the basin. Developing accurate chronological control is essential for these tasks. One sediment core (BW11-2; 3.5 m length) from the central basin has been dated using artificial radionuclide measurements (210Pb, 137Cs, 241Am) for the uppermost sediments and radiocarbon (14C) for lower sediments. The core appears to span the past 1500 years, however a number of problems have arisen. We present our explanations for these errors, the independent chronological techniques used to generate an accurate age-depth model for this core and methods for its transferral to the other 13 cores extracted from the basin. Two distinct 137Cs markers, corresponding to the 1986 Chernobyl disaster and 1960s weapons testing, confirm the 210Pb profile for sediment deposition since ~1950, but calculations prior to this appear erroneous, possibly due to a hiatus in the sediment record. We used high-resolution geochemical profiles (measured by XRF) to cross-correlate with a second 210Pb-dated chronology from a more distal location, which returned more sensible results. Unfortunately, the longer 14C sequence exhibits two age-reversals (radiocarbon dates that are too old). We believe the uppermost two dates are erroneous, due to a shift in inflow location as a flood prevention method ~1900 A.D., dated using information from historical maps. The lower age-reversal coincides with greater supply of terrigenous material to the lake (increased Zr, K, Ti concentrations

  20. Solid partitioning and solid-liquid distribution of 210Po and 210Pb in marine anoxic sediments: roads of Cherbourg at the northwestern France.

    PubMed

    Connan, O; Boust, D; Billon, G; Solier, L; Rozet, M; Bouderbala, S

    2009-10-01

    A sequential extraction protocol has been used to determine the solid-phase partition of (210)Po and (210)Pb in anoxic marine sediment from the roads of Cherbourg (France) in the central English Channel. Measurements were also obtained in pore waters, in which (210)Po activities range between 1 and 20 mBq L(-1) and (210)Pb activities between 2.4 and 3.8 mBq L(-1), with highest activities in the topmost layer. These activities are higher than in seawater, suggesting that sediment act as a source of both (210)Po and (210)Pb for overlying water. The (210)Po profile in the pore waters is apparently correlated with those obtained for Fe, Mn and SO(4)(2)(-), suggesting an influence of early diagenetic processes on the (210)Po solid-liquid distribution. In the sediment, (210)Po is predominantly bound to organic matter or chromium reducible sulphides, and residuals (clay minerals and refractory oxides). Our results indicate that (210)Po is not significantly bound to AVS, i.e. acid volatile sulphides: bioturbation could play a role by the early redistribution of (210)Po bound to acid volatile sulphides in the sediment. (210)Po, (210)Pb and Pb exhibit differences in terms of distribution, probably due to a different mode of penetration in the sediment. This work provides information on solid and liquid distribution of (210)Po and (210)Pb in marine sediment. These data are very scarce in the literature.

  1. Floodplain development in engineered and natural settings determined with novel, high resolution 210-Pb geochronology: Insights from sedimentation studies along the lower Sacramento River, California

    NASA Astrophysics Data System (ADS)

    Aalto, R.; Singer, M. B.

    2008-12-01

    This presentation summarizes results from studies of floodplain sedimentation along the middle and lower Sacramento River that investigate processes using a new, high resolution methodology for 210Pb geochronology of 1-5 m floodplain cores. This approach accounts both for grain-size effects and radon ventilation and can resolve both deposition and erosional events. Therefore, it was possible to assess sedimentation over the past century within a wide array of sedimentary environments throughout the Sacramento Valley, where other techniques are limited. In particular, the Sacramento Valley has naturally low 210Pb activity due to its proximity to the Pacific Ocean, high rates of radon ventilation due to dry, porous floodplain sediment, and deposition of widely varying grain sizes - challenges that we have addressed with our enhanced methodology. The analytical approach affords a new ability to assess and directly compare dates and rates of sedimentation and erosion in disparate sedimentary environments throughout this complex fluvial dispersal system. We compare and contrast sediment deposition in engineered floodplains called bypasses, levied ancestral floodplains which serve as floodways during high flow, with sedimentation occurring in some remaining natural floodplains adjacent to the Sacramento River. We find that bypasses tend to accumulate sand and silt at their entrances, but that rates and textures decline rapidly with distance away from the channel. Essentially, a quasi-natural physical process of levee construction by advective overbank transport and deposition of sediment is operating (Singer and Aalto, ESPL, in press). These engineered floodways tend to siphon sediment out of the active channel, such that relatively low sedimentation rates prevail in floodplains and oxbow lakes within the active meander corridor that is bypassed. However, we document significant accumulation of fine-grained material in sedimentary sinks throughout floodplains upstream

  2. Use of 210Pb and 137Cs to simultaneously constrain ages and sources of post-dam sediments in the Cordeaux reservoir, Sydney, Australia.

    PubMed

    Simms, Ava D; Woodroffe, Colin; Jones, Brian G; Heijnis, Henk; Mann, Rob A; Harrison, Jennifer

    2008-07-01

    Environmental radionuclides can be employed as tracers of sediment movement and delivery to water bodies such as lakes and reservoirs. The chronologies of sediments that have accumulated in the Cordeaux reservoir in Sydney, Australia, were determined by the rate of change of (210)Pb(ex) with depth and indicate slow accretion in the reservoir. The ratio of enrichment of radionuclides in sediment cores to (210)Pb(ex) and (137)Cs concentrations in a reference soil sample within the Cordeaux catchment indicates that the dominant source of sediment in the Cordeaux reservoir is surface erosion (detachment and removal of sediment at depths less than 30 cm). However, in the Kembla Creek arm of the reservoir a mixture of sources was detected and includes sheet and rill erosion together with sub-soil contributions. Implications for the utility of these radionuclide sedimentation assessments, especially where samples are limited, are that well-constrained chronologies and sources of soil erosion are facilitated.

  3. Sediment accumulation, stratigraphic order, and the extent of time-averaging in lagoonal sediments: a comparison of 210Pb and 14C/amino acid racemization chronologies

    NASA Astrophysics Data System (ADS)

    Kosnik, Matthew A.; Hua, Quan; Kaufman, Darrell S.; Zawadzki, Atun

    2015-03-01

    Carbon-14 calibrated amino acid racemization (14C/AAR) data and lead-210 (210Pb) data are used to examine sediment accumulation rates, stratigraphic order, and the extent of time-averaging in sediments collected from the One Tree Reef lagoon (southern Great Barrier Reef, Australia). The top meter of lagoonal sediment preserves a stratigraphically ordered deposit spanning the last 600 yrs. Despite different assumptions, the 210Pb and 14C/AAR chronologies are remarkably similar indicating consistency in sedimentary processes across sediment grain sizes spanning more than three orders of magnitude (0.1-10 mm). Estimates of long-term sediment accumulation rates range from 2.2 to 1.2 mm yr-1. Molluscan time-averaging in the taphonomically active zone is 19 yrs, whereas below the depth of final burial (~15 cm), it is ~110 yrs/5 cm layer. While not a high-resolution paleontological record, this reef lagoon sediment is suitable for paleoecological studies spanning the period of Western colonization and development. This sedimentary deposit, and others like it, should be useful, albeit not ideal, for quantifying anthropogenic impacts on coral reef systems.

  4. High-resolution historical records from Pettaquamscutt River basin sediments: 1. 210Pb and varve chronologies validate record of 137Cs released by the Chernobyl accident

    NASA Astrophysics Data System (ADS)

    Lima, Ana Lúcia; Hubeny, J. Bradford; Reddy, Christopher M.; King, John W.; Hughen, Konrad A.; Eglinton, Timothy I.

    2005-04-01

    Cesium-137 derived from the explosion of the Chernobyl reactor in 1986 was preserved in anoxic sediments from a coastal environment in southern Rhode Island. Although the radioactive plume was detected in surface air samples at several locations in the United States, this is the first known record of a Chernobyl 137Cs peak in sediments from North America. The inventory of Chernobyl 137Cs that was preserved in the Pettaquamscutt River is small compared to European counterparts and should only be detectable for the next 15-20 yr. However, the presence of two 137Cs peaks (1963 and 1987) identifies a well-dated segment of the sediment column that could be exploited in understanding the decomposition and preservation of terrestrial and aquatic organic matter. Different methods for calculating the 210Pb chronology were also evaluated in this study and checked against independent varve counting. The end result is a detailed chronology of a site well suited for reconstruction of historical records of environmental change.

  5. Recent atmospheric lead deposition recorded in an ombrotrophic peat bog of Great Hinggan Mountains, Northeast China, from 210Pb and 137Cs dating.

    PubMed

    Bao, K; Xia, W; Lu, X; Wang, G

    2010-09-01

    Radioactive markers are useful in dating lead deposition patterns from industrialization in peat archive. Peat cores were collected in an ombrotrophic peat bog in the Great Hinggan Mountains in Northeast China in September 2008 and dated using (210)Pb and (137)Cs radiometric techniques. The mosses in both cores were examined systematically for dry bulk density, water and ash content. Lead also was measured using atomic emission spectroscopy with inductively coupled plasma (ICP-AES). Both patterned peat profiles were preserved well without evident anthropogenic disturbance. Unsupported (210)Pb and (137)Cs decreased with the depth in both of the two sample cores. The (210)Pb chronologies were established using the constant rate of supply model (CRS) and are in good agreement with the (137)Cs time marker. Recent atmospheric (210)Pb flux in Great Hinggan Mountains peat bog was estimated to be 337 Bq m(-2)y(-1), which is consistent with published data for the region. Lead deposition rate in this region was also derived from these two peat cores and ranged from 24.6 to 55.8 mg m(-2)y(-1) with a range of Pb concentration of 14-262 microg g(-1). The Pb deposition patterns were consistent with increasing industrialization over the last 135-170 y, with a peak of production and coal burning in the last 50 y in Northeast China. This work presents a first estimation of atmospheric Pb deposition rate in peatlands in China and suggests an increasing trend of environmental pollution due to anthropogenic contaminants in the atmosphere. More attention should be paid to current local pollution problems, and society should take actions to seek a balance between economic development and environmental protection.

  6. (210)Pb, (137)Cs and (7)Be in the sediments of coastal lakes on the polish coast: Implications for sedimentary processes.

    PubMed

    Woszczyk, Michał; Poręba, Grzegorz; Malinowski, Łukasz

    2017-04-01

    In this study we combined radioisotopes ((210)Pb, (137)Cs and (7)Be) and hydrodynamic modeling to investigate sedimentary processes in three coastal lakes on the Polish Baltic coast. The research aimed at establishing the depth of sediment mixing and its effects on sediment geochemistry as well as showing the relationship between lake water salinity and radionuclide distribution in the sediment cores. We established that the intensity of mixing displayed appreciable variability throughout the lakes and the thickness of sediment mixing layer was between <2 and 22 cm. The mixing was primarily due to wind-induced waves. The vertical mixing was shown to shift sulfidation of the sediments towards deeper layers. We found that the distributions of radioisotopes, (137)Cs in particular, in the sediment cores from coastal lakes were strongly affected by the early diagenetic processes, which caused diffusive migration of radionuclides. The inventories of (210)Pbex and (137)Cs in the lakes were positively related to salinity. The high inventories of both isotopes (3.2-10.9 kBq ·m(-2) for (210)Pbex and 3.0-6.0 kBq·m(-2) for (137)Cs) in coastal lakes were explained by enhanced sedimentation within estuarine mixing zone and delivery of "additional" (210)Pb and (137)Cs to the lakes during saltwater ingressions. The results of this study have implications for the paleolimnology, sedimentology and biogeochemistry of coastal lakes.

  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. Sediment chronology in San Francisco Bay, California, defined by 210Pb, 234Th, 137Cs, and 239,340Pu

    USGS Publications Warehouse

    Fuller, C.C.; van Geen, Alexander; Baskaran, M.; Anima, R.

    1999-01-01

    Sediment chronologies based on radioisotope depth profiles were developed at two sites in the San Francisco Bay estuary to provide a framework for interpreting historical trends in organic compound and metal contaminant inputs. At Richardson Bay near the estuary mouth, sediments are highly mixed by biological and/or physical processes. Excess  penetration ranged from 2 to more than 10 cm at eight coring sites, yielding surface sediment mixing coefficients ranging from 12 to 170 cm2/year. At the site chosen for contaminant analyses, excess  activity was essentially constant over the upper 25 cm of the core with an exponential decrease below to the supported activity between 70 and 90 cm. Both  and  penetrated to 57-cm depth and have broad subsurface maxima between 33 and 41 cm. The best fit of the excess  profile to a steady state sediment accumulation and mixing model yielded an accumulation rate of 0.825 g/cm2/year (0.89 cm/year at sediment surface), surface mixing coefficient of 71 cm2/year, and 33-cm mixed zone with a half-Gaussian depth dependence parameter of 9 cm. Simulations of  and  profiles using these parameters successfully predicted the maximum depth of penetration and the depth of maximum  and  activity. Profiles of successive 1-year hypothetical contaminant pulses were generated using this parameter set to determine the age distribution of sediments at any depth horizon. Because of mixing, sediment particles with a wide range of deposition dates occur at each depth. A sediment chronology was derived from this age distribution to assign the minimum age of deposition and a date of maximum deposition to a depth horizon. The minimum age of sediments in a given horizon is used to estimate the date of first appearance of a contaminant from its maximum depth of penetration. The date of maximum deposition is used to estimate the peak year of input for a contaminant from the depth interval with the highest concentration of that contaminant

  9. Atmospheric residence time of (210)Pb determined from the activity ratios with its daughter radionuclides (210)Bi and (210)Po.

    PubMed

    Semertzidou, P; Piliposian, G T; Appleby, P G

    2016-08-01

    The residence time of (210)Pb created in the atmosphere by the decay of gaseous (222)Rn is a key parameter controlling its distribution and fallout onto the landscape. These in turn are key parameters governing the use of this natural radionuclide for dating and interpreting environmental records stored in natural archives such as lake sediments. One of the principal methods for estimating the atmospheric residence time is through measurements of the activities of the daughter radionuclides (210)Bi and (210)Po, and in particular the (210)Bi/(210)Pb and (210)Po/(210)Pb activity ratios. Calculations used in early empirical studies assumed that these were governed by a simple series of equilibrium equations. This approach does however have two failings; it takes no account of the effect of global circulation on spatial variations in the activity ratios, and no allowance is made for the impact of transport processes across the tropopause. This paper presents a simple model for calculating the distributions of (210)Pb, (210)Bi and (210)Po at northern mid-latitudes (30°-65°N), a region containing almost all the available empirical data. By comparing modelled (210)Bi/(210)Pb activity ratios with empirical data a best estimate for the tropospheric residence time of around 10 days is obtained. This is significantly longer than earlier estimates of between 4 and 7 days. The process whereby (210)Pb is transported into the stratosphere when tropospheric concentrations are high and returned from it when they are low, significantly increases the effective residence time in the atmosphere as a whole. The effect of this is to significantly enhance the long range transport of (210)Pb from its source locations. The impact is illustrated by calculations showing the distribution of (210)Pb fallout versus longitude at northern mid-latitudes.

  10. Radionuclides (210Po and 210Pb) and Some Heavy Metals in Fish and Sediments in Lake Bafa, Turkey, and the Contribution of 210Po to the Radiation Dose

    PubMed Central

    Manav, Ramazan; Uğur Görgün, Aysun; Filizok, Işık

    2016-01-01

    The pollution level of Lake Bafa was investigated by collecting fish samples {Dicentrarchus labrax (sea bass), Liza ramada (mullet) and Anguilla anguilla (eel)}, surface sediment, and core samples. In all these samples, 210Po and 210Pb concentrations were estimated, and total annual dose rates were obtained for each species. Some heavy metal (Cr, Ni, Pb, Cd, Mn, Fe, and Zn) concentration levels were obtained for the fish and a core sample. The sediment mass accumulation rate was found to be 3.27 g·m−2·day−1 (0.119 g·cm−2·y−1) from a core sample. The heavy metal concentrations in the vertical profile of samples from the core were also observed. The measured concentration of Zn, Pb, Cd, and Cr were between the ERL (effects range low) and ERM (effects range median) limits, while Ni concentrations were higher than the ERM limit. The observed concentrations of Cd, Pb, and Zn in fish samples did not exceed the limits in accordance with Turkish Food Regulations. Further, the maximum effective dose equivalent of 210Po in the area was found to be 1.169 µSv·y−1. PMID:27834886

  11. 210Po-210Pb Dating and U-Series Disequilibria of a Young Basaltic Flow at 10° 44'N EPR

    NASA Astrophysics Data System (ADS)

    van der Zander, I.; Rubin, K. H.; Zierenberg, R. A.; Voight, J. R.; von Damm, K.; McClain, J.

    2004-12-01

    Divers in the submersible Alvin observed and sampled a very young appearing lava flow at 10° 44'N on the East Pacific Rise (EPR) during a November 2003 biodiversity-funded dive series (DEB-0072695 to J.R. Voight) to the area. The occurrence of the glassy, unsedimented, low-lying graben filling lava flow was unexpected on this magma-starved ridge segment just north of the Clipperton Transform Fault and so 3 dives were used to investigate a 4 km long segment of the flow. Measurements (in progress) of 210Po-210Pb disequilibrium in 4 samples of this lava flow confirm that it is likely extremely young (0-2 months old when the samples were collected). Such age dating is critical here because although this area of the EPR is covered by the SOSUS hydrophone array, data are not available in real time and will not be downloaded until November 2004. The 210Po-210Pb geochronometer (T1/2 =138.4 d) involves a time series of 3 or 4 210Po analyses over the course of 1 year or more, so that our analyses are still ongoing (just 2 data per sample so far) and our results quite preliminary. By meeting time we will have better constrained eruption ages with the addition of more data to the ingrowth curves. Results of other chemical analyses on these same samples are being used to compositionally characterize the lavas and to constrain magmatic process timescales. All 13 of the lavas sampled in Nov 2003 are low MgO (6.5-6.7 wt%) basalts, displaying inter-sample compositional variations (lava flow heterogeneity) at the higher end of the known MORB flow catalogue, in contrast to mafic (8 wt% MgO) and compositionally homogeneous lava flows erupted at the nearby and well-studied 9° 50'N EPR site. 230Th-238U disequilibria in the young 10° 44'N flow clusters around 14-15% 230Th-excesses, which overlaps the high end of the data range from "zero-age" MORB flows at 9° 50'N EPR and the Juan De Fuca Ridge (JDF). Slightly higher excesses, lower (230Th/232Th ), and higher Th/U ratios (2

  12. Radiometric dating of sediment cores from a hydrothermal vent zone off Milos Island in the Aegean Sea.

    PubMed

    Ugur, Aysun; Miquel, Juan-Carlos; Fowler, Scott W; Appleby, Peter

    2003-05-20

    Sediment cores from a hydrothermal vent zone off Milos Island in the Aegean Sea were dated using the 210Pb method. The average unsupported 210Pb inventory in the cores was calculated to be 3256 Bq m(-2). The corresponding mean annual 210Pb flux of 105 Bq m(-2) year(-1) is comparable to estimates of the atmospheric flux given in the literature. 210Pb fluxes calculated from the unsupported 210Pb inventories in cores are also comparable with the 210Pb vertical fluxes determined from settling particles off the coast of Milos Island. The highest unsupported 210Pb concentrations (89 Bq kg(-1)) were measured in the sediments nearest to the hydrothermal vent area suggesting that the sedimentation rate is lowest at this site. Direct gamma measurements of 210Pb were used to date three sediment cores that are located at different distances from the vent zone: one is in the immediate vicinity of the vent; and others are outside the zone. Sedimentation rates for these cores, calculated using the CRS and CIC models, ranged from 0.088+/-0.008 cm year(-1) to 0.14+/-0.01 cm year(-1). Where both models were applicable, the results given by the two methods were in good agreement. 137Cs concentrations in all three cores generally declined with depth but showed no clear signal of either the period of maximum fallout from weapons testing or the Chernobyl accident. 210Po activities were also measured and the maximum 210Po concentration was in the sediment surface layer (166 Bq kg(-1)).

  13. Effects of grain size, mineralogy, and acid-extractable grain coatings on the distribution of the fallout radionuclides 7Be, 10Be, 137Cs, and 210Pb in river sediment

    NASA Astrophysics Data System (ADS)

    Singleton, Adrian A.; Schmidt, Amanda H.; Bierman, Paul R.; Rood, Dylan H.; Neilson, Thomas B.; Greene, Emily Sophie; Bower, Jennifer A.; Perdrial, Nicolas

    2017-01-01

    Grain-size dependencies in fallout radionuclide activity have been attributed to either increase in specific surface area in finer grain sizes or differing mineralogical abundances in different grain sizes. Here, we consider a third possibility, that the concentration and composition of grain coatings, where fallout radionuclides reside, controls their activity in fluvial sediment. We evaluated these three possible explanations in two experiments: (1) we examined the effect of sediment grain size, mineralogy, and composition of the acid-extractable materials on the distribution of 7Be, 10Be, 137Cs, and unsupported 210Pb in detrital sediment samples collected from rivers in China and the United States, and (2) we periodically monitored 7Be, 137Cs, and 210Pb retention in samples of known composition exposed to natural fallout in Ohio, USA for 294 days. Acid-extractable materials (made up predominately of Fe, Mn, Al, and Ca from secondary minerals and grain coatings produced during pedogenesis) are positively related to the abundance of fallout radionuclides in our sediment samples. Grain-size dependency of fallout radionuclide concentrations was significant in detrital sediment samples, but not in samples exposed to fallout under controlled conditions. Mineralogy had a large effect on 7Be and 210Pb retention in samples exposed to fallout, suggesting that sieving sediments to a single grain size or using specific surface area-based correction terms may not completely control for preferential distribution of these nuclides. We conclude that time-dependent geochemical, pedogenic, and sedimentary processes together result in the observed differences in nuclide distribution between different grain sizes and substrate compositions. These findings likely explain variability of measured nuclide activities in river networks that exceeds the variability introduced by analytical techniques as well as spatial and temporal differences in erosion rates and processes. In short, we

  14. Inventories of 239+240Pu, 137Cs, and excess 210Pb in sediments from freshwater and brackish lakes in Rokkasho, Japan, adjacent to a spent nuclear fuel reprocessing plant.

    PubMed

    Ueda, Shinji; Ohtsuka, Yoshihito; Kondo, Kunio; Hisamatsu, Shun'ichi

    2009-10-01

    We investigated the vertical profiles of (239+240)Pu, (137)Cs, and excess (210)Pb ((210)Pb(ex)) in sediment core samples obtained from two freshwater lakes and two brackish lakes situated near the first commercial spent nuclear fuel reprocessing plant in Rokkasho, Japan, before the final test of the plant using actual spent nuclear fuel. The inventory of (239+240)Pu in those lakes was larger than that in soil in Rokkasho, which indicated the inflow of (239+240)Pu from the catchment area in addition to direct deposition on the lake surfaces. The (137)Cs inventory in sediments of the brackish lakes was lower than that in the soil, which showed that part of the (137)Cs was removed from the sediments by the brackish water or that it was not deposited into the sediments, because of the high solubility of Cs in brackish water. The (137)Cs inventory in sediments of the freshwater lakes was higher than that of the brackish lakes, and comparable with that in soil except for one core sample out of four. The (239+240)Pu/(137)Cs ratio in freshwater lake sediments was higher than that in soil, and that indicated that part of the (137)Cs was lost from the sediments. The low inventory of (137)Cs may be attributable to competition for absorption sites in sediments with ammonium ions formed in the reducing environment which occurs from summer to fall in the sediments. Those data will be used as background data on the artificial radionuclides in the lakes to assess the effect of released radionuclides on their concentrations.

  15. Mobility and diagenesis of Pb and sup 210 Pb in peat

    SciTech Connect

    Urban, N.R.; Eisenreich, S.J. ); Grigal, D.F. ); Schurr, K.T. )

    1990-12-01

    Peatlands long have been considered to preserve the record of atmospheric deposition of anthropogenic contaminants such as Pb. In the past two decades, {sup 210}Pb has been widely used to data recent strata of peat and to calculate accumulation rates. The assumption that Pb and {sup 210}Pb are immobile and not subject to diagenesis in peat has been questioned but not rigorously tested. The authors attempted to determine if Pb is mobile in peatlands and if Pb profiles are altered by diagenic processes by constructing a mass balance for Pb about a small peatland, by comparing inventories, concentrations, and accumulation rates of Pb and {sup 210}Pb in peatlands across northeastern North America, and by examining the relationship between concentrations of Pb in bog waters and peat in numerous sites. The results clearly demonstrate that Pb and {sup 210}Pb are mobilized by the organic-rich waters of peatlands. Profiles of Pb and {sup 210}Pb at depths below the water table do not preserve the record of atmospheric deposition, and inventories of Pb and {sup 210}Pb are depleted in peatland hollows. Concentrations of Pb in bog waters are regulated by the concentration of Pb in the peat and the concentration of dissolved organic carbon. The mass balance for one bog indicated that over the specific three-year period of study more than 30% of inputs of Pb were not retained within the peat. As a result of this mobility, dates based on {sup 210}Pb can be biased and inaccurate by as much as 30 years. Dates based on {sup 210}Pb should be verified by other techniques, especially when the inventory of {sup 210}Pb is less than that expected from local rates of deposition.

  16. Radiolead (210)Pb and (210)Po/(210)Pb activity ratios in dogs' hair.

    PubMed

    Strumińska-Parulska, Dagmara I; Szymańska, Karolina; Skwarzec, Bogdan

    2015-01-01

    The aim of this study was to determine activity concentrations of radiolead (210)Pb as well as (210)Po/(210)Pb activity ratios in dog hair. The objectives of this research were also to investigate the utility of domestic animal hair as a noninvasive indicator of metal exposure for radiotoxic, naturally occurring (210)Pb and find the correlations between (210)Pb concentration in hair and age, gender, hair type or diet of analyzed animals. The highest (210)Pb concentrations were measured in a 2-year-old Shih Tzus (9.82 ± 0.53 Bq kg(-1) dw(-1)) and a 2-year-old Bichon Maltese (8.09 ± 0.42 Bq kg(-1) dw(-1)), both longhair males, while the lowest was found in a 15-year-old Yorkshire Terrier (0.44 ± 0.02 Bq kg(-1) dw(-1)), small longhair male as well. As results showed, mainly dog hair color as well as their age and gender influenced the differences in the values of (210)Pb concentrations in analyzed hair samples. Also the values of activity ratios of (210)Po/(210)Pb in analyzed dog hair samples were calculated and obtained results were similar to those observed in human hair.

  17. Decay/ingrowth uncertainty correction of (210)Po/(210)Pb in seawater.

    PubMed

    Lin, Wuhui; Ma, Hao; Chen, Liqi; Zeng, Zhi; He, Jianhua; Zeng, Shi

    2014-11-01

    Due to increasing application of (210)Po/(210)Pb in studying particle dynamics, a consistent procedure and calculation to derive accurate and precise result of (210)Po and (210)Pb in seawater should be proposed in the framework of intercalibration by GEOTRACES. The associated uncertainty of radioactivity, which is a significant component of data report, plays a vital role in intercomparison and should be well evaluated. Although measurement uncertainty of laboratory result was well defined in ISO standards and IAEA technical documents, the decay/ingrowth uncertainty correction from laboratory result to in-situ result was less studied. It was demonstrated that the relative uncertainty of in-situ (210)Pb activity was independent of elapsed time and equal to relative uncertainty of laboratory measuring (210)Po activity at second spontaneous deposition date. The relative uncertainty of in-situ (210)Po activity decreases with in-situ activity ratio of (210)Po to (210)Pb and increases with elapsed time between sampling date and separation date, relative uncertainty of laboratory measuring (210)Po activity at first spontaneous deposition date and relative uncertainty of in-situ (210)Pb activity. It was more important to improve precision of (210)Po at first spontaneous deposition date than that of (210)Po at second spontaneous deposition date. To obtain a desirable relative uncertainty of in-situ (210)Po activity, the maximum allowing elapsed time for (210)Po, which was important for sampling strategy making and quality assurance, was calculated by in-situ activity ratio of (210)Po to (210)Pb and precision of analytical method for (210)Po. The methodology of decay/ingrowth uncertainty correction could also be applied for other radionuclide pairs ((234)Th/(238)U, (90)Y/(90)Sr, (210)Bi/(210)Pb), sample matrixes (aerosols), and disciplines.

  18. Apparent discrepancy in contamination history of a sub-tropical estuary evaluated through 210Pb profile and chronostratigraphical markers.

    PubMed

    Marques, Aguinaldo N; Monna, Fabrice; da Silva Filho, Emmanoel V; Fernex, François E; Fernando Lamego Simões Filho, F

    2006-05-01

    Zn and Cd concentrations, stable lead isotopes and 210Pb-derived chronology were determined in a sediment core sampled at Sepetiba Bay (South-eastern Brazil). During the last decades, the bay's watershed has been modified by the increase of industrial activities and human interventions. In particular, Zn and Cd ore treatment plants were built near the coast in 1960 and 1970, respectively, and water has been diverted from the adjacent Paraíba do Sul River watershed since 1950. The core collected at shallow depth near the industrial area exhibits four successive events: (i) at 50 cm depth, a change in the 206Pb/207Pb ratio from about 1.162 to more than 1.18 might be the result of the São Francisco Channel opening and water diversion from Paraíba do Sul river; (ii) at 40 cm depth, Zn concentration starts to increase (up to 0.8 mg g(-1)) (iii) above 30 cm depth, relatively high Cd concentrations (up to 1.6 microg g(-1)) are observed and (iv) at 16 cm depth, change in unsupported 210Pb slope is probably related to a waste dam built to prevent strong metal contamination in the bay. Sediment accumulation rates evaluated by Zn and Cd profiles used as time-markers are higher than those calculated from 210Pb-based chronology models. Using the constant initial concentration (CIC) model both events are supposed to date back to about 1884 and 1902, respectively, while using the constant rate of supply (CRS) model it shifts to about 1925 and 1935. Such discrepancies are probably assigned to the fact that these models do not take into account site-specific local sedimentation dynamics. In the study area, particles deposition seems to be controlled by enrichment with unsupported 210Pb transported by runoff from a mangrove flat bank. Chronology derived from a model that assumes an exponential increase of the initial 210Pb activity fits well with the estimated rates obtained from historical events.

  19. 210Pb and 210Po determination in environmental samples using liquid scintillation counting and alpha spectrometry

    NASA Astrophysics Data System (ADS)

    Pérez Sánchez, D.; Martin Sánchez, A.; Jurado Vargas, M.

    2003-01-01

    A simple radiochemical procedure has been developed to determine 210Pb and 210Po in environmental samples from the same matrix. Sediment samples are decomposed by leaching with mineral acids or by microwave digestion, while water samples are pre-concentrated. One part of the resulting solution, spiked with 209Po, is used for 210Po determination by spontaneous deposition onto nickel disks (α-spectrometry). The other part is assayed for 210Pb, separating the Pb either by anion-exchange (sediment samples), or by solvent extraction (water samples). The 210Pb source is finally prepared by precipitation as oxalate and the chemical recovery determined by gravimetry. The 210Pb activity concentration is determined by liquid scintillation. A standard sediment sample supplied by IAEA and spiked water samples were analysed to check the procedure. The 210Pb and 210Po measurements agreed well with the certifications, deviations being less than 10%. The mean recoveries for Pb and Po were (70±12)% and (77±8%) for sediments, and (70±10)% and (81±7)% for waters, respectively.

  20. Use of fallout radionuclides ((7)Be, (210)Pb) to estimate resuspension of Escherichia coli from streambed sediments during floods in a tropical montane catchment.

    PubMed

    Ribolzi, Olivier; Evrard, Olivier; Huon, Sylvain; Rochelle-Newall, Emma; Henri-des-Tureaux, Thierry; Silvera, Norbert; Thammahacksac, Chanthamousone; Sengtaheuanghoung, Oloth

    2016-02-01

    Consumption of water polluted by faecal contaminants is responsible for 2 million deaths annually, most of which occur in developing countries without adequate sanitation. In tropical aquatic systems, streambeds can be reservoirs of persistent pathogenic bacteria and high rainfall can lead to contaminated soils entering streams and to the resuspension of sediment-bound microbes in the streambed. Here, we present a novel method using fallout radionuclides ((7)Be and (210)Pbxs) to estimate the proportions of Escherichia coli, an indicator of faecal contamination, associated with recently eroded soil particles and with the resuspension of streambed sediments. We show that using these radionuclides and hydrograph separations we are able to characterize the proportion of particles originating from highly contaminated soils and that from the resuspension of particle-attached bacteria within the streambed. We also found that although overland flow represented just over one tenth of the total flood volume, it was responsible for more than two thirds of the downstream transfer of E. coli. We propose that data obtained using this method can be used to understand the dynamics of faecal indicator bacteria (FIB) in streams thereby providing information for adapted management plans that reduce the health risks to local populations. Graphical Abstract Graphical abstract showing (1) the main water flow processes (i.e. overland flow, groundwater return flow, blue arrows) and sediment flow components (i.e. resuspension and soil erosion, black arrows) during floods in the Houay Pano catchment; (2) the general principle of the method using fallout radionuclide markers (i.e. (7)Be and (210)Pbxs) to estimate E. coli load from the two main sources (i.e. streambed resuspension vs soil surface washoff); and 3) the main results obtained during the 15 May 2012 storm event (i.e. relative percentage contribution of each process to the total streamflow, values in parentheses).

  1. 210Pb mass accumulation rates in the depositional area of the Magra River (Mediterranean Sea, Italy)

    NASA Astrophysics Data System (ADS)

    Delbono, I.; Barsanti, M.; Schirone, A.; Conte, F.; Delfanti, R.

    2016-08-01

    Nine sediment cores were collected between 2009 and 2012 in the inner continental shelf (Mediterranean Sea, Italy) mainly influenced by the Magra River, at water depths ranging from 11 to 64 m. Mass Accumulation Rates (MARs) were calculated through 210Pb analysed by Gamma spectrometry. Three different dating models (single and two-layer CF-CS, CRS) were applied to clay normalised 210Pbxs profiles and 137Cs was used to validate the 210Pb geochronology. The maximum MAR values (>2 g cm-2 yr-1) were found in the region adjacent to the Magra River mouth and outside the Gulf of La Spezia (0.9±0.1 g cm-2 yr-1 at St. 3-C6 and 4-C4). Results from 137Cs/210Pbxs ratios calculated in Surface Mixed Layers (SMLs) evidenced the coastal boundaries of the Magra River depositional area, which is very limited towards south. Differently, in the north-west sector, fine sediments are generally driven by the Ligurian Current and move towards north-west: at the deepest and most distant station from the River mouth, the MAR value is the lowest one in the study area. Few major Magra River floods occurred during the sediment core sampling period. By using the short-lived radioisotope 7Be as a tracer of river floods, a clear 7Be signature of 2009 flood is present at St. 1-SA1C. Finally, by analyzing the clay normalised 210Pbxs profiles, a decrease of its activity dating the years 1999 and 2000 is observed in four cores, corresponding to two major Magra River floods occurring in those years.

  2. 210Pb balance and implications for particle transport on the continental shelf, U.S. Middle Atlantic Bight

    USGS Publications Warehouse

    Bacon, M.P.; Belastock, Rebecca A.; Bothner, Michael H.

    1994-01-01

    Supply of 210Pb to the continental shelf off the northeastern United States is dominated by the deposition from the atmosphere, the rate of which is reliably known from previously published work. Excess 210Pb inventories in the shelf sediments show accumulations that are nearly in balance with the supply, even in areas of relict sands where it is believed that no net accumulation of sediment presently occurs. The 210Pb distributions in shelf and slope water indicate that the two-way fluid exchange at the shelf-slope front and the net transport in the alongshore flow make comparatively small contributions to the shelf 210Pb budget. The near balance between supply and decay of 210Pb on the shelf implies a limit to the particle export flux. It is concluded that the export of particulate organic carbon does not exceed 60 g m-2 y-1 (???25% of primary production) and is probably lower. The hypothesis is advanced that fine particulate matter introduced to the continental shelf is detained in its transit of the shelf because of bioturbational trapping in the sediment due to benthic animals. Distributions of 210Pb in suspended particulate matter and in the fine fraction of shelf sediments suggest that the average fine particle must undergo several cycles of deposition-bioturbation-resuspension-redeposition and requires a number of decades for its transit and ultimate export from the shelf. Thus, only the most refractory organic matter is likely to be exported. ?? 1994.

  3. Using 137Cs and 210Pb ex measurements to estimate soil redistribution rates on semi-arid grassland in Mongolia

    NASA Astrophysics Data System (ADS)

    Kato, H.; Onda, Y.; Tanaka, Y.

    2010-02-01

    In this study, two small experimental catchments were selected in semi-arid grassland in Mongolia. The Kherlen-bayan Ulaan (KBU) catchment has been subjected to intensive grazing as a wintering shelter for domestic livestock animals, and the number of livestock animals in the Baganuur (BGN) catchment has been increasing over the last few decades. The rates and patterns of soil erosion within the catchments were estimated based on cesium-137 ( 137Cs) and lead-210 ( 210Pb ex) inventories in bulk soil core samples. The medium-term (~ 40 years) soil erosion rates based on the 137Cs measurements indicated that annual soil loss from the KBU catchment was approximately three times greater than that from the BGN catchment. The 137Cs-derived rates and patterns of soil erosion indicated that soil in the KBU catchment was susceptible to surface erosion, with facilitated transport of eroded sediment to the catchment outlet. The 210Pb ex-derived soil erosion rates were generally greater than those derived from 137Cs in both catchments. If we assume that the soil erosion rate has been increasing with increasing domestic livestock numbers, the most plausible explanation is that the 210Pb ex-derived estimates represent recent increases in soil erosion. Furthermore, the 210Pb ex/ 137Cs inventory ratio showed a tendency to increase with downslope distance on the eroded hillslope in the BGN catchment. Assuming that the increase in inventory ratio is a result of constant fallout input of 210Pb ex on the eroded sediment during its transportation along the hillslope, the 210Pb ex inventory may not be suitable to estimate soil erosion rates at sites where downslope movement of sediment is slow. Further discussion regarding interpretation of 210Pb ex-derived soil loss is required, and the applicability of the 210Pb ex technique on semi-arid hillslopes remains to be determined.

  4. Assessment of (210)Po and (210)Pb in marine biota of the Mallipattinam ecosystem of Tamil Nadu, India.

    PubMed

    Suriyanarayanan, S; Brahmanandhan, G M; Samivel, K; Ravikumar, S; Hameed, P Shahul

    2010-11-01

    To provide baseline data on background radiation levels for the future assessment of the impact of nuclear and thermal power stations, a systematic study was carried out in the Mallipattinam ecosystem of Tamil Nadu, India. Mallipattinam is located between the Kudankulam and Kalpakkam nuclear power plants and near to Tuticorin thermal power plant. Water, sediments, seaweeds, crustaceans, molluscs, and fish were collected to measure the concentrations of (210)Po and (210)Pb. The concentrations of (210)Po and (210)Pb in most samples are comparable to values reported worldwide. In fish, the concentrations of (210)Po and (210)Pb are in the range 16-190 Bq kg(-1) and 8-153 Bq kg(-1), respectively. The concentration factors of (210)Po and (210)Pb for the biotic components ranges from 10(3) to 10(6).

  5. Measurement of 210Pb and its Application to Evaluate Contamination in an Area Affected by NORM Releases

    NASA Astrophysics Data System (ADS)

    Mosqueda, F.; Villa, M.; Hurtado, S.; Absi, A.; Manjón, G.; Vaca, F.; García-Tenorio, R.

    2008-08-01

    Liquid scintillation counting (LSC) is an easy and straightforward technique, and combined with its low limit of detection, makes it a powerful tool for both routine and low level measurements that can be applied to 210Pb low level counting in environmental samples. 210Pb can be easily measured following a sulphate co-precipitation method; the addition of a carrier and the weighing of the recovered amount is a widespread technique to evaluate radiochemical yield, however, this evaluation of the recovery is sometimes questioned. The samples employed in this work were recollected in 1999 and 2005 from the estuary of the Odiel and Tinto rivers (SW of Spain), which were affected by phosphogypsum (pg.) discharges until 1998. Phosphogypsum contains most of the 210Pb from the treated raw material, for that reason analysed riverbed sediments have enhanced 210Pb activity concentrations and hence, enhanced activity concentration of its daughter 210Po, both in secular equilibrium after two years.

  6. The behavior of scavenged isotopes in marine anoxic environments: 210Pb and 210Po in the water column of the Black Sea

    NASA Astrophysics Data System (ADS)

    Wei, Ching-Ling; Murray, James W.

    1994-04-01

    Vertical profiles of dissolved and particulate 210Pb and 210Po were determined at two stations in the Black Sea in June 1988. Vertical fluxes of 210Pb and 210Po were also measured in the upper 150 m, using floating sediment traps. The fractionation of 210Pb between dissolved and particulate phases in the Black Sea is strongly influenced by the redox conditions in the water column. Dissolved 210Pb dominates in the oxic zone, while particulate 210Pb is the major form in the deep sulfide-rich anoxic zone. The distribution of 210Pb across the suboxic zone appears to be mainly controlled by redox cycling of manganese and iron. In the sulfide-rich layer coprecipitation of lead with iron sulfide is probably the dominant scavenging mechanism. A simple scavenging model was used to calculate the residence times of dissolved and particulate 210Pb in the oxic, suboxic, and anoxic zones. The residence times of dissolved 210Pb relative to scavenging by particles are 0.5-1, 2-3, and 3.5 years in the oxic, suboxic, and anoxic layers, respectively. The corresponding residence times of particulate 210Pb relative to particle removal processes in the same layers are 0.1, 1.5-2.5, and 8.5 years, respectively. A particle settling velocity of about 40 m y -1 was derived from the 210Pb /226Ra disequilibrium in the deep Black Sea. The relatively short residence times of 210Pb support the hypothesis that anoxic basins are important sites for boundary scavenging of 210Pb. The 210Po profiles indicate that biological rather than inorganic particles are the major carrier phases for polonium in the Black sea. Dissolved 210Po is deficient relative to dissolved 210Pb in the euphotic zone, suggesting preferential uptake of 210Po over 210Pb by particles residing in that layer. The residence time of dissolved 210Po, with respect to scavenging by particles in the euphotic zone, is about 200 days. Below the mid-depth of the suboxic zone, 210Po is in excess relative to 210Pb, and is thought to originate

  7. The self-absorption correction factors for (210)Pb concentration in mining waste and influence on environmental radiation risk assessment.

    PubMed

    Bonczyk, Michal; Michalik, Boguslaw; Chmielewska, Izabela

    2017-03-01

    The radioactive lead isotope (210)Pb occurs in waste originating from metal smelting and refining industry, gas and oil extraction and sometimes from underground coal mines, which are deposited in natural environment very often. Radiation risk assessment requires accurate knowledge about the concentration of (210)Pb in such materials. Laboratory measurements seem to be the only reliable method applicable in environmental (210)Pb monitoring. One of the methods is gamma-ray spectrometry, which is a very fast and cost-effective method to determine (210)Pb concentration. On the other hand, the self-attenuation of gamma ray from (210)Pb (46.5 keV) in a sample is significant as it does not depend only on sample density but also on sample chemical composition (sample matrix). This phenomenon is responsible for the under-estimation of the (210)Pb activity concentration level often when gamma spectrometry is applied with no regard to relevant corrections. Finally, the corresponding radiation risk can be also improperly evaluated. Sixty samples of coal mining solid tailings (sediments created from underground mining water) were analysed. Slightly modified and adapted to the existing laboratory condition, a transmission method has been applied for the accurate measurement of (210)Pb concentration . The observed concentrations of (210)Pb range between 42.2 ÷ 11,700 Bq·kg(-1) of dry mass. Experimentally obtained correction factors related to a sample density and elemental composition range between 1.11 and 6.97. Neglecting this factor can cause a significant error or underestimations in radiological risk assessment. The obtained results have been used for environmental radiation risk assessment performed by use of the ERICA tool assuming exposure conditions typical for the final destination of such kind of waste.

  8. Natural radionuclides (210)Po and (210)Pb in the Delaware and Chesapeake Estuaries: modeling scavenging rates and residence times.

    PubMed

    Marsan, D; Rigaud, S; Church, T

    2014-12-01

    During the spring and summer months of 2012, (210)Po and (210)Pb activity were measured in the dissolved and particulate phases from the Delaware and upper Chesapeake estuaries. The upper Delaware estuary, near the freshwater end member, was characterized by high-suspended matter concentrations that scavenged dissolved (210)Po and (210)Pb. Box models were applied using mass balance calculations to assess the nuclides residence times in each estuary. Only 60% of the dissolved (210)Po and 55% of the dissolved (210)Pb from the Delaware estuary were exported to coastal waters. A large fraction of soluble (210)Po and (210)Pb within the estuary was either reversibly adsorbed onto suspended particles, trapped in sediment accumulation zones (such as intertidal marshes), bioaccumulated into phytoplankton and discharged to the coastal ocean. The upper Chesapeake estuary was largely characterized by sub-oxic bottom waters that contained higher concentrations of dissolved (210)Po and (210)Pb, hypothesized to be subjected to redox cycling of manganese. The Delaware and Chesapeake estuary mean residence times for (210)Po differed significantly at 86 ± 7 and 126 ± 10 days respectively, while they were similar for (210)Pb (67 ± 6-55 ± 5 days). The difference in residence times corresponds to the greater extent of biogeochemical scavenging and regeneration processes within the upper Chesapeake.

  9. 210Po and 210Pb distributions and residence times in the nearshore region of Lake Superior

    NASA Astrophysics Data System (ADS)

    Chai, Yingtao; Urban, Noel R.

    2004-10-01

    The naturally occurring radionuclide, 210Pb, and its decay daughter, 210Po, were measured in the Keweenaw Peninsula region of Lake Superior. Water, suspended particles, sediment trap material (settling particles), and sediment cores and grab samples were collected along three transects that stretched from 1 to 20 km from shore. Departures from secular equilibrium (activity ratio of 210Po:210Pb = 1) were observed for most samples. 210Po-deficiency was observed in both suspended particles (TSP) with a ratio of 0.43 ± 0.05 (±95% confidence interval (CI)) and settling particles with a ratio of 0.57 ± 0.04; higher ratios in the settling particles resulted from an admixture of resuspended sediments. Ratios in the dissolved phase were 0.45 ± 0.12. Approximately 83% and 85% of total 210Po and 210Pb in the water column was in the particulate phase. No evidence of biological uptake of Po was found. Seasonal and spatial variability in activities and ratios was small. Using steady state solutions to the mass balance equations for both isotopes, similar residence times in the water column were calculated for 210Po and 210Pb (55 ˜ 75 days in a 150-m-deep water column). It was possible to calibrate a one-box model for the paired isotopes so that the model output closely matched rates of sediment and isotope resuspension estimated from sediment traps. However, this calibration required a fractionation of the isotopes during resuspension. The particle settling velocity was estimated to be 2.3 m d-1, which also is in agreement with the estimate (2.4 ± 2.2 m d-1) from sediment traps. These results indicate rapid fluxes of radioisotopes and sediments through the water column largely driven by resuspension of sediments in nearshore areas.

  10. 210Po and 210Pb as Tracers of Particle Cycling and Resuspension in a Dynamic Freshwater System: Case Study from the Clinton River, Southeast Michigan

    NASA Astrophysics Data System (ADS)

    Mudbidre, R.; Baskaran, M. M.; Schweitzer, L.

    2013-12-01

    Polonium-210 and 210Pb are constantly delivered to the surface waters through atmospheric deposition with a 210Po/210Pb activity ratio (AR) of < 0.10. Freshly produced suspended particles in surface waters are ';tagged' with this ratio which tends to grow towards the secular equilibrium value of 1.0. This disequilibrium between 210Po and 210Pb in freshwater system with a relatively short hydrological residence time can be utilized to quantify sediment resuspension rates and to investigate the extent of recycling of sedimentary particulate matter. From the measurements of 210Po and 210Pb in particulate matter collected in sediment traps and surficial bottom sediments at 5 different sites in the Clinton River in southeast Michigan over a period of 6 months (April - September, 2005) and subsequent modeling of these data, we report the following: i) The direct atmospheric deposition of 210Po and 210Pb collected in the sediment trap materials accounted for 1% and 0.1%, respectively, of the total deposited in the sediment trap; ii) The ranges and mean values of the 210Po and 210Pb in the sediment trap material and bottom sediments are comparable, with near identical 210Po/210Pb ratios, indicating that most of the trapped 210Po and 210Pb were delivered by the resuspension of bottom sediments; iii) The particle residence times varied from 0.3 to 4 days for 210Pb and 0.9 to 13.4 days for 210Po; and iv) The sediment resuspension rates calculated via single box model approach yielded resuspension rates ranging from 0.2 to 14.2 g cm-2 yr-1 using 210Pb and 0.1 to 1.0 g cm-2 yr-1 using 210Po. We propose that the distribution of 210Bi (and 210Bi/210Pb) would provide better insight on particle cycling in short-time scales and a brief discussion will be presented on the utility of 210Bi/210Pb ratio as a powerful tool for short-term particle cycling and as tracers of POC, PON export studies in deeper freshwater lakes.

  11. Balance and residence times of 210Pb and 210Po in surface waters of the northwestern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Masqué, P.; Sanchez-Cabeza, J. A.; Bruach, J. M.; Palacios, E.; Canals, M.

    2002-10-01

    Concentrations of the naturally occurring radionuclides 210Pb and 210Po were determined in both the dissolved (<0.2 μm) and particulate (>0.2 μm) fractions in surface waters of the northwestern Mediterranean Sea. About 4-8% of the 210Pb activity was observed to be associated to particles, which were determined as being mostly biogenic. The 210Po content in the particulate fraction was generally greater than that of 210Pb, accounting for about 20% of the total activity. Total activities of 210Pb and 210Po were found to be in equilibrium. 226Ra concentrations were also determined in an effort to investigate its occurrence in Mediterranean waters. 226Ra was in excess to both 210Pb and 210Po, with a mean concentration of 1.72±0.03 Bq m -3. Steady-state balance equations of the three radionuclides permit calculation of residence times for 210Pb and 210Po in surface waters (0.8 and 3.0 yr, respectively). 210Po residence times were almost one order of magnitude higher than mostly reported values. Polonium is known to manifest higher affinity and different binding mechanisms (by entering the organic cycle) to biogenic material than 210Pb. Several processes, such as 210Po uptake by buoyant particles and recycling of organic matter in the surface layer, could lead to such long residence times of 210Po and, therefore, of organic particles in surface waters. Larger 210Po atmospheric fluxes than those here considered and inputs from rivers and/or fine-grained sediment resuspension could also help to explain the observation, although presumably to a lesser extent.

  12. 210Pb balance and implications for particle transport on the continental shelf, U.S. Middle Atlantic Bight

    USGS Publications Warehouse

    Bacon, M.P.; Belastock, Rebecca A.; Bothner, Michael H.

    1994-01-01

    Supply of 210Pb to the continental shelf off the northeastern United States is dominated by the deposition from the atmosphere, the rate of which is reliably known from previously published work. Excess 210Pb inventories in the shelf sediments show accumulations that are nearly in balance with the supply, even in areas of relict sands where it is believed that no net accumulation of sediment presently occurs. The 210Pb distributions in shelf and slope water indicate that the two-way fluid exchange at the shelf-slope front and the net transport in the alongshore flow make comparatively small contributions to the shelf 210Pb budget. The near balance between supply and decay of 210Pb on the shelf implies a limit to the particle export flux. It is concluded that the export of particulate organic carbon does not exceed 60 g m−2 y−1 (∼25% of primary production) and is probably lower. The hypothesis is advanced that fine particulate matter introduced to the continental shelf is detained in its transit of the shelf because of bioturbational trapping in the sediment due to benthic animals. Distributions of 210Pb in suspended particulate matter and in the fine fraction of shelf sediments suggest that the average fine particle must undergo several cycles of deposition-bioturbation-resuspension-redeposition and requires a number of decades for its transit and ultimate export from the shelf. Thus, only the most refractory organic matter is likely to be exported.

  13. Dual-core mass-balance approach for evaluating mercury and 210Pb atmospheric fallout and focusing to lakes.

    PubMed

    Van Metre, Peter C; Fuller, Christopher C

    2009-01-01

    Determining atmospheric deposition rates of mercury and other contaminants using lake sediment cores requires a quantitative understanding of sediment focusing. Here we present a novel approach that solves mass-balance equations fortwo cores algebraicallyto estimate contaminant contributions to sediment from direct atmospheric fallout and from watershed and in-lake focusing. The model is applied to excess 210Pb and Hg in coresfrom Hobbs Lake, a high-altitude lake in Wyoming. Model results for excess 210Pb are consistent with estimates of fallout and focusing factors computed using excess 210Pb burdens in lake cores and soil cores from the watershed and model results for Hg fallout are consistent with fallout estimated using the soil-core-based 210Pb focusing factors. The lake cores indicate small increases in mercury deposition beginning in the late 1800s and large increases after 1940, with the maximum at the tops of the cores of 16-20 microg/m2 x year. These results suggest that global Hg emissions and possibly regional emissions in the western United States are affecting the north-central Rocky Mountains. Hg fallout estimates are generally consistent with fallout reported from an ice core from the nearby Upper Fremont Glacier, but with several notable differences. The model might not work for lakes with complex geometries and multiple sediment inputs, but for lakes with simple geometries, like Hobbs, it can provide a quantitative approach for evaluating sediment focusing and estimating contaminant fallout.

  14. Dual-core mass-balance approach for evaluating mercury and210Pb atmospheric fallout and focusing to lakes

    USGS Publications Warehouse

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

    2009-01-01

    Determining atmospheric deposition rates of mercury and other contaminants using lake sediment cores requires a quantitative understanding of sediment focusing. Here we present a novel approach that solves mass-balance equations for two cores algebraically to estimate contaminant contributions to sediment from direct atmospheric fallout and from watershed and in-lake focusing. The model is applied to excess 210Pb and Hg in cores from Hobbs Lake, a high-altitude lake in Wyoming. Model results for excess 210Pb are consistent with estimates of fallout and focusing factors computed using excess 210Pb burdens in lake cores and soil cores from the watershed and model results for Hg fallout are consistent with fallout estimated using the soil-core-based 210Pb focusing factors. The lake cores indicate small increases in mercury deposition beginning in the late 1800s and large increases after 1940, with the maximum at the tops of the cores of 16-20 ??g/m 2year. These results suggest that global Hg emissions and possibly regional emissions in the western United States are affecting the north-central Rocky Mountains. Hg fallout estimates are generally consistent with fallout reported from an ice core from the nearby Upper Fremont Glacier, but with several notable differences. The model might not work for lakes with complex geometries and multiple sediment inputs, but for lakes with simple geometries, like Hobbs, it can provide a quantitative approach for evaluating sediment focusing and estimating contaminant fallout.

  15. Dating sediments using luminescence signals

    SciTech Connect

    Wintle, A. )

    1993-05-01

    Before siting a nuclear power station or a nuclear waste repository, it is necessary to establish that the area has been free of earthquake activity for a sufficient period of time. Evidence of past earthquake activity is often provided by faults in surface sediments. Age limits for fault formation can be set by obtaining the depositional ages of the sediment unit in which the fault was formed and the overlying sediment. A useful technique would be one that dating could be applied to the mineral grains that make up the sediments and that would give the time that has passed since the grains were blown or washed into position. Luminescence dating techniques, of which the most well known is thermo-luminescence (TL), provide such information. This approach has been successful in dating movement on the Wasatch Fault in Utah. A combination of TL and radiocarbon dates indicated that three faulting events had occurred within the past 5000 years. 2 refs., 1 fig.

  16. Intercomparison of radiocarbon bomb pulse and 210Pb age models. A study in a peat bog core from North Poland

    NASA Astrophysics Data System (ADS)

    Piotrowska, Natalia; De Vleeschouwer, François; Sikorski, Jarosław; Pawlyta, Jacek; Fagel, Nathalie; Le Roux, Gaël; Pazdur, Anna

    2010-04-01

    Radiocarbon and 210Pb were measured on the uppermost 40 cm of a Wardenaar peat core retrieved from a Baltic raised bog at Słowińskie Błota (Pomerania, North Poland). This site is the subject of ongoing multiproxy studies covering the last 1300 years. Radiocarbon age model was constructed on the basis of 14 AMS dates obtained on selected Sphagnum spp. fragments, with use of P_Sequence tool. We present here a comparison of this model with the age model obtained using CRS model classically applied to 210Pb measurements.

  17. 210Pb geochronology and trace metal fluxes (Cd, Cu and Pb) in the Gulf of Tehuantepec, South Pacific of Mexico.

    PubMed

    Ruiz-Fernández, Ana Carolina; Páez-Osuna, Federico; Machain-Castillo, María Luisa; Arellano-Torres, Elsa

    2004-01-01

    Distributions of Al, Cd, Cu, Fe, Li, Mn and Pb were analyzed in a sediment core collected in the Gulf of Tehuantepec, an important fisheries region located in the South Pacific of Mexico, where data on metal accumulation and accretion rates were previously almost nonexistent. Depth profiles of metal concentrations were converted to time-based profiles by using a 210Pb-derived vertical accretion rate, estimated to be 0.05 cm year(-1) on the average. Sediments were dated up to 8 cm depth, corresponding to a layer of ca. 140 years old. The historical changes of metal accumulation along the sediment core have shown a moderate enrichment of Cd, Cu and Pb concentrations at present, of about threefold the corresponding background concentrations. Chronological trace metal records showed that metal fluxes have increased over the last 20 years, reaching the maximum values at present of 2.5, 22.5 and 45.8 (microg cm(-2) year(-1)) for Cd, Pb and Cu, respectively. These increments in metal fluxes are likely influenced by the development of anthropogenic land-based activities since over this period of time oil production activities in the region have had a significant development.

  18. Measurement of {sup 210}Pb and its Application to Evaluate Contamination in an Area Affected by NORM Releases

    SciTech Connect

    Mosqueda, F.; Vaca, F.; Villa, M.; Hurtado, S.; Absi, A.; Manjon, G.; Garcia-Tenorio, R.

    2008-08-07

    Liquid scintillation counting (LSC) is an easy and straightforward technique, and combined with its low limit of detection, makes it a powerful tool for both routine and low level measurements that can be applied to {sup 210}Pb low level counting in environmental samples. {sup 210}Pb can be easily measured following a sulphate co-precipitation method; the addition of a carrier and the weighing of the recovered amount is a widespread technique to evaluate radiochemical yield, however, this evaluation of the recovery is sometimes questioned. The samples employed in this work were recollected in 1999 and 2005 from the estuary of the Odiel and Tinto rivers (SW of Spain), which were affected by phosphogypsum (pg.) discharges until 1998. Phosphogypsum contains most of the {sup 210}Pb from the treated raw material, for that reason analysed riverbed sediments have enhanced {sup 210}Pb activity concentrations and hence, enhanced activity concentration of its daughter {sup 210}Po, both in secular equilibrium after two years.

  19. Studies on the distribution of 210Po and 210Pb in the ecosystem of Point Calimere Coast (Palk Strait), India.

    PubMed

    Suriyanarayanan, S; Brahmanandhan, G M; Malathi, J; Ravi Kumar, S; Masilamani, V; Shahul Hameed, P; Selvasekarapandian, S

    2008-04-01

    A systematic study on the natural radionuclides such as 210Po and 210Pb in the environmental matrices of Point Calimere ecosystem has been undertaken to establish a baseline data on the radiation profile of Point Calimere environment. The environmental samples such as water, sediment and biota (seaweeds, crustaceans, molluscs and fish) have been subjected to analyses. It has been observed that the concentration of 210Po and 210Pb in the water samples of Point Calimere to be 0.5 mBq/l and 1.3 mBq/l, respectively. The soft tissues of the organisms accumulated higher 210Po content while shells and bones contained more 210Pb. The bivalve molluscs Meretrix casta have been identified to accumulate higher concentration of 210Po suggesting that they could serve as bio-indicator of radionuclides like 210Po in the Point Calimere ecosystem. The concentration factor of 210Po for the biotic components ranged from approximately 10(3) to 10(6) while for 210Pb it ranged from approximately 10(3) to 10(5).

  20. High-resolution 14C dating of a 25,000-year lake-sediment record from equatorial East Africa

    NASA Astrophysics Data System (ADS)

    Blaauw, Maarten; van Geel, Bas; Kristen, Iris; Plessen, Birgit; Lyaruu, Anna; Engstrom, Daniel R.; van der Plicht, Johannes; Verschuren, Dirk

    2011-10-01

    We dated a continuous, ˜22-m long sediment sequence from Lake Challa (Mt. Kilimanjaro area, Kenya/Tanzania) to produce a solid chronological framework for multi-proxy reconstructions of climate and environmental change in equatorial East Africa over the past 25,000 years. The age model is based on a total of 168 AMS 14C dates on bulk-organic matter, combined with a 210Pb chronology for recent sediments and corrected for a variable old-carbon age offset. This offset was estimated by i) pairing bulk-organic 14C dates with either 210Pb-derived time markers or 14C dates on grass charcoal, and ii) wiggle-matching high-density series of bulk-organic 14C dates. Variation in the old-carbon age offset through time is relatively modest, ranging from ˜450 yr during glacial and late glacial time to ˜200 yr during the early and mid-Holocene, and increasing again to ˜250 yr today. The screened and corrected 14C dates were calibrated sequentially, statistically constrained by their stratigraphical order. As a result their constrained calendar-age distributions are much narrower, and the calibrated dates more precise, than if each 14C date had been calibrated on its own. The smooth-spline age-depth model has 95% age uncertainty ranges of ˜50-230 yr during the Holocene and ˜250-550 yr in the glacial section of the record. The δ 13C values of paired bulk-organic and grass-charcoal samples, and additional 14C dating on selected turbidite horizons, indicates that the old-carbon age offset in Lake Challa is caused by a variable contribution of old terrestrial organic matter eroded from soils, and controlled mainly by changes in vegetation cover within the crater basin.

  1. Seasonal variations on the residence times and partitioning of short-lived radionuclides (234Th, 7Be and 210Pb) and depositional fluxes of 7Be and 210Pb in Tampa Bay, Florida

    USGS Publications Warehouse

    Baskaran, M.; Swarzenski, P.W.

    2007-01-01

    Historically, Tampa Bay has been impacted heavily by a wide range of anthropogenic perturbations that may include, agricultural-, shipping-, phosphate mining/distribution-related activities, as well as a burgeoning coastal population. Due to the presence of U-rich underlying sediments, elevated activities of U- and Th-series daughter products may be naturally released into this system. This region is also known for summer thunderstorms and corresponding increases in precipitation and surface water runoff. Only limited work has been conducted on the partitioning of particle-reactive radionuclides (such as 7Be, 210Pb, and 234Th) in such a dynamic coastal system. We investigated both the removal residence time and partitioning of these radionuclides between filter-retained particulate matter (≥ 0.5 μm) and the filtrate ( Our results indicate that the partitioning of 7Be, 210Pb, and 234Th between filtrate and filter-retained phase is controlled foremost by enhanced bottom resuspension events during summer thunderstorms. As a consequence, no significant relationship exists between the distribution coefficients (Kd values) of these isotopes and the concentration of suspended particulate matter (SPM). Relatively faster recycling rates of atmospheric water vapor derived from the ocean results in lower atmospheric depositional fluxes of 210Pb to the study site than predicted. The relationship between 7Be and 210Pb in bulk (wet + dry) deposition is compared to their respective water column activities. The residence times of particulate and dissolved 234Th, 7Be and 210Pb, as well the distribution coefficients of these radionuclides, are then compared to values reported in other coastal systems.

  2. Particle Dynamics in the Temporary Deposition Zone of Lake Superior: Insights From 210Pb,137Cs and 7Be

    NASA Astrophysics Data System (ADS)

    Chai, Y.; Urban, N. R.; Auer, M. T.

    2005-05-01

    With the aim of understanding particle dynamics in the slope-profundal region in coastal areas of the Great Lakes and the particulate organic carbon availability to benthic organisms, sediment cores were taken along three transects in the nearshore region of Lake Superior. Inventories of 137Cs and excess 210Pb and focusing factors (based on both isotopes) were calculated for 28 cores. 7Be was only found in the fluff layer of the sediments at most sites, but its presence in deep-water sites attests to the rapidity of sedimentation. The 210Pb-derived focusing factors ranged from 0.04 to 2.3 with mean and median values of 0.36 and 0.15, respectively. The study region is thus categorized as a temporary deposition zone. A 2-dimensional steady-state nested-box model was developed and applied to individual transects with the 210Pb inventories as model input. Model output included isotope residence times and cross-margin fluxes of sediments and isotopes. The time scale for the particles focusing from the shelf zone to the profundal zone of the transect was on the order of 10 years. The predicted residence times also indicate the existence of local enrichment zones for both isotopes and sediments as well as depletion zones along each transect. The results suggest that food availability may explain the observed Diporeia distributions along the transects. High ratios of 137Cs:210Pb were interpreted to indicate longshore transport by the Keweenaw Current and the general counter-clockwise circulation in the lake. This circulation entrains older sediments into the nearshore zone where they remain for periods of 10-30 years.

  3. Identifying sediment discontinuities and solving dating puzzles using monitoring and palaeolimnological records

    NASA Astrophysics Data System (ADS)

    Dong, Xuhui; Sayer, Carl D.; Bennion, Helen; Maberly, Stephen C.; Yang, Handong; Battarbee, Richard W.

    2016-05-01

    Palaeolimnological studies should ideally be based upon continuous, undisturbed sediment sequences with reliable chronologies. However for some lake cores, these conditions are not met and palaeolimnologists are often faced with dating puzzles caused by sediment disturbances in the past. This study chooses Esthwaite Water from England to illustrate how to identify sedimentation discontinuities in lake cores and how chronologies can be established for imperfect cores by correlation of key sediment signatures in parallel core records and with long-term monitoring data (1945-2003). Replicated short cores (ESTH1, ESTH7, and ESTH8) were collected and subjected to loss-on-ignition, radiometric dating (210Pb, 137Cs, and 14C), particle size, trace metal, and fossil diatom analysis. Both a slumping and a hiatus event were detected in ESTH7 based on comparisons made between the cores and the long-term diatom data. Ordination analysis suggested that the slumped material in ESTH7 originated from sediment deposited around 1805-1880 AD. Further, it was inferred that the hiatus resulted in a loss of sediment deposited from 1870 to 1970 AD. Given the existence of three superior 14C dates in ESTH7, ESTH1 and ESTH7 were temporally correlated by multiple palaeolimnological proxies for age-depth model development. High variability in sedimentation rates was evident, but good agreement across the various palaeolimnological proxies indicated coherence in sediment processes within the coring area. Differences in sedimentation rates most likely resulted from the natural morphology of the lake basin. Our study suggests that caution is required in selecting suitable coring sites for palaeolimnological studies of small, relatively deep lakes and that proximity to steep slopes should be avoided wherever possible. Nevertheless, in some cases, comparisons between a range of contemporary and palaeolimnological records can be employed to diagnose sediment disturbances and establish a chronology.

  4. Identifying sediment discontinuities and solving dating puzzles using monitoring and palaeolimnological records

    NASA Astrophysics Data System (ADS)

    Dong, Xuhui; Sayer, Carl D.; Bennion, Helen; Maberly, Stephen C.; Yang, Handong; Battarbee, Richard W.

    2016-12-01

    Palaeolimnological studies should ideally be based upon continuous, undisturbed sediment sequences with reliable chronologies. However for some lake cores, these conditions are not met and palaeolimnologists are often faced with dating puzzles caused by sediment disturbances in the past. This study chooses Esthwaite Water from England to illustrate how to identify sedimentation discontinuities in lake cores and how chronologies can be established for imperfect cores by correlation of key sediment signatures in parallel core records and with long-term monitoring data (1945-2003). Replicated short cores (ESTH1, ESTH7, and ESTH8) were collected and subjected to loss-on-ignition, radiometric dating (210Pb, 137Cs, and 14C), particle size, trace metal, and fossil diatom analysis. Both a slumping and a hiatus event were detected in ESTH7 based on comparisons made between the cores and the long-term diatom data. Ordination analysis suggested that the slumped material in ESTH7 originated from sediment deposited around 1805-1880 AD. Further, it was inferred that the hiatus resulted in a loss of sediment deposited from 1870 to 1970 AD. Given the existence of three superior 14C dates in ESTH7, ESTH1 and ESTH7 were temporally correlated by multiple palaeolimnological proxies for age-depth model development. High variability in sedimentation rates was evident, but good agreement across the various palaeolimnological proxies indicated coherence in sediment processes within the coring area. Differences in sedimentation rates most likely resulted from the natural morphology of the lake basin. Our study suggests that caution is required in selecting suitable coring sites for palaeolimnological studies of small, relatively deep lakes and that proximity to steep slopes should be avoided wherever possible. Nevertheless, in some cases, comparisons between a range of contemporary and palaeolimnological records can be employed to diagnose sediment disturbances and establish a chronology.

