Impact of Mining Methods and Mine Types on Heavy Metal (Loid) Contamination in Mine Soils: A Multi-Index Assessment

Mining activities caused heavy metal enrichment in mine soils. Sixty-six soil samplings of 26 mines in the central Tianshan Mountains of China were conducted to reveal heavy metal pollution for the single-factor (Pi), Nemerow comprehensive pollution (PN), geo-accumulation (Igeo), potential ecological risk (Ei), and health risks. The results indicate that mines in Bayingolin and Aksu exhibit the most severe pollution (PN = 26.64 and 25.28), characterized by Cd (Pi = 115.18) and As (Pi = 67.20), forming a Cd-As compound pattern. While Ili mines show Ni-Cu co-exceedance, and Turpan mines have lower overall pollution but localized Cd enrichment. Additionally, Cd is identified as the most severe by Igeo, with moderate or higher pollution levels observed in 61.00% of samplings. The Ei assessment revealed that Cd posed the greatest threat, with 100%, 53.80%, and 30.70% of samplings indicating slight, high, and extremely high ecological risk levels, respectively. Health risk assessment indicated that non-carcinogenic risks were dominated by Cr (affecting 19.20% of samplings), while carcinogenic risks were primarily from As (7.70%) and Cd (11.50% of samplings), with Cr exhibiting the highest carcinogenic risk. Furthermore, comparative analysis showed that underground mines led to higher pollution levels (Igeo) for Cd, Cu, Mn, Pb, and Zn compared to open-pit mines, and metal mines incurred greater heavy metal(loid) contamination than non-metal mines. These findings could provide data for mine soil pollution remediation in the central Tianshan Mountains.