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Sample records for 210pb spiked soils

  1. {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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. [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.

  7. 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. Copyright © 2014 Elsevier Ltd. All rights reserved.

  8. Atmospheric fluxes and marsh-soil inventories of /sup 7/Be and /sup 210/Pb

    SciTech Connect

    Olsen, C.R.; Larsen, I.L.; Lowry, P.D.; Cutshall, N.H.; Todd, J.F.; Wong, G.T.F.; Casey, W.H.

    1996-10-20

    The atmospheric flux of /sup 7/Be over a 2-year period at a coastal site (Norfolk, Virginia) and at an inland site (Oak Ridge, Tennessee) typically supports inventories ranging from 1.0 to 2.0 pCi/cm/sup 2/ (1 pCi = 0.037 Bq), with the highest inventories generally occurring in the spring and the lowest occurring in the fall. The calculated average daily fluxes required to support these inventories range from 0.013 to 0.026 pCi cm/sup -2/ d/sup -1/. Despite the different production-source terms for /sup 7/Be and /sup 210/Pb, there is a high degree of correlation between their measured total monthly deposition reflecting the importance of washout in removing both radionuclides from the atmosphere. Beryllium 7 inventories in soil and vegetated marsh cores compare favorably with inventories calculated from the atmospheric deposition data. Lead 210 inventories in soil and vegetated marsh cores may be enriched (by 20--30%) in relation to inventories calculated from its depositional flux to bucket samples. Possible explanations for this enrichment are that above-ground vegetation is more efficient at collecting dry aerosols (containing short-lived radon daughters) than buckets or that foliage is an effective trap for particles containing sorbed /sup 210/Pb which may be eroded from unvegetated surfaces by wind or water. The vertical distribution and inventory of both /sup 7/Be and /sup 210/Pb in marsh cores are affected by the presence of vegetation and the location of the groundwater table.

  9. (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

  10. (The determination of sup 222 Rn flux from soils based on sup 210 Pb and sup 226 Ra disequilibrium)

    SciTech Connect

    Turekian, K.K.

    1991-01-01

    The emanating fraction of radon in soils from the southern part of the United States is about 40% greater than in those from the northern part. The mean {sup 226}Ra activity in the southern soils is also slightly higher and as a consequence the {sup 222}Rn flux derived from the top 50 cm. is greater in the southern samples. We tentatively attribute these observations to the greater degree of weathering associated with the pre-glacial age of the parent material of many of the southern soils. The weathering has concentrated {sup 226}Ra near grain surfaces and results in an increased emanating power for {sup 222}Rn. The estimated correction in {sup 210}Pb analyses described above results in a small decrease in our estimate of the mean loss rate of {sup 222}Rn from the upper 50 cm of soils.

  11. 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.

  12. Atmospheric (210)Pb as a tracer for soil organic carbon transport in a coniferous forest.

    PubMed

    Teramage, Mengistu T; Onda, Yuichi; Wakiyama, Yoshifumi; Kato, Hiroaki; Kanda, Takashi; Tamura, Kenji

    2015-01-01

    Core soils and falling litter samples were collected in a Japanese cypress forest (Chamaecyparis obtusa) to determine the litter-fed (210)Pbex and organic carbon transfer from the forest canopy to soil and their subsequent distribution. Of the canopy residing (210)Pbex pool, litterfall annually transports 53% to the forest floor while it adds 117 g m(-2) per year of organic carbon to the forest soil, implying that litterfall dynamics can influence the distribution of (210)Pbex and soil organic carbon (SOC). (210)Pbex and SOC showed identical profile shapes and strong correlation in spatial as well as along the soil depth, indicating that both are affected by a similar process. Given the ubiquitous natural source of (210)Pbex, it is plausible to infer that radiolead can be a possible tracer to study the SOC redistribution at regional and global scales.

  13. 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.

  14. Using plot experiments to test the validity of mass balance models employed to estimate soil redistribution rates from 137Cs and 210Pb(ex) measurements.

    PubMed

    Porto, Paolo; Walling, Des E

    2012-10-01

    Information on rates of soil loss from agricultural land is a key requirement for assessing both on-site soil degradation and potential off-site sediment problems. Many models and prediction procedures have been developed to estimate rates of soil loss and soil redistribution as a function of the local topography, hydrometeorology, soil type and land management, but empirical data remain essential for validating and calibrating such models and prediction procedures. Direct measurements using erosion plots are, however, costly and the results obtained relate to a small enclosed area, which may not be representative of the wider landscape. In recent years, the use of fallout radionuclides and more particularly caesium-137 ((137)Cs) and excess lead-210 ((210)Pb(ex)) has been shown to provide a very effective means of documenting rates of soil loss and soil and sediment redistribution in the landscape. Several of the assumptions associated with the theoretical conversion models used with such measurements remain essentially unvalidated. This contribution describes the results of a measurement programme involving five experimental plots located in southern Italy, aimed at validating several of the basic assumptions commonly associated with the use of mass balance models for estimating rates of soil redistribution on cultivated land from (137)Cs and (210)Pb(ex) measurements. Overall, the results confirm the general validity of these assumptions and the importance of taking account of the fate of fresh fallout. However, further work is required to validate the conversion models employed in using fallout radionuclide measurements to document soil redistribution in the landscape and this could usefully direct attention to different environments and to the validation of the final estimates of soil redistribution rate as well as the assumptions of the models employed. Copyright © 2012 Elsevier Ltd. All rights reserved.

  15. [The determination of {sup 222}Rn flux from soils based on {sup 210}Pb and {sup 226}Ra disequilibrium]. Progress report

    SciTech Connect

    Turekian, K.K.

    1991-12-31

    The emanating fraction of radon in soils from the southern part of the United States is about 40% greater than in those from the northern part. The mean {sup 226}Ra activity in the southern soils is also slightly higher and as a consequence the {sup 222}Rn flux derived from the top 50 cm. is greater in the southern samples. We tentatively attribute these observations to the greater degree of weathering associated with the pre-glacial age of the parent material of many of the southern soils. The weathering has concentrated {sup 226}Ra near grain surfaces and results in an increased emanating power for {sup 222}Rn. The estimated correction in {sup 210}Pb analyses described above results in a small decrease in our estimate of the mean loss rate of {sup 222}Rn from the upper 50 cm of soils.

  16. Soil to rice transfer factors for (226)Ra, (228)Ra, (210)Pb, (40)K and (137)Cs: a study on rice grown in India.

    PubMed

    Karunakara, N; Rao, Chetan; Ujwal, P; Yashodhara, I; Kumara, Sudeep; Ravi, P M

    2013-04-01

    India is the second largest producer of rice (Oryza sativa L.) in the world and rice is an essential component of the diet for a majority of the population in India. However, detailed studies aimed at the evaluation of radionuclide transfer factors (F(v)) for the rice grown in India are almost non-existent. This paper presents the soil to rice transfer factors for natural ((226)Ra, (228)Ra, (40)K, and (210)Pb) and artificial ((137)Cs) radionuclides for rice grown in natural field conditions on the West Coast of India. A rice field was developed very close to the Kaiga nuclear power plant and the water required for this field was drawn from the cooling water discharge canal of the power plant. For a comparative study of the radionuclide transfer factors, rice samples were also collected from the rice fields of nearby villages. The study showed that the (226)Ra and (228)Ra activity concentrations were below detection levels in different organs of the rice plant. The soil to un-hulled rice grain (40)K transfer factor varied in the range of 6.5 × 10(-1) to 2.9 with a mean of 0.15 × 10(1), and of (210)Pb varied in the range of <1.2 × 10(-2) to 8.1 × 10(-1) with a mean of 1.4 × 10(-1), and of (137)Cs varied in the range of 6.6 × 10(-2) to 3.4 × 10(-1) with a mean of 2.1 × 10(-1). The mean values of un-hulled grain to white rice processing retention factors (F(r)) were 0.12 for (40)K, 0.03 for (210)Pb, and 0.14 for (137)Cs. Using these processing retention factors, the soil to white rice transfer factors were estimated and these were found to have mean values of 1.8 × 10(-1), 4.2 × 10(-3), and 3.0 × 10(-2) for (40)K, (210)Pb, and (137)Cs, respectively. The study has shown that the transfer of (40)K was higher for above the ground organs than for the root, but (210)Pb and (137)Cs were retained in the root and their transfer to above the ground organs of the rice plant is significantly lower. Copyright © 2012 Elsevier Ltd. All rights

  17. 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.

  18. Plant uptake of (238)U, (235)U, (232)Th, (226)Ra, (210)Pb and (40)K from a coal ash and slag disposal site and control soil under field conditions: A preliminary study.

    PubMed

    Skoko, Božena; Marović, Gordana; Babić, Dinko; Šoštarić, Marko; Jukić, Mirela

    2017-06-01

    The aim of this study was to investigate the uptake of (238)U, (235)U, (232)Th, (226)Ra, (210)Pb and (40)K by plants that grow on a coal ash and slag disposal site known for its higher content of naturally occurring radionuclides. Plant species that were sampled are common for the Mediterranean flora and can be divided as follows: grasses & herbs, shrubs and trees. To compare the activity concentrations and the resultant concentration ratios of the disposal site with those in natural conditions, we used control data specific for the research area, obtained for plants growing on untreated natural soil. Radionuclide activity concentrations were determined by high resolution gamma-ray spectrometry. Media parameters (pH, electrical conductivity and organic matter content) were also analysed. We confirmed significantly higher activity concentrations of (238)U, (235)U, (226)Ra and (210)Pb in ash and slag compared to control soil. However, a significant increase in the radionuclide activity concentration in the disposal site's vegetation was observed only for (226)Ra. On the contrary, a significantly smaller activity concentration of (40)K in ash and slag had no impact on its activity concentration in plant samples. The calculated plant uptake of (238)U, (235)U, (226)Ra and (210)Pb is significantly smaller in comparison with the uptake at the control site, while it is vice versa for (40)K. No significant difference was observed between the disposal site and the control site's plant uptake of (232)Th. These results can be the foundation for further radioecological assessment of this disposal site but also, globally, they can contribute to a better understanding of nature and long-term management of such disposal sites. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. 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.

  20. Distributions of 210Pb around a uraniferous coal-fired power plant in Western Turkey.

    PubMed

    Uğur, A; Ozden, B; Yener, G; Saç, M M; Kurucu, Y; Altinbaş, U; Bolca, M

    2009-02-01

    In the present study the spatial and the vertical distributions of 210Pb were investigated in the soils around a uranifereous coal fired power plant (CPP) in Yatagan Basin, in Western Turkey. The variation of 226Ra activity along the soil profiles was studied to assess the unsupported 210Pb distribution in the same samples. 226Ra was measured by gamma spectroscopy and 210Pb activities were determined from 210Po activities using radiochemical deposition and alpha spectroscopy. The total 210Pb activity concentrations in bulk core samples varied in the range of 38-250 Bq kg(-1) in the study sites and of 22-78 Bq kg(-1) in reference site. In the sectioned cores sampled from the study areas the ranges for activity concentrations of 226Ra, total 210Pb and unsupported 210Pb are 24-77; 39-344 and 4-313 Bq kg(-1), respectively. Corresponding ranges for reference site are 37-39; 39-122 and 1-83 Bq kg(-1).

  1. 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.

  2. Modeling Peat Ages Using 7Be Data to Account for Downwash of 210Pb

    NASA Astrophysics Data System (ADS)

    Manies, K.; Fuller, C.; Jones, M.

    2016-12-01

    In order to determine the amount of peat, and thus carbon, which has accumulated since the last thaw event, we are interested in dating the surface layers of boreal thermokarst bogs. However, there can often be a mismatch by several decades between dates obtained using 210Pb, 14C, or 137Cs. We found that 210Pb-based dates were almost always younger than 14C-based dates. One of the limitations often cited regarding the use of 210Pb dating for peatlands is the potential for this radionuclide to be transported down the soil profile, biasing the mean accumulation rate (MAR) towards higher values which, in turn, results in younger ages at a specific horizon. 7Be, which has similar depositional behaviors as 210Pb but a much shorter half-life (53.22 days), can be used to help determine if there is movement of 210Pb through surface layers and the depths to which 210Pb-bearing particles are transported (over the mean life of 7Be). These data can then be used in new models, such as the Linked Radionuclide aCcumulation model (LRC; Landis et al., 2016, http://dx.doi.org/10.1016/ j.gca.2016.02.2013), which account for 210Pb downwash when calculating soil horizon ages. To this end, we measured 7Be within a bog four times over the growing season. 7Be was found to 4 cm in May, reached its maximum depth of penetration in July (7 cm), and then receded again to 4 cm. The maximum integrated 7Be activity was also found in July. This pattern is similar to other studies which found 7Be deposition decreased over the rainy season. Next, we will calculate peat ages with models that include downwash of 210Pb, the depths of which will be based on the penetration depth of 7Be. These ages will be compared to 210Pb ages obtained with both the Constant Rate of Supply (CRS) and Constant Flux - Constant Sedimentation (CF:CS) models and to 137Cs- and 14C-derived ages. We anticipate that dates based on models that include some transport of 210Pb into the soil profile will provide more accurate peat

  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. 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.

  5. Speciation of 210Po and 210Pb in air particulates determined by sequential extraction.

    PubMed

    Al-Masri, M S; Al-Karfan, K; Khalili, H; Hassan, M

    2006-01-01

    Speciation of (210)Po and (210)Pb in air particulates of two Syrian phosphate sites with different climate conditions has been studied. The sites are the mines and Tartous port at the Mediterranean Sea. Air filters were collected during September 2000 until February 2002 and extracted chemically using different selective fluids in an attempt to identify the different forms of these two radionuclides. The results have shown that the inorganic and insoluble (210)Po and (210)Pb (attached to silica and soluble in mineral acids) portion was found to be high in both sites and reached a maximum value of 94% and 77% in the mine site and Tartous port site, respectively. In addition, only 24% of (210)Pb in air particulates was found to be associated with organic materials probably produced from the incomplete burning of fuel vehicle and similar activities. Moreover, the (210)Po/(210)Pb activity ratio in air particulates was higher than that in all samples at both sites and varied between 3.85 in November 2000 at Tartous port site and 20 in April 2001 at the mine area. These activity ratios were also higher than the natural levels. The (210)Po/(210)Pb activity ratio was also determined in each portion resulting from the selective extraction and found to be higher than that in most samples. The sources of (210)Po excess in these portions are discussed. Soil suspension, which is common in the dry climate dominant in the area, sea water spray and heating of phosphate ores were considered; polonium is more volatile than the lead compounds at even moderate temperature. Furthermore, variations in the chemical forms of (210)Po and (210)Pb during the year were also investigated. However, the results of this study can also be utilized for dose assessment to phosphate industry workers.

  6. 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.

  7. 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.

  8. Analyses of 210Pb concentrations in surface air and in rain water at the central Guizhou, China

    NASA Astrophysics Data System (ADS)

    Wan, G. J.; Lee, H. N.; Wan, E. Y.; Wang, S. L.; Yang, W.; Wu, F. C.; Chen, J. A.; Wang, C. S.

    2008-02-01

    Samples of surface air and rain water were collected at the Mt. Guanfeng site located at Guiyang, China. The monthly mean 210Pb concentrations in surface air exhibited a U-pattern with high values appearing in winter and low values in summer and early autumn. The annual mean of 210Pb concentrations in surface air was estimated to be 2.7 +/- 0.6 mBq m-3, which was at least four times higher than the annual mean reported from a large number of monitoring stations located throughout the world. The amounts of enriched Uranium in soil at the region could significantly contribute a great deal of release of 222Rn that decay to 210Pb which gets attached to the atmospheric aerosols. The site was under the influence of a monsoon climate. The distribution of monthly mean of 210Pb concentrations in surface air correlates well with the reciprocal of monthly average of observed air temperature and rainfall. The partition coefficients of 210Pb between rain water-surface air in the winter and spring were larger than those in the summer and autumn. The type and duration of rain depending on season played key roles for the changes of partition coefficients, although the rain amount is important.

  9. 210Pb as a tool for establishing sediment chronologies: examples of potentials and limitations of conventional dating models.

    PubMed

    Kirchner, Gerald

    2011-05-01

    For aquatic sediments, the use of (210)Pb originating from the decay of atmospheric (222)Rn is a well-established methodology to estimate sediment ages and sedimentation rates. Traditionally, the measurement of (210)Pb in soils and sediments involved laborious and time-consuming radiochemical separation procedures. Due to the recent development of advanced planar ('n-type') semi-conductors with high efficiencies in the low-energy range which enable the gamma-spectrometric analysis of the 46.5 keV decay line of (210)Pb, sediment dating using this radionuclide has gained renewed interest. In this contribution, potentials and limitations of the (210)Pb methodology and of the models used for estimating sediment ages and sedimentation rates are discussed and illustrated by examples of freshwater and marine sediments. Comparison with the use of (137)Cs shows that the information which may be gained by these two tracers is complementary. As a consequence, both radionuclides should be used in combination for dating of recent sediments. It is shown that for various sedimentation regimes additional information from other sources (e.g. sediment lithology) may be needed to establish a reliable chronology. A strategy for sediment dating using (210)Pb is recommended. Copyright © 2010 Elsevier Ltd. All rights reserved.

  10. Quantitative retention of atmospherically deposited elements by native vegetation is traced by the fallout radionuclides 7Be and 210Pb.

    PubMed

    Landis, Joshua D; Renshaw, Carl E; Kaste, James M

    2014-10-21

    Atmospheric deposition is the primary mechanism by which remote environments are impacted by anthropogenic contaminants. Vegetation plays a critical role in intercepting atmospheric aerosols, thereby regulating the timing and magnitude of both contaminant and nutrient delivery to underlying soils. However, quantitative models describing the fate of atmospherically derived elements on vegetation are limited by a lack of long-term measurements of both atmospheric flux and foliar concentrations. We addressed this gap in understanding by quantifying weekly atmospheric deposition of the naturally occurring radionuclide tracers (7)Be and (210)Pb, as well as their activities in leaves of colocated trees, for three years in New Hampshire, U.S. The accumulation of both (7)Be and (210)Pb in deciduous and coniferous vegetation is predicted by a model that is based solely on measured atmospheric fluxes, duration of leaf exposure, and radioactive decay. Any "wash off" processes that remove (7)Be and (210)Pb from foliage operate with a maximum half-time of greater than 370 days (P > 99%), which is an order of magnitude longer than previously assumed. The retention of both (7)Be and (210)Pb on leaves is thus quantitative and permanent, coupling the fate of (7)Be, (210)Pb and similar atmospheric species to that of the leaf matter itself. These findings demonstrate that the long-standing paradigm of a short "environmental half-life" for atmospheric contaminants deposited on natural surfaces must be re-evaluated.

  11. 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.

  12. 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.

  13. 210Pb sediment dating in coastal transition zones: tropical saltmarshes.

    NASA Astrophysics Data System (ADS)

    Ruiz-Fernandez, A. C.; Sanchez-Cabeza, J. A.; Carnero-Bravo, V.; Perez-Bernal, L. H.

    2016-12-01

    Sea level rise (SLR) is one of the climate change effects expected to have the largest impact on coastal environments. SLR rates are not uniform around the planet and, therefore, local and regional data and trends are needed for proper adaptation plans. As long term monitoring stations of SLR are very scarce in most of the world, SLR trends obtained from 210Pb-dated sediment cores from tropical saltmarshes have become a practical alternative to obtain SLR trends within the past century, under the assumption that these ecosystems accrete at a similar rate to SLR. However, tropical saltmarshes are challenging environments for 210Pb dating: they are regularly dry, intermittently covered by seawater only during the highest tides, and sedimentary records often reflect the transition between terrestrial and marine environments (e.g. changes in grain size distribution, organic matter content and elemental composition) with all these factors contributing for atypical 210Pb depth profiles. In addition, 137Cs, the chronostratigraphic marker most commonly used to corroborate 210Pb dating, fails to be preserved in the sedimentary record in tropical areas, owing to its solubility in marine waters, if at all detectable. The present study describes the challenges and proposed solutions for 210Pb dating saltmarsh sediment cores from two saltmarsh areas (southern Gulf of California and Yucatan Peninsula) including the use of plutonium isotopes for corroboration purposes. Acknowledgements: projects CONACYT CB2010/153492 and PDCPN201301/214349; UNAM PAPIIT-IN203313 and the PRODEP network "Aquatic contamination: levels and effects" (year 3).

  14. Biomonitoring of 210Po and 210Pb using lichens and mosses around a uraniferous coal-fired power plant in western Turkey

    NASA Astrophysics Data System (ADS)

    Uğur, A.; Özden, B.; Saç, M. M.; Yener, G.

    In Gökova region where Yatağan is located there are three major uraniferous coal-fired power plants (CPPs) and they cause some pollution in the surroundings. Studies were realized over a wide area around the coal-fired power station located at Yatağan to evaluate the possible increase of natural radioactivity level due to the operation of the plant. The lichens Rhizoplaca melanophthalma, Cladonia convoluta, Cladonia pyxidata and the mosses Grimmia pulvinata, Hypnum cupressiforme were investigated for potential use as bioindicators for 210Po and 210Pb deposition. The maximum 210Po and 210Pb activities were observed around the hill close to ash stacks. The capture efficiency was the highest in one of the moss species, G. pulvinata with the activity concentration ranges of 600±19-1228±36 and 446±15-650±21 Bq kg -1 for 210Po and 210Pb, respectively. Soil samples were also collected and analysed in order to investigate any possible contamination in soil profiles due to CPPs and to determine unsupported 210Pb flux. The 210Pb and 226Ra concentrations in uncultivated soil profiles varied between 58±2 and 258±6 Bq kg -1, 50±5 and 58±5 Bq kg -1, respectively. The unsupported 210Pb inventory in the core was calculated to be 3312 Bq m -2. The corresponding annual 210Pb flux of 103 Bq m -2yr -1 is high with compare to estimates of the atmospheric flux given in literature for the same region.

  15. 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.

  16. 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.

  17. 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.

  18. Geochemistry of /sup 210/Pb in the southeastern, US estuarine system

    SciTech Connect

    Storti, F.W.

    1980-11-01

    This study was an attempt to determine the geochemical behavior of /sup 210/Pb in southeastern salt marsh estuaries. As a part of this study the /sup 210/Pb dating technique was applied to natural and anthropogenic deposits of the region. /sup 210/Pb activity of sediment and water from the Georgia coastal area was measured by alpha spectroscopy. The effects of grain size and carbon content of the sediment on /sup 210/Pb concentrations was evaluated and the activity of /sup 210/Pb in dissolved and particulate phases of rivers was measured as a function of salinity. Ages and sedimentation rates of sedimentary deposits were also determined for some deposits. /sup 210/Pb activity in dissolved and particulate phases of rivers showed no clear trends as functions of salinity. River particulate activities were three to four times higher than dissolved activities. The relationship between /sup 210/Pb activity in salt marsh sediments and grain size was highly significant. Direct application of the /sup 210/Pb method to date and determine sedimentation rates of natural and anthropogenic deposits was partially successful. The anthropogenic deposits, however, had to be dated on the basis of normalizing /sup 210/Pb activities to grain size (% silt and clay) and carbon content (% carbon).

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  20. 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.

  1. Fast procedure for self-absorption correction for low γ energy radionuclide (210)Pb determination in solid environmental samples.

    PubMed

    Długosz-Lisiecka, Magdalena; Bem, Henryk

    Low-energy X and γ radiations (for example of (210)Pb: Eγ = 46.5 keV) are effectively self-absorbed even in thin environmental samples, including air filters with captured dust or contaminated soil, as well as in bottom sediment matrixes with limited quantities of the samples. In this paper, a simple method for the direct analysis of (210)Pb (T1/2 = 22.3 years) by gamma-ray spectrometry in environmental samples with self-absorption correction is described. The method is based on the comparison of two γ peak activities coming from other natural radionuclides, usually present in environmental samples. We have analyzed the dependence of the self-absorption correction factor for the (210)Pb activity on the activity ratios of 911 and 209 keV peaks and 609 and 295 keV peaks coming from nuclides of (238)U or (232)Th rows, present in typical environmental samples.

  2. 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.

  3. 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.

  4. {sup 210}Po and {sup 210}Pb intake by the Portuguese population: The contribution of seafood in the dietary intake of {sup 210}Po and {sup 210}Pb

    SciTech Connect

    Carvalho, F.P.

    1995-10-01

    Through analysis of {sup 210}Po and {sup 210}Pb in the diet, the average ingestion rate for the Portuguese population is estimated at 1.2 and 0.47 Bq d{sup -1} per capita for {sup 210}Po and {sup 210}Pb, respectively. Detailed analysis of foods indicate that seafood alone contributes up to 70% of the {sup 210}Po ingestion rate, whereas cerals, vegetables, and meat altogether contribute 79% of the {sup 210}Pb ingestion rate. Consumption of seafood, both in terms of quantities (kg d{sup -1} per person) and preferential consumption of certain marine species, is the cause of the relatively high intake of {sup 210}Po and high {sup 210}Po:{sup 210}Pb ratio in the diet in comparison with other countries. Other {sup 210}Po and {sup 210}Pb sources, namely inhalation of surface air and cigarette smoke, contribute only a small percentage of the adsorption of these radionuclides in the blood. Estimated total body burdens of {sup 210}Po and {sup 210}Pb in adult men, 70 Bq, are 3.5 times higher than estimates for humans living in normal radioactivity regions and consuming a reference diet. Average whole body effective doses for the adult from the Portuguese population are estimated at about 85 {mu}Sv y{sup -1} from {sup 210}Po and 170 {mu}Sv y{sup -1} from {sup 210}Pb adsorbed with the diet. Effective dose from {sup 210}Po in the diet may vary from 25 {mu}Sv y{sup -1} in an heavy consumer of sardines, to 1,000 {mu}Sv y{sup -1} in an hypothetical heavy consumer of molluscs. 46 refs., 2 figs., 4 tabs.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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. Copyright © 2014 Elsevier Ltd. All rights reserved.

  11. 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.

  12. Atmospheric deposition patterns of (210)Pb and (7)Be in Cienfuegos, Cuba.

    PubMed

    Alonso-Hernández, Carlos M; Morera-Gómez, Yasser; Cartas-Águila, Héctor; Guillén-Arruebarrena, Aniel

    2014-12-01

    The radiometric composition of bulk deposition samples, collected monthly for one year, February 2010 until January 2011, at a site located in Cienfuegos (22° 03' N, 80° 29' W) (Cuba), are analysed in this paper. Measurement of (7)Be and (210)Pb activity concentrations were carried out in 12 bulk deposition samples. The atmospheric deposition fluxes of (7)Be and (210)Pb are in the range of 13.2-132 and 1.24-8.29 Bq m(-2), and their mean values are: 56.6 and 3.97 Bq m(-2), respectively. The time variations of the different radionuclide have been discussed in relation with meteorological factors and the mean values have been compared to those published in recent literature from other sites located at different latitudes. The annual average flux of (210)Pb and (7)Be were 47 and 700 Bq m(-2) y(-1), respectively. Observed seasonal variations of deposition data are explained in terms of different environmental features. The atmospheric deposition fluxes of (7)Be and (210)Pb were moderately well correlated with precipitation and well correlated with one another. The (210)Pb/(7)Be ratios in the monthly depositions samples varied in the range of 0.05-0.10 and showed a strong correlation with the number of rainy days. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. 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.

  14. Modeling the downward transport of (210)Pb in Peatlands: Initial Penetration-Constant Rate of Supply (IP-CRS) model.

    PubMed

    Olid, Carolina; Diego, David; Garcia-Orellana, Jordi; Cortizas, Antonio Martínez; Klaminder, Jonatan

    2016-01-15

    The vertical distribution of (210)Pb is commonly used to date peat deposits accumulated over the last 100-150 years. However, several studies have questioned this method because of an apparent post-depositional mobility of (210)Pb within some peat profiles. In this study, we introduce the Initial Penetration–Constant Rate of Supply (IP-CRS) model for calculating ages derived from 210Pb profiles that are altered by an initial migration of the radionuclide. This new, two-phased, model describes the distribution of atmospheric-derived (210)Pb ((210)Pbxs) in peat taking into account both incorporation of (210)Pb into the accumulating peat matrix as well as an initial flushing of (210)Pb through the uppermost peat layers. The validity of the IP-CRS model is tested in four anomalous (210)Pb peat records that showed some deviations from the typical exponential decay profile not explained by variations in peat accumulation rates. Unlike the most commonly used (210)Pb-dating model (Constant Rate of Supply (CRS)), the IP-CRS model estimates peat accumulation rates consistent with typical growth rates for peatlands from the same areas. Confidence in the IP-CRS chronology is also provided by the good agreement with independent chronological markers (i.e. (241)Am and (137)Cs). Our results showed that the IP-CRS can provide chronologies from peat records where (210)Pb mobility is evident, being a valuable tool for studies reconstructing past environmental changes using peat archives during the Anthropocene.

  15. 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.

  16. 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.

  17. 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.

  18. Temporal variations of 7Be and 210Pb activity in aerosols at Xiamen, China

    NASA Astrophysics Data System (ADS)

    Huang, Dekun

    2016-04-01

    The radionuclides serve as powerful tracers to identify and quantify several atmospheric processes, such as source, transport and mixing of air masses, air masses exchanging between various atmospheric layers, residence times of atmospheric gasses and pollutants. 7Be and 210Pb activities in aerosols were measurement from October, 2013 to September, 2015 at Xiamen (24°26'7.44″N, 118°5'31.30″N) in South China. The activity of 7Be and 210Pb in aerosols from 2013 to 2015 in Xiamen ranged from 0.26 to 9.05 (mean:4.15) mBq m-3 and from 0.14 to 2.64 (mean:1.05) mBq m-3, respectively. The mean activity of 7Be was comparable with the activities of other places in the same latitude, while the mean activity of 210Pb was lower than the activity of the locations at high altitudes. The possible reason is that Xiamen is a coastal city located on southwest Pacific. The activities of 7Be and 210Pb had a commonly low value in summer (July-September) and a high value in autumn (October-December), it may be controlled by the rainfall. There is significant relationship between the monthly 210Pb activities and the concentration of PM 2.5 and PM 10. In contrast, monthly 7Be activities only show significant correlation with the concentration of PM 10, which implies that 7Be and 210Pb can be used to trace the different sources of the aerosols. And the dry 7Be depositional fluxes increased with latitude along the coast of China (R2=0.92, n=8).

  19. 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.

  20. 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

  1. 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

  2. Impact of air masses on the distribution of (210)Pb in the southeast of Iberian Peninsula air.

    PubMed

    Chham, E; Piñero-García, F; González-Rodelas, P; Ferro-García, M A

    2017-10-01

    The current research has been developed in the southern of the Iberian Peninsula in order to better understand the atmospheric processes and also the influence of the air masses origin and pathways in the transport of (210)Pb-aerosols in the atmosphere. Simultaneous measurements of the radionuclides (7)Be and (210)Pb on airborne have been routinely carried out at Granada (Spain 37.177N, 3.598 W, 687 m a.s.l.) from 2010 to 2014. The long term monitoring evolution on (210)Pb is discussed in this study and also the useful ratio (7)Be/(210)Pb. The maximum monthly activity concentration for (210)Pb at ground level in Granada was detected during summer and early autumn (September), whereas minimum activity was measured in the winter. The monthly mean activity concentration for (210)Pb was 617.8 ± 33.0 μBq·m(-3). The results show that the annual average (210)Pb concentrations in samples collected during the same period were almost constant. The lowest activity concentration for (210)Pb are associated with maritime air masses coming from Atlantic and Norwest of Spain, while the highest activity concentrations for this radiotracers were positively correlated with the arrival of mineral dust linked to continental air masses coming from Mediterranean, Africa and Local area. The concentrations values show a nice agreement with the relevant reported results. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Radiometric studies of Lake Nyos (Cameroon) sediments: evidence of strong mixing and excess 210Pb

    NASA Astrophysics Data System (ADS)

    Piboule, M.; Pourchet, M.; Bouchez, R.; Amosse, J.; Brenac, P.; Maley, J.; Pinglot, J. F.; Vincent, C.

    1990-08-01

    A one-meter-long sediment core was extracted from the middle of Lake Nyos six months after the August 1986 gas burst disaster. Major and trace elements have been determined in twenty samples, including alpha and gamma spectrometry for the radioisotopes. Preliminary results show that: - 137Cs is present in uniform concentrations throughout the core. The measured activity (7.3 Bq kg -1) corresponds to a total deposit of approximately 1800 Bq m -2 in the one-meter-thick sediment layer, similar in magnitude to the average amounts deposited at these latitudes by atmospheric thermonuclear tests. - 210Pb, with a half-life of 22 years, is also uniformly distributed, showing a measured activity of 233 Bq kg -1, three to four times higher than the values observed in other Cameroon lakes. The activity ratio of 210Pb to 226Ra is about 4. These data are interpreted as follows: - The uniformly distributed 137Cs and 210Pb concentrations suggest complete mixing of the top of sediments at the sample location.; - From the amount of deposited 137Cs found in the core, this sediment mixing process does not appear to have involved significantly more than that top layer. - The 210Pb excess, not supported by 226Ra, can be explained by an upwards release of radon gas ( 222Rn) prior to the CO 2 burst.

  8. 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

  9. 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.

  10. 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.

  11. (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.

  12. 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.

  13. Distribution of 7Be, 210Pb and 210Po in Size Fractionated Aerosols From Northern Taiwan

    NASA Astrophysics Data System (ADS)

    Su, C.; Huh, C.

    2003-12-01

    The partition of 7Be, 210Pb and 210Po in size fractionated aerosols was studied using samples collected from Nankang (northern Taiwan) during July 2002-July 2003. A TSP air sampler coupled to a 6-stage cascade impactor was used to collect large-volume samples and separate the aerosols into six size classes with the cut-off points at 7.2 μ m, 3 μ m, 1.5 μ m, 0.95 μ m and 0.49 μ m. The total mass concentrations of the aerosol samples ranged from 23 to 99 μ g m-3, with a maximum (18-50 %) falling at the sixth stage (< 0.49 μ m) and a minimum (5-13 %) at the third stage (1.5-3.0 μ m). Total concentrations of 7Be, 210Pb and 210Po in the samples were 0.11-0.56, 0.012-0.100 and 0.0009-0.0158 dpm m-3, respectively. For most of the samples, more than 70 % of the radioactivities are found in the fifth and sixth stages (< 0.95 μ m). Concurrent with the measurements of 7Be and 210Pb concentrations in aerosols, we have also measured the fluxes of these nuclides. Coupling the concentration data with the flux data, we obtained an overall deposition velocity of 0.02-3.71 cm s-1 for 7Be and 0.09-6.18 cm s-1 for 210Pb, without any obvious seasonal variation during the experimental periods. The size of aerosol particles and the height of cloud are the major factors controlling the deposition velocity of 7Be and 210Pb. The time series of 210Po/210Pb was in phase with that of 7Be/210Pb and showed an increase during the spring and summer, probably reflecting stratospheric folding in the spring and more vigorous tropospheric mixing (e.g., due to typhoons) in the summer.

  14. 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.

  15. 210Pb-derived ages for the reconstruction of terrestrial contaminant history into the Mexican Pacific coast: potential and limitations.

    PubMed

    Ruiz-Fernández, A C; Hillaire-Marcel, C

    2009-01-01

    (210)Pb is widely used for dating recent sediments in the aquatic environment; however, our experiences working in shallow coastal environments in the Pacific coast of Mexico have demonstrated that the potential of (210)Pb for reliable historical reconstructions might be limited by the low (210)Pb atmospheric fallout, sediment mixing, abundance of coarse sediments and the lack of (137)Cs signal for (210)Pb corroboration. This work discusses the difficulties in obtaining adequate sedimentary records for geochronological reconstruction in such active and complex settings, including examples of (210)Pb geochronologies based on sediment profiles collected in two contrasting areas coastal areas (mudflats associated to coastal lagoons of Sinaloa State and the continental shelf of the Gulf of Tehuantepec), in which geochemical data was used to support the temporal frame established and the changes in sediment supply recorded in the sediment cores which were related to the development of land-based activities during the last century.

  16. 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.

  17. (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

  18. 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

  19. Mobility indices and doses from (210)Po and (210)Pb activity concentrations data in Brazilian spas groundwaters.

    PubMed

    Bonotto, Daniel Marcos; Oliveira, Ana Maria Marinello Assis de

    2017-06-01

    (210)Po and (210)Pb activity concentrations in spas groundwaters occurring at São Paulo (SP) and Minas Gerais (MG) states, Brazil, have been reported in this paper with a dual purpose: to compare different indices for evaluating the radionuclides mobility into waters and to evaluate the drinking water quality from dose calculations. The waters (75 sampling points) are extensively used for drinking in public places, bottling and bathing purposes, among other. The samples were taken from springs and wells drilled at different aquifer systems inserted in Paraná and Southeastern Shield hydrogeological provinces. The WHO guideline reference value for (210)Pb and (210)Po of 0.1 Bq/L in drinking water was not reached for (210)Pb but the (210)Po levels were equal or above it in four spas groundwaters from MG State. The maximum WHO guidance dose level of 0.1 mSv/yr was also reached or surpassed in them. The (210)Pb "mobility index" taking into account the ratio of the weight of the dissolved (210)Pb per unit volume of solution to its weight per unit weight of the rock matrix yielded values in the range of 0.01-5.2 kg/m(3). Another "mobility index" (Preference Ratio) expressing the ratio of (210)Pb and (238)U in the waters divided by the ratio of (210)Pb and (238)U in the rock matrices provided values between 0.004 and 7994. The (210)Pb/(238)U activity ratios of some spas groundwaters suggested preferential (238)U transport relative to (210)Pb into the liquid phase, whereas the ratio of the (210)Pb to (238)U mobility indices indicated the opposite. Such finding showed a better usefulness of the mobility indices for evaluating processes affecting the radionuclides release into the liquid phase during the water/rock interactions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. 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.

  1. Extraction of polycyclic aromatic hydrocarbons from spiked soil

    SciTech Connect

    Coover, M.P.; Sims, R.C.; Doucette, W.

    1987-11-01

    A homogenization method was evaluated for extracting polycyclic aromatic hydrocarbons (PAHs) from soils. Fifteen PAHs were spiked and recovered from 2 soils at concentrations ranging from 1 to 1000 micrograms/g, using the homogenization method and a Soxhlet extraction method. Each extraction method performed well in removing the 15 PAHs from both soils over a broad range of concentrations. In general, Soxhlet extraction yielded slightly but significantly (P less than 0.05) higher recoveries than did the homogenization method. The homogenization method, however, was easy to use, and the extraction step turnaround time was less than 15 min/sample. The method should be suitable for other applications requiring the extraction of hydrophobic organic compounds from soils.

  2. (210)Pb and compositional data of sediments from Rondonian lakes, Madeira River basin, Brazil.

    PubMed

    Bonotto, Daniel Marcos; Vergotti, Marcelo

    2015-05-01

    Gold exploration has been intensive in Brazilian Amazon over the last 40 years, where the use of mercury as an amalgam has caused abnormal Hg concentrations in water bodies. Special attention has been directed to Madeira River due to fact it is a major tributary of Amazon River and that since 1986, gold exploration has been officially permitted along a 350km sector of the river. The (21)(0)Pb method has been used to date sediments taken from nine lakes situated in Madeira River basin, Rondônia State, and to verify where anthropogenic Hg might exist due to gold exploitation in Madeira River. Activity profiles of excess (21)(0)Pb determined in the sediment cores provided a means to evaluate the sedimentation rates using a Constant Flux: Constant Sedimentation (CF:CS) and Constant Rate of Supply (CRS) of unsupported/excess (21)(0)Pb models. A significant relationship was found between the CF:CS sedimentation rates and the mean values of the CRS sedimentation rates (Pearson correlation coefficient r=0.59). Chemical data were also determined in the sediments for identifying possible relationships with Hg occurring in the area. Significant values were found in statistical correlation tests realized among the Hg, major oxides and Total Organic Carbon (TOC) content in the sediments. The TOC increased in the sediment cores accompanied by a loss on ignition (LOI) increment, whereas silica decreased following a specific surface area raising associated to the TOC increase. The CRS model always provided ages within the permitted range of the (21)(0)Pb-method in the studied lakes, whereas the CF:CS model predicted two values above 140 years. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. 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.

  4. 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.

  5. 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.

  6. An efficient quantitative technique for the simultaneous analyses of radon daughters (210)Pb, (210)Bi and (210)Po.

    PubMed

    Church, T M; Hussain, N; Ferdelman, T G; Fowler, S W

    1994-02-01

    An improved and time efficient technique has been developed for quantitative determination of the long-lived (222)Rn daughters ((210)Pb, (210)Po and (210)Bi) in atmospheric and oceanic samples. The sample is first spiked with yield tracers for polonium (208 or 209), bismuth (207), and lead (stable lead carrier). These nuclides may then be scavenged through iron hydroxide precipitation and redissolved in a dilute (pH approximately 2) nitric acid plating medium with citrate and hydroxylamine hydrochloride at 90 degrees centrigrade with constant stirring. First a silver planchet is suspended in the solution which plates polonium to high efficiency. Second, a nickel planchet is suspended in the same solution which is maintained hermetic (e.g. bubbling with helium) and bismuth is plated next with high efficiency. Third, lead is purified from the same solution using anion exchange techniques and isolated for beta counting as the sulfate. Polonium is analyzed by isotope dilution alpha spectrometry. Bismuth and lead are analyzed by anti-coincident beta counting in a low level shield. In the case of bismuth, the 207 tracer is added in quantities at least comparable to the background of the beta system such that counting before and after the decay of (210)Bi gives the bismuth yield. The unique characteristics of this technique are its speed and efficiency; all three radon daughters can be isolated for counting within 4 hr of pre-treating the sample. The remaining solution can be treated subsequently for other analyses as appropriate.

  7. 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. Copyright © 2013 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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

    behaviour of 210Pb and total Pb in the mosses may reflect differences in the particle size distribution of the corresponding aerosols, their physical and chemical properties, the extent of their interaction with plant surfaces, or some combination of these factors. The 206Pb/207Pb ratios from NBF (HO = 1.159 ± 0.002, n = 19; WI = 1.157 ± 0.003, n = 48) and OB (GS = 1.157 ± 0.003, n = 28; KL = 1.159 ± 0.003, n = 15) are uniform and indicate that both regions are impacted by Pb from predominately anthropogenic sources. Although Sphagnum moss represents an established receptor in monitoring atmospheric Pb deposition, the physical characteristics (size, morphology, composition) of the three predominant kinds of Pb-bearing aerosols considered here, namely 210Pb (adsorbed onto aerosol surfaces, following decay of 222Rn), anthropogenic Pb (sub-micron aerosols from high temperature combustion processes) and lithogenic Pb soil-derived mineral dusts (tens of microns, from chemical weathering of crustal rocks), are fundamentally different and these have consequences for the retention efficiency of the three kinds of particles.