  5. Tracking legacy radionuclides in St. Louis, Missouri, via unsupported (210)Pb.

    PubMed

    Kaltofen, Marco P J; Alvarez, Robert; Hixson, Lucas

    2016-03-01

    Analysis of 287 soil, sediment and house dust samples collected in a 200 km(2)-zone in northern St. Louis County, Missouri, establish that offsite migration of radiological contaminants from Manhattan Project-era uranium processing wastes has occurred in this populated area. Specifically, 48% of samples (111 of a subset of 229 soils and sediments tested) had (210)Pb concentrations above the risk-based soil cleanup limits for residential farming established by the US Department of Energy at the Fernald, OH, uranium plant, which handled and stored the same concentrated Manhattan Project-era wastes; the geographical distribution of the exceedances are consistent with water and radon gas releases from a landfill and related sites used to store and dispose of legacy uranium wastes; and offsite soil and house dust samples proximal to the landfill showed distinctive secular disequilibrium among uranium and its progeny indicative of uranium ore processing wastes. The secular disequilibrium of uranium progeny in the environment provides an important method for distinguishing natural uranium from industrial uranium wastes. In this study, the detection of unsupported (210)Pb beyond expected atmospheric deposition rates is examined as a possible indicator of excessive radon emissions from buried uranium and radium-containing wastes.

  6. 234Th, 210Pb, 210Po and stable Pb in the central equatorial Pacific: Tracers for particle cycling

    USGS Publications Warehouse

    Murray, J.W.; Paul, B.; Dunne, J.P.; Chapin, T.

    2005-01-01

    Samples were collected during the 1992 US JGOFS EqPac Survey I and II cruises from 12??N to 12??S at 140??W in the central equatorial Pacific for water column profiles of dissolved, particulate and total 234Th, 210Pb and 210Po and total acid soluble stable Pb and sediment trap fluxes of 234Th, 210Pb and 210Po. Survey I occurred in February/March with moderate El Nino conditions while Survey II was conducted in September/October when there was a well developed cold-tongue. 234Th, 210Pb and 210Po are all particle reactive yet they partition differently between dissolved and particulate phases. Fractionation factors (the ratios of the distribution coefficients) show that the selectivity for suspended and sediment trap particles follows Th>Po>Pb. Scavenging residence times (??) for 234Th, 210Pb and 210Po ranged from 25 to 100 d, 3 to 8 years and 100 to 500 d, respectively. These particle reactive tracers have very different distributions in the water column, which reflect differences in their sources and sinks. The deficiency of 234Th relative to 238U was fairly uniformly distributed meridionally, though deficiencies were higher during Survey II when there was higher new production. Excess 210Pb relative to 226Ra was very asymmetrical with much higher excess values north of the equator. The distributions were similar for Surveys I and II. The deficiency of 210Po relative to 210Pb had a symmetrical distribution about the equator for both Survey I and II but the deficiencies were larger during Survey I when upwelling was smaller. Stable Pb was generally higher at the surface than at 250 m and there was no meridional trend from 12??N to 12??S. A mass balance for 210Pb was used to determine the atmospheric input of 210Pb. The average values for Surveys I and II were 0.12 and 0.32 dpm cm-2 year-1, respectively. There was no general increase in atmospheric input of 210Pb north of the equator but there was a strong maximum at 2-3??N during Survey I coincident with the

  7. Recent peat accumulation rates in minerotrophic peatlands of the Bay James region, Eastern Canada, inferred by 210Pb and 137Cs radiometric techniques.

    PubMed

    Ali, Adam A; Ghaleb, Bassam; Garneau, Michelle; Asnong, Hans; Loisel, Julie

    2008-10-01

    (210)Pb and (137)Cs dating techniques are used to characterise recent peat accumulation rates of two minerotrophic peatlands located in the La Grande Rivière hydrological watershed, in the James Bay region (Canada). Several cores were collected during the summer 2005 in different parts of the two selected peatlands. These minerotrophic patterned peatlands are presently affected by erosion processes, expressed by progressive mechanical destruction of their pools borders. This erosion process is related to a water table rise induced by a regional increase of humidity since the last century. The main objective of the present paper is to (1) evaluate if (210)Pb and (137)Cs dating techniques can be applied to build accurate chronologies in these environments and (2) detect changes in the peat accumulation rates in regard to this amplification of humidity. In both sites, unsupported (210)Pb shows an exponential decreasing according to the depth. Chronologies inferred from (210)Pb allow to reconstruct peat accumulation rates since ca. 1855 AD. The (137)Cs data displayed evident mobility and diffusion, preventing the establishment of any sustained chronology based on these measurements. In the two sites, peat accumulation rates inferred from (210)Pb chronologies fluctuate between 0.005 and 0.038 g cm(-2) yr(-1). As a result, the rise of the water table during the last decade has not yet affected peat accumulation rates.

  8. Evaluation of uncertainty and detection limits in 210Pb and 210Po measurement in water by alpha spectrometry using 210Po spontaneous deposition onto a silver disk.

    PubMed

    Fernández, Pedro L; Gómez, José; Ródenas, Carmen

    2012-04-01

    An easy and accurate method for the determination of (210)Pb and (210)Po in water using (210)Po spontaneous deposition onto a silver disk is proposed and assessed for its detection capabilities according to the ISO Guide for the expression of uncertainty in measurement (GUM) and ISO Standard 11929-7 concerning the evaluation of the characteristic limits for ionizing radiation measurements. The method makes no assumption on the initial values of the activity concentrations of (210)Pb, (210)Bi and (210)Po in the sample to be analyzed, and is based on the alpha spectrometric measurement of (210)Po in two different aliquots: the first one measured five weeks after the sampling date to ensure radioactive equilibrium between (210)Pb and (210)Bi and the second after a sufficient time for the ingrowth of (210)Po from (210)Pb to be significant. As shown, for a recommended time interval of seven months between (210)Po measurements, the applicability of the proposed method is limited to water samples with a (226)Ra to (210)Pb activity ratio C(Ra)/C(Pb) ≤ 4, as usual in natural waters. Using sample and background counting times of 24h and 240 h, respectively, the detection limit of the activity concentration of each radionuclide at the sampling time for a 1L sample typically varies between 0.7 and 16 mBq L(-1) for (210)Pb in water samples with an initial activity of (210)Po in the range 0-200 mBq L(-1), and between 0.6 and 8.5 mBq L(-1) for (210)Po in water samples with an initial activity of (210)Pb in the same range.

  9. 210Pb-226Ra chronology reveals rapid growth rate of Madrepora oculata and Lophelia pertusa on world's largest cold-water coral reef

    NASA Astrophysics Data System (ADS)

    Sabatier, P.; Reyss, J.-L.; Hall-Spencer, J. M.; Colin, C.; Frank, N.; Tisnérat-Laborde, N.; Bordier, L.; Douville, E.

    2012-03-01

    Here we show the use of the 210Pb-226Ra excess method to determine the growth rate of two corals from the world's largest known cold-water coral reef, Røst Reef, north of the Arctic circle off Norway. Colonies of each of the two species that build the reef, Lophelia pertusa and Madrepora oculata, were collected alive at 350 m depth using a submersible. Pb and Ra isotopes were measured along the major growth axis of both specimens using low level alpha and gamma spectrometry and trace element compositions were studied. 210Pb and 226Ra differ in the way they are incorporated into coral skeletons. Hence, to assess growth rates, we considered the exponential decrease of initially incorporated 210Pb, as well as the increase in 210Pb from the decay of 226Ra and contamination with 210Pb associated with Mn-Fe coatings that we were unable to remove completely from the oldest parts of the skeletons. 226Ra activity was similar in both coral species, so, assuming constant uptake of 210Pb through time, we used the 210Pb-226Ra chronology to calculate growth rates. The 45.5 cm long branch of M. oculata was 31 yr with an average linear growth rate of 14.4 ± 1.1 mm yr-1 (2.6 polyps per year). Despite cleaning, a correction for Mn-Fe oxide contamination was required for the oldest part of the colony; this correction corroborated our radiocarbon date of 40 yr and a mean growth rate of 2 polyps yr-1. This rate is similar to the one obtained in aquarium experiments under optimal growth conditions. For the 80 cm-long L. pertusa colony, metal-oxide contamination remained in both the middle and basal part of the coral skeleton despite cleaning, inhibiting similar age and growth rate estimates. The youngest part of the colony was free of metal oxides and this 15 cm section had an estimated a growth rate of 8 mm yr-1, with high uncertainty (~1 polyp every two to three years). We are less certain of this 210Pb growth rate estimate which is within the lowermost ranges of previous growth

  10. Adsorption characteristics of 210Pb, 210Po and 7Be onto micro-particle surfaces and the effects of macromolecular organic compounds

    NASA Astrophysics Data System (ADS)

    Yang, Weifeng; Guo, Laodong; Chuang, Chia-Ying; Schumann, Dorothea; Ayranov, Marin; Santschi, Peter H.

    2013-04-01

    210Po, 210Pb and Be isotopes (e.g. 7Be and 10Be) have long been used as proxies of particle/sediment dynamics, carbon cycling, and oceanographic investigations of coupled processes. However, adsorption characteristics and interactions between these nuclides and particle surfaces remain poorly understood. Laboratory studies have been conducted to examine the adsorption of 210Po, 210Pb and 7Be onto micro-particles, including marine suspended particulate matter, kaolinite, Al2O3, SiO2, CaCO3, Fe2O3, MnO2, and chitin in natural seawater (<1 kDa), and the role of macromolecular organic compounds (MOCs), including humic acids (HA), acid polysaccharides (APS) and proteins (BSA) in regulating the adsorption process. In the absence of MOCs, the partition coefficients (Kd, reported in log Kd) range from 3.02 to 5.19 for 210Po, from 3.22 to 6.29 for 210Pb, and from 3.57 to 4.65 for 7Be. Ferric and manganese oxides are the strongest sorbents of 210Po and 210Pb, comparing with SiO2 and CaCO3. In the presence of the protein BSA, both SiO2 and CaCO3 preferentially adsorb 210Po over 210Pb, whereas the opposite effect was observed in the presence of acid polysaccharides, indicating that proteins could enhance the adsorption of 210Po and acid polysaccharides enhance the adsorption of 210Pb. The log Kd values of both 210Po and 210Pb in the presence of MOCs become similar (log Kd at ˜4.0) for all lithogenic and biogenic particles, suggesting that their adsorption is likely controlled by specific natural organic compounds associated with particle surfaces. For 7Be, the highest and lowest log Kd value was measured, in general, on SiO2 and CaCO3, respectively, consistent with field observations. Nevertheless, the log Kd values of 7Be varied little between particle types regardless of the presence or absence of MOCs, suggesting that the adsorption of Be on particle surfaces is less affected by particle composition or MOCs. These results indicate that 7Be and 10Be could quantitatively

  11. Determining soil erosion rates on semi-arid watersheds using radioisotope-derived sedimentation chronology 2327

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study investigates erosion dynamics of the past 90 years on three small semi-arid watersheds with histories of grazing and vegetation change. Activity of 137Cs and excess 210Pb from 18 cores collected from sedimentation ponds were measured using a gamma spectrometer. The sediment was dated usi...

  12. Radiocarbon Dating, Chronologic Framework, and Changes in Accumulation Rates of Holocene Estuarine Sediments from Chesapeake Bay

    NASA Astrophysics Data System (ADS)

    Colman, Steven M.; Baucom, Pattie C.; Bratton, John F.; Cronin, Thomas M.; McGeehin, John P.; Willard, Debra; Zimmerman, Andrew R.; Vogt, Peter R.

    2002-01-01

    Rapidly accumulating Holocene sediments in estuaries commonly are difficult to sample and date. In Chesapeake Bay, we obtained sediment cores as much as 20 m in length and used numerous radiocarbon ages measured by accelerator mass spectrometry methods to provide the first detailed chronologies of Holocene sediment accumulation in the bay. Carbon in these sediments is a complex mixture of materials from a variety of sources. Analyses of different components of the sediments show that total organic carbon ages are largely unreliable, because much of the carbon (including coal) has been transported to the bay from upstream sources and is older than sediments in which it was deposited. Mollusk shells (clams, oysters) and foraminifera appear to give reliable results, although reworking and burrowing are potential problems. Analyses of museum specimens collected alive before atmospheric nuclear testing suggest that the standard reservoir correction for marine samples is appropriate for middle to lower Chesapeake Bay. The biogenic carbonate radiocarbon ages are compatible with 210Pb and 137Cs data and pollen stratigraphy from the same sites. Post-settlement changes in sediment transport and accumulation is an important environmental issue in many estuaries, including the Chesapeake. Our data show that large variations in sediment mass accumulation rates occur among sites. At shallow water sites, local factors seem to control changes in accumulation rates with time. Our two relatively deep-water sites in the axial channel of the bay have different long-term average accumulation rates, but the history of sediment accumulation at these sites appears to reflect overall conditions in the bay. Mass accumulation rates at the two deep-water sites rapidly increased by about fourfold coincident with widespread land clearance for agriculture in the Chesapeake watershed.

  13. Radiocarbon dating, chronologic framework, and changes in accumulation rates of holocene estuarine sediments from Chesapeake Bay

    USGS Publications Warehouse

    Colman, Steven M.; Baucom, P.C.; Bratton, J.F.; Cronin, T. M.; McGeehin, J.P.; Willard, D.; Zimmerman, A.R.; Vogt, P.R.

    2002-01-01

    Rapidly accumulating Holocene sediments in estuaries commonly are difficult to sample and date. In Chesapeake Bay, we obtained sediment cores as much as 20 m in length and used numerous radiocarbon ages measured by accelarator mass spectrometry methods to provide the first detailed chronologies of Holocene sediment accumulation in the bay. Carbon in these sediments is a complex mixture of materials from a variety of sources. Analyses of different components of the sediments show that total organic carbon ages are largely unreliable, because much of the carbon (including coal) has been transported to the bay from upstream sources and is older than sediments in which it was deposited. Mollusk shells (clams, oysters) and foraminifera appear to give reliable results, although reworking and burrowing are potential problems. Analyses of museum specimens collected alive before atmospheric nuclear testing suggest that the standard reservoir correction for marine samples is appropriate for middle to lower Chesapeake Bay. The biogenic carbonate radiocarbon ages are compatible with 210 Pb and 137 Cs data and pollen stratigraphy from the same sites. Post-settlement changes in sediment transport and accumulation is an important environmental issue in many estuaries, including the Chesapeake. Our data show that large variations in sediment mass accumulation rates occur among sites. At shallow water sites, local factors seem to control changes in accumulation rates with time. Our two relatively deep-water sites in the axial channel of the bay have different long-term average accumulation rates, but the history of sediment accumulation at these sites appears to reflect overall conditions in the bay. Mass accumulation rates at the two deep-water sites rapidly increased by about fourfold coincident with widespread land clearance for agriculture in the Chesapeake watershed.

  14. Skeletal sup 210 Pb from inhalation of sup 222 Rn and its decay products

    SciTech Connect

    Keane, A.T.; Schlenker, R.A.; Stebbings, J.H.

    1990-01-01

    Concern about health effects of radon and its decay products has recently broadened to include the potential role of radon in the causation of myeloid leukemia, multiple myeloma, and melanoma, kidney cancer, and certain childhood cancers. Description of the distribution of radon and its daughters in the skeleton and the marrow, and the dose delivered to red marrow, are of particular relevance. Our interest in a metabolic model for inhaled radon and radon decay products originated with an interest in the use of radioactivity measurement techniques in vivo to quantify the {sup 210}Pb activity of bone. In this paper we estimate the rates of transfer to body fluids of {sup 210}Pb originating from inhaled radon and radon decay products and the quantity of {sup 210}Pb deposited in compact and in cancellous bone for the ideal case of continuous exposure to a constant level of radon and its daughters. We review the contributions of ambient airborne {sup 210}Pb, diet, and active and passive smoking to skeletal levels of {sup 210}Pb, and finally, from the magnitude and the variability of the natural {sup 210}Pb content of the skeleton, we estimate the minimal rate of exposure to airborne radon and its decay products that is required to elevate the skeletal {sup 210}Pb content of an individual to a statistically significant level above the population mean skeletal {sup 210}Pb content derived from all the other environmental sources combined. 55 refs., 4 tabs.

  15. Estimating sediment accumulation rates in Manila Bay, a marine pollution hot spot in the Seas of East Asia.

    PubMed

    Sta Maria, E J; Siringan, F P; Bulos, A dM; Sombrito, E Z

    2009-01-01

    The GEF/UNDP/IMO/PEMSEA project identifies Manila Bay as among the marine pollution hot spots in the Seas of East Asia. (210)Pb dating of its sediment can provide a historical perspective of its pollution loading. However, the validity of (210)Pb dating in a complex dynamic coastal system of Manila Bay may come into question. Land-based sediment input can be high and physical and biological processes can possibly disturb the sediment layers. In this report, the (210)Pb profiles of sediment cores from different parts of the bay are presented. The linear sedimentation rates are shown to be higher in the recent past and are also variable across the bay. The largest change in sedimentation rate, coincided with the occurrence of a volcanic eruption in 1991 and is shown by applying a variant of the CIC model in sedimentation rate calculations. The data suggest that (210)Pb dating can be useful in estimating relative magnitudes of sedimentation rates, even in a complex dynamic coastal system like Manila Bay.

  16. Spatial and temporal variability of (7)Be and (210)Pb wet deposition during four successive monsoon storms in a catchment of northern Laos.

    PubMed

    Gourdin, E; Evrard, O; Huon, S; Reyss, J-L; Ribolzi, O; Bariac, T; Sengtaheuanghoung, O; Ayrault, S

    2014-10-01

    Fallout radionuclides (7)Be and (210)Pb have been identified as potentially relevant temporal tracers for studying soil particles dynamics (surface vs. subsurface sources contribution; remobilization of in-channel sediment) during erosive events in river catchments. An increasing number of studies compared (7)Be: (210)Pb activity ratio in rainwater and sediment to estimate percentages of freshly eroded particles. However, the lack of data regarding the spatial and temporal variability of radionuclide wet deposition during individual storms has been identified as one of the main gaps in these estimates. In order to determine these key parameters, rainwater samples were collected at three stations during four storms that occurred at the beginning of the monsoon (June 2013) in the Houay Xon mountainous catchment in northern Laos. Rainwater (7)Be and (210)Pb activities measured using very low background hyperpure Germanium detectors ranged from 0.05 to 1.72 Bq L(-1) and 0.02 to 0.26 Bq L(-1), respectively. Water δ(18)O were determined on the same samples. Total rainfall amount of the four sampled storms ranged from 4.8 to 26.4 mm (51 mm in total) at the time-fractionated collection point. Corresponding cumulative (7)Be and (210)Pb wet depositions during the sampling period were 17.6 and 2.9 Bq m(-2), respectively. The (7)Be: (210)Pb activity ratio varied (1) in space from 6 to 9 for daily deposition and (2) in time from 3 to 12 for samples successively collected. Intra-event evolution of rainwater (7)Be and (210)Pb activities as well as δ(18)O highlighted the progressive depletion of local infra-cloud atmosphere radionuclide stock with time (washout), which remains consistent with a Raleigh-type distillation process for water vapour. Intra-storm ratio increasing with time showed the increasing contribution of rainout scavenging. Implications of such variability for soil particle labelling and erosion studies are briefly discussed and recommendations are formulated

  17. Determination of (210)Pb and (210)Po in water using the extractive scintillation cocktail Polex™.

    PubMed

    Landstetter, Claudia; Hiegesberger, Bernd; Sinojmeri, Merita; Katzlberger, Christian

    2014-11-01

    Method validation was performed to achieve the accreditation for our determination method of (210)Pb and (210)Po in water. A Pb(NO3)2 carrier is added to the sample and lead is precipitated with Na2SxH2O. (210)Po is co-precipitated and the extractive scintillation cocktail Polex(™) is used to determine (210)Po and (210)Pb. Uranium is also extracted by Polex(™). It can be removed by washing the precipitate with 1% HNO3. The ingrowth of (210)Pb from (222)Rn during transportation time must be calculated. It has to be subtracted from the original (210)Pb in the sample and taken into account for the calculation of the lower limit of detection.

  18. 210Pb-226Ra chronology reveals rapid growth rate of Madrepora oculata and Lophelia pertusa on world's largest cold-water coral reef

    NASA Astrophysics Data System (ADS)

    Sabatier, P.; Reyss, J.-L.; Hall-Spencer, J. M.; Colin, C.; Frank, N.; Tisnérat-Laborde, N.; Bordier, L.; Douville, E.

    2011-12-01

    and growth rate estimates. However, the youngest branch was free of Mn enrichment and this 15 cm section reveals a growth rate of 8 mm yr-1 (~1 polyp every two to three years). However, the 210Pb growth rate estimate is within the lowermost ranges of previous growth rate estimates and may thus reflect that the coral was not developing at optimal growth conditions. Overall, 210Pb-226Ra dating can be successfully applied to determine the age and growth rate of framework-forming cold-water corals, however, removal of post-depositional Mn-Fe oxide deposits is a prerequisite. If successful, large branching M. oculata and L. pertusa coral skeletons provide unique oceanographic archive for studies of intermediate water environmentals with an up to annual time resolution and spanning over many decades.

  19. Influence of submarine groundwater discharge on (210)Po and (210)Pb bioaccumulation in fish tissues.

    PubMed

    Garcia-Orellana, J; López-Castillo, E; Casacuberta, N; Rodellas, V; Masqué, P; Carmona-Catot, G; Vilarrasa, M; García-Berthou, E

    2016-05-01

    This study presents the results of the accumulation of (210)Po and (210)Pb in fish tissues and organs in a brackish-water marshland that is characterized by high concentrations of (222)Rn and (226)Ra supplied by submarine groundwater discharge (SGD). Tissues and organs from Cyprinus carpio, Chelon labrosus and Carassius auratus in the wetland were significantly enriched by both (210)Pb and (210)Po (up to 55 and 66 times, respectively) compared to blanks. The major input route of (210)Pb and (210)Po into the fish body seems to be through ingestion, due to the high levels of (210)Pb and (210)Po found in the gut content as well as in organs involved in digestion and metabolism (i.e. gut, kidney and hepatopancreas). Results showed that (210)Po was more accumulated in all fish tissues and organs except for the spine, which showed a higher affinity for (210)Pb, due to its capacity to replace Ca from apatite in bones. Over all the variables analyzed, fish tissues/organs and, secondarily, fish species were the most important factors explaining the concentration of radionuclides, whereas fish length and the sampling location played a minor role. The relationship of the two radionuclides varied markedly among tissues and their concentration levels were only correlated in gills, gut and, marginally, in spines. In general, the highest values of (210)Pb and (210)Po concentrations in tissues were found on C. labrosus tissues rather C. auratus and C. carpio. This study demonstrates that inputs of natural radionuclides supplied by SGD to coastal semi-enclosed areas (such as marshlands, lagoons or ponds) may significantly increase the contents of (210)Pb and (210)Po in fish tissues/organs. Thus, this study represents one of the first evidences of direct ecological effects derived from SGD.

  20. Atmospheric fluxes of 210Pb to the western Mediterranean Sea and the Saharan dust influence

    NASA Astrophysics Data System (ADS)

    Garcia-Orellana, J.; Sanchez-Cabeza, J. A.; Masqué, P.; ÀVila, A.; Costa, E.; Loã¿E-Pilot, M. D.; Bruach-MenchéN, J. M.

    2006-08-01

    Pb 210 is a well known tracer of particle dynamics in the marine environment. Geochemical models partially rely on the knowledge of its atmospheric input. Unfortunately, this is poorly known in the western Mediterranean Sea, especially regarding long-term records. In this work we have evaluated the 210Pb annual atmospheric flux to this region from the analysis of 12 soil cores collected from coastal and island sites and total atmospheric deposition collected in Corsica during 1 year. The 210Pb fluxes ranged from 34 ± 3 to 121 ± 12 Bq m-2 yr-1, with an average of 75 Bq m-2 yr-1, and were strongly correlated (R2 = 0.95) with mean annual rainfall. This provides the possibility to determine 210Pb fluxes in a given location if the mean annual rainfall is well known, a useful outcome for both marine biogeochemical and soil erosion studies in this region. We have also estimated the mean annual atmospheric flux of 210Pb due to Saharan dust events registered in total deposition north of Barcelona during the last 17 years, yielding a value of 20 Bq m-2 yr-1. This flux represents a fraction of about 16% of the total atmospheric deposition of 210Pb in this area, but it could be up to 50% in sites with lower rainfall.

  1. Detection of /sup 210/Pb in the lungs of smokers by in-vivo gamma spectrometry

    SciTech Connect

    Berger, C.D.; Lane, B.H.

    1982-09-01

    Since mainstream smoke is highly enriched in /sup 210/Pb, alpha radiation from inhaled cigarette smoke particles has been proposed as a cancer-producing agent in cigarette smokers. /sup 210/Po and /sup 210/Pb have been observed in tobacco, cigarette smoke and in the lungs of smokers. Since /sup 210/Pb is highly enriched in mainstream smoke, there have been estimates of yearly excesses of /sup 210/Pb in the lungs of one-pack-a-day smokers of 3 to 10 pCi (0.11 to 0.37 Bq). The ORNL Whole Body Counter was used to verify this estimate by the methodology of high-resolution, in vivo gamma spectrometry. Measurements were made on 113 adult male non-radiation workers who have either smoked at least one pack of cigarettes per day for at least five years, or have never smoked cigarettes. An analysis-of-variance table was generated based on the Pb-ratio for each individual which revealed that there was no statistically significant increase in the amount of /sup 210/Pb in the lungs of smokers over those of non-smokers. Sources of error are also discussed.

  2. Metrological Determination of Natural Radioactive Isotopes {sup 226}Ra, {sup 228}Ra and {sup 210}Pb by Means of Ge Detector

    SciTech Connect

    Almeida, Maria Candida M. de; Delgado, Jose U.; Poledna, Roberto; Oliveira, Estela Maria de; Silva, Ronaldo L. da

    2008-08-07

    A metrological method to determine the activity per mass unity (activity concentration) of {sup 226}Ra and {sup 210}Pb ({sup 238}U decay series) and {sup 228}Ra ({sup 232}Th series) by gamma-ray spectrometers based on hyper-pure coaxial germanium detector was developed. In the soil the {sup 22}Ra (half-life = 1600 years) exhibits the same level of radioactivity as {sup 238}U (half-life 4.5x10{sup 9} years) because of a natural phenomenon called secular equilibrium. {sup 226}Ra decays into {sup 222}Rn (half-life = 3.8 days), a radioactive inert gas. After several days, the {sup 222}Rn naturally decays to {sup 218}Po (half-life = 3 minutes), where finally {sup 210}Pb (half-life = 22 years) is produced. The metrological capability of high-resolution gamma-ray spectrometry for naturally occurring radionuclides at environmental levels is showed, with emphasis on the use of 2 mL standard sources volume in a glass ampoule. Source preparation and calibration procedures are described. Radionuclide standards in an activity range of 10 to 250 Bq/g were produced which can be applied in a variety of environmental sample analysis (water, plant material, sediment, etc.). Uncertainties for {sup 226}Ra and {sup 210}Pb around 3% (k = 1) were obtained.

  3. (210)Po and (210)Pb in medicinal plants in the region of Karnataka, Southern India.

    PubMed

    Chandrashekara, K; Somashekarappa, H M

    2016-08-01

    The activity concentrations of naturally occurring radionuclides (210)Po and (210)Pb were estimated in some selected medicinal plants and soil samples of coastal Karnataka in India. The mean activity concentrations of (210)Po and (210)Pb varied in the range of 4.7-42.9 Bq kg(-1) (dry weight) and 36.1-124 Bq kg(-1) (dry weight) in the soil samples, and 3.3-63.7 Bq kg(-1) (dry weight) and 12.0-406 Bq kg(-1) (dry weight), in the medicinal plant samples, respectively. The plants, Ocimum sanctum L. and Plectranthus amboinicus (Lour.) Spreng had significantly higher activity concentrations of (210)Po and (210)Pb than other species sampled. In spite of disequilibrium between them, these two radionuclides were well correlated in both soil and medicinal plants.

  4. Determination of 210Pb and 210Po in seawater and marine particulate matter

    NASA Astrophysics Data System (ADS)

    Fleer, A. P.; Bacon, M. P.

    1984-06-01

    Natural 210Pb and 210Po are determined in seawater and suspended particulate matter by alpha spectrometry with silicon surface-barrier detectors. Procedures used at WHOI include a pre-concentration, based on co-precipitation with cobalt-APDC, which can be carried out at sea. Source preparation is by spontaneous deposition of polonium on silver, with 210Pb being determined by measurement of 210Po ingrowth. Yields are monitored by the addition of 208Po and stable lead tracers. A desk-top computer is programmed to process the alpha spectra and make radioactive growth and decay computations. The accuracy of oceanic 210Pb data is estimated to be ±10%, somewhat worse than the attainable precision.

  5. Rapid determination of (210)Pb and (210)Po in water and application to marine samples.

    PubMed

    Villa-Alfageme, M; Mas, J L; Hurtado-Bermudez, S; Masqué, P

    2016-11-01

    Measurement of radionuclides in marine samples, specifically radioactive pairs disequilibrium, has gained interest lately due to their ability to trace cutting edge biogeochemical processes. In this context, we developed a fast, direct method for determining (210)Pb and (210)Po water through the use of ultra low-level liquid scintillation counting and alpha-particle spectrometry respectively and through Eichrom Sr resins for the Po-Pb separation. For (210)Pb analysis, the method uses stable lead as a yield tracer measured by a robust ICP-MS technique, and (210)Po is determined through self-deposition using the conventional (209)Po yield tracer. The improvements of the method over other techniques are: a) the analysis can be completed within 6 days, simplifying other methods, b) very low limits of detection have been achieved -0.12 and 0.005mBqL(-1) for (210)Pb and (210)Po, respectively - and c) most of the method could be carried out in on-board analysis. We applied the method to different aqueous samples and specifically to marine samples. We determined (210)Pb and (210)Po in the dissolved fraction of Mediterranean Sea water and an estuary at the South-West of Spain. We found that it can be successfully employed to marine samples but we recommend to i) use a minimum of 20L water to measure the (210)Pb in the dissolved phase by LSC and lower volumes to measure total concentrations; ii) wait for (210)Pb and (210)Bi in secular equilibrium and measure the total spectrum to minimise the limit of detection and improve accuracy.

  6. {sup 210}Po and {sup 210}Pb in Forest Soil and in Wild Berries in Finland

    SciTech Connect

    Vaaramaa, Kaisa; Lehto, Jukka; Solatie, Dina; Aro, Lasse

    2008-08-07

    The behaviour of {sup 210}Po and {sup 210}Pb was investigated in forests in the Southern Finland site and in the Northern Finland site. Sampling sites were in Scots pine (Pinus sylvestris) forests. Maximum activities of {sup 210}Po and {sup 210}Pb in soil columns were found in organic layers. According to preliminary results of wild berry samples, the lowest {sup 210}Po concentrations were found in berries. The highest concentration of {sup 210}Po was found in stems of the blueberry (Vaccinium myrtillus) and the lingonberry (Vaccinium vitis-idaea) samples.

  7. 210Po and 210Pb in Forest Soil and in Wild Berries in Finland

    NASA Astrophysics Data System (ADS)

    Vaaramaa, Kaisa; Solatie, Dina; Aro, Lasse; Lehto, Jukka

    2008-08-01

    The behaviour of 210Po and 210Pb was investigated in forests in the Southern Finland site and in the Northern Finland site. Sampling sites were in Scots pine (Pinus sylvestris) forests. Maximum activities of 210Po and 210Pb in soil columns were found in organic layers. According to preliminary results of wild berry samples, the lowest 210Po concentrations were found in berries. The highest concentration of 210Po was found in stems of the blueberry (Vaccinium myrtillus) and the lingonberry (Vaccinium vitis-idaea) samples.

  8. Sinking fluxes of (210)Pb and (210)Po in the deep basin of the northern South China Sea.

    PubMed

    Wei, Ching-Ling; Chia, Chao-Yuan; Chou, Wen-Chen; Lee, Wen-Huei

    2016-06-07

    Vertical fluxes of total mass (Fmass), particulate organic carbon (FPOC), particulate inorganic carbon (FPIC), (210)Pb (FPb-210), and (210)Po (FPo-210) were determined by sediment traps deployed at two depths, 2000 m and 3500 m, at SEATS (South East Asian Time-series Study, 116°00°E, 18°00°N) in the northern South China Sea during June 2008-June 2009. The Fmass ranges from 12.2 to 55.1 mg m(-2) d(-1) and from 89.3 to 250.8 mg m(-2) d(-1), at 2000 m and 3500 m, respectively, and shows seasonal and inter-annul variation. The temporal variation of FPOC, FPIC, and FPb-210 were in phase with the Fmass, which was coupled with the seasonal cycles of primary production in the euphotic layer. The FPb-210 ranges from 5 to 48 dpm m(-2)d(-1) and from 38 to 105 dpm m(-2)d(-1), at 2000 m and 3500 m, respectively. Contrasting with (210)Pb, the FPo-210 shows poor correlation with Fmass. The FPo-210 ranges from 3 to 146 dpm m(-2)d(-1) and from 50 to 309 dpm m(-2)d(-1), at 2000 m and 3500 m, respectively. Episodic events of the settling of biological particles from the surface layer and the regeneration processes the deep layer control the (210)Po removal in the water column of the South China Sea. Strong correlations of the flux and source ratio of (210)Pb, (F/P)Pb-210, and the particulate carbon fluxes were found, which give relationships of FPOC (μg cm(-2)y(-1)) = 26.8 + 371.0 (F/P)Pb-210 and FPIC (μg cm(-2)y(-1)) = -1.4 + 533.1 (F/P)Pb-210.

  9. Constraints from Airborne (210)Pb Observations on Aerosol Scavenging and Lifetime in a Global Chemical Transport Model

    NASA Technical Reports Server (NTRS)

    Zhang, Bo; Liu, Hongyu; Crawford, James H.; Fairlie, Duncan T.; Chen, Gao; Dibb, Jack E.; Shah, Viral; Sulprizio, Melissa P.; Yantosca, Robert M.

    2016-01-01

    Lead-210 distribution and lifetime in the atmosphere are not sensitive to ice in-cloud scavenging in convective updraft. Ice in-cloud scavenging in stratiform clouds reduce tropospheric (210)Pb lifetime by approximately 1 day and results in better agreements with observed surface observations and aircraft measured profiles. However, the process results in significant underestimate of (210)Pb in UT/LS.

  10. The Transport and Fate of Particulate Material in a Shallow, Turbid Estuary: Seasonal and Decadal Characteristics from 7-Be and 210-Pb Techniques

    NASA Technical Reports Server (NTRS)

    Booth, J. G.; McKee, Brent A.; Meriwether, John R.

    1999-01-01

    Seasonal and long-term sediment transport characteristics were examined using surficial sediment 7-Be inventories and the down core distribution of excess 210-Pb. Data were collected in the Barataria Basin, LA over the fifteen month period from September 1995 to January 1997. Seasonal sediment transport rates based on 7-Be inventories ranged from -1.6E3 to 1.42E4 g/m2/yr, whereas decadal sediment burial rates based on excess 210-Pb ranged from 3.83E2 to 2.00E3 g/m2/yr, respectively. Seasonal transport characteristics vary with location in the basin and appear to be largely controlled by seasonal weather patterns and the associated winds. It appears that, at less sheltered locations, long term rates of sediment burial are controlled by frontal passages and the associated strong northerly and southerly component winds; whereas at fetch limited locations burial rates are likely controlled by stronger weather events such as tropical storms and hurricanes.

  11. Multi-proxy dating of Holocene maar lakes and Pleistocene dry maar sediments in the Eifel, Germany

    NASA Astrophysics Data System (ADS)

    Sirocko, Frank; Dietrich, Stephan; Veres, Daniel; Grootes, Pieter M.; Schaber-Mohr, Katja; Seelos, Klemens; Nadeau, Marie-Josée; Kromer, Bernd; Rothacker, Leo; Röhner, Marieke; Krbetschek, Matthias; Appleby, Peter; Hambach, Ulrich; Rolf, Christian; Sudo, Masafumi; Grim, Stephanie

    2013-02-01

    During the last twelve years the ELSA Project (Eifel Laminated Sediment Archive) at Mainz University has drilled a total of about 52 cores from 27 maar lakes and filled-in maar basins in the Eifel/Germany. Dating has been completed for the Holocene cores using 6 different methods (210Pb and 137Cs activities, palynostratigraphy, event markers, varve counting, 14C). In general, the different methods consistently complement one another within error margins. Event correlation was used for relating typical lithological changes with historically known events such as the two major Holocene flood events at 1342 AD and ca 800 BC. Dating of MIS2-MIS3 core sections is based on greyscale tuning, radiocarbon and OSL dating, magnetostratigraphy and tephrochronology. The lithological changes in the sediment cores demonstrate a sequence of events similar to the North Atlantic rapid climate variability of the Last Glacial Cycle. The warmest of the MIS3 interstadials was GI14, when a forest with abundant spruce covered the Eifel area from 55 to 48 ka BP, i.e. during a time when also other climate archives in Europe suggested very warm conditions. The forest of this "Early Stage 3 warm phase" developed subsequently into a steppe with scattered birch and pine, and finally into a glacial desert at around 25 ka BP. Evidence for Mono Lake and Laschamp geomagnetic excursions is found in two long cores. Several large eruptions during Middle and Late Pleistocene (Ulmener Maar - 11,000 varve years BP, Laacher See - 12,900 varve years BP, Mosenberg volcanoes/Meerfelder Maar 41-45 cal ka BP, Dümpel Maar 116 ka BP, Glees Maar - 151 ka BP) produced distinct ash-layers crucial for inter-core and inter-site correlations. The oldest investigated maar of the Eifel is 40Ar/39Ar dated to the time older than 520 ka BP.

  12. Distribution of 7Be, 210Pb and 137Cs in watersheds of different scales in the Seine River basin: inventories and residence times.

    PubMed

    Le Cloarec, Marie-Françoise; Bonté, Philippe; Lefèvre, Irène; Mouchel, Jean-Marie; Colbert, Steven

    2007-04-01

    The activity of environmental radionuclides ((7)Be, (210)Pb and (137)Cs) was monitored in nested catchments, inside the Seine River basin. Suspended matter data was collected at 8 different watersheds, ranging from order 1 to order 7, and ranging in size over 4 orders of magnitude. Suspended matter was analyzed for (210)Pb, (137)Cs and (7)Be, and used to calculate the flux of sediments out of each watershed. Monthly atmospheric flux data of (210)Pb and (7)Be was analyzed to assess the input flux of each into the watersheds, taking into account the rainfall during sampling periods. Taking advantage of the different half-lives of (7)Be (53 days) and (210)Pb (22 years), a two-box model was built for each of the catchments following a methodology previously developed by Dominik et al. [Dominik J, Burrus D, Vernet JP. Transport of the environmental radionuclides in alpine watershed. Earth Planet Sci Letters 1987; 84: 165-180.]. The model divides the watershed into a soil box and a rapid reservoir and provides insight into the removal rate of suspended matter from the surrounding watershed. The model enables the assessment of the surface area and the residence time of slow and rapid reservoirs to describe the fate of contaminants of atmospheric origin inside the river basin. The model was improved by considering the dissolved fraction in the total flux and adding the (137)Cs inventory as an additional constraint. The effects of these changes are discussed. Residence times in the soil box, characterized by low transport velocity, range between 4800 years at Melarchez (order 1) to about 30000 years at Andresy and Poses (order 7). They remain constant in each watershed over a large range of variation of atmospheric fluxes of (7)Be and (210)Pb during the whole study, but are sensitive to SM variations. The residence time in the rapid box, which includes the surface of the river and immediate surroundings, is less than one year, while its surface area is in the range 0.6% to

  13. Distribution of (210)Pb and (210)Po in boreal forest soil.

    PubMed

    Vaaramaa, Kaisa; Aro, Lasse; Solatie, Dina; Lehto, Jukka

    2010-11-15

    Vertical distribution and activity contents of (210)Pb and (210)Po were investigated in forest soils of Scots pine-dominated (Pinus sylvestris L.) stands from seven different locations in Finland. The mean total inventory in the soil profile, up to 20cm, of (210)Pb was 4.0kBqm(-2) (range3.1-5.0kBqm(-2)) and (210)Po 5.5kBqm(-2) (range 4.0-7.4kBqm(-2)), the organic soil layer containing 45% of the total inventory of both nuclides. In both the organic and the mineral layers the (210)Po/(210)Pb ratio was close to unity indicating a radioactive equilibrium between them. In the litter layer there was, however, a clear excess of (210)Po suggesting that polonium is recycled via root uptake from the root zone to the ground surface. The activity concentration (Bqkg(-1)) of (210)Pb clearly correlated with organic matter and the Fe, Al and Mn concentrations in soil indicating that radioactive lead is associated both with humic substances and the oxides of iron, aluminium and manganese. Radioactive lead was also seen to follow the behavior of stable lead. No systematic correlation between polonium and soil properties was seen.

  14. (210)Pb-(226)Ra disequilibria in young gas-laden magmas.

    PubMed

    Reagan, Mark; Turner, Simon; Handley, Heather; Turner, Michael; Beier, Christoph; Caulfield, John; Peate, David

    2017-03-24

    We present new (238)U-(230)Th-(226)Ra-(210)Pb and supporting data for young lavas from southwest Pacific island arcs, Eyjafjallajökull, Iceland, and Terceira, Azores. The arc lavas have significant (238)U and (226)Ra excesses, whereas those from the ocean islands have moderate (230)Th and (226)Ra excesses, reflecting mantle melting in the presence of a water-rich fluid in the former and mantle melting by decompression in the latter. Differentiation to erupted compositions in both settings appears to have taken no longer than a few millennia. Variations in the ((210)Pb/(226)Ra)0 values in all settings largely result from degassing processes rather than mineral-melt partitioning. Like most other ocean island basalts, the Terceira basalt has a (210)Pb deficit, which we attribute to ~8.5 years of steady (222)Rn loss to a CO2-rich volatile phase while it traversed the crust. Lavas erupted from water-laden magma systems, including those investigated here, commonly have near equilibrium ((210)Pb/(226)Ra)0 values. Maintaining these equilibrium values requires minimal persistent loss or accumulation of (222)Rn in a gas phase. We infer that degassing during decompression of water-saturated magmas either causes these magmas to crystallize and stall in reservoirs where they reside under conditions of near stasis, or to quickly rise towards the surface and erupt.

  15. Growth rate of a deep-sea coral using sup 210 Pb and other isotopes

    SciTech Connect

    Druffel, E.R.M.; King, L.I.; Belastock, R.A.; Buesseler, K.O. )

    1990-05-01

    A deep-sea coral was studied to determine its growth rate and to reconstruct time histories of isotope distributions in the deep ocean. The specimen was collected at a depth of 600 m off Little Bahama Banks using the Deep Submergence Vehicle (DSV) Alvin. The growth rate of the calcitic coral trunk was determined using excess {sup 210}Pb measured in concentric bands. Excess {sup 210}Pb was found in the outer half of the coral's radius, and a growth rate of 0.11 {plus minus} 0.02 mm/a is calculated. Assuming a constant growth rate during formation of the entire trunk, an age of 180 {plus minus} 40 a is estimated for the coral. The decrease observed in radiocarbon activities measured on the same bands (Griffin and Druffel, 1989) concurred with the growth rate estimated from excess {sup 210}Pb activity. {sup 239,240}Pu activities measured by mass spectrometry were also detected in the outer two bands of the coral, as expected from the {sup 210}Pb chronology. Stable oxygen and carbon isotopes measured in samples collected by a variety of techniques are positively correlated. This is evidence of a variable kinetic isotope effect most likely caused by variations in the skeletal growth rate. Long-lived corals such as this specimen have the potential for serving as integrators of seawater chemistry in the deep-sea over several century timescales.

  16. 210Pb-226Ra disequilibria in young gas-laden magmas

    NASA Astrophysics Data System (ADS)

    Reagan, Mark; Turner, Simon; Handley, Heather; Turner, Michael; Beier, Christoph; Caulfield, John; Peate, David

    2017-03-01

    We present new 238U-230Th-226Ra-210Pb and supporting data for young lavas from southwest Pacific island arcs, Eyjafjallajökull, Iceland, and Terceira, Azores. The arc lavas have significant 238U and 226Ra excesses, whereas those from the ocean islands have moderate 230Th and 226Ra excesses, reflecting mantle melting in the presence of a water-rich fluid in the former and mantle melting by decompression in the latter. Differentiation to erupted compositions in both settings appears to have taken no longer than a few millennia. Variations in the (210Pb/226Ra)0 values in all settings largely result from degassing processes rather than mineral-melt partitioning. Like most other ocean island basalts, the Terceira basalt has a 210Pb deficit, which we attribute to ~8.5 years of steady 222Rn loss to a CO2-rich volatile phase while it traversed the crust. Lavas erupted from water-laden magma systems, including those investigated here, commonly have near equilibrium (210Pb/226Ra)0 values. Maintaining these equilibrium values requires minimal persistent loss or accumulation of 222Rn in a gas phase. We infer that degassing during decompression of water-saturated magmas either causes these magmas to crystallize and stall in reservoirs where they reside under conditions of near stasis, or to quickly rise towards the surface and erupt.

  17. Source areas of airborne 7Be and 210Pb measured in Northern Finland.

    PubMed

    Paatero, J; Hatakka, J

    2000-12-01

    Daily aerosol samples were collected at Sodankylä, Northern Finland, from July 1995 to June 1997. The filter samples were analyzed for 7Be by semiconductor gamma spectrometry and for 210Pb by alpha counting of the in-grown 210Po. The concentrations were lognormally distributed with median concentrations of 2,500 and 160 muBq m(-3) for 7Be and 210Pb, respectively. The trajectory analysis performed showed that the highest 210Pb activity concentrations were associated with continental air masses originating in Central Russia. High 7Be activity concentrations were found in air masses from Central Russia and, during springtime, also in air masses coming from southwest. The latter cases were attributed to the transfer of stratospheric air masses into the troposphere along the polar front. Slightly elevated 7Be and 210Pb concentrations were found in air masses coming to Sodankyla from northwest between 70th and 80th latitudes. This was attributed to the long-range transport from continental North America.

  18. Contribution of 210Pb bremsstrahlung to the background of lead shielded gamma spectrometers

    NASA Astrophysics Data System (ADS)

    Mrđa, D.; Bikit, I.; Vesković, M.; Forkapić, S.

    2007-03-01

    Lead, which is often used as a shielding material, contains 210Pb ( T1/2=22.3 y). The 46.54 keV γ-intensity of 210Pb can be easily reduced by an inner lining, but the bremsstrahlung caused by the β-decay of its daughter, 210Bi, with a maximal electron energy of 1.16 MeV, will contribute to the gamma detector background. The spectrum of this bremsstrahlung is calculated by numerically fitting the β-spectrum and integrating the Koch-Motz formula. The absorption of the bremsstrahlung in the lead and detection efficiencies for the HPGe detector are calculated by the effective solid angle algorithm, using corrections for the photopeak/Compton ratio of cross-sections in Ge. By comparison with the measured background spectrum, it is shown that, for the lead with 25 Bq/kg of 210Pb up to 500 keV of gamma spectrum, the bremsstrahlung contribution to the background is about 20% for our surface-based detector system. Also, we compared our calculations with a Monte Carlo simulation of another detector system with a shield containing 1 Bq/kg of 210Pb and found that our analytical method gives a value of roughly two times higher than the Monte Carlo one for the total bremsstrahlung contribution. The quality of the analytical semi-empirical method is proved by the reasonable agreement with the experimental results published.

  19. Lead precipitation fluxes at tropical oceanic sites determined from /sup 210/Pb measurements

    SciTech Connect

    Settle, D.M.; Patterson, C.C.; Turekian, K.K.; Cochran, J.K.

    1982-02-20

    Concentrations of lead, /sup 210/Pb, and /sup 210/Po were measured in rain selected for least influence by local sources of contamination at several tropical and subtropical islands (Enewetak; Pigeon Key, Florida; and American Samoa) and shipboard stations (near Bermuda and Tahiti). Ratios expressed as ng Pb/dpm /sup 210/Pb in rain were 250--900 for Pigeon Key (assuming 12% adsorption for /sup 210/Pb and no adsorption for lead), depending on whether the air masses containing the analyzed rain came from the Caribbean or from the continent, respectively; about 390 for the northern Sargasso Sea downwind from emissions of industrial lead in North America; 65 for Enewetak, remote from continental emissions of industrial lead in the northern hemisphere; and 14 near Tahiti, a remote location in the southern hemisphere where industrial lead emissions to the atmosphere are much less than in the northern hemisphere. (The American Samoa sample yielded a higher ratio than Tahiti; the reason for this is not clear but may be due to local Pb sources). The corresponding fluxes of lead to the oceans, based on measured or modeled /sup 210/Pb precipitation fluxes, are about 4 ng Pb/cm/sup 2/y for Tahiti, 10 for Enewetak, and 270 for the Sargasso Sea site, and between 110 to 390 at Pigeon Key.

  20. 210Pb-226Ra disequilibria in young gas-laden magmas

    PubMed Central

    Reagan, Mark; Turner, Simon; Handley, Heather; Turner, Michael; Beier, Christoph; Caulfield, John; Peate, David

    2017-01-01

    We present new 238U-230Th-226Ra-210Pb and supporting data for young lavas from southwest Pacific island arcs, Eyjafjallajökull, Iceland, and Terceira, Azores. The arc lavas have significant 238U and 226Ra excesses, whereas those from the ocean islands have moderate 230Th and 226Ra excesses, reflecting mantle melting in the presence of a water-rich fluid in the former and mantle melting by decompression in the latter. Differentiation to erupted compositions in both settings appears to have taken no longer than a few millennia. Variations in the (210Pb/226Ra)0 values in all settings largely result from degassing processes rather than mineral-melt partitioning. Like most other ocean island basalts, the Terceira basalt has a 210Pb deficit, which we attribute to ~8.5 years of steady 222Rn loss to a CO2-rich volatile phase while it traversed the crust. Lavas erupted from water-laden magma systems, including those investigated here, commonly have near equilibrium (210Pb/226Ra)0 values. Maintaining these equilibrium values requires minimal persistent loss or accumulation of 222Rn in a gas phase. We infer that degassing during decompression of water-saturated magmas either causes these magmas to crystallize and stall in reservoirs where they reside under conditions of near stasis, or to quickly rise towards the surface and erupt. PMID:28338093

  1. Distributions of (137)Cs and (210)Pb in moss collected from Belarus and Slovakia.

    PubMed

    Aleksiayenak, Yu V; Frontasyeva, M V; Florek, M; Sykora, I; Holy, K; Masarik, J; Brestakova, L; Jeskovsky, M; Steinnes, E; Faanhof, A; Ramatlhape, K I

    2013-03-01

    In the present work, moss samples collected in Slovakia and Belarus were assayed with respect to gamma-emitting radionuclides. The results for (137)Cs and (210)Pb are discussed. Moss was used for the first time in Belarus, as a biological indicator of radioactive environmental pollution in consequence of the Chernobyl accident in 1986. In Belarus, the maximum activity of (137)Cs was observed in the Gomel region near Mazyr (6830 Bq/kg) and the minimum activity in the Vitebsyevsk Region near Luzhki-Yazno (5 Bq/kg). "Hot spots" were also observed near the towns Borisow and Yuratsishki. The results of measurements of (137)Cs in moss samples collected in 2000, 2006 and 2009 in the same localities of Slovakia are presented and compared with the results of air monitoring of (137)Cs carried out in Slovakia from 1977 until 2010. Measurements of the (210)Pb concentration in moss samples collected over the territory of Slovakia showed, that the median value exceed 2.3 times median value of (210)Pb obtained for Belarus moss. For that reason, the inhalation dose for man from (210)Pb and (137)Cs in Slovakia is more than twice as high as in Belarus, in spite of the initially very high (137)Cs exposure in the latter country.

  2. Determination of (210)Po and (210)Pb in red-capped scaber (Leccinum aurantiacum): bioconcentration and possible related dose assessment.

    PubMed

    Strumińska-Parulska, Dagmara I; Szymańska, Karolina; Krasińska, Grażyna; Skwarzec, Bogdan; Falandysz, Jerzy

    2016-11-01

    The paper presents the studies on (210)Po and (210)Pb activity determination in red-capped scaber (Leccinum aurantiacum (Bulliard) Gray) collected in northern Poland. The aims of the studies were to determine (210)Po and (210)Pb content in analyzed mushrooms, evaluate the bioconcentration levels, and estimate possible related annual effective radiation dose to mushrooms consumers. The activities of (210)Po and (210)Pb in red-capped scaber were un-uniform and depended on sampling sites. But (210)Po and (210)Pb activity concentrations did not reflect their concentrations in topsoil. The results showed that the consumption of analyzed mushrooms should not increase significantly the total effective radiation dose from (210)Po and (210)Pb decay.

  3. Aerosol deposition and origin in French mountains estimated with soil inventories of 210Pb and artificial radionuclides

    NASA Astrophysics Data System (ADS)

    Le Roux, Gaël; Pourcelot, Laurent; Masson, Olivier; Duffa, Céline; Vray, Françoise; Renaud, Philippe

    Radionuclide inventories were measured in soils from different French mountainous areas: Chaîne des Puys (Massif Central), Eastern Corsica, Jura, Montagne Noire, Savoie, Vosges and Rhine Valley. 210Pb soil inventories were used to estimate long-term (>75 yr) deposition of submicron aerosols. Whereas 210Pb total deposition is explained partly by wet deposition, as demonstrated by increase of 210Pb inventory with annual rainfall; a part of 210Pb in the soils of higher altitude is caused by orographic depositions. Using measurements of radionuclides coming from nuclear aerial weapon tests ( 137Cs and Pu isotopes), we were able to estimate the origin of aerosols deposited in high-altitude sites and to confirm the importance of occult deposition and feeder-seeder mechanism. Using a simple mass balance model, we estimate that occult deposition and feeder-seeder mechanisms account to more than 50% of total deposition of 210Pb and associated submicron aerosols in French altitude sites.

  4. Temporal variation of 7Be and 210Pb size distributions in ambient aerosol

    NASA Astrophysics Data System (ADS)

    Winkler, R.; Dietl, F.; Frank, G.; Tschiersch, J.

    The size distributions of the cosmogenic 7Be and of the long-lived radon progeny 210Pb in ambient aerosols were measured continuously from December 1994 to the end of March 1996 in ground-level air at a semi-rural location in south Germany. Aerosol sampling was performed at a height of 4 m above ground with a low-pressure cascade impactor of the Berner type covering the size range from 0.06 to 16 μm and simultaneously with an high-volume sampler. Each sampling period was 10 d. Activities of 7Be and 210Pb were measured by gamma spectrometry and aerosol mass was determined gravimetrically. In all experiments the activity distributions of 7Be as well as of 210Pb were unimodal (log-normal) and associated with submicron aerosols of about 0.5-0.6 μm aerodynamic diameter. On average, the activity median diameters of 7Be (AMD: 0.57 μm) and of 210Pb (AMD: 0.53 μm) have been found to be significantly lower than the average mass median diameter (MMD: 0.675 μm) and higher or at most equal than the respective surface median diameter (SMD: 0.465 μm) of the aerosols: SMD⩽AMD Pb210210Pb. While in the winter months (October to April) a difference between the activity distributions of 210Pb (AMD: 0.595 μm) and 7Be (AMD: 0.59 μm) was not detectable, in summer, 210Pb was associated with significantly smaller aerosols (AMD: 0.43 μm) than 7Be (AMD: 0.52 μm). Comparing the activity median diameters observed in summer with those in winter, on average significantly lower diameters were found in summer pointing to shorter residence times in the summer months.

  5. (7)Be, (210)Pb, and (210)Po in the surface air from the Arctic to Antarctica.

    PubMed

    Persson, Bertil R R; Holm, Elis

    2014-12-01

    In the present study we have investigated the activity concentrations of (210)Pb, (210)Po as well as (7)Be in surface air of the North and South Atlantic (1988-1989), the Arctic Ocean (1991), and along the coastline of Siberia (1994) during succeeding expeditions in the Swedish Polar Research program. During the cruises in the Arctic Ocean during 1991-07-28 to 1991-10-04 the average air concentrations of (7)Be was 0.6 ± 0.4 mBq/m(3), (210)Pb 40 ± 4 μBq/m(3) and (210)Po-38 ± 10 μBq/m(3). During the Swedish-Russian Tundra Ecology-94 expedition along the Siberian coastline the average air concentrations of (7)Be and (210)Pb measured during May-July were 11 ± 3, and 2.4 ± 0.4 mBq/m(3), and during July-September they were 7.2 ± 2 and 2.7 ± 1.1 mBq/m(3) respectively. The results from measurements of the activity concentration of (210)Pb in the air over the Arctic Ocean vary between 75 and 176 μBq/m(3). In the air close to land masses, however, the activity concentration of (210)Pb in the air increases to 269-2712 μBq/m(3). The activity concentration of (7)Be in the South Atlantic during the cruise down to Antarctica varied between 1.3 and 1.7 with an average of 1.5 ± 0.8 mBq/m(3). The activity concentration of (210)Pb in the South Atlantic down to Antarctica varied between 6 and 14 μBq/m(3). At the Equator the activity concentration recorded in November 1988 was 630 μBq/m(3) and in April 1989 it was 260 μBq/m(3). The average activity concentration of (210)Pb during the route Gothenburg-Montevideo in 1988 was 290 and on the return Montevideo-Gothenburg it was 230 μBq/m(3). The activity concentration of (210)Po in the South Atlantic down to Antarctica varied between 15 and 58 μBq/m(3). At the Equator the activity concentration in November 1988 was 170 and in April 1989 it was 70 μBq/m(3). The average activity concentration of (210)Po during the route Gothenburg-Montevideo in 1988 was 63 and on the return Montevideo

  6. Sediment-Tracing Technology: An Overview

    DTIC Science & Technology

    2006-09-01

    the 210Pb radioisotope to understand sediment processes and application of these methods over various depositional environments spans more than 40...103114.0 26.22 2ln −== yλ , the radioactive decay constant Considerations in Application of 210Pb. Factors influencing the accuracy of 210Pb analysis...in a lacustrine environment (Pennington 1973; Ritchie et al. 1983; Appleby et al. 2003). Considerations in Application of 137Cs. The basis for using

  7. Sediment Dating With Short-Lived Radioisotopes In Monterey Canyon, California Imply Episodes Of Rapid Deposition And Erosion

    NASA Astrophysics Data System (ADS)

    Lorenson, T. D.; Swarzenski, P. W.; Maier, K. L.; Gwiazda, R.; Paull, C. K.; Sumner, E.; Symons, W. O.

    2015-12-01

    Submarine canyons are a major conduit for terrestrial material to the deep sea. To better constrain the timing and rates in which sediment is transported down-canyon, we collected a series of sediment cores along the axis of Monterey Canyon, and quantified mass accumulation rates using short-lived radio-isotopes. A suite of sediment cores were carefully collected perpendicular to the canyon thalweg in water depths of approximately 300m, 500m, 800m, and 1500m using a remotely operated vehicle (ROV). We choose cores that were between 60m and 75m above the canyon thalweg on canyon side bench features for correlation with moored instrument deployments. The sediment cores reveal a complex stratigraphy that includes copious bioturbation features, sand lenses, subtle erosional surfaces, subtle graded bedding, and abrupt changes sediment texture and color. Downcore excess 210Pb and 137Cs profiles imply episodic deposition and remobilization cycles on the canyon benches. Excess 210Pb activities in cores reach depths of up to 1m, implying very rapid sedimentation. Sedimentation rates vary with water depth, generally with the highest sedimentation rate in closest to land, but vary substantially on adjacent canyon benches. Preliminary results demonstrate that sediment movement within Monterey Canyon is both dynamic and episodic on human time-scales and can be reconstructed used short-lived radio-isotopes.

  8. Transfer of {sup 210}Po and {sup 210}Pb through the lichen-caribou-wolf food chain of northern Canada

    SciTech Connect

    Thomas, P.A.; Sheard, J.W.; Swanson, S.

    1994-06-01

    Natural background activity and food chain transfer of the uranium decay products, {sup 210}Po and {sup 210}Pb, were examined in the lichen-caribou-wolf food chain at two locations in the Northwest Territories of Canada. {sup 210}Po and {sup 210}Pb activities in lichens differed with species and location. Both {sup 210}Po and {sup 210}Pb were markedly higher in caribou bone than in wolf bone. {sup 210}Po activities in liver, kidney, and muscle were similar in both species. Caribou fetuses had lower activities of {sup 210}Po but higher activities of {sup 210}Pb than maternal muscle and placenta, suggesting greater placental transport of {sup 210}Pb than {sup 210}Po. Concentration ratios (CR = Bq kg{sup {minus}1} in consumer/Bq kg{sup {minus}1} in its food source) and f{sub f} values (f{sub f} in d kg{sup {minus}1} = Bq kg{sup {minus}1} in muscle/Bq d{sup {minus}1} ingested) showed that wolves retain more {sup 210}Po and less {sup 210}Pb from their diet than do caribou. {sup 210}Po CRs averaged 0.38 for caribou/lichens, 0.26 for caribou/rumen contents, and 0.40 for wolves/caribou. {sup 210}Pb CRs averaged 0.36 for caribou/lichens, 0.57 for caribou/rumen contents, and 0.13 for wolves/caribou. 43 refs., 4 figs., 5 tabs.

  9. Minimum speed limit for ocean ridge magmatism from 210Pb-226Ra-230Th disequilibria.

    PubMed

    Rubin, K H; van der Zander, I; Smith, M C; Bergmanis, E C

    2005-09-22

    Although 70 per cent of global crustal magmatism occurs at mid-ocean ridges-where the heat budget controls crustal structure, hydrothermal activity and a vibrant biosphere-the tempo of magmatic inputs in these regions remains poorly understood. Such timescales can be assessed, however, with natural radioactive-decay-chain nuclides, because chemical disruption to secular equilibrium systems initiates parent-daughter disequilibria, which re-equilibrate by the shorter half-life in a pair. Here we use 210Pb-226Ra-230Th radioactive disequilibria and other geochemical attributes in oceanic basalts less than 20 years old to infer that melts of the Earth's mantle can be transported, accumulated and erupted in a few decades. This implies that magmatic conditions can fluctuate rapidly at ridge volcanoes. 210Pb deficits of up to 15 per cent relative to 226Ra occur in normal mid-ocean ridge basalts, with the largest deficits in the most magnesium-rich lavas. The 22-year half-life of 210Pb requires very recent fractionation of these two uranium-series nuclides. Relationships between 210Pb-deficits, (226Ra/230Th) activity ratios and compatible trace-element ratios preclude crustal-magma differentiation or daughter-isotope degassing as the main causes for the signal. A mantle-melting model can simulate observed disequilibria but preservation requires a subsequent mechanism to transport melt rapidly. The likelihood of magmatic disequilibria occurring before melt enters shallow crustal magma bodies also limits differentiation and heat replenishment timescales to decades at the localities studied.

  10. Atmospheric 210Pb and anthropogenic trace metals in the continental outflow to the Bay of Bengal

    NASA Astrophysics Data System (ADS)

    Bikkina, Srinivas; Sarin, M. M.; Chinni, Venkatesh

    2015-12-01

    Atmospheric 210Pb and trace metals (Pb, Cd, Cu, Mn, Cr, Co, Ni and Zn) have been studied in fine mode aerosols (PM2.5) from a sampling site (Kharagpur: 22.3°N, 87.3°E) in the Indo-Gangetic Plain (IGP) during the continental outflow (November-March) to the Bay of Bengal (BoB). The aerosol 210Pb activity (1.3-6.6 mBq m-3) is significantly high in the wintertime (December-January) compared to model based data in the literature. The cause for higher 210Pb activity is attributed to enhanced 222Rn emanation from Alluvium in the IGP as well as lower boundary layer height. The trace metal concentrations (in ng m-3) also exhibit pronounced temporal variability (Pb: 8-296, Mn: 8-568, Cr: 4.5-33, Cu: 2.1-29.3, Ni: 2.3-14.3, Co: 0.5-1.6 and Cd: 1-29.5) and are of comparable magnitude with those documented over the BoB (Srinivas and Sarin, 2013b), suggesting dominant impact of IGP-outflow on marine atmospheric boundary layer. The enrichment factors (EFcrust) of Pb, Cd, Cu, Mn, Cr, Co and Ni in PM2.5, relative to upper continental crust, varied as 105-1561, 1265-24006, 13-87, 3-99, 7-27, 3-19 and 9-27, respectively. Significant linear relationship among trace metals and chemical species (non-sea-salt-K+, nss-SO42- and EC) emphasizes their anthropogenic source. The high concentrations and EFcrust of Pb, Cd and Cu, together with residence time of PM2.5 (2-13 days, assessed from 210Pb) in the IGP-outflow has implications to increase in the aerosol toxicity and their impact on biogeochemistry of ocean surface waters via air-sea deposition.

  11. Technologically enhanced 210Pb and 210Po in iron and steel industry.

    PubMed

    Khater, Ashraf E M; Bakr, Wafaa F

    2011-05-01

    Iron and steel manufacture has been ranked as the largest industrial source of environmental contamination in the USA; the wastes generated in their production processes contain heavy elements that can be a source of contamination, and natural radionuclides that can produce an occupational and/or public radiological impact. In this work the potential occupational effective dose rate (μSv/y) due to inhalation in four integrated steel-making factories from Egypt has been evaluated, by assuming a well defined scenario and with basis in the (210)Pb and (210)Po activity concentrations determined in ore and wastes collected in the aforementioned factories. Activity concentrations, in Bq/kg, of (210)Pb and (210)Po, and leachable Pb and Fe were measured using gamma-ray spectrometry based on HPGe detector, alpha particle spectrometry based on PIPS detector, and inductively coupled plasma-mass spectrometry (ICP-MS). Levels of (210)Pb and (210)Po in the range of

  12. A method for simultaneous determination of 210Pb and 212Pb in drinking water samples

    NASA Astrophysics Data System (ADS)

    Jia, Guogang; Torri, G.; Leandro, M.

    2012-04-01

    A sensitive and accurate method for determination of 210Pb and 212Pb in drinking water samples was developed. In the method Pb was pre-concentrated as hydroxides, separated from alkaline earth elements as PbS precipitate, purified by an anion exchange resin chro-matography column, precipitated as PbSC4 for source preparation and counted by a low background β-counter. The procedure was checked with a reference material supplied by the IAEA, and the obtained data were in good agreement with the recommended values, showing the recommended procedure can provide reliable results. The minimum detectable activity of the method was 0.039 mBq L-1 for 210Pb and 0.033 mBq L-1 for 212Pb if a 48 liter of water sample was analyzed. Seventeen drinking water samples were analyzed with a Pb recovery of 88.8 ± 5.5%, and the typical activity concentration was in the range of 0.191-15.1 mBq L-1 for 210Pb and of 1.12-5.77 mBq L-1 for 212Pb.

  13. Concentration of 210Po and 210Pb in the diet at the Marshall Islands.

    PubMed

    Noshkin, V E; Robison, W L; Wong, K M

    1994-09-30

    The concentrations of 210Po and 210Pb have been determined in many local foods consumed by societies residing on different atolls in the Marshall Islands. The average daily intake of these two naturally occurring radionuclides from local and imported food is estimated to be 2.18 and 0.36 Bq, respectively. Local foods contribute 87% of the 210Po and 47% of the 210Pb associated with the diet. The items contributing the majority of the activity to the diet are derived from the marine environment and include parts of fish, invertebrates, seabirds and eggs of seabirds. The committed effective dose from ingestion of 210Po and 210Pb is approximately 2 mSv/year (200 mrem/year). This pathway now contributes 83% of the natural background irradiation received by residents in the Marshall Islands. Because the naturally occurring radionuclides are omnipresent in terrestrial and marine foods at all atolls, the annual intake and computed dose can be considered as typical values for individuals with comparable diets and inhabiting other islands in the Pacific.

  14. Levels and transfer of 210Po and 210Pb in Nordic terrestrial ecosystems.

    PubMed

    Brown, J E; Gjelsvik, R; Roos, P; Kålås, J A; Outola, I; Holm, E

    2011-05-01

    Recent developments regarding environmental impact assessment methodologies for radioactivity have precipitated the need for information on levels of naturally occurring radionuclides within and transfer to wild flora and fauna. The objectives of this study were therefore to determine activity concentrations of the main dose forming radionuclides (210)Po and (210)Pb in biota from terrestrial ecosystems thus providing insight into the behaviour of these radioisotopes. Samples of soil, plants and animals were collected at Dovrefjell, Central Norway and Olkiluoto, Finland. Soil profiles from Dovrefjell exhibited an approximately exponential fall in (210)Pb activity concentrations from elevated levels in humus/surface soils to "supported" levels at depth. Activity concentrations of (210)Po in fauna (invertebrates, mammals, birds) ranged between 2 and 123 Bq kg(-1)d.w. and in plants and lichens between 20 and 138 Bq kg(-1)d.w. The results showed that soil humus is an important reservoir for (210)Po and (210)Pb and that fauna in close contact with this media may also exhibit elevated levels of (210)Po. Concentration ratios appear to have limited applicability with regards to prediction of activity concentrations of (210)Po in invertebrates and vertebrates. Biokinetic models may provide a tool to explore in a more mechanistic way the behaviour of (210)Po in this system.

