Zerovalent iron retards Cd uptake by rice through immobilization

摘要

Cadmium in rice grown in the paddy soils contaminated with heavy metals from closed metal mines in Korea generally exceeds the safety guideline of KFDA (Korea Food and Drug Administration), 0.2mg (Cd)·kg<'-1> in rice grains. The objective of this research was to apply chemical agents such as zerovalent iron (ZVI), lime, humus, and compost to immobilize Cd in contaminated rice paddy soils. Sequential extraction of the rice paddy soil revealed that treatment with such chemical agents reduced the adsorbed Cd fractions from 29% to 54% and the exchangeable Cd fractions from 39% to 99%, as compared to those in the untreated soil (control). Efficiency of the chemical agents to inhibit Cd accumulation in rice grains was in the order of lime> compost>ZVI>humus in the greenhouse experiment and compost> ZVI>humus>lime in the field experiment. Moreover, ZVI treatment did not influence the rice yield and inhibited Cd accumulation in rice grains by about 70% as compared to that in the control. Overall results indicated that ZVI was a more effective amendment to stabilize phytoavailable Cd fractions in contaminated rice paddy soils.