Induction and Stability of Pb-containing Carbonate Precipitation by Brevibacillus laterosporus ZN5 in Soil
Microbially induced carbonate precipitation can immobilize available Pb in soil,which has attracted more and more attention in the remediation of Pb contaminated soil.The carbonation fixation of Pb in soil by ammonification and nitrate assimilation fermentation broth of one strain of Brevibacillus laterosporus ZN5 was investigated,and the stability of the induced carbonate precipi-tates in soil was studied.The results showed that the proportion of exchangeable Pb to total Pb in soil decreased by 20.28％and 17.38％,the proportion of organic matter bound Pb decreased by 5.65％and 3.76％,the proportion of residual Pb decreased by 4.28％and 2.35％,the proportion of car-bonate bound Pb increased by 28.93％and 21.92％,and the proportion of Fe-Mn oxides bound Pb increased by 1.17％and 0.66％,respectively,through the fermentation suspension of strain ZN5 in-duced by ammonification and nitrate assimilation,which led to a decrease of 71.50％and 62.30％of the available Pb content in the soil,respectively,so that pakchoi could grow normally in the heavily polluted soil with a Pb content of 980.77 mg/kg.Two kinds of Pb-containing carbonate precipitates induced by ammonification and nitrate assimilation processes of strain ZN5 were added to the soil,even if the total Pb content of the soil reached about 500 mg/kg.The growth of pakchoi was affected to some extent,but the Pb enrichment coefficient decreased significantly.The results showed that strain ZN5 could reduce the toxicity of Pb to pakchoi through the formation of Pb-containing carbon-ate precipitates induced by ammonification and nitrate assimilation processes,and the stability of Pb-containing carbonate precipitate induced by nitrate assimilation process in soil was better,which had important application value in the remediation of Pb contaminated soil.
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