  15. Scavenging and fractionation of particle-reactive radioisotopes 7Be, 210Pb and 210Po in the atmosphere

    NASA Astrophysics Data System (ADS)

    Chen, Jinfang; Luo, Shangde; Huang, Yipu

    2016-09-01

    The scavenging and fractionation of 7Be, 210Pb, and 210Po in the atmosphere are investigated by measuring their activities in rainwater collected from 68 rain events during March 2004 to April 2006 at a coastal station of Xiamen, southeastern China. In addition to documenting the large temporal variations in activities, fluxes, and isotope ratios of 7Be, 210Pb and 210Po in rainwater and the role of rainfall intensity in radionuclide scavenging, our results show that an enhanced deposition of 7Be and 210Pb occurs in the spring than in other seasons and is attributed to the "funnel effect" due to the increased atmospheric vertical convective mixing in the spring. This latter hypothesis is further supported by the observed seasonal and inter-annual variations in 7Be/210Pb and 210Po/210Pb ratios showing that the weakening of vertical convective mixing or stratosphere-troposphere exchange (STE) at the study site is linked with the enhancement of summer monsoons. It appears that the rainfall intensity, in connection with the vertical (e.g., STE) and horizontal (summer monsoons) air transport, exerts an important control on the activities, fluxes, and isotope ratios of 7Be, 210Pb, and 210Po in the atmosphere. Application of the observational data to a theoretical model shows that there are significant fractionations among 7Be, 210Pb, and 210Po in the atmosphere, with the scavenging rate constant or reciprocal of the residence time of radionuclide in the atmosphere being 210Pb > 7Be > 210Po. A revised Poet et al. (1972)'s method is proposed for quantitative constraint on the scavenging behavior of radionuclide, aerosols, and aerosol-associated trace pollutants in the atmosphere.

  16. Assessment of soil contamination by (210)Po and (210)Pb around heavy oil and natural gas fired power plants.

    PubMed

    Al-Masri, M S; Haddad, Kh; Doubal, A W; Awad, I; Al-Khatib, Y

    2014-06-01

    Soil contamination by (210)Pb and (210)Po around heavy oil and natural gas power plants has been investigated; fly and bottom ash containing enhanced levels of (210)Pb and (210)Po were found to be the main source of surface soil contamination. The results showed that (210)Pb and (210)Po in fly-ash (economizer, superheater) is highly enriched with (210)Pb and (210)Po, while bottom-ash (boiler) is depleted. The highest (210)Pb and (210)Po activity concentrations were found to be in economizer ash, whereas the lowest activity concentration was in the recirculator ash. On the other hand, (210)Pb and (210)Po activity concentrations in soil samples were found to be higher inside the plant site area than those samples collected from surrounding areas. The highest levels were found in the vicinity of Mhardeh and Tishreen power plants; both plants are operated by heavy oil and natural fuels, while the lowest values were found to be in those samples collected from Nasrieh power plant, which is only operated by one type of fuel, viz. natural gas. In addition, the levels of surface soil contamination have decreased as the distance from the power plant site center increased.

  17. Leaves of higher plants as biomonitors of radionuclides (137Cs, 40K, 210Pb and 7Be) in urban air.

    PubMed

    Todorović, Dragana; Popović, Dragana; Ajtić, Jelena; Nikolić, Jelena

    2013-01-01

    Leaves of linden (Tilia tomentosa L. and Tilia cordata Mill.) and horse chestnut (Aesculus hippocastanum L.) were analysed as biomonitors of radionuclides in urban air. Samples of soils, leaves and aerosols were collected in Belgrade, Serbia. Activities of (137)Cs, (40)K, (210)Pb and (7)Be in the samples were measured on an HPGe detector by standard gamma spectrometry. "Soil-to-leaves" transfer factors were calculated. Student's t test and linear Pearson correlation coefficients were used for statistical analysis. Differences in local conditions at the sampling sites were not significant, and the mechanisms of the radionuclides' accumulation in both plant species are similar. Ceasium-137 was detected in some of the leaf samples only. Transfer factors for (137)Cs and (40)K were (0.03-0.08) and 1.3, respectively. The concentrations of (210)Pb and (7)Be in leaves were higher in autumn than in spring, and there were some similarities in their seasonal patterns in leaves and in air. Weak to medium correlation was obtained for the (210)Pb and (7)Be activities in leaves and aerosols. Large positive correlation was obtained for the (210)Pb activities in linden leaves and the mean activity in aerosols for the preceding months. Different primary modes of radionuclides accumulation in leaves were observed. Since large positive correlation was obtained for the (210)Pb activity in linden leaves and the mean in aerosols for the preceding months, mature linden leaves could be used as biomonitors of recent (210)Pb activity in air.

  18. Distribution of 210Pb and 210Po concentrations in wild berries and mushrooms in boreal forest ecosystems.

    PubMed

    Vaaramaa, Kaisa; Solatie, Dina; Aro, Lasse

    2009-12-15

    The activity concentrations and distribution of 210Pb and 210Po in wild berries and edible mushrooms were investigated in Finnish forests. The main study areas were located in Scots pine (Pinus sylvestris L.) forests in southern and northern Finland. The activity concentrations of 210Pb and 210Po in blueberry (Vaccinium myrtillus L.) and lingonberry (Vaccinium vitis-idaea L.) samples decreased in the order: stems>leaves>berries (i.e. fruits). The activity ratios of 210Po/210Pb in the wild berry samples were mainly higher than one, indicating elevated activity concentrations of polonium in the samples. In mushrooms the activity concentrations of 210Pb and especially 210Po were higher than in fruits of the wild berries. The highest activity concentration of 210Pb was detected in Cortinarius armillatus L. (16.2 Bq kg(-1) d.w.) and the lowest in Leccinum vulpinum L. (1.38 Bq kg(-1) d.w.). The 210Po activity concentrations of the whole fruiting bodies ranged from 7.14 Bq kg(-1) d.w. (Russula paludosa L.) to 1174 Bq kg(-1) d.w. (L. vulpinum L.). In general, the highest activity concentrations of 210Po were recorded in boletes. The caps of mushrooms of the Boletaceae family showed higher activity concentrations of 210Po compared to the stipes. In most of the mushrooms analyzed, the activity concentrations of 210Po were higher than those of 210Pb. 210Po and 210Pb dominate the radiation doses received via ingestion of wild berries and mushrooms in northern Finland, while in southern Finland the ingested dose is dominated by 137Cs from the Chernobyl fallout.

  19. Residence times of fine tropospheric aerosols as determined by {sup 210}Pb progeny.

    SciTech Connect

    Marley, N. A.; Gaffney, J. S.; Drayton, P. J.; Cunningham, M. M.; Mielcarek, C.; Ravelo, R.; Wagner, C.

    1999-10-05

    Fine tropospheric aerosols can play important roles in the radiative balance of the atmosphere. The fine aerosols can act directly to cool the atmosphere by scattering incoming solar radiation, as well as indirectly by serving as cloud condensation nuclei. Fine aerosols, particularly carbonaceous soots, can also warm the atmosphere by absorbing incoming solar radiation. In addition, aerosols smaller than 2.5 {micro}m have recently been implicated in the health effects of air pollution. Aerosol-active radioisotopes are ideal tracers for the study of atmospheric transport processes. The source terms of these radioisotopes are relatively well known, and they are removed from the atmosphere only by radioactive decay or by wet or dry deposition of the host aerosol. The progeny of the primordial radionuclide {sup 238}U are of particular importance to atmospheric studies. Uranium-238 is common throughout Earth's crust and decays to the inert gas {sup 222}Rn, which escapes into the atmosphere. Radon-222 decays by the series of alpha and beta emissions shown in Figure 1 to the long-lived {sup 210}Pb. Once formed, {sup 210}Pb becomes attached to aerosol particles with average attachment times of 40 s to 3 min.

  20. Recent Bremsstrahlung-based assays of (210)Pb in lead and comments on current availability of low-background lead in North America.

    PubMed

    Keillor, Martin E; Aalseth, C E; Arnquist, I J; Eggemeyer, T A; Fuller, E S; Glasgow, B D; Hoppe, E W; Morley, S M; Myers, A W; Orrell, J L; Overman, C T; Seifert, A; Shaff, S M; Thommasson, K S

    2017-03-03

    Low-background lead for radiation measurement shielding is often assayed for (210)Pb to ensure acceptable backgrounds. Samples of lead assayed with a germanium spectrometer calibrated for bremsstrahlung-based assay of (210)Pb provide a view into the (210)Pb content of commercial lead in the U.S. (other than stockpiled Doe Run lead). Results suggest that the loss of lead smelting in the U.S. has eliminated the traditional supply of "low background" lead (~30Bqkg(-1)), and indicate current commercial supplies contain roughly an order of magnitude higher (210)Pb levels.

  1. 210Po and 210Pb disequilibrium in the hydrothermal vent fluids and chimney deposits from Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Hussain, N.; Church, T. M.; Luther, G. W., III; Moore, W. S.

    Significantly deficient 210Po/210Pb activity ratios (0.14±0.14) are measured in the hydrothermal vent fluids collected from Juan de Fuca Ridge. Chimney deposits generally showed <5 dpm of excess 210Po. However, one sample from the outermost layer of a sealed spire yielded >1200 dpm g-1 of excess 210Po.If the observed 210Po-210Pb disequilibrium in vent fluids is a result of 210Po removal by the precipitates, residence time of polonium with respect to its irreversible removal from hot fluids is estimated to be of the order of a few minutes. Alternatively, if the disequilibrium is a result of an insufficient growth of 210Po from in-situ 210Pb following heating, the residence time of hot fluids within the hydrothermal system can be shown to be less than 30 days, which is considerably lower than previously reported values.

  2. Distribution and biokinetic analysis of 210Pb and 210Po in poultry due to ingestion of dicalcium phosphate.

    PubMed

    Casacuberta, N; Traversa, F L; Masqué, P; Garcia-Orellana, J; Anguita, M; Gasa, J; Garcia-Tenorio, R

    2010-09-15

    Dicalcium phosphate (DCP) is used as a calcium supplement for food producing animals (i.e., cattle, poultry and pig). When DCP is produced via wet acid digestion of the phosphate rock and depending on the acid used in the industrial process, the final product can result in enhanced (210)Pb and (210)Po specific activities (approximately 2000 Bq.kg(-1)). Both (210)Pb and (210)Po are of great interest because their contribution to the dose received by ingestion is potentially large. The aims of this work are to examine the accumulation of (210)Pb and (210)Po in chicken tissues during the first 42 days of life and to build a suitable single-compartment biokinetic model to understand the behavior of both radionuclides within the entire animal using the experimental results. Three commercial corn-soybean-based diets containing different amounts and sources of DCP were fed to broilers during a period of 42 days. The results show that diets containing enhanced concentrations of (210)Pb and (210)Po lead to larger specific accumulation in broiler tissues compared to the blank diet. Radionuclides do not accumulate homogeneously within the animal body: (210)Pb follows the calcium pathways to some extent and accumulates largely in bones, while (210)Po accumulates to a large extent in liver and kidneys. However, the total amount of radionuclide accumulation in tissues is small compared to the amounts excreted in feces. The single-compartment non-linear biokinetic model proposed here for (210)Pb and (210)Po in the whole animal takes into account the size evolution and is self-consistent in that no fitting parameterization of intake and excretions rates is required.

  3. [Using 137Cs and 210Pb(ex) to trace the impact of soil erosion on soil organic carbon at a slope farmland in the black soil region].

    PubMed

    Fang, Hai-Yan; Sheng, Mei-Ling; Sun, Li-Ying; Cai, Qiang-Guo

    2013-07-01

    Soil cores were collected from a 28.5 hm2 slope farmland in the black soil region of Northeast China. Based on the sampled data of 137Cs, 210Pb(ex) and SOC, the potentials of applying 137Cs and 210Pb(ex) for assessing SOC redistribution were evaluated, aimed to approach the impact of soil erosion on soil organic carbon (SOC) in black soil region. At both planar and vertical directions, the 137Cs, 210Pb(ex) and SOC in the farmland had similar distribution patterns. Although there were large planar variations in the 137Cs and 210Pb(ex) areal activities and the SOC stock as affected by soil erosion and deposition, the 137Cs, 210Pb(ex) and SOC had similar changing trends over the landscape. Two depth distribution profiles were also used to study the relations of 137Cs and 210Pb(ex) with SOC. At eroded site, the radioactivities of 137Cs and 210Pb(ex) and the SOC mass fraction did not show large variations in 0-25 cm soil layer, but decreased sharply below 25 cm. For the deposition sample, the radioactivities of 137Cs and 210Pb(ex) in 0-100 cm soil increased firstly and then decreased. The SOC mass fraction also had similar depth distribution pattern in this soil layer. The 137Cs and 210Pb(ex) presented positive linear correlations with the SOC, indicating that 137Cs, 210Pb(ex) and SOC moved with the same physical mechanism in the farmland, and fallout 137Cs and 210Pb(ex) could be used to study spatio-temporal distribution characteristics of SOC in the black soil region under the condition of soil erosion.

  4. 7Be, 210Pb and 137Cs concentrations in cloud water.

    PubMed

    Bourcier, L; Masson, O; Laj, P; Paulat, P; Pichon, J-M; Chausse, P; Gurriaran, R; Sellegri, K

    2014-02-01

    Cloud water was sampled during 8 months, in 2008 and 2009, at the puy de Dome high-altitude atmospheric research station (France). The concentrations of (7)Be and (210)Pb, both naturally occurring radionuclides, and (137)Cs of anthropogenic origin, were determined. Those values are useful for a better knowledge of the aftermath cloud deposition and more generally for wet deposition assessment of radionuclides. This is of primary interest in case of a nuclear accident, especially considering (137)Cs deposition, both for high-altitude locations that are regularly embedded by clouds and also for lowlands where fog can occur. The (7)Be and (210)Pb average activity concentrations in cloud water found were 1.9±0.11 mBq m(-3) air and 140±10 μBq m(-3) air, respectively. For (137)Cs, the average concentration was 0.14±0.02 μBq m(-3) air. This very low-level is representative of the long term post-accidental background level. Indeed, for the studied period, the last accidental (137)Cs release was that of Chernobyl accident, in April 1986. To our knowledge this is the first data about (137)Cs reference level determination in cloud water. The comparison between cloud water and rain water concentrations showed a ratio cloud/rain ranging between 3.4 and 8.1, in agreement with previous studies performed on inorganic compounds. Scavenging efficiencies of aerosols by cloud droplets were also calculated with the additional aerosol concentrations routinely measured at the station and were quite low (0.13-0.40) compared to what has previously been observed for inorganic soluble ions.

  5. Age Dating Fluvial Sediment Storage Reservoirs to Construct Sediment Waiting Time Distributions

    NASA Astrophysics Data System (ADS)

    Skalak, K.; Pizzuto, J. E.; Benthem, A.; Karwan, D. L.; Mahan, S.

    2015-12-01

    Suspended sediment transport is an important geomorphic process that can often control the transport of nutrients and contaminants. The time a particle spends in storage remains a critical knowledge gap in understanding particle trajectories through landscapes. We dated floodplain deposits in South River, VA, using fallout radionuclides (Pb-210, Cs-137), optically stimulated luminescence (OSL), and radiocarbon dating to determine sediment ages and construct sediment waiting time distributions. We have a total of 14 age dates in two eroding banks. We combine these age dates with a well-constrained history of mercury concentrations on suspended sediment in the river from an industrial release. Ages from fallout radionuclides document sedimentation from the early 1900s to the present, and agree with the history of mercury contamination. OSL dates span approximately 200 to 17,000 years old. We performed a standard Weibull analysis of nonexceedance to construct a waiting time distribution of floodplain sediment for the South River. The mean waiting time for floodplain sediment is 2930 years, while the median is approximately 710 years. When the floodplain waiting time distribution is combined with the waiting time distribution for in-channel sediment storage (available from previous studies), the mean waiting time shifts to approximately 680 years, suggesting that quantifying sediment waiting times for both channel and floodplain storage is critical in advancing knowledge of particle trajectories through watersheds.

  6. Radiocarbon dating of plant macrofossils from tidal-marsh sediment

    USGS Publications Warehouse

    Kemp, A.C.; Nelson, Alan R.; Horton, B.P.

    2013-01-01

    Tidal-marsh sediment is an archive of Holocene environmental changes, including movements of sea and land levels, and extreme events such as hurricanes, earthquakes, and tsunamis. Accurate and precise radiocarbon dating of environmental changes is necessary to estimate rates of change and the recurrence interval (frequency) of events. Plant macrofossils preserved in growth position (or deposited soon after death) in tidal-marsh sediment are ideal samples for dating such changes. In this chapter, we focus on the selection of plant macrofossils for radiocarbon dating and the application of ages from different types of macrofossils to varied research projects, and make recommendations for selection and preparation of tidal-marsh samples for dating.

  7. 210Po and 210Pb Activity Concentrations in Cigarettes Produced in Vietnam and Their Estimated Dose Contribution Due to Smoking

    NASA Astrophysics Data System (ADS)

    Tran, Thuy-Ngan N.; Le, Cong-Hao; Chau, Van-Tao

    Smoking cigarettes contributes significantly to the increase of radiation in human body because 210Po and 210Pb exist relatively high in tobacco leaves. Therefore, these two radioisotopes in eighteen of the most frequently sold cigarette brands produced in Vietnam were examined in this study. 210Po was determined by alpha spectroscopy using a passivated implanted planar silicon (PIPS) detector after a procedure including radiochemical separation and spontaneous deposition of polonium on a copper disc (the deposition efficiency of 210Po on a copper disc was approximately 94%). Sequentially, 210Pb was determined through the ingrowth of 210Po after storing the sample solutions for approximately six months. The activity concentrations of 210Po in cigarettes ranged from 13.8 to 82.6 mBq/cigarette (the mean value was 26.4 mBq/cigarette) and the activity concentrations of 210Pb in cigarettes ranged from 13.9 to 78.8 mBq/cigarette (the mean value was 25.8 mBq/cigarette). The annual committed effective dose for smokers who smoke one pack per day was also estimated to be 295.4 µSv/year (223.0 µSv/year and 72.4 µSv/year from 210Po and 210Pb, respectively). These indicated that smoking increased the risk of developing lung cancer was approximately 60 times greater for smokers than for non-smokers.

  8. Polonium (210Po) and lead (210Pb) in marine organisms and their transfer in marine food chains.

    PubMed

    Carvalho, Fernando P

    2011-05-01

    The determination of (210)Po and (210)Pb was performed in marine organisms from the seashore to abyssal depths, encompassing a plethora of species from the microscopic plankton to the sperm whale. Concentrations of those radionuclides ranged from low values of about 5 × 10(-1) Bq kg(-1) (wet wt.) in jellyfish, to very high values of about of 3 × 10(4) Bq kg(-1) (wet wt.) in the gut walls of sardines, with a common pattern of (210)Po > (210)Pb.These radionuclides are primarily absorbed from water and concentrated by phyto- and microzooplankton, and then are transferred to the next trophic level along marine food chains. Investigation in epipelagic, mesopelagic, bathypelagic and abyssobenthic organisms revealed that (210)Po is transferred in the marine food webs with transfer factors ranging from 0.1 to 0.7, and numerically similar to those of the energy transfer in the marine food chains. As (210)Po preferentially binds to amino acids and proteins, its transfer in food chains likely traces protein transfer and, thus, (210)Po transfer factors are similar to ecotrophic coefficients. (210)Pb is transferred less efficiently in marine food chains and this contributes to increased (210)Po:(210)Pb activity ratios in some trophic levels.

  9. Association between radionuclides ((210)Po and (210)Pb) and antioxidant enzymes in oak (Quercus coccifera) and mastic tree (Pistacia lentiscus).

    PubMed

    Uğur Görgün, A; Aslan, E; Kül, M; İlhan, S; Dimlioğlu, G; Bor, M; Özdemir, F

    2016-08-27

    The activity levels of naturally occurring radionuclides Polonium-210 and lead-210 in different subjects including plant species have direct or indirect impact on human beings. High levels of ionising radiation cause oxidative stress and the interaction between antioxidative defense and radionuclides is not well established in plant systems. In this study, we aimed to understand the impact of oxidative stress caused by (210)Po and (210)Pb in two Mediterranean plants; Quercus coccifera and Pistacia lentiscus. We analysed the constitutive and seasonal levels of (210)Po, (210)Pb, lipid peroxidation levels, superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities in the field-collected samples. The highest activity concentrations of (210)Po and (210)Pb were detected in both plants in summer and Q. coccifera had higher levels than that of P. lentiscus. SOD and APX activity trends were different between oak and mastic; as compared to P. lentiscus, Q. coccifera efficiently used the two major components of antioxidative defense. Lipid peroxidation levels were low in both plants in all seasons except that of spring which were in good agreement with high antioxidant enzyme activities. In conclusion, we found that high (210)Po and (210)Pb activity concentrations in oak and mastic did not interfere with their growth and life cycles. The ability of both plants for survival and adaptation to Mediterranean environmental constraints provided an additional advantage for coping radionuclide induced oxidative stress as well.

  10. Degassing dynamics at Mount Etna inferred from radioactive disequilibria (210Pb-210Bi-210Po) in volcanic gases

    NASA Astrophysics Data System (ADS)

    Terray, Luca; Gauthier, Pierre-Jean; Salerno, Giuseppe; La Spina, Alessandro; Giammanco, Salvatore; Sellitto, Pasquale; Briole, Pierre

    2016-04-01

    Volcanic gases are significantly enriched in the last short-half-life radionuclides of the 238U series, namely the so-called Radon daughters 210Pb, 210Bi and 210Po. Because of their contrasted volatilities, these isotopes are strongly fractionated upon degassing, which gives rise to significant radioactive disequilibria between them in the gas phase. These disequilibria carry precious information on shallow degassing processes beneath active volcanoes: they remarkably constrain the magma residence time in the degassing reservoir and the duration of gas extraction from magma to surface. On Mount Etna (Sicily), where the study of these disequilibria was initiated thirty years ago (Lambert et al., EPSL, 1985-86), no measurement of 210Pb, 210Bi and 210Po in the gases has been performed for the last twenty years. Here we present new 210Pb-210Bi-210Po radioactive disequilibria measurements in volcanic plume gases of Mount Etna. Samples were collected in the bulk diluted plume at kilometric distance from the summit area during the May 2015 eruption, then in more concentrated plumes arising from each summit crater of Etna during quiescent degassing in July 2015. We found values of (210Bi/210Pb) = 7.0 ± 0.3 and (210Po/210Pb) = 80 ± 6 during both periods. These results suggest that 210Pb, 210Bi and 210Po are not significantly fractionated during the transport of the plume from the crater rim to close-downslope sites (<1 km). None of the previous degassing models (Lambert et al., EPSL, 1985-86 ; Gauthier et al., JVGR, 2000) satisfactorily explain measured activity ratios. We propose here a new degassing model based on the previous conceptualization designed for basaltic open-conduit volcanoes, like Stromboli. This model considers extreme Radon enrichments in volcanic gases as a source of 210Pb atoms produced by radioactive decay of 222Rn within gas bubbles travelling to surface. We constrain a magma residence time of 470 ± 170 days and an extraction time of the gases of 4

  11. There is no 1954 in that core! Interpreting sedimentation rates and contaminant trends in marine sediment cores.

    PubMed

    Johannessen, S C; Macdonald, R W

    2012-04-01

    Marine sediment preserves a useful archive for contaminants and other properties that associate with particles. However, biomixing of sediments can smear the record on a scale of years to thousands of years, depending on sedimentation rate and on the depth and vigour of mixing within a particular sediment. Where such mixing occurs, dates can no longer be associated with discrete sediment depths. Nevertheless, much can still be learned from biomixed profiles, provided that mixing is accounted for. With no modelling at all, it is possible to calculate an inventory of a contaminant at a site and a maximum possible sedimentation rate, and to determine whether the contaminant has increased or decreased over time. Radiodating the core with (210)Pb permits the estimation of sedimentation and mixing rates, which can be combined with the surface contaminant concentration to estimate an approximate flux of the contaminant. Numerical models that incorporate sedimentation and mixing rates (determined using (210)Pb and other transient signals with known deposition histories) can provide the basis to propose plausible histories for contaminant fluxes.

  12. Sediment deposition and inventory of chemical contaminants in the tidal Anacostia River, Washington, DC

    SciTech Connect

    Velinsky, D.J.; Wade, T.L.; Gammisch, B.; Cornwell, J.

    1995-12-31

    To determine the historical inputs and loads of sediment contaminants in the lower Anacostia River, six 3 meter gravity cores were collected in 1995. The down-core distributions of trace metals and organic contaminants (e.g., PCBs, DDTs, and PAHs) were determined. Dating of three cores using {sup 210}Pb indicate a substantial mixed layer in the upper 10 to 25 cm and an exponential {sup 210}Pb decrease to 3 meters. Sedimentation rates of 2 to 3 cm/yr were estimated and are in agreement with estimates based on pollen and sediment mass balance calculations. This suggests that bottom core sections are between 100 and 150 yrs old. However, contaminant levels were elevated in the bottom sections of most cores with levels of Pb, Cd, tPCBs, and tPAHs ranging from 23 to 610 {micro}g/g, 0.15 to 5.2 {micro}g/g, 3.9 to 1,745 ng/g, and 110 to 49,000 ng/g, respectively. These levels suggest either post-depositional migration of material or that {sup 210}Pb profiles are not representative of the true deposition. To help validate the {sup 210}Pb-age-depth profiles, the distribution of {sup 137}Cs is currently being determined for these cores. Generally, the depth distribution of most contaminants were surface maximum with lower concentrations at depth, or mid-depth maximum. However some cores had contaminant concentrations that increased with depth. The down core distributions and the results of the sub-bottom profiling will be used to help establish a better contaminant mass balance for the Anacostia River.

  13. Advancing knowledge gained from sediment budgets through sediment age dating and fingerprinting in small watersheds

    NASA Astrophysics Data System (ADS)

    Skalak, K.; Benthem, A.; Gellis, A.; Harvey, J. W.; Hupp, C. R.; Larsen, L.; Noe, G. B.; Pizzuto, J. E.; Schenk, E.

    2013-12-01

    Dynamics and long-term trajectories of fine sediment generally remain poorly quantified in rivers, which have implications for nutrient and contaminant transport and remediation strategies. Here we focus on two streams within the Chesapeake Bay watershed, Difficult Run and Accotink Creek. These streams have varying degrees of urbanization and diverse best management practices, making possible a comparison of sediment sources, sinks, and residence times to illuminate how land management impacts fine sediment transport. Bank erosion and floodplain accumulation in Difficult Run has been previously determined and is ongoing in Accotink Creek. Current work advances sediment budgets by quantifying the role of in-channel fine sediment storage in the bed and margins. To understand the relative storage timescales for various geomorphic features (floodplain, in-channel, etc.) and develop age distributions, sediment is dated using radionuclides of varying half-lives such as Pb-210, Cs-137, Be-7, bomb radiocarbon, and optically stimulated luminescence (OSL). To determine the source of sediment that is transported in suspension, sediment fingerprinting has been completed in Difficult Run and initiated in Accotink Creek. Furthermore, the present study furthers our understanding of fine sediment dynamics by fingerprinting sources of stored sediment and evaluating how they evolve over storm events and stream size. For this, we sampled sediment in storage zones before and after storm events of a specified magnitude to determine their chemical signatures with respect to various source-tracking elements and isotopes. This study represents the first such work to integrate sediment dating, sediment fingerprinting and an analysis of storage zones to understand fine sediment dynamics and long-term trajectories.

  14. Sedimentation rates and pollution history of a dried lake: Al-Oteibeh Lake.

    PubMed

    Al-Masri, M S; Aba, A; Khalil, H; Al-Hares, Z

    2002-07-03

    Sediment accumulation rates as well as the distribution of selected elements in a dried Syrian lake (Al-Oteibeh Lake), near Damascus City, are reported. Five core samples from different locations of the lake were collected, and four major elements (Fe, K, Mg and Na) and six trace metals (Co, Ni, Cr, Pb, Zn, U and Cu) were analyzed. Sedimentation rates were determined applying the 210Pb dating method and found to vary between 0.100 and 0.793 cm year(-1). The results showed that the constant flux constant sedimentation rate (CF:CS) simple dating model is applicable for dating recent dried sediment and recording the past historical pollution of the last 100 years. However, the method was found to be only applicable for dating trace and major elements, which cannot be leached to deeper layers by rainwater. In addition, the obtained records can be used to verify the date of water level declining.

  15. Dating floodplain sediments using tree-ring response to burial

    USGS Publications Warehouse

    Friedman, J.M.; Vincent, K.R.; Shafroth, P.B.

    2005-01-01

    Floodplain sediments can be dated precisely based on the change in anatomy of tree rings upon burial. When a stem of tamarisk (Tamarix ramosissima) or sandbar willow (Salix exigua) is buried, subsequent annual rings in the buried section resemble the rings of roots: rings become narrower, vessels within the rings become larger, and transitions between rings become less distinct. We combined observations of these changes with tree-ring counts to determine the year of deposition of sedimentary beds exposed in a 150-m-long trench across the floodplain of the Rio Puerco, a rapidly filling arroyo in New Mexico. This method reliably dated most beds thicker than about 30 cm to within a year of deposition. Floodplain aggradation rates varied dramatically through time and space. Sediment deposition was mostly limited to brief overbank flows occurring every few years. The most rapid deposition occurred on channel-margin levees, which migrated laterally during channel narrowing. At the decadal timescale, the cross-section-average sediment deposition rate was steady, but there was a shift in the spatial pattern of deposition in the 1980s. From 1936 to 1986, sediment deposition occurred by channel narrowing, with little change in elevation of the thalweg. After 1986 sediment deposition occurred by vertical aggradation. From 1936 to 2000 about 27 per cent of the arroyo cross-section filled with sediment. The rate of filling from 1962 to 2000 was 0-8 vertical m/decade or 85 m2/decade. Published in 2005 by John Wiley & Sons, Ltd.

  16. Uptake and kinetics of /sup 226/Ra, /sup 210/Pb and /sup 210/Po in big sagebrush. [Artemisia tridentata

    SciTech Connect

    Simon, S.L.

    1985-01-01

    Root uptake of /sup 226/Ra, /sup 210/Pb and /sup 210/Po by mature sagebrush was studied using a soil injection method for spiking the soil with minimal root disturbance. The main objective was to measure vegetation concentrations and determine concentration ratios (CR's) due to root uptake as a function of time in mature big sagebrush. Concentration ratios obtained in mature vegetation and in steady-state situations may be valuable in assessing the impact of uranium mining and milling. The vegetation was sampled approximately every 3 months for a 2 year period. Significant levels of activity were detected in the vegetation beginning at the first sampling (81 days after soil injection for /sup 226/Ra, 28 days for /sup 210/Pb and /sup 210/Po). There was an exponential decrease in concentration to an apparent steady-state value. Mean values (geometric) of the data pooled over the second year period indicated that the steady-state CR's for /sup 226/Ra, /sup 210/Pb and /sup 210/Po, as determined in mature sagebrush, were 0.04, 0.009, and 0.08, respectively. A three compartment mathematical model was formulated to help understand mechanisms of plant uptake and to predict, if possible, the concentration of /sup 226/Ra, /sup 210/Pb and /sup 210/Po in vegetation as a function of time after soil spiking. A numerical solution was determined by 'calibrating' the general model solution with constants determined from regressions of concentrations in vegetation, soil leaching and leaf leaching data. Validation of the model is currently not possible because of an absence of similar time-dependent uptake studies. 168 refs., 19 figs., 18 tabs.

  17. Factors affecting 210Po and 210Pb activity concentrations in mussels and implications for environmental bio-monitoring programmes.

    PubMed

    Carvalho, Fernando P; Oliveira, João M; Alberto, G

    2011-02-01

    The activity of (210)Po and (210)Pb was determined in mussels of the same size (3.5-4.0 cm shell length) sampled monthly over a 17-month period at the Atlantic coast of Portugal. Average radionuclide concentration values in mussels were 759±277 Bq kg(-1) for (210)Po (range 460-1470 Bq kg(-1) dry weight), and 45±19 Bq kg(-1) for (210)Pb (range 23-96 Bq kg(-1) dry weight). Environmental parameters and mussel biometric parameters were monitored during the same period. Although there was no seasonal variation of radionuclide concentrations in sea water during the study period, the concentration of radionuclide activity in mussels varied seasonally displaying peaks of high concentrations in winter and low concentrations in summer. Analysis of radionuclide data in relation to the physiological Condition Index of mussels revealed that (210)Po and (210)Pb activities in the mussel (average activity per individual) remained nearly constant during the investigation period, while mussel body weight fluctuated due to fat storage/expenditure in the soft tissues. Similar variation of radionuclide concentrations was observed in mussels transplanted from the sea coast into the Tejo Estuary. However, under estuarine environmental conditions and with higher food availability throughout the year, transplanted mussel Condition Index was higher than in coastal mussels and average radionuclide concentrations were 210±75 Bq kg(-1) (dry weight) for (210)Po and 10±4 Bq kg(-1) (dry weight) for (210)Pb, therefore lower than in coastal mussels with similar shell length. It is concluded that the apparent seasonal fluctuation and inter-site difference of radionuclide concentrations were mostly caused by mussel body weight fluctuation and not by radionuclide body burden fluctuation. This interpretation can be extended to the apparent seasonal fluctuation in concentrations of lipophilic and lipophobic contaminants in mussels, and provides an explanation for occasional high concentrations of

  18. Natural variation in 210Po and 210Pb activity concentrations in the urine of Finnish population groups.

    PubMed

    Muikku, Maarit; Heikkinen, Tarja; Solatie, Dina; Vesterbacka, Pia

    2011-11-01

    A study to determine activity concentrations of (210)Pb and (210)Po in the urine of certain Finnish population groups was conducted, to investigate the variation in natural background level of urinary excretion. The study participants were divided into three groups mainly based on their diet. The first group comprised recreational fishermen and the second group represented people consuming more reindeer meat than an average Finn, while people using drinking water with very high activity concentrations of (210)Po were selected for the third group. The fourth group was a control group. The mean urinary excretion of (210)Po in groups 1 and 2 was 73 and 100 mBq d(-1), respectively. These values were higher than the value of the control group (20 mBq d(-1)) and the mean values reported in the literature. The mean daily urinary excretion of (210)Pb in groups 1 and 2, 70 and 52 mBq d(-1), was also slightly higher than that in the control group (32 mBq d(-1)). In contrast, the excretion rates of both (210)Po and (210)Pb for the members of group 3 were one to two orders of magnitude higher than those reported in the literature. This was clearly due to the elevated levels of natural radionuclides in their drinking water. The present study demonstrates the importance of possessing good knowledge of the background levels, in order to allow the determination of the additional exposure due, for example, to the malevolent use of radiation.

  19. /sup 238/U, /sup 226/Ra and /sup 210/Pb in some vent waters of the Galapagos spreading center

    SciTech Connect

    Krishnaswami, S.; Turekian, K.K.

    1982-08-01

    The concentrations of /sup 226/Ra, /sup 238/U and /sup 210/Pb have been measured in waters from the Mussel Bed and the Rose Garden thermal fields at the Galapagos spreading center over a temperature range of approx.2.5--16 /sup 0/C. The /sup 226/Ra-T plots yield slopes of 0.112 and 0.036 dpm/kg /sup 0/C for the Mussel Bed and the Rose Garden respectively yielding a global hydrothermal /sup 226/Ra flux less than 5% of that required to sustain the oceanic inventory. /sup 238/U concentration in waters <9 /sup 0/C is the same as that in ambient sea water whereas water hotter than approx.9 /sup 0/C shows a decreasing trend with temperature to zero /sup 238/U at approx.29 /sup 0/C. /sup 210/Pb concentration in Mussel Bed increases with temperature, and extrapolated to approx.350 /sup 0/C yields a /sup 210/Pb concentration considerably less than that expected from /sup 222/Rn decay and basalt alteration.

  20. Particulate organic carbon export fluxes on Chukchi Shelf, western Arctic Ocean, derived from 210Po/210Pb disequilibrium

    NASA Astrophysics Data System (ADS)

    He, Jianhua; Yu, Wen; Lin, Wuhui; Men, Wu; Chen, Liqi

    2015-05-01

    Fluxes of particulate organic carbon (POC) were derived from 210Po/210Pb disequilibrium during the 4th Chinese National Arctic Research Expedition (CHINARE-4) from July 1 to September 28, 2010. Average residence times of particulate 210Po in the euphotic zone were -16.00 a to 1.54 a, which are higher than those of dissolved 210Po (-6.89 a to -0.70 a). Great excesses of dissolved 210Po were observed at all stations, with an average 210Po/210Pb ratio of 1.91±0.20, resulting from 210Pb atmospheric deposition after sea ice melt. POC fluxes from the euphotic zone were estimated by two methods (E and B) in the irreversible scavenging model. Estimated POC fluxes were 945-126 mmol C/(m2·a) and 1 848-109 mmol C/(m2·a) by methods E and B, respectively, both decreasing from low to high latitude. The results are comparable to previous works for the same region, indicating efficient biological pumping in the Chukchi Sea. The results can improve understanding of the carbon cycle in the western Arctic Ocean.

  1. Dating Historical Sediments in Estuaries: A Multi-Proxy Approach

    NASA Astrophysics Data System (ADS)

    Reynolds, L.; Truong, M.; Ejarque, A.; Simms, A.; Anderson, R. S.

    2015-12-01

    Interpretation of recent estuarine stratigraphy, especially differentiation between events with similar sedimentological features such as storm and tsunami deposits, requires a high resolution geochronology in order to accurately identify and differentiate between historically documented events. Dating sediments deposited in the last few centuries is difficult due to the uncertainty range of radiocarbon ages, bioturbation, and anthropogenic disturbance of systems. Here we show a variety of proxy records throughout the top 2 m of sediment in Carpinteria Marsh, southern California including charcoal, grain size, pollen, scanning XRF, and spheroidal carbon particle stratigraphies. We use the combination of these records to correlate stratigraphy and identify sedimentological evidence of documented historical storm occurrences, tsunami impacts, land use changes, and fire events. We show the sedimentation rate of the historical period varies from ~1 mm/yr to 5 mm/yr throughout the marsh, while long term rates of sedimentation are ~2 mm/yr. Sedimentation rates are also not consistent temporally, since the record is punctuated by periods of rapid or absent deposition. Multi-proxy comparisons can aid attempts to identify evidence of historical coastal hazards and correlate deposits despite variability in sedimentary processes throughout an estuary.

  2. Atmospheric fluxes of (7)Be and (210)Pb on monthly time-scales and during rainfall events at Stony Brook, New York (USA).

    PubMed

    Renfro, Alisha A; Cochran, J Kirk; Colle, Brian A

    2013-02-01

    The particle-reactive radionuclides (7)Be and (210)Pb have been employed extensively as tracers and chronometers for a variety of aquatic and terrestrial processes. Both radionuclides are delivered to the Earth's surface from the atmosphere, and in order to use them effectively as natural tracers, an understanding of variations in atmospheric fluxes of these radionuclides due to latitudinal differences and storm events is required. The monthly atmospheric fluxes of (7)Be and (210)Pb, measured from April-2008 to December-2009 at Stony Brook, NY, ranged from 67 to 385 Bq m(-2) and 6.7 to 16.7 Bq m(-2), respectively. Composite annual atmospheric fluxes over the sampling period were 3110 ± 1200 Bq m(-2) y(-1) for (7)Be and 146 ± 50 Bq m(-2) y(-1) for (210)Pb and were similar to geographically comparable sites. The monthly atmospheric fluxes of (7)Be and (210)Pb were significantly correlated with rainfall. The (7)Be/(210)Pb ratio in the monthly samples varied seasonally, with values of ∼10-11 during the winter months and ∼20-28 during the spring - fall. The pattern of seasonal variation in (7)Be fluxes and (7)Be/(210)Pb ratios is most consistent with that observed in surface air at continental sites in which more frequent deep convective storms occur during the summer and therefore result in an increased transport of (7)Be from the upper troposphere to the Earth's surface. An additional factor may be that the winds at Stony Brook were dominantly from the northwest during the winter of 2009 and so were characterized by low (7)Be/(210)Pb ratios while in the spring, winds from the southwest brought marine air with higher (7)Be/(210)Pb ratios to the sampling site. Fluxes of (7)Be and (210)Pb also were measured over two long (16-24 h) and two short (∼1 h) intense periods of rainfall in June and July 2009. Fluxes of (7)Be and (210)Pb continued throughout the short events, but the two radionuclides showed different patterns during the long events. While the entirety of

  3. Incorporation of 210Pb and 210Po to Poultry through the Addition of Dicalcium Phosphate (DCP) to the Diet

    NASA Astrophysics Data System (ADS)

    Casacuberta, N.; Masqué, P.; Garcia-Orellana, J.; Gasa, J.; Anguita, M.

    2008-08-01

    Due to the replacement of calcium by uranium in the phosphorite, sedimentary phosphate rock contains high concentrations of 238U (i.e. from 1500 Bqṡkg-1 in Morocco to 4000 Bqṡkg-1 in Tanzania ores). Dicalcium Phosphate (DCP) is produced by the wet acid digestion of the phosphorite, and is used as a source of calcium and phosphorus for livestock feed supplement. If the phosphorite acid digestion is made with hydrochloric acid, DCP may present specific activities of about 103 Bqṡkg-1 of 238U and some of its decay chain daughters. In particular, due to its radiological implications, the presence of 210Pb and 210Po in DCP is of special relevance. The aim of this work was to investigate the potential incorporation of these radionuclides to poultry through its diet. Three different diets were therefore prepared with different contents of both DCP and 210Pb and 210Po. Diet A was used as a blank, and had a 2.5% in weight of monocalcium phosphate (MCP); diet B, with a 5% in weight of DCP; and diet C, with a 2.5% of DCP. Concentrations of 210Pb were 0.93, 101.4 and 51.2 Bqṡkg-1; whereas concentrations of 210Po were 0.92, 74 and 36 Bqṡkg-1 of food for diets A, B and C, respectively. Accumulation of 210Pb and 210Po was analysed at several times during poultry growth in samples of bone, liver, kidney, muscle, excrements as well as entire animals, with a total of 30 broilers fed with the 3 different diets. Results showed clear enhancements in the accumulation of both 210Pb and 210Po in chicken for diets B and C, and in particular in liver and bone. However, total accumulation of radionuclides in chicken, and especially in edible parts, is low compared to its expulsion through excrements. These results are interpreted in terms of the potential dose through consumption of chicken.

  4. Stream sediment detailed geochemical survey for Date Creek Basin, Arizona

    SciTech Connect

    Butz, T.R.; Tieman, D.J.; Grimes, J.G.; Bard, C.S.; Helgerson, R.N.; Pritz, P.M.

    1980-06-30

    Results of the Date Creek Basin detailed geochemical survey are reported. Field and laboratory data are reported for 239 stream sediment samples. Statistical and areal distributions of uranium and possible uranium-related variables are displayed. A generalized geologic map of the area is provided, and pertinent geologic factors which may be of significance in evaluating the potential for uranium mineralization are briefly discussed. Based on stream sediment geochemical data, significant concentrations of uranium are restricted to the Anderson Mine area. The 84th percentile concentrations of U-FL, U-NT, and U-FL/U-NT combined with low thorium/U-NT values reflect increased mobility and enrichment of uranium in the carbonate host rocks of that area. Elements characteristically associated with the uranium mineralization include lithium and arsenic. No well defined diffusion halos suggesting outliers of similar uranium mineralization were observed from the stream sediment data in other areas of the Date Creek Basin. Significant concentrations of U-FL or U-NT found outside the mine area are generally coincident with low U-FL/U-NT values and high concentrations of zirconium, titanium, and phosphorus. This suggests that the uranium is related to a resistate mineral assemblage derived from surrounding crystalline igneous and metamorphic rocks.

  5. Influence of organic matter on the adsorption of 210Pb, 210Po and 7Be and their fractionation on nanoparticles in seawater

    NASA Astrophysics Data System (ADS)

    Yang, Weifeng; Guo, Laodong; Chuang, Chia-Ying; Santschi, Peter H.; Schumann, Dorothea; Ayranov, Marin

    2015-08-01

    Improved applications of 210Po, 210Pb and 7Be as geochemical proxies require more detailed understanding of their interactions with particles. Here, laboratory sorption experiments were carried out to examine the adsorption of 210Po, 210Pb and 7Be and their fractionation on inorganic nanoparticles, including SiO2, CaCO3, Al2O3, TiO2 and Fe2O3, in the presence or absence of macromolecular organic compounds (MOCs) that include humic acids (HA), acid polysaccharides (APS) and proteins (BSA), in natural seawater. Results showed that nanoparticle sorption was not greatly enhanced over that of microparticles as would be expected from their much higher specific surface areas, likely indicating their aggregation in seawater. It was found that synergistic interactions between inorganic nanoparticles, MOCs, and radionuclides determined the sorption, although their adsorption was particle composition-dependent. MOCs enhanced the sorption of selected nuclides on most nanoparticles. On average, in the presence of MOCs, partition coefficients (Kc) of 210Po, 210Pb, and 7Be on nanoparticles increased 2.9-, 5.0- and 5.9-fold, respectively. The effect of MOCs could be explained for 210Po and 210Pb from their different log ⁡Kc values on inorganic nanoparticles. In addition, fractionation effects between 210Po and 210Pb (or between 210Pb and 7Be) could be quantified from their relative log ⁡Kc values on end-member sorbent components. Applications of both 210Po-210Pb and 7Be-210Pb pairs as particle dynamics tracers could be more quantitative when the nature of the organic coatings is taken into account.

  6. Bioaccumulation of 210Po and 210Pb in cephalopods collected from Kudankulam (Southeastern coast of Gulf of Mannar, India) and assessment of dose in human beings.

    PubMed

    Khan, M Feroz; Wesley, S Godwin

    2011-11-01

    Activities of (210)Po and (210)Pb in various tissues of two common species of cephalopod molluscs (cuttlefishes) of Kudankulam coast were studied. Of all the tissues, (210)Po and (210)Pb were found accumulated more in the digestive gland, shell gland and intestine. Urotheuthis duvauceli accumulated more (210)Po and (210)Pb in certain organs when compared with Sepiella inermis. The activity ratio of (210)Po/(210)Pb fell within the range of 0.6-29.3 in the organs. The biological concentration factor for the organs ranged from 1.2×10(3) to 2×10(5) for (210)Po and 3.6×10(2) to 7.6×10(4) for (210)Pb. A significant variation in the accumulation of (210)Po and (210)Pb was noted between species, organs and seasons (p < 0.05). The whole-body internal dose rate due to (210)Po was 1.24 and 0.83 µGy h(-1) and it was 2×10(-3) and 3×10(-3) µGy h(-1) due to (210)Pb for both the species. The effective dose in humans due to (210)Po intake ranged from 96.3 to 376.6 µSv y(-1) and that of (210)Pb ranged from 35.2 to 105.7 µSv y(-1), respectively. The data generated will act as a reference database for these organisms of this coast in which a nuclear power station is under construction.

  7. Effects of greenhouse warming and N-fertilization on carbon accumulation rates in a nutrient-poor boreal mire: decadal effects assessed using 210Pb

    NASA Astrophysics Data System (ADS)

    Olid, Carolina; Nilsson, Mats B.; Eriksson, Tobias; Klaminder, Jonatan

    2013-04-01

    Boreal peatlands represent a major long-term reservoir of atmospheric carbon (C) and play an important role in the global C cycle. How C accumulation in these peatlands responds to changing temperature and nutrient conditions is under debate. In this study, we assessed how peat and C accumulation rates have responded to increased annual nitrogen additions (30 kg ha-1 yr-1) and increased air temperatures (+3.6°C) in the longest ongoing boreal mire manipulation experiment. Accumulation rates for the uppermost 40 cm of peat in nitrogen and temperature treated plots (n=11) were assessed by 210Pb dating covering the last ~100yrs. A reference surface, installed in 1995 was used as independent validation of the dating model. An empirically based model of organic matter accumulation/degradation was applied to evaluate changes in both peat inputs and organic matter decay rates in response to the treatments. A significant increase in C-accumulation (15 g C m-2 yr-1) was observed in peat subjected to nitrogen additions, while greenhouse warming did not seem to significantly affect C-accumulation or decay rates. Based on our findings we argue that C-accumulation in nutrient poor boreal mires is mainly altered in near-surface peat layers (~15 cm) in response to nitrogen additions and that the uppermost peat layers (<40 cm) in nutrient poor boreal peatlands will continue to function as net C-sinks during the first decades of global warming.

  8. Improvements to luminescence dating of Quaternary sediments deformed by earthquakes

    NASA Astrophysics Data System (ADS)

    Lawson, M. J.; Rhodes, E. J.; Barrera, W. A.; Ochoa, G. T.

    2012-12-01

    Luminescence dating of sediments on timescales of decades to several hundred thousand years provides the potential to improve our understanding of the dynamics of fault movement and earthquake generation. Sedimentary structures offset by fault slip such as terrace risers, and deposits deformed by seismicity may be dated over timescales that help bridge the gap between direct observation and the geologic record. Neotectonic environments offer unique challenges for the optical dating of quartz, using optically stimulated luminescence (OSL) signals. Quartz grains eroded from bedrock often display low OSL sensitivity, high thermal transfer, and in some cases suffer from signal contributions from microscopic inclusions of other minerals. Anomalous fading of feldspar, and differing responses to specific measurement protocols by different minerals, make signal contamination a potential issue with quartz OSL. A previous test to assess quartz signal purity (the "quartziness" test) has been expanded to include more components for analysis. These include not only normalized thermal quenching (OSL signal response to measurement at different temperatures), but also IRSL (infra-red stimulated luminescence intensity, a ratio of IRSL signal to OSL intensity (post IRSL bleach) and a ratio of OSL (post-IRSL bleach) to non IRSL bleached OSL signal intensities. When graphed, feldspar and quartz samples occupy distinct regions that aid in the assessment of signal contributions for new samples as a check on sample preparation and OSL dating suitability. We examine the performance of this approach for detecting quartz signal contamination using samples from Southern California, New Zealand and High Asia.

  9. Accumulation rate and mixing of shelf sediments in the Monterey Bay National Marine Sanctuary

    USGS Publications Warehouse

    Lewis, R.C.; Coale, K.H.; Edwards, B.D.; Marot, M.; Douglas, J.N.; Burton, E.J.

    2002-01-01

    The distribution of excess 210Pb in 31 sediment cores was used to determine modern (last 100 yr) mass accumulation rates and the depth of sediment mixing on the continental shelf between Pacifica and Monterey, California, USA. Apparent mass accumulation rates average 0.27 g cm-2 yr-1 and range from 0.42 g cm-2 yr-1 to 0.12 g cm-2 yr-1. Accumulation rates were highest at mid-shelf water depths (60-100 m) adjacent to major rivers and near the head of the Ascension submarine canyon. Cores from water depths of less than 65 m had low, uniform 210Pb activity profiles and sandy textures. The uppermost 5-13 cm of 15 cores had uniform 210Pb activity profiles above a region of steadily decreasing 210Pb activity. This phenomenon was attributed to sediment mixing. The thickness of this upper layer of uniform 210Pb activity decreased southward from 13 cm, west of Pacifica, to less than 5 cm, near Monterey Canyon. This southward decrease may be attributed to shallower bioturbation in the southern study area. Integrated excess 210Pb activities were generally higher where sedimentation rates were high. They were also higher with increasing distance from major rivers. Thus, sedimentation rate alone does not explain the distribution of integrated excess 210Pb in this study area. Excess 210Pb in the seafloor is controlled by other factors such as sediment texture, the atmospheric deposition rate of 210Pb, and the residence time of sediment particles in the water column. ?? 2002 Elsevier Science B.V. All rights reserved.

  10. Distribution of artificial radionuclides in deep sediments of the Mediterranean Sea.

    PubMed

    Garcia-Orellana, J; Pates, J M; Masqué, P; Bruach, J M; Sanchez-Cabeza, J A

    2009-01-01

    Artificial radionuclides enter the Mediterranean Sea mainly through atmospheric deposition following nuclear weapons tests and the Chernobyl accident, but also through the river discharge of nuclear facility effluents. Previous studies of artificial radionuclides impact of the Mediterranean Sea have focussed on shallow, coastal sediments. However, deep sea sediments have the potential to store and accumulate pollutants, including artificial radionuclides. Deep sea marine sediment cores were collected from Mediterranean Sea abyssal plains (depth >2000 m) and analysed for (239,240)Pu and (137)Cs to elucidate the concentrations, inventories and sources of these radionuclides in the deepest areas of the Mediterranean. The activity - depth profiles of (210)Pb, together with (14)C dating, indicate that sediment mixing redistributes the artificial radionuclides within the first 2.5 cm of the sedimentary column. The excess (210)Pb inventory was used to normalize (239,240)Pu and (137)Cs inventories for variable sediment fluxes. The (239,240)Pu/(210)Pb(xs) ratio was uniform across the entire sea, with a mean value of 1.24x10(-3), indicating homogeneous fallout of (239,240)Pu. The (137)Cs/(210)Pb(xs) ratio showed differences between the eastern (0.049) and western basins (0.030), clearly significant impact of deep sea sediments from the Chernobyl accident. The inventory ratios of (239,240)Pu/(137)Cs were 0.041 and 0.025 in the western and eastern basins respectively, greater than the fallout ratio, 0.021, showing more efficient scavenging of (239,240)Pu in the water column and major sedimentation of (137)Cs in the eastern basin. Although areas with water depths of >2000 m constitute around 40% of the entire Mediterranean basin, the sediments in these regions only contained 2.7% of the (239,240)Pu and 0.95% of the (137)Cs deposited across the Sea in 2000. These data show that the accumulation of artificial radionuclides in deep Mediterranean environments is much lower than

  11. Foraminiferal Distributions, Sedimentation Rates and Patterns in the Albemarle Estuarine System, North Carolina

    NASA Astrophysics Data System (ADS)

    Vance, D. J.; Corbett, D. R.; Culver, S. J.

    2002-12-01

    The modern distribution of benthic foraminifera of the Albemarle Estuarine System (AES) has been characterized by studying 50 strategically chosen sites to provide a model for paleoenvironmental interpretations of short sediment cores (15-75 cm). Water bodies studied within the AES include Albemarle Sound, Currituck Sound, Roanoke Sound, Croatan Sound, northern Pamlico Sound, North River, Pasquotank River, Alligator River, as well as Oregon Inlet and the adjacent foreshore and shoreface of the Atlantic Ocean. Sedimentation rates in the study area have been addressed using 210Pb and 137Cs dating methods. Five foraminiferal assemblages are present: an inner estuary biofacies characterized by two dominant genera, Ammobaculites and Ammotium, with moderate percentages of Miliammina fusca and minor percentages of Ammoastuta salsa; an outer estuary biofacies characterized again by Ammobaculites and Ammotium, but with lower percentages of Miliammina fusca; a marsh shoreline biofacies characterized by a mixed assemblage dominated by Ammobaculites and Ammotium with minor to moderate percentages of adjacent marsh foraminifera; a marsh biofacies characterized by varying abundances of Ammoastuta inepta, Arenoparella mexicana, Haplophragmoides wilberti, Jadammina macrescens, Miliammina earlandi, Miliammina fusca, Tiphotrocha comprimata, Trochammina inflata, as well as the genera Ammobaculites and Ammotium; and a marine (normal salinity) biofacies characterized mainly by Elphidium excavatum and minor percentages of other elphidiids. Sedimentation rates were studied from 28 short cores taken along transects in all the major water bodies. Rates were as high as 0.45 cm/yr at the head of Albemarle Sound and as little as 0.05 cm/yr 60 km away in the eastern part of the Albemarle. The embayed tributaries exhibited sedimentation rates on the order of 0.25 cm/yr. Limited information on sedimentation rates was provided by cores in eastern sounds, which had only a few centimeters of recent

  12. Radiometric dating of sediments using fission tracks in conodonts

    USGS Publications Warehouse

    Sachs, H.M.; Denkinger, M.; Bennett, C.L.; Harris, A.G.

    1980-01-01

    Conodonts are microfossils which are commonly found in marine rocks of Cambrian to Triassic age. Although their biological affinities are difficult to assess, conodonts are valuable stratigraphical indices for much of their geological range1. Recent work has also established that conodont colour alteration indices (CAI) are useful guides to diagenetic temperatures and hence burial depth2. Fission tracks3 in conodonts allow measurement of uranium concentrations and estimates of 'age' to be made using isotopic methods4. We report here that fission tracks counted in irradiated, thermally unaltered (as indicated by CAI) middle Palaeozoic conodonts indicate typical uranium concentrations of ???1 part in 10 9, with some samples higher. A single specimen of Siphonodella from the Lower Mississippian yielded an age estimate of 380??140 Myr consistent with conventional interpolations. This method may also allow the unroofing of deeply buried sediments to be dated. ?? 1980 Nature Publishing Group.

  13. Enhanced scavenging of 210Pb and 210Po by processes associated with the East Pacific Rise near 8°45'N

    NASA Astrophysics Data System (ADS)

    Kadko, David; Bacon, Michael P.; Hudson, Andrew

    1987-02-01

    In 1977 and 1981 a hydrothermal plume was detected at the East Pacific Rise (EPR) near 8°45'N and at MANOP Site M, 25 km east of the EPR, by anomalous 222Rn and Mn concentrations. In 1981, samples were also taken for 210Pb, 210Po and 226Ra analyses to determine if enhanced scavenging of these elements occurred in the plume. At both the ridge crest and at Site M, the 210Pb/ 226Ra ratios range from 0.09 to 0.35, which are among the lowest values ever measured. It appears that removal of the 210Pb is occurring by processes operating at or near the seafloor. There is also significant 210Po/ 210Pb disequilibrium at both locations, which appears to increase away from the seafloor towards the plume (as indicated by elevated Mn concentrations). An in-situ water column scavenging process is suggested by correlation of [ 210Pb- 210Po] and Mn concentrations in the plume. The residence time of the 210Po is only about 1 year, which is close to its residence time in surface waters but quite short compared to typical deep sea values. Thus rapid scavenging of the polonium in the plume and relatively rapid settling of particles from the plume is suggested.

  14. A study on possible use of Urtica dioica (common nettle) plant as polonium (210)Po and lead (210)Pb contamination biomonitor in the area of phosphogypsum stockpile.

    PubMed

    Olszewski, Grzegorz; Boryło, Alicja; Skwarzec, Bogdan

    2016-04-01

    The aim of this study was to test a possible use of Urtica dioica (common nettle) plant as a biomonitor of polonium (210)Po and lead (210)Pb contamination near phosphogypsum stacks by determining concentrations of these radionuclides in samples collected from the area of phosphogypsum stockpile in Wiślinka (northern Poland). The (210)Po and (210)Pb contents in roots depended on their concentrations in soils. Bioconcentration factor values from soil to root of the plant did not depend on (210)Po and (210)Pb contents in soils that leads to the conclusion that different polonium and lead species have different affinities to U. dioica plants. The main sources of both analyzed radionuclides in green parts of plants are wet and dry air deposition and transportation from soil. The values of (210)Po/(210)Pb activity ratio indicate natural origin of these radioisotopes in analyzed plants. (210)Po and (210)Pb concentration in U. dioica roots is negatively weakly correlated with distance from phosphogypsum stockpile.

  15. 210Po and 210Pb trophic transfer within the phytoplankton-zooplankton-anchovy/sardine food web: a case study from the Gulf of Lion (NW Mediterranean Sea).

    PubMed

    Strady, Emilie; Harmelin-Vivien, Mireille; Chiffoleau, Jean François; Veron, Alain; Tronczynski, Jacek; Radakovitch, Olivier

    2015-05-01

    The transfer of (210)Po and (210)Pb in the food web of small pelagic fishes (from phytoplankton and zooplankton to anchovy Engraulis encrasicolus and sardine Sardina pilchardus) is investigated in the Gulf of Lion (GoL). We present original data of (210)Po and (210)Pb activity concentrations, C and N stable isotope ratios, measured (i) from different size classes of phytoplankton and zooplankton during spring and winter in different environments of the GoL, and (ii) in two fish species. Significant spatial patterns based on (210)Po, (210)Pb activity concentrations and (210)Po/(210)Pb ratios in the different plankton size classes are evidenced by hierarchical clustering, both in spring and winter. This variability, also observed for C and N stable isotopes ratios, is connected to local specific pelagic habitats and hydrodynamics. The sampling strategy suggests that (210)Po bioaccumulation in the GoL remains at a constant level from the first (dominated by phytoplankton) to the second trophic level (zooplankton), while (210)Pb bioaccumulation shows an increase in winter. Based on stable N isotope ratios and (210)Po activity concentrations measured in anchovies and sardines, we evidence (210)Po bio-magnification along the trophic food web of these two planktivorous pelagic fishes.

  16. Seasonal and spatial variations of 210Po and 210Pb activity concentrations in Mytilus galloprovincialis from Croatian coast of the Adriatic Sea.

    PubMed

    Rožmarić, Martina; Rogić, Matea; Benedik, Ljudmila; Štrok, Marko; Barišić, Delko

    2013-11-01

    Results of 2 years monitoring of (210)Po and (210)Pb activity concentrations in soft tissue of the species Mytilus galloprovincialis from Croatian part of the Adriatic coast are presented. The samples were collected at thirteen coastal stations (some of which are also a part of the Mediterranean Mussel Watch Project) in spring and autumn of 2010 and 2011. The collected mussels were ranging between 4 cm and 6 cm in shell length. After sample pre-treatment lead and polonium were radiochemically separated on Sr resin. (210)Po was determined by alpha-particle spectrometry and (210)Pb was determined, via (210)Bi, by a low-level gas proportional counter. The results of (210)Po activity concentrations were found to vary between (104±11) and (1421±81) Bq kg(-1) dry weight while (210)Pb activity concentrations were much lower and in range (8.2±5.3)-(94.1±29.8) Bq kg(-1) dry weight. Higher (210)Po and (210)Pb activity concentrations were determined in spring period. The inter-site differences seen in their activity concentrations can be due to natural background levels of sites. The (210)Po/(210)Pb activity concentration ratios in all cases exceeded unity for all mussel samples and ranged between 4.0 and 47.9.

  17. In vivo measurements of 210Pb in skull and knee geometries as an indicator of cumulative 222Rn exposure in a underground coal mine in Brazil.

    PubMed

    Dantas, A L A; Dantas, B M; Lipsztein, J L; Spitz, H B

    2007-01-01

    Cumulative exposure to radon can be evaluated by measuring 210Pb in bone. The skull and knee are two convenient parts of the skeleton for in vivo measuring 210Pb because these regions of the body present a high concentration of bone, the detectors are easily positioned and the likelihood of cross contribution from other organs or tissues is low. A radiological survey of non-uranium mines in Brazil indicated that an underground coal mine in Paraná, located in the south of Brazil, exhibited a high radon concentration. In vivo measurements of 32 underground coal miners were performed in the IRD-CNEN Whole Body Counter shielded room using an array of four high-resolution germanium detectors. Estimations of 210Pb in the total skeleton were determined from direct in vivo measurements of 210Pb in the head and knees. In vivo measurements of 210Pb in 6 out of 32 underground coal miners ranged from 80 to 164 Bq, suggesting that these workers were significantly exposed to 222Rn.

  18. Offshore sediments record the history of onshore iron ore mining in Goa State, India.

    PubMed

    Sebastian, Tyson; Nath, B Nagender; Naik, Sangeeta; Borole, D V; Pierre, Salou; Yazing, Armoury Kazip

    2017-01-30

    Environmental magnetic and geochemical analyses combined with (210)Pb dating were carried out on a sediment core off Goa from Arabian Sea to reconstruct the sedimentation history of last three and a half centuries and to investigate the impact of onshore iron ore mining on the offshore sedimentation. A drastic increase in sedimentation rate and mineral magnetic concentration parameters divides the core into two units (1 & 2) at a depth of 41cm (1982CE). The high magnetic susceptibility values in Unit 1 sediments are coeval with increased iron ore production on land and illustrate the role of terrestrial mining on the increased offshore sedimentation. The early diagenetic signals were observed in Unit 2 of the core with low concentration parameters, coarse magnetic grain size and magnetically hard mineralogy. The geochemical data of the core also record the Little Ice Age (LIA) climatic events of Dalton and Maunder solar minima.

  19. Accelerator-mass spectrometer (AMS) radiocarbon dating of Pleistocene lake sediments in the Great Basin

    USGS Publications Warehouse

    Thompson, R.S.; Toolin, L.J.; Forester, R.M.; Spencer, R.J.

    1990-01-01

    Pleistocene lake sediments in the Great Basin typically contain little organic carbon, and thus are difficult to date reliably by conventional radioccarbon methods. Paleoenvironmental data are abundant in these sediments, but are of limited value without adequate age controls. With the advent of accelerator-mass spectrometer (AMS) radiocarbon dating, it is now possible to date these paleolacustrine sediments. AMS dates were obtained on sediment cores from the Bonneville, Franklin, and Lahontan Basins. In the Bonneville Basin, the AMS-based chronology compares well with other chronologies constructed from dated shore-zone features. In the Bonneville and Franklin basins, AMS dates delimit unconformities not apparent by other means. We found that dispersed organic carbon from sediments deposited during relatively freshwater intervals provided apparently reliable AMS radiocarbon dates. Carbonate microfossils from the Lahontan Basin also produced results that appear reasonable, while bulk carbonate yielded erroneous results. ?? 1990.

  20. Assessment of committed effective dose due to the ingestion of (210)Po and (210)Pb in consumed Lebanese fish affected by a phosphate fertilizer plant.

    PubMed

    Aoun, M; El Samad, O; Bou Khozam, R; Lobinski, R

    2015-02-01

    Ingestion of radionuclides through seafood intake is a one of the sources contributing to the internal effective dose in the human organism. In order to evaluate the internal exposure and potential risks due to (210)Po and (210)Pb associated with fish consumption, these radionuclides were measured in commonly consumed fish species from a clean area and an area subjected to the impact of a Lebanese phosphate fertilizer plant. The highest concentration of (210)Pb was 98.7 Bq/kg fresh weight while (210)Po activity concentrations varied from 3.6 Bq/kg to 140 Bq/kg. A supplementary radiation exposure was detected; the highest committed effective dose due to (210)Po and (210)Pb was found to be 1110 μSv/y and 450 μSv/y, respectively. Moreover, the average mortality and morbidity risks due to the fish consuming were estimated.

  1. 210Po and 210Pb distribution, dissolved-particulate exchange rates, and particulate export along the North Atlantic US GEOTRACES GA03 section

    NASA Astrophysics Data System (ADS)

    Rigaud, S.; Stewart, G.; Baskaran, M.; Marsan, D.; Church, T.

    2015-06-01

    Vertical profiles of 210Po and 210Pb in the water column were measured in the dissolved phase (<0.45 μm), and small (0.8-51 μm) and large (>51 μm) particles at seven stations along the US GEOTRACES North Atlantic Zonal Transect (GA03). Mass balance calculations were employed to assess nuclide exchange rates at the dissolved-small particle interface and between small and large particles, and to quantify export with settling large particles. In the surface ocean, 210Po scavenging is linearly correlated with the concentration of particulate organic carbon (POC) in large particles, supporting the role of biogenic particle in 210Po bioaccumulation and export. In stations near the coast, this link is more complex due to the variable source of biogenic material and temporal changes in the surface biogeochemical and physical conditions. At depth, 210Po exhibits significant widespread deficit with respect to 210Pb that could in part be attributed to in situ 210Po scavenging and may be related to surface biological productivity. As previously reported the 210Pb scavenging rates in the surface ocean were higher at ocean margins. At depth, 210Pb scavenging increases with depth and eastward due to the increase of adsorption sites available in the benthic layers and to a regional contribution of benthic 210Pb scavenging and/or particle flux, respectively. The benthic nepheloid layer (BNL) and the Hydrothermal TAG plume distinctly enhance 210Pb scavenging due to increased surface adsorption in association with resuspended or freshly formed particles. In contrast, 210Po is not seen to be significantly scavenged in these environments due to its relatively short half-life and the long residence time of particles.

  2. Partitioning and Fractionation of 210Pb, 210Po and 7Be During Their Interactions With Inorganic and Organic Nanoparticles in Seawater

    NASA Astrophysics Data System (ADS)

    Guo, L.; Yang, W.; Chuang, C.; Santschi, P. H.; Schumann, D.; Ayranov, M.

