[Health Risk Assessment of Soil Heavy Metals in a Small Watershed of a Mining Area in Yunnan]

The purpose of this study was to explore the pollution of soil heavy metals and the health risk of the contaminated soil to residents, which was affected by the copper mine in a small basin of a mining area in Yunnan Province. Soil (39 samples), sediment (six samples), water, and corresponding suspended particle (six samples) and dust (one sample) samples were collected. The contents of Cd, Pb, Hg, As, Zn, Cu, Ni, and Cr in the samples and the soil pH were determined. The spatial distribution of heavy metals was analyzed, and the source of soil heavy metals was innovatively traced by the relative proportion of heavy metals in various media. The geo-accumulation index, Nemerow comprehensive pollution index, and potential ecological risk index were used to evaluate and analyze the pollution status and the potential ecological risk of soil heavy metals in the watershed, whereas the health risk model recommended by USEPA was applied to evaluate the health risk. The results showed that the heavy metals in the soil of the upstream area might be derived from the synergistic input of irrigation, atmospheric deposition, and soil erosion. In the middle reaches and lower reaches, the irrigation and the soil erosion of sloping land mainly contributed the heavy metal input, respectively. It was also found that the pollution degree in the upstream area was higher than that in the downstream area. The farmland soil was seriously polluted by Cd, Zn, Pb, and Cu, and Cd, Zn, and Pb had high potential ecological risks. Although residents did not face the risk of non-cancer diseases, the carcinogenic risk had exceeded the acceptable level, and children were at higher risk of cancer. In addition, although the content of As in the soil was lower than that of Cd, Zn, and Pb, it had a higher carcinogenic risk.