Dissolved black carbon (DBC) with a hyperconjugated structure is ubiquitous in nature, and plays a crucial role in the migration and transformation of environmental contaminants due to its prominent properties of accepting electrons and sorption. However, little is known about the DBC-induced phototransformation of pharmaceutical and personal care products (PPCPs) in natural waters. Herein, the photodegradation kinetics of PPCPs were investigated in DBC solution under simulated solar irradiation and compared with those in Suwannee River natural organic matter (SRNOM) solution. The decay rates for the positively charged PPCPs (mean 1.484 ± 0.041 h^-1) were significantly higher than those for the negatively charged PPCPs (mean 0.014 ± 0.002 h^-1) in DBC solution due to the charge interaction. Moreover, the decay rates for the positively charged PPCPs in DBC solution were approximately 3–16 times of those in SRNOM solution due to the discrepant sorption and ability to produce bonded HO^•. Finally, a microheterogeneous photodegradation mechanism of HO^•-labile PPCPs in DBC solution involving the sorption and subsequent reaction with bonded HO^• in the DBC microphase was proposed, which was verified using isopropanol and isopropamide as selective HO^• scavengers. This work will provide useful insights into the photochemistry of DBC and also the DBC-involved phototransformation of PPCPs in aquatic environments.

中文翻译：

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医药和个人护理产品在溶解黑碳溶液中的间接光降解：羟基自由基微异质分布和吸附的作用


具有超共轭结构的溶解黑碳 （DBC） 在自然界中无处不在，由于其接受电子和吸附的突出特性，在环境污染物的迁移和转化中起着至关重要的作用。然而，人们对天然水中 DBC 诱导的药物和个人护理产品 （PPCP） 的光转化知之甚少。本文在模拟太阳照射下研究了 PPCPs 在 DBC 溶液中的光降解动力学，并与 Suwannee River 天然有机物 （SRNOM） 溶液中的光降解动力学进行了比较。由于电荷相互作用，在 DBC 溶液中，带正电荷的 PPCP 的衰减速率 （平均值 1.484 ± 0.041 ^h-1） 显著高于带负电荷的 PPCP （平均值 0.014 ± 0.002 ^h-1）。此外，由于存在差异的吸附和产生键合 HO^•的能力，DBC 溶液中带正电荷的 PPCP 的衰变速率约为 SRNOM 溶液中 3-16 倍。最后，提出了 DBC 溶液中 HO^•-不稳定 PPCPs 的微异质光降解机制，涉及在 DBC 微相中与键合 HO^• 的吸附和随后的反应，并使用异丙醇和异丙酰胺作为选择性 HO^• 清除剂进行了验证。这项工作将为 DBC 的光化学以及 PPCP 在水生环境中涉及 DBC 的光转化提供有用的见解。