    2012-12-01

    Controlled laboratory experiments were carried out to examine the role of natural organic matter in regulating the partitioning and fractionation of particle-reactive radionuclides 210Pb(II), 210Po(-II, II, IV) and 7Be(II) during their interactions with colloidal or nanoparticles in seawater. Selected nanoparticles with similar sizes (20 nm), including SiO2, CaCO3, Al2O3, TiO2, and Fe2O3, and macromolecular organic matter including humic acids (HA), acid polysaccharides (APS, carrageenan type V), proteins (bovine serum albumin, BSA), and extracellular polymeric substances (EPS) were used to examine the partition coefficients (Kd) of 210Pb, 210Po and 7Be between dissolved and colloidal phases in the <1 kDa seawater. Similar Kd values were observed for 210Pb, 210Po and 7Be during their interactions with either HA or BSA, showing no significant fractionation between these isotopes. However, there was a significant fractionation between nuclides in the APS or EPS treatment, with 1-2 orders of magnitude difference in Kd values following the order of Po > Pb > Be. For inorganic nanoparticles, SiO2 and CaCO3 had lower affinity for both 210Po and 210Pb, while TiO2 or Fe2O3 had the highest affinity for 210Pb with an overall high Kd value. Fe2O3 also had the highest affinity for 7Be with a Kd value 400 times higher than that of CaCO3. In binary systems with both inorganic and organic nanoparticles, except for Fe2O3, the Kd values for 210Pb, 210Po and 7Be all increased by varying degrees compared to pure inorganic sorbents, implying that the interactions between organic and inorganic particles in most cases promote stronger sorption of these nuclides on nanoparticles. In contrast, experimental treatments with Fe2O3 and model organic compounds decreased the Kd values for 210Pb and 7Be, suggesting the coating of organic matter on high affinity sorbents would depress the sorption of trace elements on nanoparticle surfaces. These results highlight the importance of chemical

  3. Sediment isotope tomography (SIT) model version 1

    SciTech Connect

    Carroll, J.; Abraham, J.D.

    1996-03-08

    Geochronology using {sup 210}Pb is the principal method used to quantify sediment accumulation in rapidly depositing aquatic environments such as lakes, estuaries, continental shelves, and submarine canyons. This method is based on the radioactive decay of {sup 210}Pb with depth in a column of sediment. The decay through time of {sup 210}Pb P(t) is governed by the exponential law P(t) = P{sub 0} exp( -{lambda}t) where P{sub 0} is the surficial concentration at time t = 0, and {lambda} is the decay constant (3.114 {sm_bullet} 10{sup -2} year [yr]{sup -1} for {sup 210}Pb). If the sedimentation rate is constant, then elapsed time t is connected to burial depth x, through x = Vt where V is the sedimentation velocity. Accordingly, P(x) = P{sub 0}exp( -{lambda}x/V). The sedimentation velocity is obtained from an exponential fit to the measured {sup 210}Pb data P(x), with depth x.

  4. An Improved Method to Determine {sup 210}Pb, {sup 210}Bi and {sup 210}Po in air Aerosol Filters

    SciTech Connect

    Miguel, E. G. San; Bolivar, J. P.; Teran, T.

    2008-08-07

    {sup 222}Rn daughters (e.g. {sup 210}Pb, {sup 210}Po, {sup 210}Bi) have been widely used to study a variety of atmospheric processes. Many works in literature about {sup 222}Rn daughters do not specify the way by the activities of these radionuclides are calculated. Besides, {sup 210}Po corrections due to the in-growth of {sup 210}Bi, if taken into account, are not indicated. In this work, the increase in uncertainties of radionuclides activities due to delay between air sampling and radionuclides determinations have been evaluated and the influence of neglecting the contribution of {sup 210}Bi in-growth to {sup 210}Po determination has been estimated. The results indicate that, in general, ignoring the {sup 210}Bi in-growth in {sup 210}Po determinations lead to significant differences (could reach until 100%) between the estimation of {sup 210}Po activity and its true value.

  5. Geochronology of Danube Delta sediments The PN-II-RU-TE-2012-3-0351 project

    NASA Astrophysics Data System (ADS)

    Robert-Csaba, Begy; Andra-Rada, Iurian; (Rusu) Oana Alexandra, Dumitru; Luminita, Preoteasa; Hedvig, Simon; Alida, Timar-Gabor; Szabolcs, Kelemen

    2014-05-01

    The sedimentation processes and the associated morphological changes within the Danube Delta and along the deltaic coast are complex and less understood.One of the main objectives of the project is the determination of sedimentation rates in several lacustrine units from the Danube Delta area, lakes in which the sedimentation rate clearly reflects the variation of the rivers solid discharge. Several undisturbed bottom lake sediments form the Danube Delta were extruded and the analysis of the vertical variation of the sedimentary facies, combined with 210Pb and 137Cs radiometric methods is undertaken in order to get a high resolution data of the sedimentation rates during the last one century. Additionally, sedimentation pattern in the proximity of the fluvial levees will be investigated for the first time at several locations in order to get insight into the lateral and temporal variations in sediment accumulation rates. Another objective is the assessment of the sedimentation rates on the Danubian continental shelf. This investigation will identify the tendency of the sediment deposition rates offshore of the closure depths during the last century and, more importantly, the main actual depocenters repartition and the associated sedimentation rates will be identified. The sedimentation rates data will contribute to the analysis of the sedimentary linkage between the river discharge, the longshore currents and the shoreline dynamics in order to isolate and quantify the role of the river solid discharge contribution to the long shore transport and to the shoreline dynamics and river distributaries mouth changes. The third objective is the geochronological investigation of the youngest deltaic lobes (Sfântu Gheorghe, Sfântu Gheorghe secondary delta, Chilia secondary delta) by means of luminescence dating in order to obtain a high accuracy of their evolution in time (e.g. last 3000 years). This study represents the first investigation of sedimentation rates and

  6. Dating of Pliocene Colorado River sediments: implications for cosmogenic burial dating and the evolution of the lower Colorado River

    USGS Publications Warehouse

    Matmon, Ari; Stock, Greg M.; Granger, Darryl E.; Howard, Keith A.

    2011-01-01

    We applied cosmogenic 26Al/10Be burial dating to sedimentary deposits of the ancestral Colorado River. We compared cosmogenic burial ages of sediments to the age of an independently well-dated overlying basalt flow at one site, and also applied cosmogenic burial dating to sediments with less precise independent age constraints. All dated gravels yielded old ages that suggest several episodes of sediment burial over the past ∼5.3 m.y. Comparison of burial ages to the overlying 4.4 Ma basalt yielded good agreement and suggests that under the most favorable conditions, cosmogenic burial dating can extend back 4–5 m.y. In contrast, results from other sites with more broadly independent age constraints highlight the complexities inherent in burial dating; these complexities arise from unknown and complicated burial histories, insufficient shielding, postburial production of cosmogenic isotopes by muons, and unknown initial 26Al/10Be ratios. Nevertheless, and in spite of the large range of burial ages and large uncertainties, we identify samples that provide reasonable burial age constraints on the depositional history of sediment along the lower ancestral Colorado River. These samples suggest possible sediment deposition and burial at ca. 5.3, 4.7, and 3.6 Ma. Our calculated basinwide erosion rate for sediment transported by the modern Colorado River (∼187 mm k.y.−1) is higher than the modern erosion rates inferred from the historic sediment load (80–100 mm k.y.−1). In contrast, basinwide paleo-erosion rates calculated from Pliocene sediments are all under 40 mm k.y.−1 The comparatively lower denudation rates calculated for the Pliocene sediment samples are surprising given that the sampled time intervals include significant Pliocene aggradation and may include much incision of the Grand Canyon and its tributaries. This conflict may arise from extensive storage of sediment along the route of the Colorado River, slower paleobedrock erosion, or the inclusion

  7. [Limnology of high mountain tropical lake, in Ecuador: characteristics of sediments and rate of sedimentation].

    PubMed

    Gunkel, Günter

    2003-06-01

    Equatorial high mountain lakes are a special type of lake occurring mainly in the South American Andes as well as in Central Africa and Asia. They occur at altitudes of a few thousand meters above sea level and are cold-water lakes (< 20 degrees C). Relatively little is known about them. A long-term limnological study was therefore undertaken at Lake San Pablo, Ecuador, to analyze the basic limnological processes of the lake, which has a tendency for eutrophication. Sediment quality of San Pablo Lake is given under consideration of horizontal and vertical distribution using sediment cores. Significance of sediments for eutrophication process of lakes is demonstrated using phosphorus concentration of sediments as well as the phosphorus retention capacity of the sediments by ratio Fe/P. Dating of the sediments is done using 137Cs and 210Pb, but the activity of 137Cs in the sediment was very low nearly at the detection level. Sedimentation rate is determined to be 3.5 mm/year and the sediment cores represent about 110 years. P concentration of the sediments is high (approximately 5 g/kg dry substance), and P retention capacity by Fe is insufficient (Fe/P = 4). The sediment quality did not change significantly during the past decades, and the trophic state of San Pablo Lake was already less or more eutrophic 110 years ago. The contamination of the lake sediments by heavy metals is insignificant.

  8. Constraints on the sedimentation history of San Francisco Bay from 14C and 10Be

    USGS Publications Warehouse

    VanGeen, A.; Valette-Silver, N. J.; Luoma, S.N.; Fuller, C.C.; Baskaran, M.; Tera, F.; Klein, J.

    1999-01-01

    Industrialization and urbanization around San Francisco Bay as well as mining and agriculture in the watersheds of the Sacramento and San Joaquin rivers have profoundly modified sedimentation patterns throughout the estuary. We provide some constraints on the onset of these erosional disturbances with 10Be data for three sediment cores: two from Richardson Bay, a small embayment near the mouth of San Francisco Bay, and one from San Pablo Bay, mid-way between the river delta and the mouth. Comparison of pre-disturbance sediment accumulation determined from three 14C-dated mollusk shells in one Richardson Bay core with more recent conditions determined from the distribution of 210Pb and 234Th [Fuller, C.C., van Geen, A., Baskaran, M, Anima, R.J., 1999. Sediment chronology in San Francisco Bay, California, defined by 210Pb, 234Th, 239,240Pu.] shows that the accumulation rate increased by an order of magnitude at this particular site. All three cores from San Francisco Bay show subsurface maxima in 10Be concentrations ranging in magnitude from 170 to 520 x 106 atoms/g. The transient nature of the increased 10Be input suggests that deforestation and agricultural develop- ment caused basin-wide erosion of surface soils enriched in 10Be. probably before the turn of the century.

  9. Impact of sedimentation on wetland carbon sequestration in an agricultural watershed.

    PubMed

    McCarty, Gregory; Pachepsky, Yakov; Ritchie, Jerry

    2009-01-01

    Landscape redistribution of soil C is common within agricultural ecosystems. Little is known about the effects of upland sediment deposition on C dynamics within riparian wetlands. To assess sedimentation impact, we obtained profile samples of wetland soil and used the combination of (137)Cs, (210)Pb, and (14)C chronological markers to determine rates of C sequestration and mineral deposition over the history of a wetland within a first-order catchment under agricultural management in the coastal plains of the United States. Substantial post settlement deposition in the wetland soil was evidenced in places by a 20- to 40-cm layer of mineral soil that buried the original histosol. Soil profiles contained a minimum in C content within the top 35 cm of the profile which originated from a rapid deposition from low C upland soils. Radiocarbon and radioisotope dating showed that increases in C above this minimum were the result of C sequestered in the past approximately 50 yr. Modeling the kinetics of modern C dynamics using the (137)Cs and (210)Pb markers within these surface profiles provides strong evidence for accelerated C sequestration associated with mineral sediment deposition in the ecosystem. These findings indicate that at the landscape scale, dilution of ecosystem C by import of low C upland sediment into wetlands stimulates C sequestration by pulling soil C content below some pedogenic equilibrium value for the ecosystem. They also indicate that over the history of the wetland, rates of C accretion may be linked to mineral soil deposition.

  10. Use of the mercury record in Red Tarn sediments to reveal air pollution history and the implications of catchment erosion.

    PubMed

    Yang, Handong; Smyntek, Peter

    2014-11-01

    Red Tarn is a cirque lake with a small ratio of terrestrial area to lake area, surrounded by glacial edges with little soil in the catchment. A sediment core taken from the deepest area of the lake was (210)Pb dated and validated by (137)Cs and (241)Am stratigraphic records. The core was analysed for mercury (Hg) and other elements. The results show Hg pollution before the mid-19th century, and thereafter, a rapid increase in Hg pollution into modern time, followed by a decline in pollution since 1968-1970. This agrees well with the decline in UK Hg emissions since the Clear Air Act of 1968. The results suggest that the core has recorded Hg air pollution history, and it can be used to benchmark Hg changes in the sediments from other lakes in the region up to the late 1980s. However, increased (210)Pb fluxes after the late 1980s indicate enhanced catchment erosion, which has brought more legacy Hg in the catchment into the lake. As a consequence, since 2000, the Hg in the sediment record no longer reflects the atmospheric Hg deposition. The core shows how dominant Hg sources for the lake changed from atmospheric deposition to the catchment inputs, and demonstrates that contaminated catchment inputs have not only increased Hg fluxes to the lake sediments but have also increased Hg concentrations in the sediments.

  11. 210Pb and 210Po, manganese and iron cycling across the O2/H2S interface of a permanently anoxic fjord: Framvaren, Norway

    USGS Publications Warehouse

    Swarzenski, Peter W.; McKee, Brent A.; Sorenson, Kai; Todd, James F.

    1999-01-01

    Vertical profiles of dissolved and particulate 201Po and 210Pb were measured across the redox transition zone at Station F1 in Framvaren Fjord, Norway. In this fjord, a sharp decrease in pH above the O2/H2S interface facilitates the aerobic dissolution of MnO2. In contrast, Fe(II) concentrations begin to increase only at the O2/H2S interface depth. Activity profiles reveal that dissolved 210Po and 210Pb are sequestered efficiently by particulates in surface waters. As polonium-210 and lead-210 activities descend down into the aerobic manganese reduction (AMR) zone, they are remobilized during the reductive dissolution of the carrier phase oxyhydroxides. Both 210Po and 210Pb are highly enriched at the O2/H2S interface where an active community of microbes, such as anoxygenic phototrophs (e.g., Chromatium, Chlorobium sp.), thrives. The coincident peaks in 210Po and 210Pb and microbial biomass suggest a strong biological influence on the behavior of these radionuclides. There is a strong covariance between the vertical distribution of Mn and Pb, indicating that their redox cycling is closely coupled and is likely microbially mediated.

  12. A study on lead (210Pb) and polonium (210Po) contamination from phosphogypsum in the environment of Wiślinka (northern Poland).

    PubMed

    Boryło, Alicja; Olszewski, Grzegorz; Skwarzec, Bogdan

    2013-08-01

    The results of polonium ((210)Po) and lead ((210)Pb) determination in different environmental soil samples collected in the vicinity of the phosphogypsum stack in Wiślinka (northern Poland) are presented and discussed in this paper. The (210)Po and (210)Pb concentrations in soil samples from the phosphogypsum stack recorded in this study are significantly higher only in areas that are close to the heap. The relationship between atmospheric deposition and elevated analyzed radionuclides concentrations in top soil layers, especially in the vicinity of the phosphogypsum stack, was showed in this study. (210)Po and (210)Pb radionuclides were detected in concentrations which could have harmful effects on human health or the environment. The considerably high concentrations of (210)Po and (210)Pb in soil samples collected from the vicinity of the phosphogypsum stack obtained in this study can lead to the conclusion that the presently undertaken recultivation process is successful and the 300 m(2) protection zone around the phosphogypsum stack seems to be able to offset the negative influence of the phosphogypsum stack on the surrounding environment.

  13. (210)Po and (210)Pb activity concentrations in Mytilus galloprovincialis from Croatian Adriatic coast with the related dose assessment to the coastal population.

    PubMed

    Rožmarić, Martina; Rogić, Matea; Benedik, Ljudmila; Štrok, Marko; Barišić, Delko; Gojmerac Ivšić, Astrid

    2012-06-01

    Activity concentrations of (210)Po and (210)Pb in the species Mytilus galloprovincialis from Croatian Adriatic coast were determined. The samples were collected in thirteen sampling places which are also a part of Croatian Mediterranean mussel watch project. The results of (210)Po and (210)Pb activity concentrations were found to vary between (22.1±2.5)-(207±21) Bq kg(-1) fresh weight and (2.8±1.4)-(9.3±0.7) Bq kg(-1) fresh weight, respectively. (210)Po/(210)Pb ratio ranged between 6.2 and 30.7. The highest measured activities were found in the enclosed basins of the Neretva channel, where the majority of Croatian mussel cultivation is taking place. The estimated consequent average total annual effective ingestion dose due to (210)Po and (210)Pb from mussel consumption in Croatian coastal region is 202±99 μSv with 96% contribution of (210)Po to the total effective dose.

  14. Carbon and nitrogen cycling in the Zhubi coral reef lagoon of the South China Sea as revealed by 210Po and 210Pb.

    PubMed

    Yang, W F; Huang, Y P; Chen, M; Qiu, Y S; Li, H B; Zhang, L

    2011-05-01

    The radionuclides (210)Po and (210)Pb were examined to trace the cycling of particulate organic carbon (POC) and particulate organic nitrogen (PON) in the Zhubi coral reef lagoon. The net export flux of POC to the open sea is 14 mg Cm(-2) d(-1). However, the net exchange of PON has not yet been observed. On average, the vertical export fluxes in the lagoon of POC and PON, as derived from (210)Po/(210)Pb disequilibria, are 43 mg Cm(-2) d(-1) and 13.8 mg Nm(-2) d(-1), respectively. The deficit of (210)Po relative to (210)Pb in particulate matter provides evidence for the degradation of particulate organic matter. According to the mass balance budgets, 310 mg Cm(-2) d(-1) and 121 mg Nm(-2) d(-1) were recycled into dissolved fractions. Based on a first-order kinetics model, the degradation rate constants of POC and PON are 0.28 and 0.30 m(-1), respectively. Thus, (210)Po and (210)Pb can quantify the cycling of carbon and nitrogen in this coral lagoon.

  15. Comparative analysis of (239)Pu, (137)Cs, (210)Pb and (40)K spatial distributions in the top soil layer at the Baltic coast.

    PubMed

    Luksiene, B; Druteikiene, R; Gvozdaite, R; Gudelis, A

    2006-01-01

    This paper presents the results of an investigation into the spatial distribution of radionuclides of artificial ((239,240)Pu, (137)Cs) and natural ((210)Pb, (40)K) origins in the upper (0-5 cm) soil layers on the Baltic coastline of Lithuania ( approximately 5 km(2) area). The samples were analysed by gamma ray spectrometry and combined radiochemical procedures. The highest (210)Pb, (239,240)Pu and (137)Cs activity concentrations were determined in the forest samples, whereas (40)K activity was rather homogeneous across the study area. Relatively high (239,240)Pu and (40)K activity concentrations were determined along the surf zone. The (210)Pb and (137)Cs activity concentrations showed a gradual increase from the surf zone to the forest. The average activity concentrations of (239,240)Pu, (137)Cs, (210)Pb and (40)K in the beach and forest samples, respectively, were as follows: 0.32+/-0.08 and 0.74+/-0.14; 50+/-4 and 1190+/-50; 4.7+/-2.0 and 48+/-6; 186+/-15 and 216+/-17 Bq/kg.

  16. Assay Methods for 238U, 232Th, and 210Pb in Lead and Calibration of 210Bi Bremsstrahlung Emission from Lead

    SciTech Connect

    Orrell, John L.; Aalseth, Craig E.; Arnquist, Isaac J.; Eggemeyer, Tere A.; Glasgow, Brian D.; Hoppe, Eric W.; Keillor, Martin E.; Morley, Shannon M.; Myers, Allan W.; Overman, Cory T.; Shaff, Sarah M.; Thommasson, Kimbrelle S.

    2016-02-13

    Assay methods for measuring 238U, 232Th, and 210Pb concentrations in refined lead are presented. The 238U and 232Th concentrations are assayed via inductively coupled plasma mass spectrometry (ICP-MS) after anion exchange column separation on dissolved lead samples. The 210Pb concentration is inferred through α-spectroscopy of a daughter isotope, 210Po, after chemical precipitation separation on dissolved lead samples. Subsequent to the 210Po α-spectroscopy assay, a method for evaluating 210Pb concentrations in solid lead samples was developed via measurement of bremsstrahlung radiation from β-decay of a daughter isotope, 210Bi, by employing a 14-crystal array of high purity germanium (HPGe) detectors. Ten sources of refined lead were assayed. The 238U concentrations were <34 microBq/kg and the 232Th concentrations ranged <0.6 – 15 microBq/kg, as determined by the ICP-MS assay method. The 210Pb concentrations ranged from ~0.1 – 75 Bq/kg, as inferred by the 210Po α-spectroscopy assay method.

  17. Behaviour mechanisms and correlation between lead (Pb) and its isotope (210)Pb in industrial residue as an indicator for waste characterization.

    PubMed

    Vaasma, Taavi; Bityukova, Liidia; Kiisk, Madis; Özden, Banu; Tkaczyk, Alan Henry

    2016-12-01

    Total lead and (210)Pb concentrations were determined in various ash fractions (collected from two of the world's largest oil shale-fired power plants) by inductively coupled plasma mass-spectrometry (ICP-MS) and gamma spectrometry. Results show a clear increase in total lead (values up to 193 ppm in filter ashes) and (210)Pb (values up to 148 Bq kg(-1) in filter ashes) concentrations in the ash fractions from the furnace towards the filter ashes. A strong positive linear correlation (Pearson's bivariate correlation remained between 0.86 and 0.99) was determined between total lead concentration (ppm) and (210)Pb activity concentration (Bq kg(-1)) within all the boilers under observation. The constant concentration ratio between total lead and (210)Pb remained around one (with minor exceptions), independent of the sampling location and the used combustion technology. The determined concentration ratio can be applicable as an indicative tool in waste material characterization. It also provides multiple additions to the general material characterization approach, by integrating radiological and elemental studies and providing an option to rapidly obtain initial indicative information about the residues. This in turn helps to generate the initial information to work out the next steps in waste material management.

  18. Time series study of a 17-year record of (7)Be and (210)Pb fluxes in northern Taiwan using ensemble empirical mode decomposition.

    PubMed

    Lee, H-I; Huh, C-A; Lee, T; Huang, N E

    2015-09-01

    Using the ensemble empirical mode decomposition (EEMD) and a significance test method, we have analyzed time series data on the fluxes of (7)Be and (210)Pb collected over a span of 17 y in Northern Taiwan. Among nine intrinsic mode functions (IMFs) extracted from the method five (IMF4-8) are non-trivial for (210)Pb and have adequate S/N with significant power in localized windows around the periodicities of 0.5 y, 1 y, 2 y, 5 y, and 11 y, respectively. For (7)Be, IMF5 and IMF8 with periods around 1 y and 11 y, respectively, have adequate S/N. The semi-annual and annual cycles represented by IMF4 and IMF5, respectively, are dominated by East Asian monsoon. The sum of IMF6 and IMF7 reveals an inter-annual cycle where both (7)Be and (210)Pb fluxes are well-correlated with the East Asian winter monsoon index (EAWMI). The close tracking of the (210)Pb and (7)Be in IMF8 cases may reflect an 11 y cycle; implying that it is caused by common climatologic factors, likely related to solar cycle, rather than their distinct production modes.

  19. Environmental evolution records reflected by radionuclides in the sediment of coastal wetlands: A case study in the Yellow River Estuary wetland.

    PubMed

    Wang, Qidong; Song, Jinming; Li, Xuegang; Yuan, Huamao; Li, Ning; Cao, Lei

    2016-10-01

    Vertical profiles of environmental radionuclides ((210)Pb, (137)Cs, (238)U, (232)Th, (226)Ra and (4)(0)K) in a sediment core (Y1) of the Yellow River Estuary wetland were investigated to assess whether environmental evolutions in the coastal wetland could be recorded by the distributions of radionuclides. Based on (210)Pb and (137)Cs dating, the average sedimentation rate of core Y1 was estimated to be 1.0 cm y(-1). Vertical distributions of natural radionuclides ((238)U, (232)Th, (226)Ra and (40)K) changed dramatically, reflecting great changes in sediment input. Concentrations of (238)U, (232)Th, (226)Ra and (40)K all had significant positive relationships with organic matter and clay content, but their distributions were determined by different factors. Factor analysis showed that (238)U was determined by the river sediment input while (226)Ra was mainly affected by the seawater erosion. Environmental changes such as river channel migrations and sediment discharge variations could always cause changes in the concentrations of radionuclides. High concentrations of (238)U and (226)Ra were consistent with high accretion rate. Frequent seawater intrusion decreased the concentration of (226)Ra significantly. The value of (238)U/(226)Ra tended to be higher when the sedimentation rate was low and tide intrusion was frequent. In summary, environmental evolutions in the estuary coastal wetland could be recorded by the vertical profiles of natural radionuclides.

  20. Effects of sample mass and macrofossil type on radiocarbon dating of arctic and boreal lake sediments

    SciTech Connect

    Oswald, W W; Anderson, P M; Brown, T A; Brubaker, L B; Hu, F S; Lozhkin, A V; Tinner, W; Kaltenrieder, P

    2006-05-29

    Dating lake sediments by accelerator mass spectrometry (AMS) {sup 14}C analysis of plant macrofossils overcomes one of the main problems associated with dating bulk sediment samples, the presence of old organic matter. Even so, many AMS dates from arctic and boreal sites appear to misrepresent the age of the sediment. To understand the nature of these apparent dating anomalies better, we conducted a series of {sup 14}C dating experiments using samples from Alaskan and Siberian lake-sediment cores. First, to test whether our analytical procedures introduced a sample-mass bias, we obtained {sup 14}C dates for different-sized pieces of single woody macrofossils. In these sample-mass experiments, sized statistically equivalent ages were found for samples as small as 0.05 mg C. Second, to assess whether macrofossil type influenced dating results, we conducted sample-type experiments in which {sup 14}C dates were obtained for different macrofossil types sieved from the same depth in the sediment. We dated materials from multiple levels in sediment cores from Upper Capsule Lake (North Slope, northern Alaska) and Grizzly Lake (Copper River Basin, southern Alaska), and from single depths in other records from northern Alaska. In several of the experiments there were significant discrepancies between dates for different plant tissues, and in most cases wood and charcoal were older than other macrofossil types, usually by several hundred years. This pattern suggests that {sup 14}C dates for woody macrofossils may misrepresent the age of the sediment by centuries, perhaps due to their longer terrestrial residence time and the potential in-built age of long-lived plants. This study identifies why some {sup 14}C dates appear to be inconsistent with the overall age-depth trend of a lake-sediment record, and it may guide the selection of {sup 14}C samples in future studies.

  1. 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...

  2. Radionuclide activities and metal concentrations in sediments of the Sebou Estuary, NW Morocco, following a flooding event.

    PubMed

    Laissaoui, A; Mas, J L; Hurtado, S; Ziad, N; Villa, M; Benmansour, M

    2013-06-01

    This study presents metal concentrations (Fe, Mg, Mn, Co, Cu, Zn, Pb, As, Sr and V) and radionuclide activities ((40)K, (137)Cs, (210)Pb, (226)Ra, (228)Ac, (234)Th and (212)Pb) in surface deposits and a sediment core from the Sebou Estuary, Northwest Morocco. Samples were collected in April 2009, about 2 months after a flooding event, and analysed using a well-type coaxial gamma-ray detector and inductively coupled plasma-quadrupole mass spectrometry. Activities of radionuclides and concentrations of almost all elements in surface samples displayed only moderate spatial variation, suggesting homogenous deposition of eroded local soil in response to intense precipitation. Excess (210)Pb displayed relatively constant activity throughout the sediment core, preventing dating and precluding determination of the historical accumulation rates of pollutants at the core site. Some elements showed non-systematic trends with depth and displayed local maxima and minima. Other elements presented relatively systematic concentration trends or relatively constant levels with discrete maxima and/or minima. Except for Mn, Sr and Cr, all metal concentrations in sediment were below levels typical of polluted systems, suggesting little human impact or losses of metals from sediment particles.

  3. Linking the distribution of (210)Po and (210)Pb with plankton community along Line P, Northeast Subarctic Pacific.

    PubMed

    Choi, Hiu Yan; Stewart, Gillian M; Lomas, Michael W; Kelly, Roger P; Moran, S Bradley

    2014-12-01

    Depth profiles of (210)Po and (210)Pb activity and phytoplankton and zooplankton abundance were collected during two cruises along the Canadian time-series Line P in the Northeast Subarctic Pacific (ranging from 48o39 N to 50o00 N and 126o40 W to 145o00 W) in August 2010 and February 2011 to evaluate connections between the planktonic community and distributions of these radionuclides in the upper 500 m of the water column. Statistical analysis indicates that (210)Po is more effectively removed from the surface ocean when large (>0.1 mg ind(-1) dry wt) zooplankton dominate, and is less effectively scavenged when the picoplankton Synechococcus is present at high concentrations (>1 × 10(5) cells ml(-1)). While the zooplankton field data are consistent with previous lab studies and field observations, the phytoplankton results seem to conflict with recent evidence that small cells may contribute significantly to export in other oligotrophic regions. Differences in ecosystem mechanisms between the Subarctic Pacific and other oligotrophic systems that limit the contribution of small cells to sinking flux remain to be identified.

  4. Halogenated compounds in a dated sediment core of the Teltow Canal, Berlin: time related sediment contamination.

    PubMed

    Heim, S; Ricking, M; Schwarzbauer, J; Littke, R

    2005-12-01

    To study the recent contamination history of DDT (1,1,1-trichloro-2,2-bis(chlorophenyl)ethane) and its metabolites, as well as methoxychlor (1,1,1-trichloro-2,2-bis(p-methoxyphenyl)ethane), chlorfenson (4-chlorophenyl-p-chlorobenzenesulfonate), and further halogenated aromatics, a sediment core was collected from the Teltow Canal in Berlin (Germany). The sampling site is located nearby a former industrial point source, where recently analyses on pre-samples have indicated high concentrations of halogenated organic compounds. The deposition time of the investigated sediments was determined by gamma-spectrometrical dating. Pollution trends of selected contaminants were attributed to a time period between 5 and 10 years. Concentration profiles reflect not only the recent pollution history of these compounds, but also the time-depending effects of the ban, restriction and termination of DDT-production in the German Democratic Republic (GDR). DDT and other chlorinated aromatic compounds were produced onsite until the late 1980s. Maximum values of 133 mg kg(-1) (dry weight) for p,p'-DDD (1,1-dichloro-2,2-bis(chlorophenyl)ethane) and approximately 100 mg kg(-1) (dry weight) for p,p'-DDMS (1-chloro-2,2-bis(chlorophenyl)ethane), main metabolites of the anaerobic degradation of DDT, were determined. The occurrence of all selected contaminants, most of which have been banned more than 10 years ago, demonstrate recent contamination pathways, and the necessity of a continuous long-term monitoring of the affected environment.

  5. Sediment dynamics and heavy metal pollution history of the Cruhlig Lake (Danube Delta, Romania).

    PubMed

    Begy, Róbert-Csaba; Preoteasa, Luminita; Timar-Gabor, Alida; Mihăiescu, Radu; Tănăselia, Claudiu; Kelemen, Szabolcs; Simon, Hedvig

    2016-03-01

    This is the first study reporting recent sedimentation rates data (e.g. the past 120-150 years) for the Cruhlig Lake situated in the Danube Delta. The aim of this study is to analyse the recent sedimentation rates using the (210)Pb dating method and identifying the heavy metal pollutants and their variability in time. Five sediment cores were taken with a gravity corer and - after drying the sliced samples-physical parameters, organic material and inorganic carbon content were determined. The total (210)Pb content was measured via (210)Po by alpha spectrometry, while supported (210)Pb was measured by (226)Ra (trough short life (222)Rn daughters) with HPGe detectors. Heavy metals were determined by ICP-MS; from the 64 measured elements, only exceeding values of Al, As, Cd, Co, Cs, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Ni, Pb and Zn are discussed. After applying the CRS model, ages and sedimentation rates were calculated. The average sedimentation rate of the Cruhlig Lake is 0.21 ± 0.02 g/cm(2)y, Minimum values (0.05 ± 0.003 g/cm(2)y) are registered along the eastern shoreline of the lake before 1913, while maximum values are recorded due to the flooding in 2006 in the western side (1.34 ± 0.12 g/cm(2)y). Recent sedimentation rates divide the lake into three areas: the secluded eastern near shore part (0.63 ± 0.07 g/cm(2)y), the centre of the lake (0.92 ± 0.05 g/cm(2)y) and the dynamic western area, where most sediment transport takes place (1.13 ± 0.01 g/cm(2)y). The sedimentation pattern proves this lake to be very sensitive to fluvial discharge fluctuations. The building of the Iron Gate dams (1972 and 1985) had a negative impact on the sedimentation decreasing it with 58.74%, while after 1989 these values grew 2.25 times. The lake received a quantity of sediment rich in heavy metals in 1992 ± 3 y, which settled mostly on the eastern part. Values for Cd, Co, Cr, Hg, Pb and Zn are up to five times higher in 1980 ± 5 y in the eastern part of the lake, while Cd, Co

  6. Recent increases in sediment and nutrient accumulation in Bear Lake, Utah/Idaho, USA

    USGS Publications Warehouse

    Smoak, J.M.; Swarzenski, P.W.

    2004-01-01

    This study examines historical changes in sediment and nutrient accumulation rates in Bear Lake along the northeastern Utah/Idaho border, USA. Two sediment cores were dated by measuring excess 210Pb activities and applying the constant rate of supply (CRS) dating model. Historical rates of bulk sediment accumulation were calculated based on the ages within the sediment cores. Bulk sediment accumulation rates increased throughout the last 100 years. According to the CRS model, bulk sediment accumulation rates were <25mg cm-2 year-1 prior to 1935. Between 1935 and 1980, bulk sediment accumulation rates increased to approximately 40mg cm -2 year-1. This increase in sediment accumulation probably resulted from the re-connection of Bear River to Bear Lake. Bulk sediment accumulation rates accelerated again after 1980. Accumulation rates of total phosphorus (TP), total nitrogen (TN), total inorganic carbon (TIC), and total organic carbon (TOC) were calculated by multiplying bulk sediment accumulation rates times the concentrations of these nutrients in the sediment. Accumulation rates of TP, TN, TIC, and TOC increased as a consequence of increased bulk sediment accumulation rates after the re-connection of Bear River with Bear Lake.

  7. 210Pb and 210Po, manganese and iron cycling across the O2/H2S interface of a permanently anoxic fjord: Framvaren, Norway

    USGS Publications Warehouse

    Swarzenski, Peter W.; McKee, Brent A.; Sorensen, Kai; Todd, James F.

    1999-01-01

    Vertical profiles of dissolved and particulate 210Po and 210b were measured across the redox transition zone at Station F1 in Framvaren Fjord, Norway. In this fjord, a sharp decrease in pH above the O2/H2S interface facilitates the aerobic dissolution of MnO2. In contrast, Fe(II) concentrations begin to increase only at the O2/H2S interface depth. Activity profiles reveal that dissolved 210Po and 210Pb are sequestered efficiently by particulates in surface waters. As polonium-210 and lead-210 activities descend down into the aerobic manganese reduction (AMR) zone, they are remobilized during the reductive dissolution of the carrier phase oxyhydroxides. Both 210Po and 210Pb are highly enriched at the O2/H2S interface where an active community of microbes, such as anoxygenic phototrophs (e.g., Chromatium, Chlorobium sp.), thrives. The coincident peaks in 210Po, 210Pb and microbial biomass suggest a strong biological influence on the behavior of these radionuclides. There is a strong covariance between the vertical distribution of Mn and Pb, indicating that their redox cycling is closely coupled and is likely microbially mediated.

  8. 210Po, 210Pb, 40K and 137Cs in edible wild berries and mushrooms and ingestion doses to man from high consumption rates of these wild foods.

    PubMed

    Gwynn, Justin P; Nalbandyan, Anna; Rudolfsen, Geir

    2013-02-01

    This paper discusses activity concentrations of (210)Po, (210)Pb, (40)K and (137)Cs in edible wild berries and mushrooms collected from Øvre Dividalen national park, Northern Norway and derives committed effective ingestion doses to man based on high consumption rates of these wild foods. Edible wild berries and mushrooms accumulated similar levels of (210)Pb, but mushrooms accumulated higher levels of (210)Po and (40)K than berries. There appears to be a clear difference in the ability of Leccinum spp. of fungi to accumulate (210)Po and/or translocate (210)Po to mushrooms compared to Russula spp. of fungi. Activity concentrations of (137)Cs in edible wild berries and mushrooms from Øvre Dividalen national park reflected the lower levels of fallout of this radionuclide in Northern Norway compared to more central areas following the Chernobyl accident. For mushrooms, ingestion doses are dominated by (210)Po, while for berries, (40)K is typically the main contributor to dose. Based on high consumption rates, ingestion doses arising from the combination of (210)Po, (210)Pb and (40)K were up to 0.05 mSv/a for berries and 0.50 mSv/a for mushrooms. Consumption of such wild foods may result in a significant contribution to total annual doses when consumed in large quantities, particularly when selecting mushrooms species that accumulate high activity concentrations of (210)Po.

  9. Processes controlling the seasonal variations in 210Pb and 7Be at the Mt. Cimone WMO-GAW global station, Italy: a model analysis

    NASA Astrophysics Data System (ADS)

    Brattich, Erika; Liu, Hongyu; Tositti, Laura; Considine, David B.; Crawford, James H.

    2017-01-01

    We apply the Global Modeling Initiative (GMI) chemistry and transport model driven by NASA's MERRA assimilated meteorological data to simulate the seasonal variations in two radionuclide aerosol tracers (terrigenous 210Pb and cosmogenic 7Be) at the WMO-GAW station of Mt. Cimone (44°12' N, 10°42' E; 2165 m a.s.l.; Italy), which is representative of free-tropospheric conditions most of the year, during 2005 with an aim to understand the roles of transport and precipitation scavenging processes in controlling their seasonality. The total precipitation field in the MERRA data set is evaluated with the Global Precipitation Climatology Project (GPCP) observations, and generally good agreement is found. The model reproduces reasonably the observed seasonal pattern of 210Pb concentrations, characterized by a wintertime minimum due to lower 222Rn emissions and weaker uplift from the boundary layer and summertime maxima resulting from strong convection over the continent. The observed seasonal behavior of 7Be concentrations shows a winter minimum, a summer maximum, and a secondary spring maximum. The model captures the observed 7Be pattern in winter-spring, which is linked to the larger stratospheric influence during spring. However, the model tends to underestimate the observed 7Be concentrations in summer, partially due to the sensitivity to spatial sampling in the model. Model sensitivity experiments indicate a dominant role of precipitation scavenging (vs. dry deposition and convection) in controlling the seasonality of 210Pb and 7Be concentrations at Mt. Cimone.

  10. ESR dating of quartz extracted from quaternary and neogene sediments: method, potential and actual limits

    NASA Astrophysics Data System (ADS)

    Laurent, M.; Falguères, C.; Bahain, J. J.; Rousseau, L.; Van Vliet Lanoé, B.

    ESR dating of fluvial, fluvio-marine and beach sediment has been tested using the Al centre in quartz grains from a basin and fossil beaches located around the Manche Channel. Dating was performed in conjunction with sedimentological, stratigraphical and neotectonical studies. The technical basis of the method is presented in the light of the study made on recent and fossil sediment in order to establish a procedure for the determination of the palaeodose. The application on a Neogene Basin samples allows to push back the dating ESR limits. Results show that ESR dating of sediment can provide chronozons which are necessary to the uderstanding of the history of a basin where classical chronological markers do not exist.

  11. Snežna jama (Slovenia): Interdisciplinary dating of cave sediments and implication for landscape evolution

    PubMed Central

    Häuselmann, Philipp; Mihevc, Andrej; Pruner, Petr; Horáček, Ivan; Čermák, Stanislav; Hercman, Helena; Sahy, Diana; Fiebig, Markus; Hajna, Nadja Zupan; Bosák, Pavel

    2015-01-01

    Caves are important markers of surface evolution, since they are, as a general rule, linked with ancient valley bottoms by their springs. However, caves can only be dated indirectly by means of the sediments they contain. If the sediment is older than common dating methods, one has to use multiple dating approaches in order to get meaningful results. U/Th dating, palaeomagnetic analysis of flowstone and sediment profiles, cosmogenic dating of quartz pebbles, and mammalian dating allowed a robust estimate of speleogenesis, sediment deposition, climatic change at the surface, and uplift history on the Periadriatic fault line during the Plio-Pleistocene. Our dates indicate that Snežna jama was formed in the (Upper) Miocene, received its sedimentary deposits during the Pliocene in a rather low-lying, hilly landscape, and became inactive due to uplift along the Periadriatic and Sava faults and climatic changes at the beginning of the Quaternary. Although it is only a single cave, the information contained within it makes it an important site of the Southern Alps. PMID:26516294

  12. Snežna jama (Slovenia): Interdisciplinary dating of cave sediments and implication for landscape evolution

    NASA Astrophysics Data System (ADS)

    Häuselmann, Philipp; Mihevc, Andrej; Pruner, Petr; Horáček, Ivan; Čermák, Stanislav; Hercman, Helena; Sahy, Diana; Fiebig, Markus; Hajna, Nadja Zupan; Bosák, Pavel

    2015-10-01

    Caves are important markers of surface evolution, since they are, as a general rule, linked with ancient valley bottoms by their springs. However, caves can only be dated indirectly by means of the sediments they contain. If the sediment is older than common dating methods, one has to use multiple dating approaches in order to get meaningful results. U/Th dating, palaeomagnetic analysis of flowstone and sediment profiles, cosmogenic dating of quartz pebbles, and mammalian dating allowed a robust estimate of speleogenesis, sediment deposition, climatic change at the surface, and uplift history on the Periadriatic fault line during the Plio-Pleistocene. Our dates indicate that Snežna jama was formed in the (Upper) Miocene, received its sedimentary deposits during the Pliocene in a rather low-lying, hilly landscape, and became inactive due to uplift along the Periadriatic and Sava faults and climatic changes at the beginning of the Quaternary. Although it is only a single cave, the information contained within it makes it an important site of the Southern Alps.

  13. Duration of gas accumulation before the 2010 Eyjafjallajökull eruption constrained by 210Po-210Pb-226Ra disequilibria

    NASA Astrophysics Data System (ADS)

    Sigmarsson, Olgeir; Gauthier, Pierre-Jean; Condomines, Michel

    2014-05-01

    Excess gas phase in magmas erupting explosively is well known world-wide. However, the origin of this gas phase, in excess of what can be dissolved in the erupting magma at depth, and the duration of gas accumulation, is less well defined. The 2010 mildly explosive eruption at Eyjafjallajökull, Iceland, produced mingled tephra of benmoreiitic and trachytic composition whereas alkali basalt (MgO > 8 %) was emitted during the preceding flank eruption. The silicic tephra of the first explosive phase is composed of three glass types, alkaline rhyolite, mixed benmoreiite, and evolved basalt (MgO < 5 %). The rhyolitic glass is indistinguishable from tephra glass composition emitted during the penultimate eruption of Eyjafjallajökull in 1821-23 AD (Sigmarsson et al., 2011). Tephra from the first explosive phase, emitted on 15 and 17 April, had large 210Po in excess of 210Pb ((210Po/210Pb)0 as high as 2!) and a small, but significant, 210Pb excess over its parent 226Ra ((210Pb/226Ra)0= 1.05 and 1.04, respectively). These excesses suggest rapid accumulation of Po and Rn together with the major gas species in the residual rhyolitic magma from the 1821-23 eruption. The gas most likely originates from the basalt recharge that eventually provoked the eruption. Basalts emitted a month earlier during the flank eruption at Fimmvörðuháls lost all their Po upon eruption and had (210Po/210Pb)0 equal to 0). From a simple model of radon and polonium degassing and accumulation, the mass of basalt magma degassing over the mass of silicic magma accumulating the excess gas can be calculated. Moreover, the duration of gas accumulation can be shown to be close to 300 days. This duration suggests that gas was liberated from the basaltic magma since June 2009, a month that corresponds to the initial seismic swarm beneath Eyjafjallajökull preceding the explosive eruption of 14 April 2010.

  14. Incorporation of {sup 210}Pb and {sup 210}Po to Poultry through the Addition of Dicalcium Phosphate (DCP) to the Diet

    SciTech Connect

    Casacuberta, N.; Masque, P.; Garcia-Orellana, J.; Gasa, J.; Anguita, M.

    2008-08-07

    Due to the replacement of calcium by uranium in the phosphorite, sedimentary phosphate rock contains high concentrations of {sup 238}U (i.e. from 1500 Bq{center_dot}kg{sup -1} in Morocco to 4000 Bq{center_dot}kg{sup -1} in Tanzania ores). Dicalcium Phosphate (DCP) is produced by the wet acid digestion of the phosphorite, and is used as a source of calcium and phosphorus for livestock feed supplement. If the phosphorite acid digestion is made with hydrochloric acid, DCP may present specific activities of about 10{sup 3} Bq{center_dot}kg{sup -1} of {sup 238}U and some of its decay chain daughters. In particular, due to its radiological implications, the presence of {sup 210}Pb and {sup 210}Po in DCP is of special relevance. The aim of this work was to investigate the potential incorporation of these radionuclides to poultry through its diet. Three different diets were therefore prepared with different contents of both DCP and {sup 210}Pb and {sup 210}Po. Diet A was used as a blank, and had a 2.5% in weight of monocalcium phosphate (MCP); diet B, with a 5% in weight of DCP; and diet C, with a 2.5% of DCP. Concentrations of {sup 210}Pb were 0.93, 101.4 and 51.2 Bq{center_dot}kg{sup -1}; whereas concentrations of {sup 210}Po were 0.92, 74 and 36 Bq{center_dot}kg{sup -1} of food for diets A, B and C, respectively. Accumulation of {sup 210}Pb and {sup 210}Po was analysed at several times during poultry growth in samples of bone, liver, kidney, muscle, excrements as well as entire animals, with a total of 30 broilers fed with the 3 different diets. Results showed clear enhancements in the accumulation of both {sup 210}Pb and {sup 210}Po in chicken for diets B and C, and in particular in liver and bone. However, total accumulation of radionuclides in chicken, and especially in edible parts, is low compared to its expulsion through excrements. These results are interpreted in terms of the potential dose through consumption of chicken.

  15. Using natural radionuclides 210Po and 210Pb in GEOTRACES data from the North Atlantic to estimate particulate and biologically reactive trace element scavenging and regeneration

    NASA Astrophysics Data System (ADS)

    Rigaud, Sylvain; Church, Thomas

    2016-04-01

    Central to understanding the coupling of oceanic carbon and nutrient cycles are trace elements that can limit ocean production and ultimately climate change. These include elements that are both lithogenic (particle reactive) and biogenic (biologically reactive) central to particle scavenging, exchange and bioavailability. The natural 210Po and 210Pb radionuclide (granddaughter/parent) pair provides the radiometric means to model particle scavenging and exchange in the ocean on monthly to annual time scales. Data on dissolved (<0.2 μm) and particulate (>0.2 μm, >53μm) 210Po (t1/2= 138.4 d) and 210Pb (T1/2 = 22.3 y) are available from seven complete water profiles during two U.S. GEOTRACES cruises that transited the North Atlantic during fall 2010 and 2011. The transects correspond to a wide range of marine environments: coastal slopes at the western and eutrophic up-welling at the eastern margins, Saharan dust sources from the east, hydro-thermal vents in the TAG plume on the Mid-Atlantic Ridge, and oligotrophic gyres in both the western and eastern basins. Steady state box modeling at each depth interval was employed to estimate radionuclide exchange rates at the fine-large particle and fine particulate-dissolved interface, in terms of biological uptake, and net of radioactive support or decay. By proxy, the results should predict the rates of biological (210Po) and particle reactive (210Pb) trace element adsorption and resorption, vertical particulate and carbon export, and respective residence times. The model results show the contrasting chemical behaviour of the two nuclides over the large range of oceanic conditions encountered in the North Atlantic. In the surface ocean, 210Po scavenging is linearly correlated with the concentration of particulate organic carbon (POC) in large particles, supporting the role of biogenic particles in 210Po bioaccumulation and export. At depth, 210Po exhibits significant widespread deficit with respect to 210Pb, which could

  16. Application of compound-specific radiocarbon dating for Antarctic margin sediments

    NASA Astrophysics Data System (ADS)

    Ohkouchi, N.; Koizumi, M.; Anderson, J. B.; Eglinton, T. I.; Miura, H.; Yokoyama, Y.

    2008-12-01

    Radiocarbon dating has been extensively applied for the development of chronologies of Antarctic margin sediments deposited during the late Quaternary. However, the problems are 1) the DIC reservoir age in the surface mixed layer is much older than that of the other oceans, 2) Antarctic margin sediments generally lack calcareous foraminifera conventionally used for radiocarbon dating and as stratigraphic tool, and 3) the sediments are subjected to significant "contamination" of relict organic matter eroded from the Antarctic continent, leading to substantially older radiocarbon ages of bulk sedimentary organic matter. Ohkouchi et al. (2003) first applied compound-specific radiocarbon dating to the surface sediments collected from Ross Sea, Antarctica for resolving the problem. They reported that the radiocarbon ages of solvent-extractable, short-chain (C14, C16, and C18) fatty acids are consistent with the modern DIC reservoir age (Pre-bomb: 14C -150, Post-bomb: 14C -100). Furthermore, the radiocarbon ages of these fatty acids at five down-core intervals progressively increase with the core depth. These results clearly show a utility of the compound- specific radiocarbon dating for developing sediment chronologies in Antarctic margin sediments. We also determined radiocarbon ages of the fatty acids from a core recovered in the NW Ross Sea to reconstruct sediment chronologies. Furthermore, we determined hydrogen isotopic compositions of sedimentary biomarkers in the core. Around 6.8, 5.7, 4.1, 2.5, and 1.5 kyr ago, the reconstructed D values of paleo- seawater were -200 or lower, suggesting a large amount of meltwater influx to the Ross Sea. Currently, we are applying the method to more sediment samples collected from wider area of Ross Sea to investigate the timing and pattern of retreat of West Antarctic Ice Sheet in the Holocene. I will present the up-dated results in my talk.

  17. Stepped-combustion 14C dating of bomb carbon in lake sediment

    USGS Publications Warehouse

    McGeehin, J.; Burr, G.S.; Hodgins, G.; Bennett, S.J.; Robbins, J.A.; Morehead, N.; Markewich, H.

    2004-01-01

    In this study, we applied a stepped-combustion approach to dating post-bomb lake sediment from north-central Mississippi. Samples were combusted at a low temperature (400 ??C) and then at 900 ??C. The CO2 was collected separately for both combustions and analyzed. The goal of this work was to develop a methodology to improve the accuracy of 14C dating of sediment by combusting at a lower temperature and reducing the amount of reworked carbon bound to clay minerals in the sample material. The 14C fraction modern results for the low and high temperature fractions of these sediments were compared with well-defined 137Cs determinations made on sediment taken from the same cores. Comparison of "bomb curves" for 14C and 137Cs indicate that low temperature combustion of sediment improved the accuracy of 14C dating of the sediment. However, fraction modern results for the low temperature fractions were depressed compared to atmospheric values for the same time frame, possibly the result of carbon mixing and the low sedimentation rate in the lake system.

  18. Increasing sediment accumulation rates in La Fonera (Palamós) submarine canyon axis and their relationship with bottom trawling activities

    NASA Astrophysics Data System (ADS)

    Puig, P.; Martín, J.; Masqué, P.; Palanques, A.

    2015-10-01

    Previous studies conducted in La Fonera (Palamós) submarine canyon (NW Mediterranean) found that trawling activities along the canyon flanks cause resuspension and transport of sediments toward the canyon axis. 210Pb chronology supported by 137Cs dating applied to a sediment core collected at 1750 m in 2002 suggested a doubling of the sediment accumulation rate since the 1970s, coincident with the rapid industrialization of the local trawling fleet. The same canyon area has been revisited a decade later, and new data are consistent with a sedimentary regime shift during the 1970s and also suggest that the accumulation rate during the last decade could be greater than expected, approaching ~2.4 cm yr-1 (compared to ~0.25 cm yr-1 pre-1970s). These results support the hypothesis that commercial bottom trawling can substantially affect sediment dynamics and budgets on continental margins, eventually initiating the formation of anthropogenic depocenters in submarine canyon environments.

  19. Mercury profiles in sediments of the Pearl River Estuary and the surrounding coastal area of South China.

    PubMed

    Shi, Jian-bo; Ip, Carman C M; Zhang, Gan; Jiang, Gui-bin; Li, Xiang-dong

    2010-05-01

    The spatial and temporal variations of mercury (Hg) in sediments of the Pearl River Estuary (PRE) and the surrounding coastal area (South China Sea) were studied. In surface sediments, the concentrations of Hg ranged from 1.5 to 201ng/g, with an average of 54.4ng/g, displaying a decreasing trend with the distance from the estuary to the open sea. This pattern indicates that the anthropogenic emissions from the Pearl River Delta (PRD) region are probably the main sources of Hg in this coastal region. Using the (210)Pb dating technique, the historical changes in the concentrations and influxes of Hg in the last 100 years were also investigated. The variations in Hg influxes in sediment cores obviously correlate with the economic development and urbanization that has occurred the PRD region, especially in the last three decades.

  20. Pb Concentration and Stable PB Isotopes in Dated-Core Sediments in the Ulleung Basin, East/japan Sea

    NASA Astrophysics Data System (ADS)

    Woo, J.; Choi, M.; Kim, D.

    2008-12-01

    This study investigated temporal and spatial variation of Pb and stable Pb isotopes accumulated in Ulleung Basin core sediments (12) using MC ICP/MS in order to identify the sources of anthropogenic Pb in the East/Japan Sea. Leached (1M HCl) Pb concentration and isotope ratios (207Pb/206Pb and 208Pb/206Pb) ware constant at around 20 mg/kg and 0.845 and 2.092 from 1700 to 1930 year, respectively and increased steadily up to 40 mg/kg and 0.873 to 2.129 at the beginning of 2000s, increased up to twice in concentration and as much as 3.31% and 1.64%. On the other hand, residual Pb concentrations were nearly constant for past 400 yrs. From the vertical profiles of Pb concentration and two end-members mixing model, anthropogenic Pb concentration and isotope ratios were estimated. The transport pathways of anthropogenic Pb could be estimated from 1) the comparison between the inventories of excess 210Pb in each sediment column and the input fluxes from the atmosphere and seawater column, 2) between the accumulation rate of anthropogenic Pb and mass accumulation rate of sediments. From the detailed evaluation for the pathways and isotope ratios of anthropogenic Pb, we proposed probable source of anthropogenic Pb. Pb emission by coal burning from the China and Korea initiated the accumulation of anthropogenic Pb in the sediments of East/Japan Sea from 1930s. The accumulation of Pb increased by the addition of anti-nocking agents from both countries untill beginning of 1990s, but from the middle of 1990s to the present, the phase-out of gasoline additives and the rapid increase of coal burning from China maintained the atmospheric Pb levels in the Ulleung basin nearly similar to before. However the local sources (e.g. ocean dumping) within this basin might take an important role in the rapid increase of anthropogenic Pb accumulation in slope areas from the middle of 1990s.

  1. 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

  2. Bulk sediment 14C dating in an estuarine environment: How accurate can it be?

    NASA Astrophysics Data System (ADS)

    Lougheed, Bryan C.; Obrochta, Stephen P.; Lenz, Conny; Mellström, Anette; Metcalfe, Brett; Muscheler, Raimund; Reinholdsson, Maja; Snowball, Ian; Zillén, Lovisa

    2017-02-01

    Due to a lack of marine macrofossils in many sediment cores from the estuarine Baltic Sea, researchers are often forced to carry out 14C determinations on bulk sediment samples. However, ambiguity surrounding the carbon source pathways that contribute to bulk sediment formation introduces a large uncertainty into 14C geochronologies based on such samples, and such uncertainty may not have been fully considered in previous Baltic Sea studies. We quantify this uncertainty by analyzing bulk sediment 14C determinations carried out on densely spaced intervals in independently dated late-Holocene sediment sequences from two central Baltic Sea cores. Our results show a difference of 600 14C yr in median bulk sediment reservoir age, or R(t)bulk, between the two core locations ( 1200 14C yr for one core, 620 14C yr for the other), indicating large spatial variation. Furthermore, we also find large downcore (i.e., temporal) R(t)bulk variation of at least 200 14C yr for both cores. We also find a difference of 585 14C yr between two samples taken from the same core depth. We propose that studies using bulk sediment 14C dating in large brackish water bodies should take such spatiotemporal variation in R(t)bulk into account when assessing uncertainties, thus leading to a larger, but more accurate, calibrated age range.

  3. Early chromite mining and agricultural clearance: Opportunities for the investigation of agricultural sediment dynamics in the Eastern Piedmont (USA)

    USGS Publications Warehouse

    Bain, D.J.; Brush, G.S.

    2005-01-01

    Many flood plains in the Eastern Piedmont (USA) are buried under deposits of sediment resulting from European agricultural clearance. Classic radioisotopic dating techniques cover temporal periods too short (137Cs, 210Pb) or too long (14C) to reliably date sediments deposited during periods of local European activity (1660-1900). Moreover, many potential biomarkers, such as pollen, degrade in oxic flood plain sediments. In the Baltimore, Maryland (USA) region, early chromite mining (1820 - 1880) occurred during periods of rapid agricultural clearance. Use of chromium (Cr) chemostratigraphic profiles in flood plain sediments tied to historical mining activity can provide improved precision in overbank accumulation rates and timing. Sediment cores were collected from the Red Run basin, which is part of the Baltimore Ecosystem Study, an urban Long-Term Ecological Research site. Trace metal chemostratigraphic profiles were measured and peaks in Cr concentration tied to historic mining activity. Dates from Cr chemostratigraphic profiles were combined with 137Cs dating to reconstruct flood plain sedimentation rates. Red Run early sedimentation rates (1820 - 1880) were higher (0.45 - 1.19 cm/yr) than more recent (1880 - 1963) rates (0.08 - 0.46 cm/yr). This indicates that Piedmont flood plain vertical sediment accumulation might have peaked before the peak in agricultural clearance, earlier than assumed by regional models. The Cr chemostratigraphy is applicable to a wider region including much of the Maryland and Pennsylvania (USA) Piedmont.

  4. Thermoluminescence dating of sediments: a re-extension of age range for loess

    SciTech Connect

    Johnson, R.J.; Stipp, J.J.; Wintle, A.G.; Tamers, M.A.

    1985-01-01

    Thermoluminescence (TL) dating of wind blown minerals provides a technique whereby non-carbonaceous sediments could be dated to several hundred thousand years. Two recent reports, however, indicate age underestimates on feldspar in some European loesses older than 50 ka, the effect increasing in severity with age. Suggested causes include decay of luminescence centers, or does dependent sensitivity changes. Data presented in this paper do not support these limitations or explanations. TL provides 3 separate techniques of dating sediments, which, when used together, prove to be efficient internal cross checks for mineralogical anomalies or inconsistencies created by any of the individual methods. In the authors studies each sample was dated by all 3 methods whereas the Europeans analyses employed only the Regeneration technique. This work presents results from loess sections in Mississippi, Illinois and Alaska. These show excellent internal consistency, and consistency with both independent dating methods and stratigraphy, with 2 exceptions. Both exceptions were by the Regen technique giving age underestimates up to 30%. The underestimates were found to be caused by a change in mineral sensitivity resulting from the Regen requirements of strong laboratory light-bleaching followed by irradiations. A simple method to test and correct for this condition is presented. TL thus appears to remain a powerful and increasingly flexible method of sediment dating.

  5. Luminescence Dating of Sediments: An Increasingly Diverse Family of Methods and Range of Applications

    NASA Astrophysics Data System (ADS)

    Roberts, H. M.

    2015-12-01

    In recent years, the term 'luminescence dating' has expanded its meaning such that today it encompasses a range of luminescence dating methods and materials. Whilst the fundamental principles that underlie these different dating methods are essentially the same, namely that the event typically being recorded is the last exposure of the material to light or to heat, the various luminescence dating techniques do differ in their suitability in different situations. Today, in the field of luminescence dating of sediments, there are a number of minerals that can be used for dating (quartz and feldspar being the most commonly used), and for each mineral it is possible to obtain a number of different luminescence signals (some obtained using optical stimulation, and some obtained by heating). These different luminescence signals may build-up and deplete in the natural environment at different rates from each other, and can span quite different time ranges. Additionally, the scale of analysis used in luminescence dating can now be varied (ranging from single sand-sized grains to multiple grains), as can the size range of the materials used for dating (ranging from fine-silt, coarse-silt, and sand-sized grains, through to large clasts and rock surfaces). Having such flexibility in the range of minerals, luminescence signals, grain sizes, and the scales of analysis available for dating, means that it is now possible to optimise the materials and methods selected for dating in any particular study in response to the precise scientific question to be addressed, the time-range of interest, and the likely mechanisms of re-setting of the luminescence signal in the context that is to be dated. In this paper, the flexibility offered by the growing family of luminescence techniques will be outlined by considering some of the different minerals, luminescence signals, and dramatically different timescales (tens of years to millions of years) potentially available for sediment dating

  6. Chemical composition of scales generated from oil industry and correlation to radionuclide contents and gamma-ray measurements of (210)Pb.

    PubMed

    Al Attar, Lina; Safia, Bassam; Abdul Ghani, Basem

    2016-03-01

    Scale generated from the maintenance of equipment contaminated by naturally occurring radioactive materials may contain also chemical components that cause hazardous pollution to human health and the environment. This study spotlights the characterisation of chemical pollutants in scales in relation to home-made comparison samples as no reference material for such waste exists. Analysis by energy dispersive x-ray fluorescence, with accuracy and precision better than 90%, revealed that barium was the most abundant element in scale samples, ranging from 1.4 to 38.2%. The concentrations of the toxic elements such as lead and chromium were as high as 2.5 and 1.2% respectively. Statistically, high correlation was observed between the concentration of Ba and Sr, sample density, radionuclide contents ((210)Pb and (226)Ra) and self-attenuation factor used for the radio-measurements. However, iron showed a reverse correlation. Interpretation of data with regards to the mineralogical components indicated that (226)Ra and (210)Pb co-precipitated with the insoluble salt Ba0.75Sr0.25SO4. Since both Ba and Sr have high Z, samples of high density (ρ) were accompanied with high values of self-attenuation correction factors (Cf) for the emitted radiation; correlation matrix of Pearson reached 0.935 between ρ and Cf. An attempt to eliminate the effect of the elemental composition and improve gamma measurements of (210)Pb activity concentration in scale samples was made, which showed no correction for self-attenuation was needed when sample densities were in the range 1.0-1.4 g cm(-3). For denser samples, a mathematical model was developed. Accurate determinations of radionuclide and chemical contents of scale would facilitate future Environmental Impact Assessment for the petroleum industry.

  7. 210Pb and 210Po Abundances in Dacites Erupted May, 2003 From Anatahan Volcano: Implications for the Time-scales of Magma Generation and Degassing

    NASA Astrophysics Data System (ADS)

    Reagan, M. K.; Matthew, W.; Brian, H.

    2003-12-01

    Six samples of dacite pumice and scoria erupted in May, 2003 and collected from a number of sites around Anathan by Tobias Fischer and David Hilton were analyzed for 210Po activities on three occasions between early June and the time of this writing. With two exceptions, all scoria and pumice samples have 210Po activities that plot on a single growth curve indicating initial (210Po)=0.15 +/-0.07 (1σ ) dpm/g and (210Pb)=1.08+/-0.20 dpm/g. More precise values for these initial activities will be presented at the meeting after further analyses are performed in November. Preliminary alpha spectrometry analyses for U and Th, and ICPMS analyses distributed by Terry Plank suggest that the average (238U) is about 0.53 dpm/g. Equilibrium (228Th)/( 232Th) ratios indicate that these samples do not have excess 228Ra. Assuming that (210Pb )< (226Ra) because of minor degassing of 210Pb (see Gauthier and Condomines, 1999, EPSL, v. 172), the degassing efficiency factor for 210Po is greater than or equal to about 0.85, which is identical to the value calculated for a basaltic andesitic lava from Arenal volcano in Costa Rica (Gill et al., 1985, GRL, v. 12). This is surprising, as the May 10 plinian eruption of Anatahan should have resulted in more closed-system degassing than a lava eruption. This and the similar 210Po values for the scoria and pumice samples suggest that the shallow-level degassing history has little impact on the efficiency of polonium degassing. The scoria and pumice samples from sample 8-1e both have significant excesses of 210Po over the calculated initial (210Pb) value for the other samples. These excesses were partially leachable, indicating that 210Po was sublimated onto these samples, and that these ejecta resided in the vent before being ejected and redeposited The high inferred (226Ra)/( 230Th) for the Anatahan dacites despite the nearly equilibrium (238U)/( 230Th) value measured for one sample contrasts with the values for these ratios in more mafic

  8. Impact of northern and southern air mass transport on the temporal distribution of atmospheric (210)Po and (210)Pb in the east coast of Johor, Malaysia.

    PubMed

    Sabuti, Asnor Azrin; Mohamed, Che Abd Rahim

    2016-09-01

    Concentration activities of (210)Pb and (210)Po in the PM10 were determined to discuss their distribution and chemical behavior in relation to meteorological parameters especially in air mass transport during monsoon events. Marine aerosol samples were collected between January 2009 and December 2010 at the coastal region of Mersing, which is located in the southern South China Sea and is about 160 km northeast of Johor Bahru, as part of the atmosphere-ocean interaction program in Malaysia. About 47 PM10 samples were collected using the Sierra-Andersen model 1200 PM10 sampler over a 2-year sampling campaign between January 2009 and December 2010. Samples were processed using acid digestion sequential extraction techniques to analyze various fractions such as Fe and Mn oxides, organic matter, and residual fractions. While, (210)Pb and (210)Po activities were measured with the Gross Alpha/Beta Counting System model XLB-5 Tennelec® Series 5 and the Alpha Spectrometry (model Alpha Analyst Spectroscopy system with a silicon-surface barrier detector), respectively. The distribution activities of (210)Pb and (210)Po in the PM10 samples were varied from 162 to 881 μBq/m(3) with mean value of 347 ± 170 μBq/m(3) and from 85 to 1009 μBq/m(3) with mean value of 318 ± 202 μBq/m(3), respectively. The analysis showed that (210)Po activity in our samples lies in a border and higher range than global distribution values due to contributions from external sources injected to the atmosphere. The speciation of (210)Pb and (210)Po in marine aerosol corresponds to transboundary haze; e.g., biomass burning especially forest fires and long-range air mass transport of terrestrial dust has enriched concentrations of particle mass in the local atmosphere. The monsoon seems to play an important role in transporting terrestrial dust from Indo-China and northern Asia especially during the northeast monsoon, as well as biogenic pollutants originating from Sumatra and the southern

  9. 210Po/210Pb dynamics in relation to zooplankton biomass and trophic conditions during an annual cycle in northwestern Mediterranean coastal waters.

    PubMed

    Färber Lorda, Jaime; Fowler, Scott W; Miquel, Juan-Carlos; Rodriguez y Baena, Alessia; Jeffree, Ross A

    2013-01-01

    Monthly sampling in northwestern Mediterranean coastal waters was undertaken to better understand the relationship between zooplankton biomass and the cycling of the natural radionuclide (210)Po/(210)Pb pair during a one-year period (October 1995-November 1996). In conjunction with mesozooplankton collections and (210)Po/(210)Pb measurements in seawater, zooplankton and their fecal pellets, the biochemical composition of particulate organic matter (POM) was also examined at three depths (0, 20 and 50 m) as an indicator of trophic conditions. During May 1996, a strong zooplankton "bloom" was observed which was preceded by a prolonged increase in POM (protein + carbohydrates + lipids) starting at the end of March, and further demonstrated by a concomitant increase in the concentration of smaller particles, two features that are typical of mesotrophic waters. Simultaneous measurements of (210)Po in sea water and zooplankton showed an inverse trend between these two parameters during the sampling period, with the two lowest (210)Po concentrations in the dissolved phase of seawater coincident with the highest radionuclide concentrations in the zooplankton; however, this apparent relationship was not statistically significant over the entire year. Freshly excreted mesozooplankton and salp fecal pellets, which have been strongly implicated in the removal and downward transport of these radionuclides from the upper water column, contained (210)Po and (210)Pb levels ranging from 175 to 878 and 7.5-486 Bq kg(-1) dry weight, respectively. Salp pellets contained 5 and 10 times more (210)Po and (210)Pb than in fecal pellets produced by mixed zooplankton, a finding most likely related to their different feeding strategies. During the zooplankton biomass peak observed in May, the (210)Po concentration in zooplankton was at a minimum; however, in contrast to what has been reported to occur in some open sea oligotrophic waters, over the year no statistically significant inverse

  10. A sequential method for the determination of 210Pb, 226Ra, and uranium and thorium radioisotopes by LSC and alpha-spectrometry.

