Electron Transfer Capacities of Dissolved Organic Matter Derived from Swine Manure Based on Eletrochemical Method

Dissolved organic matter (DOM) is the most active fraction of compost organic matter. The presence of the redox-active functional groups in DOM allows it to act an electron shuttle to promote the electron transfer between microorganisms and terminal electron acceptors. In this study, the electron transfer capacities (ETCs) of compost DOM samples at eight different composting stages were determined by electrochemical method. The 2, 2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and Diquat dibro-mide monohydrate (DQ) were used to measured electron donating capacity (EDC) and electron accepting capacity (EAC) with working voltage 0.61 V/-0.49 V, respective. The evolution characteristics of the chemical structures and components were analyzed by combining the three. dimensional fluorescence spectra, fourier transform infrared (FTIR) spectra and elemental analysis. The results showed that the electron donating capacity (EDC) of DOMincreased from 16.850 mu mol e(-)/(g C) to 22.077 mu mol e(-)/(g C), The corresponding electron accepting capacity (EAC) decreased from 1.866. mol e(-)/(g C) to 1.779. mol e(-)/(g C). The results of three. dimensional fluorescence spectroscopy show that the relative contents of humuc-likeand protein-like components gradually increased and decreased, respectively, during the composting process. The humuc-like components were the main contributor for the ETC of DOM-FTIR spectra shows that there was no significant change in the hydroxyl and carboxyl group contentsof DOM during composting, suggesting no contribution of these function groups to the ETC of DOM. The elemental analysis showed that the content of oxygen in the DOM increased during the composting process, while the sulfur. containing group may be dominated contributor forits ETC.