上海市奉贤区农田土壤-农产品中的重金属含量特征和污染评价OACSTPCD

To analyze the contamination status of heavy metals in farmland soils and agricultural products in Fengxian District,the topsoil and agricultural product samples were collected in grain field,vegetable field and orchard.The content characteristic of eight heavy metals(Hg,As,Cd,Cr,Pb,Cu,Zn and Ni)in soil and five heavy metals(Pb,Cd,Cr,As and Hg)in agricultural products were determined The pollution status was evaluated by single pollution index,comprehensive pollution index,geoaccumulation index and enrichment factor.The geostatistics method combined with factor analysis was applied to analyze the spatial distribution and sources of soil heavy metals.The results showed that the average contents of Hg,Cd,Cr,Zn and Ni in Fengxian farmland soils were 1.40,1.36,1.06,1.15 and 1.44 times of the background values in Shanghai soils,respectively.The single pollution index and comprehensive pollution index revealed that heavy metals in soils were uncontaminated,while the geoaccumulation index indicated that Cd,Ni and Hg were at uncontaminated to moderately contaminated level,of which Hg in 4.92％samples was at moderately contaminated levels.The content of Hg was continuously distributed in the region.The As and Cd were low and distributed between the north region and the south regions.The Cr and Zn were distributed in strips and increased from the south region to the north region.The Pb was distributed as scattered dots.The Cu was high and decreased gradient from the west region to the east region,but the Ni was distributed as an island.Factor analysis demonstrated that Cu and Zn could be attributed to Factor 1,and Factor 3 was the main contributors to Cd and Cr.In addition,Factor 2,4,5,and 6 showed heavily loadings for Pb,Ni,As and Hg,respectively.The heavy metal contents in Fengxian District were mainly affected by industrial source,agricultural source,traffic source and natural source.Therefore,it is necessary to strengthen the source controlling and reduction strategies.The contents of heavy metals in 64 agricultural product samples were all lower than the limit standards.The single pollution index and comprehensive pollution index indicated that the products belonged to clean level.Although the contents of heavy metals showed similarity between soil and product samples in a certain level,but no significant correlation was detected,which result to the low enrichment factor.The heavy metal content in soil and agricultural product from different land use were significantly different:Cd was sensitive in vegetable field and had a high absorbing ability,while orchard was contrary to vegetable field where the pollution index was lower.In order to reduce heavy metals pollution,the planting structure could be adjusted according to the heavy metals absorption characteristic in different crops.In sum,the accumulation of heavy metals in the soil-product system of Fengxian District was relatively low,but the content of heavy metals in soil was slightly polluted in local farmland,which should be paid enough attention.