    PubMed

    Lozano, J C; Tomé, F Vera; Rodríguez, P Blanco; Prieto, C

    2010-01-01

    A procedure for the determination of (210)Pb, and alpha-emitting radioisotopes of uranium, thorium, and radium from the same aliquot of a sample has been proposed. The key step consisted in the recovery of Pb(II) and Ra by precipitation of insoluble Pb(NO(3))(2), the uranium and thorium radioisotopes remaining in solution. Afterwards, the fractions were handled by specific, well consolidated procedures. Lead-210 was determined by the LSC technique while the uranium, thorium, and radium radioisotopes were measured with silicon alpha-spectrometers. The procedure was applied to a reference sample and several environmental samples obtaining satisfactory results.

  11. Concepts and approaches to in situ luminescence dating of Martian sediments.

    PubMed

    McKeever, S W S; Banerjee, D; Blair, M; Clifford, S M; Clowdsley, M S; Kim, S S; Lamothe, M; Lepper, K; Leuschen, M; McKeever, K J; Prather, M; Rowland, A; Reust, D; Sears, D W G; Wilson, J W

    2003-01-01

    In this paper we present the concept of a robotic instrument for in situ luminescence dating of near-surface sediments on Mars. The scientific objectives and advantages to be gained from the development of such an instrument are described, and the challenges presented by the Mars surface environment to the design and operation of the instrument are outlined.

  12. 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 ...

  13. 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...

  14. Dating the upper Cenozoic sediments in Fisher Valley, southeastern Utah ( USA).

    USGS Publications Warehouse

    Colman, Steven M.; Choquette, Anne F.; Rosholt, J.M.; Miller, G.H.; Huntley, D.J.

    1986-01-01

    More than 140 m of upper Cenozoic basin-fill sediments were deposited and then deformed in Fisher Valley between about 2.5 and 0.25 m.y. ago, in response to uplift of the adjacent Onion Creek salt diapir. In addition to these basin-fill sediments, minor amounts of eolian and fluvial sand were depositd in Holocene time. The sediments, whose relative ages are known from the stratigraphy, are predominantly sandy, second-cycle red beds derived from nearby Mesozoic rocks; most were deposited in a vertical sequence, filling a sedimentary basin now exposed by fluvial dissection. We have applied a variety of established and experimental dating methods to the sediments in Fisher Valley to establish their age and to provide time control for the recent history of the Onion Creek salt diapir.-from Authors

  15. (210)Po and (210)Pb in the tissues of the deep-sea hydrothermal vent mussel Bathymodiolus azoricus from the Menez Gwen field (Mid-Atlantic Ridge).

    PubMed

    Charmasson, Sabine; Le Faouder, Antoine; Loyen, Jeanne; Cosson, Richard P; Sarradin, Pierre-Marie

    2011-01-15

    The hydrothermal deep-sea vent fauna is naturally exposed to a highly specific environment enriched in potentially toxic species such as sulfides, metals and natural radionuclides due to the convective seawater circulation inside the oceanic crust and its interaction with basaltic or ultramafic host rocks. However, data on radionuclides in biota from such environment are very limited. An investigation was carried out on tissue partitioning of (210)Po and (210)Pb, two natural radionuclides within the (238)U decay chain, in Bathymodiolus azoricus specimens from the Mid-Atlantic Ridge (Menez Gwen field). These two elements showed different distributions with high (210)Pb levels in gills and high (210)Po levels in both gills and especially in the remaining parts of the body tissue (including the digestive gland). Various factors that may explain such partitioning are discussed. However, (210)Po levels encountered in B. azoricus were not exceptionally high, leading to weighted internal dose rate in the range 3 to 4 μGy h⁻¹. These levels are slightly higher than levels characterizing coastal mussels (~1 μGy h⁻¹).

  16. Air mass origin and its influence on radionuclide activities ( 7Be and 210Pb) in aerosol particles at a coastal site in the western Mediterranean

    NASA Astrophysics Data System (ADS)

    Dueñas, C.; Orza, J. A. G.; Cabello, M.; Fernández, M. C.; Cañete, S.; Pérez, M.; Gordo, E.

    2011-07-01

    Studies of radionuclide activities in aerosol particles provide a means for evaluating the integrated effects of transport and meteorology on the atmospheric loadings of substances with different sources. Measurements of aerosol mass concentration and specific activities of 7Be and 210Pb in aerosols at Málaga (36° 43' 40″ N; 4° 28' 8″ W) for the period 2000-2006 were used to obtain the relationships between radionuclide activities and airflow patterns by comparing the data grouped by air mass trajectory clusters. The average concentration values of 7Be and 210Pb over the 7 year period have been found to be 4.6 and 0.58 mBq m -3, respectively, with mean aerosol mass concentration of 53.6 μg m -3. The identified air flow types arriving at Málaga reflect the transitional location of the Iberian Peninsula and show significant differences in radionuclide activities. Air concentrations of both nuclides and the aerosol mass concentration are controlled predominantly by the synoptic scenarios leading to the entrance of dust-laden continental flows from northern Africa and the arrival of polar maritime air masses, as implied by the strong correlations found between the monthly frequencies of the different air masses and the specific activities of both radionuclides. Correlations between activity concentrations and precipitation are significant though lower than with air masses.

  17. Spatial and temporal distribution of polycyclic aromatic hydrocarbons (PAHs) in sediments of the Nansi Lake, China.

    PubMed

    Li, Hong-Li; Gao, Hong; Zhu, Chen; Li, Guo-Gang; Yang, Fan; Gong, Zheng-Yu; Lian, Jun

    2009-07-01

    Polycyclic aromatic hydrocarbons (PAHs) were measured in surface sediments and dated core sediments from the Nansi Lake of China to investigate the spatial and temporal distribution characteristics. The concentrations of 16 kinds priority PAH compounds were determined by GC-MS method. And (210)Pb isotope dating method was used to determine the chronological age of the sediment as well as the deposition rate. The results indicated that the total PAHs concentration ranges in surface and core sediment samples were 160 approximately 32,600 and 137 approximately 693 ng/g (dry wt.), respectively. The sediment rate and the average mass sedimentation were calculated to be 0.330 cm x year(-1) and 0.237 g x cm(-2) x yr(-1) and the sediment time of the collected core sample ranged from 1899 to 2000. The peak of PAH concentrations came at recent years. The source analysis showed PAHs mainly came from the contamination of low temperature pyrogenic processes, such as coal combustion. The PAHs concentrations were lower than ERL and LEL values for most collected samples. However, in several surface sediment samples especially in estuary sites, the PAHs concentrations were not only higher than ERL and LEL values, but also higher than ERM values.

  18. Radiocarbon Dating and age Inversions in Lake Chapala Late Holocene Sediments, Western Mexico.

    NASA Astrophysics Data System (ADS)

    Zarate-Del Valle, P.; Israde-Alcantara, I.; Ramírez-Sánchez, H.; Gómez-Salazar, S.; Ríos-Donato, N.

    2006-12-01

    Neotectonic Lake Chapala, the major Mexican freshwater reservoir lies at the north and northeast of the Citala Rift and is linked to history of the active Plio-Quaternary Transmexican Volcanic Belt geological province. Eight radiocarbon 14C dates were obtained on shallow sediment samples from a gravity corer (T46) of 5 cm in diameter and 1.7 m long. The core was collected from the western sector of Lake Chapala (103° 15.43' W, 20° 14.45' N) at water depth of 3.7 m (june 2000). In general, shallow sediments (<2m deep) in Lake Chapala are dark and silty with granulometric median ranging from 10 to 50 μm. Major oxides in sediments are: SiO2 (54.05%), Al2O3 (18.94%), Fe2O3 (6.75%) and CaO (2.57%). The major mineralogical composition of sediments is as follows: plagioclases (25.86%), quartz (20.92%), clays (38.5%), carbonates (2.99%) and TiO2 (1.05%). Radiocarbon ages were measured by accelerator mass spectrometry (AMS) and were obtained through the organic carbon fraction extracted from the bulk sediment samples sliced every 20 cm taken from the whole core. Stratigraphically ordered from highest to lowest, the eight ages reported are: 1) 2,000 ±40 yr on sediments at 30 cm deep; 2) 1,920 ±35 yr on sediments at 50 cm deep; 3) 1,900 ±35 yr on sediments at 70 cm deep; 4) 2,080 ±35 yr on sediments at 90 cm deep; 5) 2,090 ±50 yr on sediments at 110 cm deep; 6) 2,190 ±35 yr on sediments at 130 cm deep; 7) 2,050 ±35 yr on sediments at 150 cm deep and, 8) 1,500 ±35 yr on sediments at 170 cm deep. From the top until 70 cm and from 130 to bottom we observe two age inversions; the interval apparently with no age inversions is from 70cm to 130cm. As it is known the age inversions observed may be due to a) ancient carbon being incorporated into the sediment during deposition; b) unrecognized bioturbation, c) Postdepositional alteration and, d) variations in the apparent geological ages of the different chemical phases comprising the total sediment. Basically, the factors

  19. OSL dating of sediments from Negro and Solimões rivers - Amazon, Brazil

    NASA Astrophysics Data System (ADS)

    Fiore, M.; Soares, E. A. A.; Mittani, J. C. R.; Yee, M.; Tatumi, S. H.

    2014-02-01

    In this work, the OSL dating results of Quaternary fluvial deposits from the confluence of Negro and Solimões rivers were studied. The equivalent doses (De) of sediments were obtained using a Single Aliquot Regeneration (SAR) protocol. Statistic studies were made using frequency histogram, weighted histogram and Radial plot in order to analyze the De fluctuations. Ages from 74.5 to 205 thousand of years (Pleistocene) were recorded. The gamma-ray spectroscopy was used to evaluate the natural radioisotopes concentrations of the samples and low concentrations were found with values between 0.64 and 3.71 ppm for 235U and 238U; 2.01-9.77 ppm for 232Th; already, for 40K, the concentration was negligible. The OSL dating of sediments has contributed to a better understanding of the evolution of Negro and Solimões rivers, in Amazon, Brazil.

  20. Determination of 210Pb, 210Po, 226Ra, 228Ra and uranium isotopes in drinking water in order to comply with the requirements of the EU ‘Drinking Water Directive.

    PubMed

    Vasile, M; Loots, H; Jacobs, K; Verheyen, L; Sneyers, L; Verrezen, F; Bruggeman, M

    2016-03-01

    The European Union published in 2013 a new Drinking Water Directive with stricter requirements for measuring natural radioactivity. In order to adhere to this, a method for sequential separation of 210Pb, 210Po, 238U and 234U in drinking water was applied using UTEVA® and Sr resins. Polonium-210, 238U and 234U were quantified using alpha-particle spectrometry and 210Pb using liquid scintillation counting. Radium-226 and 228Ra were determined using 3M Empore Radium RAD Disks, and their quantification was done using a Quantulus™ 1220 liquid scintillation counter.

  1. AMS radiocarbon analyses from Lake Baikal, Siberia: Challenges of dating sediments from a large, oligotrophic lake

    USGS Publications Warehouse

    Colman, Steven M.; Jones, Glenn A.; Rubin, M.; King, J.W.; Peck, J.A.; Orem, W.H.

    1996-01-01

    A suite of 146 new accelerator-mass spectrometer (AMS) radiocarbon ages provides the first reliable chronology for late Quaternary sediments in Lake Baikal. In this large, highly oligotrophic lake, biogenic and authigenic carbonate are absent, and plant macrofossils are extremely rare. Total organic carbon is therefore the primary material available for dating. Several problems are associated with the TOC ages. One is the mixture of carbon sources in TOC, not all of which are syndepositional in age. This problem manifests itself in apparent ages for the sediment surface that are greater than zero. However, because most of the organic carbon in Lake Baikal sediments is algal (autochthonous) in origin, this effect is limited to about 1000+500 years, which can be corrected, at least for young deposits. The other major problem with dating Lake Baikal sediments is the very low carbon contents of glacial-age deposits, which makes them extremely susceptible to contamination with modern carbon. This problem can be minimized by careful sampling and handling procedures. The ages show almost an order of magnitude difference in sediment-accumulation rates among different sedimentary environments in Lake Baikal, from about 0.04 mm/year on isolated banks such as Academician Ridge, to nearly 0.3 mm/year in the turbidite depositional areas beneath the deep basin floors, such as the Central Basin. The new AMS ages clearly indicate that the dramatic increase in diatom productivity in the lake, as evidenced by increases in biogenic silica and organic carbon, began about 13 ka, in contrast to previous estimates of 7 ka for the age of this transition. Holocene net sedimentation rates may be less than, equal to, or greater than those in the late Pleistocene, depending on the site. This variability reflects the balance between variable terrigenous sedimentation and increased biogenic sedimentation during interglaciations. The ages reported here, and the temporal and spatial variation in

  2. Investigations on the activity concentrations of 238U, 226RA, 228RA, 210PB and 40K in Jordan phosphogypsum and fertilizers.

    PubMed

    Al-Jundi, J; Al-Ahmad, N; Shehadeh, H; Afaneh, F; Maghrabi, M; Gerstmann, U; Höllriegl, V; Oeh, U

    2008-01-01

    The activity concentrations of naturally occurring radionuclides ((238)U, (226)Ra, (228)Ra, (210)Pb and (40)K) in Jordanian phosphate ore, fertilizer material and phosphogypsum piles were investigated. The results show the partitioning of radionuclides in fertilizer products and phosphogypsum piles. The outcome of this study will enrich the Jordanian radiological map database, and will be useful for an estimation of the radiological impact of this industrial complex on the immediate environment. The activity concentration of (210)Pb was found to vary from 95 +/- 8 to 129 +/- 8 Bq kg(-1) with a mean value of 111 +/- 14 Bq kg(-1) in fertilizer samples, and from 364 +/- 8 to 428 +/- 10 Bq kg(-1) with a mean value of 391 +/- 30 Bq kg(-1) in phosphogypsum samples; while in phosphate wet rock samples, it was found to vary between 621 +/- 9 and 637 +/- 10 Bq kg(-1), with a mean value of 628 +/- 7 Bq kg(-1). The activity concentration of (226)Ra in fertilizer samples (between 31 +/- 4 and 42 +/- 5 Bq kg(-1) with a mean value of 37 +/- 6 Bq kg(-1)) was found to be much smaller than the activity concentration of (226)Ra in phosphogypsum samples (between 302 +/- 8 and 442 +/- 8 Bq kg(-1) with a mean value of 376 +/- 62 Bq kg(-1)). In contrast, the activity concentration of (238)U in fertilizer samples (between 1011 +/- 13 and 1061 +/- 14 Bq kg(-1) with a mean value of 1033 +/- 22 Bq kg(-1)) was found to be much higher than the activity concentration of (238)U in phosphogypsum samples (between 14 +/- 5 and 37 +/- 7 Bq kg(-1) with a mean value of 22 +/- 11 Bq kg(-1)). This indicates that (210)Pb and (226)Ra show similar behaviour, and are concentrated in phosphogypsum piles. In addition, both isotopes enhanced the activity concentration in phosphogypsum piles, while (238)U enhanced the activity concentration in the fertilizer. Due to the radioactivity released from the phosphate rock processing plants into the environment, the highest collective dose commitment for the lungs

  3. Isotope exchange between natural and anthropogenic Pb in the coastal waters of Singapore: exchange experiment, Kd model, and implications for the interpretation of coastal 210Pb data

    NASA Astrophysics Data System (ADS)

    Boyle, E. A.; Chen, M.; Zurbrick, C.; Carrasco, G. G.

    2015-12-01

    Observations from annually-banded corals and seawater samples show that marine lead (Pb) in the coastal waters of Singapore has an isotopic composition that does not match that of the anthropogenic aerosols in this region, unlike what is seen in most parts of the open ocean. The 206Pb/207Pb composition of Singaporean marine Pb is 1.18-1.20 whereas the local aerosols are 1.14-1.16. In order to explore this discrepancy further, we collected a large volume water from the Johor River estuary (flowing from Malaysia to the northern border of Singapore), added a distinct isotope spike (NBS981, 206Pb/207Pb =1.093) to an unfiltered sample, and followed the dissolved isotope composition of the mixture during the following two months. The initial dissolved Pb concentration was 18.3 pmol/kg with 206Pb/207Pb of 1.200. "Total dissolvable" Pb released after acidification of the in the unfiltered sample was 373 pmol/kg with 206Pb/207Pb of 1.199, indicating that there is a large particulate Pb reservoir with an isotopic composition comparable to regional crustal natural Pb. The isotope spike should have brought the dissolved 206Pb/207Pb to 1.162, but less than a day after isotope spiking, the dissolved Pb had risen to 1.181 and continued a slow increase to 1.197 over the next two months. This experiment demonstrates that Johor estuary particulate matter contains a large reservoir of exchangeable Pb that will modify the isotopic composition of deposited aeolian aerosol anthropogenic Pb. We have modeled the evolution of Pb and Pb isotopes in this experiment with a single Kd -type model that assumes that there are two or three different Pb reservoirs with different exchange time constants. This observation has implications for isotope equilibrium between high Pb/210Pb continental particles and low Pb/210Pb ocean waters - what is merely isotope equilibration may appear to be 210Pb scavenging.

  4. OSL dating of fine-grained quartz from Holocene Yangtze delta sediments

    NASA Astrophysics Data System (ADS)

    Sugisaki, S.; Buylaert, J. P.; Murray, A. S.; Tada, R.; Zheng, H.; Ke, W.; Saito, K.; Irino, T.; Chao, L.; Shiyi, L.; Uchida, M.

    2014-12-01

    Flood events in the Yangtze River are associated with variation in East Asian Summer Monsoon (EASM) precipitation. Understanding the frequency and scale of the EASM precipitation during the Holocene is a key to understanding the mechanism and cyclicity of floods and droughts. Because about 70% of the annual discharge occurs during the flood season, the Yangtze delta sediments provide a good archive of EASM precipitation. In this study, we investigate the possibility of applying OSL dating to establishing high-resolution chronologies for the Yangtze delta sediment cores YD13-1H and G3. The objectives of this study are: (1) test whether fine grained quartz in present day suspended particle matter (SPM) is fully bleached or reset before deposition, (2) where possible, test quartz fine- and coarse-grain OSL dating against radiocarbon shell ages, (3) interpret the sediment transport processes through the differential bleaching of quartz and feldspar OSL signals. We show that the SPM collected from the surface water column of the Yangtze River during the flood season is well-bleached (offset ~60 years). Fine-grained pro-delta sediments are thus potentially a good dosimeter for OSL dating. OSL ages sediment cores indicate a pronounced change in sedimentation rate at ~6 ka and ~2ka. These events are consistent with what is known of the evolution of the Yangtze catchment and delta. The delta began to build at ~6 ka (Zhao et al., 1979), and human activities increased significantly in the catchment at ~2ka (Chen et al., 1985). It is however surprising that the entire top 9 m of sediment only records these two events. The question of whether significant deposition was limited to 2 ka and 6 ka, or whether the record has been disturbed by erosion/reworking remains. These issues are discussed in terms of the reliability of the quartz OSL ages, the degree of bleaching by comparison with polymineral OSL signals, and the relationship of the OSL ages to the sedimentary record.

  5. Long-term agricultural non-point source pollution loading dynamics and correlation with outlet sediment geochemistry

    NASA Astrophysics Data System (ADS)

    Ouyang, Wei; Jiao, Wei; Li, Xiaoming; Giubilato, Elisa; Critto, Andrea

    2016-09-01

    Some agricultural non-point source (NPS) pollutants accumulate in sediments in the outlet sections of watersheds. It is crucial to evaluate the historical interactions between sediment properties and watershed NPS loading. Therefore, a sediment core from the outlet of an agricultural watershed was collected. The core age was dated using the 210Pb method, and sedimentation rates were determined using the constant rate of supply (CRS) model. The total nitrogen (TN), total phosphorus (TP), Cd, Pb, Cu, Ni and Cr accumulations in the sediment generally showed fluctuating increases, with the highest sedimentation fluxes all occurring in approximately 1998. The measurement of specific mass sedimentation rates reflected a record of watershed soil erosion dynamics. Using SWAT (Soil and Water Assessment Tool) to simulate long-term watershed agricultural NPS pollution loadings, the historical interactions between sediment properties and NPS loadings were further evaluated. The N leaching process weakened these interactions, but the historical accumulations of TP and heavy metals in sediments generally correlated well with watershed NPS TP loading. The regression analysis suggested that Pb and Cr were the most suitable indexes for assessing long-term NPS TN and TP pollution, respectively. Assessing the NPS loading dynamics using the vertical characteristics of sediment geochemistry is a new method.

  6. Luminescence Dating of Marine Terrace Sediments Between Trabzon and Rize, Eastern Black Sea Basin: Preliminary Results

    NASA Astrophysics Data System (ADS)

    Softa, Mustafa; Spencer, Joel Q. G.; Emre, Tahir; Sözbilir, Hasan; Turan, Mehmet

    2016-04-01

    Quaternary marine terraces in the coastal region of Pontides in Northeastern Turkey are valuable archives of past sea level change. Until recently, dates of raised marine terraces undeciphered in the coastal region between Trabzon and Rize because of chronologic limitations. In this paper was to determine ages of the terrace deposits by applying optically stimulated luminescence (OSL) dating methods using single aliquot regenerative dose (SAR) techniques on quartz minerals from extracted marine terraces. Several samples were collected from three orders of Quaternary marine terraces which are reproducible at all sampling location in between cities of Trabzon and Rize, Turkey, coastal of Eastern Pontides, at the front of the thrust system. The terrace deposits mainly consist of clays, silts, sands and gravels. The sediments in these deposits are mainly derived from basaltic, andesitic, and limestone geology, and have elipsoid, square and flat shapes. The terrace deposits have heights ranging from 1 to 17 meters and increases in height and thickness from west to east. Initial OSL results from 1 mm and 3 mm quartz aliquots demonstrate good luminescence characteristics. Preliminary equivalent dose analysis results ranging from 17.6 Gy to 79.6 Gy have been calculated using the Central Age Model (CAM) and Minimum Age Model (MAM). According to ages obtained from three separate terrace is ~8 ka, ~42 ka and ~78 ka, respectively. Results of marine terrace sediments indicate this region has three sedimentation periods and coastal region of Pontides has been remarkably tectonically active since latest Pleistocene to earlier Holocene. This study will present preliminary OSL dating results obtained from samples of Quaternary marine terrace formation. Keywords: optically stimulated luminescence (OSL) dating, single grain, marine terraces, Eastern Pontides.

  7. Relationship between variations of (7)Be, (210)Pb and (212)Pb concentrations and sub-regional atmospheric transport: Simultaneous observation at distant locations.

    PubMed

    Abe, Takuya; Kosako, Toshiso; Komura, Kazuhisa

    2010-02-01

    In order to investigate the applicability of (212)Pb as a tracer for atmospheric transport in the sub-regional scale (few hundred kilometers in horizontal direction and up to approximately 1km by height), we measured the air concentrations of the short-lived radionuclide (212)Pb along with the long-lived (7)Be and (210)Pb near the ground surface. For this purpose, simultaneous observations were continued for several days at three locations: a reference point representative for standard land surface atmosphere conditions, a second location at an altitude 650 m near the reference point, and on a solitary island approximately 180 km from the reference point. Measurements of radioactivity in aerosol particle samples collected at intervals of 2-3h with a high-volume air sampler were performed by extremely low background gamma-ray spectrometry with the use of Ge detectors located at the Ogoya Underground Laboratory. Concentration of (7)Be or (210)Pb and their variation patterns was found to be similar among the three points during the whole observation period except for moment of the passage of a cold front. The results indicate that distributions of concentrations of the long-lived nuclides were uniform in this range. On the other hand, concentration levels and the variation patterns of the short-lived (212)Pb differed greatly from one location to another, reflecting differences in geographical location and altitude of the observation points. Additionally, there were certain indications that observed concentration of (212)Pb contained two components: an autogenous component from sources nearby and a heterogenous one from faraway sources carried by atmospheric horizontal transport. Results of this study provide experimental proof that (212)Pb can be used as a tracer of sub-regional atmospheric transport.

  8. 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.

  9. Uranium-series dating of sediments from searles lake: differences between continental and marine climate records.

    PubMed

    Bischoff, J L; Rosenbauer, R J; Smith, G I

    1985-03-08

    One of the major unresolved questions in Pleistocene paleoclimatology has been whether continental climatic transitions are consistent with the glacial delta(18)O marine record. Searles Lake in California, now a dry salt pan, is underlain by sediment layers deposited in a succession of lakes whose levels and salinities have fluctuated in response to changes in climate over the last 3 x 10(6) years. Uraniumseries dates on the salt beds range from 35 x 10(3) to 231x 10(3) years. This range of dates allows identification of lake-sediment horizons that are time correlatives of the boundaries of marine isotope stages from the recent 3/4 boundary back to the 8/9 boundary. The 5/6 boundary coincided with a deepening of the lake, but the analogous 1/2 boundary coincided with desiccation. The 3/4, 4/5, 6/7, 7/8, and 8/9 boundaries correspond in age to horizons that record little or no change in sedimentation or climate. These hydrologic results demonstrate that the continental paleoclimate record at this mid-latitude site does not mimic the marine record.

  10. Uranium-series dating of sediments from Searles Lake: Differences between continental and marine climate records

    USGS Publications Warehouse

    Bischoff, J.L.; Rosenbauer, R.J.; Smith, G.I.

    1985-01-01

    One of the major unresolved questions in Pleistocene paleoclimatology has been whether continental climatic transitions are consistent with the glacial ??18O marine record. Searles Lake in California, now a dry salt pan, is underlain by sediment layers deposited in a succession of lakes whose levels and salinities have fluctuated in response to changes in climate over the last 3 ?? 106 years. Uranium-series dates on the salt beds range from 35 ?? 103 to 231 ?? 103 years. This range of dates allows identification of lake-sediment horizons that are time correlatives of the boundaries of marine isotope stages from the recent 3/4 boundary back to the 8/9 boundary. The 5/6 boundary coincided with a deepening of the lake, but the analogous 1/2 boundary coincided with desiccation. The 3/4, 4/5, 6/7, 7/8, and 8/9 boundaries correspond in age to horizons that record little or no change in sedimentation or climate. These hydrologic results demonstrate that the continental paleoclimate record at this mid-latitude site does not mimic the marine record.

  11. Stable (206Pb, 207Pb, 208Pb) and radioactive (210Pb) lead isotopes in 1 year of growth of Sphagnum moss from four ombrotrophic bogs in southern Germany: Geochemical significance and environmental implications

    NASA Astrophysics Data System (ADS)

    Shotyk, William; Kempter, Heike; Krachler, Michael; Zaccone, Claudio

    2015-08-01

    The surfaces of Sphagnum carpets were marked with plastic mesh and 1 year later the production of plant matter was harvested in four ombrotrophic bogs from two regions of southern Germany: Upper Bavaria (Oberbayern, OB) and the Northern Black Forest (Nordschwarzwald, NBF). Radioactive, 210Pb was determined in solid samples using ultralow background gamma spectrometry while total Pb concentrations and stable isotopes (206Pb, 207Pb, 208Pb) were determined in acid digests using ICP-SMS. Up to 12 samples (40 × 40 cm) were collected per site, and 6-10 sites investigated per bog. The greatest variations within a given sampling site were in the range 212-532 Bq kg-1 for 210Pb activity, whereas 206Pb/207Pb and 208Pb/206Pb varied less than 1%. The median values of all parameters for the sites (6-10 per bog) were not significantly different. The median activities of 210Pb (Bq kg-1) in the mosses collected from the bogs in NBF (HO = 372 ± 56, n = 55; WI = 342 ± 58, n = 93) were slightly less from those in OB (GS = 394 ± 50, n = 55; KL = 425 ± 58, n = 24). However, the mosses in the NBF bogs exhibited much greater productivity (187-202 g m-2 a-1) compared to those of OB (71-91 g m-2 a-1), and this has a profound impact on the accumulation rates of 210Pb (Bq m-2 a-1), with the bogs in the NBF yielding fluxes (HO = 73 ± 30; WI = 65 ± 20) which are twice those of OB (GS = 29 ± 11; KL = 40 ± 13). Using the air concentrations of 210Pb measured at Schauinsland (SIL) in the southern Black Forest and average annual precipitation, the atmospheric fluxes of 210Pb at SIL (340 Bq m-2 a-1) exceeds the corresponding values obtained from the mosses by a factor of five, providing the first quantitative estimate of the net retention efficiency of 210Pb by Sphagnum. When the 210Pb activities of all moss samples are combined (n = 227), a significant decrease with increasing plant production rate is observed; in contrast, total Pb concentrations show the opposite trend. The contrasting

  12. Strontium Isotope Dating of Metalliferous Sediment in the SW Pacific Basin

    NASA Astrophysics Data System (ADS)

    Stancin, A. M.; Gleason, J. D.; Owen, B. M.; Rea, D. K.; Moore, T. C.; Hendy, I. L.; Lyle, M. W.; Blum, J. D.

    2007-12-01

    A 2 million km2 region virtually devoid of sediment was identified in the remote SW Pacific Basin during the TUIM- 3 2005 drill site survey cruise. This region, termed the "South Pacific Bare Zone", comprises ocean floor dating back to the Late Cretaceous. Within the Bare Zone, a small (1km2) abyssal valley containing sediment to a depth of 24 m was sampled using a large diameter piston core (MV0502-15JC, 31 ° 42.194'S, 143 ° 30.331'W), leading to recovery of 8.35 m of metalliferous sediment at 5082 m water depth. Fish-teeth Sr-isotope stratigraphy reveals a continuous record of sedimentation from 31 Ma to present at this site. The fish teeth age-depth profile and INAA geochemistry reveal an exponentially decreasing hydrothermal flux, with sedimentation rates approaching 0.05 mm/kyr after 20 Ma. The source of hydrothermal activity at this site was likely the Pacific- Farallon Ridge, which went extinct at 20 Ma. A second piston core (MV0502-16JC; 28 ° 05.151'S, 140 ° 14.140'W) was collected near MacDonald Seamounts located on the southeastern end of the Cook-Austral island chain outside the Bare Zone and recovered 10.5 m of hydrothermal sediment and biogenic ooze. The lower 65 cm of the core consists of a coccolith ooze. From 10 mbsf depth to 1.5 mbsf depth, the core contians reddish black zeolitic clay, while the upper 1.5 mbsf contains biogenic ooze associated with abundant Late Pleistocene foraminifera remains. Concordant nannofossil and fish teeth ages at the base of the core (27-28 Ma), and Pleistocene ages near the top of the core reinforce the validity of the Sr fish teeth method for dating hydrothermal cores. These independent records suggest that regional hydrothermal activity during the Oligocene may have been related to a series of late Eocene/early Oligocene ridge jumps, propagating rifts and seafloor spreading centers that accompanied large-scale plate tectonic reorganization of South Pacific seafloor.

  13. TL, OSL and C-14 dating results of the sediments and bricks from mummified nuns' grave.

    PubMed

    Tudela, Diego R G; Tatumi, Sonia H; Yee, Márcio; Brito, Silvio L M; Morais, José L; Morais, Daisy de; Piedade, Silvia C; Munita, Casimiro S P; Hazenfratz, Roberto

    2012-06-01

    This paper presents the results of TL and OSL dating of soil and fragments of bricks from a grave, which was occupied by two mummified nuns, found at "Luz" Monastery, located in the state of São Paulo, Brazil. The TL and OSL ages were compared to C-14 dating ones obtained from bone collagens of the mummies. The majority of the ages is related to the eighteenth century. The gamma-ray spectroscopy was used to evaluate natural radioisotope concentrations in the samples, and by using these concentrations the annual dose rates, from 3.0 to 5.3 Gy/kyr, were obtained. Neutron activation analysis was performed and the radioisotope contents results are in agreement with those obtained by gamma-ray spectroscopy. The contents of U, Th and Ce elements were higher than those found in usual sediments.

  14. Exploration Of Activity Measurements And Equilibrium Checks For Sediment Dating Using Thick-Window Germanium Detectors

    SciTech Connect

    Warner, Jacob A.; Gladkis, Laura G.; Timmers, Heiko; Fitzsimmons, Kathryn E.; Reynolds, Eva M.

    2011-06-01

    Activity measurements on sediment samples for trapped-charge geological dating using gamma-ray spectroscopy are an important verification of the field-site dose rate determination. Furthermore gamma-ray spectroscopy can check if the natural decay series are in secular equilibrium which is a crucial assumption in such dating. Typically the activities of leading members of the Thorium and Uranium decay series are measured, which requires Germanium detectors with thin windows and good energy resolution in order to effectively detect the associated low energy gamma-rays. Such equipment is not always readily available. The potential of conventional Germanium detectors with thick entrance window has been explored towards routine gamma-ray spectroscopy of sediment samples using higher energy gamma-rays. Alternative isotopes, such as Ac-228 and Pb-212 for the Thorium series, and Pa-234m, Ra-226 and Bi-214 for the Uranium series, have been measured in order to determine the mass-specific activity for the respective series and possibly provide a check of secular equilibrium. In addition to measurements of the K-40 activity, with the alternative approach, the activities of both decay series can be accurately determined. The secular equilibrium condition may be tested for the Thorium series. Measurement accuracy for Pa-234m is, however, not sufficient to permit also a reliable check of equilibrium for the Uranium series.

  15. 10Be depth-profile dating of glaciofluvial sediments in the northern Alpine Foreland

    NASA Astrophysics Data System (ADS)

    Claude, Anne; Akçar, Naki; Ivy-Ochs, Susan; Schlunegger, Fritz; Kubik, Peter; Christl, Marcus; Vockenhuber, Christof; Dehnert, Andreas; Rahn, Meinert; Schlüchter, Christian

    2016-04-01

    10Be depth-profile dating is based on the fact that nuclide production is decreasing as an exponential function of depth. This method requires collecting at least four sediment samples in a vertical profile. The obtained nuclide concentrations are plotted against depth and fitted depth-profiles to the measured dataset. The age is then calculated based on the best-fit. The requirements for this method are the following: sampling geological units in artificial outcrops with minimum thickness of soil (less than around 80 cm), preferably with a flat-topped landform in order to guarantee that the uppermost surface of the deposit remains as unmodified as possible and is related to a defined geomorphologic process. Additionally at least one sample, preferably three, from the uppermost one meter of the profile as the exponential decrease mainly occurs around this depth. No sample is collected from the overlying soil. In this study, we aim to establish the chronology of the oldest Quaternary sediments in the northern Alpine Foreland using depth-profile dating with 10Be. These ages contribute to the understanding of the Quaternary landscape evolution of the Alpine Foreland. Here, we unravel the chronology of five sites at different morphostratigraphic positions: Mandach and Ängi (canton Aargau), Stadlerberg and Irchel (canton Zurich) and Rechberg (Germany, 4 km from the border to Switzerland). All sites are abandoned gravel pits and at each site we collected between four and seven sediment samples. First results yielded chronologies between 0.8 and 2 Ma for these glaciofluvial deposits. Our study shows that this relatively new method is successful when the geological setting matches the methodological requirements.

  16. Modeled tephra ages from lake sediments, base of Redoubt Volcano, Alaska

    SciTech Connect

    Schiff, C J; Kaufman, D S; Wallace, K L; Werner, A; Ku, T L; Brown, T A

    2007-02-25

    A 5.6-m-long lake sediment core from Bear Lake, Alaska, located 22 km southeast of Redoubt Volcano, contains 67 tephra layers deposited over the last 8750 cal yr, comprising 15% of the total thickness of recovered sediment. Using 12 AMS {sup 14}C ages, along with the {sup 137}Cs and {sup 210}Pb activities of recent sediment, we evaluated different models to determine the age-depth relation of sediment, and to determine the age of each tephra deposit. The age model is based on a cubic smooth spline function that was passed through the adjusted tephra-free depth of each dated layer. The estimated age uncertainty of the 67 tephras averages {+-} 105 yr (1{sigma}). Tephra-fall frequency at Bear Lake was among the highest during the past 500 yr, with eight tephras deposited compared to an average of 3.7 per 500 yr over the last 8500 yr. Other periods of increased tephra fall occurred 2500-3500, 4500-5000, and 7000-7500 cal yr. Our record suggests that Bear Lake experienced extended periods (1000-2000 yr) of increased tephra fall separated by shorter periods (500-1000 yr) of apparent quiescence. The Bear Lake sediment core affords the most comprehensive tephrochronology from the base of the Redoubt Volcano to date, with an average tephra-fall frequency of once every 130 yr.

  17. Ground water contamination with (238)U, (234)U, (235)U, (226)Ra and (210)Pb from past uranium mining: cove wash, Arizona.

    PubMed

    Dias da Cunha, Kenya Moore; Henderson, Helenes; Thomson, Bruce M; Hecht, Adam A

    2014-06-01

    The objectives of the study are to present a critical review of the (238)U, (234)U, (235)U, (226)Ra and (210)Pb levels in water samples from the EPA studies (U.S. EPA in Abandoned uranium mines and the Navajo Nation: Red Valley chapter screening assessment report. Region 9 Superfund Program, San Francisco, 2004, Abandoned uranium mines and the Navajo Nation: Northern aum region screening assessment report. Region 9 Superfund Program, San Francisco, 2006, Health and environmental impacts of uranium contamination, 5-year plan. Region 9 Superfund Program, San Franciso, 2008) and the dose assessment for the population due to ingestion of water containing (238)U and (234)U. The water quality data were taken from Sect. "Data analysis" of the published report, titled Abandoned Uranium Mines Project Arizona, New Mexico, Utah-Navajo Lands 1994-2000, Project Atlas. Total uranium concentration was above the maximum concentration level for drinking water (7.410-1 Bq/L) in 19 % of the water samples, while (238)U and (234)U concentrations were above in 14 and 17 % of the water samples, respectively. (226)Ra and (210)Pb concentrations in water samples were in the range of 3.7 × 10(-1) to 5.55 × 102 Bq/L and 1.11 to 4.33 × 102 Bq/L, respectively. For only two samples, the (226)Ra concentrations exceeded the MCL for total Ra for drinking water (0.185 Bq/L). However, the (210)Pb/(226)Ra ratios varied from 0.11 to 47.00, and ratios above 1.00 were observed in 71 % of the samples. Secular equilibrium of the natural uranium series was not observed in the data record for most of the water samples. Moreover, the (235)U/(total)U mass ratios ranged from 0.06 to 5.9 %, and the natural mass ratio of (235)U to (total)U (0.72 %) was observed in only 16 % of the water samples, ratios above or below the natural ratio could not be explained based on data reported by U.S. EPA. In addition, statistical evaluations showed no correlations among the distribution of the radionuclide concentrations

  18. Dating Plio-Pleistocene glacial sediments using the cosmic-ray-produced radionuclides 10Be and 26Al

    USGS Publications Warehouse

    Balco, G.; Stone, J.O.H.; Jennings, C.

    2005-01-01

    We use the cosmic-ray-produced radionuclides 26Al and 10Be to date Plio-Pleistocene glacial sediment sequences. These two nuclides are produced in quartz at a fixed ratio, but have different decay constants. If a sample is exposed at the surface for a time and then buried by overburden and thus removed from the cosmic-ray flux, the 26Al/10Be ratio is related to the duration of burial. We first attempted to date pre-Wisconsinan tills by measuring 26Al and 10Be in fluvial sediments beneath them and applying the method of "burial dating," which previous authors have used to date river sediment carried into caves. This method, however, requires simplifying assumptions about the 26Al and 10Be concentrations in the sediment at the time of burial. We show that these assumptions are not valid for river sediment in glaciated regions. 26Al and 10Be analyses of such sediment do not provide accurate ages for these tills, although they do yield limiting ages in some cases. We overcome this difficulty by instead measuring 26Al and 10Be in quartz from paleosols that are buried by tills. We use a more general mathematical approach to determine the initial nuclide concentrations in the paleosol at the time it was buried, as well as the duration of burial. This technique provides a widely applicable improvement on other means of dating Plio-Pleistocene terrestrial glacial sediments, as well as a framework for applying cosmogenic-nuclide dating techniques in complicated stratigraphic settings. We apply it to pre-Wisconsinan glacial sediment sequences in southwest Minnesota and eastern South Dakota. Pre-Wisconsinan tills underlying the Minnesota River Valley were deposited 0.5 to 1.5 Ma, and tills beneath the Prairie Coteau in eastern South Dakota and adjacent Minnesota were deposited 1 to 2 Ma.

  19. Anthropogenically induced changes in sediment and biogenic silica fluxes in Chesapeake Bay

    USGS Publications Warehouse

    Colman, Steven M.; Bratton, John F.

    2003-01-01

    Sediment cores as long as 20 m, dated by 14C, 210Pb, and 137Cs methods and pollen stratigraphy, provide a history of diatom productivity and sediment-accumulation rates in Chesapeake Bay. We calculated the flux of biogenic silica and total sediment for the past 1500 yr for two high-sedimentation-rate sites in the mesohaline section of the bay. The data show that biogenic silica flux to sediments, an index of diatom productivity in the bay, as well as its variability, were relatively low before European settlement of the Chesapeake Bay watershed. In the succeeding 300–400 yr, the flux of biogenic silica has increased by a factor of 4 to 5. Biogenic silica fluxes still appear to be increasing, despite recent nutrient-reduction efforts. The increase in diatom-produced biogenic silica has been partly masked (in concentration terms) by a similar increase in total sediment flux. This history suggests the magnitude of anthropogenic disturbance of the estuary and indicates that significant changes had occurred long before the twentieth century.

  20. Antropogenically induced changes in sediment and biogenic silica fluxes in Chesapeake Bay

    USGS Publications Warehouse

    Colman, Steven M.; Bratton, J.F.

    2003-01-01

    Sediment cores as long as 20 m, dated by 14C, 210Pb, and 137Cs methods and pollen stratigraphy, provide a history of diatom productivity and sediment-accumulation rates in Chesapeake Bay. We calculated the flux of biogenic silica and total sediment for the past 1500 yr for two high-sedimentation-rate sites in the mesohaline section of the bay. The data show that biogenic silica flux to sediments, an index of diatom productivity in the bay, as well as its variability, were relatively low before European settlement of the Chesapeake Bay watershed. In the succeeding 300-400 yr, the flux of biogenic silica has increased by a factor of 4 to 5. Biogenic silica fluxes still appear to be increasing, despite recent nutrient-reduction efforts. The increase in diatom-produced biogenic silica has been partly masked (in concentration terms) by a similar increase in total sediment flux. This history suggests the magnitude of anthropogenic disturbance of the estuary and indicates that significant changes had occurred long before the twentieth century.

  1. Molecular level characterization of diatom-associated biopolymers that bind 234Th, 233Pa, 210Pb, and 7Be in seawater: A case study with Phaeodactylum tricornutum

    NASA Astrophysics Data System (ADS)

    Chuang, Chia-Ying; Santschi, Peter H.; Xu, Chen; Jiang, Yuelu; Ho, Yi-Fang; Quigg, Antonietta; Guo, Laodong; Hatcher, Patrick G.; Ayranov, Marin; Schumann, Dorothea

    2015-09-01

    In order to investigate the importance of biogenic silica associated biopolymers on the scavenging of radionuclides, the diatom Phaeodactylum tricornutum was incubated together with the radionuclides 234Th, 233Pa, 210Pb, and 7Be during their growth phase. Normalized affinity coefficients were determined for the radionuclides bound with different organic compound classes (i.e., proteins, total carbohydrates, uronic acids) in extracellular (nonattached and attached exopolymeric substances), intracellular (ethylene diamine tetraacetic acid and sodium dodecyl sulfate extractable), and frustule embedded biopolymeric fractions (BF). Results indicated that radionuclides were mostly concentrated in frustule BF. Among three measured organic components, Uronic acids showed the strongest affinities to all tested radionuclides. Confirmed by spectrophotometry and two-dimensional heteronuclear single quantum coherence-nuclear magnetic resonance analyses, the frustule BF were mainly composed of carboxyl-rich, aliphatic-phosphoproteins, which were likely responsible for the strong binding of many of the radionuclides. Results from this study provide evidence for selective absorption of radionuclides with different kinds of diatom-associated biopolymers acting in concert rather than as a single compound. This clearly indicates the importance of these diatom-related biopolymers, especially frustule biopolymers, in the scavenging and fractionation of radionuclides used as particle tracers in the ocean.

  2. Historical changes of sediments and mollusk assemblages in the Gulf of Batabanó (Caribbean Sea) in the twentieth century.

    PubMed

    Armenteros, Maickel; Díaz-Asencio, Misael; Fernández-Garcés, Raúl; Eriksson, Mats; Alonso-Hernández, Carlos; Sanchez-Cabeza, Joan-Albert

    2012-08-01

    The first paleoecological reconstruction of the biogeochemical conditions of the Gulf of Batabanó, Caribbean Sea was performed from (210)Pb-dated sediment cores. Depth profiles of 20 major elements and trace metals, organic compounds, grain size, and mollusk assemblage composition were determined from 9 stations encompassing unconsolidated sediments in the gulf. Spatial heterogeneity was evident for the geochemistry of sediments and for the mollusk assemblage composition. Our reconstruction indicates that pollution is not a critical threat to the ecosystem, although a slight historical increase of lead enrichment factor was detected probably due to long-range atmospheric fallout. Mollusk assemblages were composed by 168 species belonging to 59 families and no temporal trends in the species diversity or assemblage composition were detected, suggesting no depletion of diversity or habitat loss. Other signals of habitat loss such as changes in organic budget or increase of fine sediment fraction were absent or weak. Nitrogen retained in sediments changed by <1% in the century, indicating no historical events of eutrophication or oligotrophication in the gulf. Historical decrease of fine sediment fraction in the eastern sector would be linked to modifications in sedimentation rate, land use, and/or particle transport from the shelf border; this also suggests that both sectors have different sedimentary dynamics. Although, on theoretical grounds, historical fishery may have caused deleterious ecosystem effects by overexploitation of spiny lobster stocks, no evidence of habitat degradation or loss, caused by fisheries, could be detected.

  3. Determination of (210)Pb and (226)Ra/(228)Ra in continental water using HIDEX 300SL LS-spectrometer with TDCR efficiency tracing and optimized α/β-discrimination.

    PubMed

    Eikenberg, J; Beer, H; Jäggi, M

    2014-11-01

    An analytical method for determination of (210)Pb, (226)Ra and (228)Ra is presented based on adsorption on 3M Empore RadDiscs, and measurement applying liquid scintillation spectrometry (LSC) after elution. The LSC measurement was performed with optimized α/β-discrimination and isotope standardization using the triple to double coincidence ratio (TDCR). The consistency of measurement results between radioactive parent-daughter pairs (210)Pb/(210)Bi, (226)Ra/(222)Rn and (228)Ra/(228)Ac was checked in long-term counting experiments and the influence ofinterference of in-growing daughters from (226)Ra into the β-spectrum of (228)Ra+(228)Ac was studied as well. Recommendations for optimized LSC (228)Ra measurement besides presence of (226)Ra are given.

  4. Modeled tephra ages from lake sediments, base of Redoubt Volcano, Alaska

    USGS Publications Warehouse

    Schiff, C.J.; Kaufman, D.S.; Wallace, K.L.; Werner, A.; Ku, T.-L.; Brown, T.A.

    2008-01-01

    A 5.6-m-long lake sediment core from Bear Lake, Alaska, located 22 km southeast of Redoubt Volcano, contains 67 tephra layers deposited over the last 8750 cal yr, comprising 15% of the total thickness of recovered sediment. Using 12 AMS 14C ages, along with the 137Cs and 210Pb activities of recent sediment, we evaluated different models to determine the age-depth relation of the core, and to determine the age of each tephra deposit. The selected age model is based on a mixed-effect regression that was passed through the adjusted tephra-free depth of each dated layer. The estimated age uncertainty of the 67 tephras averages ??105 yr (95% confidence intervals). Tephra-fall frequency at Bear Lake was among the highest during the past 500 yr, with eight tephras deposited compared to an average of 3.7/500 yr over the last 8500 yr. Other periods of increased tephra fall occurred 2500-3500, 4500-5000, and 7000-7500 cal yr. Our record suggests that Bear Lake experienced extended periods (1000-2000 yr) of increased tephra fall separated by shorter periods (500-1000 yr) of apparent quiescence. The Bear Lake sediment core affords the most comprehensive tephrochronology from the base of the Redoubt Volcano to date, with an average tephra-fall frequency of one every 130 yr. ?? 2007 Elsevier Ltd. All rights reserved.

  5. Radiocarbon dating of individual lignin phenols: a new approach for establishing chronology of late quaternary lake sediments.

    PubMed

    Hou, Juzhi; Huang, Yongsong; Brodsky, Corynn; Alexandre, Marcelo R; McNichol, Ann P; King, John W; Hu, Feng Sheng; Shen, Ji

    2010-09-01

    The reliability of chronology is a prerequisite for meaningful paleoclimate reconstructions from sedimentary archives. The conventional approach of radiocarbon dating bulk organic carbon in lake sediments is often hampered by the old carbon effect, i.e., the assimilation of ancient dissolved inorganic carbon (DIC) derived from carbonate bedrocks or other sources. Therefore, radiocarbon dating is ideally performed on organic compounds derived from land plants that use atmospheric CO(2) and rapidly delivered to sediments. We demonstrate that lignin phenols isolated from lake sediments using reversed phase high performance liquid chromatography (HPLC) can serve as effective (14)C dating materials for establishing chronology during the late Quaternary. We developed a procedure to purify lignin phenols, building upon a published method. By isolating lignin from standard wood reference substances, we show that our method yields pure lignin phenols and consistent ages as the consensus ages and that our procedure does not introduce radiocarbon contamination. We further demonstrate that lignin phenol ages are compatible with varve counted and macrofossil dated sediment horizons in Steel Lake and Fayetteville Green Lake. Applying the new method to lake sediment cores from Lake Qinghai demonstrates that lignin phenol ages in Lake Qinghai are consistently younger than bulk total organic carbon (TOC) ages which are contaminated by old carbon effect. We also show that the age offset between lignin and bulk organic carbon differs at different Lake Qinghai sedimentary horizons, suggesting a variable hard water effect at different times and that a uniform age correction throughout the core is inappropriate.

  6. Historical trends of concentrations, source contributions and toxicities for PAHs in dated sediment cores from five lakes in western China.

    PubMed

    Xu, Jian; Guo, Jian-Yang; Liu, Gui-Rong; Shi, Guo-Liang; Guo, Chang-Sheng; Zhang, Yuan; Feng, Yin-Chang

    2014-02-01

    In this work, sixteen U.S. EPA priority PAH compounds in the dated sediment cores were detected from five lakes in western China. In most lakes, the concentrations of the total PAHs (ΣPAHs) increased from the deep layers to the surface sediments. Two source categories, i.e. vehicular emission and biomass & domestic coal combustion were identified by Unmix, a factor analysis receptor model to explore the source contributions of PAHs in the dated sediments. The source apportionment results showed that biomass & domestic coal combustion contributed larger proportion of PAHs in the five lakes. The toxicities of PAHs in the dated sediments, assessed by BaP equivalent (BaPE) values showed that the BaPE increased gradually from the deep layers to the surface sediments in most lakes. For the first effort, the contribution of each source to BaPE was apportioned by Unmix-BaPE method, and the result indicated that the vehicular emission posed the highest toxic risk. The percentage contribution of vehicular emission for PAHs and BaPE also increased from the deep layers to the surface sediments, while biomass & domestic coal combustion exhibited the opposite tendency.

  7. Historical changes in the concentrations of polycyclic aromatic hydrocarbons (PAHs) in Lake Peipsi sediments.

    PubMed

    Punning, Jaan-Mati; Terasmaa, Jaanus; Vaasma, Tiit; Kapanen, Galina

    2008-09-01

    The distribution of 11 individual polycyclic aromatic hydrocarbons (PAHs) was analysed in a (210)Pb dated sediment core from the deepest area of Lake Peipsi and in four surface sediment samples taken from littoral areas. According to the concentrations in the core three groups of PAHs may be distinguished: (1) relatively stable concentrations of PAHs within the whole studied time interval; (2) very low concentrations in sediments accumulated before intensive anthropogenic impact (from 19th century up to the 1920s) following a slight increase and (3) an overall increase in PAH concentrations since the 1920s up to the present. Comprehensive analysis of PAHs in the core and monitoring data obtained in the 1980s together with the lithology of sediments show that an increase of anthropogenically induced PAHs correlates well with the history of fuel consumption in Estonia and speaks about atmospheric long-distance transport of PAHs. The continuous increase of PAH concentrations since the 1920s do not support the earlier hypothesis about the dominating impact of the oil shale fired power plants near the lake, because their emissions decreased significantly in the 1990s. The concentration of PAHs in the deep lake core sample correlates well with the content of organic matter, indicating absorption and co-precipitation with plankton in the sediment.

  8. [Vertical distribution characteristics of organochlorine pesticides and polychlorinated biphenyls in sediment core from Lake Nansihu].

    PubMed

    Li, Hong-li; Li, Guo-gang; Yang, Fan; Gao, Hong; Gong, Zheng-yu; Zhu, Chen; Lian, Jun

    2007-07-01

    The organochlorinne pesticides (OCPs) and the polychlorinated biphenyls (PCBs) in sediment core collected from Lake Nansihu were quantificationally analyzed by GC-ECD. The pollution history of OCPs and PCBs in this area was reconstructed by analysis of the concentrations of OCPs and PCBs connected with the deposition time by 210Pb isotope dating method. The results indicated that the concentration ranges of OCPs, HCHs, DDTs and PCBs were 1.64 - 17.9, 0.66 - 12.5, 0.24 - 2.99 and 7.84 - 42.8 ng g(-1) respectively. The sediment rate and the average mass sedimentation were calculated to be 0.330 cm a(-1) and 0.237 g (cm2 a)(-1), and the sediment time of this core sample ranged from 1899 to 2000. OCPs and PCBs had the peak value at 1960s and 1970s. The source analysis showed HCH came from HCH products and lindane, and HCH and DDT came from historic using. The source of PCBs had been deduced to be the blench process of paper making and incinerator emission. Except the concentration of beta-HCH, gamma-HCH and aldrin at 14 - 16 cm depth, the other concentrations of OCPs and PCBs were all less than the low ecologic risk value. The whole sediment core of Lake Nansihu belonged to the low ecologic risk level.

  9. Long-Term Trends in Trace Metals Concentrations in Sediment in Lakes in Adirondack Park, NY

    NASA Astrophysics Data System (ADS)

    Bari, A.; Judd, C. D.; Swami, K.; Ahmed, T.; Husain, L.

    2007-12-01

    The industrial Midwestern states consume large quantities of fossil fuel and emit large quantities of trace elements, SO2 and other chemicals. Owing to their long residence time these pollutants can be transported hundreds of miles downwind. These chemical species are removed from the atmosphere by wet and dry deposition and are ultimately deposited in lake sediments. Through the sedimentation process the pollution records can be stored for centuries. In this work we have attempted to retrieve the deposition of 25 trace elements for the past ~170 years by analyzing lake sediment cores from lakes located in the Adirondack Mountains. Sediment cores were collected from four lakes (Clear Pond, West Pine Pond, Bear Pond and Deer Pond) located in the Adirondack Park, NY. These lakes are at high altitude and some are inaccessible except by boat, and have minimum human activity (no motor boats, no camping and away from major roads). Coring was carried out by a gravity driven coring device. The cores were sectioned, weighed, freeze-dried, ground to a fine powder, and homogenized for analysis. The sediment cores were dated using 210Pb radioactive dating. The 137Cs activity was measured for an independent verification of 210Pb technique. Trace metals concentration were determined by microwave digestion method followed by inductively coupled plasma mass spectrometric (ICP-MS) analysis. The top sixteen sections of the West Pine Pond sediment core (representing from about 1835 to 2005) were analyzed for Sr, Ba, As, Se, Mo, Cd, Sn, Sb, Co, Ni, Cu, Ag,Ti, V, Cr, Mn, Fe, Zn, K, Na, Ca, Mg, Be, Tl, and Pb. During pre industrial era the concentrations of Pb, Se and Tl were very low and constant. Pb showed a sharp increase in concentration after around 1880 and a sharp decrease in concentration after about 1990. The concentration of Se increased slowly after pre industrial era. The concentrations of about eight of these elements were determined in quarterly composites of daily aerosol

  10. IRSL dating of Middle Pleistocene interglacial sediments from southern Quebec (Canada) using multiple and single grain aliquots

    USGS Publications Warehouse

    Balescu, S.; Lamothe, M.; Auclair, M.; Shilts, W.W.

    2001-01-01

    The IRSL dating of Middle Pleistocene interglacial fluvial sediments from Southern Quebec, correlated with oxygen isotopic stage 7, yields optical dates much younger than the expected geological age. Single grain IRSL measurements on alkali-feldspars, following the fadia protocol developed by Lamothe and Auclair (Earth and Planetary Science Letters, 171, 319-323, 1999), suggest that anomalous fading is the most probable cause for this severe age underestimation. The IRSL dates corrected for this anomalous fading are in better agreement with the expected ages. ?? 2000 Elsevier Science Ltd.

  11. Dating of sediment record at two contrasting sites of the Seine River using radioactivity data and hydrological time series.

    PubMed

    Vrel, Anne; Boust, Dominique; Lesueur, Patrick; Deloffre, Julien; Dubrulle-Brunaud, Carole; Solier, Luc; Rozet, Marianne; Thouroude, Coralie; Cossonnet, Catherine; Thomas, Sandrine

    2013-12-01

    Sediment cores were collected at the outlet of the highly anthropogenized catchment of the Seine River at two contrasting sites: a flood plain of the lower Seine River and a quasi-permanently submerged harbour basin (or wet dock) in the upper tidal estuary. Analyses of artificial radionuclides ((137)Cs and plutonium isotopes), coupled with hydrological and bathymetric data, lead to a precise dating of the sediment cores collected at the two sites. (137)Cs signals originating from global fallout (early 1960s) and from the Chernobyl accident (1986) are identified, but at different levels due to the incomplete nature or variable continuity of the records. Anomalous (238)Pu concentrations found at both sites (1-2 Bq kg(-1)) are attributed to unknown industrial releases originating from upstream. Interpolating (137)Cs sediment activities under the assumption of a constant sediment rate, those releases were dated back to 1975 ± 1, thus providing a local but reliable time-marker. Age models have highlighted a very contrasting sediment filling dynamics in these two sites. This study presents the first sediment record of alpha- and gamma-emitting artificial radionuclides obtained at the outlet of the huge catchment area of the River Seine, over a period covering the last 50 years.

  12. High-resolution dating of Cenozoic sediments from northern North Sea using /sup 87/Sr//sup 86/Sr stratigraphy

    SciTech Connect

    Rundberg, Y.; Smalley, P.C.

    1989-03-01

    The authors demonstrate the potential of Sr isotope stratigraphy as a tool in basin analysis by dating bioclastic carbonate and phosphate fragments from eight seismic units in Cenozoic sedimentary rocks along two east-west profiles in the northern North Sea. The dates, which agree well with available Rb/Sr glauconite dates, have precisions in the range /+-/0.5 to 3 m.y., thereby providing important chronostratigraphic information for sediments that otherwise are difficult to date. Basinward (southwest) in this area, the most important seismic sequence boundaries are dated at approximately 53 Ma, 33 Ma, 22 Ma, 8 Ma, and 2 Ma. Northeastward toward the basin margin, these boundaries represent important periods of erosion or nondeposition. Deep-water sedimentation predominated from the Paleocene until the early Oligocene (33 Ma), a time of high global sea levels. Close to the basin margin, local tectonic activity contributed turbiditic clastic sediments. An important sequence boundary at 30 Ma involves erosion in the northern area and correlates with a sharp eustatic drop in sea level. Post-early Oligocene seismic sequence boundaries are controlled mainly by basin-margin tectonics related to uplift events in Fennoscandia and in the Shetland Platform area. 7 figures, 3 tables.

  13. Anthropogenic metal contamination and sapropel imprints in deep Mediterranean sediments.

    PubMed

    Angelidis, M O; Radakovitch, O; Veron, A; Aloupi, M; Heussner, S; Price, B

    2011-05-01

    Sediment cores from the deep Balearic basin and the Cretan Sea provide evidence for the accumulation of Cd, Pd and Zn in the top few centimeters of the abyssal Mediterranean sea-bottom. In both cores, 206Pb/207Pb profiles confirm this anthropogenic impact with less radiogenic imprints toward surface sediments. The similarity between excess 210Pb accumulated in the top core and the 210Pb flux suggests that top core metal inventories reasonably reflect long-term atmospheric deposition to the open Mediterranean. Pb inventory in the western core for the past 100 years represents 20-30% of sediment coastal inventories, suggesting that long-term atmospheric deposition determined from coastal areas has to be used cautiously for mass balance calculations in the open Mediterranean. In the deeper section of both cores, Al normalized trace metal profiles suggest diagenetic remobilization of Fe, Mn, Cu and, to a lesser extent, Pb that likely corresponds to sapropel event S1.

  14. Detecting, sourcing, and age-dating dredged sediments on the open shelf, southern California, using dead mollusk shells.

    PubMed

    Bizjack, Matthew T; Kidwell, Susan M; Velarde, Ronald G; Leonard-Pingel, Jill; Tomašových, Adam

    2017-01-15

    Molluscan shell debris is an under-exploited means of detecting, sourcing, and age-dating dredged sediments in open-shelf settings. Backscatter features on the Southern California shelf are suggestive of dredged sediment hauled from San Diego Bay but deposited significantly inshore of the EPA-designated ocean disposal site. We find that 36% of all identifiable bivalve shells >2mm (44% of shells >4mm) in sediment samples from this 'short dump' area are from species known to live exclusively in the Bay; such shells are absent at reference sites of comparable water depth, indicating that their presence in the short-dump area signals non-compliant disposal rather than natural offshore transport or sea level rise. These sediments lack the shells of species that invaded California bays in the 1970s, suggesting that disposal preceded federal regulations. This inexpensive, low-tech method, with its protocol for rejecting alternative hypotheses, will be easy to adapt in other settings.

  15. 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

  16. Accumulation and diagenesis of chlorinated hydrocarbons in lacustrine sediments

    USGS Publications Warehouse

    Elsenreich, S.J.; Capel, P.D.; Robbins, J.A.; Bourbonniere, R.

    1989-01-01

    Two sediment cores were taken from the Rochester Basin of eastern Lake Ontario and analyzed for the radionuclides 210Pb and 137Cs and several high molecular weight chlorinated hydrocarbons (CHs). The two sites are geographically proximate but differ in sedimentation rate, permitting sedimentation-dependent processes to be factored out. The 210Pb chronology showed a mixed depth of 3-5 cm and an intrinsic time resolution of 11-14 years. Vertically integrated numbers of deposit-feeding oligochaete worms and burrowing organisms are insufficient to homogenize the sediment on the time scale of CH inputs, which are non steady state. U.S. production and sales of polychlorinated biphenyls (PCBs), DDT, Mirex, and hexachlorobenzene (HCB), as determinants of the shape of the input function, adequately predict the overall shape and, in many cases, details in the sedimentary profile. Sediment focusing factors (FF) inferred from 137Cs and 210Pb inventories averaged 1.17 and 1.74 for cores E-30 and G-32, respectively. This permitted CH accumulation rates to be corrected for focusing. Apparent molecular diffusion coefficients modeled for many of the CHs were about (1-3) ?? 10-9 cm2/s.

  17. Luminescence Dating of Sediments from the Luthern Valley, Central Switzerland, and Implications for the Chronology of the Last Glacial Cycle

    NASA Astrophysics Data System (ADS)

    Preusser, Frank; Müller, Benjamin U.; Schlüchter, Christian

    2001-03-01

    The advancing glaciers of the last glacial maximum either eroded or deeply buried older sediments in the Swiss Alpine Foreland. However, part of the Swiss Plateau was not covered by ice and is therefore an excellent area for investigating climate and environmental change during the Upper Pleistocene. Repeated fluvial sequences can be studied in several pits along the Luthern Valley. The chronological framework is based on lithostratigraphy, pollen analysis, U/Th dating, and, recently, heavy mineral analysis and luminescence dating. The oldest unit, the Untere Zeller Schotter braided river deposit, represents cold climate conditions and presumably a glaciation prior to the Eemian Interglaciation. The last interglacial period and the very beginning of the last glacial cycle is represented by the Mittlere Zeller Schotter, sediments of a meandering fluvial system. Younger braided river sediments, the Obere Zeller Schotter, seem to correlate with the cold climate of oxygen isotope stage (OIS) 4. Weathering of the top of the Obere Zeller Schotter is likely to represent the OIS 3. The advancing Reuss glacier caused erosion of the recent Luthern Valley, cutting into older sediments, with local loess accumulation during the last glacial maximum as indicated by cover sediments on top of the fluvial sequence.

  18. Effects of land use change and sediment mobilization on coastal contamination (Coatzacoalcos River, Mexico)

    NASA Astrophysics Data System (ADS)

    Ruiz-Fernández, Ana Carolina; Sanchez-Cabeza, Joan-Albert; Alonso-Hernández, Carlos; Martínez-Herrera, Víctor; Pérez-Bernal, Libia Hascibe; Preda, Michel; Hillaire-Marcel, Claude; Gastaud, Janine; Quejido-Cabezas, Alberto José

    2012-04-01

    Coastal ecosystems are subject to many anthropogenic pressures, including pollution and the enhancement of sedimentation due to human activities. The lower reach of the Coatzacoalcos River is considered to be the most polluted coastal area of Mexico due to the presence of major petrochemical production centers in its watershed. In order to show the impact of land use change and industrial activities on the adjacent coastal environment of the Coatzacoalcos River, we reconstructed the historical changes of sediment transport and trace metals contamination based on the study of a 210Pb dated sediment core. Several geochemical indicators, such as clay mineral content, the concentrations of reference elements (Al, Ca, Sr, Rb) and the carbon isotope ratio (δ13C) revealed a change of sediment and contamination sources since the early 80s, in coincidence with the large industrial and urban development in the area. We conclude that the increased contaminant loads were related to terrestrial sources, likely contaminated and eroded soils from the catchment, due to extensive land use changes. Although the contaminant enrichment since the early 80s was low, As, Hg and Ni concentrations show potentially dangerous levels and exceed the USEPA-ERL concentration benchmarks, thus constituting a potential threat to marine aquatic life and humans through seafood consumption.

  19. Reconstructing the rise of recent coastal anoxia; molybdenum in Chesapeake Bay sediments

    USGS Publications Warehouse

    Adelson, J.M.; Helz, G.R.; Miller, C.V.

    2001-01-01

    Sporadic, direct observations over a 50 yr period inadequately characterize the history of seasonal hypoxia and anoxia in Chesapeake Bay, alarge estuary threatened by eutrophication. Here, we undertake a reconstruction of 20th century oxygen depletion in this estuary using Mo concentrations in 210Pb-dated sediments; Cu concentrations are used to control for anthropogenic influences. Cores from the central channel display mild Mo enrichments above crustal backgrounds (up to 5 ??g/g) and strong Cu enrichments (up to 35 ??g/g). Temporally, Cu enrichment (mostly anthropogenic) began earlier and stabilized in the last two thirds of the 20th century. In contrast, Mo enrichment has grown during the last two thirds of the century. Molybdenum enrichment is mostly hydrogenic, except in a section of the channel that receives additional Mo from erosion of Early Miocene shore deposits. Two geochemical mechanisms promote Mo enrichment: Manganese refluxing concentrates dissolved MoO24- at the sediment-water interface and sulfide substitution into MoO24- produces thiomolybdates, which can be fixed by particles. The Mo enrichment mechanisms operate primarily during periods when bottom waters are anoxic and thiomolybdate formation can occur near the sediment-water interface. This implies a temporal coupling between water-column anoxia and Mo fixation even though fixation occurs only within sediments. The Mo enrichment profiles suggest that Chesapeake Bay has experienced growing O2 depletion since the first half of the 20th century, but especially after 1960. Copyright ?? 2001 Elsevier Science Ltd.

  20. Speciation and toxicity of arsenic in mining-affected lake sediments in the Quinsam watershed, British Columbia.

    PubMed

    Moriarty, Maeve M; Lai, Vivian W-M; Koch, Iris; Cui, Longpeng; Combs, Chris; Krupp, Eva M; Feldmann, Jörg; Cullen, William R; Reimer, Kenneth J

    2014-01-01

    Anthropogenic arsenic inputs into fresh water lakes in the Quinsam watershed, British Columbia, were probed by using multiple methods of inquiry including sediment coring combined with (210)Pb dating, a principal components analysis of elemental composition of sediments, arsenic speciation, bioaccessibility, and toxicity testing. The quantification of arsenic inputs from anthropogenic sources was not trivial because a variety of processes redistribute the element throughout lakes. However, elevated arsenic and sulfate concentrations in Long Lake, a lake that receives arsenic from a seep, suggest that this lake is influenced by mine operations. X-ray absorption near edge structure (XANES) spectra reveal similar arsenic speciation for all sediments within the studied lakes. Bioaccessibility tests, which in this study were used to approximate the solubility and availability of arsenic to benthic organisms, indicate moderate bioaccessibility of arsenic in sediments (7.9-35%). Toxicity testing indicates that not all benthic organisms should be used for evaluating arsenic toxicity, and suggests that the amphipod, Corophium volutator, shows promise as a candidate for widespread use for arsenic sediment toxicity testing.

