Evaluation of the potential risks of heavy metal contamination in rice paddy soils around an abandoned Hg mine area in Southwest China

To assess the potential ecological and health risks of trace elements (Hg, Cd, As, Mn, Sb, Pb, Cu, Ni, Cr, and Zn), a total of 138 soil samples from rice paddies were collected during the rice harvest season in the Wanshan mining area, Guizhou Province, Southwest China. Factors of the pollution load index (PLI), geo-accumulation index (I-Geo), enrichment factor (EF), and risk index (RI) were determined. High concentrations of Hg, Sb, As, Zn, Cd, Cu, and Mn were observed in the soils. The PLI, I-Geo, and EF results all showed high levels of contamination by Hg and Sb and moderate levels of contamination by As, Pb, Zn, Cu, Cd, and Mn. There was no significant contamination from Ni and Cr. The RI was very high, with Hg as the dominant pollutant, as expected, indicating that the historical large-scale Hg mining, as well as artisanal mining, has had a significant impact on the Wanshan area. Moreover, coal combustion, manganese factories, and the use of agrochemicals by the local population could also have an impact on the soil through the introduction of heavy metal loads. To address the current state of contamination, pollutant remediation and the regulation control of the anthropogenic activities in Wanshan are urgently needed.