Pollution Status and Risk Assessment of Sedimentary Heavy Metals in the Special Mine Basin of China

The spatiotemporal distribution and potential ecological risks of eight heavy metals, including chromium (Cr), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd), mercury (Hg), lead (Pb), and tungsten (W) in the sediments of the Taojiang River in southern Jiangxi Province, were investigated over three hydrographic periods. Sediment samples were collected from 36 sampling sites surrounding and downstream of the Taojiang River for deeply distributed tungsten (W) and rare earth ores. Results revealed that the average concentration of W in the sediment samples was more than three times higher than the soil background value of Jiangxi Province during high-water and normal-water periods and nine times higher during the low-water period; the variation coefficient of W was more than 100%, which indicated that W distribution was extremely heterogeneous. The Er-i revealed that Cr, Cu, Zn, Pb, As, and W showed slight ecological risks. On the other hand, Cd and Hg showed high ecological risks and their total contribution rates to risk index were above 96% in all three hydrological periods. Therefore, in terms of heavy metal contamination in the Taojiang River, especially Cd and Hg, necessary measures should be undertaken to protect rivers in southern Jiangxi.