State Environmental Protection Key Laboratory of Integrated Surface Water-Groundwater Pollution Control, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China; Climate & Energy College, School of Geography, Earth and Atmospheric Sciences, The University of Melbourne, Melbourne, VIC 3010, Australia.
State Environmental Protection Key Laboratory of Integrated Surface Water-Groundwater Pollution Control, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China.
Chemosphere. 2022 Dec;308(Pt 3):136384. doi: 10.1016/j.chemosphere.2022.136384. Epub 2022 Sep 9.
Riverine dissolved organic matter (DOM) transport was a key step in the carbon biogeochemical cycle while we had limited understanding of its contribution to the estuary DOM dynamics. This study focused on the river downstream-to-tidal estuary DOM variation and the control of environmental factors on it. The contributions of three tributaries with varing urbanization degrees to the tidal DOM dynamics were evaluated. Though more aromatics were introduced to the urban tributary, the A/A values and fluorescent index values indicated the DOM molecular size was uniformly reduced due to the enhanced microbial degradation during transport. The tidal DOM showed less varied spectroscopic indexes than the tributary DOM, but tidal cycles strongly impacted the fluorescent DOM quantified by the fluorescence regional integration (FRI). Salinity range can differentiate the fluorescent DOM variation patterns in river tributaries (e.g., <2.5, positive correlations; >2.5, negative correlations) and tidal cycles (>10, negative correlations). For tidal DOM, the high salinity decreased more humic-related components, resulting in increased proportions of protein-related components in high tides. The dissolved oxygen and nitrogen contents were negatively correlated with salinity, suggesting the microbial contributions and anthropogenic inputs in tributaries increased the tidal DOM quantity. The less urbanized tributaries contributed more to the low-tide DOM compositions/properties while the dynamic contribution of the urban tributary impacted more the tidal DOM dynamics. Our results highlighted the uneven declines of FRI values of different components by freshwater-saltwater mixing in estuaries and suggested the different functioning of urban, agro-urban, and suburban tributaries contributed to tidal DOM dynamics.
河流溶解性有机物质（DOM）的输运是碳生物地球化学循环的关键步骤，而我们对其对河口 DOM 动态的贡献知之甚少。本研究侧重于下游到潮汐河口 DOM 的变化以及环境因素对其的控制。评估了具有不同城市化程度的三个支流对潮汐 DOM 动态的贡献。尽管更多的芳烃被引入城市支流，但 A/A 值和荧光指数值表明，由于在运输过程中增强的微生物降解，DOM 分子大小均匀减小。与支流 DOM 相比，潮汐 DOM 的光谱指数变化较小，但潮汐周期对通过荧光区域积分（FRI）定量的荧光 DOM 有强烈影响。盐度范围可以区分河流支流中荧光 DOM 的变化模式（例如，<2.5，正相关；>2.5，负相关）和潮汐周期（>10，负相关）。对于潮汐 DOM，高盐度降低了更多与腐殖质相关的成分，导致高潮汐中蛋白质相关成分的比例增加。溶解氧和氮含量与盐度呈负相关，表明支流中的微生物贡献和人为输入增加了潮汐 DOM 的数量。城市化程度较低的支流对低潮汐 DOM 的组成/性质贡献更大，而城市化程度较高的支流的动态贡献对潮汐 DOM 的动态影响更大。我们的研究结果强调了河口淡水 - 盐水混合对不同成分 FRI 值的不均匀下降，并表明城市、农业城市和郊区支流的不同功能对潮汐 DOM 动态有贡献。
