Ranking of mechanisms governing the phytoavailability of cadmium in agricultural soils using a mechanistic model
2016
Lin, Zhongbing | Schneider, Andre | Sterckeman, Thibault | Nguyen, Christophe
Aims The objective of this study was to rank the mechanisms influencing the phytoavailability of cadmium(Cd) in agricultural soils.Methods We developed a model that simulates the transport by diffusion and convection, the kinetics ofsorption and complexation in solution and the root uptake of Cd. The ranking of mechanisms was performed by simulating the Cd2+ uptake by 1 cm2 root for 30 days for French agricultural soil characteristics.Results The initial Cd2+ concentration was the most influential parameter followed by the soil buffer power for Cd2+ and by the soil water content and impedance factor. The Cd2+ was generally strongly depleted at theroot surface and the convection was almost negligible. In general, the Cd complex dissociation contributedlittle to the uptake due to a strong kinetics limitation. Conversely, the kinetics of sorption was little influential.Conclusions The initial concentration and diffusion of Cd2+ were the dominant processes governing the phytoavailability in non-polluted soils. A model considering only the transport and sorption of Cd2+ without kineticswould be adequate to predict the phytoavailability. The particular situations where these simplifications do nothold (relative error >10 %) corresponded to a high supply of labile Cd complex toward plant roots.
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