Heavy Metals In Soil-Crop System From Some Area Of Southern Jiangsu And Potential Food Exposure Risks

Samples of soil and agro-products from non-polluted and polluted farmland near a Smelter in the Tai Lake region, China were collected and the total contents of Pb, Cd, Hg, As, Cu, Zn, Ni, Cr, were analysed in 2005. The pollution status of soil and agro-products were assessed by the values of the National Background and Guideline values of State Environmental Quality Category II, and by the values of State Food Security Guideline. Finally a general evaluation of the exposure risk by the diet intake of the agro-products from these farmlands was given, taking the R_fD values recommended by USEPA(2000).Seven profiles (6 paddy soils plus 1 reference dry cropland soil) from southern Jiangsu were chosen to study the profile distribution of total contents of Cu, Pb, Hg, As, Cd, Zn, Cr, Ni under different environmental impacts. The results indicated weak migration of Cu, Pb, Hg , As, Cd et al. analyzed metals down to deep soil profile possibly due to the impermeability of the plowpan layer in the paddy soils. However, remarkable vertical variation of Hg, Cu and Pb was found under industrial impact with sharper peak contents at the surface layer compared to that under non-industrial impact. Particularly, as high as0.097 mg·kg^-1 and 56.93mg·kg^-1 of total Cd and As at surface with a sharp decreasing trend down profile was found in a paddy soil adjacent to a smelter factory in Yixing City, which was beyond the guideline limit of the State Soil Environmental Quality Category Ⅱ. Compared to the profile of a sandy dry cropland, the surface enrichment coefficient values of the 8 elements were significantly higher in the paddy soils, which could be partially attributed to the limited water percolation due to the plowpan and intense retention by clay and organic matter. It seems that the topsoil contents of the heavy metals and their vertical distributions in the paddy soils is governed primarily by the pollution input under industry development. On the other hand, soil physical and chemical properties could play a considerable role in their migration down to profile. The profile distribution can be indicative of soil heavy metal pollution in the paddy soilsThe contents of studied 8 metals both of the paddy and vegetable farm were much...