Publications by authors named "Yves Thiry"

38 Publications

Selenium distribution in French forests: Influence of environmental conditions.

Sci Total Environ 2021 Jun 1;774:144962. Epub 2021 Feb 1.

CNRS/Univ. Pau & Pays de l'Adour/E2S UPPA, Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux (IPREM), UMR 5254, 64053 Pau, France. Electronic address:

Selenium is a trace element and an essential nutrient. Its long-lived radioisotope, selenium 79 is of potential radio-ecological concern in surface environment of deep geological repository for high-level radioactive waste. In this study, the influence of environmental, climatic and geochemical conditions on stable Se (as a surrogate of Se) accumulation was statistically assessed (PCA analysis, Kruskall-Wallis and Spearman tests) based on the analysis of its concentration in litterfall, humus, and soil samples collected at 51 forest sites located in France. Selenium concentrations were in the ranges: 22-369, 57-1608 and 25-1222 μg kg respectively in litterfall, humus, and soil. The proximity of the ocean and oceanic climate promoted Se enrichment of litterfall, likely due to a significant reaction of wet deposits with forest canopy. Se content was enhanced by humification (up to 6 times) suggesting that Se concentrations in humus were affected by atmospheric inputs. Selenium stock in humus decreased in the order of decreasing humus biomass and increasing turnover of organic matter: mor > moder > mull. Positive correlations between Se content and geochemical parameters such as organic carbon content, total Al and total Fe confirmed the important role of organic matter (OM) and mineral Fe/Al oxides in Se retention in soils.
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http://dx.doi.org/10.1016/j.scitotenv.2021.144962DOI Listing
June 2021

A dataset of Cs activity concentration and inventory in forests contaminated by the Fukushima accident.

Sci Data 2020 12 18;7(1):431. Epub 2020 Dec 18.

Research and Development Division, Andra, 1-7 Rue Jean-Monnet, 92298, Châtenay-Malabry cedex, France.

The majority of the area contaminated by the Fukushima Daiichi Nuclear Power Plant accident is covered with forests. We developed a dataset for radiocaesium (Cs) in trees, soil, and mushrooms measured at numerous forest sites. The Cs activity concentration and inventory data reported in scientific journal papers written in English and Japanese, governmental reports, and governmental monitoring data on the web were collated. The ancillary information describing the forest stands were also collated, and further environmental information (e.g. climate) was derived from the other databases using longitude and latitude coordinates of the sampling locations. The database contains 8593, 4105, and 3189 entries of activity concentration data for trees, soil, and mushrooms, and 471 and 3521 entries of inventory data for trees and soil, respectively, which were collected from 2011 to 2017, and covers the entire Fukushima prefecture. The data can be used to document and understand the spatio-temporal dynamics of radiocaesium in the affected region and to aid the development and validation of models of radiocaesium dynamics in contaminated forests.
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http://dx.doi.org/10.1038/s41597-020-00770-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7749123PMC
December 2020

Atmospheric iodine, selenium and caesium depositions in France: I. Spatial and seasonal variations.

Chemosphere 2021 Jun 13;273:128971. Epub 2020 Nov 13.

CNRS/Univ. Pau & Pays de L'Adour/E2S UPPA, Institut des Sciences Analytiques et de Physico-Chimie pour L'Environnement et Les Matériaux, UMR 5254, Avenue Du Président Angot, 64000, Pau, France. Electronic address:

The spatial distribution and seasonal variations of atmospheric iodine (I), selenium (Se) and caesium (Cs) depositions remain unclear and this precludes adequate inputs for biogeochemical models. We quantified total concentrations and fluxes of these elements in rainfalls from 27 monitoring sites in France with contrasted climatic conditions; monthly measurements were taken over one year (starting in 2016/09). Since speciation of I and Se can impact their behaviour in the environment, analysis of their inorganic compounds was also conducted. Our results showed that annual I concentrations in rainfall were much higher than those of Se and Cs (annual means = 1.56, 0.044 and 0.005 μg L, respectively). The annual iodine concentrations were highly positively correlated with those of marine elements (i.e. Na, Cl and Mg), involving higher I concentrations under oceanic climate than for transition, continental and mountainous ones. Furthermore, common patterns were found between Se concentrations and both marine and terrestrial components consistent with the various sources of Se in atmosphere. The association of Cs with two anthropogenic components (i.e. NH and NO) used in agriculture supports the hypothesis of its terrestrial origin (i.e. from atmospheric dusts) in rainfall. We found higher rainfall concentrations of I during the warmest months for all climates. However, no specific seasonal trend occurred for Se and Cs. On annual average, rainfall contained mostly unidentified selenium compounds (inorganic Se proportions = 25-54%) and equal proportions of inorganic and unidentified I compounds. Concentrations of iodate were higher under oceanic climate consistent with an iodine marine-origin.
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http://dx.doi.org/10.1016/j.chemosphere.2020.128971DOI Listing
June 2021

Atmospheric iodine, selenium and caesium depositions in France: II. Influence of forest canopies.

Chemosphere 2021 Jun 13;273:128952. Epub 2020 Nov 13.

CNRS/Univ. Pau & Pays de l'Adour/E2S UPPA, Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux, UMR 5254, Avenue du Président Angot, 64000, Pau, France. Electronic address:

Estimation of the canopy influence on atmospheric inputs of iodine (I), selenium (Se) and caesium (Cs) in terrestrial ecosystems is an essential condition for appropriate biogeochemical models. However, the processes involved in rain composition modifications after its passage through forest canopy have been barely studied for these elements. We monitored I, Se and Cs concentrations in both rainfall and throughfall of fourteen French forested sites throughout one year, and estimated dry deposition and canopy exchange fluxes for these elements, as well as speciation of I and Se. Comparison of rainfall and throughfall elemental composition highlighted an important impact of forest canopy on both (i) concentrations and fluxes of I, Se and Cs, and (ii) I and Se species. For the three elements, most of their throughfall concentrations were higher than corresponding rainfall. The increase of throughfall elemental fluxes was mostly due to dry deposition for I and Se although the canopy exchange model revealed some sorption within the canopy in most cases; for Cs, foliage leaching was most influencing. Regarding speciation, iodine species in rainfall were highly modified by forest canopy with an important increase of unidentified I proportion in throughfall (on average 49 and 82% in rainfall and throughfall, respectively), possibly due to washoff of dry deposition and/or to transformation into organic forms. Similarly, while rainfall was composed of 26-54% of inorganic Se, inorganic species were undetectable in throughfall. This dataset represents key information to improve modelling of I, Se and Cs cycling within forest ecosystems.
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http://dx.doi.org/10.1016/j.chemosphere.2020.128952DOI Listing
June 2021

Vertical distributions of radiocesium in Japanese forest soils following the Fukushima Daiichi Nuclear Power Plant accident: A meta-analysis.

