沣河沿岸土壤重金属分布特征及来源分析

在野外调查的基础上，以陕西省沣河沿岸土壤为研究对象，结合数据统计与GIS制图，对Co、Cr、Cu、Mn、Pb、Zn、Ni和V 8种重金属元素富集特征、空间分布、生态风险及来源进行分析。结果表明：研究区各重金属元素含量在人群、工厂密集地显著富集，并均有着随水流方向呈总体升高的趋势。土壤中Co、Cr、Mn、Pb和V的几何均值分别为21.5、92.1、611.1、32.9 mg?kg^-1和75.4 mg?kg^-1，均高于陕西省土壤背景值。其中，Co、Cr、Mn和Pb含量的超标率达100%、75%、63%和25%，表现为以Co为主的多种重金属复合污染。污染评价结果表明：研究区存在不同程度的重金属污染，其中，Co、Cr、Pb和Ni污染主要集中在沣河中下游河段，Cu污染主要集中在沣河中上游河段。沣河沿岸土壤重金属污染与人类活动关系密切，应引起重视。

Spatial Distribution and Sources of Heavy Metals in Soil Samples Collected from the Riparian Area of the Fenghe River

Soils in the riparian area of river are ecologically the main components of stream system, and they act as a part of maintaining the normal status of aquatic habitats. With the rapid industrialization and urbanization, however, excessive sewage sludge or solid wastes containing heavy metals was discharged into river by various human activities, such as mining, smelting, waste incineration, fossil fuel combustion and transportation, which interferes the natural growth of aquatic flora and fauna, causes the deterioration of water quality, and impairs human health through a contaminated food chain, especially in drinking water source area. But few studies on soils in riparian area of river have been carried out, therefore, the research in this aspect will contribute to a better understanding of heavy metal pollution, and affect stream system and environmental protection of aquatic habitats. The concentrations of Co, Cr, Cu, Mn, Pb, Zn, Ni and V in topsoil samples collected from the riparian area from the headwaters to the estuary of the Fenghe River in Shaanxi Province were measured with X ray fluorescence spectroscopy. GIS mapping and multivariate analysis were used to analyze the spatial distribution, accumulation, potential risk and sources of heavy metals in the study area. The results showed that a significant spatial accumulation of heavy metals except Cu in soils were found at midstream and downstream. The geometrical mean concentrations of Co, Cr, Mn, Pb and V in soils were 21.5, 92.1, 611.1, 32.9 mg•kg-1 and 75.4 mg•kg-1 respectively, all of them exceeded the corresponding background values in Shaanxi. The Environmental Quality Standard (GB15618-1995, Grade Ⅰ) was taken as a reference of soils, the over-limit ratios of heavy metals in the soil samples were 100% for Co, 75% for Cr, 19% for Cu, 63% for Mn, 25% for Pb, 6% for Ni and 25% for V, that means the soils were mainly polluted by Co and Cr. The Nemero Index showed that the pollution of soils was slight. The Geo accumulation Index displayed that the contamination of Cu was accumulated in the headwaters and at the midstream, and that of Co, Cr, Pb and Ni at the midstream and downstream of the Fenghe River. Factor analysis and correlation coefficient analysis were used to identify the main sources of heavy metals in soils. The results illustrated that Co, Cr, Cu, Pb, Zn and Ni derived mainly from industry sources, traffic and garbage, and Mn and V from natural sources. It is very necessary to prevent and remediate the polluted soil to reduce soil contamination by heavy metals and to focus on the potential risk of heavy metals in soils in the riparian area of the Fenghe River for water safety and human health.