| Autor: |
Huang H; College of Resources and Environmental Sciences and Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing Agricultural University, Nanjing 210095, China., Ji XB; College of Resources and Environmental Sciences and Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing Agricultural University, Nanjing 210095, China., Cheng LY; College of Resources and Environmental Sciences and Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing Agricultural University, Nanjing 210095, China., Zhao FJ; College of Resources and Environmental Sciences and Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing Agricultural University, Nanjing 210095, China., Wang P; College of Resources and Environmental Sciences and Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing Agricultural University, Nanjing 210095, China. |
| Abstrakt: |
Most of the cadmium (Cd) accumulated in rice grains is derived from its remobilization in soils during the grain filling period when paddy water is drained. The factors affecting Cd remobilization upon drainage remain poorly understood. Here, we show that the free radical effect produced from the oxidation of ferrous sulfides is an important mechanism affecting the oxidative remobilization of Cd during soil drainage. When soils were flooded, microbial sulfate reduction results in the formation of various metal sulfides including CdS and FeS. Upon soil drainage, the oxidation of FeS produced considerable amounts of hydroxyl free radicals (OH • ), which could oxidize CdS directly and thereby promote the oxidative dissolution of CdS and increase Cd mobilization in soils. FeS and CdS could also form a within-sulfide voltaic cell, with FeS protecting the oxidative dissolution of CdS due to the lower electrochemical potential of the former. However, this voltaic effect was short-lived and was surpassed by the free radical effect. The amounts and composition of metal sulfides formed during soil flooding vary with soils, and the oxidative dissolution of CdS is affected by both the free radical and voltaic effects offered by different metal sulfides. These effects are also applicable to the biogeochemistry of other chalcophile trace elements coupled with sulfur and iron redox cycles during the anoxic-oxic transition in many environments. |
