贵州遵义下寒武统黑色页岩区土壤重金属污染和人体健康风险评价

为清晰认识贵州遵义地区下寒武统牛蹄塘组底部黑色页岩区土壤及农作物重金属健康风险，以该黑色页岩区的表层土壤及农作物为研究对象，分析其重金属含量，采用单因子污染指数、内梅罗综合污染指数法和健康风险评价模型分别评价土壤和农作物重金属污染程度及健康风险，厘定主要的重金属污染物及其暴露途径.结果表明:①研究区土壤Cd、Cu、Ni和Zn平均含量均超过贵州省土壤元素背景值和GB 15168-2018《土壤环境质量农用地土壤污染风险管控标准（试行）》中土壤风险筛选值.研究区粮食类作物水稻中Cr、Ni、Zn含量，玉米中Cr、Pb含量，以及甘薯中Cr、Ni、Cd、Pb含量均超过国家相关标准中的标准限量；蔬菜类作物（白菜、辣椒、萝卜）中Cr、Ni、Zn、Cd和Pb含量均超过国家相关标准中的标准限量.②内梅罗综合污染指数法评价结果表明，研究区旱地土壤重金属综合污染等级为中度污染，内梅罗综合污染指数（NIP）为4.10，水田土壤则为重度污染（NIP=5.38）；粮食类农作物水稻、玉米和甘薯NIP值分别为10.7、8.99和36.9，重金属综合污染等级均为重度污染；蔬菜类农作物白菜、辣椒和萝卜NIP值分别为10.4、11.4和26.1，重金属综合污染等级均为重度污染.③健康风险评价模型结果表明，在摄食农作物、手口摄入和皮肤接触3种暴露途径下，研究区土壤和农作物重金属对成人和儿童的非致癌总风险指数（HI）分别为10.2和25.7，各重金属的非致癌风险大小排序为Cr > Pb > Cd > Ni > Zn > Cu.土壤Cd和Cr对成人和儿童的致癌健康风险均在可接受范围内；Ni存在一定的致癌健康风险.研究显示，贵州遵义地区下寒武统牛蹄塘组底部黑色页岩区土壤和农作物重金属复合污染已给当地居民造成一定程度的健康风险，摄食农作物是主要的重金属暴露途径，其中水稻和白菜中Cr、Cd和Pb是造成非致癌健康风险的主要污染物. 

Assessment of Pollution and Human Health Risk from Heavy Metals in Soils and Crops in the Lower Cambrian Black Shale Area,Zunyi, Guizhou Province

In order to understand the human health risk from heavy metals of soils and crops in the Lower Cambrian black shale area, Zunyi, Guizhou Province in China, the concentrations of the heavy metals in the soils and crops collected from the area were analyzed. Meanwhile, the pollution level, and the health risk of the heavy metals were evaluated using thesingle factor index method, Nemerow integrated pollution index (NIP) and health risk index, respectively. Through the evaluation, this study identified the main contaminants in the soils and crops and the major exposure pathway of the metals. The results show that the averaged concentrations of Cd, Cu, Ni and Zn in the soils are significantly higher than the corresponding background values of these elements in the soil of Guizhou Province, and are also higher than the limits of Soil Environmental Quality Risk Control Standard for Soil Contamination of Agricultural Land (GB 15168-2018), respectively. Cr, Ni and Zn in rice, Cr and Pb in maize, and Cr, Ni, Cd and Pb in sweet potato exceed the limits of relevant standards in China, respectively. Furthermore, the Cr, Ni, Zn, Cd and Pb in Chinese cabbage, radish, and pepper exceed the limit standards of China. The calculated Nemerow integrated pollution index (NIP) indicates that the integrated contamination levels of the heavy metals in upland and paddy soils are moderate and high, respectively. For crops, the exceeding standard levels of heavy metals in rice, maize, sweet potato, Chinese cabbage, radish, and pepper are all high, and their NIP values are 10.7, 8.99, 36.9, 10.4, 11.4 and 26.1 respectively. The health risk assessment results show that the total hazard index (HI) of heavy metals of soils and crops caused by the consumption of corps, oral intake and dermal absorptionby adults and children are 10.2 and 25.7, respectively. The relative contribution of various heavy metals to the total HI value follows an order of Cr > Pb > Cd > Ni > Zn > Cu. Under the exposure pathway of oral intake and dermal absorption, Cd and Cr in soils pose acceptable carcinogenic health risks to adults and children, while Ni leads to certain carcinogenic health risks. The study shows that a certain degree of non-carcinogenic health risks have occurred to local residents due to the integrated pollution of heavy metals in soils and crops in the Lower Cambrian black shale area, Zunyi, Guizhou Province in China. Consuming crops is the major exposure pathway of the six heavy metals to the residents. Cr, Pb and Cd in rice and Chinese cabbage are the main risk sources and pollutants.