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Sample records for 210pb spiked soils

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

    OpenAIRE

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

    2008-01-01

    International audience; 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 al...

  2. {sup 210}Pb and stable lead content in fungi: Its transfer from soil

    Energy Technology Data Exchange (ETDEWEB)

    Guillen, J., E-mail: fguillen@unex.es [LARUEX, Dpt. Applied Physics, C.U.M. University of Extremadura, c/ Sta. Teresa de Jornet, 38, 06800 Merida (Badajoz) (Spain); Baeza, A. [LARUEX, Dpt. Applied Physics, Faculty of Veterinary Science, University of Extremadura, Avda. Universidad, s/n, 10071 Caceres (Spain); Ontalba, M.A. [LARUEX, Dpt. Applied Physics, Polytechnics School, University of Extremadura, Avda. Universidad, s/n, 10071 Caceres (Spain); Miguez, M.P. [Unit of Toxicology, Faculty of Veterinary Science, University of Extremadura, Avda. Universidad, s/n, 10071 Caceres (Spain)

    2009-07-01

    The uptake and transfer of natural radionuclides, other than {sup 40}K, from soil to mushrooms has been somewhat overlooked in the literature. Their contribution to the dose due to the consumption of mushrooms was considered negligible. But the contribution of {sup 210}Pb in areas unaffected by any recent radioactive fallout has been found to be significant, up to 35% of the annual dose commitment in Spain. More than 30 species of mushrooms were analyzed, and the {sup 210}Pb detected was in the range of 0.75-202 Bq/kg d.w. A slight difference was observed between species with different nutritional mechanisms (saprophytes {>=} mycorrhizae). The {sup 210}Pb content was correlated with the stable lead content, but not with its predecessor in the uranium radioactive series, {sup 226}Ra. This suggested that {sup 210}Pb was taken up from the soil by the same pathway as stable lead. The bioavailability of {sup 210}Pb in soil was determined by means of a sequential extraction procedure (NH{sub 4}OAc, 1M HCl, 6M HCl, and residue). About 30% of the {sup 210}Pb present in the soil was available for transfer to mushrooms, more than other natural radionuclides in the same ecosystem. Lycoperdon perlatum, Hebeloma cylindrosporum, and Amanita curtipes presented the highest values of the available transfer factor, ATF. As reflected in their ATF values, the transfer from soil to mushroom of some natural and anthropogenic radionuclides was in the following order: {sup 228,230,232}Th {approx} {sup 40}K {>=} {sup 137}Cs {>=} {sup 234,238}U {approx} {sup 226}Ra {>=} {sup 90}Sr {>=} {sup 210}Pb {approx} {sup 239+240}Pu {approx} {sup 241}Am.

  3. Distribution of {sup 210}Pb and {sup 210}Po in boreal forest soil

    Energy Technology Data Exchange (ETDEWEB)

    Vaaramaa, Kaisa, E-mail: kaisa.vaaramaa@stuk.fi [Laboratory of Radiochemistry, Department of Chemistry, P.O. Box 55, FIN-00014 University of Helsinki (Finland); Aro, Lasse [Finnish Forest Research Institute (METLA), Parkano Research Unit, Kaironiementie 54, 39700 Parkano (Finland); Solatie, Dina [STUK-Radiation and Nuclear Safety Authority, Regional Laboratory in Northern Finland, Laehteentie 2, 96400 Rovaniemi (Finland); Lehto, Jukka [Laboratory of Radiochemistry, Department of Chemistry, P.O. Box 55, FIN-00014 University of Helsinki (Finland)

    2010-11-15

    Vertical distribution and activity contents of {sup 210}Pb and {sup 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 20 cm, of {sup 210}Pb was 4.0 kBq m{sup -2} (range 3.1-5.0 kBq m{sup -2}) and {sup 210}Po 5.5 kBq m{sup -2} (range 4.0-7.4 kBq m{sup -2}), the organic soil layer containing 45% of the total inventory of both nuclides. In both the organic and the mineral layers the {sup 210}Po/{sup 210}Pb ratio was close to unity indicating a radioactive equilibrium between them. In the litter layer there was, however, a clear excess of {sup 210}Po suggesting that polonium is recycled via root uptake from the root zone to the ground surface. The activity concentration (Bq kg{sup -1}) of {sup 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. {sup 137}Cs and {sup 210}Pb inventories in soils and sediments from Chapala Lake (Mexico)

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz-Fernandez, A.C.; Perez-Bernal, L.H. [Unidad Academica Mazatlan, Instituto de Ciencias del Mar y Limnologia, Universidad Nacional Autonoma de Mexico (Mexico); Sanchez-Cabeza, J.A. [Unidad Academica de Procesos Oceanicos y Costeros, Instituto de Ciencias del Mar y Limnologia, Universidad Nacional Autonoma de Mexico (Mexico); Ontiveros-Cuadras, J.F. [Posgrado en Ciencias del Mar y Limnologia, Instituto de Ciencias del Mar y Limnologia, Universidad Nacional Autonoma de Mexico (Mexico)

    2014-07-01

    Chapala Lake is the largest natural freshwater reservoir in Mexico and it is located in Central Mexico, at 1524 m above sea level. The lake is considered to be fairly anthropized and it has experienced periods of extremely low water level as a result of recent climate change and water extraction. The study of recent manifestations of global change in Chapala Lake requires accurate {sup 210}Pb chronological reconstructions, taking into account the expected variability of sediment accumulation rates by using the Constant Flux model. For a reliable application of this dating model, it is important that {sup 210}Pb flux values in the lacustrine sedimentary record are in correspondence with the local atmospheric fluxes. With the aim to estimate the fluxes of the fallout radionuclides {sup 210}Pb and {sup 137}Cs in the region, sediment and soil cores were collected in the Chapala Lake. Sediment profiles were evaluated and estimated fluxes in sediments and soils were compared. Some geochemical properties (e.g. grain size distribution, organic matter concentration, XRF-derived elemental composition and magnetic susceptibility) were also evaluated to understand how diagenesis changes and sediment provenance can affect the {sup 210}Pb and {sup 137}Cs depth profiles and inventories. Document available in abstract form only. (authors)

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

    Science.gov (United States)

    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.

  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].

    Science.gov (United States)

    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.

    Science.gov (United States)

    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.

  8. Effects of the composition of standard reference material on the accuracy of determinations of {sup 210}Pb and {sup 137}Cs in soils with gamma spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Li, Y., E-mail: yongli32@hotmail.co [State Key Laboratory of Dryland Farming and Soil Erosion in the Loess Plateau, Institute of Soil and Water Conservation, CAS and MWR, Yangling 712100 (China); Institute of Environment and Sustainable Development in Agriculture, CAAS, No. 12 Zhongguancun South Street, Beijing 100081 (China); Geng, X.C.; Yu, H.Q. [Institute of Environment and Sustainable Development in Agriculture, CAAS, No. 12 Zhongguancun South Street, Beijing 100081 (China); Wan, G.J. [State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang (China)

    2011-02-15

    The effect of the composition of the used standard reference material (SRM) on results of determination of fallout radionuclides in soil samples was studied. Using five soil types as SRMs, we measured the specific activity of {sup 210}Pb and {sup 137}Cs in six target samples of Chestnut soil. It was observed that the determination of the {sup 210}Pb activity in the samples depended on the chemical composition of SRMs used to create the efficiency curves. Thus, using SRMs similar in chemical composition to the target samples should improve accuracy in the determination of {sup 210}Pb in environmental samples.

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

    Science.gov (United States)

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

    Science.gov (United States)

    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.

  11. Transfer of {sup 40}K, {sup 238}U, {sup 210}Pb, and {sup 210}Po from soil to plant in various locations in south of Syria

    Energy Technology Data Exchange (ETDEWEB)

    Al-Masri, M.S. [Atomic Energy Commission of Syria, Damascus, P.O. Box 6091 (Syrian Arab Republic)], E-mail: scientific1@aec.org.sy; Al-Akel, B.; Nashawani, A.; Amin, Y.; Khalifa, K.H.; Al-Ain, F. [Atomic Energy Commission of Syria, Damascus, P.O. Box 6091 (Syrian Arab Republic)

    2008-02-15

    Transfer factors of {sup 40}K, {sup 238}U, {sup 210}Pb, and {sup 210}Po from soil to some agriculture crops in various locations in south of Syria (Dara'a and Assuwaydaa districts) have been determined. Soil and vegetable crops (green pepper, cucumber, tomato, and eggplant), legumes crops (lentil, chickpea, and broad bean), fruit trees (apple, grape, and olives) and cereals (barley and wheat) were collected and analyzed for {sup 238}U, {sup 210}Pb, and {sup 210}Po. The results have shown that higher transfer factors (calculated as Bq kg{sup -1} dry wt. plant material per Bq kg{sup -1} dry wt. soil) for {sup 210}Po, {sup 210}Pb and {sup 238}U were observed in vegetable leaves than fruits and cereals leaves; the highest values of transfer factor (TF) for {sup 238}U were found to be 0.1 for straw of chickpea. Transfer factors for {sup 210}Po varied between 2.8 x 10{sup -2} and 2 in fruits of eggplant and grain of barley, respectively. In addition, several parameters affecting transfer factors of the radionuclides were evaluated. The results can be considered as base values for TF of natural radionuclides in the region.

  12. 210Pb dating

    Science.gov (United States)

    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.

  13. Transfer of {sup 238}U, {sup 230}Th, {sup 226}Ra, and {sup 210}Pb from soils to tree and shrub species in a Mediterranean area

    Energy Technology Data Exchange (ETDEWEB)

    Blanco Rodriguez, P. [Natural Radioactivity Group, Facultad de Ciencias, Universidad de Extremadura, Avda. de Elvas s/n, 06071 Badajoz (Spain); Vera Tome, F. [Natural Radioactivity Group, Facultad de Ciencias, Universidad de Extremadura, Avda. de Elvas s/n, 06071 Badajoz (Spain)], E-mail: fvt@unex.es; Lozano, J.C. [Natural Radioactivity Group, Facultad de Ciencias, Universidad de Extremadura, Avda. de Elvas s/n, 06071 Badajoz (Spain); Laboratorio de Radiaciones Ionizantes, Facultad de Ciencias, Universidad de Salamanca, 37008 Salamanca (Spain); Perez Fernandez, M.A. [Natural Radioactivity Group, Facultad de Ciencias, Universidad de Extremadura, Avda. de Elvas s/n, 06071 Badajoz (Spain); Area de Ecologia, Universidad Pablo Olavide, Carretera de Utrera km. 1, 41013 Sevilla (Spain)

    2010-06-15

    The soil-to-plant transfer factors of natural uranium isotopes ({sup 238}U and {sup 234}U), {sup 230}Th, {sup 226}Ra, and {sup 210}Pb were studied in a disused uranium mine located in the Extremadura region in the south-west of Spain. The plant samples included trees (Quercus ilex, Quercus suber, and Eucalyptus cameldulensis) and one shrub (Cytisus multiflorus). All of them are characteristic of Mediterranean environments. The activity concentrations in leaves and fruit were determined for the tree species at different stages of growth. For the shrub, the total above-ground fraction was considered in three seasons. For old leaves and fruit, the highest activity concentrations were found in Eucalyptus cameldulensis for all the radionuclides studied, except in the case of {sup 230}Th that presented similar activity concentrations in all of the tree species studied. In every case, the transfer to fruit was less than the transfer to leaves. In the shrub, the results depended on the season of sampling, with the highest value obtained in spring and the lowest in autumn. Important correlations were obtained for {sup 238}U and {sup 226}Ra between the activity ratio in soils with that in leaves or fruit.

  14. Variations of 210Pb concentrations in surface air at Thessaloniki, Greece (40°N

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    Papastefanou C.

    2012-04-01

    Full Text Available Atmospheric concentrations of 210Pb were measured over the year 2009 in ground level air at Thessaloniki, Northern Greece (40°62′ N, 22°95′E. The mean activity concentrations of 210Pb in surface air have been found to be 671 ± 213 μBq m−3. The highest values of monthly atmospheric concentrations of 210Pb were observed in the autumn and the lowest in the spring period. The higher values of 210Pb during autumn were attributed to frequent inversion conditions of the surface layers, resulting in an enrichment of radon and its decay products in surface air. The lower values during the winter months might be due to the low emanation of radon from the frozen or snow-covered soil. The minima of 210Pb concentrations during spring might reflect on higher washout during this period, which results in less emanation of radon from saturated with water soil, resulting in less production of 210Pb near ground-level air. The relative high values during summer are probably due to the higher 222Rn exhalation from the ground and due to the higher air mixing within the troposphere, which has as a result to carry down to the surface layer 210Pb whose origin is older air masses which entered into the free troposphere.

  15. 210Pb and 210Po determination in environmental samples using liquid scintillation counting and alpha spectrometry

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  17. Validation of {sup 226}Ra, {sup 228}Ra and {sup 210}Pb measurements in soil and sediment samples through high resolution gamma ray spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Dias, Danila Carrijo da Silva; Silva, Nivaldo Carlos da; Bonifacio, Rodrigo Leandro; Guerrero, Eder Tadeu Zenun [Comissao Nacional de Energia Nuclear (LAPOC/CNEN-MG), Pocos de Caldas, MG (Brazil). Laboratorio de Pocos de Caldas

    2013-07-01

    Radionuclides found in ore extraction waste materials are a great source of concern regarding public health and environmental safety. One technique to determine the concentration of substances is high resolution gamma ray spectrometry using HPGe. Validating a measurement technique is essential to warrant high levels of quality to any scientific work. The Laboratory of Pocos de Caldas of the Brazilian Commission for Nuclear Energy partakes into a Quality Management System project, seeking Accreditation under ISO/IEC 17025 through the validation of techniques of chemical and radiometric analysis of environmental samples from water, soil and sediment. The focus of the Radon Laboratory at LAPOC is validation of Ra-226, Ra-228 and Pb-210 concentration determinations in soil and sediment through a gamma spectrometer system. The stages of this validation process included sample reception and preparation, detector calibration and sample analyses. Dried samples were sealed in metallic containers and analyzed after radioactive equilibrium between Ra-226 and daughters Pb-214 and Bi-214. Gamma spectrometry was performed using CANBERRA HPGe detector and gamma spectrum software Genie 2000. The photo peaks used for Ra-226 determination were 609 keV and 1020 keV of Bi-214 and 351 keV of Pb-214. For the Ra-228 determination a photopeak of 911 keV was used from its short half-life daughter Ac-228 (T1/2 = 6.12 h). For Pb-210, the photopeak of 46.5 keV was used, which, due to the low energy, self-absorption correction was needed. Parameters such as precision, bias/accuracy, linearity, detection limit and uncertainty were evaluated for that purpose. The results have pointed to satisfying results. (author)

  18. Development of instrumentation for {sup 210} Pb dating method

    Energy Technology Data Exchange (ETDEWEB)

    Reinikainen, P.; Rekikoski, I.; Virtanen, A.; Aeystoe, J. [Institute for Environmental Research, Jyvaeskylae Univ. (Finland); Merilaeinen, J.; Witick, A. [Department of Physics, Jyvaeskylae Univ. (Finland)

    1998-08-01

    The presentation reviews shortly the project started in 1993 developing alpha- and gamma-ray spectroscopy systems and routines for a study of environmental samples. Particular interest has been focused to the {sup 210}Pb dating for lake sediments. So far, about 40 sediment profiles from all around Finland have been analysed and dated using the {sup 210}Pb method

  19. Levels and transfer of {sup 210}Po and {sup 210}Pb in Nordic terrestrial ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Brown, J.E., E-mail: justin.brown@nrpa.n [Norwegian Radiation Protection Authority, PO Box 55, N-1332, Osteras (Norway); Gjelsvik, R. [Norwegian Radiation Protection Authority, PO Box 55, N-1332, Osteras (Norway); Roos, P. [RISO-DTU P.O. Box 49 DK-4000 Roskilde (Denmark); Kalas, J.A. [Norwegian Institute for Nature Research (NINA), Tungasletta 2, 7485 Trondheim (Norway); Outola, I. [STUK, Laippatie 4/P.O. BOX 14, 00881 Helsinki (Finland); Holm, E. [Norwegian Radiation Protection Authority, PO Box 55, N-1332, Osteras (Norway)

    2011-05-15

    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 {sup 210}Po and {sup 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 {sup 210}Pb activity concentrations from elevated levels in humus/surface soils to 'supported' levels at depth. Activity concentrations of {sup 210}Po in fauna (invertebrates, mammals, birds) ranged between 2 and 123 Bq kg{sup -1} d.w. and in plants and lichens between 20 and 138 Bq kg{sup -1} d.w. The results showed that soil humus is an important reservoir for {sup 210}Po and {sup 210}Pb and that fauna in close contact with this media may also exhibit elevated levels of {sup 210}Po. Concentration ratios appear to have limited applicability with regards to prediction of activity concentrations of {sup 210}Po in invertebrates and vertebrates. Biokinetic models may provide a tool to explore in a more mechanistic way the behaviour of {sup 210}Po in this system.

  20. Comparison of electrodialytic removal of Cu from spiked kaolinite, spiked soil and industrially polluted soil.

    Science.gov (United States)

    Ottosen, Lisbeth M; Lepkova, Katarina; Kubal, Martin

    2006-09-01

    Electrokinetic remediation methods for removal of heavy metals from polluted soils have been subjected for quite intense research during the past years since these methods are well suitable for fine-grained soils where other remediation methods fail. Electrodialytic remediation is an electrokinetic remediation method which is based on applying an electric dc field and the use of ion exchange membranes that ensures the main transport of heavy metals to be out of the pollutes soil. An experimental investigation was made with electrodialytic removal of Cu from spiked kaolinite, spiked soil and industrially polluted soil under the same operational conditions (constant current density 0.2 mA/cm(2) and duration 28 days). The results of the present paper show that caution must be taken when generalising results obtained in spiked kaolinite to remediation of industrially polluted soils, as it was shown that the removal rate was higher in kaolinite than in both spiked soil and industrial polluted soil. The duration of spiking was found to be an important factor too, when attempting to relate remediation of spiked soil or kaolinite to remediation of industrially polluted soils. Spiking for 2 days was too short. However, spiking for 30 days resulted in a pattern that was more similar to that of industrially polluted soils with similar compositions both regarding sequential extraction and electrodialytic remediation result, though the remediation still progressed slightly faster in the spiked soil. Generalisation of remediation results to a variety of soil types must on the other hand be done with caution since the remediation results of different industrially polluted soils were very different. In one soil a total of 76% Cu was removed and in another soil no Cu was removed only redistributed within the soil. The factor with the highest influence on removal success was soil pH, which must be low in order to mobilize Cu, and thus the buffering capacity against acidification was

  1. Geochronology of the Rio Formoso estuarine by {sup 210}Pb

    Energy Technology Data Exchange (ETDEWEB)

    Arruda, Gilberto N.; Lyra, Denilson T.; Melo, Julyanne T.B.; Farias, Emerson E.G.; Franca, Elvis J.; Santos, Thiago O., E-mail: gnarruda@cnen.gov.br, E-mail: denilsonengseg@gmail.com, E-mail: julyanne.melo@ufpe.br, E-mail: emersonemiliano@yahoo.com.br, E-mail: ejfranca@cnen.gov.br [Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE/CNEN-PE), Recife, PE (Brazil); Souza Neto, Joao A., E-mail: adauto@ufpe.br [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil)

    2015-07-01

    Uranium series disequilibrium is useful for dating methods, in which profile sediments can be considered as historical records of anthropogenic events regarding the distribution and impacts of chemical substances on the environment. In this study, 2 deep sediment profiles (about 1 m) were collected, layered at each 3 cm, oven-dried and homogenized. The radiochemical separation of {sup 210}Pb consisted of using hydrobromic acid and an ion exchange resin (DOWEX) for precipitating {sup 210}Pb in the form of lead chromate. After 10 days, the radioactivity was therefore measured by means of the low level gas flow proportional counter, model S5-XLB, from Canberra. Sedimentation rate were obtained by CIC (Constant Initial Concentration) model assumes a constant sedimentation rate throughout the period over which unsupported {sup 210}Pb is measurable. Some sediment profiles were not dated since the percentage of sand was quite high in top layers or a high percentage of organic matter and water in excess were observed in the all sediment samples. {sup 210}Pb geochronology was successfully applied to age nine sediment profiles, in which higher sedimentation rates were observed in the middle portion of the estuarine probably related to shrimp farming impacts. By using geochronology, the detection of human impacts on chemical element distribution could be enhanced in the case of environmental monitoring studies in the Rio Formoso estuarine. (author)

  2. Radiometric evaluation of the {sup 210}Pb in the estuary of the SUAPE Pole in the State of Pernambuco

    Energy Technology Data Exchange (ETDEWEB)

    Carneiro, Paula Frassinetti P.; Antonio Filho, Joao; Mendonca, Keyla Mary C., E-mail: jaf@ufpe.com [Departamento de Energia Nuclear (DEN/UFPE), Recife, PE (Brazil); Carvalho, Wellington S. [Faculdade Integrada de Pernambuco (FACIPE), Recife, PE (Brazil)

    2011-07-01

    Nowadays there is a growing interest in the study of natural radioactivity levels, mainly of radionuclide {sup 210}Pb present in the environment. The environmental radioactivity control is of extreme importance for attainment of information on the exposition of humans and vegetables the potential sources in natural radioactive occurrences. Industrial processes involving mining and extraction and production of oil foster concentration of radionuclides, contributing to the occurrence of what is known as TENORM Technologically Enhanced Naturally Occurring Radioactive Material. This work aims to assess the environmental radiological impact on the Estuarine Region of the SUAPE Industrial Pole, due to the installation of an oil refinery and the consequent introduction on the environment of natural radioactive materials from other regions. For this, were determined the concentrations of {sup 210}Pb in samples de soil, sediments, roots and levels of fen and fishes in the region above reported, these data will serve of parameters of reference for a radiometric evaluation on future radioecology impacts caused by the functioning of the refinery of SUAPE oil. To determine the concentration of {sup 210}Pb was used the Ionic Resin Exchange method, for in such a way, the detector was used alpha-beta. Concentrations of {sup 210}Pb in the soils, sediments, roots and levels of fen samples vary respectively from 27 {+-} 2 to 60 {+-} 5, from 18 {+-} 5 to 60 {+-} 6, from 65 {+-} 2 to 117 {+-} 3, from 217 {+-} 6 to 239 {+-} 7 Bq.kg-1. Concentrations of the {sup 210}Pb in samples of some species of fish found in the studied region, such as Mullet, Salema, Catfish and Carapitinga, was also determined varying from 26 {+-} 11 to 62 {+-} 6 Bq.kg-1. The results obtained in the samples of soils, sediments, roots of fen e fishes showed that the concentrations of {sup 210}Pb in the environment are normal for the patterns of the area and are in accordance with data the found ones in literature

  3. 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.

    Science.gov (United States)

    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.

  4. A record of atmospheric 210Pb accumulation in the industrial city

    CERN Document Server

    Buraeva, E A; Stasov, V V; Zorina, L V; Shramenko, B I

    2013-01-01

    The deposition flux of total atmospheric 210Pb in the industrial city Rostov-on-Don, Russia from 2002 to 2010 has been measured. The variations in annual 210Pb deposition flux appear to be mainly correlated with the number of rains and significant amount of anthropogenic 210Pb, polluted into the surface layer of air in the home-heating period. The average 210Pb deposition is 1.75 mBq/m3. Several meteorological parameters which are strongly associated with the fluctuations of concentrations of 210Pb are identified. These results are useful to provide typical information on the atmosphere radioactivity in an industrial city.

  5. Comparison of electrodialytic removal of Cu from spiked kaolinite, spiked soil and industrially polluted soil

    DEFF Research Database (Denmark)

    Ottosen, Lisbeth M.; Lepkova, Katarina; Kubal, Martin

    2006-01-01

    Electrokinetic remediation methods for removal of heavy metals from polluted soils have been subjected for quite intense research during the past years since these methods are well suitable for fine-grained soils where other remediation methods fail. Electrodialytic remediation is an electrokinetic...... polluted soil under the same operational conditions (constant current density 0.2 mA/cm2 and duration 28 days). The results of the present paper show that caution must be taken when generalising results obtained in spiked kaolinite to remediation of industrially polluted soils, as it was shown...... remediation method which is based on applying an electric DC field and the use of ion exchange membranes that ensures the main transport of heavy metals to be out of the pollutes soil. An experimental investigation was made with electrodialytic removal of Cu from spiked kaolinite, spiked soil and industrially...

  6. Comparison of electrodialytic removal of Cu from spiked kaolinite, spiked soil and industrially polluted soil

    DEFF Research Database (Denmark)

    Ottosen, Lisbeth M.; Lepkova, Katarina; Kubal, Martin

    2006-01-01

    Electrokinetic remediation methods for removal of heavy metals from polluted soils have been subjected for quite intense research during the past years since these methods are well suitable for fine-grained soils where other remediation methods fail. Electrodialytic remediation is an electrokinetic...... remediation method which is based on applying an electric DC field and the use of ion exchange membranes that ensures the main transport of heavy metals to be out of the pollutes soil. An experimental investigation was made with electrodialytic removal of Cu from spiked kaolinite, spiked soil and industrially...... polluted soil under the same operational conditions (constant current density 0.2 mA/cm2 and duration 28 days). The results of the present paper show that caution must be taken when generalising results obtained in spiked kaolinite to remediation of industrially polluted soils, as it was shown...

  7. Assessment of {sup 210}Pb concentration in Nicotiana tabacum L., burley variety, cultivated in Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Rocha, Rique J.F.X.; Silva, Carolina F.; Frujuele, Jonatan V.; Bovolini, Raquel R.; Damatto, Sandra R., E-mail: rjrocha@ipen.br, E-mail: cfsilva@ipen.br, E-mail: jonatanfrujuele@hotmail.com, E-mail: ra_bovolini@yahoo.com.br, E-mail: damatto@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Lab. de Radiometria Ambiental

    2013-07-01

    Tobacco products are extensively used throughout the world and the most consumed are cigarettes, cigars and narghile. The damaging effects that these products cause to human health are discussed worldwide and many researches are performed with the aim of relating the use of these products with various diseases. Brazil is the largest exporter and second largest producer of tobacco worldwide, according to the crop year 2009/2010 production. The tobacco plant (Nicotiana tabacum L.) is used to manufacture all derivatives and the chemical composition of the resulting tobacco varies with the type of tobacco leaves, how they are grown, the region where they are cultivated, the characteristics of preparation and the temperature variations resulting from the tobacco incomplete combustion. There is lack of information about the chemical and radiological characterization of the tobacco plant both in international and Brazilian literature. Thus a project was established with the objectives of characterizing chemically and radiologically the three varieties most cultivated in Brazil of Nicotiana tobacum L., Virginia, Burley and Common; this paper presents the preliminary results of {sup 210}Pb concentrations for the Burley variety. Plants from this variety were cultivated in pots with organic substrate and fertilizer and in a small farm in natural conditions. The entire plant was analyzed, the organic substrates, the fertilizers and the soil. The results obtained presented higher values for {sup 210}Pb in leaves when compared with the other parts of the plant. Comparing the three study areas the highest results of {sup 210}Pb concentration were obtained in the plants cultivated in the urban area probably due to its atmospheric deposition. (author)

  8. Sedimentation rate and {sup 210}Pb sediment dating at Apipucos reservoir, Recife, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Figueiredo, Marcela D.C. de; Silva, Danubia B. da; Cunha, Manuela S. da; Rodrigues, Kelia R.G.; Pedroza, Eryka H.; Melo, Roberto T. de; Oliveira, Aristides; Hazin, Clovis A.; Souza, Vivianne L.B. de, E-mail: rtmelo@cnen.gov.b, E-mail: chazin@cnen.gov.b, E-mail: vlsouza@cnen.gov.b [Centro Regional de Ciencias Nucleares (CRCN-NE/CNEN-PE), Recife, PE (Brazil)

    2011-07-01

    The Apipucos Reservoir is located in Recife, State of Pernambuco, and, several districts of the metropolitan area use this reservoir to dispose waste and sewage. Dating sediments uses {sup 210}Pb from the atmosphere which is formed as a result of {sup 222}Rn emanation from the soil. Atmospheric lead, carried by rain, is called non-supported {sup 21}'0Pb, to differentiate it from the one contained in the sediment, in balance with the {sup 226}Ra. The model chosen for dating sediments depends on certain conditions: in an environment where the amount of sediment influx can vary, the constant rate of supply model is adopted. On the other hand, in environments where the sedimentation rate is constant and the sediment can be considered to have a constant initial concentration of unsupported {sup 210}Pb and the (CIC) model is applied. A 70-cm long, 5-cm internal-diameter wide core was collected for sediment dating. Each core was sliced, into 5 or 10 cm intervals. Samples were dried at 105 deg C, and about 5 g dry material from each sample was dissolved with acids. The {sup 210}Pb and {sup 226}Ra contents were separated and determined by beta and alpha counting by using a gas-flow proportional counter. Sediment ages were calculated by the two models, and for the second and fourth sampling points, both models could be used. The results showed an increase in sedimentation rate over the last 50 - 60 years. We can conclude that the top sediment layer is dated from 30 years ago. We can also conclude that the CRS is the best applicable model to use in this area. (author)

  9. The Radiological Impact of 210Pb and 210Po Released from the Iron- and Steel-Making Plant ILVA in Taranto (Italy on the Environment and the Public

    Directory of Open Access Journals (Sweden)

    Guogang Jia

    2013-01-01

    Full Text Available Lead-210 and 210Po are naturally occurring radionuclides. Due to volatile characteristic of lead and polonium, environmental pollution of 210Pb and 210Po released from the coal power plant, steel-making industry and refractory material industry has been an exposure problem for the members of public. In this paper studies on the activity concentrations of 210Po and 210Pb in the raw materials, dust particles, surficial soils and atmospheric particulate samples collected in the area of the Iron- and Steel-Making Plant ILVA Taranto (Italy were made. These data have been used to evaluate the source-term, distributions, inventories, mass balance, biological availability, ecological migration processes and public exposure risk of 210Pb and 210Po in the concerned environment.

  10. Radiolead (210)Pb and (210)Po/(210)Pb activity ratios in calcium supplements and the assessment of their possible dose to consumers.

    Science.gov (United States)

    Strumińska-Parulska, Dagmara I

    2016-08-23

    This paper presents the results of pioneer study of the most popular calcium supplements as a potential additional source of radiolead (210)Pb in human diet. The analyzed calcium pharmaceutics contained organic or inorganic calcium compounds; some came from natural sources as mussels' shells, fish extracts, or sedimentary rocks. The idea was to investigate the naturally occurring (210)Pb activity in different calcium supplements and calculate the annual effective radiation dose from radiolead (210)Pb decay in consumed calcium supplement. The results showed (210)Pb concentrations in natural origin calcium supplements (especially sedimentary rocks) were significantly higher. The highest (210)Pb activity concentrations were determined in mineral tablets made from dolomite - 2.97 ± 0.18 mBq g(-1), while the lowest was observed in organic calcium compounds - both calcium lactate - 0.08 ± 0.01 and 0.13 ± 0.01 mBq g(-1). The highest annual radiation dose from (210)Pb taken with 1 tablet of calcium supplement per day was calculated for soluble calcium lactate sample - 1.19 ± 0.03 µSv year(-1), while the highest annual radiation dose from (210)Pb taken daily with 1 g of pure Ca for dolomite - 5.57 ± 0.34 µSv year(-1).

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  13. 7Be and 210Pb radioactivity and implications on sources of surface ozone at Mt. Waliguan

    Institute of Scientific and Technical Information of China (English)

    ZHENG Xiangdong; WANG Guojiang; TANG Jie; ZHANG Xiaochun; YANG Wei; H. N. Lee; WANG Changsheng

    2005-01-01

    Beryllium-7 (7Be) and lead-210 (210Pb) radioac- tivity in aerosols collected, from October 2002 to January 2004 at Mt. Waliguan, by the Global Atmospheric Watch (GAW) Station, Qinghai Province is presented. The data were analyzed together with simultaneously measured surface ozone concentrations. We found that short time variations of 7Be and 210Pb were linked to alternations of synoptic weather around the Mt. Waliguan region. 210Pb showed the lowest concentration in summer while 7Be showed no obvious sea- sonal changes. Relatively high 7Be and 210Pb radioactivity was observed at Mt. Waliguan when compared with the ob- servations at other mountain sites in other parts of the world. Surface ozone and 7Be showed a consistent seasonal variation. Surface ozone correlated fairly well with 7Be/210Pb ratio. This suggested that vertical transport from higher altitudes of the atmosphere has predominant effects on the budget of surface ozone at Mt. Waliguan.

  14. Cerenkov counting: an alternative for determining {sup 210} Pb low-levels

    Energy Technology Data Exchange (ETDEWEB)

    Mingote, Raquel Maia; Gomes, Nilton Carlos [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), Belo Horizonte, MG (Brazil). Servico de Quimica e Radioquimica]. E-mail: mingote@cdtn.br; Oliveira, Arno Heeren de [Minas Gerais Univ., Belo Horizonte, MG (Brazil). Dept. de Engenharia Nuclear]. E-mail: heeren@nuclear.ufmg.br

    2005-07-01

    Determining the {sup 210}Pb by Cerenkov counting is an indirect method which is measured by the Cerenkov radiation produced by its daughter {sup 210}Bi. {sup 210}Pb does not interfere because it does not produce Cerenkov radiation and only the lead chemical recovery is necessary, decreasing the uncertainty sources. This work presents a methodology for determining {sup 210}Pb in water for Cerenkov counting by using a conventional spectrometer liquid scintillation and lead pre-concentration. Several factors that affect the {sup 210}Pb determination were evaluated. Some reference material was analysed showing that the procedure gives accurate and reproducible results. The lower limit of detection for {sup 210}Pb of 0.10 Bq/L was obtained (500 minutes counting time, 70 % of lead chemical recovery and, the Cerenkov counting efficiency about 14 % and 800 mL of the sample). (author)

  15. {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

    Energy Technology Data Exchange (ETDEWEB)

    Carvalho, F.P. [Instituto Nacional de Engenharia e Tecnolgia Industrial, Savavem (Portugal)

    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.

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

    Science.gov (United States)

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

    2014-10-01

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

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

    Science.gov (United States)

    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.

  18. Behavior of ambient concentrations of natural radionuclides (7)Be, (210)Pb, (40)K in the Mediterranean coastal city of Málaga (Spain).

    Science.gov (United States)

    Gordo, E; Dueñas, C; Fernández, M C; Liger, E; Cañete, S

    2015-05-01

    During a 4-year period (January 2009-December 2012), the (7)Be, (210)Pb, and (40)K activity concentrations in airborne particulate matter were weekly determined at the Málaga (Spain) located in the southern Iberian Peninsula. Totally 209 polypropylene filters were analyzed in the mentioned period. In 100% of the filters, (7)Be and (40)K activity concentrations were detected while (210)Pb activity concentration was detected in 96% of the filters. The results from individual measurements of (7)Be, (210)Pb, and (40)K concentrations were analyzed to derive the statistical estimates characterizing the distributions. Principal components analysis (PCA) was applied to the datasets and the results of the study reveal that aerosol behavior is represented by two principal components which explain 73.2% of total variance. Components PC1 and PC2 respectively explain 46.0 and 27.2% of total variance. PC1 was related positively to dust content, (7)Be and (40)K concentrations and negatively to sunspot numbers. In contrast, PC2 was related positively to temperature and (210)Pb activity and negatively to precipitation and relative humidity. The (7)Be levels showed a significant correlation with sunspot numbers due to the cosmogenic origin. (40)K activities showed a good correlation with dust deposition in filters mainly because it was transported to the air as resuspended particle from the soil. An inverse relationship was observed between the (210)Pb concentrations and monthly rainfall, indicating washout of atmospheric aerosols carrying these radionuclides and a pronounced positive correlation with the average monthly temperature of air.

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

    Institute of Scientific and Technical Information of China (English)

    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·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 coincide 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.

  20. Method for spiking soil samples with organic compounds

    DEFF Research Database (Denmark)

    Brinch, Ulla C; Ekelund, Flemming; Jacobsen, Carsten S

    2002-01-01

    We examined the harmful side effects on indigenous soil microorganisms of two organic solvents, acetone and dichloromethane, that are normally used for spiking of soil with polycyclic aromatic hydrocarbons for experimental purposes. The solvents were applied in two contamination protocols to either...... higher than in control soil, probably due mainly to release of predation from indigenous protozoa. In order to minimize solvent effects on indigenous soil microorganisms when spiking native soil samples with compounds having a low water solubility, we propose a common protocol in which the contaminant...... the whole soil sample or 25% of the soil volume, which was subsequently mixed with 75% untreated soil. For dichloromethane, we included a third protocol, which involved application to 80% of the soil volume with or without phenanthrene and introduction of Pseudomonas fluorescens VKI171 SJ132 genetically...

  1. Measurement and Meteorological Analysis of 7Be and 210Pb in Aerosol at Waliguan Observatory

    Institute of Scientific and Technical Information of China (English)

    ZHENG Xiangdong; WAN Guojiang; CHEN Zunyu; TANG Jie

    2008-01-01

    Beryllium-7 (7Be) and lead-210 (210Pb) activities were measured from October 2002 to January 2004 at Waliguan Observatory (WO: 36.287 N, 100.898 E, 3816 m a.s.l (above sea level) in northwest China. 7Be and 210Pb activities are high with overall averages of 14.7 3.5 mBq m-3 and 1.8 0.8 mBq m-3 respectively. For both 7Be and 210Pb, there are significant short-term and seasonal variations with a commonly low value in summer (May-September) and a monthly maximum in April (for 7Be) and in December (for 210Pb). The ratio of 7Be/210Pb showed a broad maximum extending from April to July, coinciding with a seasonal peak in surface ozone (O3). The seasonal cycles of 7Be and 210Pb activities were greatly influenced by precipitation and thermal dynamical conditions over the boundary layer, especially for 210Pb. The vertical mixing process between the boundary layer and the aloft air modulates the variations of 7Be and 210Pb at WO in summer. It is indicated that air mass had longer residence time and originated from higher altitudes at WO in the spring-summer time and the winter in 2003. During an event with extremely high weekly-averaged 7Be concentration (24.8 mBq m-3) together with high O3 levels and low water mixing ratio, we found that air masses had been convectively transported a long distance to WO from high latitude source regions in central Asia, where significant subsiding motions were observed. In another case with the extreme 210Pb activity of 5.7 mBq m-3 high CO2 level and specific humidity (in winter), air masses had come from south China and north Indian regions where 222Rn activities were high. This study, using 7Be and 210Pb as atmospheric tracers, has revealed that complex interactions of convective mixing from the upper troposphere and long-range transports exist at WO.

  2. Method for spiking soil samples with organic compounds

    DEFF Research Database (Denmark)

    Brinch, Ulla C; Ekelund, Flemming; Jacobsen, Carsten S

    2002-01-01

    We examined the harmful side effects on indigenous soil microorganisms of two organic solvents, acetone and dichloromethane, that are normally used for spiking of soil with polycyclic aromatic hydrocarbons for experimental purposes. The solvents were applied in two contamination protocols to either...... the whole soil sample or 25% of the soil volume, which was subsequently mixed with 75% untreated soil. For dichloromethane, we included a third protocol, which involved application to 80% of the soil volume with or without phenanthrene and introduction of Pseudomonas fluorescens VKI171 SJ132 genetically...

  3. Evaluation of the uncertainty for the efficiency curve determination of {sup 210}Pb by liquid scintillation; Avaliacao da incerteza para a curva de eficiencia da determinacao de {sup 210}Pb por cintilacao liquida

    Energy Technology Data Exchange (ETDEWEB)

    Sampaio, C.S.; Sousa, W.O.; Dantas, B.M., E-mail: camilla@ird.gov.br [Instituto de Radioprotecao e Dosimetria, (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2014-07-01

    Methodologies for the evaluation of uncertainties associated with the determination of the efficiency curve of {sup 210}Pb by liquid scintillation counting (LSC) are presented. No statistical difference were found when compared the uncertainties of the curves that represented the counting net before and after the secular equilibrium between {sup 210}Pb and {sup 210}Bi, nether when compared the curves when counting only {sup 210}Pb and the curve with the total count of {sup 210}Pb and {sup 210}Bi, for the same time interval after precipitation. (author)

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

    Science.gov (United States)

    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.

  5. Calibration and measurement of {sup 210}Pb using two independent techniques

    Energy Technology Data Exchange (ETDEWEB)

    Villa, M. [Centro de Investigacion, Tecnologia e Innovacion, CITIUS, Universidad de Sevilla, Av. Reina Mercedes 4B, 41012 Sevilla (Spain)], E-mail: mvilla@us.es; Hurtado, S. [Centro de Investigacion, Tecnologia e Innovacion, CITIUS, Universidad de Sevilla, Av. Reina Mercedes 4B, 41012 Sevilla (Spain); Manjon, G.; Garcia-Tenorio, R. [Departamento de Fisica Aplicada II, E.T.S. Arquitectura, Universidad de Sevilla, Av. Reina Mercedes 2, 41012 Sevilla (Spain)

    2007-10-15

    An experimental procedure has been developed for a rapid and accurate determination of the activity concentration of {sup 210}Pb in sediments by liquid scintillation counting (LSC). Additionally, an alternative technique using {gamma}-spectrometry and Monte Carlo simulation has been developed. A radiochemical procedure, based on radium and barium sulphates co-precipitation have been applied to isolate the Pb-isotopes. {sup 210}Pb activity measurements were done in a low background scintillation spectrometer Quantulus 1220. A calibration of the liquid scintillation spectrometer, including its {alpha}/{beta} discrimination system, has been made, in order to minimize background and, additionally, some improvements are suggested for the calculation of the {sup 210}Pb activity concentration, taking into account that {sup 210}Pb counting efficiency cannot be accurately determined. Therefore, the use of an effective radiochemical yield, which can be empirically evaluated, is proposed. {sup 210}Pb activity concentration in riverbed sediments from an area affected by NORM wastes has been determined using both the proposed method. Results using {gamma}-spectrometry and LSC are compared to the results obtained following indirect {alpha}-spectrometry ({sup 210}Po) method.

  6. Determination of 210Pb and 222Rn in ground water of Okinawa Island

    Science.gov (United States)

    Ito, M.; Tanahara, A.

    2012-12-01

    In this study, we developed the method of 210Pb measurement from a large amount of ground water. The chelating resin (NOBIAS CHELATE-PA1; Hitachi High-technology) column combined with the ion-exchange resin (DOWEX-88; Dow Chemical Company) column were used for pre-treatment of 210Pb from ground water of 20 litter. It should be mentioned that this determination procedure is simple, fast, and give high recovery (more than 80 %). It avoids precipitation and large consumption of chemicals. Finally 210Pb was precipitated as PbSO4 and determined with low background 2πgas flow counter. 210Pb concentration in ground water of Okinawa Island ranged from 1.40-16.7 mBq/L. We also found that the organo-210Pb complex which could not be detected by this method was involved in some water samples. By increasing the column radius and the resin mass, while keeping a constant height of the resin column, it is possible to additionally increase the flow rate and accelerate the isolation procedure. 222Rn was determined by the direct method. The emulsion scintillation cocktail (10 mL) and water sample (10 mL) were put into a vial. After shaking and stand for 200 min, 222Rn was counted by LSC for 120 min. 222Rn concentration in ground water of Okinawa Island ranged from 0.71-14.0 Bq/L.

  7. Activity of 210Po and 210Pb in the riverine environs of coastal Kerala on the southwest coast of India

    Directory of Open Access Journals (Sweden)

    N. Venunathan

    2016-10-01

    Full Text Available The paper presents the systematic investigations on the activity concentrations of 210Po and 210Pb in the riverine environs of Bharathapuzha, Periyar and Kallada, the three major rivers of coastal Kerala. The radionuclides 210Po and 210Pb in sediment and water samples were separated using radiochemical methods and activity was counted using scintillation based alpha counting system. The mean value of 210Po activity in sediment samples was found to be 3.4 Bq kg−1, 40.0 Bq kg−1 and 22.5 Bq kg−1 in Bharathapuzha, Periyar and Kallada river respectively. The mean value of 210Pb activity was found to be 13.5 Bq kg−1, 88.7 Bq kg−1 and 60.8 Bq kg−1 in the sediment samples of Bharathapuzha, Periyar and Kallada river respectively. The activity ratio 210Po/210Pb shows that the radionuclides 210Po and 210Pb are not in equilibrium in the riverine environs and the accumulation of 210Pb in sediment is greater than that of 210Po. The disequilibrium between 210Po and 210Pb and the higher activity of 210Pb indicates the presence of unsupported 210Pb in the sediments. A significant correlation was observed between the concentrations of these radionuclides and organic matter content and clay minerals of the sediment samples. The low activity of 210Po and 210Pb was observed in the dissolved phase due to the removal of these particle reactive radionuclides from solution to particle. High Kd value for 210Po and 210Pb in water column indicates that there is a strong adsorption of these radionuclides on to the suspended particles in the aquatic environment, where suspended particulate matter acts as a carrier to transport and removal of 210Po and 210Pb from their site of production.

  8. Determination of {sup 210}Pb and {sup 210}Po in cigarette tobacco; Determinacao de {sup 210}Pb e {sup 210}Po em tabaco de cigarros nacionais

    Energy Technology Data Exchange (ETDEWEB)

    Peres, Ana Claudia

    1999-07-01

    Cigarette smoking is one of the important pathways that could contribute to enhance the radiation dose to man, due to the relatively large concentrations of {sup 210}Pb and {sup 210}Po found in tobacco leaves. In this work, concentrations of these two radionuclides were determined in eight of the most commercialized cigarette brands produced in Brazil. The samples analyzed were bought randomly in the market. The {sup 210}Pb was determined by counting the beta activity of the {sup 210}Bi in a gas flow proportional detector, after radiochemical separation and precipitation of the PbCr0{sub 4}. The {sup 210}Po was determined by alpha spectrometry, using a surface barrier detector, after radiochemical separation and spontaneous deposition of Po in copper disk. The results showed concentrations ranging from 11,9 to 30,2 mBq per gram of dry tobacco for {sup 210}Pb and from 10,9 to 27,4 mBq per gram of dry tobacco for {sup 210}Po. (author)

  9. Electrokinetic Remediation of Petroleum Hydrocarbons Spiked Soils

    OpenAIRE

    , M. Bilgin; , G. Akıncı

    2011-01-01

    In the presented study, remediation studies were conducted to determine the effectiveness of electrokinetic method on the treatment of natural soil contaminated with petroleum hydrocarbons, in laboratory scale reactors. Electokinetic remediation of agricultural soil with an initial TPHs (Total Petroleum Hydrocarbons) concentration of 10000 ppm was investigated under 20 V or 40 V direct current by using NaOH and acetic acid as electrolyte solution, treatment efficiencies were observed accordin...

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

    Science.gov (United States)

    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.

  11. Onderzoek naar de verbetering van de bepaling van 210Po en 210Pb in depositie

    NARCIS (Netherlands)

    Glastra P; LSO

    1998-01-01

    In 1995 is gebleken dat de chemische opbrengst van het als merker toegevoegde 208Po bij de bepaling van 210Po en 210Pb in depositiemonsters vaak minder is dan de vereiste 50%. De oorzaak van de lage chemische opbrengsten is onderzocht. Dit rapport beschrijft de uitvoering van het onderzoek en de

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

    Science.gov (United States)

    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 (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.

  13. Super(210) Pb based trace element fluxes in the nearshore and estuarine sediments off Bombay, India

    Digital Repository Service at National Institute of Oceanography (India)

    Sharma, P.; Borole, D; Zingde, M.D

    16 dpm/cm super(2), for the core from the southern area, to 187 dpm/cm super(2), for the northernmost core, which was much higher compared to the atmospheric fallout inventory of 40-50 dpm/cm super(2). The inner creek acted as a sink for super(210) Pb...

  14. Enrichment and vertical profiles of 210Po and 210Pb in monazite areas of coastal Karnataka.

    Science.gov (United States)

    Narayana, Y; Prakash, V

    2010-06-01

    A study on radiation level and radionuclide distribution in the environment of coastal Karnataka has revealed the presence of low-level monazite deposit in the Ullal beach area. The paper presents systematic studies on the distribution, enrichment and vertical profiles of (210)Po and (210)Pb, important daughter products of (238)U, in Ombattu Kere, Summer Sand and the Bhagavathi Temple region of the Ullal beach area of coastal Karnataka. Sand samples collected at different depths from these locations were analyzed for (210)Po and (210)Pb activities to understand the distribution, enrichment and vertical profiles of these radionuclides in monazite area. The activity of (210)Po in the Ullal region is found to vary from 1.7 to 43.2 Bq kg(-1) with a mean value of 11.2 Bq kg(-1) and that of (210)Pb varies from 1.0 to 66.7 Bq kg(-1) with a mean value of 19.1 Bq kg(-1). The mean (210)Po/(210)Pb ratio was observed to be 0.6. The absorbed gamma dose rate in the region varies in the range 39-460 nGy h(-1) with a mean value of 193 nGy h(-1).

