Data from: Optical and molecular signatures of dissolved organic matter reflect anthropogenic influence in a coastal river, Northeast China

Sources and molecular composition of dissolved organic matter (DOM) in coastal rivers have been tightly linked with its reactivity and fate, thus influencing element and nutrient cycling. The DOM in coastal rivers is usually sourced from both terrestrial and marine inputs, with further complication by anthropogenic activities, which is less understood in coastal rivers located near populated industrial regions. In this study, DOM in a typical anthropogenically influenced coastal river, Daliao River, was analyzed for optical analyses and for molecular composition via Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to give a better scope of composition and sources of DOM. The DOM was enriched in autochthonous and anthropogenic inputs at upstream sites according to high chlorophyll a concentrations, strong protein-like fluorescence, and nonoxygen heteroatomic CHOS formulae (19–24% by relative peak intensity) detected by FT-ICR MS analysis. A series of surfactant-like formulae, indicative of wastewater inputs, were identified and showed a decreasing trend from upstream to the river mouth. Compared with large world rivers, the DOM of Daliao River is characterized by higher abundances of heteroatomic (excluding O) formulae and molecular lability, which is likely caused by strong autochthonous and anthropogenic inputs. In general, we demonstrate that in addition to optical properties, the molecular composition can assess the specific anthropogenic imprints and molecular lability of DOM, which is essential for constraining sources and identifying processes during the transit of DOM from the river to estuary with increasing urbanization and industrialization.

沿海河流中溶解态有机物（dissolved organic matter, DOM）的来源与分子组成与其反应性及归趋紧密相关，进而调控元素与养分循环过程。沿海河流中的溶解态有机物通常兼具陆源与海源双重输入，且受人类活动影响而进一步复杂化，目前针对人口密集工业区附近沿海河流的相关研究仍相对不足。本研究针对受人类活动显著影响的典型沿海河流——辽河（Daliao River），通过光学分析与傅里叶变换离子回旋共振质谱（Fourier transform ion cyclotron resonance mass spectrometry, FT-ICR MS）技术解析其溶解态有机物的分子组成，以更全面地刻画DOM的组成特征与来源路径。研究发现，上游点位的DOM显著富集内源与人为输入特征，这一点可通过较高的叶绿素a浓度、显著的类蛋白荧光信号，以及傅里叶变换离子回旋共振质谱检测到的不含氧杂原子CHOS分子式（相对峰强度占比19%~24%）得到佐证。本研究还识别出一系列类表面活性剂分子式，这类分子式可指示废水输入信号，且其相对丰度自上游至河口呈逐步递减趋势。与全球大型河流相比，辽河（Daliao River）溶解态有机物的特征为含杂原子（不含氧）分子式与分子易变性丰度更高，该特征大概率由强烈的内源与人为输入共同导致。总体而言，本研究证实：除光学特性外，分子组成分析可用于评估DOM的特定人为影响印记与分子易变性，这对于明确城市化与工业化进程中，DOM从河流向河口输运过程中的来源约束与过程识别具有关键意义。