[Distribution Characteristic and Environment Response of DOM in Different Regions of Northern City].

To explore the source information and composition characteristics of dissolved organic matter （DOM） in different regions of water bodies in northern cities, considering the urban water system of Shijiazhuang, Hebei Province as an example, ultraviolet-visible spectroscopy （UV-vis） and three-dimensional fluorescence parallel factor analysis （EEM-PARAFAC） were used to explain the optical parameters, abundance, and proportion of different components of DOM in water bodies of different regions. The results showed that： ① The concentrations of NO-N, NO-N, NH-N, TN, TP, and COD in the upstream were significantly lower than those in urban water bodies and downstream （<0.01）, and TSI increased after the water entered the city. ② The ultraviolet parameter indicated that the concentration of DOM significantly increased after entering the city （<0.001）. / showed that the relative molecular weight of DOM in different regions was： upstream<urban water<downstream, and the of DOM in different regions was >1, indicating that the main source of DOM was endogenous input. ③ Three fluorescent components were identified, namely C1 （visible light region fulvic acid）, C2 （tryptophan）, and C3 （long wave humic substance）. The upstream and urban water bodies were mainly composed of protein-like components （C2）, while the downstream humic substances （C1+C3） accounted for a relatively high proportion （80.1%）. The PCA analysis showed significant spatial distribution differences. According to the results, >1, FI>1.8, and HIX<4 indicated that DOM exhibited low humification and strong autogenesis in different regions. ④ A significant correlation （<0.01） was observed between C1 and C3 in the upstream and downstream. C1, C2, and C3 in urban water bodies were all significantly correlated （<0.01）. In addition, C1 and C3 posed a significant correlation with NO-N in different regional water bodies. RDA indicated that NO-N, TDN, TDP, and COD were the main environmental driving factors for DOM distributions. In summary, the multiple pressures of the city exhibited a significant influence on the spectral properties of DOM in the flowing water system.