IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 BOOK OF ABSTRACTS 126 NOM and Aquatic Systems Thursday, 27 August 2026 / Hall C SL60 Natural and Anthropogenic Drivers of DOM Heterogeneity Dictate Disinfection Byproduct Formation and Cytotoxicity in Drinking Water of Yangtze River Basin, China Huiyu Dong* Key Laboratory of Drinking Water Science and Technology, Research Center for EcoEnvironmental Sciences, Chinese Academy of Sciences, Beijing 100085, China As a primary water source for hundreds of millions of people in China, the Yangtze River Basin underpins national water security. However, disinfection byproduct (DBP) risks remain difficult to control because its precursor, dissolved organic matter (DOM) exhibits strong heterogeneity driven by coupled natural and anthropogenic factors, which become more pronounced along the river’s ~6300 km continuum. Here, we assessed basin-scale variations in DOM composition and DBP formation potential across 21 cities and over 500 monitoring stations in the Yangtze River Basin, revealing how natural and anthropogenic factors reshaped DOM profiles and DBP formation along with associated cytotoxicity. By integrating the newly developed SEC-MD-CMF method with FT-ICR MS for DOM characterization, three major source-related underlying components of DOM in the Yangtze River were identified. Aromatic terrestriallike DOM associated with forest and grassland cover increased by 1.5-fold along the Yangtze River, and its upstream dominance (>80%) made haloacetic acids (HAAs) and haloacetaldehydes (HALs) the primary contributors to DBP-associated cytotoxicity. In contrast, eutrophic lakes adjacent to the middle and lower reaches enhanced the nitrogen-rich biogenic-like component by 4.1-fold, facilitating more toxic N-DBP (e.g., haloacetonitrile (HAN)) formation and shifting cytotoxicity drivers toward HALs and HANs. Moreover, intensified human activity therein not only increased the low-molecular-weight anthropogeniclike component (3.4-fold), but also elevated bromide levels, which further favored the formation of highly-toxic brominated DBPs. These findings establish a quantitative framework linking water background profiles and harmful byproduct formation during drinking water supply, highlighting the need for region-specific watershed controls.
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