The present study aimed to investigate the changes in the chemical composition, and in the optical and photooxidant properties of Suwannee River Natural Organic Matter (SRNOM) induced by UVC (254 nm) treatment. The extent of the photodegradation was first assessed by UV–visible/fluorescence spectroscopies and organic carbon analysis. An in-depth investigation of the chemical changes was also conducted using liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry after derivatizations. A series of mono, di and tricarbonyls and mono and dicarboxylic acids in C₁C₆ were identified in samples irradiated from 1 to 4 h. After 3 h of irradiation, carbonyls accounted for 46% of the organic carbon remaining in solution whereas carboxylic acids represented about 2%. Then, we investigated the modifications of the photooxidant properties of SRNOM induced by these chemical changes. At 254 nm, UVC pre-irradiated SRNOM photodegraded glyphosate 29 times faster than original SRNOM and the reaction was fully inhibited by 2-propanol (5 × 10⁻³ M). This enhanced photooxidant properties at 254 nm toward glyphosate was therefore reasonably due to •OH radicals formation, as confirmed by additional ESR measurements. A mechanism involving a chain reaction was proposed based on independent experiments conducted on carbonyl compounds, particularly pyruvic acid and acetone. The findings of this study show that UVC pre-treatment of NOM can enhance the removal of water pollutants and suggests a possible integration of a NOM pre-activation step in engineered water treatment sytems.

本研究旨在研究由 UVC (254 nm) 处理引起的 Suwannee River 天然有机物 (SRNOM) 化学成分的变化以及光学和光氧化特性的变化。光降解的程度首先通过紫外-可见光/荧光光谱和有机碳分析进行评估。衍生化后还使用液相色谱-质谱法和气相色谱-质谱法对化学变化进行了深入研究。C ₁ C _{6 中的}一系列单、二和三羰基以及单和二羧酸在照射 1 至 4 小时的样品中鉴定出。照射 3 小时后，羰基化合物占溶液中剩余有机碳的 46%，而羧酸占约 2%。然后，我们研究了由这些化学变化引起的 SRNOM 光氧化特性的改变。在 254 nm 处，UVC 预辐照 SRNOM 光降解草甘膦的速度是原始 SRNOM 的 29 倍，反应完全被 2-丙醇（5 × 10 ^-3 米）。因此，这种在 254 nm 处对草甘膦增强的光氧化性能是由于形成了 •OH 自由基，这在额外的 ESR 测量中得到证实。基于对羰基化合物，特别是丙酮酸和丙酮进行的独立实验，提出了涉及链式反应的机制。这项研究的结果表明，NOM 的 UVC 预处理可以增强水污染物的去除，并表明可能将 NOM 预活化步骤集成到工程水处理系统中。