  15. Sedimentation rates in Atibaia River basin, Sao Paulo State, Brazil, using {sup 210}Pb as geochronometer

    Energy Technology Data Exchange (ETDEWEB)

    Sabaris, T.P.P. [Departamento de Petrologia e Metalogenia, Universidade Estadual Paulista (UNESP), Av. 24-A, No. 1515, C.P. 178, CEP 13506-900, Rio Claro, Sao Paulo (Brazil); Bonotto, D.M., E-mail: danielbonotto@yahoo.com.b [Departamento de Petrologia e Metalogenia, Universidade Estadual Paulista (UNESP), Av. 24-A, No. 1515, C.P. 178, CEP 13506-900, Rio Claro, Sao Paulo (Brazil)

    2011-01-15

    The constant initial concentration (CIC) of unsupported/excess {sup 210}Pb model was successfully used to assess {sup 210}Pb data of nine sediment cores from Atibaia River basin, Sao Paulo State, Brazil. The {sup 210}Pb-based apparent sediment mass accumulation rates ranged from 47.7 to 782.4 mg/cm{sup 2} yr, whereas the average linear sedimentation rates between 0.16 and 1.32 cm/yr, which are compatible with the calculated sediment mass fluxes, i.e. a higher sediment mass accumulation rate yielded a higher linear sedimentation rate. The higher long-term based accumulation rate tended to be found in topographically softer regions. This occurs because the sediments are preferentially transported in topographically steeper regions instead of being deposited. Anthropic activities like deforestation possibly interfered with the natural/normal sedimentation processes, which increased in accordance with modifications on the channel drainage. The radionuclide geochronology as described in this paper allows determination of sedimentation rates that are compatible with values estimated elsewhere. The adoption of an appropriate factor generated from previous laboratory experiments resulted in a successful correction for the {sup 222}Rn-loss from the sediments, bringing the estimate of the parent-supported (in-situ produced) {sup 210}Pb to reliable values required by the CIC model.

  16. Modeling 210Pb-derived mixing activity in ocean margin sediments: Diffusive versus nonlocal mixing

    NARCIS (Netherlands)

    Soetaert, K.E.R.; Herman, P.M.J.; Middelburg, J.J.; Heip, C.H.R.; De Stigter, H.; Van Weering, T.C.E.; Epping, E.; Helder, W.

    1996-01-01

    The influence of sediment mixing on activity versus depth profiles of the radionuclide (210)pb in the upper 20 cm of the sediments has been investigated along a depth transect (208 m- 4500 m, 17 stations) in the OMEX study area (Goban Spur, NE Atlantic Ocean). A hierarchical family of bioturbation/n

  17. 210Pb-derived ages for the reconstruction of terrestrial contaminant history into the Mexican Pacific coast: potential and limitations.

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

  19. Bioavailability of radionuclides {sup 226}Ra, {sup 228}Ra and {sup 210}Pb present in the brazilian phosphate fertilizers and phosphogypsum; Avaliacao da biodisponibilidade dos radionuclideos {sup 226}Ra, {sup 228}Ra e {sup 210}Pb presentes nos fertilizantes fosfatados e no fosfogesso de procedencia nacional

    Energy Technology Data Exchange (ETDEWEB)

    Russo, Ana Carolina

    2013-08-01

    Phosphogypsum, also called gypsum, by-product of the phosphate fertilizer industry, can be used as soil conditioner since it provides improvements in the soil-plant system. However, this by-product concentrates radionuclides of the U and Th series, present in the phosphate rock used as raw material, which can impact the environment. In order to study the bioavailability of radionuclides, samples of phosphogypsum and phosphate fertilizers (monoammonium phosphate and triple superphosphate) were analyzed. The concentration of {sup 226}Ra, {sup 228}Ra and {sup 210}Pb were determined by gamma spectrometry. The samples were leached with a mild EDTA solution and the radionuclides present in the final solution were determined by total alpha and beta counting on a gas flow proportional counter. The percentage of extraction varied from 1.6% to 1.7% for {sup 210}Pb, from 0.5% to 1.4% for {sup 226}Ra and from 0.1% to 1.0% for the {sup 228}Ra in phosphogypsum samples. The low percentage of extraction obtained for the radionuclides can be partly explained by the low solubility of phosphogypsum, which ranged from 7.7% to 16%. For the monoammonium phosphate samples the percentage of extraction were less than 26% for {sup 226}Ra, less than 10% for '2{sup 28}Ra and less than 10% for {sup 210}Pb. In spite of the high solubility of 77% of monoammonium phosphate in the EDTA solution, low concentrations of radionuclides were observed in the leached solution. For the triple superphosphate samples, the percentage of extraction was 2.3% for {sup 226}Ra, 1.2% for {sup 228}Ra and 11.3% for {sup 210}Pb. In spite of the high solubility of 66% of triple superphosphate in the EDTA solution, low concentrations of radionuclides were observed in the leached solution. (author)

  20. Analysis of {sup 210} Pb and {sup 137} Cs in diets of university students; Analise de {sup 210} Pb e {sup 137} Cs em dietas de estudantes universitarios

    Energy Technology Data Exchange (ETDEWEB)

    Saito, Roberto T.; Cunha, Ieda I.L.; Maihara, Vera A.; Favaro, Deborah I.T. [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil). Supervisao de Radioquimica]. E-mail: biologia@curiango.ipen.br; Cozzolino, Silvia M.F. [Sao Paulo Univ., SP Faculdade de Ciencias Farmaceuticas (Brazil)

    2000-07-01

    In this work, {sup 210} P and {sup 137} Cs were determined in the male students diets (age: 19-25) of Sao Paulo University, by gamma spectrometry. The sampling was made using the duplicate portion methodology, which consists in collecting duplicate portions of all food and beverage consumed during three days of a week. The levels obtained for {sup 210} Pb in these samples varied from the Minimum Detectable Concentration (0.43 Bq.kg{sup -1} ) to 1.68 Bq.kg{sup -1} . For {sup 137} Cs, the values ranged from the Minimum Detectable Concentration (0.17 Bq.kg{sup -1} ) to 0.95 Bq.kg{sup -1} . An estimate of the daily ingestion of those radionuclides was made according to the data obtained. The values varied from 78 to 309 mBq.d{sup -1} for {sup 210} Pb, and 53 to 157 mBq.d{sup -1} , for {sup 137} Cs, among the diets analyzed. The data obtained these diets agreed with the data obtained for other authors. (author)

  1. Disequilibria between 210Po and 210Pb in surface waters of the southern South China Sea and their implications

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Activities of the naturally occurring radionuclides, 210Pb and 210Po, were measured in both dissolved (0.45 μm) phases from surface waters of the southern South China Sea. The average activity of particulate 210Pb, 0.23 Bq/m3 (n=23), accounted for about 12% of the total 210Pb, which corresponds with values of open oceans. Particulate 210Po, with an average activity of 0.43 Bq/m3, accounted for about 40% of the total 210Po, which was much higher than those of open and eutrophic oceans. The residence times of total 210Po and 210Pb in surface waters estimated from an irreversible steady-state model were 0.82 a and 1.16 a, respectively. The consistently high fractionation factor calculated either by scavenging rate constants (5.42) or Kd values (6.69) suggested that a significant fractionation occurred between 210Po and 210Pb during their removal from solution to particles and that the two radionuclides had different biogeochemical cycling pathways in the oligotrophic South China Sea. Furthermore, our results indicated that there exist different fractionation mechanisms between 210Po and 210Pb in different marine environments: in eutrophic ocean, plankton detritus and fecal pellets are the main carrier of 210Po and 210Pb, by which 210Po and 210Pb have been scavenged and removed; while in oligotrophic ocean, microbes could become the main carrier of 210Po and fractionate 210Po and 210Pb significantly as a result of scarce plankton detritus and fecal pellets. These results suggest the use of 210Po to trace marine biogeochemical processes relating to microbial activities and the cycling of sulfur group elements (S, Se, Te and Po).

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

    Science.gov (United States)

    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. Evaluating gully erosion using {sup 137}Cs and {sup 210}Pb/{sup 137}Cs ratio in a reservoir catchment

    Energy Technology Data Exchange (ETDEWEB)

    Li, Y. [Institute of Agricultural Environment and Sustainable Development, CAAS, Beijing (China) and Institute for Application of Atomic Energy, CAAS, Beijing (China)]. E-mail: yongli32@hotmail.com and yongli@ami.ac.cn; Poesen, J. [Laboratory for Experimental Geomorphology, Catholic University Leuven, Leuven (Belgium); Yang, J.C.; Zhang, J.H. [Institute of Agricultural Environment and Sustainable Development, CAAS, Beijing (China); Institute for Application of Atomic Energy, CAAS, Beijing (China); Fu, B. [Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing (China)

    2003-02-15

    Water erosion in the hilly areas of west China is the main process contributing to the overall sediment of the Yellow River and the Yangtze River. The impact of gully erosion in total sediment output has been mostly neglected. Our objective was to assess the sediment production and sediment sources at both the hillslope and catchment scales in the Yangjuangou reservoir catchment of the Chinese Loess Plateau, northwest China. Distribution patterns in sediment production caused by water erosion on hills and gully slopes under different land use types were assessed using the fallout {sup 137}Cs technique. The total sediment production from the catchment was estimated by using the sediment record in a reservoir. Sediment sources and dominant water erosion processes were determined by comparing {sup 137}Cs activities and {sup 210}Pb/{sup 137}Cs ratios in surface soils and sub-surface soils with those of sediment deposits from the reservoir at the outlet of the catchment. Results indicated that landscape location had the most significant impact on sediment production for cultivated hillslopes, followed by the terraced hillslope, and the least for the vegetated hillslope. Sediment production increased in the following order: top>upper>lower>middle for the cultivated hillslope, and top>lower>upper>middle for the terraced hillslope. The mean value of sediment production declined by 49% for the terraced hillslope and by 80% for the vegetated hillslope compared with the cultivated hillslope. Vegetated gully slope reduced the sediment production by 38% compared with the cultivated gully slope. These data demonstrate the effectiveness of terracing and perennial vegetation cover in controlling sediment delivery at a hillslope scale. Averaged {sup 137}Cs activities and {sup 210}Pb/{sup 137}Cs ratios in the 0-5 cm surface soil (2.22-4.70 Bq kg{sup -1} and 20.70-22.07, respectively) and in the 5-30 cm subsoil (2.60 Bq kg{sup -1} and 28.57, respectively) on the cultivated hills and

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

  6. 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

    Science.gov (United States)

    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.

  7. 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

    Science.gov (United States)

    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.

  8. Trace metals and {sup 210}Po ({sup 210}Pb) concentrations in mussels (Mytilus galloprovincialis) consumed at western Anatolia

    Energy Technology Data Exchange (ETDEWEB)

    Ugur, Aysun E-mail: aysun@bornova.ege.edu.tr; Yener, G.Guengoer; Bassari, Asiye

    2002-10-01

    The mussels (Mytilus galloprovincialis) have been evaluated for their bioavailability as biomonitors of trace and toxic elements in coastal water of western Anatolia. The levels of Fe, Cu, Zn, Pb, Br and Sr in the edible part of mussels were determined using X-ray fluorescence method during the period of September 1999-July 2000. Distribution of {sup 210}Po and {sup 210}Pb activities were measured by radiometric methods and their ratios were calculated. The activity concentrations of {sup 210}Po and {sup 210}Pb were found to vary between 52{+-}6-1344{+-}108 and 6{+-}2-167{+-}10 Bq kg{sup -1} dry wt, respectively. The highest values for {sup 210}Po and {sup 210}Pb were measured in Foca mussels and also observed the highest Fe, Zn and Br concentrations in the same species. {sup 210}Po/{sup 210}Pb activity ratio were derived as between 3.1 and 25.0.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  12. Low 210Pb in the upper thermocline in the Canadian Basin:scavenge process over the Chukchi Sea

    Institute of Scientific and Technical Information of China (English)

    HU Wangjiang; CHEN Min; YANG Weifeng; ZHANG Run; QIU Yusheng; ZHENG Minfang

    2014-01-01

    210Pb was measured during the 3rd Chinese National Arctic Research Expedition cruise to investigate its spa-tial pattern in the western Arctic Ocean, as well as its relation with the thermocline in the Canadian Basin. The specific activities varied from 0.04 to 2.72,<0.013 to 4.37, and 0.1 to 4.85 Bq/m3 for dissolved, particu-late, and bulk 210Pb, respectively, corresponding to respective averages of 0.65, 0.43, and 1.08 Bq/m3. In the Canadian Basin, the minimum 210Pb activities occurred in the thermocline, which was characterized by low temperature of-1.52°C and salinity of 33.1. Combining the spatial distribution of 210Pb and hydrographical characteristics in the western Arctic Ocean, this scenario was ascribed to the effective scavenging of 210Pb when the Pacific water flowed across the Chukchi Shelf. Quantitatively, this interpretation was supported by both the shorter residence times and higher scavenging efficiencies (SE) of dissolved 210Pb over the Chukchi Shelf. The highest SE values were observed in the Herald Shoal and bottom waters over the slope.

  13. Bioavailability pf radionuclides {sup 226}Ra, {sup 228}Ra and {sup 210}Pb present in Brazilian phosphogypsum and phosphate fertilizers

    Energy Technology Data Exchange (ETDEWEB)

    Russo, Ana Carolina; Saueia, Catia H.R.; Mazzilli, Barbara P., E-mail: chsaueia@ipen.br [Instituto de Pesquisas Energeticas e Nucleares(IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2011-07-01

    Phosphogypsum (PG) is a by-product of phosphate fertilizers industries. The USEPA classified PG as a - Technologically Enhanced Naturally Occurring Radioactive Material (TENORM). Its worldwide production on 2006 was estimated in 150 million tons. Annually the three main phosphate industries in Brazil are responsible for 5.5x106 tons of phosphogypsum, which is stored in stacks. The level of radionuclides present in phosphogypsum is well-known and makes its disposal or reutilization an environmental concern. Part of this byproduct can be reused, for example, to improve fertility of agricultural soils. To assess the long term environmental impact of radioactive contamination of ecosystems, information on source term including radionuclide speciation, mobility and biological uptakes have high importance. This paper intends to evaluate the bioavailability of the radionuclides {sup 226}Ra, {sup 228}Ra and {sup 210}Pb to the environment by following a procedure established by the EC (European Community), which includes a single EDTA-NH{sub 4} 0.05M extraction at pH 7.0 prior to the analyses. These results is compared with the total activity concentration of these radionuclides in Brazilian PG and the most used phosphate fertilizers (SSP, TSP, MAP and DAP). This procedure intends to represent on a more realistic way the leaching of radionuclides from PG and fertilizers to soil and agricultural products. (author)

  14. The use of {sup 210}Pb and {sup 137}Cs in environmental studies

    Energy Technology Data Exchange (ETDEWEB)

    Heijnis, H. [Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW (Australia). Environmental Radiochemistry Group, Environment Division

    1999-11-01

    The use of natural radioactivity in environmental studies has proven a very powerful tool to determine the dynamics of both natural and antrophogenic processes in our environment. The use of {sup 14}C in archaeology and past climate studies has led to many scientific discoveries (the shroud of Turin and Utze {sup t}he ice-man from Austria are two examples). The use of the {sup 238}U-decay series is of at least equal value to studies in archaeology and of past climates. Some of the Isotopes studied supplement {sup 14}C (which is limited to 40,000 years) data and allow dating of samples formed up to 500,000 years ago (see McCullough, this book of abstracts, pages 19-23), others can be utilised to date very young sediments, which can`t be dated by {sup 14}C.The so-called {sup 210}Pb dating method has been used over the past 3 decades to date recent sediment. The method uses the disequilibrium in the {sup 238}U decay chain, caused by the escape of the intermediate daughter {sup 222}Rn, a noble gas, from the earth`s crust. In the atmosphere the {sup 222}Rn decays via short-lived daughter isotopes to {sup 210}Pb. This {sup 210}Pb with a very convenient half-life of 22,3 years decays to stable {sup 206}Pb. By measuring the surface activity of a sediment core and subsequent samples at regular intervals, a chronology for the sediment core can be established (relative to the surface). In addition to {sup 210}Pb dating one could analyse the samples for {sup l37}Cs to establish an independent chronology based on a pulse of radioactive Caesium. The pulse of {sup 137}Cs originates from the atmospheric atomic-bomb test of the early sixties. The maximum of Caesium activity found in a core should correspond to the height of the tests (approximately 1963 in the Northern hemisphere). A combination of the two dating methods often leads to more reliable results in the chronology. Another use of {sup 137}Cs is to test if the sediment has been subject to bio-turbation or other mixing. In

  15. Distribution of {sup 210}Pb and {sup 210}Po concentrations in wild berries and mushrooms in boreal forest ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Vaaramaa, Kaisa, E-mail: Kaisa.Vaaramaa@Helsinki.fi [Laboratory of Radiochemistry, Department of Chemistry, P.O. Box 55, FI-00014 University of Helsinki (Finland); Solatie, Dina [STUK-Radiation and Nuclear Safety Authority, Regional Laboratory in Northern Finland, FI-96500 Rovaniemi (Finland); Aro, Lasse [Finnish Forest Research Institute (METLA), Parkano Research Unit, FI-39700 Parkano (Finland)

    2009-12-15

    The activity concentrations and distribution of {sup 210}Pb and {sup 210}Po 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 {sup 210}Pb and {sup 210}Po 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 {sup 210}Po/{sup 210}Pb 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 {sup 210}Pb and especially {sup 210}Po were higher than in fruits of the wild berries. The highest activity concentration of {sup 210}Pb was detected in Cortinarius armillatus L. (16.2 Bq kg{sup -1} d.w.) and the lowest in Leccinum vulpinum L. (1.38 Bq kg{sup -1} d.w.). The {sup 210}Po activity concentrations of the whole fruiting bodies ranged from 7.14 Bq kg{sup -1} d.w. (Russula paludosa L.) to 1174 Bq kg{sup -1} d.w. (L. vulpinum L.). In general, the highest activity concentrations of {sup 210}Po were recorded in boletes. The caps of mushrooms of the Boletaceae family showed higher activity concentrations of {sup 210}Po compared to the stipes. In most of the mushrooms analyzed, the activity concentrations of {sup 210}Po were higher than those of {sup 210}Pb. {sup 210}Po and {sup 210}Pb 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 {sup 137}Cs from the Chernobyl fallout.

  16. Applications of PB-210/RA-226 and PO-210/PB-210 disequilibria in the study of marine geochemical processes

    Energy Technology Data Exchange (ETDEWEB)

    Bacon, M. P.

    1976-02-01

    The distribution of /sup 210/Pb and /sup 210/Po in dissolved (less than 0.4 micron) and particulate (greater than 0.4 micron) phases was measured at ten stations in the tropical and eastern North Atlantic and at two stations in the Pacific. Both radionuclides occur principally in the dissolved phase. Unsupported /sup 210/Pb activities, maintained by flux from the atmosphere, were present in the surface mixed layer and penetrated into the thermocline to depths of about 500 m. Dissolved /sup 210/Po was ordinarily present in the mixed layer at less than equilibrium concentrations, suggesting rapid biological removal of this nuclide. Particulate matter was enriched in /sup 210/Po, with /sup 210/Po//sup 210/Pb activity ratios greater than 1.0, similar to those reported for phytoplankton. Box-model calculations yield a 2-y residence time for /sup 210/Pb and a 0.6-y residence time for /sup 210/Po in the mixed layer. These residence times are considerably longer than the time calculated for turnover of particles in the mixed layer (about 0.1 y). At depths of 100 to 300 m, /sup 210/Po maxima occurred and unsupported /sup 210/Po was frequently present. Calculations indicate that at least 50 percent of the /sup 210/Po removed from the mixed layer is re-cycled within the thermocline. Similar calculations for /sup 210/Pb suggest much lower re-cycling efficiencies.

  17. Behavior of 210Po and 210Pb in Shallow Water Region of Mersing Estuary, Johor, Malaysia

    Directory of Open Access Journals (Sweden)

    Noor Affizah Bujang Saili

    2014-06-01

    Full Text Available 210Po and 210Pb activities were determined in dissolved and particulate phases in order to understand the behavior of both natural radionuclides in shallow water regions such as Mersing Estuary. Strong statistical correlations between the distribution coefficient values of polonium and lead in dissolved phases with SPM proved that the natural nuclides of polonium and lead have a high affinity to suspended particle materials in the water column, where the SPM acts as a carrier to transport and remove natural isotopes of polonium and lead from their geochemical behavior. However a low statistical correlation (r=0.414 found between chlorophyll-a with an activity ratio of 210Po/210Pb and SPM implies that the enrichment of 210Po was not associated with the abundance of chlorophyll-a. But a strong correlation between soluble reactive phosphorus (SRP and 210Po in the dissolved phase proved that the contribution of phosphate element as catalysis increasing the activity levels of 210Po at coastal waters.

  18. Hair and feathers as indicator of internal contamination of 210Po and 210Pb

    Energy Technology Data Exchange (ETDEWEB)

    Holm, E. (ed.); Gwynn, J.; Zaborska, A.; Gaefvert, T. (Norwegian Radiation Protection Authority (Norway)); Roos, P. (Technical Univ. of Denmark, Risoe National Lab. for Sustainable Energy, Roskilde (Denmark)); Henricsson, F. (Lund Univ., Lund (Sweden))

    2010-03-15

    The activities of the NKS-B HAIRPOL project is summarised in this report. The objective was to investigate if hair and feathers were suitable matrices for the estimation of the intake of 210Po. Human hair from people of different sex and age was analysed for 210Po showing concentrations between 0.4 to 11 Bq/kg dry weight. Samples from horses, mane, fur and tail showed concentration from 6 to 17 Bq/kg with no significant difference between the different sample types. Musk ox from Greenland showed much higher concentrations since the animal has to graze a large surface. In fur the concentration was 260 Bq/kg. A considerable fraction of the total 210Po in this animal is contained in the hair. Also different organs were analysed and the highest concentration was found in kidney, 2 700 Bq/kg. The 210Pb concentration in hair was estimated to about 20 Bq/kg. Three different seabirds from Svalbard were analysed. Feathers from all three seabird species show increasing activity concentrations of 210Po and 210Pb from the base to the tip of the feather, but it was difficult to relate feather concentrations to muscle concentrations due to a number of complicating factors. (author)

  19. Sediment flux and source in northern Yellow Sea by 210Pb technique

    Institute of Scientific and Technical Information of China (English)

    LI Fengye; LI Xuegang; SONG Jinming; WANG Guizhi; CHENG Peng; GAO Shu

    2006-01-01

    Sedimentation of fine-grained deposits on coastal zones and continental shelves are important because of the association with chemical pollutants, and the implication to the impact on biological processes, the stratigraphic correlations, and changes in sedimentary environments. The Yellow Sea continental shelf receives large quantities of sediment from the Huanghe (Yellow) River. Unfortunately, little attention has been yet paid to the sedimentation on the shallow shelf and its features, and the vertical sediment flux in the area is poorly understood. In this study, nine cores were collected in northern Yellow Sea by the R/V Science 1 in September, 1998 and 1999 to examine the sedimentation rate, sediment flux and the provenance with 210Pb analysis. The 210Pb activity profiles showed that the vertical sediment flux ranged from 0.06 to 1.18 g/cm2·a in the region. In central part of the area, there was a patch of fine-grained mud, with the flux below 0.33 g/cm2·a. Most profiles were featured in two-segment model. Differences in the profiles reflected spatial and temporal variations in hydrodynamic and sedimentary processes. In order to determine the provenance and sedimentary setting in the area, the geochemistry of Ca, Fe, Sr, Cu, Ti and Rb in 11 surficial sediment samples were studied, which showed that in the central northern Yellow Sea, the mud deposit was from multi-source but mainly from the Huanghe River.

  20. Dissolved {sup 210}Po and {sup 210}Pb in Guarani aquifer groundwater, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Bonotto, D.M. [Departamento de Petrologia e Metalogenia, Universidade Estadual Paulista (UNESP), Av. 24-A No. 1515, C.P. 178, CEP 13506-900 Rio Claro, Sao Paulo (Brazil)], E-mail: danielbonotto@yahoo.com.br; Caprioglio, L.; Bueno, T.O.; Lazarindo, J.R. [Departamento de Petrologia e Metalogenia, Universidade Estadual Paulista (UNESP), Av. 24-A No. 1515, C.P. 178, CEP 13506-900 Rio Claro, Sao Paulo (Brazil)

    2009-03-15

    The huge Guarani aquifer located in the South American continent is a very important resource for the region, and its drinking water quality has been investigated according to international standards, inclusive radiological parameters. This paper describes {sup 210}Po and {sup 210}Pb activity concentration data in groundwater samples collected at the Brazilian portion of Guarani aquifer, that is characterized by a great variability of temperature (18-70 deg. C), pH (4.0-9.9), sodium content (0.3-322 mg/l), bicarbonate content (0.1-318 mg/l), etc. Non-expensive alpha counting following some radiochemical steps for extracting and depositing dissolved {sup 210}Po was used. The results of the measurements for samples collected in duplicate yielded a maximum {sup 210}Po activity concentration of 3.7 mBq/L and a maximum {sup 210}Pb activity concentration of 6.7 mBq/l, that are values greatly lower than the guidance level of 0.1 Bq/l established by the WHO for their presence in drinking water. The high sensitivity of the method allowed its applicability on the identification of complexes geochemical and hydrogeological processes occurring in Guarani aquifer as well on the evaluation of the drinking water quality in terms of dose calculations.

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

    Science.gov (United States)

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Casacuberta, N., E-mail: Nuria.Casacuberta@uab.es [Departament de Fisica and Institut de Ciencia i Tecnologia Ambientals, Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain); Traversa, F.L. [Departament d' Electronica, Escola Tecnica Superior d' Enginyeria, Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain); Masque, P.; Garcia-Orellana, J. [Departament de Fisica and Institut de Ciencia i Tecnologia Ambientals, Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain); Anguita, M.; Gasa, J. [Departament de Ciencia Animal i dels Aliments, Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain); Garcia-Tenorio, R. [Universidad de Sevilla, Avda. Reina Mercedes s/n, 41012 Sevilla (Spain)

    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 {sup 210}Pb and {sup 210}Po specific activities ({approx} 2000 Bq.kg{sup -1}). Both {sup 210}Pb and {sup 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 {sup 210}Pb and {sup 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 {sup 210}Pb and {sup 210}Po lead to larger specific accumulation in broiler tissues compared to the blank diet. Radionuclides do not accumulate homogeneously within the animal body: {sup 210}Pb follows the calcium pathways to some extent and accumulates largely in bones, while {sup 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 {sup 210}Pb and {sup 210}Po in the whole animal takes into account the size evolution and is self-consistent in that no fitting parameterization of intake and excretions rates is required.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  6. 7Be, 210Pb and 137Cs concentrations in cloud water.

    Science.gov (United States)

    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.

  7. 210Pb mass accumulation rates in the depositional area of the Magra River (Mediterranean Sea, Italy)

    Science.gov (United States)

    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.

    Science.gov (United States)

    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. Dynamics of bacterial communities in two unpolluted soils after spiking with phenanthrene: soil type specific and common responders

    Directory of Open Access Journals (Sweden)

    Guo-Chun eDing

    2012-08-01

    Full Text Available Considering their key role for ecosystem processes, it is important to understand the response of microbial communities in unpolluted soils to pollution with polycyclic aromatic hydrocarbons (PAH. Phenanthrene, a model compound for PAH, was spiked to a Cambisol and a Luvisol soil. Total community DNA from phenanthrene-spiked and control soils collected on days 0, 21 and 63 were analyzed based on PCR-amplified 16S rRNA genefragments. Denaturing gradient gel electrophoresis (DGGE fingerprints of bacterial communities increasingly deviated with time between spiked and control soils. In taxon specific DGGE, significant responses of Alphaproteobacteria and Actinobacteria became only detectable after 63 days, while significant effects on Betaproteobacteria were detectable in both soils after 21 days. Comparison of the taxonomic distribution of bacteria in spiked and control soils on day 63 as revealed by pyrosequencing indicated soil type specific negative effects of phenanthrene on several taxa, many of them belonging to the Gamma-, Beta- or Deltaproteobacteria. Bacterial richness and evenness decreased in spiked soils. Despite the significant differences in the bacterial community structure between both soils on day 0, similar genera increased in relative abundance after PAH spiking, especially Sphingomonas and Polaromonas. However, this did not result in an increased overall similarity of the bacterial communities in both soils.

  10. 210Pb and 137Cs measurements in the Circum Bohai Sea coastal region: sedimentation rates and implications

    Institute of Scientific and Technical Information of China (English)

    Fu WANG; Hong WANG; Jianfen LI; Yandong PEI; Changfu FAN; Lizhu TIAN; Zhiwen SHANG; Meiyu SONG; Yan GENG

    2008-01-01

    The representative 210Pb and 137Cs age-depth profiles were selected from more than 100 sites in the Circum Bohai Sea (CBS)coastal region to examine the sedimentation rates and associated environmental changes.There are three unique 210Pbexc distribution patterns:1)ideal-decaying type,representing relatively constant sediment supply and quieter environmental setting;2)wiggling type,but with approximately equivalent amplitude,representing coarser sediments and associated stronger flow current environment;and 3) episodic-eventinfluencing type,each representing typhoon storm-influenced depositional environment.Our results also show that there is a lower sedimentation rate(ca.0.1 cm/a)in the coastal lowlands,a higher sedimentation rate(ca.0.53 cm/a)in the intertidal flat and an intermediate rate of ca.0.58 cm/a in the subtidal zone near the Huanghua Harbor.The interbedded silt layer occurring in the core sediment reveals lower 210Pb activities,indicating a discontinuous sedimentation mostly due to typhoon events which dwarfs against 210Pb and 137Cs applicability.Overall,the 210Pb and 137Cs measurements of the present study provide physical insight into the evaluation of the coastal-marine ecological environment and associated management.

  11. 210Po and 210Pb Activity Concentrations in Cigarettes Produced in Vietnam and Their Estimated Dose Contribution Due to Smoking

    Science.gov (United States)

    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.

  12. {sup 210}Pb atmospheric flux and growth rates of a microbial mat from the northwestern Mediterranean Sea (Ebro River Delta)

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Cabeza, J.A.; Masque, P.; Martinez-Alonso, M.; Mir, J.; Esteve, I.

    1999-11-01

    Environmental archives are needed to study the variability of natural systems and the impact of man on them. Microbial mats, modern homologues of stromatolites, can be found in extreme environments such as the Ebro River Delta and were studied as potential environmental archives of atmospheric deposition. {sup 210}Pb, a radiotracer widely used in geochronology studies, was used both to determine the growth rates of a microbial mat from this environment and to estimate the {sup 210}Pb atmospheric flux in the northwestern Mediterranean Sea. The {sup 210}Pb profile showed the presence of three distinct peaks related to low growth-rate periods. This variability indicted the sensitivity of the system to external forcing. The annual atmospheric flux of {sup 210}Pb was 81.2 {+-} 1.4 B1 m{sup {minus}2}yr{sup {minus}1}, which is similar to other values found in the literature. The age profile showed two layers of differing growth rates, being 0.99 {+-} 0.10 mm yr{sup {minus}1} from the surface down to 10 mm depth. The accumulated mass profile showed a change at about 9 mm depth, corresponding to year 1983 {+-} 1. It is noteworthy that this is coincident with a strong El Nino Southern Oscillation event during 1982--1983, which has been shown to affect other ecosystems, including some in the Mediterranean area.

  13. Polonium ({sup 210}Po) and lead ({sup 210}Pb) in marine organisms and their transfer in marine food chains

    Energy Technology Data Exchange (ETDEWEB)

    Carvalho, Fernando P., E-mail: carvalho@itn.p [Instituto Tecnologico e Nuclear, Departamento de Proteccao Radiologica e Seguranca Nuclear, E.N. 10, 2686-953 Sacavem (Portugal)

    2011-05-15

    The determination of {sup 210}Po and {sup 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 x 10{sup -1} Bq kg{sup -1} (wet wt.) in jellyfish, to very high values of about of 3 x 10{sup 4} Bq kg{sup -1} (wet wt.) in the gut walls of sardines, with a common pattern of {sup 210}Po > {sup 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 {sup 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 {sup 210}Po preferentially binds to amino acids and proteins, its transfer in food chains likely traces protein transfer and, thus, {sup 210}Po transfer factors are similar to ecotrophic coefficients. {sup 210}Pb is transferred less efficiently in marine food chains and this contributes to increased {sup 210}Po:{sup 210}Pb activity ratios in some trophic levels.

  14. Enrichment and vertical profiles of {sup 210}Po and {sup 210}Pb in monazite areas of coastal Karnataka

    Energy Technology Data Exchange (ETDEWEB)

    Narayana, Y. [Department of Studies in Physics, Mangalore University, Mangalagangothri 574199 (India)], E-mail: narayanay@yahoo.com; Prakash, V. [Department of Studies in Physics, Mangalore University, Mangalagangothri 574199 (India)

    2010-06-15

    A study on radiation level and radionuclide distribution in the environment of coastal Karnataka has revealed the presence of low-level monazite deposit in the Ullal beach area. The paper presents systematic studies on the distribution, enrichment and vertical profiles of {sup 210}Po and {sup 210}Pb, important daughter products of {sup 238}U, in Ombattu Kere, Summer Sand and the Bhagavathi Temple region of the Ullal beach area of coastal Karnataka. Sand samples collected at different depths from these locations were analyzed for {sup 210}Po and {sup 210}Pb activities to understand the distribution, enrichment and vertical profiles of these radionuclides in monazite area. The activity of {sup 210}Po in the Ullal region is found to vary from 1.7 to 43.2 Bq kg{sup -1} with a mean value of 11.2 Bq kg{sup -1} and that of {sup 210}Pb varies from 1.0 to 66.7 Bq kg{sup -1} with a mean value of 19.1 Bq kg{sup -1}. The mean {sup 210}Po/{sup 210}Pb ratio was observed to be 0.6. The absorbed gamma dose rate in the region varies in the range 39-460 nGy h{sup -1} with a mean value of 193 nGy h{sup -1}.

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

    Science.gov (United States)

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

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

    2016-08-27

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

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

    Science.gov (United States)

    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.

  19. Modeling the downward transport of {sup 210}Pb in Peatlands: Initial Penetration‐Constant Rate of Supply (IP-CRS) model

    Energy Technology Data Exchange (ETDEWEB)

    Olid, Carolina, E-mail: olid.carolina@gmail.com [Department of Ecology and Environmental Science, Umeå University, SE-90187, Umeå (Sweden); Diego, David [Department of Earth Science, University of Bergen, NO-5020 Bergen (Norway); Garcia-Orellana, Jordi [Departament de Física, Universitat Autònoma de Barcelona, E-08193 Bellaterra (Spain); Institut de Ciència i Tecnologia Ambientals (ICTA), Universitat Autònoma de Barcelona, E-08193 Bellaterra (Spain); Cortizas, Antonio Martínez [Departamento de Edafoloxía e Química Agrícola, Universidade de Santiago de Compostela, E-15782 Santiago de Compostela (Spain); Klaminder, Jonatan [Department of Ecology and Environmental Science, Umeå University, SE-90187, Umeå (Sweden)

    2016-01-15

    The vertical distribution of {sup 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 {sup 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 {sup 210}Pb profiles that are altered by an initial migration of the radionuclide. This new, two-phased, model describes the distribution of atmospheric-derived {sup 210}Pb ({sup 210}Pb{sub xs}) in peat taking into account both incorporation of {sup 210}Pb into the accumulating peat matrix as well as an initial flushing of {sup 210}Pb through the uppermost peat layers. The validity of the IP-CRS model is tested in four anomalous {sup 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 {sup 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. {sup 241}Am and {sup 137}Cs). Our results showed that the IP-CRS can provide chronologies from peat records where {sup 210}Pb mobility is evident, being a valuable tool for studies reconstructing past environmental changes using peat archives during the Anthropocene. - Highlights: • Accurate age dating of peat and sediment cores is critical for evaluating change. • A new {sup 210}Pb dating model that includes vertical transport of {sup 210}Pb was developed. • The IP-CRS model provided consistent peat accumulation rates. • The IP-CRS ages were consistent with independent chronological markers. • The IP-CRS model derives peat ages where downward {sup 210}Pb transport is

  20. 234Th, 210Pb, 210Po and stable Pb in the central equatorial Pacific: Tracers for particle cycling

    Science.gov (United States)

    Murray, James W.; Paul, Barbara; Dunne, John P.; Chapin, Thomas

    2005-11-01

    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 ( τ) 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

  1. Separation of 210Pb, 210Bi and 210Po by ion exchange and their Iiquid scintillation standardization; Separacion del 210Pb, 210Bi y 2I0Po mediante columna de cambio ionico y su calibracion por centelleo liquido

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, L.; Jimenez, A.; Grau, A.

    1996-07-01

    We applied the CIEMAT/NIST method and alpha/beta discrimination to ''210Pb samples in equilibrium with its daughters, by preparing homogeneous and gel samples. The stability of samples was tested in different available cocktails, HiSafe''TM II, HiSafe''TM III, Ultima-Gold''TM, Ultima-Gold''TM XR, Ultima-Gold''TM AB, Insta-Gel''R and e Insta-Gel''R lI. Also we analyzed the disequilibrium of the radioactive chain 210Pb+210Bi+210Po, achieving an excellent agreement between the results of the spectrum unfolding method and the experimental values. (Author) 13 refs.

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

    Science.gov (United States)

    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.

  3. Bioturbation in near-surface sediments from the COMRA Polymetallic Nodule Area:evidence from excess 210Pb measurements

    Institute of Scientific and Technical Information of China (English)

    YANG Qunhui; ZHOU Huaiyang

    2004-01-01

    In order to evaluate bioturbation in sediments from the COMRA Polymetallic Nodule Area in the northeast tropical Pacific, excess 210Pb profiles in sediments cores collected with multiple corers during R/V DAYANGYIHAO Environmental Program Cruise in 1998 were measured by direct gamma assay using Ortec HPGe GWL series well-type coaxial low background intrinsic germanium detectors. A steady-state diffusion model of excess 210Pb profiles suggests that bioturbation mixing depths and biodiffusion coefficients are 16 cm and 2.75 cm2/a in East Zone, and 6 cm and 0.26 cm2/a in West Zone, respectively. Furthermore, the observations of macrofauna and measurements of total organic carbon (TOC) content in sediments suggest that bioturbation is directly controlled by species and abundance of benthic fauna, such as polychaete, and the bioturbation mixing depth and intensity are positively correlated with the organic matter content.

  4. Application of the {sup 210}Pb-dating technique to evaluate environmental changes resulting from recent human activities

    Energy Technology Data Exchange (ETDEWEB)

    Jenkinson, A.V.; Chisari, R.; Farrar, Y.J.; Heijnis, H.; McOrist, G.D. [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW (Australia); Hallegraeff, G. [University of Tasmania, Tasmania, (Australia). Department of Plant Science; Hughes, M.; Napoli, M. [University of Sydney, Sydney, NSW (Australia). Department of Geology and Geophysics; James, J.M. [University of Sydney, NSW, (Australia). School of Chemistry; McMinn, A.; Thomson, P. [University of Tasmania, Tasmania, (Australia). Institute of Antartic and Southern Ocean Studies; Smith, J.D.; Tinker, R.A. [University of Melbourne, Parkville, VIC (Australia). School of Chemistry, Marine Chemistry Laboratory

    1997-10-01

    The {sup 210}Pb-dating technique has shown particular promise for the study of recent environmental change by enabling the establishment of chronologies for contemporary environmental processes. In this paper two case studies are discussed. Case Study (1) looks at trace element and heavy metal levels in the estuaries of the Georges River and the Hacking River which are partly located in suburban Sydney and Case Study (2) looks at blooms of the toxic dinoflagellate Gymnodinium catenatum which were first observed in Tasmanian waters, principally the Huon and Derwent Rivers in 1980. In both cases the {sup 210}Pb dating technique has been used to establish the sequence of sediment deposition in order to associate an age to the sediment layer which contains the entity under investigation 7 refs., 5 figs.

  5. Evaluation of the Siltation of River Taquari, Pantanal, Brazil, through 210Pb Geochronology of Floodplain Lake Sediments

    Directory of Open Access Journals (Sweden)

    Godoy José M.

    2002-01-01

    Full Text Available This work presents the 210Pb geochronology of seven bottom sediment cores, collected in three floodplain lakes located in the area of the middle Taquari River, Pantanal, Brazil. In five of them, a significant increase in the sediment mass deposition rate was observed, reflecting an increase of the sediment input to the Pantanal. Additionally, in order to validate the 210Pb results, the mercury content was determined for two sediment cores, showing that despite a constant concentration, the flux of Hg has increased due to an increase in the mass sedimentation rate. This increase can be attributed to the expansion of agricultural activity in the upper Taquari River during the last 25 years.

  6. Analysis of sup(210)Pb in sediment trap samples and sediments from the northern Arabian Sea: Evidence for boundary scavenging

    Digital Repository Service at National Institute of Oceanography (India)

    Borole, D.V.

    samples varied from 11 to 108 dpm g sup(-1) at 1024 m and 58 dpm g sup(-1) to 588 dpm g sup(-1) at 3024 m. The mean annual sup(210)Pb flux increased from 0.27 dpm cm sup(-2) yr sup(-1) in the 1024 m trap to 0.65 dpm cm sup(-2) yr sup(-1) in the 3024 m trap...

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

    Science.gov (United States)

    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 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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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 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.

  13. Comparison of degradation between indigenous and spiked bisphenol A and triclosan in a biosolids amended soil

    Energy Technology Data Exchange (ETDEWEB)

    Langdon, Kate A., E-mail: Kate.Langdon@csiro.au [School of Agriculture, Food and Wine and Waite Research Institute, University of Adelaide, South Australia, 5005, Adelaide (Australia); Water for a Healthy Country Research Flagship, Commonwealth Scientific and Industrial Research Organisation (CSIRO), PMB 2, Glen Osmond, South Australia, 5064, Adelaide (Australia); Warne, Michael StJ. [Water for a Healthy Country Research Flagship, Commonwealth Scientific and Industrial Research Organisation (CSIRO), PMB 2, Glen Osmond, South Australia, 5064, Adelaide (Australia); Smernik, Ronald J. [School of Agriculture, Food and Wine and Waite Research Institute, University of Adelaide, South Australia, 5005, Adelaide (Australia); Shareef, Ali; Kookana, Rai S. [Water for a Healthy Country Research Flagship, Commonwealth Scientific and Industrial Research Organisation (CSIRO), PMB 2, Glen Osmond, South Australia, 5064, Adelaide (Australia)

    2013-03-01

    This study compared the degradation of indigenous bisphenol A (BPA) and triclosan (TCS) in a biosolids-amended soil, to the degradation of spiked labelled surrogates of the same compounds (BPA-d{sub 16} and TCS-{sup 13}C{sub 12}). The aim was to determine if spiking experiments accurately predict the degradation of compounds in biosolids-amended soils using two different types of biosolids, a centrifuge dried biosolids (CDB) and a lagoon dried biosolids (LDB). The rate of degradation of the compounds was examined and the results indicated that there were considerable differences between the indigenous and spiked compounds. These differences were more marked for BPA, for which the indigenous compound was detectable throughout the study, whereas the spiked compound decreased to below the detection limit prior to the study completion. The rate of degradation for the indigenous BPA was approximately 5-times slower than that of the spiked BPA-d{sub 16}. The indigenous and spiked TCS were both detectable throughout the study, however, the shape of the degradation curves varied considerably, particularly in the CDB treatment. These findings show that spiking experiments may not be suitable to predict the degradation and persistence of organic compounds following land application of biosolids. - Highlights: ► Degradation of indigenous and spiked compounds from biosolids were compared. ► Differences were observed for both the rate and pattern of degradation. ► Spiked bisphenol A entirely degraded however the indigenous compound remained. ► TCS was detectable during the experiment however the degradation patterns varied. ► Spiking experiments may not be suitable to predict degradation of organic compounds.

  14. Inventory of {sup 226}Ra, {sup 228}Ra and {sup 210}Pb in marine sediments cores of Southwest Atlantic Ocean

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Alice M.R.; Oliveira, Joselene de, E-mail: alice.costa@usp.br, E-mail: jolivei@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Gerencia de Metrologia das Radiacoes. Lab. de Radiometria Ambiental; Figueira, Rubens C.L.; Mahiques, Michel M.; Sousa, Silvia H.M., E-mail: rfigueira@usp.br, E-mail: mahiques@usp.br, E-mail: smsousa@usp.br [Universidade de Sao Paulo (USP), Sao Paulo, SP (Brazil). Instituto Oceanografico

    2015-07-01

    {sup 210}Pb (22.3 y) is a radioactive isotope successfully applied as tracer of sediment dating of the last 100-150 years. The application of {sup 226}Ra and {sup 228}Ra as paleoceanographic tracers (half-lives of 1,600 y and 5.7 y, respectively) also gives some information of ocean's role in past climate change. In this work, it was analyzed 2 sediment cores collect at Southwest Atlantic Ocean. The sediments samples were freeze-dried and acid digested in microwave. It was carried out a radiochemical separation of {sup 226}Ra, {sup 228}Ra and {sup 210}Pb and performed a gross alpha and gross beta measurement of both precipitates Ba(Ra)SO{sub 4} and PbCrO{sub 4} in a low background gas-flow proportional counter. Activity concentrations of {sup 226}Ra ranged from 45 Bq kg{sup -1} to 70 Bq kg{sup -1} in NAP-62 and from 57 Bq kg{sup -1} to 82 Bq kg{sup -1} in NAP-63 samples. The concentration of {sup 228}Ra varied between 37 Bq kg{sup -1} and 150 Bq kg{sup -1} in NAP-62 and between 23 Bq kg{sup -1} and 111 Bq kg{sup -1} in NAP-63 samples. The concentration of total {sup 210}Pb ranged from 126 Bq kg{sup -1} to 256 Bq kg{sup -1} in NAP-62 and from 63 Bq kg{sup -1} to 945 Bq kg{sup -1} in NAP-63 samples. Results of {sup 210}Pb{sub uns} varied from 68 Bq kg{sup -1} to 192 Bq kg{sup -1} for NAP-62, while varied from <4.9 Bq kg{sup -1} to 870 Bq kg{sup -1} in NAP-63 profile. Increased values of {sup 210}Pb{sub uns} were found on the top of both NAP-62 and NAP- 63 sediment profile. (author)

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  17. Radiochemical determination of {sup 210} Pb and {sup 226}Ra in petroleum sludges and scales; Determinacao radioquimica de {sup 210} Pb e {sup 226}Ra em borras e incrustacoes de petroleo

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, Andressa Arruda de

    2005-07-01

    The oil extraction and production, both onshore and offshore, can generate different types of residues, such as sludge, that is deposited in the water/oil separators, valves and storage tanks and scales, which form i the inner surface of ducts and equipment. Analyses already carried out through gamma spectrometry indicated the existence of high radioisotope concentration. However, radionuclides emitting low-energy gamma-rays, such as {sup 210} Pb, are hardly detected by that technique. Consequently, there is a need to test alternative techniques to determine this and other radionuclides from the {sup 238} U series. This work, therefore, focuses on the radiochemical determination of the concentration of {sup 210}Pb, and {sup 226} Ra in samples of sludge and scale from the oil processing stations of the UN-SEAL, a PETROBRAS unit responsible for the exploration and production of petroleum in Sergipe and Alagoas. The sludge and scale samples went through a preliminary process of extraction of oil, in order to separate the solid phase, where the largest fraction of the radioactivity is concentrated. After oil removal, the samples were digested using alkaline fusion as an option for dissolution. Finally, their activity concentration was determined for the samples of sludge and scales, using and alternative radiochemical method, which is based on ionic exchange. The activity concentration found for {sup 210}Pb varied from 1,14 to 507,3 kBq kg{sup -1}. The values for {sup 226}Ra were higher, varying from 4,36 to 3.445 kBq kg{sup -1}. The results for {sup 226}Ra were then compared with the ones found for the same samples of sludge and scales using gamma spectrometry. The results of the comparison confirm the efficiency of the methodology used int hi work, that is, radiochemical determination by means of ionic exchange. (author)

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

    Science.gov (United States)

    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

  19. Particle-reactive radionuclides (234Th, 210Pb, 210Po as tracers for the estimation of export production in the South China Sea

    Directory of Open Access Journals (Sweden)

    P. H. Santschi

    2011-09-01

    Full Text Available The time-series station, SEATS (18° N, 116° E in the South China Sea was visited six times during October 2006–December 2008 to carry out seawater sampling and floating trap deployments for the determination of distributions and fluxes of POC, PIC, PN, 234Th, 210Pb, and 210Po in the upper 200 m of the water column. Radionuclide deficiencies resulted in removal fluxes from the euphotic layer of 1.1 × 103–1.8 × 103 dpm m−2 d−1 and 7.1–40.2 dpm m−2 d−1 for 234Th and 210Po, respectively. Due to atmospheric input, an excess of 210Pb relative to 226Ra is commonly observed in the upper water column. Sinking fluxes of total mass, POC, PIC, PN, 234Th, 210Pb, and 210Po measured at the euphotic depth were low in summer-fall and high in winter-spring, reflecting the seasonal variability of biological pumping. Excluding the suspiciously low primary productivity data point in July 2007, a relatively high e-ratio of 0.28–0.69 was estimated by the ratio of the POC flux at the euphotic depth and the integrated primary productivity. The ratios of 234Th, 210Pb, and 210Po to organic carbon, inorganic carbon, and nitrogen in the sinking particles were combined with the disequilibria of 234Th-238U, 210Pb-226Ra, and 210Po-210Pb to estimate export fluxes of POC, PIC, and PN from the euphotic layer. Compared with measured fluxes by the sediment trap and estimated fluxes by other approaches, it is concluded that the export production in the South China Sea, ranging from 1.8 to 21.3 mmol-C m−2 d−1, can be reasonably estimated using 234Th, 210Pb, and 210Po as carbon proxies.

