| The differences of contents of exchangeable fraction of heavy metals (Cu, Fe, Mn, Ni, Pb, and Zn) in the soils at pH=6.0, 7.0,8.0,and the variation trend of the contents with the change of pH were Studied. The conditions for the ultrasound-assisted extraction of heavy metals in soil were optimized. The efficiency of removing of Cu, Fe ,Mn, Ni, Pb and Zn in contaminated soils by EDTA, citric acid, oxalic acid, tartaric acid, gallic acid, tri-sodium citrate and sodium oxalate were compared. The optimization conditions for extraction of heavy metals in the contaminated soil by using EDTA were studied.And in this condition ,based on extraction of 5 kinds of soil sample taken from the sides around galvanoplastic factories, the influence of the speciation distribution of heavy metal in soil on the chemical extraction was analysed;The absorptive capacity of the Yushu, Shi lian and Li bei ge in remediation of heavy metals in contaminated soil was compared, different concentrations of heavy metal on the impact of plant absorption of heavy metals were analysed.The concentrations of exchangeable heavy metals (Cu, Fe, Mn, Ni, Pb, and Zn )at pH=6.0,pH=7.0,andpH=8.0 were determined, according to the Tessier extraction method.The results showed that the concentration of exchangeable heavy metals in the neutral and alkaline soil were almost same,and the concentration was a little low for the alkaline base soil,the highest for the slight acid soil.The best extraction conditions were optimized and they were as follows: the extraction time,temperature and power were 20min, 60℃and 120W,respectively.Remediation on heavy metal of contaminated siol is a hot topic in recent years. Chemical remediation is one of the most mature and efficient methods. The present study focused on the choice of a cheap, efficient and no secondary pollution extract agent. Several agents were selected and their treatment efficiency were compared.The results showed that EDTA can be better to remove a variety of heavy metals in soil, while others is targeted at a particular heavy metal. As a result,EDTA was selected as the extraction reagent for this test .The optimization conditions of EDTA were as fllows: concentration of 0.100 mol/L, pH=6.0 and liquid-solid ratio 7.5:1.Under the conditions, EDTA was used for extraction of soil samples taken from the sides around 5 galvanoplastic factories in xiangcheng district and wangting town of Suzhou. The extraction efficiencies of five kinds of samples were in 2.0%-45.2%, a greater difference was mainly due to the various physical and chemical properties of soil and heavy metals in the different species.The Phytoremediation is a new and the most potential restoration technology. At present the phytoextraction technology is more applied and the key point for this technology is to find phyeraccumlator to heavy metals.Yushu, Shi lian and Li bei ge plants were chosen for study their accumulation capabilities for Ni, Pb and Cd in soil. The results showed that, Shi lian and Li bei had greater ability to accumulate heavy metal, but the growth and development of shilian were seriously affected when the concentration of heavy metals are high. |
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