Analysis of Toxic Elements Pollution Sources and Crop Health Risks in Soil of Typical Thallium Mining Area

The investigation focused on Tl, Hg, As, and Sb as the targeted contaminants in the soil surrounding a thallium mining region in southwestern China. Potential sources of toxic elements were identified using correlation analysis and principal component analysis. By interpreting the results of correlation and principal component analysis, the potential sources of Tl, Hg, As, and Sb were identified to include the mining and smelting industry. Additionally, Tl, Hg, and As are influenced by agricultural activities, while Sb is also associated with the soil parent material. Various analytical methods including the Nemerow comprehensive pollution index, Hakanson potential ecological risk index and hazard quotient assessment were employed to evaluate the sources of heavy metal pollution and associated health risks to crops. Results indicated elevated exceedance rates of Tl, Hg, and Sb in the farmland soil. Approximately 37.9% and 16.7% of the sampling locations were classified as highly and moderately polluted, respectively. Furthermore, toxic elements posed significant ecological risks to the soil, particularly with substantial contributions from Hg and Tl toward the overall risk index. Crop samples collected showed elevated levels of Tl, Hg, and As, particularly in leafy vegetables compared to cereals. Notably, the hazard quotient (HQ) values for Tl in cabbage and Lotus were 1.462 and 5.511, respectively, whereas the HQ value for Hg in Allium chinense was 1.773, posing a significant threat to human health. These findings offer valuable data and theoretical foundation for further investigations into the sources and risks associated with toxic elements in farmland near thallium mining sites.