  20. Evaluation of the activity concentration of {sup 226}Ra, {sup 228}Ra and {sup 210}Pb in sediments from Antarctica in the Admiralty Bay region

    Energy Technology Data Exchange (ETDEWEB)

    Mora, Tamires de A.; Oliveira, Joselene de, E-mail: tamires.mora@usp.br, E-mail: jolivei@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Figueira, Rubens C.L.; Mahiques, Michel M.; Sousa, Silvia H.M., E-mail: rfigueira@usp.br, E-mail: mahiques@usp.br, E-mail: smsousa@usp.br [Universidade de Sao Paulo (USP), Sao Paulo, SP (Brazil). Instituto Oceanografico

    2015-07-01

    In this study, we performed the radiochemical characterization of a sedimentary record (1B profile), collected in the vicinity of Admiralty Bay, King George Island in Antarctic Operation XXXI (January/2013). The activities of {sup 226}Ra, {sup 228}Ra and {sup 210}Pb were determined by the counting of gross alpha and gross beta activities in the precipitates of Ba(Ra)SO{sub 4} and PbCrO{sub 4}. Those measurements were carried out in a low background gas flow proportional detector. The {sup 226}Ra and {sup 228}Ra were measured after 21 days of the final precipitation. The {sup 210}Pb activity was determined after 10 days of the precipitation date by gross beta counting of its {sup 210}Bi decay product. The activity concentration of {sup 226}Ra ranged from 11±1 (mBq g-1) to 54±3 (mBq g{sup -1}), and the {sup 228}Ra ranged from 48±5 (mBq g{sup -1}) to 155±16 (mBq g{sup -1}). The activity concentration of {sup 210}Pb varied from 8±1 (mBq g{sup -1}) to 458±46 (mBq g{sup -1}), while unsupported {sup 210}Pb ranged from 6±1 (mBq g{sup -1}) to 434±65 (mBq g{sup -1}). The {sup 210}Pb concentrations in sediments have often been used to dating events like deposition and accumulation in various marine environments. Taking into account the results of {sup 210}Pb and {sup 226}Ra activities obtained in testimony-1B it was estimated the unsupported {sup 210}Pb activity which was applied to the CIC geochronological dating model (Constant Initial Concentration). Based in these data, the sedimentation rate obtained was 0.63±0.02 cm year{sup -1}. (author)

  1. 210Pb-226Ra chronology reveals rapid growth rate of Madrepora oculata and Lophelia pertusa on world's largest cold-water coral reef

    Directory of Open Access Journals (Sweden)

    N. Tisnérat-Laborde

    2012-03-01

    Full Text Available 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

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

    Science.gov (United States)

    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.

  3. Analysis of the gamma spectrometry {sup 210}Pb radioisotope in river bottom sediments of the hydrographic sub-basins around the UTM-Caldas

    Energy Technology Data Exchange (ETDEWEB)

    Dutra, Pedro H.; Carvalho Filho, Carlos A.; Moreira, Rubens M.; Menezes, Maria Angela B.C.; Oliveira, Aline F.G. de, E-mail: pedrohenrique.dutra@gmail.com [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Silva, Nivaldo C., E-mail: ncsilva@cnen.gov.br [Comissao Nacional de Energia Nuclear (LAPOC/CNEN-MG), Pocos de Caldas, MG (Brazil). Laboratorio de Pocos de Caldas; Viana, Valquiria F.L., E-mail: valquiria.flviana@gmail.com [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Instituto de Ciencias Biologicas

    2015-07-01

    The uranium mine of Caldas, currently named Ore Treatment Unit (UTM-Caldas), is sited at the Pocos de Caldas Plateau (Minas Gerais State) and was the first uranium mineral-industrial complex in Brazil. It has been installed since 1982 and now it is under decommissioning process. Taking into account the potential sources of contamination and the assessment of the impact of the mine, based on the presence of radionuclides from the radioactive decay series of natural {sup 238}U, the aim of the article is to present the distribution of {sup 210}Pb in the stream bottom sediments of the study area that consists of the Taquari watershed, sub-divided by its three major sub-basins: Consulta stream, Soberbo stream and Taquari river. The radionuclide activity concentrations were measured in sediment samples that were collected in twelve collecting points, during four sampling campaigns, carried out in the dry and rainy seasons of 2010 and 2011. The results of the {sup 210}Pb concentration activity were obtained by gamma spectrometry performed in both high and low energy CANBERRA detectors. The results point out that the UTM-Caldas is influencing on the bottom sediment distribution of {sup 210}Pb activity in its neighborhood. However, a more detailed study should be done in order to identify if there is another source of {sup 210}Pb in the study area, such as a geogenic anomaly, that may contributing to the local increment of {sup 210}Pb activity. (author)

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

    Science.gov (United States)

    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.

  5. Determination of {sup 226}Ra, {sup 228}Ra, and {sup 210}Pb in mushroom from a naturally high radioactive region

    Energy Technology Data Exchange (ETDEWEB)

    Rosa, Mychelle M.L.; Custodio, Luis Gustavo; Cheberle, Luan T.V.; Taddei, Maria Helena T., E-mail: mychelle@cnen.gov.br, E-mail: lgcustodio@hotmail.com, E-mail: lt.cheberle@bol.com.br, E-mail: mhtaddei@cnen.gov.br [Comissao Nacional de Energia Nuclear (LAPOC/CNEN-MG), Pocos de Caldas, MG (Brazil). Laboratorio de Pocos de Caldas; Maihara, Vera A., E-mail: vmaihara@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (CNEN/IPEN-SP), Sao Paulo, SP (Brazil)

    2013-07-01

    Many studies have shown that mushrooms are organisms which efficiently accumulate radionuclides and can be used as indicators of environmental contamination and ecosystem quality. The Pocos de Caldas plateau, in Minas Gerais, is a region that has elevated natural radioactivity due to the presence of radiological anomalies of volcanic origin. Seventy areas of radioactive anomalies have been identified in this region. From the radiological point of view the determination of {sup 226}Ra, {sup 228}Ra, and {sup 210}Pb is relevant because they are decay products of the natural series of {sup 238}U and {sup 232}Th, mainly responsible for natural radioactive exposures of man. The present paper is part of a broader study conducted in the Pocos de Caldas plateau, in which the concentration activities of {sup 226}Ra, {sup 228}Ra, and {sup 210}Pb in mushroom samples were determined. The mushrooms were collected at different points of the plateau under the influence of radioactive anomalies and away from the influence of anomalies. From statistical studies a correlation between the accumulation of radionuclides in mushrooms and anomalies was established and it was possible to confirm the efficiency that the mushrooms present as environmental contamination indicators. (author)

  6. Distribution of some chemical elements between dissolved and particulate phases in the ocean. Research period: August 1, 1975--July 31, 1976. [Fallout /sup 210/Po and /sup 210/Pb diffusion in oceans

    Energy Technology Data Exchange (ETDEWEB)

    1976-01-01

    Progress is reported on studies on the distributions of fallout /sup 210/Pb and /sup 210/Po in dissolved and particulate states in the Gulf of Maine and a transect of the equatorial North Atlantic Ocean. The ratio of /sup 210/Pb//sup 226/Ra and /sup 210/Po//sup 210/Pb in seawater and suspended particulate matter in samples collected from 10 stations in the tropical and eastern North Atlantic and two stations in the Pacific was also determined. (CH)

  7. Biomonitoring of {sup 210}Po and {sup 210}Pb using lichens and mosses around coal-fired power plants in Western Turkey

    Energy Technology Data Exchange (ETDEWEB)

    Sert, Emel, E-mail: emel.sert@mail.ege.edu.tr [Ege University, Institute of Nuclear Sciences, 35100 Bornova, Izmir (Turkey); Ugur, Aysun, E-mail: aysun.ugur@ege.edu.tr [Ege University, Institute of Nuclear Sciences, 35100 Bornova, Izmir (Turkey); Ozden, Banu, E-mail: banu.ozden@ege.edu.tr [Ege University, Institute of Nuclear Sciences, 35100 Bornova, Izmir (Turkey); Sac, Mueslim Murat, E-mail: muslum.murat.sac@ege.edu.tr [Ege University, Institute of Nuclear Sciences, 35100 Bornova, Izmir (Turkey); Camgoez, Berkay, E-mail: berkay.camgoz@ege.edu.tr [Ege University, Institute of Nuclear Sciences, 35100 Bornova, Izmir (Turkey)

    2011-06-15

    Mosses and lichens are useful biological indicators of environmental contamination for a variety of metals and radionuclides of both natural and artificial origin. These plants lack a well-developed root system and rely largely on atmospheric deposition for nourishment. Therefore in the study, different lichens (Cladonia convoluta, Cladonia foliacea) and mosses (Homalothecium sericeum, Hypnum lacunosum, Hypnum cupressiforme, Tortella tortuosa, Didymodon acutus, Syntrichia ruralis, Syntrichia intermedia, Pterogonium graciale, Isothecium alopecuroides, Pleurochatae squarrosa) were collected around the Yatagan (Mugla), Soma (Manisa), Seyitoemer - Tuncbilek (Kuetahya) coal-fired power plants and investigated for potential use as biomonitors for {sup 210}Po and {sup 210}Pb deposition. While the activity concentrations of {sup 210}Po and {sup 210}Pb in lichens are in the ranges of 151 {+-} 7-593 {+-} 21 and 97 {+-} 5-364 {+-} 13 Bq kg{sup -1}, for mosses the ranges for {sup 210}Po and {sup 210}Pb are 124 {+-} 5-1125 {+-} 38 and 113 {+-} 4-490 {+-} 17 Bq kg{sup -1}, respectively. In the study, the moss samples were observed to accumulate more {sup 210}Po and {sup 210}Pb compared to lichens. While the most suitable biomonitor was a moss species (H. lacunosum) for Yatagan (Mugla), it was another moss species (S. intermedia) for Soma (Manisa) and Seyitoemer - Tuncbilek (Kuetahya) sites. {sup 210}Po concentrations were found higher than {sup 210}Pb concentrations at the all sampling stations. - Highlights: > Lichens and mosses have been used as biomonitors of 210Po and 210Pb deposition. > The morphology of lichens and mosses does not vary with seasons. > Lichens and mosses retain and accumulate pollutants deposited from the atmosphere. > Canopy is an important factor causing differences in the concentrations of radionuclides.

  8. Distribution, cycling and mean residence time of {sup 226}Ra, {sup 210}Pb and {sup 210}Po in the Tagus estuary

    Energy Technology Data Exchange (ETDEWEB)

    Carvalho, Fernando P. [Direccao Geral do Ambiente, Departamento de Proteccao e Seguranca Radiologica, Sacavem (Portugal)

    1997-02-28

    Results for dissolved and particulate {sup 226}Ra, {sup 210}Pb and {sup 210}Po in the Tagus river, estuary and coastal sea system show different distribution and chemical behaviour patterns for these radionuclides in the three aquatic environments. {sup 226}Ra from riverborne particles dissolves in the estuary and contributes to increased concentrations of dissolved {sup 226}Ra in estuarine water. In the estuary, dissolved {sup 210}Pb and {sup 210}Po from river discharge and atmospheric deposition are scavenged by suspended matter, which in turn becomes enriched in these nuclides in comparison with riverborne particles. As a result of these processes, the estuarine water flowing into the coastal sea contains enhanced concentrations of dissolved {sup 226}Ra, but is depleted in dissolved {sup 210}Pb and {sup 210}Po. Under average river flow conditions, mass balance calculations for dissolved {sup 210}Po and {sup 210}Pb in the estuary allowed their mean residence times to be estimated as 18 and 30 days, respectively. Due to the rapid sorption of these radionuclides on to settling particles, bottom sediments in the estuary represent a sink for {sup 210}Pb and {sup 210}Po from both natural sources and industrial waste releases. Results also suggest that partial re-dissolution of these radionuclides from bottom sediments and intertidal mudflats is likely to occur in the mid- and low-estuary zones. Nevertheless, box-model computations indicate that the discharge of {sup 210}Pb and {sup 210}Po into the coastal sea takes place mainly with the transport of sediment, whereas the discharge in the dissolved fraction can only account for one third of the activities entering the estuary in the soluble phase. Implications of these results to the cycling of radionuclides in phosphate waste releases into estuarine environments are discussed.

  9. Particle-reactive radionuclides (234Th, 210Pb, 210 as tracers for the estimation of export production in the South China Sea

    Directory of Open Access Journals (Sweden)

    P. H. Santschi

    2011-12-01

    Full Text Available The time-series station, SEATS (18° N, 116° E in the South China Sea was visited six times during October 2006–December 2008 to carry out seawater sampling and floating trap deployments for the determination of distributions and fluxes of POC, PIC, PN, 234Th, 210Pb, and 210Po in the upper 200 m of the water column. Radionuclide deficiencies resulted in removal fluxes from the euphotic layer of 1.1×103–1.8×103 dpm m−2d−1 and 7.1–40.2 dpm m−2d−1 for 234Th and 210Po, respectively. Due to atmospheric input, an excess of 210Pb relative to 226Ra is commonly observed in the upper water column. Sinking fluxes of total mass, POC, PIC, PN, 234Th, 210Pb, and 210Po measured at the euphotic depth were low in summer-fall and high in winter-spring, reflecting the seasonal variability of biological pumping. Excluding the suspiciously low primary productivity data point in July 2007, a relatively high e-ratio of 0.28–0.69 was estimated by the ratio of the POC flux at the euphotic depth and the integrated primary productivity. The ratios of 234Th, 210Pb, and 210Po to organic carbon, inorganic carbon, and nitrogen in the sinking particles were combined with the disequilibria of 234Th–238U, 210Pb–226Ra, and 210Po–210Pb to estimate export fluxes of POC, PIC, and PN from the euphotic layer. Compared with measured fluxes by the sediment trap and estimated fluxes by other approaches, it is concluded that the export production in the South China Sea, ranging from 1.8 to 21.3 mmol-C m−2d−1, can be reasonably estimated using 234Th, 210Pb, and 210Po as carbon proxies.

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

    Energy Technology Data Exchange (ETDEWEB)

    Piotrowska, Natalia, E-mail: natalia.piotrowska@polsl.p [Department of Radioisotopes, Institute of Physics, Silesian University of Technology, Krzywoustego, 2, Gliwice 44100 (Poland); Vleeschouwer, Francois De; Sikorski, Jaroslaw; Pawlyta, Jacek [Department of Radioisotopes, Institute of Physics, Silesian University of Technology, Krzywoustego, 2, Gliwice 44100 (Poland); Fagel, Nathalie; Roux, Gael Le [Clays and Palaeoclimate Unit, Department of Geology, University of Liege, Allee du 6 Aout, B18, Sart Tilman, Liege 4000 (Belgium); Pazdur, Anna [Department of Radioisotopes, Institute of Physics, Silesian University of Technology, Krzywoustego, 2, Gliwice 44100 (Poland)

    2010-04-15

    Radiocarbon and {sup 210}Pb were measured on the uppermost 40 cm of a Wardenaar peat core retrieved from a Baltic raised bog at Slowinskie Blota (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{sub S}equence tool. We present here a comparison of this model with the age model obtained using CRS model classically applied to {sup 210}Pb measurements.

  11. Uptake and accumulation of phenanthrene and pyrene in spiked soils by Ryegrass( Lolium perenne L.)

    Institute of Scientific and Technical Information of China (English)

    XU Sheng-you; CHEN Ying-xu; LIN Qi; WU Wei-xiang; XUE Sheng-guo; SHEN Chao-feng

    2005-01-01

    Phytoremediation has long been recognized as a cost-effective method for the removal of polycyclic aromatic hydrocarbons (PAHs) from soil. A study was conducted to investigate the uptake and accumulation of PAHs in root and shoot of Lolium perenne L. Pot experiments were conducted with series of concentrations of 3.31-378.37 mg/kg for phenanthrene and those of 4.22-365.38 mg/kg for pyrene in a greenhouse. The results showed that both ryegrass roots and shoots did take up PAHs from spiked soils, and generally increased with increasing concentrations of PAH in soil. Bioconcentration factors(BCFs) of phenanthrene by shoots and roots were 0.24-4.25 and 0.17-2.12 for the same treatment. BCFs of pyrene by shoots were 0.20-1.5, except for 4.06 in 4.32 mg/kg treatment, much lower than BCFs of pyrene by roots (0.58-2.28). BCFs of phenanthrene and pyrene tended to decrease with increasing concentrations of phenanthrene and pyrene in soil. Direct uptake and accumulation of these compounds by Lolium perenne L. was very low compared with the other loss pathways, which meant that plant-promoted microbial biodegradation might be the main contribution to plant-enhanced removal of phenanthrene and pyrene in soil. However, the presence of Lolium perenne L. significantly enhanced the removal of phenanthrene and pyrene in spiked soil. At the end of 60 d experiment, the extractable concentrations of phenanthrene and pyrene were lower in planted soil than in non-planted soil, about 83.24%-91.98% of phenanthrene and 68.53%-84.10% of pyrene were removed from soils, respectively. The results indicated that the removal of PAHs in contaminated soils was a feasible approach by using Lolium perenne L.

  12. The particulate {sup 7}Be/{sup 210}Pb{sub xs} and {sup 234}Th/{sup 210}Pb{sub xs} activity ratios as tracers for tidal-to-seasonal particle dynamics in the Gironde estuary (France): Implications for the budget of particle-associated contaminants

    Energy Technology Data Exchange (ETDEWEB)

    Saari, Hanna-Kaisa [Universite de Bordeaux, UMR5805 EPOC, F-33405 Talence Cedex (France); Schmidt, Sabine, E-mail: s.schmidt@epoc.u-bordeaux1.fr [CNRS, UMR5805 EPOC, F-33405 Talence Cedex (France); Castaing, Patrice; Blanc, Gerard [Universite de Bordeaux, UMR5805 EPOC, F-33405 Talence Cedex (France); Sautour, Benoit [Universite de Bordeaux, UMR5805 EPOC, Station Marine d' Arcachon, F-33120 Arcachon (France); Masson, Olivier [IRSN, BP 3, 13115 Saint Paul Lez Durance (France); Cochran, J. Kirk [Marine Sciences Research Center, School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, New York 11794-5000 (United States)

    2010-09-15

    The short-lived natural radionuclides {sup 7}Be (T{sub 1/2} = 53 days), {sup 234}Th{sub xs} (T{sub 1/2} = 24.1 days) and {sup 210}Pb{sub xs} (T{sub 1/2} = 22.3 years), i.e. {sup 234}Th and {sup 210}Pb in excesses of that supported within particles by the decay of their parent isotopes, were analysed in suspended particulate matter (SPM) to study the particle dynamics in the Gironde fluvial estuarine system (France), strongly impacted by heavy metal pollution. From surveys of this land-ocean interface in 2006 and 2007, we established a times series of these radioisotopes and of their activity ratios ({sup 7}Be/{sup 210}Pb{sub xs} and {sup 234}Th/{sup 210}Pb{sub xs} ARs) in particles sampled under different hydrological conditions. The particulate {sup 7}Be/{sup 210}Pb{sub xs} AR varies along the fluvial estuarine system mainly due to variations in {sup 7}Be activities, controlled by riverine, oceanic and atmospheric inputs and by resuspension of old {sup 7}Be-deficient sediments. These processes vary with river discharge, tidal cycle and season. Therefore, seasonal particle transport processes can be described using variations of the SPM {sup 7}Be/{sup 210}Pb{sub xs} ARs. During high river discharge, the SPM {sup 7}Be/{sup 210}Pb{sub x} ARs decrease from river to the ocean. The turbidity maximum zone (TMZ) is dispersed and the particles, and the associated contaminants, are rapidly transported from river to coastal waters, without significant retention within the TMZ. During low river discharge, the TMZ intrudes into the fluvial estuary, and the lowest {sup 7}Be/{sup 210}Pb{sub x} ARs are observed there due to resuspension of {sup 7}Be-deficient sediments. Away from the TMZ, from the middle to lower estuary, SPM {sup 7}Be/{sup 210}Pb{sub x} ARs increase, indicating that the particles have been recently tagged with {sup 7}Be. We explain this trend as being caused by marine input of dissolved radionuclides, as traced by SPM {sup 234}Th/{sup 210}Pb{sub xs} ARs

  13. Continuous 25-yr aerosol records at coastal Antarctica. Part 2: variability of the radionuclides 7Be, 10Be and 210Pb

    Energy Technology Data Exchange (ETDEWEB)

    Elsaesser, Christoph; Wagenbach, Dietmar (Institut fur Umweltphysik, Univ. of Heidelberg, Heidelberg (Germany)), e-mail: Christoph.Elsaesser@iup.uni-heidelberg.de; Weller, Rolf (Alfred Wegener Inst. for Polar and Marine Research, Bremerhaven (Germany)); Auer, Matthias (Institut fur Umweltphysik, Univ. of Heidelberg, Heidelberg (Germany); Vienna Environmental Research Accelerator, Univ. of Vienna, Vienna (Austria)); Wallner, Anton (Vienna Environmental Research Accelerator, Univ. of Vienna, Vienna (Austria)); Christl, Marcus (Laboratory for Ion Beam Physics, ETH-Zurich, Zurich (Switzerland))

    2011-11-15

    We investigated the variability of 210Pb, 7Be and 10Be in coastal Antarctic aerosol samples based on continuous,monthly and annually resolved time series obtained from Neumayer Station over the period 1983 to 2008. Clear seasonal cycles peaking in the local summer half year stand out as a common feature of all three radionuclide records. Time series analyses suggest that significant multiannual changes are confined to a 4-6 yr periodicity resembling that of the Southern Annual Mode index in case of 210Pb and to the expected decadal solar cycle in case of the cosmogenic Be-isotopes. Both, changes in the meridional transport and surface inversion strength appear to drive the seasonal 210Pb cycle, which generally peaks in November. In contrast, stratospheric air mass intrusions are proved to be the main reason for the Be-isotopes seasonality. This finding is revealed by enhanced 10Be/7Be ratios occurring during late summer / early autumn broadly concurrently with the individual Be-isotopes and the 7Be/210Pb ratio. The 10Be and 7Be records clearly reflect the decadal, solar-modulated production signal but, for unknown reasons, they substantially differ in their detailed pattern. It is ruled out, that an excess 7Be production by solar energetic particles was responsible for this mismatch

  14. De dosis ten gevolge van eenheidslozingen 226Ra, 210Pb en 210Po in de Nieuwe Waterweg; een herberekening op basis van nieuwe inzichten

    NARCIS (Netherlands)

    Lembrechts J; LSO

    1998-01-01

    Lozingen door de fosfaatertsverwerkende industrieen van 1 TBq/a van de radionucliden 226Ra, 210Pb en 210Po in de Nieuwe Waterweg veroorzaken een potentiele individuele dosis van ten hoogste 0,53 mSv/a. Circa 96% van deze dosis wordt veroorzaakt door blootstelling aan 222Rn in woningen en 4% door

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Connan, O. [Laboratoire de Radioecologie de Cherbourg-Octeville, Institut de Radioprotection et de Surete nucleaire (IRSN), Service d' Etudes et du Comportement des Radionucleides dans l' Environnement (SECRE), rue Max Pol Fouchet, 50130 Cherbourg-Octeville (France)], E-mail: olivier.connan@irsn.fr; Boust, D. [Laboratoire de Radioecologie de Cherbourg-Octeville, Institut de Radioprotection et de Surete nucleaire (IRSN), Service d' Etudes et du Comportement des Radionucleides dans l' Environnement (SECRE), rue Max Pol Fouchet, 50130 Cherbourg-Octeville (France); Billon, G. [Laboratoire de Chimie Analytique et Marine, Universite des sciences et technologies de Lille, 59655 Villeneuve d' Ascq Cedex (France); Solier, L.; Rozet, M.; Bouderbala, S. [Laboratoire de Radioecologie de Cherbourg-Octeville, Institut de Radioprotection et de Surete nucleaire (IRSN), Service d' Etudes et du Comportement des Radionucleides dans l' Environnement (SECRE), rue Max Pol Fouchet, 50130 Cherbourg-Octeville (France)

    2009-10-15

    A sequential extraction protocol has been used to determine the solid-phase partition of {sup 210}Po and {sup 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 {sup 210}Po activities range between 1 and 20 mBq L{sup -1} and {sup 210}Pb activities between 2.4 and 3.8 mBq L{sup -1}, with highest activities in the topmost layer. These activities are higher than in seawater, suggesting that sediment act as a source of both {sup 210}Po and {sup 210}Pb for overlying water. The {sup 210}Po profile in the pore waters is apparently correlated with those obtained for Fe, Mn and SO{sub 4}{sup 2-}, suggesting an influence of early diagenetic processes on the {sup 210}Po solid-liquid distribution. In the sediment, {sup 210}Po is predominantly bound to organic matter or chromium reducible sulphides, and residuals (clay minerals and refractory oxides). Our results indicate that {sup 210}Po is not significantly bound to AVS, i.e. acid volatile sulphides: bioturbation could play a role by the early redistribution of {sup 210}Po bound to acid volatile sulphides in the sediment. {sup 210}Po, {sup 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 {sup 210}Po and {sup 210}Pb in marine sediment. These data are very scarce in the litterature.

  17. Immobilization of Cadmium in a Cd-Spiked Soil by Different Kinds of Amendments

    Directory of Open Access Journals (Sweden)

    Mahboub Saffari

    2015-07-01

    Full Text Available    Chemical stabilization of heavy metals is one of the soil remediation methods based on the application amendments to reduce mobility of heavy metals. A laboratory study was conducted to investigate the influence of different kinds of amendments on cadmium (Cd stabilization in a Cd-spiked soil. The amendments were municipal solid waste compost (MSWC, Coal fly ash (CFA, rice husk biochars prepared at 300°C (B300 and 600°C (B600, zero valent iron (Fe0 and zero valent manganese (Mn0. The Cd-spiked soils were separately incubated with selected amendments at the rates of 2 and 5% (W/W for 90 days at 25 °C. Soil samples were extracted by EDTA for periods of 5 to 975min. In addition, sequential extraction was used as a suitable method for identification of chemical forms of Cd and their plant availability. The addition of amendments to soil had significant effects on desorption and chemical forms of Cd. Changes in Cd fractions and their conversion into less soluble forms were clear in all treated soils. The addition of amendments resulted in a significant reduction in mobility factor of Cd compared to the control treatment. Among all amendments tested, Fe0 was the most effective treatment in decreasing dynamic of Cd. Biphasic pattern of Cd desorption kinetic was fitted well by the model of two first-order reactions. In general, from the practical point of view, Fe0, MSWC and Mn0 treatments are effective in Cd immobilization, while application of  Fe0 at 5% (W/W was the best treatment for stabilization of Cd. 

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Miglietta, Maria Lucia, E-mail: mara.miglietta@enea.it; Rametta, Gabriella; Manzo, Sonia; Salluzzo, Antonio; Rimauro, Juri; Francia, Girolamo Di [ENEA, Portici Technical Unit, C.R. Portici (Italy)

    2015-07-15

    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 (ZnCl{sub 2}) 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.

  20. 210Pb-226Ra chronology reveals rapid growth rate of Madrepora oculata and Lophelia pertusa on world's largest cold-water coral reef

    Directory of Open Access Journals (Sweden)

    N. Tisnérat-Laborde

    2011-12-01

    Full Text Available 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

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

  3. 210Pb- 226Ra and 228Ra- 232Th systematics in young arc lavas: implications for magma degassing and ascent rates

    Science.gov (United States)

    Turner, Simon; Black, Stuart; Berlo, Kim

    2004-10-01

    New data show that island arc rocks have ( 210Pb/ 226Ra) o ratios which range from as low as 0.24 up to 2.88. In contrast, ( 228Ra/ 232Th) appears always within error of 1 suggesting that the large 226Ra-excesses observed in arc rocks were generated more than 30 years ago. This places a maximum estimate on melt ascent velocities of around 4000 m/year and provides further confidence that the 226Ra excesses reflect deep (source) processes rather than shallow level alteration or seawater contamination. Conversely, partial melting must have occurred more than 30 years prior to eruption. The 210Pb deficits are most readily explained by protracted magma degassing. Using published numerical models, the data suggest that degassing occurred continuously for periods up to several decades just prior to eruption but no link with eruption periodicity was found. Longer periods are required if degassing is discontinuous, less than 100% efficient or if magma is recharged or stored after degassing. The long durations suggest much of this degassing occurs at depth with implications for the formation of hydrothermal and copper-porphyry systems. A suite of lavas erupted in 1985-1986 from Sangeang Api volcano in the Sunda arc are characterised by deficits of 210Pb relative to 226Ra from which 6-8 years of continuous 222Rn degassing would be inferred from recent numerical models. These data also form a linear ( 210Pb)/Pb-( 226Ra)/Pb array which might be interpreted as a 71-year isochron. However, the array passes through the origin suggesting displacement downwards from the equiline in response to degassing and so the slope of the array is inferred not to have any age significance. Simple modelling shows that the range of ( 226Ra)/Pb ratios requires thousands of years to develop consistent with differentiation occurring in response to cooling at the base of the crust. Thus, degassing post-dated, and was not responsible for magma differentiation. The formation, migration and extraction

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

    Science.gov (United States)

    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.

  5. Trace element records in wetlands from Pantanal, Mato Grosso do Sul, Brazil dated by {sup 210}Pb

    Energy Technology Data Exchange (ETDEWEB)

    Damatto, S.R.; Favaro, D.I.T.; Sakamoto, A.Y.; Mazzilli, B.P.; Valles, V. [Instituto de Pesquisas Energeticas e Nucleares IPEN, Centro de Metrologia das Radiacoes -Divisao de Radiometria Ambiental/CMRA, Butanta, SP (Brazil)

    2004-07-01

    The Pantanal in southwest Brazil is one of world largest freshwater wetlands. This natural ecosystem has been affected due to urban contamination, irregular use of the land, tourism without control, excessive agricultural defensive utilization, etc. In order to verify possible changes in this environment, a study was established in Pantanal da Nhecol dia, Mato Grosso do Sul, Brazil. Two sediment cores were collected in 2001 and the elements As, Ba, Br, Ce, Co, Cr, Cs, Eu, Fe, Hf, La, Lu, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th, U, Yb, Zn and Zr were determined by neutron activation analysis technique - NAA. The radioactive {sup 210}Pb was used to determine sedimentation rates and the sediment age. The element concentrations ranged from mg kg{sup -1} to %. The majority of the elements and rare earths analyzed showed concentrations lower when compared with shale and earth crust values. Factorial analysis, mode R, was applied to the data. Only the elements Br, Hf and Zr showed concentrations slightly higher, probably due to variations on water level in flooding periods. A mean sedimentation rate of 0.61cmy{sup -1} was found for one core, which is in agreement with data from literature for this kind of ecosystem. (author)

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

    Science.gov (United States)

    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.

  7. Enrichment of {sup 210}Po and {sup 210}Pb in ash samples from oil shale-fired power plants in Estonia

    Energy Technology Data Exchange (ETDEWEB)

    Ozden, B. [University of Tartu, Institute of Physics/Ege University, Institute of Nuclear Sciences (Estonia); Vaasma, T.; Kiisk, M.; Suursoo, S.; Tkaczyk, A.H. [University of Tartu,Institute of Physics (Estonia)

    2014-07-01

    Energy production in Estonia is largely dependent on the oil shale industry. Oil shale is a fossil fuel typically characterized by relatively high mineral composition, modest organic fraction (varying between 10 and 65%), high ash content (usually 45% to 50%), and average lower heating value of 8.4 MJ/kg{sup -1}. Oil shale-fired power plants account for 85% of Estonian electricity production and produce up to 6 million tons of oil shale ash annually. This ash contains elevated amounts of natural radionuclides (from the {sup 238}U and {sup 232}Th series and {sup 40}K), which were bound to oil shale during its formation. These radionuclides become enriched in ash fractions during the combustion process and are partially emitted to the atmosphere via fly ash and flue gases. Oil shale-fired electricity production is foreseen to remain a dominant trend in Estonia, suggesting that the radionuclide emissions to the atmosphere will continue in the future. The natural radionuclides {sup 210}Po and {sup 210}Pb, with half-lives of 138 days and 22.3 years respectively, originate from the radioactive decay of radionuclides of {sup 238}U series present in the earth's crust. These radionuclides are also built up artificially in the environment due to waste discharge from phosphate, oil, and gas industries, combustion of fossil fuels and other energy production as technically enhanced natural radionuclides. There are few studies on oil shale power plants influence on the levels of natural radioactivity in the surrounding areas. Realo, et al. reported that the annual doses from fly ash depositions over a 30 year period are in the range 90 - 200 μSv a{sup -1}. A study previously initiated by the University of Tartu, Institute of Physics (IPh) evaluated enrichment in the activity concentrations of {sup 238}U, {sup 226}Ra, {sup 210}Pb, {sup 232}Th, {sup 228}Ra and {sup 40}K in ash samples collected from Eesti Power Plant's circulating fluidized bed (CFB) boiler. According

  8. Application of {sup 137}Cs and {sup 210}Pb radionuclides to determine sedimentation rates of recent sediments from Admiralty Bay, Antarctica Peninsula

    Energy Technology Data Exchange (ETDEWEB)

    Nascimento, Mylene Giseli do; Martins, Cesar de Castro [Universidade Federal do Parana (UFPR), Pontal do Parana, PR (Brazil). Centro de Estudos do Mar (CEM); Figueira, Rubens C.L.; Montone, Rosalinda C.; Mahiques, Michel M. de; Tessler, Moyses G., E-mail: rfigueira@usp.b [Universidade de Sao Paulo (USP), SP (Brazil). Inst. Oceanografico. Dept. de Oceanografia Fisica, Quimica e Geologica; Vendrame, Antonio C. [Universidade Cruzeiro do Sul, Sao Paulo, SP (Brazil)

    2009-07-01

    Studies about natural and artificial radionuclides in areas such as the Antarctic are key to understand natural and dynamic processes in marine environments. These studies are important to determine levels of radioactive elements and local sedimentation rates. Five marine sediment cores were collected in different points of Admiralty Bay, in the Antarctic Peninsula. The purpose of this study was to determine {sup 137}Cs, {sup 226}Ra and {sup 210}Pb and sedimentation rates at each site. {sup 137}Cs, {sup 210}Pb and {sup 226}Ra were assayed by gamma-counting through direct measurement of the peak at 661 keV, 47 keV and 609 keV, respectively. Sedimentation rates were obtained by {sup 137}Cs and {sup 210}Pb (CIC and CRS). The activities for {sup 137}Cs ranged from 0.84 to 7.09 Bq kg{sup -1}; to {sup 226}Ra from 6.77 to 31.07 Bq kg{sup -1} for {sup 210}Pb ranged from 1.10 to 36.90 Bq kg{sup -1}. The sedimentation rates obtained by the three models ranged from 0.11+-0.01 cm y{sup -1} to 0.46+-0.05 cm y{sup -1}. The levels of {sup 137}Cs registered in this study, as well as in other studies in the Antarctic region indicate that global fallout is the main cause of artificial radionuclides present in this environment, since the Antarctic has not suffered a direct action of human activities that released radioactive elements. The possible grain size variations that occur in the studied points of Admiralty Bay may explain the differences found in the vertical distribution of radionuclides, because of the different values of sedimentation rates and respective dating determined in their profiles. (author)

  9. Variation of the activity concentrations and fluxes of natural (210Po, 210Pb) and anthropogenic (239,240Pu, 137Cs) radionuclides in the Strait of Gibraltar (Spain).

    Science.gov (United States)

    Gascó, C; Antón, M P; Delfanti, R; González, A M; Meral, J; Papucci, C

    2002-01-01

    The activity concentrations and fluxes of natural (210Pb, 210Po) and anthropogenic (239,240Pu, 137Cs) radionuclides have been determined in the different water masses crossing the Strait of Gibraltar. New data have been gathered during four multidisciplinary and multinational sampling campaigns, performed between 1997 and 1999 within the framework of the CANIGO-FLUGIST Project. Mean activity concentrations of 210Po (1.53+/-0.34 Bq m(-3), n = 30) and 210Pb (1.16+/-0.50 Bq m(-3), n = 31) in the Atlantic water entering the Mediterranean basin are about double those measured in the Mediterranean outflow, namely 0.84+/-0.34 Bq m(-3) (n = 22) for 210Po and 0.66+/-0.34 Bq m(-3) (n = 22) for 210Pb. The opposite trend is observed for 231,240Pu, with average concentrations of 9.9+/-3.0 mBq m(-3) (n = 29) in the incoming Atlantic flow and 22.0+/-3.0 mBq m(-3) (n = 22) in the outpouring Mediterranean water. In the case of 137Cs, the same concentrations were quantified in the waters moving inwards (2.52+/-0.28 Bq m(-3), n = 27) and outwards (2.14+/-0.52 Bq m(-3), n = 21) from the Mediterranean Sea. On this basis, the Mediterranean basin experiences a net annual input flux of 14 TBq of 210Pb and 19 TBq of 210Po, and a net annual loss of 0.34 TBq of 239,240Pu, while--at present--137Cs input and output fluxes appear to be balanced.

  10. Comparative trends and seasonal variation of {sup 7}Be, {sup 210}Pb and {sup 137}Cs at two altitude sites in the central part of France

    Energy Technology Data Exchange (ETDEWEB)

    Bourcier, L., E-mail: laureline.bourcier@ec.europa.e [Laboratoire de Meteorologie Physique, Observatoire de Physique du Globe de Clermont-Ferrand, Universite Blaise Pascal - CNRS, 24 avenue des Landais, 63 177 Aubiere cedex (France); Masson, O. [Institut de Radioprotection et de Surete Nucleaire (IRSN), DEI/SESURE/LERCM, Cadarache, BP 3, 13 115 saint Paul lez Durance (France); Laj, P.; Pichon, J.M. [Laboratoire de Meteorologie Physique, Observatoire de Physique du Globe de Clermont-Ferrand, Universite Blaise Pascal - CNRS, 24 avenue des Landais, 63 177 Aubiere cedex (France); Paulat, P. [Institut de Radioprotection et de Surete Nucleaire (IRSN), DEI/SESURE/LERCM, Cadarache, BP 3, 13 115 saint Paul lez Durance (France); Freney, E.; Sellegri, K. [Laboratoire de Meteorologie Physique, Observatoire de Physique du Globe de Clermont-Ferrand, Universite Blaise Pascal - CNRS, 24 avenue des Landais, 63 177 Aubiere cedex (France)

    2011-03-15

    The atmospheric concentrations of {sup 137}Cs, {sup 210}Pb, and {sup 7}Be were measured over a three-year period at two research stations located less than 12 km apart and at different altitudes (puy de Dome, 1465 m a.s.l. and Opme, 660 m a.s.l., France). Seasonal trends in all radionuclides were observed at both stations, with high concentration measured during the summer and low concentrations during the winter. The {sup 210}Pb concentrations at both stations were similar to each other. Higher concentrations of both {sup 7}Be and {sup 137}Cs were measured at puy de Dome than at Opme. These observations can be explained by the stratospheric and upper tropospheric sources of {sup 7}Be and the long-range transportation of {sup 137}Cs at high altitudes. Air mass origins during sampling periods were classified into several groups by their route to the stations (marine, marine modified, continental and mediterranean). We observed that {sup 7}Be concentrations were constant regardless of the air mass origins, unlike {sup 137}Cs and {sup 210}Pb concentrations that increased when influenced by continental air masses. Higher {sup 7}Be concentrations were observed when air masses were arriving from the upper troposphere than from the boundary layer, the opposite was observed for {sup 137}Cs. The temporal trend in concentrations of {sup 7}Be shows good agreement with previous modelling studies suggesting that there is a good understanding of its sources and the atmospheric vertical mixing of this radionuclide. The sources and mixing of {sup 210}Pb, however, seem to be more complex than it appeared to be in previous modelling studies.

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

    Energy Technology Data Exchange (ETDEWEB)

    Bao, K.; Xia, W.; Lu, X.; Wang, G. [Chinese Academy of Sciences, Changchun (China). Key Laboratory of Wetland Ecology & Environment

    2010-09-15

    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 {sup 210}Pb and {sup 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 {sup 210}Pb and {sup 137}Cs decreased with the depth in both of the two sample cores. The {sup 210}Pb chronologies were established using the constant rate of supply model (CRS) and are in good agreement with the {sup 137}Cs time marker. Recent atmospheric {sup 210}Pb flux in Great Hinggan Mountains peat bog was estimated to be 337 Bq m{sup -2} y{sup -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{sup -2} y{sup -1} with a range of Pb concentration of 14-262 {mu} g g{sup -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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  14. 210Po, 210Pb, 40K and 137Cs in edible wild berries and mushrooms and ingestion doses to man from high consumption rates of these wild foods.

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  16. 210Pb and 210Po, manganese and iron cycling across the O2/H2S interface of a permanently anoxic fjord: Framvaren, Norway

    Science.gov (United States)

    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.

  17. Determination of {sup 210}Pb e {sup 226}Ra in tobacco leaves cultivated in the states of Rio de Grande do Sul e Alagoas - Brazil; Determinacao de {sup 210}Pb e {sup 226}Ra em folhas de tabaco cultivadas nos estados do Rio de Grande do Sul e Alagoas - Brasil

    Energy Technology Data Exchange (ETDEWEB)

    Brandao, Y.B. [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Energia Nuclear; Valentim, E.; Hazin, C.A. [Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE/CNEN-PE), Recife, PE (Brazil); Antonio Filho, J. [Universidade Catolica de Pernambuco (UNICAP), Recife, PE (Brazil); Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Energia Nuclear

    2005-07-01

    The literature has shown that tobacco use causes damage to the health of cigarette users, manifesting itself in diseases with high mortality. Among these diseases include respiratory failure, pulmonary emphysema and lung cancer, among others. On the other hand, smoking contributes significantly to increasing the dose of natural radiation received by man, due to the presence of uranium series radionuclides, such as {sup 226}Ra, {sup 210}Pb and {sup 210}Po, in relatively high concentrations in fresh tobacco leaves. The determination of these radionuclides in this matrix is of great interest, once they can be incorporated not only by the active smoker, but also by the passive smoker. The results of this study confirmed the significant presence of {sup 226}Ra and {sup 210}Pb in tobacco samples collected and analyzed. The average values of activity concentration found in samples from the State of Alagoas were of Bq.kg{sup -1} 0.8 to {sup 210}Pb and 183.5 Bq.kg{sup -1} to {sup 226}Ra. For samples coming from the State of Rio Grande do Sul, these values were 4,0 Bq.kg{sup -1} to {sup 210}Pb and 161.3 Bq.kg{sup -1} to {sup 226}Ra.

  18. {sup 210}Pb geochronology and chemical characterization of sediment cores from lakes of the Parana river alluvial plain

    Energy Technology Data Exchange (ETDEWEB)

    Teixeira, L.F.L.; Damatto, S.R.; Scapin, M.A. [IPEN - Instituto de Pesquisas Energeticas e Nucleares (Brazil); Remor, M.B.; Sampaio, S.C. [UNIOESTE - Universidade Estadual do Oeste do Parana (Brazil)

    2014-07-01

    The flood plain of the upper Parana River is located among the lakes formed by the Brazilian hydroelectric plants being the last part of the Parana river, in Brazil, where there is an ecosystem with interaction river-flood plain. This flood plain has considerable habitat variability, with great diversity of terrestrial and aquatic species, and the floods are the main factor that regulates the operation of this ecosystem. The seasonality of the flood pulses is mainly influenced by the El Nino phenomenon, which increases precipitation in the drainage basin of the flood plain of the upper Parana River. Because of its unique characteristics this ecosystem is the subject of intense study since 1980, mainly from the ecological point of view. Therefore, two sediment cores were collected in the ponds formed by the floods, Patos pond and Garcas pond, in order to characterize the sediment chemically and evaluate a possible historic contamination. The trace element concentrations As, Ba, Br, Ce, Co, Cr, Cs, Eu, Hf, La, Lu, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th, U, Yb and Zn (mg.kg{sup -1}) and the major elements Si, Al, Fe, Ti, K, Ca, Mg, P, V, Mn, and Na (%) were determined in the sediment cores dated by {sup 210}Pb method, using instrumental neutron activation analysis, X-ray fluorescence and gross beta counting, respectively. The results obtained for the elements Ce, Cr, Cs, La, Nd, Sc, Sm and Th are higher than the values of Upper Continental Crust for both ponds. The sedimentation rates obtained for Garca pond, 0.77 cm.y{sup -1}, and Patos pond, 0.62 cm.y{sup -1} are in agreement with studies performed in sedimentary environments similar to the present work, such as Brazilian wetland Pantanal. The enrichment factor and the geo-accumulation index were used to assess the presence of anthropogenic sources of pollution. Document available in abstract form only. (authors)

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  20. Studies on sup(226) Ra and sup(210) Pb activities and the concentration factors of sup(226) Ra in the surface organic layers of the estuarine sediments of Mindola and Purna rivers in India

    Digital Repository Service at National Institute of Oceanography (India)

    Joshi, L.U.; Zingde, M.D.; Desai, B.N.

    consumed by humans The sampling techniques, experimental procedures and the distribution of the isotopes of sup(226) Ra and sup(210) Pb in the estuarine regions and the concentration factors of sup(226) Ra in the region are detailed....

  1. {sup 210}Pb and {sup 210}Po in sediments and suspended matter in the Tagus estuary, Portugal: Local enhancement of natural levels by wastes from phosphate ore processing industry

    Energy Technology Data Exchange (ETDEWEB)

    Carvalho, Fernando P. [International Atomic Energy Agency, Marine Environment Laboratory, Monaco (Monaco)

    1994-12-09

    Results of analyses of uranium series radionuclides in phosphate ore and in wastes released by the phosphate fertilizer industry confirm their potential for the enhancement of environmental radioactivity levels. Therefore, concentrations of {sup 210}Pb and {sup 210}Po were measured in bottom sediments and suspended matter in the Tagus estuary, Portugal, to assess the enhancement of radioactivity due to wastes from the phosphate industry. The concentration of {sup 210}Pb in surface sediments in the estuary increased inversely with sediment grain-size; conversely, increased percentage of sand has a dilution effect on the concentration of {sup 210}Pb measured in bulk sediment samples. By normalizing the data to the <63-{mu}m fraction, the naturally-occurring {sup 210}Pb in sediments was found to be 68 {+-} 19 Bq kg{sup -1} (dry wt.) in background sediments. Higher {sup 210}Pb levels, up to 1580 Bq kg{sup -1} (dry wt.), were measured in some bulk sediment samples. It was verified that this radionuclide has been introduced by the discharge of wastes from a phosphate fertilizer plant but enhanced concentrations are localized near the point of discharge. In other zones of the estuary, the concentrations of {sup 210}Pb in sediments and suspended matter were generally below those measured in the zone of phosphatic releases at the Barreiro Peninsula. Concentrations higher than the predicted average concentration of unsupported {sup 210}Pb from natural sources (atmospheric deposition, river input) were also measured in the upper estuary, both in bottom sediments and in suspended matter. It is suggested that these relatively elevated concentrations are due to the highly efficient scavenging of soluble naturally-occurring unsupported {sup 210}Pb onto suspended matter and to co-precipitation with iron-manganese hydroxides in the fresh water-salt water mixing zone.

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

    Science.gov (United States)

    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, >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 in part be attributed to in

  3. Study of the particulate matter transfer and dumping using {sup 210} Po et le {sup 210} Pb. Application to the Gulf of Biscary (NE Atlantic Ocean) and the Gulf of Lion (NW Mediterranean Sea) continental margins; Etude du transfert et du depot du materiel particulaire par le {sup 210} Po et le {sup 210} Pb. Application aux marges continentales du Golfe de Gascogne (NE Atlantique) et du Golfe du Lion (NW Mediterranee)

    Energy Technology Data Exchange (ETDEWEB)

    Radakovitch, O.

    1995-07-07

    {sup 210} Po and {sup 210} Pb activities and fluxes were measured on seawater, sediment-trapped material collected during one year and sediment. Focalization of {sup 210} Pb is clearly noticed on the Cap-Ferret canyon (Gulf of Biscary) and the Lacaze-Duthiers canyon (western part of the Gulf of Lion). In both sites, {sup 210} Pb fluxes in traps and sediment are always higher than {sup 210} Pb flux available from atmospheric and in situ production. On the contrary, Grand-Rhone canyon and its adjacent open slope exhibit a {sup 210} Pb budget near equilibrium in the near-bottom sediment traps, but focalization is important in the sediment. For the entire Gulf of Lion margin, focalization of {sup 210} Pb in the sediment occurred principally between 500 and 1500 m water depth on the slope, and on the middle shelf mud-patch. {sup 210} Po and {sup 210} Pb have been used in the Cap Ferret and Grand-Rhone canyons to characterize the origin of the particulate trapped material. Two main sources feed the water column. The first source, localized in surface waters, is constituted by biogenic particles from primary production and lithogenic material. The second source, deeper, is due to resuspension at the shelf break and/or on the open slope. In each site, {sup 210} Po and {sup 210} Pb activities of the trapped particles did not show any relations with the major constituents. Quantity of particles appeared to be the main factor regulating adsorption processes of these nuclides. Sedimentation rates based on {sup 210} Po profiles decreased with increasing water depth, from 0.4 ti 0.06 cm y-1 on the Cap Ferret canyon (400 to 3000 m water depth) and from 0.5 to 0.05 cm y-1 for the entire Gulf of Lion margin (50 to 2000 m water depth). (author). 243 refs.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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).