  13. 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.

  14. 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).

  15. 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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. 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.

  17. 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.

  18. Recent (210)Pb, (137)Cs and (241)Am accumulation in an ombrotrophic peatland from Amsterdam Island (Southern Indian Ocean).

    PubMed

    Li, Chuxian; Le Roux, Gaël; Sonke, Jeroen; van Beek, Pieter; Souhaut, Marc; Van der Putten, Nathalie; De Vleeschouwer, François

    2017-09-01

    Over the past 50 years, (210)Pb, (137)Cs and (241)Am have been abundantly used in reconstructing recent sediment and peat chronologies. The study of global aerosol-climate interaction is also partially depending on our understanding of (222)Rn-(210)Pb cycling, as radionuclides are useful aerosol tracers. However, in comparison with the Northern Hemisphere, few data are available for these radionuclides in the Southern Hemisphere, especially in the South Indian Ocean. A peat core was collected in an ombrotrophic peatland from the remote Amsterdam Island (AMS) and was analyzed for (210)Pb, (137)Cs and (241)Am radionuclides using an underground ultra-low background gamma spectrometer. The (210)Pb Constant Rate of Supply (CRS) model of peat accumulations is validated by peaks of artificial radionuclides ((137)Cs and (241)Am) that are related to nuclear weapon tests. We compared the AMS (210)Pb data with an updated (210)Pb deposition database. The (210)Pb flux of 98 ± 6 Bq·m(-2)·y(-1) derived from the AMS core agrees with data from Madagascar and South Africa. The elevated flux observed at such a remote location may result from the enhanced (222)Rn activity and frequent rainfall in AMS. This enhanced (222)Rn activity itself may be explained by continental air masses passing over southern Africa and/or Madagascar. The (210)Pb flux at AMS is higher than those derived from cores collected in coastal areas in Argentina and Chile, which are areas dominated by marine westerly winds with low (222)Rn activities. We report a (137)Cs inventory at AMS of 144 ± 13 Bq·m(-2) (corrected to 1969). Our data thus contribute to the under-represented data coverage in the mid-latitudes of the Southern Hemisphere. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. 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).

  20. sup 210 Po and sup 210 Pb remobilization from lake sediments in relation to iron and manganese cycling

    SciTech Connect

    Benoit, G.; Hemond, H.F. )

    1990-08-01

    The behavior of {sup 210}Po and {sup 210}Pb was studied in the water column of an oligotrophic, dimictic lake. Direct uptake of the radionuclides by sediments was negligible compared to removal on particles, and {sup 210}Pb scavenging was 4 times that of {sup 210}Po. Both nuclides were found to be significantly remobilized from sediments into the stratified, anoxic water column. Releases seem to be linked to the cycling of the transition metals, iron and possibly manganese. The distribution of both iron and {sup 210}Pb in stratified, anoxic waters can be modeled as constant release and rapid horizontal mixing/dilution; vertical turbulent transport had a negligible effect on element distributions. Upon contact with oxygen, iron rapidly reprecipitates, forming a particulate maximum and rescavenging {sup 210}Pb. Unlike {sup 210}Pb, much {sup 210}Po is released from sediments before overlying water becomes completely anoxic, leading to unsupported {sup 210}Po. {sup 210}Po cycling in the stratified water column is more complex than that of {sup 210}Pb, and additional removal mechanism(s) may be active, including perhaps oxidation of soluble Po(II) to insoluble Po(IV).

  1. 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.

  2. 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. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. 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.

  4. Phytoremediation potential of Brassica juncea in Cu-pyrene co-contaminated soil: comparing freshly spiked soil with aged soil.

    PubMed

    Chigbo, Chibuike; Batty, Lesley

    2013-11-15

    A comparison was made between the dissipation of pyrene as well as the uptake of copper (Cu) in soil freshly spiked with Cu, pyrene or Cu + pyrene and in aged soil. The potential of B juncea for phytoremediation was also investigated. The biomass of Brassica juncea significantly decreased (>50% reduction) in freshly spiked soil when compared to aged soil in all treatments. However, the accumulation of Cu in shoot was significantly reduced (60-88%) in aged soil after 60 days of planting. The total removal of Cu from co-contaminated soil was always higher (>2-3 fold) in aged soil than in freshly spiked soil when lower Cu concentration (50 mg kg(-1)) was co-contaminated with 250 or 500 mg kg(-1) of pyrene while in other co-contaminated treatments, the total removal of Cu from aged soil were significantly lower. The level of pyrene in both planted and un-planted freshly spiked soil decreased significantly (>67%) over the 60 days of plant trial. In aged soils, there were no significant differences in residual pyrene concentration between planted and unplanted soil. This suggests that the presence of B. juncea in aged soil did not enhance the dissipation of pyrene and that the prediction of pyrene dissipation in laboratory prepared soil may not have reflected the true situation in the fields.

  5. Comparisons of 210Pb and pollen methods for determining rates of estuarine sediment accumulation

    NASA Astrophysics Data System (ADS)

    Brush, Grace S.; Martin, E. Ann; DeFries, Ruth S.; Rice, Cynthia A.

    1982-09-01

    Comparisons of sedimentation rates obtained by 210Pb and pollen analyses of 1-m cores collected throughout the Potomac Estuary show good agreement in the majority of cores that can be analyzed by both methods. Most of the discrepancy between the methods can be explained by the analytical precision of the 210Pb method and by the exactness with which time horizons can be identified and dated for the pollen method. X-radiographs of the cores and the distinctness of the pollen horizons preclude significant displacement by reworking and/or mixing of sediments. Differences between the methods are greatest where uncertainties exist in assigning a rate by one or both methods (i.e., 210Pb trends and/or "possible" horizon assignments). Both methods show the same relative rates, with greater sediment accumulation more common in the upper and middle estuary and less toward the mouth. The results indicate that geochronologic studies of estuarine sediments should be preceded by careful observation of sedimentary structures, preferably by X-radiography, to evaluate the extent of mixing of the sediments. Time horizons, whether paleontologic or isotopic, are generally blurred where mixing has occurred, precluding precise identification. Whenever possible, two methods should be used for dating sediments because a rate, albeit erroneous, can be obtained isotopically in sediments that are mixed; accurate sedimentation rates are also difficult to determine where the time boundary is a zone rather than a horizon, where the historical record does not provide a precise date for the pollen horizon, or where scouring has removed some of the sediment above a dated pollen horizon.

  6. Comparisons of 210Pb and pollen methods for determining rates of estuarine sediment accumulation

    USGS Publications Warehouse

    Brush, G.S.; Martin, E.A.; DeFries, R.S.; Rice, C.A.

    1982-01-01

    Comparisons of sedimentation rates obtained by 210Pb and pollen analyses of 1-m cores collected throughout the Potomac Estuary show good agreement in the majority of cores that can be analyzed by both methods. Most of the discrepancy between the methods can be explained by the analytical precision of the 210Pb method and by the exactness with which time horizons can be identified and dated for the pollen method. X-radiographs of the cores and the distinctness of the pollen horizons preclude significant displacement by reworking and/or mixing of sediments. Differences between the methods are greatest where uncertainties exist in assigning a rate by one or both methods (i.e., 210Pb trends and/or "possible" horizon assignments). Both methods show the same relative rates, with greater sediment accumulation more common in the upper and middle estuary and less toward the mouth. The results indicate that geochronologic studies of estuarine sediments should be preceded by careful observation of sedimentary structures, preferably by X-radiography, to evaluate the extent of mixing of the sediments. Time horizons, whether paleontologic or isotopic, are generally blurred where mixing has occurred, precluding precise identification. Whenever possible, two methods should be used for dating sediments because a rate, albeit erroneous, can be obtained isotopically in sediments that are mixed; accurate sedimentation rates are also difficult to determine where the time boundary is a zone rather than a horizon, where the historical record does not provide a precise date for the pollen horizon, or where scouring has removed some of the sediment above a dated pollen horizon. ?? 1982.

  7. 210Pb and 210Po concentrations in Italian cigarettes and effective dose evaluation.

    PubMed

    Taroni, Mattia; Zagà, Vincenzo; Bartolomei, Paolo; Gattavecchia, Enrico; Pacifici, Roberta; Zuccaro, Piergiorgio; Esposito, Massimo

    2014-09-01

    It has been known for a long time that cigarette tobacco contains naturally occurring radioactive nuclides such as 210Pb and 210Po. In this study, the concentrations of 210Pb and 210Po in the 10 most widely sold cigarette brands in Italy during the year 2010 were measured, and the effective dose to smokers has been calculated. The results of this study show that 210Pb concentration ranged from 11.6 to 20.0 mBq cig-1 with an arithmetic mean of 14.6 mBq cig-1, while the activity concentration of 210Po ranged from 13.1 to 19.0 mBq cig-1 with an arithmetic mean of 15.7 mBq cig-1, thus confirming previous results and showing that the radioactivity concentration was not reduced in the last few years. The annual effective dose for a typical smoker consuming 20 cigarettes per day ranged from an average of 55 μSv y-1 to about 81 μSv y-1. It is finally put in evidence the need to improve the knowledge about crucial data needed for accurate dose assessment deriving from the inhalation of both radioisotopes contained in the cigarettes, namely the dose conversion coefficients, which strongly depend on several parameters such as the inhalation speed through the mouth, the real fraction of radionuclide transferred from cigarette to mainstream smoke, the lung absorption behavior of the radioisotopes inhaled with mainstream smoke, and the AMAD of particles inhaled by smokers.

  8. 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.

  9. 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.

  10. Interaction of sea ice sediments and surface sea water in the Arctic Ocean: Evidence from excess 210Pb

    NASA Astrophysics Data System (ADS)

    Baskaran, M.

    2005-06-01

    We measured the activities of 210Pb, 226Ra, 238U and 137Cs in a suite of ice-rafted sediments (IRS) from the Arctic Ocean in an attempt to assess the interaction of sea ice sediments and surface water. The concentrations of these nuclides were compared to those of the benthic sediments in the coastal and shelf regions of the Arctic Ocean, which are believed to be the major source region for the IRS. The concentration factors (CF = activity of a nuclide in IRS/average activity in benthic sediments) are ~1 and 4-92 for 137Cs and 210Pb, respectively. The CF values for 137Cs are comparable to the values that can be obtained from the previously published data while we report the first set of high CF values of 210Pb. A major portion of 210Pb in some IRS samples is likely derived from surface waters and thus, the concentrations of 210Pb combined with another particle-reactive radionuclide (such as 7Be, 234Th) in IRS might provide information on the residence time and transit time of sea ice-laden sediments.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. A brief review of 210Pb sediment dating models and uncertainties in a world of global change

    NASA Astrophysics Data System (ADS)

    Sanchez-Cabeza, J. A.; Ruiz-Fernandez, A. C.

    2016-12-01

    Irrespective of the model names used, assumptions and (usually forgotten) uncertainties, the fact is that 210Pb sediment dating is an increasingly relevant tool in our world of global change. 210Pb dating results are needed to assess historical trends of sea level rise, quantify blue carbon fluxes and reconstruct environmental records of biogeochemical proxies for diverse processes in the aquatic ecosystems (such as ocean acidification, hypoxia and pollution). Although in the past 210Pb profiles departing from "ideal" decay trends were usually discarded, all profiles have useful information. In this work we review the principles and assumptions of the most common 210Pb dating models, and propose a logical formulation and classification of the models. 210Pb dating models provide two kinds of results: chronologies (i.e. age models) and accumulation rates. In many cases, the use of sediment and/or mass accumulation rates (SAR and MAR) is needed to assess environmental fluxes or, simply, to describe changes, such as catchment erosion or saltmarsh accretion. Although uncertainty quadratic propagation is a well-known technique, it requires that all variables are fully independent and requires demanding mathematical expressions which might lead to wrong results. We present here a Monte Carlo method that makes calculation easier and, likely, error-free. Not unexpectedly, the most important uncertainty sources are measurement uncertainties, which impose limitations on common techniques such as gamma spectrometry. 210Pb chronology does not cover all anthropogenic impacts, such as those caused by ancient civilizations, so radiocarbon also plays an important role in this kind of work. We also conceptually revise the limitations of both techniques and encourage scientists to link both dating techniques with a symmetrically open mind. Acknowledgements: projects CONACYT PDCPN2013-01/214349 and CB2010/153492, UNAM PAPIIT-IN203313, PRODEP network "Aquatic contamination: levels and

  16. 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

    2017-06-01

    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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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. Copyright © 2013 Elsevier Ltd. All rights reserved.

  6. 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.

  7. 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.

  8. Mercury in mercury(II)-spiked soils is highly susceptible to plant bioaccumulation.

    PubMed

    Hlodák, Michal; Urík, Martin; Matúš, Peter; Kořenková, Lucia

    2016-01-01

    Heavy metal phytotoxicity assessments usually use soluble metal compounds in spiked soils to evaluate metal bioaccumulation, growth inhibition and adverse effects on physiological parameters. However, exampling mercury phytotoxicity for barley (Hordeum vulgare) this paper highlights unsuitability of this experimental approach. Mercury(II) in spiked soils is extremely bioavailable, and there experimentally determined bioaccumulation is significantly higher compared to reported mercury bioaccumulation efficiency from soils collected from mercury-polluted areas. Our results indicate this is not affected by soil sorption capacity, thus soil ageing and formation of more stable mercuric complexes with soil fractions is necessary for reasonable metal phytotoxicity assessments.

  9. 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.

  10. 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

    2017-08-01

    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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. 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.

  12. 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.

  13. 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).

  14. 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. Copyright © 2010 Elsevier Ltd. All rights reserved.

  15. 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.

  16. 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.

  17. 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

  18. SUPPLEMENTARY COMPARISON: Activity measurements of a suite of radionuclides (90Sr, 137Cs, 210Pb, 210Po, 228Ra, 234U, 235U, 238U, 238Pu, 239,240Pu) in soil reference material (Rocky Flats II): CCRI(II)-S2

    NASA Astrophysics Data System (ADS)

    Nour, S.; Inn, K. G. W.; Karam, L. R.

    2009-01-01

    In 2005, the CCRI decided that a comparison undertaken from 2002 to 2007 by the NIST (SIM) in the development of a new soil (Rocky Flats II) standard reference material (SRM) was sufficiently well constructed that it could be converted into a supplementary comparison under CCRI(II), with comparison identifier CCRI(II)-S2, so as to support calibration and measurement capability (CMC) claims for radionuclide measurements in reference material (specifically, low calcium-content soils). Previous comparisons of radionuclides have been of single or multiple nuclides in non-complex matrices and results of such could not be extended to support capabilities to measure the same nuclides in reference materials. The results of this comparison have been reported to the participants, and have been used to determine the certified reference value of the SRM. The key comparison working group (KCWG) of the CCRI(II) has approved this approach as a mechanism to link all the results to certified 'reference values' in lieu of the key comparison reference value (KCRV) of these specified radionuclides in this type of matrix (soil) so as to support CMCs of similar materials. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section II, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

  19. Effect of heavy metals on pH buffering capacity and solubility of Ca, Mg, K, and P in non-spiked and heavy metal-spiked soils.

    PubMed

    Najafi, Sarvenaz; Jalali, Mohsen

    2016-06-01

    In many parts of the world, soil acidification and heavy metal contamination has become a serious concern due to the adverse effects on chemical properties of soil and crop yield. The aim of this study was to investigate the effect of pH (in the range of 1 to 3 units above and below the native pH of soils) on calcium (Ca), magnesium (Mg), potassium (K), and phosphorus (P) solubility in non-spiked and heavy metal-spiked soil samples. Spiked samples were prepared by cadmium (Cd), copper (Cu), nickel (Ni), and zinc (Zn) as chloride salts and incubating soils for 40 days. The pH buffering capacity (pHBC) of each sample was determined by plotting the amount of H(+) or OH(-) added (mmol kg(-1)) versus the related pH value. The pHBC of soils ranged from 47.1 to 1302.5 mmol kg(-1) for non-spiked samples and from 45.0 to 1187.4 mmol kg(-1) for spiked soil samples. The pHBC values were higher in soil 2 (non-spiked and spiked) which had higher calcium carbonate content. The results indicated the presence of heavy metals in soils generally decreased the solution pH and pHBC values in spiked samples. In general, solubility of Ca, Mg, and K decreased with increasing equilibrium pH of non-spiked and spiked soil samples. In the case of P, increasing the pH to about 7, decreased the solubility in all soils but further increase of pH from 7, enhanced P solubility. The solubility trends and values for Ca, Mg, and K did not differed significantly in non-spiked and spiked samples. But in the case of P, a reduction in solubility was observed in heavy metal-spiked soils. The information obtained in this study can be useful to make better estimation of the effects of soil pollutants on anion and cation solubility from agricultural and environmental viewpoints.

  20. A tale of two cores: Evaluation of 210Pb dating methods of salt marsh sediments for two cores collected 30 years apart

    NASA Astrophysics Data System (ADS)

    Fuller, C.; Drexler, J. Z.

    2016-12-01

    210Pb dating of wetland sediments is commonly used to constrain recent C accumulation rates and contaminant input histories. However, uncertainties in 210Pb-derived rates and validation of accumulation and accretion rates using an independent tracer are often not reported. We describe here 210Pb and 137Cs profiles in two cores from a salt marsh in south San Francisco Bay, California, collected in 1981 and 2011 within 5 m of each other, to compare and evaluate 210Pb dating methods. In the 1981 core, unsupported 210Pb (210PbXS) was detected to 12 cm and yielded mass accumulation rates (MAR) of 0.043 and 0.036 g/cm2/y using the Constant Flux-Constant Sedimentation method (CF:CS) and Constant Rate of Supply (CRS) methods, respectively. Accretion rates (S) of 0.17 (CF:CS) and 0.12 cm/y (CRS) were calculated from these MARs. The distinct 137Cs peak at 4-6 cm in the 1981 core is in good agreement with the210Pb-based 1963 depth (3.4 and 4 cm, CF:CS and CRS, respectively). 210PbXS was detectable to 18 cm in the 2011 core, and yielded a CF:CS MAR (0.077 g/cm2/y; S = 0.35 cm/y) that is about two times greater than the mass-weighted average CRS MAR (0.044 g/cm2/y; S = 0.16 cm/y). Broad subsurface maxima in 137Cs and 239Pu were observed between 16 and 24 cm in the 2011 core, which are 5 to 11 cm deeper than the 1963 depth calculated by the 2011 and 1981 210Pb-derived MARs. The apparent migration and broadening of bomb-fallout radionuclide peaks over 30 years negates their use in validating 210Pb dating. Because of low 210PbXS activities in both cores, the base of the 210PbXS profile and integrated activity used in CRS are underestimated, resulting in the lower CRS MARs that decrease with increasing depth. The range of MARs determined for two cores within 5 m but separated by 30 years will be used as an example to evaluate the uncertainties that need to be reported with C accumulation rates and contaminant histories derived from 210Pb dating of sediment archives.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. Phytotoxicity of trace metals in spiked and field-contaminated soils: Linking soil-extractable metals with toxicity.

    PubMed

    Hamels, Fanny; Malevé, Jasmina; Sonnet, Philippe; Kleja, Dan Berggren; Smolders, Erik

    2014-11-01

    Soil tests have been widely developed to predict trace metal uptake by plants. The prediction of metal toxicity, however, has rarely been tested. The present study was set up to compare 8 established soil tests for diagnosing phytotoxicity in contaminated soils. Nine soils contaminated with Zn or Cu by metal mining, smelting, or processing were collected. Uncontaminated reference soils with similar soil properties were sampled, and series of increasing contamination were created by mixing each with the corresponding soil. In addition, each reference soil was spiked with either ZnCl2 or CuCl2 at several concentrations. Total metal toxicity to barley seedling growth in the field-contaminated soils was up to 30 times lower than that in corresponding spiked soils. Total metal (aqua regia-soluble) toxicity thresholds of 50% effective concentrations (EC50) varied by factors up to 260 (Zn) or 6 (Cu) among soils. For Zn, variations in EC50 thresholds decreased as aqua regia > 0.43 M HNO3  > 0.05 M ethylenediamine tetraacetic acid (EDTA) > 1 M NH4 NO3  > cobaltihexamine > diffusive gradients in thin films (DGT) > 0.001 M CaCl2 , suggesting that the last extraction is the most robust phytotoxicity index for Zn. The EDTA extraction was the most robust for Cu-contaminated soils. The isotopically exchangeable fraction of the total soil metal in the field-contaminated soils markedly explained the lower toxicity compared with spiked soils. The isotope exchange method can be used to translate soil metal limits derived from soils spiked with metal salts to site-specific soil metal limits.

  6. The estimation of the 210Pb bremsstrahlung contribution to the background of lead shielded {gamma}-spectrometers

    SciTech Connect

    Mrdja, Dusan; Bikit, Istvan; Veskovic, Miroslav; Slivka, Jaroslav; Conkic, Ljiljana; Varga, Ester

    2006-04-26

    The 46.5 keV {gamma}-intensity of 210Pb in the background can be easily reduced by inner lining, but the bremsstrahlung from the 1.2 MeV maximal energy {beta}-decay will reach the lead shielded Ge detector. The spectrum of this bremsstrahlung is calculated by numerically fitting the {beta}-spectrum and integrating the Koch-Motz formula. The adsorption of the bremsstrahlung spectrum in the lead is calculated by the effective solid angle algorithm by comparison with the measured background spectrum. It is shown, that for the lead with 25 Bq/kg of 210Pb, at 100 keV the bremsstrahlung contribution to the background is about 20%.

  7. 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.

  8. /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.

  9. 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.

  10. 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.

  11. 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.

  12. The 210Po and 210Pb levels in surface sediment samples in the Izmir Bay (Aegean Sea-Turkey).

    PubMed

    Saçan, Sezen; Uğur, Aysun; Sunlu, Uğur; Büyükişik, Baha; Aksu, Mehmet; Sunlu, F Sanem

    2010-02-01

    Bottom sediments reflect in general the relative contamination of a sea area. Therefore, a great deal of monitoring work has been dedicated to the analysis of bottom sediments. Izmir Bay is a very important pollution centre in Turkish Aegean coast region due to a densely populated community, industrial complex and maritime transportation, and there are many streams flowing into the bay that pass through a number of industrial and agricultural areas. It had received the majority of domestic and industrial wastewaters until the wastewater treatment plant was constructed. It is well known that sediments play an important role as reservoirs of a fraction of the pollution in aquatic systems. Therefore, sediment samples were collected monthly from three stations which are located in the inner part of the bay during the period January to December 2003. Temporal variations and seasonal changes on their (210)Po and (210)Pb contents were examined, and the activity concentrations of (210)Po and (210)Pb were found to vary from 43+/-6 to 132+/-12 and 27+/-5 to 91+/-9 Bq kg(-1) dry wt, respectively. The highest values of those natural radionuclides were measured at Karşiyaka Station because of the current systems of the bay. Seasonally, the (210)Pb levels were found to increase during the winter time for all the stations.

  13. 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.

  14. 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.

  15. Estimation of dose due to ingestion of (210)pb in milk from dairy cattle in the semi-arid region of Pernambuco, Brazil.

    PubMed

    Silva, C M; Amaral, R S; Tabosa, J N; Júnior, J A S; Menezes, R S C; Ribeiro, F C A

    2010-08-01

    (210)Pb is widely distributed in the environment. In this context, the aim of this research has been: (1) to determine (210)Pb concentrations in milk and dairy products from farms located in the cities of Pedra and Venturosa in Pernambuco, Brazil; and (2) to calculate the dose due to the ingestion of (210)Pb in these products. The ion exchange resin method was used and the concentration of (210)Pb varied from 62 to 650 mBq l(-1) in fresh milk, from 202 to 1,494 mBq kg(-1) in curdled cheese and from 11 to 253 mBq l(-1) in milk whey. The estimated dose due to ingestion of milk and dairy products in this region was 0.2 Sv, which is at least two orders of magnitude above the maximum recommended levels.

  16. 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

  17. Variations of 210Po and 210Pb concentration in mussels (Mytilus galloprovincialis) from Didim and Izmir Bay (Turkish coast of Aegean Sea).

    PubMed

    Aközcan, S; Uğur Görgün, A

    2013-03-15

    In this study, the activity concentrations of (210)Po and (210)Pb were determined in mussels (Mytilus galloprovincialis) collected from Didim and Izmir Bay (Turkish coast of Aegean Sea) during the period of April 2006-March 2007. The concentrations activity of (210)Po were determined spectroscopically through its 5.30 MeV alpha particle emission, using (209)Po as an internal tracer. The (210)Pb activity concentrations were determined from the ingrowth of (210)Po, assuming zero initial (210)Po activity. The results of (210)Po and (210)Pb activity concentrations were found to vary between 34 ± 9 and 1855 ± 98 Bq kg(-1) dry weight and ND (lower than limit of detection) - 64 ± 6 Bq kg(-1) dry weight, respectively. (210)Po/(210)Pb ratio ranged between 1.00 and 106.87. The highest (210)Po activities were found in mussels collected from Didim. Copyright © 2012 Elsevier Ltd. All rights reserved.

  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. 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.

  20. 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.

  1. 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.

  2. The behavior of particle-reactive tracers in a high turbidity environment: {sup 234}Th and {sup 210}Pb on the Amazon continental shelf

    SciTech Connect

    Smoak, J.M.; DeMaster, D.J.; Pope, R.H.; Kuehl, S.A.; McKee, B.A.

    1996-06-01

    Excess {sup 234}Th and {sup 210}Pb seabed inventories were measured in cores collected from the Amazon continental shelf to examine particle scavenging and seabed dynamics. Typical excess {sup 210}Pb inventories range from 100 to 300 dpm cm{sup {minus}2}, and the total excess {sup 210}Pb inventory for the Amazon shelf was determined to be 2.7 x 10{sup 17} dpm. The {sup 210}Pb measurements indicate that particle-reactive species are scavenged not only form the Amazon River but also from the lateral advection of offshore water. In order to sustain the {sup 210}Pb inventories, the volume of water supplied by the lateral advection from offshore must be approximately five to ten times the water discharge of the Amazon River. This lateral advection supplies about 67% of the total excess {sup 210}Pb to the Amazon continental shelf with relatively small contributions from riverine input (31%), atmospheric fallout (2.3%), and in-situ production (0.1%). The {sup 234}Th inventories were measured on four cruises, which occurred during periods of differing river discharge, wind stress, and flow rates of the North Brazil Current. The {sup 234}Th excess seabed inventories show large spatial and seasonal variability, with a range from 0 to 22 dpm cm{sup {minus}2}. This approach indicates that for most of the shelf, the inventories of the shorter-term tracer ({sup 234}Th) are less than predicted by the inventories of the longer-term tracer ({sup 210}Pb). There are two explanations for this trend. The first is that a larger portion of the {sup 234}Th inventory occurs in the fluid muds or the water column relative to {sup 210}Pb. The second is that the supply of offshore water, scavenging efficiency, and/or deposition have been lower over the two year study period relative to the last one hundred years. 38 refs., 7 figs.

  3. Soil fluoride spiking effects on olive trees (Olea europaea L. cv. Chemlali).

    PubMed

    Zouari, M; Ben Ahmed, C; Fourati, R; Delmail, D; Ben Rouina, B; Labrousse, P; Ben Abdallah, F

    2014-10-01

    A pot experiment under open air conditions was carried out to investigate the uptake, accumulation and toxicity effects of fluoride in olive trees (Olea europaea L.) grown in a soil spiked with inorganic sodium fluoride (NaF). Six different levels (0, 20, 40, 60, 80 and 100mM NaF) of soil spiking were applied through NaF to irrigation water. At the end of the experiment, total fluoride content in soil was 20 and 1770mgFkg(-1) soil in control and 100mM NaF treatments, respectively. The comparative distribution of fluoride partitioning among the different olive tree parts showed that the roots accumulated the most fluoride and olive fruits were minimally affected by soil NaF spiking as they had the lowest fluoride content. In fact, total fluoride concentration varied between 12 and 1070µgFg(-1) in roots, between 9 and 570µgFg(-1) in shoots, between 12 and 290µgFg(-1) in leaves, and between 10 and 29µgFg(-1) in fruits, respectively for control and 100mM NaF treatments. Indeed, the fluoride accumulation pattern showed the following distribution: roots>shoots>leaves>fruits. On the other hand, fluoride toxicity symptoms such as leaf necrosis and leaf drop appeared only in highly spiked soils (60, 80 and 100mM NaF).

  4. Methodological issues about techniques for the spiking of standard OECD soil with nanoparticles: evidence of different behaviours

    NASA Astrophysics Data System (ADS)

    Miglietta, Maria Lucia; Rametta, Gabriella; Manzo, Sonia; Salluzzo, Antonio; Rimauro, Juri; Di Francia, Girolamo

    2015-07-01

    The aim of this study is to investigate at what extent the results of standard nanoparticle (NP) toxicity testing methodologies are affected by the different exposure procedures on soil organisms. In this view, differences in physicochemical properties of ZnO NPs (<100 nm), ZnO bulk (<200 nm) and ionic Zinc (ZnCl2) and their ecotoxicological potential toward Lepidium sativum were investigated with respect to three different spiking methods. Results show that the spiking procedures give homogeneous distribution of the testing nanomaterial in soil but the physicochemical and ecotoxicological properties of the testing species differ according to the spiking procedure. Dry spiking produced the highest ZnO solubility whereas spiking through dispersions of ZnO in water and in aqueous soil extracts produced the lowest. At the same time, the ecotoxic effects showed different trends with regard to the spiking route. The need for a definition of agreed methods concerning the NP spiking procedures is, therefore, urgent.

  5. Controls on net carbon accumulation in North American peatlands: Insights from 210Pb dated cores

    NASA Astrophysics Data System (ADS)

    Wieder, R.; Scott, K. D.; Vile, M. A.; Vitt, D. H.; Burke-Scoll, M.

    2012-12-01

    Northern peatlands cover only 3-4 % of the Earth's land surface area, yet store hugh quantities (250-450 Pg) of carbon as peat. These peatlands generally are believed to function as net sinks for atmospheric CO2 today, with C fixation by net primary production at the peat surface exceeding C losses by organic matter mineralization throughout the peat column. Various aspects of peatland structure and function are influenced by a variety of factors, including local climatic conditions and atmospheric deposition of N and S. Here we examine continental-scale patterns in recent net C accumulation in peatlands across North America, combining the published data for eastern Canada from Moore et al. (2004, Global Change Biology) and Turunen et al. (2004, Global Biogeochemical Cycles) with our data from boreal sites in western Canada (Alberta) and from temperate sites in the U.S. Across these sites, mean annual, January, and July temperatures ranged from 0.6 to 9.1, -20.5 to -1.6, and 11.3 to 20.8 oC, respecticely, mean annual precipitation, rainfall, and snowfall ranged from 406 to 1480, 289 to 1156 and 112 to 415 mm, respectively, growing degree days (above 5 oC) ranged from 947 to 4467, and annual wet N and S deposition ranged from 0.9 to 8.1 and 0.4 to 13.4 kg/ha/yr. For 67 cores, net C accumulation in peat over the past 50 years was determined by 210Pb dating and ranged from 492 to 1781 kg/ha/yr. Net C accumulation (kg/ha/yr) was positively correlated with mean annual precipitation (p = 0.0129), mean annual snowfall (p = 0.0010) and wet deposition of both N (p < 0.0001) and S (p = 0.0003). However, both the climatic and wet deposition variables exhibit similar gradients across North America, and hence are coufounded. Stepwise regression revealed that 53% of the overall variation in net C accumulation could be explained by only two variables, wet N deposition (p < 0.0001; R2 = 0.35) and mean annual temperature (p = 0.0106; R2 = 0.07), with the regression model of net C

  6. Short-term changes of metal availability in soil. Part I: comparing sludge-amended with metal-spiked soils.

    PubMed

    Natal-da-Luz, T; Ojeda, G; Costa, M; Pratas, J; Lanno, R P; Van Gestel, C A M; Sousa, J P

    2012-08-01

    Sewage sludge application to soils is regulated by its total metal content. However, the real risk of metals is determined by the fraction that is biologically available. The available fraction is highly related to the strength of metal binding by the matrix, which is a dynamic process. The evaluation of the fate of metals in time can contribute increased accuracy of ecological risk assessment. Aiming to evaluate short-term changes in metal availability when metals were applied to soil directly (metal-spiked) or by way of an organic matrix (sludge-amended), a laboratory experiment was performed using open microcosms filled with agricultural soil. A concentration gradient of industrial sludge (11, 15, 55, and 75 t/ha) that was contaminated predominantly with chromium, copper, nickel, and zinc, or soil freshly spiked with the same concentrations of these metals, were applied on top of the agricultural soil. After 0, 3, 6, and 12 weeks, total (HNO(3) 69 %) and 0.01 M CaCl(2)-extractable metal concentrations in soil and metal content in the percolates were measured. Results demonstrated that comparison between sludge-amended and metal-spiked soils may give important information about the role of sludge matrix on metal mobility and availability in soil. In sludge-amended soils, extractable-metal concentrations were independent of the sludge concentration and did not change over time. In metal-spiked soils, metal extractability decreased with time due to ageing and transport of metals to deeper layers. In general, the sludge matrix increased the adsorption of metals, thus decreasing their mobility in soils.

  7. 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

  8. 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.

  9. (210)Pb and (137)Cs as tracers of recent sedimentary processes in two water reservoirs in Cuba.

    PubMed

    Díaz-Asencio, Misael; Corcho-Alvarado, José Antonio; Cartas-Aguila, Héctor; Pulido-Caraballé, Anabell; Betancourt, Carmen; Smoak, Joseph M; Alvarez-Padilla, Elizabeth; Labaut-Betancourt, Yeny; Alonso-Hernández, Carlos; Seisdedo-Losa, Mabel

    2017-10-01

    Hanabanilla and Paso Bonito Reservoirs are the main fresh water sources for about half a million inhabitants in central Cuba. Prior to this investigation precise information about the losses of storage capacity was not available. Sedimentation is the dominant process leading to reduction in water storage capacity. We investigated the sedimentation process in both reservoirs by analyzing environmental radionuclides (e.g. (210)Pb, (226)Ra and (137)Cs) in sediment cores. In the shallow Paso Bonito Reservoir (mean depth of 6.5 m; water volume of 8 × 10(6) m(3)), we estimated a mean mass accumulation rate (MAR) of 0.4 ± 0.1 g cm(-2)y(-1) based on (210)Pb chronologies. (137)Cs was detected in the sediments, but due to the recent construction of this reservoir (1975), it was not possible to use it to validate the (210)Pb chronologies. The estimated MAR in this reservoir is higher than the typical values reported in similar shallow fresh water reservoirs worldwide. Our results highlight a significant loss of water storage capacity during the past 30 years. In the deeper and larger Hanabanilla Reservoir (mean depth of 15.5 m; water volume of 292 × 10(6) m(3)), the MAR was investigated in three different sites of the reservoir. The mean MARs based on the (210)Pb chronologies varied between 0.15 and 0.24 g cm(-2)y(-1). The MARs calculated based on the (137)Cs profiles further validated these values. We show that the sediment accumulation did not change significantly over the last 50 years. A simple empirical mixing and sedimentation model that assumes (137)Cs in the water originated from both, direct atmospheric fallout and the catchment area, was applied to interpret the (137)Cs depth profiles. The model consistently reproduced the measured (137)Cs profiles in the three cores (R(2) > 0.9). Mean residence times for (137)Cs in the water and in the catchment area of 1 y and 35-50 y, respectively were estimated. The model identified areas where the catchment

  10. 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

  11. 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

  12. 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??.

  13. 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.

  14. Role of Arbuscular Mycorrhizal Fungi in Phytoremediation of Soil Rhizosphere Spiked with Poly Aromatic Hydrocarbons

    PubMed Central

    2005-01-01

    Results from an innovative approach to improve remediation in the rhizosphere by encouraging healthy plant growth and thus enhancing microbial activity are reported. The effect of arbuscular mycorrhizal fungi (Am) on remediation efficacy of wheat, mungbean and eggplant grown in soil spiked with polyaromatic hydrocarbons (PAH) was assessed in a pot experiment. The results of this study showed that Am inoculation enhanced dissipation amount of PAHs in planted soil, plant uptake PAHs, dissipation amount of PAHs in planted versus unplanted spiked soil and loss of PAHs by the plant-promoted biodegradation. A number of parameters were monitored including plant shoot and root dry weight, plant tissue water content, plant chlorophyll, root lipid content, oxido-reductase enzyme activities in plant and soil rhizosphere and total microbial count in the rhizospheric soil. The observed physiological data indicate that plant growth and tolerance increased with Am, but reduced by PAH. This was reflected by levels of mycorrhizal root colonization which were higher for mungbean, moderate for wheat and low for eggplant. Levels of Am colonization increased on mungbean > wheat > eggplant. This is consistent with the efficacy of plant in dissipation of PAHs in spiked soil. Highly significant positive correlations were shown between of arbuscular formation in root segments (A)) and plant water content, root lipids, peroxidase, catalase polyphenol oxidase and total microbial count in soil rhizosphere as well as PAH dissipation in spiked soil. As consequence of the treatment with Am, the plants provide a greater sink for the contaminants since they are better able to survive and grow. PMID:24049473

  15. 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

  16. 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

  17. 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. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. Aspects of the geographical variations of naturally occurring 210Pb/210Po in permanent teeth of juveniles in the UK.

    PubMed

    James, P R; Close, J J; Keitch, P A; Allen, J E; Fews, A P; Henshaw, D L

    2004-03-01

    To study geographical variations in the level of naturally occurring 210Pb-supported 210Po in permanent teeth of juveniles in the UK. Permanent teeth extracted from 278 juveniles for orthodontic purposes were obtained from 48 counties in the UK. 210Po activity concentration was measured on the outer enamel surface using TASTRAK alpha-particle-sensitive plastic track detectors. Geometric mean +/- SE activity concentrations in teeth from urban, suburban and rural areas, excluding the high radon area of Devon, were 8.41 + 0.25/-0.24, 7.76 + 0.37/-0.35 and 7.20 +0.49/-0.46 Bq kg(-1), respectively. Overall, there was no significant association between alpha-activity on the outer enamel surface of permanent teeth and proximity to the major UK motorways. However, when the data were considered with respect to the prevailing south-westerly wind on the western side of the UK, a statistically significant association with respect to donors living downwind (on the easterly side) of the motorways was found. This effect was greater for sections of the M5 and M6 motorways that traverse urban areas. 210Po levels in teeth were also associated with domestic radon concentration. This effect was comparable with that from traffic and urban pollution. Higher levels of 210Pb-supported 210Po are seen in permanent teeth of juveniles near sources of increased exposure in the UK. Inhalation uptake is an important pathway of exposure, especially with respect to domestic radon exposure. The results might be important in assessing integrated exposure to 210Po in the skeleton and consequent high linear energy transfer dose to bone marrow.

  10. 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.

  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. 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.

  13. 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.

  14. 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.

  15. 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.

  16. High-resolution age modelling of peat bog profiles using pre and post-bomb 14C, 210Pb and cryptotephra data from six Albertan peat bogs

    NASA Astrophysics Data System (ADS)

    Davies, L. J.; Froese, D. G.; Appleby, P.; van Bellen, S.; Magnan, G.; Mullan-Boudreau, G.; Noernberg, T.; Shotyk, W.; Zaccone, C.

    2016-12-01

    Age modelling of recent peat profiles is frequently undertaken for high-resolution modern studies, but the most common techniques applied (e.g. 14C, 210Pb, cryptotephra) are rarely combined and used for testing and inter-comparison. Here, we integrate three age-dating approaches to produce a single age model to comprehensively investigate variations in the chronometers and individual site histories since 1900. OxCal's P_Sequence function is used to model dates produced using 14C (pre- and post-bomb), 210Pb (corroborated with 137Cs and 241Am) from six peat bogs in central and northern Alberta. Physical and chemical characteristics of the cores (e.g. macrofossils, humification, ash content, dry density) provide important constraints for the model by highlighting periods with significant changes in accumulation rate (e.g. fire events, permafrost development, prolonged surficial drying). Sub-cm resolution output shows there are consistent differences in how the 14C and 210Pb signals are preserved in peat profiles, with 14C commonly showing a slight bias toward older ages at the same depth relative to 210Pb data. These methods can successfully be combined in a Bayesian model and used to produce a single age model that more accurately accounts for the uncertainties inherent in each method. Understanding these differences and combining the results of these methods results in a stronger chronology at each site investigated here despite observed differences in ecological setting, accumulation rates, fire events/frequency and permafrost development.

  17. (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.

  18. 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.

  19. 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.

  20. Assessing the phytoremediation potential of crop and grass plants for atrazine-spiked soils.

    PubMed

    Sánchez, Virtudes; López-Bellido, Francisco Javier; Cañizares, Pablo; Rodríguez, Luis

    2017-10-01

    Pollution of soil and groundwater by atrazine has become an increasing environmental concern in the last decade. A phytoremediation test using plastic pots was conducted in order to assess the ability of several crops and grasses to remove atrazine from a soil of low permeability spiked with this herbicide. Four plant species were assessed for their ability to degrade or accumulate atrazine from soils: two grasses, i.e., ryegrass (Lolium perenne) and tall fescue (Festuca arundinacea), and two crops, i.e., barley (Hordeum vulgare) and maize (Zea mays). Three different doses of atrazine were used for the contamination of the pots: 2, 5 and 10 mg kg(-1). 16 days after spiking, the initial amount of atrazine was reduced by 88.6-99.6% in planted pots, while a decrease of only 63.1-78.2% was found for the unplanted pots, thus showing the contribution of plants to soil decontamination. All the plant species were capable of accumulating atrazine and its N-dealkylated metabolites, i.e., deethylatrazine and deisopropylatrazine, in their tissues. Some toxic responses, such as biomass decreases and/or chlorosis, were observed in plants to a greater or lesser extent for initial soil doses of atrazine above 2 mg kg(-1). Maize was the plant species with the highest ability to accumulate atrazine derivatives, reaching up to 38.4% of the initial atrazine added to the soil. Rhizosphere degradation/mineralization by microorganisms or plant enzymes, together with degradation inside the plants, have been proposed as the mechanisms that contributed to a higher extent than plant accumulation to explain the removal of atrazine from soils. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. VULNERABILITY OF HEADWATER CATCHMENT RESOURCES TO INCIDENCES OF 210PB EXCESS AND 137CS RADIONUCLIDE FALLOUT

    EPA Science Inventory

    Recent identification of elevated excess 210Pb (≤302.6 mBq L-1) and 137Cs (≤ 111.3 mBq L-1) activity in drinking water wells up to 20 m depth indicates some transport of airborne radionuclide fallout beyond soils in the Shaker Village c...

