Reactive Oxygen Species and Chromophoric Dissolved Organic Matter Drive the Aquatic Photochemical Pathways and Photoproducts of 6PPD-quinone under Simulated High-Latitude Conditions
Reactive Oxygen Species and Chromophoric Dissolved Organic Matter Drive the Aquatic Photochemical Pathways and Photoproducts of 6PPD-quinone under Simulated High-Latitude Conditions
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DOI：
10.1021/acs.est.3c05742
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发表时间：
2023-11-30
影响因子：
11.4
通讯作者：
Tomco，Patrick L.
中科院分区：
文献类型：
--
作者：
Redman，Zachary C.;Begley，Jessica L.;Tomco，Patrick L.
在模拟高纬度地表沃茨典型光照条件下，研究了轮胎抗臭氧剂6 PPD的毒性转化产物6 PPD-醌（6 PPDQ，6 PPD-Q）的光化学降解途径。直接光化学降解导致6-PPDQ的半衰期从20 °C下的17.5小时到4 °C下的48小时内没有可观察到的降解。使用Cs+和Ar吹扫的激发三重态途径的敏化表明，6PPDQ相对于单重态不从三重态显著分解。然而，涉及活性氧（ROS）猝灭剂和敏化剂的过程的评估表明，单线态氧和羟基自由基显着有助于6PPDQ的降解。对天然湖泊沃茨中这些过程的调查表明，在20 °C时，直接光化学过程的衰减率没有差别。这表明，直接光化学降解将占主导地位，在温暖的沃茨，而间接的光化学途径将占主导地位，在寒冷的沃茨，涉及活性氧介导的发色溶解有机物（CDOM）。总体而言，6 PPDQ的水生光降解速率将受到环境因素（如光屏蔽和温度）对直接和间接光化学过程的复合效应的强烈影响。通过UHPLC-Orbitrap质谱鉴定转化产物，揭示了四个主要过程：（1）在ROS存在下醌环的氧化和裂解，（2）脱烷基化，（3）重排和（4）脱氨基。这些数据表明，在适当的条件下，6 PPDQ可以在凉爽的阳光照射的沃茨中光降解：t1/2= 17.4 h，无明显下降（直接）;t1/2= 5.2-11.2 h（间接，CDOM）。
The photochemical degradation pathways of 6PPD-quinone (6PPDQ, 6PPD-Q), a toxic transformation product of the tire antiozonant 6PPD, were determined under simulated sunlight conditions typical of high-latitude surface waters. Direct photochemical degradation resulted in 6PPDQ half-lives ranging from 17.5 h at 20 °C to no observable degradation over 48 h at 4 °C. Sensitization of excited triplet-state pathways using Cs+and Ar purging demonstrated that 6PPDQ does not decompose significantly from a triplet state relative to a singlet state. However, assessment of processes involving reactive oxygen species (ROS) quenchers and sensitizers indicated that singlet oxygen and hydroxyl radical do significantly contribute to the degradation of 6PPDQ. Investigation of these processes in natural lake waters indicated no difference in attenuation rates for direct photochemical processes at 20 °C. This suggests that direct photochemical degradation will dominate in warm waters, while indirect photochemical pathways will dominate in cold waters, involving ROS mediated by chromophoric dissolved organic matter (CDOM). Overall, the aquatic photodegradation rate of 6PPDQ will be strongly influenced by the compounding effects of environmental factors such as light screening and temperature on both direct and indirect photochemical processes. Transformation products were identified via UHPLC-Orbitrap mass spectrometry, revealing four major processes: (1) oxidation and cleavage of the quinone ring in the presence of ROS, (2) dealkylation, (3) rearrangement, and (4) deamination. These data indicate that 6PPDQ can photodegrade in cool, sunlit waters under the appropriate conditions:t1/2= 17.4 h tono observable decrease (direct);t1/2= 5.2–11.2 h (indirect, CDOM).