Inter-University Instrumentation Centre (IUIC), Mahatma Gandhi University (MGU), Kottayam, 686560, Kerala, India.
School of Environmental Studies, Cochin University of Science & Technology (CUSAT), Kochi, 682022, Kerala, India.
Chemosphere. 2024 Aug;361:142484. doi: 10.1016/j.chemosphere.2024.142484. Epub 2024 Jun 1.
The natural phototransformation of organic pollutants in the environment depends on several water constituents, including inorganic ions, humic substances, and pH. However, the literature information concerning the influence of various water components on the amount of phototransformation and their impact on the development of various transformation products (TPs) is minimal. This study investigated the phototransformation of ofloxacin (OFL), a fluoroquinolone antibiotic, in the presence of various water components such as cations (K, Na, Ca, NH, Mg), anions (NO, SO, HCO, CO, PO), pH, and humic substances when exposed to natural sunlight. The study reveals that neutral pH levels (0.39374 min⁻) enhance the phototransformation of OFL in aquatic environments. Carbonate, among anions, shows the highest rate constant (2.89966 min⁻), significantly influencing OFL phototransformation, while all anions exhibit a notable impact. In aquatic environments, indirect phototransformation of OFL, driven by increased reactive oxygen species, expedites light-induced reactions, potentially enhancing OFL phototransformation. A clear difference was visible in the type of transformation products (TPs) formed during direct and indirect photolysis. The impact of indirect photolysis in the product profile was evaluated by examining the unique properties of TPs in direct and indirect photolysis. The primary transformation products were generated by oxidation and cleavage processes directed towards the ofloxacin piperazinyl, oxazine, and carboxyl groups. The toxicity assessment of TPs derived from OFL revealed that among the 26 identified TPs, TP3 (demethylated product), TP7 and TP8 (decarboxylated products), and TP15 (piperazine ring cleaved product) could potentially have some toxicological effects. These findings suggest that the phototransformation of OFL in the presence of various water components is necessary when assessing this antibiotic's environmental fate.
环境中有机污染物的自然光转化取决于几种水成分，包括无机离子、腐殖质和 pH 值。然而，关于各种水成分对光转化量的影响及其对各种转化产物 (TP) 发展的影响的文献信息很少。本研究调查了氟喹诺酮类抗生素氧氟沙星 (OFL) 在存在各种水成分（如阳离子 (K、Na、Ca、NH、Mg)、阴离子 (NO、SO、HCO、CO、PO)、pH 值和腐殖质时在自然阳光下的光转化。研究表明，中性 pH 值 (0.39374 min⁻) 增强了水生环境中 OFL 的光转化。在阴离子中，碳酸根表现出最高的速率常数 (2.89966 min⁻)，显著影响 OFL 的光转化，而所有阴离子都表现出显著的影响。在水生环境中，由活性氧增加驱动的间接光转化加速了光诱导反应，可能增强 OFL 的光转化。在直接和间接光解过程中形成的转化产物 (TP) 的类型明显不同。通过检查直接和间接光解中 TP 的独特性质，评估了间接光解对产物分布的影响。主要的转化产物是通过氧化和裂解过程生成的，针对 OFL 的哌嗪基、噁嗪基和羧基。从 OFL 衍生的 TP 的毒性评估表明，在所鉴定的 26 个 TP 中，TP3（去甲基产物）、TP7 和 TP8（脱羧产物）和 TP15（哌嗪环裂解产物）可能具有一些毒理学效应。这些发现表明，在评估这种抗生素的环境命运时，有必要考虑各种水成分存在下 OFL 的光转化。
