Heavy Metals In The Soil-crop System And Potential Food Exposure Risk Under Different Environmental Impacts From A Municipality In Southern Jiangsu, China

Samples of topsoil and sub-top soil and the crops grown on them from typical farms under industrial environment and non-industrial environment were collected in a municipality from southern Jiangsu, China, and determination of their heavy metal contents were conducted. Pollution status of soil and crops were assessed by National Background values 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).The results indicated that, tatal content and DTPA extractable pool of heavy metals under industrial environment were higher than them under non-industrial environment. The concentration of all the 8 elements both under industrial and non-industrial environment has enriched in the topsoil in different degree, for they were higher than National Background values, while they were basically below the guideline limit of the State Soil Environmental Quality Category II. It seems that contents of the heavy metals in topsoil were governed primarily by the pollution input under industry development, for the surface enrichment coeffient values of heavy metals in topsoil under industrial environment significantly increased compared to under non-industrial environment.Compared with a sandy dry cropland, the surface enrichment coeffient values of the 8 elements were significantly higher in paddy soils, which could be partially attributed to the limited water percolation due to the plowpan and intense retention by clay and organic matter. Soil physical and chemical properties could play a considerable role in heavy metal transfering process.Concent in crops of all the elements, but As, were beyond the values of State Food Security Guideline, especially Cd, Zn, Cr. Heavy metals could be accumulated by roots of leafy vegetables more than the other portions evidently. Concentration of heavy metal in unpolished rice is higher, compared with it in polished rice.The heavy metals accumulation in crops was as follows: leafy vegetables>grain cereals> root and tuber crops. Among the studied heavy metals, accumulation of Cd, Cu and Zn were more apparent than of the others in crop organs. Attention should be paid to the soil pollution and the potential impacts on human food security of heavy metals while the industry is developing in this area.The agro-products such as rice tend to favor Cd uptake and Zn depletion in grains and the fact that such process significantly enhanced in acid paddys could raise the serious health risk problem for subsistence diet of farmer in South China rice area.