Influence of Soil Layer Management Via Soil Reversal on the Cd and Pb Bioavailability to Rice (Oryza sativa L.) in the Mining-Impacted Soil

Abstract

Various soil remediation techniques are available to remove or stabilize the metal in contaminated soil, inorder to retard the metal toxicity or bioavailability. However, according to the inherent characteristics of thoseremedial techniques, several methods deteriorate the soil properties and produce secondary contaminants. Weaim to the soil layer reversal method to retard the metal availability to rice and at the same time to leave intactthe soil properties in paddy soil that are polluted with metals. The experimental paddy soil showed a relativelyuniform profile in physicochemical properties up to 100 cm in depth. Surface soil (0 - 50 cm) was contaminatedwith Cd and Pb but their concentrations as the soil depth increased, which was lower than Korean pollutionthreshold levels (1.5 and 100 mg kg-1, respectively). The contaminated surface soil layers and theuncontaminated deeper soil layers were reversed with each other, and then rice (Oryza sativa L.) wascultivated in paddy fields. Concentrations of 0.1 M HCl extractable Cd and Pb in the reversed surface soilwere 84 - 91% and 78 - 86% lower than those of the initial surface soils, respectively. Translocations of Cdand Pb to the rice in the reversed surface soil were relatively low (Cd 0.22-0.24 mg kg-1; Pb 1.1-1.3 mg kg-1),as compared to those of the control (Cd 0.95 mg kg-1; Pb 2.9 mg kg-1). The results demonstrate that the soilreversal technique can be an option to reduce the metal bioavailability in the paddy field, whereas theimplication of the current soil remediation technology is not feasible from the practical or economicviewpoint.