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

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.

[Assessment and Source Analysis of Heavy Metal Pollution in Farmland Soils in Southern Youyang County, Chongqing].

To investigate the impact of mining activities and geological background on the soil environment, 156 soil samples were collected from an agricultural land in southern Youyang County, Chongqing. The content and pH of heavy metals in the soil were analyzed, and the Nemerow index method was used to evaluate the pollution status of soil heavy metals. The source of soil heavy metals was discussed using the principal component analysis/absolute principal component score (PCA/APCS) receptor model. The results showed that the soil Cd pollution was distributed in a planar shape, while soil Hg mainly appeared as point pollution. The medium-severe soil pollution was mainly distributed at the junction of Tushi Town, Mawang Town, and Longtan Town, where the soil was predominantly acidic and there was a higher risk of crop contamination; the indicator Kriging evaluation results showed that there was a higher probability of soil contamination at the junction of the three towns and the northern part of Tushi Township. The results of the PCA/APCS receptor model analysis showed that the sources of soil As, Cd, Cr, and Ni were mainly controlled by geological background; soil Hg, Pb, and Zn were mainly controlled by mining activities; further, soil Cu was affected by both geological background and mining activities. In addition, the agricultural activities were also one of the sources of soil As, Cd, Pb, Cu, and Zn. The medium-heavy pollution of the soil in the study area was mainly caused by mining activities, while the heavy metal pollution of the soil caused by geological background was mainly light pollution. This study can provide a theoretical basis for the safe use of land and the prevention and control of soil pollution in typical regions.