J Environ Radioact 2020 Dec 24;225:106422. Epub 2020 Sep 24.

School of Biosciences, University of Nottingham, Sutton Bonington, LE12 5RD, UK.

This study investigated the temporal change in vertical distributions of radiocesium inventories in Japanese forest soils during the early phase (from 2011 to 2017) following the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, using three simple parameters. We calculated the fraction in the organic layer (F), the migration center (X) and the relaxation depth (α) using 99 soil inventory data sets. F decreased significantly from 2011 to 2017 (logistic analysis, p < 0.001). In addition, F in the FDNPP zone rapidly decreased compared to that in the Chernobyl Nuclear Power Plant (ChNPP) zone from the first year to the second year. Different migration rates from organic to mineral soil layers between previous studies in the ChNPP and this study have several possible causes such as organic litter features, climate and physico-chemical forms of initial deposition. In mineral soil layers in the FDNPP zone, only X increased significantly with time according to generalized mixed model analysis (p < 0.01). However, X and α in the ChNPP zone decreased from two to five years after the accident in 1986, which shows a high Cs retention in the organic layer even in the fifth year after the accident. The vertical migration of Cs in the mineral soil layer in the FDNPP zone appears to be due to low input of Cs from organic to surface mineral soil layer after the second year. These results indicate that Cs retention capacity of the organic layer can affect the apparent vertical migration of Cs in the underlying mineral soil layer.
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http://dx.doi.org/10.1016/j.jenvrad.2020.106422DOI Listing
December 2020

Soil organic matter affects arsenic and antimony sorption in anaerobic soils.

Environ Pollut 2020 Feb 4;257:113566. Epub 2019 Nov 4.

KU Leuven, Department of Earth and Environmental Sciences, Kasteelpark Arenberg 20 Bus 2459, 3001, Leuven, Belgium.

Soil organic matter (SOM) affects arsenic (As) and antimony (Sb) mobility in soils under waterlogged conditions by acting as an electron donor, by catalyzing redox-cycling through electron shuttling and by acting as a competing ligand. This study was set up to disentangle these different effects of SOM towards As and Sb sorption in anaerobic soils. Nine samples were taken at different depths in an agricultural soil profile to collect samples with a natural SOM gradient (<1-40 g soil organic carbon kg). The samples were incubated either or not under waterlogged conditions in an anaerobic chamber for 63-70 days, and glucose (5 g C kg) was either or not added to the anaerobic incubated samples as an electron donor that neither acts as an electron shuttle nor as a competing ligand. The solid-liquid distribution coefficients (K) of As and Sb were measured at trace levels. The K values of As decreased ∼2 orders of magnitude upon waterlogging the SOM rich topsoil, while no additional changes were observed when glucose was added. In contrast, smaller changes in the As K values were found in the low SOM containing subsoil samples, unless glucose was added that mobilised As. The Sb K values increased upon reducing conditions up to factor 20, but again only in the high SOM topsoil samples. Surprisingly, the Sb immobilisation during waterlogging only occurred in Sb amended soils whereas the geogenic Sb was mobilised upon reducing conditions, although total dissolved Sb concentrations remained low (<10 nM). The change in As and Sb sorption upon waterlogging was similar in the SOM rich topsoil as in the low SOM subsoil amended with glucose. This suggests that the SOM dependent changes in As and Sb mobility in response to soil waterlogging are primarily determined by the role of SOM as electron donor.
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http://dx.doi.org/10.1016/j.envpol.2019.113566DOI Listing
February 2020

Assessing the recycling of chlorine and its long-lived Cl isotope in terrestrial ecosystems through dynamic modeling.

Sci Total Environ 2020 Jan 4;700:134482. Epub 2019 Oct 4.

Andra, Research and Development Division, 1-7 Rue Jean-Monnet, 92298 Châtenay-Malabry cedex, France. Electronic address:

It is unclear to what extent chlorine (Cl) and its long-lived isotope Cl are recycled in different terrestrial environments in response to time-variable inputs. A new version of a dynamic compartment model was developed to examine the transformation and transfer processes influencing the partitioning and persistence of both Cl and Cl in forest ecosystems. The model's performance was evaluated by comparing simulations and field observations of scenarios of stable Cl atmospheric deposition and of global Cl fallout. The model reproduced Cl storage in soil reasonably well, despite wide heterogeneity in environmental conditions and atmospheric deposits. Sensitivity analysis confirmed that the natural production of organochlorine in soil plays a major role in Cl build-up and affects long-term Cl dynamics. The timeframe required for the soil organochlorine pool to reach equilibrium in a steady-state system was several thousands of years. Interestingly, root uptake flux, a predominant pathway of the inorganic cycle, was found to affect both inorganic and organic pools in soil, highlighting the importance of plant-soil interactions in Cl dynamics. Model outputs agreed well with local Cl measurements, and demonstrated that 90% of the Cl found in soil may have come from bomb-test fallout. The pattern of estimated Cl/Cl ratios showed that soil Cl was not in equilibrium with Cl levels in rain input in the post-bomb period. Complete recovery of a natural isotopic ratio in drainage water will need a time close to the residence time of organic Cl in soil: i.e., 800 years. A simple dynamic model concept was found to be suitable to illustrate the plant-soil interactions combining both the inorganic and organic Cl cycles acting over different time scales.
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http://dx.doi.org/10.1016/j.scitotenv.2019.134482DOI Listing
January 2020

Iodine budget in forest soils: Influence of environmental conditions and soil physicochemical properties.

Chemosphere 2019 Jun 15;224:20-28. Epub 2019 Feb 15.

