Characteristics, source analysis, and ecological impacts of soil heavy metals in typical lithium mining areas with recommendations for green mining development: A case study of the Alabo and Guanyinqiao lithium mining areas in Western Sichuan

This paper is the result of ecological geological survey engineering.

Objective This paper aims to thoroughly understand the characteristics of heavy metals in soils of mined rare metal mining areas, analyze the sources of heavy metals and their impact on the ecological environment, and propose recommendations for the green development of lithium resources in western Sichuan.

Methods This study focused on the depleted Alabo and Guanyinqiao lithium mining areas within the large lithium resource base in western Sichuan. A total of 48 and 25 surface soil samples were collected from the two sites, respectively. The contents of eight heavy metals (Cu, Pb, Cr, Ni, Cd, As, Hg, Zn) and pH values were measured. The pollution status and potential ecological risks of heavy metals were comprehensively evaluated using the Single Factor Pollution Index, Nemerow Comprehensive Pollution Index, Geo-accumulation Index, and Potential Ecological Risk Assessment. Correlation analysis and principal component analysis were employed to explore the sources of heavy metals.

Results The heavy metal contents in the soils of both lithium mining areas were either lower than or similar to the background values. Spatially, heavy metals showed patchy enrichment, concentrated in areas with intensive human activities. Both the Single Factor and Comprehensive Pollution Indices indicated no pollution in the soils of the two mining areas. The Geo-accumulation Index showed no accumulation of pollution for all elements except Cd. The Potential Ecological Risk Assessment revealed slight to moderate potential risks from Cd and Hg, but the comprehensive ecological risk index indicated an overall low risk in the mining areas. Source analysis indicated that Cu, Cr, Ni, Pb, and Zn were primarily derived from natural sources (e.g., rock weathering), Cd and Hg were mainly attributed to human activities (particularly mineral processing), while As was influenced by both natural and anthropogenic factors.

Conclusions Lithium mining in western Sichuan poses limited ecological risks, with Cd and Hg enrichment observed only in human activity-intensive areas (e.g., processing ponds, tailings dams). Strengthened source control can mitigate mining-related ecological impacts. Based on heavy metal characteristics, source attribution, and ecological evaluations, practical recommendations for green mining development are proposed.