  2. VULNERABILITY OF HEADWATER CATCHMENT RESOURCES TO INCIDENCES OF 210PB EXCESS AND 137CS RADIONUCLIDE FALLOUT

    EPA Science Inventory

    Recent identification of elevated excess 210Pb (≤302.6 mBq L-1) and 137Cs (≤ 111.3 mBq L-1) activity in drinking water wells up to 20 m depth indicates some transport of airborne radionuclide fallout beyond soils in the Shaker Village c...

  3. Dissipation and phytoremediation of polycyclic aromatic hydrocarbons in freshly spiked and long-term field-contaminated soils.

    PubMed

    Wei, Ran; Ni, Jinzhi; Li, Xiaoyan; Chen, Weifeng; Yang, Yusheng

    2017-03-01

    Pot experiments were used to compare the dissipation and phytoremediation effect of alfalfa (Medicago sativa L.) for polycyclic aromatic hydrocarbons (PAHs) in a freshly spiked soil and two field-contaminated soils with different soil organic carbon (SOC) contents (Anthrosols, 1.41% SOC; Phaeozems, 8.51% SOC). In spiked soils, the dissipation rates of phenanthrene and pyrene were greater than 99.5 and 94.3%, respectively, in planted treatments and 95.0 and 84.5%, respectively, in unplanted treatments. In field-contaminated Anthrosols, there were limited but significant reductions of 10.2 and 15.4% of total PAHs in unplanted and planted treatments, respectively. In field-contaminated Phaeozems, there were no significant reductions of total PAHs in either unplanted or planted treatments. A phytoremediation effect was observed for the spiked soils and the Anthrosols, but not for the Phaeozems. The results indicated that laboratory tests with spiked soils cannot reflect the real state of field-contaminated soils. Phytoremediation efficiency of PAHs in field-contaminated soils was mainly determined by the content of SOC. Phytoremediation alone has no effect on the removal of PAHs in field-contaminated soils with high SOC content.

  4. Evaluation of two extraction procedures for the recovery of organic chemicals from spiked soils

    SciTech Connect

    Huebner, H.J.; Brown, K.W.; Donnelly, K.C.; He, L.Y.

    1994-12-31

    The objective of this study was to evaluate the efficiencies of the automatic Soxtec and US EPA SW846 Soxhlet soil extraction methods. In phases one and two of the experiment, extractions were performed on silicon dioxide matrices and silt-loam soils spiked with benz(a)pyrene, pentachlorophenol, and naphthalene at three concentration levels. Each test sample contained either an individual chemical or a 1:1:1 mixture of all three chemicals. Phase three consisted of extractions performed on a silt-loam soil spiked with a coal tar complex mixture. Soxtec samples were sequentially extracted with dichloromethane and methanol while Soxhlet samples were extracted with dichloromethane. Gas chromatographic results obtained from sample extract analysis were used to calculate percent recoveries of the chemicals. The recoveries of benz(a)pyrene and pentachlorophenol in the Soxtec procedure ranged from 55--88% and 49--88%, respectively. For the Soxhlet method, the recoveries ranges from 46--73% and 52--87%, respectively. Complex mixture recoveries ranged from 50--60% for both procedures. The mutagenic potentials of the solvent extracts were evaluated using Salmonella typhimurium strain TA98 with and without metabolic activation.

  5. Occurrence and distribution of 210Pb and 210Po in selected California groundwater wells.

    PubMed

    Ruberu, Shiyamalie R; Liu, Yun-Gang; Perera, S Kusum

    2007-05-01

    Groundwater wells from across the State of California were sampled and analyzed for Pb and Po. The separation method involved Fe(OH)3 precipitation from a 5-L groundwater sample followed by electrodeposition of Po on a nickel disk. The resulting solution was passed through an ion-exchange resin column for the isolation of Pb. De-ionized water spiked at a concentration range from 4.92 mBq L(-1) to 755 mBq L(-1) with these radionuclide standards showed excellent accuracy and precision of the method. In the groundwater wells, overall activity of Pb ranged from 3.7 mBq L(-1) to 1,481 mBq L(-1) and the Po activity ranged from 0.25 mBq L(-1) to 555 mBq L(-1). Of the select wells tested, 27% for Pb and 19% for Po were above the proposed maximum contamination limits for these radionuclides, which are set at 37 mBq L(-1) and 26 mBq L(-1), respectively. From a public health perspective this is a concern, since the drinking water screening levels for gross alpha is at 555 mBq L(-1) and gross beta is at 1,850 mBq L(-1). At such high screening levels Pb and Po will not be captured, and this situation was found in several of the wells studied. The occurrence of Pb and Po are not correlated within the sources, however; the polonium concentrations were always lower than the lead concentrations. Activities of Pb measured from wells two years apart clearly demonstrated the continuous flux of groundwater within aquifers.

  6. 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

    Here we show the use of the 210Pb-226Ra excess method to determine the growth rate of corals from one of the world's largest known cold-water coral reef, the Røst Reef off Norway. Two large branching framework-forming cold-water coral specimens, one Lophelia pertusa and one Madrepora oculata were collected alive at 350 m water depth from the Røst Reef at ~67° N and ~9° E. Pb and Ra isotopes were measured along the major growth axis of both specimens using low level alpha and gamma spectrometry and the corals trace element compositions were studied using ICP-QMS. Due to the different chemical behaviors of Pb and Ra in the marine environment, 210Pb and 226Ra were not incorporated the same way into the aragonite skeleton of those two cold-water corals. Thus to assess of the growth rates of both specimens we have here taken in consideration the exponential decrease of initially incorporated 210Pb as well as the ingrowth of 210Pb from the decay of 226Ra. Moreover a~post-depositional 210Pb incorporation is found in relation to the Mn-Fe coatings that could not be entirely removed from the oldest parts of the skeletons. The 226Ra activities in both corals were fairly constant, then assuming constant uptake of 210Pb through time the 210Pb-226Ra chronology can be applied to calculate linear growth rate. The 45.5 cm long branch of M. oculata reveals an age of 31 yr and a~linear growth rate of 14.4 ± 1.1 mm yr-1, i.e. 2.6 polyps per year. However, a correction regarding a remaining post-depositional Mn-Fe oxide coating is needed for the base of the specimen. The corrected age tend to confirm the radiocarbon derived basal age of 40 yr (using 14C bomb peak) with a mean growth rate of 2 polyps yr-1. This rate is similar to the one obtained in Aquaria experiments under optimal growth conditions. For the 80 cm-long specimen of L. pertusa a remaining contamination of metal-oxides is observed for the middle and basal part of the coral skeleton, inhibiting similar accurate age

  7. Agricultural soils spiked with copper mine wastes and copper concentrate: implications for copper bioavailability and bioaccumulation.

    PubMed

    Ginocchio, Rosanna; Sánchez, Pablo; de la Fuente, Luz María; Camus, Isabel; Bustamante, Elena; Silva, Yasna; Urrestarazu, Paola; Torres, Juan C; Rodríguez, Patricio H

    2006-03-01

    A better understanding of exposure to and effects of copper-rich pollutants in soils is required for accurate environmental risk assessment of copper. A greenhouse experiment was conducted to study copper bioavailability and bioaccumulation in agricultural soils spiked with different types of copper-rich mine solid wastes (copper ore, tailing sand, smelter dust, and smelter slag) and copper concentrate. A copper salt (copper sulfate, CuSO4) that frequently is used to assess soil copper bioavailability and phytotoxicity also was included for comparison. Results showed that smelter dust, tailing sand, and CuSO4 are more likely to be bioavailable and, thus, toxic to plants compared with smelter slag, concentrate, and ore at equivalent total copper concentrations. Differences may be explained by intrinsic differences in copper solubilization from the source materials, but also by their capability to decrease soil pH (confounding effect). The copper toxicity and bioaccumulation in plants also varied according to soil physicochemical characteristics (e.g., pH and total organic carbon) and the available levels of plant nutrients, such as nitrogen, phosphorus, and potassium. Chemistry/mineralogy of mine materials, soil/pore-water chemistry, and plant physiological status thus should be integrated for building adequate models to predict phytotoxicity and environmental risk of copper.

  8. Remediation of hexavalent chromium spiked soil by using synthesized iron sulfide particles.

    PubMed

    Li, Yujie; Wang, Wanyu; Zhou, Liqiang; Liu, Yuanyuan; Mirza, Zakaria A; Lin, Xiang

    2017-02-01

    Carboxymethyl cellulose (CMC) stabilized microscale iron sulfide (FeS) particles were synthesized and applied to remediate hexavalent chromium (Cr(VI)) spiked soil. The effects of parameters including dosage of FeS particles, soil moisture, and natural organic matter (NOM) in soil were investigated with comparison to iron sulfate (FeSO4). The results show that the stabilized FeS particles can reduce Cr(VI) and immobilize Cr in soil quickly and efficiently. The soil moisture ranging from 40% to 70% and NOM in soil had no significant effects on Cr(VI) remediation by FeS particles. When molar ratio of FeS to Cr(VI) was 1.5:1, about 98% of Cr(VI) in soil was reduced by FeS particles in 3 d and Cr(VI) concentration decreased from 1407 mg kg(-1) to 16 mg kg(-1). The total Cr and Cr(VI) in Toxicity Characteristic Leaching Procedure (TCLP) leachate were reduced by 98.4% and 99.4%, respectively. In FeS particles-treated soil, the exchangeable Cr fraction was mainly converted to Fe-Mn oxides bound fraction because of the precipitation of Cr(III)-Fe(III) hydroxides. The physiologically based extraction test (PBET) bioaccessibility of Cr was decreased from 58.67% to 6.98%. Compared to FeSO4, the high Cr(VI) removal and Cr immobilization efficiency makes prepared FeS particles a great potential in field application of Cr(VI) contaminated soil remediation. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Particle mixing rates in sediments of the eastern equatorial Pacific: Evidence from 210Pb, 239,240Pu and 137Cs distributions at MANOP sites

    NASA Astrophysics Data System (ADS)

    Cochran, J. Kirk

    1985-05-01

    Particle mixing rates ( DB) calculated from excess 210Pb gradients in sediments of the east equatorial Pacific range from 0.04 to 0.5 cm 2/y, with variation of a factor of 3-4 at a single site. Diffusion of the 236Ra daughter 222Rn may affect 210Pb distributions under conditions of slow mixing and low 210Pb flux to the seafloor, as shown by a siliceous ooze-clay core which contained the fallout radionuclides 239,240Pu and 137Cs but no excess 210Pb (relative to 226Ra). There is no clear relationship between 210Pbderived mixing rates and sediment type, accumulation rate or organic carbon flux to the sediments. Comparison of 210Pb mixing rates with those calculated from 239,240Pu and 137Cs distributions reveals better agreement for a pulse input of the fallout radionuclides ( DB = 0.03-0.4 cm2/ y) than for continuous input at a constant rate ( DB = 0.1-1.6 cm2/ y), although the Pu and 137Cs data are better fit by the latter model. The agreement may be fortuitous because 239,240Pu and 137Cs appear significantly deeper than 210Pb in at least one core. Tracer separation could be caused by particle size-selective mixing by the benthic fauna or by chemical mobilization. If the fallout radionuclides are scavenged from surface waters by large, organic-rich particles such as fecal pellets, their release and migration may result from decomposition of the carrier in surface sediments. Either a relatively unreactive form of Pu (e.g. oxidized Pu) has been released by this process or a one-dimensional model is inadequate to explain its observed penetration into the sediments. Activity ratios of 239,240Pu /137Cs in the sediments decrease with increasing north latitude, and the trend reflects higher fluxes of 239,240Pu near the weapons test site at Christmas Island (2°N). The 239,240Pu /137Cs ratios and fluxes to the sediment (assuming constant input) at the siliceous ooze-red clay site are consistent with published sediment trap data from a nearby site. Thus if fallout

  10. Experimental determinations of soil copper toxicity to lettuce (Lactuca sativa) growth in highly different copper spiked and aged soils.

    PubMed

    Christiansen, Karen S; Borggaard, Ole K; Holm, Peter E; Vijver, Martina G; Hauschild, Michael Z; Peijnenburg, Willie J G M

    2015-04-01

    Accurate knowledge about factors and conditions determining copper (Cu) toxicity in soil is needed for predicting plant growth in various Cu-contaminated soils. Therefore, effects of Cu on growth (biomass production) of lettuce (Lactuca sativa) were tested on seven selected, very different soils spiked with Cu and aged for 2 months at 35 °C. Cu toxicity was expressed as pEC50(Cu(2+)), i.e., the negative logarithm of the EC50(Cu(2+)) activity to plant growth. The determined pEC50(Cu(2+)) was significantly and positively correlated with both the analytically readily available soil pH and concentration of dissolved organic carbon [DOC] which together could explain 87% of the pEC50(Cu(2+)) variation according to the simple equation: pEC50(Cu(2+)) = 0.98 × pH + 345 × [DOC] - 0.27. Other soil characteristics, including the base cation concentrations (Na(+), K(+), Ca(2+), Mg(2+)), the cation exchange capacity at soil pH (ECEC), and at pH 7 (CEC7), soil organic carbon, clay content, and electric conductivity as well as the distribution coefficient (Kd) calculated as the ratio between total soil Cu and water-extractable Cu did not correlate significantly with pEC50(Cu(2+)). Consequently, Cu toxicity, expressed as the negative log of the Cu(2+) activity, to plant growth increases at increasing pH and DOC, which needs to be considered in future management of plant growth on Cu-contaminated soils. The developed regression equation allows identification of soil types in which the phytotoxicity potential of Cu is highest.

  11. 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.

  12. Persistent chlordane concentrations in long island sound sediment: Implications from chlordane, 210Pb, and 137Cs profiles

    USGS Publications Warehouse

    Yang, L.; Li, X.; Crusius, J.; Jans, U.; Melcer, M.E.; Zhang, P.

    2007-01-01

    Concentrations of chlordane, a banned termiticide and pesticide, were examined in recently collected surficial sediment (10 sites) and sediment cores (4 sites) in Long Island Sound (LIS).The highest chlordane concentrations were observed in western LIS, near highly urbanized areas. Chlordane concentrations did not decrease significantly in the past decade when compared to the data collected in 1996, consistent with the observation of near-constant chlordane levels in blue mussel tissues collected during the same time period. Chlordane concentrations in many of the sites exceeded levels above which harmful effects on sediment-dwelling organisms are expected to frequently occur. Chlordane concentrations in two of the four sediment cores showed a peak below the sediment surface, suggesting reduced chlordane inputs in recent years. The lack of a chlordane concentration maximum below the sediment surface in the other two cores, coupled with the lack of a well-defined 137Cs peak, indicated significant sediment mixing. Simulations of 137Cs and 210Pb profiles in sediment cores with a simple sediment-mixing model were used to constrain both the deposition rate and the bioturbation rate of the sediment. Simulations of the chlordane profiles indicated continued chlordane input to LIS long after chlordane was phased out in the U.S. Continued chlordane input and significant sediment mixing may have contributed to the persistent chlordane concentrations in surficial sediment, which poses long-term threats to benthic organisms in LIS.

  13. 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.

  14. Persistent chlordane concentrations in Long Island Sound sediment: implications from chlordane, 210Pb, and 137Cs profiles.

    PubMed

    Yang, Lijia; Li, Xiqing; Crusius, John; Jans, Urs; Melcer, Michael E; Zhang, Pengfei

    2007-11-15

    Concentrations of chlordane, a banned termiticide and pesticide, were examined in recently collected surficial sediment (10 sites) and sediment cores (4 sites) in Long Island Sound (LIS). The highest chlordane concentrations were observed in western LIS, near highly urbanized areas. Chlordane concentrations did not decrease significantly in the past decade when compared to the data collected in 1996, consistent with the observation of near-constant chlordane levels in blue mussel tissues collected during the same time period. Chlordane concentrations in many of the sites exceeded levels above which harmful effects on sediment-dwelling organisms are expected to frequently occur. Chlordane concentrations in two of the four sediment cores showed a peak below the sediment surface, suggesting reduced chlordane inputs in recent years. The lack of a chlordane concentration maximum below the sediment surface in the other two cores, coupled with the lack of a well-defined 137Cs peak, indicated significant sediment mixing. Simulations of 137Cs and 210Pb profiles in sediment cores with a simple sediment-mixing model were used to constrain both the deposition rate and the bioturbation rate of the sediment. Simulations of the chlordane profiles indicated continued chlordane input to LIS long after chlordane was phased out in the U.S. Continued chlordane input and significant sediment mixing may have contributed to the persistent chlordane concentrations in surficial sediment, which poses long-term threats to benthic organisms in LIS.

  15. Comparison of Five Commercial DNA Extraction Kits for the Recovery of Francisella Tularensis DNA from Spiked Soil Samples

    DTIC Science & Technology

    2007-01-01

    locate/ymcprComparison of five commercial DNA extraction kits for the recovery of Francisella tularensis DNA from spiked soil samples Chris A...The organism is known to persist in water or mud for long periods of time and Francisella-specific DNA has been identified from water and soil . To...Therefore, methods must be established to efficiently extract Francisella-specific DNA from the soil and be able to eliminate potential PCR

  16. Effects of arsenic and cadmium on bioaccessibility of lead in spiked soils assessed by Unified BARGE Method.

    PubMed

    Xia, Qing; Peng, Cheng; Lamb, Dane; Kader, Mohammed; Mallavarapu, Megharaj; Naidu, Ravi; Ng, Jack C

    2016-07-01

    The bioaccessibility of lead (Pb) in contaminated soils has been extensively studied, including the influence of soil properties on Pb bioaccessibility. However, little is known about the effects of other metals/metalloid, such as arsenic (As), cadmium (Cd) on the bioaccessibility of Pb, i.e. whether As or Cd could increase or decrease the solubility of Pb in human gastrointestinal tract when Pb-contaminated soil and As-contaminated (or Cd-contaminated) soil are ingested simultaneously. Furthermore, it is far from clear that if soil property could make a difference to these effects. In this study, seven types of soils were collected in Australia and spiked with As, Cd or Pb. Gastric bioaccessibility of Pb ranged from 44 ± 0.9% to 100 ± 6.7% whilst intestinal bioaccessibility dropped to 1 ± 0.2% to 36 ± 1.7%. Statistical analysis shows total Pb in soil was the most significant controller for bioaccessible Pb. Effects of As and Cd on the bioaccessibility of Pb in simulated human digestive system were studied by mixing As-spiked soil (or Cd-spiked soil) with Pb-spiked soil of the same type during bioaccessibility test. Results reveal that neither As nor Cd had impact on Pb bioaccessibility, which indicates when As, Cd and Pb aged in soils separately, they may behave independently in the bioaccessibility measuring system. This finding can be part of evidence to assume additive effect when it comes to estimate the bioaccessibility of mixtures of independently-aged As and Pb (or Cd and Pb) in soils. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. 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.

  18. Toxicokinetics of polycyclic aromatic hydrocarbons in Eisenia andrei (Oligochaeta) using spiked soil

    SciTech Connect

    Jager, T.; Anton Sanchez, F.A.; Muijs, B.; Velde, E.G. van der; Posthuma, L.

    2000-04-01

    The accumulation of four polycyclic aromatic hydrocarbons ([PAHs]; phenanthrene, pyrene, fluoranthene, and benzo[a]pyrene) was tested in the earthworm Eisenia andrei in a spiked artificial soil medium. A typical peak in the body residues was observed for all PAHs around day 7, which could not be explained from changes in the total soil concentration. It is argued that the most likely cause of this peak is a decrease in the concentration in pore water, the main bioavailable phase for earthworms. The decrease is caused by biodegradation while the low rate of mass transfer from the solid state precludes replenishment. To describe the data, bioavailability was assumed to decline exponentially in time, but the shape of the accumulation curves suggests a more abrupt change. Estimates of the uptake rate (k{sub 1}) are similar for all PAHs when expressed on soil solution basis (approximately 2,000 L/kg/d); the elimination rate (k{sub 2}) shows a decrease with K{sub ow} as expected, but the values tend to be slightly lower than literature data. The dynamic bioconcentration factors (k{sub 1}/k{sub 1}) agree well with an equilibrium partitioning between soil water and the phases inside the organism.

  19. Degradation of phenanthrene and pyrene in spiked soils by single and combined plants cultivation.

    PubMed

    Cheema, Sardar Alam; Imran Khan, Muhammad; Shen, Chaofeng; Tang, Xianjin; Farooq, Muhammad; Chen, Lei; Zhang, Congkai; Chen, Yingxu

    2010-05-15

    The present study was conducted to investigate the capability of four plant species (tall fescue, ryegrass, alfalfa, and rape seed) grown alone and in combination to the degradation of phenanthrene and pyrene (polycyclic aromatic hydrocarbons, PAHs) in spiked soil. After 65 days of plant growth, plant biomass, dehydrogenase activity, water-soluble phenolic (WSP) compounds, plant uptake and accumulation and residual concentrations of phenanthrene and pyrene were determined. Our results showed that presence of vegetation significantly enhanced the dissipation of phenanthrene and pyrene from contaminated soils. Higher degradation rates of PAHs were observed in the combined plant cultivation (98.3-99.2% phenanthrene and 88.1-95.7% pyrene) compared to the single plant cultivation (97.0-98.0% phenanthrene and 79.8-86.0% pyrene). Contribution of direct plant uptake and accumulation of phenanthrene and pyrene was very low compared to the plant enhanced dissipation. By contrast, plant-promoted biodegradation was the predominant contribution to the remediation enhancement. The correlation analysis indicates a negative relation between biological activities (dehydrogenase activity and WSP compounds) and residual concentrations of phenanthrene and pyrene in planted soils. Our results suggest that phytoremediation could be a feasible choice for PAHs contaminated soil. Moreover, the combined plant cultivation has potential to enhance the process. Copyright (c) 2010 Elsevier B.V. All rights reserved.

  20. 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.

  1. 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.

  2. 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.

  3. Extraction of Plutonium From Spiked INEEL Soil Samples Using the Ligand-Assisted Supercritical Fluid Extraction (LA-SFE) Technique

    SciTech Connect

    Fox, R.V.; Mincher, B.J.; Holmes, R.G.G.

    1999-08-01

    In order to investigate the effectiveness of ligand-assisted supercritical fluid extraction for the removal of transuranic contaminations from soils an Idaho National Engineering and Environmental Laboratory (INEEL) silty-clay soil sample was obtained from near the Radioactive Waste Management Complex area and subjected to three different chemical preparations before being spiked with plutonium. The spiked INEEL soil samples were subjected to a sequential aqueous extraction procedure to determine radionuclide portioning in each sample. Results from those extractions demonstrate that plutonium consistently partitioned into the residual fraction across all three INEEL soil preparations whereas americium partitioned 73% into the iron/manganese fraction for soil preparation A, with the balance partitioning into the residual fraction. Plutonium and americium were extracted from the INEEL soil samples using a ligand-assisted supercritical fluid extraction technique. Initial supercritical fluid extraction runs produced plutonium extraction technique. Initial supercritical fluid extraction runs produced plutonium extraction efficiencies ranging from 14% to 19%. After a second round wherein the initial extraction parameters were changed, the plutonium extraction efficiencies increased to 60% and as high as 80% with the americium level in the post-extracted soil samples dropping near to the detection limits. The third round of experiments are currently underway. These results demonstrate that the ligand-assisted supercritical fluid extraction technique can effectively extract plutonium from the spiked INEEL soil preparations.

  4. {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.

  5. Isotopic equilibration between dissolved and suspended particulate lead in the Atlantic Ocean: Evidence from 210Pb and stable Pb isotopes

    NASA Astrophysics Data System (ADS)

    Sherrell, Robert M.; Boyle, Edward A.; Hamelin, Bruno

    1992-07-01

    Decreased consumption of leaded gasoline in the United States over the past two decades has drastically altered the flux and isotopic composition of Pb entering the western North Atlantic from the atmosphere. Here we exploit the resulting temporal changes in the distribution and isotopic composition of oceanic Pb to investigate interactions between dissolved and particulate Pb in the oceanic water column. Measurements of dissolved Pb isotopic composition on samples collected in 1987 in the upper water column near Bermuda demonstrate that surface water 206Pb/207Pb decreased from ˜1.203 to ˜1.192 since 1983 and that a measurable change propagated to 300-500 m since the 1984 profile of Shen and Boyle (1988). The first accurate measurements of suspended particulate Pb in an open ocean profile show concentrations of 1-3 pmol/L, equal to 2-4% of total Pb. Vertical profiles of (1) the stable lead isotopic composition and (2) the ratio of total Pb to 210Pb in suspended particles closely track contemporaneous depth variations in these ratios for dissolved Pb throughout the upper 2000 m of the Sargasso Sea near Bermuda. Thus suspended particles reach isotopic equilibrium with ambient sea water Pb on a time scale which is shorter than their residence time with respect to vertical removal, in agreement with equilibrium scavenging hypotheses based on interpretations of Th isotope distributions. A simple flux model suggests that the effect of deep ocean scavenging processes on the flux and isotopic composition of Pb sinking on large particles was minor throughout the preanthropogenic and most of the anthropogenic era but has become important as surface inputs decrease to pre-leaded gasoline levels and may exceed the contribution of surface-derived Pb flux in the next decade.

  6. 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.

  7. 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.

  8. An estimate of hydrothermal fluid residence times and vent chimney growth rates based on 210Pb Pb ratios and mineralogic studies of sulfides dredged from the Juan de Fuca Ridge

    USGS Publications Warehouse

    Kadko, D.; Koski, R.; Tatsumoto, M.; Bouse, R.

    1985-01-01

    The 210Pb Pb ratios across two sulfide samples dredged from the Juan de Fuca Ridge are used to estimate the growth rate of the sulfide material and the residence time of the hydrothermal fluid within the oceanic crust from the onset of basalt alteration. 210Pb is added to the hydrothermal fluid by two processes: (1) high-temperature alteration of basalt and (2) if the residence time of the fluid is on the order of the 22.3-year half-life of 210Pb, by in-situ growth from 222Rn (Krishnaswami and Turekian, 1982). Stable lead is derived only from the alteration of basalt. The 210Pb Pb ratio across one sample was ??? 0.5 dpm/10-6 g Pb, and across the other it was ??? 0.4 dpm/10-6 g Pb. These values are quite close to the 238U Pb ratios of basalts from the area, suggesting that the residence time of the hydrothermal fluid from the onset of basalt alteration is appreciably less than the mean life of 210Pb, i.e., the time required for ingrowth from the radon. An apparent growth rate of 1.2 cm/yr is derived from the slope of the 210Pb Pb curve for one of the samples. This is consistent with its mineralogy and texture which suggest an accretionary pattern of development. There is no obvious sequential growth pattern, and virtually no gradient in 210Pb Pb across the second sample. This is consistent with alteration of the original 210Pb Pb distribution by extensive remobilization reactions which are inferred from the mineralogic and textural relationships of the sample. ?? 1985.

  9. 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

  10. Removal of oxyfluorfen from spiked soils using electrokinetic soil flushing with the surrounding arrangements of electrodes.

    PubMed

    Risco, C; Rubí-Juárez, H; Rodrigo, S; López-Vizcaíno, R; Saez, C; Cañizares, P; Barrera-Díaz, C; Navarro, V; Rodrigo, M A

    2016-07-15

    This work reports the results of a study in which the remediation of soil that undergoes an accidental discharge of oxyfluorfen is carried out by using electrokinetic soil flushing (EKSF). Two different electrode configurations were tested, consisting of several electrodes surrounding an electrode of different polarity (so-called 1A6C, one anode surrounded by six cathodes, and 1C6A, one cathode surrounded by six cathodes). A pilot plant scale was used (with a soil volume of 175dm(3)) to perform the studies. During the tests, different parameters were measured daily (flowrates, pH, electrical conductivity and herbicide concentration in different sampling positions). Furthermore, at the end of the test, a complete post-mortem analysis was carried out to obtain a 3-D map of the pollution, pH and electrical conductivity in the soil. The results demonstrate that electrode arrangement is a key factor for effective pollutant removal. In fact, the 1A6C configuration improves the removal rate by 41.3% versus the 27.0% obtained by the 1C6A configuration after a period of 35days. Finally, a bench mark comparison of this study of soil remediation polluted with 2,4-D allows for significant conclusions about the scale-up and full-scale application of this technology. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. In situ stabilization of trace metals in a copper-contaminated soil using P-spiked Linz-Donawitz slag.

    PubMed

    Negim, Osama; Mench, Michel; Bes, Clémence; Motelica-Heino, Mikael; Amin, Fouad; Huneau, Frédéric; Le Coustumer, Philippe

    2012-03-01

    A former wood exploitation revealing high Cu and As concentration of the soils served as a case study for assisted phytoextraction. P-spiked Linz-Donawitz (LD) slag was used as a soil additive to improve physico-chemical soil properties and in situ stabilize Cu and other trace metals in a sandy Cu-contaminated soil (630 mg kg⁻¹ soil). The LD slag was incorporated into the contaminated soil to consist four treatments: 0% (T1), 1% (T2), 2% (T3), and 4% (T4). A similar uncontaminated soil was used as a control (CTRL). After a 1-month reaction period, potted soils were used for a 2-week growth experiment with dwarf beans. Soil pH increased with the incorporation rate of LD slag. Similarly the soil electrical conductivity (EC, in millisiemens per centimetre) is ameliorated. Bean plants grown on the untreated soil (T1) showed a high phytotoxicity. All incorporation rates of LD slag increased the root and shoot dry weight yields compared to the T1. The foliar Ca concentration of beans was enhanced for all LD slag-amended soil, while the foliar Mg, K, and P concentrations were not increased. Foliar Cu, Zn, and Cr concentrations of beans decreased with the LD slag incorporation rate. P-spiked LD slag incorporation into polluted soil allow the bean growth and foliar Ca concentration, but also to reduce foliar Cu concentration below its upper critical value avoiding an excessive soil EC and Zn deficiency. This dual effect can be of interest for soil remediation at larger scale.

  12. Soil acidification as a confounding factor on metal phytotoxicity in soils spiked with copper-rich mine wastes.

    PubMed

    Ginocchio, Rosanna; De la Fuente, Luz María; Sánchez, Pablo; Bustamante, Elena; Silva, Yasna; Urrestarazu, Paola; Rodríguez, Patricio H

    2009-10-01

    Pollution of soil with mine wastes results in both Cu enrichment and soil acidification. This confounding effect may be very important in terms of phytotoxicity, because pH is a key parameter influencing Cu solubility in soil solution. Laboratory toxicity tests were used to assess the effect of acidification by acidic mine wastes on Cu solubility and on root elongation of barley (Hordeum vulgare L.). Three contrasting substrates (two soils and a commercial sand) and two acidic, Cu-rich mine wastes (oxidized tailings [OxT] and smelter dust [SmD]) were selected as experimental materials. Substrates were spiked with a fixed amount of either SmD or OxT, and the pH of experimental mixtures was then modified in the range of 4.0 to 6.0 and 7.0 using PIPES (piperazine-1,4-bis(2-ethanesulfonic acid)), MES (2-(N-morpholino)ethanesulfonic acid), and MOPS (3-(N-Morpholino)-propanesulfonic acid) buffers. Chemical (pore-water Cu and pH) and toxicological (root length of barley plants) parameters were determined for experimental mixtures. Addition of SmD and OxT to substrates resulted in acidification (0.11-1.16 pH units) and high levels of soluble Cu and Zn. Neutralization of experimental mixtures with MES (pH 6.0) and MOPS (pH 7.0) buffers resulted in a marked decrease in soluble Cu and Zn, but the intensity of the effect was substrate-dependent. Adjustment of soil pH above the range normally considered to be toxic to plants (pH in water extract, > 5.5) significantly reduced metal toxicity in barley, but phytotoxicity was not completely eliminated. The present results stress the importance of considering confounding effects on derivation of toxicity thresholds to plants when using laboratory phytotoxicity tests.

  13. Temporal succession of soil antibiotic resistance genes following application of swine, cattle and poultry manures spiked with or without antibiotics.

    PubMed

    Zhang, Yu-Jing; Hu, Hang-Wei; Gou, Min; Wang, Jun-Tao; Chen, Deli; He, Ji-Zheng

    2017-09-27

    Land application of animal manure is a common agricultural practice potentially leading to dispersal and propagation of antibiotic resistance genes (ARGs) in environmental settings. However, the fate of resistome in agro-ecosystems over time following application of different manure sources has never been compared systematically. Here, soil microcosm incubation was conducted to compare effects of poultry, cattle and swine manures spiked with or without the antibiotic tylosin on the temporal changes of soil ARGs. The high-throughput quantitative PCR detected a total of 185 unique ARGs, with Macrolide-Lincosamide-Streptogramin B resistance as the most frequently encountered ARG type. The diversity and abundance of ARGs significantly increased following application of manure and manure spiked with tylosin, with more pronounced effects observed in the swine and poultry manure treatments than in the cattle manure treatment. The level of antibiotic resistance gradually decreased over time in all manured soils but was still significantly higher in the soils treated with swine and poultry manures than in the untreated soils after 130 days' incubation. Tylosin-amended soils consistently showed higher abundances of ARGs than soils treated with manure only, suggesting a strong selection pressure of antibiotic-spiked manure on soil ARGs. The relative abundance of ARGs had significantly positive correlations with integrase and transposase genes, indicative of horizontal transfer potential of ARGs in manure and tylosin treated soils. Our findings provide evidence that application of swine and poultry manures might enrich more soil ARGs than cattle manure, which necessitates the appropriate treatment of raw animal manures prior to land application to minimise the spread of environmental ARGs. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Enhancement of plant growth and decontamination of nickel-spiked soil using PGPR.

    PubMed

    Tank, Neelam; Saraf, Meenu

    2009-04-01

    Phytoremediation i.e. the use of plants to adsorb, accumulate or detoxify contaminants is an emerging area of interest. A viable technology needs optimum biomass production in metal contaminated soil. Five strains of microbes were selected after testing their potential as plant growth promoters, on the basis of their phosphate solubilization ability, IAA, siderophore and HCN production and biocontrol potentials. They were examined for growth in synthetic medium supplemented with nickel and their MIC (2 mM) was determined. These isolates were also able to grow and produce siderophores in presence of heavy metals like Ni, Zn and Cd. A positive response of bacterial inoculants was observed in chickpea plants towards toxic effect of nickel present in soil at different concentration (0, 1 and 2 mM). Bacterial inoculants enhanced fresh and dry weight of plants even at 2 mM nickel concentration. Pot experiments indicated that presence of nickel at upto 1 mM enhanced plant growth compared to uninoculated nickel free plants. The accumulation of nickel/plant was just 50% in Pseudomonas inoculated plants as compared to uninoculated plants with 2 mM nickel concentration along with increased biomass. The results suggest the use of these PGPR to enhance plant growth in nickel-spiked land and remediate nickel from contaminated sites. ((c) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim).

  15. Influence of long-range atmospheric transport pathways and climate teleconnection patterns on the variability of surface (210)Pb and (7)Be concentrations in southwestern Europe.

    PubMed

    Grossi, C; Ballester, J; Serrano, I; Galmarini, S; Camacho, A; Curcoll, R; Morguí, J A; Rodò, X; Duch, M A

    2016-12-01

    The variability of the atmospheric concentration of the (7)Be and (210)Pb radionuclides is strongly linked to the origin of air masses, the strength of their sources and the processes of wet and dry deposition. It has been shown how these processes and their variability are strongly affected by climate change. Thus, a deeper knowledge of the relationship between the atmospheric radionuclides variability measured close to the ground and these atmospheric processes could help in the analysis of climate scenarios. In the present study, we analyze the atmospheric variability of a 14-year time series of (7)Be and (210)Pb in a Mediterranean coastal city using a synergy of different indicators and tools such as: the local meteorological conditions, global and regional climate indexes and a lagrangian atmospheric transport model. We particularly focus on the relationships between the main pathways of air masses and sun spots occurrence, the variability of the local relative humidity and temperature conditions, and the main modes of regional climate variability, such as the North Atlantic Oscillation (NAO) and the Western Mediterranean Oscillation (WeMO). The variability of the observed atmospheric concentrations of both (7)Be and (210)Pb radionuclides was found to be mainly positively associated to the local climate conditions of temperature and to the pathways of air masses arriving at the station. Measured radionuclide concentrations significantly increase when air masses travel at low tropospheric levels from central Europe and the western part of the Iberian Peninsula, while low concentrations are associated with westerly air masses. We found a significant negative correlation between the WeMO index and the atmospheric variability of both radionuclides and no significant association was observed for the NAO index. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Patterns and Sources of Sediment and Particulate Organic Carbon in Lake Melville, Labrador, Canada: Inferences from 210Pb, 137Cs, and δ13C

    NASA Astrophysics Data System (ADS)

    Kamula, C. M.

    2016-12-01

    Modern sedimentological processes, sources and distribution of sediment and organic carbon (OC) were investigated in recently deposited sediment from Lake Melville, Labrador, Canada to better understand the impacts of anthropogenic and climatic changes to the system over the last 100-150 years. Fifteen sediment cores collected across Lake Melville in 2013 and 2014 were analysed for 210Pb and 137Cs while stable isotope δ13Corg and percentage OC were measured down select cores and surface sediment. Mass accumulation rates (MARs) were established by fitting 210Pbex profiles to a two-layer advection diffusion model and validated with 137Cs. MARs varied between 0.04 and 0.41 g cm-2 yr-1 and decreased with distance from the Churchill River, the greatest source of sediment to the system. MARs were greatest in western Lake Melville immediately east of Goose Bay, reflecting the combined contributions of fine material carried eastward in the Churchill River plume and coarser particles from the Kenamu River. The sources of sediment were investigated by comparing inventories of 137Cs and excess 210Pb (210Pbex) to expected atmospheric inputs, which suggested sediment in Lake Melville is largely sourced from the watershed. In the eastern end of Lake Melville, an elevated 210Pbex inventory was associated with particle scavenging of dissolved 210Pb from inflowing marine water and is likely linked to increased primary production in the area. Surface sediment δ13Corg values (mean = -26.2 ± 1.75‰ SD) support a mixture of both terrestrial and marine organic carbon to the system. Using a transient tracer mixing model, the depth in each core corresponding to 90% sediment deposited pre and post hydroelectric development at Churchill Falls (1970) was established and applied to profiles of δ13Corg. This approach revealed an increase of terrestrial OC to Lake Melville post 1970 which we interpret to reflect change in climate and/or hydrology of the Churchill River.

  17. 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. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. 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.

  19. 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

  20. 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

  1. 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

  2. Plant uptake and enhanced dissipation of di(2-ethylhexyl) phthalate (DEHP) in spiked soils by different plant species.

    PubMed

    Li, Yan-Wen; Cai, Quan-Ying; Mo, Ce-Hui; Zeng, Qiao-Yun; Lü, Huixiong; Li, Qu-Sheng; Xu, Guo-Sheng

    2014-01-01

    This study was conducted to investigate the uptake, accumulation and the enhanced dissipation of di(2-ethylhexyl) phthalate (DEHP) spiked in soil (with a concentration of 117.4 +/- 5.2 mg kg(-1)) by eleven plants including eight maize (Zea mays) cultivars and three forage species (alfalfa, ryegrass and teosinte). The results showed that, after 40 days of treatment, the removal rates of DEHP ranged from 66.8% (for the control) to 87.5% (for the maize cultivar of Huanong-1). Higher removal rate was observed during the first 10 days than the following days. Plants enhanced significantly the dissipation of DEHP in soil. Enhanced dissipation amount in planted soil was 13.3-122 mg pot(-1) for DEHP, and a net removal of 2.2%-20.7% of the initial DEHP was obtained compared with non-plant soil. The contribution of plant uptake to the total enhanced dissipation was < 0.3%, and the enhanced dissipation of soil DEHP might be derived from plant-promoted biodegradation and sorption stronger to the soil. Nevertheless, the capability in accumulation and enhanced dissipation of DEHP from spiked soils varied within different species and cultivars.

  3. Continuous and Episodic Modern Sediment Accumulation on Monterey Fan: Evidence from Ddt, 137Cs and Excess 210Pb

    NASA Astrophysics Data System (ADS)

    Gwiazda, R.; Paull, C. K.; Alexander, C. R.; Ussler, W.

    2012-12-01

    The mode and magnitude of fine-grained sediment accumulation on the Monterey Fan off the California central coast was investigated using pesticide concentrations and radioactive tracer profiles in sediment cores. DDT is a man-made pesticide that was used extensively in central California between 1945 and 1970. As such, its presence in marine sediments is a telltale sign of a modern sedimentation age. DDT and its metabolites, DDE and DDD, (collectively referred to as DDTr) were measured in fifty-five ~20cm-long sediment cores collected from the surface of the Monterey Fan up to 250 km to the south and 210 km to the west of the Monterey Canyon head, and in four transects across the Monterey Canyon channel at maximum water depths of 3160, 3380, 3580, and 3880 meters. Profiles of excess 210Pb (210Pbxs) and 137Cs were measured in 5 cores from the Fan to estimate recent sedimentation rates. Detectable levels of DDTr were observed in all but one of these cores, with DDTr concentrations characteristically highest at the surface and decreasing with depth. The area-normalized and depth-integrated DDTr content measured in all the cores in the Fan and in the deepest two channel transects was geographically fairly homogenous, with no statistical relationship between DDTr inventory and distance from the main channel crossing the Fan. The total sediment mass deposited on the Fan over the last 60 years, inferred from the total inventory of DDTr present in the area surveyed, is consistent with the amount of sediment delivered by the Salinas River over the same time period. 210Pbxs activities are fairly homogeneous within an uppermost layer of variable thickness (4.6-8cm) and decrease exponentially below it, but these exponential decreases are often interrupted by horizons with constant or increased 210Pbxs activity. Moreover, the coexistence of variable DDTr concentrations with homogeneous 210Pbxs activities in the top sediment indicates that the uniformity of 210Pbxs is not due

  4. 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.

