Department of Environmental Science & Engineering, Fudan University, Shanghai 200433, P. R. China.
Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, P. R. China.
Environ Sci Technol. 2020 Mar 17;54(6):3199-3208. doi: 10.1021/acs.est.9b06018. Epub 2020 Mar 2.
The photochemical formation and decay rates of superoxide radical ions (O) in irradiated dissolved organic matter (DOM) solutions were directly determined by the chemiluminescent method. Under irradiation, uncatalyzed and catalyzed O dismutation account for ∼25% of the total O degradation in air-saturated DOM solutions. Light-induced O loss, which does not produce HO, was observed. Both the O photochemical formation and light-induced loss rates are positively correlated with the electron-donating capacities of the DOM, suggesting that phenolic moieties play a dual role in the photochemical behavior of O. In air-saturated conditions, the O quantum yields of 12 DOM solutions varied in a narrow range, from 1.8 to 3.3‰, and the average was (2.4 ± 0.5)‰. The quantum yield of O nonlinearly increased with increasing dissolved oxygen concentration. Therefore, the quantum yield of one-electron reducing intermediates, the precursor of O, was calculated as (5.0 ± 0.4)‰. High-energy triplets (DOM*, > 200 kJ mol) and O quenching experiments indicate that DOM* and O play minor roles in O production. These results are useful for predicting the photochemical formation and decay of O in sunlit surface waters.
辐照溶解有机物（DOM）溶液中超氧自由基离子（O）的光化学形成和衰减速率可通过化学发光法直接测定。辐照下，非催化和催化的 O 歧化反应占空气饱和 DOM 溶液中总 O 降解的约 25%。观察到了不产生 HO 的光诱导 O 损失。O 的光化学形成和光诱导损失速率均与 DOM 的供电子能力呈正相关，表明酚基在 O 的光化学行为中起双重作用。在空气饱和条件下，12 种 DOM 溶液的 O 量子产率在很窄的范围内变化，从 1.8 到 3.3‰，平均值为（2.4±0.5）‰。O 的量子产率随溶解氧浓度的增加呈非线性增加。因此，O 的前体一电子还原中间体的量子产率计算为（5.0±0.4）‰。高能三重态（DOM*，>200kJmol）和 O 猝灭实验表明，DOM*和 O 在 O 生成中作用较小。这些结果有助于预测阳光照表面水中 O 的光化学形成和衰减。
