Characteristics, Occurrence and Photoreactivity of Dissolved Organic Matter in an Effluent Dominating Urban River

摘要

We studied characteristics and occurrence of dissolved organic matter (DOM) in an urban river, where effluent from wastewater treatment plant flows. Samples were taken in seven study sites from upstream to downstream once a month throughout the year and analyzed with excitation-emission matrix (EEM) method combined with parallel factor analysis (PARAFAC). The EEM spectra of samples were divided into six individual fluorescent components with PARAFAC, which consists of three humic-like components (C1-C3), two protein-like components (C4 and C5) and a wastewater-derived component (C6). Fluorescent intensities of each component and dissolved organic carbon (DOC) immediately increase at the point where effluent flow in, and it shows that effluent is major source of DOM. Additionally, the fluorescent intensities of C1, C2, C4 and C6 gradually decreased with flow down the river although DOC remains constant. The result indicates that DOM transmute during transportation. Photolysis experiment using a sunlight simulator also revealed that C6 immediately degrade, with only 19.9% remaining after 6h of photolysis. These results may be used to source identification and environmental fate prediction of fluorescent components in river downstream and coastal environments.