【稻田土壤中的镉】Beate Fulda † Andreas Voegelin *‡ and Ruben Kretzschmar †. Redox-Controlled Changes in Cadmium Solubility and Solid-Phase Speciation in a Paddy Soil As Affected by Reducible Sulfate and Copper.Environ. Sci. Technol. 2013 47 (22) pp 12775–12783

Abstract

The solubility of Cd in contaminated paddy soils controls Cd uptake by rice which is an important food safety issue. We investigated the solution and solid-phase dynamics of Cd in a paddy soil spiked with 20 mg kg^–1 Cd during 40 days of soil reduction followed by 28 days of soil reoxidation as a function of the amounts of sulfate available for microbial reduction and of Cu that competes with Cd for precipitation with biogenic sulfide. At an excess of sulfate over (Cd + Cu) dissolved Cd decreased during sulfate reduction and Cd was transformed into a poorly soluble phase identified as Cd-sulfide using Cd K-edge X-ray absorption spectroscopy (XAS). The extent of Cd-sulfide precipitation decreased with decreasing sulfate and increasing Cu contents even if sulfate exceeded Cd. When both Cu and Cd exceeded sulfate dissolved and mobilizable Cd remained elevated after 40 days of soil reduction. During soil reoxidation Cd-sulfide was readily transformed back into more soluble species. Our data suggest that Cd-sulfide formation in flooded paddy soil may be limited when the amounts of Cd and other chalcophile metals significantly exceed reducible sulfate Therefore in multimetal contaminated paddy soils with low sulfate contents Cd may remain labile during soil flooding which enhances the risk for Cd transfer into rice.

【稻田土壤中的IPP】Juying Li †§ Jianbo Zhang † Chao Li ‡ Wei Wang † Zhen Yang † <