Assessment of trace metal contamination and ecological risk in the forest ecosystem of dexing mining area in northeast Jiangxi Province, China

Samples of soil, earthworms, and tree roots from the forest ecosystem in the Dexing Pb/Zn mining area of Jiangxi Province were collected and the status of trace metal pollution analyzed to assess potential ecological risks. Chemometric and geographic information system methods were used to identify and describe the spatial distributions and the main contamination sources of trace metals. The order of potential ecological risks of trace metals in this area are as follows: cadmium (Cd) > arsenic (As) > copper (Cu) > nickel (Ni) > lead (Pb) > chromium (Cr) > zinc (Zn). Elemental spatial distribution maps showed the existence of zones heavily polluted by trace metals around the mining area. Earthworms and roots of three tree species were also heavily contaminated, with concentrations of trace metals in earthworms much higher than in previous studies. The potential ecological risk index and other soil quality indices indicated that soil had moderate to severe contamination and there were high ecological risks, with Cd making the greatest contribution. Multivariate statistical analyses showed that Cd, As, Cu, Pb, and Zn in soil came from a mining activity source, whereas Ni and Cr primarily originated from a natural source.