Study On Approach And Mechanism Of Improving Meadow Cinnamon Soil Polluted With Cadmium And Lead With Organic Acids

Aiming at the difficult problem of remediation of Cd and Pb pollution in soil, this paper studies the effect of four kinds of organic acids such as EDTA, DTPA, cysteine and alicylic acid to the content of Cd and Pb speciation in soil and the content absorbed of rape and the output, on the basis of adopting potted experiment and sequential extraction technique with the meadow cinnamon soil and rape as materials. It also presents the approaches and mechanism of controlling Cd and Pb pollution with organic acid. Its main conclusions are as follows:1.With the increase of DTPA, the content of exchangeable Cd enhances and the change current is like parabola. When the mol ratio of DTPA/Cd equals 2 and the content of Cd is 70.00mg/kg, the content of exchangeable Cd is on tiptop, the absorbed content of Cd by rape is only 37% to contrast, and the output of rape gets to the tiptop, it is 7.13 times to contrast. So DTPA can be chosen as depressor. The best content of DTPA is double to the mol content of Cd in soil during the course of planting; the best content of DTPA is three times to the mol content of Cd in soil during the slack season.2. With the increase of cysteine, the content of exchangeable Cd enhances. When cysteine/Cd equals 1/2, the content of exchangeable Cd is 1.16 times to contrast, and the content of residual Cd gets to tiptop which is 1.79 times to contrast. Under this ondition, the absorbed content of Cd by rape is only 38.64% to contrast, While the output of rape gets to tiptop which is 6.87 times to contrast. So cysteine can be chosen as depressor to Cd pollution in soil. The best content of cysteine is 0.5 time to the mol content of Cd in soil.3. With the increase of EDTA, the content of all speciation of Cd has different change currents. The content of exchangeable Cd enhances, but the absorbed content of Cd by rape all drops, While the output of rape increases at a different degree, but it does not increase with the increase of EDTA. It is a "M" shape change, So EDTA can not just because of this be chosen as depressor to Cd pollution in soil.4. With the increase of alicylic acid, the content of exchangeable Cd enhances, but it has no distinct rule. Alicylic acid can increase the transformation intensity of residual Cd changing to exchangeable Cd and cabonate-bound Cd. The compound cabonate-bound Cd...