  1. A comparison of factors controlling sedimentation rates and wetland loss in fluvial deltaic systems, Texas Gulf coast

    NASA Astrophysics Data System (ADS)

    White, William A.; Morton, Robert A.; Holmes, Charles W.

    2002-04-01

    Submergence of coastal marshes in areas where rates of relative sea-level rise exceed rates of marsh sedimentation, or vertical accretion, is a global problem that requires detailed examination of the principal processes that establish, maintain, and degrade these biologically productive environments. Using a simple 210Pb-dating model, we measured sedimentation rates in cores from the Trinity, Lavaca-Navidad, and Nueces bayhead fluvial-deltaic systems in Texas where more than 2000 ha of wetlands have been lost since the 1950s. Long-term average rates of fluvial-deltaic aggradation decrease southwestward from 0.514±0.008 cm year -1 in the Trinity, 0.328±0.022 cm year -1 in the Lavaca-Navidad, to 0.262±0.034 cm year -1 in the Nueces. The relative magnitudes of sedimentation and wetland loss correlate with several parameters that define the differing fluvial-deltaic settings, including size of coastal drainage basin, average annual rainfall, suspended sediment load, thickness of Holocene mud in the valley fill, and rates of relative sea-level rise. There is some evidence that upstream reservoirs have reduced wetland sedimentation rates, which are now about one-half the local rates of relative sea-level rise. The extant conditions indicate that fluvial-deltaic marshes in these valleys will continue to be lost as a result of submergence and erosion.

  2. A comparison of factors controlling sedimentation rates and wetland loss in fluvial-deltaic systems, Texas Gulf coast

    USGS Publications Warehouse

    White, W.A.; Morton, R.A.; Holmes, C.W.

    2002-01-01

    Submergence of coastal marshes in areas where rates of relative sea-level rise exceed rates of marsh sedimentation, or vertical accretion, is a global problem that requires detailed examination of the principal processes that establish, maintain, and degrade these biologically productive environments. Using a simple 210Pb-dating model, we measured sedimentation rates in cores from the Trinity, Lavaca-Navidad, and Nueces bayhead fluvial-deltaic systems in Texas where more than 2000 ha of wetlands have been lost since the 1950s. Long-term average rates of fluvial-deltaic aggradation decrease southwestward from 0.514 ?? 0.008 cm year -1 in the Trinity, 0.328 ?? 0.022 cm year -1 in the Lavaca-Navidad, to 0.262 ?? 0.034 cm year -1 in the Nucces. The relative magnitudes of sedimentation and wetland loss correlate with several parameters that define the differing fluvial-deltaic settings, including size of coastal drainage basin, average annual rainfall, suspended sediment load, thickness of Holocene mud in the valley fill, and rates of relative sea-level rise. There is some evidence that upstream reservoirs have reduced wetland sedimentation rates, which are now about one-half the local rates of relative sea-level rise. The extant conditions indicate that fluvial-deltaic marshes in these valleys will continue to be lost as a result of submergence and erosion. ?? 2002 Elsevier Science B.V. All rights reserved.

  3. Apatite triple dating of Andrill AND-2A sediments (McMurdo Sound, Antarctica)

    NASA Astrophysics Data System (ADS)

    Andreucci, B.; Zattin, M.; Reiners, P. W.; Sandroni, S.; Talarico, F.; Thomson, S. N.

    2011-12-01

    The Andrill AND-2A drill core documents the last 20 myr of the geological history of the Ross Sea region. In this work we date detrital apatites from the upper 1000 m by three different techniques on the same grain: U-Pb (UPb), fission-track (AFT) and U-Th/He (AHe) analysis. The UPb data clearly indicate that most of apatites derive from a crystalline source that cooled at about 500 Ma. Similar intrusion ages are compatible with UPb data on zircon which are widespread along the Transantarctic Mountains (TAM) and are related to Ross Orogeny that took place in the Early Paleozoic. Most of the AFT ages from the core are younger than 40 Ma, thus suggesting the presence of active tectonics (Zattin et al., Terra Nova, 2010) or re-heating events at the end of the Oligocene. Most of the AHe data on these samples are only slightly younger than AFT ages, thus documenting high rates of cooling. Furthermore, as AHe ages are nearly all older than 20 Ma, these data document very low erosion rates from Miocene onwards, confirming what observed on bedrock data (Fitzgerald et al, Chem. Geol., 2006). A significant group of apatite crystals, nearly all from a sample collected from the deepest section of the core, has been dated by the UPb method at 30 Ma. The same grains yield AFT and AHe ages some Myr younger. These data are not related to exhumation but provide the evidence for the occurrence of a magmatic event which is much older than the Miocene alkaline volcanism of the McMurdo Volcanic Group. Actually, volcanoclastic sediments and tephra found in other drill cores extend the history of alkaline volcanism back to 26 Ma (e.g. Sandroni & Talarico, Terra Antarctica, 2004) but late Eocene-Oligocene plutons and dikes occur only along the Northern Victoria Land (Rocchi et al., JGR, 2002). Therefore, these ages raise the issue of location of this magmatic source. According to petrographic and AFT data, main provenance is from the Mulock-Skelton Glacier area but the possible presence

  4. Sediment redox tracers in Strait of Georgia sediments--can they inform us of the loadings of organic carbon from municipal wastewater?

    PubMed

    Macdonald, R W; Johannessen, S C; Gobeil, C; Wright, C; Burd, B; van Roodselaar, A; Pedersen, T F

    2008-12-01

    Organic carbon composition and redox element (Mn, Cd, U, Re, Mo, SigmaS, AVS) distributions are examined in seven 210Pb-dated box cores collected from the Strait of Georgia, British Columbia to evaluate the potential for redox elements to reveal impacts of anthropogenic loadings of labile organic carbon to sediments. In particular, the cores have been collected widely including regions far from local anthropogenic inputs and from locations within the zone of influence of two municipal outfalls where sediments are exposed to enhanced organic loadings from outfalls. We find a wide natural range in organic carbon forcing within the basin sediments generally reflected as Mn enrichments near the surface in cores exhibiting slow organic oxidation and sulphide, Cd, Mo, U and Re enrichments in cores exhibiting higher organic oxidation rates. Concentration profiles for redox elements or organic carbon are misleading by themselves, as they are influenced strongly by sediment porosity and sedimentation rate, and the organic matter remaining in sediment cores is predominantly recalcitrant. Fluxes of redox elements together with rates of organic metabolism estimated from sedimentation rates provide a better picture of the organic forcing. One core, GVRD-3, collected within the zone of influence of the Iona municipal outfall (0.5 km away), exhibits the highest organic carbon oxidation rates, enhanced Ag fluxes in the sediment surface mixed layer and altered delta15N composition, all of which implicate outfall particulates. Cd is also elevated in the GVRD-3 surface sediments, but evidence points to contamination and not redox forcing supporting this observation. Uranium also shows enrichment at sites near the outfalls, possibly in response to enhanced microbial metabolism. Predominantly these cores exhibit a wide natural range of organic carbon fluxes and organic carbon oxidation rates, supported by fluxes of marine and terrigenous organic carbon, within which it is difficult to

  5. OSL dating as a possible tool for provenance study of fine grained quartz/polymineral from Lake Suigetsu sediments

    NASA Astrophysics Data System (ADS)

    Sugisaki, S.; Murray, A. S.; Buylaert, J.; Tada, R.; Suzuki, Y.; Nagashima, K.; Schwenninger, J.; Haraguchi, T.; Gotanda, K.; Nakagawa, T.

    2013-12-01

    Lake Suigetsu in central Japan is known for its unusually well-developed sequence of varved sediments. These were first drilled in 1993 (SG93), and in the second attempt in 2006 the first complete sediment profile (SG06) was successfully recovered (Nakagawa et al. 2012). Several dating methods including varve counting, radiocarbon dating, tephrochronology have been applied to the sediments and a robust age model developed that covers the last ~70 kyr (Bronk Ramsey et al., 2012, Staff et al., 2013). OSL dating has the potential to extend this age range beyond 70ka, a period in which other dating methods have of limited applicability. Since reliable OSL dating requires the dosimeter to be reset by exposure to sunlight before deposition, we have tried to identify the lithology that is dominated by well-reset sediment such as aeolian dust; this is most likely to be the most suitable material for OSL dating. During 2012, Lake Suigetsu was re-drilled and cores from the fourth hole were extruded under orange light to avoid loss of OSL signal. We started our study by selecting sections 2 and 5, taken from intervals corresponding to the late Holocene (499 × 8-837 ×13 SG06 2012 yr BP and 2653 × 40-3173 ×29 SG06 2012 yr BP, respectively, based on the SG06 age model). The sediments of late Holocene Lake Suigetsu are classified into 3 lithological types: 1) faintly laminated (varves) olive gray to dark gray clay; 2) light gray homogeneous clay; and 3) olive gray-reddish brown graded silty clay to clay . Layer types 2) and 3) are generally thicker than varves. Unfortunately, sediments in sections 2 and 5 are weakly to moderately mixed and preservation of lamination is generally poor. As a result it is sometimes difficult to identify the three types of lithologies. 18 samples were taken from sediments representing an olive gray to dark gray layer (probably corresponding to type 1) and from types 2 and 3 (presumed event layers). Quartz and polymineral material in the 4-11

  6. Developing inorganic carbon-based radiocarbon chronologies for Holocene lake sediments in arid NW China

    NASA Astrophysics Data System (ADS)

    Zhang, Jiawu; Ma, Xueyang; Qiang, Mingrui; Huang, Xiaozhong; Li, Shuang; Guo, Xiaoyan; Henderson, Andrew C. G.; Holmes, Jonathan A.; Chen, Fahu

    2016-07-01

    Inorganic carbonates are often used to establish radiocarbon (14C) chronologies for lake sediments when terrestrial plant remains (TPR) are rare or when bulk organic matter is insufficient for dating, a problem that is common for many lakes in arid regions. However, the reservoir effect (RE), as well as old carbon contributed from the lakes catchment make it difficult to establish reliable chronologies. Here we present a systematic study of inorganic 14C ages of two lake-sediment sequences, one from a small-enclosed saline lake - Lake Gahai in Qaidam Basin, and the other from a large freshwater lake - Lake Bosten in Xinjiang. Modern dissolved inorganic carbon (DIC) of the lakes, paleo-lake sediments exposed in the catchment, and mollusk shells in core sediments from Lake Gahai were dated to assess the RE and the contribution of pre-aged carbon to the old ages in the cores. We propose a statistical regression to assess more than one RE for the 14C carbonate ages within our sedimentary sequences. Old radiocarbon ages contributed by detrital carbonates were assessed by comparing the ages of mollusk shells with those of carbonates at the same sediment depths. We established the RE of the authigenic component and assessed detrital old carbon contributions to our two sites, and this was used to correct the 14C ages. Based on this approach, we developed age models for both cores, and tested them using 210Pb ages in both cores and TPR-based 14C-ages recovered from Lake Bosten. We further tested our age models by comparing carbonate-based oxygen isotope (δ18O) records from both lakes to an independently-dated regional speleothem δ18O record. Our results suggest if sedimentary sequences are densely dated and the RE and the contribution of old carbon from detrital carbonates can be ascertained, robust chronological frameworks based on carbonate-based 14C determinations can be established.

  7. Timing of degassing and plagioclase growth in lavas erupted from Mount St. Helens, 2004-2005, from 210Po-210Pb-226Ra disequilibria: Chapter 37 in A volcano rekindled: the renewed eruption of Mount St. Helens, 2004-2006

    USGS Publications Warehouse

    Reagan, Mark K.; Cooper, Kari M.; Pallister, John S.; Thornber, Carl R.; Wortel, Matthew; Sherrod, David R.; Scott, William E.; Stauffer, Peter H.

    2008-01-01

    Disequilibrium between 210Po, 210Pb, and 226Ra was measured on rocks and plagioclase mineral separates erupted during the first year of the ongoing eruption of Mount St. Helens. The purpose of this study was to monitor the volatile fluxing and crystal growth that occurred in the weeks, years, and decades leading up to eruption. Whole-rock samples were leached in dilute HCl to remove 210Po precipitated in open spaces. Before leaching, samples had variable initial (210Po) values, whereas after leaching, the groundmasses of nearly all juvenile samples were found to have had (210Po) ≈ 0 when they erupted. Thus, most samples degassed 210Po both before and after the magmas switched from open- to closed-system degassing. All juvenile samples have (210Pb)/(226Ra) ratios within 2 δ of equilibrium, suggesting that the magmas involved in the ongoing eruption did not have strong, persistent fluxes of 222Rn in or out of magmas during the decades and years leading to eruption. These equilibrium values also require a period of at least a century after magma generation and the last significant differentiation of the Mount St. Helens dacites. Despite this, the elevated (210Pb)/(226Ra) value measured in a plagioclase mineral separate from lava erupted in 2004 suggests that a significant proportion of this plagioclase grew within a few decades of eruption. The combined dataset suggests that for most 2004-5 lavas, the last stage of open-system degassing of the dacite magmas at Mount St. Helens is confined to the period between 1-2 years and 1-2 weeks before eruption, whereas plagioclase large enough to be included in the mineral separate grew around the time of the 1980s eruption or earlier.

  8. Chronology of sediment deposition in Upper Klamath Lake, Oregon

    USGS Publications Warehouse

    Colman, Steven M.; Bradbury, J.P.; McGeehin, J.P.; Holmes, C.W.; Edginton, D.; Sarna-Wojcicki, A. M.

    2004-01-01

    A combination of tephrochronology and 14C, 210Pb, and 137Cs measurements provides a robust chronology for sedimentation in Upper Klamath Lake during the last 45 000 years. Mixing of surficial sediments and possible mobility of the radio-isotopes limit the usefulness of the 137Cs and 210Pb data, but 210Pb profiles provide reasonable average sediment accumulation rates for the last 100-150 years. Radiocarbon ages near the top of the core are somewhat erratic and are too old, probably as a result of detrital organic carbon, which may have become a more common component in recent times as surrounding marshes were drained. Below the tops of the cores, radiocarbon ages in the center of the basin appear to be about 400 years too old, while those on the margin appear to be accurate, based on comparisons with tephra layers of known age. Taken together, the data can be combined into reasonable age models for each site. Sediments have accumulated at site K1, near the center of the basin, about 2 times faster than at site CM2, on the margin of the lake. The rates are about 0.10 and 0.05 cm/yr, respectively. The chronological data also indicate that accumulation rates were slower during the early to middle Holocene than during the late Holocene, consistent with increasing wetness in the late Holocene.

  9. Impact of a river system on carbon sedimentation and sequestration in Cook's Bay of Lake Simcoe, Ontario

    NASA Astrophysics Data System (ADS)

    Blodau, Christian; Agethen, Svenja; Spangenberg, Ines; Broder, Tanja; Gimbel, Nicole; Strauss, Harald; Knorr, Klaus-Holger

    2016-04-01

    The influence of sedimentation rates and organic matter quality on carbon sequestration and mineralization at the land-water interface of lakes is not well understood. To study this issue we investigated shallow Cook's Bay of temperate Lake Simcoe in southern Ontario. The elongated bay provides gradients in morphometry, trophic level, and distance to a major tributary as a potential point source of nutrients and terrestrial organic carbon. At five sampling sites of increasing distance to the river outlet the water column was examined during stratification regarding physio-chemical parameters, dissolved organic matter (DOM) characteristics, sedimentation rates and mineralization of settling material and sediments. To quantify actual organic carbon burial, sedimentation rates and mineralization were determined in situ and by diffusive flux modeling. Long-term carbon burial and sedimentation rates were determined using 210Pb dated sediment cores. Organic carbon quality and origin were analyzed in water samples via fluorescence spectroscopy, solid DOM and settling particles via elemental analysis and 13C isotopic data. Results showed that actual and long-term carbon burial were highest at the central sites of the transect (52-63%) and lowest at the profundal sites (0-25%). Current organic carbon deposition was highest near the river outlet (max. 0.3 g C m-2 d-1) and there the settling material reaching the sediments and in the sediments was also most highly decomposable. Total sedimentation rates and organic carbon burial were closely related. Compared to the outer sites, the DOM quality was significantly different at the site closest to the river outlet but already strongly influenced by lacustrine carbon cycling. Permanent organic carbon burial was mainly influenced by sedimentation related to lake morphometry and dependent parameters. The relation between sedimentation and carbon burial rates underlined the importance of oxygen exposure time and burial for

  10. Sediment carbon sink in low-density temperate eelgrass meadows (Baltic Sea)

    NASA Astrophysics Data System (ADS)

    Jankowska, Emilia; Michel, Loïc. N.; Zaborska, Agata; Włodarska-Kowalczuk, Maria

    2016-12-01

    Seagrass meadows are highly productive habitats that can act as "blue carbon sinks" in coastal ecosystems by facilitating sedimentation and trapping particles. However, the magnitude and occurrence of these effects may be species and density dependent. The present study is the first estimation of seagrass sediment carbon sink in the temperate Zostera marina beds in the Baltic Sea. Several descriptors of organic matter characteristics, along with possible organic matter sources in the sediment were compared at vegetated and unvegetated bottoms. The 210Pb dating of the sediment has been used for accumulation rate assessment. The photopigments and POC concentrations in sediments were higher in vegetated bottoms. The SIAR (Stable Isotopes in R) mixing model based on nitrogen and carbon stable isotope values, indicated that higher percentages of organic matter originated from seagrass production in vegetated sediments (40-45%) compared to unvegetated ones (5-21%). The carbon stock in the upper 10 cm of the vegetated sediments ranged from 50.2 ± 2.2 to 228.0 ± 11.6 (g m-2), whereas the annual C accumulation amount from 0.84 ± 0.2 to 3.85 ± 1.2 (g m-2 yr-1). Our study shows that even the relatively weakly developed vegetation of the small temperate seagrass species enhance organic carbon concentration in the sediments. Estimated carbon stock was much lower than those reported for most of the seagrass meadows elsewhere, and the carbon burial rate was the lowest ever reported. Evidently, the global calculations of sediment carbon stock should be reconsidered by taking into account density and species-related variability.

  11. Magnitude and variability of Holocene sediment accumulation in Santa Monica Bay, California

    USGS Publications Warehouse

    Sommerfield, C.K.; Lee, H.J.

    2003-01-01

    The spatial variability of Holocene (past 10,000 years) sediment accumulation in Santa Monica Bay (California) was examined to identify controls sediment trapping in a bathymetrically complex coastal embayment and to provide geologic context for the post-industrial sedimentary record and associated pollution gradients. Sediment chronologies based on downcore AMS 14C dates were used to quantify long-term (millennia) accumulation rates in an effort to elucidate particle-transport pathways and sinks. Sediment accumulation rates for the full range of bayfloor environments (50-630 m water depths) range from 22 to 102 mg/cm2/year (15-88 mm/100 year), have an overall mean of 51??21 mg/cm2/year (1??, n=11), and are comparable to rates reported for adjacent borderland basins. Maximal accumulation rates on the Malibu shelf and within a reentrant to Redondo canyon are interpreted to reflect (1) proximity to sediment sources and (2) localized oceanographic and topographic conditions conducive to sediment trapping and deposition. The 14C-derived accumulation rates are 2-10 times lower than rates determined through 210Pb geochronology for the same sites in a related study, revealing that Holocene sediment accumulation has been non-steady-state. Santa Monica Bay is an important sink for suspended matter; averaged over the past several millennia a mass of sediment equivalent to 10-80% of the modern annual river supply is sequestered yearly. Net influx of suspended matter derived from the adjacent Palos Verdes shelf is evinced by a concentration gradient of p,p???-DDE in bayfloor sediments, whereas the distribution of anthropogenic silver suggests transport from Santa Monica shelf to the southeastern boundary of the bay. The results of this study provide new insight to the long-term fates of particulate matter in Los Angeles coastal waters. ?? 2003 Elsevier Science Ltd. All rights reserved.

  12. Certified reference materials for radionuclides in Bikini Atoll sediment (IAEA-410) and Pacific Ocean sediment (IAEA-412).

    PubMed

    Pham, M K; van Beek, P; Carvalho, F P; Chamizo, E; Degering, D; Engeler, C; Gascó, C; Gurriaran, R; Hanley, O; Harms, A V; Herrmann, J; Hult, M; Ikeuchi, Y; Ilchmann, C; Kanisch, G; Kis-Benedek, G; Kloster, M; Laubenstein, M; Llaurado, M; Mas, J L; Nakano, M; Nielsen, S P; Osvath, I; Povinec, P P; Rieth, U; Schikowski, J; Smedley, P A; Suplinska, M; Sýkora, I; Tarjan, S; Varga, B; Vasileva, E; Zalewska, T; Zhou, W

    2016-03-01

    The preparation and characterization of certified reference materials (CRMs) for radionuclide content in sediments collected offshore of Bikini Atoll (IAEA-410) and in the open northwest Pacific Ocean (IAEA-412) are described and the results of the certification process are presented. The certified radionuclides include: (40)K, (210)Pb ((210)Po), (226)Ra, (228)Ra, (228)Th, (232)Th, (234)U, (238)U, (239)Pu, (239+240)Pu and (241)Am for IAEA-410 and (40)K, (137)Cs, (210)Pb ((210)Po), (226)Ra, (228)Ra, (228)Th, (232)Th, (235)U, (238)U, (239)Pu, (240)Pu and (239+240)Pu for IAEA-412. The CRMs can be used for quality assurance and quality control purposes in the analysis of radionuclides in sediments, for development and validation of analytical methods and for staff training.

  13. Reconstruction of metal pollution and recent sedimentation processes in Havana Bay (Cuba): a tool for coastal ecosystem management.

    PubMed

    Díaz-Asencio, M; Alvarado, J A Corcho; Alonso-Hernández, C; Quejido-Cabezas, A; Ruiz-Fernández, A C; Sanchez-Sanchez, M; Gómez-Mancebo, M B; Froidevaux, P; Sanchez-Cabeza, J A

    2011-11-30

    Since 1998 the highly polluted Havana Bay ecosystem has been the subject of a mitigation program. In order to determine whether pollution-reduction strategies were effective, we have evaluated the historical trends of pollution recorded in sediments of the Bay. A sediment core was dated radiometrically using natural and artificial fallout radionuclides. An irregularity in the (210)Pb record was caused by an episode of accelerated sedimentation. This episode was dated to occur in 1982, a year coincident with the heaviest rains reported in Havana over the XX century. Peaks of mass accumulation rates (MAR) were associated with hurricanes and intensive rains. In the past 60 years, these maxima are related to strong El Niño periods, which are known to increase rainfall in the north Caribbean region. We observed a steady increase of pollution (mainly Pb, Zn, Sn, and Hg) since the beginning of the century to the mid 90 s, with enrichment factors as high as 6. MAR and pollution decreased rapidly after the mid 90 s, although some trace metal levels remain high. This reduction was due to the integrated coastal zone management program introduced in the late 90 s, which dismissed catchment erosion and pollution.

  14. Hard-water dynamics and their reservoir effects on radiocarbon dating of Lake Heihai sediments (NE Tibetan Plateau, Qinghai, China)

    NASA Astrophysics Data System (ADS)

    Lockot, Gregori; Hartmann, Kai; Wünnemann, Bernd; Ramisch, Arne; Diekmann, Bernhard

    2014-05-01

    Age determination of lake sediments with radiocarbon dating can always entail a perturbation with hard water. Atmospheric carbon (expressing the "real" ages) can be mixed with older carbon from allochthonous input (e.g. marl or limestone), causing an overestimation of 14C ages. The usual approach to eliminate this effect is to date living plants or shells to determine the modern offset in age. Subsequently, this offset is subtracted from 14C ages of a sediment core to attain hard water corrected ages. However, this approach assumes a constant hard water effect over the entire period under consideration, which generally is unlikely. Here we present a highly variable hard water effect through time determined from a combined chronology of two long sediment cores from Lake Heihai (NE Tibetan Plateau). The chronology is based on 20 14C AMS dates of Potamogeton spec. Based on the relation between 14C ages and the input of allochthonous carbonates as well as calculated sedimentation rates, we developed an age-depth-model that estimates the actual ages of the sediments and allows the quantification of hard water effect through time. As a result this model suggests a fluctuating hard water effect varying between 102 to 103 ka. Ages in the lower 3 meter of the core, which corresponds to late glacial times, strongly correlate with the input of dolomite (CaMg(CO3)2). The correlation suggests a strong linkage between the allochthonous input of old carbon and the variations in dating results. In this section, the estimated hard water effect shows its highest values. Results of XRD, grain size and pollen data confirm a shallow lake with high rates of detrital input. The Late Glacial - Holocene transition to warmer and wetter conditions is marked by prominent changes in the mineralogy of lacustrine carbonates and the composition of pollen taxa. During this time the lake constantly rose and increasingly buffered the influence of allochthonous carbonates. The episode is

  15. Mercury in sediments of Ulhas estuary.

    PubMed

    Ram, Anirudh; Rokade, M A; Borole, D V; Zingde, M D

    2003-07-01

    Hg levels in water, suspended particulate matter and sediment of the Ulhas estuary are under considerable environmental stress due to the indiscriminate release of effluents from a variety of industries including chlor-alkali plants. Concentration ranges of dissolved (0.04-0.61 micro gl(-1)) and particulate (1.13-6.43 micro gg(-1)) Hg reveal a definite enhancement of levels in the estuary. The Hg burden in sediment upstream of the weir that limits the tidal influence is low (0.08-0.19 micro gg(-1)) with low C(org) content (1.8-2.9%). The high Hg content of the sediment just below the weir varies seasonally (highest concentration recorded being 38.45 micro gg(-1)) due to incremental accretion of sediment as the fresh water flow over the weir progressively decreases. The 30 km segment of the estuary sustains markedly high levels of Hg in the sediment with an exponential decrease in the seaward direction from the weir. Higher concentrations than the expected background prevail in all the estuarine cores up to the bottom, though the overall concentration decreases from about 20 micro gg(-1) in core 7 (inner estuary) to 1 micro gg(-1) in core 31 (outer estuary). The Hg in sediment is associated with C(org), while its correlation with Al, Fe and Mn is poor. The Hg profiles in cores from the Arabian Sea (stations 34, 35 and 37) have a distinct horizon of enhanced concentration in the 5-60 cm segment. Based on 210Pb dating of core 37, the sediment at the bottom of this core is inferred to have been deposited in the year 1949, roughly two year prior to the establishment of the first chlor-alkali plant and represents the background (0.06-0.10 micro gg(-1)). The Hg profiles in the offshore cores indicate a marked increase in transfer of Hg to sediment subsequent to 1980, with a peak around 1990-1992. Based on the index of geoaccumulation it is considered that the estuarine segment between stations 4 and 23 is extremely polluted, while the sediment from the open coast is

  16. Impact of Bottom Trawling on Deep-Sea Sediment Properties along the Flanks of a Submarine Canyon

    PubMed Central

    Martín, Jacobo; Puig, Pere; Masqué, Pere; Palanques, Albert; Sánchez-Gómez, Anabel

    2014-01-01

    The offshore displacement of commercial bottom trawling has raised concerns about the impact of this destructive fishing practice on the deep seafloor, which is in general characterized by lower resilience than shallow water regions. This study focuses on the flanks of La Fonera (or Palamós) submarine canyon in the Northwestern Mediterranean, where an intensive bottom trawl fishery has been active during several decades in the 400–800 m depth range. To explore the degree of alteration of surface sediments (0–50 cm depth) caused by this industrial activity, fishing grounds and control (untrawled) sites were sampled along the canyon flanks with an interface multicorer. Sediment cores were analyzed to obtain vertical profiles of sediment grain-size, dry bulk density, organic carbon content and concentration of the radionuclide 210Pb. At control sites, surface sediments presented sedimentological characteristics typical of slope depositional systems, including a topmost unit of unconsolidated and bioturbated material overlying sediments progressively compacted with depth, with consistently high 210Pb inventories and exponential decaying profiles of 210Pb concentrations. Sediment accumulation rates at these untrawled sites ranged from 0.3 to 1.0 cm y−1. Sediment properties at most trawled sites departed from control sites and the sampled cores were characterized by denser sediments with lower 210Pb surface concentrations and inventories that indicate widespread erosion of recent sediments caused by trawling gears. Other alterations of the physical sediment properties, including thorough mixing or grain-size sorting, as well as organic carbon impoverishment, were also visible at trawled sites. This work contributes to the growing realization of the capacity of bottom trawling to alter the physical properties of surface sediments and affect the seafloor integrity over large spatial scales of the deep-sea. PMID:25111298

  17. An alternative radiometric method for calculating the sedimentation rates: application to an intertidal region (SW of Spain).

    PubMed

    Ligero, R A; Casas-Ruiz, M; Barrera, M; Barbero, L; Meléndez, M J

    2010-09-01

    A new method using the inventory determined for the activity of the radionuclide (137)Cs, coming from global radioactive fallout has been utilised to calculate the sedimentation rates. The method has been applied in a wide intertidal region in the Bay of Cádiz Natural Park (SW Spain). The sedimentation rates estimated by the (137)Cs inventory method ranged from 0.26 cm/year to 1.72 cm/year. The average value of the sedimentation rate obtained is 0.59 cm/year, and this rate has been compared with those resulting from the application of the (210)Pb dating technique. A good agreement between the two procedures has been found. From the study carried out, it has been possible for the first time, to draw a map of sedimentation rates for this zone where numerous physico-chemical, oceanographic and ecological studies converge, since it is situated in a region of great environmental interest. This area, which is representative of common environmental coastal scenarios, is particularly sensitive to perturbations related to climate change, and the results of the study will allow to make short and medium term evaluations of this change.

  18. A comprehensive study on water balance, sedimentation and physico-chemical characteristics of Sagar Lake in India.

    PubMed

    Singh, Surjeet; Kumar, Bhishm; Thakural, L N; Galkate, Ravi

    2009-01-01

    In this study, an attempt has been made to work out water balance, determine rate of sedimentation and physico-chemical analysis of the lake water. The water balance is carried out using the mass balance equation to account for various input and output components. Sedimentation rates and pattern are estimated using (137)Cs and (210)Pb radiometric dating techniques. The physico-chemical analysis of the lake water is done by collecting samples from twelve locations of the lake at three different depths. The major inflow to the lake is catchment runoff, which accounts for nearly 56% of the total annual inflow and about 98% inflow takes place during monsoon period. The major outflow from the lake is weir overflow, which occurs in monsoon season only and accounts for about 85% of the total annual outflow. The estimated mean sedimentation rate in the lake is 0.58 +/- 0.028 cm/year. The estimated useful life of the lake based on post-1964 (appearance of the major peak of (137)Cs due to weapon fallout record pattern) average sedimentation rate is around 467 +/- 23 years. The lake has attained the hyper-eutrophic state due to high nitrogen and phosphorous contents in the lake water. Based on the trophic state index (TSI), the lake has become unsuitable for drinking, bathing and even for fish culture.

  19. Late Holocene sedimentation in coastal areas of the northwestern Ross Sea (Antarctica)

    NASA Astrophysics Data System (ADS)

    Colizza, Ester; Finocchiaro, Furio; Kuhn, Gerhard; Langone, Leonardo; Melis, Romana; Mezgec, Karin; Severi, Mirko; Traversi, Rita; Udisti, Roberto; Stenni, Barbara; Braida, Martina

    2013-04-01

    Sediment cores and box cores collected in two coastal areas of the northwestern Ross Sea (Antarctica) highlight the possibility of studying the Late Holocene period in detail. In this work we propose a study on two box cores and two gravity cores collected in the Cape Hallett and Wood Bay areas during the 2005 PNRA oceanographic cruise. The two sites are feed by Eastern Antarctic Ice Shelf (EAIS) and previous studies have highlighted a complex postglacial sedimentary sequence, also influenced by local morphology. This study is performed within the framework of the PNRA-ESF PolarCLIMATE HOLOCLIP (Holocene climate variability at high-southern latitudes: an integrated perspective) Project. The data set includes: magnetic susceptibility, X-ray analyses, 210Pb, 14C dating, diatoms and foraminifera assemblages, organic carbon, and grain-size analyses. Furthermore XRF core scanner analyses, colour analysis from digital images, and major, minor and trace element concentration analyses (ICP-AES) are performed. Data show that the box core and upper core sediments represent a very recent sedimentation in which it is possible to observe the parameter variability probably linked to climate variability/changes: these variation will be compared with isotopic record form ice cores collected form the same Antarctic sector.

  20. Hydrological variability for the last two millennia: palynological and organic proxies extracted from lacustrine sediments of Lake Dahu, northeastern subtropical Taiwan

    NASA Astrophysics Data System (ADS)

    Yang, T.; Zeng, F.; Wang, L.; Huh, C.; Lee, T.; Chan, Y.; Meyers, P. A.; Lee, M.; Chen, S.; Wu, J.; Wei, K.; Chen, Y.

    2009-12-01

    Hydrological variability inferred from palynological composition and organic proxies extracted from a sediment core of Lake Dahu, northeastern subtropical Taiwan is presented for the last two millennia. The lake is situated at the foot of northeastern Shuehshan Range and the northwestern margin of Ilan Plain, an alluvial fan, which is formed by Lanyang River. The age model is figured by 210Pb and 4 14C dates for the ~12 m lacustrine sediment core. Two modes of sedimentation are distinguishable. During 0-1400 AD, high sedimentation rate (~0.8 cm/year) and content of spores and in association with several layers containing fine sands and silts existed, while low pollen abundance and organic matters, and rare Pediastrum. Massive suspension accompanying with high frequency of flood from Lanyang River were deposited in the Lake Dahu in the period. On the contrary, decrease of sedimentation rate and spores happened, whereas increasing abundance of pollens, Pediastrum, and organic materials since 1400 AD. Primary productivity might be raised since 1700 AD. An enriched trend in 13C in organic matters is witnessed during interval 1700-1900 AD, thereafter depleting in 13C till the contemporary age. It is suggested that high primary productivity coinciding with less negative signatures of delta 13C were resulted from strong lake water mixing triggered by strengthening East Asian winter monsoon during the Little ice Age. While the depleting trend is indicative of the Suess effect, dilution of the atmospheric 13CO2 by fossil-fuel derived carbon dioxide.

  1. Radiocarbon dating Arctic deep marine sediment to refine the usage of Mn pattern as a stratigraphic tool

    NASA Astrophysics Data System (ADS)

    Chiu, Pin-Yao Bernie; Löwemark, Ludvig

    2016-04-01

    The distinctive pattern of Mn content in Arctic deep marine sediment has been used as a proxy to indicate glacial-interglacial cyclicity (Löwemark et al., 2014). As has been observed in many sediment cores, Mn peaks correspond to warm interglacial periods. In order to improve the preciseness of Mn pattern as a proxy, we collected the foraminifera Neogloboquadrina pachyderma (sinistral) from brownish, Mn-rich layers, and performed radiocarbon dating on selected cores collected during the LOMROG07, LOMROG09 and LOMROG12 expeditions. Additional cores form the YMER and AO96 expeditions are also included. Based on our general understanding of the Mn system in the Arctic Ocean, we predicted a Mn pattern with a high peak in the uppermost core top, representing the Holocene. This Holocene peak in Mn is separated from the underlying warm period MIS 3 by a Mn-poor interval also characterized by a drop in Ca. This Mn and Ca poor interval reperesents MIS 2 and the LGM. Older warm periods, such as MIS 3, 5, 7 etc will display a similar pattern with distinct Mn peaks, separated by Mn minima representing cold iperiods For example, the MIS 5 sometimes shown a distinct pattern with three Mn peaks representing MIS 5a, 5c and 5e. However, there are still some limitations in the applicability of Mn stratigraphy, such as the remobilization of the Mn layer and the core-top loss during coring. We performed AMS carbon 14 dating on more than 10 cores, and the result revealed several cases of lost core tops, leading to depletion or complete loss of the Holocene interval. In several cores, our AMS dating revealed a hiatus in the MIS2 interval. The complete lack of MIS2 sediment likely is the result of extremely slow sedimentation rate due to severe sea ice conditions, while places with records of LGM may be the result of polynyas within the sea ice, or certain circulation pattern. Consequently, although Mn pattern can be used as a preliminary tool to identify glacial-interglacial cycles

  2. Exploring the use of paleomagnetic secular variations to date young sediments from the hardwater lake Tangra Yumco (Tibet)

    NASA Astrophysics Data System (ADS)

    Haberzettl, T.; Kasper, T.; Long, H.; Su, Y.; Ahlborn, M.; Appel, E.; Daut, G.; Henkel, K.; St-Onge, G.; Wang, J.; Zhu, L.; Maeusbacher, R.

    2013-12-01

    Magnetostratigraphy has been serving as a valuable tool for dating and confirming chronologies of lacustrine sediments. Although the coverage of suitable paleomagnetic records on the Tibetan Plateau (TP) and around has been extremely scarce, recently emerging records enable a validation of existing age-depth models using magnetostratigraphy. This is very important, since almost all radiocarbon ages obtained from lacustrine sediments on the TP are affected by a reservoir effect. For example at Nam Co (co = lake) on the eastern TP the chronology for the past 4 ka cal BP was supported by the comparison of paleomagnetic secular variation (PSV) and results from spherical harmonic geomagnetic field models. In addition, this approach was confirmed by comparison of the directional data of Nam Co to a varved record from the Makran accretionary wedge which is much further to the south-west but shows remarkable similarities. Here we present PSV data from multiple sediment cores from lake Tangra Yumco, located ~400 km west of Nam Co. Inclination and declination data from the different sediment cores are very similar, but only one core has been sufficiently dated yet. Unfortunately, validation of the reservoir corrected radiocarbon based age scale from this core is very poor although it contains one age from a part of wood (which because of its terrestrial nature was not reservoir corrected). On this chronology, the Tangra Yumco PSV data shows neither similarities with the Nam Co record, nor with geomagnetic field model outputs. Interestingly, if the chronology from Tangra Yumco is tuned to the chronology of the validated Nam Co record using inclination data, the minerogenic input proxies become almost identical. The minerogenic input is indicative of runoff and hence hydrological variations due to changes in the monsoon strength. Very similar hydrological variations can also be observed in the independently-dated Hongyuan peat bog (further to the north-east) which suggests

  3. Time-averaged fluxes of lead and fallout radionuclides to sediments in Florida Bay

    USGS Publications Warehouse

    Robbins, J.A.; Holmes, C.; Halley, R.; Bothner, M.; Shinn, E.; Graney, J.; Keeler, G.; TenBrink, M.; Orlandini, K.A.; Rudnick, D.

    2000-01-01

    Recent, unmixed sediments from mud banks of central Florida Bay were dated using 210Pb/226Ra, and chronologies were verified by comparing sediment lead temporal records with Pb/Ca ratios in annual layers of coral (Montastrea annularis) located on the ocean side of the Florida Keys. Dates of sediment lead peaks (1978 ?? 2) accord with prior observations of a 6 year lag between the occurrence of maximum atmospheric lead in 1972 and peak coral lead in 1978. Smaller lags of 1-2 years occur between the maximum atmospheric radionuclide fallout and peaks in sediment temporal records of 137Cs and Pu. Such lags are consequences of system time averaging (STA) in which atmospherically delivered particle-associated constituents accumulate and mix in a (sedimentary?) reservoir before transferring to permanent sediments and coral. STA model calculations, using time-dependent atmospheric inputs, produced optimized profiles in excellent accord with measured sediment 137Cs, Pu, lead, and coral lead distributions. Derived residence times of these particle tracers (16 ?? 1, 15.7 ?? 0.7, 19 ?? 3, and 16 ?? 2 years, respectively) are comparable despite differences in sampling locations, in accumulating media, and in element loading histories and geochemical properties. For a 16 year weighted mean residence time, STA generates the observed 6 year lead peak lag. Evidently, significant levels of nondegradable, particle-associated contaminants can persist in Florida Bay for many decades following elimination of external inputs. Present results, in combination with STA model analysis of previously reported radionuclide profiles, suggest that decade-scale time averaging may occur widely in recent coastal marine sedimentary environments. Copyright 2000 by the American Geophysical Union.

  4. The importance of radiocarbon dates and tephra for developing chronologies of Holocene environmental changes from lake sediments, North Far East

    DOE PAGES

    Lozhkin, Anatoly V.; Brown, Thomas A.; Anderson, Patricia M.; ...

    2016-08-12

    One problem with developing continuous chronologies of paleoenvironmental change in northern areas of the Far East using 14C is the low organic content in lake sediments. However, Holocene age-models can be supplemented by widespread tephra deposits reported in the Magadan region. The best documented of these tephras has been correlated to the KO tephra from southern Kamchatka dated to 7600 BP. Though a key chronostratigraphic marker, no detailed compendium of the distribution of this tephra and its associated 14C dates has been available from sites in the northern Far East. We provide such a summary. Known locally as the Elikchanmore » tephra, lake cores indicate an ash fall that extended ~1800 km north of the Kamchatkan caldera with a ~500 km wide trajectory in the Magadan region. Other Holocene tephras preserved in lake sediments have poorer age control and possibly date to ~2500 BP, ~2700 BP and ~6000 BP. These ashes seem to be restricted to coastal or near-coastal sites. Finally, a single record of a ~25,000 BP tephra has also been documented ~100 km to the northeast of Magadan.« less

  5. The importance of radiocarbon dates and tephra for developing chronologies of Holocene environmental changes from lake sediments, North Far East

    SciTech Connect

    Lozhkin, Anatoly V.; Brown, Thomas A.; Anderson, Patricia M.; Glushkova, Olga Yu; Melekestsev, Ivan V.

    2016-08-12

    One problem with developing continuous chronologies of paleoenvironmental change in northern areas of the Far East using 14C is the low organic content in lake sediments. However, Holocene age-models can be supplemented by widespread tephra deposits reported in the Magadan region. The best documented of these tephras has been correlated to the KO tephra from southern Kamchatka dated to 7600 BP. Though a key chronostratigraphic marker, no detailed compendium of the distribution of this tephra and its associated 14C dates has been available from sites in the northern Far East. We provide such a summary. Known locally as the Elikchan tephra, lake cores indicate an ash fall that extended ~1800 km north of the Kamchatkan caldera with a ~500 km wide trajectory in the Magadan region. Other Holocene tephras preserved in lake sediments have poorer age control and possibly date to ~2500 BP, ~2700 BP and ~6000 BP. These ashes seem to be restricted to coastal or near-coastal sites. Finally, a single record of a ~25,000 BP tephra has also been documented ~100 km to the northeast of Magadan.

  6. Examining offshore sediment-hosted contaminant transport from Hurricane Katrina: Chapter 7A in Science and the storms-the USGS response to the hurricanes of 2005

    USGS Publications Warehouse

    Swarzenski, Peter W.; Campbell, Pamela L.; Poore, Richard Z.; Osterman, Lisa E.; Rosenbauer, Robert J.

    2007-01-01

    A rapid-response expedition was organized after the passage of Hurricane Katrina to investigate potential offshore environmental impacts and storm-induced sediment-transport processes. Both water-column and sediment samples were collected on the Louisiana shelf for a full complement of organic, inorganic, and geochronological tracers. Based on excess lead-210 (210Pb) inventories in cores collected before and after Katrina, the surface sediments and their associated geochemical signatures were considerably affected by the passage of this storm.

  7. Assessment of sediments in the riverine impoundments of national wildlife refuges in the Souris River Basin, North Dakota

    USGS Publications Warehouse

    Tangen, Brian A.; Laubhan, Murray K.; Gleason, Robert A.

    2014-01-01

    Accelerated sedimentation of reservoirs and riverine impoundments is a major concern throughout the United States. Sediments not only fill impoundments and reduce their effective life span, but they can reduce water quality by increasing turbidity and introducing harmful chemical constituents such as heavy metals, toxic elements, and nutrients. U.S. Fish and Wildlife Service national wildlife refuges in the north-central part of the United States have documented high amounts of sediment accretion in some wetlands that could negatively affect important aquatic habitats for migratory birds and other wetland-dependent wildlife. Therefore, information pertaining to sediment accumulation in refuge impoundments potentially is important to guide conservation planning, including future management actions of individual impoundments. Lands comprising Des Lacs, Upper Souris, and J. Clark Salyer National Wildlife Refuges, collectively known as the Souris River Basin refuges, encompass reaches of the Des Lacs and Souris Rivers of northwestern North Dakota. The riverine impoundments of the Souris River Basin refuges are vulnerable to sedimentation because of the construction of in-stream dams that interrupt and slow river flows and because of post-European settlement land-use changes that have increased the potential for soil erosion and transport to rivers. Information regarding sediments does not exist for these refuges, and U.S. Fish and Wildlife Service personnel have expressed interest in assessing refuge impoundments to support refuge management decisions. Sediment cores and surface sediment samples were collected from impoundments within Des Lacs, Upper Souris, and J. Clark Salyer National Wildlife Refuges during 2004–05. Cores were used to estimate sediment accretion rates using radioisotope (cesium-137 [137Cs], lead-210 [210Pb]) dating techniques. Sediment cores and surface samples were analyzed for a suite of elements and agrichemicals, respectively. Examination of

  8. Post-depositional remanent magnetization lock-in depth in precisely dated varved sediments assessed by archaeomagnetic field models

    NASA Astrophysics Data System (ADS)

    Mellström, Anette; Nilsson, Andreas; Stanton, Tania; Muscheler, Raimund; Snowball, Ian; Suttie, Neil

    2015-01-01

    Accurate and precise chronologies are needed to evaluate the existence and effect of a post-depositional remanent magnetization lock-in process on sedimentary palaeomagnetic records. Here we present lock-in modelling results of two palaeomagnetic records from varved lake sediments (lakes Kälksjön and Gyltigesjön) in Sweden by using model predictions based on archaeomagnetic data. We used the 14C wiggle-match dating technique to improve the precision of the Kälksjön varve chronology in the period between 3000 and 2000 cal BP, which is characterized by pronounced palaeomagnetic secular variation. This method allowed us to infer an age model with uncertainties of ±20 years (95.4% probability range). Furthermore, we compared the palaeomagnetic record of Kälksjön to Gyltigesjön, which has a corresponding 14C wiggle-matched chronology. The ages of palaeomagnetic features derived from the wiggle-matched varve chronologies are older than those predicted by the archaeomagnetic models. Lock-in modelling was performed with different filter functions to explain the temporal offset and the amplitude of the lake sediment palaeomagnetic data. The analyses suggest that a linear lock-in function with lock-in depths (the depth below which no more natural magnetic remanence is acquired) that range between 30 and 80 cm in Kälksjön and 50 and 160 cm in Gyltigesjön are most appropriate to explain the data. These relatively deep lock-in depths in sediments without a bioturbated 'mixed-zone' can be attributed to the relatively high organic contents and low density of the lake sediments, which contribute to a thick unconsolidated upper zone of the sediment sequence in which re-alignment of magnetic particles can take place.

  9. Natural rates of sediment containment of PAH, PCB and metal inventories in Sydney Harbour, Nova Scotia.

    PubMed

    Smith, J N; Lee, K; Gobeil, C; Macdonald, R W

    2009-08-15

    Analyses of metal and organic contaminants were carried out on 41 sediment cores, dated using (210)Pb and (137)Cs, from the heavily industrialized region of Sydney Harbour, N.S. to evaluate the history of contamination and to predict the rates of natural containment of the harbour by sediment burial. Geochronologies for metals (eg. Pb, As) and polycyclic aromatic hydrocarbons (PAHs) are correlated with the development of the steel and coke industries in the Sydney region while polychlorinated biphenyl (PCB) geochronologies reflect the disposal of electrical equipment used in the steel mill/coking operations. Pb was derived mainly from atmospheric emissions and its concentration has declined exponentially with time in harbour sediments since the closure of the steel mill/coke ovens in the 1980s with a time constant of about 15 years. This represents the time scale for the circulation of this particle-associated contaminant in transient catchment basins prior to permanent deposition in the sediments. PAH and PCB sediment concentrations have also declined exponentially with time since the 1980s, but with a smaller time constant of 10 years owing to the fact that they enter the harbour directly with steel mill and coke oven effluent rather than through atmospheric pathways. Since the time dependence for the burial of metal and organic inventories can be modeled by first order processes, future contaminant levels can be predicted for surface sediments in Sydney Harbour. Mean sediment concentrations of metal and organic contaminants in the upper 5 cm throughout most of the harbour are predicted to decline to levels below the effects range-medium (above which organisms are very likely to be negatively affected by the presence of a contaminant) by 2030.

  10. Holocene environment changes around the Sara Us River, northern China, revealed by optical dating of lacustrine-aeolian sediments

    NASA Astrophysics Data System (ADS)

    Zhao, Hui; Sheng, Yongwei; Li, Bo; Fan, Yuxin

    2016-04-01

    The Sara Us River is located along the boundary of the Mu Us Desert and the Chinese Loess Plateau in northern China. The river has cut down through Quaternary sediments creating 70-80 m deep valleys with thick lacustrine/aeolian sequences exposed. We applied optical stimulated luminescence on sediments from a Holocene section of aeolian sand/lacustrine deposits in the top of the river valley. The dating results show that a humid period existed from 7.1 to 2.0 ka ago as evidenced by two layers of peat and lacustrine sediments. However, compared to other published Holocene sections in the Sara Us River valleys close to the section under studying, the local environment experienced very complicated changes during the Holocene. All of the sections recorded a period with drought and/or cold before the Holocene at around 13 ka, and an episode of aridity after about 2 ka ago as evidenced by the layers of aeolian sand. However, the ages of the lacustrine and peat layers in these sections are substantially different. Geomorphological analysis by digital elevation models does not support the existence of a mega lake covering the study area at 2 ka. The intricate environmental changes may have been caused by the meandering of the Sara Us River. Environmental changes also strongly affected human migration in this area, which is documented by Chinese historical records.

  11. Using the U-Pb system of calcretes to date the time of sedimentation of clastic sedimentary rocks

    NASA Astrophysics Data System (ADS)

    Wang, Z. S.; Rasbury, E. T.; Hanson, G. N.; Meyers, W. J.

    1998-08-01

    The time of sedimentation of rapidly deposited clastic sedimentary rocks in fluvial environments may be directly dated with an uncertainty of less than three million years using U-Pb dating of pure micritic calcite from calcretes developed in overbank deposits. This conclusion is based on results obtained for calcretes (soil calcite, caliche) formed in the late Triassic New Haven Arkose, Hartford Basin, Connecticut, USA. The paragenesis of calcrete samples from the New Haven Arkose was determined using plane-polarized light and cathodoluminesence petrography, uranium fission track analysis, as well as trace element and stable isotope geochemistry. These calcretes contain an abundance of paleosol microfabrics and diagenetic calcite. The first-generation micritic calcite and second-generation blocky calcite have characteristics consistent with soil calcite. The third generation blocky calcite is a later diagenetic calcite (post-soil calcite). The U-Pb data for pure micritic calcite (first generation) in a horizontal sheet calcrete in sedimentary rocks of Norian age gives a 238U/ 207Pb- 206Pb/ 207Pb isochron age of 211.9 ± 2.1 Ma (2-sigma, and used hereafter for all ages). This age and the stratigraphic position for this sample are in excellent agreement with the ages proposed by Gradstein et al. (1994) for the Norian/Rhaetian boundary of 209.6 ± 4.1 Ma and the Carnian/Norian boundary of 220.7 ± 4.4 Ma. The U-Pb data for two samples of first generation micrite in rhizoliths with about 15% insoluble residues give "ages" of 7 ± 66 Ma and 20 ± 36 Ma. These results suggest that relatively recent events disturbed the U-Pb system of these detrital rich samples, perhaps due to redistribution of U during weathering or during chemical dissolution for analysis. The U-Pb data for a sample of pure third generation blocky calcite cement in a rhizolith yields a 206Pb/ 238U- 207Pb/ 235U isochron age of 81 ± 11 Ma. This age suggests that this sample of third generation blocky

  12. C:N:P Molar Ratios, Sources and 14C Dating of Surficial Sediments from the NW Slope of Cuba.

    PubMed

    de la Lanza Espino, Guadalupe; Soto, Luis A

    2015-01-01

    The surficial sediments recovered from 12 sites located near the channel axis of the Florida Straits and the lower slope off NW Cuba were analyzed for total organic carbon (TOC), nitrogen (TN), phosphorus (TP), elemental C:N:P ratios, C and N isotopic values, and 14C dating. The depth profiles of TOC, TN, and TP (0-18 cm) displayed a downcore trend and a significant variation. The TOC values were low (0.15 to 0.62%; 66 to 516 µmol g(-1)). Sites near the island's lower slope had lower TOC average concentrations (158-333 µmol g(-1)) than those closer to the channel axis (averaging 341-516 µmol g(-1); p <0.05). The TN concentrations near the lower slope attained 0.11% (80 µmol g(-1)), whereas, towards the channel axis, they decreased to 0.07% (55 µmol g(-1); p<0.05). The C:N ratios ranged from 1.9 to 10.2. The mean molar C:N ratio (5.4) indicated a marine hemipelagic deposition. The TP was lower at sites near the lower slope (38.4 to 50.0 µmol gv; 0.12% to 0.16%) than those near the channel axis (50.0 to 66 µmol g(-1); 0.15 to 0.21%). C:P fluctuated from 7.7 to 14.1 in the surficial sediment layer. The bulk organic δ13Corg and δ15N values confirmed pelagic organic sources, and the 14C dating revealed that the sediments were deposited during the Holocene (1000-5000 yr BP). We suggest that the hydrodynamic conditions in the Straits influence vertical and advective fluxes of particulate organic material trapped in the mixed-layer, which reduces the particulate matter flux to the seabed.

  13. Studying and Dating Indian Ocean Tsunamis by Using Benthic Foraminifera in the Sediment Stratigraphy of South Andaman Islands, India

    NASA Astrophysics Data System (ADS)

    Johnson, F. C.

    2015-12-01

    We analyzed the foraminifera and dated them to identify the sea level fluctuations in the coastal sediment stratigraphy of Andaman Islands. Our recent paleotsunami investigations are specially focused on unusual large magnitude earthquake and tsunamis in the south coast of Andaman. Our detailed study on the foraminifers preserved in the near sub surface stratigraphy and AMS ages show a strong signature of the tsunami event very much similar to the modern tsunami of December 2004. We found that foraminifer is an ideal geological key to bracket paleotsunami events. The AMS ages of these foraminifers supports the ages given by corals of Sumatra with a small error bar. The recent research approach to identify the ruptures and tsunami based on the corals of south Sumatra suggests a large time span of 1000 years for such mega events. Our foraminiferal archives obtained from 10g soil samples from the 2.5m deep Holocene stratigraphy suggests four seismic predecessors similar to the 2004 event with ~Mw9 with huge rupture. Huge foraminiferal population in the sedimentary stratigraphy is an indicative of sea level changes and the signatures of abrasion in the foraminifer's test (180µm) indicate strong wave surges and bead load transport during tsunami events. Spontaneous death of organisms due to tsunami waves gives an exact time frame with a narrow age limit than the charcoal. Sediment stratigraphy of south Andaman had such changes in each millennium. Sediment stratigraphy sections shows the huge population and assemblages and the AMS dates of this foraminifera in south Andaman shows four mega events. This kind of fossil assemblages are commonly associated with the sea regression and transgressions in the geological time scale. Tamil 'Sangam literatures' one of the oldest literature available in Indian main land and the corals ages from Sumatra are also emphasizes the predecessors of such unusual large magnitude earthquakes and tsunamis in the Indian Ocean. All these

  14. C:N:P Molar Ratios, Sources and 14C Dating of Surficial Sediments from the NW Slope of Cuba

    PubMed Central

    de la Lanza Espino, Guadalupe; Soto, Luis A.

    2015-01-01

    The surficial sediments recovered from 12 sites located near the channel axis of the Florida Straits and the lower slope off NW Cuba were analyzed for total organic carbon (TOC), nitrogen (TN), phosphorus (TP), elemental C:N:P ratios, C and N isotopic values, and 14C dating. The depth profiles of TOC, TN, and TP (0-18 cm) displayed a downcore trend and a significant variation. The TOC values were low (0.15 to 0.62%; 66 to 516 µmol g-1). Sites near the island’s lower slope had lower TOC average concentrations (158-333 µmol g-1) than those closer to the channel axis (averaging 341-516 µmol g-1; p <0.05). The TN concentrations near the lower slope attained 0.11% (80 µmol g-1), whereas, towards the channel axis, they decreased to 0.07% (55 µmol g-1; p<0.05). The C:N ratios ranged from 1.9 to 10.2. The mean molar C:N ratio (5.4) indicated a marine hemipelagic deposition. The TP was lower at sites near the lower slope (38.4 to 50.0 µmol g-1; 0.12% to 0.16%) than those near the channel axis (50.0 to 66 µmol g-1; 0.15 to 0.21%). C:P fluctuated from 7.7 to 14.1 in the surficial sediment layer. The bulk organic δ13Corg and δ15N values confirmed pelagic organic sources, and the 14C dating revealed that the sediments were deposited during the Holocene (1000-5000 yr BP). We suggest that the hydrodynamic conditions in the Straits influence vertical and advective fluxes of particulate organic material trapped in the mixed-layer, which reduces the particulate matter flux to the seabed. PMID:26110791

  15. Analyzing the contribution of climate change to long-term variations in sediment nitrogen sources for reservoirs/lakes.

    PubMed

    Xia, Xinghui; Wu, Qiong; Zhu, Baotong; Zhao, Pujun; Zhang, Shangwei; Yang, Lingyan

    2015-08-01

    We applied a mixing model based on stable isotopic δ(13)C, δ(15)N, and C:N ratios to estimate the contributions of multiple sources to sediment nitrogen. We also developed a conceptual model describing and analyzing the impacts of climate change on nitrogen enrichment. These two models were conducted in Miyun Reservoir to analyze the contribution of climate change to the variations in sediment nitrogen sources based on two (210)Pb and (137)Cs dated sediment cores. The results showed that during the past 50years, average contributions of soil and fertilizer, submerged macrophytes, N2-fixing phytoplankton, and non-N2-fixing phytoplankton were 40.7%, 40.3%, 11.8%, and 7.2%, respectively. In addition, total nitrogen (TN) contents in sediment showed significant increasing trends from 1960 to 2010, and sediment nitrogen of both submerged macrophytes and phytoplankton sources exhibited significant increasing trends during the past 50years. In contrast, soil and fertilizer sources showed a significant decreasing trend from 1990 to 2010. According to the changing trend of N2-fixing phytoplankton, changes of temperature and sunshine duration accounted for at least 43% of the trend in the sediment nitrogen enrichment over the past 50years. Regression analysis of the climatic factors on nitrogen sources showed that the contributions of precipitation, temperature, and sunshine duration to the variations in sediment nitrogen sources ranged from 18.5% to 60.3%. The study demonstrates that the mixing model provides a robust method for calculating the contribution of multiple nitrogen sources in sediment, and this study also suggests that N2-fixing phytoplankton could be regarded as an important response factor for assessing the impacts of climate change on nitrogen enrichment.

  16. Persistence and metallic composition of paint particles in sediments from a tidal inlet.

    PubMed

    Takahashi, C K; Turner, Andrew; Millward, G E; Glegg, G A

    2012-01-01

    Concentrations of Cu, Pb, Sn and Zn have been determined in sediment (<500 μm) and macroscopic paint particles (>500 μm) retrieved from sections of two cores collected from a tidal inlet of the Plym estuary, southwest England. Paint particles contributed up to about 0.2% of the total mass retrieved from each section and were most abundant towards the base of the cores where, according to (210)Pb dating, deposition took place about a decade prior to sampling. Metal concentrations in the paint particles pooled from the sections were highly variable, typically spanning two orders of magnitude in each core, and were greatest for Cu and Zn (up to 460,000 and 170,000 μg g(-1), respectively) due to their use in contemporary antifouling formulations applied to boat hulls. Concentrations of metals in the sediment were, however, relatively invariant, an effect attributed to the abundance and dispersion of microscopic paint particles throughout the cores.

  17. Possibility of radiologic dating based on the glauconite from the paleogene sediments in the eastern mediterranean

    SciTech Connect

    Nikolaeva, I.V.; Golovii, D.I.; Ivanovskaya, T.A.; Krasheninnikov, V.A.

    1986-05-01

    Mineralogic studies and K-Ar age determinations of 11 glauconite specimens from the Paleogene of Syria suggest the need for a comprehensive approach to analyzing the stratigraphy, lithology, mineralogy, and isotope geochemistry, and the use of physical methods of investigation for interpreting the age values obtained by K-Ar methods. The authors conclude that, at the current stage of development K-Ar dating cannot be regarded as a reliable correlation method in stratigraphy.

  18. Extensive MIS 3 glaciation in southernmost Patagonia revealed by cosmogenic nuclide dating of outwash sediments

    NASA Astrophysics Data System (ADS)

    Darvill, Christopher M.; Bentley, Michael J.; Stokes, Chris R.; Hein, Andrew S.; Rodés, Ángel

    2015-11-01

    The timing and extent of former glacial advances can demonstrate leads and lags during periods of climatic change and their forcing, but this requires robust glacial chronologies. In parts of southernmost Patagonia, dating pre-global Last Glacial Maximum (gLGM) ice limits has proven difficult due to post-deposition processes affecting the build-up of cosmogenic nuclides in moraine boulders. Here we provide ages for the Río Cullen and San Sebastián glacial limits of the former Bahía Inútil-San Sebastián (BI-SSb) ice lobe on Tierra del Fuego (53-54°S), previously hypothesised to represent advances during Marine Isotope Stages (MIS) 12 and 10, respectively. Our approach uses cosmogenic 10Be and 26Al exposure dating, but targets glacial outwash associated with these limits and uses depth-profiles and surface cobble samples, thereby accounting for surface deflation and inheritance. The data reveal that the limits formed more recently than previously thought, giving ages of 45.6 ka (+139.9/-14.3) for the Río Cullen, and 30.1 ka (+45.6/-23.1) for the San Sebastián limits. These dates indicate extensive glaciation in southern Patagonia during MIS 3, prior to the well-constrained, but much less extensive MIS 2 (gLGM) limit. This suggests the pattern of ice advances in the region was different to northern Patagonia, with the terrestrial limits relating to the last glacial cycle, rather than progressively less extensive glaciations over hundreds of thousands of years. However, the dates are consistent with MIS 3 glaciation elsewhere in the southern mid-latitudes, and the combination of cooler summers and warmer winters with increased precipitation, may have caused extensive glaciation prior to the gLGM.

  19. Uranium series isotopes concentration in sediments at San Marcos and Luis L. Leon reservoirs, Chihuahua, Mexico

    NASA Astrophysics Data System (ADS)

    Méndez-García, C.; Renteria-Villalobos, M.; García-Tenorio, R.; Montero-Cabrera, M. E.

    2014-07-01

    Spatial and temporal distribution of the radioisotopes concentrations were determined in sediments near the surface and core samples extracted from two reservoirs located in an arid region close to Chihuahua City, Mexico. At San Marcos reservoir one core was studied, while from Luis L. Leon reservoir one core from the entrance and another one close to the wall were investigated. 232Th-series, 238U-series, 40K and 137Cs activity concentrations (AC, Bq kg-1) were determined by gamma spectrometry with a high purity Ge detector. 238U and 234U ACs were obtained by liquid scintillation and alpha spectrometry with a surface barrier detector. Dating of core sediments was performed applying CRS method to 210Pb activities. Results were verified by 137Cs AC. Resulting activity concentrations were compared among corresponding surface and core sediments. High 238U-series AC values were found in sediments from San Marcos reservoir, because this site is located close to the Victorino uranium deposit. Low AC values found in Luis L. Leon reservoir suggest that the uranium present in the source of the Sacramento - Chuviscar Rivers is not transported up to the Conchos River. Activity ratios (AR) 234U/overflow="scroll">238U and 238U/overflow="scroll">226Ra in sediments have values between 0.9-1.2, showing a behavior close to radioactive equilibrium in the entire basin. 232Th/overflow="scroll">238U, 228Ra/overflow="scroll">226Ra ARs are witnesses of the different geological origin of sediments from San Marcos and Luis L. Leon reservoirs.

  20. Milankovitch hypothesis supported by precise dating of coral reefs and deep-sea sediments.

    PubMed

    Broecker, W S; Thurber, D L; Goddard, J; Ku, T L; Matthews, R K; Mesolella, K J

    1968-01-19

    Barbados provides a possibly unique opportunity for reconstruction of the times and elevations of late-Pleistocene high stands of the sea. The island appears to be rising from the sea at a uniform rate that is fast enough to separate in elevation coral-reef tracts formed at successive high stands of the sea. Unaltered coral found in the lower terraces enables high-precision Th(230): U(234) and Pa(231): U(235) dating. Three distinct high stands of the sea are found about 122,000, 103,000, and 82,000 years ago. New Pa(231) and Th(230) dates from a deep-sea core also indicate that Ericson's W-X cold-to-warm climatic change occurred close to 126,000 years ago. These data show a parallelism over the last 150,000 years between changes in Earth's climate and changes in the summer insolation predicted from cycles in the tilt and precession of Earth's axis.

  1. A Holocene Sediment Record of Phosphorus Accumulation in Shallow Lake Harris, Florida (USA) Offers New Perspectives on Recent Cultural Eutrophication

    PubMed Central

    Kenney, William F.; Brenner, Mark; Curtis, Jason H.; Arnold, T. Elliott; Schelske, Claire L.

    2016-01-01

    We studied a complete Holocene sediment record from shallow (zmax = 9.7 m) Lake Harris, Florida (USA) to infer the historical development of the lake and its current eutrophic status. We used 210Pb and 14C to date the 5.9-m sediment sequence (core LH-6-13) and determined accumulation rates for bulk sediment, organic matter, calcium carbonate, phosphorus fractions and biogenic silica fractions. The chronology of changes in sediment characteristics for LH-6-13 is consistent with the general paleoenvironmental framework established by core studies from other Florida lakes. Lake Harris began to fill with water in the early Holocene, ca. 10,680 cal a BP. A shift from carbonate-dominated to organic-rich sediments ca. 5,540 cal a BP corresponds to a transition to wetter climate in the middle Holocene. A rapid increase in diatom biogenic silica concentrations and accumulation rates ca. 2,600 cal a BP signals that the lake had deepened to its modern limnetic state. In LH-6-13, an up-core decrease in rates of accumulation for several sediment variables indicates time-course oligotrophication of the lake through the Holocene. In near-surface sediments, abrupt increases in the accumulation rates of these same variables indicate progressive cultural eutrophication after ca. AD 1900. Comparison of the modern state of Lake Harris to its condition 50–100 years ago provides a measure of the impact of recent cultural eutrophication. Because the pre-disturbance trajectory of this lake was one of oligotrophication, the true impact of cultural eutrophication is even greater than what is inferred from the changes over the past century. PMID:26789518

  2. A Holocene Sediment Record of Phosphorus Accumulation in Shallow Lake Harris, Florida (USA) Offers New Perspectives on Recent Cultural Eutrophication.

    PubMed

    Kenney, William F; Brenner, Mark; Curtis, Jason H; Arnold, T Elliott; Schelske, Claire L

    2016-01-01

    We studied a complete Holocene sediment record from shallow (zmax = 9.7 m) Lake Harris, Florida (USA) to infer the historical development of the lake and its current eutrophic status. We used (210)Pb and (14)C to date the 5.9-m sediment sequence (core LH-6-13) and determined accumulation rates for bulk sediment, organic matter, calcium carbonate, phosphorus fractions and biogenic silica fractions. The chronology of changes in sediment characteristics for LH-6-13 is consistent with the general paleoenvironmental framework established by core studies from other Florida lakes. Lake Harris began to fill with water in the early Holocene, ca. 10,680 cal a BP. A shift from carbonate-dominated to organic-rich sediments ca. 5,540 cal a BP corresponds to a transition to wetter climate in the middle Holocene. A rapid increase in diatom biogenic silica concentrations and accumulation rates ca. 2,600 cal a BP signals that the lake had deepened to its modern limnetic state. In LH-6-13, an up-core decrease in rates of accumulation for several sediment variables indicates time-course oligotrophication of the lake through the Holocene. In near-surface sediments, abrupt increases in the accumulation rates of these same variables indicate progressive cultural eutrophication after ca. AD 1900. Comparison of the modern state of Lake Harris to its condition 50-100 years ago provides a measure of the impact of recent cultural eutrophication. Because the pre-disturbance trajectory of this lake was one of oligotrophication, the true impact of cultural eutrophication is even greater than what is inferred from the changes over the past century.

