The Research On The Redox Properties Of Different Components Of Soil Organic Matter

Soil organic matter(SOM)play an important role in biogeochemical cycle as a electron shuttle in soil.Its redox properties is closely related to urgent to solved soil pollution problems.The composition of SOM is complex and has a wide range of sources.Humic substances(HS),mainly including humic acids(HA)and fulvic acid(FA),are the most redox active components in SOM.Dissolved organic matter(DOM)is a dissolvble component in SOM,which plays an important role in the initiation or acceleration of oxidation-reduction reactions in soil micropores.The main subjects of this study are HA,FA and DOM.The microbial method was used to determin the redox properties of different components of SOM,combined with fluorescence method to determin the redox functional group,and established the relationship between redox properties and functional groups of different components of SOM.Meanwhile,the particle size distribution of HA was analyzed by laser scattering,and calculated the average molecular distance of HA(LPPHA).DOM were separated by dialysis method,and the redox ability of humic stibstances was quantified by chemical methods and furtller explored the relationship between the dynamic macromolecular structure and redox properties of SOM.The results are as follows:PPHA electron transport capacity is greater than PPFA.Fluorescence method showed that PPFA contained more proteins and low energy n structure.This explains that the aromatic ring structure in humus is conducive to the transport of electrons by humus as an electron shuttle,whereas electrons are not readily accepted by the structure of protein like structures and low energy n bonds.At low concentrations of the same humus,there was an exponential correlation between the electronic transport capacity and the maximum fluorescence intensity;the electron transport capacity of different humus was negatively correlated with the fluorescence intensity.This relationship can be used to establish a fluorescence detection method for SOM redox ability.PPHA and PPFA for accelerating the microbial reduction of ferrihydrite has synergistic effect,the combined effect of PPHA-PPFA combined with fluorescence method was found when no new redox groups,this synergistic effect may be due to the better distribution and combination.HA particle size is not uniform distribution.At low concentrations,both large and small molecules of HA were exist,and HA may be a dynamic macromolecular structure.The concentration of PPHA in 0.01?0.05 mg/mL,LPPHA-0.5 change with concentration and electron transfer ability with the concentration change trend are similar,indicating that there was a relationship between HA redox properties and molecular structure.During the DOM dialysis process,small molecules are continuously dissociated and the redox capacities of small molecules is stronger.The total electron transfer number of DOM increases sharply after dialysis.It is shown that the DOM in the solution contains a large number of encapsulated redox functional groups,which can be exposed during dialysis and enhancing the redox capacities of the whole system.