Health risk assessment and source apportionment of heavy metals in the surrounding soil of a sandstone copper mine area in Central Yunnan

This paper is the result of environmental geological survey engineering.

Objective Central Yunnan area is an important copper mine and grain production area. Analyzing the spatial distribution of heavy metals in soil around sandstone copper mine areas, identifying pollution sources and health risks is of great practical significance for ecological environment protection and governance in metal mine areas and ensuring agricultural safety.

Methods Based on the grid sampling method, 780 soil samples were collected around a typical sandstone copper mine. The contents of Corg, As, Cd, Cr, Cu, Hg, Ni, Pb, Zn and pH in soil were analyzed. The potential sources of heavy metals were analyzed through positive definite matrix factor analysis (PMF) model and Geodetector. The non−carcinogenic and carcinogenic risks generated by different pollution sources were assessed using a health risk model.

Results The maximum concentrations of the eight heavy metals were 2.49−36.88 times the background value. Some Cd and As concentrations exceeded the risk screening and control values stipulated by China’s national standards. The areas with high metal levels were mainly near copper mining and smelting areas. Source analysis revealed that the accumulation of heavy metals was affected by 6 sources: natural sources from parent rock weathering (27.9%), waste residues source (17.8%), natural sources of lead−bearing parent rock (15.4%), natural sources of copper−bearing parent rock (15.2%), copper mining and smelting practices with outdated technology source (12.5%), and atmospheric deposition source (11.2%). Health risk assessment results demonstrated that copper mining and smelting practices with outdated technology source contributed the most to the hazard index (HI) in both children and adults (35.6% and 5.8%, respectively). The potential non−carcinogenic risk to adults from soil heavy metals was regarded as acceptable. However, among the samples, 12.31% presented a higher potential non−carcinogenic risk to children. Additionally, 1.14% and 5.51% of the samples that exceeded the established limits posed a higher carcinogenic risk to adults and children respectively. Among all exposure pathways, the soil ingestion pathway (86.84% to 93.28%) contributed the most to health risks.

Conclusions To reduce children's heavy metal ingestion risk via the oral route, more attention and guidance are needed. When formulating soil protection strategies near sandstone copper mining areas, regulating backward technologies (such as ancient copper smelting) in mining and smelting should be a top priority. The research findings support formulating targeted pollution source prevention and control measures.