Environmental Risk in an Abandoned Peruvian Mine Using Soil Quality Indices and Bioindicators

Soil samples were taken from the abandoned Cobre Cata Acaril mining unit in Lima, Peru, to analyze soil quality for heavy metal contamination and assess environmental risk using simple and complex indices, Peruvian and international regulations, and two bioindicators: the land snail Cantareus aspersus and the earthworm Eisenia fetida. The two bioindicators were exposed to three types of soil (contaminated, background, and semi-contaminated). The values of the simple indices showed that the soil presented a low to moderate level of contamination, except for Cu (copper), which is at an extremely contaminated level. The complex indices show a moderate level of contamination. In C. aspersus, mortality and body mass reduction were evaluated at 15 and 30 days; while in E. fetida, they were evaluated at 10, 15, and 30 days. Heavy metals were analyzed for both bioindicator species to obtain the Excess Transfer Sum (SET) Index and the Risk Assessment Index of Transferred Metallic Elements (Eritme). The snail showed a higher abnormal transfer of heavy metals and an environmental risk at 15 days of exposure (SET = 8.20; Eritme = 352.24); whereas the earthworm showed a higher transfer and environmental risk at 10 days of exposure (SET = 13.89; Eritme = 149.09), which shows that the soils of the abandoned mine present an environmental risk through the accumulation quotient.