深圳市不同功能区土壤表层重金属污染及其综合生态风险评价

Heavy metal pollution and comprehensive ecological risk assessment of surface soil in diffe-rent functional areas of Shenzhen,China

在综合考虑深圳市城市功能区分异特征的基础上,进行全市表层土壤系统采样,全面监测土壤表层8种重金属元素污染状况,分析不同重金属元素含量的统计学特征,探讨不同城市功能区对土壤表层重金属污染的影响,采用内梅罗指数和潜在生态危害指数评估不同重金属元素和不同城市功能区的生态风险水平,分别进行基于两种方法的全市重金属污染生态风险分区。结果表明:1)深圳市土壤表层的Mn、Ni、Cr和Pb 4种元素受人为活动的影响程度较低,Cd、Zn、Cu和As 4类元素受人为活动影响较大。地表环境约束因素背景下的高强度城市化和工业化过程,是各种重金属污染区域分异和功能区分异的决定性因素。2)深圳市土壤重金属污染风险较高的重金属元素为Cd、Zn、Cu和Pb,特别是Pb污染问题尤为突出,必须加强管控工作。深圳市总体土壤表层重金属污染风险水平高于国内相关城市,需要引起足够重视。3)内梅罗指数法和潜在生态危害指数法的侧重点不同,在单一重金属元素风险判断、不同城市功能区生态风险的总体评价,以及市域土壤重金属污染生态风险分级评价方面结果差异较大,组合使用效果更好。

To explore the impact of urban functional zones on surface soil metal pollution,we analyzed the concentrations and pollution status of eight heavy metals(i.e.,Mn,Ni,Cr,Pb,Cd,Zn,Cu,and As)in surface soils from various urban functional zones of Shenzhen City.Nemero index and potential ecological hazard indices were used to quantify the ecological risk levels of different heavy metals in different urban functional zones.Moreover,we spatially classified ecological risk zones for soil heavy metal pollution.Results showed that:1)concentrations of Cd,Zn,Cu,and As in the surface soil were heavily impacted by human activities,while those of Mn,Ni,Cr,and Pb were not.High-intensity urbanization and industrialization with the constraints of physical environment were identified as the determining factors for regional and functional variation of heavy metal pollution.2)Pb,Cd,Zn,and Cu had high pollution risks in the surface soils,with Pb having the highest risk,which necessitated further management and control of heavy metals.The overall level of heavy metal pollution risk in the surface soils of Shenzhen was higher than that of other cities in China.3)Nemero index and potential ecological hazard indices had different emphases in terms of assessing the risk level of heavy metals.Those indices showed different performances in the risk assessment of single heavy metal,overall ecological risks in the different urban functional zones,and ecological risk classification of heavy metal pollution in the urban surface soils.We suggest that those indices should be combined to provide more holistic information about urban heavy metal pollution.