CNRS/ Univ. Pau & Pays de l'Adour/E2S UPPA, Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux, UMR 5254, Avenue du Président Angot, 64000, Pau, France. Electronic address:

Due to its longevity, radioisotope I is a health concern following potential releases in the environment which raises questions about residence and exposure times relevant for risk assessments. We determined I concentrations (as a surrogate for I) in a series of French forest soils (i.e. litters, humus and mineral soils) under different vegetation and climate conditions in order to identify the major processes affecting its accumulation and persistence in the soil column. The input fluxes linked to rainfall, throughfall and litterfall were also characterized. Main results obtained showed that: (i) rainfall iodine concentrations probably influenced those of litterfall through absorption by leaves/needles returning to the ground; (ii) throughfall was the major iodine input to soils (mean = 83%), compared to litterfall (mean = 17%); (iii) humus represented a temporary storage of iodine from atmospheric and biomass deposits; (iv) iodine concentrations in soils depended on both the iodine inputs and the soil's ability to retain iodine due to its organic matter, total iron and aluminium concentrations; (v) these soil properties were the main factors influencing the accumulation of iodine in the soil column, resulting in residence times of 419-1756 years; and (vi) the leaching of iodine-containing organic matter dissolved in soil solution may be an important source of labile organic iodine for groundwater and streams.
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http://dx.doi.org/10.1016/j.chemosphere.2019.02.060DOI Listing
June 2019

Iodine distribution and cycling in a beech (Fagus sylvatica) temperate forest.

Sci Total Environ 2018 Dec 18;645:431-440. Epub 2018 Jul 18.

CNRS/Univ. Pau & Pays de l'Adour, Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux, UMR 5254, Avenue du Président Angot, 64000 Pau, France. Electronic address:

Radioiodine is of health concerns in case of nuclear events. Possible pathways and rates of flow are essential information for risk assessment. Forest ecosystems could influence the global cycle of long-lived radioiodine isotope (I) with transfer processes similar to stable isotope (I). Understanding iodine cycling in forest involves study of the ecosystem as a whole. In this context, we determined the I contents and distribution in soil, tree compartments and atmospheric inputs during a three years in situ monitoring of a temperate beech forest stand. The iodine cycle was first characterized in terms of stocks by measuring its concentrations in: tree, litterfall, humus, soil, rainfall, throughfall, stemflow and soil solutions. Main annual fluxes (requirement, uptake and internal transfers) and forest input-output budget were also estimated using conceptual model calculations. Our findings show that: (i) soil is the main I reservoir accounting for about 99.9% of ecosystem total stock; (ii) iodine uptake by tree represents a minor fraction of the available pool in soil (<0.2%); (iii) iodine allocation between tree compartments involves low immobilization in wood and restricted location in the roots; (iv) translocation of excess iodine towards senescing foliage appears as an elimination process for trees, and (v) litterfall is a major pathway in the I biological cycling. In our soil conditions, the input - output budget shows that the ecosystem behaves as a potential source of I for groundwater.
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http://dx.doi.org/10.1016/j.scitotenv.2018.07.039DOI Listing
December 2018

Development and assessment of a simple ecological model (TRIPS) for forests contaminated by radiocesium fallout.

J Environ Radioact 2018 Oct 21;190-191:149-159. Epub 2018 May 21.

EDF R&D, LNHE, 6 quai Watier, 78400 Chatou, France.

The management of vast forested zones contaminated by radiocesium (rCs) following the Chernobyl and Fukushima fallout is of great social and economic concern in affected areas and requires appropriate dynamic models as predictive or questioning tools. Generally, the existing radio-ecological models need less fragmented data and more ecological realism in their quantitative description of the rCs cycling processes. The model TRIPS ("Transfer of Radionuclide In Perennial vegetation Systems") developed in this study privileged an integrated approach which makes the best use of mass balance studies and available explicit experimental data for Scots pine stands. A main challenge was the differentiation and calibration of foliar absorption as well as root uptake in order to well represent the rCs biocycling. The general dynamics of rCs partitioning was simulated with a relatively good precision against an independent series of observed values. In our scenario the rCs biological cycling enters a steady-state about 15 years after the atmospheric deposits. At that time, the simulations showed an equivalent contribution of foliage and root uptake to the tree contamination. But the root uptake seems not sufficient to compensate the activity decline in the tree. The initial foliar uptake and subsequent internal transfers were confirmed to have a great possible impact on the phasing of tree contamination. An extra finding concerns the roots system acting as a buffer in the early period. The TRIPS model is particularly useful in cases where site-specific integrated datasets are available, but it could also be used with adequate caution to generic sites. This development paves the way for simplification or integration of new modules, as well as for a larger number of other applications for the Chernobyl or Fukushima forests once the appropriate data become available. According to the sensitivity analysis that involves in particular reliable estimates of net foliar uptake as well as root uptake not disconnected from rCs exchange reactions in soil.
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http://dx.doi.org/10.1016/j.jenvrad.2018.05.009DOI Listing
October 2018

Radiocaesium partitioning in Japanese cedar forests following the "early" phase of Fukushima fallout redistribution.

Sci Rep 2016 11 23;6:37618. Epub 2016 Nov 23.

Andra, Research and Development Division, 1-7 rue Jean-Monnet, 92298 Châtenay-Malabry, France.

Our study focused on radiocaesium (Cs) partitioning in forests, three vegetation periods after the Fukushima Daiichi nuclear power plant accident. Cs distribution in forest components (organic and mineral soil layers as well as tree compartments: stem, bark, needles, branches and roots) was measured for two Japanese cedar stand ages (17 and 33 years old). The results showed that around 85% of the initial deposit was found in the forest floor and topsoil. For the youngest stand almost 70% of the deposit is present in the forest floor, whereas for the oldest stand 50% is present in the 0-3 cm mineral soil layer. For trees, old and perennial organs (including dead and living needles and branches, litter fall and outer bark) directly exposed to the fallout remained the most contaminated. The crown concentrated 61-69% of the total tree contamination. Surprisingly the dead organs concentrated 25 ± 9% (young cedars) to 36 ± 20% (mature cedar) of the trees' residual activity, highlighting the importance of that specific compartment in the early post-accident phase for Japanese cedar forests. Although the stem (including bark) represents the highest biomass pool, it only concentrates 3.3% and 4.6% of the initial Cs deposit for mature and young cedars, respectively.
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http://dx.doi.org/10.1038/srep37618DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5120304PMC
November 2016

Influence of Se concentrations and species in hydroponic cultures on Se uptake, translocation and assimilation in non-accumulator ryegrass.

Plant Physiol Biochem 2016 Nov 2;108:372-380. Epub 2016 Aug 2.

Sorbonne Universités, UPMC Univ Paris 06, CNRS, EPHE, UMR7619 METIS, 4 Place Jussieu, 75005 Paris, France.

