Department of Civil and Environmental Engineering, University of Wisconsin-Madison, 660 N. Park St., Madison, WI 53706, USA.
Environ Sci Process Impacts. 2017 Aug 16;19(8):1040-1050. doi: 10.1039/c7em00235a.
Excited triplet states of dissolved organic matter (DOM) are quantified directly with the species-specific probes trans,trans-hexadienoic acid (HDA) and 2,4,6-trimethylphenol (TMP), and indirectly with the singlet oxygen (O) probe furfuryl alcohol (FFA). Although previous work suggests that these probe compounds may be sensitive to solution conditions, including dissolved organic carbon concentration ([DOC]) and pH, and may quantify different DOM subpopulations, the probes have not been systematically compared. Therefore, we quantify the apparent photoreactivity of diverse environmental waters using HDA, TMP, and FFA. By conducting experiments under ambient [DOC] and pH, with standardized [DOC] and pH, and with solid phase extraction isolates, we demonstrate that much of the apparent dissimilarity in photochemical measurements is attributable to solution conditions, rather than intrinsic differences in DOM production. In general, apparent quantum yields (Φ ≥ Φ ≫ Φ) and pseudo-steady state concentrations ([O] > [DOM] > [DOM]) show consistent relationships in all waters under standardized conditions. However, intrinsic differences in DOM photoreactivity are apparent between DOM from diverse sources, as seen in the higher Φ and lower Φ of wastewater effluents compared with oligotrophic lakes. Additionally, while conflicting trends in photoreactivity are observed under ambient conditions, all probes observe quantum yields increasing from surface wetlands to terrestrially influenced waters to oligotrophic lakes under standardized conditions. This work elucidates how probe selection and solution conditions influence the apparent photoreactivity of environmental waters and confirms that DOM or O probes cannot be used interchangeably in waters that vary in [DOC], pH, or DOM source.
溶解有机物（DOM）的激发三重态直接用特有的探针反,反-己二烯酸（HDA）和 2,4,6-三甲基苯酚（TMP）进行量化，并通过单线态氧（O）探针糠醇（FFA）进行间接量化。虽然先前的工作表明这些探针化合物可能对溶液条件（包括溶解有机碳浓度[DOC]和 pH 值）敏感，并且可能量化不同的 DOM 亚群，但这些探针尚未进行系统比较。因此，我们使用 HDA、TMP 和 FFA 来量化各种环境水样的表观光反应性。通过在环境[DOC]和 pH 值下进行实验，以及在标准化[DOC]和 pH 值下进行实验，并用固相萃取分离物进行实验，我们证明了光化学测量中明显的差异很大程度上归因于溶液条件，而不是 DOM 产生的固有差异。一般来说，在所有标准化条件下的水样中，表观量子产率（Φ≥Φ＞Φ）和准稳态浓度（[O]＞[DOM]＞[DOM]）显示出一致的关系。然而，不同来源的 DOM 之间的光反应固有差异是明显的，如废水与贫营养湖泊相比具有更高的Φ和更低的Φ。此外，虽然在环境条件下观察到光反应性的冲突趋势，但所有探针在标准化条件下都观察到从湿地到受陆地影响的水到贫营养湖泊的量子产率增加。这项工作阐明了探针选择和溶液条件如何影响环境水样的表观光反应性，并证实了在[DOC]、pH 值或 DOM 来源不同的水样中，DOM 或 O 探针不能互换使用。
