Study On The Combined Application Of EDTA And Biodegradable Chelator To Promote Dwarf Bamboo Phytoremediation Efficiency In Pb-contaminated Soils

In recent years,the phytoremediation technology of soil contaminated by heavy metals has attracted widespread attention due to its economical and environmental friendliness.The application of Ethylenediaminetetraacetic acid(EDTA)can greatly improve the efficiency of phytoremediation of Pb contaminated soil,but it will bring certain environmental risks.Choosing a suitable biodegradable chelator to use with EDTA can not only reduce the environmental risks brought by the chelator,but also increase the efficiency of phytoremediation of Pb contaminated plants in the soil.In this experiment,Sasa argenteostriata(Regel)E.G.Camus was selected as the research material,and four kinds of biodegradable chelators were selected-Nitrilotriacetic acid(NTA),Sodium tripolyphosphate(STPP),N,N-Bis(carboxymethyl)-L-glutamic acid(GLDA)and Polyaspartic acid(PASP),co-administered with EDTA in different ratios(1:1,1:2),compare the efficiency of different chelator combinations to promote phytoremediation of dwarf bamboo,and compare their environmental risks,screen out the better biodegradable chelating agents and their compounding ratio with EDTA.Then,the selected chelator combinations were applied to Indocalamus decorus Q.H.Dai and Sasa argenteostriata(Regel)E.G.Camus to study the effectiveness and safety of chelator combinations to promote dwarf bamboo phytoremediation,and screen out the induced dwarf bamboo to accumulate the highest efficiency and the smallest environmental risks chelator combination,and choose Sasa argenteostriata(Regel)E.G.Camus to deeply study its physiological response and detoxification mechanism.Finally,Sasa argenteostriata(Regel)E.G.Camus was used to study the application mode of chelating agent on the best chelator combination selected in the previous step.Comparing the effects of different chelating agent concentrations(900,1200,1500 mg/kg)and application methods(1application,3 applications)on phytoremediation efficiency,environmental risk,and dwarf bamboo physiological response,detoxification mechanism,then screen out the best chelating agent application method.The research results are as follows:(1)The results of the study on combined application of 4 biodegradable chelators and EDTA to promote dwarf bamboo phytoremediation showed that:(1)The application of chelators significantly increased the Pb content of dwarf bamboo organs.In addition to EDTA treatment,EN1:1,ES1:1 and EG1:1 treatment also improved the phytoremediation efficiency of dwarf bamboo;(2)The content of acid-soluble Pb in the soil of each treatment increased significantly,and the maximum value appeared in the EDTA treatment;After reaching the same level as the EDTA treatment,the remaining treatments are significantly lower than the EDTA treatment within 25 days;(4)In terms of comprehensive analysis,the combination of NTA and GLDA with EDTA 1:1 has relatively high repair efficiency and lower environmental risk.(2)The results of the study on chelator combinations improved dwarf bamboo phytoremediation showed that:(1)After the application of the chelators,both dwarf bamboos showed a high tolerance,especially Sasa argenteostriata(Regel)E.G.Camus,the total biomass of each treatment compared with CK were higher;(2)The maximum value of total Pb accumulation of Meizhuo bamboo and Paddy bamboo in each treatment appeared in EN treatment,which were 1.53 times and 1.25 times of CK respectively;(3)The use of chelator combinations significantly increased the content of acid-soluble Pb and water-soluble Pb in the soil,both of which were expressed as EDTA>EN≈EG;(4)The soil urease activity increased in each treatment,and the maximum value appeared in EN treatment;the soil catalase activity in EDTA and EG treatment decreased significantly;(5)Sasa argenteostriata(Regel)E.G.Camus accumulates Pro to maintain cell osmotic balance and alleviate the negative effects of chelating agents and Pb on leaves;(6)Plant cell chelation is of great significance in Sasa argenteostriata(Regel)E.G.Camus to alleviate the toxicity of chelator and Pb;(7)The EDTA and NTA 1:1 combined application is the combination of chelators with the highest effectiveness and safety in inducing dwarf bamboo phytoremediation.(3)The results of studies on the effects of different methods of combined application of EDTA and NTA on dwarf bamboo phytoremediation and environmental risks showed that:(1)The total biomass of dwarf bamboo decreased with the increase of chelating agent concentration and application frequency,and the highest value of total biomass appeared in One application of 900 mg/kg chelating agent treatment;(2)The total amount of Pb accumulation of dwarf bamboo treated by chelator treatment in three times is less than application of chelator treatment in one time,application of 900 mg/kg chelator in one time on dwarf bamboo aerial and underground parts Pb accumulation has a significant promotion effect;(3)When the application frequency is the same,the content of acid-soluble Pb and water-soluble Pb in the soil increases with the increase of the concentration of the chelating agent;the treatment of applying the chelating agent in three times increases the water-soluble Pb content of the soil with time,After 20 d,it was significantly higher than the same concentration of chelator treatment;(4)After comprehensive analysis and comparison,it is believed that the combination of 900 mg/kg chelator in one application is more beneficial to the accumulation and transportation of Pb by dwarf bamboo,and the environmental risk is lower.