Cory Rose M, McKnight Diane M
The Institute of Arctic and Alpine Research and Civil and Environmental Engineering, University of Colorado, Boulder, Colorado, USA.
Environ Sci Technol. 2005 Nov 1;39(21):8142-9. doi: 10.1021/es0506962.
Excitation-emission matrixes (EEMs) of 379 dissolved organic matter (DOM) samples from diverse aquatic environments were modeled by parallel factor analysis (PARAFAC). Thirteen components likely representing groups of similarly fluorescing moieties were found to explain the variation in this data set. Seven of the thirteen components were identified as quinone-like based on comparison of their excitation and emission spectra to spectra of model quinones. These quinone-like fluorophores were found to vary in redox state and degree of conjugation. Two components were identified as amino acid-like based on comparison to tyrosine and tryptophan fluorescence spectra. The other four components are not yet associated with any class of molecules. The quinone-like fluorophores account for about 50% of the fluorescence for every sample analyzed, showing that quinone-like fluorophores are an important and ubiquitous fluorescing moiety and in natural waters. Further, the distribution of the quinone-like fluorophores was evaluated as a function of environmental and laboratory redox gradients. Under reducing conditions, the contribution of the reduced quinone-like fluorophores increased concurrentwith a decrease in the oxidized quinone-like fluorophores, indicating that DOM fluorescence is a function of redox state of quinone-like moieties. Lastly, a ratio of two quinone-like fluorophores was found to explain the variation in the fluorescence index. These results provide new insight into the redox reactivity of DOM and have implications for the application of fluorescence spectroscopy as a tool to characterize DOM.
通过平行因子分析（PARAFAC）对来自不同水生环境的379个溶解有机物（DOM）样品的激发-发射矩阵（EEMs）进行了建模。发现13个可能代表类似荧光部分基团的成分可以解释该数据集的变化。基于将其激发和发射光谱与模型醌的光谱进行比较，13个成分中的7个被鉴定为醌类。发现这些醌类荧光团在氧化还原状态和共轭程度上有所不同。基于与酪氨酸和色氨酸荧光光谱的比较，两个成分被鉴定为氨基酸类。其他四个成分尚未与任何一类分子相关联。在所分析的每个样品中，醌类荧光团约占荧光的50%，这表明醌类荧光团是天然水体中一种重要且普遍存在的荧光部分。此外，评估了醌类荧光团的分布作为环境和实验室氧化还原梯度的函数。在还原条件下，还原型醌类荧光团的贡献增加，同时氧化型醌类荧光团减少，这表明DOM荧光是醌类部分氧化还原状态的函数。最后，发现两种醌类荧光团的比例可以解释荧光指数的变化。这些结果为DOM的氧化还原反应性提供了新的见解，并对将荧光光谱作为表征DOM的工具的应用具有启示意义。
