Evaluation of DGT and DGT-PROFS modeling approach to estimate desorption kinetics of Cs in soils

International audienceThe aim of this paper is to assess the suitability of DGT to extract kinetic rates of desorption of cesium (Cs) from soils. For this purpose, laboratory experiments with a natural soil spiked with Cs were carried out under three different contamination conditions, reflecting either an increase in Cs contamination level or an ageing of the contamination within the soil. The experimental results (i.e. the Cs accumulation kinetics onto DGT probes) were interpreted by the DGT-PROFS model. The latter calculates the partitioning of Cs between two particulate pools, describing weak and strong interactions respectively, as well as kinetic rates describing exchange reactions. It was shown that experimental conditions did not show any major impact on desorption rates, suggesting that desorption kinetics were not significantly affected by contamination level and ageing. Instead, the distribution of Cs among weak and strong sites was shown to be the predominant factor governing the differences observed in the remobilization of Cs to porewater among experimental conditions. The DGT technique combined with the DGT-PROFS modelling approach was proved to be efficient in estimating the desorption kinetic rates of Cs in soils

Influence of non-equilibrium and nonlinear sorption of 137Cs in soils. Study with stirred flow-through reactor experiments and quantification with a nonlinear equilibrium-kinetic model

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Comparison of soil/solution distribution of a fresh radionuclides contamination (137Cs, 129I and 233U) added under organic or water pathways with their natural endogenous isotopes

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Iodine distribution and volatilization in contrasting forms of forest humus during a laboratory incubation experiment

International audienceRadionuclides 129I (t1/2 = 15.7×106 years) and 131I (t1/2 = 8.02 days) are both introduced into the environment as a result of nuclear human activities. Environmental transfer pathways and fluxes between and within ecosystems are essential information for risk assessment. In forest ecosystems, humus degradation over time could result in re-mobilization and then downward migration and/or volatilization of intercepted 129I. In order to estimate the scale of these processes, humus (mull and moder forms) sampled under deciduous and coniferous forests were spiked with 125I– (t1/2 = 59.4 days), as a surrogate for 129I, in order to study the evolution of its water-soluble and organic fractions as well as the volatilization rate during humus degradation at laboratory scale. To our knowledge, this is the first time that interactions between iodine and contrasting forms of forest humus have been investigated. The evolution of native stable iodine (127I) pools in unspiked humus was also studied.The nature of the humus’ organic matter appears to be a factor that impacts on the proportions of water-soluble and organic fractions of iodine and on their evolution. Iodine-125 was mainly organically bound (fraction for mulls and moders: ~54-59 and 41-49%, respectively) and no clear evolution was observed within the 4-month incubation period. A large decrease in 125I water-solubility occurred, being more marked for mull (from ~14-32 to 3-7%) than for moder (from ~21-37 to 7-19%) humus. By contrast, a significant fraction was not extractible (~38-43%) and varied in inverse proportion to the water-soluble fraction, suggesting a stabilisation of iodine in humus after wet deposit. The nature of the humus organic matter also impacted on 125I volatilization. Although of the same order of magnitude, the total volatilization of 125I was higher for moders (~0.039-0.323%) than for mulls (~0.015-0.023%) within the 4-month incubation period. Volatilization rates for mulls were correlated with the water-soluble fraction, implying that volatilization of 125I could occur from the humus solution. Our results showed that humus is thus a zone of iodine accumulation by association with organic matter and that potential losses by lixiviation are significantly more important compared to volatilization

Uptake and translocation of cesium by Arabidopsis thaliana in hydroponics conditions: Links between kinetics and molecular mechanisms

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Tritiated Water Exposure in Zebrafish (Danio rerio): Effects on the Early‐Life Stages

International audienceTritium, a radioactive isotope of hydrogen of natural and anthropogenic origin, is ubiquitously present in theenvironment. Effluents of nuclear centers of production are significant anthropogenic sources. With the upcoming project of thermonuclear fusion, tritium releases in the environment may increase. It is therefore important to characterize the ecologicalrisk linked to tritium. The effects of tritiated water (HTO) were therefore studied in zebrafish larvae exposed for 10 d todifferent dose rates, 1.1 × 102, 4.1 × 102, and 3.8 × 103 μGy/h for larvae corresponding, respectively, to a water contaminationof 104, 105, and 106 Bq/mL of HTO. Those dose rates were higher than 10 μGy/h, which is the threshold recommended tostart monitoring ecosystems where radiological contaminants are present. Mortality, embryo‐larval development, immune toxicity, genotoxicity, neurotoxicity, and alterations of tissues were investigated. The results showed that HTO exposure induced DNA damage and reactive oxygen species production and modulated the expression of genes involved in detoxificationprocesses. Moreover, modifications of the muscular tissues (degradation of myofibrils at 4 d post fertilization anddisorganization of mitochondria at later stages) were observed. The results differed with HTO dose rates and with developmentalstages. These results will drive future research for the development of new HTO‐sensitive biomarkers and willallow us to progress in the characterization of the modes of action of tritium in fish

Former uranium mine-induced effects in caged roach: a multiparametric approach for the evaluation of in situ metal toxicity

To characterize environmental risks linked to former uranium mines in the Limousin region of France, a study was conducted on fish health effects from uranium releases. Two private ponds were compared in this study, one with uranium contamination and one background site, upstream of the mining zone. Roach, Rutilus rutilus, were caged for 28 days in both ponds. Physico-chemical parameters of water and sediments and bioaccumulation of metals in several organs were determined. After 14 and 28 days of caging, immune, oxidative stress, biotransformation, neurotoxicity and physiological parameters were measured. Iron and aluminium were quantified in the water of both sites however, barium and manganese were only present in the water of the uranium contaminated site. Uranium was present in both sites but at very different concentrations. The sediments from the uranium contaminated site contained high levels of radioactive elements coming from the disintegration chain of uranium. Results of biological parameters indicated stimulation of immune parameters and of oxidative stress and a decrease of AChE in fish caged in the uranium contaminated pond compared to the uranium-free pond. Overall, the results determined roach health status in the context of pollution from poly-metallic mining. The data strengthen our knowledge of the environmental risk assessment associated with radioactive substances in the environment