Characterization of dissolved organic matter extracted from fermentation effluent of swine manure slurry using spectroscopic techniques and parallel factor analysis (PARAFAC)

Abstract

Dissolved organic matter (DOM) is the most active component in environmental system, and its chemical and structural characteristics are most likely to affect its biodegradation. DOM has several different fluorophores whose fluorescent characteristics contain a lot of information about structure and functional groups. Fluorescence spectroscopy and Fourier-transform infrared (FTIR) were used to examine the structural and biodegradable characteristics of DOM extracted from fermentation effluent of swine manure slurry. Humic-like acid, fulvic-like acid and protein-like fluorophores were observed in fluorescence spectra. Fluorescence index (FI) indicated that the fluorophores in the samples were representative of both terrestrial and microbially-derived organic matter. FTIR spectroscopy showed that DOM featured aliphatic CH, aromatic CC and carbohydrate CO functional groups. With PARAFAC model, four fluorescent components were identified: component 1 (protein-like), component 2 (soluble microbial byproduct-like), component 3 (non-humic like) and component 4 (fulvic-like). Component 1 was a dominant fluorescent component. Components 2, 3 and 4 were degraded by microorganisms as the anaerobic fermentation processes. The C/N ratio of DOM in F1 has a more significant decrease than that in F0, indicating the loss of carbon (CH4 and CO2) during this process. The C/N ratio of DOM in F2 obviously increased when additional swine manure slurry was added.