Competition For Electron Donator Between V(v) Reduction And Fe(Ⅲ) Reduction During Anaerobic Incubation

Electrons flow could be affected by microbial Fe(III) reduction process, which wouldresult in heavy metal vanadium oxidation-reduction reactions, making V(V) be reduced tolower valence state and reducing the mobility and toxicity of vanadium. Therefore, it hastheoretical significance and practical value in soil pollution restoration by doing study oncoexistence of microbial Fe(III) reduction and V(V) reduction process in the anaerobic systemand determine the electron flow competition relationship between the two processes, and thendiscusses the mechanism of soil pollution control by the microbial V(V) reduction process.This study chose four kinds of paddy soils from Jiangxi, Jilin, Ningxia and Zhejiang and usedslurry anaerobic culture and soil extracts anaerobic culture to study the mechanism ofinteraction between V(V) reduction and Fe(III) reduction in anaerobic environment. Addingexogenous iron oxide and V(V) to the slurry anaerobic culture to study the effect ofexogenous iron oxide and V(V) on the microbial Fe(III) reduction and V(V) reduction. Paddysoil water extracted from the same soil samples were sued as inoculums, in addition to ironoxide, glutouse and different concentrations of vanadium were added to the soil extractsanaerobic culture. This was to study the effect of Fe(III) on the microbial community V(V)reduction ability and the effect of different concentrations of V(V) on the microbialcommunity Fe(III) reduction ability. The main conclusions of this study are as followed:(1) Adding ron oxide can not only promote the Fe(III) reduction rate in the anaerobicslurry cultivation system and significantly promote the Fe(III) reduction potential, but alsoreduce the time corresponding to Vmax(TVmax). Add V(V) treatment can promote the soil Fe(III)reduction rate and the final Fe(II) concentration in the cultivation system and reduce TVmaxatthe same time. However, its effect is limited.(2) Adding exogenous iron oxide to the anaerobic slurry cultivation system canprolongedthe intial V(V) reduction time and decreased V(V) reduction rate compared with noexogenous iron oxide added system and the ultimately V(V) reduction amount decreasedaccordingly. (3) In the soil extracts anaerobic culture system, Fe(III) reduction rate could be promotedwith adding V(V). But there was not significant promotion in the treatments of lowerconcentration V(V). Fe(III) reduction rate increased with raising concentration of V(V) insuch system. The ultimate concentration of Fe(II) was equal in different concentrationtreatment, which indicated that the ultimate concentration of Fe(II) was determined byamount of the added iron oxide.(4) The interaction relationship betewwn Fe(III) reduction and V(V) reduction can bedivided into two categories: combination and collaboration, which reflects the differences ofmicrobial population. Combination relationship shows that there is no obvious selectivitybetween electron acceptor Fe(III) and V(V) and reduction sequence can be controlled by theredox potential. Collaborative relationship is that the reduction product VO2+promotes theFe(III) reduction process, resulting in collaborative relationship between microbial reductionand chemical reduction.