Research On In-situ Remediation Of Pb,Cd Contaminated By Leaching-Immobilization In Vegetable Soil

With the rapid development of modern society, the environmental pollution has been a serious threat to human health. Vegetable base of heavy metals Pb, Cd content in soil continue to accumulate through vegetables, to a great extent endangering people’s health. Compared with other soils,vegetable soil has the characteristics of strong productivity, wide area pollution and low concentration.The combination of situ leaching-Immobilization repairing technology can ensure the vegetables’safety, and minimiz the farmers’ economic loss at the same time,It is the repairing method of heavy metals that the famers can accept, therefore it has received extensive attention.This study is mainly divided into three parts, including the soil column leaching-curing test experiment, pot simulation experiment and field test of restoration experiment.Through the soil column leaching-immobilization test experiment learning the effect of leaching agents types, curing agents types and consumption of leaching agent on heavy metal pollution Pb, Cd in soil. The results show that, the better leaching amount of tartaric acid was 0.16L/kg, whose concentration was 0.30mol/L; the better leaching amount of EDTA was 0.47L/kg, whose concentration wsa 0.05mol/L. The leaching effect of EDTA to Pb,Cd in soil was better than tartaric acid,The maximum removal rate of EDTA leaching to Pb,Cd were 64.1%,57%;The maximum removal rate oftartaric acid leaching to Pb,Cd were 38.4%,36.1%; the immobilization effect of sodium sulfide and lime to Pb were better than that of humic acid; the curing effect of humic acid to Cd were better than that of sodium sulfide and lime.Through pot simulation experiment, learning that the effect of situ leaching immobilization repairing technology to vegetable yield, the content of heavy metals and metals Pb.Cd in soil. The results showed that:(1) surface leaching-deep immobilization combination treatment technology can effectively reduce the content of heavy metals in surface soil, and solidified in 20-40cm depth of soil; (2) leaching treatment of Pb, Cd in soil, EDTA repairing effect is better than tartaric acid; (3) curing treatment of Pb.Cd in soil, sodium sulfide is suitable for Pb, humic acid is suitable for Cd; (4) EDTA leaching-lime solidified combination treatment is the best surface leaching-deep immobilization combination treatment technology to Pb;EDTA leaching-humic acid immobilization combination treatment is the best to Cd; (5) surface leaching- deep immobilization combination treatment technology can effectively reduce the content of heavy metals in vegetables, but it will bring out the low germination rate of vegetables, germination time delay and other questions.Through field experiment, learning that the repairing effect of situ leaching-immobilization combination technology to heavy metals in soil and vegetables in practical application. The results showed that, EDTA leaching has reduced the yield of vegetable production, tartaric acid leaching improving vegetable yield;Considering the effect of repairing technology to vegetables and heavy metals in soil can be drawn that, in 9 processings, repair effect of the combination of tartaric acid leaching-sodium sulfide curing leaching of EDTA-humic acid curing combinationto Cd,Pb were better. Among them,the reduction rate of tartaric acid leaching-sulfide immobilization combination to Pb,Cd in vegetables were 65.3%,46.4%, Pb, Cd reduction rate to the surface soil were 44.76%,8.45%, the cumulative rate of Pb, Cd were 13.21%,9.3% in deep soil. The reduction rate of EDTA leaching-humic acid immobilization combination to Pb,Cd in vegetables were 12.4%,11.8%, Pb, Cd reduction rate to the surface soil were 30.33%、31.69%, the cumulative rate of Pb, Cd were12.84%、20.16% in deep soil.In situ surface leaching-deep immobilization combination remediation technology of heavy metals in soil and vegetable can effectively reduce the surface soil Pb, Cd content, and it will be fixed in the deep soil, without affecting the normal production activities at the same time, reduce the content of heavy metals in vegetables, which can ensure the safety of vegetables, but also as far as possible to reduce farmers’ economic loss, is the effective remediation technology of mild soil pollution.Among them, the better repair effect of Pb, Cd was the combination of tartaric acid leaching-sodium curing、EDTA leaching-humic acid immobilization combination, it is worthy promoting to farmers who is moderate pollution.