中国193个城市规划区土壤微量元素污染与健康风险

Trace Metals Pollution and Health Risks for Planning Area Soils of 193 Chinese Cities

随着城市化进程的加快,城市表层土壤微量元素含量发生了不同程度的变化,城市土壤污染所引发的环境问题进一步凸显.为了系统研究我国31个省(自治区、直辖市)193个地级以上城市规划区表层土壤13种微量元素的含量特征、污染水平和暴露风险,利用地累积指数(Igeo)和综合污染指数(IPI)对土壤微量元素的污染水平进行了评价,采用美国环保署(USEPA)推荐的健康风险评估方法量化了居民暴露于城市土壤的健康风险.研究结果显示:城市规划区表层土壤As、Be、Cd、Co、Cr、Cu、Hg、Ni、Pb、Se、Tl、V和Zn等13个元素含量中位值分别是9.25、2.14、0.174、12.4、68.4、28.2、0.095、27.7、31.1、0.29、0.61、82.7和82.2 mg·kg^-1,相比于城市土壤背景值,Cd、Hg和Se是含量变化比较显著的元素.Igeo值表明城市规划区表层土壤污染最严重的是Hg,其次是Se和Cd,污染程度介于无污染至中度污染之间,其他元素无污染.综合污染指数IPIN显示:全国有22个城市规划区土壤已达到重度污染,16个城市达到中度污染,湖南省株洲市是全国土壤污染最严重的城市.健康风险评估结果表明:郴州市、黄石市、株洲市、湘潭市和龙岩市等5个城市规划区土壤暴露对未成年人具有潜在非致癌风险,其中土壤Pb摄入是引发风险的主要因素.建议在综合污染已达中度到重度污染的城市开展详查,摸清土壤污染状况及污染地块分布,建立污染地块清单和优先管控名录,实施污染调控和修复治理.

Urban soils are more easily subjected to modification,especially by contamination because of various human activities,and the environmental problems caused by urban soil pollution have become more prominent.To systematically investigate concentration characteristics,pollution levels,and exposure risks of 13 trace metals in urban soils of planning areas for 193 cities above the prefectural level,located in 31 provinces(autonomous regions and municipalities)of China,levels of pollution in urban soil were evaluated using the geoaccumulation index and integrated pollution index of trace metals,and health risks of residents exposed to urban soils were quantified using the health risk assessment method recommended by the US Environmental Protection Agency(USEPA).The results show that the median concentrations of As,Be,Cd,Co,Cr,Cu,Hg,Ni,Pb,Se,Tl,V,and Zn in topsoils of urban planning areas were 9.25,2.14,0.174,12.4,68.4,28.2,0.095,27.7,31.1,0.29,0.61,82.7,and 82.2 mg·kg^-1,respectively.Compared with the corresponding urban soil background values,the concentrations of Cd,Hg,and Se changed significantly.The geoaccumulation index(Igeo)values showed that Hg in urban soils of the planning area was the most severe pollutant,followed by Se and Cd,which caused pollution levels of uncontaminated to moderately contaminated levels,while other trace metals were uncontaminated.The Nemerow IPI(IPIN)revealed that the soils in 22 urban planning areas were heavily polluted and 16 urban planning areas were moderately polluted;in addition,the most polluted city in China was Zhuzhou in the Hunan province.The results of health risk assessment indicate that the soils in the five urban planning areas-Chenzhou City,Huangshi City,Zhuzhou City,Xiangtan City,and Longyan City-posed potential non-carcinogenic risks to children,and the major factor triggering risks was ingestion of Pb.To understand the soil pollution status and distribution of contaminated land parcel,it is suggested to carry out detailed investigation in cities with integrated moderate to heavy pollution to establish the list of contaminated land parcel and implement pollution control and restoration.