Pollution Of Heavy Metals In Soils And In Agro-Products (Vegetables) In Nantong Area

The paper discussed the impact of heavy metals'pollution in Nantong soil on agro-productions'quality. 906 soil samples were collected from 912 spots in Nantong area and mensurated separately. Among the 906 spots, 32 representative spots were selected for us to collect agro-production samples which are mainly vegetables. Soil samples were analyzed for the concentration of heavy metals(Hg, As, Pb, Cd, Cr)and pesticides(666 and DDT) and agro-production samples were analyzed for the concentration of heavy metals(Hg, As, Pb, Cd, Cr)to estimate the pollution. We also discussed the relation between heavy metal content in vegetables and that in soil (available content).Following conclusions were achieved:1 The result analyzed according to county showed: Compare with the background value, two kinds of these elements have some soil samples in the seven counties exceed the soil background value, suggesting those spots have been polluted by heavy metals. Only one element of one spot exceed the green-food standard. This kind of heavy metal is Pb. All metal content in soil are under the safe-food standard. (Attention: all the pollution indexes are less than 2)2 The result analyzed according to town showed: Firstly, compare with the background value, the synthesis pollution indexes of 120 towns exceed 0.7, among the 120 towns , 57 towns' synthesis indexes exceed 1 and 7 towns' synthesis indexes exceed 2 , suggesting these spots have all been polluted by heavy metal. Secondly, compare with the green-food value, 6 towns' synthesis indexes exceed 1, suggesting that 120 towns can develop green-food. Finally, compare with safe-food value, all towns' indexes are under 0.7, suggesting that all towns can develop safe-food.3 The order of metal content in vegetables are as follows :Tomato: As>Pb>Cd>Hg Green soy been: Pb>Cd>Hg>As Green pepper: As>Pb>Cd>Hg White gourd: Pb>Cd>Hg>As Cucumber: Pb>Cd>Hg>As4 The order of vegetables of heavy metals are as follows:Pb: tomato > green soy been > green pepper > white gourd > cucumberCd: white gourd>tomato>cucumber>green pepper>green soy been Hg: green pepper>tomato As: green pepper>tomato5, The order of different types of vegetables : Vegetables like melon: Pb>Cd>As =Hg; Vegetables like fruits: As > Pb > Cd > Hg; Vegetables like leaves: As > Pb > Cd > Hg;6, The order of different varieties of vegetables :Hg: Vegetables like leaves = Vegetables like fruits > Vegetables like melon; As: Vegetables like fruits > Vegetables like leaves > Vegetables like melon; Pb: Vegetables like leaves > Vegetables like fruits = Vegetables like melon; Cd: Vegetables like leaves > Vegetables like melon > Vegetables like fruits;7, According to the evaluation of vegetables in Nantong , all the single indexes are under land all the synthes indexes are under 0.7. Among the sythes indexes of different types of vegetables, the index of tomato is the highest and that of cucumber is the lowest. In addition, among the sythes indexes of different varieties of vegetables, the index of vegetables like leaves is the highest and that of vegetables of Vegetables like melon is the lowest.