Effects Of EDTA And Citric Acid On Heavy Metal Contaminated Soil In Houttuynia Cordata

Heavy metals compound pollution of mining area soil on agricultural production and the harm of human body health more and more get the attention of people, phytoremediation with its unique advantage has been generally regarded as one of the effective technical means to control heavy metal compound pollution of soil. This paper takes patience plants Houttuynia cordata Thunb were used as the material, the use of EDTA and citric acid as exogenous additives and compound pollution in soil in Pb, Zn, field and pot experiments were studied respectively EDTA and citric acid to its biomass, content and distribution of heavy metals and the actual repair effect. The main results were as follows:(1) The low concentration of EDTA and citric acid to Houttuynia cordate Thunb growth without obvious effect, grew well and above ground biomass increased, but with the increase of concentration of EDTA and citric acid can inhibit the growth of them, biomass, plant height and branch number decreased than the control, to varying degrees showing short plant height, yellow leaves and withering black root rot.(2) The comprehensive pot and field experiments shows that, EDTA addition can effectively promote its absorption and accumulation of Pb, Zn, Cd in the soil, the enrichment coefficient increases to 0.421,0.421 and 0.541, the influence of Cr, Cu take second place; EDTA can effectively promote Pb, Cd transfer to the ground part in the body of Houttuynia cordata Thunb, the highest transfer coefficient increases to 1.60 and 1.60, the influence on Cr, Cu, Zn take second place, Zn is mainly accumulated in its roots and worse off to the ground part.Citric acid addition can effectively promote its absorption and accumulation of Pb, Cd in the soil, the enrichment coefficient increases to 0.108 and 1.65, the influence on Zn, Cr, Cu take second place; Citric acid can effectively promote Pb transfer to the ground part in the body of Houttuynia cordata Thunb, transfer coefficient increases to 0.949, the influence on Zn, Cd, Cu shows inhibitory effect on different level, although the transfer coefficient of Cr is bigger than 1 but under the same inhibition compared with the control.The promoting effect of EDTA is better than citric acid on heavy metals accumulation of Houttuynia cordata Thunb in soil.(3) EDTA can effectively improve its extracting amount of Pb, Zn, respectively increased by 35.53% and 32.98%, the influence on Cr take second place, increased by 27.97% than the control, no obvious promoting effect on Cd, Cu, the extracting amount of Cu decreased; Citric acid can effectively improve its extracting amount of Pb, Zn, respectively increased by 35.16% and 34.39%, and only under the 1 mmol/kg citric acid the extracting amount of Cr increased by 59.00% than control, and less influence on Cd, Cu, showing a certain selectivity.(4) From the perspective of environmental and economic consideration, add a small amount of citric acid can prevent the water environmental pollution, as well as saving the cost of repair. Comprehensive the biomass and the heavy metals extracting amount of Houttuynia cordata Thunb, add low concentration of EDTA and citric acid on 1mmol/kg not only increase the biomass of Houttuynia cordata Thunb, but also make the heavy metals extraction quantity to reach a higher level at the same time, mostly accord with the requirement and purpose of phytoremediation. Thus determine the 1mmol/kg concentration of EDTA and citric acid as the optimal concentration to help Houttuynia cordata Thunb repair the compound pollution of soil heavy metals.