Abstract
Chemical washing with iron （III） chloride is a recently developed method for extracting cadmi-um （Cd） for the remediation of Cd-contaminated ara-ble soils. On-site washing using iron （III） chloride was conducted in a paddy field having a high Cd content of 0.56 mg kg‒1, a clay content of 0.15 kg kg‒1 and a cat-ion exchange capacity of 13 cmolc kg‒1, and its effects on the physical and chemical properties of the soil as well as on the growth of okra （Abelmoschus esculentus）were investigated. The chemical washing, which involved intensive pud-dling, exerted adverse effects on the uniaxial compres-sive strength of soil before tillage and the clod size dis-tribution of the tilled soil in the first year. Emergence and subsequent growth of okra were also adversely af-fected. However, these effects were not persistent; in the second and the third years, there was little diff er-ence in the clod size distribution or the growth of okra between the washed and unwashed plots. In contrast, the Cd contents of okra grown in the washed plot were consistently lower, and 0.3‒0.5 times as large as those in the unwashed plot, demonstrating the persist-ing effects of the chemical washing on Cd uptake by the plant. The chemical washing, at the same time, caused considerable losses of magnesium and potassi-um from the soil. The cation imbalance could, however, be easily rectified with inorganic and organic amend-ments. These results demonstrates that the chemical washing using iron （III） chloride is an effective tech-nique for remedying Cd-contaminated soils and reduc-ing Cd uptake by okra.
