Catchment-driven trend of dissolved organic matter characteristics in the Hailar River, China

The association of dissolved organic matter (DOM) with natural watershed backgrounds and anthropogenic activities is crucial for environmental assessment and sustainable development of basins. This study investigated the catchment-driven trend of DOM characteristics in the Hailar River basin, China. The results identified three fluorescent components through EEM-PARAFAC models: a terrestrial humic-like component (C1), a humic-like component related to microbial activity (C2), and a UVA humic-like component (C3), which were influenced by Cl⁻ and HCO₃⁻ derived from rock weathering. The contents of water-extractable organic carbon (WEOC) extracted from soils surrounding the watershed significantly correlated with the concentrations of DOC and COD_Cr. Furthermore, COD_Cr exhibits heightened sensitivity to precipitation and temperature fluctuations, revealing the synergistic effects of environmental factors and natural background. The hydrochemical composition and DOM characteristics are predominantly influenced by their origins from the Greater Khingan forests, indicating a catchment-driven trend of DOM in the studied river. What's more, COD in Hailar river basin was mainly controlled by refractory dissolved organic matter (RDOM). This research underscores the need for context-specific environmental standards rather than a “one-size-fits-all” approach and offers scientific insights and methodologies for the rational assessment of water quality and aquatic ecosystem health in similar riverine systems.