南京市城乡公路绿地土壤重金属变化及其评价

ASSESSMENT ON VARIATION OF HEAVY METALS IN THE GREENBELT SOILS ALONGSIDE URBAN-RURAL ROADWAYS IN NANJING CITY

通过对南京市公路绿地系统(城市干线、绕城公路和城郊公路)土壤重金属的调查和分析,并与相对清洁点植物园植被土壤进行比较,研究了公路绿地土壤重金属分布的特点:公路绿地土壤重金属元素含量一般高于“清洁区”,其中土壤Mo、Zn、As、Cd、Cr、Cu、Fe、Mn的含量以绕城公路最高,土壤Pb的含量以城市干线最高,土壤Al的含量以城郊公路最高。城市干线、绕城公路、城郊公路和相对清洁点的土壤重金属多样性指数分别为0 .2 6 1、0 .2 93、0 2 38、0 2 36 ,仍以绕城公路最高,城市干线次之,城郊公路最低,公路土壤重金属多样性指数均高于“相对清洁点”。应用主成分分析方法对土壤样本进行了排序和聚类分析,结果表明:样本点表现了较好的以取样路线聚类的特点,各取样点土壤重金属含量存在明显的演变分异。土壤重金属演变的趋势可解释为:绕城公路是高Zn、Mo、Cd、As、Cr、Fe、Mg、Cu、Mn、Pb区,城市干线是高Pb区,城郊公路是高Al和Fe区。

Soils of greenbelts alongside in road system (urban trunk roads, belt highways and suburban roads) as well as of the Nanjing Botanical Garden cited as a clean zone were surveyed and assessed for heavy metals. The results show that the contents of most heavy metals in the soils of on the roadside are higher than in the soil of the clean zone. The highest concentrations of Mo, Zn, As, Cd, Cr, Cu, Fe and Mn are found in the soils alongside the belt highways, that of Pb in the soils alongside the urban trunk roads and that of Al in the soils alongside the suburban roads. This phenomenon could be further confirmed with the Shannon Weaner Index, indicating a declining order of belt highways (0.293)>urban trunk roads (0.261)>suburban roads (0.238)>'clean zone' (0 236). This result reflects significant variation of soils accumulating heavy metals;The principal component plot reveals that the belt highways are areas high in heavy metals;the urban trunk roads areas high in Pb, the suburban roads areas in Al and Fe, and the clean zone 'Botanical Garden' an area low in heavy metals.