  6. 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.

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  8. {sup 210}Pb and composition data of near-surface sediments and interstitial waters evidencing anthropogenic inputs in Amazon River mouth, Macapa, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Cardoso Nery, Jose Reinaldo, E-mail: jrnery@unifap.b [Universidade Federal do Amapa (UNIFAP), Campus Marco Zero, Rodovia Juscelino Kubitschek, km 2, CEP 68902-280, Macapa, Amapa (Brazil); Marcos Bonotto, Daniel, E-mail: danielbonotto@yahoo.com.b [Departamento de Petrologia e Metalogenia, Universidade Estadual Paulista (UNESP), Campus de Rio Claro, Av. 24-A No.1515, C.P. 178, CEP 13506-900, Rio Claro, Sao Paulo (Brazil)

    2011-04-15

    Activity profiles of excess {sup 210}Pb determined in three sediment cores from Amazon River mouth, Macapa 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 Amapa 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 Amapa 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{sub 2}O, K{sub 2}O, CaO, MgO, Al{sub 2}O{sub 3}, P{sub 2}O{sub 5}, Fe{sub 2}O{sub 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{sup -2} yr{sup -1} were obtained, and are compatible with the results of others studies. The {sup 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, Amapa 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. - Highlights: {yields} New 210Pb and composition dataset at the Amazon River mouth. {yields} Chemical and 210Pb data revealed anthropogenic inputs in the area. {yields} Mining activities at

  9. Determination of the sedimentation rates in the Sepetiba bay northeastern area by using dating with the excesses {sup 210} Pb radioisotope; Determinacao das taxas de sedimentacao na porcao nordeste da baia de Sepetiba utilizando datacao com o radioisotopo {sup 210} Pb em excesso

    Energy Technology Data Exchange (ETDEWEB)

    Forte, Cristiane Maria Sampaio

    1996-07-01

    {sup 210} Pb dating, using two modes of data analysis, CIC and CRS, was used to determine sedimentation in the North East part of Sepetiba Bay. {sup 210} Pb was leached from samples using dilute HBr and subsequently separated onto anionic exchange columns, followed by re-extraction and precipitation as Pb CrO{sub 4}. The original method was modified by the introduction of a pre-digestion step whose purpose was to liberate the lead bound as sulphide. The sedimentation rates found o.68 - 0.98 cm.y{sup -1} were moderate, compared to other authors estimates. Dating using the CRS model showed a maximum rate of sedimentation in the period between 1954 and 1977, when the riverine input was probably at its greatest. The CRS model appears to be more applicable to the data, since it works over longer periods and allows for variations in sedimentation rate. (author)

  10. Grain yield and arsenic uptake of upland rice inoculated with arbuscular mycorrhizal fungi in As-spiked soils.

    Science.gov (United States)

    Wu, Fuyong; Hu, Junli; Wu, Shengchun; Wong, Ming Hung

    2015-06-01

    A pot trial was conducted to investigate the effects of three arbuscular mycorrhizal (AM) fungi species, including Glomus geosporum BGC HUN02C, G. versiforme BGC GD01B, and G. mosseae BGC GD01A, on grain yield and arsenic (As) uptake of upland rice (Zhonghan 221) in As-spiked soils. Moderate levels of AM colonization (24.1-63.1 %) were recorded in the roots of upland rice, and up to 70 mg kg(-1) As in soils did not seem to inhibit mycorrhizal colonization. Positive mycorrhizal growth effects in grain, husk, straw, and root of the upland rice, especially under high level (70 mg kg(-1)) of As in soils, were apparent. Although the effects varied among species of AM fungi, inoculation of AM fungi apparently enhanced grain yield of upland rice without increasing grain As concentrations in As-spiked soils, indicating that AM fungi could alleviate adverse effects on the upland rice caused by As in soils. The present results also show that mycorrhizal inoculation significantly (p < 0.05) decreased As concentrations in husk, straw, and root in soils added with 70 mg kg(-1) As. The present results suggest that AM fungi are able to mitigate the adverse effects with enhancing rice production when growing in As-contaminated soils.

  11. γ谱法测量环境中的210Pb%The Environmental 210 Pb Determination byγ-ray Spectrometry WANG Ke-bin1,XIANG Yuan-yi2,CAO Zhong-gang2,YANG Yang2

    Institute of Scientific and Technical Information of China (English)

    王克斌; 向元益; 曹钟港; 杨阳

    2015-01-01

    In this work, the γ-ray spectrometry is introduced to measure the activity concentration of 210 Pb in the environmental samples .By measuring the γ-ray of 210 Pb at 46.5 keV, the activity concentration of 210 Pb is determined in aerosol sample collected by cellulose acetate membranes filter and in water sample in Marinelli Beaker .The great advantage of this method is rapid , non-destructive , without preliminary chemical separation and sample preparation , but it is limited by the low emission and high self -absorption probability of this line at such low energy .The key point in the analysis is the efficiency calibration of this line .The experimental results show that the gamma ray spectrometry can be employed to determine the 210 Pb activity in the environmental sample.%介绍了用γ谱仪测量环境中210 Pb的分析方法。用醋酸纤维滤膜采集气溶胶样品,或用马林杯直接封装环境水样,在γ谱仪上测量210 Pb发射的46.5 keV射线,通过解谱分析技术获得210 Pb的放射性活度。该方法具有快速、非破坏性、无需化学分离及样品处理等优点,但存在低γ发射几率及射线能量低导致的高自吸收等不足,分析的关键在于γ谱仪效率刻度。实验结果表明:γ谱法可用于环境样品中210 Pb的放射性活度测量。

  12. Verification of the correlation between the {sup 210} Pb and the chemical composition of the incrustations found on gas pipelines and the implication on radiological protection; Verificacao da correlacao entre a atividade de {sup 210}Pb e a composicao quimica de incrustacoes encontradas em linhas de gas e a implicacao em protecao radiologica

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, Franciane Martins de Carvalho

    2004-07-01

    In the last decades, the occurrence of solid residual deposits, known as black powder, in natural-gas pipelines, gathering systems and compression equipment from gas industries has raised increasing regulatory concerns in terms of radiological protection. Concerns are also raised about the waste disposal and management of the radioactive residues eventually produced. Recent projections indicate a significant increase in the production of natural-gas and its products, due to a growing commercial demand, which leads to the production of huge amounts of residues. Thus, more information is needed in order to allow a preliminary evaluation of the radiological profile of this type of industry. In black powder residues, the most prevalent radioisotope is {sup 210}Pb. The present work aimed to investigate the correlation between the chemical composition of the residue and the concentration of {sup 210}Pb, in black powder samples collected at Bacia de Campos, in the State of Rio de Janeiro, Brazil. The main objective was to generate information to regulatory authorities, to the National Commission of Nuclear Energy (CNEN) and to companies that produce natural-gas, such as PETROBRAS. Based on the information, the gas producing companies could elaborate radiological protection guidelines, and also decide about the need for implementation of a waste management program at the installation. The samples of black powder analyzed at the present work have confirmed the existence of such correlation between the concentration of {sup 210}Pb and chemical parameters. In principle, the present results make the use of such correlation feasible for preliminary evaluations of the {sup 210}Pb levels in natural-gas installations. On the other hand, given the geographic limitations, a broader study is recommended, in order to evaluate the investigated correlation, which could be used as a guiding tool for the Brazilian industry of production and processing of natural-gas.(author)

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

    Science.gov (United States)

    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

  14. {sup 210}Pb and {sup 137}Cs as chronometers for salt marsh accretion in the Venice Lagoon - links to flooding frequency and climate change

    Energy Technology Data Exchange (ETDEWEB)

    Bellucci, L.G. [Istituto di Scienze Marine - Sede di Bologna - Geologia Marina, Consiglio Nazionale delle Ricerche, Via P. Gobetti 101, 40129 Bologna (Italy)], E-mail: luca.bellucci@ismar.cnr.it; Frignani, M. [Istituto di Scienze Marine - Sede di Bologna - Geologia Marina, Consiglio Nazionale delle Ricerche, Via P. Gobetti 101, 40129 Bologna (Italy); Cochran, J.K. [Marine Sciences Research Center, Stony Brook University, Stony Brook, New York 11794-5000, NY (United States); Albertazzi, S. [Istituto di Scienze Marine - Sede di Bologna - Geologia Marina, Consiglio Nazionale delle Ricerche, Via P. Gobetti 101, 40129 Bologna (Italy); Zaggia, L. [Istituto di Scienze Marine, Consiglio Nazionale delle Ricerche - S. Polo 1364, 30125 Venezia (Italy); Cecconi, G. [Consorzio Venezia Nuova - S. Croce 505, 30135 Venezia (Italy); Hopkins, H. [Marine Sciences Research Center, Stony Brook University, Stony Brook, New York 11794-5000, NY (United States)

    2007-10-15

    Five salt marsh sediment cores from different parts of the Venice Lagoon were studied to determine their depositional history and its relationship with the environmental changes occurred during the past {approx}100 years. X-radiographs of the cores show no disturbance related to particle mixing. Accretion rates were calculated using a constant flux model applied to excess {sup 210}Pb distributions in the cores. The record of {sup 137}Cs fluxes to the sites, determined from {sup 137}Cs profiles and the {sup 210}Pb chronologies, shows inputs from the global fallout of {sup 137}Cs in the late 1950s to early 1960s and the Chernobyl accident in 1986. Average accretion rates in the cores are comparable to the long-term average rate of mean sea level rise in the Venice Lagoon ({approx}0.25 cm y{sup -1}) except for a core collected in a marsh presumably affected by inputs from the Dese River. Short-term variations in accretion rate are correlated with the cumulative frequency of flooding, as determined by records of Acqua Alta, in four of the five cores, suggesting that variations in the phenomena causing flooding (such as wind patterns, storm frequency and NAO) are short-term driving forces for variations in marsh accretion rate.

  15. Vertical distribution of Th-isotope ratios, {sup 210}Pb, {sup 226}Ra and {sup 137}Cs in sediment cores from an estuary affected by anthropogenic releases

    Energy Technology Data Exchange (ETDEWEB)

    San Miguel, E.G.; Bolivar, J.P. [Dpto Fisica Aplicada, E.P.S. La Rabida, Ctra Palos S/N, Huelva 21819 (Spain); Garcia-Tenorio, R. [Dpto Fisica Aplicada, E.T.S. Arquitectura, Avda, Reina Mercedes, 2, Sevilla 41012 (Spain)

    2004-01-05

    In an estuary system highly polluted by mining and industrial activities, the sections of sediment cores affected by anthropogenic inputs of U-series radionuclides (due to fertilizer plants releases) were determined through the vertical profiles of Th-isotopic ratio ({sup 230}Th/{sup 232}Th). Also, when possible, a modified version of the {sup 210}Pb dating method was applied in the uncontaminated sections of these cores. Using the information provided by the Th-isotopic ratio and {sup 210}Pb methods, we were able to establish confident chronologies, covering the last century, in several of the analysed sediment cores. These chronologies will be used in forthcoming research to study the time evolution of pollutant concentrations in the estuary. Additionally, and based on the established chronologies, we have found that sedimentation rates have drastically increased in some zones of the estuary since the commencement of several industrial activities in the surrounding environment and since the construction of two dikes in the area.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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 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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

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

    2016-03-01

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

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

  3. Uranium-series radionuclides as tracers of geochemical processes in Long Island Sound. [Natural /sup 210/Pb tracer study of estuarine geochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Benninger, L.K.

    1976-05-01

    An estuary can be visualized as a membrane between land and the deep ocean, and the understanding of the estuarine processes which determine the permeability of this membrane to terrigenous materials is necessary for the estimation of fluxes of these materials to the oceans. Natural radionuclides are useful probes into estuarine geochemistry because of the time-dependent relationships among them and because, as analogs of stable elements, they are much less subject to contamination during sampling and analysis. In this study the flux of heavy metals through Long Island Sound is considered in light of the material balance for excess /sup 210/Pb, and analyses of concurrent seston and water samples from central Long Island Sound are used to probe the internal workings of the estuary.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  5. Sterilization affects soil organic matter chemistry and bioaccumulation of spiked p,p'-DDE and anthracene by earthworms

    Energy Technology Data Exchange (ETDEWEB)

    Kelsey, Jason W., E-mail: kelsey@muhlenberg.ed [Program in Environmental Science and Department of Chemistry, Muhlenberg College, 2400 Chew Street, Allentown, PA 18104 (United States); Slizovskiy, Ilya B.; Peters, Richard D.; Melnick, Adam M. [Program in Environmental Science and Department of Chemistry, Muhlenberg College, 2400 Chew Street, Allentown, PA 18104 (United States)

    2010-06-15

    Laboratory experiments were conducted to assess the effects of soil sterilization on the bioavailability of spiked p,p'-DDE and anthracene to the earthworms Eisenia fetida and Lumbricus terrestris. Physical and chemical changes to soil organic matter (SOM) induced by sterilization were also studied. Uptake of both compounds added after soil was autoclaved or gamma irradiated increased for E. fetida. Sterilization had no effect on bioaccumulation of p,p'-DDE by L. terrestris, and anthracene uptake increased only in gamma-irradiated soils. Analyses by FT-IR and DSC indicate sterilization alters SOM chemistry and may reduce pollutant sorption. Chemical changes to SOM were tentatively linked to changes in bioaccumulation, although the effects were compound and species specific. Artifacts produced by sterilization could lead to inaccurate risk assessments of contaminated sites if assumptions derived from studies carried out in sterilized soil are used. Ultimately, knowledge of SOM chemistry could aid predictions of bioaccumulation of organic pollutants. - Soil sterilization affects soil organic matter chemistry and pollutant bioaccumulation.

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

    Science.gov (United States)

    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. Radiochemistry determination of activity concentration of {sup 210}Pb in sludge and scale samples of UN-SEAL PETROBRAS, Sergipe; Determinacao radioquimica das concentracoes de atividade de {sup 210}Pb em amostras de borras e incrustacoes da UN-SEAL PETROBRAS, Sergipe

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, Andressa A. de; Hazin, Clovis A. [Pernambuco Univ., Recife, PE (Brazil). Dept. de Energia Nuclear]. E-mail: andressa.arruda@globo.com; hazin@ufpe.br; Valentim, Eliane [Centro Regional de Ciencias Nucleares (CRCN), Recife, PE (Brazil)]. E-mail: valentim@cnen.gov.br

    2005-07-01

    The presence of radionuclides of the {sup 238}U and {sup 232}Th series in sludge and scales generated inactivities of oil E and P is a well known phenomenon. Scales formed in the inner surface of ducts are constituted basically of CaCO{sub 3} and BaSO{sub 4} precipitates, being responsible for the gradual reduction in oil production. Sludge, on the other hand, is a mixture of solid debris (sand and rust particles) and oil that accumulate in the bottom of vessels (storage tanks and separators) normally in the form of sulfate and carbonate deposits. The most important radionuclides normally found in sludge and scale are {sup 226}Ra, {sup 228}Ra, {sup 210}Pb and {sup 228}Th. The presence of these radionuclides may cause a significant dose to workers, with the consequent increase in the risk of stochastic effects. A program of studies aiming to determine the activity concentration of radionuclides of the two above mentioned series in scales and sludge samples collected in an E and P unit of PETROBRAS in the State of Sergipe (UN-SEAL), is under way in the Department of Nuclear Energy of the Federal University of Pernambuco (DEN/UFPE). The analyses already carried through by gamma spectrometry had indicated the existence of high concentrations of radium, showing the necessity of extending the survey for other elements of the {sup 238}U series. This work, therefore, aims to determine the activity concentrations of {sup 210}Pb through radiochemical analysis, as well as, to evaluate some available techniques for the determination of {sup 210}Pb in the above-mentioned matrix. (author)

  8. Data base structure and Management for Automatic Calculation of ''210 Pb Dating Methods Applying Different Models; Estructura de la Base de Datos y Modo de Operacion para Realizar el Calculo Automatizado de Datacion mediante ''210 Pb Aplicando Diversos Modelos

    Energy Technology Data Exchange (ETDEWEB)

    Gasco, C.; Anton, M. P.; Ampudia, J.

    2003-07-01

    The introduction of macros in trie calculation sheets allows the automatic application of various dating models using unsupported ''210 Pb data from a data base. The calculation books the contain the models have been modified to permit the implementation of these macros. The Marine and Aquatic Radioecology group of CIEMAT (MARG) will be involved in new European Projects, thus new models have been developed. This report contains a detailed description of: a) the new implement macros b) the design of a dating Menu in the calculation sheet and c) organization and structure of the data base. (Author) 4 refs.

  9. Ultrasonic Extraction and TLC Determination of Glyphosate in the Spiked Red Soils

    Directory of Open Access Journals (Sweden)

    Sandra Babić

    2005-09-01

    Full Text Available Pesticides that get into soil bind mostly to its solid phase by physical or chemical processes. In the valley of the Neretva River the use of herbicides, especially of glyphosate is widespread and sometimes uncontrolled. In this work ultrasonic solvent extraction (USE followed by thin-layer chromatography (TLC was applied for determining glyphosate presence in soil. The experiments were conducted with two characterised soil types. The impact of soil composition on extraction efficiency is discussed. Chemical analysis showed that soil 1 contained much more iron and aluminium oxides than soil 2, which was richer in humic substances. Low glyphosate efficiency (ca 44 % in both soils could be attributed either to its binding to iron and aluminium oxides (soil 1, or to chemisorption on humic macromolecules (soil 2.

  10. Evaluation of recent trends of sedimentation in Indian lakes of western Himalayan region using {sup 210}Pb and {sup 137}Cs dating techniques

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, B.; Rai, S.P.; Nachippan, R.P. [National Institute of Hydrology, UA (India)

    2004-07-01

    In the present study, environmental {sup 210}Pb and {sup 137}Cs dating techniques were employed to determine the recent sedimentation rates of Nainital, Bhimtal, Sat-tal, Naukuchiyatal and Mansar and Dal-Nagin lake of Western Himalayan region. The expected useful life of these lakes have also been estimated. These studies are part of the project funded by Government of India. Three to five sediment cores were collected from the each lakes namely Nainital, Bhimtal, Naukuchiyatal, Sat-tal and Mansar and 14 sediment cores from Dal-Nagin lake using a gravity corer. The sediment cores ranging from 19 to 53 cm in length were sliced at 2 cm intervals. Sliced core sections were brought to laboratory and subjected to various physical and chemical process before measuring {sup 137}Cs and {sup 210}Pb activities. After the chemical treatment of the sliced samples, the extracted solution containing {sup 210}Pb was allowed to stay for a period of one month as 4 to 5 half lives are sufficient for this purpose for getting {sup 210}Bi in secular equilibrium with {sup 210}Pb activity. The {sup 210}Pb activity was measured in terms of beta radiations using {sup 210}Bi which is its daughter product and has half life of {approx}5 days. The activity of {sup 210}Bi was measured using a Ultra Low level Liquid Scintillation spectrometer and CRS model was applied for estimating rates of sedimentation. The {sup 137}Cs activity in each section was determined by gamma counting in the oven-dried samples using Hyper Pure Germanium detector coupled with a 4096 channel multichannel analyser system. A {sup 137}Cs standard, having essentially the same geometry and density was used. The detection limit for {sup 137}Cs by this method is 0.25 mBq.g{sup -1} and the standard counting error was less than 10% in the core sections. The sedimentation rate varies between 1.74 cm/yr to 3.87 cm/yr (weighted mean 1.44 {+-} 0.18 cm/y) in Bhimtal lake, 0.38 cm/yr to 0.95 cm/yr (weighted mean 0.74 {+-} 0.04 cm

  11. Activity and population dynamics of heterotrophic and ammonia-oxidizing microorganisms in soil surrounding sludge bands spiked with linear alkylbenzene sulfonate

    DEFF Research Database (Denmark)

    Brandt, K. K.; Sørensen, J.; Krogh, P. H.

    2003-01-01

    Recent research has documented soil microorganisms to be rather sensitive to linear alkylbenzene sulfonates (LAS), which may enter the soil environment in considerable quantities following sewage sludge disposal. We here report field effects of LAS on selected microbial populations present...... in a sandy soil surrounding well-defined sludge bands spiked with high but realistic LAS levels (7.1 or 31.3 g/kg). Surprisingly, LAS had no effect on heterotrophic respiration in the sludge compartment per se but stimulated activity and metabolic quotient (microbial activity per unit of biomass......) in the surrounding soil. By contrast, autotrophic ammonia oxidation was initially inhibited in the LAS-spiked sludge. This led to dramatic transient increases of NH+4 availability in the sludge and surrounding soil, subsequently stimulating soil ammonia oxidizers. As judged from a Nitrosomonas europaea...

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

    NARCIS (Netherlands)

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

    2015-01-01

    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

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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 (psoil. Our results suggest that adding of PAHs-degrading bacteria to soil can enhance remediation of PAHs contaminated soil, while improving plant growth.

  15. Activity and population dynamics of heterotrophic and ammonia-oxidizing microorganisms in soil surrounding sludge bands spiked with linear alkylbenzene sulfonate: a field study.

    Science.gov (United States)

    Brandt, Kristian Koefoed; Krogh, Paul Henning; Sørensen, Jan

    2003-04-01

    Recent research has documented soil microorganisms to be rather sensitive to linear alkylbenzene sulfonates (LAS), which may enter the soil environment in considerable quantities following sewage sludge disposal. We here report field effects of LAS on selected microbial populations present in a sandy soil surrounding well-defined sludge bands spiked with high but realistic LAS levels (7.1 or 31.3 g/kg). Surprisingly, LAS had no effect on heterotrophic respiration in the sludge compartment per se but stimulated activity and metabolic quotient (microbial activity per unit of biomass) in the surrounding soil. By contrast, autotrophic ammonia oxidation was initially inhibited in the LAS-spiked sludge. This led to dramatic transient increases of NH4+ availability in the sludge and surrounding soil, subsequently stimulating soil ammonia oxidizers. As judged from a Nitrosomonas europaea bioluminescence toxicity assay, however, LAS or other sludge components never accumulated to toxic levels in the soil compartments and the LAS tolerance of the indigenous microbes further remained unchanged following LAS exposure. LAS effects on the investigated microbial populations largely occurred during the first two months and were confined to soil closer than 30 mm from LAS-spiked sludge. Our results strongly suggest that disposal of LAS-contaminated sludge does not pose a major risk to the function of the soil microbial community under field conditions.

  16. 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

    Science.gov (United States)

    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

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

    DEFF Research Database (Denmark)

    Christiansen, Karen Søgaard; Borggaard, Ole K.; Holm, Peter Engelund

    2015-01-01

    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...

  18. Temporal evolution of natural radionuclides distributions {sup 238}U, {sup 234}Th, {sup 226}Ra, {sup 228}Ra, {sup 210}Pb and {sup 210}Po in the Bransfield strait, Antarctica peninsula; Evolucao temporal das distribuicoes dos radionuclideos naturais {sup 238}U, {sup 234}Th, {sup 226}Ra, {sup 228}Ra, {sup 210}Pb and {sup 210}Po no estreito de Bransfiel, peninsula Antartica

    Energy Technology Data Exchange (ETDEWEB)

    Lapa, Flavia Valverde

    2013-07-01

    Research on the distribution of natural radionuclides in Antarctica is rare and thus, there is great interest in to know their occurrence and factors related to its mobilization, transference and accumulation in this extremely fragile environment. Natural radionuclides have been used intensively as tracers in the ocean, helping to better understand processes as sinking and particle resuspension, water masses mixture and oceanic circulation. {sup 234}Th (t½ = 24.1 days) is a particle-reactive radionuclide produced continuously in seawater by the decay of its soluble precursor conservative with salinity {sup 238}U (t½ = 4.5 10{sup 9} years). Since {sup 234}Th presents relatively short half-life, it is used to quantify processes that occur in temporal scale varying from days to weeks. The disequilibrium {sup 234}Th/{sup 238}U in the surface ocean has been applied to estimate carbon fluxes exported via sinking material. The flux of particles biologically productive out of the euphotic zone in the Southern Ocean has special attention due to its importance in the control of CO{sub 2} atmospheric concentrations. The radionuclides {sup 210}Pb (t½ = 22.3 years) and {sup 210}Po (t½ = 138 days) are also particle-reactive. The disequilibrium {sup 210}Po/{sup 210}Pb has been used to estimate fluxes of particles exported in the ocean in the time scale of weeks. The long-lived Ra isotopes, {sup 226}Ra (t½ = 1,600 years) and {sup 228}Ra (t½ = 5.75 years) are soluble in seawater, presenting unique properties that make them excellent tracers of water masses. This research work had the aim to study the distributions of natural radionuclides {sup 238}U, {sup 234}Th, {sup 22}'6Ra, {sup 22}'8Ra, {sup 210}Pb and {sup 210}Po in the Bransfield Strait during 2 samplings carried out in the 2011 Austral Summer (OPERANTAR XXIX and XXX). (author)

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

    Science.gov (United States)

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

    2005-04-01

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

  20. Application of 210Pb-derived sedimentation rates and dinoflagellate cyst analyses in understanding Pyrodinium bahamense harmful algal blooms in Manila Bay and Malampaya Sound, Philippines.

    Science.gov (United States)

    Sombrito, E Z; Bulos, A dM; Sta Maria, E J; Honrado, M C V; Azanza, Rhodora V; Furio, Elsa F

    2004-01-01

    The number of areas affected by toxic harmful algal bloom (HAB) in the Philippines has been increasing since its first recorded occurrence in 1983. Thus far, HAB has been reported in about 20 areas in the Philippines including major fishery production areas. The HAB-causing organism (Pyrodinium bahamense var. compressum) produces a cyst during its life cycle. Pyrodinium cysts which are deposited in the sediment column may play a role in initiating a toxic bloom. 210Pb-derived sedimentation rate studies in the two important fishing grounds of Manila Bay and Malampaya Sound, Palawan have shown that Pyrodinium cysts may have been present in the sediment even before the first recorded toxic algal bloom in these areas. High sedimentation rates (approximately 1 cm/year) have been observed in the northern and western parts of Manila Bay. The results indicate that the sedimentation processes occurring in these bays would require subsurface cyst concentration analysis in evaluating the potential of an area to act as seed bed.

  1. Application of {sup 210}Pb-derived sedimentation rates and dinoflagellate cyst analyses in understanding Pyrodinium bahamense harmful algal blooms in Manila Bay and Malampaya Sound, Philippines

    Energy Technology Data Exchange (ETDEWEB)

    Sombrito, E.Z. E-mail: ezsombrito@pnri.dost.gov.ph; Bulos, A.M.; Sta Maria, E.J.; Honrado, M.C.V.; Azanza, Rhodora V.; Furio, Elsa F

    2004-07-01

    The number of areas affected by toxic harmful algal bloom (HAB) in the Philippines has been increasing since its first recorded occurrence in 1983. Thus far, HAB has been reported in about 20 areas in the Philippines including major fishery production areas. The HAB-causing organism (Pyrodinium bahamense var. compressum) produces a cyst during its life cycle. Pyrodinium cysts which are deposited in the sediment column may play a role in initiating a toxic bloom. {sup 210}Pb-derived sedimentation rate studies in the two important fishing grounds of Manila Bay and Malampaya Sound, Palawan have shown that Pyrodinium cysts may have been present in the sediment even before the first recorded toxic algal bloom in these areas. High sedimentation rates (approximately 1 cm/year) have been observed in the Northern and Western parts of Manila Bay. The results indicate that the sedimentation processes occurring in these bays would require subsurface cyst concentration analysis in evaluating the potential of an area to act as sea bed.

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

    Science.gov (United States)

    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.

  3. 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.

    Science.gov (United States)

    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).

  4. 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

    Science.gov (United States)

    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

  5. 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

    Directory of Open Access Journals (Sweden)

    Ramazan Manav

    2016-11-01

    Full Text Available 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.

  6. Prediction of mono- and polycyclic aromatic hydrocarbon degradation in spiked soils using cyclodextrin extraction

    Energy Technology Data Exchange (ETDEWEB)

    Allan, Ian J. [School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ (United Kingdom); Semple, Kirk T. [Department of Environmental Sciences, Lancaster University, LA1 4YQ (United Kingdom); Hare, Rina [Alcontrol Laboratories, Chester CH5 3US (United Kingdom); Reid, Brian J. [Alcontrol Laboratories, Chester CH5 3US (United Kingdom)]. E-mail: b.reid@uea.ac.uk

    2006-11-15

    In this study, an aqueous-based hydroxypropyl-{beta}-cyclodextrin (HPCD) extraction technique was assessed for its capacity to determine the microbially degradable fraction of mono- and polycyclic aromatic hydrocarbons in four dissimilar soils. A linear relationship (slope = 0.90; R {sup 2} = 0.89), approaching 1:1 between predicted and observed phenanthrene mineralization, was demonstrated for the cyclodextrin extraction; however, the water only extraction underestimated the microbially available fraction by a factor of three (slope = 3.35; R {sup 2} = 0.64). With respect to determining the mineralizable fraction of p-cresol in soils, the cyclodextrin extraction (slope = 0.94; R {sup 2} = 0.84) was more appropriate than the water extraction (slope = 1.50; R {sup 2} = 0.36). Collectively, these results suggested that the cyclodextrin extraction technique was suitable for the prediction of the mineralizable fraction of representative PAHs and phenols present in dissimilar soils following increasing soil-contaminant contact times. The assessment of the microbial availability of contaminants in soils is important for a more representative evaluation of soil contamination. - An aqueous-based HPCD extraction technique was more appropriate than the water extraction in prediction of the mineralizable fraction of phenanthrene and p-cresol present in a range of dissimilar soils.

  7. Effect of Soil Filtration and Ozonation in the Change of Baseline Toxicity in Wastewater Spiked with Organic Micro-pollutants

    KAUST Repository

    Gan, Alexander

    2012-07-01

    Bioassays for baseline toxicity, which measure toxicants’ non-specific effects, have been shown in previous studies to effectively correlate with the increased presence of pharmaceuticals, personal care products, endocrine-disrupting compounds, and other synthetic organics in treated sewage effluent. This study investigated how the baseline toxicity of anthropogenic compounds-spiked wastewater changed during the treatment of biofiltration and ozone oxidation, as measured by the bioluminescence inhibition of the Vibrio fischeri bacterium. The water quality parameters of dissolved organic carbon, seven common anions, and fluorescence spectroscopy were used to corroborate and collate with the toxicity results. Water quality was evaluated on two bench-scale soil filtration columns, which were configured for pre-ozonation and post-ozonation. Both systems’ soil aerobically removed similar amounts of dissolved organic carbon, and the reduction ranged between 57.7% and 62.1% for the post-ozonation and pre-ozonation systems, respectively. Biological removal of DOC, protein-like, humic-like, and soluble microbial product-like material was highest in the first 28.5 cm of each 114 cm-long system. While bioluminescence inhibition showed that ozonation was effective at lowering baseline toxicity, this study’s bioassay procedure was a very poor indicator of soil filtration treatment; both system’s effluents were significantly more toxic than their non-ozonated influents.

  8. Effect of Wetting-Drying Cycles on Redistribution of Lead in Some Semi-Arid Zone Soils Spiked with a Lead Salt

    Institute of Scientific and Technical Information of China (English)

    H.KHODAVERDILOO; M.RAHMANIAN; S.REZAPOUR; S.GHORBANI DASHTAKI; H.HADI; F.X.HAN

    2012-01-01

    Mobility and bioavailability of lead (Pb) could be affected considerably by soil physicochemical properties; however,less is known about the effect of Pb levels and aging time.This study was conducted to evaluate the effects of Pb levels and wetting-drying (WD) cycles on distribution and bioavailability of Pb in three semi-arid zone soils treated with different levels of Pb(NO3)2.Wetting-drying cycles simulated the actual field irrigation in the semi-arid soils.A soil with a long history of Pb contamination was also taken as a reference soil.The soils were spiked with various levels of Pb and incubated under WD cycles for 160 d.Sequential extractions and batch sorption experiments were performed to assess the fractionation of Pb in the spiked soils.Redistribution index (Uts) and reduced partitioning parameter (IR) were applied to semi-quantify the distribution of Pb in the spiked soils.A small amount of Pb sorbed was desorbed by the soils,indicating a strong and irreversible binding of Pb in the studied soils.Contribution of carbonate-bound (Car) and residual (Res) Pb fractions to the total Pb of the soils was more than 97%.The Car,soluble plus exchangeable (SE),and organic matter-bound (OMB) fractions of Pb were transferred to the Res fraction under the WD cycles.The IR and Uts values were influenced by Pb loading levels and WD; therefore,the Pb lability and/or redistribution pattern could semi-quantitatively be assessed via these parameters.At the end of the experiment,the IR and Uts values for the Pb salt-spiked soils did not show the quasiequilibrium state.The lability of Pb in the soils decreased with increasing incubation time and showed a strong dependence on Pb levels and soil chemical composition.WD cycles significantly affected the overall lability of Pb in soils through influencing the redistribution of Pb among solid-phase components.

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

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xueqin [Southwest University, College of Resources and Environment (China); Wang, Fayuan, E-mail: wfy1975@163.com; Shi, Zhaoyong [Henan University of Science and Technology, Agricultural College (China); Tong, Ruijian [Luoyang Normal University, Life Science Department (China); Shi, Xiaojun, E-mail: shixj@swu.edu.cn [Southwest University, College of Resources and Environment (China)

    2015-04-15

    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 (ZnSO{sub 4}) 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 ZnSO{sub 4}. Although significantly lower compared to bulk ZnO and ZnSO{sub 4}, at least 16 % of the Zn from ZnO NPs was converted into DTPA-extractable (bioavailable) forms. The dissolved Zn{sup 2+} 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.

  10. Temporal changes in Hg, Pb, Cd and Zn environmental concentrations in the southern Baltic Sea sediments dated with 210Pb method

    Directory of Open Access Journals (Sweden)

    Tamara Zalewska

    2015-01-01

    Full Text Available The article presents data on heavy metal – Hg, Pb, Cd and Zn – distribution in the layers of marine sediments from the off-shore areas of the southern Baltic Sea: Gdańsk Deep, SE Gotland Basin and Bornholm Deep. Depth profiles of metal concentrations were converted to time-based profiles using the 210Pb dating method and verified by 137Cs distribution in the vertical profile. The linear sedimentation rates in the Gdańsk Deep and SE Gotland Basin are similar, 0.18 cm yr−1 and 0.14 cm yr−1, respectively, while the region of the Bornholm Deep is characterized by a greater sedimentation rate: 0.31 cm yr−1. Regarding anthropogenic pressure, Gdańsk Deep receives the largest share among the analyzed regions. The maximal metal concentrations detected in this area were Zn – 230 mg kg−1, Pb – 77 mg kg−1, Cd – 2.04 mg kg−1 and Hg – 0.27 mg kg−1. The least impact of anthropogenic pressure was noticeable in SE Gotland Basin. The combination of sediment dating with the analysis of vertical distribution of heavy metals in sediments benefited in the determination of target metal concentrations used in environmental status assessments. Reference values of heavy metal concentrations in marine sediments were determined as: Zn – 110 mg kg−1, Pb – 30 mg kg−1, Cd – 0.3 mg kg−1 and Hg – 0.05 mg kg−1 from the period of minor anthropogenic pressure. Basing on the determined indices: enrichment factor (EF, geoaccumulation indicator (Igeo and contamination factor (CF the status of marine environment was assessed regarding the pollution with heavy metals.

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

    Science.gov (United States)

    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

    Science.gov (United States)

    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. Root uptake of lead by Norway spruce grown on Pb-210 spiked soils

    DEFF Research Database (Denmark)

    Hovmand, M.F.; Nielsen, Sven Poul; Johnsen, I.

    2009-01-01

    . Calculations of the specific activity in plant material and in the supporting pot soil showed that less than 2% of the Pb content of needles and twigs originates from root uptake and approximately 98% are deposited from the atmosphere. Atmospheric Pb has declined by a factor of 7 from 1980 to 2007 but is still...... a major pathway of Pb to vegetation and topsoils. The conclusion from the experiment is that the internal circulation of Pb through root uptake, translocation and litterfall, gives an insignificant input of Pb to the forest floor compared to atmospheric deposition....

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

    Science.gov (United States)

    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.

  15. Bioaccumulation and single and joint toxicities of penta-BDE and cadmium to earthworms (Eisenia fetida) exposed to spiked soils

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Bioaccumulation of penta-BDE(DE-71) in earthworms(Eisenia fetida) and the induced toxicities on the growth and reproduction of earthworms were investigated.All the major congeners in DE-71 could be bioaccumulated in earthworms and the concentration found in earthworms correlated to the spiked concentration in soil.DE-71 might inhibit the growth and reproduction of cocoons and juveniles of earthworms.The toxicities were dose dependent and increased with exposure time.Exposing earthworms to combination of DE-71 and Cd resulted in enhanced mortality and reduction of cocoons or juveniles in a synergistic mode.The presence of DE-71 may affect the relocation of Cd in earthworms.When the earthworms were exposed to Cd alone,Cd up-taken by earthworms was mainly partitioned in the cytosolic fraction.While DE-71 was present,Cd in the cytosolic fraction decreased significantly.It is perhaps that DE-71 inhibits the synthesis of matallothioneins,and then reduces the detoxification ability of earthworms.This is the first report about the toxicity of PBDEs to earthworms.The result would be useful for ecological risk assessment of PBDEs in terrestrial ecosystem.

  16. 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.

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  18. 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

    Science.gov (United States)

    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

  19. 长江口水下三角洲粒度与210Pb特征的空间分布%SPATIAL DISTRIBUTIONS OF GRAIN SIZE AND 210Pb CHARACTERISTICS OVER THE CHANGJIANG SUBAQUEOUS DELTA

    Institute of Scientific and Technical Information of China (English)

    谢文静; 高抒; 杨旸

    2012-01-01

    The coastal waters adjacent to the Changjiang estuary is characterized by abundant supply of fine-grained sediments and active hydrodynamic effects. The growth of the Changjiang delta is constrained by a number of factors such as sea-level rise, the original topography, sediment supply, sediment retention in the estuary, ground subsidence and large water conservancy and hydropower projects ( e. g., the Three Gorges Dam ) . Hence, the sedimentation sequence of the Changjiang subaqueous delta in response to physical processes(i. e.,changes in material source, migration of tidal channels,storm events,etc. ) and anthropogenic activities( i. e.,dredging of navigational channels) have become important scientific problems. Sediment cores were obtained from 31 stations over the Changjiang subaqueous delta,during April 13 to April 27, 2009,by utilizing a gravity corer. We took sub-samples from the cores in 2cm intervals. Grain size distribution was derived for 2468 sub-samples. The grain size parameters indicate that the material of the Changjiang subaqueous delta is mainly from modern river input, with a few stations where sandy deposits that are indicative of submarine erosion were present. The vertical variations of grain size parameters show 4 patterns: (Ⅰ) fining upwards; (Ⅱ) uniform;(Ⅲ) sectional or cyclical vertical variations; and (Ⅳ) coarsening upwards. Core samples with different patterns of sediments grain size profiles located at different topographical region with various erosion or siltation dynamics. 210Pb activities of sediments were determined for 511 sub-samples, in 4 ~ 10cm intervals, taken from the 30 sediment cores of the Changjiang sub-aqueous delta. The vertical variation patterns of 210Pb activities can be classified into:(1) normal 210Pbex decay profiles;(2 ) uniform total 210Pb activity profiles;( 3 ) sectional 210Pbex decay profile; and (4) sectional 210Pbex decay and inverse 210Pbex decay profiles(topsy-turvy 210Pb activity profiles). The

  20. Use of radionuclide techniques {sup 137}Cs, {sup 210}Pb{sub E}X and Be to assess soil erosion in Moroccan agriculture lands

    Energy Technology Data Exchange (ETDEWEB)

    Nouira, A.; Benmansour, M.; Benkedad, A.; Bouksirate, H.

    2009-07-01

    Water erosion is one of the major environmental and agricultural problems causing serious socio-economic impairment for not only develop countries but also developing countries. It reduces the fertility and productivity of agricultural lands and it is besides a major source of surface water pollution. On the other hand, intensive or improper farming accelerates greatly this phenomenon. (Author)

  1. 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.

    Science.gov (United States)

    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.

  2. Study of natural radionuclides - {sup 226}Ra, {sup 228}Ra and {sup 210}PB - in marine sediment cores from Southwest Atlantic during the Holocene; Estudo dos radionuclideos naturais - Ra226, Ra-228 e Pb-210 - em alguns registros sedimentares do Atlantico sudoeste ao longo do holoceno

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Alice Miranda Ribeiro

    2016-07-01

    Natural radionuclides from {sup 238}U and {sup 232}Th series have been successfully applied as tracers of environmental process and climate changes. The {sup 210}Pb (half-life of 22.2 years) is used in the geochronological dating technique of sediment cores of the last 100-150 years, and its respective sedimentation rate determination. The study of {sup 226}Ra and {sup 228}Ra concentrations (half-lives of 1,600 years and 5.75 years, respectively) helps calculate the activity of {sup 210}Pb in excess in the environment, besides being important tracers of marine processes, as ground water discharge. In this work it was determined the activity concentrations of {sup 226}Ra, {sup 228}Ra and {sup 210}Pb in four short marine cores collected since the continental platform to upper slope of Southwest Atlantic Ocean. Taking into account the results obtained, sedimentation rates and the ages of each sediment layer were determined using the geochronological dating method with {sup 210}Pb. All sediment samples were total acid digested in microwave. The sequential radiochemical separation of {sup 226}Ra, {sup 228}Ra, {sup 210}Pb were performed, obtaining in the end the precipitation of Ba(Ra)SO{sub 4} and PbCrO{sub 4}. The gross α measurements of {sup 226}Ra and gross β measurements of {sup 228}Ra and {sup 210}Pb from the precipitates were carried out in a gas-flow low background proportional counter. Concerning all cores analyzed, the activities concentrations of {sup 226}Ra ranged from 14 Bq.kg{sup -1} to 154 Bq.kg{sup -1}; the concentrations of {sup 228}Ra ranged from 17 Bq.kg{sup -1} to 45 Bq.kg{sup -1}; and the concentrations of {sup 210}Pb ranged from 20 Bq.kg{sup -1} to 2,073 Bq.kg{sup -1}. High values of {sup 210}Pb were observed on the top of all the cores studied, mainly related to atmospheric deposition. The results obtained in this work were of the same order of magnitude of those reported in the literature available on non contaminated areas of Southeast

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

    Science.gov (United States)

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

    2017-07-01

    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 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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Vertical distribution of natural radionuclides in soils

    Directory of Open Access Journals (Sweden)

    Lozano J. C.

    2012-04-01

    Full Text Available Low-level alpha spectrometry techniques using semiconductor detectors (PIPS and liquid scintillation counters (LKB Quantulus 1220™ were used in order to determine the activity concentration of 238U, 232Th, 234U, 230Th, 226Ra, and 210Pb in soil samples. The soils were collected from an old disused uranium mine located in southwest Spain. The soils were selected with different levels of influence from the installation, in such a way that they had different levels of radioactive contamination. The vertical profiles in the soils (down to 40 cm depth were studied in order to evaluate the vertical distribution of the natural radionuclides. The possible contamination of subsurface waters depends strongly on vertical migration, and the transfer to plants (herbs, shrubs, and trees also will depend on the distribution of the radionuclides in the root zone. The study of the activity ratios between radionuclides belonging to the same series allowed us to assess the differing behaviour of the radionuclides involved. The vertical profiles for these radionuclides were different at each sampling point, showing the local impact of the installation. However, the profiles per point were similar for the long-lived radionuclides of the 238TJ series (238U, 234U, 230Th, and 226Ra. Also, a major disequilibrium was observed between 210Pb and 226Ra in the surface layer, due to 222Rn emanation and subsequent surface deposition of 210Pb.

  5. 环境水中210Pb、210Po快速联测方法及应用%A combined method for the determination of 210pb and 210po in environmental water samples

    Institute of Scientific and Technical Information of China (English)

    覃连敬; 李美丽; 覃浩

    2016-01-01

    本文对210pb、210po快速联测方法作了深入研究,确定了适用于环境水样中210pb、210po联测的最优实验条件.在未经萃取分离情况下,以坑坏血酸+盐酸羟胺混合体系作还原剂,当盐酸浓度为0.5 mol·L-1,沉积时间为2h,沉积温度为90℃,溶液体积为50 mL时,210Bi、210po可同时自发沉积在铜片上.利用在同一衰变链上活度最终平衡的特点,通过测量210Bi计数计算得到水中210pb的活度,然后通过209 Po示踪α能谱法求得水中210po的活度.方法精密度优于10%,加标回收率在95.3%-107.6%,210pb、210po探测限分别达到1.2 mBq· L-1和0.15 mBq·L-1.利用该联测方法对粤北矿山地区环境水样进行了分析,结果表明,饮用水中210pb、210po活度浓度范围分别为(2.4-38.7) mBq·L-1和(1.0-4.1)mBq·L-1;河溪水中210pb、210Po活度浓度范围分别为(4.3-181.5) mBq·L-1和(0.7-23.3) mBq·L-1.%The optimum measurement conditions were investigated and it was found that 210Bi and 210Po were deposited on copper sheet simultaneously and spontaneously under the conditions of 0.5 mol·L-1 HCl at 90 ℃ for 2 hours,with ascorbic acid and hydroxylamine hydrochloride mixed system as reducing agents,in a total of 50 mL solution without extraction separation.By using 210Bi and 210po equilibrium in radioactive decay chain,the activity of 210Pb was measured based on β counting of 210Bi,and then the activity of 210Po was determined by alpha spectrometry with 209po as a yield-tracing isotope.The relative deviation of duplicate analysis was less than 10% with the recovery of standard addition between 95.3% and 107.6% for the two nuclides,and the detection limits were 1.2 mBq· L-1 and 0.15 mBq·L-1 for 210Pb and 210Po,respectively.The method was used for the measurement of 210Pb and 210Po in the environmental water samples from uranium mining area of northern Guangdong Province,China.The results showed that the activities of 210Pb and 210po in drinking

  6. Dating of a sediment core from Lake Biel (Switzerland) and source characterization of fallout Pu; {sup 210}Pb- und {sup 137}Cs-Datierung eines Sedimentbohrkerns aus dem Bieler See (CH) und Ursprungsbestimmung von Pu-Fallout

    Energy Technology Data Exchange (ETDEWEB)

    Pregler, Anja

    2016-08-01

    A sediment core from Lake Biel was dated by means of the naturally occurring radioactive isotope {sup 210}Pb as well as by the anthropogenic isotope {sup 137}Cs. The latter one can be detected as radioactive fallout of certain events in the sediment layers and accordingly be correlated with a distinct date. A verification of the correlated events is accomplished by particular isotope ratios of the anthropogenic isotopes {sup 238}Pu, {sup 239}Pu and {sup 240}Pu as well as {sup 241}Am as a decay product of the short-lived {sup 241}Pu. Furthermore, the percentage of the total {sup 137}Cs fallout was calculated corresponding to the specific events.

  7. 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.

    Science.gov (United States)

    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.

  8. Evaluation of the activity concentration of {sup 226}Ra, {sup 228}Ra and {sup 210}Pb in sediments from Antarctica in the Admiralty bay region; Avaliacao da concentracao de atividade de Ra-226, Ra-228 e Pb-210 em sedimentos provenientes da Antartica na regiao da baia do Almirantado

    Energy Technology Data Exchange (ETDEWEB)

    Mora, Tamires de Araujo

    2015-07-01

    The natural radionuclides from radioactive series of {sup 238}U, {sup 235}U and {sup 232}Th have been applied as tracers in environmental studies for understanding the dynamics that occur in both marine and terrestrial environment, as for example, in research of oceanic processes and management of the coastal region. In the marine environment, these radionuclides can be used to estimate biogeochemical fluxes of marine particles and nutrients that occur in the water column as well as in the sediment. Several research works applied the distribution and the respective disequilibrium degree of natural radionuclides in the environment, including geochronological models for obtaining historical information on samples of certain sediment profile. In this study we performed a radiochemical characterization of the distribution of {sup 226}Ra, {sup 228}Ra and {sup 210}Pb from a sedimentary column called 1B (248 cm long) collected in the Admiralty Bay, Antarctic Peninsula region. The methodology used included the acid leaching of sediment samples followed by the radiochemical sequential separation of {sup 226}Ra and {sup 228}Ra by co-precipitation with Ba(Ra)SO{sub 4} and {sup 210}Pb by co-precipitation with PbCrO{sub 4}. All measurements were carried out by counting of gross alpha and gross beta measures in a low background gas flow proportional detector. The activity concentrations of {sup 226}Ra and {sup 210}Pb were used to estimate the unsupported {sup 210}Pb activities present in sediment profile 1 B. Based on unsupported {sup 210}Pb data and the application of the CIC model (Constant Initial Concentration), it was possible to determine the sedimentation rate of 0.59 ± 0.05 cm /year. (author)

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

    Science.gov (United States)

    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).

