化学
氧化剂
激发态
量子产额
光化学
溶解有机碳
激进的
单线态氧
有色溶解有机物
水溶液
三重态
有机质
分析化学(期刊)
氧气
环境化学
分子
原子物理学
物理化学
荧光
有机化学
浮游植物
量子力学
营养物
物理
作者
Richie Kaur,Cort Anastasio
标识
DOI:10.1021/acs.est.7b06699
摘要
Photooxidants chemically transform organic compounds in atmospheric drops and particles. Photooxidants such as hydroxyl radical (•OH) and singlet molecular oxygen (1O2*) have been characterized in cloud and fog drops, but there are no measurements of the triplet excited states of organic matter (3C*). These “triplets”, which are formed from excitation of chromophoric dissolved organic matter (CDOM), i.e., brown carbon, are difficult to measure because they are a mixture of species instead of a single entity. Here, we use a two-probe technique to measure the steady-state concentrations, rates of photoformation, and quantum yields of oxidizing triplet states during simulated-sunlight illumination of bulk fog waters. Concentrations of 3C* are (0.70–15) × 10–14 M with an average (±σ) value of 5.0 (±5.1) × 10–14 M. The average 3C* photoformation rate is 130 (±130) μM h–1, while the average quantum yield is 3.7 (±4.5)%. Based on our previous measurements of •OH and 1O2* in the same fog samples, the ratio of the steady-state concentrations for 1O2*:3C*:•OH is approximately 3:1:0.04, respectively. At our measured concentrations, triplet excited states can be the dominant aqueous oxidants for organic compounds such as phenols from biomass combustion.
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