贵州罗甸北部喀斯特地区耕地土壤镉含量特征与风险评价

贵州碳酸盐岩区镉(Cd)呈较高地球化学背景分布.为了解喀斯特地区耕地土壤Cd的含量特征,特选取小尺度区域——罗甸北部喀斯特地区土壤作为研究对象,以非喀斯特地区土壤作为对照组,运用地统计分析和GIS相结合的方法研究土壤Cd含量的空间分布特征,并采用潜在生态风险指数法和健康风险评价法对土壤Cd污染的潜在生态风险程度以及对成人和儿童的健康风险进行评价.结果表明,喀斯特区土壤Cd含量显著高于非喀斯特区(P 0. 05),其中耕地土壤Cd几何平均值分别为1. 33 mg·kg-1和0. 27 mg·kg-1,林地土壤Cd几何平均值分别为1. 57 mg·kg-1和0. 22 mg·kg-1.以GB 15618-2018中Cd的风险筛选值和风险管控值为限定值,喀斯特区耕地土壤Cd样点超标率分别为90%和22%,非喀斯特区耕地土壤Cd样点超标率分别为30%和12%,表现出不同程度的Cd富集.从空间分布来看,耕地土壤Cd含量中值风险区和高值风险区主要分布在喀斯特地区,分别呈现中-强程度的潜在生态风险和极强潜在生态风险;低值风险区分布在交砚乡等部分非喀斯特地区,呈低潜在生态风险;健康风险评价表明耕地土壤Cd虽尚未对人体产生非致癌健康风险和致癌健康风险,但喀斯特区成人和儿童3种暴露途径的非致癌风险值和致癌风险值均高于非喀斯特区.综上,贵州罗甸北部喀斯特地区耕地土壤Cd污染风险问题突出,应进一步加强土壤-植物-人体体系Cd风险评估研究,并针对不同耕地土壤Cd污染风险区采取合理的方案措施加以防控和治理.

Cd Accumulation and Risk Assessment for Arable Soils in the Karst Region of Northern Luodian, Guizhou

Background levels of cadmium (Cd) in carbonate rock areas of Guizhou Province are high. In order to understand the characteristics of Cd in arable soils in these karst areas, the soils in the northern county of Luodian were selected as the study object. By comparing soils in non-karst areas, the distribution characteristics of soil Cd were studied by combining geostatistical analysis and GIS, and the potential ecological risk index and health risk were used to evaluate the potential level of risk to adults and children. The results show that the arable soil Cd content in this karst area is significantly higher than that in non-karst areas (P<0.05), with a geometric mean of 1.33mg·kg^-1 and 0.27 mg·kg^-1, respectively. In comparison, the geometric mean of soil Cd content in forested land in the same areas is 1.57mg·kg^-1 and 0.22 mg·kg^-1, respectively. Based on "soil pollution risk control standards", the Cd content of 90% and 22% of arable soil samples was higher than the risk screening value and the risk control value for karst and non-karst areas, respectively. The areas with medium and high Cd values were mainly distributed in the karst areas, presenting medium to strong ecological risks and extremely strong ecological risks, respectively. In contrast, the areas with the lowest Cd concentrations were distributed in the non-karst areas of Jiaoyan, presenting low potential ecological risk. The health risk assessment showed that the non-carcinogenic risk and carcinogenic risk of the three exposure pathways for adults and children in the karst areas are significantly higher than those in the non-karst areas, but the Cd content in the soil does not present non-carcinogenic and carcinogenic risks to local residents. Overall, the problem of Cd pollution in arable soils in the karst area of northern Luodian, Guizhou, is prominent. Therefore, the study of the risks posed by Cd pollution to the soil-plant-human system should be strengthened, and appropriate measures should be taken to prevent and control Cd pollution in the areas at risk.