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

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• 作者：Pamela Di Tullo^a ; ^b ; ^{pamela.ditullo@univ-pau.fr" class="auth_mail" title="E-mail the corresponding author} ; Florence Pannier^a ; ^{florence.pannier@univ-pau.fr" class="auth_mail" title="E-mail the corresponding author} ; Yves Thiry^b ; ^{yves.thiry@andra.fr" class="auth_mail" title="E-mail the corresponding author} ; Isabelle Le Hé ; cho^a ; ^{isabelle.lehecho@univ-pau.fr" class="auth_mail" title="E-mail the corresponding author} ; Maï ; té ; Bueno^a ; ^{maite.bueno@univ-pau.fr" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Selenium ; Stable isotope tracer ; Speciation ; Soil ; Kinetic equations ; Sorption
• 刊名：Science of the Total Environment
• 出版年：2016
• 出版时间：15 August 2016
• 年：2016
• 卷：562
• 期：Complete
• 页码：280-288
• 全文大小：874 K

文摘

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 ⁷⁷Se 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 ⁷⁷Se(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 K_d distribution coefficient, they should be at least reliant on ambient Se which is supposed to be at equilibrium.