The Study On Chelating Agent And Plant Growth Regulator To Strengthen Plant Phytoextract Cadmium/lead Contaminated Soil

In recent years,plant remediation technology with characteristics of green economy and environmental protection has been widely researched and applied in the field of soil heavy metal remediation.However,there are some deficiencies in phytoremediation technology,such as the low extraction efficiency of heavy metals from plants and the small aboveground biomass of super-enriched plants,which restrict the promotion and application of phytoremediation technology.Therefore,the strengthening measures of phytoremediation technology is a hot spot in current phytoremediation research.In this study,the heavy metal Cd and Pb contaminated soil,through the soil leaching experiment,to study the extraction efficiency of five chelating agents EDTA,CA,GLDA,OA,DTP A on heavy metals in the soil.Through the soil pot experiment,the effects of three different types of chelating agents,GLDA,EDTA and CA,on the growth and enrichment of ryegrass and the accumulation of Cd and Pb were studied.At the same time,the biodegradable chelating agent GLDA and the plant growth regulators IAA,GA3 and DA-6 were jointly applied to carry out research on fortified ryegrass to remediate Cd and Pb contaminated soil,aiming to provide a certain reference for plant remediation and strengthening technology.The main results of the study are as follows:(1)Soil leaching experiments show that the five chelating agents have different extraction efficiency for heavy metals Cd and Pb in soil.The order of extraction efficiency for Cd is GLDA>EDTA>DTPA>CA>OA;the order of extraction efficiency for Pb is EDTA>DTPA>GLDA>CA>OA.At the same time,the application of chelating agents can also improve the fertility of the soil,but also increase the risk of nitrogen and phosphorus pollution of groundwater.The chelating agent has different extraction effects on different forms of heavy metals in the soil.The extraction effect on the weak acid extractable and reducible heavy metals in the soil is good,but the extraction effect on the heavy metals in the soil residues is poor.(2)The application of chelating agents has a negative impact on the biomass of ryegrass,but different chelating agents have different effects on the biomass of ryegrass.With the increase of the concentration of chelating agent EDTA,the biomass of rye grassland and underground parts has been continuously reduced.With the increasing concentration of the chelating agent GLDA,the biomass of the upper part of the rye grassland first increased and then decreased,and the biomass of the underground part continuously decreased.The addition of chelating agent CA had no significant effect on the biomass of ryegrass.All three chelating agents can promote the absorption of ryegrass to heavy metals in the soil,but different types of chelating agents promote different absorption effects.The specific performance is Pb:EDTA>GLDA>CA;Cd:GLDA>EDTA>CA.And the concentration of heavy metals in the underground part is significantly higher than that in the above-ground part.(3)Different chelating agents have different effects on the extraction of Cd and Pb in ryegrass.Under the same concentration,the extraction amounts of Cd and Pb in the soil by the three chelating agents are GLDA>EDTA>CA.When the concentration of chelating agent GLDA is 2mmol/kg,the extraction effect of Cd and Pb in soil is the best,which is 1.42 and 1.32 times higher than that of the untreated group.The application of chelating agents also increases the activity of extractable heavy metals in rhizosphere and non-rhizosphere soils.Different chelating agents have different activation effects on heavy metals in soil.(4)Plant growth regulator combined with chelating agent can effectively relieve the stress of Cd and Pb in the soil on ryegrass and promote the growth and development of ryegrass.Different kinds of plant growth regulators have different effects on the biomass of ryegrass under different concentration conditions,and the promotion effect is DA-6>GA3>IAA from high to low.Among them,when the concentration of DA-6 was 1?mol/kg,the above-ground and underground parts of rye grass had the best effect of improving biomass,and the above-ground and underground parts biomass of the chelator treatment group increased by 55.0%and 30.9%,respectively.The three plant growth regulators increased the concentrations of Cd and Pb in different parts of ryegrass to varying degrees,and the DA-6 concentration was 1?mol/kg,which had the best effect of promoting promotion.(5)The application of plant growth regulators can promote the accumulation of heavy metals Cd and Pb on the rye grassland and underground parts,and improve the extraction efficiency of ryegrass to Cd and Pb in the soil.On the whole,DA-6 is better than GA3,and GA3 is better than IAA.When the concentration of DA-6 treatment was 1 ?mol/kg,the total enrichment of ryegrass to Cd and Pb was the largest,and the extraction amounts of Cd and Pb per kg of soil were 348.25?g and 11.35 mg,respectively,which was higher than that of the non-addition group.85.37%and 44.54%.However,the addition of plant growth regulators did not significantly increase the content of available heavy metals in the soil.