Three-dimensional Fluorescence Spectrum Characteristics and Source Analysis of Dissolved Organic Matter in Sewage Outfall into the Sea of Dongguan

The composition and source analysis of dissolved organic matter (DOM) in sewage outfall into the sea is an effective means of pollutant traceability, which is of great significance to the ecological environment protection in coastal areas. This paper selects Dongguan, an important coastal industrial city in China’s Pearl River, for research. Water samples from 42 sewage outfalls into the sea were measured by three-dimensional fluorescence spectroscopy (3D-EEM). Combined with fluorescence characteristic parameters, similarity analysis and parallel factor analysis (PARAFAC), the spectral characteristics, DOM composition and source were analyzed. The average values of fluorescence parameters fluorescence index (FI), biological index (BIX) and humification index (HIX) were 1.80, 0.94 and 0.55, respectively. The overall PARAFAC analysis found that DOM in the sewage outfall of Dongguan was mainly composed of two fluorescent components, namely tyrosine-like (C1) and humus-like (C2), where tyrosine-like fluorescence was higher than humus-like. This indicates that DOM comes from both terrestrial and endogenous biological activities, but endogenous sources are the primary sources. The similarity analysis divided sewage outfalls into four categories, namely urban rainwater drainage characteristics, typical urban sewage, Jiulong paper-related wastewater and aquaculture water in fish ponds. At the same time, in the PARAFAC analysis, the fluorescence components of 14 urban rainwater outfalls were consistent with the overall analysis results. There are 3 effective parallel factor fluorescence components in 23 outfalls most likely to be contaminated by domestic sewage, namely tyrosine (C1) Humus-like (C2) and tryptophan (C3), C3 components in the characterization of the protein fluorescent tryptophan substance region appeared a strong response peak, belonging to the source pollution, consistent with similarity analysis results. This study suggests that the same source sewage outfalls should be classified management, strengthen the source tracing of sewage outfalls into the sea in neighboring cities, and build a collaborative pollution control system for river basins, estuaries and coastal.