Study On The Effect Of S-valencestate Bidirectional Regulation Behavior On The Occurrence Of Cd In Typical Bacteria

In the process of microbial remediation of heavy metals in soils,the oxidation/reduction process of s and the occurrence of heavy metals in different conditions of typical s strains were explored to provide a new understanding and reference for soil heavy metal pollution.In this study,the common heavy metal ions Cd²⁺in farmland soil are taken as the representative.And chooses the common soil S reducing bacteria sulfate reducing bacterium,S oxidizing bacterium thiobacillus denitrificans as the target strain,and probes into the reduction of S in the anaerobic condition of sulfate-reducing bacteria and the influence on Cd's occurrence state.Study on S oxidation and Cd occurrence in aerobic condition of thiobacillus denitrificans,and further study of two strains on the reduction-oxidation bidirectional regulation S process and the influence on Cd occurrence.The single strains of sulfate-reducing bacteria and thiobacillus denitrificans were isolated from pollution-free soil/sludge.The growth characteristics of two strains were analyzed.The fully growth period of sulfate-reducing bacteria was7d,and it could grow rapidly under the Eh<-150m V,the p H increased and the SO₄^2-produced a lot of S^2-.However,under aerobic conditions,the growth period of thiobacillus denitrificans was 10d,the p H of the growth process decreased and the oxidation S₂O₃^2-produced a lot of SO₄^2-.The two strains were separately analyzed for the growth resistance of Cd²⁺,and the oxidation/reduction process of S during the growth process and the effect on the occurrence of Cd were explored.The results showed that sulfate reducing bacteria have a certain tolerance to Cd²⁺,and mineralized Cd²⁺can form Cd S crystals.Different concentrations of Cd had a certain effect on the morphological change of S,and the total Cd S content was relatively low.The concentration of liquid Cd²⁺in the process of oxidizing S₂O₃^2-to SO₄^2-was decreased,and the formation of SO₄^2-was mainly formed during the transformation of S.The tolerance of both strains to Cd²⁺was about 30 mg/L,and the final removal rate of Cd²⁺was up to 90%and 92%.Through the analysis of the characteristics of S-bidirectional control system of two strains with anaerobic-aerobic as the main process,the results showed that:thiobacillus denitrificans can use different concentrations of S^2-to achieve its own growth,and the growth process showed S^2-?S?SO₄^2-of S oxidation process;The sulfate reducing bacteria mineralization product Cd S was placed in the thiobacillus denitrificans bacterium culture system for study,there was no significant change in the initial stage,but there was a brief rapid oxidation and dissolution process in the log phase Cd S.However,due to the high concentration of Cd²⁺in the later period,the growth of thiobacillus denitrificans was inhibited,and the oxidation of Cd S by Thiobacillus denitrificans was maintained at a certain level.In this study,the effects of different S strains on the oxidation/reduction process of S and the one-sided and two-sided regulation of Cd were preliminarily explored.The prevalence and dynamic changes of Cd under the action of different S strains were preliminarily explored and analyzed.The intrinsic mechanism of action will be expected to provide some basic references for rapid in-situ treatment of heavy metal pollution in soils.