Recent studies have shown that photochemical reactions occurring at the air–water interface are a source of volatile organic compounds (VOCs) to the atmosphere. We report here the photosensitized formation of VOCs from illuminated freshwater and seawater mimics containing nonanoic acid (NA) and/or Suwannee River natural organic matter (SRNOM). Under an atmosphere of air, the total blank-corrected steady-state concentration of VOCs formed from illuminated seawater coated with nonanoic acid is somewhat smaller than that formed from freshwater, suggesting some differences in photochemical pathways for the two substrates. The total blank-corrected steady-state concentration of VOCs more than doubles from both freshwater and seawater NA-coated surfaces under nitrogen compared to air. The addition of SRNOM as a photosensitizer induces some photochemistry from the seawater sample under air, but no chemistry is seen with freshwater or under nitrogen for either substrate. Adding SRNOM to the nonanoic acid-containing solutions roughly doubles the total steady-state concentration of VOCs emitted from both freshwater and seawater surfaces under air. The small differences in product formation for the two substrates imply some difference in the photochemical mechanisms operating in freshwater versus seawater, which may be due to the presence of halides and metals as well as pH differences between the two aqueous systems.

中文翻译：

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从光照海水和淡水表面光敏释放 VOC 的差异

最近的研究表明，发生在空气-水界面的光化学反应是大气中挥发性有机化合物 (VOC) 的来源。我们在此报告了从含有壬酸 (NA) 和/或 Suwannee 河天然有机物 (SRNOM) 的光照淡水和海水模拟物中光敏形成 VOC。在空气气氛下，由涂有壬酸的光照海水形成的 VOC 的总空白校正稳态浓度略小于淡水形成的 VOC，这表明两种基材的光化学途径存在一些差异。与空气相比，在氮气下的淡水和海水 NA 涂层表面的 VOC 总空白校正稳态浓度增加了一倍以上。添加 SRNOM 作为光敏剂后，空气中的海水样品会产生一些光化学反应，但在淡水或氮气下，两种底物均未观察到化学反应。将 SRNOM 添加到含壬酸的溶液中，可使淡水和海水表面在空气中排放的 VOC 的总稳态浓度大约增加一倍。两种底物的产物形成的微小差异意味着在淡水和海水中操作的光化学机制存在一些差异，这可能是由于卤化物和金属的存在以及两种水系统之间的 pH 值差异。将 SRNOM 添加到含壬酸的溶液中，可使淡水和海水表面在空气中排放的 VOC 的总稳态浓度大约增加一倍。两种底物的产物形成的微小差异意味着在淡水和海水中操作的光化学机制存在一些差异，这可能是由于卤化物和金属的存在以及两种水系统之间的 pH 值差异。将 SRNOM 添加到含壬酸的溶液中，可使淡水和海水表面在空气中排放的 VOC 的总稳态浓度大约增加一倍。两种底物的产物形成的微小差异意味着在淡水和海水中操作的光化学机制存在一些差异，这可能是由于卤化物和金属的存在以及两种水系统之间的 pH 值差异。