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 NO3--N,NO2--N,NH4+-N,TN,TP,and COD in the upstream were significantly lower than those in urban water bodies and downstream(P＜0.01),and TSIM increased after the water entered the city.② The ultraviolet parameter a254 indicated that the concentration of DOM significantly increased after entering the city(P＜0.001).E2/E3 showed that the relative molecular weight of DOM in different regions was:upstream＜urban water＜downstream,and the SR 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,SR＞1,FI＞1.8,and HIX＜4 indicated that DOM exhibited low humification and strong autogenesis in different regions.④ A significant correlation(P＜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(P＜0.01).In addition,C1 and C3 posed a significant correlation with NO3-N in different regional water bodies.RDA indicated that NO2-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.
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