Heavy metal contamination and health risk assessment in the vicinity of the abandoned Songcheon Au–Ag mine in Korea

Abstract

The objective of this study is, firstly, to investigate the contamination levels and dispersion patterns of As and heavy metals, secondly, to estimate the bioaccessible fraction of the metals in soil and crop plant and, finally, to assess the risk of health effects on the residence in the vicinity of the abandoned Songcheon Au–Ag mine, Korea. Samples of tailing, soil, crop plant and water were collected around the mine site. After appropriate preparation, all samples were analyzed for As, Cd, Cu, Pb and Zn by ICP-AES and ICP-MS. Elevated levels of As and heavy metals were found in tailing. Mean concentrations of As in agricultural soil were higher than the permissible level. Especially, maximum levels of As and Hg in farmland soil were up to 626 mg/kg and 4.9 mg/kg, respectively. The highest levels in crop plant were 33 mg As/kg and 3.8 mg Pb/kg (in green onion root), 0.87 mg Cd/kg and 226 mg Zn/kg (in lettuce root), 16.3 mg Cu/kg (in sesame leaves). The concentration of heavy metals in leaves is much higher than those in grains and stalk. Vegetables grown on the contaminated soil were rich in As and heavy metals. Concentrations of As, Cd, and Zn in most stream waters which are used for drinking water around the mine area were higher than the permissible levels regulated in Korea. Maximum levels of As, Cd and Zn in stream waters were 0.71 mg/L, 0.19 mg/L and 5.4 mg/L, respectively. These results indicate that mine tailings can be the main contamination sources of As and heavy metals in the soil–water system of the mine site. The average of estimated human-bioaccessible fraction in soil in simulated stomach was 3% As, 40% Cd, 15% Cu, 31% Pb and 21% Zn, and that in simulated small intestine 12% As, 2.2% Cd, 5.6% Cu, 0.5% Pb and 1.2% Zn. The highest value of human-bioaccessible fraction of metal in farmland soil was 85% for Cd. The estimated human-bioaccessible fraction of plant was up to 97% for Cd in simulated stomach, and to 51% for Pb in simulated small intestine. The highest human-bioaccessible fractions were found in Chinese cabbage (in stomach) and potato leaves (in small intestine). The average human-bioaccessible fraction in plants were 47% As, 70% Cd, 62% Cu, 0% Pb and 62% Zn in simulated stomach and 22% As, 7% Cd, 27% Cu, 9% Pb and 23% Zn in simulated small intestine. The HQ (hazard quotient) value of the mine site was 16, and especially, the HI (hazard index) value of only As was 15. The carcinogenic risk of the mine site was 2.7E−03. This value means the probable possibility that about 3 cancer patients among 1000 people happen. Carcinogenic risk exceeded in the generally accepted range of E−04 to E−06.