Characterization of heavy metal migration, the microbial community, and potential bioremediating genera in a waste-rock pile field of the largest copper mine in Asia

Abstract

Long-term metal(loid) pollution in waste rock piles is an underestimated environmental problem during ore production. To investigate the factors affecting the distribution of metal(loid)s, various physicochemical and microbial properties were analyzed in 70 soil and water samples taken from a waste rock pile field. The results were analyzed using different methods, such as interpolation and multivariate statistical analyses. The results showed that the distribution of metal(loid)s in the topsoil (0–20 cm) was characterized by large variations in Cu (38.33–5834.18 mg/kg), Cd (0.14–29.29 mg/kg), Cr (7.08–326.16 mg/kg), and As (3.68–91.06 mg/kg). The mean pH value of the soil in the waste rock pile field was 3.85, while it was 5.03 outside of the rock pile. The Shannon–Wiener diversity and Chao's richness indices decreased from 5.46 and 1855.62 outside of the rock pile to 3.95 and 817.82 inside the rock pile, respectively. Multivariate statistical analysis indicated that significant spatial heterogeneity in the soil properties led to differences in the metal(loid) fractions, and the residual fraction of different metal(loid)s varied from 20.69% to 99.98%. Acidification of the media and increasing the number of acidophilic bacteria mobilized Cu and Cr but did not affect As. Mobilization of Cu/Cr iron oxides and organic matter (OM) on As was detected in situ compared with previous studies. The results of this study can provide useful reference data for the remediation of metal(loid)–contaminated soil in acidic waste rock pile fields.