Characteristics of Heavy Metal Accumulation in Soil-Corn System Contents and Their Health Risks in Nandan,Guangxi

Nandan is famous for its mining of nonferrous metals. In order to investigate effects of the mining activities on the soil and corn, the staple grain crop of this county, a total of 139 soil samples and 139 corn samples were collected for analysis of concentrations of Cd, Pb, As, Cu and Zn. Results show that the mean concentration of Cd, Pb, As, Cu and Zn in the soil samples was 1.205, 79.31, 29.42, 27.91 and 132.4 mg·kg^-1, respectively. The over-standard rate of Cd, Pb and As in the corn was calculated to be 8.4%, 28.3% and 3.0% respectively, by GB 2762-2012 "Thresholds for Pollutants in Food". Correlation analysis shows that the corn was significantly related to the soil in concentration of Cd, Zn and As (P<0.05), but not so much in concentration of Pb and Cu. Environmental quality evaluation of the farmland soils based on the above analysis of heavy metal concentrations in the corn and soil shows that ⅡCQ was 2.70 on average, indicating that the soil was slightly over the standard. Human health risk assessment shows that both HQ (single element risk coefficient) and HI (multi-element integrated risk coefficient) were below 1; and the annual health risk of corn consumption to people in Nandan County was also lower than the highest level recommended by the International Commission on Radiological Protection (ICRP), which suggests that long term ingestion of locally produced corn will not have any significant health risk. The corn is a safe food in the area.