Photochemical reactions contribute to the attenuation and transformation of pharmaceuticals and personal care products (PPCPs) in surface natural waters. Nevertheless, effects of DOM and halogen ions on phototransformation of PPCPs remain elusive. This work selected disparate PPCPs as target pollutants to investigate their aquatic phototransformation processes. Results show that PPCPs containing multiple electron-donating groups (–OH, –NH, –OR, etc.) are more reactive with photochemically produced reactive intermediates (PPRIs) such as triplet DOM (DOM*), singlet oxygen (O), and reactive halogen species (RHSs), relative to PPCPs containing electron-withdrawing groups (–NOR, –COOR, –OCR, etc.). The generation of RHSs as a result of the coexistance of DOM and halide ions changed the contribution of PPRIs to the photochemical conversion of PPCPs during their migration from fresh water to seawater. For PPCPs (AMP, SMZ, PN, NOR, CIP, etc) with highly reactive groups toward RHSs, the generation of RHSs facilitated their photolysis in halide ion-rich waters, where Cl plays a critical role in the photochemical transformation of PPCPs. Density functional theory (DFT) calculations showed that single electron transfer and H-abstraction are main reaction pathways of RHSs with the PPCPs. These results demonstate the irreplaceable roles of PPRIs and revealing the underlying reaction mechanisms during the phototransformation of PPCPs, which contributes to a better understanding of the environmental behaviors of PPCPs in complex aquatic environments.

中文翻译：

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水生环境中溶解有机物和卤素离子对药品和个人护理产品光转化的影响

光化学反应有助于药物和个人护理产品 (PPCP) 在地表天然水中的衰减和转化。然而，DOM 和卤素离子对 PPCP 光转化的影响仍然难以捉摸。这项工作选择不同的 PPCP 作为目标污染物来研究它们的水生光转化过程。结果表明，含有多个给电子基团（–OH、–NH、–OR 等）的 PPCP 与光化学产生的反应中间体（PPRI）如三线态 DOM (DOM*)、单线态氧 (O) 和活性卤素物质 (RHS)，相对于含有吸电子基团（–NOR、–COOR、–OCR 等）的 PPCP。 DOM 和卤离子共存而产生的 RHS 改变了 PPRI 对 PPCP 从淡水迁移到海水过程中光化学转化的贡献。对于具有对 RHS 高反应性基团的 PPCP（AMP、SMZ、PN、NOR、CIP 等），RHS 的生成促进了它们在富含卤离子的水中的光解，其中 Cl 在 PPCP 的光化学转化中起着关键作用。密度泛函理论（DFT）计算表明，单电子转移和H-抽象是RHSs与PPCPs的主要反应途径。这些结果证明了PPRI不可替代的作用，并揭示了PPCP光转化过程中的潜在反应机制，有助于更好地理解PPCP在复杂水生环境中的环境行为。