The success of biofortification and phytoremediation practices, addressing Se deficiency and Se pollution issues, hinges crucially on the fate of selenium in the plant media in response to uptake, translocation and assimilation processes. We investigate the fate of selenium in root and shoot compartments after 3 and 6 weeks of experiment using a total of 128 plants grown in hydroponic solution supplied with 0.2, 2, 5, 20 and 100 mg L of selenium in the form of selenite, selenate and a mixture of both species. Selenate-treated plants exhibited higher root-to-shoot Se translocation and total Se uptake than selenite-treated plants. Plants took advantage of the selenate mobility and presumably of the storage capacity of leaf vacuoles to circumvent selenium toxicity within the plant. Surprisingly, 28% of selenate was found in shoots of selenite-treated plants, questioning the ability of plants to oxidize selenite into selenate. Selenomethionine and methylated organo-selenium amounted to 30% and 8% respectively in shoots and 35% and 9% in roots of the identified Se, suggesting that selenium metabolization occurred concomitantly in root and shoot plant compartments and demonstrating that non-accumulator plants can synthesize notable quantities of precursor compound for volatilization. The present study demonstrated that non-accumulator plants can develop the same strategies as hyper-accumulator plants to limit selenium toxicity. When both selenate and selenite were supplied together, plants used selenate in a storage pathway and selenite in an assimilation pathway. Plants might thereby benefit from mixed supplies of selenite and selenate by saving enzymes and energy required for selenate reduction.
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http://dx.doi.org/10.1016/j.plaphy.2016.07.029DOI Listing
November 2016

Field study of time-dependent selenium partitioning in soils using isotopically enriched stable selenite tracer.

Sci Total Environ 2016 08 18;562:280-288. Epub 2016 Apr 18.

Laboratoire de Chimie Analytique Bio-Inorganique et Environnement (LCABIE), Université de Pau et des Pays de l'Adour/CNRS, UMR 5254, IPREM, Hélioparc, 2 Avenue du Président Angot, 64053 Pau Cedex 9, France. Electronic address:

A better understanding of selenium fate in soils at both short and long time scales is mandatory to consolidate risk assessment models relevant for managing both contamination and soil fertilization issues. The purpose of this study was thus to investigate Se retention processes and their kinetics by monitoring time-dependent distribution/speciation changes of both ambient and freshly added Se, in the form of stable enriched selenite-77, over a 2-years field experiment. This study clearly illustrates the complex reactivity of selenium in soil considering three methodologically defined fractions (i.e. soluble, exchangeable, organic). Time-dependent redistribution of Se-77 within solid-phases having different reactivity could be described as a combination of chemical and diffusion controlled processes leading to its stronger retention. Experimental data and their kinetic modeling evidenced that transfer towards less labile bearing phases are controlled by slow processes limiting the overall sorption of Se in soils. These results were used to estimate time needed for (77)Se to reach the distribution of naturally present selenium which may extend up to several decades. Ambient Se speciation accounted for 60% to 100% of unidentified species as function of soil type whereas (77)Se(IV) remained the more abundant species after 2-years field experiment. Modeling Se in the long-term without taking account these slow sorption kinetics would thus result in underestimation of Se retention. When using models based on Kd distribution coefficient, they should be at least reliant on ambient Se which is supposed to be at equilibrium.
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http://dx.doi.org/10.1016/j.scitotenv.2016.03.207DOI Listing
August 2016

Chlorination and dechlorination rates in a forest soil - A combined modelling and experimental approach.

Sci Total Environ 2016 Jun 5;554-555:203-10. Epub 2016 Mar 5.

Department of Thematic Studies - Environmental Change, Linköping University, 581 83 Linköping, Sweden.

Much of the total pool of chlorine (Cl) in soil consists of naturally produced organic chlorine (Clorg). The chlorination of bulk organic matter at substantial rates has been experimentally confirmed in various soil types. The subsequent fates of Clorg are important for ecosystem Cl cycling and residence times. As most previous research into dechlorination in soils has examined either single substances or specific groups of compounds, we lack information about overall bulk dechlorination rates. Here we assessed bulk organic matter chlorination and dechlorination rates in coniferous forest soil based on a radiotracer experiment conducted under various environmental conditions (additional water, labile organic matter, and ammonium nitrate). Experiment results were used to develop a model to estimate specific chlorination (i.e., fraction of Cl(-) transformed to Clorg per time unit) and specific dechlorination (i.e., fraction of Clorg transformed to Cl(-) per time unit) rates. The results indicate that chlorination and dechlorination occurred simultaneously under all tested environmental conditions. Specific chlorination rates ranged from 0.0005 to 0.01 d(-1) and were hampered by nitrogen fertilization but were otherwise similar among the treatments. Specific dechlorination rates were 0.01-0.03d(-1) and were similar among all treatments. This study finds that soil Clorg levels result from a dynamic equilibrium between the chlorination and rapid dechlorination of some Clorg compounds, while another Clorg pool is dechlorinated more slowly. Altogether, this study demonstrates a highly active Cl cycling in soils.
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http://dx.doi.org/10.1016/j.scitotenv.2016.02.208DOI Listing
June 2016

Stable isotope tracing: a powerful tool for selenium speciation and metabolic studies in non-hyperaccumulator plants (ryegrass Lolium perenne L.).

Anal Bioanal Chem 2015 Dec 1;407(30):9029-42. Epub 2015 Oct 1.

Laboratoire de Chimie Analytique Bio-Inorganique et Environnement (LCABIE), Université de Pau et des Pays de l'Adour/CNRS, UMR 5254, IPREM, Hélioparc, 2 Avenue du Président Angot, 64053, Pau Cedex 9, France.

Selenium is both essential and toxic for mammals; the range between the two roles is narrow and not only dose-dependent but also related to the chemical species present in foodstuff. Unraveling the metabolism of Se in plants as a function of Se source may thus lead to ways to increase efficiency of fertilization procedures in selenium deficient regions. In this study, stable-isotope tracing was applied for the first time in plants to simultaneously monitor the bio-incorporation of two inorganic Se species commonly used as foodstuff enrichment sources. Occurrence and speciation of Se coming from different Se sources were investigated in root and leaf extracts of ryegrass (Lolium perenne L.), which had been co-exposed to two labeled Se species ((77)SeIV and (82)SeVI). Although the plant absorbed similar amounts of Se when supplied in the form of selenite or selenate, the results evidenced marked differences in speciation and tissues allocation. Selenite was converted into organic forms incorporated mostly into high molecular weight compounds with limited translocation to leaves, whereas selenate was highly mobile being little assimilated into organic forms. Double-spike isotopic tracer methodology makes it possible to compare the metabolism of two species-specific Se sources simultaneously in a single experiment and to analyze Se behavior in not-hyperaccumulator plants, the ICP-MS sensitivity being improved by the use of enriched isotopes.
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http://dx.doi.org/10.1007/s00216-015-9069-4DOI Listing
December 2015

Experimental evidence of large changes in terrestrial chlorine cycling following altered tree species composition.

