Study On The Remediation Of Soil Cd And Pb Heavy Metal Pollution By Alfalfa

Cd and Pb are the main heavy metal pollutants in soil,which have great influence and harm on soil environment,plant growth and breeding and human health.Therefore,it is an urgent problem for environmental workers to find suitable and effective methods for the treatment and remediation of soil heavy metal pollution.Phytoremediation,as a new green remediation method for heavy metal contamination in soil,has attracted much attention due to its low cost,no secondary pollution and environmental friendliness.In this study,alfalfa,known as "King of Herbage",was used as material to study the effects of single and combined pollution of heavy metals Cd and Pb on Seed Germination and seedling growth of Alfalfa by soil culture germination method.The pot culture method was used to study the enhancement of Alfalfa by chelating agent EDTA(ethylenediaminetetraacetic acid)and Gallic acid(gallic acid)alone or in combination with DA-6(Aminofresh ester).Effects of Cd and Pb on remediation of contaminated soil.The following results are obtained:1.The results of soil culture germination test showed that the trend of Alfalfa Seed Germination and seedling growth under Cd and Pb treatment was similar to that under compound treatment.The single and combined pollution(Cd concentration < 15 mg/kg,Pb concentration < 600 mg/kg)of medium and low concentration had little effect on alfalfa seed germination,and the germination potential and germination rate of alfalfa seeds had no significant difference compared with the control.With the increase of exogenous Cd and Pb concentration,the growth of alfalfa seedlings was inhibited.Under the conditions of Cd concentration > 15 mg/kg,Pb concentration > 600 mg/kg and combined treatment,seed vigor index decreased significantly,and root length,bud length and fresh weight of seedlings were negatively correlated with Cd or Pb concentration at 0.01 level.2.The pot experiment of soil culture showed that the degradable chelating agent Gallic acid could replace the artificial hard-degradable chelating agent EDTA to strengthen the alfalfa remediation of Cd and Pb contaminated soil.When the concentration of exogenous Cd was 0-20 mg/kg,the extraction efficiency of Cd from alfalfa was increased by 3.56-0.22 times and 4.2-0.32 times by EDTA or Gallic acid alone.When the concentration of Pb was 0-1000 mg/kg,the extraction efficiency of Pb from alfalfa was increased by 1.03-5.01 times and 0.8-4.99 times by EDTA or Gallic acid alone.DA-6 can alleviate the toxic effects of heavy metals and chelating agents on alfalfa,and further improve the repair efficiency.Compared with EDTA or Gallic acid alone,the extraction efficiency of Cd and Pb increased by 4.90%-49.05% and 0.42-2.1 times by EDTA and DA-6,respectively.The extraction efficiency of Cd and Pb increased by 9.16%-34.95% and 0.39-1.47 times by Gallic acid and DA-6.3.Hard-degradable chelating agent EDTA and easy-degradable chelating agent Gallic acid have good effects on alfalfa remediation of Cd and Pb contaminated soil.The synergistic effect of two chelating agents and DA-6 can further improve the remediation efficiency and provide a good reference for the remediation of heavy metal contaminated plants.However,Gallic acid is easy to degrade in the environment and not easy to cause secondary pollution,so its potential for environmental protection applications is huge.