Dissolved organic matter sources in urban outfall water before and during rainfall, indicated via its fluorescence fingerprinting

Abstract

Pollution source identification is the key foundation of urban river water quality management. In this study, fluorescence fingerprinting was employed to analyze changes in dissolved organic matter (DOM) sources in urban river outfalls P1–P3 in Hefei City, China, before and during a rainfall event. The water quality of the outfalls varied before and during rainfall, with an apparent dilution in P2 and a combined effect of urban non-point runoff and dilution in P3. The fluorescent components of the DOM in the outfall water were fulvic acid-like substances C1, terrestrial humic-like substances C2, and tryptophan-like substances C3. The dominant C1 in P1 was diluted by rainfall runoff, decreasing the total fluorescence intensity (F_T) of the DOM. The increased F_T and proportion of C1 + C2 in P2 during early rainfall indicated runoff inputs, whereas those in P3 increased and decreased thereafter, suggesting that rainfall led to an influx of domestic sewage. Fluorescence fingerprinting analysis indicated that the DOM in P1 originated primarily from rainwater and domestic wastewater treatment plant (WWTP) effluent. The DOM in P2 originated from domestic WWTP effluent pre-rainfall, rainwater, and domestic WWTP effluent during early rainfall and urban non-point runoff during later rainfall, whereas that in P3 originated from domestic sewage before and during early rainfall and urban non-point runoff during later rainfall. Identifying sources of pollution provides a basis for urban outfall and river water quality management before and during rainfall events.