Electron Transfer Capability Of Dissolved Organic Matter And Its Strengthening Effects On Dissimilatory Fe(Ⅲ) Reduction

Dissolved organic matter (DOM) represents one of the most mobile and reactive organic matter fractions, thereby controlling a number of physical, chemical and biological processes in both terrestrial and aquatic environments. DOM can accept electronic form microbiological and chemical reducing and transfer to the iron minerals and organic pollutants, or act as electron shuttle between the surface of micro-organisms and iron oxides.The paper suggests a rapid method for determining the electron transfer of DOM, combined with fluorescence spectroscopy, Fourier transform infrared and cyclic voltammetry were characterized on the DOM. Shewanella putrefaciens 200 were employed as electronic driving force to study the various properties of DOM and its mediated role of iron reduction, as well as the impact of micro-organisms of iron. The main conclusions are as follows:(1)A rapid electrochemical approach was applied to investigate the EAC and EDC of DOM extracted from sewage sludge compost. The acquired values of EAC and EDC were comparable with those measured by chemical methods that using zinc as the reductant and ferric iron as the oxidant. The determination could be completed in tens of seconds, which was faster and more direct than conventional chemical methods.(2) Using different sources of dissolved organic matter (DOM) as materials, electrochemical methods and fluorescence spectroscopy were employed for researching the relationship between electrochemical activity and the fluorescence intensity. Use fluorescence emission spectroscopy (EEMS) to determine DOM's fulvic-like fluorescence intensity which were compared with the DOM electron transfer ability. It was found a significant correlation between DOM's fuvic-like fluorescence intensity and DOM electronic recycling rate (R= 0.94).(3) DOM derived from sludge compost is fractionated into three fractions with different molecular weight distributions. The research reveals the electrochemical properties of the DOM fractions as the electron shuttles, which provides a better understanding of the role of DOM in biogeochemical redox process.Electrochemical methods show that the electron-transfer abilities of DOM depend on its molecular weight, and the ETC follows the sequence of H-DOM>M-DOM> L-DOM. The same trend is discovered in the DOM-stimulated iron(Ⅲ) oxide bioreduction in which the DOM fractions act as the electron shuttles to transfer electrons from the Fe(Ⅲ)-reducing bacteria to the iron oxide. Fuorescentspectrometry and cyclic voltammetry showed H-DOM had the best electron transfer capacity.