Cadmium contamination of soils and rice plants caused by zinc mining

Abstract

Summary Areas in Fukui Prefecture where zinc mining was suspected as a cause of metal contamination in the paddy fields have been surveyed by the authors since 1970. 1.According to the detailed analyses of unpolished rice harvested along the Kuzuryu River, contents of Cd ranged from 0.02 to 1.82 ppm, and high Cd rice of more than 1 ppm was found in a limited area near the mine station. 2. Contents of Cd in soil varied from 0.2 to 10.4 ppm with no apparent relation to Cd in rice, suggesting other influencing factors of the soil and climatic conditions. In this investigation, exchangeable Ca and Zn-Cd ratio in soluble form had negative and positive correlations with rice Cd, respectively. 3. Accumulation of the heavy metals was mainly limited to the upper soil layer. Tracing the total metals in soil along the river, Pb appeared to precipitate predominantly on the upper streams probably due to the greater specific gravity of Pb minerals and the sloweddown current of the river during the past flood times. Cd ...