Screening Of Sulfate Reducing Bacteria Tolerant To Cadmium And Arsenic And Study On Their Effects On Passivation Of Cadmium And Arsenic In Soil Sediments

Arable land pollution is related to the livelihood of the country and the people,and has always been widely concerned.High level of cadmium and arsenic in rice is one of the most common pollutions aroused by arable land pollution in China,which poses a great threat to China’s food security.In recent years,microbial technology has been intensively applied into soil remediation.Some microbial strains could reduce sulfates to H₂S,HS^-,S^2-and then react with heavy metal ions to form insoluble metal sulfides.In this study,a strain of Enterobacter with sulfate reduction function was screened from cadmium arsenic contaminated farmland soil,and their fixation mechanisms of cadmium and arsenic were explained from a microscopic perspective by means of fixation rate experiments and characterization experiment;then the soil culture experiment was carried out to obtain the effects of this strain on pH,Eh,microbial community structure in soil and morphologies of cadmium and arsenic morphology and colony structure through changing the target bacterial solution and water management;Based on above results,optimal regulation effects were selected to conduct pot experiments to examine the effects of strain addition on the absorption and accumulation of cadmium arsenic in rice.Finally,it provides novel sights and data for the treatment for heavy metal combined pollution of soil.The main findings are as follows:（1）A strain M5 tolerant to cadmium and arsenic was isolated from the arable soil polluted by cadmium and arsenic,which was identified as Enterobacter sp.that was gram-negative,facultative anaerobic bacteria and could reduce sulfate.（2）In the simulation system,the removal rate of cadmium and arsenic by strain M5 was94.13%and 27.26%,respectively.The characterization results have confirmed that Cd（II）and As（V）were fixed to CdS and As2S3;（3）The combined treatment of addition of strain M5 and submergence could reduce the content of acid soluble Cd and increase the contents of residual and oxidation form of cadmium.This combined treatment also could increase the contents of exchangeable,aluminium and iron bound of arsenic.Furthermore,it could increase relative abundance of Enterobacter by8.14%and make them dominant.（4）In rice pot experiment,combined submergence and addition of 900 m L bacteria solution attained the most treatment performance,which could decrease contents of cadmium and arsenic in each part of rice,facilitate the formation of rice root iron plaque and decrease the contents of available cadmium and arsenic in soil.