Spatial Distribution Characteristics, Pollution, and Ecological Risk Assessment of Soil Heavy Metals Around Mercury Mining Areas

Abstract

To ascertain the impact of mercury mining on the surrounding soil environment and human health, 42 surface soil composite samples were collected around a mercury mining area in Youyang County, Chongqing, and the heavy metals (Cd, Hg, Pb, As, Cr, Cu, Zn, and Ni) contents and pH of the soil, the spatial distribution of heavy metals, pollution degree, and ecological risk were studied. The results show that the surface soil layer in the study area is significantly enriched in heavy metals. According to the soil environmental quality risk control standard for soil contamination of agricultural land (GB15618-2018), soil Cd, Hg, Pb, As, and Zn showed different degrees of excess. A certain degree of pollution and ecological risk was also identified in the studied soil. Moderate-to-severe pollution and strong ecological risk areas are distributed around the mining sites, indicating the impact of mining activities on the soil environment. The content of Cr, Cu, and Ni in the soil may be affected by weathering and soil formation from the parent rock; Hg, Pb, and Zn content may be affected by human activities such as mineral mining; and Cd and As content may be affected by both geological processes and human activities. Heavy metals pose less of a health risk for adults but have a greater probability of causing health risks for children. Soil As is the main contributor to human health risks, and the oral intake of the eight heavy metals has the highest contribution rate. The mining of mercury is the main cause of soil pollution and ecological risk in the study area.