  3. A revised burial dose estimation procedure for optical dating of youngand modern-age sediments

    USGS Publications Warehouse

    Arnold, L.J.; Roberts, R.G.; Galbraith, R.F.; DeLong, S.B.

    2009-01-01

    The presence of genuinely zero-age or near-zero-age grains in modern-age and very young samples poses a problem for many existing burial dose estimation procedures used in optical (optically stimulated luminescence, OSL) dating. This difficulty currently necessitates consideration of relatively simplistic and statistically inferior age models. In this study, we investigate the potential for using modified versions of the statistical age models of Galbraith et??al. [Galbraith, R.F., Roberts, R.G., Laslett, G.M., Yoshida, H., Olley, J.M., 1999. Optical dating of single and multiple grains of quartz from Jinmium rock shelter, northern Australia: Part I, experimental design and statistical models. Archaeometry 41, 339-364.] to provide reliable equivalent dose (De) estimates for young and modern-age samples that display negative, zero or near-zero De estimates. For this purpose, we have revised the original versions of the central and minimum age models, which are based on log-transformed De values, so that they can be applied to un-logged De estimates and their associated absolute standard errors. The suitability of these 'un-logged' age models is tested using a series of known-age fluvial samples deposited within two arroyo systems from the American Southwest. The un-logged age models provide accurate burial doses and final OSL ages for roughly three-quarters of the total number of samples considered in this study. Sensitivity tests reveal that the un-logged versions of the central and minimum age models are capable of producing accurate burial dose estimates for modern-age and very young (<350??yr) fluvial samples that contain (i) more than 20% of well-bleached grains in their De distributions, or (ii) smaller sub-populations of well-bleached grains for which the De values are known with high precision. Our results indicate that the original (log-transformed) versions of the central and minimum age models are still preferable for most routine dating applications

  4. 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.

  5. Relationship between polycyclic aromatic hydrocarbons (PAHs) and particle size in dated core sediments in Lake Lianhuan, Northeast China.

    PubMed

    Sun, Li; Zang, Shuying

    2013-09-01

    Atmospheric particle associated with pyrogenic polycyclic aromatic hydrocarbons (PAHs) poses serious threats to human health by inhalation exposure, especially in semiarid areas. Hence, the distributions of PAHs and particle size in two core sediments collected from Lake Lianhuan, Northeast China were studied. The sediments were dated radiometrically, and particle size distribution and PAH concentration were evaluated and potential human health risk was assessed. From 1980 to 2007, the dominant PAHs in the two cores were 2- and 3-ring PAHs, and the concentrations of 3-6 ring PAHs gradually increased from the early 1990s. Diagnostic ratios indicated that pyrogenic PAHs were the main sources of PAHs which changed over time from combustions of wood and coal to liquid fossil fuel sources. Fine particles (<65 μm) were the predominant particle size (56-97%). Lacustrine source (with the peak towards 200-400 μm) and eolian sources derived from short (2.0-10 and 30-65 μm) and long (0.4-1.0 μm) distance suspension were indentified from frequency distribution pattern of particle size. Significant correlations between 3-6 ring PAHs (especially carcinogenic 5-6 ring PAHs) and 10-35 μm particulate fractions indicated that eolian particles played an important role in adsorbing pyrogenic PAHs. Petroleum source of PAHs was only identified during the 1980s in one core sediments, in which positive correlations between 2-ring PAHs and particulate fractions of >125 μm were found. Future research should focus on the seven carcinogenic pyrogenic PAHs due to a rapidly increasing trend since 1995 based on the assessment of toxic equivalency factors.

  6. Recent high-energy marine events in the sediments of Lagoa de Óbidos and Martinhal (Portugal): recognition, age and likely causes

    NASA Astrophysics Data System (ADS)

    Costa, P. J. M.; Leroy, S. A. G.; Dinis, J. L.; Dawson, A. G.; Kortekaas, S.

    2012-05-01

    A key issue in coastal hazards research is the need to distinguish sediments deposited by past extreme storms from those of past tsunamis. This study contributes to this aim by investigating patterns of sedimentation associated with extreme coastal flood events, in particular, within the Lagoa de Óbidos (Portugal). The recent stratigraphy of this coastal lagoon was studied using a wide range of techniques including visual description, grain-size analysis, digital and x-ray photography, magnetic susceptibility and geochemical analysis. The sequence was dated by 14C, 210Pb and Optically Stimulated Luminescence. Results disclose a distinctive coarser sedimentary unit, within the top of the sequence studied, and shown in quartz sand by the enrichment of elements with marine affinity (e.g., Ca and Na) and carbonates. The unit fines upwards and inland, thins inland and presents a sharp erosive basal contact. A noticeable post-event change in the sedimentary pattern was observed. The likely agent of sedimentation is discussed here and the conceivable association with the Great Lisbon tsunami of AD 1755 is debated, while a comparison is attempted with a possibly synchronous deposit from a tsunami in Martinhal (Algarve, Portugal). The possibility of a storm origin is also discussed in the context of the storminess of the western Portuguese coast and the North Atlantic Oscillation. This study highlights certain characteristics of the sedimentology of the deposits that may have a value in the recognition of extreme marine inundation signatures elsewhere in the world.

  7. 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.

  8. Radioactivity levels in mussels and sediments of the Golden Horn by the Bosphorus Strait, Marmara Sea.

    PubMed

    Kılıç, Önder; Belivermiş, Murat; Gözel, Furkan; Carvalho, Fernando P

    2014-09-15

    The Golden Horn is an estuary located in the center of İstanbul receiving freshwater discharges from two creeks and connecting to the Bosphorus Strait. Activity concentrations of natural and artificial radionuclides were determined in mussels (Mytilus galloprovincialis) and sediments from the Golden Horn sampled in February 2012. Mean activity concentrations of (137)Cs, (40)K, (226)Ra, (228)Ra, (210)Po and (210)Pb in the mussels were determined at 1.03±0.23, 389±41.6, 2.61±1.23, not detected (ND), 91.96±37.88 and 11.48±4.85 Bq kg(-1), respectively. In sediments, it was observed that (137)Cs, (40)K, (226)Ra, (228)Ra, (210)Po and (210)Pb activity concentrations in<63 μm particle fraction of sediment were generally higher than those determined in mussels. Po-210 and (210)Po/(210)Pb ratios in mussels from the Golden Horn were much lower than in mussels from other coastal regions and this was related to low plankton productivity and eutrophication of the Golden Horn.

  9. Sediment provenance, reworking and transport processes in the Indus River by U-Pb dating of detrital zircon grains

    NASA Astrophysics Data System (ADS)

    Alizai, Anwar; Carter, Andrew; Clift, Peter D.; VanLaningham, Sam; Williams, Jeremy C.; Kumar, Ravindra

    2011-03-01

    We present new major and trace element data, together with U-Pb ages for zircon sand grains from the major tributaries of the Indus River, as well as the adjacent Ghaggar and Yamuna Rivers and from bedrocks within the Sutlej Valley, in order to constrain the origin of the sediment reaching the Arabian Sea. Zircon grains from the upper Indus are generally younger than 200 Ma and contrast with those from the eastern tributaries eroded from Himalayan sources. Grains younger than 15 Ma, which typify the Nanga Parbat Massif, comprise no more than 1-2% of the total, even in the upper Indus, showing that this terrain is not a major sediment producer, in contrast with the Namche Barwe Massif in the eastern Himalayan syntaxis. The Sutlej and Yamuna Rivers in particular are very rich in Lesser Himalayan-derived 1500-2300 Ma zircons, while the Chenab is dominated by 750-1250 Ma zircons, mostly eroded from the Greater Himalaya. The upper Indus, Chenab and Ravi yield zircon populations broadly consistent with the outcrop areas, but the Jhelum and the Sutlej contain many more 1500-2300 Ma zircons than would be predicted from the area of Lesser Himalayan rock within their drainages. A significant population of grains younger than 200 Ma in the sands of the Thar Desert indicates preferential eolian, monsoon-related transport from the Indus lower reaches, rather than reworking from the local rivers. Modelling of observed zircon ages close to the delta contrasts with modern water discharge. The delta is rich in zircons dating 1500-2300 Ma, while discharge from modern rivers carrying such grains is low. The modest size of the Sutlej, the richest source of these materials in the modern system, raises the possibility that the compositionally similar Yamuna used to flow westwards in the recent past. Our data indicate a non-steady state river with zircon transport times of 5-10 k.y. inferred from earlier zircon dating of delta sands. The modern delta zircons image an earlier, likely

  10. Radionuclide activities, geochemistry, and accumulation rates of sediments in the Gulf of Thailand

    NASA Astrophysics Data System (ADS)

    Srisuksawad, Kanitha; Porntepkasemsan, Boonsom; Nouchpramool, Sunun; Yamkate, Pathom; Carpenter, Roy; Peterson, Michael L.; Hamilton, Terry

    1997-07-01

    Downcore concentration profiles of 210Pb, U, and Th isotopes, Al, Fe, Ti, Mn and Sc were measured in sediment box cores collected at 22 stations (16-70 m water depth) covering most of the Thai zone of the Gulf of Thailand. Distributions of excess 210Pb and the detrital elements were used to study spatial variations in sedimentary processes, mineralogy, and geochemistry between different regions of the gulf. Steady-state depositional concentrations and fluxes of excess 210Pb are 3-10 times lower in Gulf of Thailand sediments than in sediments from mid-latitudes in the northern hemisphere, reflecting lower 210Pb inputs from atmospheric fallout at 6-13°N latitude and from lower production of 210Pb from 226Ra in the shallower waters of the Gulf. U and Th concentrations are approximately 2-3 times higher than those in shelf sediments from mid-latitudes of North America, consistent with a higher proportion of granitic source rocks in the Thai environment. Downcore variations in 228Th/ 232Th activity ratios and in U activities reveal that exchange of interstitial and overlying waters and their dissolved chemicals occurs down to 20 cm in 8 of 10 cores. This benthic exchange may be important in budgets of fluxes of other soluble chemicals in this shallow shelf sea. A net flux of U isotopes from overlying water into Gulf of Thailand sediments occurs, in contrast to their release from sediments of the tropical Amazon shelf. Detectable levels of 137Cs were found only in sediments near the mouth of the largest river, the Chao Phraya. The detrital elements 232Th, 230Th, Al, Ti, and Sc all show relatively uniform downcore concentration profiles. This supports a key assumption in calculations of sediment accumulation rates from downcore profiles of 210Pb activity, that steady-state depositional conditions exist and that basic sediment mineralogy and grain size does not change. 210Pb model derived mass accumulation rates vary between 270 and 490 mg/cm 2 per year in the upper Gulf

  11. Magnetostratigraphic Dating of Paleogene Sediments in the Seymour Island (Antarctic Peninsula): A Preliminary Chronostratigraphy

    NASA Astrophysics Data System (ADS)

    Beamud, E.; Montes, M. J.; Santillana, S.; Nozal, F.; Marenssi, S.

    2015-12-01

    Seymour Island is located at 64 º S, close to the northeastern tip of the Antarctic Peninsula. This glacier-free island contains the southernmost exposures of the K/Pg boundary and it has the most complete record of the Paleogene in Antarctica. The base of the Paleogene is represented by the Early Paleocene shallow marine shelf deposits of the Marambio Group; which are unconformably overlain by the Late Paleocene to Late Eocene Seymour Island Group. The Marambio Group is divided into the quartz-rich silty sandstones and mudstones of the López de Bertodano Fm and the mudstones to quartz-rich sandstones of the Sobral Fm. The overlaying Seymour Island Group records the erosion and filling of incised valleys. This group is made up by the Cross Valley-Wiman, La Meseta and the uppermost new Submeseta Formations. Main regressive periods are evidenced by the erosional unconformities and their related time gaps at the base of these three Formations. The La Meseta and Submeseta Formations are composed by poorly consolidated marine sandstones and siltstones deposited in a shallow coastal (possibly estuarine) environment. Several biostratigraphic and isotopic studies have been conducted in the Seymour Island due to its extremely rich fossil record, and the age of the López de Bertodano Fm has been recently refined by magnetostratigraphy. However, the overlying Paleogene formations lack a reliable absolute continuous dating. To solve this problem, a composite magnetostratigraphic section spanning more than 1300 m from the K/Pg boundary up to the top of the Submeseta Fm was conducted, with an average sampling resolution of 3 m per site. Although many samples yielded weak results, a local magnetostratigraphy was obtained which has been correlated to the GPTS. The new derived ages range from Danian (~ 66 Ma) up to Priabonian (~ 34 Ma). These results have been integrated with previous litho-, bio- and isotopic data to build a new Paleogene chronostratigraphy for the Seymour

  12. Bayesian methods applied to the interpretation of multiple OSL dates: high precision sediment ages from Old Scatness Broch excavations, Shetland Isles

    NASA Astrophysics Data System (ADS)

    Rhodes, E. J.; Bronk Ramsey, C.; Outram, Z.; Batt, C.; Willis, L.; Dockrill, S.; Bond, J.

    2003-05-01

    In this paper, we illustrate the ways in which Bayesian statistical techniques may be used to enhance chronological resolution when applied to a series of OSL sediment dates. Such application can achieve an optimal chronological model by incorporating stratigraphic and age information. The application to luminescence data is not straightforward owing to the sources of uncertainty in each date, and here we present one solution to overcoming these difficulties, and introduce the concept of "unshared systematic" errors. Using OSL sediment dates from the site of Old Scatness Broch, Shetland Isles, UK, many measured with a high degree of precision, we illustrate some of the ways in which Bayesian techniques may be applied, as a tool for assessing systematic errors when combined with independent chronological information, and to determine the optimum chronological information for specific events and contexts. We provide a detailed procedure for the application of Bayesian methods to OSL dates using the widely available radiocarbon calibration programme OxCal.

  13. Floodplains and Sedimentation Processes in a Changing Basin: Case Study Sacramento Valley

    NASA Astrophysics Data System (ADS)

    Singer, M. B.; Aalto, R.

    2006-12-01

    The diverse floodplains of the Sacramento Valley in California have undergone dramatic post-glaciation changes. The natural reduction in sediment supply following glacial melting appears to have altered channel pattern of the in the Middle Sacramento River from braided to meandering. This trend has been exacerbated by recent dam construction, gravel and sand mining, and bank protection, which have apparently increased the frequency of chute cutoff and decreased channel sinuosity. The sum of factors controlling sediment supply and channel pattern are evidently converting the Sacramento from an aggraded river with frequent access to its natural floodplain to a degrading river with limited connectivity. We have documented via 210Pb dating low volumes of recent sediment transfer to: inset floodplains in Upper Sacramento River canyons; meander belt deposits, low-lying sinks bounding natural levees, and oxbow lakes along the Middle Sacramento River; and crevasses splay deposits and lowland floodways in the Lower Sacramento Valley. These observations are contrasted with historical maps and preserved deposits from the previous era of floodplain creation, which suggest higher rates of sediment accumulation. The presence of high sand content in recent deposits along channel margins determined via granulometry and its rapid decline with depth and distance from the channel attests to recent erosion of channel sediments throughout the Sacramento River. Most of the natural crevasses splays that once dominated sediment transfer into floodplains along the Sacramento's lower course have been cut off from the channel by flood control levees built upon channel banks. However, several splay fans were retrofitted for use in the valley's flood control system (c. 1920's) as lateral spill weirs that shunt flood flow out of the mainstem Sacramento River. These weirs focus flow and sediment transport into engineered floodways (i.e., leveed portions of natural low gradient flood basins

  14. An assessment of butyltins and metals in sediment cores from the St. Thomas East End Reserves, USVI.

    PubMed

    Hartwell, S Ian; Apeti, Dennis A; Mason, Andrew L; Pait, Anthony S

    2016-11-01

    Tributyltin (TBT) concentrations near a marina complex in Benner Bay on St. Thomas, US Virgin Islands, were elevated relative to other areas in a larger study of the southeastern shore of the island. At the request of the USVI Coastal Zone Management Program, sediment cores and surface sediment samples were collected to better define the extent and history of TBT deposition in the vicinity of Benner Bay. The sediment cores were sectioned into 2-cm intervals and dated with (210)Pb and (137)Cs. The core sections and the surface samples were analyzed for butyltins and 16 elements. Deposition rates varied from 0.07-5.0 mm/year, and were highest in the marina complex. Core ages ranged from 54 to 200 years. The bottoms of the cores contained shell hash, but the top layers all consisted of much finer material. Surface concentrations of TBT exceeded 2000 ng Sn/g (dry weight) at two locations. At a depth of 8 cm TBT exceeded 8800 ng Sn/g in the marina complex sediment. Based on the ratio of tributyltin to total butyltins, it appears that the marina sediments are the source of contamination of the surrounding area. There is evidence that vessels from neighboring islands may also be a source of fresh TBT. Copper concentrations increase over time up to the present. Gradients of virtually all metals and metalloids extended away from the marina complex. NOAA sediment quality guidelines were exceeded for As, Pb, Cu, Zn, and Hg.

  15. 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

  16. Reconstructing 2000 years of hydrological variation derived from laminated proglacial sediments of Lago del Desierto at the eastern margin of the South Patagonian Ice Field, Argentina

    NASA Astrophysics Data System (ADS)

    Kastner, Stephanie; Enters, Dirk; Ohlendorf, Christian; Haberzettl, Torsten; Kuhn, Gerhard; Lücke, Andreas; Mayr, Christoph; Reyss, Jean-Louis; Wastegård, Stefan; Zolitschka, Bernd

    2010-06-01

    Lago del Desierto (49°02'S, 72°51'W) is situated in the climatically sensitive area of Southern Patagonia close to the Hielo Patagonico Sur (HPS or South Patagonian Ice Field, Argentina). Next to marine records and Antarctic ice cores, this continental area is important to reveal hemispheric and global climate trends. As instrumental climate records from this region are generally short and scarce, environmental archives are the only source of long-term records of climate variations. In this study, the potential of laminated proglacial sediments from Lago del Desierto as a palaeoclimate archive is evaluated. Two parallel gravity cores (max. length 283 cm) were analysed using a multi-proxy approach. Radiometric dating ( 14C, 210Pb and 137Cs) and tephrochronology document that the sediment cover the last 2000 years. Especially in the middle part of the record, numerous turbidites make climate variations difficult to decipher. However, after exclusion of event layers changes in sedimentological, mineralogical, and geochemical parameters reveal a long-term trend of runoff variations and sediment accessibility controlled by changes in temperature and precipitation. An abrupt transition in sediment composition occurred around AD 850 and is interpreted as a change in sediment availability related to the initial exposure of formerly glaciated areas in the catchment. This striking change mirrors the onset of warmer climate conditions during the Medieval Climate Anomaly. Moreover, the Little Ice Age cooling and the subsequent 20th century warming can be traced in the sediment record corresponding to an overall trend observed for southern South America. The proglacial lacustrine sediment record of Lago del Desierto thus constitutes a link between glacier studies of the HPS and other terrestrial climate archives in a region were long, and continuous climate records are still rare.

  17. Vertical stability of mercury in historic and prehistoric sediments from Clear Lake, California.

    PubMed

    Suchanek, Thomas H; Richerson, Peter J; Zierenberg, Robert A; Slotton, Darell G; Mullen, Lauri H

    2008-12-01

    Clear Lake, California, USA, is the site of the Sulphur Bank Mercury Mine, now a U.S. Environmental Protection Agency Superfund Site. Intermittent mining from 1873 to 1957 resulted in approximately 100 Mg of mercury (Hg) being deposited into the lake's ecosystem. Sediment cores to approximately 2.5 m depth (dated using 210Pb and 14C) represent approximately 3000 years of sedimentation. Clear Lake sediments have experienced Hg deposition from anthropogenic sources (mining) during historic times (to the mid-1900s) and geologic sources during prehistoric times (prior to the mid-1800s). This provides a unique opportunity to evaluate hypotheses relating to (1) the influence of the mine on Hg loading to the lake and (2) the potential upward mobilization of Hg by diagenetic processes proposed by some as an alternative explanation for increased Hg concentrations at the surface of the sediment column believed to be caused by increased global atmospheric deposition. Although Hg mining began in 1873, no significant evidence of anthropogenic Hg loading was detected in cores prior to open-pit mining ca. 1927, which also involved bulldozing mine waste rock and tailings into the lake. Exponential increases in total Hg (TotHg) and methylmercury (MeHg) were observed above the 1927 horizon, where estimated sedimentation rates were 2.2-20.4 mm/yr and peaks of both forms of Hg maintained vertical stability within the sediment column. Below the 1927 horizon, a slow increase in both TotHg and MeHg with depth was observed from approximately 1000 to 3000 years before present, where sedimentation rates ranged from approximately 0.6 to 2.0 mm/yr and elevated Hg profiles appear stable. Vertical stability of Hg in the shallow and deep sediment column suggests that both TotHg and MeHg do not undergo diagenetic upward mobilization within the sediment column under rapid or slow sedimentation rates. Because (1) these data were collected at a site with known anthropogenic and geologic sources and

  18. Climatic variability in the eastern United States over the past millenium from Chesapeake Bay sediments

    USGS Publications Warehouse

    Cronin, T.; Willard, D.; Karlsen, A.; Ishman, S.; Verardo, S.; McGeehin, J.; Kerhin, R.; Holmes, C.; Colman, S.; Zimmerman, A.

    2000-01-01

    Salinity oscillations caused by multidecadal climatic variability had major impacts on the Chesapeake Bay estuarine ecosystem during the past 1000 yr. Microfossils from sediments dated by radiometry (14C, 137Cs, 210Pb) and pollen stratigraphy indicate that salinity in mesohaline regions oscillated 10-15 ppt during periods of extreme drought (low fresh-water discharge) and wet climate (high discharge). During the past 500 yr, 14 wet-dry cycles occurred, including sixteenth and early seventeenth century megadroughts that exceeded twentieth century droughts in their severity. These droughts correspond to extremely dry climate also recorded in North American tree-ring records and by early colonists. Wet periods occurred every ~60-70 yr, began abruptly, lasted <20 yr, and had mean annual rainfall ~25%-30% and fresh-water discharge ~40%-50% greater than during droughts. A shift toward wetter regional climate occurred in the early nineteenth century, lowering salinity and compounding the effects of agricultural land clearance on bay ecosystems.

  19. Using the U-Pb system of calcretes to date the time of sedimentation of clastic sedimentary rocks

    SciTech Connect

    Wang, Z.S.; Rasbury, E.T.; Hanson, G.N.; Meyers, W.J.

    1998-08-01

    The time of sedimentation of rapidly deposited clastic sedimentary rocks in fluvial environments may be directly dated with an uncertainty of less than three million years using U-Pb dating of pure micritic calcite from calcretes developed in overbank deposits. This conclusion is based on results obtained for calcretes (soil calcite, caliche) formed in the late Triassic New Haven Arkose, Hartford Basin, Connecticut, USA. The paragenesis of calcrete samples from the New Haven Arkose was determined using plane-polarized light and cathodoluminescence petrography, uranium fission track analysis, as well as trace element and stable isotope geochemistry. These calcretes contain an abundance of paleosol microfabrics and diagenetic calcite. The first-generation micritic calcite and second-generation blocky calcite have characteristics consistent with soil calcite. The third generation blocky calcite is a later diagenetic calcite (post-soil calcite). The U-Pb data for pure micritic calcite (first generation) in a horizontal sheet calcrete in sedimentary rocks of Norian age gives a {sup 238}U/{sup 207}Pb-{sup 206}Pb/{sub 207}Pb isochron age of 211.9 {+-} 2.1 Ma (2-sigma, and used hereafter for all ages). The U-Pb data for two samples of first generation micrite in rhizoliths with about 15% insoluble residues give ages of 7 {+-} 66 Ma and 20 {+-} 36 Ma. These results suggest that relatively recent events disturbed the U-Pb system of these detrital rich samples, perhaps due to redistribution of U during weathering or during chemical dissolution for analysis. The U-Pb data for a sample of pure third generation blocky calcite cement in a rhizolith yields a {sup 206}Pb/{sup 238}U-{sup 207}Pb/{sup 235}U isochron age of 81 {+-} 11 Ma. This age suggests that this sample of third generation blocky calcite precipitated during the late Cretaceous perhaps over an extended period.

  20. Plutonium as a chronomarker in Australian and New Zealand sediments: a comparison with (137)Cs.

    PubMed

    Hancock, G J; Leslie, C; Everett, S E; Tims, S G; Brunskill, G J; Haese, R

    2011-10-01

    The construction of high resolution chronologies of sediment profiles corresponding to the last 50-100 years usually entails the measurement of fallout radionuclides (210)Pb and (137)Cs. The anthropogenic radionuclide, (137)Cs, originating from atmospheric nuclear weapons testing can provide an important "first appearance" horizon of known age (1954-1955), providing much-needed validation for the sometimes uncertain interpretations associated with (210)Pb geochronology. However, while (137)Cs usually provides a strong signal in sediment in the northern hemisphere, total fallout of (137)Cs in the southern hemisphere was only 25% that of the north and the low activities of (137)Cs seen in Australian and New Zealand sediments can make its horizon of first appearance somewhat arguable. Low (137)Cs fallout also limited the size of the 1963-1964 fallout peak, a peak that is usually seen in northern hemisphere sediment profiles but is often difficult to discern south of the equator. This paper shows examples of the use of nuclear weapons fallout Pu as a chronomarker in sediment cores from Australia (3 sites) and New Zealand (1 site). The Pu profiles of five cores are examined and compared with the corresponding (137)Cs profiles and (210)Pb geochronologies. We find that Pu has significant advantages over (137)Cs, including greater measurement sensitivity using alpha spectrometry and mass spectrometric techniques compared to (137)Cs measurements by gamma spectrometry. Moreover, Pu provides additional chronomarkers associated with changes in the Pu isotopic composition of fallout during the 1950s and 1960s. In particular, the (238)Pu/(239+240)Pu activity ratio shows distinct shifts in the early 1950s and the mid to late 1960s, providing important known-age horizons in southern hemisphere sediments. For estuarine and near-shore sediments Pu sometimes has another significant advantage over (137)Cs due to its enrichment in bottom sediment relative to (137)Cs resulting from the

  1. Chronicling a century of lead pollution in Mexico: stable lead isotopic composition analyses of dated sediment cores.

    PubMed

    Soto-Jimenez, Martin F; Hibdon, Sharon A; Rankin, Charley W; Aggarawl, Jugdeep; Ruiz-Fernandez, A Carolina; Paez-Osuna, Federico; Flegal, A Russell

    2006-02-01

    Analyses of lead isotopic compositions (204Pb, 206Pb, 207Pb, and 208Pb) of dated sediment cores from two coastal estuaries and two inland lakes chronicle the predominance of industrial lead emissions in Mexico over the past century. These isotopic ratios exhibit a shift in composition from the turn of the previous century (1900) that corresponds with measurable increases (from 2- to 10-fold) in lead concentrations in the cores above their baseline values (3-22 microg/g)--both changes are consistent with the development of Mexican lead production for export and the manufacture of tetraethyl lead additives for Mexican gasolines. While subsequent changes in lead concentrations in the cores correspond with calculated emissions from the combustion of leaded gasoline in Mexico, isotopic compositions of the cores remain relatively constant throughout most of the 1900s (e.g., 206Pb/207Pb = 1.200 +/- 0.003; 208Pb/207Pb = 2.463 +/- 0.004). That isotopic constancy is attributed to the widespread pollution from lead production in Mexico and the dispersion of some of that lead used as an additive in Mexican gasolines.

  2. A luminescence dating study of the sediment stratigraphy of the Lajia Ruins in the upper Yellow River valley, China

    NASA Astrophysics Data System (ADS)

    Zhang, Yuzhu; Huang, Chun Chang; Pang, Jiangli; Zhou, Yali; Zha, Xiaochun; Wang, Longsheng; Zhou, Liang; Guo, Yongqiang; Wang, Leibin

    2014-06-01

    Pedo-sedimentological fieldwork were carried out in the Lajia Ruins within the Guanting Basin along the upper Yellow River valley. In the eolian loess-soil sections on the second river terrace in the Lajia Ruins, we find that the land of the Qijia Culture (4.20-3.95 ka BP) are fractured by several sets of earthquake fissures. A conglomerated red clay covers the ground of the Qijia Culture and also fills in the earthquake fissures. The clay was deposited by enormous mudflows in association with catastrophic earthquakes and rainstorms. The aim of this study is to provide a luminescence chronology of the sediment stratigraphy of the Lajia Ruins. Eight samples were taken from an eolian loess-soil section (Xialajia section) in the ruins for optically stimulated luminescence (OSL) dating. The OSL ages are in stratigraphic order and range from (31.94 ± 1.99) ka to (0.76 ± 0.02) ka. Combined OSL and 14C ages with additional stratigraphic correlations, a chronological framework is established. We conclude that: (1) the second terrace of the upper part of Yellow River formed 35.00 ka ago, which was followed by the accumulation of the eolian loess-soil section; and (2) the eolian loess-soil section is composed of the Malan Loess of the late last glacial (MIS-2) and Holocene loess-soil sequences.

  3. Depositional variability of estuarine intertidal sediments and implications for metal distribution: An example from Moreton Bay (Australia)

    NASA Astrophysics Data System (ADS)

    Morelli, Guia; Gasparon, Massimo

    2015-10-01

    This study examines the patterns of depositional variability, sediment geochemistry and metal distribution in intertidal areas of Moreton Bay, southeast Queensland, Australia. Recent concern over increasing human impact on the bay has generated the need to obtain evidence on how the disturbance of the depositional setting might affect the natural estuarine environment. Sediment stratigraphy, major, and trace element analyses of sediment cores show that the sedimentation pattern is unique to each intertidal site. Disturbed 210Pb and 137Cs activity profiles of some of the cores indicate that sediment reworking occurs across the intertidal flats up to a depth of at least 80 cm. With some notable exceptions, an accurate geochronology of the surface sediments could not be established due to low 210Pb activities and sediment mixing. Thus, an increase in Pb, Zn and Cu towards the surface sediments observed at various sites is attributed to both anthropogenic contribution following the rapid urban development in the last century and to post-depositional diagenetic processes, bioturbation and sediment re-suspension induced by tides, storms or floods. Sediment cores are representative only of the local sedimentation and may not always allow extensive correlation to larger areas. Vertical profiles of heavy metals reflect the different depositional environment controlled by the complex hydrodynamics of the bay. Local hydrologic, physical, and tidal conditions might induce metals redistribution at different scales. This information is of critical importance in view of sediment remobilization caused by future development such as dredging, intertidal areas reclamation or excavation of new navigational channels.

  4. Dating of prehistoric caves sediments and flints using 10Be and 26Al in quartz from Tabun Cave (Israel): Progress report

    NASA Astrophysics Data System (ADS)

    Boaretto, E.; Berkovits, D.; Hass, M.; Hui, S. K.; Kaufman, A.; Paul, M.; Weiner, S.

    2000-10-01

    There is an important need to develop additional dating methods beyond the 14C limit and independent of thermoluminescence (TL) and electron spin resonance (ESR). We propose to apply the method of burial dating to prehistoric sites using the decay of in situ produced radioisotopes 10Be and 26Al. The Tabun Cave, Mt. Carmel (Israel) has a sedimentary sequence which represents the type section for about the last 800,000 years in the Levant. The sediments in the cave are mainly of aeolian origin and are rich in quartz. Flint tools are also found in the sediments. Sediment samples and flint tools were selected from the same layer. Physical and chemical procedures to extract 10Be and 26Al atoms from the quartz fraction of the sediments and from the flint samples were developed, while measuring the natural Al levels as a monitor of the atmospheric component of the cosmogenic nuclides. AMS measurements were performed at the 14UD Pelletron Koffler Accelerator Laboratory, Weizmann Institute, and sensitivities of the order of 1×10 -14, in isotopic abundances for both 10Be and 26Al respectively (corresponding to ˜5 × 10 5 atoms) were obtained. First, measurements of a number of Tabun Cave sediment samples and flints show that 10Be and 26Al analyses have the potential for dating prehistoric cave sediments, provided problems relating to the presence of relatively large amounts of stable Al can be solved, as well as obtaining a better understanding of the burial history of the flints prior to being brought into the cave.

  5. K/Ar Dating of Fine Grained Sediments Near Prydz Bay, Antarctica: East Antarctic Ice Sheet Behavior During the Middle-Miocene Climate Transition

    NASA Astrophysics Data System (ADS)

    Duchesne, A. E.; Pierce, E. L.; Williams, T.; Hemming, S. R.; Johnson, D. L.; May, T.; Gombiner, J.; Torfstein, A.

    2012-12-01

    ¶ The Middle Miocene Climate Transition (MMCT) (~14 Ma) represents a time of major East Antarctic Ice-Sheet (EAIS) expansion, with research suggesting major global sea level fall on the order of ~60 meters (John et al., 2011, EPSL). Ocean Drilling Program (ODP) core data from Site 1165B near Prydz Bay shows an influx of cobbles deposited ~13.8-13.5 Ma, representing a sudden burst of ice-rafted detritus (IRD) during the MMCT. Based on 40Ar/39Ar dating of hornblendes and/or biotite grains, 5 of 6 dated pebbles from a companion study show Wilkes Land origins, indicating transport from over 1500 kilometers away. However, samples throughout this time interval have an anomalously low abundance of sand, thus we seek to understand the sedimentary processes that led to the deposition of these isolated dropstones in a fine matrix through provenance studies of the core's terrigenous fine fraction. Geochemical provenance studies of the terrigenous fraction of marine sediments can aid in identifying past dynamic EAIS behavior; the few outcrops available on the continent provide specific rock characterizations and age constraints from which cored marine sediments can then be matched to using established radiogenic isotope techniques. Here we apply the K/Ar dating method as a provenance tool for identifying the source area(s) of fine-grained terrigenous sediments (<63 μm) deposited during the MMCT. ¶ After source area characterization, we find that the fine-grained sediments from the mid-Miocene show a mixture of both local Prydz Bay sourcing (~400 Ma signature) and Wilkes Land provenance (~900 Ma signature). While locally-derived Prydz Bay sediments are likely to have been delivered via meltwater from ice and deposited as hemipelagic sediments (with some possible bottom current modification, as this is a drift site), sediments sourced from Wilkes Land required transport via large icebergs. Future work will involve further provenance determination on both the fine

  6. Mercury contamination chronologies from Connecticut wetlands and Long Island Sound sediments

    USGS Publications Warehouse

    Varekamp, J.C.; Kreulen, B.; Buchholtz ten Brink, M. R.; Mecray, E.L.

    2003-01-01

    Sediment cores were used to investigate the mercury deposition histories of Connecticut and Long Island Sound. Most cores show background (pre-1800s) concentrations (50-100 ppb Hg) below 30-50 cm depth, strong enrichments up to 500 ppb Hg in the core tops with lower Hg concentrations in the surface sediments (200-300 ppb Hg). A sediment core from the Housatonic River has peak levels of 1,500 ppb Hg, indicating the presence of a Hg point source in this watershed. The Hg records were translated into Hg contamination chronologies through 210Pb dating. The onset of rig contamination occurred in ???1840-1850 in eastern Connecticut, whereas in the Housatonic River the onset is dated at around 1820. The mercury accumulation profiles show periods of peak contamination at around 1900 and at 1950-1970. Peak Hg* (Hg*= Hg measured minus Hg background) accumulation rates in the salt marshes vary, dependent on the sediment character, between 8 and 44 ng Hg/cm2 per year, whereas modern Hg* accumulation rates range from 4-17 ng Hg/cm2 per year; time-averaged Hg* accumulation rates are 15 ng Hg/cm2 per year. These Hg* accumulation rates in sediments are higher than the observed Hg atmospheric deposition rates (about 1-2 ng Hg/cm2 per year), indicating that contaminant Hg from the watershed is focused into the coastal zone. The Long Island Sound cores show similar Hg profiles as the marsh cores, but time-averaged Hg* accumulation rates are higher than in the marshes (26 ng Hg/cm2 a year) because of the different sediment characteristics. In-situ atmospheric deposition of Hg in the marshes and in Long Island Sound is only a minor component of the total Hg budget. The 1900 peak of Hg contamination is most likely related to climatic factors (the wet period of the early 1900s) and the 1950-1970 peak was caused by strong anthropogenic Hg emissions at that time. Spatial trends in total Hg burdens in cores are largely related to sedimentary parameters (amount of clay) except for the high

  7. Quantifying sources of fine sediment supplied to post-fire debris flows using fallout radionuclide tracers

    NASA Astrophysics Data System (ADS)

    Smith, Hugh G.; Sheridan, Gary J.; Nyman, Petter; Child, David P.; Lane, Patrick N. J.; Hotchkis, Michael A. C.; Jacobsen, Geraldine E.

    2012-02-01

    Fine sediment supply has been identified as an important factor contributing to the initiation of runoff-generated debris flows after fire. However, despite the significance of fines for post-fire debris flow generation, no investigations have sought to quantify sources of this material in debris flow affected catchments. In this study, we employ fallout radionuclides ( 137Cs, 210Pb ex and 239,240Pu) as tracers to measure proportional contributions of fine sediment (< 10 μm) from hillslope surface and channel bank sources to levee and terminal fan deposits formed by post-fire debris flows in two forest catchments in southeastern Australia. While 137Cs and 210Pb ex have been widely used in sediment tracing studies, application of Pu as a tracer represents a recent development and was limited to only one catchment. The ranges in estimated proportional hillslope surface contributions of fine sediment to individual debris flow deposits in each catchment were 22-69% and 32-74%. The greater susceptibility of 210Pb ex to apparent reductions in the ash content of channel deposits relative to hillslope sources resulted in its exclusion from the final analysis. No systematic change in the proportional source contributions to debris flow deposits was observed with distance downstream from channel initiation points. Instead, spatial variability in source contributions was largely influenced by the pattern of debris flow surges forming the deposits. Linking the tracing analysis with interpretation of depositional evidence allowed reconstruction of temporal sequences in sediment source contributions to debris flow surges. Hillslope source inputs dominated most elevated channel deposits such as marginal levees that were formed under peak flow conditions. This indicated the importance of hillslope runoff and fine sediment supply for debris flow generation in both catchments. In contrast, material stored within channels that was deposited during subsequent surges was predominantly

  8. Reconstructing a 180 yr record of natural and anthropogenic induced low-oxygen conditions from Louisiana continental shelf sediments

    USGS Publications Warehouse

    Osterman, L.E.; Poore, R.Z.; Swarzenski, P.W.; Turner, R.E.

    2005-01-01

    Hypoxia on the Louisiana continental shelf is tied to nutrient Loading and freshwater stratification from the Mississippi River. Variations in the relative abundance of low-oxygen-tolerant benthic foraminifers in four sediment cores from the Louisiana shelf provide a proxy record of low-oxygen events. Core chronologies are obtained using 210Pb dating techniques. The foraminiferal data are consistent with previous studies indicating that the intensity of hypoxic events (oxygen <2 mg /L) has increased over the past 50 yr owing to the higher nutrient loading associated with the use of commercial fertilizer, and also reveal several low-oxygen events between A.D. 1817 and 1910, prior to the widespread use of fertilizer. The pre-1910 low-oxygen events are associated with high Mississippi River discharge rates, indicating that these low-oxygen episodes are related to natural variations in river drainage that enhance transport of nutrients and freshwater to the continental shelf. Our data show that the low-oxygen events of the past few decades were more extreme than any that occurred in the previous ???180 yr, and support the interpretation that the increased use of fertilizer has amplified an otherwise naturally occurring process. ?? 2005 Geological Society of America.

  9. Amino acid racemization analysis (AAR) as a successful tool for dating Holocene coastal sediments: Stratigraphy of a barrier island spit (Southern Sylt/North Sea)

    NASA Astrophysics Data System (ADS)

    Tillmann, Tanja; Ziehe, Daniel

    2014-05-01

    Dating of Holocene sediments in shallow coastal areas of the German North Sea by conventional techniques is commonly problematic. In particular the marine reservoir effect of radiocarbon means that radiocarbon dating cannot be applied to sediments younger than about 400 years. Amino acid racemization dating (AAR) is a viable alternative for dating young sediments. The method is based on the determination of ratios of D and L amino acid enantiomers in organic matrices of biogenic carbonates. In this study we use AAR as a tool for dating Holocene barrier islands sediments. Based on an AAR derived chronological framework we develop a model of barrier spit accretion which describes the interaction between extreme events, fair weather coastal processes and sedimentary development that constrains the major episodes of barrier island evolution. The stratigraphy was defined using ground-penetrating radar (GPR) surveys complemented by sedimentological coring data. The stratigraphy is then conceptualised in a AAR chronostratigraphic framework to define a chronological order and allow the development of a stratigraphic model of the evolution of Southern Sylt. The AAR data provide high temporal resolution and have been used for dating stages of barrier spit accretion. The time lines are marked as storm surge generated erosion unconformities in the stratigraphic profile. Individual shells and shell fragments of Cerastoderma edule, Mya arenaria, Mytilus edulis and Scrobicularia plana have been accumulated by short-term storm events as shell layers associated with the erosion unconformities and have been dated by AAR. Time lines reveal that the barrier spit accretion occurred episodically, and is dependant on the provided rate of sand delivery. The general trend is that sequences young to the. South. The AAR derived time lines have been verified and correlated by historic maps and sea charts. It is apparent that spit enlargement at this site increased significantly during the

  10. Physical resuspension and vertical mixing of sediments on a high energy continental margin (Sydney, Australia).

    PubMed

    Matthai, C; Birch, G F; Jenkinson, A; Heijnis, H

    2001-01-01

    Four sediment cores from the continental margin adjacent to Sydney were analyzed for 210Pb, 137Cs, trace metals (Ag, Cd, Co, Cu, Mn, Ni, Pb, Zn), iron, dry bulk density, mud and moisture content. The concentrations of trace metals in the total sediment are low at all sites, although slightly elevated concentrations of Ag, Cu, Pb and Zn are present in the fine fraction of sediment (< 62.5 microns) near a major ocean outfall. Concentrations of trace metals in the fine fraction of sediment are similar in the upper 10-15 cm, indicating strong vertical mixing of the sediments, whereas an upward coarsening grain size in the upper 1-3 cm of sediment supports physical resuspension during storms. Sediment accumulation rates on the middle shelf adjacent to Sydney were estimated from downcore profiles of 210Pb and 137Cs and range between 0.2 and 0.4 cm yr-1. Although the mass fluxes of Cu, Pb and Zn within a distance of 2 km from the outfall (up to 36.1, 30.8 and 86.2 micrograms cm-2 yr-1, respectively) are greater than 20 km north of the outfall (< 23.5 micrograms cm-2 yr-1), the low concentrations of trace metals in sediments near the outfall support an efficient dispersal of anthropogenic contaminants on this continental margin.

  11. Historical Distribution of Polycyclic Aromatic Hydrocarbons in Shallow Sediments from Lake Chapala, Mexico

    NASA Astrophysics Data System (ADS)

    Zárate-Del Valle, P. F.; Macías-Pérez, M. P.; Barajas-Martínez, C. D.; Gómez-Hermosillo, C. M.

    2008-12-01

    The incomplete combustion of fossil fuels and burning of vegetation and other organic materials release into the environment pollutants like polycyclic aromatic hydrocarbons (PAHs) which are ubiquitous pollutants. The environmental behavior of PAHs is characterized by very low solubility, high hydrophobic sorptive capacity (kow), low volatility and general chemical stability. These characteristics mean, in practice, that PAHs are environmentally persistent compounds that in aquatic systems, are strongly held to solid surfaces present as both suspended particles and bottom sediment. Additionally, because of their high partition to organic carbon, PAHs show a high rate of bioconcentration and an easy way to enter the food chain. A benthos type sediment core was collected (CHA-C: N20° 15.105'; W103° 03.104') from the depocenter of lake Chapala. The first 40 cm of the sedimentary column representing an ecological history of ~ 150 years (210Pb dating) were cutted every 2 cm (n=20). For each core sectioned, the presence of PAHs was evaluated by GC-MS following methods from the USEPA (EPA 3540C, EPA 3620C, EPA 8270C). For the first 30 cm deep only products resulting of PAHs degradation were identified, namely: Butilisobutilphtalate, 1,2-benzenedicarboxaldehyde, phenol and, cinnamaldehyde; we attibute the presence of these products to a faster transformation of PAHs by photo and metabolic degradation as well as to chemical oxydation. For the 30-40 cm deep, the presence of the follwing PAHs was detected: 1H-indene, 1,2- difluor-3,4,5-trimetylbenzenethylnaphthalene, naphthalene, anthracene, and phenantren. A study is in progress to determine the presence of PAHs in other sites of the lake. We conclude that shallow sediment (40 cm deep) from Lake Chapala could constitute a potentially large pool of PAHs.

  12. Spatial distributions and deposition chronology of short chain chlorinated paraffins in marine sediments across the Chinese Bohai and Yellow Seas.

    PubMed

    Zeng, Lixi; Chen, Ru; Zhao, Zongshan; Wang, Thanh; Gao, Yan; Li, An; Wang, Yawei; Jiang, Guibin; Sun, Liguang

    2013-10-15

    As the most complex halogenated contaminants, short chain chlorinated paraffins (SCCPs) are scarcely reported in marine environments. In this work, a total of 117 surficial sediment (0-3 cm) samples and two sediment cores were collected from the Chinese Bohai and Yellow Seas to systematically study the spatial and temporal trends of SCCPs at a large scale in the Chinese marine environment. Total SCCP concentrations in the surficial sediments were in the range of 14.5-85.2 ng g(-1) (dry weight, d.w.) with an average level of 38.4 ng g(-1) d.w. Spatial distribution showed a decreasing trend with the distance from the coast to the open waters. Compositional pattern analysis suggested that C10 was the most predominant homologue group, followed by C11, C12, and C13 homologue groups. The concentrations of total SCCPs in sediment cores ranged from 11.6 to 94.7 ng g(-1) d.w. for YS1 and from 14.7 to 195.6 ng g(-1) d.w. for YS2, with sharp rise from the early 1950s to present based on (210)Pb dating technique. The historical records in cores correspond well to the production and usage changes of CPs in China. Multivariate regression statistics indicate TOC, latitude and longitude are the major factors influencing surficial SCCP levels in the Chinese East Seas by combining analysis with the data from the East China Sea (R(2) = 0.332, p < 0.01). These findings indicated that the sources of SCCPs were mainly from river outflows via ocean current and partly from atmospheric depositions by East Asian monsoon in the sampling areas.

  13. Carbon export fluxes and export efficiency in the central Arctic during the record sea-ice minimum in 2012: a joint 234Th/238U and 210Po/210Pb study

    NASA Astrophysics Data System (ADS)

    Roca-Martí, Montserrat; Puigcorbé, Viena; Rutgers van der Loeff, Michiel M.; Katlein, Christian; Fernández-Méndez, Mar; Peeken, Ilka; Masqué, Pere

    2016-07-01

    The Arctic sea-ice extent reached a record minimum in September 2012. Sea-ice decline increases the absorption of solar energy in the Arctic Ocean, affecting primary production and the plankton community. How this will modulate the sinking of particulate organic carbon (POC) from the ocean surface remains a key question. We use the 234Th/238U and 210Po/210Pb radionuclide pairs to estimate the magnitude of the POC export fluxes in the upper ocean of the central Arctic in summer 2012, covering time scales from weeks to months. The 234Th/238U proxy reveals that POC fluxes at the base of the euphotic zone were very low (2 ± 2 mmol C m-2 d-1) in late summer. Relationships obtained between the 234Th export fluxes and the phytoplankton community suggest that prasinophytes contributed significantly to the downward fluxes, likely via incorporation into sea-ice algal aggregates and zooplankton-derived material. The magnitude of the depletion of 210Po in the upper water column over the entire study area indicates that particle export fluxes were higher before July/August than later in the season. 210Po fluxes and 210Po-derived POC fluxes correlated positively with sea-ice concentration, showing that particle sinking was greater under heavy sea-ice conditions than under partially ice-covered regions. Although the POC fluxes were low, a large fraction of primary production (>30%) was exported at the base of the euphotic zone in most of the study area during summer 2012, indicating a high export efficiency of the biological pump in the central Arctic.

  14. Methodological issues and preliminary results from a combined sediment fingerprinting and radioisotope dating approach to explore changes in sediment sources with land-use change in the Brantian Catchment, Borneo.

    NASA Astrophysics Data System (ADS)

    Walsh, Rory; Higton, Sam; Marshall, Jake; Bidin, Kawi; Blake, William; Nainar, Anand

    2015-04-01

    This paper reports some methodological issues and early results of a project investigating the erosional impacts of land use changes (multiple selective logging and progressive, partial conversion to oil palm) over the last 25-40 years in the 600km2 Brantian river catchment in Sabah, Borneo. A combined sediment fingerprinting and radioisotope dating approach is being applied to sediment cores taken in stream hierarchical fashion across the intermediate catchment scale. Changes in sediment sources and sedimentation rates over time can be captured by changes in the relative importance of geochemical elements with depth in downstream sediment cores, which in turn can be linked to parallel changes in upstream cores by the application of unmixing models and statistical techniques. Radioisotope analysis of the sediment cores allows these changes to be dated and sedimentation rates to be estimated. Work in the neighbouring Segama catchment had successfully demonstrated the potential of such an approach in a rainforest environment (Walsh et al. 2011). The paper first describes steps taken to address methodological issues. The approach relies on taking continuous sediment cores which have aggraded progressively over time and remain relatively undisturbed and uncontaminated. This issue has been tackled (1) through careful core sampling site selection with a focus on lateral bench sites and (2) deployment of techniques such as repeat-measurement erosion bridge transects to assess the contemporary nature of sedimentation to validate (or reject) candidate sites. The issue of sediment storage and uncertainties over lag times has been minimised by focussing on sets of above- and below-confluence sites in the intermediate zone of the catchment, thus minimising sediment transit times between upstream contributing and downstream destination core sites. This focus on the intermediate zone was also driven by difficulties in finding suitable core sites in the mountainous headwaters

  15. Rapid Changes on Sediment Accumulation Rates within Submarine Canyons Caused By Bottom Trawling Activities

    NASA Astrophysics Data System (ADS)

    Puig, P.; Masque, P.; Martin, J.; Paradis, S.; Juan, X.; Toro, M.; Palanques, A.

    2014-12-01

    The physical disturbance of the marine sedimentary environments by commercial bottom trawling is a matter of concern. The direct physical effects of this fishing technique include scraping and ploughing of the seabed and increases of the near-bottom water turbidity by sediment resuspension. However, the quantification of the sediment that has been resuspended by this anthropogenic activity over years and has been ultimately exported across the margin remains largely unaddressed. The analysis of sediment accumulation rates from sediment cores collected along the axes of several submarine canyons in the Catalan margin (northwestern Mediterranean) has allowed to estimate the contribution of this anthropogenic activity to the present-day sediment dynamics. 210Pb chronologies, occasionally supported by 137Cs dating, indicate a rapid increase of sediment accumulation rates since the 1970s, in coincidence with a strong impulse in the industrialization of the trawling fleets of this region. Such increase has been associated to the enhanced delivery of sediment resuspended by trawlers from the shelves and upper slope regions towards the canyon's interior, and to the rapid technical development at that time, in terms of engine power and gear size. This change has been observed in La Fonera (or Palamós) Canyon at depths greater than 1700 m, while in other canyons it is restricted to shallower regions (~1000 m in depth) closer to fishing grounds. Two sampling sites from La Fonera and Foix submarine canyons that exhibited high sediment accumulation rates (0.6-0.7 cm/y) were reoccupied several years after the first chronological analyses. These two new cores reveal a second and more rapid increase of sediment accumulation rates in both canyons occurring circa 2002 and accounting for about 2 cm/y. This second change at the beginning of the XXI century has been attributed to a preferential displacement of the trawling fleet towards slope fishing grounds surrounding submarine

  16. Geochemistry of Florida Bay sediments: Nutrient history at five sites in eastern and central Florida Bay

    USGS Publications Warehouse

    Orem, W.H.; Holmes, C.W.; Kendall, C.; Lerch, H.E.; Bates, A.L.; Silva, S.R.; Boylan, A.; Corum, M.; Marot, M.; Hedgman, C.

    1999-01-01

    Recent seagrass dieoff and massive microalgal blooms have focused attention on the health of the Florida Bay ecosystem. Changes in nutrient input and the nutrient dynamics of Florida Bay are hypothesized to be linked to these problems, but crucial baseline information is still lacking. Efforts to restore Florida Bay to its natural condition will require information on the nutrient history of the bay. The purpose of this study was to examine distributions of organic C, total N, and total P in carbonate sediments from sites of continuous and known sedimentation rate (210Pb and 137Cs dated), in eastern and central Florida Bay. These sediments provide a record of historical changes in the C, N, and P load to the eastern and central bay. Analyses were conducted on sediments from cores collected at five sites, and on buried seagrass fragments at two sites. At three of the sites, sediments from seagrass-covered and adjacent barren areas were examined to determine differences in sedimentary geochemistry. Stable isotope analyses (??13C and ??15N) of sedimentary organic C and total N and of buried seagrass fragments were also carried out at two sites to examine possible changes in nutrient sources to the estuary. Results were consistent with recent increases in N and P in eastern Florida Bay, beginning in the early to mid 1980's. The timing of the increase in nutrient load observed in the sediment data directly preceded the first observations of massive microalgal blooms and seagrass dieoff in Florida Bay in 1987. The observed nutrification was greater for P than N, and was most pronounced at the most northeasterly site sampled (Pass Key). Isotope data (??15N) suggested that an increase in algal production accompanied the increase in N load at the Pass Key site. Along record of organic C, total N, and total P distributions from Whipray Basin in central Florida Bay showed historical peaks (mid 1700's and late 1800's) in organic C and total N, but not total P; these

  17. Historical deposition of mercury and selected trace elements to high-elevation National Parks in the Western U.S. inferred from lake-sediment cores

    NASA Astrophysics Data System (ADS)

    Mast, M. Alisa; Manthorne, David J.; Roth, David A.

    2010-07-01

    Atmospheric deposition of Hg and selected trace elements was reconstructed over the past 150 years using sediment cores collected from nine remote, high-elevation lakes in Rocky Mountain National Park in Colorado and Glacier National Park in Montana. Cores were age dated by 210Pb, and sedimentation rates were determined using the constant rate of supply model. Hg concentrations in most of the cores began to increase around 1900, reaching a peak sometime after 1980. Other trace elements, particularly Pb and Cd, showed similar post-industrial increases in lake sediments, confirming that anthropogenic contaminants are reaching remote areas of the Rocky Mountains via atmospheric transport and deposition. Preindustrial (pre-1875) Hg fluxes in the sediment ranged from 5.7 to 42 μg m -2 yr -1 and modern (post-1985) fluxes ranged from 17.7 to 141 μg m -2 yr -1. The average ratio of modern to preindustrial fluxes was 3.2, which is similar to remote lakes elsewhere in North America. Estimates of net atmospheric deposition based on the cores were 3.1 μg m -2 yr -1 for preindustrial and 11.7 μg m -2 yr -1 for modern times. Current-day measurements of wet deposition range from 5.0 to 8.6 μg m -2 yr -1, which are lower than the modern sediment-based estimate of 11.7 μg m -2 yr -1, perhaps owing to inputs of dry-deposited Hg to the lakes.

  18. Historical deposition of mercury and selected trace elements to high-elevation National Parks in the Western U.S. inferred from lake-sediment cores

    USGS Publications Warehouse

    Mast, M. Alisa; Manthorne, David J.; Roth, David A.

    2010-01-01

    Atmospheric deposition of Hg and selected trace elements was reconstructed over the past 150 years using sediment cores collected from nine remote, high-elevation lakes in Rocky Mountain National Park in Colorado and Glacier National Park in Montana. Cores were age dated by 210Pb, and sedimentation rates were determined using the constant rate of supply model. Hg concentrations in most of the cores began to increase around 1900, reaching a peak sometime after 1980. Other trace elements, particularly Pb and Cd, showed similar post-industrial increases in lake sediments, confirming that anthropogenic contaminants are reaching remote areas of the Rocky Mountains via atmospheric transport and deposition. Preindustrial (pre-1875) Hg fluxes in the sediment ranged from 5.7 to 42 μg m−2 yr−1 and modern (post-1985) fluxes ranged from 17.7 to 141 μg m−2 yr−1. The average ratio of modern to preindustrial fluxes was 3.2, which is similar to remote lakes elsewhere in North America. Estimates of net atmospheric deposition based on the cores were 3.1 μg m−2 yr−1 for preindustrial and 11.7 μg m−2 yr−1for modern times. Current-day measurements of wet deposition range from 5.0 to 8.6 μg m−2 yr−1, which are lower than the modern sediment-based estimate of 11.7 μg m−2 yr−1, perhaps owing to inputs of dry-deposited Hg to the lakes.

  19. Inconsistencies between (14)C and short-lived radionuclides-based sediment accumulation rates: Effects of long-term remineralization.

    PubMed

    Baskaran, M; Bianchi, T S; Filley, T R

    2016-09-06

    (14)C is the most widely utilized geochronometer to investigate geological, geochemical and geophysical problems over the past 5 decades. Establishment of precise sedimentation rates is crucial for the reconstruction of paleo-climate, -ecological and - environmental studies when extrapolation of sedimentation rates is utilized for time scales beyond the dating range. However, agreement between short-term and long-term sedimentation rates in anthropogenically unperturbed sediment cores has not been shown. Here we show that the AMS (14)C-based long-term mass accumulation rate (MAR) of an organic-rich (>70%) sediment core from Mud Lake, Florida to be ∼5 times lower than the short-term MAR obtained using (239,240)Pu, (137)Cs and excess (210)Pb ((210)Pbxs). The measured sediment inventories of (210)Pbxs, (137)Cs and (239,240)Pu are comparable to the atmospheric fallout for the sampling site, indicating very little accelerated sediment erosion over the past several decades. Presence of sharp fallout peaks of (239,240)Pu indicates very little sediment mixing. The penetration depths of (137)Cs and (239,240)Pu were found to be much deeper than expected and this is attributed to their post-depositional mobility. MAR calculated using (14)C-ages in successive layers also indicated decreasing MARs with depth, and was reflective of progressive remineralization. Using first-order kinetics, the sediment remineralization rate was found to be 4.4 × 10(-4) y(-1) and propose that over the long-term, remineralization of organic-rich sediment affected the long-term MAR, but not the ratio of (14)C/(12)C. Thus, the MAR and linear sedimentation rate obtained using (14)C (and other isotope-based methods) could be erroneous, although (14)C ages may not be affected by such remineralization. Long-term remineralization rates of organic matter has a direct bearing on the biogeochemical cycling of elements in aqueous systems and mass balance of elements needs to be taken into consideration.

  20. Using an independent geochronology based on palaeomagnetic secular variation (PSV) and atmospheric Pb deposition to date Baltic Sea sediments and infer 14C reservoir age

    NASA Astrophysics Data System (ADS)

    Lougheed, Bryan C.; Snowball, Ian; Moros, Matthias; Kabel, Karoline; Muscheler, Raimund; Virtasalo, Joonas J.; Wacker, Lukas

    2012-05-01

    Dating of sediment cores from the Baltic Sea has proven to be difficult due to uncertainties surrounding the 14C reservoir age and a scarcity of macrofossils suitable for dating. Here we present the results of multiple dating methods carried out on cores in the Gotland Deep area of the Baltic Sea. Particular emphasis is placed on the Littorina stage (8 ka ago to the present) of the Baltic Sea and possible changes in the 14C reservoir age of our dated samples. Three geochronological methods are used. Firstly, palaeomagnetic secular variations (PSV) are reconstructed, whereby ages are transferred to PSV features through comparison with varved lake sediment based PSV records. Secondly, lead (Pb) content and stable isotope analysis are used to identify past peaks in anthropogenic atmospheric Pb pollution. Lastly, 14C determinations were carried out on benthic foraminifera (Elphidium spec.) samples from the brackish Littorina stage of the Baltic Sea. Determinations carried out on smaller samples (as low as 4 μg C) employed an experimental, state-of-the-art method involving the direct measurement of CO2 from samples by a gas ion source without the need for a graphitisation step - the first time this method has been performed on foraminifera in an applied study. The PSV chronology, based on the uppermost Littorina stage sediments, produced ten age constraints between 6.29 and 1.29 cal ka BP, and the Pb depositional analysis produced two age constraints associated with the Medieval pollution peak. Analysis of PSV data shows that adequate directional data can be derived from both the present Littorina saline phase muds and Baltic Ice Lake stage varved glacial sediments. Ferrimagnetic iron sulphides, most likely authigenic greigite (Fe3S4), present in the intermediate Ancylus Lake freshwater stage sediments acquire a gyroremanent magnetisation during static alternating field (AF) demagnetisation, preventing the identification of a primary natural remanent magnetisation for

  1. Coastal lake sediments reveal 5500 years of tsunami history in south central Chile

    NASA Astrophysics Data System (ADS)

    Kempf, Philipp; Moernaut, Jasper; Van Daele, Maarten; Vandoorne, Willem; Pino, Mario; Urrutia, Roberto; De Batist, Marc

    2017-04-01

    We present an exceptionally long and continuous coastal lacustrine record of ∼5500 years from Lake Huelde on the west coast of Chiloé Island in south central Chile. The study area is located within the rupture zone of the giant 1960 CE Great Chilean Earthquake (MW 9.5). The subsequent earthquake-induced tsunami inundated Lake Huelde and deposited mud rip-up clasts, massive sand and a mud cap in the lake. Long sediment cores from 8 core sites within Lake Huelde reveal 16 additional sandy layers in the 5500 year long record. The sandy layers share sedimentological similarities with the deposit of the 1960 CE tsunami and other coastal lake tsunami deposits elsewhere. On the basis of general and site-specific criteria we interpret the sandy layers as tsunami deposits. Age-control is provided by four different methods, 1) 210Pb-dating, 2) the identification of the 137Cs-peak, 3) an infrared stimulated luminescence (IRSL) date and 4) 22 radiocarbon dates. The ages of each tsunami deposit are modelled using the Bayesian statistic tools of OxCal and Bacon. The record from Lake Huelde matches the 8 regionally known tsunami deposits from documented history and geological evidence from the last ∼2000 years without over- or underrepresentation. We extend the existing tsunami history by 9 tsunami deposits. We discuss the advantages and disadvantages of various sedimentary environments for tsunami deposition and preservation, e.g. we find that Lake Huelde is 2-3 times less sensitive to relative sea-level change in comparison to coastal marshes in the same region.

  2. Discriminating Sediment Supply versus Accommodation Controls on Foreland Basin Stratigraphic Architecture in the Book Cliffs, central Utah using Detrital Double Dating

    NASA Astrophysics Data System (ADS)

    Bartschi, N.; Saylor, J. E.; Blum, M. D.

    2014-12-01

    Middle-late Campanian strata of the Book Cliffs record the deposition of three clastic wedges in the foreland basin east of the Sevier fold-thrust belt. Variations in wedge geometries provide an opportunity to evaluate the effects of sediment supply versus accommodation on foreland basin architecture. There is an increase in eastward progradation rate between the L. and M. Castlegate Sandstone, followed by a return to slower progradation rates in the overlying Bluecastle Tongue, and Price River Formation, as well as their lateral equivalents. Rapid progradation may be caused by increased sediment supply, due either to rapid exhumation in the Sevier fold-thrust belt, or changes in the sediment source. Alternatively, reduced accommodation within the foreland basin due to uplift during initial Laramide deformation could produce the same rapid progradation. In this scenario, decreased progradation would be coincident with enhanced foreland basin subsidence and rapid sediment accumulation in the proximal foredeep. We test these hypotheses using thermo- and geochronology to double date individual detrital grains, enabling identification of changes in lag time and sediment provenance. Upsection decreases or increases in lag time correspond to increased or decreased exhumation rates, respectively, or introduction of a new upper crustal sedimentary source. We focus on 21 samples from 7 measured sections along depositional strike and dip. Samples were collected from the upper Blackhawk Formation, L. and M. Castlegate Sandstone, Bluecastle Tongue, Price River Formation, and their lateral equivalents. Initial results indicate major sediment provenance changes associated with the transition between slow and rapid wedge progradation, as well as minor provenance changes within individual wedges. There is also a significantly greater proportion of Cordilleran magmatic arc grains in distal locations than in proximal locations, interpreted as sediment mixing during transport.

  3. Testing the potential of OSL, TT-OSL, IRSL and post-IR IRSL luminescence dating on a Middle Pleistocene sediment record of Lake El'gygytgyn, Russia

    NASA Astrophysics Data System (ADS)

    Zander, A.; Hilgers, A.

    2012-09-01

    Lake El'gygytgyn is a 12 km wide crater lake located in remote Chukotka in the far East Russian Arctic about 100 km to the north of the Arctic Circle. It was formed by a meteorite impact about 3.58 Ma ago. This study tests the paleomagnetic and proxy data-based Mid- to Late-Pleistocene sediment deposition history using novel luminescence dating techniques of sediment cores taken from the centre of the 175 m deep lake. For dating polymineral and quartz fine grains (4-11 μm grain size range) were extracted from nine different levels from the upper 28 m of sediment cores 5011-1A and 5011-1B. Polymineral sub-samples were analysed by infra-red stimulated luminescence (IRSL) and post-IR infra-red stimulated luminescence (post-IR IRSL) using single aliquot regenerative dose (SAR) sequences. SAR protocols were further applied to measure the blue light optically stimulated luminescence (OSL) and thermally-transferred OSL (TT-OSL) of fine-grained quartz supplemented by a multiple aliquot TT-OSL approach. According to an independent age model, the lowest sample from 27.8-27.9 m below lake bottom level correlates to the Brunhes-Matuyama (B/M) reversal. Finally, the SAR post-IR-IRSL protocol applied to polymineral fine grains was the only luminescence technique able to provide dating results of acceptable accuracy up to ca. 700 ka. Major factors limiting precision and accuracy of the luminescence chronology are, for some samples, natural signals already approaching saturation level, and overall the uncertainty related to the sediment water content and its variations over geological times.

  4. Three Gorges Dam controls sediment coarsening of the mud patch on the inner East China Sea shelf

    NASA Astrophysics Data System (ADS)

    Miao, Anyang; Chu, Zhongxin; Li, Yingkun

    2016-06-01

    The well-known Three Gorges Dam (TGD) within the Yangtze catchment launched its operation in 2003. The effect of the TGD operation on the sediment size on the East China Sea shelf is rarely known. High resolution (0.5 cm sampling) grain size analysis and 137Cs and 210Pb dating of the DH8-1 core were conducted with core collected from the distal part of a main sink for the modern Yangtze sediment entering the sea, the Min-Zhe Coastal Mud Deposits (MZCMD) on the inner East China Sea shelf. The 137Cs dating results show that the core DH8-1 formed during 1946-2012 with a mean deposition rate of 0.65 cm yr-1, indicating that the 0.5 cm sampling for grain size analysis in this local area could reflect environmental changes generally on a one-year time scale. The mean grain size of DH8-1 core sediment that deposited after 2003 is significantly larger than that deposited during 1988-2002. After ruling out other possible factors, we infer that the sediment coarsening of DH8-1 core after 2003 is attributed to the TGD operation which causes the erosion of the Yangtze subaqueous delta. Specifically, the TGD operation significantly intensifies the declining trend of the Yangtze sediment loads to the sea despite no decreased water discharge, which results in extensive erosion of the Yangtze subaqueous delta. The relatively coarse sediment of the subaqueous delta is eroded and resuspended by ocean dynamics and then transported by coastal current, finally depositing on the MZCMD area. In addition, the general sediment fining of core DH8-1 that deposited during 1988-2002, comparing with 1946-1987, is mainly caused by dam construction and soil and water conservation within the Yangtze catchment. Our findings are helpful for better understanding the effects of such a huge dam as the TGD on a sediment sink like the MZCMD of such a large river as the Yangtze River.

  5. Temporal and spatial distributions of contaminants in sediments of Santa Monica Bay, California

    USGS Publications Warehouse

    Bay, S.M.; Zeng, E.Y.; Lorenson, T.D.; Tran, K.; Alexander, Corrine

    2003-01-01

    Contaminant inputs from wastewater discharge, a major source of contamination to Santa Monica Bay (SMB), have declined drastically during the last three decades as a result of improved treatment processes and better source control. To assess the concomitant temporal changes in the SMB sediments, a study was initiated in June 1997, in which 25 box cores were collected using a stratified random sampling design. Five sediment strata corresponding to the time intervals of 1890-1920, 1932-1963, 1965-1979, 1979-1989, and 1989-1997 were identified using 210Pb dating techniques. Samples from each stratum were analyzed for metals, 1,1,1-Trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and its metabolites (DDTs), polychlorinated biphenyls (PCBs), and total organic carbon (TOC). Samples from the 1965-1979, 1979-1989, and 1989-1997 strata were also analyzed for polycyclic aromatic hydrocarbons (PAHs) and linear alkylbenzenes (LABs). Sediment metal concentrations increased from 1890-1979 and were similar during the time intervals of 1965-1979, 1979-1989, and 1989-1997, although the mass emissions of trace metals from sewage inputs declined substantially during the same time period. Trace organic contamination in SMB was generally highest in sediments corresponding to deposition during the years of 1965-1979 or 1979-1989 and showed a decline in concentration in the 1989-1997 stratum. Temporal trends of contamination were greatest in sediments collected from areas near the Hyperion Treatment Plant (HTP) outfall system and on the slope of Redondo Canyon. The highest contaminant concentrations were present in sediments near the HTP 7-mile outfall in the 1965-1979 stratum. Elevated trace metal and organic concentrations were still present in the 1989-1997 stratum of most stations, suggesting that sediment contaminants have moved vertically in the sediment column since sludge discharges from the 7-mile outfall (a dominant source of contamination to the bay) ceased in 1987. The

  6. Chemical fractionation of lake sediments to determine the effects of land-use change on nutrient loading

    NASA Astrophysics Data System (ADS)

    Heathwaite, A. L.