Environ Sci Technol 2015 Apr 1;49(8):4921-8. Epub 2015 Apr 1.

†Department of Thematic Studies-Environmental Change, Linköping University, SE-581 83, Linköping, Sweden.

Organochlorine molecules (Clorg) are surprisingly abundant in soils and frequently exceed chloride (Cl(-)) levels. Despite the widespread abundance of Clorg and the common ability of microorganisms to produce Clorg, we lack fundamental knowledge about how overall chlorine cycling is regulated in forested ecosystems. Here we present data from a long-term reforestation experiment where native forest was cleared and replaced with five different tree species. Our results show that the abundance and residence times of Cl(-) and Clorg after 30 years were highly dependent on which tree species were planted on the nearby plots. Average Cl(-) and Clorg content in soil humus were higher, at experimental plots with coniferous trees than in those with deciduous trees. Plots with Norway spruce had the highest net accumulation of Cl(-) and Clorg over the experiment period, and showed a 10 and 4 times higher Cl(-) and Clorg storage (kg ha(-1)) in the biomass, respectively, and 7 and 9 times higher storage of Cl(-) and Clorg in the soil humus layer, compared to plots with oak. The results can explain why local soil chlorine levels are frequently independent of atmospheric deposition, and provide opportunities for improved modeling of chlorine distribution and cycling in terrestrial ecosystems.
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http://dx.doi.org/10.1021/acs.est.5b00137DOI Listing
April 2015

Soil-to-plant transfer factors of radioactive Ca, Sm and Pd isotopes: critical assessment of the use of analogies to derive best-estimates from existing non-specific data.

J Environ Radioact 2014 Oct 21;136:152-61. Epub 2014 Jun 21.

French Agency for Radioactive Waste Management (Andra), Parc de la Croix Blanche, 1-7, Rue Jean Monnet, 92298 Châtenay-Malabry Cedex, France.

(45)Ca, (151)Sm and (107)Pd are three radionuclides present in low to intermediate in activity radioactive wastes for which no soil-to-plant Transfer Factors (TF) values are available to be used in biosphere models for Ecological Risk Assessment. In the absence of specific radioecological studies, this work reviews and analyzes the existing literature for stable isotopes of Pd, Sm and Ca in order to derive best estimates for TF values that could be used as Transfer Factors. Alternative methods of extrapolation are also critically assessed. The values have been classified according to climatic zone, plant class and soil type for each element. The overall geometric mean TF values (for all plants and conditions) was calculated as 8.4E-02 for Pd, for which the value of radioRu in TRS-472 is also available. The mean TF for Sm was 4.2E-04. This value was lower than the TF values for radioactive Ce that are proposed as alternative values for Sm in TRS-472. The former may be relevant for long term assessments and the latter could possibly used to describe the short term (151)Sm post-release behaviour. The mean value for Ca is 2.3E-01 but varies considerably among plants of a given class due to the variety of plant Ca uptake behaviors. Alternatively, to limit this variability, Ca data content for dry plant matter, as analyzed using the phylogenetic method, could be used to derive TF values if the conservation of isotopic ratio of (45)Ca to stable Ca in soils and in plants hypothesis is taken into account. The TF for Ca in sub-tropical zones is 10-fold lower than in temperate zones. There is a lot of data available about exchangeable Ca in soil, which mean that we could calculate an available TF. The analysis shows that Ca bioavailability is also a key factor within transfer.
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http://dx.doi.org/10.1016/j.jenvrad.2014.06.003DOI Listing
October 2014

Distribution and speciation of ambient selenium in contrasted soils, from mineral to organic rich.

Sci Total Environ 2014 May 15;479-480:93-101. Epub 2014 Feb 15.

Laboratoire de Chimie Analytique Bio-Inorganique et Environnement (LCABIE), IPREM, Université de Pau et des Pays de l'Adour/CNRS UMR 5254, Hélioparc, 2 Avenue du Président Angot, 64053 Pau Cedex 9, France.

Selenium adsorption onto oxy-hydroxides mainly controls its mobility in volcanic soils, red earths and soils poor in organic matter (OM) while the influence of OM was emphasized in podzol and peat soils. This work aims at deciphering how those solid phases influence ambient Se mobility and speciation under less contrasted conditions in 26 soils spanning extensive ranges of OM (1-32%), Fe/Al oxy-hydroxides (0.3-6.1%) contents and pH (4.0-8.3). The soil collection included agriculture, meadow and forest soils to assess the influence of OM quality as well. Trace concentrations of six ambient Se species (Se(IV), Se(VI) and 4 organo-Se compounds) were analyzed by HPLC-ICP-MS in three extractants (ultrapure water, phosphate and sodium hydroxide) targeting Se associated to different soil phases. The Kd values determined from ultrapure water extraction were higher than those reported in commonly used short-term experiments after Se-spiking. Correlations of ambient Se content and distribution with soil parameters explained this difference by an involvement of slow processes in Se retention in soils. The 26 Kd values determined here for a wide variety of soils thus represent a relevant database for long-term prediction of Se mobility. For soils containing less than 20% OM, ambient Se solubility is primarily controlled by its adsorption onto crystalline oxy-hydroxides. However, OM plays an important role in Se mobility by forming organo-mineral associations that may protect adsorbed Se from leaching and/or create anoxic zones (aggregates) where Se is immobilized after its reduction. Although for the first time, inorganic Se(IV), Se(VI) and organo-Se compounds were simultaneously investigated in a large soil collection, high Se proportions remain unidentified in each soil extract, most probably due to Se incorporation and/or binding to colloidal-sized OM. Variations of environmental factors regulating the extent of OM-mineral associations/aggregation may thus lead to changes in Se mobility and bio-availability.
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http://dx.doi.org/10.1016/j.scitotenv.2014.01.079DOI Listing
May 2014

A new methodology involving stable isotope tracer to compare simultaneously short- and long-term selenium mobility in soils.

Anal Bioanal Chem 2014 Feb 19;406(4):1221-31. Epub 2013 Sep 19.