  10. Preliminary study on excess ~(210)Pb flux characteristic of lake sediment in arid regions and its implication for aeolian activity%干旱区湖泊沉积物中过剩~(210)Pb的沉积特征与风沙活动初探

    Institute of Scientific and Technical Information of China (English)

    陈永福; 赵志中

    2009-01-01

    过剩~(210)Pb不仅是沉积物年龄测定的重要手段,而且是环境示踪的一种主要方法,干旱区湖泊主要为封闭湖泊,其沉积物所接受的过剩~(210)pb沉积在大气沉降背景外,主要受风沙侵蚀来源的影响.因此,较高的过剩~(210)Pb沉积通量有可能与区域风沙活动有关.本文在对比分析近几年来发表在各期刊中的湖泊~(210)Pb数据的基础上,计算各个湖泊多年平均过剩~(210)Pb的沉积通量并与大气过剩~(210)Pb沉降背景比较,从而初步确定中国北方干旱区风沙活动的可能区域.然后对所确定的典型风沙多发区,利用过剩~(210)Pb模式(PF-CRS)计算沉积物沉积速率,并与相应区域的"尘暴"记录对比,进而论证该方法在指示风沙活动方面的可靠程度.%Excess ~(210)Pb dating is not only an important method for sediment dating, but also a major environmental tracer. In arid regions, excess ~(210)Pb deposited in lake sediment mainly depends on wind erosion recycle besides the atmospheric precipitation flux background. Therefore, the higher excess ~(210)Pb is a potential for identifying the aeolian activities. This paper makes a systematical analysis on the data published in recent years, and calculates the multi-year average excess ~(210)Pb flux in different lakes. Thus, the areas in which multi-year average excess ~(210)Pb flux thai exceeded atmosphere flux background could be recognized preliminarily as regional aeolian deposits. And then, we use the excess ~(210)Pb model (PF-CRS) to calculate the lake sedimentation rates in some typical aeolian regions. At last, we compare the results with the dust records correspondingly so as to estimate the reliability of this method.

  11. Degradation of {gamma}-HCH spiked soil using stabilized Pd/Fe{sup 0} bimetallic nanoparticles: Pathways, kinetics and effect of reaction conditions

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Ritu [Ecotoxicology Division, CSIR-Indian Institute of Toxicology Research, Post Box 80, Mahatma Gandhi Marg, Lucknow 226 001, UP (India); Department of Environmental Science, Babasaheb Bhimrao Ambedkar University, Raebareli Road, Lucknow 226 025, UP (India); Misra, Virendra, E-mail: virendra_misra2001@yahoo.co.in [Ecotoxicology Division, CSIR-Indian Institute of Toxicology Research, Post Box 80, Mahatma Gandhi Marg, Lucknow 226 001, UP (India); Mudiam, Mohana Krishna Reddy [Analytical Chemistry Division, CSIR-Indian Institute of Toxicology Research, Post Box 80, Mahatma Gandhi Marg, Lucknow 226 001, UP (India); Chauhan, Lalit Kumar Singh [Petroleum Toxicology Division, CSIR-Indian Institute of Toxicology Research, Post Box 80, Mahatma Gandhi Marg, Lucknow 226 001, UP (India); Singh, Rana Pratap [Department of Environmental Science, Babasaheb Bhimrao Ambedkar University, Raebareli Road, Lucknow 226 025, UP (India)

    2012-10-30

    Highlights: Black-Right-Pointing-Pointer This study explores the potential of CMC-Pd/nFe{sup 0} to degrade {gamma}-HCH in spiked soil. Black-Right-Pointing-Pointer Sorption-desorption characteristics and partitioning of {gamma}-HCH is investigated. Black-Right-Pointing-Pointer Three degradation pathways has been proposed and discussed. Black-Right-Pointing-Pointer {gamma}-HCH degradation mechanism and kinetics is elucidated. Black-Right-Pointing-Pointer Activation energy reveals that {gamma}-HCH degradation is a surface mediated reaction. - Abstract: This study investigates the degradation pathway of gamma-hexachlorocyclohexane ({gamma}-HCH) in spiked soil using carboxymethyl cellulose stabilized Pd/Fe{sup 0} bimetallic nanoparticles (CMC-Pd/nFe{sup 0}). GC-MS analysis of {gamma}-HCH degradation products showed the formation of pentachlorocyclohexene, tri- and di-chlorobenzene as intermediate products while benzene was formed as the most stable end product. On the basis of identified intermediates and final products, degradation pathway of {gamma}-HCH has been proposed. Batch studies showed complete {gamma}-HCH degradation at a loading of 0.20 g/L CMC-Pd/nFe{sup 0} within 6 h of incubation. The surface area normalized rate constant (k{sub SA}) was found to be 7.6 Multiplication-Sign 10{sup -2} L min{sup -1} m{sup -2}. CMC-Pd/nFe{sup 0} displayed {approx}7-fold greater efficiency for {gamma}-HCH degradation in comparison to Fe{sup 0} nanoparticles (nFe{sup 0}), synthesized without CMC and Pd. Further studies showed that increase in CMC-Pd/nFe{sup 0} loading and reaction temperature facilitates {gamma}-HCH degradation, whereas a declining trend in degradation was noticed with the increase in pH, initial {gamma}-HCH concentration and in the presence of cations. The data on activation energy (33.7 kJ/mol) suggests that {gamma}-HCH degradation is a surface mediated reaction. The significance of the study with respect to remediation of {gamma}-HCH contaminated soil using

  12. Geochemistry of natural radionuclide in soils surrounding a mining and plant uranium concentration;Geoquimica de radionuclindeos naturais em solos de areas circunvizinhas a uma unidade de mineracao e atividade de uranio

    Energy Technology Data Exchange (ETDEWEB)

    Cardoso, Gildevan Viana, E-mail: gildevan.cardoso@vta.incra.gov.b [Instituto Nacional de Colonizacao e Reforma Agraria (INCRA), Rio de Janeiro, RJ (Brazil); Amaral Sobrinho, Nelson Moura Brasil do; Mazur, Nelson, E-mail: nelmoura@ufrrj.b, E-mail: nelmazur@ufrrj.b [Universidade Federal Rural do Rio de Janeiro (UFRRJ), Seropedica, RJ (Brazil). Inst. de Agronomia. Dept. de Solos; Wasserman, Maria Angelica Vergara, E-mail: angelica@ird.gov.b [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2009-11-15

    The environmental impacts resulting from uranium exploration and processing are to a great extent identical to those caused by extractive mining activities in general. This study aimed to determine the geochemical partitioning of the natural radionuclides {sup 238}U, {sup 226}Ra and {sup 210}Pb in areas surrounding the Uranium Mining and Concentration Plant (URA) of the Brazilian Nuclear Industries S.A., in the uranium deposit region of Lagoa Real, in Caetite, southwestern Bahia state. Representative soil samples of the main regional soil classes were collected from the layer 0-20 cm, in five areas around the URA. The level of total activity and geochemical fractionation (F1 slightly acidic, F2 reducible, F3 oxidisable, F4 alkaline, and F5 residual) were determined for the five areas. The average total radioactivity levels were, in Bq kg{sup -1} soil: 50 for {sup 238}U, 51 for {sup 226}Ra, and 159 for {sup 210}Pb. During the potentially bioavailable phase (F1) 11 % were extracted for {sup 238}U, 13 % for {sup 226}Ra and 3 % for {sup 210}Pb. The bioavailability of {sup 238}U was higher in more acidic soils and the affinity for iron oxides was greater, unlike in the case of {sup 226}Ra, with the greatest bioavailability. {sup 210}Pb was predominantly associated with F5. The high percentage of {sup 238}U, {sup 226}Ra and {sup 210}Pb in the geochemical fraction F5 indicates that the concentrations observed in the five soils are predominantly associated to the parent material of these soils, rather than to an artificial contamination caused by the URA activity. (author)

  13. The Effects of Arbuscular-Mycorrhizal Fungi and Phosphorous on Arsenic Uptake by Sunflower Plant in Soils Spiked with Arsenite and Arsenate

    Directory of Open Access Journals (Sweden)

    Saeed Bagherifam

    2017-01-01

    Methods:The soil sample (Typic Haplorthids was collected, air dried and passed through 2 mm sieve and then were heated in 80 centigrade degree temperature for two times. A pot experiment was conducted in a completely randomized design with factorial arrangement and three replications in greenhouse condition. The experimental factors included two species spices of inorganic As (50 mg kg-1 of Arsenite and Arsenate, two levels of phosphorus (0 and 60 mg Kg-1 and three spices of arbuscular mycorrhizae (control, Glomus intraradices and Glomus mosseae. Soil samples spiked with Na2HAsO4.7H2O, NaAsO2 (Arsenite and Arsenate and Ca (H2PO42 (phosphorus and incubated in greenhouse condition for 4 week. Sunflower seeds were planted and seedlings harvested after 60 day of sowing and then dry weight of sunflower, concentration of As and phosphorus in shoot and root of plant and root colonization percentage determined using standard methods. Results and Discussion:The results revealed that Glomus intraradices (GI and Glomus mosseae (GM symbiosis significantly (P

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

    Science.gov (United States)

    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.

  15. 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

    Science.gov (United States)

    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.

  16. Geoquímica de radionuclídeos naturais em solos de áreas circunvizinhas a uma Unidade de Mineração e Atividade de Urânio Geochemistry of natural radionuclide in soils surrounding a Mining and Plant Uranium Concentration

    Directory of Open Access Journals (Sweden)

    Gildevan Viana Cardoso

    2009-12-01

    of the Brazilian Nuclear Industries S.A., in the uranium deposit region of Lagoa Real, in Caetité, southwestern Bahia state. Representative soil samples of the main regional soil classes were collected from the layer 0-20 cm, in five areas around the URA. The level of total activity and geochemical fractionation (F1slightly acidic, F2 reducible, F3 oxidisable, F4 alkaline, and F5 residual were determined for the five areas. The average total radioactivity levels were, in Bq kg-1 soil: 50 for 238U, 51 for 226Ra, and 159 for 210Pb. During the potentially bioavailable phase (F1 11 % were extracted for 238U, 13 % for 226Ra and 3 % for 210Pb. The bioavailability of 238U was higher in more acidic soils and the affinity for iron oxides was greater, unlike in the case of 226Ra, with the greatest bioavailability. 210Pb was predominantly associated with F5. The high percentage of 238U, 226Ra and 210Pb in the geochemical fraction F5 indicates that the concentrations observed in the five soils are predominantly associated to the parent material of these soils, rather than to an artificial contamination caused by the URA activity.

  17. 东北四海龙湾玛珥湖沉积物纹层计年与137Cs、210Pb测年%VARVECHRONOLOGY AND RADIOMETRIC DATING (137Cs,210Pb)FROM THE SIHAILONGWAN MAAR,NORTHEASTERN CHINA

    Institute of Scientific and Technical Information of China (English)

    储国强; 顾兆炎; 许冰; 刘强; 孙青; 汉景泰; 刘嘉麒

    2005-01-01

    对东北四海龙湾玛珥湖SHL-F6孔纹层沉积物的137Cs放射性测量表明:137Cs比活度的最大值出现在5.5cm处,对应于1963年世界原子弹试爆高峰期.纹层计年表明0~6cm共有35个纹层层偶.从7.5cm到6.5cm,137Cs比活度从2.56±0.09dpm/g急剧增加到18.68±0.17dpm/g,可能6.5cm对应于1954年.通过测量226Ra子核214Pb和214Bi(能量为295keV,352keV和609keV)放射的光子数获得226Ra比活度数据,然后求得过剩210Pb比活度(210Pbuns). 210Pbuns比活度随深度增加而呈指数衰减,其异常波动可能与人类活动以及沉积速率变化有关,例如5.5cm处210Pb比活度较高,与137Cs的峰值对应,这可能与1963年前后人工核实验的高峰有关,因为核试验不仅产生137Cs,而且可以产生208Pb和210Pb; 4.5cm处210Pb比活度较低,而226Ra较高,可能与人类活动加剧,导致沉积速率增加有关.根据210PbunsCRS模式, SHL-F6孔0~19cm的平均沉积速率为20mg/cm2 · a,或约为0.11cm/a.210Pb测年数据与137Cs时标及纹层计年均有很好的一致性.四海龙湾玛珥湖发育的纹层为年纹层,可以建立高分辨率时间序列.

  18. Monitoring spike train synchrony

    CERN Document Server

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

    2012-01-01

    Recently, the SPIKE-distance has been proposed as a parameter-free and time-scale 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 event-like firing patterns. Here we present a substantial improvement of this measure which 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 ...

  19. Monitoring spike train synchrony.

    Science.gov (United States)

    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.

  20. Effect of spiking strategy and ratio on calibration of on-line visible and near infrared soil sensor for measurement in European farms

    OpenAIRE

    Kuang, Boyan Y.; Mouazen, Abdul Mounem

    2013-01-01

    A previously developed on-line visible and near infrared (vis-NIR) spectroscopy-based soil measurement system was implemented for the measurement of soil organic carbon (OC), total nitrogen (TN) and moisture content (MC) in three fields at three European farms. The on-line sensor platform was coupled with a mobile, fibre type, vis-NIR spectrophotometer (AgroSpec from tec5 Technology for Spectroscopy, Germany), with a measurement range of 305-2200 nm, to acquire soil spectra in diffuse reflect...

  1. Dynamical laser spike processing

    CERN Document Server

    Shastri, Bhavin J; Tait, Alexander N; Rodriguez, Alejandro W; Wu, Ben; Prucnal, Paul R

    2015-01-01

    Novel materials and devices in photonics have the potential to revolutionize optical information processing, beyond conventional binary-logic approaches. Laser systems offer a rich repertoire of useful dynamical behaviors, including the excitable dynamics also found in the time-resolved "spiking" of neurons. Spiking reconciles the expressiveness and efficiency of analog processing with the robustness and scalability of digital processing. We demonstrate that graphene-coupled laser systems offer a unified low-level spike optical processing paradigm that goes well beyond previously studied laser dynamics. We show that this platform can simultaneously exhibit logic-level restoration, cascadability and input-output isolation---fundamental challenges in optical information processing. We also implement low-level spike-processing tasks that are critical for higher level processing: temporal pattern detection and stable recurrent memory. We study these properties in the context of a fiber laser system, but the addit...

  2. Solar Decameter Spikes

    Science.gov (United States)

    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.

  3. Radon migration in the soils of the Irno Valley (Southern Italy inferred from radioactive disequilibrium

    Directory of Open Access Journals (Sweden)

    P. Gasparini

    1995-06-01

    Full Text Available Radon migration along vertical profiles in the soils of Irno River alluvial Valley (Southern Italy was studied using radioactive disequilibrium between 226 Ra and 210 Pb. Fractional Radon loss, migration length, diffusion and emanation coefficient and Radon flux density were determined. Our results are in agreement with a migra- tion model by simple diffusion. The migration parameters are within typical values, except the Radon flux density, which is about one order of magnitude higher than the values reported in literature. The values of fractional Radon loss are sensitive to changes in the physical properties of the soil.

  4. Activity and population dynamics of heterotrophic and ammonia-oxidizing microorganisms in soil surrounding sludge bands spiked with linear alkylbenzene sulfonate

    DEFF Research Database (Denmark)

    Brandt, K. K.; Sørensen, J.; Krogh, P. H.

    2003-01-01

    bioluminescence toxicity assay, however, LAS or other sludge components never accumulated to toxic levels in the soil compartments and the LAS tolerance of the indigenous microbes further remained unchanged following LAS exposure. LAS effects on the investigated microbial populations largely occurred during...

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

    Science.gov (United States)

    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.

  6. 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,

    Science.gov (United States)

    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

  7. Response Features Determining Spike Times

    Directory of Open Access Journals (Sweden)

    Barry J. Richmond

    1999-01-01

    redundant with that carried by the coarse structure. Thus, the existence of precisely timed spike patterns carrying stimulus-related information does not imply control of spike timing at precise time scales.

  8. Radioactivity measurements in soils surrounding four coal-fired power plants in Serbia by gamma-ray spectrometry and estimated dose

    Directory of Open Access Journals (Sweden)

    Vukašinović Ivana Ž.

    2014-01-01

    Full Text Available The study of spatial distribution of activity concentration of 238U, 226Ra, 210Pb, 232Th, 40K, and 137Cs radionuclides in the surface soil samples (n = 42 collected in the vicinity of four coal-fired power plants in Serbia is presented. Radioactivity measurements in soils performed by gamma-ray spectrometry showed values [Bqkg-1] in the range: 15-117 for 238U, 21-115 for 226Ra, 33-65 for 210Pb, 20-69 for 232Th, 324-736 for 40K, and 2-59 for 137Cs. Surface soil radio-activity that could have resulted from deposition of radionuclides from airborne discharges or resuspension of ash from disposal sites showed no enhanced levels. It was found that variation of soil textural properties, pH values, and carbonate content influenced activity levels of natural radionuclides while radiocesium activities were associated with soil organic matter content. Modification of some soil properties was observed in the immediate vicinity (<1 km of power plants where the soil was more alkaline with coarser particles (0.2-0.05 mm and carbonates accumulated. Calculated average values of the absorbed gamma dose rate and annual external effective dose originating from the terrestrial radionuclides were 69.4 nGy/h and 0.085 mSv, respectively. [Projekat Ministarstva nauke Republike Srbije, br. 4007: Studying climate change and its influence on the environment: impacts, adaptation and mitigation

  9. Radioxenon spiked air.

    Science.gov (United States)

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

    2015-12-01

    Four of the radioactive xenon isotopes ((131m)Xe, (133m)Xe, (133)Xe and (135)Xe) 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 paper 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.

  10. Preliminary study of radium-contaminated soils

    Energy Technology Data Exchange (ETDEWEB)

    Healy, J.W.; Rodgers, J.C.

    1978-10-01

    A preliminary study was made of the potential radiation exposures to people from radium-226 contamination in the soil in order to provide guidance on limits to be applied in decontaminating land. Pathways included were inhalation of radium from resuspension; ingestion of radium with foods; external gamma radiation from radium daughters; inhalation of radon and daughter, both in the open air and in houses; and the intake of /sup 210/Pb and /sup 210/Po from both inhalation and ingestion. The depth of the contaminated layer is of importance for external exposure and especially for radon emanation. The most limiting pathway was found to be emanation of the radon into buildings with limiting values comparable to those found naturally in many areas.

  11. Coronavirus spike-receptor interactions

    NARCIS (Netherlands)

    Mou, H.

    2015-01-01

    Coronaviruses cause important diseases in humans and animals. Coronavirus infection starts with the virus binding with its spike proteins to molecules present on the surface of host cells that act as receptors. This spike-receptor interaction is highly specific and determines the virus’ cell, tissue

  12. Mapping spikes to sensations

    Directory of Open Access Journals (Sweden)

    Maik Christopher Stüttgen

    2011-11-01

    Full Text Available 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 neural candidate 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.

  13. Soils

    Science.gov (United States)

    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...

  14. Rayleigh--Taylor spike evaporation

    Energy Technology Data Exchange (ETDEWEB)

    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.

  15. Wavelet analysis of epileptic spikes

    CERN Document Server

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

    2003-01-01

    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.

  16. Wavelet analysis of epileptic spikes

    Science.gov (United States)

    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.

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

    OpenAIRE

    2014-01-01

    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 th...

  18. Wavelet transform of neural spike trains

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  20. Computing with Spiking Neuron Networks

    NARCIS (Netherlands)

    Paugam-Moisy, H.; Bohte, S.M.; Rozenberg, G.; Baeck, T.H.W.; Kok, J.N.

    2012-01-01

    Abstract Spiking Neuron Networks (SNNs) are often referred to as the 3rd gener- ation of neural networks. Highly inspired from natural computing in the brain and recent advances in neurosciences, they derive their strength and interest from an ac- curate modeling of synaptic interactions between neu

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

    Science.gov (United States)

    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.

  2. Automatic spike sorting using tuning information.

    Science.gov (United States)

    Ventura, Valérie

    2009-09-01

    Current spike sorting methods focus on clustering neurons' characteristic spike waveforms. The resulting spike-sorted data are typically used to estimate how covariates of interest modulate the firing rates of neurons. However, when these covariates do modulate the firing rates, they provide information about spikes' identities, which thus far have been ignored for the purpose of spike sorting. This letter describes a novel approach to spike sorting, which incorporates both waveform information and tuning information obtained from the modulation of firing rates. Because it efficiently uses all the available information, this spike sorter yields lower spike misclassification rates than traditional automatic spike sorters. This theoretical result is verified empirically on several examples. The proposed method does not require additional assumptions; only its implementation is different. It essentially consists of performing spike sorting and tuning estimation simultaneously rather than sequentially, as is currently done. We used an expectation-maximization maximum likelihood algorithm to implement the new spike sorter. We present the general form of this algorithm and provide a detailed implementable version under the assumptions that neurons are independent and spike according to Poisson processes. Finally, we uncover a systematic flaw of spike sorting based on waveform information only.

  3. A simple algorithm for averaging spike trains.

    Science.gov (United States)

    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.

  4. Epileptiform spike detection via convolutional neural networks

    DEFF Research Database (Denmark)

    Johansen, Alexander Rosenberg; Jin, Jing; Maszczyk, Tomasz

    2016-01-01

    The EEG of epileptic patients often contains sharp waveforms called "spikes", occurring between seizures. Detecting such spikes is crucial for diagnosing epilepsy. In this paper, we develop a convolutional neural network (CNN) for detecting spikes in EEG of epileptic patients in an automated fash...

  5. Automatic spikes detection in seismogram

    Institute of Scientific and Technical Information of China (English)

    王海军; 靳平; 刘贵忠

    2003-01-01

    @@ Data processing for seismic network is very complex and fussy, because a lot of data is recorded in seismic network every day, which make it impossible to process these data all by manual work. Therefore, seismic data should be processed automatically to produce a initial results about events detection and location. Afterwards, these results are reviewed and modified by analyst. In automatic processing data quality checking is important. There are three main problem data thatexist in real seismic records, which include: spike, repeated data and dropouts. Spike is defined as isolated large amplitude point; the other two problem datahave the same features that amplitude of sample points are uniform in a interval. In data quality checking, the first step is to detect and statistic problem data in a data segment, if percent of problem data exceed a threshold, then the whole data segment is masked and not be processed in the later process.

  6. Prospective Coding by Spiking Neurons.

    Directory of Open Access Journals (Sweden)

    Johanni Brea

    2016-06-01

    Full Text Available 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.

  7. Measuring multiple spike train synchrony.

    Science.gov (United States)

    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.

  8. Reliability of Spike Timing in Neocortical Neurons

    Science.gov (United States)

    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.

  9. Multiscale analysis of neural spike trains.

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  11. Elevated CO2 increases Cs uptake and alters microbial communities and biomass in the rhizosphere of Phytolacca americana Linn (pokeweed) and Amaranthus cruentus L. (purple amaranth) grown on soils spiked with various levels of Cs.

    Science.gov (United States)

    Song, Ningning; Zhang, Ximei; Wang, Fangli; Zhang, Changbo; Tang, Shirong

    2012-10-01

    General concern about increasing global atmospheric CO(2) levels owing to the ongoing fossil fuel combustion and elevated levels of radionuclides in the environment, has led to growing interest in the responses of plants to interactive effects of elevated CO(2) and radionuclides in terms of phytoremediation and food safety. To assess the combined effects of elevated CO(2) and cesium contamination on plant biomass, microbial activities in the rhizosphere soil and Cs uptake, Phytolacca americana Linn (pokeweed, C3 specie) and Amaranthus cruentus L. (purple amaranth, C4 specie) were grown in pots of soils containing five levels of cesium (0, 100, 300, 500 and 1000 mg Cs kg(-1)) under two levels of CO(2) (360 and 860 μL L(-1), respectively). Shoot and root biomass of P. americana and Amaranthus crentus was generally higher under elevated CO(2) than under ambient CO(2) for all treatments. Both plant species exhibited higher Cs concentration in the shoots and roots under elevated CO(2) than ambient CO(2). For P. americana grown at 0, 100, 300, 500 and 1000 mg Cs kg(-1), the increase magnitude of Cs concentration due to elevated CO(2) was 140, 18, 11, 34 and 15% in the shoots, and 150, 20, 14, 15 and 19% in the roots, respectively. For A. cruentus, the corresponding value was 118, 28, 21, 14 and 17% in the shoots, and 126, 6, 11, 17 and 22% in the roots, respectively. Higher bioaccumulation factors were noted for both species grown under elevated CO(2) than ambient CO(2). The populations of bacteria, actinomycetes and fungi, and the microbial C and N in the rhizosphere soils of both species were higher at elevated CO(2) than at ambient CO(2) with the same concentration of Cs. The results suggested that elevated CO(2) significantly affected plant biomass, Cs uptake, soil C and N concentrations, and community composition of soil microbes associated with P. americana and A. cruentus roots. The knowledge gained from this investigation constitutes an important advancement in

  12. Effects of phase on homeostatic spike rates.

    Science.gov (United States)

    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.

  13. Rate-adjusted spike-LFP coherence comparisons from spike-train statistics.

    Science.gov (United States)

    Aoi, Mikio C; Lepage, Kyle Q; Kramer, Mark A; Eden, Uri T

    2015-01-30

    Coherence is a fundamental tool in the analysis of neuronal data and for studying multiscale interactions of single and multiunit spikes with local field potentials. However, when the coherence is used to estimate rhythmic synchrony between spiking and any other time series, the magnitude of the coherence is dependent upon the spike rate. This property is not a statistical bias, but a feature of the coherence function. This dependence confounds cross-condition comparisons of spike-field and spike-spike coherence in electrophysiological experiments. Taking inspiration from correction methods that adjust the spike rate of a recording with bootstrapping ('thinning'), we propose a method of estimating a correction factor for the spike-field and spike-spike coherence that adjusts the coherence to account for this rate dependence. We demonstrate that the proposed rate adjustment is accurate under standard assumptions and derive distributional properties of the estimator. The reduced estimation variance serves to provide a more powerful test of cross-condition differences in spike-LFP coherence than the thinning method and does not require repeated Monte Carlo trials. We also demonstrate some of the negative consequences of failing to account for rate dependence. The proposed spike-field coherence estimator accurately adjusts the spike-field coherence with respect to rate and has well-defined distributional properties that endow the estimator with lower estimation variance than the existing adjustment method.

  14. Multineuronal Spike Sequences Repeat with Millisecond Precision

    Directory of Open Access Journals (Sweden)

    Koki eMatsumoto

    2013-06-01

    Full Text Available Cortical microcircuits are nonrandomly wired by neurons. As a natural consequence, spikes emitted by microcircuits are also nonrandomly patterned in time and space. One of the prominent spike organizations is a repetition of fixed patterns of spike series across multiple neurons. However, several questions remain unsolved, including how precisely spike sequences repeat, how the sequences are spatially organized, how many neurons participate in sequences, and how different sequences are functionally linked. To address these questions, we monitored spontaneous spikes of hippocampal CA3 neurons ex vivo using a high-speed functional multineuron calcium imaging technique that allowed us to monitor spikes with millisecond resolution and to record the location of spiking and nonspiking neurons. Multineuronal spike sequences were overrepresented in spontaneous activity compared to the statistical chance level. Approximately 75% of neurons participated in at least one sequence during our observation period. The participants were sparsely dispersed and did not show specific spatial organization. The number of sequences relative to the chance level decreased when larger time frames were used to detect sequences. Thus, sequences were precise at the millisecond level. Sequences often shared common spikes with other sequences; parts of sequences were subsequently relayed by following sequences, generating complex chains of multiple sequences.

  15. Supervised Learning in Multilayer Spiking Neural Networks

    CERN Document Server

    Sporea, Ioana

    2012-01-01

    The current article introduces a supervised learning algorithm for multilayer spiking neural networks. The algorithm presented here overcomes some limitations of existing learning algorithms as it can be applied to neurons firing multiple spikes and it can in principle be applied to any linearisable neuron model. The algorithm is applied successfully to various benchmarks, such as the XOR problem and the Iris data set, as well as complex classifications problems. The simulations also show the flexibility of this supervised learning algorithm which permits different encodings of the spike timing patterns, including precise spike trains encoding.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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).

  18. Rate-adjusted spike-LFP coherence comparisons from spike-train statistics

    OpenAIRE

    2014-01-01

    Coherence is a fundamental tool in the analysis of neuronal data and for studying multiscale interactions of single and multiunit spikes with local field potentials. However, when the coherence is used to estimate rhythmic synchrony between spiking and any other time series, the magnitude of the coherence is dependent upon the spike rate. This property is not a statistical bias, but a feature of the coherence function. This dependence confounds cross-condition comparisons of spike-field and s...

  19. Spiking neuron network Helmholtz machine.

    Science.gov (United States)

    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.

  20. Natural radioactivity measurements in agricultural soil, fertilizer and crops in some specific areas of Kingdom of Saudi Arabia

    Energy Technology Data Exchange (ETDEWEB)

    Latif, Shaikh Abdul; Kinsara, Abdulraheem Abdulrahman; Molla, Nurul Islam; Nassef, Mohamed Hamed [King Abdulaziz Univ., Jeddah (Saudi Arabia). Faculty of Engineering

    2014-09-01

    High Purity Germanium (HPGe) detector gamma-ray spectrometry with 500 cc Marinelli beaker geometry was used for radioactivity measurement in some specific areas of Kingdom of Saudi Arabia (KSA). The detection limits of {sup 210}Pb, {sup 238}U, {sup 226}Ra, {sup 232}Th and {sup 40}K in soil, fertilizers, and vegetables lie mostly below 1 Bq/kg. The activity concentrations of {sup 238}U and {sup 226}Ra in local phosphate fertilizers were measured in the range of 236.8-879.0 Bq/kg and 101.5-297.0 Bq/kg, respectively. The respective activity concentrations of {sup 238}U and {sup 226}Ra measured in one charge of German phosphate fertilizer are in the range of 552.7-790.0 Bq/kg and 280.6-317.0 Bq/kg. The activity concentrations of {sup 232}Th are assessed to have maximum values up to 2.24 Bq/kg in locally manufactured phosphate fertilizers. Local urea exhibited concentration level (Bq/kg) of {sup 210}Pb, {sup 238}U, {sup 226}Ra, {sup 232}Th and {sup 40}K below the detection limit. Mean values of activity concentrations of {sup 238}U in agricultural soil of Wadi Fatima, Taif, Hada Al-Sham, Madina City and Abyar Al-MashiMadina are 21.7 ± 3.24, 38.2 ± 4.1, 17.6 ± 2.1, 34.3 ± 3.5 and 32.7 ± 2.4 Bq/kg, respectively. The respective mean of {sup 226}Ra activity concentrations in those areas are 12.16 ± 1.16, 20.2 ± 1.33, 11.21 ± 0.4, 21.4 ± 1.7 and 21.0 ± 1.22 Bq/kg. The specific activity of {sup 232}Th in the respective areas has been measured as 12.6 ± 1.3, 25.3 ± 0.8, 11.5 ± 0.9, 20.4 ± 2.4 and 20.0 ± 1.2 Bq/kg. Activity concentrations of {sup 210}Pb, {sup 238}U, {sup 226}Ra and {sup 232}Th in the vegetable samples are mostly found in the range of 0.37 Bq/kg to 37.8 Bq/kg. The {sup 40}K specific activity lies in the range of 44.4-196 Bq/kg. The calculated absorbed dose rates in the representative locations are 24.07-53.28 nGy/h. (orig.)

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

    Science.gov (United States)

    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.

  2. Statistical properties of superimposed stationary spike trains.

    Science.gov (United States)

    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.

  3. Linking investment spikes and productivity growth

    NARCIS (Netherlands)

    Geylani, P.C.; Stefanou, S.E.

    2013-01-01

    We investigate the relationship between productivity growth and investment spikes using Census Bureau’s plant-level dataset for the U.S. food manufacturing industry. There are differences in productivity growth and investment spike patterns across different sub-industries and food manufacturing indu

  4. Motor control by precisely timed spike patterns

    DEFF Research Database (Denmark)

    Srivastava, Kyle H; Holmes, Caroline M; Vellema, Michiel

    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...

  5. What causes a neuron to spike?

    CERN Document Server

    Arcas, B A; Arcas, Blaise Aguera y; Fairhall, Adrienne

    2003-01-01

    The computation performed by a neuron can be formulated as a combination of dimensional reduction in stimulus space and the nonlinearity inherent in a spiking output. White noise stimulus and reverse correlation (the spike-triggered average and spike-triggered covariance) are often used in experimental neuroscience to `ask' neurons which dimensions in stimulus space they are sensitive to, and to characterize the nonlinearity of the response. In this paper, we apply reverse correlation to the simplest model neuron with temporal dynamics--the leaky integrate-and-fire model--and find that even for this simple case standard techniques do not recover the known neural computation. To overcome this, we develop novel reverse correlation techniques by selectively analyzing only `isolated' spikes, and taking explicit account of the extended silences that precede these isolated spikes. We discuss the implications of our methods to the characterization of neural adaptation. Although these methods are developed in the con...

  6. Stochastic Variational Learning in Recurrent Spiking Networks

    Directory of Open Access Journals (Sweden)

    Danilo eJimenez Rezende

    2014-04-01

    Full Text Available The ability to learn and perform statistical inference with biologically plausible recurrent network of spiking neurons is an important step towards 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 bothstationary 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.

  7. Stochastic variational learning in recurrent spiking networks.

    Science.gov (United States)

    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.

  8. Spiking neural P systems with multiple channels.

    Science.gov (United States)

    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.

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

    CERN Document Server

    Mulansky, Mario

    2016-01-01

    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 bi- and multivariate dissimilarity profiles, averaged values and bivariate 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.

  10. Spike generation estimated from stationary spike trains in a variety of neurons in vivo.

    Science.gov (United States)

    Spanne, Anton; Geborek, Pontus; Bengtsson, Fredrik; Jörntell, Henrik

    2014-01-01

    To any model of brain function, the variability of neuronal spike firing is a problem that needs to be taken into account. Whereas the synaptic integration can be described in terms of the original Hodgkin-Huxley (H-H) formulations of conductance-based electrical signaling, the transformation of the resulting membrane potential into patterns of spike output is subjected to stochasticity that may not be captured with standard single neuron H-H models. The dynamics of the spike output is dependent on the normal background synaptic noise present in vivo, but the neuronal spike firing variability in vivo is not well studied. In the present study, we made long-term whole cell patch clamp recordings of stationary spike firing states across a range of membrane potentials from a variety of subcortical neurons in the non-anesthetized, decerebrated state in vivo. Based on the data, we formulated a simple, phenomenological model of the properties of the spike generation in each neuron that accurately captured the stationary spike firing statistics across all membrane potentials. The model consists of a parametric relationship between the mean and standard deviation of the inter-spike intervals, where the parameter is linearly related to the injected current over the membrane. This enabled it to generate accurate approximations of spike firing also under inhomogeneous conditions with input that varies over time. The parameters describing the spike firing statistics for different neuron types overlapped extensively, suggesting that the spike generation had similar properties across neurons.

  11. Spiking neural P systems with anti-spikes and without annihilating priority as number acceptors

    Institute of Scientific and Technical Information of China (English)

    Gangjun Tan,Tao Song,; Zhihua Chen

    2014-01-01

    Spiking neural P systems with anti-spikes (ASN P sys-tems) are variant forms of spiking neural P systems, which are inspired by inhibitory impulses/spikes or inhibitory synapses. The typical feature of ASN P systems is when a neuron contains both spikes and anti-spikes, spikes and anti-spikes wil immediately an-nihilate each other in a maximal way. In this paper, a restricted variant of ASN P systems, cal ed ASN P systems without anni-hilating priority, is considered, where the annihilating rule is used as the standard rule, i.e., it is not obligatory to use in the neuron associated with both spikes and anti-spikes. If the annihilating rule is used in a neuron, the annihilation wil consume one time unit. As a result, such systems using two categories of spiking rules (iden-tified by (a, a) and (a, ¯a)) can achieve Turing completeness as number accepting devices.

  12. Spike generation estimated from stationary spike trains in a variety of neurons in vivo

    Directory of Open Access Journals (Sweden)

    Anton eSpanne

    2014-07-01

    Full Text Available To any model of brain function, the variability of neuronal spike firing is a problem that needs to be taken into account. Whereas the synaptic integration can be described in terms of the original Hodgkin-Huxley (H-H formulations of conductance-based electrical signaling, the transformation of the resulting membrane potential into patterns of spike output is subjected to stochasticity that may not be captured with standard single neuron H-H models. The dynamics of the spike output is dependent on the normal background synaptic noise present in vivo, but the neuronal spike firing variability in vivo is not well studied. In the present study, we made long-term whole cell patch clamp recordings of stationary spike firing states across a range of membrane potentials from a variety of subcortical neurons in the non-anesthetized, decerebrated state in vivo. Based on the data, we formulated a simple, phenomenological model of the properties of the spike generation in each neuron that accurately captured the stationary spike firing statistics across all membrane potentials. The model consists of a parametric relationship between the mean and standard deviation of the inter-spike intervals, where the parameter is linearly related to the injected current over the membrane. This enabled it to generate accurate approximations of spike firing also under inhomogeneous conditions with input that varies over time. The parameters describing the spike firing statistics for different neuron types overlapped extensively, suggesting that the spike generation had similar properties across neurons.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

  15. Memristors Empower Spiking Neurons With Stochasticity

    KAUST Repository

    Al-Shedivat, Maruan

    2015-06-01

    Recent theoretical studies have shown that probabilistic spiking can be interpreted as learning and inference in cortical microcircuits. This interpretation creates new opportunities for building neuromorphic systems driven by probabilistic learning algorithms. However, such systems must have two crucial features: 1) the neurons should follow a specific behavioral model, and 2) stochastic spiking should be implemented efficiently for it to be scalable. This paper proposes a memristor-based stochastically spiking neuron that fulfills these requirements. First, the analytical model of the memristor is enhanced so it can capture the behavioral stochasticity consistent with experimentally observed phenomena. The switching behavior of the memristor model is demonstrated to be akin to the firing of the stochastic spike response neuron model, the primary building block for probabilistic algorithms in spiking neural networks. Furthermore, the paper proposes a neural soma circuit that utilizes the intrinsic nondeterminism of memristive switching for efficient spike generation. The simulations and analysis of the behavior of a single stochastic neuron and a winner-take-all network built of such neurons and trained on handwritten digits confirm that the circuit can be used for building probabilistic sampling and pattern adaptation machinery in spiking networks. The findings constitute an important step towards scalable and efficient probabilistic neuromorphic platforms. © 2011 IEEE.

  16. Fitting Neuron Models to Spike Trains

    Science.gov (United States)

    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

  17. Frequency of Rolandic Spikes in ADHD

    Directory of Open Access Journals (Sweden)

    J Gordon Millichap

    2003-10-01

    Full Text Available The frequency of rolandic spikes in nonepileptic children with attention deficit hyperactivity disorder (ADHD was compared with a control group of normal school-aged children in a study at the University of Frankfurt, Germany.

  18. Supervised Learning of Logical Operations in Layered Spiking Neural Networks with Spike Train Encoding

    CERN Document Server

    Grüning, André

    2011-01-01

    Few algorithms for supervised training of spiking neural networks exist that can deal with patterns of multiple spikes, and their computational properties are largely unexplored. We demonstrate in a set of simulations that the ReSuMe learning algorithm can be successfully applied to layered neural networks. Input and output patterns are encoded as spike trains of multiple precisely timed spikes, and the network learns to transform the input trains into target output trains. This is done by combining the ReSuMe learning algorithm with multiplicative scaling of the connections of downstream neurons. We show in particular that layered networks with one hidden layer can learn the basic logical operations, including Exclusive-Or, while networks without hidden layer cannot, mirroring an analogous result for layered networks of rate neurons. While supervised learning in spiking neural networks is not yet fit for technical purposes, exploring computational properties of spiking neural networks advances our understand...

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

    CERN Document Server

    Urdapilleta, Eugenio

    2016-01-01

    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.

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

    Science.gov (United States)

    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.

  1. Training Deep Spiking Neural Networks Using Backpropagation.

    Science.gov (United States)

    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.

  2. Training Deep Spiking Neural Networks using Backpropagation

    Directory of Open Access Journals (Sweden)

    Jun Haeng Lee

    2016-11-01

    Full Text Available 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  4. Spike Detection Based on Normalized Correlation with Automatic Template Generation

    Directory of Open Access Journals (Sweden)

    Wen-Jyi Hwang

    2014-06-01

    Full Text Available A novel feedback-based spike detection algorithm for noisy spike trains is presented in this paper. It uses the information extracted from the results of spike classification for the enhancement of spike detection. The algorithm performs template matching for spike detection by a normalized correlator. The detected spikes are then sorted by the OSortalgorithm. The mean of spikes of each cluster produced by the OSort algorithm is used as the template of the normalized correlator for subsequent detection. The automatic generation and updating of templates enhance the robustness of the spike detection to input trains with various spike waveforms and noise levels. Experimental results show that the proposed algorithm operating in conjunction with OSort is an efficient design for attaining high detection and classification accuracy for spike sorting.

  5. Spiking Neurons for Analysis of Patterns

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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

  7. Nonsmooth dynamics in spiking neuron models

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

  9. Wavelet analysis of solar decimeter spikes

    Science.gov (United States)

    Fernandes, F. C. R.; Bolzan, M. J. A.; Rosa, R. R.; Prestes, A.; Cecatto, J. R.; Sawant, H. S.

    2012-04-01

    The Brazilian Solar Spectroscope (BSS), in operation at INPE, Brazil, have recorded a group of radio spikes observed on June 24, 1999 (16:53 - 16: 56 UT), in the decimeter frequency range of 1000-2500 MHz, with high temporal resolution of 100 ms and spectral resolution of 10 MHz. This event presents distinct clusters of spikes with intermittent behavior. The spectral and temporal behaviors of the observed groups of spikes of radio were investigated, applying wavelet techniques, which permits to determine the cadence of the clusters. From the dynamic spectra, the following observational parameters were determined: the total duration of the event and of each cluster, the total frequency band and cluster bands, in the case of the harmonic structures. The wavelet analysis shows an average periodicity of about 17 seconds (and harmonics) for the cadence of intermittent clusters of spikes. The analysis also suggested a semi-harmonic frequency ratio of 1:1.2. The same methodology of analysis is being applied to other selected groups of spikes recorded by BSS. These results will be presented and discussed.

  10. Spike Code Flow in Cultured Neuronal Networks.

    Science.gov (United States)

    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.

  11. Elemental and mineralogical changes in soils due to bioturbation along an earthworm invasion chronosequence in Northern Minnesota

    Energy Technology Data Exchange (ETDEWEB)

    Resner, Kathryn [Dept. of Soil, Water, and Climate, University of Minnesota, 439 Borlaug Hall, 1991 Upper Buford Circle, St. Paul, MN, 55108-6028 (United States); Yoo, Kyungsoo, E-mail: kyoo@umn.edu [Dept. of Soil, Water, and Climate, University of Minnesota, 439 Borlaug Hall, 1991 Upper Buford Circle, St. Paul, MN, 55108-6028 (United States); Hale, Cindy [University of Minnesota Duluth, The Natural Resources Research Institute, 5013 Miller Trunk Hwy. Duluth, MN 55811 (United States); Aufdenkampe, Anthony [Assistant Research Scientist - Isotope and Organic Geochemistry, Stroud Water Research Center, 970 Spencer Road, Avondale, PA 19311 (United States); Blum, Alex [US Geological Survey, 3215 Marine St., Boulder, CO 80303 (United States); Sebestyen, Stephen [Research Hydrologist, USDA Forest Service, Northern Research Station, Grand Rapids, MN 55744-3399 (United States)

    2011-06-15

    Minnesota forested soils have evolved without the presence of earthworms since the last glacial retreat. When exotic earthworms arrive, enhanced soil bioturbation often results in dramatic morphological and chemical changes in soils with negative implications for the forests' sustainability. However, the impacts of earthworm invasion on geochemical processes in soils are not well understood. This study attempts to quantify the role of earthworm invasion in mineral chemical weathering and nutrient dynamics along an earthworm invasion chronosequence in a sugar maple forest in Northern Minnesota. Depth and rates of soil mixing can be tracked with atmospherically derived short lived radioisotopes {sup 210}Pb and {sup 137}Cs. Their radioactivities increase in the lower A horizon at the expense of the peak activities near the soil surface, which indicate that soil mixing rate and its depth reach have been enhanced by earthworms. Enhanced soil mixing by earthworms is consistent with the ways that the vertical profiles of elemental and mineralogical compositions were affected by earthworm invasion. Biologically cycled Ca and P have peak concentrations near the soil surface prior to earthworm invasion. However, these peak abundances significantly declined in the earthworm invaded soils presumably due to enhanced soil mixing. It is clear that enhanced soil mixing due to earthworms also profoundly altered the vertical distribution of most mineral species within A horizons. Though the mechanisms are not clear yet, earthworm invasion appears to have contributed to net losses of clay mineral species and opal from the A horizons. As much as earthworms vertically relocated minerals and elements, they also intensify the contacts between organic matter and cations as shown in the increased amount of Ca and Fe in organically complexed and in exchangeable pools. With future studies on soil mixing rates and elemental leaching, this study will quantitatively and mechanically

  12. Spiking models for level-invariant encoding

    Directory of Open Access Journals (Sweden)

    Romain eBrette

    2012-01-01

    Full Text Available Levels of ecological sounds vary over several orders of magnitude,but the firing rate and membrane potential of a neuron are much more limited in range.In binaural neurons of the barn owl, tuning to interaural delays is independent oflevel differences. Yet a monaural neuron with a fixed threshold should fire earlier in responseto louder sounds, which would disrupt the tuning of these neurons. %, resulting in shifts in delay tuning for interaural level differences.How could spike timing be independent of input level?Here I derive theoretical conditions for a spiking model tobe insensitive to input level.The key property is a dynamic change in spike threshold.I then show how level invariance can be physiologically implemented,with specific ionic channel properties.It appears that these ingredients are indeed present inmonaural neurons of the sound localization pathway of birds and mammals.

  13. Filter based phase distortions in extracellular spikes.

    Science.gov (United States)

    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.

  14. Filter based phase distortions in extracellular spikes

    Science.gov (United States)

    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

  15. Implementing Signature Neural Networks with Spiking Neurons.

    Science.gov (United States)

    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

  16. Implementing Signature Neural Networks with Spiking Neurons

    Science.gov (United States)

    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

  17. Evoking prescribed spike times in stochastic neurons

    Science.gov (United States)

    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.

  18. Assessing Soil Erosion Rates on Manually-Tilled Hillslopes in the Sichuan Hilly Basin Using 137Cs and 210Pbex Measurements

    Institute of Scientific and Technical Information of China (English)

    ZHENG Jin-Jun; HE Xiu-Bin; D. WALLING; ZHANG Xin-Bao; D. FLANAGAN; QI Yong-Qing

    2007-01-01

    Purple soils are widely distributed in the Sichuan Hilly Basin and are highly susceptible to erosion, especially on the cultivated slopes. Quantitative assessment of the erosion rates is, however, difficult due to small size of the plots of the manually-tilled land, the complex land use, and steep hillslopes. 137Cs and 210Pbex (excess 210Pb) tracing techniques were used to investigate the spatial pattern of soil erosion rates associated with slope-land under hoe tillage in Neijiang of the Sichuan Hilly Basin. The 137Cs and 210Pbex inventories at the top of the cultivated slope were extremely low, and the highest inventories were found at the bottom of the cultivated slope. By combining the erosion rates estimates provided by both 137Cs and 210Pbex measurements, the weighted mean net soil loss from the study slope was estimated to be 3100 t km-2 year-1, which was significantly less than 6930 t km-2 year-1 reported for runoff plots on a 10°cultivated slope at the Suining Station of soil Erosion. The spatial pattern of soil erosion rates on the steep agricultural land showed that hoe tillage played an important role in soil redistribution along the slope. Also, traditional farming practices had a significant role in reducing soil loss, leading to a lower net erosion rate for the field.

  19. Improved SpikeProp for Using Particle Swarm Optimization

    Directory of Open Access Journals (Sweden)

    Falah Y. H. Ahmed

    2013-01-01

    Full Text Available A spiking neurons network encodes information in the timing of individual spike times. A novel supervised learning rule for SpikeProp is derived to overcome the discontinuities introduced by the spiking thresholding. This algorithm is based on an error-backpropagation learning rule suited for supervised learning of spiking neurons that use exact spike time coding. The SpikeProp is able to demonstrate the spiking neurons that can perform complex nonlinear classification in fast temporal coding. This study proposes enhancements of SpikeProp learning algorithm for supervised training of spiking networks which can deal with complex patterns. The proposed methods include the SpikeProp particle swarm optimization (PSO and angle driven dependency learning rate. These methods are presented to SpikeProp network for multilayer learning enhancement and weights optimization. Input and output patterns are encoded as spike trains of precisely timed spikes, and the network learns to transform the input trains into target output trains. With these enhancements, our proposed methods outperformed other conventional neural network architectures.

