Investigation of plant species and their heavy metal accumulation in manganese mine tailings in Pingle Mn mine, China

Mine tailings are a characteristic of landscapes where mineral extraction has occurred and provide a prime opportunity for vegetation succession. In this study, soil heavy metal concentrations, plant composition and biodiversity, heavy metal accumulation, and their relationships were studied in the tailings of the Pingle Mn mine (abandoned for over 15 years) in South China. The total heavy metal concentrations ranged from 440 to 15,590 mg kg⁻¹ for Mn, 5.01 to 20.7 mg kg⁻¹ for Cd, 101 to 319 mg kg⁻¹ for Pb, 546 to 1693 mg kg⁻¹ for Zn, and 116 to 180 mg kg⁻¹ for Cu. According to soil contamination assessment by single contamination indexes and the Nemerow multifactor index, the tailing soil had a heavy pollution level. According to ecological risk assessment by monomial potential ecological risk factors and potential ecological risk indexes, the tailing soil presented a high ecological risk level, to which Cd was the key contributor. A total of 13 plant species from 2 families (Gramineae and Compositae) successfully colonized the tailings. Importance values based on relative height, relative coverage, relative abundance, and relative frequency indicated that Neyraudia reynaudiana K. and Paspalum orbiculare F. were the dominant species. The species were multi-metal-tolerant species, and most of them were shoot accumulators, as their translocation factor values were above 1. Plants exhibited the highest bioconcentration factor for Pb, and the average values for roots, stems, and leaves were 2.56, 1.45, and 1.70, respectively. There were positive relationships (P < 0.01) between soil Mn, Cd, Zn, and Cu and plant Pb; similar results were found for soil heavy metals and leaf/stem Mn. The species composition in the tailings of the Pingle Mn mine was reflective of long-term vegetation succession, and the results obtained in this study provide insight for selecting plant species and reconstruction practices for Mn wasteland restoration.