Laboratoire de Chimie Analytique Bio-Inorganique et Environnement (LCABIE), IPREM, Université de Pau et des Pays de l'Adour/CNRS UMR 5254, Hélioparc, 2 Avenue du Président Angot, 64053, Pau Cedex 9, France,

A better understanding of Se fate in soils is required for different environmental issues, such as radioactive waste management or soil fertilization procedures. In these contexts, the mobility and speciation of Se have to be studied at both short and long terms after Se inputs. Here, we present a new methodology to monitor simultaneously the reactivity of added (isotopic enriched tracers) and ambient Se at trace level in soils by high-performance liquid chromatography inductively coupled plasma mass spectrometry (ICP-MS) following specific extractions. To do so, the collision/reaction cell of the ICP-MS instrument and the interference corrections were optimized to measure reliably the four major Se isotopes. To exemplify the method capabilities, the behaviors of added (77)Se(IV) and ambient Se were followed up in two soils submitted to an ageing process during 3 months. The solid/liquid distribution of added Se reached a steady state after 1 month while its speciation and distribution among soil solid phases were still changing after 3 months. The results clearly demonstrate that slow processes are involved in Se retention and transformation in soils. The usual short-term experiments (<1 month) performed after Se addition are thus not suitable for long-term risk assessment. Interestingly, the behavior of added Se tended to that of ambient Se, suggesting that ambient Se would be useful to infer the fate of Se input over long time scales.
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http://dx.doi.org/10.1007/s00216-013-7323-1DOI Listing
February 2014

Modelling of the natural chlorine cycling in a coniferous stand: implications for chlorine-36 behaviour in a contaminated forest environment.

J Environ Radioact 2012 May 8;107:56-67. Epub 2012 Jan 8.

SCK-CEN, Biosphere Impact Studies Unit, 200 Boeretang, 2400 Mol, Belgium.

Considered as one of the most available radionuclide in soil-plant system, ³⁶Cl is of potential concern for long-term management of radioactive wastes, due to its high mobility and its long half-life. To evaluate the risk of dispersion and accumulation of ³⁶Cl in the biosphere as a consequence of a potential contamination, there is a need for an appropriate understanding of the chlorine cycling dynamics in the ecosystems. To date, a small number of studies have investigated the chlorine transfer in the ecosystem including the transformation of chloride to organic chlorine but, to our knowledge, none have modelled this cycle. In this study, a model involving inorganic as well as organic pools in soils has been developed and parameterised to describe the biogeochemical fate of chlorine in a pine forest. The model has been evaluated for stable chlorine by performing a range of sensitivity analyses and by comparing the simulated to the observed values. Finally a range of contamination scenarios, which differ in terms of external supply, exposure time and source, has been simulated to estimate the possible accumulation of ³⁶Cl within the different compartments of the coniferous stand. The sensitivity study supports the relevancy of the model and its compartments, and has highlighted the chlorine transfers affecting the most the residence time of chlorine in the stand. Compared to observations, the model simulates realistic values for the chlorine content within the different forest compartments. For both atmospheric and underground contamination scenarios most of the chlorine can be found in its organic form in the soil. However, in case of an underground source, about two times less chlorine accumulates in the system and proportionally more chlorine leaves the system through drainage than through volatilisation.
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http://dx.doi.org/10.1016/j.jenvrad.2011.12.014DOI Listing
May 2012

Organic matter chlorination rates in different boreal soils: the role of soil organic matter content.

Environ Sci Technol 2012 Feb 17;46(3):1504-10. Epub 2012 Jan 17.

Department of Thematic Studies, Water and Environmental Studies, Linköping University, 58183 Linköping, Sweden.

Transformation of chloride (Cl(-)) to organic chlorine (Cl(org)) occurs naturally in soil but it is poorly understood how and why transformation rates vary among environments. There are still few measurements of chlorination rates in soils, even though formation of Cl(org) has been known for two decades. In the present study, we compare organic matter (OM) chlorination rates, measured by (36)Cl tracer experiments, in soils from eleven different locations (coniferous forest soils, pasture soils and agricultural soils) and discuss how various environmental factors effect chlorination. Chlorination rates were highest in the forest soils and strong correlations were seen with environmental variables such as soil OM content and Cl(-) concentration. Data presented support the hypothesis that OM levels give the framework for the soil chlorine cycling and that chlorination in more organic soils over time leads to a larger Cl(org) pool and in turn to a high internal supply of Cl(-) upon dechlorination. This provides unexpected indications that pore water Cl(-) levels may be controlled by supply from dechlorination processes and can explain why soil Cl(-) locally can be more closely related to soil OM content and the amount organically bound chlorine than to Cl(-) deposition.
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http://dx.doi.org/10.1021/es203191rDOI Listing
February 2012

Relevance of Radiocaesium Interception Potential (RIP) on a worldwide scale to assess soil vulnerability to 137Cs contamination.

J Environ Radioact 2012 Feb 2;104:87-93. Epub 2011 Oct 2.

SCK•CEN, Belgian Nuclear Research Center, Foundation of Public Utility, Biosphere Impact Studies, Boeretang 200, 2400 Mol, Belgium.

The extent of radiocaesium retention in soil is important to quantify the risk of further foodchain contamination. The Radiocaesium Interception Potential (RIP -Cremers et al., 1988, Nature 335, 247-249) is an intrinsic soil parameter which can be used to categorize soils or minerals in terms of their capacity to selectively adsorb radiocaesium. In this study, we measured RIP for a large soil collection (88 soil samples) representative of major FAO soil reference groups on a worldwide scale and tested the possibility to predict the RIP on the basis of other easily accessible or measurable soil data. We also compared RIP values with those obtained from separate chemical extraction experiments. The range of measured RIP values (1.8-13300 mmol kg(-1)) was shown to include nearly all possible cases of agricultural soil contamination. Only Podzols, Andosols and Ferralsols were clearly characterized by a very low RIP (<2000 mmol kg(-1)). On a worldwide scale, RIP was in fact slightly related to soil reference type or other simple major physicochemical parameters such as clay percentage or organic matter. Conversely our results indicated a link between the RIP and radiocaesium extractability across very different soils. We showed that, with the proposed scale of RIP values, a simple acid extraction method can provide an operational result highly predictive of potential RIP despite very contrasting soil properties. The RIP could be estimated from the empirical equation: RIP = (-31.701 ∗ log(AER) + 58.886)(2) where AER is the fraction of acid-extractable radiocaesium.
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http://dx.doi.org/10.1016/j.jenvrad.2011.09.002DOI Listing
February 2012

Chloride and organic chlorine in forest soils: storage, residence times, and influence of ecological conditions.

Environ Sci Technol 2011 Sep 3;45(17):7202-8. Epub 2011 Aug 3.

Andra, Research and Development Division, 1-7 rue Jean Monnet, 92298 Châtenay-Malabry, France.