  5. (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.

  6. The effect of {sup 210}Pb and stable lead on the induction of menta deformities in Chironomus tentans larvae and on their growth and survival

    SciTech Connect

    Bird, G.A.; Schwartz, W.J.; Joseph, D.L.

    1995-12-01

    To determine whether menta deformities in chironomid larvae collected from Port Hope Harbor, Ontario, were the result of exposure to ionizing radiation or to heavy metals in the sediment, Chironomus tentans larvae were exposed in the laboratory to concentrations of {sup 210}Pb and stable lead representative of contaminant levels in the harbor. Exposure to 100, 1,000, and 2,000 Bq {sup 210}Pb g{sup {minus}1} dry sediment had no effect on larval survival, growth, or frequency of deformities. Likewise, exposure to 0.5 and 5.0 mg lead g{sup {minus}1} dry sediment had no effect on the larvae, but exposure to 35.0 mg lead g{sup {minus}1} dry sediment (the maximum levels observed in Port Hope Harbor) resulted in 100% mortality of the larvae. These results indicate that the observed mouthpart deformities in chironomid larvae of Port Hope Harbor are not the result of radiation exposure. They also indicate that heavy metals (lead) may be having an impact on the Port Hope Harbor population. Deformities were observed in all treatments and were confined mainly to the median tooth, with cleft or forked median teeth being the most common deformity. Restriction of the deformities to the median tooth is consistent with an inherited genetic effect, and they consider them to be natural abnormalities. These natural abnormalities must be considered when using chironomid mouthpart deformities as an index of environmental degradation.

  7. 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.

  8. 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.

  9. (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). Copyright © 2010 Elsevier B.V. All rights reserved.

  10. Residence times of surface water and particle-reactive sup 210 Pb and sup 210 Po in the East China and Yellow seas

    SciTech Connect

    Nozaki, Yoshiyuki ); Tsubota, Hiroyuki; Kasemsupaya, Vimonrut ); Yashima, Mayumi; Ikuta, Naoko )

    1991-05-01

    {sup 228},{sup 226}Ra, {sup 210}Pb, and {sup 210}Po were measured in the surface waters of the East China and Yellow seas. Using mass balance equations for the Ra isotopes. The authors estimated the total flux of diffusion from sediments and desorption from suspended particles to be 0.1 dpm {sup 226}Ra cm{sup {minus}2} a{sup {minus}1} and 1 dpm {sup 228}Ra cm{sup {minus}2} a{sup {minus}1}, and residence times to be 2-3 years for the waters on the East China Sea Shelf and 5-6 years for Yellow Sea waters. Box-model calculations yielded generally congruent scavenging residence times for {sup 210}Pb and {sup 210}Po in the waters of {approximately}2 months on the shelf and {approximately}7 months in the Kuroshio Current. These suggest that reactive heavy metals and pollutants discharged through rivers from the continent to the East Asian continental shelf are largely deposited on the bottom sediments prior to transport to the pelagic ocean by lateral mixing.

  11. 210Pb chronology and trace metal geochemistry at Los Tuxtlas, Mexico, as evidenced by a sedimentary record from the Lago Verde crater lake

    NASA Astrophysics Data System (ADS)

    Carolina Ruiz-Fernández, Ana; Hillaire-Marcel, Claude; Páez-Osuna, Federico; Ghaleb, Bassam; Caballero, Margarita

    2007-03-01

    Lago Verde is a fresh-water maar found on the lower slopes of San Martin volcano, at the Sierra de Los Tuxtlas, Mexico, currently the northernmost remnant of the tropical rain forest in America. 210Pb and 137Cs analyzed in a sediment core were used to reconstruct the historical fluxes of Ag, Cd, Cu, Pb, Hg and Zn to the site during the last ˜ 150 yr. The 210Pb xs-derived sediment accumulation rates, the magnetic susceptibility, C/N ratios and δ13C data evidenced background conditions at the lake until 1960s, when enhanced erosion related to the clearing of large forested areas at Los Tuxtlas promoted higher accumulation rates of a heavier and more magnetic sedimentary material. Recent sediments from Lago Verde were found enriched by Pb (26-fold natural concentration level [NCLs]) and moderately enriched by Cd > Cu > Zn and Hg (6-, 5-, 4- and 4-fold corresponding NCLs, respectively). The fluxes of Cu, Hg, Pb and Zn have significantly increased since 1940s, with peak ratios of total modern to pre-industrial fluxes of 11, 11, 19 and 49, respectively. The lake occupies a relatively pristine, non-industrialized basin, and therefore the increased metal fluxes might be related to long-distance aeolian transport of trace metals.

  12. Long-term variation (1992-1999) of gross-beta, 210Pb and 90Sr concentrations in rainwater and deposition to ground

    NASA Astrophysics Data System (ADS)

    DueñAs, C.; FernáNdez, M. C.; Carretero, J.; Liger, E.; CañEte, S.

    2003-06-01

    After the end of atmospheric nuclear weapons tests and after the Chernobyl accident, the deposition characteristics of radionuclides changed from a predominant wet deposition to the present resuspension mechanism characterised by predominant dry deposition. To study the deposition, monthly deposition data from a collector located at a coastal station (Málaga, South Spain) were compared from 1992 to 1999. The measurement of artificial and natural radionuclide activity concentrations in bulk deposition material by non-destructive ultra low-level gamma-ray spectrometry and long-term deposition fluxes at this sampling site are reported. The range in annual fluxes for gross-beta is 60.1-97.2 Bq m-2 yr-1. A measure of the annual deposition velocity for the total beta activity has been obtained using specific concentrations in air and deposition fluxes. The annual total deposition fluxes of 210Pb varied between 12.4 Bq m-2 [1998] and 464.15 Bq m-2 [1996], showing a minimum in the years 1994, 1995 and 1999. The average atmospheric fallout value for 210Pb (135.7 Bq m-2 yr-1) measured over 8 years (1992-1999) is compared with values from other stations. The annual total deposition fluxes of 90Sr varied between <2.15 Bq m-2 [1999] and 13.3 Bq m-2 [1994], showing a significant decrease as expected for natural removal and radioactive decay and no new releases from nuclear facilities or weapons testing.

  13. 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.

  14. 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.

  15. Toxicity in lead salt spiked soils to plants, invertebrates and microbial processes: Unraveling effects of acidification, salt stress and ageing reactions.

    PubMed

    Smolders, Erik; Oorts, Koen; Peeters, Sofie; Lanno, Roman; Cheyns, Karlien

    2015-12-01

    The fate and effects of toxic trace metals in soil freshly spiked soluble metal salts do not mimic those of metals in the field. This study was set up to test the magnitude of effects of salinity, acidification, and ageing on toxicity of lead (Pb) to plants, invertebrates and soil microbial processes. Three soils were spiked with Pb2+ salts up to a concentration of 8000 mg Pb/kg and were tested either after spiking, after soil leaching followed by pH correction, or after a 5-year outdoor ageing period with free drainage followed by pH correction. Soil solution ionic strength exceeded 150 mmol/L in soils tested directly after spiking and this decreased partially after leaching and returned back to background values after 5-year outdoor equilibration. Chronic toxicity to two plants, two invertebrates, and three microbial endpoints was consistently found in all spiked soils that were not leached. This toxicity significantly decreased or became absent after 5 years of ageing in 19 of the 20 toxicity tests by a factor 8 (median factor; range: 1.4->50), measured by the factor increase of total soil Pb dose required to induce 10% inhibition. The toxicity of Pb in leached soils was intermediate between the other two treatments. The lowest detectable chronic thresholds (EC10) in aged soils ranged 350-5300 mg Pb/kg. Correlation analysis, including data of Pb2+ speciation in soil solution, suggests that reduced ionic strength rather than acidification or true ageing is the main factor explaining the soil treatment effects after spiking. It is suggested that future toxicity studies should test fine PbO powder as a relevant source for Pb in soils to exclude the confounding salt effects.

  16. Removal of polycyclic aromatic hydrocarbons in soil spiked with model mixtures of petroleum hydrocarbons and heterocycles using biosurfactants from Rhodococcus ruber IEGM 231.

    PubMed

    Ivshina, Irina; Kostina, Ludmila; Krivoruchko, Anastasiya; Kuyukina, Maria; Peshkur, Tatyana; Anderson, Peter; Cunningham, Colin

    2016-07-15

    Removal of polycyclic aromatic hydrocarbons (PAHs) in soil using biosurfactants (BS) produced by Rhodococcus ruber IEGM 231 was studied in soil columns spiked with model mixtures of major petroleum constituents. A crystalline mixture of single PAHs (0.63g/kg), a crystalline mixture of PAHs (0.63g/kg) and polycyclic aromatic sulfur heterocycles (PASHs), and an artificially synthesized non-aqueous phase liquid (NAPL) containing PAHs (3.00g/kg) dissolved in alkanes C10-C19 were used for spiking. Percentage of PAH removal with BS varied from 16 to 69%. Washing activities of BS were 2.5 times greater than those of synthetic surfactant Tween 60 in NAPL-spiked soil and similar to Tween 60 in crystalline-spiked soil. At the same time, amounts of removed PAHs were equal and consisted of 0.3-0.5g/kg dry soil regardless the chemical pattern of a model mixture of petroleum hydrocarbons and heterocycles used for spiking. UV spectra for soil before and after BS treatment were obtained and their applicability for differentiated analysis of PAH and PASH concentration changes in remediated soil was shown. The ratios A254nm/A288nm revealed that BS increased biotreatability of PAH-contaminated soils.

  17. 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.

  18. 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

  19. AMS 14C and 210Pb dating on a 51-cm sediment core from Santa Barbara Basin, CA: old carbon source

    NASA Astrophysics Data System (ADS)

    Chang, YiWei; Berelson, William M.; Li, HongChun

    2017-04-01

    A 51-cm gravity core, SBB-8-2012, was collected from Santa Barbara Basin (SBB) of California in 2012. Lamination counting of the core yields ˜160 layers. A total of 17 horizons of the core have been analyzed for 210Pb dating through alpha spectrometry method which provides a mean sedimentation rate of 0.24cm/y. Thus, the 51-cm long core covers about 210 years of depositional history of the sampling site in the basin. Up-to-date, we have measured AMS 14C dates on TOC of the bulk sediments in 34 layers from the upper 40.1 cm of the core. Except the 14C date (2983 yr BP) at 35-35.2 cm depth, the 33 uncorrected 14C dates range from 508 yr BP to 2214 yr BP, and form two groups which give two linear lines: age = 417 + 35.9 depth (cm), R2 = 0.976 and age = 665 + 37.4 depth (cm), R2 = 0.949. These equations allow us to observe the following phenomena: (1) TOC of the bulk sediments in the SSB contains old carbon. The old carbon may come from terrestrial input (allogenic/allochthonous) and/or from endogenic input (autochthonous) through photosynthesis in the water column. (2) The reservoir age can exist for both organic carbon of TOC and carbonate. At 35.5-37 cm depth, the AMS 14C date of a plant remain sample was 520±12 yr BP. If this age subtracts the reservoir age of 417 years, the corrected age is close to the result of 210Pb dating. A shell sample at 38.5 cm depth provides a 14C age of 915±47 yr BP, showing older reservoir age for carbonate. (3) The reservoir age for TOC may vary through time depending on water mixing rate in the basin. This is because the endogenic input may be a function of water mixing in the basin. When the mixing rate of the water column in the basin was slower, the reservoir age became older. Based on the chronology from the 210Pb dating, we are able to determine the Δ14C fluctuations of the TOC in the bulk sediments of the core. The variation of the Δ14C may let us evaluate basin mixing during the past 200 years.

  20. Effect of soil metal contamination on glyphosate mineralization: role of zinc in the mineralization rates of two copper-spiked mineral soils.

    PubMed

    Kim, Bojeong; Kim, Young Sik; Kim, Bo Min; Hay, Anthony G; McBride, Murray B

    2011-03-01

    A systematic investigation into lowered degradation rates of glyphosate in metal-contaminated soils was performed by measuring mineralization of [(14)C]glyphosate to (14)CO(2) in two mineral soils that had been spiked with Cu and/or Zn at various loadings. Cumulative (14)CO(2) release was estimated to be approximately 6% or less of the amount of [(14)C]glyphosate originally added in both soils over an 80-d incubation. For all but the highest Cu treatments (400 mg kg(-1)) in the coarse-textured Arkport soil, mineralization began without a lag phase and declined over time. No inhibition of mineralization was observed for Zn up to 400 mg kg(-1) in either soil, suggesting differential sensitivity of glyphosate mineralization to the types of metal and soil. Interestingly, Zn appeared to alleviate high-Cu inhibition of mineralization in the Arkport soil. The protective role of Zn against Cu toxicity was also observed in the pure culture study with Pseudomonas aeruginosa, suggesting that increased mineralization rates in high Cu soil with Zn additions might have been due to alleviation of cellular toxicity by Zn rather than a mineralization specific mechanism. Extensive use of glyphosate combined with its reduced degradation in Cu-contaminated, coarse-textured soils may increase glyphosate persistence in soil and consequently facilitate Cu and glyphosate mobilization in the soil environment.

  1. {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.

  2. Effects and bioavailability of 2,4,6-trinitrotoluene in spiked and field-contaminated soils to indigenous microorganisms

    SciTech Connect

    Gong, P.; Siciliano, S.D.; Greer, C.W.; Paquet, L.; Hawari, J.; Sunahara, G.I.

    1999-12-01

    The response of potential nitrification activity (PNA), nitrogen-fixation activity (NFA), and dehydrogenase activity (DHA) in soil to 2,4,6-trinitrotoluene (TNT) was assessed. Two garden soils of contrasting texture were spiked with TNT. Soil microbial activities and TNT residues were analyzed 1 week later. The estimated IC50 ranged from 39 to 533 mg/kg of the acetonitrile-extractable (AE) TNT, depending on indicators and soils. The lowest LOEC (lowest-observed-effect concentration) was 1 mg AE TNT/kg. Field soil was collected from three known contaminated sites in an abandoned TNT manufacturing facility. Microbial toxicity significantly correlated to TNT levels in these soils. The LOEC and NOEC (no-observed-effect concentration) values were site and indicator specific, with the lowest LOEC being 1 mg AE TNT/kg and the lowest NOEC being 0.4 mg AE TNT/kg. The IC50 of the pooled field samples was 51 mg AE TNT/kg for PNA or 157 mg AE TNT/kg for DHA. These results indicate that microbial responses were consistent and comparable between the laboratory and the field and that TNT could significantly inhibit soil microbial activities at very low levels. Both AE TNT and deionized water-extractable (DW) TNT concentrations correlated well with microbial toxicity, but AE TNT provided a better evaluation of TNT bioavailability than did DW TNT.

  3. (210)Pb and composition data of near-surface sediments and interstitial waters evidencing anthropogenic inputs in Amazon River mouth, Macapá, Brazil.

    PubMed

    Nery, José Reinaldo Cardoso; Bonotto, Daniel Marcos

    2011-04-01

    Activity profiles of excess (210)Pb determined in three sediment cores from Amazon River mouth, Macapá city, Brazil, provided the evaluation of sedimentation rates, contributing to a better knowledge of the hydrological conditions in the site that is the capital of Amapá State and is drained by the waters of the huge Amazon River. Chemical data were also determined in the sediments, allowing identify signatures coupled to anthropogenic inputs held in the past in Amapá State. Significant direct relationships between LOI (loss on ignition) and organic matter were found for all sediments profiles. Silica was found to be inversely related to organic matter in the three profiles; its decrease accompanied an increase on the specific surface of the sediments. This relationship was confirmed by a great number of inverse significant correlations among silica and oxides Na(2)O, K(2)O, CaO, MgO, Al(2)O(3), P(2)O(5), Fe(2)O(3) and MnO. It was possible to identify the role of organic matter on adsorption of several oxides in the core sediments profiles. Apparent sediment mass accumulation rates corresponding to values between 450 and 2510 mg cm(-2)yr(-1) were obtained, and are compatible with the results of others studies. The (210)Pb activities in one sampling point suggested the occurrence of anthropogenic inputs related to the initial period of the mining activities conducted in Serra do Navio, Amapá State, for the commercialization of Mn ores. This was reinforced by the abrupt fluctuations in chemical data obtained for the sediments and composition of the interstitial waters occurring there. The Atlantic hurricane activity also appeared to affect the sedimentation rates in the area, as two different values were recorded in each profile. Copyright © 2011 Elsevier Ltd. All rights reserved.

  4. 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.

  5. Importance of coccolithophore-associated organic biopolymers for fractionating particle-reactive radionuclides (234Th, 233Pa, 210Pb, 210Po, and 7Be) in the ocean

    NASA Astrophysics Data System (ADS)

    Lin, Peng; Xu, Chen; Zhang, Saijin; Sun, Luni; Schwehr, Kathleen A.; Bretherton, Laura; Quigg, Antonietta; Santschi, Peter H.

    2017-08-01

    Laboratory incubation experiments using the coccolithophore Emiliania huxleyi were conducted in the presence of 234Th, 233Pa, 210Pb, 210Po, and 7Be to differentiate radionuclide uptake to the CaCO3 coccosphere from coccolithophore-associated biopolymers. The coccosphere (biogenic calcite exterior and its associated biopolymers), extracellular (nonattached and attached exopolymeric substances), and intracellular (sodium-dodecyl-sulfate extractable and Fe-Mn-associated metabolites) fractions were obtained by sequentially extraction after E. huxleyi reached its stationary growth phase. Radionuclide partitioning and the composition of different organic compound classes, including proteins, total carbohydrates (TCHO), and uronic acids (URA), were assessed. 210Po was closely associated with the more hydrophobic biopolymers (high protein/TCHO ratio, e.g., in attached exopolymeric substances), while 234Th and 233Pa showed similar partitioning behavior with most activity being distributed in URA-enriched, nonattached exopolymeric substances and intracellular biopolymers. 234Th and 233Pa were nearly undetectable in the coccosphere, with a minor abundance of organic components in the associated biopolymers. These findings provide solid evidence that biogenic calcite is not the actual main carrier phase for Th and Pa isotopes in the ocean. In contrast, both 210Pb and 7Be were found to be mostly concentrated in the CaCO3 coccosphere, likely substituting for Ca2+ during coccolith formation. Our results demonstrate that even small cells (E. huxleyi) can play an important role in the scavenging and fractionation of radionuclides. Furthermore, the distinct partitioning behavior of radionuclides in diatoms (previous studies) and coccolithophores (present study) explains the difference in the scavenging of radionuclides between diatom- and coccolithophore-dominated marine environments.

  6. A 210Pb sediment budget and granulometric record of sediment fluxes in a subarctic deltaic system: The Great Whale River, Canada

    NASA Astrophysics Data System (ADS)

    Hülse, Peter; Bentley, Samuel J.

    2012-08-01

    To elucidate how modern river discharge conditions of the Great Whale River (GWR) are represented in the marine sedimentary record, eight box and gravity cores were examined in terms of 210Pb and 137Cs radiochemistry, granulometry and physical sedimentary structures. These data were analyzed to provide insights into sedimentary processes and patterns at the study site. Sediment accumulation in the study area appears to be a relatively steady process over time-scales of 50-100 yr, allowing biological activity to overprint the primary depositional fabric. Subtle differences between 137Cs and 210Pb sediment accumulation rates (SARs) suggest an offshore shift in the locus of fine sediment deposition during the past ˜150 yr, which may be a result of ongoing climatic warming leading to decreasing sea-ice coverage and a more energetic marine environment. Under present day conditions 23% (40,000 t/yr) of the discharged sediment appear to accumulate in a 25 km2 area off the river mouth. The remaining 77% (136,000 t/yr) are either deposited further offshore, possibly along the northeastern shore as a result of Hudson Bay's counterclockwise circulation, or dispersed into the Hudson Bay system. Grain diameter frequency analyses suggest that environmental processes controlling sediment transport and deposition vary over decadal time scales. Although, we cannot define an exact cause for this pattern, these shifts may be related to variations in river discharge, wave climate, possibly due to windier conditions or less sea-ice dampening, bioturbation or a combination of all. This suggests that also longer term river discharge signals are preserved in the marine sedimentary record offshore the Great Whale River. In summary, no major change in sediment discharge over the past ˜150 yr was observed. However, the offshore shift in the locus of sediment deposition suggests, that a warming climate will lead to more energetic marine conditions, less sea-ice coverage, and an increased

  7. Estrogenic effect of leachates and soil extracts from lysimeters spiked with sewage sludge and reference endocrine disrupters.

    PubMed

    Dizer, Halim; Fischer, Birgit; Sepulveda, Isabel; Loffredo, Elisabetta; Senesi, Nicola; Santana, Fernando; Hansen, Peter-D

    2002-01-01

    Several experiments were conducted to evaluate the behavior and performance of some potential endocrine disrupters (ECDs). Two in vitro screening assays, one based on MCF7-cell proliferation (E-screen test) and the other on estrogenic receptor activity [enzyme-linked receptor assay (ELRA)], were used for the tests, which were done in lysimeters 80 cm in diameter with depth of 30 cm (shallow) or 90 cm (deep). A sandy soil was used to fill in all lysimeters, which were spiked on the surface with either: (a) a sewage sludge (SS) at a dose equivalent to 20 tons ha-1; (b) a mixture of reference ECDs, comprising 17 alpha- and 17 beta-estradiol (E2), nonylphenol, octylphenol, and bisphenol A at doses 100 times higher than the maximum concentrations respectively found in the applied SS; or (c) a mixture of ECDs and SS. After percolation of the lysimeters with rain and/or artificial water, five leachates were sampled from each lysimeter during a period of 210 days. Immediately after the lysimeter percolation experiments, four and six soil fractions were dissected from, respectively, the 30-cm and 90-cm lysimeters and extracted by water. Both the leachate and soil extract samples were analyzed for their estrogenicity using the assays indicated above. The E-screen assay was highly sensitive only for some leachate and extract samples but gave no response for most leachates and soil extracts. The results of the ELRA assay suggests a significantly higher estrogenicity of leachate samples from shallow lysimeters compared with that of leachates from deep lysimeters. In contrast, the estrogenic effect measured for soil extracts of shallow lysimeters was lower than that measured for soil extracts of deep lysimeters. The results of the E-screen assay suggests the occurrence of a fast mobilization of applied ECDs and a moderate retardation effect of native ECDs contained in applied SS in the sandy soil used in the lysimeters. In lysimeters spiked with a mixture of SS and ECDs, the

  8. Accumulation of 2,4-dinitroanisole in the earthworm Eisenia fetida from chemically spiked and aged natural soils.

    PubMed

    Lotufo, Guilherme R; Coleman, Jessica G; Harmon, Ashley R; Chappell, Mark A; Bednar, Anthony J; Russell, Amber L; Smith, Jared C; Brasfield, Sandra M

    2016-07-01

    An initiative within the US military is targeting the replacement of traditional munitions constituents with insensitive munitions to reduce the risk of accidental detonation. The bioavailability and bioaccumulative potential of the insensitive munitions compound 2,4-dinitroanisole (DNAN) to Eisenia fetida was assessed in soils with different geochemical characteristics. Prior to exposure, soils were chemically spiked with DNAN and aged for 1 wk or 29 wk. Transformation products 2- and 4-amino-nitroanisole (2A-4NAN and 4A-2NAN) occurred in aged soils and their porewater but never at concentrations higher than the residual DNAN. The sum of DNAN, 2A-4NAN, and 4A-2NAN (sumDNAN) in soil decreased with aging, likely by irreversible binding. Both clay and organic matter contents of the soil appeared to affect the bioavailability of DNAN. The sumDNAN body residues of earthworms approached apparent steady state after 1 d and remained relatively constant through to day 7. Higher concentrations of 2A-4NAN and 4A-2NAN measured in worm tissues relative to those in soil suggest reductive transformation of DNAN in the tissues. Mean bioaccumulation factors (ratio of tissue to soil concentrations) varied from 1.2 to 4.3, whereas mean bioconcentration factors (ratio of tissue to porewater concentrations) ranged from 1.4 to 3.2. Porewater seems to play a significant role in the accumulation of DNAN in earthworms, consistent with equilibrium partitioning theory. The concentration of DNAN in soil porewater could serve as an indicator of bioavailability as well as a predictor of the concentration of that compound in earthworms. Environ Toxicol Chem 2016;35:1835-1842. Publlished 2015 SETAC. This article is a US Government work, and as such, is in the public domain in the United States of America. Publlished 2015 SETAC. This article is a US Government work, and as such, is in the public domain in the United States of America.

  9. TNT, RDX, and HMX decrease earthworm (Eisenia andrei) life-cycle responses in a spiked natural forest soil.

    PubMed

    Robidoux, P Y; Hawari, J; Bardai, G; Paquet, L; Ampleman, G; Thiboutot, S; Sunahara, G I

    2002-11-01

    Sublethal and chronic toxicities of 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) on earthworm Eisenia andrei in a sandy forest soil were assessed. Various reproduction parameters of fecundity (total and hatched number of cocoons, number of juveniles, and their biomass) were significantly decreased by TNT (> or = 58.8 +/- 5.1 mg/kg dry soil), RDX (> or = 46.7 +/- 2.6 mg/kg), and HMX (> or = 15.6 +/- 4.6 mg/kg). These effects occurred at much lower concentrations than those reported earlier using artificial soil preparations. Growth of adults was significantly decreased in the TNT-spiked natural soils at 136.2 +/- 25.6 mg/kg dry soil, the highest concentration having no significant mortality. In contrast, survival and growth were not significantly reduced at relatively high measured concentrations of RDX (167.3 mg/kg) and HMX (711.0 mg/kg). Although TNT, RDX, and HMX share a common life-cycle response ( i.e., decreased juvenile counts), a number of differences related to other reproduction parameters (e.g., productivity of cocoons) was observed. These results indicate that the tested explosives do not support a common mechanism of toxicity, at least in the earthworm, probably due to differences in their physical-chemical properties as well as metabolites formed during exposure.

  10. 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

  11. 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

  12. Bioavailability of Zn in ZnO nanoparticle-spiked soil and the implications to maize plants

    NASA Astrophysics Data System (ADS)

    Liu, Xueqin; Wang, Fayuan; Shi, Zhaoyong; Tong, Ruijian; Shi, Xiaojun

    2015-04-01

    Little is known about the relationships between Zn bioavailability in ZnO nanoparticle (NP)-spiked soil and the implications to crops. The present pot culture experiment studied Zn bioavailability in soil spiked with different doses of ZnO NPs, using the diethylenetriaminepentaacetic acid (DTPA) extraction method, as well as the toxicity and Zn accumulation in maize plants. Results showed that ZnO NPs exerted dose-dependent effects on maize growth and nutrition, photosynthetic pigments, and root activity (dehydrogenase), ranging from stimulatory (100-200 mg/kg) through to neutral (400 mg/kg) and toxic effect (800-3200 mg/kg). Both Zn concentration in shoots and roots correlated positively ( P < 0.01) with ZnO NPs dose and soil DTPA-extractable Zn concentration. The BCF of Zn in shoots and roots ranged from 1.02 to 3.83 when ZnO NPs were added. In most cases, the toxic effects on plants elicited by ZnO NPs were overall similar to those caused by bulk ZnO and soluble Zn (ZnSO4) at the same doses, irrespective of some significant differences suggesting a higher toxicity of ZnO NPs. Oxidative stress in plants via superoxide free radical production was induced by ZnO NPs at 800 mg/kg and above, and was more severe than the same doses of bulk ZnO and ZnSO4. Although significantly lower compared to bulk ZnO and ZnSO4, at least 16 % of the Zn from ZnO NPs was converted into DTPA-extractable (bioavailable) forms. The dissolved Zn2+ from ZnO NPs may make a dominant contribution to their phytotoxicity. Although low amounts of ZnO NPs exhibited some beneficial effects, the accumulation of Zn from ZnO NPs into maize tissues could pose potential health risks for both plants and human.

  13. Dynamics of PAHs and derived organic compounds in a soil-plant mesocosm spiked with (13)C-phenanthrene.

    PubMed

    Cennerazzo, Johanne; de Junet, Alexis; Audinot, Jean-Nicolas; Leyval, Corinne

    2017-02-01

    Polycyclic Aromatic Hydrocarbons (PAHs) are ubiquitous and persistent soil pollutants. Their fate and the influence of the plant rhizosphere on their dynamics has been extensively studied, but studies mainly focused on their dissipation rate. We conducted a plant-soil mesocosm experiment to study the fate and distribution of PAHs or derived compounds in the extractable fraction, the residual soil, the shoot biomass and the root biomass. The experiment was conducted for 21 days using ryegrass and a forest soil spiked with (13)C-labeled phenanthrene (PHE), using combined IRMS and NanoSIMS for analyses. Almost 90% of the initial extractable PHE content was dissipated within 3 weeks, but no rhizospheric effect was highlighted on PHE dissipation. More than 40% of (13)C-PHE was still in the soil at the end of the experiment, but not as PHE or PAH-derived compounds. Therefore it was under the form of new compounds (metabolites) and/or had been incorporated into the microbial biomass. About 0.36% of the initial (13)C-PHE was recovered in the root and shoot tissues, representing similar (13)C enrichment (E(13)C) as in the soil (E(13)C ≈ 0.04 at.%). Using NanoSIMS, (13)C was also localized at the microscale in the roots and their close environment. Global (13)C enrichment confirmed the results obtained by IRMS. Some hotspots of (13)C enrichment were found, with a high (32)S/(12)C(14)N ratio. Comparing the ratios, sizes and shapes of these hotspots suggested that they could be bacteria.

  14. Mineralization of pyrene induced by interaction between Ochrobactrum sp. PW and ryegrass in spiked soil.

    PubMed

    Liu, Tuo; Wei, Lianshuang; Qiao, Min; Zou, Dexun; Yang, Xiaojin; Lin, Aijun

    2016-11-01

    This study was conducted to investigate the capability of pyrene-degrading bacterium Ochrobactrum sp. PW and ryegrass (Lolium multiflorum) grown alone and in combination on the degradation of pyrene in soil. After 60 days of ryegrass growth, plant biomass, pyrene-degrading microbial mass, soil enzyme activity (catalase activity and polyphenol oxidase activity) and residual concentration of pyrene in soils were determined. Higher dissipation rates were observed in PW inoculation treatments: ryegrass+PW rhizosphere soil (RP-r) and ryegrass+PW non-rhizosphere soil (RP-nr), than planting of ryegrass alone, rhizosphere (R-r) or non-rhizosphere (R-nr). The inoculation with PW significantly (p<0.05) increased the dry weight of ryegrass root and shoot, nearly 2.8 and 3.3 times higher than ryegrass treatment. The pyrene-degrading microbial mass indicated that a much larger mass of bacteria, actinobacteria were present in RP treatment. The catalase activity in all different treatments were significantly (p<0.05) higher than in with treatment R-nr, and the polyphenol oxidase activity was also significantly (p<0.05) increased by inoculation with PW, leading to enhanced mineralization of pyrene from soil. Our results suggest that adding of PAHs-degrading bacteria to soil can enhance remediation of PAHs contaminated soil, while improving plant growth.

  15. 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.

  16. 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

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

    PubMed

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

    2016-11-09

    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, (210)Po and (210)Pb 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 (210)Po in the area was found to be 1.169 µSv·y(-1).

  18. 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.

  19. One century sedimentary record of Hg and Pb pollution in the Sagua estuary (Cuba) derived from 210Pb and 137Cs chronology.

    PubMed

    Díaz-Asencio, M; Alonso-Hernández, C M; Bolanos-Alvarez, Y; Gómez-Batista, M; Pinto, V; Morabito, R; Hernández-Albernas, J I; Eriksson, M; Sanchez-Cabeza, J A

    2009-01-01

    The vertical distribution of Hg and Pb were determined in a sediment core collected from the Sagua estuary (North Cuba) that receives input from the Sagua river, one of the most polluted rivers discharging into the Cuban coastal environment. Depth profiles of metal concentrations were converted to time-based profiles using the (210)Pb dating method and confirmed with the (137)Cs fallout peak. The mean mass accumulation rate was estimated to be 0.17+/-0.04 g cm(-2)y(-1) (mean sediment accumulation rate 0.52+/-0.13 cm y(-1)) and the core bottom was estimated to date back about 130 years. The historical sedimentary record showed a strong enrichment of mercury concentrations in the past decades, caused by the incomplete treatment of industrial wastes from a chlor-alkali plant with mercury-cell technology in the Sagua river basin. Lead fluxes to sediments showed a gradual increase from the 1920s to present, which agrees with a population increase in Sagua la Grande City. Fluxes of both metals have increased the past 25 years, with values reaching a maximum of 0.5 and 3.9 microg cm(-2)y(-1) for Hg and Pb, respectively.

  20. 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.

  1. Preparation of spiked soils by vapor fortification for volatile organic compounds analysis

    SciTech Connect

    Hewitt, A.D.

    1994-05-01

    This paper describes a vapor fortification method for preparing quality assurance/quality control soils for volatile organic compound analysis. Treatment of soils with volatile organic compounds occurs in a closed container in a manner somewhat analogous to the way the vadose zone often becomes contaminated. One advantage of this method for preparing soils for quality assurance/quality control purposes is that the efficiency of various extraction methods can be reliably compared. Furthermore, by substantially reducing the error due to sample inhomogeneity, the error associated with the determinative step can also be properly evaluated. 15 refs., 3 tabs.

  2. Asymmetric flow field-flow fractionation of manufactured silver nanoparticles spiked into soil solution.

    PubMed

    Koopmans, G F; Hiemstra, T; Regelink, I C; Molleman, B; Comans, R N J

    2015-05-01

    Manufactured metallic silver nanoparticles (AgNP) are intensively utilized in consumer products and this will inevitably lead to their release to soils. To assess the environmental risks of AgNP in soils, quantification of both their concentration and size in soil solution is essential. We developed a methodology consisting of asymmetric flow field-flow fractionation (AF4) in combination with on-line detection by UV-vis spectroscopy and off-line HR-ICP-MS measurements to quantify the concentration and size of AgNP, coated with either citrate or polyvinylpyrrolidone (PVP), in water extracts of three different soils. The type of mobile phase was a critical factor in the fractionation of AgNP by AF4. In synthetic systems, fractionation of a series of virgin citrate- and PVP-coated AgNP (10-90 nm) with reasonably high recoveries could only be achieved with ultrahigh purity water as a mobile phase. For the soil water extracts, 0.01% (w:v) sodium dodecyl sulfate (SDS) at pH 8 was the key to a successful fractionation of the AgNP. With SDS, the primary size of AgNP in all soil water extracts could be determined by AF4, except for PVP-coated AgNP when clay colloids were present. The PVP-coated AgNP interacted with colloidal clay minerals, leading to an overestimation of their primary size. Similar interactions between PVP-coated AgNP and clay colloids can take place in the environment and facilitate their transport in soils, aquifers, and surface waters. In conclusion, AF4 in combination with UV-vis spectroscopy and HR-ICP-MS measurements is a powerful tool to characterize AgNP in soil solution if the appropriate mobile phase is used. Copyright © 2015 Elsevier B.V. All rights reserved.

  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. Determination of the mean aerosol residence times in the atmosphere and additional (210)Po input on the base of simultaneous determination of (7)Be, (22)Na, (210)Pb, (210)Bi and (210)Po in urban air.

    PubMed

    Długosz-Lisiecka, Magdalena; Bem, Henryk

    The significant differences in the activities of (210)Pb, (210)Bi, (210)Po and cosmogenic (7)Be and (22)Na radionuclides in the urban aerosol samples collected in the summers 2010 and 2011 in the Lodz city of Poland were observed. Simultaneous measurement of these radionuclides, after a simple modification of the one compartment model, allows us to calculate both: the corrected aerosol residence times in the troposphere (1 ÷ 25 days) and in the lower stratosphere (103 ÷ 205 days). The relative input of the additional sources (beside of the (222)Rn decay in the air) to the total activity concentrations of (210)Pb, (210)Bi and (210)Po radionuclides in the urban air, plays a substantial role (up to 97% of the total activity) only in the case of (210)Po.

  5. Do drying and rewetting cycles modulate effects of sulfadiazine spiked manure in soil?

    PubMed

    Jechalke, Sven; Radl, Viviane; Schloter, Michael; Heuer, Holger; Smalla, Kornelia

    2016-05-01

    Naturally occurring drying-rewetting events in soil have been shown to affect the dissipation of veterinary antibiotics entering soil by manure fertilization. However, knowledge of effects on the soil microbial community structure and resistome is scarce. Here, consequences of drying-rewetting cycles on effects of sulfadiazine (SDZ) in soil planted with Dactylis glomerata L. were investigated in microcosms. Manure containing SDZ or not was applied to the pregrown grass and incubated for 56 days in a climate chamber. Water was either added daily or reduced during two drying events of 7 days, each followed by a recovery phase. Total community DNA was analyzed to reveal the effects on the bacterial community structure and on the abundance of sul1, sul2, intI1 ,intI2, qacE+qacEΔ1, traN and korB genes relative to 16S rRNA genes. 16S rRNA gene-based DGGE fingerprints indicated that drying-rewetting cycles modulated the effects of SDZ on the bacterial community structure in the soil. Furthermore, the SDZ treatment increased the relative abundance of sulfonamide resistance and integrase genes compared to the control. However, this increase was not different between moisture regimes, indicating that drying-rewetting had only a negligible effect on the selection of the resistome by SDZ in the manured soil.

  6. 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.

  7. Urease activity in aged copper and zinc-spiked soils: relationship to CaCl2-extractable metals and Cu2+ activity.

    PubMed

    Kim, Bojeong; McBride, Murray B; Hay, Anthony G

    2008-12-01

    In the present study, the utilization of dilute CaCl2 extraction and free metal ion activity was tested for its ability to predict urease activity in soils that was measured by a simple and rapid urease assay. Two soil series (an Arkport sandy loam and a Hudson silty clay loam) were spiked with Cu and Zn, both singly and in combination, and then field aged for over a year prior to use. For both the metal-spiked Arkport and Hudson soils, much of the inhibition in measured urease activity was explained by increased CaCl2-extractable Cu, with a lesser effect from increased Zn extractability. A positive but weak interaction between Cu and Zn suggested by regression analysis indicates the toxicity of Cu-Zn mixtures to soil urease is slightly less than additive (antagonistic). Copper extractability using CaCl2 was able to predict urease activity in only one of the tested soils. By contrast, measurements of Cu2+ activity were predictive of reduced urease activity in both soils (R2adj = 0.726, p < 0.0001), indicating that Cu2+ activity is a more useful predictor of urease inhibition in soils than CaCl2-extractable Cu. The present study also highlighted the importance that clay mineral content had on controlling the availability of added metals in soils over time since a greater aging effect on Cu toxicity was found for the fine-textured Hudson than the coarse-textured Arkport soil.

  8. 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

  9. Sedimentary fluxes of 90Sr, 137Cs, 239,240Pu and 210Pb in the East Sea (Sea of Japan).

    PubMed

    Hong, G H; Lee, S H; Kim, S H; Chung, C S; Baskaran, M

    1999-09-30

    Sediment cores collected from the deep basins of the East Sea (Sea of Japan) provide an ongoing and historical record of artificial radionuclides contamination into one of the most highly publicized radioactive waste dumping areas in the world ocean. The depth distributions of 90Sr, 137Cs and 239,240Pu in sediment cores were investigated with the aid of 210Pb-derived sediment accumulation and mixing rates in the deep basins of the East Sea (Sea of Japan). Five box core samples were collected from the northern Yamato Ridge, Korea Plateau, Ulleung and Japan Basins below 1000-m depth. Sediment inventories of 137Cs and 239,240Pu are inversely correlated with water depth and linearly correlated with sediment accumulation rates. The inventories of these nuclides are linearly correlated with the accumulation rates of organic carbon in sediments. The 238Pu/239,240Pu activity ratios in sediments are 0.036 +/- 0.009 suggesting that most of the Pu to the study area is derived from the global fallout. The activity ratios of 239,240Pu/137Cs, and 90Sr/137Cs in bottom sediments are much lower than those of global fallout due to the differences of particle affinity and biological uptake of these nuclides. Sediment inventories of 90Sr and 137Cs constitute < 4% of the anticipated inventories from the global fallout, while those of 239,240Pu constitute 30-150% of the anticipated inventories from the global fallout. The residence time of the dissolved 239,240Pu in the study area is estimated to be 200-400 years based on the sediment inventory and/or sediment accumulation rate, and water column inventory.

  10. 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.

  11. Chemometric treatment of multimode laser-induced fluorescence (LIF) data of fuel-spiked soils

    NASA Astrophysics Data System (ADS)

    Van Benthem, Mark H.; Mitchell, Ben C.; Gillispie, Gregory D.; St. Germain, Randy W.

    1996-11-01

    Field screening of fuel-contaminated soils using laser- induced fluorescence is a cost effective and timely method of characterizing contaminated sites. Data collected with laser-based screening tools are often extensive and difficult to interpret. Pattern recognition algorithms can be utilized to enable less highly trained personnel to identify contaminants. In this work, fluorescence intensity of various hydrocarbon fuels deposited on various soil types was measured as a function of emission wavelength and decay time, generating wavelength-time matrices. The data were arranged into a three mode array and subjected to trilinear decomposition (TLD). The results of the TLD were then utilized in pattern recognition schemes, specifically, linear discrimination and classification and hierarchical cluster analysis. Classification rates and clustering results indicate that these techniques can be very valuable tools in site characterization.

  12. Beryllium-7 and lead-210 chronometry of modern soil processes: The Linked Radionuclide aCcumulation model, LRC

    NASA Astrophysics Data System (ADS)

    Landis, Joshua D.; Renshaw, Carl E.; Kaste, James M.