  20. U-Sries Disequilibra in Soils, Pena Blanca Natural Analog, Chihuahua, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    D. French; E. Anthony; P. Goodell

    2006-03-16

    The Nopal I uranium deposit located in the Sierra Pena Blanca, Mexico. The deposit was mined in the early 1980s, and ore was stockpiled close by. This stockpile area was cleared and is now referred to as the Prior High Grade Stockpile (PHGS). Some of the high-grade boulders from the site rolled downhill when it was cleared in the 1990s. For this study soil samples were collected from the alluvium surrounding and underlying one of these boulders. A bulk sample of the boulder was also collected. Because the Prior High Grade Stockpile had no ore prior to the 1980s a maximum residence time for the boulder is about 25 years, this also means that the soil was at background as well. The purpose of this study is to characterize the transport of uranium series radionuclides from ore to the soil. Transport is characterized by determining the activities of individual radionuclides and daughter to parent ratios. Isotopes of the uranium series decay chain detected include {sup 210}Pb, {sup 234}U, {sup 230}Th, {sup 226}Ra, {sup 214}Pb, and {sup 214}Bi. Peak areas for each isotope are determined using gamma-ray spectroscopy with a Canberra Ge (Li) detector and GENIE 2000 software. The boulder sample is close to secular equilibrium when compared to the standard BL-5 (Beaver Lodge Uraninite from Canada). Results for the soils, however, indicate that some daughter/parent pairs are in secular disequilibrium. These daughter/parent (D/P) ratios include {sup 230}Th/{sup 234}U, which is greater than unity, {sup 226}Ra/{sup 230}Th, which is also greater than unity, and {sup 210}Pb/{sup 214}Bi, which is less than unity. The gamma-ray spectrum for organic material lacks {sup 230}Th peaks, but contains {sup 234}U and {sup 226}Ra, indicating that plants preferentially incorporate {sup 226}Ra. Our results, combined with previous studies require multistage history of mobilization of the uranium series radionuclides. Earlier studies at the ore zone could limit the time span for mobilization only

  1. Effect of Music on Interictal Epileptiform Spikes

    OpenAIRE

    J Gordon Millichap

    2004-01-01

    The effect of listening to Mozart’s Sonata for Two Pianos (K448) on the frequency of interictal epileptiform discharges (IEDs) in the EEGs of four children, ages 5 – 9 years, with benign childhood epilepsy with centrotemporal spikes (BCECTS) was studied in a prospective, randomized, crossover, placebo-controlled trial at the Medical University of South Carolina, Charleston, SC.

  2. Effect of Music on Interictal Epileptiform Spikes

    Directory of Open Access Journals (Sweden)

    J Gordon Millichap

    2004-10-01

    Full Text Available The effect of listening to Mozart’s Sonata for Two Pianos (K448 on the frequency of interictal epileptiform discharges (IEDs in the EEGs of four children, ages 5 – 9 years, with benign childhood epilepsy with centrotemporal spikes (BCECTS was studied in a prospective, randomized, crossover, placebo-controlled trial at the Medical University of South Carolina, Charleston, SC.

  3. Spike-timing theory of working memory.

    Directory of Open Access Journals (Sweden)

    Botond Szatmáry

    Full Text Available Working memory (WM is the part of the brain's memory system that provides temporary storage and manipulation of information necessary for cognition. Although WM has limited capacity at any given time, it has vast memory content in the sense that it acts on the brain's nearly infinite repertoire of lifetime long-term memories. Using simulations, we show that large memory content and WM functionality emerge spontaneously if we take the spike-timing nature of neuronal processing into account. Here, memories are represented by extensively overlapping groups of neurons that exhibit stereotypical time-locked spatiotemporal spike-timing patterns, called polychronous patterns; and synapses forming such polychronous neuronal groups (PNGs are subject to associative synaptic plasticity in the form of both long-term and short-term spike-timing dependent plasticity. While long-term potentiation is essential in PNG formation, we show how short-term plasticity can temporarily strengthen the synapses of selected PNGs and lead to an increase in the spontaneous reactivation rate of these PNGs. This increased reactivation rate, consistent with in vivo recordings during WM tasks, results in high interspike interval variability and irregular, yet systematically changing, elevated firing rate profiles within the neurons of the selected PNGs. Additionally, our theory explains the relationship between such slowly changing firing rates and precisely timed spikes, and it reveals a novel relationship between WM and the perception of time on the order of seconds.

  4. Physics of volleyball: Spiking with a purpose

    Science.gov (United States)

    Behroozi, F.

    1998-05-01

    A few weeks ago our volleyball coach telephoned me with a problem: How high should a player jump to "spike" a "set" ball so it would clear the net and land at a known distance on the other side of the net?

  5. Some Applications of Spiking Neural P Systems

    OpenAIRE

    Mihai Ionescu; Dragoş Sburlan

    2012-01-01

    In this paper we investigate some applications of spiking neural P systems regarding their capability to solve some classical computer science problems. In this respect versatility of such systems is studied to simulate a well known parallel computational model, namely the Boolean circuits. In addition, another notorious application -- sorting -- is considered within this framework.

  6. An Unsupervised Online Spike-Sorting Framework.

    Science.gov (United States)

    Knieling, Simeon; Sridharan, Kousik S; Belardinelli, Paolo; Naros, Georgios; Weiss, Daniel; Mormann, Florian; Gharabaghi, Alireza

    2016-08-01

    Extracellular neuronal microelectrode recordings can include action potentials from multiple neurons. To separate spikes from different neurons, they can be sorted according to their shape, a procedure referred to as spike-sorting. Several algorithms have been reported to solve this task. However, when clustering outcomes are unsatisfactory, most of them are difficult to adjust to achieve the desired results. We present an online spike-sorting framework that uses feature normalization and weighting to maximize the distinctiveness between different spike shapes. Furthermore, multiple criteria are applied to either facilitate or prevent cluster fusion, thereby enabling experimenters to fine-tune the sorting process. We compare our method to established unsupervised offline (Wave_Clus (WC)) and online (OSort (OS)) algorithms by examining their performance in sorting various test datasets using two different scoring systems (AMI and the Adamos metric). Furthermore, we evaluate sorting capabilities on intra-operative recordings using established quality metrics. Compared to WC and OS, our algorithm achieved comparable or higher scores on average and produced more convincing sorting results for intra-operative datasets. Thus, the presented framework is suitable for both online and offline analysis and could substantially improve the quality of microelectrode-based data evaluation for research and clinical application.

  7. JFK in Blackface: Spike Lee's "Malcolm X."

    Science.gov (United States)

    Walker, Clarence E.

    1993-01-01

    Discusses the failure of filmmaker Spike Lee to grapple with the real politics of Malcolm X before and after he left the Nation of Islam. Acknowledging the complexity of the man and his context would avoid creating a mythical figure similar to Oliver Stone's movie "JFK." (SLD)

  8. Implementing Signature Neural Networks with Spiking Neurons

    Directory of Open Access Journals (Sweden)

    José Luis Carrillo-Medina

    2016-12-01

    Full Text Available Spiking Neural Networks constitute the most promising approach to develop realistic ArtificialNeural Networks (ANNs. Unlike traditional firing rate-based paradigms, information coding inspiking models is based on the precise timing of individual spikes. 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, majorbreakthroughs in neuroscience research have discovered new relevant computational principles indifferent living neural systems. Could ANNs benefit from some of these recent findings providingnovel elements of inspiration? This is an intriguing question and the development of spiking ANNsincluding novel bio-inspired information coding and processing strategies is gaining attention. Fromthis perspective, in this work, we adapt the core concepts of the recently proposed SignatureNeural Network paradigm – i.e., neural signatures to identify each unit in the network, localinformation contextualization during the processing and multicoding strategies for informationpropagation regarding the origin and the content of the data – to be employed in a spiking neuralnetwork. To the best of our knowledge, none of these mechanisms have been used yet in thecontext of ANNs of spiking neurons. This paper provides a proof-of-concept for their applicabilityin such networks. Computer simulations show that a simple network model like the discussed hereexhibits complex self-organizing properties. The combination of multiple simultaneous encodingschemes allows the network to generate coexisting spatio-temporal patterns of activity encodinginformation in different spatio-temporal spaces. As a function of the network and/or intra-unitparameters shaping the corresponding encoding modality, different forms of competition amongthe evoked patterns can emerge even in the absence of inhibitory connections. These parametersalso

  9. Effects of visual stimulation on LFPs, spikes, and LFP-spike relations in PRR.

    Science.gov (United States)

    Hwang, Eun Jung; Andersen, Richard A

    2011-04-01

    Local field potentials (LFPs) have shown diverse relations to the spikes across different brain areas and stimulus features, suggesting that LFP-spike relationships are highly specific to the underlying connectivity of a local network. If so, the LFP-spike relationship may vary even within one brain area under the same task condition if neurons have heterogeneous connectivity with the active input sources during the task. Here, we tested this hypothesis in the parietal reach region (PRR), which includes two distinct classes of motor goal planning neurons with different connectivity to the visual input, i.e., visuomotor neurons receive stronger visual input than motor neurons. We predicted that the visual stimulation would render both the spike response and the LFP-spike relationship different between the two neuronal subpopulations. Thus we examined how visual stimulations affect spikes, LFPs, and LFP-spike relationships in PRR by comparing their planning (delay) period activity between two conditions: with or without a visual stimulus at the reach target. Neurons were classified as visuomotor if the visual stimulation increased their firing rate, or as motor otherwise. We found that the visual stimulation increased LFP power in gamma bands >40 Hz for both classes. Moreover, confirming our prediction, the correlation between the LFP gamma power and the firing rate became higher for the visuomotor than motor neurons in the presence of visual stimulation. We conclude that LFPs vary with the stimulation condition and that the LFP-spike relationship depends on a given neuron's connectivity to the dominant input sources in a particular stimulation condition.

  10. Spike timing dependent plasticity finds the start of repeating patterns in continuous spike trains.

    Directory of Open Access Journals (Sweden)

    Timothée Masquelier

    Full Text Available Experimental studies have observed Long Term synaptic Potentiation (LTP when a presynaptic neuron fires shortly before a postsynaptic neuron, and Long Term Depression (LTD when the presynaptic neuron fires shortly after, a phenomenon known as Spike Timing Dependent Plasticity (STDP. When a neuron is presented successively with discrete volleys of input spikes STDP has been shown to learn 'early spike patterns', that is to concentrate synaptic weights on afferents that consistently fire early, with the result that the postsynaptic spike latency decreases, until it reaches a minimal and stable value. Here, we show that these results still stand in a continuous regime where afferents fire continuously with a constant population rate. As such, STDP is able to solve a very difficult computational problem: to localize a repeating spatio-temporal spike pattern embedded in equally dense 'distractor' spike trains. STDP thus enables some form of temporal coding, even in the absence of an explicit time reference. Given that the mechanism exposed here is simple and cheap it is hard to believe that the brain did not evolve to use it.

  11. Generalized Volterra kernel model identification of spike-timing-dependent plasticity from simulated spiking activity.

    Science.gov (United States)

    Robinson, Brian S; Song, Dong; Berger, Theodore W

    2014-01-01

    This paper presents a methodology to estimate a learning rule that governs activity-dependent plasticity from behaviorally recorded spiking events. To demonstrate this framework, we simulate a probabilistic spiking neuron with spike-timing-dependent plasticity (STDP) and estimate all model parameters from the simulated spiking data. In the neuron model, output spiking activity is generated by the combination of noise, feedback from the output, and an input-feedforward component whose magnitude is modulated by synaptic weight. The synaptic weight is calculated with STDP with the following features: (1) weight change based on the relative timing of input-output spike pairs, (2) prolonged plasticity induction, and (3) considerations for system stability. Estimation of all model parameters is achieved iteratively by formulating the model as a generalized linear model with Volterra kernels and basis function expansion. Successful estimation of all model parameters in this study demonstrates the feasibility of this approach for in-vivo experimental studies. Furthermore, the consideration of system stability and prolonged plasticity induction enhances the ability to capture how STDP affects a neural population's signal transformation properties over a realistic time course. Plasticity characterization with this estimation method could yield insights into functional implications of STDP and be incorporated into a cortical prosthesis.

  12. Laguerre-Volterra identification of spike-timing-dependent plasticity from spiking activity: a simulation study.

    Science.gov (United States)

    Robinson, Brian S; Song, Dong; Berger, Theodore W

    2013-01-01

    This paper presents a Laguerre-Volterra methodology for identifying a plasticity learning rule from spiking neural data with four components: 1) By analyzing input-output spiking data, the effective contribution of an input on the output firing probability can be quantified with weighted Volterra kernels. 2) The weight of these Volterra kernels can be tracked over time using the stochastic state point processing filtering algorithm (SSPPF) 3) Plasticity system Volterra kernels can be estimated by treating the tracked change in weight over time as the plasticity system output and the spike timing data as the input. 4) Laguerre expansion of all Volterra kernels allows for minimization of open parameters during estimation steps. A single input spiking neuron with Spike-timing-dependent plasticity (STDP) and prolonged STDP induction is simulated. Using the spiking data from this simulation, the amplitude of the STDP learning rule and the time course of the induction is accurately estimated. This framework can be applied to identify plasticity for more complicated plasticity paradigms and is applicable to in vivo data.

  13. Detection of bursts in neuronal spike trains by the mean inter-spike interval method

    Institute of Scientific and Technical Information of China (English)

    Lin Chen; Yong Deng; Weihua Luo; Zhen Wang; Shaoqun Zeng

    2009-01-01

    Bursts are electrical spikes firing with a high frequency, which are the most important property in synaptic plasticity and information processing in the central nervous system. However, bursts are difficult to identify because bursting activities or patterns vary with phys-iological conditions or external stimuli. In this paper, a simple method automatically to detect bursts in spike trains is described. This method auto-adaptively sets a parameter (mean inter-spike interval) according to intrinsic properties of the detected burst spike trains, without any arbitrary choices or any operator judgrnent. When the mean value of several successive inter-spike intervals is not larger than the parameter, a burst is identified. By this method, bursts can be automatically extracted from different bursting patterns of cultured neurons on multi-electrode arrays, as accurately as by visual inspection. Furthermore, significant changes of burst variables caused by electrical stimulus have been found in spontaneous activity of neuronal network. These suggest that the mean inter-spike interval method is robust for detecting changes in burst patterns and characteristics induced by environmental alterations.

  14. The remediation of lead contaminated soils using solvent extraction chelation techniques. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Price, M.; Hanson, A.T.; Rudd, B.; Pickins, D.; Krause, K. [New Mexico State Univ., Las Cruces, NM (United States)

    1998-08-01

    This report describes preliminary work leading to the development of an innovative technology for treating a mixed waste problem at Los Alamos National Laboratory (LANL). The specific problem being addressed by this research is the result of research activity at the Meson Physics Facility (LAMPH). The LAMPH facility conducts high energy neutron research. Lead BB`s were placed in containers and used as shielding during experiments.This lead was stored in piles on the ground when it was not in use, and it sometimes sat for extended periods of time, perhaps as long as 20 years. The lead was mobilized overtime, and contaminated the underlying soil. Because of the neutron bombardment, a portion of the lead {sup 207}Pb became radioactive {sup 210}Pb, and the lead became both a listed waste and radioactive, which classified it as a mixed waste. The contaminated soil has been removed from the site and placed in drums for storage until a suitable treatment technology can be identified. The contents of the barrels consists of a mixture of lead contaminated soil and lead BB`s.

  15. Comparing soil chemistries of leached and nonleached copper-amended soils.

    Science.gov (United States)

    Schwertfeger, D M; Hendershot, W H

    2012-10-01

    Leaching metal-spiked samples has been proposed as a means to reduce the artifacts of the spiking procedure (e.g., salt effect, increased metal solubility) that can artificially increase metal bioaccessibility and toxicity in laboratory ecotoxicity tests. The effects on soil chemistry from leaching Cu-spiked samples were investigated by comparing chemistries of freshly spiked samples to samples that underwent the spike/leach procedure. Chemical parameters investigated included electrical conductivity (EC), pH, ethylenediaminetetraacetic acid- and CaCl(2) -extractable Cu, soil-solution Cu, Cu(2+) activity (estimated using Visual MINTEQ), and other solution parameters (dissolved organic carbon [DOC], Ca, Mg, Al). In leached samples, the electrical conductivity values of the spiked samples did not vary significantly from those of the control samples (p > 0.05), confirming that the leaching procedure had sufficiently minimized the salt effect. In the range of soil Cu concentrations where Cu ecotoxicity is expected, the pH in freshly spiked samples was as much as 0.52 units lower than the pH from leached samples at the same total-soil Cu concentration. The CaCl(2) -extractable fraction was up to 2.3-fold smaller in leached samples and inversely related to the pH of the spiked soil. Despite little to no difference in soil-solution Cu, up to 100-fold less Cu(2+) activity was observed in leached samples. Reduced Cu(2+) activity was related to less Al(3+) competition for DOC. Leaching resulted in solution chemistries that were more consistent with those of the control samples and reduced the artifacts of traditional soil-spiking procedures.

  16. The Mutation Frequency in Different Spike Categories in Barley

    DEFF Research Database (Denmark)

    Frydenberg, O.; Doll, Hans; Sandfær, J.

    1964-01-01

    After gamma irradiation of barley seeds, a comparison has been made between the chlorophyll-mutant frequencies in X1 spikes that had multicellular bud meristems in the seeds at the time of treatment (denoted as pre-formed spikes) and X1 spikes having no recognizable meristems at the time...

  17. Collision-spike Sputtering of Au Nanoparticles.

    Science.gov (United States)

    Sandoval, Luis; Urbassek, Herbert M

    2015-12-01

    Ion irradiation of nanoparticles leads to enhanced sputter yields if the nanoparticle size is of the order of the ion penetration depth. While this feature is reasonably well understood for collision-cascade sputtering, we explore it in the regime of collision-spike sputtering using molecular-dynamics simulation. For the particular case of 200-keV Xe bombardment of Au particles, we show that collision spikes lead to abundant sputtering with an average yield of 397 ± 121 atoms compared to only 116 ± 48 atoms for a bulk Au target. Only around 31 % of the impact energy remains in the nanoparticles after impact; the remainder is transported away by the transmitted projectile and the ejecta. The sputter yield of supported nanoparticles is estimated to be around 80 % of that of free nanoparticles due to the suppression of forward sputtering.

  18. Spiking neural P systems with weights.

    Science.gov (United States)

    Wang, Jun; Hoogeboom, Hendrik Jan; Pan, Linqiang; Păun, Gheorghe; Pérez-Jiménez, Mario J

    2010-10-01

    A variant of spiking neural P systems with positive or negative weights on synapses is introduced, where the rules of a neuron fire when the potential of that neuron equals a given value. The involved values-weights, firing thresholds, potential consumed by each rule-can be real (computable) numbers, rational numbers, integers, and natural numbers. The power of the obtained systems is investigated. For instance, it is proved that integers (very restricted: 1, -1 for weights, 1 and 2 for firing thresholds, and as parameters in the rules) suffice for computing all Turing computable sets of numbers in both the generative and the accepting modes. When only natural numbers are used, a characterization of the family of semilinear sets of numbers is obtained. It is shown that spiking neural P systems with weights can efficiently solve computationally hard problems in a nondeterministic way. Some open problems and suggestions for further research are formulated.

  19. Hardware implementation of stochastic spiking neural networks.

    Science.gov (United States)

    Rosselló, Josep L; Canals, Vincent; Morro, Antoni; Oliver, Antoni

    2012-08-01

    Spiking Neural Networks, the last generation of Artificial Neural Networks, are characterized by its bio-inspired nature and by a higher computational capacity with respect to other neural models. In real biological neurons, stochastic processes represent an important mechanism of neural behavior and are responsible of its special arithmetic capabilities. In this work we present a simple hardware implementation of spiking neurons that considers this probabilistic nature. The advantage of the proposed implementation is that it is fully digital and therefore can be massively implemented in Field Programmable Gate Arrays. The high computational capabilities of the proposed model are demonstrated by the study of both feed-forward and recurrent networks that are able to implement high-speed signal filtering and to solve complex systems of linear equations.

  20. Spiked Instantons from Intersecting D-branes

    CERN Document Server

    Nekrasov, Nikita

    2016-01-01

    The moduli space of spiked instantons that arises in the context of the BPS/CFT correspondence is realised as the moduli space of classical vacua, i.e. low-energy open string field configurations, of a certain stack of intersecting D1-branes and D5-branes in Type IIB string theory. The presence of a constant B-field induces an interesting dynamics involving the tachyon condensation.

  1. Spiked instantons from intersecting D-branes

    Directory of Open Access Journals (Sweden)

    Nikita Nekrasov

    2017-01-01

    Full Text Available The moduli space of spiked instantons that arises in the context of the BPS/CFT correspondence [22] is realised as the moduli space of classical vacua, i.e. low-energy open string field configurations, of a certain stack of intersecting D1-branes and D5-branes in Type IIB string theory. The presence of a constant B-field induces an interesting dynamics involving the tachyon condensation.

  2. Spiked instantons from intersecting D-branes

    Science.gov (United States)

    Nekrasov, Nikita; Prabhakar, Naveen S.

    2017-01-01

    The moduli space of spiked instantons that arises in the context of the BPS/CFT correspondence [22] is realised as the moduli space of classical vacua, i.e. low-energy open string field configurations, of a certain stack of intersecting D1-branes and D5-branes in Type IIB string theory. The presence of a constant B-field induces an interesting dynamics involving the tachyon condensation.

  3. Stochastic synchronization in finite size spiking networks

    Science.gov (United States)

    Doiron, Brent; Rinzel, John; Reyes, Alex

    2006-09-01

    We study a stochastic synchronization of spiking activity in feedforward networks of integrate-and-fire model neurons. A stochastic mean field analysis shows that synchronization occurs only when the network size is sufficiently small. This gives evidence that the dynamics, and hence processing, of finite size populations can be drastically different from that observed in the infinite size limit. Our results agree with experimentally observed synchrony in cortical networks, and further strengthen the link between synchrony and propagation in cortical systems.

  4. Stochastically gating ion channels enable patterned spike firing through activity-dependent modulation of spike probability.

    Directory of Open Access Journals (Sweden)

    Joshua T Dudman

    2009-02-01

    Full Text Available The transformation of synaptic input into patterns of spike output is a fundamental operation that is determined by the particular complement of ion channels that a neuron expresses. Although it is well established that individual ion channel proteins make stochastic transitions between conducting and non-conducting states, most models of synaptic integration are deterministic, and relatively little is known about the functional consequences of interactions between stochastically gating ion channels. Here, we show that a model of stellate neurons from layer II of the medial entorhinal cortex implemented with either stochastic or deterministically gating ion channels can reproduce the resting membrane properties of stellate neurons, but only the stochastic version of the model can fully account for perithreshold membrane potential fluctuations and clustered patterns of spike output that are recorded from stellate neurons during depolarized states. We demonstrate that the stochastic model implements an example of a general mechanism for patterning of neuronal output through activity-dependent changes in the probability of spike firing. Unlike deterministic mechanisms that generate spike patterns through slow changes in the state of model parameters, this general stochastic mechanism does not require retention of information beyond the duration of a single spike and its associated afterhyperpolarization. Instead, clustered patterns of spikes emerge in the stochastic model of stellate neurons as a result of a transient increase in firing probability driven by activation of HCN channels during recovery from the spike afterhyperpolarization. Using this model, we infer conditions in which stochastic ion channel gating may influence firing patterns in vivo and predict consequences of modifications of HCN channel function for in vivo firing patterns.

  5. Analysis of Neuronal Spike Trains, Deconstructed.

    Science.gov (United States)

    Aljadeff, Johnatan; Lansdell, Benjamin J; Fairhall, Adrienne L; Kleinfeld, David

    2016-07-20

    As information flows through the brain, neuronal firing progresses from encoding the world as sensed by the animal to driving the motor output of subsequent behavior. One of the more tractable goals of quantitative neuroscience is to develop predictive models that relate the sensory or motor streams with neuronal firing. Here we review and contrast analytical tools used to accomplish this task. We focus on classes of models in which the external variable is compared with one or more feature vectors to extract a low-dimensional representation, the history of spiking and other variables are potentially incorporated, and these factors are nonlinearly transformed to predict the occurrences of spikes. We illustrate these techniques in application to datasets of different degrees of complexity. In particular, we address the fitting of models in the presence of strong correlations in the external variable, as occurs in natural sensory stimuli and in movement. Spectral correlation between predicted and measured spike trains is introduced to contrast the relative success of different methods.

  6. Superbubbles, Galactic Dynamos and the Spike Instability

    CERN Document Server

    Kulsrud, Russell M

    2015-01-01

    We draw attention to a problem with the alpha-Omega dynamo when it is applied to the origin of the galactic magnetic field under the assumption of perfect flux freezing. The standard theory involves the expulsion of undesirable flux and, because of flux freezing, the mass anchored on this flux also must be expelled. The strong galactic gravitational field makes this impossible on energetic grounds. It is shown that if only short pieces of the undesirable field lines are expelled, then mass can flow down along these field lines without requiring much energy. This expulsion of only short lines of force can be accomplished by a spike instability associated with gigantic astrophysical superbubbles. The physics of this instability is discussed and the results enable an estimate to be made of the number of spikes in the galaxy. It appears that there are probably enough spikes to cut all the undesirable lines into pieces as short as a couple of kiloparsecs during a dynamo time of a billion years. These cut pieces th...

  7. Millisecond precision spike timing shapes tactile perception.

    Science.gov (United States)

    Mackevicius, Emily L; Best, Matthew D; Saal, Hannes P; Bensmaia, Sliman J

    2012-10-31

    In primates, the sense of touch has traditionally been considered to be a spatial modality, drawing an analogy to the visual system. In this view, stimuli are encoded in spatial patterns of activity over the sheet of receptors embedded in the skin. We propose that the spatial processing mode is complemented by a temporal one. Indeed, the transduction and processing of complex, high-frequency skin vibrations have been shown to play an important role in tactile texture perception, and the frequency composition of vibrations shapes the evoked percept. Mechanoreceptive afferents innervating the glabrous skin exhibit temporal patterning in their responses, but the importance and behavioral relevance of spike timing, particularly for naturalistic stimuli, remains to be elucidated. Based on neurophysiological recordings from Rhesus macaques, we show that spike timing conveys information about the frequency composition of skin vibrations, both for individual afferents and for afferent populations, and that the temporal fidelity varies across afferent class. Furthermore, the perception of skin vibrations, measured in human subjects, is better predicted when spike timing is taken into account, and the resolution that predicts perception best matches the optimal resolution of the respective afferent classes. In light of these results, the peripheral representation of complex skin vibrations draws a powerful analogy with the auditory and vibrissal systems.

  8. Effect of soil ageing on in vivo arsenic bioavailability in two dissimilar soils.

    Science.gov (United States)

    Juhasz, Albert L; Smith, Euan; Weber, John; Naidu, Ravi; Rees, Matthew; Rofe, Allan; Kuchel, Tim; Sansom, Lloyd

    2008-05-01

    Arsenic (As) bioavailability in spiked soils aged for up to 12 months was assessed using in vitro and in vivo methodologies. Ageing (natural attenuation) of spiked soils resulted in a decline in in vivo As bioavailability (swine assay) of over 75% in soil A (Red Ferrosol) but had no significant effect on in vivo As bioavailability even after 12 months of ageing in soil B (Brown Chromosol). Sequential fractionation, however, indicated that there was repartitioning of As within the soil fractions extracted during the time course investigated. In soil A, the As fraction associated with the more weakly bound soil fractions decreased while the residual fraction increased from 12% to 35%. In contrast, little repartitioning of As was observed in soil B indicating that natural attenuation may be only applicable for As in soils containing specific mineralogical properties.

  9. Quantifying bioturbation and soil thickening over the late Quaternary

    Science.gov (United States)

    Wilkinson, M. T.; Pietsch, T.; Fox, J. F.

    2009-04-01

    We present geochemistry and biochemistry data to explore how bioturbation has operated in a residual sandstone-derived soil that thickened during the Holocene following aeolian deflation during the Last Glacial Maximum. Our site is located on a plateau cut into Triassic sandstones in humid Blue Mountains, SE Australia, where precipitation is ~1100 mm/a, and the mean annual maximum and minimum temperatures are 17°C and 5°C, respectively. Vegetation cover increase occurred ~13 ka, based on nearby palaeodune activity and pollen data from other highland sites. Our interpretation of terrestrial cosmogenic radionuclides (TCN) data suggests that ~30 cm of soil thickening has taken place since 13 ka, which includes 16 cm of bedrock lowering. Biofabrics preserve a short-term picture of biotically-displaced soil. In general, bioturbation decreases exponentially with increasing soil depth. The upper 21 cm of the profile is ~95% bioturbated; the middle 13 cm is 13 - 32% bioturbated; and the lowest 52 cm is 1 - 6% bioturbated. Tree roots penetrate weakness in the sandstone below this depth. Fallout radionuclides (7Be, 210Pb, and 137Cs) in the profile also suggest that vertical mixing in the upper 20 - 40 cm occurs over short—decadal—timescales. Optically stimulated luminescene (OSL) data records the time that quartz grains were last at the surface, and are used here to demonstrate vertical mixing of the profile over tens of thousands of years. OSL data indicates that some soil grains at all burial depths were once at the surface, consistent with modern process observations. Carbon and nitrogen isotopic values (delta 13C and delta 15N) of soil organic matter support the existence of soil organic matter turnover in the upper 30 cm of the soil column when regressed with log(SOC) and log(TN). Our carbon isotope data defy typical trends below ~30 cm for residual, undisturbed soils. We suggest this may reflect the absence of bioturbation during the LGM when the climate was cold

  10. Branching Shoots and Spikes from Lateral Meristems in Bread Wheat.

    Directory of Open Access Journals (Sweden)

    Ying Wang

    Full Text Available Wheat grain yield consists of three components: spikes per plant, grains per spike (i.e. head or ear, and grain weight; and the grains per spike can be dissected into two subcomponents: spikelets per spike and grains per spikelet. An increase in any of these components will directly contribute to grain yield. Wheat morphology biology tells that a wheat plant has no lateral meristem that forms any branching shoot or spike. In this study, we report two novel shoot and spike traits that were produced from lateral meristems in bread wheat. One is supernumerary shoot that was developed from an axillary bud at the axil of leaves on the elongated internodes of the main stem. The other is supernumerary spike that was generated from a spikelet meristem on a spike. In addition, supernumerary spikelets were generated on the same rachis node of the spike in the plant that had supernumerary shoot and spikes. All of these supernumerary shoots/spikes/spikelets found in the super wheat plants produced normal fertility and seeds, displaying huge yield potential in bread wheat.

  11. Analyzing multiple spike trains with nonparametric Granger causality.

    Science.gov (United States)

    Nedungadi, Aatira G; Rangarajan, Govindan; Jain, Neeraj; Ding, Mingzhou

    2009-08-01

    Simultaneous recordings of spike trains from multiple single neurons are becoming commonplace. Understanding the interaction patterns among these spike trains remains a key research area. A question of interest is the evaluation of information flow between neurons through the analysis of whether one spike train exerts causal influence on another. For continuous-valued time series data, Granger causality has proven an effective method for this purpose. However, the basis for Granger causality estimation is autoregressive data modeling, which is not directly applicable to spike trains. Various filtering options distort the properties of spike trains as point processes. Here we propose a new nonparametric approach to estimate Granger causality directly from the Fourier transforms of spike train data. We validate the method on synthetic spike trains generated by model networks of neurons with known connectivity patterns and then apply it to neurons simultaneously recorded from the thalamus and the primary somatosensory cortex of a squirrel monkey undergoing tactile stimulation.

  12. Introduction to spiking neural networks: Information processing, learning and applications.

    Science.gov (United States)

    Ponulak, Filip; Kasinski, Andrzej

    2011-01-01

    The concept that neural information is encoded in the firing rate of neurons has been the dominant paradigm in neurobiology for many years. This paradigm has also been adopted by the theory of artificial neural networks. Recent physiological experiments demonstrate, however, that in many parts of the nervous system, neural code is founded on the timing of individual action potentials. This finding has given rise to the emergence of a new class of neural models, called spiking neural networks. In this paper we summarize basic properties of spiking neurons and spiking networks. Our focus is, specifically, on models of spike-based information coding, synaptic plasticity and learning. We also survey real-life applications of spiking models. The paper is meant to be an introduction to spiking neural networks for scientists from various disciplines interested in spike-based neural processing.

  13. Complementary contributions of spike timing and spike rate to perceptual decisions in rat S1 and S2 cortex.

    Science.gov (United States)

    Zuo, Yanfang; Safaai, Houman; Notaro, Giuseppe; Mazzoni, Alberto; Panzeri, Stefano; Diamond, Mathew E

    2015-02-02

    When a neuron responds to a sensory stimulus, two fundamental codes [1-6] may transmit the information specifying stimulus identity--spike rate (the total number of spikes in the sequence, normalized by time) and spike timing (the detailed millisecond-scale temporal structure of the response). To assess the functional significance of these codes, we recorded neuronal responses in primary (S1) and secondary (S2) somatosensory cortex of five rats as they used their whiskers to identify textured surfaces. From the spike trains evoked during whisker contact with the texture, we computed the information that rate and timing codes carried about texture identity and about the rat's choice. S1 and S2 spike timing carried more information about stimulus and about choice than spike rates; the conjunction of rate and timing carried more information than either code alone. Moreover, on trials when our spike-timing-decoding algorithm extracted faithful texture information, the rat was more likely to choose correctly; when our spike-timing-decoding algorithm extracted misleading texture information, the rat was more likely to err. For spike rate information, the relationship between faithfulness of the message and correct choice was significant but weaker. These results indicate that spike timing makes crucial contributions to tactile perception, complementing and surpassing those made by rate. The language by which somatosensory cortical neurons transmit information, and the readout mechanism used to produce behavior, appears to rely on multiplexed signals from spike rate and timing.

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

    DEFF Research Database (Denmark)

    Brown, J.E.; Gjelsvik, R.; Roos, Per

    2011-01-01

    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...... of 210Po in invertebrates and vertebrates. Biokinetic models may provide a tool to explore in a more mechanistic way the behaviour of 210Po in this system....

  15. Soil mineral composition matters: response of microbial communities to phenanthrene and plant litter addition in long-term matured artificial soils.

    Directory of Open Access Journals (Sweden)

    Doreen Babin

    Full Text Available The fate of polycyclic aromatic hydrocarbons (PAHs in soil is determined by a suite of biotic and abiotic factors, and disentangling their role in the complex soil interaction network remains challenging. Here, we investigate the influence of soil composition on the microbial community structure and its response to the spiked model PAH compound phenanthrene and plant litter. We used long-term matured artificial soils differing in type of clay mineral (illite, montmorillonite and presence of charcoal or ferrihydrite. The soils received an identical soil microbial fraction and were incubated for more than two years with two sterile manure additions. The matured artificial soils and a natural soil were subjected to the following spiking treatments: (I phenanthrene, (II litter, (III litter + phenanthrene, (IV unspiked control. Total community DNA was extracted from soil sampled on the day of spiking, 7, 21, and 63 days after spiking. Bacterial 16S rRNA gene and fungal internal transcribed spacer amplicons were quantified by qPCR and subjected to denaturing gradient gel electrophoresis (DGGE. DGGE analysis revealed that the bacterial community composition, which was strongly shaped by clay minerals after more than two years of incubation, changed in response to spiked phenanthrene and added litter. DGGE and qPCR showed that soil composition significantly influenced the microbial response to spiking. While fungal communities responded only in presence of litter to phenanthrene spiking, the response of the bacterial communities to phenanthrene was less pronounced when litter was present. Interestingly, microbial communities in all artificial soils were more strongly affected by spiking than in the natural soil, which might indicate the importance of higher microbial diversity to compensate perturbations. This study showed the influence of soil composition on the microbiota and their response to phenanthrene and litter, which may increase our

  16. Soil mineral composition matters: response of microbial communities to phenanthrene and plant litter addition in long-term matured artificial soils.

    Science.gov (United States)

    Babin, Doreen; Vogel, Cordula; Zühlke, Sebastian; Schloter, Michael; Pronk, Geertje Johanna; Heister, Katja; Spiteller, Michael; Kögel-Knabner, Ingrid; Smalla, Kornelia

    2014-01-01

    The fate of polycyclic aromatic hydrocarbons (PAHs) in soil is determined by a suite of biotic and abiotic factors, and disentangling their role in the complex soil interaction network remains challenging. Here, we investigate the influence of soil composition on the microbial community structure and its response to the spiked model PAH compound phenanthrene and plant litter. We used long-term matured artificial soils differing in type of clay mineral (illite, montmorillonite) and presence of charcoal or ferrihydrite. The soils received an identical soil microbial fraction and were incubated for more than two years with two sterile manure additions. The matured artificial soils and a natural soil were subjected to the following spiking treatments: (I) phenanthrene, (II) litter, (III) litter + phenanthrene, (IV) unspiked control. Total community DNA was extracted from soil sampled on the day of spiking, 7, 21, and 63 days after spiking. Bacterial 16S rRNA gene and fungal internal transcribed spacer amplicons were quantified by qPCR and subjected to denaturing gradient gel electrophoresis (DGGE). DGGE analysis revealed that the bacterial community composition, which was strongly shaped by clay minerals after more than two years of incubation, changed in response to spiked phenanthrene and added litter. DGGE and qPCR showed that soil composition significantly influenced the microbial response to spiking. While fungal communities responded only in presence of litter to phenanthrene spiking, the response of the bacterial communities to phenanthrene was less pronounced when litter was present. Interestingly, microbial communities in all artificial soils were more strongly affected by spiking than in the natural soil, which might indicate the importance of higher microbial diversity to compensate perturbations. This study showed the influence of soil composition on the microbiota and their response to phenanthrene and litter, which may increase our understanding of

  17. Encoding Chaos in Neural Spike Trains

    Science.gov (United States)

    Richardson, Kristen A.; Imhoff, Thomas T.; Grigg, Peter; Collins, James J.

    1998-03-01

    Recently, it has been shown that interspike interval (ISI) series from driven model neurons can be used to discriminate between chaotic and stochastic inputs. Here we extend this work to in vitro experimental studies with rat cutaneous mechanoreceptors. For each of the neurons tested, we show that a chaotically driven ISI series can be distinguished from a stochastically driven ISI series on the basis of a nonlinear prediction measure. This work demonstrates that dynamical information can be preserved when an analog chaotic signal is converted into a spike train by a sensory neuron.

  18. Marsh soils as potential sinks for Bacteroides fecal indicator bacteria, Waccamaw National Wildlife Refuge, Georgetown, SC, USA

    Science.gov (United States)

    Drexler, Judith Z.; Johnson, Heather E.; Duris, Joseph W.; Krauss, Ken W.

    2014-01-01

    A soil core collected in a tidal freshwater marsh in the Waccamaw National Wildlife Refuge (Georgetown, SC) exuded a particularly strong odor of cow manure upon extrusion. In order to test for manure and determine its provenance, we carried out microbial source tracking using DNA markers for Bacteroides, a noncoliform, anaerobic bacterial group that represents a broad group of the fecal population. Three core sections from 0-3 cm, 9-12 cm and 30-33 were analyzed for the presence of Bacteroides. The ages of core sediments were estimated using 210Pb and 137Cs dating. All three core sections tested positive for Bacteroides DNA markers related to cow or deer feces. Because cow manure is stockpiled, used as fertilizer, and a source of direct contamination in the Great Pee Dee River/Winyah Bay watershed, it is very likely the source of the Bacteroides that was deposited on the marsh. The mid-points of the core sections were dated as follows: 0-3 cm: 2009; 9-12 cm: 1999, and 30-33 cm: 1961. The presence of Bacteroides at different depths/ages in the soil profile indicates that soils in tidal freshwater marshes are, at the least, capable of being short-term sinks for Bacteroides and, may have the potential to be long-term sinks of stable, naturalized populations.

  19. Solving constraint satisfaction problems with networks of spiking neurons

    Directory of Open Access Journals (Sweden)

    Zeno eJonke

    2016-03-01

    Full Text Available Network of neurons in the brain apply – unlike processors in our current generation ofcomputer hardware – an event-based processing strategy, where short pulses (spikes areemitted sparsely by neurons to signal the occurrence of an event at a particular point intime. Such spike-based computations promise to be substantially more power-efficient thantraditional clocked processing schemes. However it turned out to be surprisingly difficult todesign networks of spiking neurons that can solve difficult computational problems on the levelof single spikes (rather than rates of spikes. We present here a new method for designingnetworks of spiking neurons via an energy function. Furthermore we show how the energyfunction of a network of stochastically firing neurons can be shaped in a quite transparentmanner by composing the networks of simple stereotypical network motifs. We show that thisdesign approach enables networks of spiking neurons to produce approximate solutions todifficult (NP-hard constraint satisfaction problems from the domains of planning/optimizationand verification/logical inference. The resulting networks employ noise as a computationalresource. Nevertheless the timing of spikes (rather than just spike rates plays an essential rolein their computations. Furthermore, networks of spiking neurons carry out for the Traveling Salesman Problem a more efficient stochastic search for good solutions compared with stochastic artificial neural networks (Boltzmann machines and Gibbs sampling.

  20. Spike-based population coding and working memory.

    Directory of Open Access Journals (Sweden)

    Martin Boerlin

    2011-02-01

    Full Text Available Compelling behavioral evidence suggests that humans can make optimal decisions despite the uncertainty inherent in perceptual or motor tasks. A key question in neuroscience is how populations of spiking neurons can implement such probabilistic computations. In this article, we develop a comprehensive framework for optimal, spike-based sensory integration and working memory in a dynamic environment. We propose that probability distributions are inferred spike-per-spike in recurrently connected networks of integrate-and-fire neurons. As a result, these networks can combine sensory cues optimally, track the state of a time-varying stimulus and memorize accumulated evidence over periods much longer than the time constant of single neurons. Importantly, we propose that population responses and persistent working memory states represent entire probability distributions and not only single stimulus values. These memories are reflected by sustained, asynchronous patterns of activity which make relevant information available to downstream neurons within their short time window of integration. Model neurons act as predictive encoders, only firing spikes which account for new information that has not yet been signaled. Thus, spike times signal deterministically a prediction error, contrary to rate codes in which spike times are considered to be random samples of an underlying firing rate. As a consequence of this coding scheme, a multitude of spike patterns can reliably encode the same information. This results in weakly correlated, Poisson-like spike trains that are sensitive to initial conditions but robust to even high levels of external neural noise. This spike train variability reproduces the one observed in cortical sensory spike trains, but cannot be equated to noise. On the contrary, it is a consequence of optimal spike-based inference. In contrast, we show that rate-based models perform poorly when implemented with stochastically spiking neurons.

  1. Consensus-Based Sorting of Neuronal Spike Waveforms

    Science.gov (United States)

    Fournier, Julien; Mueller, Christian M.; Shein-Idelson, Mark; Hemberger, Mike

    2016-01-01

    Optimizing spike-sorting algorithms is difficult because sorted clusters can rarely be checked against independently obtained “ground truth” data. In most spike-sorting algorithms in use today, the optimality of a clustering solution is assessed relative to some assumption on the distribution of the spike shapes associated with a particular single unit (e.g., Gaussianity) and by visual inspection of the clustering solution followed by manual validation. When the spatiotemporal waveforms of spikes from different cells overlap, the decision as to whether two spikes should be assigned to the same source can be quite subjective, if it is not based on reliable quantitative measures. We propose a new approach, whereby spike clusters are identified from the most consensual partition across an ensemble of clustering solutions. Using the variability of the clustering solutions across successive iterations of the same clustering algorithm (template matching based on K-means clusters), we estimate the probability of spikes being clustered together and identify groups of spikes that are not statistically distinguishable from one another. Thus, we identify spikes that are most likely to be clustered together and therefore correspond to consistent spike clusters. This method has the potential advantage that it does not rely on any model of the spike shapes. It also provides estimates of the proportion of misclassified spikes for each of the identified clusters. We tested our algorithm on several datasets for which there exists a ground truth (simultaneous intracellular data), and show that it performs close to the optimum reached by a support vector machine trained on the ground truth. We also show that the estimated rate of misclassification matches the proportion of misclassified spikes measured from the ground truth data. PMID:27536990

  2. Limits of spiked random matrices I

    CERN Document Server

    Bloemendal, Alex

    2010-01-01

    Given a large, high-dimensional sample from a spiked population, the top sample covariance eigenvalue is known to exhibit a phase transition. We show that the largest eigenvalues have asymptotic distributions near the phase transition in the rank-one spiked real Wishart setting and its general beta analogue, proving a conjecture of Baik, Ben Arous and P\\'ech\\'e. We also treat shifted mean Gaussian orthogonal and beta ensembles. Such results are entirely new in the real case; in the complex case we strengthen existing results by providing optimal scaling assumptions. One obtains the known limiting random Schr\\"odinger operator on the half-line, but the boundary condition now depends on the perturbation. We derive several characterizations of the limit laws in which beta appears as a parameter, including a simple linear boundary value problem. This PDE description recovers known explicit formulas at beta=2,4, yielding in particular a new and simple proof of the Painlev\\'e representations for these Tracy-Widom d...

  3. Phase Diagram of Spiking Neural Networks

    Directory of Open Access Journals (Sweden)

    Hamed eSeyed-Allaei

    2015-03-01

    Full Text Available In computer simulations of spiking neural networks, often it is assumed that every two neurons of the network are connected by a probablilty of 2%, 20% of neurons are inhibitory and 80% are excitatory. These common values are based on experiments, observations. but here, I take a different perspective, inspired by evolution. I simulate many networks, each with a different set of parameters, and then I try to figure out what makes the common values desirable by nature. Networks which are configured according to the common values, have the best dynamic range in response to an impulse and their dynamic range is more robust in respect to synaptic weights. In fact, evolution has favored networks of best dynamic range. I present a phase diagram that shows the dynamic ranges of different networks of different parameteres. This phase diagram gives an insight into the space of parameters -- excitatory to inhibitory ratio, sparseness of connections and synaptic weights. It may serve as a guideline to decide about the values of parameters in a simulation of spiking neural network.

  4. Communication through resonance in spiking neuronal networks.

    Science.gov (United States)

    Hahn, Gerald; Bujan, Alejandro F; Frégnac, Yves; Aertsen, Ad; Kumar, Arvind

    2014-08-01

    The cortex processes stimuli through a distributed network of specialized brain areas. This processing requires mechanisms that can route neuronal activity across weakly connected cortical regions. Routing models proposed thus far are either limited to propagation of spiking activity across strongly connected networks or require distinct mechanisms that create local oscillations and establish their coherence between distant cortical areas. Here, we propose a novel mechanism which explains how synchronous spiking activity propagates across weakly connected brain areas supported by oscillations. In our model, oscillatory activity unleashes network resonance that amplifies feeble synchronous signals and promotes their propagation along weak connections ("communication through resonance"). The emergence of coherent oscillations is a natural consequence of synchronous activity propagation and therefore the assumption of different mechanisms that create oscillations and provide coherence is not necessary. Moreover, the phase-locking of oscillations is a side effect of communication rather than its requirement. Finally, we show how the state of ongoing activity could affect the communication through resonance and propose that modulations of the ongoing activity state could influence information processing in distributed cortical networks.

  5. Terraced agriculture protects soil from erosion: Case studies in Madagascar

    Science.gov (United States)

    Rabesiranana, Naivo; Rasolonirina, Martin; Fanantenansoa Solonjara, Asivelo; Nomenjanahary Ravoson, Heritiana; Mabit, Lionel

    2016-04-01

    - Soil degradation is a major concern in Madagascar but quantitative information is not widely available. Due to its impact on the sustainability of agricultural production, there is a clear need to acquire data on the extent and magnitude of soil erosion/sedimentation under various agricultural practices in order to promote effective conservation strategies. Caesium-137 and 210Pbex fallout radionuclides (FRNs) possess particular characteristics that make them effective soil tracers for erosion studies. After fallout, 137Cs and 210Pbex are rapidly adsorbed onto fine soil particles. But to date, combined use of these FRNs has never been used to document soil erosion in Madagascar. The study area is located 40 km east of Antananarivo, in Madagascar highlands. Two adjacent cultivated fields have been selected (i.e. a sloped field and a terraced field) as well as an undisturbed reference site in the vicinity of these agricultural fields. Soil samples were collected along downslope transects using motorized corer. The 137Cs and 210Pb gamma analysis were performed at the Institut National des Sciences et Techniques Nucléaires (INSTN-Madagascar) using a high resolution and low background N-type HPGe detector. Results showed that at the terraced field, 137Cs and 210Pbex inventories reached 145 Bq/m2 to 280 Bq/m2 and 2141 Bq/m2 to 4253 Bq/m2, respectively. At the sloped field, the 137Cs and 210Pbex inventories values ranged from 110 Bq/m2 to 280 Bq/m2 and from 2026 Bq/m2 to 4110 Bq/m2, respectively. The net soil erosion determined for the sloped field were 9.6 t/ha/y and 7.2 t/ha/y for 137Cs and 210Pbex methods, respectively. In contrast, at the terraced field, the net soil erosion rates reached only 3.4 t/ha/y and 3.8 t/ha/y, respectively. The preliminary results of this research highlighted that terraced agricultural practice provides an efficient solution to protect soil resources of the Malagasy highlands.

  6. Effects of Spike Anticipation on the Spiking Dynamics of Neural Networks

    Directory of Open Access Journals (Sweden)

    Daniel ede Santos-Sierra

    2015-11-01

    Full Text Available Synchronization is one of the central phenomena involved in information processing in living systems. It is known that the nervous system requires the coordinated activity of both local and distant neural populations. Such an interplay allows to merge different information modalities in a whole processing supporting high-level mental skills as understanding, memory, abstraction, etc. Though the biological processes underlying synchronization in the brain are not fully understood there have been reported a variety of mechanisms supporting different types of synchronization both at theoretical and experimental level. One of the more intriguing of these phenomena is the anticipating synchronization, which has been recently reported in a pair of unidirectionally coupled artificial neurons under simple conditions cite{Pyragas}, where the slave neuron is able to anticipate in time the behaviour of the master one. In this paper we explore the effect of spike anticipation over the information processing performed by a neural network at functional and structural level. We show that the introduction of intermediary neurons in the network enhances spike anticipation and analyse how these variations in spike anticipation can significantly change the firing regime of the neural network according to its functional and structural properties. In addition we show that the interspike interval (ISI, one of the main features of the neural response associated to the information coding, can be closely related to spike anticipation by each spike, and how synaptic plasticity can be modulated through that relationship. This study has been performed through numerical simulation of a coupled system of Hindmarsh-Rose neurons.