Recent studies have shown that extensive chlorination of natural organic matter significantly affects chlorine (Cl) residence time in soils. This natural biogeochemical process must be considered when developing the conceptual models used as the basis for safety assessments regarding the potential health impacts of 36-chlorine released from present and planned radioactive waste disposal facilities. In this study, we surveyed 51 French forested areas to determine the variability in chlorine speciation and storage in soils. Concentrations of total chlorine (Cl(tot)) and organic chlorine (Cl(org)) were determined in litterfall, forest floor and mineral soil samples. Cl(org) constituted 11-100% of Cl(tot), with the highest concentrations being found in the humus layer (34-689 mg Cl(org) kg(-1)). In terms of areal storage (53 - 400 kg Cl(org) ha(-1)) the mineral soil dominated due to its greater thickness (40 cm). Cl(org) concentrations and estimated retention of organochlorine in the humus layer were correlated with Cl input, total Cl concentration, organic carbon content, soil pH and the dominant tree species. Cl(org) concentration in mineral soil was not significantly influenced by the studied environmental factors, however increasing Cl:C ratios with depth could indicate selective preservation of chlorinated organic molecules. Litterfall contributions of Cl were significant but generally minor compared to other fluxes and stocks. Assuming steady-state conditions, known annual wet deposition and measured inventories in soil, the theoretical average residence time calculated for total chlorine (inorganic (Cl(in)) and organic) was 5-fold higher than that estimated for Cl(in) alone. Consideration of the Cl(org) pool is therefore clearly important in studies of overall Cl cycling in terrestrial ecosystems.
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http://dx.doi.org/10.1021/es2011918DOI Listing
September 2011

Selenium speciation analysis at trace level in soils.

Anal Chim Acta 2011 Jan 9;684(1-2):126-33. Epub 2010 Nov 9.

Laboratoire de Chimie Analytique Bio-Inorganique et Environnement (LCABIE), Université de Pau et des Pays de l'Adour/CNRS, UMR 5254, IPREM, Hélioparc, 2 Avenue du Président Angot, 64053 Pau Cedex 9, France.

This paper describes the development of an analytical methodology to determine speciation of selenium present in soils at trace level (μg kg(-1)). The methodology was based on parallel single extractions and high performance liquid chromatography hyphenated to inductively coupled plasma mass spectrometry (HPLC-ICPMS). Two complementary chromatographic separations were used to confirm Se species identity. Different extractants, selected on the basis of sequential extraction schemes, were compared. Ultrapure water, 0.1 molL(-1) phosphate buffer (KH(2)PO(4)/K(2)HPO(4)) at pH 7 and 0.1 molL(-1) sodium hydroxide extractants were finally chosen owing to their efficiency in extracting Se and compatibility with Se species stability. These extractants allow also assessing respectively water-soluble Se (i.e. the most mobile Se fraction), exchangeable Se (i.e. sorbed onto soil component surface) and Se bound to soil organic matter. This methodology gives thus information on Se mobility related to its distribution in soil with preservation of original Se speciation. Detection limits range from 3 to 29ng(Se)L(-1) and from 0.1 to 10 μg(Se)kg(-1), allowing determination of Se species concentrations in extracts from soils containing native Se at trace level. The methodology was applied to three soils with total Se concentrations between 210 and 1560 μg(Se)kg(-1).
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http://dx.doi.org/10.1016/j.aca.2010.10.044DOI Listing
January 2011

Radiocesium transfer between Medicago truncatula plants via a common mycorrhizal network.

Environ Microbiol 2010 Aug 4;12(8):2180-9. Epub 2009 Dec 4.

Université catholique de Louvain, Unité de Microbiologie, Croix du Sud 3, 1348 Louvain-Neuve, Belgium.

Common mycorrhizal networks of arbuscular mycorrhizal fungi have been reported to transfer cesium between plants. However, a direct hyphae-mediated transfer (via cytoplasm/protoplasm) cannot be distinguished from an indirect transfer. Indeed, cesium released by the roots of the donor plant can be taken up by the receiver plant or fungal hyphae. In the present study, Medicago truncatula plants were connected by a common mycorrhizal network and Prussian Blue (ammonium-ferric-hexacyano ferrate) was added in the growth medium to adsorb the released radiocesium. A direct transfer of radiocesium to roots and shoots of the receiver plant was clearly demonstrated for the first time. Even though this transfer was quantitatively low, it suggested that shared mycorrhizal networks could contribute to the redistribution of this radionuclide in the environment, which otherwise would be restricted both in time and space. This finding may also help to understand the behaviour of its chemical analogue, potassium.
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http://dx.doi.org/10.1111/j.1462-2920.2009.02118.xDOI Listing
August 2010

Impact of Scots pine (Pinus sylvestris L.) plantings on long term (137)Cs and (90)Sr recycling from a waste burial site in the Chernobyl Red Forest.

J Environ Radioact 2009 Dec 13;100(12):1062-8. Epub 2009 Jun 13.

SCK-CEN, Belgian Nuclear Research Center, Foundation of Public Utility, Boeretang 200, 2400 Mol, Belgium.

Plantings of Scots pine (Pinus sylvestris L.) on a waste burial site in the Chernobyl Red Forest was shown to greatly influence the long term redistribution of radioactivity contained in sub-surfaces trenches. After 15 years of growth, aboveground biomass of the average tree growing on waste trench no.22 had accumulated 1.7 times more (137)Cs than that of trees growing off the trench, and 5.4 times more (90)Sr. At the scale of the trench and according to an average tree density of 3300 trees/ha for the study zone, tree contamination would correspond to 0.024% of the (137)Cs and 2.52% of the (90)Sr contained in the buried waste material. A quantitative description of the radionuclide cycling showed a potential for trees to annually extract up to 0.82% of the (90)Sr pool in the trench and 0.0038% of the (137)Cs. A preferential (90)Sr uptake from the deep soil is envisioned while pine roots would take up (137)Cs mostly from less contaminated shallow soil layers. The current upward flux of (90)Sr through vegetation appeared at least equal to downward loss in waste material leaching as reported by Dewiere et al. (2004, Journal of Environmental Radioactivity 74, 139-150). Using a prospective calculation model, we estimated that maximum (90)Sr cycling can be expected to occur at 40 years post-planting, resulting in 12% of the current (90)Sr content in the trench transferred to surface soils through biomass turnover and 7% stored in tree biomass. These results are preliminary, although based on accurate methodology. A more integrated ecosystem study leading to the coupling between biological and geochemical models of radionuclide cycling within the Red Forest seems opportune. Such a study would help in the adequate management of that new forest and the waste trenches upon which they reside.
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http://dx.doi.org/10.1016/j.jenvrad.2009.05.003DOI Listing
December 2009

Plant uptake of radiocaesium from artificially contaminated soil monoliths covering major European soil types.

