Spatial Variability And Pollution Source Apportionment Of Heavy Metals In Vegetable Fields Of Peri-urban Area

Peri-urban area is an area dominated by private industry, as well as an important production area of agricultural products such as vegetables and grain food for local and urban residents. In this study, with the vegetable field in the peri-urban areas of Hangzhou city as study area, we investigated the soil heavy metals pollution and their spatio-temporal variations from2005to2010based on the geography information system (GIS) and geostatistics techniques. The heavy metal content, primary pollution sources, spatial variation, scale effect, and dynamic changes were all studied. The main results were summarized as follows:(1) The studied soils were polluted by metal Cu, Cd, and Hg.Based on Chinese Environmental Quality Standard for Soils (GB15618-1995),96.55%,44.83%,13.79%soil samples exceeded the pollution level for Cd,Cu, Hg and Zn, respectively.Nemerow pollution index showed that there are27samples were exceeded the standard,with overproof rate of93.10%,7samples reached the heavy pollution level,I value>3.The Hakanson evaluation results based on ecotoxicology showed that the soil Hg pollution reached a critical level. Pb and Cr concentrations in Brassica Sinensis exceeded the threshold of the national food hygienic standard,86.21%and48.28%respectively.(2) The pollution trends of soil Pb, As, Cd and Cr decreased from west to east in the study area, according to the effects of busy traffic line. Soil heavy metal concentrations are mainly influenced by the environmental factors such as pH and organic matter. The spatial and temporal variation of soil heavy metals during2005-2010in the study area indicated that the concentrations of soil As and Hg significantly increased with the urban planning policy of East Hangzhou expansion. Heavy metal elements mainly influenced by pH, organic matter. Canonical Correlation Analysis (CCA) results revealed that the traffic factors and soil properties could explain59.53%variations. Therefore, traffic factors and soil physicochemical properties meanwhile strongly influenced the spatial distribution of soil metals.