  7. An Overview of Bayesian Methods for Neural Spike Train Analysis

    Directory of Open Access Journals (Sweden)

    Zhe Chen

    2013-01-01

    Full Text Available Neural spike train analysis is an important task in computational neuroscience which aims to understand neural mechanisms and gain insights into neural circuits. With the advancement of multielectrode recording and imaging technologies, it has become increasingly demanding to develop statistical tools for analyzing large neuronal ensemble spike activity. Here we present a tutorial overview of Bayesian methods and their representative applications in neural spike train analysis, at both single neuron and population levels. On the theoretical side, we focus on various approximate Bayesian inference techniques as applied to latent state and parameter estimation. On the application side, the topics include spike sorting, tuning curve estimation, neural encoding and decoding, deconvolution of spike trains from calcium imaging signals, and inference of neuronal functional connectivity and synchrony. Some research challenges and opportunities for neural spike train analysis are discussed.

  8. A new supervised learning algorithm for spiking neurons.

    Science.gov (United States)

    Xu, Yan; Zeng, Xiaoqin; Zhong, Shuiming

    2013-06-01

    The purpose of supervised learning with temporal encoding for spiking neurons is to make the neurons emit a specific spike train encoded by the precise firing times of spikes. If only running time is considered, the supervised learning for a spiking neuron is equivalent to distinguishing the times of desired output spikes and the other time during the running process of the neuron through adjusting synaptic weights, which can be regarded as a classification problem. Based on this idea, this letter proposes a new supervised learning method for spiking neurons with temporal encoding; it first transforms the supervised learning into a classification problem and then solves the problem by using the perceptron learning rule. The experiment results show that the proposed method has higher learning accuracy and efficiency over the existing learning methods, so it is more powerful for solving complex and real-time problems.

  9. Geomagnetic spikes on the core-mantle boundary

    Science.gov (United States)

    Davies, Christopher; Constable, Catherine

    2017-05-01

    Extreme variations of Earth's magnetic field occurred in the Levant region around 1000 BC, when the field intensity rapidly rose and fell by a factor of 2. No coherent link currently exists between this intensity spike and the global field produced by the core geodynamo. Here we show that the Levantine spike must span >60° longitude at Earth's surface if it originates from the core-mantle boundary (CMB). Several low intensity data are incompatible with this geometric bound, though age uncertainties suggest these data could have sampled the field before the spike emerged. Models that best satisfy energetic and geometric constraints produce CMB spikes 8-22° wide, peaking at O(100) mT. We suggest that the Levantine spike reflects an intense CMB flux patch that grew in place before migrating northwest, contributing to growth of the dipole field. Estimates of Ohmic heating suggest that diffusive processes likely govern the ultimate decay of geomagnetic spikes.

  10. Cytoplasmic tail of coronavirus spike protein has intracellular targeting signals

    Indian Academy of Sciences (India)

    JIBIN SADASIVAN; MANMEET SINGH; JAYASRI DAS SARMA

    2017-06-01

    Intracellular trafficking and localization studies of spike protein from SARS and OC43 showed that SARS spikeprotein is localized in the ER or ERGIC compartment and OC43 spike protein is predominantly localized in thelysosome. Differential localization can be explained by signal sequence. The sequence alignment using Clustal Wshows that the signal sequence present at the cytoplasmic tail plays an important role in spike protein localization. Aunique GYQEL motif is identified at the cytoplasmic terminal of OC43 spike protein which helps in localization in thelysosome, and a novel KLHYT motif is identified in the cytoplasmic tail of SARS spike protein which helps in ER orERGIC localization. This study sheds some light on the role of cytoplasmic tail of spike protein in cell-to-cell fusion,coronavirus host cell fusion and subsequent pathogenicity.

  11. Stochastic optimal control of single neuron spike trains

    DEFF Research Database (Denmark)

    Iolov, Alexandre; Ditlevsen, Susanne; Longtin, Andrë

    2014-01-01

    Objective. External control of spike times in single neurons can reveal important information about a neuron's sub-threshold dynamics that lead to spiking, and has the potential to improve brain–machine interfaces and neural prostheses. The goal of this paper is the design of optimal electrical...... stimulation of a neuron to achieve a target spike train under the physiological constraint to not damage tissue. Approach. We pose a stochastic optimal control problem to precisely specify the spike times in a leaky integrate-and-fire (LIF) model of a neuron with noise assumed to be of intrinsic or synaptic...... to the spike times (open-loop control). Main results. We have developed a stochastic optimal control algorithm to obtain precise spike times. It is applicable in both the supra-threshold and sub-threshold regimes, under open-loop and closed-loop conditions and with an arbitrary noise intensity; the accuracy...

  12. The local field potential reflects surplus spike synchrony

    DEFF Research Database (Denmark)

    Denker, Michael; Roux, Sébastien; Lindén, Henrik;

    2011-01-01

    While oscillations of the local field potential (LFP) are commonly attributed to the synchronization of neuronal firing rate on the same time scale, their relationship to coincident spiking in the millisecond range is unknown. Here, we present experimental evidence to reconcile the notions...... of synchrony at the level of spiking and at the mesoscopic scale. We demonstrate that only in time intervals of significant spike synchrony that cannot be explained on the basis of firing rates, coincident spikes are better phase locked to the LFP than predicted by the locking of the individual spikes....... This effect is enhanced in periods of large LFP amplitudes. A quantitative model explains the LFP dynamics by the orchestrated spiking activity in neuronal groups that contribute the observed surplus synchrony. From the correlation analysis, we infer that neurons participate in different constellations...

  13. A spiking neuron circuit based on a carbon nanotube transistor.

    Science.gov (United States)

    Chen, C-L; Kim, K; Truong, Q; Shen, A; Li, Z; Chen, Y

    2012-07-11

    A spiking neuron circuit based on a carbon nanotube (CNT) transistor is presented in this paper. The spiking neuron circuit has a crossbar architecture in which the transistor gates are connected to its row electrodes and the transistor sources are connected to its column electrodes. An electrochemical cell is incorporated in the gate of the transistor by sandwiching a hydrogen-doped poly(ethylene glycol)methyl ether (PEG) electrolyte between the CNT channel and the top gate electrode. An input spike applied to the gate triggers a dynamic drift of the hydrogen ions in the PEG electrolyte, resulting in a post-synaptic current (PSC) through the CNT channel. Spikes input into the rows trigger PSCs through multiple CNT transistors, and PSCs cumulate in the columns and integrate into a 'soma' circuit to trigger output spikes based on an integrate-and-fire mechanism. The spiking neuron circuit can potentially emulate biological neuron networks and their intelligent functions.

  14. Combined soil washing and CDEO for the removal of atrazine from soils

    OpenAIRE

    Vieira Santos, Elisama; Saez, C.; Martínez-Huitle, Carlos A.; Cañizares Cañizares, Pablo; Rodrigo Rodrigo, Manuel Andrés

    2015-01-01

    In this work, it is studied the removal of atrazine from spiked soils by soil washing using surfactant fluids, followed by the treatment of the resulting washing waste by electrolysis with boron doped diamond anode. Results confirm that combination of both technologies is efficient for the removal and total mineralization of atrazine. Ratio surfactant/soil is a key parameter for the removal of atrazine from soil and influences significantly in the characteristic of the wastewater produced, af...

  15. Estimating nonstationary input signals from a single neuronal spike train

    OpenAIRE

    Kim, Hideaki; Shinomoto, Shigeru

    2012-01-01

    Neurons temporally integrate input signals, translating them into timed output spikes. Because neurons nonperiodically emit spikes, examining spike timing can reveal information about input signals, which are determined by activities in the populations of excitatory and inhibitory presynaptic neurons. Although a number of mathematical methods have been developed to estimate such input parameters as the mean and fluctuation of the input current, these techniques are based on the unrealistic as...

  16. The Role of Spike Temporal Latencies in Artificial Olfaction

    Science.gov (United States)

    Polese, D.; Martinelli, E.; Dini, F.; Paolesse, R.; Filippini, D.; Lundström, I.; Di Natale, C.

    2011-09-01

    In this paper we investigate the recognition power of spike time latencies in an artificial olfactory system. For the scope we used a recently introduced platform for artificial olfaction implementing an artificial olfactory epithelium, formed by thousands sensors, and an abstract olfactory bulb1. Results show that correct volatile compounds classification can be achieved considering only the first two spikes of the neural network output evidencing that the latency of the first spikes contains actually enough information for odor identification.

  17. Finding the event structure of neuronal spike trains.

    Science.gov (United States)

    Toups, J Vincent; Fellous, Jean-Marc; Thomas, Peter J; Sejnowski, Terrence J; Tiesinga, Paul H

    2011-09-01

    Neurons in sensory systems convey information about physical stimuli in their spike trains. In vitro, single neurons respond precisely and reliably to the repeated injection of the same fluctuating current, producing regions of elevated firing rate, termed events. Analysis of these spike trains reveals that multiple distinct spike patterns can be identified as trial-to-trial correlations between spike times (Fellous, Tiesinga, Thomas, & Sejnowski, 2004 ). Finding events in data with realistic spiking statistics is challenging because events belonging to different spike patterns may overlap. We propose a method for finding spiking events that uses contextual information to disambiguate which pattern a trial belongs to. The procedure can be applied to spike trains of the same neuron across multiple trials to detect and separate responses obtained during different brain states. The procedure can also be applied to spike trains from multiple simultaneously recorded neurons in order to identify volleys of near-synchronous activity or to distinguish between excitatory and inhibitory neurons. The procedure was tested using artificial data as well as recordings in vitro in response to fluctuating current waveforms.

  18. Spike Inference from Calcium Imaging using Sequential Monte Carlo Methods

    OpenAIRE

    NeuroData; Paninski, L

    2015-01-01

    Vogelstein JT, Paninski L. Spike Inference from Calcium Imaging using Sequential Monte Carlo Methods. Statistical and Applied Mathematical Sciences Institute (SAMSI) Program on Sequential Monte Carlo Methods, 2008

  19. Solving Constraint Satisfaction Problems with Networks of Spiking Neurons.

    Science.gov (United States)

    Jonke, Zeno; Habenschuss, Stefan; Maass, Wolfgang

    2016-01-01

    Network of neurons in the brain apply-unlike processors in our current generation of computer hardware-an event-based processing strategy, where short pulses (spikes) are emitted sparsely by neurons to signal the occurrence of an event at a particular point in time. Such spike-based computations promise to be substantially more power-efficient than traditional clocked processing schemes. However, it turns out to be surprisingly difficult to design networks of spiking neurons that can solve difficult computational problems on the level of single spikes, rather than rates of spikes. We present here a new method for designing networks of spiking neurons via an energy function. Furthermore, we show how the energy function of a network of stochastically firing neurons can be shaped in a transparent manner by composing the networks of simple stereotypical network motifs. We show that this design approach enables networks of spiking neurons to produce approximate solutions to difficult (NP-hard) constraint satisfaction problems from the domains of planning/optimization and verification/logical inference. The resulting networks employ noise as a computational resource. Nevertheless, the timing of spikes plays an essential role in their computations. Furthermore, networks of spiking neurons carry out for the Traveling Salesman Problem a more efficient stochastic search for good solutions compared with stochastic artificial neural networks (Boltzmann machines) and Gibbs sampling.

  20. A VLSI array of low-power spiking neurons and bistable synapses with spike-timing dependent plasticity.

    Science.gov (United States)

    Indiveri, Giacomo; Chicca, Elisabetta; Douglas, Rodney

    2006-01-01

    We present a mixed-mode analog/digital VLSI device comprising an array of leaky integrate-and-fire (I&F) neurons, adaptive synapses with spike-timing dependent plasticity, and an asynchronous event based communication infrastructure that allows the user to (re)configure networks of spiking neurons with arbitrary topologies. The asynchronous communication protocol used by the silicon neurons to transmit spikes (events) off-chip and the silicon synapses to receive spikes from the outside is based on the "address-event representation" (AER). We describe the analog circuits designed to implement the silicon neurons and synapses and present experimental data showing the neuron's response properties and the synapses characteristics, in response to AER input spike trains. Our results indicate that these circuits can be used in massively parallel VLSI networks of I&F neurons to simulate real-time complex spike-based learning algorithms.

  1. Persistence of glyphosate and aminomethylphosphonic acid in loess soil under different combinations of temperature, soil moisture and light/darkness

    NARCIS (Netherlands)

    Martins Bento, Celia; Yang, Xiaomei; Gort, Gerrit; Xue, Sha; Dam, van Ruud; Zomer, Paul; Mol, Hans G.J.; Ritsema, Coen J.; Geissen, Violette

    2016-01-01

    The dissipation kinetics of glyphosate and its metabolite aminomethylphosphonic acid (AMPA) were studied in loess soil, under biotic and abiotic conditions, as affected by temperature, soil moisture (SM) and light/darkness. Nonsterile and sterile soil samples were spiked with 16 mg kg− 1

  2. Persistence of glyphosate and aminomethylphosphonic acid in loess soil under different combinations of temperature, soil moisture and light/darkness

    NARCIS (Netherlands)

    Martins Bento, Celia; Yang, Xiaomei; Gort, Gerrit; Xue, Sha; Dam, van Ruud; Zomer, Paul; Mol, Hans G.J.; Ritsema, Coen J.; Geissen, Violette

    2016-01-01

    The dissipation kinetics of glyphosate and its metabolite aminomethylphosphonic acid (AMPA) were studied in loess soil, under biotic and abiotic conditions, as affected by temperature, soil moisture (SM) and light/darkness. Nonsterile and sterile soil samples were spiked with 16 mg kg− 1

  3. Self-control with spiking and non-spiking neural networks playing games.

    Science.gov (United States)

    Christodoulou, Chris; Banfield, Gaye; Cleanthous, Aristodemos

    2010-01-01

    Self-control can be defined as choosing a large delayed reward over a small immediate reward, while precommitment is the making of a choice with the specific aim of denying oneself future choices. Humans recognise that they have self-control problems and attempt to overcome them by applying precommitment. Problems in exercising self-control, suggest a conflict between cognition and motivation, which has been linked to competition between higher and lower brain functions (representing the frontal lobes and the limbic system respectively). This premise of an internal process conflict, lead to a behavioural model being proposed, based on which, we implemented a computational model for studying and explaining self-control through precommitment behaviour. Our model consists of two neural networks, initially non-spiking and then spiking ones, representing the higher and lower brain systems viewed as cooperating for the benefit of the organism. The non-spiking neural networks are of simple feed forward multilayer type with reinforcement learning, one with selective bootstrap weight update rule, which is seen as myopic, representing the lower brain and the other with the temporal difference weight update rule, which is seen as far-sighted, representing the higher brain. The spiking neural networks are implemented with leaky integrate-and-fire neurons with learning based on stochastic synaptic transmission. The differentiating element between the two brain centres in this implementation is based on the memory of past actions determined by an eligibility trace time constant. As the structure of the self-control problem can be likened to the Iterated Prisoner's Dilemma (IPD) game in that cooperation is to defection what self-control is to impulsiveness or what compromising is to insisting, we implemented the neural networks as two players, learning simultaneously but independently, competing in the IPD game. With a technique resembling the precommitment effect, whereby the

  4. Presynaptic spike broadening reduces junctional potential amplitude.

    Science.gov (United States)

    Spencer, A N; Przysiezniak, J; Acosta-Urquidi, J; Basarsky, T A

    1989-08-24

    Presynaptic modulation of action potential duration may regulate synaptic transmission in both vertebrates and invertebrates. Such synaptic plasticity is brought about by modifications to membrane currents at presynaptic release sites, which, in turn, lead to changes in the concentration of cytosolic calcium available for mediating transmitter release. The 'primitive' neuromuscular junction of the jellyfish Polyorchis penicillatus is a useful model of presynaptic modulation. In this study, we show that the durations of action potentials in the motor neurons of this jellyfish are negatively correlated with the amplitude of excitatory junctional potentials. We present data from in vitro voltage-clamp experiments showing that short duration voltage spikes, which elicit large excitatory junctional potentials in vivo, produce larger and briefer calcium currents than do long duration action potentials, which elicit small excitatory junctional potentials.

  5. A Spiking Neural Learning Classifier System

    CERN Document Server

    Howard, Gerard; Lanzi, Pier-Luca

    2012-01-01

    Learning Classifier Systems (LCS) are population-based reinforcement learners used in a wide variety of applications. This paper presents a LCS where each traditional rule is represented by a spiking neural network, a type of network with dynamic internal state. We employ a constructivist model of growth of both neurons and dendrites that realise flexible learning by evolving structures of sufficient complexity to solve a well-known problem involving continuous, real-valued inputs. Additionally, we extend the system to enable temporal state decomposition. By allowing our LCS to chain together sequences of heterogeneous actions into macro-actions, it is shown to perform optimally in a problem where traditional methods can fail to find a solution in a reasonable amount of time. Our final system is tested on a simulated robotics platform.

  6. [Wide QRS tachycardia preceded by pacemaker spikes].

    Science.gov (United States)

    Romero, M; Aranda, A; Gómez, F J; Jurado, A

    2014-04-01

    The differential diagnosis and therapeutic management of wide QRS tachycardia preceded by pacemaker spike is presented. The pacemaker-mediated tachycardia, tachycardia fibrillo-flutter in patients with pacemakers, and runaway pacemakers, have a similar surface electrocardiogram, but respond to different therapeutic measures. The tachycardia response to the application of a magnet over the pacemaker could help in the differential diagnosis, and in some cases will be therapeutic, as in the case of a tachycardia-mediated pacemaker. Although these conditions are diagnosed and treated in hospitals with catheterization laboratories using the application programmer over the pacemaker, patients presenting in primary care clinic and emergency forced us to make a diagnosis and treat the haemodynamically unstable patient prior to referral. Copyright © 2012 Sociedad Española de Médicos de Atención Primaria (SEMERGEN). Publicado por Elsevier España. All rights reserved.

  7. A novel spatiotemporal analysis of peri-ictal spiking to probe the relation of spikes and seizures in epilepsy.

    Science.gov (United States)

    Krishnan, Balu; Vlachos, Ioannis; Faith, Aaron; Mullane, Steven; Williams, Korwyn; Alexopoulos, Andreas; Iasemidis, Leonidas

    2014-08-01

    The relation between epileptic spikes and seizures is an important but still unresolved question in epilepsy research. Preclinical and clinical studies have produced inconclusive results on the causality or even on the existence of such a relation. We set to investigate this relation taking in consideration seizure severity and spatial extent of spike rate. We developed a novel automated spike detection algorithm based on morphological filtering techniques and then tested the hypothesis that there is a pre-ictal increase and post-ictal decrease of the spatial extent of spike rate. Peri-ictal (around seizures) spikes were detected from intracranial EEG recordings in 5 patients with temporal lobe epilepsy. The 94 recorded seizures were classified into two classes, based on the percentage of brain sites having higher or lower rate of spikes in the pre-ictal compared to post-ictal periods, with a classification accuracy of 87.4%. This seizure classification showed that seizures with increased pre-ictal spike rate and spatial extent compared to the post-ictal period were mostly (83%) clinical seizures, whereas no such statistically significant (α = 0.05) increase was observed peri-ictally in 93% of sub-clinical seizures. These consistent across patients results show the existence of a causal relation between spikes and clinical seizures, and imply resetting of the preceding spiking process by clinical seizures.

  8. Assessment of arsenic toxicity in spiked soils and water solutions by the use of bioassays Evaluación de la toxicidad del arsénico en suelos y soluciones contaminadas mediante el uso de bioensayos Avaliação da toxicidade de arsénio em solos contaminados e em soluções aquosas com recurso a bioensaioS

    Directory of Open Access Journals (Sweden)

    Francisco José Martín Peinado

    2012-11-01

    Full Text Available Arsenic (As has become a serious environmental problem due to its extensive use and its potential high toxicity. Furthermore, it tends to accumulate in soils because of its low mobility in this medium. In this study, an assessment of potential As toxicity based on bioassays with Vibrio fischeri and Lactuca sativa was made in soil and water solutions of laboratory-contaminated samples. Soils spiked with 100 ppm of arsenic registered a reduction in As solubility in the soil solution over time, while for the longest incubation periods (8 weeks, the toxicity responses in all of the samples proved negligible for these bioassays. In spiked water solutions with increasing concentrations (0, 0.1, 1, 10, 12.5, 25, 50, and100 ppm As, significant reductions in root elongation and luminescence were found in lettuce and bacteria bioassays, respectively. The effective concentrations (EC50 of As were 1.52 ppm for L. sativa and 4.98 ppm for V. fischeri; this indicated that the L. sativa bioassay was more sensitive to arsenic concentrations in spiked solutions.El arsénico es un elemento que causa serios problemas medioambientales debido a su uso extensivo y a su alta toxicidad, tendiendo a acumularse en suelos debido a su baja movilidad en este medio. En este estudio realizamos la evaluación de la toxicidad potencial de arsénico a partir de bioensayos con Vibrio fischeri y Lactuca sativa en suelos y soluciones acuosas contaminados en laboratorio. Los suelos contaminados con 100 mg kg-1 de arsénico registraron una fuerte reducción de la solubilidad de este contaminante con el tiempo, obteniéndose una respuesta a la toxicidad prácticamente nula a las ocho semanas de incubación. En las soluciones acuosas contaminadas con concentraciones crecientes de arsénico (0, 0,1, 1, 10, 12,5, 25, 50 y 100 ppm As se produjo una reducción significativa en la elongación de raíces y en la luminiscencia en los bioensayos con lechuga y bacterias, respectivamente. La

  9. Neuronal spike sorting based on radial basis function neural networks

    Directory of Open Access Journals (Sweden)

    Taghavi Kani M

    2011-02-01

    Full Text Available "nBackground: Studying the behavior of a society of neurons, extracting the communication mechanisms of brain with other tissues, finding treatment for some nervous system diseases and designing neuroprosthetic devices, require an algorithm to sort neuralspikes automatically. However, sorting neural spikes is a challenging task because of the low signal to noise ratio (SNR of the spikes. The main purpose of this study was to design an automatic algorithm for classifying neuronal spikes that are emitted from a specific region of the nervous system."n "nMethods: The spike sorting process usually consists of three stages: detection, feature extraction and sorting. We initially used signal statistics to detect neural spikes. Then, we chose a limited number of typical spikes as features and finally used them to train a radial basis function (RBF neural network to sort the spikes. In most spike sorting devices, these signals are not linearly discriminative. In order to solve this problem, the aforesaid RBF neural network was used."n "nResults: After the learning process, our proposed algorithm classified any arbitrary spike. The obtained results showed that even though the proposed Radial Basis Spike Sorter (RBSS reached to the same error as the previous methods, however, the computational costs were much lower compared to other algorithms. Moreover, the competitive points of the proposed algorithm were its good speed and low computational complexity."n "nConclusion: Regarding the results of this study, the proposed algorithm seems to serve the purpose of procedures that require real-time processing and spike sorting.

  10. Spike sorting for polytrodes: a divide and conquer approach

    Directory of Open Access Journals (Sweden)

    Nicholas V. Swindale

    2014-02-01

    Full Text Available In order to determine patterns of neural activity, spike signals recorded by extracellular electrodes have to be clustered (sorted with the aim of ensuring that each cluster represents all the spikes generated by an individual neuron. Many methods for spike sorting have been proposed but few are easily applicable to recordings from polytrodes which may have 16 or more recording sites. As with tetrodes, these are spaced sufficiently closely that signals from single neurons will usually be recorded on several adjacent sites. Although this offers a better chance of distinguishing neurons with similarly shaped spikes, sorting is difficult in such cases because of the high dimensionality of the space in which the signals must be classified. This report details a method for spike sorting based on a divide and conquer approach. Clusters are initially formed by assigning each event to the channel on which it is largest. Each channel-based cluster is then sub-divided into as many distinct clusters as possible. These are then recombined on the basis of pairwise tests into a final set of clusters. Pairwise tests are also performed to establish how distinct each cluster is from the others. A modified gradient ascent clustering (GAC algorithm is used to do the clustering. The method can sort spikes with minimal user input in times comparable to real time for recordings lasting up to 45 minutes. Our results illustrate some of the difficulties inherent in spike sorting, including changes in spike shape over time. We show that some physiologically distinct units may have very similar spike shapes. We show that RMS measures of spike shape similarity are not sensitive enough to discriminate clusters that can otherwise be separated by principal components analysis. Hence spike sorting based on least-squares matching to templates may be unreliable. Our methods should be applicable to tetrodes and scaleable to larger multi-electrode arrays (MEAs.

  11. Clustering predicts memory performance in networks of spiking and non-spiking neurons

    Directory of Open Access Journals (Sweden)

    Weiliang eChen

    2011-03-01

    Full Text Available The problem we address in this paper is that of finding effective and parsimonious patterns of connectivity in sparse associative memories. This problem must be addressed in real neuronal systems, so that results in artificial systems could throw light on real systems. We show that there are efficient patterns of connectivity and that these patterns are effective in models with either spiking or non-spiking neurons. This suggests that there may be some underlying general principles governing good connectivity in such networks. We also show that the clustering of the network, measured by Clustering Coefficient, has a strong linear correlation to the performance of associative memory. This result is important since a purely static measure of network connectivity appears to determine an important dynamic property of the network.

  12. Reading spike timing without a clock: intrinsic decoding of spike trains.

    Science.gov (United States)

    Panzeri, Stefano; Ince, Robin A A; Diamond, Mathew E; Kayser, Christoph

    2014-03-05

    The precise timing of action potentials of sensory neurons relative to the time of stimulus presentation carries substantial sensory information that is lost or degraded when these responses are summed over longer time windows. However, it is unclear whether and how downstream networks can access information in precise time-varying neural responses. Here, we review approaches to test the hypothesis that the activity of neural populations provides the temporal reference frames needed to decode temporal spike patterns. These approaches are based on comparing the single-trial stimulus discriminability obtained from neural codes defined with respect to network-intrinsic reference frames to the discriminability obtained from codes defined relative to the experimenter's computer clock. Application of this formalism to auditory, visual and somatosensory data shows that information carried by millisecond-scale spike times can be decoded robustly even with little or no independent external knowledge of stimulus time. In cortex, key components of such intrinsic temporal reference frames include dedicated neural populations that signal stimulus onset with reliable and precise latencies, and low-frequency oscillations that can serve as reference for partitioning extended neuronal responses into informative spike patterns.

  13. Parvalbumin tunes spike-timing and efferent short-term plasticity in striatal fast spiking interneurons.

    Science.gov (United States)

    Orduz, David; Bischop, Don Patrick; Schwaller, Beat; Schiffmann, Serge N; Gall, David

    2013-07-01

      Striatal fast spiking interneurons (FSIs) modulate output of the striatum by synchronizing medium-sized spiny neurons (MSNs). Recent studies have broadened our understanding of FSIs, showing that they are implicated in severe motor disorders such as parkinsonism, dystonia and Tourette syndrome. FSIs are the only striatal neurons to express the calcium-binding protein parvalbumin (PV). This selective expression of PV raises questions about the functional role of this Ca(2+) buffer in controlling FSI Ca(2+) dynamics and, consequently, FSI spiking mode and neurotransmission. To study the functional involvement of FSIs in striatal microcircuit activity and the role of PV in FSI function, we performed perforated patch recordings on enhanced green fluorescent protein-expressing FSIs in brain slices from control and PV-/- mice. Our results revealed that PV-/- FSIs fired more regularly and were more excitable than control FSIs by a mechanism in which Ca(2+) buffering is linked to spiking activity as a result of the activation of small conductance Ca(2+)-dependent K(+) channels. A modelling approach of striatal FSIs supports our experimental results. Furthermore, PV deletion modified frequency-specific short-term plasticity at inhibitory FSI to MSN synapses. Our results therefore reinforce the hypothesis that in FSIs, PV is crucial for fine-tuning of the temporal responses of the FSI network and for the orchestration of MSN populations. This, in turn, may play a direct role in the generation and pathology-related worsening of motor rhythms.

  14. Spike Sorting by Joint Probabilistic Modeling of Neural Spike Trains and Waveforms

    Science.gov (United States)

    Matthews, Brett A.; Clements, Mark A.

    2014-01-01

    This paper details a novel probabilistic method for automatic neural spike sorting which uses stochastic point process models of neural spike trains and parameterized action potential waveforms. A novel likelihood model for observed firing times as the aggregation of hidden neural spike trains is derived, as well as an iterative procedure for clustering the data and finding the parameters that maximize the likelihood. The method is executed and evaluated on both a fully labeled semiartificial dataset and a partially labeled real dataset of extracellular electric traces from rat hippocampus. In conditions of relatively high difficulty (i.e., with additive noise and with similar action potential waveform shapes for distinct neurons) the method achieves significant improvements in clustering performance over a baseline waveform-only Gaussian mixture model (GMM) clustering on the semiartificial set (1.98% reduction in error rate) and outperforms both the GMM and a state-of-the-art method on the real dataset (5.04% reduction in false positive + false negative errors). Finally, an empirical study of two free parameters for our method is performed on the semiartificial dataset. PMID:24829568

  15. Reliability of spike and burst firing in thalamocortical relay cells

    NARCIS (Netherlands)

    Zeldenrust, F.; Chameau, P.J.P.; Wadman, W.J.

    2013-01-01

    The reliability and precision of the timing of spikes in a spike train is an important aspect of neuronal coding. We investigated reliability in thalamocortical relay (TCR) cells in the acute slice and also in a Morris-Lecar model with several extensions. A frozen Gaussian noise current, superimpose

  16. A new class of metrics for spike trains.

    Science.gov (United States)

    Rusu, Cătălin V; Florian, Răzvan V

    2014-02-01

    The distance between a pair of spike trains, quantifying the differences between them, can be measured using various metrics. Here we introduce a new class of spike train metrics, inspired by the Pompeiu-Hausdorff distance, and compare them with existing metrics. Some of our new metrics (the modulus-metric and the max-metric) have characteristics that are qualitatively different from those of classical metrics like the van Rossum distance or the Victor and Purpura distance. The modulus-metric and the max-metric are particularly suitable for measuring distances between spike trains where information is encoded in bursts, but the number and the timing of spikes inside a burst do not carry information. The modulus-metric does not depend on any parameters and can be computed using a fast algorithm whose time depends linearly on the number of spikes in the two spike trains. We also introduce localized versions of the new metrics, which could have the biologically relevant interpretation of measuring the differences between spike trains as they are perceived at a particular moment in time by a neuron receiving these spike trains.

  17. No WIMP mini-spikes in dwarf spheroidal galaxies

    NARCIS (Netherlands)

    Wanders, M.; Bertone, G.; Volonteri, M.; Weniger, C.

    2015-01-01

    The formation of black holes inevitably affects the distribution of dark and baryonic matter in their vicinity, leading to an enhancement of the dark matter density, called spike, and if dark matter is made of WIMPs, to a strong enhancement of the dark matter annihilation rate. Spikes at the center

  18. Spectral components of cytosolic [Ca2+] spiking in neurons

    DEFF Research Database (Denmark)

    Kardos, J; Szilágyi, N; Juhász, G

    1998-01-01

    . Delayed complex responses of large [Ca2+]c spiking observed in cells from a different set of cultures were synthesized by a set of frequencies within the range 0.018-0.117 Hz. Differential frequency patterns are suggested as characteristics of the [Ca2+]c spiking responses of neurons under different...

  19. Spike wave location and density disturb sleep slow waves in patients with CSWS (continuous spike waves during sleep).

    Science.gov (United States)

    Bölsterli Heinzle, Bigna K; Fattinger, Sara; Kurth, Salomé; Lebourgeois, Monique K; Ringli, Maya; Bast, Thomas; Critelli, Hanne; Schmitt, Bernhard; Huber, Reto

    2014-04-01

    In CSWS (continuous spike waves during sleep) activation of spike waves during slow wave sleep has been causally linked to neuropsychological deficits, but the pathophysiologic mechanisms are still unknown. In healthy subjects, the overnight decrease of the slope of slow waves in NREM (non-rapid eye movement) sleep has been linked to brain recovery to regain optimal cognitive performance. Here, we investigated whether the electrophysiologic hallmark of CSWS, the spike waves during sleep, is related to an alteration in the overnight decrease of the slope, and if this alteration is linked to location and density of spike waves. In a retrospective study, the slope of slow waves (0.5-2 Hz) in the first hour and last hour of sleep (19 electroencephalography [EEG] electrodes) of 14 patients with CSWS (3.1-13.5 years) was calculated. The spike wave "focus" was determined as the location of highest spike amplitude and the density of spike waves as spike wave index (SWI). There was no overnight change of the slope of slow waves in the "focus." Instead, in "nonfocal" regions, the slope decreased significantly. This difference in the overnight course resulted in a steeper slope in the "focus" compared to "nonfocal" electrodes during the last hour of sleep. Spike wave density was correlated with the impairment of the overnight slope decrease: The higher the SWI, the more hampered the slope decrease. Location and density of spike waves are related to an alteration of the physiologic overnight decrease of the slow wave slope. This overnight decrease of the slope was shown to be closely related to the recovery function of sleep. Such recovery is necessary for optimal cognitive performance during wakefulness. Therefore we propose the impairment of this process by spike waves as a potential mechanism leading to neuropsychological deficits in CSWS. A PowerPoint slide summarizing this article is available for download in the Supporting Information section here. Wiley Periodicals

  20. Reliability of SEMG spike parameters during concentric contractions.

    Science.gov (United States)

    Gabriel, D A

    2000-01-01

    This study examined the reliability of four surface electromyographic (SEMG) spike parameters during concentric (isotonic) contractions: mean spike amplitude, mean spike frequency, mean spike slope, and the mean number of peaks per spike. Eighteen subjects performed rapid elbow flexion on a horizontal angular displacement device that was used to measure joint torque. The SEMG activity of the biceps brachii was monitored with Beckman Ag/AgCl electrodes. The testing schedule consisted of four hundred trials distributed equally over four sessions. The stability of the means across sessions and the consistency of scores within subjects was determined for the first five (1-5) and last five (96-100) trials of each session to examine the possible influence of a "warm up" effect. All measures exhibited a significant (p contractions enhanced the ability to recruit more fast-twitch motor units across test days.

  1. Wicket spikes: clinical correlates of a previously undescribed EEG pattern.

    Science.gov (United States)

    Reiher, J; Lebel, M

    1977-02-01

    From an analysis of the electroencephalograms of 4,458 patients who underwent recording during both wakefulness ans sleep, through the years 1969 to 1975, wicket spikes-- recorded in 39 patients-- may be described as follows: They were found during both wakefulness ans sleep, almost exclusively in adults. Their cardinal feature is a changing mode of occurrence through any single recording: from intermittent trains of more or less sustained, arciform, discharges resembling mu rhythm, to sporadic, urinary, single spikes. When occurring singly, wicket spikes can be mistaken for anterior or middle temporal spikes, since they predominate in eith er area, and since they share with them other characteristics such as amplitude (60 to 210 microvolts), polarity (surface negative) duration, and configuration. Wicket spikes should not be considered interictal abnormalities; they do nor correlate with epilepsy or with any particular symptom complex.

  2. Stochastic optimal control of single neuron spike trains

    DEFF Research Database (Denmark)

    Iolov, Alexandre; Ditlevsen, Susanne; Longtin, Andrë

    2014-01-01

    Objective. External control of spike times in single neurons can reveal important information about a neuron's sub-threshold dynamics that lead to spiking, and has the potential to improve brain–machine interfaces and neural prostheses. The goal of this paper is the design of optimal electrical...... stimulation of a neuron to achieve a target spike train under the physiological constraint to not damage tissue. Approach. We pose a stochastic optimal control problem to precisely specify the spike times in a leaky integrate-and-fire (LIF) model of a neuron with noise assumed to be of intrinsic or synaptic...... of control degrades with increasing intensity of the noise. Simulations show that our algorithms produce the desired results for the LIF model, but also for the case where the neuron dynamics are given by more complex models than the LIF model. This is illustrated explicitly using the Morris–Lecar spiking...

  3. Unsupervised Spike Sorting Based on Discriminative Subspace Learning

    CERN Document Server

    Keshtkaran, Mohammad Reza

    2014-01-01

    Spike sorting is a fundamental preprocessing step for many neuroscience studies which rely on the analysis of spike trains. In this paper, we present two unsupervised spike sorting algorithms based on discriminative subspace learning. The first algorithm simultaneously learns the discriminative feature subspace and performs clustering. It uses histogram of features in the most discriminative projection to detect the number of neurons. The second algorithm performs hierarchical divisive clustering that learns a discriminative 1-dimensional subspace for clustering in each level of the hierarchy until achieving almost unimodal distribution in the subspace. The algorithms are tested on synthetic and in-vivo data, and are compared against two widely used spike sorting methods. The comparative results demonstrate that our spike sorting methods can achieve substantially higher accuracy in lower dimensional feature space, and they are highly robust to noise. Moreover, they provide significantly better cluster separab...

  4. Gamma Oscillations of Spiking Neural Populations Enhance Signal Discrimination

    Science.gov (United States)

    Masuda, Naoki; Doiron, Brent

    2007-01-01

    Selective attention is an important filter for complex environments where distractions compete with signals. Attention increases both the gamma-band power of cortical local field potentials and the spike-field coherence within the receptive field of an attended object. However, the mechanisms by which gamma-band activity enhances, if at all, the encoding of input signals are not well understood. We propose that gamma oscillations induce binomial-like spike-count statistics across noisy neural populations. Using simplified models of spiking neurons, we show how the discrimination of static signals based on the population spike-count response is improved with gamma induced binomial statistics. These results give an important mechanistic link between the neural correlates of attention and the discrimination tasks where attention is known to enhance performance. Further, they show how a rhythmicity of spike responses can enhance coding schemes that are not temporally sensitive. PMID:18052541

  5. Gamma oscillations of spiking neural populations enhance signal discrimination.

    Directory of Open Access Journals (Sweden)

    Naoki Masuda

    2007-11-01

    Full Text Available Selective attention is an important filter for complex environments where distractions compete with signals. Attention increases both the gamma-band power of cortical local field potentials and the spike-field coherence within the receptive field of an attended object. However, the mechanisms by which gamma-band activity enhances, if at all, the encoding of input signals are not well understood. We propose that gamma oscillations induce binomial-like spike-count statistics across noisy neural populations. Using simplified models of spiking neurons, we show how the discrimination of static signals based on the population spike-count response is improved with gamma induced binomial statistics. These results give an important mechanistic link between the neural correlates of attention and the discrimination tasks where attention is known to enhance performance. Further, they show how a rhythmicity of spike responses can enhance coding schemes that are not temporally sensitive.

  6. Property Analysis and Suppression Method of Real Measured Sea Spikes

    Directory of Open Access Journals (Sweden)

    Huang Yong

    2015-06-01

    Full Text Available In case of high-resolution, low grazing angle, high sea state, and horizontal transmitting, horizontal receiving polarization, the radar returns are strengthened, resulting in sea spikes. The sea spikes have the characteristics of high amplitudes, nonstationary, and non-Gaussian, which have a strong impact on the radar detection of weak marine moving targets. This study proposes a method for sea clutter suppression. Firstly, based on the sea spikes identification and selection method, the amplitude, temporal correlation, Doppler spectrum, and fractional power spectrum properties of sea spikes are analyzed. Secondly, the data to be detected are chosen by selecting the background clutter with minimum mean power, which can also eliminate the sea spikes. Correspondingly, sea clutter is suppressed with improved Signal-to-Clutter Ratio (SCR. Finally, the results of experiment with real radar data verify the effectiveness of the proposed method.

  7. Effect of Soil Aging on the Phytoremediation Potential of Zea mays in Chromium and Benzo[a]Pyrene Contaminated Soils.

    Science.gov (United States)

    Chigbo, Chibuike

    2015-06-01

    This study compared the phytoremediation potential of Zea mays in soil either aged or freshly amended with chromium (Cr) and benzo[a]pyrene (B[a]P). Z. mays showed increased shoot biomass in aged soils than in freshly spiked soils. The shoot biomass in contaminated soils increased by over 50% in aged soil when compared to freshly amended soils, and over 29% more Cr was accumulated in the shoot of Z. mays in aged soil than in freshly amended soil. Planting Z. mays in aged soil helped in the dissipation of more than 31% B[a]P than in freshly spiked soil, but in the absence of plants, there seemed to be no difference between the dissipation rates of B[a]P in freshly and aged co-contaminated soil. Z. mays seemed to enhance the simultaneous removal of Cr and B[a]P in aged soil than in freshly spiked soil and hence can be a good plant choice for phytoremediation of co-contaminated soils.

  8. Limits of spiked random matrices II

    CERN Document Server

    Bloemendal, Alex

    2011-01-01

    The top eigenvalues of rank r spiked real Wishart matrices and additively perturbed Gaussian orthogonal ensembles are known to exhibit a phase transition in the large size limit. We show that they have limiting distributions for near-critical perturbations, fully resolving the conjecture of Baik, Ben Arous and P\\'ech\\'e (2005). The starting point is a new (2r+1)-diagonal form that is algebraically natural to the problem; for both models it converges to a certain random Schr\\"odinger operator on the half-line with r x r matrix-valued potential. The perturbation determines the boundary condition, and the low-lying eigenvalues describe the limit jointly over all perturbations in a fixed subspace. We treat the real, complex and quaternion (beta = 1,2,4) cases simultaneously. We also characterize the limit laws in terms of a diffusion related to Dyson's Brownian motion, and further in terms of a linear parabolic PDE; here beta is simply a parameter. At beta = 2 the PDE appears to reconcile with known Painlev\\'e fo...

  9. Recurrent Spiking Networks Solve Planning Tasks

    Science.gov (United States)

    Rueckert, Elmar; Kappel, David; Tanneberg, Daniel; Pecevski, Dejan; Peters, Jan

    2016-02-01

    A recurrent spiking neural network is proposed that implements planning as probabilistic inference for finite and infinite horizon tasks. The architecture splits this problem into two parts: The stochastic transient firing of the network embodies the dynamics of the planning task. With appropriate injected input this dynamics is shaped to generate high-reward state trajectories. A general class of reward-modulated plasticity rules for these afferent synapses is presented. The updates optimize the likelihood of getting a reward through a variant of an Expectation Maximization algorithm and learning is guaranteed to convergence to a local maximum. We find that the network dynamics are qualitatively similar to transient firing patterns during planning and foraging in the hippocampus of awake behaving rats. The model extends classical attractor models and provides a testable prediction on identifying modulating contextual information. In a real robot arm reaching and obstacle avoidance task the ability to represent multiple task solutions is investigated. The neural planning method with its local update rules provides the basis for future neuromorphic hardware implementations with promising potentials like large data processing abilities and early initiation of strategies to avoid dangerous situations in robot co-worker scenarios.

  10. Memory recall and spike-frequency adaptation

    Science.gov (United States)

    Roach, James P.; Sander, Leonard M.; Zochowski, Michal R.

    2016-05-01

    The brain can reproduce memories from partial data; this ability is critical for memory recall. The process of memory recall has been studied using autoassociative networks such as the Hopfield model. This kind of model reliably converges to stored patterns that contain the memory. However, it is unclear how the behavior is controlled by the brain so that after convergence to one configuration, it can proceed with recognition of another one. In the Hopfield model, this happens only through unrealistic changes of an effective global temperature that destabilizes all stored configurations. Here we show that spike-frequency adaptation (SFA), a common mechanism affecting neuron activation in the brain, can provide state-dependent control of pattern retrieval. We demonstrate this in a Hopfield network modified to include SFA, and also in a model network of biophysical neurons. In both cases, SFA allows for selective stabilization of attractors with different basins of attraction, and also for temporal dynamics of attractor switching that is not possible in standard autoassociative schemes. The dynamics of our models give a plausible account of different sorts of memory retrieval.

  11. Asynchronous Rate Chaos in Spiking Neuronal Circuits

    Science.gov (United States)

    Harish, Omri; Hansel, David

    2015-01-01

    The brain exhibits temporally complex patterns of activity with features similar to those of chaotic systems. Theoretical studies over the last twenty years have described various computational advantages for such regimes in neuronal systems. Nevertheless, it still remains unclear whether chaos requires specific cellular properties or network architectures, or whether it is a generic property of neuronal circuits. We investigate the dynamics of networks of excitatory-inhibitory (EI) spiking neurons with random sparse connectivity operating in the regime of balance of excitation and inhibition. Combining Dynamical Mean-Field Theory with numerical simulations, we show that chaotic, asynchronous firing rate fluctuations emerge generically for sufficiently strong synapses. Two different mechanisms can lead to these chaotic fluctuations. One mechanism relies on slow I-I inhibition which gives rise to slow subthreshold voltage and rate fluctuations. The decorrelation time of these fluctuations is proportional to the time constant of the inhibition. The second mechanism relies on the recurrent E-I-E feedback loop. It requires slow excitation but the inhibition can be fast. In the corresponding dynamical regime all neurons exhibit rate fluctuations on the time scale of the excitation. Another feature of this regime is that the population-averaged firing rate is substantially smaller in the excitatory population than in the inhibitory population. This is not necessarily the case in the I-I mechanism. Finally, we discuss the neurophysiological and computational significance of our results. PMID:26230679

  12. Studying a Chaotic Spiking Neural Model

    Directory of Open Access Journals (Sweden)

    Mohammad Alhawarat

    2013-09-01

    Full Text Available Dynamics of a chaotic spiking neuron model are being studied mathematically and experimentally. The Nonlinear Dynamic State neuron (NDS is analysed to further understand the model and improve it.Chaos has many interesting properties such as sensitivity to initial conditions, space filling, control and synchronization. As suggested by biologists, these properties may be exploited and play vital role in carrying out computational tasks in human brain. The NDS model has some limitations; in thus paper the model is investigated to overcomesome of these limitations in order to enhance the model. Therefore,the model’s parameters are tuned and the resulted dynamics are studied. Also, the discretization method of the model is considered. Moreover, a mathematical analysis is carried out to reveal the underlying dynamics of the model after tuning of its parameters. The results of the aforementioned methods revealedsome facts regarding the NDS attractor and suggest the stabilization of a large number of unstable periodic orbits (UPOs which might correspond to memories in phase space

  13. Uroguanylin induces electroencephalographic spikes in rats

    Directory of Open Access Journals (Sweden)

    MDA. Teixeira

    Full Text Available Uroguanylin (UGN is an endogenous peptide that acts on membrane-bound guanylate cyclase receptors of intestinal and renal cells increasing cGMP production and regulating electrolyte and water epithelial transport. Recent research works demonstrate the expression of this peptide and its receptor in the central nervous system. The current work was undertaken in order to evaluate modifications of electroencephalographic spectra (EEG in anesthetized Wistar rats, submitted to intracisternal infusion of uroguanylin (0.0125 nmoles/min or 0.04 nmoles/min. The current observations demonstrate that 0.0125 nmoles/min and 0.04 nmoles/min intracisternal infusion of UGN significantly enhances amplitude and frequency of sharp waves and evoked spikes (p = 0.03. No statistical significance was observed on absolute alpha and theta spectra amplitude. The present data suggest that UGN acts on bioelectrogenesis of cortical cells by inducing hypersynchronic firing of neurons. This effect is blocked by nedocromil, suggesting that UGN acts by increasing the activity of chloride channels.

  14. Uroguanylin induces electroencephalographic spikes in rats.

    Science.gov (United States)

    Teixeira, M D A; Nascimento, N R F; Fonteles, M C; Vale, O C

    2013-08-01

    Uroguanylin (UGN) is an endogenous peptide that acts on membrane-bound guanylate cyclase receptors of intestinal and renal cells increasing cGMP production and regulating electrolyte and water epithelial transport. Recent research works demonstrate the expression of this peptide and its receptor in the central nervous system. The current work was undertaken in order to evaluate modifications of electroencephalographic spectra (EEG) in anesthetized Wistar rats, submitted to intracisternal infusion of uroguanylin (0.0125 nmoles/min or 0.04 nmoles/min). The current observations demonstrate that 0.0125 nmoles/min and 0.04 nmoles/min intracisternal infusion of UGN significantly enhances amplitude and frequency of sharp waves and evoked spikes (p = 0.03). No statistical significance was observed on absolute alpha and theta spectra amplitude. The present data suggest that UGN acts on bioelectrogenesis of cortical cells by inducing hypersynchronic firing of neurons. This effect is blocked by nedocromil, suggesting that UGN acts by increasing the activity of chloride channels.

  15. STUDYING A CHAOTIC SPIKING NEURAL MODEL

    Directory of Open Access Journals (Sweden)

    Mohammad Alhawarat

    2013-09-01

    Full Text Available Dynamics of a chaotic spiking neuron model are being studied mathematically and experimentally. The Nonlinear Dynamic State neuron (NDS is analysed to further understand the model and improve it. Chaos has many interesting properties such as sensitivity to initial conditions, space filling, control and synchronization. As suggested by biologists, these properties may be exploited and play vital role in carrying out computational tasks in human brain. The NDS model has some limitations; in thus paper the model is investigated to overcome some of these limitations in order to enhance the model. Therefore, the model’s parameters are tuned and the resulted dynamics are studied. Also, the discretization method of the model is considered. Moreover, a mathematical analysis is carried out to reveal the underlying dynamics of the model after tuning of its parameters. The results of the aforementioned methods revealed some facts regarding the NDS attractor and suggest the stabilization of a large number of unstable periodic orbits (UPOs which might correspond to memories in phase space.

