Promoting Effect Of Microorganisms On Phytoremediation Of Soil Lead Pollution

Phytoremediation of heavy metal pollution in soil is considered as the most potential and clean remediation technology for heavy metal pollution in soil because of its advantages of green,simple operation,less secondary pollution and low cost.However,this technique has some disadvantages in practical application,such as plant species is not easy to be selected and plant growth is short.In principle,adding microbial strains to the soil in which plants are grown can improve plant growth.Therefore,the addition of microbial strains in phytoremediation has become one of the important researches in soil remediation of heavy metal pollution.In this paper,leadtolerant microorganisms were screened from the soil in the leadzinc residue stacking area,and their effects on the repairing effect of Pb contaminated soil by ryegrass and chrysanthemum were studied.1.Two strains with Pb tolerance of 2500mg/kg were screened from lead-zinc residue contaminated soil,and the fungus was Paecilomyces sp.the bacteria were S.maltophilia.2.Paecilomyces sp.and S.maltophilia promoted the growth of ryegrass and chrysanthemum in lead-contaminated soil,significantly increased the content of Pb in plants,increased the Pb enrichment coefficient of ryegrass on soil,and increased the Pb transport coefficient of chrysanthemum on soil.The sequence ofpromoting effects of microorganisms on plants was:Paecilomyces sp.+ S.maltophilia> Paecilomyces sp.>S.maltophilia.When Pb concentration was 1500mg/kg,the translocation coefficient of b.hei was >1 under the treatment of Paecilomyces sp.And S.maltophilia.When Pb concentration was 2000mg/kg,under the treatment of double inoculation of Paecilomyces sp.And S.maltophilia,the maximum Pb enrichment coefficient of ryegrass on soil reached 2.96,which had the best promoting effect on the biomass of ryegrass3..The joint restoration of ryegrass with Paecilomyces sp.and S.maltophilia is suitable for the soil of cultivated land contaminated with heavy metals.The soil pollution can be repaired,and the overground part of the soil can be harvested and fed to livestock to ensure another function of cultivated land:generating economic income.In combination with Paecilomyces sp.and S.maltophilia,when the soil Pb concentration is1500mg/kg,it is suitable for the remediation of cultivated land pollution.A large amount of Pb is transferred to the overground and Pb in the soil is removed by harvesting.When soil Pb>1500mg/kg,it is suitable for the restoration of heavy metal waste,which can make the environment green and achieve the ornamental value.4.After Paecilomyces sp.and S.maltophilia were added to the pot treatment of ryegrass,the existing forms of Pb in the soil were changed,mainly by increasing the exchangeable state,carbonate binding state,iron and manganese oxidation state and decreasing the residual Pb content.After Paecilomyces sp.And S.maltophilia were added to the pot treatment,the transformation of residual Pb in soil to carbonate binding state,iron manganese oxidation state and organic Pb was mainly promoted.The existing forms of heavy metals in soil vary with microbial species,plant species,soil pH value and soil organic matter content.The application of Paecilomyces sp.and S.maltophilia reduced soil p H value and increased the contents of organic matter,available phosphorus and available potassium in soil.There was a significant correlation between soil organic matter content,pH and soil heavy metal morphology.Therefore,the decrease of soil pH value and the increase of organic matter content may be the reasons for the change of soil Pb morphology.5.After Pb morphology transformation,it is beneficial to plant absorption or transport,which can effectively improve the efficiency of "microbial-plant" joint repair.