    2016-05-01

    Soil systems are known to be repositories for atmospheric carbon and metal contaminants, but the complex processes that regulate the introduction, migration and fate of atmospheric elements in soils are poorly understood. This gap in knowledge is attributable, in part, to the lack of an established chronometer that is required for quantifying rates of relevant processes. Here we develop and test a framework for adapting atmospheric lead-210 chronometry (210Pb; half-life 22 years) to soil systems. We propose a new empirical model, the Linked Radionuclide aCcumulation model (LRC, aka "lark"), that incorporates measurements of beryllium-7 (7Be; half-life 54 days) to account for 210Pb penetration of the soil surface during initial deposition, a process which is endemic to soils but omitted from conventional 210Pb models (e.g., the Constant Rate of Supply, CRS model) and their application to sedimentary systems. We validate the LRC model using the 1963-1964 peak in bomb-fallout americium-241 (241Am; half-life of 432 years) as an independent, corroborating time marker. In three different soils we locate a sharp 241Am weapons horizon at disparate depths ranging from 2.5 to 6 cm, but with concordant ages averaging 1967 ± 4 via the LRC model. Similarly, at one site contaminated with mercury (HgT) we find that the LRC model is consistent with the recorded history of Hg emission. The close agreement of Pb, Am and Hg behavior demonstrated here suggests that organo-metallic colloid formation and migration incorporates many trace metals in universal soil processes and that these processes may be described quantitatively using atmospheric 210Pb chronometry. The 210Pb models evaluated here show that migration rates of soil colloids on the order of 1 mm yr-1 are typical, but also that these rates vary systematically with depth and are attributable to horizon-specific processes of leaf-litter decay, eluviation and illuviation. We thus interpret 210Pb models to quantify (i) exposure

  13. Compost and sulfur affect the mobilization and phyto-availability of Cd and Ni to sorghum and barnyard grass in a spiked fluvial soil.

    PubMed

    Shaheen, Sabry M; Balbaa, Ali A; Khatab, Alaa M; Rinklebe, Jörg

    2017-04-25

    Soil reclamation via additives can cause contradictory effects on the mobilization of toxic elements in soils under dry and wet conditions. Therefore, our aim was to investigate the impact of compost and sulfur in two rates (1.25 and 2.5%) on fractionation, mobilization, and phyto-availability of cadmium (Cd) and nickel (Ni) to sorghum (dry soil) and barnyard grass (wet soil) in a fluvial soil spiked with 25 mg Cd or 200 mg Ni/kg soil. Compost decreased the solubility and mobilization of Cd (especially in dry soil) and Ni (in both soils). Sulfur increased the solubility of Cd (31% in dry soil-49% in wet soil) and Ni (4.6% in wet soil-8.7% in dry soil). Sulfur altered the carbonate fraction of Cd to the soluble fraction and the residual fraction of Cd and Ni to the non-residual fraction. Compost decreased Cd and increased Ni in sorghum, but enhanced Cd and degraded Ni in grass. Sulfur increased Cd and Ni in both plants, and the increasing rate of Cd was higher in grass than in sorghum, while Ni was higher in sorghum than in grass. These results suggest that compost can be used as an immobilizing agent for Cd in the dry soil and Ni in the wet soil; however, it might be used as mobilizing agent for Cd in the wet soil and Ni in the dry soil. Sulfur (with rate 2.5%) can be used for enhancing the phyto-extraction of Cd and Ni (especially Cd) from contaminated alkaline soils.

  14. Water and phosphorus content affect PAH dissipation in spiked soil planted with mycorrhizal alfalfa and tall fescue.

    PubMed

    Zhou, X B; Cébron, A; Béguiristain, T; Leyval, C

    2009-10-01

    Polycyclic aromatic hydrocarbon (PAH) dissipation efficiency can be increased in the plant rhizosphere, but may be affected by various environmental factors. We investigated the effects of the watering regime and phosphorus concentration on PAH dissipation in the rhizosphere of mycorrhizal plants in a pot experiment. Two plant species, alfalfa (Medicago sativa) and tall fescue (Festuca arundinacea), were co-cultured and inoculated with an arbuscular mycorrhizal (AM) fungus (Glomus intraradices) in PAH (phenanthrene (PHE)=500 mg kg(-1), pyrene (PYR)=500 mg kg(-1), dibenzo(a,h)anthracene (DBA)=65 mg kg(-1)) spiked agricultural soil for 6 weeks. Treatments with different phosphorus concentrations and watering regimes were compared. The PHE dissipation reached 90% in all treatments and was not affected by the treatments. The major finding was the significant positive impact of mycorrhizal plants on the dissipation of high molecular weight PAH (DBA) in high-water low-phosphorus treatment. Such an effect was not observed in high-water high-phosphorus and low-water low-phosphorus treatments, where AM colonization was very low. A positive linear relationship was detected between PYR dissipation and the percentage of Gram-positive PAH-ring hydroxylating dioxygenase genes in high-water high-phosphorus treatments, but not in the other two treatments with lower phosphorus concentrations and water contents. Such results indicated that the phosphorus and water regime were important parameters for the dissipation of HMW-PAH.

  15. Effects of randomly methylated-beta-cyclodextrins (RAMEB) on the bioavailability and aerobic biodegradation of polychlorinated biphenyls in three pristine soils spiked with a transformer oil.

    PubMed

    Fava, F; Ciccotosto, V F

    2002-03-01

    The low bioavailability of polychlorinated biphenyls (PCBs) in soils often results in their slow and partial aerobic biodegradation. The process can be enhanced by supplementing soils with cyclodextrins. However, pure cyclodextrins are expensive and we have therefore explored the use of a less costly technical grade mixture of randomly methylated-beta-cyclodextrins (RAMEB). RAMEB was tested at 0, 1, 3 and 5% (w/w) in the aerobic bioremediation and detoxification of a loamy-, a humic- and a sandy-soil, each artificially contaminated with a PCB-containing transformer oil (added PCBs: about 450 or 700 mg/kg), inoculated with an exogenous aerobic PCB-biodegrading bacterial co-culture and treated in slurry- and solid-phase laboratory conditions. Significant depletions of the spiked PCBs were observed in all microcosms of the three soils after 90 days of treatment; however, interesting yields of PCB dechlorination and detectable decreases of the original soil ecotoxicity were observed in the slurry-phase microcosms. RAMEB generally enhanced PCB-metabolism with effects which were dependent on the concentration at which it was applied, the physical-chemical nature of the amended soil, and the soil treatment conditions employed. RAMEB, which was slowly metabolized by soil microorganisms, enhanced the presence of PCBs and PCB-cometabolizing bacteria in the soil-water phase, suggesting that RAMEB enhances aerobic biodegradation of PCBs by increasing pollutant bioavailability in soil microcosms.

  16. Spiking solvent, humidity and their impact on 2,4-D and 2,4-DCP extractability from high humic matter content soils.

    PubMed

    Merini, Luciano Jose; Cuadrado, Virginia; Giulietti, Ana María

    2008-05-01

    The 2,4-dichlorophenoxyacetic acid (2,4-D) is a hormone-like herbicide widely used in agriculture. Although its half life in soil is approximately two weeks, the thousands of tons introduced in the environment every year represent a risk for human health and the environment. Considering the toxic properties of this compound and its degradation products, it is important to assess and monitor the 2,4-D residues in agricultural soils. Furthermore, experiments of phyto/bioremediation are carried out to find economic and environmental friendly tools to restore the polluted soils. Accordingly, it is essential to accurately measure the amount of 2,4-D and its metabolites in soils. There is evidence that 2,4-D extraction from soil samples seriously depends on the physical and chemical properties of the soil, especially in those soils with high content of humic acids. The aim of this work was to assess the variables that influence the recovery and subsequent analysis of 2,4-D and its main metabolite (2,4-dichlorophenol) from those soils samples. The results showed that the recovery efficiency depends on the solvent and method used for the extraction, the amount and kind of solvent used for dissolving the herbicide and the soil water content at the moment of spiking. An optimized protocol for the extraction and quantification of 2,4-D and its main metabolite from soil samples is presented.

  17. Is there a relationship between early genotoxicity and life-history traits in Vicia faba exposed to cadmium-spiked soils?

    PubMed

    Foltête, Anne-Sophie; Masfaraud, Jean-François; Férard, Jean-François; Cotelle, Sylvie

    2012-09-18

    The Vicia faba-micronucleus test is usually performed to assess the genotoxic potential of pure substances, effluents or water extracts from soil. It is also a relevant, early biological tool to detect mutagenic substances in crude soils. Nevertheless, the physiological meaning of such DNA damage for the plant in the long term remains to be elucidated. To know more about this, two experiments were carried out with the plant model V. faba. In a preliminary short-term experiment, seeds were exposed for five days to a soil spiked with different concentrations of CdCl(2) in order to identify the concentration inducing the highest number of micronuclei without affecting plant growth. Thereafter, a long-term experiment was performed in the soil spiked with such a concentration (i.e. 510μmol CdCl(2) per kg dry soil), in which V. faba seeds were directly sowed and allowed to grow during 151 days. As a result, Cd-spiked soil did not affect seed-emergence time nor the growth-rate of the plants for the first two months. The first signs of toxicity appeared after the 70th day of exposure. Interestingly, exposed plants produced their first flower earlier and had a longer flowering period than did control ones. Nevertheless, total flower production was less abundant in exposed plants than in control plants. Moreover, fruits appeared in control plants whereas no fruit was formed in exposed plants. At last, exposed plants showed a reduced life time. Our results suggest that the micronucleus assay can provide a predictive biomarker of long-term deleterious effects in plants.

  18. Bioaccessibility of arsenic and cadmium assessed for in vitro bioaccessibility in spiked soils and their interaction during the Unified BARGE Method (UBM) extraction.

    PubMed

    Xia, Qing; Peng, Cheng; Lamb, Dane; Mallavarapu, Megharaj; Naidu, Ravi; Ng, Jack C

    2016-03-01

    Recent decades have seen a growing popularity of in vitro bioaccessibility being utilised as a screening tool in human health risk assessment. However the existing bioaccessibility studies only focus on single contaminant. Considering human are likely to ingest multi-contaminants, these contaminants could interact within human gastrointestinal tract which may lead to an increase or decrease in bioaccessibility. In this study, seven different types of soil were spiked with arsenic (As) or cadmium (Cd) and aged for one year. The effects of soil properties on the bioaccessibility were examined. Moreover, the interaction between As and Cd in simulated human digestive system was studied by mixing As-spiked soil with Cd-spiked soil of the same type during bioaccessibility test. Results shows the bioaccessibility of As ranged from 40 ± 2.8 to 95 ± 1.3% in the gastric phase and 16 ± 2.0 to 96 ± 0.8% in the intestinal phase whilst a significant difference was observed between Cd gastric bioaccessibility (72 ± 4.3 to 99 ± 0.8%) and intestinal bioaccessibility (6.2 ± 0.3 to 45 ± 2.7%). Organic carbon, iron oxide and aluminium oxide were key parameters influencing the bioaccessibility of As (gastric and intestinal phases) and Cd (intestinal phase). No interactions between As and Cd during bioaccessibility test were observed in any soils, which indicates As and Cd may age independently and did not interact while being solubilised during bioaccessibility test. Thus additive effect may be proposed when estimating the bioaccessibility of mixtures of independently-aged As and Cd in soils. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. 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.

  20. 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

  1. Sequencing Bands of Ribosomal Intergenic Spacer Analysis Fingerprints for Characterization and Microscale Distribution of Soil Bacterium Populations Responding to Mercury Spiking

    PubMed Central

    Ranjard, Lionel; Brothier, Elisabeth; Nazaret, Sylvie

    2000-01-01

    Two major emerging bands (a 350-bp band and a 650-bp band) within the RISA (ribosomal intergenic spacer analysis) profile of a soil bacterial community spiked with Hg(II) were selected for further identification of the populations involved in the response of the community to the added metal. The bands were cut out from polyacrylamide gels, cloned, characterized by restriction analysis, and sequenced for phylogenetic affiliation of dominant clones. The sequences were the intergenic spacer between the rrs and rrl genes and the first 130 nucleotides of the rrl gene. Comparison of sequences derived from the 350-bp band to The GenBank database permitted us to identify the bacteria as being mostly close relatives to low G+C firmicutes (Clostridium-like genera), while the 650-bp band permitted us to identify the bacteria as being mostly close relatives to β-proteobacteria (Ralstonia-like genera). Oligonucleotide probes specific for the identified dominant bacteria were designed and hybridized with the RISA profiles derived from the control and spiked communities. These studies confirmed the contribution of these populations to the community response to the metal. Hybridization of the RISA profiles from subcommunities (bacterial pools associated with different soil microenvironments) also permitted to characterize the distribution and the dynamics of these populations at a microscale level following mercury spiking. PMID:11097911

  2. Effects of anthracene, pyrene and benzo[a]pyrene spiking and sewage sludge compost amendment on soil ecotoxicity during a bioremediation process.

    PubMed

    Hamdi, Helmi; Manusadzianas, Levonas; Aoyama, Isao; Jedidi, Naceur

    2006-11-01

    The fate of spiked anthracene, pyrene and benzo[a]pyrene in soil with or without sewage sludge compost was assessed during a 6-month bioremediation process simulating landfarming. Bioassays and physico-chemical analyses were employed to monitor toxicity change in soil samples and elutriates through ten sampling campaigns. Pearson product-moment correlation coefficient was determined to measure the strength of relationship between bioassays and physico-chemical analyses. The PAH dissipation in soil was enhanced after the first water addition, and the remaining amounts at the end of the experiment were positively correlated to the number of benzene rings and the presence of sewage sludge compost. Toxicity of soil elutriates to Daphnia magna was evident at early stages, originating exclusively from sewage sludge compost amendment. The lettuce root elongation was continuously inhibited by elutriates for all the treatments including control soil, probably due to high salinity or to unaddressed leachable phytotoxic compounds that were present in the experimental soil. The newly developed direct solid-phase chronic toxicity test using ostracod (Heterocypris incongruens) succeeded in evaluating the soil-bound PAH toxicity, as PAHs could not be detected in elutriates.

  3. Uptake of zinc, cadmium and phosphorus by arbuscular mycorrhizal maize (Zea mays L.) from a low available phosphorus calcareous soil spiked with zinc and cadmium.

    PubMed

    Shen, Hong; Christie, Peter; Li, Xiaolin

    2006-01-01

    In a multifactorial pot experiment, maize (Zea mays L.) with or without inoculation with the arbuscular mycorrhizal (AM) fungus Glomus mosseae BEG167 was grown in a sterilized soil spiked with three levels of zinc (0, 300 and 900 mg Zn kg(-1) soil) and three levels of cadmium (0, 25 and 100 mg Cd kg(-1) soil). At harvest after 8 weeks of growth, the proportion of root length of inoculated plants colonized decreased with increasing Zn or Cd addition, and was 56% in the absence of both metals and was reduced significantly to 27% in the presence of the higher levels of both metals. Mycorrhizal plants had higher biomass than non-mycorrhizal controls except at the highest soil level of Cd. Cadmium had more pronounced effects on plant biomass than did Zn at the levels studied and the two metals showed a significant interaction. The data suggest that mycorrhizal inoculation increased plant growth with enhancement of P nutrition, perhaps increasing plant tolerance to Zn and Cd by a dilution effect. AM inoculation also led to higher soil solution pH after harvest, possibly reducing the availability of the metals for plant uptake, and lowered the concentrations of soluble Zn and Cd in the soil solution, perhaps by adsorption onto the extrametrical mycelium.

  4. Is it clean or contaminated soil? Using petrogenic versus biogenic GC-FID chromatogram patterns to mathematically resolve false petroleum hydrocarbon detections in clean organic soils: a crude oil-spiked peat microcosm experiment.

    PubMed

    Kelly-Hooper, Francine; Farwell, Andrea J; Pike, Glenna; Kennedy, Jocelyn; Wang, Zhendi; Grunsky, Eric C; Dixon, D George

    2013-10-01

    The Canadian Council of Ministers of the Environment (CCME) reference method for the Canada-wide standard (CWS) for petroleum hydrocarbon (PHC) in soil provides chemistry analysis standards and guidelines for the management of contaminated sites. However, these methods can coextract natural biogenic organic compounds (BOCs) from organic soils, causing false exceedences of toxicity guidelines. The present 300-d microcosm experiment used CWS PHC tier 1 soil extraction and gas chromatography-flame ionization detector (GC-FID) analysis to develop a new tier 2 mathematical approach to resolving this problem. Carbon fractions F2 (C10-C16), F3 (C16-C34), and F4 (>C34) as well as subfractions F3a (C16-C22) and F3b (C22-C34) were studied in peat and sand spiked once with Federated crude oil. These carbon ranges were also studied in 14 light to heavy crude oils. The F3 range in the clean peat was dominated by F3b, whereas the crude oils had approximately equal F3a and F3b distributions. The F2 was nondetectable in the clean peat but was a significant component in crude oil. The crude oil–spiked peat had elevated F2 and F3a distributions. The BOC-adjusted PHC F3 calculation estimated the true PHC concentrations in the spiked peat. The F2:F3b ratio of less than 0.10 indicated PHC absence in the clean peat, and the ratio of greater than or equal to 0.10 indicated PHC presence in the spiked peat and sand. Validation studies are required to confirm whether this new tier 2 approach is applicable to real-case scenarios. Potential adoption of this approach could minimize unnecessary ecological disruptions of thousands of peatlands throughout Canada while also saving millions of dollars in management costs.

  5. 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).

  6. Remediation of PAH spiked soils: concentrated H2O2 treatment/continuous hot water extraction-oxidation.

    PubMed

    Rivas, Javier; Gimeno, Olga; de la Calle, Ruth G; Portela, Juan R; de la Ossa, Enrique Martínez

    2009-09-15

    Artificially contaminated soil with four different polynuclear aromatic hydrocarbons (acenaphthene, phenathrene, anthracene and fluoranthene) has been separately treated by two different processes: (A) concentrated hydrogen peroxide at mild conditions of temperature (343-393 K) and pressure (0.5 MPa) and (B) hot water extraction at relatively high temperature (523-657 K) and pressure (10 MPa). Both methods achieve acceptable PAH removal percentages from soil. Acenaphthene (the most soluble PAH) is completely removed with treatment A regardless of the operating conditions used. Under optimum conditions, the rest of PAHs are also eliminated to a high extent with both technologies. Temperature and hydrogen peroxide amount seem to play a major role in process A. Similarly, temperature and water flowrate are the most influencing parameters in process B. In the latter case, a post-stage for the extracting water cleaning is required.

  7. Combined effect of Cd and Pb spiked field soils on bioaccumulation, DNA damage, and peroxidase activities in Trifolium repens.

    PubMed

    Lanier, C; Bernard, F; Dumez, S; Leclercq, J; Lemière, S; Vandenbulcke, F; Nesslany, F; Platel, A; Devred, I; Cuny, D; Deram, A

    2016-01-01

    The present study was designed to investigate the combined effects of Cd and Pb on accumulation and genotoxic potential in white clover (Trifolium repens). For this purpose, T. repens was exposed to contaminated soils (2.5-20 mg kg(-1) cadmium (Cd), 250-2000 mg kg(-1) lead (Pb) and a mixture of these two heavy metals) for 3, 10 and 56 days. The resulting bioaccumulation of Cd and Pb, DNA damage (comet assay) and peroxidase activities (APOX and GPOX) were determined. The exposure time is a determinant factor in experiments designed to measure the influence of heavy metal contamination. The accumulation of Cd or Pb resulting from exposure to the two-metal mixture does not appear to depend significantly on whether the white clover is exposed to soil containing one heavy metal or both. However, when T. repens is exposed to a Cd/Pb mixture, the percentage of DNA damage is lower than when the plant is exposed to monometallic Cd. DNA damage is close to that observed in the case of monometallic Pb exposure. Peroxidase activity cannot be associated with DNA damage under these experimental conditions.

  8. Cadmium spiked soil modulates root organic acids exudation and ionic contents of two differentially Cd tolerant maize (Zea mays L.) cultivars.

    PubMed

    Javed, M Tariq; Akram, M Sohail; Tanwir, Kashif; Javed Chaudhary, Hassan; Ali, Qasim; Stoltz, Eva; Lindberg, Sylvia

    2017-07-01

    Our earlier work described that the roots of two maize cultivars, grown hydroponically, differentially responded to cadmium (Cd) stress by initiating changes in medium pH depending on their Cd tolerance. The current study investigated the root exudation, elemental contents and antioxidant behavior of the same maize cultivars [cv. 3062 (Cd-tolerant) and cv. 31P41 (Cd-sensitive)] under Cd stress. Plants were maintained in a rhizobox-like system carrying soil spiked with Cd concentrations of 0, 10, 20, 30, 40 and 50 μmol/kg soil. The root and shoot Cd contents increased, while Mg, Ca and Fe contents mainly decreased at higher Cd levels, and preferentially in the sensitive cultivar. Interestingly, the K contents increased in roots of cv. 3062 at low Cd treatments. The Cd stress caused acidosis of the maize root exudates predominantly in cv. 3062. The concentration of various organic acids was significantly increased in the root exudates of cv. 3062 with applied Cd levels. This effect was diminished in cv. 31P41 at higher Cd levels. Cd exposure increased the relative membrane permeability, anthocyanin (only in cv. 3062), proline contents and the activities of peroxidases (POD) and superoxide dismutase (SOD). The only exception was the catalase activity, which was diminished in both cultivars. Root Cd contents were positively correlated with the secretion of acetic acid, oxalic acid, glutamic acid, citric acid, and succinic acid. The antioxidants like POD and SOD exhibited a positive correlation with the organic acids under Cd stress. It is likly that a high exudation of dicarboxylic organic acids improves nutrient uptake and activities of antioxidants, which enables the tolerant cultivar to acclimatize in Cd polluted environment. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. A 2000-yr High-resolution Stalagmite Record From Zhenzhu Cave in Hebei, North China: Interpretations of AMS 14C, 230Th/U, 210Pb Dating, and δ18O, δ13C Results

    NASA Astrophysics Data System (ADS)

    Li, H. C.; Yin, J.; Rao, Z.; Mii, H. S.; Shen, C. C.; Pillutla, R. K.; Li, Y. X.

    2016-12-01

    An 11.1-cm long stalagmite (ZZ12) collected from Zhenzhu cave (38°15'N, 113°42'E, 975m a.s.l.) located at Tiangui mountain of Hebei province, North China. The 230Th/U dates on 12 horizons exhibit large uncertainties with many reversed age sequences due to low U contents and low 230Th/232Th ratios. While the 230Th/U dating is not able to provide the chronology of this stalagmite, AMS 14C dating on 27 samples from various depths of the stalagmite yields a reliable age-depth relationship. Three AMS 14C dates from the top 5 mm appear nuclear bomb carbon indicating that this part was deposited after AD 1950. Seven samples for 210Pb dating were taken from the upper 14 mm with 2 mm intervals, showing exponential decay of excess 210Pb and supporting the AMS 14C dating results. At the base of the stalagmite, charcoal grains were included in the carbonate stalagmite. This charcoal sample has a Calibrated 14C age of 1865±20 a BP. The carbonates at adjacent depths show Calibrated 14C ages of 1900±15 and 2215±75 a BP respectively. The bomb carbon and similar ages between the charcoal and carbonates indicate that dead carbon influence on the 14C dates in some horizons may not be serious. From the 27 AMS 14C dates, we select 17 AMS 14C dates which have minimal influence of dead carbon fraction to construct the chronology. The established chronology shows that slow growth rates occurred prior to 1100 a BP and after 600 a BP. This time interval involves the Medieval Warm Period, while the fast growth rate during this interval may reflect warm and wet climatic conditions. A total of 835 samples were drilled from the stalagmite for δ18O and δ13C analyses. The current 900-year δ18O and δ13C records reveal climate and vegetation changes in the study area. Strong decadal oscillations in the δ18O record reflect variations of monsoonal rain, with relatively dry between AD 1350 and AD 1550 and after AD 1960. The δ13C record appears mainly multi-centennial variations with a 4

  10. 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.

  11. Supercritical CO(2) extraction of PAHs on spiked soil Co-solvent effect and solvent regeneration by ozonization.

    PubMed

    Rivas, Javier; Gimeno, Olga; Mantell, Casimiro; Portela, Juan R; Martinez de la Ossa, Enrique J; de la Calle, Ruth G

    2009-03-15

    The supercritical CO(2) extraction of four PAHs (acenaphthene, phenanthrene, anthracene and fluoranthene) from an artificially contaminated soil has been investigated. The effect of temperature (40-60 degrees C), pressure (300-500 bar) and extraction time (90-150 min) has been assessed by conducting a Box-Behnken experimental design. The results suggest the existence of perturbation variables other than the aforementioned controlled variables leading to a significant dispersion of extraction recoveries. With the exception of anthracene, an optimum in temperature (50 degrees C) is envisaged when extracting the PAHs. Analogously, with the exception of anthracene (positive effect), pressure does not have a significant influence. The recovery yield increases as extraction time is increased to a value of 120 min. No further improvement is experienced thereafter. If a co-solvent is used (H(2)O(2) aqueous solution) a beneficial effect can be noticed. Hydrogen peroxide concentration did exert no significant influence in the process. Methanol used to collect the extracted PAHs could be regenerated by gaseous ozone and reused in several consecutive runs.

  12. Investigation of the soil-plant transfer of primordial radionuclides in tomatoes by low-level gamma-ray spectrometry.

    PubMed

    Köhler, M; Gleisberg, B; Niese, S

    2000-01-01

    The paper presents actual data from investigations of the soil-plant transfer of the primordial radionuclides 40K, 238U, 226Ra, 210Pb and 227Ac for tomatoes growing at soils from former uranium mining areas. The analysis were carried out using low-level gamma-ray spectrometry in a 47 m deep underground laboratory. For tomato fruits transfer factors of (0.0007 +/- 0.0006) for 235U, (0.0021 +/- 0.0017) for 226Ra, (0.0015 +/- 0.0009) for 210Pb and (0.0018 +/- 0.0012) for 227Ac were obtained. The investigation of the soil-plant transfer by low-level gamma-ray spectrometry is often limited by the Compton-continuum from the always present high-energy gamma-ray emitter 40K.

  13. Low level measurements of natural radionuclides in soil samples around a coal-fired power plant

    NASA Astrophysics Data System (ADS)

    Rosner, G.; Bunzl, K.; Hötzl, H.; Winkler, R.

    1984-06-01

    To detect a possible contribution of airborne radioactivity from stack effluents to the soil radioactivity, several radionuclides in the soil around a coal-fired power plant have been determined. A plant situated in a rural region of Bavaria was selected to minimize contributions from other civilisatory sources. The soil sampling network consisted of 5 concentric circles with diameters between 0.4 and 5.2 km around the plant, 16 sampling points being distributed regularly on each circle. Radiochemical analysis techniques for 210Pb and 210Po in soil samples of several grams had to be developed. They include a wet dissolution procedure, simultaneous precipitation of lead and polonium as the sulfides, purification via lead sulfate, counting of the lead as the chromate in a low-level beta counter and alpha spectrometric determination of the 210Po in a gridded ionization chamber. The 238U, 226Ra, 232Th and 40K were counted by low level gamma spectrometry. Specific activities found were in the range of 0.7 to 2.0 pCi g -1 for 210Pb and 0.3 to 1.6 pCi g -1 for 226Ra. The distribution patterns of 210Po and 210Pb around the plant were found to be similar. They were different, however, from that of 226Ra. The highest 210Pb/ 226Ra activity ratio was 3.9 at a distance of 0.76 km SSE from the plant. Nevertheless, the evidence is not considered to be sufficient to attribute these observations unambiguously to plant releases.

  14. Bioaccessibility of U, Th and Pb in solid wastes and soils from an abandoned uranium mine.

    PubMed

    Foulkes, Michael; Millward, Geoffrey; Henderson, Samuel; Blake, William

    2016-12-12

    Bioaccessible U, Th, Pb and the (238)U decay products (214)Pb and (210)Pb have been determined, using a modified Unified BARGE Method (UBM), in waste solids and soils from an abandoned uranium mine in South West England, UK. Maximum aqua regia extractable concentrations for U, Th and Pb were 16,200, 3.8 and 4750 μg g(-1), respectively. (238)U had highest activity concentrations near the mine shaft, where the decay products(214)Pb and (210)Pb had values of 235 and 180 Bq g(-1), respectively. UBM extractions gave mean gastro-intestinal bioaccessibility factors (BAFs) for U and Pb in the waste solids of 0.05 and 0.03, respectively, whereas those for the soils were significantly higher at 0.24 and 0.17. The mean BAFs for the transient radionuclides, (214)Pb and (210)Pb, were similar to those for stable Pb implying that the stable and radioactive Pb isotopes were attached to similar sites on the particles. The doses arising from the ingestion of particulate (210)Pb due to soil pica behaviour were in the range 0.2-65 and < 0.1-6.2 μSv day(-1) for a 1-year old child or an adult (>17 years), respectively. The results suggest that the health risk posed by abandoned uranium mines, with waste rock and tailings, throughout the world should take account of the dose due to both bioaccessible radionuclides, as well as their stable counterparts.

  15. Monitoring spike train synchrony.

    PubMed

    Kreuz, Thomas; Chicharro, Daniel; Houghton, Conor; Andrzejak, Ralph G; Mormann, Florian

    2013-03-01

    Recently, the SPIKE-distance has been proposed as a parameter-free and timescale-independent measure of spike train synchrony. This measure is time resolved since it relies on instantaneous estimates of spike train dissimilarity. However, its original definition led to spuriously high instantaneous values for eventlike firing patterns. Here we present a substantial improvement of this measure that eliminates this shortcoming. The reliability gained allows us to track changes in instantaneous clustering, i.e., time-localized patterns of (dis)similarity among multiple spike trains. Additional new features include selective and triggered temporal averaging as well as the instantaneous comparison of spike train groups. In a second step, a causal SPIKE-distance is defined such that the instantaneous values of dissimilarity rely on past information only so that time-resolved spike train synchrony can be estimated in real time. We demonstrate that these methods are capable of extracting valuable information from field data by monitoring the synchrony between neuronal spike trains during an epileptic seizure. Finally, the applicability of both the regular and the real-time SPIKE-distance to continuous data is illustrated on model electroencephalographic (EEG) recordings.

  16. Dendritic spikes veto inhibition.

    PubMed

    Stuart, Greg J

    2012-09-06

    How inhibition regulates dendritic excitability is critical to an understanding of the way neurons integrate the many thousands of synaptic inputs they receive. In this issue of Neuron, Müller et al. (2012) show that inhibition blocks the generation of weak dendritic spikes, leaving strong dendritic spikes intact. Copyright © 2012 Elsevier Inc. All rights reserved.

  17. Neuronal communication: firing spikes with spikes.

    PubMed

    Brecht, Michael

    2012-08-21

    Spikes of single cortical neurons can exert powerful effects even though most cortical synapses are too weak to fire postsynaptic neurons. A recent study combining single-cell stimulation with population imaging has visualized in vivo postsynaptic firing in genetically identified target cells. The results confirm predictions from in vitro work and might help to understand how the brain reads single-neuron activity.

  18. Toxicity of ZnO nanoparticles, ZnO bulk, and ZnCl₂ on earthworms in a spiked natural soil and toxicological effects of leachates on aquatic organisms.

    PubMed

    García-Gómez, C; Babin, M; Obrador, A; Álvarez, J M; Fernández, M D

    2014-11-01

    The present study assessed the uptake and toxicity of ZnO nanoparticles (NPs), ZnO bulk, and ZnCl₂ salt in earthworms in spiked agricultural soils. In addition, the toxicity of aqueous extracts to Daphnia magna and Chlorella vulgaris was analyzed to determine the risk of these soils to the aquatic compartment. We then investigated the distribution of Zn in soil fractions to interpret the nature of toxicity. Neither mortality nor differences in earthworm body weight were observed compared with the control. The most sensitive end point was reproduction. ZnCl₂ was notably toxic in eliminating the production of cocoons. The effects induced by ZnO-NPs and bulk ZnO on fecundity were similar and lower than those of the salt. In contrast to ZnO bulk, ZnO-NPs adversely affected fertility. The internal concentrations of Zn in earthworms in the NP group were greater than those in the salt and bulk groups, although bioconcentration factors were consistently <1. No relationship was found between toxicity and internal Zn amounts in earthworms. The results from the sequential extraction of soil showed that ZnCl₂ displayed the highest availability compared with both ZnO. Zn distribution was consistent with the greatest toxicity showed by the salt but not with Zn body concentrations. The soil extracts from both ZnO-NPs and bulk ZnO did not show effects on aquatic organisms (Daphnia and algae) after short-term exposure. However, ZnCl₂ extracts (total and 0.45-μm filtered) were toxic to Daphnia.

  19. Solar Decameter Spikes

    NASA Astrophysics Data System (ADS)

    Melnik, V. N.; Shevchuk, N. V.; Konovalenko, A. A.; Rucker, H. O.; Dorovskyy, V. V.; Poedts, S.; Lecacheux, A.

    2014-05-01

    We analyze and discuss the properties of decameter spikes observed in July - August 2002 by the UTR-2 radio telescope. These bursts have a short duration (about one second) and occur in a narrow frequency bandwidth (50 - 70 kHz). They are chaotically located in the dynamic spectrum. Decameter spikes are weak bursts: their fluxes do not exceed 200 - 300 s.f.u. An interesting feature of these spikes is the observed linear increase of the frequency bandwidth with frequency. This dependence can be explained in the framework of the plasma mechanism that causes the radio emission, taking into account that Langmuir waves are generated by fast electrons within a narrow angle θ≈13∘ - 18∘ along the direction of the electron propagation. In the present article we consider the problem of the short lifetime of decameter spikes and discuss why electrons generate plasma waves in limited regions.

  20. Production of a microcapsule agent of chromate-reducing Lysinibacillus fusiformis ZC1 and its application in remediation of chromate-spiked soil.

    PubMed

    Huang, Jun; Li, Jingxin; Wang, Gejiao

    2016-01-01

    Lysinibacillus fusiformis ZC1 is an efficient Cr(VI)-reducing bacterium that can transform the toxic and soluble chromate [Cr(VI)] form to the less toxic and precipitated chromite form [Cr(III)]. As such, this strain might be applicable for bioremediation of Cr(VI) in soil by reducing its bioavailability. The study objective was to prepare a microcapsule agent of strain ZC1 for bioremediation of Cr(VI)-contaminated soil. Using a single-factor orthogonal array design, the optimal fermentation medium was obtained and consisted of 6 g/L corn flour, 12 g/L soybean flour, 8 g/L NH4Cl and 6 g/L CaCl2. After enlarged fermentation, the cell and spore densities were 5.9 × 10(9) and 1.7 × 10(8) cfu/mL, respectively. The fermentation products were collected and embedded with 1 % gum arabic and 1 % sorbitol as the microcapsule carriers and were subsequently spray-dried. Strain ZC1 exhibited viable cell counts of (3.6 ± 0.44) × 10(10) cfu/g dw after 50-day storage at room temperature. In simulated soil bioremediation experiments, 67 % of Cr(VI) was reduced in 5 days with the inoculation of this microcapsule agent, and the Cr(VI) concentration was below the soil Cr(VI) standard level. The results demonstrated that the microcapsule agent of strain ZC1 is efficient for bioremediation of Cr(VI)-contaminated soil.

  1. ON RELATION OF SOIL MOISTURE TO DEVELOPMENT OF RICE BLAST DISEASE WITH SPECIAL REFERENCE TO RESULTS OF INOCULATION EXPERIMENTS ON LEAVES AND SPIKE PEDICELS OF PLANTS GROWN IN SOILS DIFFERING IN MOISTURE AND IN AMOUNTS OF SILICA AND FERTILIZER,

    DTIC Science & Technology

    moisture content, and fertilizer and silica application. The susceptibility of the rice plant to rice blast disease varied inversely with the moisture...content of the soil irrespective of the amount of fertilizer or silica applied or of the stage of growth of the plant. Dryness of the soil tended to...fertilization were more easily infected than plants grown on irrigated soil with double the amount of fertilizer . This proves that even with double the

  2. Spike sorting of synchronous spikes from local neuron ensembles

    PubMed Central

    Pröpper, Robert; Alle, Henrik; Meier, Philipp; Geiger, Jörg R. P.; Obermayer, Klaus; Munk, Matthias H. J.

    2015-01-01

    Synchronous spike discharge of cortical neurons is thought to be a fingerprint of neuronal cooperativity. Because neighboring neurons are more densely connected to one another than neurons that are located further apart, near-synchronous spike discharge can be expected to be prevalent and it might provide an important basis for cortical computations. Using microelectrodes to record local groups of neurons does not allow for the reliable separation of synchronous spikes from different cells, because available spike sorting algorithms cannot correctly resolve the temporally overlapping waveforms. We show that high spike sorting performance of in vivo recordings, including overlapping spikes, can be achieved with a recently developed filter-based template matching procedure. Using tetrodes with a three-dimensional structure, we demonstrate with simulated data and ground truth in vitro data, obtained by dual intracellular recording of two neurons located next to a tetrode, that the spike sorting of synchronous spikes can be as successful as the spike sorting of nonoverlapping spikes and that the spatial information provided by multielectrodes greatly reduces the error rates. We apply the method to tetrode recordings from the prefrontal cortex of behaving primates, and we show that overlapping spikes can be identified and assigned to individual neurons to study synchronous activity in local groups of neurons. PMID:26289473

  3. Multichannel sparse spike inversion

    NASA Astrophysics Data System (ADS)

    Pereg, Deborah; Cohen, Israel; Vassiliou, Anthony A.

    2017-10-01

    In this paper, we address the problem of sparse multichannel seismic deconvolution. We introduce multichannel sparse spike inversion as an iterative procedure, which deconvolves the seismic data and recovers the Earth two-dimensional reflectivity image, while taking into consideration the relations between spatially neighboring traces. We demonstrate the improved performance of the proposed algorithm and its robustness to noise, compared to competitive single-channel algorithm through simulations and real seismic data examples.

  4. Spiking neural network for recognizing spatiotemporal sequences of spikes

    NASA Astrophysics Data System (ADS)

    Jin, Dezhe Z.

    2004-02-01

    Sensory neurons in many brain areas spike with precise timing to stimuli with temporal structures, and encode temporally complex stimuli into spatiotemporal spikes. How the downstream neurons read out such neural code is an important unsolved problem. In this paper, we describe a decoding scheme using a spiking recurrent neural network. The network consists of excitatory neurons that form a synfire chain, and two globally inhibitory interneurons of different types that provide delayed feedforward and fast feedback inhibition, respectively. The network signals recognition of a specific spatiotemporal sequence when the last excitatory neuron down the synfire chain spikes, which happens if and only if that sequence was present in the input spike stream. The recognition scheme is invariant to variations in the intervals between input spikes within some range. The computation of the network can be mapped into that of a finite state machine. Our network provides a simple way to decode spatiotemporal spikes with diverse types of neurons.

  5. An investigation into the upward transport of uranium-series radionuclides in soils and uptake by plants.

    PubMed

    Pérez-Sánchez, D; Thorne, M C

    2014-09-01

    soil, but to assume that both (210)Pb and (210)Po can be treated as being present in secular equilibrium with the (226)Ra. This simplification is not always appropriate. Where geochemical conditions are such that the (226)Ra migrates upward in the soil column faster than (210)Pb and (210)Po, disequilibrium is not a significant issue, as the (226)Ra supports (210)Pb and (210)Po at concentrations somewhat below those estimated on the basis of assumed secular equilibrium. However, for low, but realistic, values of the distribution coefficients for (210)Pb and (210)Po and high, but realistic, distribution coefficients for (226)Ra, the (210)Pb and (210)Po can reach the surface soil in high concentrations that are not locally supported by (226)Ra. This means that models based on the assumption of secular equilibrium should not be employed without a careful consideration of the hydrological and hydrochemical situation of interest.

  6. Soil erosion under a modified form of shifting cultivation system in the monsoonal climate of the Meghalaya Plateau (India)

    NASA Astrophysics Data System (ADS)

    Prokop, Pawel; Poreba, Grzegorz

    2014-05-01

    The soil erosion rates were studied, in a small catchment under a modified form of shifting cultivation on the hilly Meghalaya Plateau, using the 137Cs and 210Pb techniques. Those methods allow assessing mid-term soil erosion for the last 50-150 years. The mass balance models were applied to calculate soil erosion for both radioisotopes. The estimated annual soil loss from cultivated fields and degraded grassland reached up to 79 t/ha/year and 0.5 t/ha/year respectively. Soil erosion and deposition patterns are much influenced by land use. Within the same land use category, soil erosion rates are strongly related to slope steepness. Both radioisotopes show similar deposition rates as well as similar maximum depth of deposition in the valley floor. This indicates acceleration of soil erosion in response to population growth in the last few decades.

  7. Lyondell outage spikes prices

    SciTech Connect

    1996-08-07

    Methanol spot markets in the US Gulf Coast cooled a bit late last week from their Monday spike in the wake of a pipeline rupture and fire that shut down Lyondell Petrochemical`s Channelview, TX complex and its 248-million gal/year methanol plant. The unit resumed production last week and was expected to return to full service by August 3. Offering prices shot up at least 10% over the pre-accident level of about 50 cts/gal fob. No actual business could be confirmed at a price of more than 52 cts-53 cts/gal, however.

  8. Radioxenon spiked air

    DOE PAGES

    Watrous, Matthew G.; Delmore, James E.; Hague, Robert K.; ...

    2015-08-27

    Four of the radioactive xenon isotopes (131mXe, 133mXe, 133Xe and 135Xe) with half-lives ranging from 9 h to 12 days are produced from nuclear fission and can be detected from days to weeks following their production and release. Being inert gases, they are readily transported through the atmosphere. Sources for release of radioactive xenon isotopes include operating nuclear reactors via leaks in fuel rods, medical isotope production facilities, and nuclear weapons' detonations. They are not normally released from fuel reprocessing due to the short half-lives. The Comprehensive Nuclear-Test-Ban Treaty has led to creation of the International Monitoring System. The Internationalmore » Monitoring System, when fully implemented, will consist of one component with 40 stations monitoring radioactive xenon around the globe. Monitoring these radioactive xenon isotopes is important to the Comprehensive Nuclear-Test-Ban Treaty in determining whether a seismically detected event is or is not a nuclear detonation. A variety of radioactive xenon quality control check standards, quantitatively spiked into various gas matrices, could be used to demonstrate that these stations are operating on the same basis in order to bolster defensibility of data across the International Monitoring System. This study focuses on Idaho National Laboratory's capability to produce three of the xenon isotopes in pure form and the use of the four xenon isotopes in various combinations to produce radioactive xenon spiked air samples that could be subsequently distributed to participating facilities.« less

  9. Rayleigh--Taylor spike evaporation

    SciTech Connect

    Schappert, G. T.; Batha, S. H.; Klare, K. A.; Hollowell, D. E.; Mason, R. J.

