Abstract We combined Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and mass spectrometric analysis of stable carbon isotopes, a traditional method for tracking DOM sources, to investigate the variation in the complexity of water samples collected along a salinity gradient in Delaware Bay in March and August 2014. Detailed analyses of optical properties (ultraviolet and visible (UV–Vis) absorbance and excitation-emission matrix (EEM) fluorescence spectroscopy) were carried out. Results from statistical parallel factor analysis (PARAFAC) of EEM data were also used to track and further constrain fluorescent DOM (FDOM). Optical analyses and FT-ICR-MS data showed large differences between late winter and summer conditions, and the stable carbon isotopic composition was more variable in summer than in late winter. Although terrestrial inputs of DOM are evident at low salinities in both seasons, our data suggest that a significant source of FDOM, from either in situ water column production or from benthic aquatic or semi-aquatic plant communities, contributes DOM to low and mid-salinity waters in Delaware Bay during summer but not in late winter.

中文翻译：

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2014 年 3 月和 8 月美国特拉华湾溶解有机物组成的季节性变化

摘要 我们将傅里叶变换离子回旋共振质谱 (FT-ICR-MS) 和稳定碳同位素质谱分析（一种传统的 DOM 源跟踪方法）相结合，研究了沿盐度梯度收集的水样复杂性的变化。 2014 年 3 月和 8 月在特拉华湾进行了详细的光学特性分析（紫外和可见光 (UV-Vis) 吸光度和激发发射矩阵 (EEM) 荧光光谱）。EEM 数据的统计平行因子分析 (PARAFAC) 的结果也用于跟踪和进一步限制荧光 DOM (FDOM)。光学分析和 FT-ICR-MS 数据显示冬末和夏末条件之间存在很大差异，夏季稳定碳同位素组成比冬末变化更大。