Investigation of heavy metals concentration in soil around a Pb-Zn mine and ecological risk assessment

Background: Soil pollution with heavy metals seriously threatens soil quality, food safety, and human health. This study was conducted to determine the soil pollution level and ecological risk assessment of different heavy metals in agricultural soils around Nakhlak Pb-Zn mine, located in Anarak district, Nain county of Isfahan province. Methods: A total of 50 soil samples were collected from agricultural land around Nakhlak mine and analyzed to determine the concentrations of Pb, Cd, Zn, Ni, Cu, and Mn. The geo-accumulation index (I-geo), enrichment factor (EF), and potential ecological-risk index (Er) were used to assess the level of soil pollution with heavy metals. Results: The mean concentrations of Pb, Cd, Zn, Ni, Cu, and Mn were 355, 2.72, 347, 26, 36, and 505 mg/kg, respectively, which were higher than the background values of world soils. Based on the Igeo index, the study area was moderately to heavily contaminated with Pb and Zn, uncontaminated to moderate contaminated with Cd and Cu, and uncontaminated with Mn and Ni. According to the EF values, the study soil was moderately contaminated with Mn, Ni, and Cu, significantly contaminated with Cd and Zn, and highly enriched with Pb. The RI values showed a moderate level of heavy metals contamination in the study soil. Conclusion: According to the results, the ecological risk of heavy metals for ecosystem in agricultural lands around Nakhlak Pb-Zn mine is moderate. However, the contamination status should be considered periodically.