Ecological and health risk assessment of heavy metals in farmland soil of northwest Xiushan, Chongqing

In order to understand the heavy metal pollution of farmland soil in northwest Xiushan, Chongqing, with quite a lot of mining activities, the authors collected 386 surface soil samples, analyzed and determined the concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb, Zn and Mn and evaluated the soil heavy metal pollution level, the ecological risk and health risk by using the geological accumulation index, potential ecological hazard index and health risk assessment model. The results show that the average values of 9 heavy metals in the surrounding soil of Xiushan mining area are higher than the soil background values of Chongqing, showing different degrees of accumulation effect. The concentrations of Cd and Hg significantly exceed the risk screening values for soil contamination of agricultural land, with the over-standard rates of 75.2% and 44.6% respectively. In the soil, Hg pollution is relatively serious, and its pollution level is medium pollution or heavy pollution, Mn, As and Cd are generally light pollution, and the remaining heavy metals are basically pollution-free. The potential ecological hazard index shows that Hg and Cd are the main ecological hazard elements, Hg ecological risk is mainly strong to extremely strong, and Cd ecological risk is mainly medium. The heavy metal health risk assessment results show that children are more susceptible to the heavy metal pollution. There are no significant non-carcinogenic risks for adults, children however show significant non-carcinogenic effect, and As and Cr are major non-carcinogenic factors. The carcinogenic risks for adults are acceptable, individual soil samples have carcinogenic effect on children, and As has a relatively higher carcinogenesis risk.