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Riparian wetlands play important roles in the enhancement of water quality by controlling nonpoint source pollution and protecting aquatic ecosystems. In the present study, we surveyed and identified vegetation types in riparian wetlands, evaluated how vegetation types influence spatial patterns of water-extracted soil organic matter (WSOM) from riparian wetland, and probed the impacts of riparian fluorescent WSOM on fluorescent dissolved organic matter (FDOM) and water trophic states in river ecosystems. We used absorption and excitation-emission-matrix (EEM) fluorescence spectroscopy to characterize the optical properties of riparian WSOM and riverine DOM from Chongming Island, China, the largest alluvial plain island in the world. Our results showed that fifty-eight spermatophytes in riparian wetland were clustered into five vegetation types, including warm coniferous forest (WCF), deciduous broad leaf forest (DBF), evergreen broad leaf forest (EBF), aquatic plants (AP) and herbaceous plants (HP). Absorption spectra revealed the effects of vegetation types on riparian chromophoric WSOM quantity. Although no difference in water-extracted soil organic carbon (WSOC) contents was observed, deciduous broad leaf forest (DBF) and evergreen broad leaf forest (EBF) fed more fluorescent WSOM quantity than did the other vegetation (AP, HP and WCF), and deciduous broad leaf forest (DBF) and aquatic plants (AP) provided more humic-like (RC.1 and RC.2) and fulvic-like (RC.3) substances into riparian wetland ( P < 0.05 or P < 0.01). In addition, we noted that humic-like and protein-like substances (RC.4) transported from riparian wetland into a river water body, and riverine terrestrial-originated components (FC.1 and FC.2) were significantly related to the four riparian fluorescent WSOM components ( P < 0.05). Furthermore, the riverine trophic state was significantly higher when the fluvial DOM and its component quantity increased ( P < 0.05). We concluded that riparian wetland can control the quantity and quality of riparian WSOM and reshaped riverine DOM compositions and riverine water quality with important management implications. [ABSTRACT FROM AUTHOR]

• Significant decrease in the concentrations of PM 2.5 and major inorganic ions during the CRP. • Contribution of NO X sources to nitrate based on isotopes and the Bayesian mixing model. • Decreased contribution of coal combustion during the CPR. • The homogeneous formation pathway in summer and heterogeneous pathway in winter. The 'Coal Replacing Project' (CRP), replacing coal with cleaner energy like natural gas and electricity, was implemented in North China to curb PM 2.5 pollution; therefore, it is important to explore the sources and transformation mechanisms of PM 2.5 nitrate under this strategy for examining its effectiveness. In this study, daytime and nighttime PM 2.5 samples of one summer (Jul-2016, C1) and two winters (Jan-2017, C2 and Jan-2018, C3, before and during the CRP, respectively) were collected in urban Tianjin. Concentrations of PM 2.5 and water-soluble inorganic ions were analyzed, and δ15N and δ18O were used to calculate the contributions of different NO X sources to nitrate based on a Bayesian mixing model. The results showed that the average concentrations of PM 2.5 and its dominant inorganic ions (SO 4 2−, NO 3 −, NH 4 +) in C3 during the CRP, compared to C2, decreased by 62.13%, 79.69%, 55.14% and 38.84%, respectively, attesting the improvement of air quality during the CRP. According to the correlation between [NO 3 −/SO 4 2−] and [NH 4 +/SO 4 2−] as well as δ18O variations, the homogeneous formation pathway might be dominant in C1, while the heterogeneous pathway would be primary in C2 and C3 during the formation of nitrate. Moreover, the heterogeneous pathway contributed more in C3 than in C2. The dominant sources in C1 were biogenic soil emission (37.0% ± 9.9%) and mobile emission (25.7% ± 19.1%), while coal combustion (42.4% ± 13.8% in C2 and 34.9% ± 14.4% in C3) and biomass burning (31.0% ± 21.2% and 34.7% ± 22.7%) were the main sources in C2 and C3. In the winter, the contribution of coal combustion dropped by about 8% during the CRP (C3) in comparison with that in C2, suggesting the implementation of CRP played an important role in reducing NO X from coal combustion. [ABSTRACT FROM AUTHOR]