Fluorescence spectroscopy reveals ubiquitous presence of oxidized and reduced quinones in dissolved organic matter
Fluorescence spectroscopy reveals ubiquitous presence of oxidized and reduced quinones in dissolved organic matter
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DOI：
10.1021/es0506962
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发表时间：
2005-11-01
影响因子：
11.4
通讯作者：
McKnight, DM
中科院分区：
文献类型：
--
作者：
Cory, RM;McKnight, DM
采用平行因子分析法（PARAFAC）对379个不同水环境中溶解有机物（DOM）样品的激发-发射矩阵（EEMs）进行了模拟。发现可能代表类似荧光部分的组的十三个组分来解释该数据集中的变化。根据它们的激发和发射光谱与模型醌的光谱的比较，13个组分中的7个被鉴定为醌样。这些醌类荧光团被发现在氧化还原状态和共轭程度的变化。基于与酪氨酸和色氨酸荧光光谱的比较，将两种组分鉴定为氨基酸样。其他四种成分还没有与任何类型的分子相关联。醌类荧光团占每个分析样品的荧光的约50%，表明醌类荧光团是一种重要的和普遍存在的荧光部分，在天然沃茨中。此外，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进行了评价。在还原条件下，减少的醌类荧光团的贡献增加的同时，在氧化的醌类荧光团的减少，表明DOM荧光是醌类部分的氧化还原状态的函数。最后，发现两个醌类荧光团的比率来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，并对荧光光谱作为表征DOM的工具的应用产生了影响。
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 concurrent with 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.