Investigations on the characteristic of dissolved organic matter released from sludge after agricultural use could help to evaluate and predict the environmental behaviors and ecological effects of the concurrent pollutants in soils.The characteristics change in concentration,molecular weight,composition,structure and other properties of DOM released from aerobic composted municipal sludge sampled from a sludge treatment plant in Luoyang City,Henan Province were characterized with Scanning Electron Microscope(SEM),total organic matter analyzer(TOC),UV-Vis absorbance spectroscopy,gel permeation chromatography(GPC),three-dimensional excitation-emission matrix(3D-EEM),Fourier transformation infrared spectroscopy(FTIR)and 1 H nuclear magnetic resonance(NMR).Results showed a significant change in the microscopic morphology of the released DOM,varying from dense lumps to irregular loose material within 60 d of the release process.Dissolved organic carbon released from sludge was in the range of 4.25 to 6.22 mg·g-1 dry sludge,presenting an early increase and later decrease trend.Significant changes in molecular weight and aromaticity of DOM were seen during the release process.The measured molecular weight of DOM increased from 2 674 g·mol-1 on the 5th day to 129 026 g·mol-1 on the 60th day.The aromatic compounds in DOM gradually accumulate during the release process.3D-EEM combined with the parallel factor analysis(PARAFAC)model was used to analyze the fluorescent substances in the released DOM,and it was found that the main fluorescent substances in DOM were fulvic-like and humic-like compounds.The humic-like compounds gradually accumulated during the process,resulting in the humification of the released DOM.The reduction of aliphatic alkane compounds and formation of aromatic compounds in DOM were indicated in FTIR.Variations in the quantity and properties of DOM released from sludge after agricultural use might significantly change the environmental behaviors and ecological effects of the coexisting pollutants in soils.These results may provide insights into the evaluation and prediction of sludge for agricultural use and have guiding significance to the utilization of municipal sludge resources.
Agricultural use of sludgeDissolved organic matterRelease characteristicMolecular weightAromaticity
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