The Assessment Of Contamination And Bioavailability Of Heavy Metals In Soil, East-South Area Of Beijing

One of the most important environmental questions is soil contamination. About 2×107 hektares of cultivation were polluted by heavy metals in our country. Heavy metals absorbed by crops from polluted soil came into human body through food chain, and affected human health seriously. The thesis is a part of the research on polluted soil in Beijing.In the thesis , Total concentration and bioavailability of Pb,Cd and Hg were measured for 41 soil samples from the East-south area of Beijing as well as investigated to evaluate the pollution of heavy metals on soil for long-term wastewater irrigation. By using pot experiments, the effects of cadmium on the growth of cabbage with added Pb,Cd and Hg. Based on the regression equations established and limit of cadmium concentration in vegetable products.Different evaluation methods and evaluation standard of heavy metals were used for comparison. The results show the soils were polluted by Cd and Hg using natural background values as evaluation standard. While using National Standard as evaluation standard, the soils were not polluted. The order of the indes of soil pollution by heavy metals was as follows:Chaoyang District〉Daxing District〉Tongzhou District.The bioavailable concentrations was very low by DTPA extracted , with the maximum up to 4.7% for Cd. There exists inferior positive correlations between the total heavy metal concentrations of soil samples and the bioavailable metal concentrations of soil samples. This indicates it is necessary to study the bioavailability and total heavy concentrations of soils.By using pot experiments showed that increased production of cabbage in low Pb and Cd , but obvious readuced production of cabbage with added Hg >0.4 mg·kg-1. Pb and Cd concentrations in edible parts of the tested cabbage were significantly linearly correlated to bioavailable metal concentrations of soil, but there no ruls in Hg concentrations of cabbage and bioavailable metal concentrations of soil. Based on the regression equations established and limit of cadmium concentration in vegetable products, the critical value of bioavailbable Pb and Cd were calculated as follows: 0.0941 mg·kg-1 and 0.0251 mg·kg-1. The soils were not polluted with Pb and Cd using criticalvalue of bioavailbable Pb and Cd as evaluation standard.