Induction of Heavy Metal Phosphate Precipitation by Rahnella sp.and Its Activity Changes in Soil
Microorganisms can immobilize available lead(Pb)in soil by inducing the formation of phosphate precipitation,which has received increasing attention in the remediation of Pb contami-nated soil.However,the characteristics of activity changes of phosphate precipitation induced by these microorganisms in soil are not well understood.The induction of single Pb and Cu-Pb com-bined phosphate precipitation was studied by Rahnella sp.LRP3,and soil culture and pot experi-ment were carried out to reveal the release and uptake by pakchoi of Pb in the phosphate precipita-tion.The results showed that strain LRP3 fermentation broth could rapidly remove Pb2+in the solu-tion when it was alone or coexisted with Cu2+,which led to formation of Pb(H2PO4)2 crystal with shape of irregular block and Pb(H2PO4)2-Cu3(PO4)2 composite crystal with shape of small sphere,respec-tively.Under the condition of short-term soil culture,the stability of Pb in composite crystal was high and Pb in it was not easily activated,while the stability of Pb in single crystal was relatively poor and could be activated,which could be promoted by soil microorganism.Single and composite phosphate crystals could release Pb in the rhizosphere soil of pakchoi,increasing Pb content in leaves and roots of pakchoi.Compared with the control soil,the enrichment coefficients of Pb in the leaves and roots of pakchoi decreased by 62.50％and 78.75％,75.50％and 83.75％,respectively.Therefore,strain LRP3 has important application value in Pb contaminated soil remediation,and the remediation effect can be enhanced by adding Cu2+into the soil.
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