Reduction Properties Of Two Fe(Ⅲ)/Humus Reduction Bacterias And The Biological-chemical Mechanism Of Fe(Ⅲ)/Humus-reducing Coupling Paraquat Degradation

Fe(Ⅲ)/humus reduction is a new microbial respiration form which occurred in kinds of anaerobic conditions, such as sediments, inundational soil and sludge. It not only plays an important role to physical geochemistry cycle, but also can degrade some types of organic contaminants in environment. Fe(Ⅲ)/humus reduction microbe become the focus of research because it is considered to be the key to the reduction process. Paraquat was used frequently in tropical paddy soils, and residued because of the strong adsorption. According to research, adding organic matter can enhance biotransformation of paraquat in anaerobic environment, but the promoting mechanism was still hazy. It is speculating that paraquat can be as the electron donor of the Fe(Ⅲ)/humus reduction process to be degraded because of its low oxidation-reduction potential.Two facultative anaerobic humus-reducing bacteria were isolated from paddy soil that was frequently used of paraquat and their humic-reduction properties was researched further more. The transformation and the mechanism of paraquat was studied in an anaerobic system of Fe(Ⅲ)/humus-reducing bacteria(Enterobacter cloacae PQ02)/Fe(Ⅲ)/humus/paraquat. The main results are as follows:(1)PQ01indicated that the closest phylogenetic relative among the valid species was Pseudomonas geniculata, and it grew well on the YPG media and the incubation temperature was25℃to37℃and the pH value ranged from6.0to9.0and the concentration of sodium chloride ranged from1%to5%. PQ02indicated that the closest phylogenetic relative among the valid species was Enterobacter cloacae, and it grew well on the YPG media and the incubation temperature was25℃to37℃and the pH value ranged from5.0to7.0and the concentration of sodium chloride ranged from1%to5%.(2) PQ01could use glucose, sucrose, acetic acid, methane acid and acetone as electron donor in the Fe(Ⅲ)/humus reduction process, and reducing power from large to small was glucose, sucrose, acetone, methane acid, acetic acid. PQ01could reduce all five types of Iron oxide and reducing power from large to small was ferrihydrite, lepidocrocite, goethite, maghemite and hematite. PQ01could also reduce all three types of humus model, and reducing power from large to small was AQS, AQDS, AQC.(3) PQ02could use glucose, sucrose, lactic acid, methane acid and acetone as electron donor in the Fe(Ⅲ)/humus reduction process, and reducing power from large to small was glucose, sucrose, acetone, methane acid, lactic acid. PQ02could reduce all five types of Iron oxide and reducing power from large to small was, goethite,lepidocrocite, ferrihydrite, maghemite and hematite. PQ01could also reduce all three types of humus model, and reducing power from large to small was AQS, AQC, AQDS.(4) Paraquat could be as the electron donor of the Fe(III)/humus reduction process, and there were three degradation approaches in this system:a) paraquat was biological degraded by PQ02, b) paraquat was oxidized by giving electron as the electron donor in the reduction process, c) the biogenic reduction product humus was shown to directly cause the degradation of paraquat when the microorganisms were moved by autoclaving from samples. It is also shown that adding extra electron donner to the anaerobic system could promote the degrading of paraquat.