Study Of Reduction Of Ferrihydrite And Functional Groups Of Different Compositions Of Organic Matter

The more serious water pollution is, the higher amounts of dissolved organic matter (DOM) becomes. Humic substance (HS) is a high molecular polymer andcomposed of carboxyl, carbonyl, quinone radicals and other functional groups. HS can be used as electron acceptors, and also be regarded as reusable electron shuttle in the process of microbial degradation of pollutants with accelerating the degradation rates. The redox characteristics of HS have an influence on the migration and transformation of heavy metals and organic pollutants in the groundwater environment, and acceleratethe reductive dissolution of some insoluble minerals. Thus, study the structure and redox properties of DOM and its compositions is of great significance in-situ remediation and biological cycle of the earth.DOM, HA, FA and the mixture of HA and FA were chosen to study the impact on the microbial degradation of contaminants. PPDOM was extracted from Pahokee Peat Soil. Both Pahokee Peat standard humic acids (PPHA) and Pahokee Peat standard fulvic Acids (PPFA) were purchased from International Humic Substances Society (IHSS). The main results are shown as follows:(1) All the samples can accelerate the reduction of ferrihydrite by Shewanella oneidensis MR-1, and PPHA> PPFA> PPDOM. This indicated that the electron shuttle ability of PPHA was strongest. These illustrate that the electron shuttle ability is directly related to the amount of quinone groups; (2) no matter what TOC concentration ratio of the mixture of PPHA and PPFA, the reduction rates of mixtures was higher than sole PPHA or PPFA. Due to the different particle sizes between HA and FA, mixture gradation can effectively cut down the distance of each molecule to provide more chance for electron hopping; (3) In the natural temperature range, both PPHA and PPFA could accelerate the reduction rates of ferrihydrite with the increasing of TOC concentrations, this may due to the enzyme activity under different temperature. In addition, results also showed that appropriately improve the HS concentration could compensate the gap between lower temperature and higher temperature; (4) pH can significantly affect the accelerating rates of microbial degradation of ferrihydritein the presence of HA. These indicate that the reduction rates of ferrihydrite with humic-like fluorophores of PPHA were higher than with protein-like fluorophores, which means that higher amount of quinones is the main reason of higher reduction rates with humic-like fluorophores.In the process of environmental ecological remediation, DOM can significantly affect the process of microbial degradation of contaminants. Study the effect of different environmental conditions on the redox ability and redox functional groups of DOM can predict the degradation and transformation time of pollutants, efficiently guide the ecological remediation process in suit.