Korean Journal of Soil Science and Fertilizer ISSN:0367-6315(Print) 2288-2162(Online) 한국토양비료학회 학회지

Various soil remediation techniques are available to remove or stabilize the metal in contaminated soil, in order to retard the metal toxicity or bioavailability. However, according to the inherent characteristics of those remedial techniques, several methods deteriorate the soil properties and produce secondary contaminants. We aim to the soil layer reversal method to retard the metal availability to rice and at the same time to leave intact the soil properties in paddy soil that are polluted with metals. The experimental paddy soil showed a relatively uniform profile in physicochemical properties up to 100 cm in depth. Surface soil (0 - 50 cm) was contaminated with Cd and Pb but their concentrations as the soil depth increased, which was lower than Korean pollution threshold levels (1.5 and 100 mg kg^-1, respectively). The contaminated surface soil layers and the uncontaminated deeper soil layers were reversed with each other, and then rice (Oryza sativa L.) was cultivated in paddy fields. Concentrations of 0.1 M HCl extractable Cd and Pb in the reversed surface soil were 84 - 91% and 78 - 86% lower than those of the initial surface soils, respectively. Translocations of Cd and 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 soil reversal technique can be an option to reduce the metal bioavailability in the paddy field, whereas the implication of the current soil remediation technology is not feasible from the practical or economic viewpoint.

Heavy metal (Cd and Pb) concentrations (mg kg^-1) in polished rice samples. C, control; RS, reversed soil; RSL, reversed soil with lime break layer; RSG, reversed soil with gravel break layer. Error bars are standard deviations.