    2001-09-01

    Laser-based experiments have shown that Rayleigh--Taylor (RT) growth in thin, perturbed copper foils leads to a phase dominated by narrow spikes between thin bubbles. These experiments were well modeled and diagnosed until this '' spike'' phase, but not into this spike phase. Experiments were designed, modeled, and performed on the OMEGA laser [T. R. Boehly, D. L. Brown, R. S. Craxton , Opt. Commun. 133, 495 (1997)] to study the late-time spike phase. To simulate the conditions and evolution of late time RT, a copper target was fabricated consisting of a series of thin ridges (spikes in cross section) 150 {mu}m apart on a thin flat copper backing. The target was placed on the side of a scale-1.2 hohlraum with the ridges pointing into the hohlraum, which was heated to 190 eV. Side-on radiography imaged the evolution of the ridges and flat copper backing into the typical RT bubble and spike structure including the '' mushroom-like feet'' on the tips of the spikes. RAGE computer models [R. M. Baltrusaitis, M. L. Gittings, R. P. Weaver, R. F. Benjamin, and J. M. Budzinski, Phys. Fluids 8, 2471 (1996)] show the formation of the '' mushrooms,'' as well as how the backing material converges to lengthen the spike. The computer predictions of evolving spike and bubble lengths match measurements fairly well for the thicker backing targets but not for the thinner backings.

  10. Radioxenon spiked air

    SciTech Connect

    Watrous, Matthew G.; Delmore, James E.; Hague, Robert K.; Houghton, Tracy P.; Jenson, Douglas D.; Mann, Nick R.

    2015-08-27

    Four of the radioactive xenon isotopes (131mXe, 133mXe, 133Xe and 135Xe) with half-lives ranging from 9 h to 12 days are produced from nuclear fission and can be detected from days to weeks following their production and release. Being inert gases, they are readily transported through the atmosphere. Sources for release of radioactive xenon isotopes include operating nuclear reactors via leaks in fuel rods, medical isotope production facilities, and nuclear weapons' detonations. They are not normally released from fuel reprocessing due to the short half-lives. The Comprehensive Nuclear-Test-Ban Treaty has led to creation of the International Monitoring System. The International Monitoring System, when fully implemented, will consist of one component with 40 stations monitoring radioactive xenon around the globe. Monitoring these radioactive xenon isotopes is important to the Comprehensive Nuclear-Test-Ban Treaty in determining whether a seismically detected event is or is not a nuclear detonation. A variety of radioactive xenon quality control check standards, quantitatively spiked into various gas matrices, could be used to demonstrate that these stations are operating on the same basis in order to bolster defensibility of data across the International Monitoring System. This study focuses on Idaho National Laboratory's capability to produce three of the xenon isotopes in pure form and the use of the four xenon isotopes in various combinations to produce radioactive xenon spiked air samples that could be subsequently distributed to participating facilities.

  11. Predictability of EEG interictal spikes.

    PubMed Central

    Scott, D A; Schiff, S J

    1995-01-01

    To determine whether EEG spikes are predictable, time series of EEG spike intervals were generated from subdural and depth electrode recordings from four patients. The intervals between EEG spikes were hand edited to ensure high accuracy and eliminate false positive and negative spikes. Spike rates (per minute) were generated from longer time series, but for these data hand editing was usually not feasible. Linear and nonlinear models were fit to both types of data. One patient had no linear or nonlinear predictability, two had predictability that could be well accounted for with a linear stochastic model, and one had a degree of nonlinear predictability for both interval and rate data that no linear model could adequately account for. PMID:8580318

  12. Scalable hybrid computation with spikes.

    PubMed

    Sarpeshkar, Rahul; O'Halloran, Micah

    2002-09-01

    We outline a hybrid analog-digital scheme for computing with three important features that enable it to scale to systems of large complexity: First, like digital computation, which uses several one-bit precise logical units to collectively compute a precise answer to a computation, the hybrid scheme uses several moderate-precision analog units to collectively compute a precise answer to a computation. Second, frequent discrete signal restoration of the analog information prevents analog noise and offset from degrading the computation. And, third, a state machine enables complex computations to be created using a sequence of elementary computations. A natural choice for implementing this hybrid scheme is one based on spikes because spike-count codes are digital, while spike-time codes are analog. We illustrate how spikes afford easy ways to implement all three components of scalable hybrid computation. First, as an important example of distributed analog computation, we show how spikes can create a distributed modular representation of an analog number by implementing digital carry interactions between spiking analog neurons. Second, we show how signal restoration may be performed by recursive spike-count quantization of spike-time codes. And, third, we use spikes from an analog dynamical system to trigger state transitions in a digital dynamical system, which reconfigures the analog dynamical system using a binary control vector; such feedback interactions between analog and digital dynamical systems create a hybrid state machine (HSM). The HSM extends and expands the concept of a digital finite-state-machine to the hybrid domain. We present experimental data from a two-neuron HSM on a chip that implements error-correcting analog-to-digital conversion with the concurrent use of spike-time and spike-count codes. We also present experimental data from silicon circuits that implement HSM-based pattern recognition using spike-time synchrony. We outline how HSMs may be

  13. Mapping Spikes to Sensations

    PubMed Central

    Stüttgen, Maik C.; Schwarz, Cornelius; Jäkel, Frank

    2011-01-01

    Single-unit recordings conducted during perceptual decision-making tasks have yielded tremendous insights into the neural coding of sensory stimuli. In such experiments, detection or discrimination behavior (the psychometric data) is observed in parallel with spike trains in sensory neurons (the neurometric data). Frequently, candidate neural codes for information read-out are pitted against each other by transforming the neurometric data in some way and asking which code’s performance most closely approximates the psychometric performance. The code that matches the psychometric performance best is retained as a viable candidate and the others are rejected. In following this strategy, psychometric data is often considered to provide an unbiased measure of perceptual sensitivity. It is rarely acknowledged that psychometric data result from a complex interplay of sensory and non-sensory processes and that neglect of these processes may result in misestimating psychophysical sensitivity. This again may lead to erroneous conclusions regarding the adequacy of candidate neural codes. In this review, we first discuss requirements on the neural data for a subsequent neurometric-psychometric comparison. We then focus on different psychophysical tasks for the assessment of detection and discrimination performance and the cognitive processes that may underlie their execution. We discuss further factors that may compromise psychometric performance and how they can be detected or avoided. We believe that these considerations point to shortcomings in our understanding of the processes underlying perceptual decisions, and therefore offer potential for future research. PMID:22084627

  14. Soils

    Treesearch

    Emily Moghaddas; Ken Hubbert

    2014-01-01

    When managing for resilient forests, each soil’s inherent capacity to resist and recover from changes in soil function should be evaluated relative to the anticipated extent and duration of soil disturbance. Application of several key principles will help ensure healthy, resilient soils: (1) minimize physical disturbance using guidelines tailored to specific soil types...

  15. Geochemistry and Chemical Weathering in Soils along an Earthworm Invasion Gradient

    NASA Astrophysics Data System (ADS)

    Resner, K.; Yoo, K.; Aufdenkampe, A. K.; Hale, C.; Sebestyen, S. D.

    2010-12-01

    One of the central tenets in geomorphology is that a chemical denudation rate is limited by the total denudation rate, which controls how fast minerals are exposed to reactive environments of the earth’s surface. Though the mineral supply rate has been routinely tied to tectonic uplifts, in soil mantled landscapes, organisms such as earthworms may also significantly contribute to exposing minerals to varying geochemical environments and thus altering chemical denudation rates of the landscapes they inhabit through mineral translocation. In glaciated parts of North America, many forests evolved without native earthworms, since the last glacial retreat, until they were invaded by exotic earthworm species that arrived with agriculture, recreational fishing, and logging. Therefore, an earthworm invasion chronosequence in northern Minnesota--the focus of this ongoing study--provides an ideal natural laboratory to quantitatively study how burrowing organisms, by mixing soils, contribute to chemically denuding the landscapes. We are currently determining the inorganic chemistry of soils along a ~200 meter long transect that includes pre earthworm invasion soils as well as soils populated with several earthworm species with different burrowing habits. Additionally, six soils pits along the transect are densely installed with lysimeters, piezometers, and gas sampling tubes. The soils’ elemental chemistry profiles show that earthworms have significantly relocated minerals vertically, which is consistent with the 210Pb activity profiles determined with gamma spectroscopy. Major elements, depending on their solubility, biological demands, and susceptibility to be complexed with organic matter, respond to the enhanced mixing rates in different ways. To constrain the impacts of earthworm burrowing on chemical denudation, we are also measuring cations, anions, and alkalinity in the water samples collected with the lysimeters and piezometers. Ultimately, the soil and water

  16. Dendritic Spikes in Sensory Perception.

    PubMed

    Manita, Satoshi; Miyakawa, Hiroyoshi; Kitamura, Kazuo; Murayama, Masanori

    2017-01-01

    What is the function of dendritic spikes? One might argue that they provide conditions for neuronal plasticity or that they are essential for neural computation. However, despite a long history of dendritic research, the physiological relevance of dendritic spikes in brain function remains unknown. This could stem from the fact that most studies on dendrites have been performed in vitro. Fortunately, the emergence of novel techniques such as improved two-photon microscopy, genetically encoded calcium indicators (GECIs), and optogenetic tools has provided the means for vital breakthroughs in in vivo dendritic research. These technologies enable the investigation of the functions of dendritic spikes in behaving animals, and thus, help uncover the causal relationship between dendritic spikes, and sensory information processing and synaptic plasticity. Understanding the roles of dendritic spikes in brain function would provide mechanistic insight into the relationship between the brain and the mind. In this review article, we summarize the results of studies on dendritic spikes from a historical perspective and discuss the recent advances in our understanding of the role of dendritic spikes in sensory perception.

  17. Dendritic Spikes in Sensory Perception

    PubMed Central

    Manita, Satoshi; Miyakawa, Hiroyoshi; Kitamura, Kazuo; Murayama, Masanori

    2017-01-01

    What is the function of dendritic spikes? One might argue that they provide conditions for neuronal plasticity or that they are essential for neural computation. However, despite a long history of dendritic research, the physiological relevance of dendritic spikes in brain function remains unknown. This could stem from the fact that most studies on dendrites have been performed in vitro. Fortunately, the emergence of novel techniques such as improved two-photon microscopy, genetically encoded calcium indicators (GECIs), and optogenetic tools has provided the means for vital breakthroughs in in vivo dendritic research. These technologies enable the investigation of the functions of dendritic spikes in behaving animals, and thus, help uncover the causal relationship between dendritic spikes, and sensory information processing and synaptic plasticity. Understanding the roles of dendritic spikes in brain function would provide mechanistic insight into the relationship between the brain and the mind. In this review article, we summarize the results of studies on dendritic spikes from a historical perspective and discuss the recent advances in our understanding of the role of dendritic spikes in sensory perception. PMID:28261060

  18. Soil

    USDA-ARS?s Scientific Manuscript database

    Soil is a diverse natural material characterized by solid, liquid, and gas phases that impart unique chemical, physical, and biological properties. Soil provides many key functions, including supporting plant growth and providing environmental remediation. Monitoring key soil properties and processe...

  19. Spikes removal in surface measurement

    NASA Astrophysics Data System (ADS)

    Podulka, P.; Pawlus, P.; Dobrzański, P.; Lenart, A.

    2014-03-01

    Several cylinder surface topographies made from grey cast iron were measured by Talysurf CCI white light interferometer with and without use of spikes filter. They were plateau honed by abrasive stones. Measured area was 3.3 mm × 3.3 mm, height resolution was 0.01 nm. The forms were eliminated using polynomial of the 3rd degree. After it, spikes were removed using four methods. These approaches were compared. Parameters of the smaller and highest sensitivity on spikes presence were selected.

  20. Spiking neural networks for cortical neuronal spike train decoding.

    PubMed

    Fang, Huijuan; Wang, Yongji; He, Jiping

    2010-04-01

    Recent investigation of cortical coding and computation indicates that temporal coding is probably a more biologically plausible scheme used by neurons than the rate coding used commonly in most published work. We propose and demonstrate in this letter that spiking neural networks (SNN), consisting of spiking neurons that propagate information by the timing of spikes, are a better alternative to the coding scheme based on spike frequency (histogram) alone. The SNN model analyzes cortical neural spike trains directly without losing temporal information for generating more reliable motor command for cortically controlled prosthetics. In this letter, we compared the temporal pattern classification result from the SNN approach with results generated from firing-rate-based approaches: conventional artificial neural networks, support vector machines, and linear regression. The results show that the SNN algorithm can achieve higher classification accuracy and identify the spiking activity related to movement control earlier than the other methods. Both are desirable characteristics for fast neural information processing and reliable control command pattern recognition for neuroprosthetic applications.

  1. Spike-timing-dependent construction.

    PubMed

    Lightheart, Toby; Grainger, Steven; Lu, Tien-Fu

    2013-10-01

    Spike-timing-dependent construction (STDC) is the production of new spiking neurons and connections in a simulated neural network in response to neuron activity. Following the discovery of spike-timing-dependent plasticity (STDP), significant effort has gone into the modeling and simulation of adaptation in spiking neural networks (SNNs). Limitations in computational power imposed by network topology, however, constrain learning capabilities through connection weight modification alone. Constructive algorithms produce new neurons and connections, allowing automatic structural responses for applications of unknown complexity and nonstationary solutions. A conceptual analogy is developed and extended to theoretical conditions for modeling synaptic plasticity as network construction. Generalizing past constructive algorithms, we propose a framework for the design of novel constructive SNNs and demonstrate its application in the development of simulations for the validation of developed theory. Potential directions of future research and applications of STDC for biological modeling and machine learning are also discussed.

  2. Spike history neural response model.

    PubMed

    Kameneva, Tatiana; Abramian, Miganoosh; Zarelli, Daniele; Nĕsić, Dragan; Burkitt, Anthony N; Meffin, Hamish; Grayden, David B

    2015-06-01

    There is a potential for improved efficacy of neural stimulation if stimulation levels can be modified dynamically based on the responses of neural tissue in real time. A neural model is developed that describes the response of neurons to electrical stimulation and that is suitable for feedback control neuroprosthetic stimulation. Experimental data from NZ white rabbit retinae is used with a data-driven technique to model neural dynamics. The linear-nonlinear approach is adapted to incorporate spike history and to predict the neural response of ganglion cells to electrical stimulation. To validate the fitness of the model, the penalty term is calculated based on the time difference between each simulated spike and the closest spike in time in the experimentally recorded train. The proposed model is able to robustly predict experimentally observed spike trains.

  3. Wavelet analysis of epileptic spikes

    NASA Astrophysics Data System (ADS)

    Latka, Miroslaw; Was, Ziemowit; Kozik, Andrzej; West, Bruce J.

    2003-05-01

    Interictal spikes and sharp waves in human EEG are characteristic signatures of epilepsy. These potentials originate as a result of synchronous pathological discharge of many neurons. The reliable detection of such potentials has been the long standing problem in EEG analysis, especially after long-term monitoring became common in investigation of epileptic patients. The traditional definition of a spike is based on its amplitude, duration, sharpness, and emergence from its background. However, spike detection systems built solely around this definition are not reliable due to the presence of numerous transients and artifacts. We use wavelet transform to analyze the properties of EEG manifestations of epilepsy. We demonstrate that the behavior of wavelet transform of epileptic spikes across scales can constitute the foundation of a relatively simple yet effective detection algorithm.

  4. A 500 year sediment lake record of anthropogenic and natural inputs to Windermere (English Lake District) using double-spike lead isotopes, radiochronology, and sediment microanalysis.

    PubMed

    Miller, Helen; Croudace, Ian W; Bull, Jonathan M; Cotterill, Carol J; Dix, Justin K; Taylor, Rex N

    2014-07-01

    A high-resolution record of pollution is preserved in recent sediments from Windermere, the largest lake in the English Lake District. Data derived from X-ray core scanning (validated against wavelength dispersive X-ray fluorescence), radiochronological techniques ((210)Pb and (137)Cs) and ultrahigh precision, double-spike mass spectrometry for lead isotopes are combined to decipher the anthropogenic inputs to the lake. The sediment record suggests that while most element concentrations have been stable, there has been a significant increase in lead, zinc, and copper concentrations since the 1930s. Lead isotope down-core variations identify three major contributory sources of anthropogenic (industrial) lead, comprising gasoline lead, coal combustion lead (most likely source is coal-fired steam ships), and lead derived from Carboniferous Pb-Zn mineralization (mining activities). Periods of metal workings do not correlate with peaks in heavy metals due to the trapping efficiency of up-system lakes in the catchment. Heavy metal increases could be due to flood-induced metal inwash after the cessation of mining and the weathering of bedrock in the catchment. The combination of sediment analysis techniques used provides new insights into the pollutant depositional history of Windermere and could be similarly applied to other lake systems to determine the timing and scale of anthropogenic inputs.

  5. Airborne radionuclides in the proglacial environment as indicators of sources and transfers of soil material.

    PubMed

    Łokas, Edyta; Wachniew, Przemysław; Jodłowski, Paweł; Gąsiorek, Michał

    2017-09-04

    A survey of artificial ((137)Cs, (238)Pu, (239+240)Pu, (241)Am) and natural ((226)Ra, (232)Th, (40)K, (210)Pb) radioactive isotopes in proglacial soils of an Arctic glacier have revealed high spatial variability of activity concentrations and inventories of the airborne radionuclides. Soil column (137)Cs inventories range from below the detection limit to nearly 120 kBq m(-2), this value significantly exceeding direct atmospheric deposition. This variability may result from the mixing of materials characterised by different contents of airborne radionuclides. The highest activity concentrations observed in the proglacial soils may result from the deposition of cryoconites, which have been shown to accumulate airborne radionuclides on the surface of glaciers. The role of cryoconites in radionuclide accumulation is supported by the concordant enrichment of the naturally occurring airborne (210)Pb in proglacial soil cores showing elevated levels of artificial radionuclides. The lithogenic radionuclides show less variability than the airborne radionuclides because their activity concentrations are controlled only by the mixing of material derived from the weathering of different parent rocks. Soil properties vary little within and between the profiles and there is no unequivocal relationship between them and the radionuclide contents. The inventories reflect the pathways and time variable inputs of soil material to particular sites of the proglacial zone. Lack of the airborne radionuclides reflects no deposition of material exposed to the atmosphere after the 1950s or its removal by erosion. Inventories above the direct atmospheric deposition indicate secondary deposition of radionuclide-bearing material. Very high inventories indicate sites where transport pathways of cryoconite material terminated. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Wavelet transform of neural spike trains

    NASA Astrophysics Data System (ADS)

    Kim, Youngtae; Jung, Min Whan; Kim, Yunbok

    2000-02-01

    Wavelet transform of neural spike trains recorded with a tetrode in the rat primary somatosensory cortex is described. Continuous wavelet transform (CWT) of the spike train clearly shows singularities hidden in the noisy or chaotic spike trains. A multiresolution analysis of the spike train is also carried out using discrete wavelet transform (DWT) for denoising and approximating at different time scales. Results suggest that this multiscale shape analysis can be a useful tool for classifying the spike trains.

  7. Sediment spiking for toxicity testing

    SciTech Connect

    Murdoch, M.H.; Norman, D.M.; Chapman, P.M.; Norman, D.M.; Quintino, V.M.

    1994-12-31

    Sediment toxicity testing integrates responses to sediment variables and hence does not directly indicate cause-and-effect. One tool for determining cause-and-effect is sediment spiking in which relatively uncontaminated sediment is amended with known amounts of contaminants, then tested for toxicity. Based on the concentration-response relationship(s), the relative toxicity of the spiked contaminants and their significance in sediment mixtures can be assessed. However, sediment spiking methods vary considerably. The present study details an appropriate methodology for amending sediments with a range of organic contaminant concentrations including different solvent schemes and an equilibration period. This methodology is described as appropriate because predicted and actual concentrations were similar, and responses in an acute 10-d amphipod test matched predictions and other data.

  8. Interictal spikes in focal epileptogenesis.

    PubMed

    de Curtis, M; Avanzini, G

    2001-04-01

    Interictal electroencephalography (EEG) potentials in focal epilepsies are sustained by synchronous paroxysmal membrane depolarization generated by assemblies of hyperexcitable neurons. It is currently believed that interictal spiking sets a condition that preludes to the onset of an ictal discharge. Such an assumption is based on little experimental evidence. Human pre-surgical studies and recordings in chronic and acute models of focal epilepsy showed that: (i) interictal spikes (IS) and ictal discharges are generated by different populations of neuron through different cellular and network mechanisms; (ii) the cortical region that generates IS (irritative area) does not coincide with the ictal-onset area; (iii) IS frequency does not increase before a seizure and is enhanced just after an ictal event; (iv) spike suppression is found to herald ictal discharges; and (v) enhancement of interictal spiking suppresses ictal events. Several experimental evidences indicate that the highly synchronous cellular discharge associated with an IS is generated by a multitude of mechanisms involving synaptic and non-synaptic communication between neurons. The synchronized neuronal discharge associated with a single IS induces and is followed by a profound and prolonged refractory period sustained by inhibitory potentials and by activity-dependent changes in the ionic composition of the extracellular space. Post-spike depression may be responsible for pacing interictal spiking periodicity commonly observed in both animal models and human focal epilepsies. It is proposed that the strong after-inhibition produced by IS protects against the occurrence of ictal discharges by maintaining a low level of excitation in a general condition of hyperexcitability determined by the primary epileptogenic dysfunction.

  9. Sparse and powerful cortical spikes.

    PubMed

    Wolfe, Jason; Houweling, Arthur R; Brecht, Michael

    2010-06-01

    Activity in cortical networks is heterogeneous, sparse and often precisely timed. The functional significance of sparseness and precise spike timing is debated, but our understanding of the developmental and synaptic mechanisms that shape neuronal discharge patterns has improved. Evidence for highly specialized, selective and abstract cortical response properties is accumulating. Singe-cell stimulation experiments demonstrate a high sensitivity of cortical networks to the action potentials of some, but not all, single neurons. It is unclear how this sensitivity of cortical networks to small perturbations comes about and whether it is a generic property of cortex. The unforeseen sensitivity to cortical spikes puts serious constraints on the nature of neural coding schemes.

  10. Leach tests on grouts made with actual and trace metal-spiked synthetic phosphate/sulfate waste

    SciTech Connect

    Serne, R.J.; Martin, W.J.; LeGore, V.L.; Lindenmeier, C.W.; McLaurine, S.B.; Martin, P.F.C.; Lokken, R.O.

    1989-10-01

    Pacific Northwest Laboratory conducted experiments to produce empirical leach rate data for phosphate-sulfate waste (PSW) grout. Effective diffusivities were measured for various radionuclides ({sup 90}Sr, {sup 99}Tc, {sup 14}C, {sup 129}I, {sup 137}Cs, {sup 60}Co, {sup 54}Mn, and U), stable major components (NO{sub 3}{sup {minus}}, SO{sub 4}{sup 2{minus}}, H{sub 3}BO{sub 3}, K and Na) and the trace constituents Ag, As, Cd, Hg, Pb, and Se. Two types of leach tests were used on samples of actual PSW grout and synthetic PSW grout: the American Nuclear Society (ANS) 16.1 intermittent replacement leach test and a static leach test. Grout produced from both synthetic and real PSW showed low leach rates for the trace metal constituents and most of the waste radionuclides. Many of the spiked trace metals and radionuclides were not detected in any leachates. None of the effluents contained measurable quantities of {sup 137}Cs, {sup 60}Co, {sup 54}Mn, {sup 109}Cd, {sup 51}Cr, {sup 210}Pb, {sup 203}Hg, or As. For those trace species with detectable leach rates, {sup 125}I appeared to have the greatest leach rate, followed by {sup 99}Tc, {sup 75}Se, and finally U, {sup 14}C, and {sup 110m}Ag. Leach rates for nitrate are between those for I and Tc, but there is much scatter in the nitrate data because of the very low nitrate inventory. 32 refs., 6 figs., 15 tabs.

  11. Hierarchical spike coding of sound

    PubMed Central

    Karklin, Yan; Ekanadham, Chaitanya; Simoncelli, Eero P.

    2014-01-01

    Natural sounds exhibit complex statistical regularities at multiple scales. Acoustic events underlying speech, for example, are characterized by precise temporal and frequency relationships, but they can also vary substantially according to the pitch, duration, and other high-level properties of speech production. Learning this structure from data while capturing the inherent variability is an important first step in building auditory processing systems, as well as understanding the mechanisms of auditory perception. Here we develop Hierarchical Spike Coding, a two-layer probabilistic generative model for complex acoustic structure. The first layer consists of a sparse spiking representation that encodes the sound using kernels positioned precisely in time and frequency. Patterns in the positions of first layer spikes are learned from the data: on a coarse scale, statistical regularities are encoded by a second-layer spiking representation, while fine-scale structure is captured by recurrent interactions within the first layer. When fit to speech data, the second layer acoustic features include harmonic stacks, sweeps, frequency modulations, and precise temporal onsets, which can be composed to represent complex acoustic events. Unlike spectrogram-based methods, the model gives a probability distribution over sound pressure waveforms. This allows us to use the second-layer representation to synthesize sounds directly, and to perform model-based denoising, on which we demonstrate a significant improvement over standard methods. PMID:25356065

  12. Learning Universal Computations with Spikes

    PubMed Central

    Thalmeier, Dominik; Uhlmann, Marvin; Kappen, Hilbert J.; Memmesheimer, Raoul-Martin

    2016-01-01

    Providing the neurobiological basis of information processing in higher animals, spiking neural networks must be able to learn a variety of complicated computations, including the generation of appropriate, possibly delayed reactions to inputs and the self-sustained generation of complex activity patterns, e.g. for locomotion. Many such computations require previous building of intrinsic world models. Here we show how spiking neural networks may solve these different tasks. Firstly, we derive constraints under which classes of spiking neural networks lend themselves to substrates of powerful general purpose computing. The networks contain dendritic or synaptic nonlinearities and have a constrained connectivity. We then combine such networks with learning rules for outputs or recurrent connections. We show that this allows to learn even difficult benchmark tasks such as the self-sustained generation of desired low-dimensional chaotic dynamics or memory-dependent computations. Furthermore, we show how spiking networks can build models of external world systems and use the acquired knowledge to control them. PMID:27309381

  13. Forms and accumulation of soil P in natural and recently restored peatlands - Upper Klamath Lake, Oregon, USA

    USGS Publications Warehouse

    Graham, S.A.; Craft, C.B.; McCormick, P.V.; Aldous, A.

    2005-01-01

    Forms, amounts, and accumulation of soil phosphorus (P) were measured in natural and recently restored marshes surrounding Upper Klamath Lake located in south-central Oregon, USA to determine rates of P accumulation in natural marshes and to assess changes in P pools caused by long-term drainage in recently restored marshes. Soil cores were collected from three natural marshes and radiometrically dated to determine recent (l37Cs-based) and long-term (210Pb-based) rates of peat accretion and P accumulation. A second set of soil cores collected from the three natural marshes and from three recently restored marshes was analyzed using a modification of the Hedley procedure to determine the forms and amounts of soil P. Total P in the recently restored marshes (222 to 311 ??g cm-3) was 2-3 times greater than in the natural marshes (103 to 117 ??g cm-3), primarily due to greater bulk density caused by soil subsidence, a consequence of long-term marsh drainage. Occluded Fe- and Al-bound Pi, calcium-bound Pi and residual P were 4 times, 22 times, and 5 times greater, respectively, in the recently restored marshes. More than 67% of the P pool in both the natural and recently restored marshes was present in recalcitrant forms (humic-acid P o and residual P) that provide long-term P storage in peat. Phosphorus accumulation in the natural marshes averaged 0.45 g m-2 yr-1 (137Cs) and 0.40 g m-2 yr-1 (210Pb), providing a benchmark for optimizing P sequestration in the recently restored marshes. Effective P sequestration in the recently restored marshes, however, will depend on re-establishing equilibrium between the P-enriched soils and the P concentration of floodwaters and a hydrologie regime similar to the natural marshes. ?? 2005, The Society of Wetland Scientists.

  14. Assessment of soil erosion and deposition rates in a Moroccan agricultural field using fallout 137Cs and 210Pbex.

    PubMed

    Benmansour, M; Mabit, L; Nouira, A; Moussadek, R; Bouksirate, H; Duchemin, M; Benkdad, A

    2013-01-01

    In Morocco land degradation - mainly caused by soil erosion - is one of the most serious agroenvironmental threats encountered. However, only limited data are available on the actual magnitude of soil erosion. The study site investigated was an agricultural field located in Marchouch (6°42' W, 33° 47' N) at 68 km south east from Rabat. This work demonstrates the potential of the combined use of (137)Cs, (210)Pb(ex) as radioisotopic soil tracers to estimate mid and long term erosion and deposition rates under Mediterranean agricultural areas. The net soil erosion rates obtained were comparable, 14.3 t ha(-1) yr(-1) and 12.1 ha(-1) yr(-1) for (137)Cs and (210)Pb(ex) respectively, resulting in a similar sediment delivery ratio of about 92%. Soil redistribution patterns of the study field were established using a simple spatialisation approach. The resulting maps generated by the use of both radionuclides were similar, indicating that the soil erosion processes has not changed significantly over the last 100 years. Over the previous 10 year period, the additional results provided by the test of the prediction model RUSLE 2 provided results of the same order of magnitude. Based on the (137)Cs dataset established, the contribution of the tillage erosion impact has been evaluated with the Mass Balance Model 3 and compared to the result obtained with the Mass Balance Model 2. The findings highlighted that water erosion is the leading process in this Moroccan cultivated field, tillage erosion under the experimental condition being the main translocation process within the site without a significant and major impact on the net erosion. Copyright © 2012 Elsevier Ltd. All rights reserved.

  15. The Computational Structure of Spike Trains

    PubMed Central

    Haslinger, Robert; Klinkner, Kristina Lisa; Shalizi, Cosma Rohilla

    2010-01-01

    Neurons perform computations, and convey the results of those computations through the statistical structure of their output spike trains. Here we present a practical method, grounded in the information-theoretic analysis of prediction, for inferring a minimal representation of that structure and for characterizing its complexity. Starting from spike trains, our approach finds their causal state models (CSMs), the minimal hidden Markov models or stochastic automata capable of generating statistically-identical time series. We then use these CSMs to objectively quantify both the generalizable structure and the idiosyncratic randomness of the spike train. Specifically, we show that the expected algorithmic information content (the information needed to describe the spike train exactly) can be split into three parts describing (1) the time-invariant structure (complexity) of the minimal spike-generating process, which describes the spike train statistically, (2) the randomness (internal entropy rate) of the minimal spike-generating process, and (3) a residual pure noise term not described by the minimal spike generating process. We use CSMs to approximate each of these quantities. The CSMs are inferred non-parametrically from the data, making only mild regularity assumptions, via the Causal State Splitting Reconstruction (CSSR) algorithm. The methods presented here complement more traditional spike train analyses by describing not only spiking probability, and spike train entropy, but also the complexity of a spike train’s structure. We demonstrate our approach using both simulated spike trains and experimental data recorded in rat barrel cortex during vibrissa stimulation. PMID:19764880

  16. Soils

    Treesearch

    John R. Jones; Norbert V. DeByle

    1985-01-01

    Edaphic and climatic characteristics of a site quite well define the quality of that site for plant growth. The importance of soil characteristics to the growth and well-being of aspen in the West is apparent from observations by many authors, from inferences resulting from work with other trees and agricultural crops, and from detailed study of aspen soils and site...

  17. A simple algorithm for averaging spike trains.

    PubMed

    Julienne, Hannah; Houghton, Conor

    2013-02-25

    Although spike trains are the principal channel of communication between neurons, a single stimulus will elicit different spike trains from trial to trial. This variability, in both spike timings and spike number can obscure the temporal structure of spike trains and often means that computations need to be run on numerous spike trains in order to extract features common across all the responses to a particular stimulus. This can increase the computational burden and obscure analytical results. As a consequence, it is useful to consider how to calculate a central spike train that summarizes a set of trials. Indeed, averaging responses over trials is routine for other signal types. Here, a simple method for finding a central spike train is described. The spike trains are first mapped to functions, these functions are averaged, and a greedy algorithm is then used to map the average function back to a spike train. The central spike trains are tested for a large data set. Their performance on a classification-based test is considerably better than the performance of the medoid spike trains.

  18. Prospective Coding by Spiking Neurons

    PubMed Central

    Brea, Johanni; Gaál, Alexisz Tamás; Senn, Walter

    2016-01-01

    Animals learn to make predictions, such as associating the sound of a bell with upcoming feeding or predicting a movement that a motor command is eliciting. How predictions are realized on the neuronal level and what plasticity rule underlies their learning is not well understood. Here we propose a biologically plausible synaptic plasticity rule to learn predictions on a single neuron level on a timescale of seconds. The learning rule allows a spiking two-compartment neuron to match its current firing rate to its own expected future discounted firing rate. For instance, if an originally neutral event is repeatedly followed by an event that elevates the firing rate of a neuron, the originally neutral event will eventually also elevate the neuron’s firing rate. The plasticity rule is a form of spike timing dependent plasticity in which a presynaptic spike followed by a postsynaptic spike leads to potentiation. Even if the plasticity window has a width of 20 milliseconds, associations on the time scale of seconds can be learned. We illustrate prospective coding with three examples: learning to predict a time varying input, learning to predict the next stimulus in a delayed paired-associate task and learning with a recurrent network to reproduce a temporally compressed version of a sequence. We discuss the potential role of the learning mechanism in classical trace conditioning. In the special case that the signal to be predicted encodes reward, the neuron learns to predict the discounted future reward and learning is closely related to the temporal difference learning algorithm TD(λ). PMID:27341100

  19. Measuring multiple spike train synchrony.

    PubMed

    Kreuz, Thomas; Chicharro, Daniel; Andrzejak, Ralph G; Haas, Julie S; Abarbanel, Henry D I

    2009-10-15

    Measures of multiple spike train synchrony are essential in order to study issues such as spike timing reliability, network synchronization, and neuronal coding. These measures can broadly be divided in multivariate measures and averages over bivariate measures. One of the most recent bivariate approaches, the ISI-distance, employs the ratio of instantaneous interspike intervals (ISIs). In this study we propose two extensions of the ISI-distance, the straightforward averaged bivariate ISI-distance and the multivariate ISI-diversity based on the coefficient of variation. Like the original measure these extensions combine many properties desirable in applications to real data. In particular, they are parameter-free, time scale independent, and easy to visualize in a time-resolved manner, as we illustrate with in vitro recordings from a cortical neuron. Using a simulated network of Hindemarsh-Rose neurons as a controlled configuration we compare the performance of our methods in distinguishing different levels of multi-neuron spike train synchrony to the performance of six other previously published measures. We show and explain why the averaged bivariate measures perform better than the multivariate ones and why the multivariate ISI-diversity is the best performer among the multivariate methods. Finally, in a comparison against standard methods that rely on moving window estimates, we use single-unit monkey data to demonstrate the advantages of the instantaneous nature of our methods.

  20. Electrophysiology of connection current spikes.

    PubMed

    Fish, Raymond M; Geddes, Leslie A

    2008-12-01

    Connection to a 60-Hz or other voltage source can result in cardiac dysrhythmias, a startle reaction, muscle contractions, and a variety of other physiological responses. Such responses can lead to injury, especially if significant ventricular cardiac dysrhythmias occur, or if a person is working at some height above ground and falls as a result of a musculoskeletal response. Physiological reactions are known to relate to intensity and duration of current exposure. The connection current that flows is a function of the applied voltage at the instant of connection, and the electrical impedance encountered by the voltage source in contact with the skin or other body tissues. In this article we describe a rarely investigated phenomenon, namely a contact, or connection, current spike that is many times higher than the steady-state current. This current spike occurs when an electrical connection is made at a non-zero voltage time in a sine wave or other waveform. Such current spikes may occur when electronic or manual switching or connecting of conductors occurs in electronic instrumentation connected to a patient. These findings are relevant to medical devices and instrumentation and to electrical safety in general.

  1. Reliability of Spike Timing in Neocortical Neurons

    NASA Astrophysics Data System (ADS)

    Mainen, Zachary F.; Sejnowski, Terrence J.

    1995-06-01

    It is not known whether the variability of neural activity in the cerebral cortex carries information or reflects noisy underlying mechanisms. In an examination of the reliability of spike generation using recordings from neurons in rat neocortical slices, the precision of spike timing was found to depend on stimulus transients. Constant stimuli led to imprecise spike trains, whereas stimuli with fluctuations resembling synaptic activity produced spike trains with timing reproducible to less than 1 millisecond. These data suggest a low intrinsic noise level in spike generation, which could allow cortical neurons to accurately transform synaptic input into spike sequences, supporting a possible role for spike timing in the processing of cortical information by the neocortex.

  2. Soil Chemical Weathering and Nutrient Budgets along an Earthworm Invasion Chronosequence in a Northern Minnesota Forest

    NASA Astrophysics Data System (ADS)

    Resner, K. E.; Yoo, K.; Sebestyen, S. D.; Aufdenkampe, A. K.; Lyttle, A.; Weinman, B. A.; Blum, A.; Hale, C. M.

    2011-12-01

    We are investigating the impact of exotic earthworms on the rate of nutrient and ion release from soil chemical weathering along an ~200 m invasion chronosequence in a northern Minnesota sugar maple forest. The earthworms belong to three ecological groups that represent different feeding and burrowing behaviors, all of which were introduced from Europe to the previously earthworm-free Great Lakes Region through fishing and agricultural activities. As earthworms digest and mix the soil, we hypothesize that they significantly alter chemical weathering processes by incorporating mineral surfaces to new geochemical environments in their intestines and at different soil depths. The effect of mixing on soil morphology is dramatic, but biogeochemical changes remain largely unknown and therefore are poorly coupled to the current and potential changes in forest ecosystems under the threat of exotic earthworms. We analyze the activities of short-lived isotopes 137-Cs and 210-Pb along with the inorganic chemistry of soil, water, and leaf litter across an invasion transect and link these measurements to the biomass and species composition of exotic earthworms. Earthworms vertically relocate minerals and organic matter largely within the top ~10 cm, which is reflected in the depth profiles of the short-lived isotopes. Among the inorganic nutrients analyzed, Ca is of particular interest due to sugar maple's aptitude for recycling Ca. Fractional mass loss values (tau) of Ca, relative to the soil's parent material, show an enrichment factor of 14 in the least invaded A horizon soils. However, such a high enrichment factor declines dramatically in the heavily invaded soils, suggesting that earthworm activities contribute to leaching Ca. In contrast, the enrichment factor of Fe increases with greater degrees of earthworm invasion, which is consistent with the extraction chemistry data showing greater quantities of pedogenic crystalline iron oxides and greater mineral specific

  3. Effects of surfactants on extraction of phenanthrene in spiked sand.

    PubMed

    Chang, M C; Huang, C R; Shu, H Y

    2000-10-01

    Problems associated with polynuclear aromatic hydrocarbon (PAH) contaminated site in environmental media have received increasing attention. To resolve such problems, innovative in situ methods are urgently required. This work investigated the feasibility of using surfactants to extract phenanthrene on spiked sand in a batch system. Phenanthrene was spiked into Ottawa sand to simulate contaminated soil. Six surfactants, Brij 30 (BR), Triton X-100 (TR), Tergitol NP-10 (TE), Igepal CA-720 (IG), sodium dodecyl sulfate (SDS) and hexadecyl trimethyl ammonium bromide (HTAB) were used. Adjusting the extraction time, mixing speed and surfactant concentration yielded the optimum extracting conditions. The concentration of phenanthrene was identified with HPLC. Under the experimental conditions, results indicated that those surfactants were highly promising on site remediation since the residual phenanthrene concentration was effectively reduced. The optimum operating conditions were obtained at 30 min, 125 rpm and surfactant concentrations in 4%.

  4. Multiscale analysis of neural spike trains.

    PubMed

    Ramezan, Reza; Marriott, Paul; Chenouri, Shojaeddin

    2014-01-30

    This paper studies the multiscale analysis of neural spike trains, through both graphical and Poisson process approaches. We introduce the interspike interval plot, which simultaneously visualizes characteristics of neural spiking activity at different time scales. Using an inhomogeneous Poisson process framework, we discuss multiscale estimates of the intensity functions of spike trains. We also introduce the windowing effect for two multiscale methods. Using quasi-likelihood, we develop bootstrap confidence intervals for the multiscale intensity function. We provide a cross-validation scheme, to choose the tuning parameters, and study its unbiasedness. Studying the relationship between the spike rate and the stimulus signal, we observe that adjusting for the first spike latency is important in cross-validation. We show, through examples, that the correlation between spike trains and spike count variability can be multiscale phenomena. Furthermore, we address the modeling of the periodicity of the spike trains caused by a stimulus signal or by brain rhythms. Within the multiscale framework, we introduce intensity functions for spike trains with multiplicative and additive periodic components. Analyzing a dataset from the retinogeniculate synapse, we compare the fit of these models with the Bayesian adaptive regression splines method and discuss the limitations of the methodology. Computational efficiency, which is usually a challenge in the analysis of spike trains, is one of the highlights of these new models. In an example, we show that the reconstruction quality of a complex intensity function demonstrates the ability of the multiscale methodology to crack the neural code.

  5. Lixiviation of natural radionuclides and heavy metals in tropical soils amended with phosphogypsum.

    PubMed

    Nisti, M B; Saueia, C R; Malheiro, L H; Groppo, G H; Mazzilli, B P

    2015-06-01

    The main phosphate industries in Brazil are responsible for the annual production of 5.5 million tons of a residue (phosphogypsum), which is stored in stacks. The presence of radionuclides and metals puts restrictions on the use of phosphogypsum in agriculture. To assure a safe utilization, it is important to estimate the lixiviation of the radionuclides ((238)U, (226)Ra, (210)Pb, (210)Po, (232)Th and (228)Ra) and metals (As, Cd, Cr, Ni, Se, Hg and Pb) present in phosphogypsum. For this purpose, an experiment was carried out, in which columns filled with sandy and clay Brazilian typical soils mixed with phosphogypsum were percolated with water, to achieve a mild extraction of these elements. The results obtained for the concentration of the radionuclides and metals in the leachate were low; giving evidence that, even when these elements are present in the phosphogypsum, they do not contribute to an enhancement of their content in water.

  6. The dynamic relationship between cerebellar Purkinje cell simple spikes and the spikelet number of complex spikes

    PubMed Central

    Burroughs, Amelia; Wise, Andrew K.; Xiao, Jianqiang; Houghton, Conor; Tang, Tianyu; Suh, Colleen Y.; Lang, Eric J.

