Characteristics and Source Analysis of Heavy Metals in the Surrounding Topsoil of Tuo Lake Nature Reserve

To study the characteristics and sources of heavy metals in the farmland surrounding Tuo Lake Nature Reserve, a total of 615 topsoil samples were collected from the study area. The concentrations of eight heavy metal elements, including As, Cd, Cr, Pb, Hg, Cu, Ni and Zn, in the topsoil were analyzed. Methods such as the geo-accumulation index, enrichment factor, pollution load index, potential ecological risk index, correlation analysis, cluster analysis, and principal component analysis were employed to evaluate the pollution distributions and investigate the sources of heavy metals. The results show that the average concentrations of As, Pb, and Hg in topsoil of the study area were higher than the background soil values. The degree of variation of Hg concentrations is significant, indicating substantial influence from external factors. The spatial distribution indicates that areas with high concentrations of Cd, Pb, and As were primarily located in the southern region of Tuo Lake, while Cu, Ni, Zn, and Cr were mainly distributed along Tuo Lake and its banks. The geo-accumulation index analysis indicates that only five points exhibited moderate Hg pollution, and the majority of points in the survey area are classified as a clean state. The enrichment shows that only 13 samples exhibited moderate enrichment of Hg, while the majority of samples displayed deficiency to minimal enrichment of heavy metals. The potential ecological risk index reveals 0.2, 1.5, and 32.8% of samples reached moderate ecological risk levels for As, Cd, and Hg, respectively, while the other five elements remained at low-risk levels. The comprehensive potential ecological risk index indicates that the study area was predominantly characterized by low potential ecological risk (96.4%), with only five points exhibiting high risks. Source analysis suggests that Cr, Cu, Ni, and Zn were primarily derived from natural sources, whereas Cd, Pb, and As were mainly attributed to industrial, agricultural, and transportation activities, and Hg mainly originated from agricultural fertilizers and pesticides. These research results provide valuable data to support the prevention and control of heavy metal pollution in soil and ecological protection in the Tuo Lake Nature Reserve.