    1994-07-01

    Lake studies allow contemporary sediment and nutrient dynamics to be placed in a historical context in order that trends and rates of change in catchment inputs may be calculated. Here, a synthesis of the temporal information contained in catchment and lake sediment records is attempted. A chemical fractionation technique is used to isolate the different sediment sources contained in the lake core, and 210Pb dates provide an accurate record of changes in lake sediment sources over the past 100 years. The extent to which land-use records, collated from agricultural census returns, and process-based studies of sediment and nutrient export from different catchment land uses can be used to explain the trends observed in the lake sediments is examined. Sediment influx to the study lake has increased from less than 2 mm year -1 prior to the Second World War to over 10 mm year -1 at present. The source of the sediment is largely unaltered and unweathered allochthonous material eroded from the catchment. Land-use records suggest that the intensification of agriculture, characterized by a shift towards arable land immediately postwar, followed by an increase in the area of temporary grass in the 1960s, may be the cause of accelerated catchment erosion; both land-use changes would have increased the area of ploughed land in the catchment. An increase in the number of cattle and sheep in the catchment from around 2000 and 6000, respectively, in the 1940s, to a peak of nearly 7000 cattle and over 15 000 sheep in the 1980s, provides a further source of sediment and nutrients. Livestock are grazed on permanent grassland which is commonly located on steep hillslopes and in riparian zones where saturation-excess surface runoff may be an important hydrological pathway. Rainfall simulation experiments show that surface runoff from heavily grazed grassland has a high suspended sediment, ammonium-nitrogen and particulate phosphorus load. The combined effect of the long-term increase

  7. Sedimentation and particle dynamics in the seasonal ice zone of the Barents Sea

    NASA Astrophysics Data System (ADS)

    Maiti, Kanchan; Carroll, JoLynn; Benitez-Nelson, Claudia R.

    2010-01-01

    The Barents Sea seasonal ice zone (SIZ) is one of the most dynamic areas in the world ocean. This biologically productive area undergoes extreme intra- and inter-annual variabilities in sea ice and water mass transport properties. Here, we investigate seafloor burial processes in three regions of the SIZ with different ice-cover frequencies: predominantly open water (POW), marginally ice-covered (MIC), and predominantly ice-covered (PIC) with approximately 0, 10 and 50% sea ice cover, respectively, in 2002-2003. Down-core sediment profiles of the radionuclides 234Th, 210Pb, and 137Cs, along with sediment carbon, nitrogen and phosphorus concentrations are examined in two to three cores from each region. Sedimentation rates and velocities using 210Pb ex (excess 210Pb) profiles and assuming negligible mixing below a surface mixed layer are relatively uniform throughout the study area, averaging 558 ± 154 g m - 2 y - 1 and 1.1 ± 0.4 mm y - 1 ( n = 7). These sedimentation velocities are confirmed using 137Cs (1.0 ± 0.4 mm y - 1 , n = 7). 234Th ex (excess 234Th) derived bioturbation rates are positively correlated with number of benthic individuals per 0.5 m 2 ( R2 = 0.83) and exhibit a pattern of higher rates in the MIC (14.5 ± 2.1 cm - 2 y - 1) relative to both the POW (6.3 ± 2.2 cm - 2 y - 1) and PIC (5.3 ± 1.2 cm - 2 y - 1) ( p < 0.01). 234Th ex inventories are also significantly higher ( p = 0.026) within the MIC, while both 210Pb ex and 137Cs sediment inventories are more regionally uniform. Furthermore, organic carbon (C org) and total nitrogen (N tot) concentrations are relatively high in both the MIC and PIC compared to POW. For this limited data set, higher bioturbation rate coefficients and higher 234Th ex sediment inventories in the MIC relative to the other sampled regions, suggest that the MIC exhibits a greater predominance of marine versus terrestrial sediment sources that support enhanced scavenging and benthic biological activity. These results

  8. The Imprints of the Solar Activity during the Little Ice Age and the Medieval Climatic Anomaly in SW Anatolia from Lake Sediments

    NASA Astrophysics Data System (ADS)

    Bauchi Danladi, Iliya; Akçer-Ön, Sena

    2016-04-01

    Due to the variability of the Little Ice Age (LIA) and Medieval Climatic Anomaly (MCA), several climatic forcing mechanisms have been invoked to enlighten the issue. The focus of this study is on the influence of the solar activity proxy (Total Solar Irradiance) during the LIA and MCA in a high altitude Lake Salda in south-western Anatolia. In order to understand this, we recovered 5 gravity cores with various lengths and from various locations in the lake. We used high-resolution multi proxy approach which includes Itrax XRF scanner at a resolution of 2mm, Multi Sensor Core Logger (MSCL) at a resolution of 5 mm and TOC/TIC analysis at a resolution of 30 mm. 210Pb-137Cs methods were employed for dating and afterwards were tuned with solar activity proxy (Total Solar Irradiance) data for age improvement. As a result, the sediment records cover the last millennium. We have observed the effect of the solar activity throughout the LIA and MCA in Lake Salda, with wet and dry spells corresponding to high and low TSI respectively. In addition, the Dalton Minimum, Maunder Minimum, Spörer Minimum, Wolf Minimum, the Medieval Maximum and the Oort Minimum have been observed.

  9. Sediment input pathways from North American highlands to the Gulf of Mexico based on detrital zircon U-Pb and U-Th/He dating

    NASA Astrophysics Data System (ADS)

    Xu, J.; Snedden, J.; Stockli, D. F.; Fulthorpe, C.

    2014-12-01

    The lower Miocene is a period of significant sediment input to the Gulf of Mexico (GOM) Basin that accompanied tectonic and climatic changes in North America. However, the resulting sediment pathways from continental upland sources to basinal sink remain poorly constrained. We employ detrital zircon (DZ) U-Pb and (U-Th)/He double dating to define both basement provenance and the exhumation histories of detrital source regions. We have collected samples from outcrops across the northern Gulf, from Texas to Florida, in order to discriminate sediment pathways. Most of our data show a mixture of source terranes, including Oligocene volcanic centers, Cordilleran Arc, Laramide uplifts, Grenville, Mid-Continent, Yavapai-Mazatzal, and Appalachian-Ouachita as major provinces and Wyoming and Superior regions as minor provinces. However, major DZ age peaks vary greatly between different samples, providing a means to differentia drainage systems. Five major sediment input pathways are defined: the Paleo-Rio Grande, Paleo-Red, Paleo-Mississippi and Paleo-Tennessee rivers and a local river system in Florida draining from Appalachians. The Paleo-Rio Grande and Paleo-Red rivers show a significant sediment input from Oligocene volcanic centers, Laramide uplift regions and the Cordilleran Arc, whereas the Paleo-Tennessee River received most of its sediments from Appalachian-Ouachita and Grenville basement. The Paleo-Mississippi River lies within a transitional zone between western and eastern North American drainage systems. By integrating (U-Th)/He ages we can further distinguish first order volcanic zircons from recycled zircons. This can increase the ability to discriminate different drainage systems because the recycled zircons come from source terranes that are different from the original basement in which they formed. For example, two different Grenville-age zircon sources are differentiated by our U-Pb and (U-Th)/He ages. Sediments in Texas show a mixed zircon source from

  10. Sources of land-derived runoff to a coral reef-fringed embayment identified using geochemical tracers in nearshore sediment traps

    NASA Astrophysics Data System (ADS)

    Takesue, Renee K.; Bothner, Michael H.; Reynolds, Richard L.

    2009-11-01

    Geochemical tracers, including Ba, Co, Th, 7Be, 137Cs and 210Pb, and magnetic properties were used to characterize terrestrial runoff collected in nearshore time-series sediment traps in Hanalei Bay, Kauai, during flood and dry conditions in summer 2006, and to fingerprint possible runoff sources in the lower watershed. In combination, the tracers indicate that runoff during a flood in August could have come from cultivated taro fields bordering the lower reach of the river. Land-based runoff associated with summer floods may have a greater impact on coral reef communities in Hanalei Bay than in winter because sediment persists for several months. During dry periods, sediment carried by the Hanalei River appears to have been mobilized primarily by undercutting of low 7Be, low 137Cs riverbanks composed of soil weathered from tholeiitic basalt with low Ba and Co concentrations. Following a moderate rainfall event in September, high 7Be sediment carried by the Hanalei River was probably mobilized by overland flow in the upper watershed. Ba-desorption in low-salinity coastal water limited its use to a qualitative runoff tracer in nearshore sediment. 210Pb had limited usefulness as a terrestrial tracer in the nearshore due to a large dissolved oceanic source and scavenging onto resuspended bottom sediment. 210Pb-scavenging does, however, illustrate the role resuspension could play in the accumulation of particle-reactive contaminants in nearshore sediment. Co and 137Cs were not affected by desorption or geochemical scavenging and showed the greatest potential as quantitative sediment provenance indicators in material collected in nearshore sediment traps.

  11. Sources of land-derived runoff to a coral reef-fringed embayment identified using geochemical tracers in nearshore sediment traps

    USGS Publications Warehouse

    Takesue, R.K.; Bothner, Michael H.; Reynolds, R.L.

    2009-01-01

    Geochemical tracers, including Ba, Co, Th, 7Be, 137Cs and 210Pb, and magnetic properties were used to characterize terrestrial runoff collected in nearshore time-series sediment traps in Hanalei Bay, Kauai, during flood and dry conditions in summer 2006, and to fingerprint possible runoff sources in the lower watershed. In combination, the tracers indicate that runoff during a flood in August could have come from cultivated taro fields bordering the lower reach of the river. Land-based runoff associated with summer floods may have a greater impact on coral reef communities in Hanalei Bay than in winter because sediment persists for several months. During dry periods, sediment carried by the Hanalei River appears to have been mobilized primarily by undercutting of low 7Be, low 137Cs riverbanks composed of soil weathered from tholeiitic basalt with low Ba and Co concentrations. Following a moderate rainfall event in September, high 7Be sediment carried by the Hanalei River was probably mobilized by overland flow in the upper watershed. Ba-desorption in low-salinity coastal water limited its use to a qualitative runoff tracer in nearshore sediment. 210Pb had limited usefulness as a terrestrial tracer in the nearshore due to a large dissolved oceanic source and scavenging onto resuspended bottom sediment. 210Pb-scavenging does, however, illustrate the role resuspension could play in the accumulation of particle-reactive contaminants in nearshore sediment. Co and 137Cs were not affected by desorption or geochemical scavenging and showed the greatest potential as quantitative sediment provenance indicators in material collected in nearshore sediment traps.

  12. Sediment record of polycyclic aromatic hydrocarbons in the Liaohe River Delta wetland, Northeast China: Implications for regional population migration and economic development.

    PubMed

    Ma, Chuanliang; Lin, Tian; Ye, Siyuan; Ding, Xigui; Li, Yuanyuan; Guo, Zhigang

    2017-03-01

    The polycyclic aromatic hydrocarbons (PAHs) of a (210)Pb-dated sediment core extracted from the Liaohe River Delta wetland were measured to reconstruct the sediment record of PAHs and its response to human activity for the past 300 years in Northeast China. The concentrations of the 16 U.S. Environmental Protection Agency priority PAHs (∑16PAHs) ranged from 46 to 1167 ng g(-1) in this sediment core. The concentrations of the 16 PAHs (especially 4- and 5+6-ring PAHs) after the 1980s (surface sediments 0-6 cm) were one or two orders of magnitudes higher than those of the down-core samples. The exponential growth of 4-ring and 5+6-ring PAH concentrations after the 1980s responded well to the increased energy consumption and number of civil vehicles resulting from the rapid economic development in China. Prior to 1950, relatively low levels of the 16 PAHs and a high proportion of 2+3-ring PAHs was indicative of biomass burning as the main source of the PAHs. A significant increase in the 2 + 3 ring PAH concentration from the 1860s-1920s was observed and could be attributed to a constant influx of population migration into Northeast China. It was suggested that the link between historical trend of PAHs and population or energy use involves two different economic stages. Typically, in an agricultural economy, the greater the population size, the greater the emission of PAHs from biomass burning, while in an industrial economy, the increase in sedimentary PAH concentrations is closely related to increasing energy consumption of fossil fuels.

  13. Biogeochemical evaluation of historical sediment contamination in the Gulf of Palermo (NW Sicily): Analysis of pseudo-trace elements and stable isotope signals

    NASA Astrophysics Data System (ADS)

    Di Leonardo, Rossella; Cundy, Andrew B.; Bellanca, Adriana; Mazzola, Antonio; Vizzini, Salvatrice

    2012-06-01

    Sedimentary biogeochemical data from the Gulf of Palermo, which borders one of the major urban and industrial areas of the central Mediterranean, provide a decennial-centennial-scale record of the effects of human activity on this coastal environment. In this study we report trace elements (TE), Corg/Ntot ratios, δ13Corg, and δ15Ntot from dated (210Pb) sediments collected in two coastal stations variably influenced by urban/fluvial loadings and illegal dumping and we compare them with published data for offshore sediments, in order to investigate at a large spatial scale the influence of on-land activities on sedimentary marine system. TE were generally low except for Hg and Pb, which exhibited moderate enrichments. Low TE enrichment factors with respect to Corg indicate that trace elements were mainly trapped by sedimentary organic matter. Corg/Ntot, δ13Corg, and δ15Ntot depth profiles showed that sediments received organic matter derived from marine sources mixed with organic matter from the erosion of terrestrial material as well as unregulated sewage discharges. Superimposed on these patterns, repeated shifts in δ13Corg towards values higher than those typical of offshore Palermo sediments were concomitant with higher Corg/Ntot. These shifts observed in the core portions covering the last 40 years reflect enhanced eutrophication as result of elevated nutrient input into marine waters. The results of this study have traced the origin and extent of the organic enrichment and emphasized the importance of utilizing a complete range of chemical and isotopic analyses from sedimentary records to reconstruct the environmental history of coastal ecosystems impacted by urbanization processes.

  14. Sediment accretion and organic carbon burial relative to sea-level rise and storm events in two mangrove forests in Everglades National Park

    USGS Publications Warehouse

    Smoak, Joseph M.; Breithaupt, Joshua L.; Smith, Thomas J.; Sanders, Christian J.

    2013-01-01

    The goal of this investigation was to examine how sediment accretion and organic carbon (OC) burial rates in mangrove forests respond to climate change. Specifically, will the accretion rates keep pace with sea-level rise, and what is the source and fate of OC in the system? Mass accumulation, accretion and OC burial rates were determined via 210Pb dating (i.e. 100 year time scale) on sediment cores collected from two mangrove forest sites within Everglades National Park, Florida (USA). Enhanced mass accumulation, accretion and OC burial rates were found in an upper layer that corresponded to a well-documented storm surge deposit. Accretion rates were 5.9 and 6.5 mm yr−1 within the storm deposit compared to overall rates of 2.5 and 3.6 mm yr−1. These rates were found to be matching or exceeding average sea-level rise reported for Key West, Florida. Organic carbon burial rates were 260 and 393 g m−2 yr−1 within the storm deposit compared to 151 and 168 g m−2 yr−1 overall burial rates. The overall rates are similar to global estimates for OC burial in marine wetlands. With tropical storms being a frequent occurrence in this region the resulting storm surge deposits are an important mechanism for maintaining both overall accretion and OC burial rates. Enhanced OC burial rates within the storm deposit could be due to an increase in productivity created from higher concentrations of phosphorus within storm-delivered sediments and/or from the deposition of allochthonous OC. Climate change-amplified storms and sea-level rise could damage mangrove forests, exposing previously buried OC to oxidation and contribute to increasing atmospheric CO2 concentrations. However, the processes described here provide a mechanism whereby oxidation of OC would be limited and the overall OC reservoir maintained within the mangrove forest sediments.

  15. Sediment accretion rates and sediment composition in Prairie Pothole wetlands under varying land use practices, Montana, United States

    USGS Publications Warehouse

    Preston, T.M.; Sojda, R.S.; Gleason, R.A.

    2013-01-01

    Increased sedimentation and nutrient cycle changes in Prairie Pothole Region wetlands associated with agriculture threaten the permanence and ecological functionality of these important resources. To determine the effects of land use on sedimentation and nutrient cycling, soil cores were analyzed for cesium-137 (137Cs), lead-210 (210Pb), and potassium-40 (40K) activities; textural composition; organic and inorganic carbon (C); and total nitrogen (N) from twelve wetlands surrounded by cropland, Conservation Reserve Program (CRP) lands, or native prairie uplands. Separate soil cores from nine of these wetlands were also analyzed for phosphorus (P), nitrate (NO3), and ammonium (NH4) concentrations. Wetlands surrounded by cropland had significantly greater linear sediment accretion rates than wetlands surrounded by CRP or native prairie. Linear sediment accretion rates from wetlands surrounded by cropland were 2.7 and 6 times greater than wetlands surrounded by native prairie when calculated from the initial and peak occurrence of 137Cs, respectively, and 0.15 cm y−1 (0.06 in yr−1) greater when calculated from 210Pb. Relative to wetlands surrounded by CRP, linear sediment accretion rates for wetlands surrounded by cropland were 4.4 times greater when calculated from the peak occurrence of 137Cs. No significant differences existed between the linear sediment accretion rates between wetlands surrounded by native prairie or CRP uplands. Wetlands surrounded by cropland had increased clay, P, NO3, and NH4, and decreased total C and N concentrations compared to wetlands surrounded by native prairie. Wetlands surrounded by CRP had the lowest P and NO3 concentrations and had clay, NH4, C, and N concentrations between those of cropland and native prairie wetlands. We documented increased linear sediment accretion rates and changes in the textural and chemical properties of sediments in wetlands with cultivated uplands relative to wetlands with native prairie uplands. These

  16. Long-term recovery of PCB-contaminated surface sediments at the Sangamo-westonl Twelvemile Creek/lake Hartwell Superfund Site.

    PubMed

    Brenner, Richard C; Magar, Victor S; Ickes, Jennifer A; Foote, Eric A; Abbott, James E; Bingler, Linda S; Crecelius, Eric A

    2004-04-15

    Natural recovery of contaminated sediments relies on burial of contaminated sediments with increasingly clean sediments over time (i.e., natural capping). Natural capping reduces the risk of resuspension of contaminated surface sediments, and it reduces the potential for contaminant transport into the food chain by limiting bioturbation of contaminated surface or near-surface sediments. This study evaluated the natural recovery of surface sediments contaminated with polychlorinated biphenyls (PCBs) at the Sangamo-Weston/Twelvemile Creek/Lake Hartwell Superfund Site (Lake Hartwell), Pickens County, SC. The primary focus was on sediment recovery resulting from natural capping processes. Total PCB (t-PCB), lead-210 (210Pb), and cesium-137 (137Cs) sediment core profiles were used to establish vertical t-PCB concentration profiles, age date sediments, and determine surface sedimentation and surface sediment recovery rates in 18 cores collected along 10 transects. Four upgradient transects in the headwaters of Lake Hartwell were impacted by historical sediment releases from three upgradient sediment impoundments. These transects were characterized by silt/ clay and sand layering. The highest PCB concentrations were associated with silt/clay layers (1.8-3.5% total organic carbon (TOC)), while sand layers (0.05-0.32% TOC) contained much lower PCB concentrations. The historical sediment releases resulted in substantial burial of PCB-contaminated sediment in the vicinity of these four cores; each core contained less than 1 mg/kg t-PCBs in the surface sand layers. Cores collected from six downgradient Lake Hartwell transects consisted primarily of silt and clay (0.91-5.1% TOC) and were less noticeably impacted by the release of sand from the impoundments. Vertical t-PCB concentration profiles in these cores began with relatively low PCB concentrations at the sediment-water interface and increased in concentration with depth until maximum PCB concentrations were measured at

  17. 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...

  18. Modern accumulation rates and a budget of sediment off the Gaoping (Kaoping) River, SW Taiwan: A tidal and flood dominated depositional environment around a submarine canyon

    NASA Astrophysics Data System (ADS)

    Huh, Chih-An; Lin, Hui-Ling; Lin, Saulwood; Huang, Ya-Wen

    2009-03-01

    Ninety-two box cores collected during 2004-2006 from an area of ~ 3000 km 2 off the Gaoping (formerly spelled Kaoping) River, SW Taiwan, were analyzed for fallout radionuclides ( 210Pb, 137Cs and 7Be) to elucidate sedimentation rates and processes, and for the calculation of a sediment budget. The study area is located at an active collision margin with a narrow shelf and a submarine canyon extending essentially into the river's mouth. The results indicate fairly constant hemipelagic sedimentation in much of the open margin and for most of the time except in the inner shelf and along the axis of the canyon where sediment transport is more dynamic and is controlled by tidal current and wave activities constantly, and by fluvial floods or gravity-driven flows episodically. Sedimentation rates in the study area derived from 210Pb and constrained by 137Cs vary from 0.04 to 1.5 cm/yr, with the highest rates (> 1 cm/yr) flanking the Gaoping canyon over the upper slope (200-600 m) and the lowest rates (< 0.1 cm/yr) in the distal basin beyond the continental slope. The depocenter delineated from 210Pb-based sedimentation rates overlaps with the area covered by a flood layer resulting from super-typhoon Haitang in July 2005. Such correspondence supports the notion that the processes operating on event timescale have bearing on the formation of the sediment strata over centennial or longer timescales. From the distribution of sedimentation rates, sediment deposited in the study area annually is estimated to be 6.6 Mton/yr, accounting for less than 20% of Gaoping River's sediment load. The calculated budget, coupled with the presence of the short-lived 7Be and non-steady-state distribution of low levels of 210Pb in sediments along the canyon floor, suggests rapid transport of sediment from Gaoping River's mountainous watershed (the source) via the Gaoping (Kaoping) Submarine Canyon and adjacent channels (as the conduit and temporary sink) to the abyssal plain and the Manila

  19. Short-term Fallout Radionuclide Ratios and Mass Balance Identify New Suspended Sediments of Channel Origin and Importance of Catchment Flowpath

    NASA Astrophysics Data System (ADS)

    Karwan, Diana; Pizzuto, James; Aalto, Rolf; Marquard, Julia; Aufdenkampe, Anthony; Harpold, Adrian; Benthem, Adam; Skalak, Katherine; Levia, Delphis; Siegert, Courtney

    2016-04-01

    Fallout radionuclides and their ratios, such as beryllium-7 (7Be) and lead-210 (210Pb), are used to determine suspended sediment source and age in catchments. The ratio of beryllium-7 to lead-210 (7Be/210Pb) on suspended sediment has been used to estimate the fraction of "new" sediment in suspension. In the application of this model, "new" suspended sediment is often assumed to originate from recent landscape surface erosion that is delivered to the stream network. Fallout radionuclide deposition can vary across watersheds and on an event basis in a single watershed due to factors such as storm type, atmospheric height, and storm origin. In the White Clay Creek watershed within the mid-Atlantic USA, single-event deposition of 7Be varies from 15 - 177 Bq m-2 and 210Pb varies from 0 - 10 Bq m-2. 7Be/210Pb ratios vary from 7.9 to 17 within event precipitation and from 0.8 to 12.8 on suspended sediment. "New" sediment varies from 6 - 100% over the course of these events. 7Be mass balance during events shows that the majority of 7Be is retained within the catchment and not exported on suspended sediment. During summer thunderstorms, less than 1% of 7Be deposited on the watershed exits the stream channel. By comparing this flux with the direct channel interception of 7Be deposition in precipitation and throughfall we can determine the minimum amount of 7Be leaving the watershed that could occur in the absence of surface erosion. For example in summer thunderstorms, the entirety of the 7Be exiting the watershed on suspended sediment is less than the total activity deposited on the channel in direct precipitation. Channel-intercepted fallout radionuclides can exit the catchment by multiple mechanisms including the tagging of subaerial fluvial deposits with event precipitation; hence "new" suspended sediment originates from within the channel rather than from surface erosion. During extreme events, such as Hurricane Irene, less of the suspended sediment has been newly

  20. 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

  1. ESR dating of barite in sulphide deposits formed by the sea-floor hydrothermal activities.

    PubMed

    Toyoda, Shin; Fujiwara, Taisei; Uchida, Ai; Ishibashi, Jun-ichiro; Nakai, Shun'ichi; Takamasa, Asako

    2014-06-01

    Barite is a mineral newly found to be practically useful for electron spin resonance (ESR) dating of sulphide deposits formed by the sea-floor hydrothermal activities. The recent studies for the properties of the ESR dating signal in barite are summarised in the present paper as well as the formulas for corrections for accurate dose-rate estimation are developed including the dose-rate conversion factors, shape correction for gamma-ray dose and decay of (226)Ra. Although development of the techniques for ESR dating of barite has been completed, further comparative studies with other dating techniques such as U-Th and (226)Ra-(210)Pb dating are necessary for the technique to be widely used.

  2. Seismically-triggered organic-rich layers in recent sediments from Göllüköy Lake (North Anatolian Fault, Turkey)

    NASA Astrophysics Data System (ADS)

    Avşar, Ulaş; Hubert-Ferrari, Aurélia; De Batist, Marc; Lepoint, Gilles; Schmidt, Sabine; Fagel, Nathalie

    2014-11-01

    Multi-proxy analyses on the sedimentary sequence of Göllüköy Lake, which is located on the eastern North Anatolian Fault (NAF), reveals a complete and high-resolution paleoseismic record for the last 650 years. Six sedimentary events are detected in a 3.1 m-long piston core. They form distinct organic-rich intercalations within the background sedimentation, which are characterized by strong anomalies on the loss-on-ignition (LOI550) and total organic carbon (TOC) profiles, as well as by lighter colours on the X-ray radiographic images. Itrax micro-XRF core scanner data are also used to contribute to the detection and characterization of the event deposits. After the detection of the sedimentary events, their temporal correlation with the earthquakes in the historical seismicity catalogue of the NAF is tested. The youngest event is dated to 1940s by using 210Pb and 137Cs profiles in sediment, which coincides with the 1939 earthquake (Ms = 7.7) on the NAF. The ages of the older five events are determined based on radiocarbon dating and regional time-stratigraphic correlation. Radiocarbon dating on the bulk sediment samples does not provide reliable results due to hard-water effect. On the other hand, dating on charcoals, Ephippia of Daphnia and phragmite remains significantly improves the results and implies a mean sedimentation rate of 0.28 cm/yr. Based on this preliminary sedimentation rate, we show that organic matter content variations through our record correlate with the varve-based δ18O record of Nar Lake, which is located 350 km southwest of Göllüköy Lake. Accordingly, high-precipitation/low-evaporation climatic episodes detected in Nar Lake are represented by higher organic matter content in Göllüköy sediments. Fine-tuning the Göllüköy LOI550 record to the Nar δ18O record reveals that the ages of the sedimentary events in Göllüköy match with well-known historical earthquakes that occurred around the lake. Finally, the origin of the organic

  3. 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.

  4. Clear Lake sediments: anthropogenic changes in physical sedimentology and magnetic response.

    PubMed

    Osleger, David A; Zierenberg, Robert A; Suchanek, Thomas H; Stoner, Joseph S; Morgan, Sally; Adam, David P

    2008-12-01

    We analyzed the sedimentological characteristics and magnetic properties of cores from the three basins of Clear Lake, California, USA, to assess the depositional response to a series of land use changes that occurred in the watershed over the 20th century. Results indicate that distinct and abrupt shifts in particle size, magnetic concentration/mineralogy, and redox conditions occur concurrently with a variety of ecological and chemical changes in lake bed sediments. This coincidence of events occurred around 1927, a datum determined by an abrupt increase in total mercury (Hg) in Clear Lake cores and the known initiation of open-pit Hg mining at the Sulphur Bank Mercury Mine, confirmed by 210Pb dating. Ages below the 1927 horizon were determined by accelerator mass spectrometry on 14C of coarse organic debris. Calculated sedimentation rates below the 1927 datum are approximately 1 mm/yr, whereas rates from 1927 to 2000 are up to an order of magnitude higher, with averages of approximately 3.5-19 mm/yr. In both the Oaks and Upper Arms, the post-1927 co-occurrence of abrupt shifts in magnetic signatures with color differences indicative of changing redox conditions is interpreted to reflect a more oxygenated diagenetic regime and rapid burial of sediment below the depth of sulfate diffusion. Post-1927 in the Oaks Arm, grain size exhibits a gradual coarsening-upward pattern that we attribute to the input of mechanically deposited waste rock related to open-pit mining activities at the mine. In contrast, grain size in the Upper Arm exhibits a gradational fining-upward after 1927 that we interpret as human-induced erosion of fine-grained soils and chemically weathered rocks of the Franciscan Assemblage by heavy earthmoving equipment associated with a road- and home-building boom, exacerbated by stream channel mining and wetlands destruction. The flux of fine-grained sediment into the Upper Arm increased the nutrient load to the lake, and that in turn catalyzed profuse

  5. Spatial and temporal distributions of polycyclic aromatic hydrocarbons in sediments from the Songhua River, China

    NASA Astrophysics Data System (ADS)

    Dong, D.; Guo, Z.; Liu, X.; Hua, X.; Liang, D.

    2013-12-01

    Polycyclic aromatic hydrocarbons (PAHs), a class of typical persistent organic pollutants, widely exist in the environment and are potentially harmful to human health. They can enter the waters through atmospheric deposition, soil leaching, shipping, sewage discharges and surface runoff. In recent years, many studies on the distributions of PAHs in major rivers, lakes and bays around the world have been carried out. In this study, 9 surface sediments (0-10cm) were sampled from the Songhua River in Jilin and Heilongjiang provinces. The contents of 16 PAHs in the US Environmental Protection Agency list of priority pollutants were determined and their spatial distributions were discussed. Sediment cores (50cm length) in three oxbow lakes in this area were also collected and cut into 2 cm thickness sub-samples. PAHs concentrations in these samples were determined and the cores were dated using a 210Pb geochronology technique. Finally, the sedimentary history of PAHs in the Songhua River since the 1920s was revealed. Results indicated that total concentration of the 16 PAHs analyzed in the surface sediments was 187-2079 ng/g (dry weight), and the mean was 1029 ng/g. Sediments collected from near urban areas (Jilin and Harbin City) contained higher PAHs content. Compared with the domestic and international rivers, the PAHs content in this river sediments is at a medium level. The PAHs profiles showed that 2-3 ring PAHs, especially naphthalene, were dominant in all of the samples. Sedimentary flux can reflect the accumulating history of pollutants better. The PAHs fluxes were low and varied little from the 1920s to 1970s, but higher PAH fluxes were found since the 1980s in each core (Fig. 1). The PAHs sedimentary flux near Harbin City (Shuangcheng) was found changed remarkably. We inferred that the PAHs might be influenced by hydrological conditions, population mobility and economic activity in this area. PAHs sedimentary record in the Songhua River revealed that the

  6. Modern rates of glacial sediment accumulation along a 15° S-N transect in fjords from the Antarctic Peninsula to southern Chile

    NASA Astrophysics Data System (ADS)

    Boldt, Katherine V.; Nittrouer, Charles A.; Hallet, Bernard; Koppes, Michele N.; Forrest, Brittany K.; Wellner, Julia S.; Anderson, John B.

    2013-12-01

    of glacial erosion in temperate climates rank among the highest worldwide, and the sedimentary products of such erosion record climatic and tectonic signals in many glaciated settings, as well as temporal changes in glacier behavior. Glacial sediment yields are expected to decrease with increasing latitude because decreased temperature and meltwater production reduce glacial sliding, erosion, and sediment transfer; however, this expectation lacks a solid supportive database. Herein we present modern 210Pb-derived sediment accumulation rates on decadal to century time scales for 12 fjords spanning 15° of latitude from the Antarctic Peninsula to southern Chile and interpret the results in light of glacimarine sediment accumulation worldwide. 210Pb records from the Antarctic Peninsula show surprisingly steady sediment accumulation throughout the past century at rates of 1-7 mm yr-1, despite rapid warming and glacial retreat. Cores from the South Shetland Islands reveal accelerated sediment accumulation over the past few decades, likely due to changes in the thermal state of the glaciers in this region, which straddles the boundary between subpolar and temperate conditions. In Patagonia and Tierra del Fuego, sediment accumulates faster (11-24 mm yr-1), and previously collected seismic profiles show that rates reach meters per year close to the glacier termini. This increase in sediment accumulation rates with decreasing latitude reflects the gradient from subpolar to temperate climates and is consistent with glacial erosion being much faster in the temperate climate of southern Chile than in the polar climate of the Antarctic Peninsula.

  7. Possibility of wine dating using the natural Pb-210 radioactive isotope.

    PubMed

    Hubert, Ph; Pravikoff, M S; Gaye, J

    2015-04-01

    To control the authenticity of an old wine without opening the bottle, we developed a few years ago a method based on the measurement of the (137)Cs activity. However, for recent vintages, the (137)Cs activity drops to far too low values (most of the time less than 10 mBq/L for a 10-year-old wine) for this method to perform correctly. In this paper we examine the possibility to date wines using the natural radio-element (210)Pb which has a 22-year period. This new method we propose implies the opening of the bottle and the follow-on destruction of the wine itself, which means that it can only be used for investigating non-expensive bottles or wine lots where there are multiple bottles of the same provenance. Uncertainties on the resulting (210)Pb radioactivity values are large, up to more than 50%, mainly due to local atmospheric variations, which prevents us to carry out precise dating. However it can be used to discriminate between an old wine (pre-1952) and a young wine (past-1990), an information that cannot be obtained with the other techniques based on other isotopes ((137)Cs, (14)C or tritium).

  8. Geomorphology-based interpretation of sedimentation rates from radiodating, lower Passaic River, New Jersey, USA.

    PubMed

    Erickson, Michael J; Barnes, Charles R; Henderson, Matthew R; Romagnoli, Robert; Firstenberg, Clifford E

    2007-04-01

    Analysis of site geomorphology and sedimentation rates as an indicator of long-term bed stability is central to the evaluation of remedial alternatives for depositional aquatic environments. In conjunction with various investigations of contaminant distribution, sediment dynamics, and bed stability in the Passaic River Estuary, 121 sediment cores were collected in the early 1990s from the lower 9.7 km of the Passaic River and analyzed for lead-210 (210Pb), cesium-137 (137Cs), and other analytes. This paper opportunistically uses the extensive radiochemical dataset to examine the spatial patterns of long-term sedimentation rates in, and associated geomorphic aspects of, this area of the river. For the purposes of computing sedimentation rates, the utility of the 210Pb and 137Cs depositional profiles was assessed to inform appropriate interpretation. Sedimentation rates were computed for 90 datable cores by 3 different methods, depending on profile utility. A sedimentation rate of 0 was assigned to 17 additional cores that were not datable and for which evidence of no deposition exists. Sedimentation patterns were assessed by grouping results within similar geomorphic areas, delineated through inspection of bathymetric data. On the basis of channel morphology, results reflect expected patterns, with the highest sedimentation rates observed along point bars and channel margins. The lowest rates of sedimentation (and the largest percentage of undatable cores) were observed in the areas along the outer banks of channel bends. Increasing sedimentation rates from upstream to downstream were noted. Average and median sedimentation rates were estimated to be 3.8 and 3.7 cm/y, respectively, reflecting the highly depositional nature of the Passaic River estuary. This finding is consistent with published descriptions of long-term geomorphology for Atlantic Coastal Plain estuaries.

  9. Radiological and multi-element analysis of sediments from the Proserpina reservoir (Spain) dating from Roman times.

    PubMed

    Baeza, A; Guillén, J; Ontalba Salamanca, M A; Rodríguez, A; Ager, F J

    2009-10-01

    The Proserpina dam was built in Roman times to provide drinking water to Emerita Augusta (today's Mérida in SW Spain). During maintenance work, a sediment core was extracted, offering an excellent opportunity to analyze the historical environmental impacts of the dam and its reservoir over the 2000 years since Roman times. In order to establish an accurate chronology, (14)C ages were determined by accelerator mass spectrometry (AMS). Core samples were assayed for their content in uranium and thorium series isotopes, (40)K, and the anthropogenic radionuclides (137)Cs, (90)Sr, and (239+240)Pu. Potassium-40 presented the highest activity level and was not constant with depth. The uranium and thorium series were generally in equilibrium, suggesting there had been no additional input of natural radionuclides. The presence of (137)Cs was only found in relation with the global fallout in the early 1960s. Multi-element assays were performed using the PIXE and PIGE techniques. Some variations in the multi-element concentrations were observed with depth, but the sediment core could be considered as clean, and no presumptive anthropogenic pollutants were found. Nevertheless, an unusually high Zn content was detected at depths corresponding to pre-Roman times, due to geological anomalies in the area.

  10. Sulfur and carbon cycling in organic-rich marine sediments

    NASA Technical Reports Server (NTRS)

    Martens, C. S.

    1985-01-01

    Nearshore, continental shelf, and slope sediments are important sites of microbially mediated carbon and sulfur cycling. Marine geochemists investigated the rates and mechanisms of cycling processes in these environments by chemical distribution studies, in situ rate measurements, and steady state kinetic modeling. Pore water chemical distributions, sulfate reduction rates, and sediment water chemical fluxes were used to describe cycling on a ten year time scale in a small, rapidly depositing coastal basin, Cape Lookout Bight, and at general sites on the upper continental slope off North Carolina, U.S.A. In combination with 210 Pb sediment accumulation rates, these data were used to establish quantitative carbon and sulfur budgets as well as the relative importance of sulfate reduction and methanogeneis as the last steps in the degradation of organic matter.

  11. Recent 137Cs deposition in sediments of Admiralty Bay, Antarctica.

    PubMed

    Sanders, Christian J; Santos, Isaac R; Patchineelam, Sambasiva R; Schaefer, Carlos; Silva-Filho, Emmanoel V

    2010-05-01

    Cesium-137, radium-226 and lead-210 profiles of a 25 cm sediment core give an indication of recent changes in land-ocean interactions at a polar coastal environment (Admiralty Bay, King George Island, Antarctica). The linear sedimentation accumulation rate at the study site calculated from the unsupported (210)Pb profile was 6.7 mm/year from 1965 to 2005. A 3.5-fold increase in (137)Cs concentrations was observed in the top layer of this sediment core. This sharp increase seems to indicate a recent redistribution of fallout radionuclides previously deposited on soil, vegetation and snow. These results imply enhanced land-ocean interactions at this site likely as a result of climate change. Because our results are based on a single core, additional investigations are needed to confirm our observations.

  12. Apportionment of polycyclic aromatic hydrocarbon sources in lower Fox River, USA, sediments by a chemical mass balance model

    SciTech Connect

    Su, M.C.; Christensen, E.R.; Karls, J.F.; Kosuru, S.; Imamoglu, I.

    2000-06-01

    Four sediment cores were collected from the lower Fox River, Wisconsin, USA, to identify possible sources of polycyclic aromatic hydrocarbons (PAHs) using a chemical mass balance model. The cores, which were obtained in 1995 from areas close to Green Bay, Wisconsin, USA, had total PAH concentrations between 19.3 and 0.34 ppm. To determine historical trends of PAH inputs, {sup 210}Pb and {sup 137}Cs dating was used, and elemental carbon particle analysis was done to characterize particles from the combustion of coal, wood, and petroleum. Source fingerprints were taken from the literature. Their results indicate that coke oven emissions, highway dust, coal gasification, and wood burning are likely sources of PAHs in the lower Fox River. Coke oven emissions are in the range of 40 to 90% of total PAHs, and this fraction decreases from 1930 to 1990, except in core Fox River-A (FR-A). The overall highway dust (HWY) contribution is between 10 and 75%, and this fraction increases from 1930 to present, except in core FR-A. The wood burning (WB) contribution is less than 7% in cores FR-B, FR-C, and FR-D. In core FR-A, a maximum ({approximately}23%) is found around 1960. The contribution of wood burning has changed from less than 6% in 1950 to between 3 and 10% in 1995. Evidence of aerobic biodegradation or photolysis in the sediment of phenanthrene, with a half-life of approximately 0.5 years has been found at the site of core FR-D, which is the shallowest (1.1 m) of the four core sites.

  13. A 2000-year palaeoflood record from northwest England from lake sediments

    NASA Astrophysics Data System (ADS)

    Schillereff, Daniel; Chiverrell, Richard; Macdonald, Neil; Hooke, Janet

    2014-05-01

    Greater insight into the relationship between climatic fluctuations and the frequency and magnitude of precipitation events over recent centuries is crucial in the context of future warming and projected intensification of hydrological extremes. However, the detection of trends in flood frequency and intensity is not a straightforward task as conventional flood series derived from instrumental sources rarely span sufficiently long timescales to capture the most extreme events. Usefully, the geomorphic effects of extreme hydrological events can be effectively recorded in upland lake basins as efficient sediment trapping preserves discharge-related proxy indicators (e.g., particle size). Provided distinct sedimentary signatures of historic floods are discernable and the sediment sequence can be well-constrained in time, these lacustrine archives offer a valuable data resource. We demonstrate that a series of sediment cores (3 - 5 m length) from Brotherswater, northwest England, contain numerous coarse-grained laminations, discerned by applying high-resolution (0.5 cm) laser granulometry, which are interpreted as reflecting a palaeoflood record extending to ~2000 yr BP. The presence of thick facies which exhibit inverse grading underlying normal grading, most likely reflecting the waxing and waning of flood-induced hyperpycnal flows, supports our palaeoflood interpretation. Data from an on-going sediment trapping protocol at Brotherswater that shows a relationship between river discharge (recorded via short-term lake level change representing flood events) and the calibre of particles captured in the traps lends further support to our interpretation. Well-constrained chronologies were constructed for the cores through integrating radionuclide (210Pb, 137Cs, 241Am, 14C) dating within a Bayesian age-depth modelling protocol. Geochemical markers of known-age that reflect phases of local point-source lead (Pb) mining were used to resolve time periods where radiocarbon

  14. Use of plutonium isotope activity ratios in dating recent sediments. [/sup 238/Pu//sup 239/Pu + /sup 240/Pu

    SciTech Connect

    Beasley, T. M.

    1982-01-01

    The majority of plutonium presently in the biosphere has come from the testing of nuclear devices. In the early 1950s, the Pu-238/239+240 activity ratio of fallout debris was > 0.04; in the more extensive test series of 1961 to 1962, the Pu-238/239+240 activity ratios were quite consistent at 0.02 to 0.03 and maximum fallout delivery occurred in mid-1963. A significant perturbation in Pu isotope activity ratios occurred in mid-1966 with the deposition of Pu-238 from the SNAP-9A reentry and burn-up. Recently deposited sediments have recorded these events and where accumulation rates are rapid (> 1 cm/y), changes in Pu isotope activity ratios can be used as a geochronological tool.

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

    USGS Publications Warehouse

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

    2001-01-01

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

  16. Use of OSL dating to establish the stratigraphic framework of Quaternary eolian sediments, Anton scarp upper trench, Northeastern Colorado High Plains, USA

    USGS Publications Warehouse

    Mahan, S.A.; Noe, D.C.; McCalpin, J.P.

    2009-01-01

    This paper contains the results of the optically stimulated luminescence (OSL) dating used to establish stratigraphic ages and relationships of eolian sediments in a trench in northeastern Colorado, USA. This trench was located in the upper face of the Anton scarp, a major topographic lineament trending NW-SE for a distance of 135 km, in anticipation of intersecting near-surface faulting. The trench was 180 m long, 4.5-6.0 m deep, and exposed 22 m of stratigraphic section, most of which dipped gently west and was truncated by gulley channeling at the face of the scarp. No direct evidence of faulting was found in the upper trench. The stratigraphy from the trench was described, mapped and dated using OSL on quartz and potassium feldspar, and 14C obtained from woody material. OSL dating identified two upper loess units as Peoria Loess and Gilman Canyon Loess, deposited between 16 and 30 ka ago. The bottom layers of the trench were substantially older, giving OSL ages in excess of 100 ka. These older ages are interpreted as underestimates, owing to saturation of the fast component of OSL. Using OSL and 14C dating, we can constrain the erosion and down cutting of the scarp face as occurring between 16 and 5.7 ka. As the trenching investigation continues in other parts of the scarp face, the results of this preliminary study will be of importance in relating the ages of the strata that underlie different parts of the scarp, and in determining whether Quaternary faulting was a mechanism that contributed to the formation of this regional geomorphic feature.

  17. Sediment accumulation and mercury (Hg) flux in Avicennia marina forest of Deep Bay, China

    NASA Astrophysics Data System (ADS)

    Li, Ruili; Chai, Minwei; Guo, Meixian; Qiu, Guo Yu

    2016-08-01

    To investigate the rate of sediment accumulation and mercury (Hg) flux in Avicennia marina forest of Deep Bay, China, sediment cores were analyzed. The results showed that Hg concentrations were much higher at all depths compared to the background level. A high correlation between Hg and total organic carbon (TOC) indicated their similar anthropogenic origin. Sedimentation rate was estimated to be 1.38 cm a-1 by 210Pb geochronology. The increase in the mass sediment accumulation rates was rapid (range: 0.5-0.94 g cm-2 a-1), and the Hg fluxes ranged between 76 and 116 ng cm-2 a-1 during the last three decades. The reduction in both Hg concentrations and flux during the last decade may be due to the adoption of contamination control policies. Our results support the notion that the Hg fluxes determined from the sediment cores reveal the effects of anthropogenic influences from the areas around Deep Bay.

  18. Remineralization of organic carbon in eastern Canadian continental margin sediments

    NASA Astrophysics Data System (ADS)

    Silverberg, Norman; Sundby, Bjørn; Mucci, Alfonso; Zhong, Shaojun; Arakaki, Takeshi; Hall, Per; Landén, Angela; Tengberg, Anders

    2000-04-01

    Undisturbed sediment samples were collected for chemical analyses at six sites during winter and summer cruises to the eastern Canadian continental margin. Micro-electrode oxygen profiles were obtained in freshly collected multicorer samples, and replicate cores were incubated at in situ temperature for 48 h to monitor changes in the concentrations of dissolved oxygen and nitrate. In addition, box cores were subsampled vertically for porewater chemistry, porosity, and particulate carbon. The data obtained are combined with estimates of sedimentation rate based on sediment trap measurements, 210Pb dating and historical data to evaluate the role of benthic processes in the carbon cycle on the eastern Canadian continental margin. With one exception, oxygen uptake rates determined from incubations and calculated from micro-profiles were very similar, indicating that exchange of oxygen across the sediment-water interface was dominated by molecular diffusion. On the basis of this observation, transport by diffusion is assumed for the calculation of the flux rates for other solutes from their respective porewater gradients. The fluxes of oxygen into the sediments were low, but generally comparable to other continental margins at comparable depths. They varied from 1.4 to 1.8 mmol/m 2/d in December 1993 and from 2.8 to 4.5 mmol/m 2/d in June 1994. Uptake of nitrate by the sediment occurred at all sites except for the continental slope off Nova Scotia. Both oxygen and nitrate uptake were higher in summer than in winter, indicative of a lingering response to the input of organic matter associated with the early spring bloom. At one of the sampling sites, Miscou Channel, the measured oxygen uptake rate far exceeded the flux calculated from the oxygen gradient. The difference suggests biologically enhanced exchange with the overlying waters at this site, consistent with the greater abundance of benthic organisms. The rate of organic carbon mineralization at the seafloor (1

  19. Causal links between Nile floods and eastern Mediterranean sapropel formation during the past 125 kyr confirmed by OSL and radiocarbon dating of Blue and White Nile sediments

    NASA Astrophysics Data System (ADS)

    Williams, M. A. J.; Duller, G. A. T.; Williams, F. M.; Woodward, J. C.; Macklin, M. G.; El Tom, O. A. M.; Munro, R. N.; El Hajaz, Y.; Barrows, T. T.

    2015-12-01

    It has long been hypothesised that beds of highly organic mud or sapropels seen in marine sediment cores retrieved from the floor of the eastern Mediterranean accumulated during times of high Nile fluvial discharge. Our recent fieldwork in the valleys of the Blue Nile, the White Nile and the main Nile has for the first time revealed a sequence of extreme flood episodes synchronous with sapropel units S5 (124 kyr), S4 (102 kyr), S3 (81 kyr), S2 (55 kyr) and S1 (13.5-6.5 kyr). There are more weakly defined links with Nile floods and sapropel units S9 (240 kyr), S8 (217 kyr), S7 (195 kyr), S6 (172 kyr), but the dating error terms are too large to allow us to be too definite. During times of extreme floods over the past 125 kyr, wide distributary channels of the Blue Nile flowed across the Gezira alluvial fan in central Sudan and transported a bed load of sand and gravel into the lower White Nile valley. The sands were reworked by wind to form source-bordering dunes, all of which contain heavy minerals of Ethiopian provenance. These source-bordering dunes were active at 115-105 kyr, 60 kyr and 12-7 kyr, all times of extreme Blue Nile floods. The flood and dune sediments were dated using a combination of optically stimulated luminescence (OSL) and radiocarbon analyses. The Quaternary record of Nile floods discussed here shows a precessional signal and reflects episodes of stronger summer monsoon and more northerly seasonal movement of the ITCZ, linked to times of higher insolation in northern tropical latitudes. Progressive aggradation of Holocene Nile channels in northern Sudan has had a profound influence upon human settlement in the last 8 kyr.

  20. Spatial and Temporal Patterns in Black Carbon Deposition to Dated Fennoscandian Arctic Lake Sediments from 1830 to 2010.

    PubMed

    Ruppel, Meri M; Gustafsson, Örjan; Rose, Neil L; Pesonen, Antto; Yang, Handong; Weckström, Jan; Palonen, Vesa; Oinonen, Markku J; Korhola, Atte

    2015-12-15

    Black carbon (BC) is fine particulate matter produced by the incomplete combustion of biomass and fossil fuels. It has a strong climate warming effect that is amplified in the Arctic. Long-term trends of BC play an important role in assessing the climatic effects of BC and in model validation. However, few historical BC records exist from high latitudes. We present five lake-sediment soot-BC (SBC) records from the Fennoscandian Arctic and compare them with records of spheroidal carbonaceous fly-ash particles (SCPs), another BC component, for ca. the last 120 years. The records show spatial and temporal variation in SBC fluxes. Two northernmost lakes indicate declining values from 1960 to the present, which is consistent with modeled BC deposition and atmospheric measurements in the area. However, two lakes located closer to the Kola Peninsula (Russia) have recorded increasing SBC fluxes from 1970 to the present, which is likely caused by regional industrial emissions. The increasing trend is in agreement with a Svalbard ice-core-BC record. The results suggest that BC deposition in parts of the European Arctic may have increased over the last few decades, and further studies are needed to clarify the spatial extent of the increasing BC values and to ascertain the climatic implications.

  1. Refined depositional history and dating of the Tongaporutuan reference section, north Taranaki, New Zealand: new volcanic ash U-Pb zircon ages, biostratigraphy and sedimentation rates

    USGS Publications Warehouse

    Maier, K.L.; Crundwell, Martin P.; Coble, Matthew A.; Kingsley-Smith, Peter R.; Graham, Stephan A.

    2016-01-01

    This study presents new radiometric ages from volcanic ash beds within a c. 1900 m thick, progradational, deep-water clastic slope succession of late Miocene age exposed along the north Taranaki coast of the North Island, New Zealand. The ash beds yield U–Pb zircon ages ranging from 10.63 ± 0.65 Ma to 8.97 ± 0.22 Ma. The new ages are compatible with and provide corroboration of New Zealand Tongaporutuan Stage planktic foraminiferal and bolboformid biostratigraphic events identified in the same section. The close accord between these two age datasets provides a stratigraphically consistent and coherent basis for examining margin evolution. The arrival of a prograding clastic wedge and ensuing upward shoaling is recorded by sedimentation rates c. 2000 m/Ma–1 that are an order of magnitude higher than sedimentation rates on the precursor deep basin floor. This outcrop study provides new constraints for interpreting analogous subsurface deposits in Taranaki Basin and complements the regional late Miocene biostratigraphic dating framework.

  2. 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

    dendrochronology for dating its lateral and terminal moraines. The upper part of the core (0-170 mm) was scanned applying X-ray fluorescent microanalysis using synchrotron radiation and sampled for dating using 137Cs and 210Pb. The assumption that the sediment stratification represents annual layering (spring flood) is generally confirmed with correlation of the Rb/Sr-ratio (that supposedly marks grain-size variations in the sediments) curve and the image of the sediment core. Calculations of Rb/Sr peaks or visual layers yield an accumulation rate of around 2 mm/yr. Analogous results (1.73 mm/yr) are derived from 137Cs-dating. With this high accumulation rate, the sediment core of Lake Donguz-Orun represents an important source of information for high-resolution reconstructions of climatic parameters and glacier variations of the region. The research project of Mikhail Alexandrin is supported by grant# 227470/F11 issued by The Research Council of Norway.

  3. The history of metals pollution in Narragansett Bay as recorded by salt-marsh sediments

    SciTech Connect

    Bricker, S.B.

    1990-01-01

    Sediment cores from 5 salt marshes from the head to the mouth of Narragansett Bay and an additional core from a lagoon on Block Island Sound were analyzed for [sup 210]Pb and for Fe, Mn, Cu, Pb, Cr, Zn, Ag, and Ni in order to examine the long-term variation of metal inputs to Narragansett Bay. The [sup 210]Pb results were used to determine accretion rates for each core. Distributions of Fe and Mn were used as indicators of chemical conditions of sediment cores and Cu, Pb, Cr, Zn, Ag, and Ni distributions with time were compared with known or estimated source inputs to examine the long-term variation of pollutant metal inputs to Narragansett Bay. At one location, duplicate cores were sampled to look at variability within a marsh. At another location, a high marsh, receiving predominantly atmospheric inputs and a low marsh, receiving waterborne and atmospheric inputs, were sampled so that atmospheric and tidal contributions could be determined. A comparison was made of the distributions of metals in bay cores and in the lagoon core. All the Rhode Island marshes accrete at rates equal to or greater than the local rise in sea level. Based on the [sup 210]Pb chronologies, pollutant metals began to increase in the mid to late 1800s, corresponding to coal burning emissions to the atmosphere. Steeper increases in the 1900s reflect industrial and sewage discharges. Maximum concentrations were reached in the 1950s and have declined almost continuously since then. Observed reductions were attributable to implementation of and improvements to sewage treatment, and controls on atmospheric emissions.

  4. Trawling-induced alterations of deep-sea sediment accumulation rates during the Anthropocene

    NASA Astrophysics Data System (ADS)

    Puig, P.; Paradis, S.; Masque, P.; Martin, J.; Juan, X.; Palanques, A.

    2015-12-01

    Commercial bottom trawling causes direct physical disturbance of the marine sedimentary environments by scraping and ploughing the seabed, generating periodic resuspension of surface sediments. However, the quantification of the sediment that is removed by trawling and exported across the continental margin remains largely unaddressed, and the preservation of the signal of such impacts in the geological record have been mostly overlooked. The analysis of sediment cores collected along the Catalan margin (NW Mediterranean) has allowed evaluating the contribution of this anthropogenic activity to the present-day sediment dynamics. Sediment cores at intensively trawled sites are characterized by over-consolidated sediments with lower 210Pb surface concentrations and inventories that indicate widespread erosion of recent sedimentary deposits. In turn, combined 210Pb and 137Cs chronologies indicate a significant increase of sediment accumulation rates within submarine canyon environments since the 1970s, coincidently with a strong impulse in the industrialization of the trawling fleets of this region. Two sampling sites that exhibited high sediment accumulation rates (0.6-0.7 cm/y) were reoccupied 1-2 decades after the first studies and revealed a second and even larger increase of sediment accumulation rates (>2 cm/y) occurring at the beginning of the XXI century. This recent change has been attributed to a preferential displacement of the trawling fleet towards fishing grounds surrounding submarine canyons and, also, to technical improvements in trawling vessels, presumably related to financial subsidies provided to the fishing sector. The alteration of sediment accumulation rates described in this continental margin may occur in many regions of the World's oceans given the wide geographical distribution of this human activity, and therefore, it could represent a potential marker of the Anthropocene in deep-sea environments.

  5. Isothermal thermoluminescence dating of K-feldspar from sediments to determine fault slip rates: development and assessment

    NASA Astrophysics Data System (ADS)

    Rhodes, E. J.; Roder, B. J.; Lawson, M. J.; Dolan, J. F.; McGill, S. F.; McAuliffe, L.

    2012-04-01

    Faults in California accommodate most of the relative motion between the Pacific and North American tectonic plates, along either one main strike-slip fault, - the San Andreas fault - or a network of sub-parallel faults (e.g., the San Jacinto, Elsinore and San Andreas faults). Slip is also accommodated along many other associated faults and folds, and the region suffers frequent damaging earthquakes. Contemporary movements of different fault-bounded blocks are relatively well established on decadal timescales using remote sensing and GPS, and on timescales of 106 to 107 years, by dating offset geologic features with radiometric methods. However, on timescales of decades to several hundred thousand years, determining total fault offset and mean slip rate is harder. Critical questions for understanding fault dynamics and improving earthquake risk assessment include the degree to which slip is clustered into episodes of more rapid movement, and how slip is accommodated by different sub-parallel faults. In many cases, streams with offset courses can be recognised, and in some cases offset terrace surfaces can be located, especially when using LiDAR data to complement field mapping. Radiocarbon and terrestrial cosmogenic nuclides have been used to date these features, but both have limitations of age range, sample suitability and availability. OSL (optically stimulated luminescence) and IRSL (infra-red stimulated luminescence) have great potential to complement these techniques, though the characteristics of quartz in some parts of southern California are suboptimal, displaying low sensitivity and other limitations. In order to overcome these limitations encountered using quartz OSL, we are developing a new geochronometer based on the isothermal thermoluminescence (ITL) signal of K feldspar measured at 250°C. Preliminary ITL age estimates from the paleoseismic site of El Paso Peaks on the Central Garlock fault in the Mojave Desert, California, agree well with a well

  6. Historical accumulation of N and P and sources of organic matter and N in sediment in an agricultural reservoir in Northern China.

    PubMed

    Ni, Zhaokui; Wang, Shengrui; Chu, Zhaosheng; Jin, Xiangcan

    2015-07-01

    Agriculture has significantly intensified in Northern China since the 1980s. This intensification has caused a series of simultaneous lake ecological environment problems in this area. However, little is known about the role of agricultural intensification in historical nutrient dynamics and lake eutrophication processes. The Yanghe reservoir, a typical artificial reservoir characterized by high-yield grain production in Northern China, has been suffering from serious eutrophication and water quality deterioration. This study evaluates the effect of agricultural intensification on nutrient retention and source in the sediments using (210)Pb and (137)Cs dating techniques combined with stable C and N isotopes (δ(13)C, δ(15)N) and total organic carbon/total nitrogen, as well as total nitrogen (TN), total phosphorus (TP), and P fractions. Results suggested that agricultural intensification was keys to the accumulation of nutrients and was a source of organic matter (OM) and N in sediment for the past three decades. N and P pollution started in the 1980s and worsened from the 1990s. Good water quality status and steady sedimentary environment with low nutrient content (mean concentrations of TN and TP were 815 and 387 mg kg(-1), respectively) were observed before the 1980s. Sediment OM was primarily derived from aquatic plants, whereas N was primarily derived from soil erosion and aquatic plants. However, water quality began to deteriorate while sediment nutrient content began to increase after the 1980s, with values of 1186 mg kg(-1) for TN and 434 mg kg(-1) for TP in 1989. Sediment OM was primarily derived from C3 (sweet potato) and aquatic plants, and the major sources of N were soil erosion, fertilizer, and sewage, which accompany the rapid development of agriculture in the watershed. Following the further growth of grain production and fertilizers, excessive external nutrient loading has resulted in dramatic water quality and ecosystem deterioration since 1990

  7. The long-term nutrient accumulation with respect to anthropogenic impacts in the sediments from two freshwater marshes (Xianghai Wetlands, Northeast China).

    PubMed

    Wang, Guo-Ping; Liu, Jing-Shuang; Tang, Jie

    2004-12-01

    Sediment cores, representing a range of watershed characteristics and anthropogenic impacts, were collected from two freshwater marshes at the Xianghai wetlands (Ramsar site no. 548) in order to trace the historical variation of nutrient accumulation. Cores were (210)Pb- and (137)Cs-dated, and these data were used to calculate sedimentation rates and sediment accumulation rates. Ranges of dry mass accumulation rates and sedimentation rates were 0.27-0.96 g m(-2)yr(-1) and 0.27-0.90 cm yr(-1), respectively. The effect of human activities on increased sediment accumulation rates was observed. Nutrients (TOC, N, P, and S) in sediment were analyzed and nutrient concentration and accumulation were compared in two marshes with different hydrologic regime: an "open" marsh (E-0) and a partly "closed" marsh (F-0). Differences in physical and chemical characteristics between sediments of "open" and partly "closed" marsh were also observed. The "open" marsh sequestered much higher amounts of TOC (1.82%), N (981.1 mg kg(-1)), P (212.17 mg kg(-1)), and S (759.32 mg kg(-1)) than partly "closed" marsh (TOC: 0.32%, N: 415.35 mg kg(-1), P: 139.64 mg kg(-1), and S: 624.45 mg kg(-1)), and the "open" marsh indicated a rather large historical variability of TOC, N, P, and S inputs from alluvial deposits. Nutrient inputs (2.16-251.80 g TOC m(-2) yr(-1), 0.43-20.12 g N m(-2) yr(-1), 0.39-3.03 g P m(-2) yr(-1), 1.60-15.13 g S m(-2) yr(-1)) into the Xianghai wetlands of China are in the high range compared with reported nutrient accumulation rates for freshwater marshes in USA. The vertical variation, particularly for N, P, and S indicated the input history of the nutrients of the Xianghai wetlands developed in three periods--before 1950s, 1950-1980s, and after 1980s. The ratios between anthropogenic and natural inputs showed that the relative anthropogenic inputs of TOC, N, P, and S have been severalfold (TOC: 1.68-11.21, N: 0.47-3.67, P: 0.24-1.36, and S: 1.46-2.96) greater than values

  8. Climatically driven variations in glacier extent as documented by the laminated proglacial sediment record from Lago del Desierto (Southern Patagonia, Argentina)

    NASA Astrophysics Data System (ADS)

    Enters, D.; Kastner, S.; Ohlendorf, C.; Haberzettl, T.; Kuhn, G.; Lücke, A.; Mayr, C.; Reyss, J.; Wastegard, S.

    2009-12-01

    The climate of southernmost South America is strongly affected by shifts in polar and mid-latitude pressure fields which are expressed in variations of the Southern Hemispheric Westerlies and the Antarctic Oscillation. Next to marine records and Antarctic ice cores this continental area is important to reveal hemispheric and global climate trends. As instrumental climate records from this region are generally short and scarce, environmental archives are the only source of providing long-term records of climate variations. In the northern hemisphere, proglacial lakes have shown to be excellent sources of palaeoenvironmental and palaeoclimatic information. In this study, we evaluate the potential of the laminated proglacial sediment sequence from Lago del Desierto (49°02’S, 72°51’W) as a palaeoclimate archive. Lago del Desierto is situated in the climatically sensitive area of Southern Patagonia close to the South Patagonian Ice Field. Two parallel gravity cores (max. length 283 cm) were analysed using a multi-proxy approach. Radiometric dating (14C, 210Pb and 137Cs) and tephrochronology document that the recovered sediments cover the last 2000 years. After exclusion of numerous event layers, the sedimentological, mineralogical, and geochemical datasets reveal a long-term trend of runoff variations and sediment accessibility controlled by changes in temperature and precipitation. An abrupt lithological change visible in sediments mineralogy and geochemistry occurred around AD 850 and is interpreted as a rearrangement in sediment availability and transfer rates related to the beginning exposure of formerly glaciated areas. Thereafter, the Medieval Climate Anomaly (MCA) period, the Little Ice Age (LIA) cooling and the subsequent 20th century warming can be traced in the sediment record corresponding to the overall trend observed for southern South America. The increased minerogenic input and a higher frequency of event layers mirror the onset of warmer climate

  9. Short-term Fallout Radionuclide Ratios and Mass Balance Identify New Suspended Sediments of Channel Origin

    NASA Astrophysics Data System (ADS)

    Karwan, D. L.; Pizzuto, J. E.; Aalto, R. E.; Marquard, J.; Aufdenkampe, A. K.; Benthem, A.; Skalak, K.; Levia, D. F., Jr.; Siegert, C. M.

    2015-12-01

    Fallout radionuclide ratios, such as the ratio of Beryllium-7 to Lead-210 (7Be/210Pb), are used to determine the age of suspended sediment or fraction of "new" sediment in suspension. In the application of these models new suspended sediment is often assumed to originate from recent landscape surface erosion that is delivered to the stream network. Fallout radionuclide deposition can vary across watersheds and on an event basis in a single watershed due to factors such as storm type, atmospheric height, and storm origin. In the White Clay Creek watershed within the mid-Atlantic USA, single-event deposition of 7Be varies from 15 - 177 Bq m-2 and 210Pb varies from 0 - 10 Bq m-2. 7Be/210Pb ratios vary from 7.9 to 20 in event precipitation and from 0.8 to 12.8 on suspended sediment. "New" sediment varies from 4 - 71% over the course of these events. A computation of the 7Be mass balance during events shows that the majority of 7Be is retained within the catchment. During summer thunderstorms, less than 1% of 7Be deposited on the watershed exits in the stream channel during that event. Therefore, the entirety of the 7Be exiting the watershed on suspended sediment is less than the total activity deposited on the channel in direct precipitation. We attribute this to the new tagging of subaerial fluvial deposits with event precipitation; hence "new" suspended sediment originates from within the channel rather than from surface erosion. During extreme events, such as Hurricane Irene, less of the suspended sediment has been newly tagged by precipitation (4 - 28%) and a larger proportion (3-4%) of the 7Be deposited on the watershed exits during the event. Ongoing work in the Difficult Run watershed in northern Virginia will test the regional applicability of these findings. Water quality efforts to determine the source of sediment using fallout radionuclides must consider the stream channel as well as landscape sources of "new" sediments, particularly during summer

  10. Natural radionuclides and plutonium in sediments from the western Arctic Ocean: Sedimentation rates and pathways of radionuclides

    USGS Publications Warehouse

    Huh, C.-A.; Pisias, N.G.; Kelley, J.M.; Maiti, T.C.; Grantz, A.

    1997-01-01

    Sediment cores collected during R.V. Polar Sea AOS94 expedition from the Chukchi Shelf to the North Poke were analyzed for several decay-series natural radionuclides and Pu isotopes to study sedimentation rates and pathways of radionuclides in the western Arctic Ocean. The measured sedimentation rates vary by more than three orders of magnitude along the transect, from 210Pb based rates of 200-700 cm kyr-1 over the Chukchi Shelf and 89 cm kyr-1 at the Chukchi Slope to 230Th-based rates of 0.02-0.3 cm kyr-1 at various settings in the deep basin. 230Th(ex) profiles in the central western Arctic Basin are characterized by a cyclic pattern and a pronounced sub-surface maximum superimposed on an overall decrease with depth. Sediment inventories of excess 210Pb and 230Th in the deep basin as a whole cannot account for their in situ production and 2610Pb fall-out. The opposite is true at the slope and shallower waters. We contend that, as with other ocean basins, boundary scavenging also exists in the Arctic Ocean. The broad continental shelves and the slope region may have the potential of removing all or moat of the particle-reactive radionuclides unaccounted for in the deep basin. The Pu isotope data are consistent with the notion of boundary scavenging. Sediment inventories and concentrations of Pu decrease rapidly offshore. Isotopic composition of Pu suggests mixing of fall-out Pu, which decreases with increasing latitudes, and fuels reprocessing Pu derived from the Russian and Atlantic sides of the Arctic Ocean. Although fuel reprocessing Pu has impinged on the Chukchi Slope, its existence over the Chukchi Shelf is not evident and probably overshadowed by fall-out Pu.

  11. Late Glacial and Holocene Fire History From Radiocarbon Dating of Charcoal in Valley-Bottom Sediments in Small Watersheds of the Oregon Coast Range

    NASA Astrophysics Data System (ADS)

    Lancaster, S. T.; Frueh, W. T.

    2011-12-01

    A large number (N = 351) of radiocarbon dates of charcoal from valley-bottom sediments in headwater valleys of the southern Oregon Coast Range provides the basis for a new index of fire frequen