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Article Dans Une Revue Journal of Environmental Radioactivity Année : 2014

Kinetics of selenate sorption in soil as influenced by biotic and abiotic conditions: A stirred flow-through reactor study

Résumé

This study (i) quantified the kinetics of selenate sorption and (ii) measured the influence of biotic processes in soil selenate stabilisation. Stirred flow-through reactor experiments were conducted on samples of a silty clay soil (pH=8, Eh=240-300mV) from Bure (France) in both non-sterile and sterile conditions. Parameters of the proposed two-site sorption model (EK), adapted from van Genuchten and Wagenet (1989), were estimated by nonlinear regression. Fast selenate sorption on type-1 sites was moderate, with an equilibrium constant of 25.5 and 39.1L/kg for non-sterile and sterile conditions. Rate-limited sorption on type-2 sites increased with time, and was predominant for longer periods of time in non-sterile conditions. At equilibrium, it would represent over 96% of the sorbed inventory, with mean sorption times of 17h and 191h for non-sterile and sterile conditions. Our results showed for Bure soil that (i) selenate sorption in flowing and mildly-oxidising conditions was strongly kinetically controlled, especially in non-sterile conditions, (ii) selenate desorption was much slower than sorption, which suggests its pseudo-irreversible stabilisation, and (iii) microbial activity increased the contribution of rate-limited sorption on type-2 sites, for which it increased sorption rate by a factor 7 but also facilitated its reversibility. This work stresses the limits of the K d approach to represent selenate sorption in flowing conditions and supports an alternative formulation like the EK model, but also points out that biotic conditions are significant sources of variability for sorption parameters. ?? 2014 Elsevier Ltd.
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hal-01394610 , version 1 (09-11-2016)

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L. Garcia-Sanchez, N. Loffredo, Stéphane Mounier, A. Martin-Garin, F. Coppin. Kinetics of selenate sorption in soil as influenced by biotic and abiotic conditions: A stirred flow-through reactor study. Journal of Environmental Radioactivity, 2014, 138, pp.38--49. ⟨10.1016/j.jenvrad.2014.07.009⟩. ⟨hal-01394610⟩
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