Abstract:
Objective To provide a theoretical basis for the prevention and control of heavy metal pollution from copper tailings, the morphological characteristics of heavy metals in the surface soil around it and the risk level of pollution were investigated.
Methods A total of 50 soil samples were collected from the soil around a copper tailing mine in northwestern Inner Mongolia. The pollution levels of heavy metals Cu, Zn, As, Pb and Cd were analyzed by single factor pollution index, local cumulative pollution index, potential ecological risk index and human health risk assessment model. The ecological risk index method and the secondary phase primary phase distribution ratio method were employed to assess the biological effectiveness of heavy metals and the risk of migration in conjunction with heavy metal morphology to briefly explore the sources of heavy metals and the influencing factors of heavy metal pollution.
Results ① The content of heavy metals Cu, Zn, As, Cd did not exceed the risk control value of GB 15618-2018, while the content of Pb (448.02 mg·kg−1) exceeded the risk control value at only one sampling point. Cu, As, Pb and Cd exceeded the risk screening value at 32, 17, 15 and 3 points respectively, while Zn did not exceed the standard. ② Zn has the lowest level of contamination, but the contamination of soil by Cu and Pb is a cause for alarm. The increase of Fe-Mn oxidation state (F3) and exchange state (F1) in the soil is the main factor why the biological effectiveness of heavy metals is in the low and no risk range and 65% of As pollution in surface soil has high migration risk. ③ As, Pb and Cd pose a higher risk to children than adults and were the main pollutants that threaten human health. ④ The pollution of heavy metals in this study is almost entirely released by tailings.
Conclusions The heavy metals of the study area are the result of long-term tailings stockpiling, which is a moderate level of contamination that exceeds risk screening values to varying degrees and requires regulation and a reduction in pastoral production and livelihoods in this area.