Leaching And Fixation Of Heavy Metals By Microorganisms On The Surface Of That Can Attach Fecal Basal Biochar Matter

The fecal basal substance biochar prepared at low temperature can be used as the carrier of microorganisms and has high application value in the remediation of heavy metal contaminated soil.However,this type of biochar often also has a high concentration of heavy metals,when used there may be a risk of heavy metal dissolution.Therefore,biochar was prepared by low temperature cracking chicken manure,on the one hand,the dissolution characteristics of heavy metals by fungi attached to the surface of biochar were studied,and on the other hand,the mineralization fixation of heavy metals by mineralized bacteria that could be attached to the surface of biochar was studied,the main findings are as follows:（1）from the surface of biochar in the soil to obtain a strong acid production capacity,can release the chicken dung biochar in the heavy metal Cu and Zn fungi,phylogenetic analysis and physiological and biochemical characteristics indicate that the strain is veined,named it as ZN1.The mycelium of strain ZN1 can enter the gap of biochar and has good affinity with biochar.Strain ZN1 has the strongest acid production capacity when the glucose content is 2%,the pH value can reach 2.8 when the fermentation liquid reaches 12days,and it can produce 5 kinds of acids,mainly malic acid and oxalic acid.Fermentation broth with different pH value has different dissolution ability of Cu and Zn in biochar,and with the increase of acidity,the dissolution ability increases obviously,the maximum dissolution ratio of biochar can reach 24.6%and 3.5%respectively,and when the pH value of fermentation broth is 2.8,the dissolution of Cu and Zn are 30.65 mg.L^-1 and 13.95mg.L^-1 respectively.When biochar and bacteria were cultured,the pH value of fermentation broth decreased slowly,the pH stabilized to 4.61 after 12 days,the release amount and release proportion decreased obviously,and the dissolution and dissolution ratio of heavy metal Cu were 5.7 mg.L^-1 and 4.57%respectively.The dissolution and dissolution ratio of heavy metal Zn were 3.5 mg.L^-1 and 0.87%respectively.（2）The maximum tolerance concentration of Phosphate mineralized bacteria LRP3 to Zn²⁺can be attached to the surface of the dung basal substance biochar is 120 mg/L,and the removal capacity of Zn²⁺in the solution is in the order of bacterial somatic cells（97.4%）>fermentation broth（88.2%）>aseptic fermentation broth（81.6%）.X--ray diffraction analysis,scanning electron microscope,energy spectrum and Fourier infrared spectroscopy show that the fermentation broth of strain LRP3 can induce the formation of cube-shaped Zn2（OH）PO3 mineral crystals with good crystallization condition through biological mineralization.After adding soil,the fermentation broth of strain LRP3 can reduce the content of DTPA-Zn quickly,the content of DTPA-Zn decreased by 78.4%after5 days of Culture,and the content of weak acid extraction and oxidizing state of Zn in soil decreased by 72.5%and 56.2%respectively after 6 days of culture.The content of reversible state and residue state increased by 85.1%and 14.8%respectively.（3）The removal capacity of the LAX2 Carbonate mineralized Bacteria,which can be attached to the biochar surface of the manure basal substance,is Pb²⁺>Cd²⁺>Cu²⁺in order to remove the coexisting heavy metals.X--ray diffraction,scanning electron microscopy,infrared spectroscopy and energy spectrum analysis showed that the LAX2 fermentation broth of three kinds of heavy metals could induce the formation of PbCO3 and CdCO3crystals,while Cu could not be metallogenic alone,and the mixed mineral crystals were long rods.Strain LAX2 fermentation broth can significantly reduce the effective state content of Cu,Pb and Cd in black calcium soil and white pulp soil,and after 30 days of mineralization repair,the effective state content of Cu,Pb and Cd in black calcium soil and white pulp was reduced by 48%and 42%,71.4%and 63.2%,62.8%and 53.6%respectively.The content of carbonate binding state and ferromanganese oxide binding state increased obviously,and the content of interchangeable state and organic binding state decreased obviously.The leaching toxicity of heavy metals in soil after mineralization was reduced with the increase of repair time,and the leaching content of Cu,Pb and Cd in black calcium soil and white pulp decreased by 90.3%and 82.5%,93.2%and 86.1%,92.8%and 84.3%respectively.The above results show that strain LRP3 and LAX2 have important application value in the repair of heavy metal contaminated soil,and these two strains have good affinity with fecal basal biochar,so the potential of low temperature preparation of fecal basal biochar is used as microbial carrier for the repair of heavy metal contaminated soil.In addition,acid fungi produced in the soil can dissolve heavy metals in biochar,posing a risk of pollution.The morphological distribution of heavy metals dissolved by manure in the soil,the mineralization fixation of strain LAX2 and LRP3 to dissolved heavy metals,and the adsorption and fixation of heavy metals by microbial-biochar complexes need to be studied further.