Fluoroquinolone (FQ) antibiotics are a group of contaminants of emerging environmental concern. In the present study, we demonstrated that norfloxacin (NORF) and ofloxacin (OFLO), two typical FQs, have photochemical reactivity analogous to chromophoric dissolved natural organic matter (DOM) in surface waters and can sensitize the photodegradation of isoproturon (IPU), a phenylurea herbicide. Such photochemical reactivity is ascribed to the quinolone chromophore that is excited to a triplet state (³FQ*) upon UV-A irradiation. ³FQ* further reacts with dissolved oxygen to give rise to singlet oxygen. ³FQ* steady-state concentrations of 6.72 × 10⁻¹⁵ and 1.27 × 10⁻¹⁵ M were measured in 10 μM NORF and OFLO solutions, respectively, under UV_365nm irradiation. The degradation of IPU was due to the reaction with ³FQ*, with bimolecular rate constants of 6.07 × 10⁹ and 1.51 × 10¹⁰ for ³NORF* and ³OFLO*, respectively. Intriguingly, NORF and OFLO per se were unstable and photolyzed during UV-A irradiation, but the photochemical reactivities of the solutions were not lost accordingly. High-resolution mass spectrometry analysis revealed that defluorination and piperazine moiety oxidation were the main photolysis pathways, while the core quinolone structure remained intact. Thus, the photolysis products largely inherited the photochemical reactivity of the parent compounds. Since all FQs share the same quinolone structure, similar photochemical reactivity is expected. The presence of FQs in surface water would affect the transformation and fate of coexisting compounds. To the best of our knowledge, this is the first study examining the environmental behavior of FQs as photosensitizers. The findings greatly advance the understandings of the influence of FQs in aquatic environment.

氟喹诺酮（FQ）抗生素是一类正在引起环境问题的污染物。在本研究中，我们证明了诺氟沙星（NORF）和氧氟沙星（OFLO）这两个典型的FQ具有与表层水中发色团溶解的天然有机物（DOM）类似的光化学反应性，并且可以使异丙基异养酮（IPU）的光降解敏感。苯脲除草剂。这种光化学反应性归因于喹诺酮生色团，该喹诺酮生色团在UV-A照射下被激发成三重态（³ FQ *）。³ FQ *进一步与溶解的氧反应生成单线态氧。³ FQ *稳态浓度为6.72×10 ^-15和1.27×10 ^-15 m的在10μMNORF和OFLO溶液，分别测得的，在UV下_365nm的照射。IPU的降解归因于与³ FQ *的反应，对于^3个NORF *和^3个OFLO * ，双分子速率常数分别为6.07×10 ⁹和1.51×10 ¹⁰。有趣的是，NORF和OFLO本身在UV-A照射过程中，它们不稳定并被光解，但是溶液的光化学反应性并没有因此而损失。高分辨率质谱分析表明，脱氟和哌嗪部分氧化是主要的光解途径，而核心喹诺酮结构保持完整。因此，光解产物很大程度上继承了母体化合物的光化学反应性。由于所有FQ都具有相同的喹诺酮结构，因此预计会有类似的光化学反应性。FQs在地表水中的存在会影响共存化合物的转化和命运。据我们所知，这是首次研究FQs作为光敏剂的环境行为。这些发现极大地促进了对FQs在水生环境中影响的理解。