[Source Analysis and Pollution Assessment of Soil Heavy Metals in Typical Geological High Background Area in Southeastern Chongqing]

In order to understand the pollution characteristics of soil heavy metals in typical geological high background areas in southeastern Chongqing, analyze its pollution sources, and put forward risk management and control suggestions, 211 topsoil samples (0-20 cm) were collected in Xinglong Town and Muye Township in the north of Youyang County, Chongqing City, and the contents of eight heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) and the soil pH value in the surface soil were analyzed. Additionally, mathematical statistics, pollution load index (P), potential ecological risk index (RI), correlation analysis, and the positive matrix factorization (PMF) model were used to study the content and spatial distribution characteristics of heavy metals in the topsoil, and pollution assessment and source analysis of heavy metals were carried out. The results showed that the average concentrations of heavy metals in the surface soil all exceeded the soil background value in Chongqing, showing different levels of enrichment. Among them, the proportion of Cd exceeding the screening value in the "soil environmental quality risk control standard for soil contamination of agricultural land" (GB 15618-2018) was as high as 83.41%, the proportion of exceeding the control value was 7.58%, and the potential risk was relatively high. The evaluation results of the pollution load index method showed that the study area was slightly polluted as a whole, and the evaluation results of the potential ecological risk index showed that the overall ecological risk of the study area was relatively high. Among them, the contribution rates of heavy metals Hg, Cd, and As were 50.27%, 28.63%, and 11.70%, respectively. The PMF results showed that there were three main sources of heavy metals in the soil in the study area:natural parent material sources, agricultural sources, and mixed sources of industrial activities and traffic emissions, accounting for 40.49%, 29.12%, and 30.39%, respectively. The quantitative source analysis results of soil heavy metals in the study area have important reference significance for soil heavy metal pollution control in geologically high background areas.