云南某矿区小流域土壤重金属健康风险评价

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

为研究云南省某矿区小流域受铜矿影响的土壤重金属污染状况以及污染土壤对当地居民构成的健康风险,采集农田土壤(39个)、底泥(6个)、水体及其中悬浮物(6个)和降尘样本(1个),测定其中Cd、Pb、Hg、As、Zn、Cu、Ni和Cr的含量以及土壤pH.分析了重金属在小流域主要介质中的空间分布,并尝试通过重金属在各类介质中的相对比例,判断土壤重金属污染来源.利用地累积指数法、内梅罗综合污染指数法和潜在生态危害指数法对流域内土壤重金属污染状况和潜在生态风险进行评价分析,采用USEPA推荐的健康风险模型对该流域进行了健康风险评价.结果表明流域上游村庄的重金属污染可能来源于浇灌、大气沉降和坡地水土流失的协同输入,而中游和下游村庄的重金属分别来源于浇灌和坡地土壤流失.流域上游农田土壤受重金属污染程度大于下游.污染负荷指数法结果显示Cd、Zn、Pb和Cu污染严重,Cd、Zn和Pb具有较高的潜在生态风险.当地居民虽然未面临患非癌症疾病的风险,但是致癌风险已超过可接受水平,并且儿童患癌症的风险更高.此外,虽然As在土壤中的含量低于Cd、Zn和Pb,却具有更高的致癌风险.

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.