Impacts of non-ferrous metal mining on soil heavy metal pollution and risk assessment

Mining activities significantly contribute to soil contamination, posing risks to the environment and human health. This study evaluates the environmental and health impacts of four non-ferrous mining types, which have been rarely examined globally. It highlights gaps in existing datasets from selected mining sites and sampling practices, correlating soil pollutants with atmospheric variables. Overall, the geoaccumulation index (Igeo) of all mine soil types were in the order Hg > Cd > As>Cu > Pb > Zn > Ni > Cr > Mn > Co indicating that Hg and Cd are the main metals posing risks from soil pollution associated with all mining activities. Notably, the highest As contamination (Igeo: class 6) occurs in copper mines in China, Russia, and Portugal, and in lead‑zinc mines in Sweden and Mexico. Cd contamination (Igeo: class 6) was most severe in lead‑zinc mine soils across Tunisia, China, Ireland, Spain, Slovenia, Mexico, France, North Macedonia, Bulgaria, and Egypt, while uranium mines in the USA showed notably lower levels of Cd contamination (Igeo: class 2). Hg contamination levels were higher in gold mine-associated soils in Iran, China, Myanmar, Brazil and Nigeria. About half of the sites faced the highest ecological risks from lead‑zinc mining areas in Vietnam, Tunisia, and Sweden, while copper mines in Cyprus, China, and Portugal had only 8 % in that category. Gold mines in China, Nigeria, and Brazil showed considerable risks from As and Hg, whereas uranium mines in Germany and Bulgaria had a lower ecological risk, due to better environmental management. The primary exposure route for heavy metals is ingestion, with the hazard index (HI) for non-carcinogenic impacts being acceptable for most elements, except for As. Carcinogenic risks are notably present in Brazil, Spain, Slovenia, Mexico, China, and the UK. Hence, this review underscores the urgent need to address heavy metal pollution from global metal mining and offers policy recommendations for effective environmental management and restoration efforts.