Using fluorescence spectroscopy of DOM as an indicator of human-derived pollution: a case study in the Chongqing-Three Gorges section of the Yangtze River.

Dissolved organic matter (DOM) is a crucial component of aquatic environments and is shaped by both natural and anthropogenic factors. In this study, we screened optical indicators associated with human-derived pollution by combining the fluorescence spectroscopy with source identification analysis. Three distinct components were identified: one microbial-like component (C1) and two terrestrial-like components (C2 and C3). Overall, the water quality was good, with autochthonous DOM dominating the composition, accounting for 66 %-69 % of the total DOM. In cluster and redundancy analyses, C2 showed a strong correlation with dichloromethane and petroleum substances, suggesting a strong correlation to gas extraction industry. While C3 was closely associated with linear alkylbenzene sulfonate, a commonly used anionic surfactant, as well as nutrients, indicating a connection to domestic wastewater discharges. This study provides a screening strategy for optical indicators which allows tracing the source of human-derived pollution in a rapid and economic way.