Ecolcgical and health risk assessment of heavy metals in farmland soil around the gold mining area in Tongguan of Shaanxi Province

In order to understand the impact of the early extensive mining activities in the Tongguan gold mine on the heavy metal pollution of the farmland soil and the evaluation of the adverse health effects of the exposed population, enginnering six farmland soils near the mine area were selected as the research object in the geological survey. Spectral analysis method was used to determine the contents of Cd, Hg, As, Pb, Cr, Cu, Ni, Zn and other 8 soil heavy metals of 68 soil samples. The soil accumulation index method, potential ecological hazard index method and health risk assessment model were used to evaluate the soil heavy metal pollution degree, potential ecological risk and human health risk in the area. The results show that the average values of Ni, Hg, Cd, Zn, Pb and Cu in the farmland soil in this area are higher than the soil background value of Tongguan County, indicating different levels of accumulation. The accumulated soil content of Pb, Hg, and Cd not only exceeds the minimum limit of the safety risk of heavy metal pollution, bu also exceeds the maximum limit of the safety risk of heavy metal pollution on the quality of agricultural products by 41.2%, 72.1%, and 14.7% of the exceedance rates respectively. The evaluation of soil heavy metal pollution in the study area shows that the total pollution degree of Hg, Cd and Pb in the soil is the heaviest, Cu and Zn are generally light to heavy pollution, and Ni, Cr and As are generally pollution-free. The ecological risk assessment shows that Hg, Cd, and Pb are the main ecological hazard elements, Hg is a very strong risk, and Cd and Pb are strong risks. Human health risks show that the non-carcinogenic risk of heavy metals to children is obvious, and Pb and Hg are the main non-carcinogenic factors. Carcinogenic risks are within a reasonable range. Cd is the most carcinogenic risk, and hand-mouth intake is the most important exposure route. Children are more vulnerable to heavy metal pollution.