    2016-01-01

    Key points Purkinje cells are the sole output of the cerebellar cortex and fire two distinct types of action potential: simple spikes and complex spikes.Previous studies have mainly considered complex spikes as unitary events, even though the waveform is composed of varying numbers of spikelets.The extent to which differences in spikelet number affect simple spike activity (and vice versa) remains unclear.We found that complex spikes with greater numbers of spikelets are preceded by higher simple spike firing rates but, following the complex spike, simple spikes are reduced in a manner that is graded with spikelet number.This dynamic interaction has important implications for cerebellar information processing, and suggests that complex spike spikelet number may maintain Purkinje cells within their operational range. Abstract Purkinje cells are central to cerebellar function because they form the sole output of the cerebellar cortex. They exhibit two distinct types of action potential: simple spikes and complex spikes. It is widely accepted that interaction between these two types of impulse is central to cerebellar cortical information processing. Previous investigations of the interactions between simple spikes and complex spikes have mainly considered complex spikes as unitary events. However, complex spikes are composed of an initial large spike followed by a number of secondary components, termed spikelets. The number of spikelets within individual complex spikes is highly variable and the extent to which differences in complex spike spikelet number affects simple spike activity (and vice versa) remains poorly understood. In anaesthetized adult rats, we have found that Purkinje cells recorded from the posterior lobe vermis and hemisphere have high simple spike firing frequencies that precede complex spikes with greater numbers of spikelets. This finding was also evident in a small sample of Purkinje cells recorded from the posterior lobe hemisphere in awake

  7. Independent component analysis in spiking neurons.

    PubMed

    Savin, Cristina; Joshi, Prashant; Triesch, Jochen

    2010-04-22

    Although models based on independent component analysis (ICA) have been successful in explaining various properties of sensory coding in the cortex, it remains unclear how networks of spiking neurons using realistic plasticity rules can realize such computation. Here, we propose a biologically plausible mechanism for ICA-like learning with spiking neurons. Our model combines spike-timing dependent plasticity and synaptic scaling with an intrinsic plasticity rule that regulates neuronal excitability to maximize information transmission. We show that a stochastically spiking neuron learns one independent component for inputs encoded either as rates or using spike-spike correlations. Furthermore, different independent components can be recovered, when the activity of different neurons is decorrelated by adaptive lateral inhibition.

  8. Effects of phase on homeostatic spike rates.

    PubMed

    Fisher, Nicholas; Talathi, Sachin S; Carney, Paul R; Ditto, William L

    2010-05-01

    Recent experimental results by Talathi et al. (Neurosci Lett 455:145-149, 2009) showed a divergence in the spike rates of two types of population spike events, representing the putative activity of the excitatory and inhibitory neurons in the CA1 area of an animal model for temporal lobe epilepsy. The divergence in the spike rate was accompanied by a shift in the phase of oscillations between these spike rates leading to a spontaneous epileptic seizure. In this study, we propose a model of homeostatic synaptic plasticity which assumes that the target spike rate of populations of excitatory and inhibitory neurons in the brain is a function of the phase difference between the excitatory and inhibitory spike rates. With this model of homeostatic synaptic plasticity, we are able to simulate the spike rate dynamics seen experimentally by Talathi et al. in a large network of interacting excitatory and inhibitory neurons using two different spiking neuron models. A drift analysis of the spike rates resulting from the homeostatic synaptic plasticity update rule allowed us to determine the type of synapse that may be primarily involved in the spike rate imbalance in the experimental observation by Talathi et al. We find excitatory neurons, particularly those in which the excitatory neuron is presynaptic, have the most influence in producing the diverging spike rates and causing the spike rates to be anti-phase. Our analysis suggests that the excitatory neuronal population, more specifically the excitatory to excitatory synaptic connections, could be implicated in a methodology designed to control epileptic seizures.

  9. The spike timing dependence of plasticity

    PubMed Central

    Feldman, Daniel E.

    2012-01-01

    In spike timing-dependent plasticity (STDP), the order and precise temporal interval between presynaptic and postsynaptic spikes determine the sign and magnitude of long-term potentiation (LTP) or depression (LTD). STDP is widely utilized in models of circuit-level plasticity, development, and learning. However, spike timing is just one of several factors (including firing rate, synaptic cooperativity, and depolarization) that govern plasticity induction, and its relative importance varies across synapses and activity regimes. This review summarizes the forms, cellular mechanisms, and prevalence of STDP, and evaluates the evidence that spike timing is an important determinant of plasticity in vivo. PMID:22920249

  10. Advantage of support vector machine for neural spike train decoding under spike sorting errors.

    PubMed

    Hwan Kim, Kyung; Shin Kim, Sung; June Kim, Sung

    2005-01-01

    Decoding of kinematic variables from neuronal spike trains is important for neuroprosthetic devices. The spike trains from single units must be extracted from extracellular neural signals and thus spike detection and sorting procedure is essential. Since the spike detection and sorting procedure may yield considerable errors, decoding algorithm should be robust against spike train errors. Here we showed that the spike train decoding algorithms employing a nonlinear mapping, especially support vector machine (SVM), may be more advantageous contrary to conventional belief that linear filter is sufficient. The advantage became more conspicuous with erroneous spike trains. Using the SVM, satisfactory performance could be obtained much more easily, compared to the case of using multilayer perceptron, which was employed for previous studies. The results suggests the possibility of neuroprosthetic device with a low-quality spike sorting preprocessor.

  11. Robust spike-train learning in spike-event based weight update.

    PubMed

    Shrestha, Sumit Bam; Song, Qing

    2017-09-12

    Supervised learning algorithms in a spiking neural network either learn a spike-train pattern for a single neuron receiving input spike-train from multiple input synapses or learn to output the first spike time in a feedforward network setting. In this paper, we build upon spike-event based weight update strategy to learn continuous spike-train in a spiking neural network with a hidden layer using a dead zone on-off based adaptive learning rate rule which ensures convergence of the learning process in the sense of weight convergence and robustness of the learning process to external disturbances. Based on different benchmark problems, we compare this new method with other relevant spike-train learning algorithms. The results show that the speed of learning is much improved and the rate of successful learning is also greatly improved. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. [Regularities of lateral distribution of uranium and thorium decay series radionuclides in the anthropogenically changed soils from the area of radium production waste storage].

    PubMed

    Evseeva, T I; Belykh, E S; Maĭstrenko, T A; Geras'kin, S A; Taskaev, A I; Vakhrusheva, O M

    2012-01-01

    Cartographical investigations of the territory of radium production waste storage has shown some changes in lateral differentiation of radionuclides of uranium and thorium decay series to occur during 27 years (1981-2008). Those changes are caused mostly by flat denudation typical for fluvial terrace. At present radionuclides of uranium and thorium decay series are concentrated mostly in flood lands and relief depressions. At the same time, decrease in the radionuclide activity concentration in 0-20 cm soil layer is observed with changes in lateral distribution. Total stocks of 226Ra, 210Pb and 210Po within catena soils studied in the northern and southern parts of the waste storage decreased 3-6 times, 238U - 2 times, and did not significantly change in case of 232Th during 27 years. Nonetheless, most of the samples studied are referred to radioactive waste both according to Russian standards (SPORO-2002) and IAEA safety norms (IAEA, 2004).

  13. Spiking neuron network Helmholtz machine.

    PubMed

    Sountsov, Pavel; Miller, Paul

    2015-01-01

    An increasing amount of behavioral and neurophysiological data suggests that the brain performs optimal (or near-optimal) probabilistic inference and learning during perception and other tasks. Although many machine learning algorithms exist that perform inference and learning in an optimal way, the complete description of how one of those algorithms (or a novel algorithm) can be implemented in the brain is currently incomplete. There have been many proposed solutions that address how neurons can perform optimal inference but the question of how synaptic plasticity can implement optimal learning is rarely addressed. This paper aims to unify the two fields of probabilistic inference and synaptic plasticity by using a neuronal network of realistic model spiking neurons to implement a well-studied computational model called the Helmholtz Machine. The Helmholtz Machine is amenable to neural implementation as the algorithm it uses to learn its parameters, called the wake-sleep algorithm, uses a local delta learning rule. Our spiking-neuron network implements both the delta rule and a small example of a Helmholtz machine. This neuronal network can learn an internal model of continuous-valued training data sets without supervision. The network can also perform inference on the learned internal models. We show how various biophysical features of the neural implementation constrain the parameters of the wake-sleep algorithm, such as the duration of the wake and sleep phases of learning and the minimal sample duration. We examine the deviations from optimal performance and tie them to the properties of the synaptic plasticity rule.

  14. Spiking neuron network Helmholtz machine

    PubMed Central

    Sountsov, Pavel; Miller, Paul

    2015-01-01

    An increasing amount of behavioral and neurophysiological data suggests that the brain performs optimal (or near-optimal) probabilistic inference and learning during perception and other tasks. Although many machine learning algorithms exist that perform inference and learning in an optimal way, the complete description of how one of those algorithms (or a novel algorithm) can be implemented in the brain is currently incomplete. There have been many proposed solutions that address how neurons can perform optimal inference but the question of how synaptic plasticity can implement optimal learning is rarely addressed. This paper aims to unify the two fields of probabilistic inference and synaptic plasticity by using a neuronal network of realistic model spiking neurons to implement a well-studied computational model called the Helmholtz Machine. The Helmholtz Machine is amenable to neural implementation as the algorithm it uses to learn its parameters, called the wake-sleep algorithm, uses a local delta learning rule. Our spiking-neuron network implements both the delta rule and a small example of a Helmholtz machine. This neuronal network can learn an internal model of continuous-valued training data sets without supervision. The network can also perform inference on the learned internal models. We show how various biophysical features of the neural implementation constrain the parameters of the wake-sleep algorithm, such as the duration of the wake and sleep phases of learning and the minimal sample duration. We examine the deviations from optimal performance and tie them to the properties of the synaptic plasticity rule. PMID:25954191

  15. Spike voltage topography in temporal lobe epilepsy.

    PubMed

    Asadi-Pooya, Ali A; Asadollahi, Marjan; Shimamoto, Shoichi; Lorenzo, Matthew; Sperling, Michael R

    2016-07-15

    We investigated the voltage topography of interictal spikes in patients with temporal lobe epilepsy (TLE) to see whether topography was related to etiology for TLE. Adults with TLE, who had epilepsy surgery for drug-resistant seizures from 2011 until 2014 at Jefferson Comprehensive Epilepsy Center were selected. Two groups of patients were studied: patients with mesial temporal sclerosis (MTS) on MRI and those with other MRI findings. The voltage topography maps of the interictal spikes at the peak were created using BESA software. We classified the interictal spikes as polar, basal, lateral, or others. Thirty-four patients were studied, from which the characteristics of 340 spikes were investigated. The most common type of spike orientation was others (186 spikes; 54.7%), followed by lateral (146; 42.9%), polar (5; 1.5%), and basal (3; 0.9%). Characteristics of the voltage topography maps of the spikes between the two groups of patients were somewhat different. Five spikes in patients with MTS had polar orientation, but none of the spikes in patients with other MRI findings had polar orientation (odds ratio=6.98, 95% confidence interval=0.38 to 127.38; p=0.07). Scalp topographic mapping of interictal spikes has the potential to offer different information than visual inspection alone. The present results do not allow an immediate clinical application of our findings; however, detecting a polar spike in a patient with TLE may increase the possibility of mesial temporal sclerosis as the underlying etiology. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Learning Precise Spike Train-to-Spike Train Transformations in Multilayer Feedforward Neuronal Networks.

    PubMed

    Banerjee, Arunava

    2016-05-01

    We derive a synaptic weight update rule for learning temporally precise spike train-to-spike train transformations in multilayer feedforward networks of spiking neurons. The framework, aimed at seamlessly generalizing error backpropagation to the deterministic spiking neuron setting, is based strictly on spike timing and avoids invoking concepts pertaining to spike rates or probabilistic models of spiking. The derivation is founded on two innovations. First, an error functional is proposed that compares the spike train emitted by the output neuron of the network to the desired spike train by way of their putative impact on a virtual postsynaptic neuron. This formulation sidesteps the need for spike alignment and leads to closed-form solutions for all quantities of interest. Second, virtual assignment of weights to spikes rather than synapses enables a perturbation analysis of individual spike times and synaptic weights of the output, as well as all intermediate neurons in the network, which yields the gradients of the error functional with respect to the said entities. Learning proceeds via a gradient descent mechanism that leverages these quantities. Simulation experiments demonstrate the efficacy of the proposed learning framework. The experiments also highlight asymmetries between synapses on excitatory and inhibitory neurons.

  17. Bayesian population decoding of spiking neurons.

    PubMed

    Gerwinn, Sebastian; Macke, Jakob; Bethge, Matthias

    2009-01-01

    The timing of action potentials in spiking neurons depends on the temporal dynamics of their inputs and contains information about temporal fluctuations in the stimulus. Leaky integrate-and-fire neurons constitute a popular class of encoding models, in which spike times depend directly on the temporal structure of the inputs. However, optimal decoding rules for these models have only been studied explicitly in the noiseless case. Here, we study decoding rules for probabilistic inference of a continuous stimulus from the spike times of a population of leaky integrate-and-fire neurons with threshold noise. We derive three algorithms for approximating the posterior distribution over stimuli as a function of the observed spike trains. In addition to a reconstruction of the stimulus we thus obtain an estimate of the uncertainty as well. Furthermore, we derive a 'spike-by-spike' online decoding scheme that recursively updates the posterior with the arrival of each new spike. We use these decoding rules to reconstruct time-varying stimuli represented by a Gaussian process from spike trains of single neurons as well as neural populations.

  18. A "Last Word" on Ice Spikes.

    ERIC Educational Resources Information Center

    Perry, Helene F.

    1995-01-01

    Attempts an explanation of how "ice spikes" are formed. The spikes are upward protrusions of ice that occur when water expands as it cools in a rigid container of low thermal conductivity. Describes the results of an investigation and includes color photos. (LZ)

  19. A "Last Word" on Ice Spikes.

    ERIC Educational Resources Information Center

    Perry, Helene F.

    1995-01-01

    Attempts an explanation of how "ice spikes" are formed. The spikes are upward protrusions of ice that occur when water expands as it cools in a rigid container of low thermal conductivity. Describes the results of an investigation and includes color photos. (LZ)

  20. Statistical properties of superimposed stationary spike trains.

    PubMed

    Deger, Moritz; Helias, Moritz; Boucsein, Clemens; Rotter, Stefan

    2012-06-01

    The Poisson process is an often employed model for the activity of neuronal populations. It is known, though, that superpositions of realistic, non- Poisson spike trains are not in general Poisson processes, not even for large numbers of superimposed processes. Here we construct superimposed spike trains from intracellular in vivo recordings from rat neocortex neurons and compare their statistics to specific point process models. The constructed superimposed spike trains reveal strong deviations from the Poisson model. We find that superpositions of model spike trains that take the effective refractoriness of the neurons into account yield a much better description. A minimal model of this kind is the Poisson process with dead-time (PPD). For this process, and for superpositions thereof, we obtain analytical expressions for some second-order statistical quantities-like the count variability, inter-spike interval (ISI) variability and ISI correlations-and demonstrate the match with the in vivo data. We conclude that effective refractoriness is the key property that shapes the statistical properties of the superposition spike trains. We present new, efficient algorithms to generate superpositions of PPDs and of gamma processes that can be used to provide more realistic background input in simulations of networks of spiking neurons. Using these generators, we show in simulations that neurons which receive superimposed spike trains as input are highly sensitive for the statistical effects induced by neuronal refractoriness.

  1. Spiking neural P systems with multiple channels.

    PubMed

    Peng, Hong; Yang, Jinyu; Wang, Jun; Wang, Tao; Sun, Zhang; Song, Xiaoxiao; Luo, Xiaohui; Huang, Xiangnian

    2017-11-01

    Spiking neural P systems (SNP systems, in short) are a class of distributed parallel computing systems inspired from the neurophysiological behavior of biological spiking neurons. In this paper, we investigate a new variant of SNP systems in which each neuron has one or more synaptic channels, called spiking neural P systems with multiple channels (SNP-MC systems, in short). The spiking rules with channel label are introduced to handle the firing mechanism of neurons, where the channel labels indicate synaptic channels of transmitting the generated spikes. The computation power of SNP-MC systems is investigated. Specifically, we prove that SNP-MC systems are Turing universal as both number generating and number accepting devices. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Stochastic variational learning in recurrent spiking networks.

    PubMed

    Jimenez Rezende, Danilo; Gerstner, Wulfram

    2014-01-01

    The ability to learn and perform statistical inference with biologically plausible recurrent networks of spiking neurons is an important step toward understanding perception and reasoning. Here we derive and investigate a new learning rule for recurrent spiking networks with hidden neurons, combining principles from variational learning and reinforcement learning. Our network defines a generative model over spike train histories and the derived learning rule has the form of a local Spike Timing Dependent Plasticity rule modulated by global factors (neuromodulators) conveying information about "novelty" on a statistically rigorous ground. Simulations show that our model is able to learn both stationary and non-stationary patterns of spike trains. We also propose one experiment that could potentially be performed with animals in order to test the dynamics of the predicted novelty signal.

  3. Representing spike trains using constant sampling intervals.

    PubMed

    Hirata, Yoshito; Aihara, Kazuyuki

    2009-10-15

    Sensory neurons encode external information by a series of times of action potentials, which is called a spike train. However, since it is a point process, it is hard to analyze. Here we propose a method for converting a spike train into a real-valued time series with a fixed sampling interval under the assumption of temporal codes. The proposed method yields time series that represent encoded signals. Especially when the method is applied to spike trains generated using integrate-and-fire models, the yielded time series look very similar to those of encoded information. The method works robustly even when a spike train is contaminated with noise. Since unlike filters it does not use its original signals for the conversion, the proposed method can be widely used for investigating spike train data in the real world.

  4. Stochastic variational learning in recurrent spiking networks

    PubMed Central

    Jimenez Rezende, Danilo; Gerstner, Wulfram

    2014-01-01

    The ability to learn and perform statistical inference with biologically plausible recurrent networks of spiking neurons is an important step toward understanding perception and reasoning. Here we derive and investigate a new learning rule for recurrent spiking networks with hidden neurons, combining principles from variational learning and reinforcement learning. Our network defines a generative model over spike train histories and the derived learning rule has the form of a local Spike Timing Dependent Plasticity rule modulated by global factors (neuromodulators) conveying information about “novelty” on a statistically rigorous ground. Simulations show that our model is able to learn both stationary and non-stationary patterns of spike trains. We also propose one experiment that could potentially be performed with animals in order to test the dynamics of the predicted novelty signal. PMID:24772078

  5. PySpike-A Python library for analyzing spike train synchrony

    NASA Astrophysics Data System (ADS)

    Mulansky, Mario; Kreuz, Thomas

    Understanding how the brain functions is one of the biggest challenges of our time. The analysis of experimentally recorded neural firing patterns (spike trains) plays a crucial role in addressing this problem. Here, the PySpike library is introduced, a Python package for spike train analysis providing parameter-free and time-scale independent measures of spike train synchrony. It allows to compute similarity and dissimilarity profiles, averaged values and distance matrices. Although mainly focusing on neuroscience, PySpike can also be applied in other contexts like climate research or social sciences. The package is available as Open Source on Github and PyPI.

  6. Millisecond Radio Spikes in the Decimetric Band

    NASA Astrophysics Data System (ADS)

    Dąbrowski, B. P.; Rudawy, P.; Karlický, M.

    We present the results of the analysis of thirteen events consisting of dm-spikes observed in Toruń between 15 March 2000 and 30 October 2001. The events were obtained with a very high time resolution (80 microseconds) radio spectrograph in the 1352 - 1490 MHz range. These data were complemented with observations from the radio spectrograph at Ondřejov in the 0.8 - 2.0 GHz band. We evaluated the basic characteristics of the individual spikes (duration, spectral width, and frequency drifts), as well as their groups and chains, the location of their emission sources, and the temporal correlations of the emissions with various phases of the associated solar flares. We found that the mean duration and spectral width of the radio spikes are equal to 0.036 s and 9.96 MHz, respectively. Distributions of the duration and spectral widths of the spikes have positive skewness for all investigated events. Each spike shows positive or negative frequency drift. The mean negative and positive drifts of the investigated spikes are equal to -776 MHz s-1 and 1608 MHz s-1, respectively. The emission sources of the dm-spikes are located mainly at disk center. We have noticed two kinds of chains, with and without frequency drifts. The mean durations of the chains vary between 0.067 s and 0.509 s, while their spectral widths vary between 7.2 MHz and 17.25 MHz. The mean duration of an individual spike observed in a chain was equal to 0.03 s. While we found some agreement between the global characteristics of the groups of spikes recorded with the two instruments located in Toruń and Ondřejov, we did not find any one-to-one relation between individual spikes.

  7. Millisecond Radio Spikes in the Decimetric Band

    NASA Astrophysics Data System (ADS)

    dąbrowski, B. P.; Rudawy, P.; Karlický, M.

    2011-11-01

    We present the results of the analysis of thirteen events consisting of dm-spikes observed in Toruń between 15 March 2000 and 30 October 2001. The events were obtained with a very high time resolution (80 microseconds) radio spectrograph in the 1352 - 1490 MHz range. These data were complemented with observations from the radio spectrograph at Ondřejov in the 0.8 - 2.0 GHz band. We evaluated the basic characteristics of the individual spikes (duration, spectral width, and frequency drifts), as well as their groups and chains, the location of their emission sources, and the temporal correlations of the emissions with various phases of the associated solar flares. We found that the mean duration and spectral width of the radio spikes are equal to 0.036 s and 9.96 MHz, respectively. Distributions of the duration and spectral widths of the spikes have positive skewness for all investigated events. Each spike shows positive or negative frequency drift. The mean negative and positive drifts of the investigated spikes are equal to -776 MHz s-1 and 1608 MHz s-1, respectively. The emission sources of the dm-spikes are located mainly at disk center. We have noticed two kinds of chains, with and without frequency drifts. The mean durations of the chains vary between 0.067 s and 0.509 s, while their spectral widths vary between 7.2 MHz and 17.25 MHz. The mean duration of an individual spike observed in a chain was equal to 0.03 s. While we found some agreement between the global characteristics of the groups of spikes recorded with the two instruments located in Toruń and Ondřejov, we did not find any one-to-one relation between individual spikes.

  8. Assessment of soil contamination with Cd, Pb and Zn and source identification in the area around the Huludao Zinc Plant.

    PubMed

    Lu, C A; Zhang, J F; Jiang, H M; Yang, J C; Zhang, J T; Wang, J Z; Shan, H X

    2010-10-15

    The distribution characteristics of heavy metals (cadmium (Cd), lead (Pb) and zinc (Zn)) in the natural soil profiles around the Huludao Zinc Plant (HZP), an old industrial base in Northeast China, were analyzed. The pollutant source was identified using (210)Pb isotope technique to evaluate the geochemical characteristics of Pb and the historical production records of HZP. The results indicated: dust precipitation from HZP was the primary source of the pollutants. The average deposition rates of Cd, Pb and Zn were 0.33, 1.75, and 30.97 g/m(2)year, respectively at 1 km away after HZP, and 0.0048, 0.035, and 0.20 g/m(2) year, respectively at 10 km away after HZP. There is a risk of secondary pollution to the environment as well as the food chain in seriously polluted areas used for cultivation. 2010 Elsevier B.V. All rights reserved.

  9. Genotoxicity assessment in Eisenia andrei coelomocytes: a study of the induction of DNA damage and micronuclei in earthworms exposed to B[a]P- and TCDD-spiked soils.

    PubMed

    Sforzini, Susanna; Boeri, Marta; Dagnino, Alessandro; Oliveri, Laura; Bolognesi, Claudia; Viarengo, Aldo

    2012-07-04

    Earthworms are useful indicators of soil quality and are widely used as model organisms in terrestrial ecotoxicology. The assessment of genotoxic effects caused by environmental pollutants is of great concern because of their relevance in carcinogenesis. In this work, the earthworm Eisenia andrei was exposed for 10 and 28 days to artificial standard soil contaminated with environmentally relevant concentrations of benzo[a]pyrene (B[a]P) (0.1, 10, 50ppm) and 2,3,7,8-tetrachloro-dibenzo-para-dioxin (TCDD) (1×10(-5), 1×10(-4), 2×10(-3)ppm). Micronucleus (MNi) induction was evaluated in earthworm coelomocytes after DNA staining with the fluorescent dye DAPI. In the same cells, the DNA damage was assessed by means of the alkaline comet assay. Induction of MNi in coelomocytes, identified according to standard criteria, was demonstrated. B[a]P exposure for 10 and 28 days induced a significant increase in MNi frequency. In TCDD-treated earthworms, a significant effect on chromosomal damage was observed at all the concentrations used; surprisingly, greater effects were induced in animals exposed to the lowest concentration (1×10(-5)ppm). The data of the comet assay revealed a significant increase in the level of DNA damage in coelomocytes of earthworms exposed for 10 and 28 days to the different concentrations of B[a]P and TCDD. The results show that the comet and MN assays were able to reveal genotoxic effects in earthworms exposed even to the lowest concentrations of both chemicals tested here. The combined application in E. andrei of the comet assay and the micronucleus test, which reflect different biological mechanisms, may be suggested to identify genotoxic effects induced in these invertebrates by environmental contaminants in terrestrial ecosystems.

  10. The Global Spike: Conserved Dendritic Properties Enable Unique Ca2+ Spike Generation in Low-Threshold Spiking Neurons

    PubMed Central

    Connelly, William M.; Crunelli, Vincenzo

    2015-01-01

    Low-threshold Ca2+ spikes (LTS) are an indispensible signaling mechanism for neurons in areas including the cortex, cerebellum, basal ganglia, and thalamus. They have critical physiological roles and have been strongly associated with disorders including epilepsy, Parkinson's disease, and schizophrenia. However, although dendritic T-type Ca2+ channels have been implicated in LTS generation, because the properties of low-threshold spiking neuron dendrites are unknown, the precise mechanism has remained elusive. Here, combining data from fluorescence-targeted dendritic recordings and Ca2+ imaging from low-threshold spiking cells in rat brain slices with computational modeling, the cellular mechanism responsible for LTS generation is established. Our data demonstrate that key somatodendritic electrical conduction properties are highly conserved between glutamatergic thalamocortical neurons and GABAergic thalamic reticular nucleus neurons and that these properties are critical for LTS generation. In particular, the efficiency of soma to dendrite voltage transfer is highly asymmetric in low-threshold spiking cells, and in the somatofugal direction, these neurons are particularly electrotonically compact. Our data demonstrate that LTS have remarkably similar amplitudes and occur synchronously throughout the dendritic tree. In fact, these Ca2+ spikes cannot occur locally in any part of the cell, and hence we reveal that LTS are generated by a unique whole-cell mechanism that means they always occur as spatially global spikes. This all-or-none, global electrical and biochemical signaling mechanism clearly distinguishes LTS from other signals, including backpropagating action potentials and dendritic Ca2+/NMDA spikes, and has important consequences for dendritic function in low-threshold spiking neurons. SIGNIFICANCE STATEMENT Low-threshold Ca2+ spikes (LTS) are critical for important physiological processes, including generation of sleep-related oscillations, and are

  11. Serial Spike Time Correlations Affect Probability Distribution of Joint Spike Events

    PubMed Central

    Shahi, Mina; van Vreeswijk, Carl; Pipa, Gordon

    2016-01-01

    Detecting the existence of temporally coordinated spiking activity, and its role in information processing in the cortex, has remained a major challenge for neuroscience research. Different methods and approaches have been suggested to test whether the observed synchronized events are significantly different from those expected by chance. To analyze the simultaneous spike trains for precise spike correlation, these methods typically model the spike trains as a Poisson process implying that the generation of each spike is independent of all the other spikes. However, studies have shown that neural spike trains exhibit dependence among spike sequences, such as the absolute and relative refractory periods which govern the spike probability of the oncoming action potential based on the time of the last spike, or the bursting behavior, which is characterized by short epochs of rapid action potentials, followed by longer episodes of silence. Here we investigate non-renewal processes with the inter-spike interval distribution model that incorporates spike-history dependence of individual neurons. For that, we use the Monte Carlo method to estimate the full shape of the coincidence count distribution and to generate false positives for coincidence detection. The results show that compared to the distributions based on homogeneous Poisson processes, and also non-Poisson processes, the width of the distribution of joint spike events changes. Non-renewal processes can lead to both heavy tailed or narrow coincidence distribution. We conclude that small differences in the exact autostructure of the point process can cause large differences in the width of a coincidence distribution. Therefore, manipulations of the autostructure for the estimation of significance of joint spike events seem to be inadequate. PMID:28066225

  12. Serial Spike Time Correlations Affect Probability Distribution of Joint Spike Events.

    PubMed

    Shahi, Mina; van Vreeswijk, Carl; Pipa, Gordon

    2016-01-01

    Detecting the existence of temporally coordinated spiking activity, and its role in information processing in the cortex, has remained a major challenge for neuroscience research. Different methods and approaches have been suggested to test whether the observed synchronized events are significantly different from those expected by chance. To analyze the simultaneous spike trains for precise spike correlation, these methods typically model the spike trains as a Poisson process implying that the generation of each spike is independent of all the other spikes. However, studies have shown that neural spike trains exhibit dependence among spike sequences, such as the absolute and relative refractory periods which govern the spike probability of the oncoming action potential based on the time of the last spike, or the bursting behavior, which is characterized by short epochs of rapid action potentials, followed by longer episodes of silence. Here we investigate non-renewal processes with the inter-spike interval distribution model that incorporates spike-history dependence of individual neurons. For that, we use the Monte Carlo method to estimate the full shape of the coincidence count distribution and to generate false positives for coincidence detection. The results show that compared to the distributions based on homogeneous Poisson processes, and also non-Poisson processes, the width of the distribution of joint spike events changes. Non-renewal processes can lead to both heavy tailed or narrow coincidence distribution. We conclude that small differences in the exact autostructure of the point process can cause large differences in the width of a coincidence distribution. Therefore, manipulations of the autostructure for the estimation of significance of joint spike events seem to be inadequate.

  13. Rates of carbonate soil evolution from carbon, U- and Th-series isotope studies: Example of the Astian sands (SE France)

    NASA Astrophysics Data System (ADS)

    Barbecot, Florent; Ghaleb, Bassam; Hillaire-Marcel, Claude

    2015-04-01

    In carbonate rich soils, C-isotopes (14C, 13C) and carbonate mass budget may inform on centennial to millennial time scale dissolution/precipitation processes and weathering rates, whereas disequilibria between in the U- and Th-decay series provide tools to document high- (228Ra-228Th-210Pb) to low- (234U, 230Th, 231Pa, 226Ra) geochemical processes rate, covering annual to ~ 1Ma time scales, governing both carbonate and silicate soil fractions. Because lithology constitutes a boundary condition, we intend to illustrate the behavior of such isotopes in soils developed over Astian sands formation (up to ~ 30% carbonate) from the Béziers area (SE France). A >20 m thick unsaturated zone was sampled firstly along a naturally exposed section, then in a cored sequence. Geochemical and mineralogical analyses, including stable isotopes and 14C-measurements, were complemented with 228U, 234U, 230Th, 226Ra, 210Pb and 228Th, 232Th measurements. Whereas the upper 7 m depict geochemical and isotopic features forced by dissolution/precipitation processes leading to variable radioactive disequilibria, but overall deficits in more soluble elements of the decay series, the lower part of the sequence shows strong excesses in 234U and 230Th over parent isotopes (i.e., 238U and 234U, respectively). These features might have been interpreted as the result of successive phases of U-loss and gains. However, 226Ra and 230Th are in near-equilibrium, thus leading to conclude at a more likely slow enrichment process in both 234Th(234U) and 230Th, which we link to dissolved U-decay during groundwater recharge events. In addition, 210Pb deficits (vs parent 226Ra) are observed down to 12 m along the natural outcropping section and below the top-soil 210Pb-excess in the cored sequence, due to gaseous 222Rn-diffusion over the cliff outcrop. Based on C-isotope and chemical analysis, reaction rates at 14C-time scale are distinct from those estimates at the short- or long-lived U-series isotopes

  14. Fuzzy logic-based spike sorting system.

    PubMed

    Balasubramanian, Karthikeyan; Obeid, Iyad

    2011-05-15

    We present a new method for autonomous real-time spike sorting using a fuzzy logic inference engine. The engine assigns each detected event a 'spikiness index' from zero to one that quantifies the extent to which the detected event is like an ideal spike. Spikes can then be sorted by simply clustering the spikiness indices. The sorter is defined in terms of natural language rules that, once defined, are static and thus require no user intervention or calibration. The sorter was tested using extracellular recordings from three animals: a macaque, an owl monkey and a rat. Simulation results show that the fuzzy sorter performed equal to or better than the benchmark principal component analysis (PCA) based sorter. Importantly, there was no degradation in fuzzy sorter performance when the spikes were not temporally aligned prior to sorting. In contrast, PCA sorter performance dropped by 27% when sorting unaligned spikes. Since the fuzzy sorter is computationally trivial and requires no spike alignment, it is suitable for scaling into large numbers of parallel channels where computational overhead and the need for operator intervention would preclude other spike sorters.

  15. Motor control by precisely timed spike patterns.

    PubMed

    Srivastava, Kyle H; Holmes, Caroline M; Vellema, Michiel; Pack, Andrea R; Elemans, Coen P H; Nemenman, Ilya; Sober, Samuel J

    2017-01-31

    A fundamental problem in neuroscience is understanding how sequences of action potentials ("spikes") encode information about sensory signals and motor outputs. Although traditional theories assume that this information is conveyed by the total number of spikes fired within a specified time interval (spike rate), recent studies have shown that additional information is carried by the millisecond-scale timing patterns of action potentials (spike timing). However, it is unknown whether or how subtle differences in spike timing drive differences in perception or behavior, leaving it unclear whether the information in spike timing actually plays a role in brain function. By examining the activity of individual motor units (the muscle fibers innervated by a single motor neuron) and manipulating patterns of activation of these neurons, we provide both correlative and causal evidence that the nervous system uses millisecond-scale variations in the timing of spikes within multispike patterns to control a vertebrate behavior-namely, respiration in the Bengalese finch, a songbird. These findings suggest that a fundamental assumption of current theories of motor coding requires revision.

  16. Activation of wicket spikes by REM sleep.

    PubMed

    Serafini, A; Crespel, A; Velizarova, R; Gélisse, P

    2014-09-01

    Wicket spikes consist of monophasic arciform waveforms seen over the temporal regions, either bilaterally or independently over the two hemispheres. They should not be misinterpreted as epileptic abnormalities. They are usually found during light NREM sleep or drowsiness. In this study, we report an activation of wicket spikes by REM sleep. Two patients underwent 48-hour video-EEG. Their sleep macrostructure was analyzed. The presence of wicket spikes was correlated to each specific sleep stage. In one case, wicket spikes appeared exclusively during REM sleep. In another patient, although wicket spikes were present throughout all sleep stages, their frequency was much higher during REM sleep (64% during REM sleep, 22% during light NREM sleep, 14% during drowsiness). This study highlights that wicket spikes may be present exclusively during REM sleep and that this stage of sleep can activate them. This para-physiological rhythm, when first described, was linked to drowsiness and light NREM sleep. The persistence of wicket spikes during REM sleep has been only recently described and an increase in their frequency during this sleep stage has never been previously observed. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  17. Spike Decomposition Technique: Modeling and Performance Tests

    NASA Astrophysics Data System (ADS)

    Nita, G. M.; Fleishman, G. D.; Gary, D. E.

    2008-05-01

    We develop an automated technique for fitting the spectral components of solar microwave spike bursts characterized by narrow-band (1-50~MHz) features of 1-10~ms duration, which are thought to be due to Electron-Cyclotron Maser emission. The algorithm is especially useful for periods when the spikes occur in densely packed clusters, where the algorithm is capable of decomposing overlapping spike structures into individual spectral components. To test the performance and applicability limits of this forward fitting algorithm, we perform comprehensive modeling of spike clusters characterized by various typical bandwidths, spike densities, and amplitude distributions. We find that, for a wide range of input parameters, the algorithm is able to recover the characteristic features of the modeled distributions within reasonable confidence intervals. Having model-tested the algorithm comprehensively against spike overlap, broadband spectral background, noise contamination, and possible contamination of cross-channel polarization, we apply the technique to observational data obtained from different instruments in different frequency ranges. Specifically, we studied spike clusters recorded by a Chinese Purple Mountain Observatory (PMO) spectrometer above 4.5 GHz and by Owens Valley Solar Array's FASR Subsystem Testbed instrument above 1 GHz. We study variation of the spike distribution parameters, such as amplitude, bandwidth and related derived physical parameters as a function of frequency and time. We discuss the implications of our results for the choice between competing models of spike generation and underlying physical processes. The method can be further applied to observations from other instruments and to other types of radio spectral fine structures. This work was supported in part by NSF grants AST-0607544 and ATM-0707319 and NASA grant NNG06GJ40G to New Jersey Institute of Technology.

  18. Capacity of a single spiking neuron

    NASA Astrophysics Data System (ADS)

    Ikeda, Shiro; Manton, Jonathan H.

    2009-12-01

    It is widely believed the neurons transmit information in the form of spikes. Since the spike patterns are known to be noisy, the neuron information channel is noisy. We have investigated the channel capacity of this "Spiking neuron channel" for both of the "temporal coding" and the "rate coding," which are two main coding considered in the neuroscience [1, 2]. As the result, we've proved that the distribution of inputs, which achieves the channel capacity, is a discrete distribution with finite mass points for temporal and rate coding under a reasonable assumption. In this draft, we show the details of the proof.

  19. Vibration (?) spikes during natural rain events

    NASA Technical Reports Server (NTRS)

    Short, David A.

    1994-01-01

    Limited analysis of optical rain gauge (ORG) data from shipboard and ground based sensors has shown the existence of spikes, possibly attributable to sensor vibration, while rain is occurring. An extreme example of this behavior was noted aboard the PRC#5 on the evening of December 24, 1992 as the ship began repositioning during a rain event in the TOGA/COARE IFA. The spikes are readily evident in the one-second resolution data, but may be indistinguishable from natural rain rate fluctuations in subsampled or averaged data. Such spikes result in increased rainfall totals.

  20. Spiking sediment with organochlorines for toxicity testing

    SciTech Connect

    Murdoch, M.H.; Chapman, P.M.; Norman, D.M.; Quintino, V.M.

    1997-07-01

    Sediment toxicity testing integrates responses to sediment variables and hence does not directly indicate cause and effect. One tool for determining cause and effect is sediment spiking, in which relatively uncontaminated sediment is amended with known amounts of contaminants, then tested for toxicity. However, sediment spiking methods vary considerably. The present study details appropriate methodologies (dry and wet spiking) for amending sediments with a range of organic contaminant concentrations, i.e., polychlorinated biphenyl (PCB). Target and actual concentrations were similar. A dose-response was determined, but PCB was not toxic in an acute sediment toxicity test. Chronic testing of these same sediments is reported in a companion article in this issue.

  1. The Second Spiking Threshold: Dynamics of Laminar Network Spiking in the Visual Cortex

    PubMed Central

    Forsberg, Lars E.; Bonde, Lars H.; Harvey, Michael A.; Roland, Per E.

    2016-01-01

    Most neurons have a threshold separating the silent non-spiking state and the state of producing temporal sequences of spikes. But neurons in vivo also have a second threshold, found recently in granular layer neurons of the primary visual cortex, separating spontaneous ongoing spiking from visually evoked spiking driven by sharp transients. Here we examine whether this second threshold exists outside the granular layer and examine details of transitions between spiking states in ferrets exposed to moving objects. We found the second threshold, separating spiking states evoked by stationary and moving visual stimuli from the spontaneous ongoing spiking state, in all layers and zones of areas 17 and 18 indicating that the second threshold is a property of the network. Spontaneous and evoked spiking, thus can easily be distinguished. In addition, the trajectories of spontaneous ongoing states were slow, frequently changing direction. In single trials, sharp as well as smooth and slow transients transform the trajectories to be outward directed, fast and crossing the threshold to become evoked. Although the speeds of the evolution of the evoked states differ, the same domain of the state space is explored indicating uniformity of the evoked states. All evoked states return to the spontaneous evoked spiking state as in a typical mono-stable dynamical system. In single trials, neither the original spiking rates, nor the temporal evolution in state space could distinguish simple visual scenes. PMID:27582693

  2. Advances in applications of spiking neuron networks

    NASA Astrophysics Data System (ADS)

    Cios, Krzysztof J.; Sala, Dorel M.

    2000-03-01

    In this paper, we present new findings in constructing and applications of artificial neural networks that use a biologically inspired spiking neuron model. The used model is a point neuron with the interaction between neurons described by postsynaptic potentials. The synaptic plasticity is achieved by using a temporal correlation learning rule, specified as a function of time difference between the firings of pre- and post-synaptic neurons. Using this rule we show how certain associations between neurons in a network of spiking neurons can be implemented. As an example we analyze the dynamic properties of networks of laterally connected spiking neurons and we show their capability to self-organize into topological maps in response to external stimulation. In another application we explore the capability networks of spiking neurons to solve graph algorithms by using temporal coding of distances in a given spatial configuration. The paper underlines the importance of temporal dimension in artificial neural network information processing.

  3. Fitting Neuron Models to Spike Trains

    PubMed Central

    Rossant, Cyrille; Goodman, Dan F. M.; Fontaine, Bertrand; Platkiewicz, Jonathan; Magnusson, Anna K.; Brette, Romain

    2011-01-01

    Computational modeling is increasingly used to understand the function of neural circuits in systems neuroscience. These studies require models of individual neurons with realistic input–output properties. Recently, it was found that spiking models can accurately predict the precisely timed spike trains produced by cortical neurons in response to somatically injected currents, if properly fitted. This requires fitting techniques that are efficient and flexible enough to easily test different candidate models. We present a generic solution, based on the Brian simulator (a neural network simulator in Python), which allows the user to define and fit arbitrary neuron models to electrophysiological recordings. It relies on vectorization and parallel computing techniques to achieve efficiency. We demonstrate its use on neural recordings in the barrel cortex and in the auditory brainstem, and confirm that simple adaptive spiking models can accurately predict the response of cortical neurons. Finally, we show how a complex multicompartmental model can be reduced to a simple effective spiking model. PMID:21415925

  4. Noise-induced interspike interval correlations and spike train regularization in spike-triggered adapting neurons

    NASA Astrophysics Data System (ADS)

    Urdapilleta, Eugenio

    2016-09-01

    Spike generation in neurons produces a temporal point process, whose statistics is governed by intrinsic phenomena and the external incoming inputs to be coded. In particular, spike-evoked adaptation currents support a slow temporal process that conditions spiking probability at the present time according to past activity. In this work, we study the statistics of interspike interval correlations arising in such non-renewal spike trains, for a neuron model that reproduces different spike modes in a small adaptation scenario. We found that correlations are stronger as the neuron fires at a particular firing rate, which is defined by the adaptation process. When set in a subthreshold regime, the neuron may sustain this particular firing rate, and thus induce correlations, by noise. Given that, in this regime, interspike intervals are negatively correlated at any lag, this effect surprisingly implies a reduction in the variability of the spike count statistics at a finite noise intensity.

