黔西北山区耕地重金属健康风险评价及环境基准

Health Risk Assessment and Environmental Benchmark of Heavy Metals in Cultivated Land in Mountainous Area of Northwest Guizhou Province

以贵州省西北某典型喀斯特山区耕地为研究区,通过对137组土壤-农作物协同样品中重金属(Cd、Hg、As、Pb和Cr)含量进行检测,系统评价了区域土壤和农作物中重金属健康暴露风险,并基于物种敏感分布模型(SSD)反推区域耕地土壤环境风险基准值.结果表明:研究区玉米和水稻土壤均受到不同程度重金属(Cd、Hg、As、Pb和Cr)污染,其中Cd为首要污染物,超标率在87%~445%之间,且玉米地>水稻田;与土壤重金属高污染水平相反,仅有3.51%和13.04%的玉米籽粒和稻米中Cd含量超过国家食品安全限量标准,重金属Cd累积能力为水稻>玉米.健康风险评价结果显示,重金属对研究区成人和儿童的致癌/非致癌风险均处于较低水平,稻米摄入的致癌风险略高于玉米,儿童的健康风险值均高于成人.研究区土壤环境基准值是基于保护95%(HC_(5))和5%(HC_(95))的作物品种安全所得的土壤风险值,玉米土壤Cd、As、Pb和Cr的HC_(5)值分别为0.67、771.99、40.85和609.88 mg·kg^(-1),HC_(95)值分别为20.83、14381.82、2427.36和8606.28 mg·kg^(-1);水稻土壤Cd、As、Pb和Cr的HC_(5)值分别为2.42、8.88、41.41和27.84 mg·kg^(-1),HC_(95)值分别为48.47、159.67、1735.68和1671.74 mg·kg^(-1).推导出的玉米和水稻土壤中重金属的HC_(5)值均不同程度地高于现行标准中的土壤风险筛选值,HC_(95)值均高于土壤风险管控值,现行土壤标准对该地区评价结果偏严.

An extensive investigation of heavy metal(Cd,Hg,As,Pb,and Cr)levels in 137 pairs of soil-maize/rice samples was conducted in cultivated land from a typical karst mountain area in the Northwest of Guizhou Province.A health risk assessment model was used to assess the health risks of those areas,and the environmental benchmarks of heavy metals in soils were evaluated using the species sensitivity distribution(SSD)model.The results showed that the soils of maize and rice were polluted by heavy metals.Cd was the primary pollutant,with an exceeding rate ranging from 87%to 445%.The contaminated level of maize fields was higher than those of rice fields.In contrast,only 3.51%and 13.4%of Cd content in maize kernels and rice grains exceeded the national threshold,and the Cd heavy metal accumulation ability of rice was higher than that of maize.The carcinogenic and non-carcinogenic risks of heavy metals for adults and children in the study area were at a low level.The carcinogenic risk of rice consumption was slightly higher than that of maize,and the health risk to children was higher than that to adults.The results derived from the SSD method showed that the 95%and 5%hazardous concentrations(HC_(5) and HC_(95))of maize fields were 0.67 for Cd,771.99 for As,40.85 for Pb and 609.88 for Cr mg·kg^(-1),and HC_(95) were 48.47 for Cd,159.67 for As,1735.68 for Pb and 1671.74 for Cr mg·kg^(-1),respectively.The HC_(5) values of rice fields were 2.42 for Cd,8.88 for As,41.41 for Pb and 27.84 for Cr mg·kg^(-1),and the HC_(95) values were 48.47 for Cd,159.67 for As,1735.68 for Pb and 1671.74 for Cr mg·kg^(-1),respectively.The HC_(5) values of Cd,As,and Cr in maize fields and Cd in rice fields were significantly higher than the soil risk screening values in the current standard,and the HC_(95) values of the two fields were higher than the soil risk intervened values.The results indicated that the current standard would be too strict to evaluate the actual pollution level of soil heavy metals in this area.