Heavy metal concentrations in soils and plants in Rongxi Manganese Mine of Chongqing, Southwest of China

Abstract

The Rongxi manganese mining area is located in Chongqing, southwest of China. In this study plants and soils from 5 different sites in this area were collected and analyzed for heavy metals. Analyses of soils in different sites showed that the total Mn, Cd, Cu, Pb and Zn concentrations were up to 48,383, 3.91, 79.97, 80.68 and 131.23 mg/kg respectively, indicating that the mine soils were polluted by these five metals. Plants collected from these sites belonged to 37 species from 24 families. The concentrations of these metals in dry shoot matters varied, ranging 323–8434 mg/kg for Mn, 0.42–1.24 mg/kg for Cd, 1.96–46.23 mg/kg for Cu, 3.90–105.84 mg/kg for Pb and 19.17–57.64 mg/kg for Zn, respectively. According to the plant–soil relationships, plants were classified into three groups: shoot accumulators, root accumulators and excluders. Shoot accumulators such as Polygonum lapathifolium and Phytolacca americana absorbing high concentrations of heavy metals in the shoots were suitable to clean up slight to moderate polluted soil with a high use value. Root accumulators like Miscanthus sinensis and Stenoloma chusanum stored high levels of heavy metals in the roots and transfer little to shoots. Excluders including Debregeasia orientalis, Boehmeria clidemioides and Artemisia annua were the plants accumulating little heavy metals in their bodies though they grow on the severely polluted soil. The latter two can be used to remediate mine soils with higher heavy metals levels.