  5. Statistical Complexity of Neural Spike Trains

    DTIC Science & Technology

    2014-08-28

    SECURITY CLASSIFICATION OF: We present closed-form expressions for the entropy rate, statistical complexity, and predictive information for the spike...Triangle Park, NC 27709-2211 information, entropy rate, statistical complexity, excess entropy , integrate and fire neuron REPORT DOCUMENTATION PAGE 11...for the entropy rate, statistical complexity, and predictive information for the spike train of a single neuron in terms of the first passage time

  6. Retractable spiked barrier strip for law enforcement

    SciTech Connect

    Marts, D.J.; Barker, S.G.

    1995-03-01

    The Idaho National Engineering Laboratory has designed an laboratory tested a prototype retractable spiked barrier strip for law enforcement. The proposed system, which is ready for controlled field testing, expands the functionality of existing spiked barrier strips. A retractable barrier strip, one that can place the spikes in either the active (vertical) or passive (horizontal) position, would allow law enforcement personnel to lay the unobtrusive strip across a road far in advance of a fleeing vehicle. No damage occurs to passing vehicles until the spikes are activated, and that can be done from a safe distance and at a strategic location when the offending vehicle is close to the strip. The concept also allows the strips to be place safely across several roadways that are potential paths of a fleeing vehicle. Since they are not activated until needed, they are harmless to nonoffending vehicles. The laboratory tests conducted on the system indicate that it will puncture tires only when the spikes are rotated to the active position and is safe to travel over when the spikes are in the down position. The strip itself will not cause instability to a vehicle driving over it, nor is the strip disturbed or adversely affected by vehicles driving over it. The spikes can be quickly rotated between the active (vertical) and passive (horizontal) position. However, the laboratory tests have only demonstrated that the retractable spiked barrier strip can perform its intended function in a laboratory environment. Field tests are needed to finalize the design and develop the system into a functional law enforcement tool.

  7. Graded Synaptic Transmission between Spiking Neurons

    NASA Astrophysics Data System (ADS)

    Graubard, Katherine; Raper, Jonathan A.; Hartline, Daniel K.

    1980-06-01

    Graded synaptic transmission occurs between spiking neurons of the lobster stomatogastric ganglion. In addition to eliciting spike-evoked inhibitory potentials in postsynaptic cells, these neurons also release functionally significant amounts of transmitter below the threshold for action potentials. The spikeless postsynaptic potentials grade in amplitude with presynaptic voltage and can be maintained for long periods. Graded synaptic transmission can be modulated by synaptic input to the presynaptic neuron.

  8. Macroscopic Description for Networks of Spiking Neurons

    NASA Astrophysics Data System (ADS)

    Montbrió, Ernest; Pazó, Diego; Roxin, Alex

    2015-04-01

    A major goal of neuroscience, statistical physics, and nonlinear dynamics is to understand how brain function arises from the collective dynamics of networks of spiking neurons. This challenge has been chiefly addressed through large-scale numerical simulations. Alternatively, researchers have formulated mean-field theories to gain insight into macroscopic states of large neuronal networks in terms of the collective firing activity of the neurons, or the firing rate. However, these theories have not succeeded in establishing an exact correspondence between the firing rate of the network and the underlying microscopic state of the spiking neurons. This has largely constrained the range of applicability of such macroscopic descriptions, particularly when trying to describe neuronal synchronization. Here, we provide the derivation of a set of exact macroscopic equations for a network of spiking neurons. Our results reveal that the spike generation mechanism of individual neurons introduces an effective coupling between two biophysically relevant macroscopic quantities, the firing rate and the mean membrane potential, which together govern the evolution of the neuronal network. The resulting equations exactly describe all possible macroscopic dynamical states of the network, including states of synchronous spiking activity. Finally, we show that the firing-rate description is related, via a conformal map, to a low-dimensional description in terms of the Kuramoto order parameter, called Ott-Antonsen theory. We anticipate that our results will be an important tool in investigating how large networks of spiking neurons self-organize in time to process and encode information in the brain.

  9. Training Deep Spiking Neural Networks Using Backpropagation

    PubMed Central

    Lee, Jun Haeng; Delbruck, Tobi; Pfeiffer, Michael

    2016-01-01

    Deep spiking neural networks (SNNs) hold the potential for improving the latency and energy efficiency of deep neural networks through data-driven event-based computation. However, training such networks is difficult due to the non-differentiable nature of spike events. In this paper, we introduce a novel technique, which treats the membrane potentials of spiking neurons as differentiable signals, where discontinuities at spike times are considered as noise. This enables an error backpropagation mechanism for deep SNNs that follows the same principles as in conventional deep networks, but works directly on spike signals and membrane potentials. Compared with previous methods relying on indirect training and conversion, our technique has the potential to capture the statistics of spikes more precisely. We evaluate the proposed framework on artificially generated events from the original MNIST handwritten digit benchmark, and also on the N-MNIST benchmark recorded with an event-based dynamic vision sensor, in which the proposed method reduces the error rate by a factor of more than three compared to the best previous SNN, and also achieves a higher accuracy than a conventional convolutional neural network (CNN) trained and tested on the same data. We demonstrate in the context of the MNIST task that thanks to their event-driven operation, deep SNNs (both fully connected and convolutional) trained with our method achieve accuracy equivalent with conventional neural networks. In the N-MNIST example, equivalent accuracy is achieved with about five times fewer computational operations. PMID:27877107

  10. Motor control by precisely timed spike patterns

    PubMed Central

    Srivastava, Kyle H.; Holmes, Caroline M.; Vellema, Michiel; Pack, Andrea R.; Elemans, Coen P. H.; Nemenman, Ilya; Sober, Samuel J.

    2017-01-01

    A fundamental problem in neuroscience is understanding how sequences of action potentials (“spikes”) encode information about sensory signals and motor outputs. Although traditional theories assume that this information is conveyed by the total number of spikes fired within a specified time interval (spike rate), recent studies have shown that additional information is carried by the millisecond-scale timing patterns of action potentials (spike timing). However, it is unknown whether or how subtle differences in spike timing drive differences in perception or behavior, leaving it unclear whether the information in spike timing actually plays a role in brain function. By examining the activity of individual motor units (the muscle fibers innervated by a single motor neuron) and manipulating patterns of activation of these neurons, we provide both correlative and causal evidence that the nervous system uses millisecond-scale variations in the timing of spikes within multispike patterns to control a vertebrate behavior—namely, respiration in the Bengalese finch, a songbird. These findings suggest that a fundamental assumption of current theories of motor coding requires revision. PMID:28100491

  11. Training Deep Spiking Neural Networks Using Backpropagation.

    PubMed

    Lee, Jun Haeng; Delbruck, Tobi; Pfeiffer, Michael

    2016-01-01

    Deep spiking neural networks (SNNs) hold the potential for improving the latency and energy efficiency of deep neural networks through data-driven event-based computation. However, training such networks is difficult due to the non-differentiable nature of spike events. In this paper, we introduce a novel technique, which treats the membrane potentials of spiking neurons as differentiable signals, where discontinuities at spike times are considered as noise. This enables an error backpropagation mechanism for deep SNNs that follows the same principles as in conventional deep networks, but works directly on spike signals and membrane potentials. Compared with previous methods relying on indirect training and conversion, our technique has the potential to capture the statistics of spikes more precisely. We evaluate the proposed framework on artificially generated events from the original MNIST handwritten digit benchmark, and also on the N-MNIST benchmark recorded with an event-based dynamic vision sensor, in which the proposed method reduces the error rate by a factor of more than three compared to the best previous SNN, and also achieves a higher accuracy than a conventional convolutional neural network (CNN) trained and tested on the same data. We demonstrate in the context of the MNIST task that thanks to their event-driven operation, deep SNNs (both fully connected and convolutional) trained with our method achieve accuracy equivalent with conventional neural networks. In the N-MNIST example, equivalent accuracy is achieved with about five times fewer computational operations.

  12. Automated stationary source dynamic spiking. Final report

    SciTech Connect

    McGaughey, J.F.

    1998-06-17

    Methods of collection and analysis for monitoring stationary sources must demonstrate conclusively that the methodology is functioning properly and according to specified EPA criteria. The appropriate procedure for demonstrating proper operation of the method is to perform dynamic spiking of the analyte in the field, at the specified source being monitored. Gaseous dynamic spiking, using certified gas mixtures as the spiking medium has been used in previous EPA stationary source sampling methods and documented in EPA reports. Liquid dynamic spiking, using mixtures of liquid and solid analytes in an organic or aqueous solvent has also been used in previous EPA field tests. To remove, as much as possible, the potential for human error, the EPA has developed a prototype liquid dynamic spiking system employing computerized operation of the analyte spiking procedure with video monitoring and control of the liquid droplet frequency and size. This report describes development of the system applicability to stationary source sampling, the individual parts incorporated into the system, and the standard operating procedures.

  13. Using soil seed banks to assess temporal patterns of genetic variation in invasive plant populations

    PubMed Central

    Fennell, Mark; Gallagher, Tommy; Vintro, Luis Leon; Osborne, Bruce

    2014-01-01

    Most research on the genetics of invasive plant species has focused on analyzing spatial differences among existing populations. Using a long-established Gunnera tinctoria population from Ireland, we evaluated the potential of using plants derived from seeds associated with different soil layers to track genetic variation through time. This species and site were chosen because (1) G. tinctoria produces a large and persistent seed bank; (2) it has been present in this locality, Sraheens, for ∼90 years; (3) the soil is largely undisturbed; and (4) the soil's age can be reliably determined radiometrically at different depths. Amplified fragment length polymorphic markers (AFLPs) were used to assess differences in the genetic structure of 75 individuals sampled from both the standing population and from four soil layers, which spanned 18 cm (estimated at ∼90 years based on 210Pb and 137Cs dating). While there are difficulties in interpreting such data, including accounting for the effects of selection, seed loss, and seed migration, a clear pattern of lower total allele counts, percentage polymorphic loci, and genetic diversity was observed in deeper soils. The greatest percentage increase in the measured genetic variables occurred prior to the shift from the lag to the exponential range expansion phases and may be of adaptive significance. These findings highlight that seed banks in areas with long-established invasive populations can contain valuable genetic information relating to invasion processes and as such, should not be overlooked. PMID:24967082

  14. Relationships between spike-free local field potentials and spike timing in human temporal cortex

    PubMed Central

    Zanos, Theodoros P.; Marmarelis, Vasilis Z.; Ojemann, George A.; Fetz, Eberhard E.

    2012-01-01

    Intracortical recordings comprise both fast events, action potentials (APs), and slower events, known as local field potentials (LFPs). Although it is believed that LFPs mostly reflect local synaptic activity, it is unclear which of their signal components are most closely related to synaptic potentials and would therefore be causally related to the occurrence of individual APs. This issue is complicated by the significant contribution from AP waveforms, especially at higher LFP frequencies. In recordings of single-cell activity and LFPs from the human temporal cortex, we computed quantitative, nonlinear, causal dynamic models for the prediction of AP timing from LFPs, at millisecond resolution, before and after removing AP contributions to the LFP. In many cases, the timing of a significant number of single APs could be predicted from spike-free LFPs at different frequencies. Not surprisingly, model performance was superior when spikes were not removed. Cells whose activity was predicted by the spike-free LFP models generally fell into one of two groups: in the first group, neuronal spike activity was associated with specific phases of low LFP frequencies, lower spike activity at high LFP frequencies, and a stronger linear component in the spike-LFP model; in the second group, neuronal spike activity was associated with larger amplitude of high LFP frequencies, less frequent phase locking, and a stronger nonlinear model component. Spike timing in the first group was better predicted by the sign and level of the LFP preceding the spike, whereas spike timing in the second group was better predicted by LFP power during a certain time window before the spike. PMID:22157112

  15. Visually Evoked Spiking Evolves While Spontaneous Ongoing Dynamics Persist

    PubMed Central

    Huys, Raoul; Jirsa, Viktor K.; Darokhan, Ziauddin; Valentiniene, Sonata; Roland, Per E.

    2016-01-01

    Neurons in the primary visual cortex spontaneously spike even when there are no visual stimuli. It is unknown whether the spiking evoked by visual stimuli is just a modification of the spontaneous ongoing cortical spiking dynamics or whether the spontaneous spiking state disappears and is replaced by evoked spiking. This study of laminar recordings of spontaneous spiking and visually evoked spiking of neurons in the ferret primary visual cortex shows that the spiking dynamics does not change: the spontaneous spiking as well as evoked spiking is controlled by a stable and persisting fixed point attractor. Its existence guarantees that evoked spiking return to the spontaneous state. However, the spontaneous ongoing spiking state and the visual evoked spiking states are qualitatively different and are separated by a threshold (separatrix). The functional advantage of this organization is that it avoids the need for a system reorganization following visual stimulation, and impedes the transition of spontaneous spiking to evoked spiking and the propagation of spontaneous spiking from layer 4 to layers 2–3. PMID:26778982

  16. Spike timing control in retinal prosthetic

    NASA Astrophysics Data System (ADS)

    Werblin, Frank

    2005-03-01

    To restore meaningful vision to blind patients requires a retinal prosthetic device that can generate precise spiking patterns in retinal ganglion cells. We sought to develop a stimulus protocol that could reliably elicit one ganglion cell spike for every stimulation pulse over a broad frequency range. Small tipped platinum-iridium epiretinal electrodes were used to deliver biphasic cathodal electrical stimulus pulses at frequencies ranging from 10 to 125 Hz. We measured spiking responses with on-cell patch clamp from ganglion cells in the flat mount rabbit retina, identified by light response and morphology. Single electrical 30 pA cathodal pulses of 1 msec duration elicited both by direct electrical activation of ganglion cells and synaptic excitation and inhibition. Direct activation elicited a single spike that followed the onset of the cathodic pulse by about 100 μsec; presynaptic activation typically elicited multiple spikes which began after 10 msec and could persist for more than 50 ms depending on pulse amplitude levels. Limiting the pulse duration to 100 μsec eliminated all presynaptic activity: only ganglion cells were driven. Each pulse elicited a single pike for stimulation frequencies tested from 10 to125 Hz. Our ability to elicit one spike per pulse provides many important advantages: This protocol can be used to generate temporal patterns of activity in ganglion cells with precision. We can now mimic normal light evoked responses for either transient or sustained cells, and we can modulate spike frequency to simulate changes in intensity, contrast, motion and other essential cues in the visual environment.

  17. GAMMA-RAY CHARACTERIZATION OF THE U-SERIES INTERMEDIATE DAUGHTERS FROM SOIL SAMPLES AT THE PENA BLANCA NATURAL ANALOG, CHIHUAHUA, MEXICO

    SciTech Connect

    D.C. French; E.Y. Anthony; P.C. Goodell

    2005-07-18

    The Pena Blanca natural analog is located in the Sierra Pena Blanca, approximately 50 miles north of Chihuahua City, Mexico. The Sierra Pena Blanca is composed mainly of ash-flow tuffs, and the uranium in the region is contained in the brecciated zones of these tuffs. The Pena Blanca site is considered a natural analog to the proposed Yucca Mountain Nuclear Waste Repository because they share similar characteristics of structure, volcanic lithology, tectonic activity, and hydrologic regime. One of the mineralized zones, the Nopal I deposit, was mined in the early 1980s and the ore was stockpiled close to the mine. This stockpile area has subsequently been cleared and is referred to as the prior high-grade stockpile (PHGS) site. Soil surrounding boulders of high-grade ore associated with the PHGS site have been sampled. The purpose of this study is to characterize the transport of uranium series radioisotopes from the boulder to the soil during the past 25 years. Transport is characterized by determining the activities of individual radionuclides and daughter to parent ratios. The daughter to parent ratios are used to establish whether the samples are in secular equilibrium. Activities are determined using gamma-ray spectroscopy. Isotopes of the uranium series decay chain detected by gamma-ray spectroscopy include {sup 210}Pb, {sup 234}U, {sup 234}Th, {sup 230}Th, {sup 226}Ra, {sup 214}Pb, {sup 214}Bi, and {sup 234}Pa. Preliminary results indicate that some daughter to parent pairs appear to be in secular disequilibrium. Thorium is in excess relative to uranium, and radium is in excess relative to thorium. A deficiency appears to exist for {sup 210}Pb relative to {sup 214}Bi and {sup 214}Pb. If these results are borne out by further analysis, they would suggest transport of nuclides from the high-grade boulder into its surroundings, followed by continued leaching of uranium and lead from the environment.

  18. Spiking Neurons for Analysis of Patterns

    NASA Technical Reports Server (NTRS)

    Huntsberger, Terrance

    2008-01-01

    Artificial neural networks comprising spiking neurons of a novel type have been conceived as improved pattern-analysis and pattern-recognition computational systems. These neurons are represented by a mathematical model denoted the state-variable model (SVM), which among other things, exploits a computational parallelism inherent in spiking-neuron geometry. Networks of SVM neurons offer advantages of speed and computational efficiency, relative to traditional artificial neural networks. The SVM also overcomes some of the limitations of prior spiking-neuron models. There are numerous potential pattern-recognition, tracking, and data-reduction (data preprocessing) applications for these SVM neural networks on Earth and in exploration of remote planets. Spiking neurons imitate biological neurons more closely than do the neurons of traditional artificial neural networks. A spiking neuron includes a central cell body (soma) surrounded by a tree-like interconnection network (dendrites). Spiking neurons are so named because they generate trains of output pulses (spikes) in response to inputs received from sensors or from other neurons. They gain their speed advantage over traditional neural networks by using the timing of individual spikes for computation, whereas traditional artificial neurons use averages of activity levels over time. Moreover, spiking neurons use the delays inherent in dendritic processing in order to efficiently encode the information content of incoming signals. Because traditional artificial neurons fail to capture this encoding, they have less processing capability, and so it is necessary to use more gates when implementing traditional artificial neurons in electronic circuitry. Such higher-order functions as dynamic tasking are effected by use of pools (collections) of spiking neurons interconnected by spike-transmitting fibers. The SVM includes adaptive thresholds and submodels of transport of ions (in imitation of such transport in biological

  19. Spiking Neural Networks Based on OxRAM Synapses for Real-Time Unsupervised Spike Sorting

    PubMed Central

    Werner, Thilo; Vianello, Elisa; Bichler, Olivier; Garbin, Daniele; Cattaert, Daniel; Yvert, Blaise; De Salvo, Barbara; Perniola, Luca

    2016-01-01

    In this paper, we present an alternative approach to perform spike sorting of complex brain signals based on spiking neural networks (SNN). The proposed architecture is suitable for hardware implementation by using resistive random access memory (RRAM) technology for the implementation of synapses whose low latency (<1μs) enables real-time spike sorting. This offers promising advantages to conventional spike sorting techniques for brain-computer interfaces (BCI) and neural prosthesis applications. Moreover, the ultra-low power consumption of the RRAM synapses of the spiking neural network (nW range) may enable the design of autonomous implantable devices for rehabilitation purposes. We demonstrate an original methodology to use Oxide based RRAM (OxRAM) as easy to program and low energy (<75 pJ) synapses. Synaptic weights are modulated through the application of an online learning strategy inspired by biological Spike Timing Dependent Plasticity. Real spiking data have been recorded both intra- and extracellularly from an in-vitro preparation of the Crayfish sensory-motor system and used for validation of the proposed OxRAM based SNN. This artificial SNN is able to identify, learn, recognize and distinguish between different spike shapes in the input signal with a recognition rate about 90% without any supervision. PMID:27857680

  20. Transitory effect of spike and spike-and-wave discharges on EEG power in children.

    PubMed

    Nair, Swayamprabha; Morse, Richard P; Mott, Stephen H; Burroughs, Scott A; Holmes, Gregory L

    2014-06-01

    Spikes and spike-and-wave discharges on the EEG of children are a strong biomarker of epilepsy. There is increasing evidence that these EEG abnormalities also impair brain function and result in transitory cognitive impairment. Studies in animal models have shown that EEG spikes alters single cell firing and that such impairment in firing may extend beyond the duration of the spike-and-wave discharge. Whether interictal epileptiform discharges have lasting effects on EEG activity in humans is not known. The EEGs of 60 consecutive children with focal or interictal spike-and-wave discharges were evaluated using power spectral analysis to determine if there were any changes in power spectra from before to after the interictal abnormalities. Neither focal spike-and-wave nor generalized spike-and-wave discharges had any effect on the EEG frequency or spectral power following the discharge. While interictal EEG discharges temporarily alter neural activity during the duration of the spike-and-wave discharge, there is no evidence that alterations of spectral power continue beyond the duration of the interictal discharge. The effects of interictal activity on EEG rhythms therefore appear to be quite transient and confined to the duration of the interictal discharge. Copyright © 2013 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.

  1. Spiking Neural Networks Based on OxRAM Synapses for Real-Time Unsupervised Spike Sorting.

    PubMed

    Werner, Thilo; Vianello, Elisa; Bichler, Olivier; Garbin, Daniele; Cattaert, Daniel; Yvert, Blaise; De Salvo, Barbara; Perniola, Luca

    2016-01-01

    In this paper, we present an alternative approach to perform spike sorting of complex brain signals based on spiking neural networks (SNN). The proposed architecture is suitable for hardware implementation by using resistive random access memory (RRAM) technology for the implementation of synapses whose low latency (<1μs) enables real-time spike sorting. This offers promising advantages to conventional spike sorting techniques for brain-computer interfaces (BCI) and neural prosthesis applications. Moreover, the ultra-low power consumption of the RRAM synapses of the spiking neural network (nW range) may enable the design of autonomous implantable devices for rehabilitation purposes. We demonstrate an original methodology to use Oxide based RRAM (OxRAM) as easy to program and low energy (<75 pJ) synapses. Synaptic weights are modulated through the application of an online learning strategy inspired by biological Spike Timing Dependent Plasticity. Real spiking data have been recorded both intra- and extracellularly from an in-vitro preparation of the Crayfish sensory-motor system and used for validation of the proposed OxRAM based SNN. This artificial SNN is able to identify, learn, recognize and distinguish between different spike shapes in the input signal with a recognition rate about 90% without any supervision.

  2. Nonsmooth dynamics in spiking neuron models

    NASA Astrophysics Data System (ADS)

    Coombes, S.; Thul, R.; Wedgwood, K. C. A.

    2012-11-01

    Large scale studies of spiking neural networks are a key part of modern approaches to understanding the dynamics of biological neural tissue. One approach in computational neuroscience has been to consider the detailed electrophysiological properties of neurons and build vast computational compartmental models. An alternative has been to develop minimal models of spiking neurons with a reduction in the dimensionality of both parameter and variable space that facilitates more effective simulation studies. In this latter case the single neuron model of choice is often a variant of the classic integrate-and-fire model, which is described by a nonsmooth dynamical system. In this paper we review some of the more popular spiking models of this class and describe the types of spiking pattern that they can generate (ranging from tonic to burst firing). We show that a number of techniques originally developed for the study of impact oscillators are directly relevant to their analysis, particularly those for treating grazing bifurcations. Importantly we highlight one particular single neuron model, capable of generating realistic spike trains, that is both computationally cheap and analytically tractable. This is a planar nonlinear integrate-and-fire model with a piecewise linear vector field and a state dependent reset upon spiking. We call this the PWL-IF model and analyse it at both the single neuron and network level. The techniques and terminology of nonsmooth dynamical systems are used to flesh out the bifurcation structure of the single neuron model, as well as to develop the notion of Lyapunov exponents. We also show how to construct the phase response curve for this system, emphasising that techniques in mathematical neuroscience may also translate back to the field of nonsmooth dynamical systems. The stability of periodic spiking orbits is assessed using a linear stability analysis of spiking times. At the network level we consider linear coupling between voltage

  3. Evolution of vegetation and soil nutrients after uranium mining in Los Ratones mine (Cáceres, Spain).

    PubMed

    Pérez-Fernández, María A; Vera-Tomé, Feliciano; Blanco-Rodríguez, María P; Lozano, Juan C

    2014-06-01

    The evolution of vegetation structure following mine rehabilitation is rather scarce in the literature. The concentration of long-lived radionuclides of the (238)U series might have harmful effects on living organisms. We studied soil properties and the natural vegetation occurring along a gradient in Los Ratones, an area rehabilitated after uranium mining located in Cáceres, Spain. Soil and vegetation were sampled seasonally and physical and chemical properties of soil were analysed, including natural isotopes of (238)U, (230)Th, (226)Ra and (210)Pb. Species richness, diversity, evenness and plant cover were estimated and correlated in relation to soil physical and chemical variables. The location of the sampling sites along a gradient had a strong explanatory effect on the herbaceous species, as well as the presence of shrubs and trees. Seasonal effects of the four natural isotopes were observed in species richness, species diversity and plant cover; these effects were directly related to the pH values in the soil, this being the soil property that most influences the plant distribution. Vegetation in the studied area resembles that of the surroundings, thus proving that the rehabilitation carried out in Los Ratones mine was successful in terms of understorey cover recovery.

  4. Mikkelson sweep/spike chisel plow shovel

    SciTech Connect

    Not Available

    1992-01-01

    Profitability comparisons are reported between the Mikkelson Sweep/Spike Chisel Plow Shovel standard sweeps. This evaluation covers the first year of testing of the new Sweep/Spike design. The data are not averaged over treatments due to significant interaction between treatments and environmental factors. The cost of fuel, fall and spring, to perform the various treatments ranged from $1.27 to $3.36 per acre. Use of the sweep/spike shovel always reduced total fuel cost. Savings varied from $0.11 to $0.71 per acre depending on prior treatment. This means there will be money saved, to off-set expenses, when converting present chisel plows or for special options on new chisel plows, needed for use of the sweep/spike shovel. A summary of 1991--1992 energy measurements. They indicate that more power will be required to pull a chisel plow equipped with the sweep/spike shovel. A larger tractor, narrower chisel plow and/or slower speed will be required to avoid the wheel slippage problems encountered on soft or wet field surfaces.

  5. Spike Code Flow in Cultured Neuronal Networks.

    PubMed

    Tamura, Shinichi; Nishitani, Yoshi; Hosokawa, Chie; Miyoshi, Tomomitsu; Sawai, Hajime; Kamimura, Takuya; Yagi, Yasushi; Mizuno-Matsumoto, Yuko; Chen, Yen-Wei

    2016-01-01

    We observed spike trains produced by one-shot electrical stimulation with 8 × 8 multielectrodes in cultured neuronal networks. Each electrode accepted spikes from several neurons. We extracted the short codes from spike trains and obtained a code spectrum with a nominal time accuracy of 1%. We then constructed code flow maps as movies of the electrode array to observe the code flow of "1101" and "1011," which are typical pseudorandom sequence such as that we often encountered in a literature and our experiments. They seemed to flow from one electrode to the neighboring one and maintained their shape to some extent. To quantify the flow, we calculated the "maximum cross-correlations" among neighboring electrodes, to find the direction of maximum flow of the codes with lengths less than 8. Normalized maximum cross-correlations were almost constant irrespective of code. Furthermore, if the spike trains were shuffled in interval orders or in electrodes, they became significantly small. Thus, the analysis suggested that local codes of approximately constant shape propagated and conveyed information across the network. Hence, the codes can serve as visible and trackable marks of propagating spike waves as well as evaluating information flow in the neuronal network.

  6. Toward a definition of MEG spike: parametric description of spikes recorded simultaneously by MEG and depth electrodes.

    PubMed

    Nowak, Rafal; Santiuste, Marta; Russi, Antonio

    2009-11-01

    There is not yet a formal definition of magnetoencephalography (MEG) spike. This study provides a parametric description and definition of clear-cut MEG spikes recorded simultaneously by MEG and depth electrodes (iEEG). A total number of 367 simultaneous MEG/iEEG spikes were selected for analysis. Distribution of morphologic spike parameters and detailed quantitative analysis of the basic morphologic characteristics of MEG spikes is provided.

  7. Filter based phase distortions in extracellular spikes.

    PubMed

    Yael, Dorin; Bar-Gad, Izhar

    2017-01-01

    Extracellular recordings are the primary tool for extracting neuronal spike trains in-vivo. One of the crucial pre-processing stages of this signal is the high-pass filtration used to isolate neuronal spiking activity. Filters are characterized by changes in the magnitude and phase of different frequencies. While filters are typically chosen for their effect on magnitudes, little attention has been paid to the impact of these filters on the phase of each frequency. In this study we show that in the case of nonlinear phase shifts generated by most online and offline filters, the signal is severely distorted, resulting in an alteration of the spike waveform. This distortion leads to a shape that deviates from the original waveform as a function of its constituent frequencies, and a dramatic reduction in the SNR of the waveform that disrupts spike detectability. Currently, the vast majority of articles utilizing extracellular data are subject to these distortions since most commercial and academic hardware and software utilize nonlinear phase filters. We show that this severe problem can be avoided by recording wide-band signals followed by zero phase filtering, or alternatively corrected by reversed filtering of a narrow-band filtered, and in some cases even segmented signals. Implementation of either zero phase filtering or phase correction of the nonlinear phase filtering reproduces the original spike waveforms and increases the spike detection rates while reducing the number of false negative and positive errors. This process, in turn, helps eliminate subsequent errors in downstream analyses and misinterpretations of the results.

  8. Filter based phase distortions in extracellular spikes

    PubMed Central

    Yael, Dorin

    2017-01-01

    Extracellular recordings are the primary tool for extracting neuronal spike trains in-vivo. One of the crucial pre-processing stages of this signal is the high-pass filtration used to isolate neuronal spiking activity. Filters are characterized by changes in the magnitude and phase of different frequencies. While filters are typically chosen for their effect on magnitudes, little attention has been paid to the impact of these filters on the phase of each frequency. In this study we show that in the case of nonlinear phase shifts generated by most online and offline filters, the signal is severely distorted, resulting in an alteration of the spike waveform. This distortion leads to a shape that deviates from the original waveform as a function of its constituent frequencies, and a dramatic reduction in the SNR of the waveform that disrupts spike detectability. Currently, the vast majority of articles utilizing extracellular data are subject to these distortions since most commercial and academic hardware and software utilize nonlinear phase filters. We show that this severe problem can be avoided by recording wide-band signals followed by zero phase filtering, or alternatively corrected by reversed filtering of a narrow-band filtered, and in some cases even segmented signals. Implementation of either zero phase filtering or phase correction of the nonlinear phase filtering reproduces the original spike waveforms and increases the spike detection rates while reducing the number of false negative and positive errors. This process, in turn, helps eliminate subsequent errors in downstream analyses and misinterpretations of the results. PMID:28358895

  9. Detecting joint pausiness in parallel spike trains.

    PubMed

    Gärtner, Matthias; Duvarci, Sevil; Roeper, Jochen; Schneider, Gaby

    2017-06-15

    Transient periods with reduced neuronal discharge - called 'pauses' - have recently gained increasing attention. In dopamine neurons, pauses are considered important teaching signals, encoding negative reward prediction errors. Particularly simultaneous pauses are likely to have increased impact on information processing. Available methods for detecting joint pausing analyze temporal overlap of pauses across spike trains. Such techniques are threshold dependent and can fail to identify joint pauses that are easily detectable by eye, particularly in spike trains with different firing rates. We introduce a new statistic called pausiness that measures the degree of synchronous pausing in spike train pairs and avoids threshold-dependent identification of specific pauses. A new graphic termed the cross-pauseogram compares the joint pausiness of two spike trains with its time shifted analogue, such that a (pausiness) peak indicates joint pausing. When assessing significance of pausiness peaks, we use a stochastic model with synchronous spikes to disentangle joint pausiness arising from synchronous spikes from additional 'joint excess pausiness' (JEP). Parameter estimates are obtained from auto- and cross-correlograms, and statistical significance is assessed by comparison to simulated cross-pauseograms. Our new method was applied to dopamine neuron pairs recorded in the ventral tegmental area of awake behaving mice. Significant JEP was detected in about 20% of the pairs. Given the neurophysiological importance of pauses and the fact that neurons integrate multiple inputs, our findings suggest that the analysis of JEP can reveal interesting aspects in the activity of simultaneously recorded neurons. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Temporal Correlations and Neural Spike Train Entropy

    SciTech Connect

    Schultz, Simon R.; Panzeri, Stefano

    2001-06-18

    Sampling considerations limit the experimental conditions under which information theoretic analyses of neurophysiological data yield reliable results. We develop a procedure for computing the full temporal entropy and information of ensembles of neural spike trains, which performs reliably for limited samples of data. This approach also yields insight to the role of correlations between spikes in temporal coding mechanisms. The method, when applied to recordings from complex cells of the monkey primary visual cortex, results in lower rms error information estimates in comparison to a {open_quotes}brute force{close_quotes} approach.

  11. Evoking prescribed spike times in stochastic neurons

    NASA Astrophysics Data System (ADS)

    Doose, Jens; Lindner, Benjamin

    2017-09-01

    Single cell stimulation in vivo is a powerful tool to investigate the properties of single neurons and their functionality in neural networks. We present a method to determine a cell-specific stimulus that reliably evokes a prescribed spike train with high temporal precision of action potentials. We test the performance of this stimulus in simulations for two different stochastic neuron models. For a broad range of parameters and a neuron firing with intermediate firing rates (20-40 Hz) the reliability in evoking the prescribed spike train is close to its theoretical maximum that is mainly determined by the level of intrinsic noise.

  12. Implementing Signature Neural Networks with Spiking Neurons

    PubMed Central

    Carrillo-Medina, José Luis; Latorre, Roberto

    2016-01-01

    Spiking Neural Networks constitute the most promising approach to develop realistic Artificial Neural Networks (ANNs). Unlike traditional firing rate-based paradigms, information coding in spiking models is based on the precise timing of individual spikes. It has been demonstrated that spiking ANNs can be successfully and efficiently applied to multiple realistic problems solvable with traditional strategies (e.g., data classification or pattern recognition). In recent years, major breakthroughs in neuroscience research have discovered new relevant computational principles in different living neural systems. Could ANNs benefit from some of these recent findings providing novel elements of inspiration? This is an intriguing question for the research community and the development of spiking ANNs including novel bio-inspired information coding and processing strategies is gaining attention. From this perspective, in this work, we adapt the core concepts of the recently proposed Signature Neural Network paradigm—i.e., neural signatures to identify each unit in the network, local information contextualization during the processing, and multicoding strategies for information propagation regarding the origin and the content of the data—to be employed in a spiking neural network. To the best of our knowledge, none of these mechanisms have been used yet in the context of ANNs of spiking neurons. This paper provides a proof-of-concept for their applicability in such networks. Computer simulations show that a simple network model like the discussed here exhibits complex self-organizing properties. The combination of multiple simultaneous encoding schemes allows the network to generate coexisting spatio-temporal patterns of activity encoding information in different spatio-temporal spaces. As a function of the network and/or intra-unit parameters shaping the corresponding encoding modality, different forms of competition among the evoked patterns can emerge even in the

  13. Implementing Signature Neural Networks with Spiking Neurons.

    PubMed

    Carrillo-Medina, José Luis; Latorre, Roberto

    2016-01-01

    Spiking Neural Networks constitute the most promising approach to develop realistic Artificial Neural Networks (ANNs). Unlike traditional firing rate-based paradigms, information coding in spiking models is based on the precise timing of individual spikes. It has been demonstrated that spiking ANNs can be successfully and efficiently applied to multiple realistic problems solvable with traditional strategies (e.g., data classification or pattern recognition). In recent years, major breakthroughs in neuroscience research have discovered new relevant computational principles in different living neural systems. Could ANNs benefit from some of these recent findings providing novel elements of inspiration? This is an intriguing question for the research community and the development of spiking ANNs including novel bio-inspired information coding and processing strategies is gaining attention. From this perspective, in this work, we adapt the core concepts of the recently proposed Signature Neural Network paradigm-i.e., neural signatures to identify each unit in the network, local information contextualization during the processing, and multicoding strategies for information propagation regarding the origin and the content of the data-to be employed in a spiking neural network. To the best of our knowledge, none of these mechanisms have been used yet in the context of ANNs of spiking neurons. This paper provides a proof-of-concept for their applicability in such networks. Computer simulations show that a simple network model like the discussed here exhibits complex self-organizing properties. The combination of multiple simultaneous encoding schemes allows the network to generate coexisting spatio-temporal patterns of activity encoding information in different spatio-temporal spaces. As a function of the network and/or intra-unit parameters shaping the corresponding encoding modality, different forms of competition among the evoked patterns can emerge even in the absence

  14. Neuronal spike trains and stochastic point processes. I. The single spike train.

    PubMed

    Perkel, D H; Gerstein, G L; Moore, G P

    1967-07-01

    In a growing class of neurophysiological experiments, the train of impulses ("spikes") produced by a nerve cell is subjected to statistical treatment involving the time intervals between spikes. The statistical techniques available for the analysis of single spike trains are described and related to the underlying mathematical theory, that of stochastic point processes, i.e., of stochastic processes whose realizations may be described as series of point events occurring in time, separated by random intervals. For single stationary spike trains, several orders of complexity of statistical treatment are described; the major distinction is that between statistical measures that depend in an essential way on the serial order of interspike intervals and those that are order-independent. The interrelations among the several types of calculations are shown, and an attempt is made to ameliorate the current nomenclatural confusion in this field. Applications, interpretations, and potential difficulties of the statistical techniques are discussed, with special reference to types of spike trains encountered experimentally. Next, the related types of analysis are described for experiments which involve repeated presentations of a brief, isolated stimulus. Finally, the effects of nonstationarity, e.g. long-term changes in firing rate, on the various statistical measures are discussed. Several commonly observed patterns of spike activity are shown to be differentially sensitive to such changes. A companion paper covers the analysis of simultaneously observed spike trains.

  15. Correcting the bias of spike field coherence estimators due to a finite number of spikes.

    PubMed

    Grasse, D W; Moxon, K A

    2010-07-01

    The coherence between oscillatory activity in local field potentials (LFPs) and single neuron action potentials, or spikes, has been suggested as a neural substrate for the representation of information. The power spectrum of a spike-triggered average (STA) is commonly used to estimate spike field coherence (SFC). However, when a finite number of spikes is used to construct the STA, the coherence estimator is biased. We introduce here a correction for the bias imposed by the limited number of spikes available in experimental conditions. In addition, we present an alternative method for estimating SFC from an STA by using a filter bank approach. This method is shown to be more appropriate in some analyses, such as comparing coherence across frequency bands. The proposed bias correction is a linear transformation derived from an idealized model of spike-field interaction but is shown to hold in more realistic settings. Uncorrected and corrected SFC estimates from both estimation methods are compared across multiple simulated spike-field models and experimentally collected data. The bias correction was shown to reduce the bias of the estimators, but add variance. However, the corrected estimates had a reduced or unchanged mean squared error in the majority of conditions evaluated. The bias correction provides an effective way to reduce bias in an SFC estimator without increasing the mean squared error.

  16. Kv1 channels control spike threshold dynamics and spike timing in cortical pyramidal neurones

    PubMed Central

    Higgs, Matthew H; Spain, William J

    2011-01-01

    Abstract Previous studies showed that cortical pyramidal neurones (PNs) have a dynamic spike threshold that functions as a high-pass filter, enhancing spike timing in response to high-frequency input. While it is commonly assumed that Na+ channel inactivation is the primary mechanism of threshold accommodation, the possible role of K+ channel activation in fast threshold changes has not been well characterized. The present study tested the hypothesis that low-voltage activated Kv1 channels affect threshold dynamics in layer 2–3 PNs, using α-dendrotoxin (DTX) or 4-aminopyridine (4-AP) to block these conductances. We found that Kv1 blockade reduced the dynamic changes of spike threshold in response to a variety of stimuli, including stimulus-evoked synaptic input, current steps and ramps of varied duration, and noise. Analysis of the responses to noise showed that Kv1 channels increased the coherence of spike output with high-frequency components of the stimulus. A simple model demonstrates that a dynamic spike threshold can account for this effect. Our results show that the Kv1 conductance is a major mechanism that contributes to the dynamic spike threshold and precise spike timing of cortical PNs. PMID:21911608

  17. The dependence of spike field coherence on expected intensity.

    PubMed

    Lepage, Kyle Q; Kramer, Mark A; Eden, Uri T

    2011-09-01

    The coherence between neural spike trains and local-field potential recordings, called spike-field coherence, is of key importance in many neuroscience studies. In this work, aside from questions of estimator performance, we demonstrate that theoretical spike-field coherence for a broad class of spiking models depends on the expected rate of spiking. This rate dependence confounds the phase locking of spike events to field-potential oscillations with overall neuron activity and is demonstrated analytically, for a large class of stochastic models, and in simulation. Finally, the relationship between the spike-field coherence and the intensity field coherence is detailed analytically. This latter quantity is independent of neuron firing rate and, under commonly found conditions, is proportional to the probability that a neuron spikes at a specific phase of field oscillation. Hence, intensity field coherence is a rate-independent measure and a candidate on which to base the appropriate statistical inference of spike field synchrony.

  18. Spike timing and information transmission at retinogeniculate synapses

    PubMed Central

    Rathbun, Daniel L.; Warland, David K.; Usrey, W. Martin

    2010-01-01

    This study examines the rules governing the transfer of spikes between the retina and LGN with the goal of determining whether the most informative retinal spikes preferentially drive LGN responses and what role spike timing plays in the process. By recording from monosynaptically-connected pairs of retinal ganglion cells and LGN neurons in vivo in the cat, we show that relayed spikes are more likely than non-relayed spikes to be evoked by stimuli that match the recorded cells’ receptive fields and that an interspike interval (ISI)-based mechanism contributes to the process. Relayed spikes are also more reliable in their timing and number where they often achieve the theoretical limit of minimum variance. As a result, relayed spikes carry more visual information per spike. Based on