Effects Of Chelating Agents On Amorpha Fruticosa And Koelreuteria Paniculata For Phytoremediation Of Lead-contaminated Soil

In order to study the effects of three kinds of green chelating agents ethylenediamine disuccinic acid(EDDS),ammonia triacetate(NTA)and citric acid(CA)for the remediation of lead contaminated soils on Amorpha fruticosa and Koelreuteria paniculata seedlings,this study was used pot experiment.The effects of three kinds of chelating agents on the growth,physiological characteristics of Amorpha fruticosa and Koelreuteria paniculata and the effects on soil enzyme activity were studied.Chelating agent application method is divided into two kinds of single and mixed.The concentrations of the three chelating agents were set five levels at 1 mmol/kg,3 mmol/kg,6 mmol/kg,9 mmol/kg,12 mmol/kg.The ratio of EDDS to NTA was 1:1,1:2,2:1,and the total concentration was 3 mmol/kg,6mmol/kg and 9mmol/kg.The concluded as follow:1.When EDDS,NTA and CA were applied separately,the lead content of A.fruticosa and K.paniculata was increasing first and then decreasing with the increase of EDDS,NTA and CA concentration.Under the CA treatment,the lead content of A.fruticosa and K.paniculata was lower than that of EDDS and NTA,and the accumulation capacity of EDDS and NTA was not significant.The average lead content of A.fruticosa and K.paniculata was the highest under the treatment of EDDS and NTA total concentration of 9 mmol/kg.At each concentration of CA,the optimum concentration of the average lead content of A.fruticosa and K.paniculata plants is not significant.The concentration of EDDS,NTA and CA was 9 mmol/kg,the leaf ofA.fruticosa had the largest transfer coefficient.The treatment of the largest transfer coefficient of the leaf of K.paniculata was 9 mmol/kg EDDS,12 mmol/kg of NTA and CA.When the concentration range of EDDS,NTA and CA was 6 mmol/kg ~ 9 mmol/kg,the enrichment coefficient of leaf of A.fruticosa was different,and higher than that of the other two concentrations,the enrichment coefficient of K.paniculata reached the maximum at 9 mmol/kg EDDS,NTA and CA treatment.Under the condition of mixed treatment,the average lead content of A.fruticosa was the highest at EDDS:NTA = 2:1 and the concentration was 6 mmol/kg,and the highest average lead content of K.paniculata was in EDDS:NTA = 1:2 and the concentration at 6 mmol/kg.The treatment conditions of A.grandiflora and K.paniculata were the highest when the transfer coefficient and enrichment coefficient were EDDS:NTA = 2:1 and the concentration was 6 mmol/kg.Under the same treatment,the accumulation of lead in A.fruticosa is higher than that of K.paniculata.2 The effects of EDDS,NTA and CA on plant height,ground diameter,root morphology and biomass of A.fruticosa and K.paniculata were studied.When the concentrations of EDDS,NTA and CA were increasing,the effects of plant height,stem diameter,root morphology and biomass of A.fruticosa and K.paniculata were first to rise and then decrease.In addition to a few treatments,the growth indices of A.fruticosa and K.paniculata were not significantly affected under most treatments.The effects on the growth indexes of the most favorable concentrations of EDDS,NTA and CA were respectively 6 mmol/kg,9 mmol/kg,9 mmol/kg.And the order of the effect of the three chelators on plant growth was EDDS> NTA> CA.When the chelating agent concentration is same,the order of the plants growth is mixed application > single application,and the proportion of chelating agent which has the least effect on plant growth is EDDS:NTA = 1:2.Indicating that the chelating agent had no significant effect on the growth of A.fruticosa and K.paniculata,and the effect of the chelating agent on the growth characteristics of the plant was different.3.The effects of EDDS and NTA on the chlorophyll content and relative conductivity of A.fruticosa and K.paniculata leaves were signifycanly affected by the application of EDDS,and CA could increase the chlorophyll content and the leaf system.The changes of chlorophyll content,net photosynthetic rate and relative electrical conductivity of EDDS,NTA,CA on K.paniculata were higher than those of A.fruticosa.The effect of chelating agent on the physiological characteristics of K.paniculata was higher than that of A.fruticosa.The order of influence on the physiological indexes of A.fruticosa and K.paniculata leaves was: EDDS> NTA> CA.At the time of mixing,the physiological indexes of A.fruticosa and K.paniculata were not significantly affected by the chelating agent.4.Except for a few treatments,EDDS,NTA and CA could not inhibit the activity of soil urease.Most of the treatments had activated the soil urease,and all treatments had activated the alkaline phosphatase.The effects of chelating agents on root soilurease activation of K.paniculata and A.fruticosawere NTA> EDDS> CA,but the intensity of soil urease activation was from strong to weak for EDDS> NTA> CA.Under the condition of EDDS:NTA = 2:1,the activation of alkaline phosphatase and urease activity was the strongest under the condition of mixed treatment.The activation of soil alkaline phosphatase was not significant,and some treatments could significantly activate the activity of soil urease.The results showed that the effect of chelating agent on the two soil enzymes was urease> alkaline phosphatase.5.The results of the principal component analysis showed that the optimal concentration of EDDS,NTA and CA was 3 mmol/kg,9 mmol/kg,9 mmol/kg when the treatment with A.fruticosa under single treatment condition,and the optimum concentration of EDDS,NTA and CA was 6 mmol/kg,6 mmol/kg and 9 mmol/kg when K.paniculata was used to repair lead contaminated soil.Under the condition of mixed treatment,when EDDS:NTA = 1:1 and the total concentration was 9 mmol/kg,the effect with A.fruticosa to repair lead contaminated soil was the best.When EDDS:NTA = 2:1 and the total concentration of 9 mmol/kg,the effect of using K.paniculata to repair lead contaminated soil was the best.The remediation effect of two kinds of tree species under the condition of single application and mixed chelating agent was thatsingle application is better than mixed.Compared the remediation effect of two kinds of tree species under the condition of applying chelating agent,A.fruticosais better thanK.paniculataand the effect of remediation of lead contaminated soil was the best under the condition of applying 9 mmol/kg NTA with A.fruticosa.