J Environ Radioact 2009 Jun 16;100(6):439-44. Epub 2009 Apr 16.

Laboratory for Soil and Water Management, Katholieke Universiteit Leuven, Heverlee, Belgium.

Uptake of (137)Cs was measured in different agricultural plant species (beans, lettuce, barley and ryegrass) grown in 5 undisturbed soil monoliths covering major European soil types. The first cultivation was made three years after soil contamination and plants were grown during 3 successive years. The plant-soil (137)Cs transfer factors varied maximally 12-fold among soils and 35-fold among species when grown on the same soil. Single correlations between transfer factors and soil properties were found, but they varied widely with plant type and can hardly be used as a predictive tool because of the few soils used. The variation of (137)Cs concentrations in plants among soils was related to differences in soil solution (137)Cs and K concentrations, consistent with previous observations in hydroponics and pot trials. Absolute values of transfer factors could not be predicted based on a model validated for pot trials. The (137)Cs activity concentration in soil solution decreased significantly (11- to 250-fold) for most soils in the 1997-1999 period and is partly explained by decreasing K in soil solution. Transfer factors of lettuce showed both increasing and decreasing trends between 2 consecutive years depending on soil type. The trends could be explained by the variation in (137)Cs and K concentrations in soil solution. It is concluded that differences in (137)Cs transfer factors among soils and trends in transfer factors as a function of time can be explained from soil solution composition, as shown previously for pot trials, although absolute values of transfer factors could not be predicted.
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http://dx.doi.org/10.1016/j.jenvrad.2008.08.011DOI Listing
June 2009

Transfer parameter values in temperate forest ecosystems: a review.

J Environ Radioact 2009 Sep 18;100(9):757-66. Epub 2008 Dec 18.

Department of Radioecology, Institute of Radioprotection and Nuclear Safety, CE Cadarache, Saint Paul-lès-Durance Cedex, France.

Compared to agricultural lands, forests are complex ecosystems as they can involve diverse plant species associations, several vegetative strata (overstorey, shrubs, herbaceous and other annual plant layer) and multi-layered soil profiles (forest floor, hemi-organic and mineral layers). A high degree of variability is thus generally observed in radionuclide transfers and redistribution patterns in contaminated forests. In the long term, the soil compartment represents the major reservoir of radionuclides which can give rise to long-term plant and hence food contamination. For practical reasons, the contamination of various specific forest products has commonly been quantified using the aggregated transfer factor (T(ag) in m(2)kg(-1)) which integrates various environmental parameters including soil and plant type, root distribution as well as nature and vertical distribution of the deposits. Long lasting availability of some radionuclides was shown to be the source of much higher transfer in forest ecosystems than in agricultural lands. This study aimed at reviewing the most relevant quantitative information on radionuclide transfers to forest biota including trees, understorey vegetation, mushrooms, berries and game animals. For both radiocaesium and radiostrontium in trees, the order of magnitude of mean T(ag) values was 10(-3)m(2)kg(-1) (dry weight). Tree foliage was usually 2-12 times more contaminated than trunk wood. Maximum contamination of tree components with radiocaesium was associated with (semi-)hydromorphic areas with thick humus layers. The transfer of radionuclides to mushrooms and berries is high, in comparison with foodstuffs grown in agricultural systems. Concerning caesium uptake by mushrooms, the transfer is characterized by a very large variability of T(ag), from 10(-3) to 10(1)m(2)kg(-1) (dry weight). For berries, typical values are around 0.01-0.1 m(2)kg(-1) (dry weight). Transfer of radioactive caesium to game animals and reindeer and the rate of activity reduction, quantified as an ecological half-life, reflect the soil and pasture conditions at individual locations. Forests in temperate and boreal regions differ with respect to soil type and vegetation, and a faster decline of muscle activity concentrations in deer occurs in the temperate zone. However, in wild boar the caesium activity concentration shows no decline because of its special feeding habits. In the late phase, i.e. at least a few months since the external radionuclide contamination on feed plants has been removed, a T(ag) value of 0.01 m(2)kg(-1) (fresh weight) is common for (137)Cs in the muscles of adult moose and terrestrial birds living in boreal forests, and 0.03 m(2)kg(-1) (fresh weight) for arctic hare. Radiocaesium concentrations in reindeer muscle in winter may exceed the summer content by a factor of more than two, the mean T(ag) values for winter ranging from 0.02 to 0.8 m(2)kg(-1) (fresh weight), and in summer from 0.04 to 0.4m(2)kg(-1). The highest values are found in the year of initial contamination, followed by a gradual reduction. In waterfowl a relatively fast decline in uptake of (137)Cs has been found, with T(ag) values changing from 0.01 to 0.002 m(2)kg(-1) (fresh weight) in the three years after the contaminating event, the rate being determined by the dynamics of (137)Cs in aquatic ecosystems.
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http://dx.doi.org/10.1016/j.jenvrad.2008.11.005DOI Listing
September 2009

Radiocaesium accumulation in stemwood: integrated approach at the scale of forest stands for contaminated Scots pine in Belarus.

J Environ Manage 2007 Oct 9;85(1):129-36. Epub 2006 Oct 9.

Centre d'Etude de l'Energie nucléaire (SCK-CEN) Boeretang, 200 B-2400 Mol, Belgium.

Twenty years after the Chernobyl accident, root uptake from the surface layers of contaminated forest soils plays a major role in radiocaesium ((137)Cs) transfer to the trees and accumulation in perennial compartments, including stemwood. Trustworthy long-term predictions (modelling) of stemwood contamination with (137)Cs should accordingly be based on a reliable picture of this source-sink relationship. Considering the complexity of the processes involved in (137)Cs cycling in forest stands, elementary ratios like transfer factors (TF) were shown to be not very relevant for that purpose. At the tree level, alternatives like the wood immobilisation potential (WIP) have therefore been proposed in order to quantify the current net (137)Cs accumulation in stemwood. Our objective was here to compare WIP values determined for a series of contaminated forest stands in Belarus with the corresponding pools of (137)Cs available in the soil for root uptake. The comparison reveals that both indices are quite proportional, whatever the forest ecosystem features. This corroborates the relevancy of WIP as an indicator of the current (137)Cs root uptake by the trees, which could accordingly help to improve the existing models of (137)Cs cycling and the long-term management of contaminated forest ecosystems.
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http://dx.doi.org/10.1016/j.jenvman.2006.08.008DOI Listing
October 2007