  16. Kinetic quantification of vertical solid matter transfers in soils by a multi-tracers approach

    Science.gov (United States)

    Jagercikova, Mariannaa; Cornu, Sophiea; Bourl`es, Didierb; Evrard, Olivierc; Alainb, V.'eron; Hatt'e, Christinec; Ayrault, Sophiec; Jérômea, Balesdent

    2015-04-01

    We will present a novel multi-tracers method - combining different isotopic systems (137 Cs, 210 Pb (xs), meteoric 10 Be, 206/207 Pb, δ13 C, 14 C) with numerical modeling based on a non-linear diffusion-convection equation with depth dependent parameters - to quantify vertical transfer of solid matter in Luvisols, namely clay translocation and bioturbation. Our results show that as much as 91 ± 9 % and 80 ± 9 % of 137Cs and 10Be, respectively, are associated with the clay size fraction (0-2 µm) and provide therefore relevant tracers to investigate vertical transfer of solid matter in soils with pH > 5 and low organic carbon contents. Lead partitioning between different solid phases is more complex. Considering two spatial distributions of isotopes (macropores or soil matrix) depending on the contribution of a fraction inherited from the loess parent material to the soil concentration, we built up a multi-tracers modeling approach that simulates the experimental data with the common set of transfer parameters and allows us to quantify the relative contributions of vertical solid matter transfers to present-day 0-2 µm vertical distributions. Clay translocation is responsible for 9 to 66 % of clay accumulation in the Bt-horizon. The diffusion coefficients quantifying the rate of soil mixing by bioturbation yields values that are significantly higher than those estimated in previous ecological studies. Modeling the kinetics of solid matter transfer at various spatial and temporal scales should become a reference method in modern pedogenic and critical zone studies.

  17. Spiking irregularity and frequency modulate the behavioral report of single-neuron stimulation.

    Science.gov (United States)

    Doron, Guy; von Heimendahl, Moritz; Schlattmann, Peter; Houweling, Arthur R; Brecht, Michael

    2014-02-01

    The action potential activity of single cortical neurons can evoke measurable sensory effects, but it is not known how spiking parameters and neuronal subtypes affect the evoked sensations. Here, we examined the effects of spike train irregularity, spike frequency, and spike number on the detectability of single-neuron stimulation in rat somatosensory cortex. For regular-spiking, putative excitatory neurons, detectability increased with spike train irregularity and decreasing spike frequencies but was not affected by spike number. Stimulation of single, fast-spiking, putative inhibitory neurons led to a larger sensory effect compared to regular-spiking neurons, and the effect size depended only on spike irregularity. An ideal-observer analysis suggests that, under our experimental conditions, rats were using integration windows of a few hundred milliseconds or more. Our data imply that the behaving animal is sensitive to single neurons' spikes and even to their temporal patterning.

  18. A method for decoding the neurophysiological spike-response transform.

    Science.gov (United States)

    Stern, Estee; García-Crescioni, Keyla; Miller, Mark W; Peskin, Charles S; Brezina, Vladimir

    2009-11-15

    Many physiological responses elicited by neuronal spikes-intracellular calcium transients, synaptic potentials, muscle contractions-are built up of discrete, elementary responses to each spike. However, the spikes occur in trains of arbitrary temporal complexity, and each elementary response not only sums with previous ones, but can itself be modified by the previous history of the activity. A basic goal in system identification is to characterize the spike-response transform in terms of a small number of functions-the elementary response kernel and additional kernels or functions that describe the dependence on previous history-that will predict the response to any arbitrary spike train. Here we do this by developing further and generalizing the "synaptic decoding" approach of Sen et al. (1996). Given the spike times in a train and the observed overall response, we use least-squares minimization to construct the best estimated response and at the same time best estimates of the elementary response kernel and the other functions that characterize the spike-response transform. We avoid the need for any specific initial assumptions about these functions by using techniques of mathematical analysis and linear algebra that allow us to solve simultaneously for all of the numerical function values treated as independent parameters. The functions are such that they may be interpreted mechanistically. We examine the performance of the method as applied to synthetic data. We then use the method to decode real synaptic and muscle contraction transforms.

  19. Cytosolic pro-apoptotic SPIKE induces mitochondrial apoptosis in cancer.

    Science.gov (United States)

    Nikolic, Ivana; Kastratovic, Tatjana; Zelen, Ivanka; Zivanovic, Aleksandar; Arsenijevic, Slobodan; Mitrovic, Marina

    2010-04-30

    Proteins of the BCL-2 family are important regulators of apoptosis. The BCL-2 family includes three main subgroups: the anti-apoptotic group, such as BCL-2, BCL-XL, BCL-W, and MCL-1; multi-domain pro-apoptotic BAX, BAK; and pro-apoptotic "BH3-only" BIK, PUMA, NOXA, BID, BAD, and SPIKE. SPIKE, a rare pro-apoptotic protein, is highly conserved throughout the evolution, including Caenorhabditis elegans, whose expression is downregulated in certain tumors, including kidney, lung, and breast. In the literature, SPIKE was proposed to interact with BAP31 and prevent BCL-XL from binding to BAP31. Here, we utilized the Position Weight Matrix method to identify SPIKE to be a BH3-only pro-apoptotic protein mainly localized in the cytosol of all cancer cell lines tested. Overexpression of SPIKE weakly induced apoptosis in comparison to the known BH3-only pro-apoptotic protein BIK. SPIKE promoted mitochondrial cytochrome c release, the activation of caspase 3, and the caspase cleavage of caspase's downstream substrates BAP31 and p130CAS. Although the informatics analysis of SPIKE implicates this protein as a member of the BH3-only BCL-2 subfamily, its role in apoptosis remains to be elucidated.

  20. Statistical technique for analysing functional connectivity of multiple spike trains.

    Science.gov (United States)

    Masud, Mohammad Shahed; Borisyuk, Roman

    2011-03-15

    A new statistical technique, the Cox method, used for analysing functional connectivity of simultaneously recorded multiple spike trains is presented. This method is based on the theory of modulated renewal processes and it estimates a vector of influence strengths from multiple spike trains (called reference trains) to the selected (target) spike train. Selecting another target spike train and repeating the calculation of the influence strengths from the reference spike trains enables researchers to find all functional connections among multiple spike trains. In order to study functional connectivity an "influence function" is identified. This function recognises the specificity of neuronal interactions and reflects the dynamics of postsynaptic potential. In comparison to existing techniques, the Cox method has the following advantages: it does not use bins (binless method); it is applicable to cases where the sample size is small; it is sufficiently sensitive such that it estimates weak influences; it supports the simultaneous analysis of multiple influences; it is able to identify a correct connectivity scheme in difficult cases of "common source" or "indirect" connectivity. The Cox method has been thoroughly tested using multiple sets of data generated by the neural network model of the leaky integrate and fire neurons with a prescribed architecture of connections. The results suggest that this method is highly successful for analysing functional connectivity of simultaneously recorded multiple spike trains.

  1. Controlling chaos in balanced neural circuits with input spike trains

    Science.gov (United States)

    Engelken, Rainer; Wolf, Fred

    The cerebral cortex can be seen as a system of neural circuits driving each other with spike trains. Here we study how the statistics of these spike trains affects chaos in balanced target circuits.Earlier studies of chaos in balanced neural circuits either used a fixed input [van Vreeswijk, Sompolinsky 1996, Monteforte, Wolf 2010] or white noise [Lajoie et al. 2014]. We study dynamical stability of balanced networks driven by input spike trains with variable statistics. The analytically obtained Jacobian enables us to calculate the complete Lyapunov spectrum. We solved the dynamics in event-based simulations and calculated Lyapunov spectra, entropy production rate and attractor dimension. We vary correlations, irregularity, coupling strength and spike rate of the input and action potential onset rapidness of recurrent neurons.We generally find a suppression of chaos by input spike trains. This is strengthened by bursty and correlated input spike trains and increased action potential onset rapidness. We find a link between response reliability and the Lyapunov spectrum. Our study extends findings in chaotic rate models [Molgedey et al. 1992] to spiking neuron models and opens a novel avenue to study the role of projections in shaping the dynamics of large neural circuits.

  2. Effects of polycyclic aromatic hydrocarbons on germination and subsequent growth of grasses and legumes in freshly contaminated soil and soil with aged PAHs residues

    Energy Technology Data Exchange (ETDEWEB)

    Smith, M.J.; Flowers, T.H.; Duncan, H.J.; Alder, J. [University of Glasgow, Glasgow (United Kingdom). Glasgow Marine Technological Centre

    2006-06-15

    The relevance of germination trials for screening plants that may have potential for use in the phytoremediation of PAH contaminated land was evaluated. The germination and subsequent growth of 7 grass and legume species were evaluated in soil spiked with a pure PAH mixture or coal tar and soil from a former coking plant heavily contaminated with aged PAHs. None of these treatments adversely affected germination of the plants. However, apart from Lolium perenne all species exhibited reduced growth in the coking plant soil after 12 weeks growth when compared to the untreated soil. In the coal tar spiked soil 4 out of the 7 species showed reduced growth, as did 3 out of the 7 in the soil spiked with a mixture of 7 PAHs. Therefore, germination studies alone would not predict the success of subsequent growth of the species tested in the ranges of soil PAH levels studied.

  3. Spectral components of cytosolic [Ca2+] spiking in neurons

    DEFF Research Database (Denmark)

    Kardos, J; Szilágyi, N; Juhász, G;

    1998-01-01

    into evolutionary spectra of a characteristic set of frequencies. Non-delayed small spikes on top of sustained [Ca2+]c were synthesized by a main component frequency, 0.132+/-0.012 Hz, showing its maximal amplitude in phase with the start of depolarization (25 mM KCI) combined with caffeine (10 mM) application....... Delayed complex responses of large [Ca2+]c spiking observed in cells from a different set of cultures were synthesized by a set of frequencies within the range 0.018-0.117 Hz. Differential frequency patterns are suggested as characteristics of the [Ca2+]c spiking responses of neurons under different...

  4. A model for determination of screening level for radioactive elements in soil; Modelo para o estabelecimento de valores orientadores para elementos radioativos no solo

    Energy Technology Data Exchange (ETDEWEB)

    Peres, Ana Claudia

    2007-07-01

    At the present, decision about clean-up of Brazilian sites contaminated with radioactive isotopes is addressed on a case-by-case basis, since there is no general guidance or recommendation to support actions in early phases of the problem identification. For chemicals, CETESB - the governmental organization responsible for preventing and controlling environmental pollution in Sao Paulo State - established background values, prevention and intervention, as the first step to implement a remediation actions based on human health risk assessment. The aim of this study was to develop a methodology for the establishment of target values for radioactive soil contamination, as far as possible consistent and compatible with the approach adopted by CETESB for sites contaminated with chemicals. The following steps have been addressed in this study: conceptual scenario and model development; codification of the equations in an electronic spreadsheet; selection of proper range and statistical distribution of the input values; derivation of the intervention levels for selected radionuclides using Monte Carlo methods. The mathematical model developed was mainly based on the equations used by the U.S. Environmental Protection Agency (EPA) and by the National Council on Radiation Protection and Measurements (NCRP) for soil screening purposes. Intervention and prevention values are presented for adult and 10 years old child, for each 3 exposure scenarios: agricultural, residential and industrial; the following radionuclides were considered: {sup 3}H, {sup 14}C, {sup 32}P, {sup 35}S, {sup 45}Ca, {sup 51}Cr, {sup 90}Sr, {sup 125}I, {sup 131}I, {sup 134}Cs, {sup 137}Cs, {sup 210}Pb, {sup 226}Ra, {sup 228}Ra, {sup 232}Th, {sup 238}U, {sup 239}Pu and {sup 241} Am. Quality reference values were determined for {sup 40}K, {sup 137}Cs, {sup 210}Pb, {sup 226}Ra, {sup 228}Ra, {sup 228}Th, Th-nat e U-nat. Results obtained in this study showed a good agreement with those reported by NCRP

  5. Contrast Adaptation Decreases Complexity in Retinal Ganglion Cell Spike Train

    Institute of Scientific and Technical Information of China (English)

    WANG Guang-Li; HUANG Shi-Yong; ZHANG Ying-Ying; LIANG Pei-Ji

    2007-01-01

    @@ The difference in temporal structures of retinal ganglion cell spike trains between spontaneous activity and firing activity after contrast adaptation is investigated. The Lempel-Ziv complexity analysis reveals that the complexity of the neural spike train decreases after contrast adaptation. This implies that the behaviour of the neuron becomes ordered, which may carry relevant information about the external stimulus. Thus, during the neuron activity after contrast adaptation, external information could be encoded in forms of some certain patterns in the temporal structure of spike train that is significantly different, compared to that of the spike train during spontaneous activity, although the firing rates in spontaneous activity and firing activity after contrast adaptation are sometime similar.

  6. Timing intervals using population synchrony and spike timing dependent plasticity

    Directory of Open Access Journals (Sweden)

    Wei Xu

    2016-12-01

    Full Text Available We present a computational model by which ensembles of regularly spiking neurons can encode different time intervals through synchronous firing. We show that a neuron responding to a large population of convergent inputs has the potential to learn to produce an appropriately-timed output via spike-time dependent plasticity. We explain why temporal variability of this population synchrony increases with increasing time intervals. We also show that the scalar property of timing and its violation at short intervals can be explained by the spike-wise accumulation of jitter in the inter-spike intervals of timing neurons. We explore how the challenge of encoding longer time intervals can be overcome and conclude that this may involve a switch to a different population of neurons with lower firing rate, with the added effect of producing an earlier bias in response. Experimental data on human timing performance show features in agreement with the model’s output.

  7. Efficiently passing messages in distributed spiking neural network simulation.

    Science.gov (United States)

    Thibeault, Corey M; Minkovich, Kirill; O'Brien, Michael J; Harris, Frederick C; Srinivasa, Narayan

    2013-01-01

    Efficiently passing spiking messages in a neural model is an important aspect of high-performance simulation. As the scale of networks has increased so has the size of the computing systems required to simulate them. In addition, the information exchange of these resources has become more of an impediment to performance. In this paper we explore spike message passing using different mechanisms provided by the Message Passing Interface (MPI). A specific implementation, MVAPICH, designed for high-performance clusters with Infiniband hardware is employed. The focus is on providing information about these mechanisms for users of commodity high-performance spiking simulators. In addition, a novel hybrid method for spike exchange was implemented and benchmarked.

  8. SPIKY: A graphical user interface for monitoring spike train synchrony

    CERN Document Server

    Bozanic, Nebojsa

    2014-01-01

    Techniques for recording large-scale neuronal spiking activity are developing very fast. This leads to an increasing demand for algorithms capable of analyzing large amounts of experimental spike train data. One of the most crucial and demanding tasks is the identification of similarity patterns with a very high temporal resolution and across different spatial scales. To address this task, in recent years three time-resolved measures of spike train synchrony have been proposed, the ISI-distance, the SPIKE-distance, and event synchronization. The Matlab source codes for calculating and visualizing these measures have been made publicly available. However, due to the many different possible representations of the results the use of these codes is rather complicated and their application requires some basic knowledge of Matlab. Thus it became desirable to provide a more user-friendly and interactive interface. Here we address this need and present SPIKY, a graphical user interface which facilitates the applicati...

  9. Preterm Birth Risk Spikes in Mothers with Sleep Disorders

    Science.gov (United States)

    ... https://medlineplus.gov/news/fullstory_167666.html Preterm Birth Risk Spikes in Mothers With Sleep Disorders Pregnant ... during pregnancy may increase the risk of preterm birth, a new study finds. The California research looked ...

  10. Benchmarking Spike Rate Inference in Population Calcium Imaging.

    Science.gov (United States)

    Theis, Lucas; Berens, Philipp; Froudarakis, Emmanouil; Reimer, Jacob; Román Rosón, Miroslav; Baden, Tom; Euler, Thomas; Tolias, Andreas S; Bethge, Matthias

    2016-05-01

    A fundamental challenge in calcium imaging has been to infer spike rates of neurons from the measured noisy fluorescence traces. We systematically evaluate different spike inference algorithms on a large benchmark dataset (>100,000 spikes) recorded from varying neural tissue (V1 and retina) using different calcium indicators (OGB-1 and GCaMP6). In addition, we introduce a new algorithm based on supervised learning in flexible probabilistic models and find that it performs better than other published techniques. Importantly, it outperforms other algorithms even when applied to entirely new datasets for which no simultaneously recorded data is available. Future data acquired in new experimental conditions can be used to further improve the spike prediction accuracy and generalization performance of the model. Finally, we show that comparing algorithms on artificial data is not informative about performance on real data, suggesting that benchmarking different methods with real-world datasets may greatly facilitate future algorithmic developments in neuroscience.

  11. Hardware/Software Co-Design for Spike Based Recognition

    CERN Document Server

    Ghani, Arfan; Maguire, Liam; Harkin, Jim

    2008-01-01

    The practical applications based on recurrent spiking neurons are limited due to their non-trivial learning algorithms. The temporal nature of spiking neurons is more favorable for hardware implementation where signals can be represented in binary form and communication can be done through the use of spikes. This work investigates the potential of recurrent spiking neurons implementations on reconfigurable platforms and their applicability in temporal based applications. A theoretical framework of reservoir computing is investigated for hardware/software implementation. In this framework, only readout neurons are trained which overcomes the burden of training at the network level. These recurrent neural networks are termed as microcircuits which are viewed as basic computational units in cortical computation. This paper investigates the potential of recurrent neural reservoirs and presents a novel hardware/software strategy for their implementation on FPGAs. The design is implemented and the functionality is ...

  12. Balanced synaptic input shapes the correlation between neural spike trains.

    Science.gov (United States)

    Litwin-Kumar, Ashok; Oswald, Anne-Marie M; Urban, Nathaniel N; Doiron, Brent

    2011-12-01

    Stimulus properties, attention, and behavioral context influence correlations between the spike times produced by a pair of neurons. However, the biophysical mechanisms that modulate these correlations are poorly understood. With a combined theoretical and experimental approach, we show that the rate of balanced excitatory and inhibitory synaptic input modulates the magnitude and timescale of pairwise spike train correlation. High rate synaptic inputs promote spike time synchrony rather than long timescale spike rate correlations, while low rate synaptic inputs produce opposite results. This correlation shaping is due to a combination of enhanced high frequency input transfer and reduced firing rate gain in the high input rate state compared to the low state. Our study extends neural modulation from single neuron responses to population activity, a necessary step in understanding how the dynamics and processing of neural activity change across distinct brain states.

  13. Balanced synaptic input shapes the correlation between neural spike trains.

    Directory of Open Access Journals (Sweden)

    Ashok Litwin-Kumar

    2011-12-01

    Full Text Available Stimulus properties, attention, and behavioral context influence correlations between the spike times produced by a pair of neurons. However, the biophysical mechanisms that modulate these correlations are poorly understood. With a combined theoretical and experimental approach, we show that the rate of balanced excitatory and inhibitory synaptic input modulates the magnitude and timescale of pairwise spike train correlation. High rate synaptic inputs promote spike time synchrony rather than long timescale spike rate correlations, while low rate synaptic inputs produce opposite results. This correlation shaping is due to a combination of enhanced high frequency input transfer and reduced firing rate gain in the high input rate state compared to the low state. Our study extends neural modulation from single neuron responses to population activity, a necessary step in understanding how the dynamics and processing of neural activity change across distinct brain states.

  14. Higher Order Spike Synchrony in Prefrontal Cortex during visual memory

    Directory of Open Access Journals (Sweden)

    Gordon ePipa

    2011-06-01

    Full Text Available Precise temporal synchrony of spike firing has been postulated as an important neuronal mechanism for signal integration and the induction of plasticity in neocortex. As prefrontal cortex plays an important role in organizing memory and executive functions, the convergence of multiple visual pathways onto PFC predicts that neurons should preferentially synchronize their spiking when stimulus information is processed. Furthermore, synchronous spike firing should intensify if memory processes require the induction of neuronal plasticity, even if this is only for short-term. Here we show with multiple simultaneously recorded units in ventral prefrontal cortex that neurons participate in 3 ms precise synchronous discharges distributed across multiple sites separated by at least 500 µm. The frequency of synchronous firing is modulated by behavioral performance and is specific for the memorized visual stimuli. In particular, during the memory period in which activity is not stimulus driven, larger groups of up to 7 sites exhibit performance dependent modulation of their spike synchronization.

  15. Efficiently passing messages in distributed spiking neural network simulation

    Directory of Open Access Journals (Sweden)

    Corey Michael Thibeault

    2013-06-01

    Full Text Available Efficiently passing spiking messages in a neural model is an important aspect of high-performance simulation. As the scale of networks has increased so has the size of the computing systems required to simulate them. In addition, the information exchange of these resources has become more of an impediment to performance. In this paper we explore spike message passing using different mechanisms provided by the Message Passing Interface (MPI. A specific implementation, MVAPICH, designed for high-performance clusters with Infiniband hardware is employed. The focus is on providing information about these mechanisms for users of commodity high-performance spiking simulators. In addition, a novel hybrid-method for spike exchange was implemented and benchmarked.

  16. Upper Limb Biomechanics During the Volleyball Serve and Spike

    OpenAIRE

    Reeser, Jonathan C.; Fleisig, Glenn S.; Bolt, Becky; Ruan, Mianfang

    2010-01-01

    Background: The shoulder is the third-most commonly injured body part in volleyball, with the majority of shoulder problems resulting from chronic overuse. Hypothesis: Significant kinetic differences exist among specific types of volleyball serves and spikes. Study Design: Controlled laboratory study. Methods: Fourteen healthy female collegiate volleyball players performed 5 successful trials of 4 skills: 2 directional spikes, an off-speed roll shot, and the float serve. Volunteers who were c...

  17. Membrane currents of spiking cells isolated from turtle retina.

    Science.gov (United States)

    Lasater, E M; Witkovsky, P

    1990-05-01

    We examined the membrane properties of spiking neurons isolated from the turtle (Pseudemys scripta) retina. The cells were maintained in culture for 1-7 days and were studied with the whole cell patch clamp technique. We utilized cells whose perikaryal diameters were greater than 15 microns since Kolb (1982) reported that ganglion cell perikarya in Pseudemys retina are 13-25 microns, whereas amacrine perikarya are less than 14 microns in diameter. We identified 5 currents in the studied cells: (1) a transient sodium current (INa) blocked by TTX, (2) a sustained calcium current (ICa) blocked by cobalt and enhanced by Bay-K 8644, (3) a calcium-dependent potassium current (IK(Ca)), (4) an A-type transient potassium current (IA) somewhat more sensitive to 4-AP than TEA, (5) a sustained potassium current (IK) more sensitive to TEA than 4-AP. The estimated average input resistance of the cells at -70 mV was 720 +/- 440 M omega. When all active currents were blocked, the membrane resistance between -130 and +20 mV was 2.5 G omega. When examined under current clamp, some cells produced multiple spikes to depolarizing steps of 0.1-0.3 nA, whereas other cells produced only a single spike irrespective of the strength of the current pulse. Most single spikers had an outward current that rose to a peak relatively slowly, whereas multiple spikers tend to have a more rapidly activating outward current. Under current clamp, 4-AP slowed the repolarization phase of the spike thus broadening it, but did not always abolish the ability to produce multiple spikes. TEA induced a depolarized plateau following the initial spike which precluded further spikes. It thus appears that the spiking patterns of the retinal cells are shaped primarily by the kinetics of INa, IK and IA and to a lesser extent by IK(Ca).

  18. Spatiotemporal Dynamics and Reliable Computations in Recurrent Spiking Neural Networks

    Science.gov (United States)

    Pyle, Ryan; Rosenbaum, Robert

    2017-01-01

    Randomly connected networks of excitatory and inhibitory spiking neurons provide a parsimonious model of neural variability, but are notoriously unreliable for performing computations. We show that this difficulty is overcome by incorporating the well-documented dependence of connection probability on distance. Spatially extended spiking networks exhibit symmetry-breaking bifurcations and generate spatiotemporal patterns that can be trained to perform dynamical computations under a reservoir computing framework.

  19. Learning probabilistic models of connectivity from multiple spike train data

    OpenAIRE

    2010-01-01

    Neuronal circuits or cell assemblies carry out brain function through complex coordinated firing patterns [1]. Inferring topology of neuronal circuits from simultaneously recorded spike train data is a challenging problem in neuroscience. In this work we present a new class of dynamic Bayesian networks to infer polysynaptic excitatory connectivity between spiking cortical neurons [2]. The emphasis on excitatory networks allows us to learn connectivity models by exploiting fast data mining alg...

  20. SPIKY: a graphical user interface for monitoring spike train synchrony.

    Science.gov (United States)

    Kreuz, Thomas; Mulansky, Mario; Bozanic, Nebojsa

    2015-05-01

    Techniques for recording large-scale neuronal spiking activity are developing very fast. This leads to an increasing demand for algorithms capable of analyzing large amounts of experimental spike train data. One of the most crucial and demanding tasks is the identification of similarity patterns with a very high temporal resolution and across different spatial scales. To address this task, in recent years three time-resolved measures of spike train synchrony have been proposed, the ISI-distance, the SPIKE-distance, and event synchronization. The Matlab source codes for calculating and visualizing these measures have been made publicly available. However, due to the many different possible representations of the results the use of these codes is rather complicated and their application requires some basic knowledge of Matlab. Thus it became desirable to provide a more user-friendly and interactive interface. Here we address this need and present SPIKY, a graphical user interface that facilitates the application of time-resolved measures of spike train synchrony to both simulated and real data. SPIKY includes implementations of the ISI-distance, the SPIKE-distance, and the SPIKE-synchronization (an improved and simplified extension of event synchronization) that have been optimized with respect to computation speed and memory demand. It also comprises a spike train generator and an event detector that makes it capable of analyzing continuous data. Finally, the SPIKY package includes additional complementary programs aimed at the analysis of large numbers of datasets and the estimation of significance levels. Copyright © 2015 the American Physiological Society.

  1. Homogeneous Spiking Neuromorphic System for Real-World Pattern Recognition

    OpenAIRE

    Wu, Xinyu; Saxena, Vishal; Zhu, Kehan

    2015-01-01

    A neuromorphic chip that combines CMOS analog spiking neurons and memristive synapses offers a promising solution to brain-inspired computing, as it can provide massive neural network parallelism and density. Previous hybrid analog CMOS-memristor approaches required extensive CMOS circuitry for training, and thus eliminated most of the density advantages gained by the adoption of memristor synapses. Further, they used different waveforms for pre and post-synaptic spikes that added undesirable...

  2. Fractionation of Heavy Metals in Soils as Affected by Soil Types and Metal Load Quantity

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Two series of soil subsamples, by spiking copper (Cu), lead (Pb), zinc (Zn) and cadmium (Cd) in anorthogonal design, were prepared using red soil and brown soil, respectively. The results indicated that heavymetal fractions in these soil subsamples depended not only on soil types, but also on metal loading quantityas well as on interactions among metals in soil. Lead and Cu in red soil appeared mostly in weakly specificallyadsorbed (WSA), Fe and Mn oxides bound (OX), and residual (RES) fractions. Zinc existed in all fractionsexcept organic bound one, and Cd was major in water soluble plus exchangeable (SE) one. Different fromthe results of red soil, Pb and Cu was present in brown soil in all fractions except organic one, but over 75%of Zn and 90% of Cd existed only in SE fraction. Meanwhile, SE fraction for any metal in red soil was lowerthan that in brown soil and WSA and OX fractions were higher. It is in agreement with low cation exchangecapacity and large amounts of metal oxides included in red soil. Metal fractions in soil, especially for watersoluble plus exchangeable one, were obviously influenced by other coexisting metals. The SE fraction ofheavy metals increased with increasing loading amounts of metals in red soil but not obviously in brown soil,which suggest that metal availability be easily affected by their total amounts spiked in red soil. In addition,more metals in red soil were extracted with 0.20 mol L-1 NH4Cl (pH 5.40) than that with 1.0 mol L-1Mg(NO3)2 (pH 7.0), but the reverse happened in brown soil, implicating significantly different mechanismsof metal desorption from red soil and brown soil.

  3. The Omega-Infinity Limit of Single Spikes

    CERN Document Server

    Axenides, Minos; Linardopoulos, Georgios

    2016-01-01

    A new infinite-size limit of strings in RxS2 is presented. The limit is obtained from single spike strings by letting their angular velocity omega become infinite. We derive the energy-momenta relation of omega-infinity single spikes as their linear velocity v-->1 and their angular momentum J-->1. Generally, the v-->1, J-->1 limit of single spikes is singular and has to be excluded from the spectrum and be studied separately. We discover that the dispersion relation of omega-infinity single spikes contains logarithms in the limit J-->1. This result is somewhat surprising, since the logarithmic behavior in the string spectra is typically associated with their motion in non-compact spaces such as AdS. Omega-infinity single spikes seem to completely cover the surface of the 2-sphere they occupy, so that they may essentially be viewed as some sort of "brany strings". A proof of the sphere-filling property of omega-infinity single spikes is given in the appendix.

  4. Neuronal spike initiation modulated by extracellular electric fields.

    Directory of Open Access Journals (Sweden)

    Guo-Sheng Yi

    Full Text Available Based on a reduced two-compartment model, the dynamical and biophysical mechanism underlying the spike initiation of the neuron to extracellular electric fields is investigated in this paper. With stability and phase plane analysis, we first investigate in detail the dynamical properties of neuronal spike initiation induced by geometric parameter and internal coupling conductance. The geometric parameter is the ratio between soma area and total membrane area, which describes the proportion of area occupied by somatic chamber. It is found that varying it could qualitatively alter the bifurcation structures of equilibrium as well as neuronal phase portraits, which remain unchanged when varying internal coupling conductance. By analyzing the activating properties of somatic membrane currents at subthreshold potentials, we explore the relevant biophysical basis of spike initiation dynamics induced by these two parameters. It is observed that increasing geometric parameter could greatly decrease the intensity of the internal current flowing from soma to dendrite, which switches spike initiation dynamics from Hopf bifurcation to SNIC bifurcation; increasing internal coupling conductance could lead to the increase of this outward internal current, whereas the increasing range is so small that it could not qualitatively alter the spike initiation dynamics. These results highlight that neuronal geometric parameter is a crucial factor in determining the spike initiation dynamics to electric fields. The finding is useful to interpret the functional significance of neuronal biophysical properties in their encoding dynamics, which could contribute to uncovering how neuron encodes electric field signals.

  5. Estimating nonstationary input signals from a single neuronal spike train.

    Science.gov (United States)

    Kim, Hideaki; Shinomoto, Shigeru

    2012-11-01

    Neurons temporally integrate input signals, translating them into timed output spikes. Because neurons nonperiodically emit spikes, examining spike timing can reveal information about input signals, which are determined by activities in the populations of excitatory and inhibitory presynaptic neurons. Although a number of mathematical methods have been developed to estimate such input parameters as the mean and fluctuation of the input current, these techniques are based on the unrealistic assumption that presynaptic activity is constant over time. Here, we propose tracking temporal variations in input parameters with a two-step analysis method. First, nonstationary firing characteristics comprising the firing rate and non-Poisson irregularity are estimated from a spike train using a computationally feasible state-space algorithm. Then, information about the firing characteristics is converted into likely input parameters over time using a transformation formula, which was constructed by inverting the neuronal forward transformation of the input current to output spikes. By analyzing spike trains recorded in vivo, we found that neuronal input parameters are similar in the primary visual cortex V1 and middle temporal area, whereas parameters in the lateral geniculate nucleus of the thalamus were markedly different.

  6. Automatic fitting of spiking neuron models to electrophysiological recordings

    Directory of Open Access Journals (Sweden)

    Cyrille Rossant

    2010-03-01

    Full Text Available Spiking models can accurately predict the spike trains produced by cortical neurons in response to somatically injected currents. Since the specific characteristics of the model depend on the neuron, a computational method is required to fit models to electrophysiological recordings. The fitting procedure can be very time consuming both in terms of computer simulations and in terms of code writing. We present algorithms to fit spiking models to electrophysiological data (time-varying input and spike trains that can run in parallel on graphics processing units (GPUs. The model fitting library is interfaced with Brian, a neural network simulator in Python. If a GPU is present it uses just-in-time compilation to translate model equations into optimized code. Arbitrary models can then be defined at script level and run on the graphics card. This tool can be used to obtain empirically validated spiking models of neurons in various systems. We demonstrate its use on public data from the INCF Quantitative Single-Neuron Modeling 2009 competition by comparing the performance of a number of neuron spiking models.

  7. Studying spike trains using a van Rossum metric with a synapse-like filter.

    Science.gov (United States)

    Houghton, Conor

    2009-02-01

    Spike trains are unreliable. For example, in the primary sensory areas, spike patterns and precise spike times will vary between responses to the same stimulus. Nonetheless, information about sensory inputs is communicated in the form of spike trains. A challenge in understanding spike trains is to assess the significance of individual spikes in encoding information. One approach is to define a spike train metric, allowing a distance to be calculated between pairs of spike trains. In a good metric, this distance will depend on the information the spike trains encode. This method has been used previously to calculate the timescale over which the precision of spike times is significant. Here, a new metric is constructed based on a simple model of synaptic conductances which includes binding site depletion. Including binding site depletion in the metric means that a given individual spike has a smaller effect on the distance if it occurs soon after other spikes. The metric proves effective at classifying neuronal responses by stimuli in the sample data set of electro-physiological recordings from the primary auditory area of the zebra finch fore-brain. This shows that this is an effective metric for these spike trains suggesting that in these spike trains the significance of a spike is modulated by its proximity to previous spikes. This modulation is a putative information-coding property of spike trains.

  8. Spike Pattern Structure Influences Synaptic Efficacy Variability under STDP and Synaptic Homeostasis. II: Spike Shuffling Methods on LIF Networks

    Science.gov (United States)

    Bi, Zedong; Zhou, Changsong

    2016-01-01

    Synapses may undergo variable changes during plasticity because of the variability of spike patterns such as temporal stochasticity and spatial randomness. Here, we call the variability of synaptic weight changes during plasticity to be efficacy variability. In this paper, we investigate how four aspects of spike pattern statistics (i.e., synchronous firing, burstiness/regularity, heterogeneity of rates and heterogeneity of cross-correlations) influence the efficacy variability under pair-wise additive spike-timing dependent plasticity (STDP) and synaptic homeostasis (the mean strength of plastic synapses into a neuron is bounded), by implementing spike shuffling methods onto spike patterns self-organized by a network of excitatory and inhibitory leaky integrate-and-fire (LIF) neurons. With the increase of the decay time scale of the inhibitory synaptic currents, the LIF network undergoes a transition from asynchronous state to weak synchronous state and then to synchronous bursting state. We first shuffle these spike patterns using a variety of methods, each designed to evidently change a specific pattern statistics; and then investigate the change of efficacy variability of the synapses under STDP and synaptic homeostasis, when the neurons in the network fire according to the spike patterns before and after being treated by a shuffling method. In this way, we can understand how the change of pattern statistics may cause the change of efficacy variability. Our results are consistent with those of our previous study which implements spike-generating models on converging motifs. We also find that burstiness/regularity is important to determine the efficacy variability under asynchronous states, while heterogeneity of cross-correlations is the main factor to cause efficacy variability when the network moves into synchronous bursting states (the states observed in epilepsy). PMID:27555816

  9. A multi-radionuclide approach to evaluate the suitability of {sup 239+240}Pu as soil erosion tracer

    Energy Technology Data Exchange (ETDEWEB)

    Meusburger, Katrin, E-mail: Katrin.Meusburger@unibas.ch [Environmental Geosciences, University of Basel, Bernoullistrasse 30, CH-4056 Basel (Switzerland); Mabit, Lionel, E-mail: L.Mabit@iaea.org [Soil and Water Management and Crop Nutrition Laboratory, FAO/IAEA Agriculture & Biotechnology Laboratory, IAEA Laboratories, Seibersdorf (Austria); Ketterer, Michael, E-mail: mkettere@msudenver.edu [Chemistry Department, Metropolitan State University of Denver, CO (United States); Park, Ji-Hyung, E-mail: jhp@ewha.ac.kr [Department of Environmental Science & Engineering, Ewha Womans University, Seoul 120-750 (Korea, Republic of); Sandor, Tarjan [Radioanalytical Reference Laboratory, Central Agricultural Office Food and Feed Safety Directorate (Hungary); Porto, Paolo, E-mail: paolo.porto@unirc.it [Dipartimento di AGRARIA, Università degli Studi “Mediterranea” di Reggio Calabria (Italy); Alewell, Christine, E-mail: Christine.Alewell@unibas.ch [Environmental Geosciences, University of Basel, Bernoullistrasse 30, CH-4056 Basel (Switzerland)

    2016-10-01

    Fallout radionuclides have been used successfully worldwide as tracers for soil erosion, but relatively few studies exploit the full potential of plutonium (Pu) isotopes. Hence, this study aims to explore the suitability of the plutonium isotopes {sup 239}Pu and {sup 240}Pu as a method to assess soil erosion magnitude by comparison to more established fallout radionuclides such as {sup 137}Cs and {sup 210}Pb{sub ex}. As test area an erosion affected headwater catchment of the Lake Soyang (South Korea) was selected. All three fallout radionuclides confirmed high erosion rates for agricultural sites (> 25 t ha{sup −1} yr{sup −1}). Pu isotopes further allowed determining the origin of the fallout. Both {sup 240}Pu/{sup 239}Pu atomic ratios and {sup 239+240}Pu/{sup 137}Cs activity ratios were close to the global fallout ratio. However, the depth profile of the {sup 239+240}Pu/{sup 137}Cs activity ratios in undisturbed sites showed lower ratios in the top soil increments, which might be due to higher migration rates of {sup 239+240}Pu. The activity ratios further indicated preferential transport of {sup 137}Cs from eroded sites (higher ratio compared to the global fallout) to the depositional sites (smaller ratio). As such the {sup 239+240}Pu/{sup 137}Cs activity ratio offered a new approach to parameterize a particle size correction factor that can be applied when both {sup 137}Cs and {sup 239+240}Pu have the same fallout source. Implementing this particle size correction factor in the conversion of {sup 137}Cs inventories resulted in comparable estimates of soil loss for {sup 137}Cs and {sup 239+240}Pu. The comparison among the different fallout radionuclides highlights the suitability of {sup 239+240}Pu through less preferential transport compared to {sup 137}Cs and the possibility to gain information regarding the origin of the fallout. In conclusion, {sup 239+240}Pu is a promising soil erosion tracer, however, since the behaviour i.e. vertical migration in the

  10. Sums of Spike Waveform Features for Motor Decoding

    Directory of Open Access Journals (Sweden)

    Jie Li

    2017-07-01

    Full Text Available Traditionally, the key step before decoding motor intentions from cortical recordings is spike sorting, the process of identifying which neuron was responsible for an action potential. Recently, researchers have started investigating approaches to decoding which omit the spike sorting step, by directly using information about action potentials' waveform shapes in the decoder, though this approach is not yet widespread. Particularly, one recent approach involves computing the moments of waveform features and using these moment values as inputs to decoders. This computationally inexpensive approach was shown to be comparable in accuracy to traditional spike sorting. In this study, we use offline data recorded from two Rhesus monkeys to further validate this approach. We also modify this approach by using sums of exponentiated features of spikes, rather than moments. Our results show that using waveform feature sums facilitates significantly higher hand movement reconstruction accuracy than using waveform feature moments, though the magnitudes of differences are small. We find that using the sums of one simple feature, the spike amplitude, allows better offline decoding accuracy than traditional spike sorting by expert (correlation of 0.767, 0.785 vs. 0.744, 0.738, respectively, for two monkeys, average 16% reduction in mean-squared-error, as well as unsorted threshold crossings (0.746, 0.776; average 9% reduction in mean-squared-error. Our results suggest that the sums-of-features framework has potential as an alternative to both spike sorting and using unsorted threshold crossings, if developed further. Also, we present data comparing sorted vs. unsorted spike counts in terms of offline decoding accuracy. Traditional sorted spike counts do not include waveforms that do not match any template (“hash”, but threshold crossing counts do include this hash. On our data and in previous work, hash contributes to decoding accuracy. Thus, using the

  11. Aspartic acid aminotransferase activity is increased in actively spiking compared with non-spiking human epileptic cortex.

    Science.gov (United States)

    Kish, S J; Dixon, L M; Sherwin, A L

    1988-01-01

    Increased concentration of the excitatory neurotransmitter aspartic acid in actively spiking human epileptic cerebral cortex was recently described. In order to further characterise changes in the aspartergic system in epileptic brain, the behaviour of aspartic acid aminotransferase (AAT), a key enzyme involved in aspartic acid metabolism has now been examined. Electrocorticography performed during surgery was employed to identify cortical epileptic spike foci in 16 patients undergoing temporal lobectomy for intractable seizures. Patients with spontaneously spiking lateral temporal cortex (n = 8) were compared with a non-spiking control group (n = 8) of patients in whom the epileptic lesions were confined to the hippocampus sparing the temporal convexity. Mean activity of AAT in spiking cortex was significantly elevated by 16-18%, with aspartic acid concentration increased by 28%. Possible explanations for the enhanced AAT activity include increased proliferation of cortical AAT-containing astrocytes at the spiking focus and/or a generalised increase in neuronal or extraneuronal metabolism consequent to the ongoing epileptic discharge. It is suggested that the data provide additional support for a disturbance of central excitatory aspartic acid mechanisms in human epileptic brain. PMID:2898010

  12. Volatilisation of o-Xylene from Sandy Soil

    DEFF Research Database (Denmark)

    Lindhardt, Bo; Christensen, Thomas Højlund; Brun, Adam

    1994-01-01

    The diffusive release of o-xylene from two soils with different contents of organic carbon (1.1 % and 0.11 % TOC) and with two different water contents (app. 5 % w/w and 15 % w/w was studied in the laboratory. The soils were spiked with o-xylene in the laboratory. The fluxes were measured over...

  13. Soil-to-plant transfer factors for natural radionuclides in the Brazilian cerrado region

    Energy Technology Data Exchange (ETDEWEB)

    Jacomino, Vanusa M.F.; Oliveira, Kerley A.; Menezes, Maria Angela de B., E-mail: vmfj@cdtn.b [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Mello, Jaime de; Silva, David F. da, E-mail: jwvmello@ufv.b [Universidade Federal de Vicosa (UFV), MG (Brazil). Dept. de Solos; Siqueira, Maria C.; Taddei, Maria H.; Dias, Fabiana F., E-mail: mc_quimica@hotmail.co, E-mail: mhtaddei@cnen.gov.b, E-mail: fdias@cnen.gov.b [Comissao Nacional de Energia Nuclear (CNEN-MG), Pocos de Caldas, MG (Brazil). Lab. de Pocos de Caldas (LAPOC)

    2009-07-01

    Large amounts of phosphogypsum produced have been attracting attention of Radiological Protection institutions and Environmental Protection agencies worldwide, given its high potential for environmental contamination. In Brazil, this material has been used for several decades, especially for agricultural purposes. Due to the presence of radionuclides in its composition, it is necessary to understand the mechanisms for natural radionuclide transfer in the soil/plant system and to evaluate if the use of phosphogypsum in soil contributes to increased exposition of humans to natural radioactivity. Experiments were accomplished in a greenhouse with lettuce cultivation in two types of soil (sandy and clayey) fertilized with four different amounts of phosphogypsum. Samples of phosphogypsum, soil, lettuce and drainage water were then analyzed for key radionuclides. {sup 238}U and {sup 232}Th analyses were carried out by Neutron Activation Analysis; {sup 226}Ra, {sup 228}Ra, and {sup 210}Pb by analyzed by Gamma Spectrometry; and {sup 210}Po by Alpha Spectrometry Technique. Finally, Transfer Factors of soil-plant were calculated as well as annual contribution to the effective dose due to the ingestion of lettuces. {sup 22}'6Ra average specific activity in phosphogypsum samples (252 Bq kg{sup -1}) was below the maximum level recommended by USEPA, which is 370 Bq.kg{sup -1} for agricultural use. Although most of the results for mean specific activity of radionuclides in lettuce presented values below the Minimum Detectable Activity (MDA), Transfer Factors were estimated for those conditions in which the mean specific activity proved to be superior to MDA. Values ranged from 1.8 10{sup -3} to 2.3 10{sup -2} for {sup 232}Th; 3.5 10{sup -}'2 to 4.1 10{sup -2} for {sup 226}Ra, 2.4 10{sup -1} to 3.2 10{sup -}'1 for {sup 228}Ra, and 3.5 10{sup -2} to 8.5 10{sup -2} for {sup 210}Po, depending on the type of soil used for planting vegetables. In general, results

  14. Fixed latency on-chip interconnect for hardware spiking neural network architectures

    NARCIS (Netherlands)

    Pande, Sandeep; Morgan, Fearghal; Smit, Gerard; Bruintjes, Tom; Rutgers, Jochem; Cawley, Seamus; Harkin, Jim; McDaid, Liam

    2013-01-01

    Information in a Spiking Neural Network (SNN) is encoded as the relative timing between spikes. Distortion in spike timings can impact the accuracy of SNN operation by modifying the precise firing time of neurons within the SNN. Maintaining the integrity of spike timings is crucial for reliable oper

  15. Dual roles for spike signaling in cortical neural populations

    Directory of Open Access Journals (Sweden)

    Dana eBallard

    2011-06-01

    Full Text Available A prominent feature of signaling in cortical neurons is that of randomness in the action potential. The output of a typical pyramidal cell can be well fit with a Poisson model, and variations in the Poisson rate repeatedly have been shown to be correlated with stimuli. However while the rate provides a very useful characterization of neural spike data, it may not be the most fundamental description of the signaling code. Recent data showing γ frequency range multi-cell action potential correlations, together with spike timing dependent plasticity, are spurring a re-examination of the classical model, since precise timing codes imply that the generation of spikes is essentially deterministic. Could the observed Poisson randomness and timing determinism reflect two separate modes of communication, or do they somehow derive from a single process? We investigate in a timing-based model whether the apparent incompatibility between these probabilistic and deterministic observations may be resolved by examining how spikes could be used in the underlying neural circuits. The crucial component of this model draws on dual roles for spike signaling. In learning receptive fields from ensembles of inputs, spikes need to behave probabilistically, whereas for fast signaling of individual stimuli, the spikes need to behave deterministically. Our simulations show that this combination is possible if deterministic signals using γ latency coding are probabilistically routed through different members of a cortical cell population at different times. This model exhibits standard features characteristic of Poisson models such as orientation tuning post-stimulus histograms and exponential interval histograms. In addition it makes testable predictions that follow from the γ latency coding.

  16. Soil erosion and sediment fluxes analysis: a watershed study of the Ni Reservoir, Spotsylvania County, VA, USA.

    Science.gov (United States)

    Pope, Ian C; Odhiambo, Ben K

    2014-03-01

    Anthropogenic forces that alter the physical landscape are known to cause significant soil erosion, which has negative impact on surface water bodies, such as rivers, lakes/reservoirs, and coastal zones, and thus sediment control has become one of the central aspects of catchment management planning. The revised universal soil loss equation empirical model, erosion pins, and isotopic sediment core analyses were used to evaluate watershed erosion, stream bank erosion, and reservoir sediment accumulation rates for Ni Reservoir, in central Virginia. Land-use and land cover seems to be dominant control in watershed soil erosion, with barren land and human-disturbed areas contributing the most sediment, and forest and herbaceous areas contributing the least. Results show a 7 % increase in human development from 2001 (14 %) to 2009 (21.6 %), corresponding to an increase in soil loss of 0.82 Mg ha(-1) year(-1) in the same time period. (210)Pb-based sediment accumulation rates at three locations in Ni Reservoir were 1.020, 0.364, and 0.543 g cm(-2) year(-1) respectively, indicating that sediment accumulation and distribution in the reservoir is influenced by reservoir configuration and significant contributions from bedload. All three locations indicate an increase in modern sediment accumulation rates. Erosion pin results show variability in stream bank erosion with values ranging from 4.7 to 11.3 cm year(-1). These results indicate that urban growth and the decline in vegetative cover has increased sediment fluxes from the watershed and poses a significant threat to the long-term sustainability of the Ni Reservoir as urbanization continues to increase.

  17. Evaluation of soil amendments as a remediation alternative for cadmium-contaminated soils under cacao plantations.

    Science.gov (United States)

    Chavez, E; He, Z L; Stoffella, P J; Mylavarapu, R; Li, Y; Baligar, V C

    2016-09-01

    Elevated plant-available cadmium (Cd) in soils results in contamination to cacao (Theobroma cacao L) beans. Effectiveness of vermicompost and zeolite in reducing available Cd in three cacao-growing soils was studied under laboratory conditions. Sorption-desorption experiments were conducted in soils and amendments. Cadmium was added at 0 or 5 mg kg(-1) (spiked), then, amendments were incorporated at 0, 0.5, or 2 %. Amended soils were incubated at room temperature for 28 days. Plant-available Cd was determined using 0.01 M CaCl2 (WSE) and Mehlich 3 (M3) extraction procedures in subsamples taken from individual bags at six time intervals. Soils and amendments displayed different sorption characteristics and a better fit was attained with Freundlich model (R (2) > 0.82). Amendments were ineffective in reducing extractable Cd in non-spiked soils. In Cd-spiked soils, vermicompost at 2 % significantly reduced WSE-Cd (P