Occurrence, Distribution and Risk Assessment of Heavy Metals in Agricultural Soil and Water Around a Lead-zinc Mine in Southwest China

Abstract

Mining activities could induce severe heavy metal pollution in soil and surface water, which would consequently pose potential ecological environment risks and human health risks. In this research, total 82 agricultural soil samples and 34 water samples were collected from a special area that surrounding a lead-zinc mine. Pollution level, source apportionment, ecological and health risks of heavy metals were evaluated based on the concentrations of cadmium (Cd), chromium (Cr), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb) and zinc (Zn). According to the results, Cd and Zn were obviously enriched metals in agricultural soil in the study area, meanwhile, the potential risks which calculated by geo-accumulation index were showed a high ecological risk due to high concentration of Cd found in local agricultural soil. Additionally, heavy metal sources analyzed by the PMF model could be classified into four categories: mining activity (Mn), parent material (Cr, Ni), atmospheric deposition caused by industrial and mining activities (Pb, Zn, Cd) and agricultural activities (Cu). Compared with the values specified by corresponding water quality standard, the heavy metals content in surface water were below these values except Cd, while the content of seven heavy metals in drinking water was within the safe limits. The bioavailability of Cd, Pb and Zn in soil were higher than other metals, and when the bioavailability of metals was consideration into health risk assessment, the total HI and TCR values were far below the accepted risk levels. Though human health risks were within the safe margin, the toxic hazards of heavy metals to residents and ecological should be taken into consideration.