Abstract：
Phototransformation is important for the fate in surface waters of the pharmaceuticals diclofenac (DIC) and naproxen (NAP) and for clofibric acid (CLO), a metabolite of the drug clofibrate. The goal of this paper is to provide an overview of the prevailing photochemical processes, which these compounds undergo in the different conditions found in freshwater environments. The modelled photochemical half-life times of NAP and DIC range from a few days to some months, depending on water conditions (chemistry and depth) and on the season. The model indicates that direct photolysis is the dominant degradation pathway of DIC and NAP in sunlit surface waters, and potentially toxic cyclic amides were detected as intermediates of DIC direct phototransformation. With modelled half-life times in the month-year range, CLO is predicted to be more photostable than DIC or NAP and to be degraded mainly by reaction with the •OH radical and with the triplet states of chromophoric dissolved organic matter (3CDOM*). The CLO intermediates arising from these processes and detected in this study (hydroquinone and 4-chlorophenol) are, respectively, a chronic toxicant to aquatic organisms and a possible carcinogen for humans. Hydroquinone is formed with only ∼5% yield upon CLO triplet-sensitised transformation, but it is highly toxic for algae and crustaceans. In contrast, the formation yield of 4-chlorophenol reaches ∼50% upon triplet sensitisation and ∼10% by ·OH reaction. The comparison of model predictions with field data from a previous study yielded a very good agreement in the case of DIC and, when using 4-carboxybenzophenone as proxy for triplet sensitisation by CDOM, a good agreement was found for CLO as well. In the case of NAP, the comparison with field data suggests that its direct photolysis quantum yield approaches or even falls below the lower range of literature values.
摘要：
光转化对于药物双氯芬酸（DIC）和萘普生（NAP）的地表水中的命运以及氯贝酸（CLO）很重要，氯贝特药物的代谢产物。本文的目的是提供流行的光化学过程的概述，这些化合物在淡水环境中的不同条件下经历。NAP和DIC的模拟光化学半衰期从几天到几个月不等，取决于水的条件（化学和深度）和季节。该模型表明，直接光解是阳光照射的地表水中DIC和NAP的主要降解途径。和潜在的毒性环状酰胺被检测为DIC直接光转化的中间体。模拟的半衰期在月-年范围内，预计CLO比DIC或NAP更具光稳定性，并且主要通过与•OH自由基和发色溶解有机物（3CDOM*）的三重态反应而降解。从这些过程中产生并在本研究中检测到的CLO中间体（氢醌和4-氯酚）是，分别,对水生生物的慢性毒物和对人类可能的致癌物。氢醌在CLO三重态敏化转化时仅形成~5%的产率，但它对藻类和甲壳类动物有很强的毒性。相比之下,三重态敏化时，4-氯苯酚的形成产率达到~50%，·OH反应达到~10%。在DIC的情况下，模型预测与先前研究的现场数据的比较得出了非常好的一致性，当使用4-羧基二苯甲酮作为CDOM三重态敏化的代表时，CLO也找到了一个很好的协议。就国家行动方案而言，与现场数据的比较表明，其直接光解量子产率接近甚至低于文献值的较低范围。
