The Ramie-chemical Combined Remediation Of Cd/Pb Contamination Soil

Soil pollution especially soil heavy metals pollution was getting worse. Physical, chemical, biological and ecological remediation procedures were four main methods of restoration and management of cadmium and plumbum polluted soils. Phytoremediation was used to remove heavy metals from the contaminated soils since early 1990 s as an ecological technique, and the mechanism of phytoremediation was to use plants to absorb, accumulate and translate heavy metals from the contaminated soils, achieving the purpose of alleviating the pollution of heavy metals. The phytoremediation technique had some advantages in comparison with the traditional remediation technologies, such as economical, non-pollution and high efficiency. Ramie is a perennial root perennial herbaceous plants, and its perennial root fixed number of year can reach more than 10 to 30 years. Since ramie has a well-developed root system and the biomass is big, it has a good effect of soil and water conservation. But the effect of phytoextraction for heavy metals in the soil is not obvious. Amendment application can promote restoration of the ramie for soil heavy metal pollution.In this study, ramie which was perennial economic fiber plants, the biological chelating agent EDDS, non-biological chelating agent EDTA and diatonmite, bentonite, limestone powder, zeolite, four kinds of curing agent were seleted. Ramie pots cultivation experiment and morphological analysis experiment was conducted in the contaminated soil. The ramie biomass and MDA content of ramie, the accumulation characteristics of Cd and Pb in ramie and Cd and Pb concentrations in soils after ramie harvest were investigated.The main results were as follows:(1) Compared to monoculture ramie, the content of Cd and Pb in each part of ramie cultivated with EDTA and EDDS increased significantly, the remediation of heavy metals in soil was promoted. At the same concentration of chelating agent, EDDS induction effect beteer than EDTA. With the increase of applying EDTA and EDDS concentration,the content of cadmium, lead in ramie parts increased.(2) An adverse effect on ramie plant growth was caused by EDTA with high concentration of EDDS. The biomass of ramie has been significantly reduced and leaf malondialdehyde content increased. Under the same applying concentration, adverse influence of EDDS on growth of ramie was weaker. Low concentration EDDS was not harmful to ramie.(3) At supplying concentration from 1.5 to 3 mmol?kg-1, EDDS strengthened ramie remediation of Cd was better, the efficiency of soil Cd remediation increased from 16% to 27%, at higher concentrations(6 to 9 mmol?kg-1), EDTA strengthened ramie remediation of Cd was better. EDTA strengthened ramie remediation of Pb was better than EDDS, the removation efficiency of soil Pb increased up to 22.6%.(4) Adding zeolite powder, high concentration(9 ~ 12 g ? kg-1) diatomite and bentonite can significantly reduced soil acid extractable content of Cd. Adding hardener diatomite, bentonite and zeolite powder had positive effect to reduce soil acid extractable Pb, and curing effect showed diatomite> bentonite> zeolite powder. When curing agent was separate applicated, the more content,the better of curing-effect for Cd/Pb. Owing to the content of acid extractable Cd and Pb was not significantly affected, limestone powder ’s curing-effect was not good enough.(5) All parts of ramie can absorb less Cd and Pb when the curing agent was applied. With the increasing of the amount of the curing agent, all parts of Cd and Pb content decreased significantly. The ramie biomass decreased when applied with limestone. The ramie biomass increased, and the stress on ramie growing decreased applied with diatomite, bentonite and zeolite powder.(6) Compared to the remediation of the curing agent applied alone, the phytoremediation of ramie planting with added curing agent can absorb and cumulate acid extractable Cd and Pb from soil. With the appropriate curing agent applying, the Cd and Pb accumulated amount in soil was still high. Added 9 g ? kg-1 diatomite and 3 ~ 9 g ? kg-1 zeolite powder with ramie remediation for Cd can produce a positive combined effect. Ramie remediate with diatomite, bentonite and zeolite powder cooperatively can produce better combined remediation results to the soil Pb.The combined bioremediation effect showed that diatomite> zeolite> bentonite.