Atmospheric chromophoric organic matter (COM) plays a fundamental role in photochemistry and aerosol aging. However, the effects of photodegradation on chemical components and photochemical reactivity of COM remain unresolved. Here, we report the potential effects of photodegradation on carbon contents, optical properties, fluorophore components and photochemical reactivity in aerosol. After 7 d of photodegradation, fluorescent intensity and the absorption coefficient of COM decrease by 71.4 % and 32.0 %, respectively. Photodegradation makes a difference to the chemical component of chromophore and the degree of aerosol aging. Low-oxidation humic-like substance (HULIS) is converted into high-oxidation HULIS due to photooxidation. Photodegradation also changes the photochemical reactivity. The generation of triplet-state COM (³COM^*) decreases slightly in ambient particulate matter (ambient PM) but increases in primary organic aerosol (POA) following photodegradation. The results highlight that the opposite effect of photodegradation on photochemical reactivity in POA and ambient PM. However, the generation of singlet-oxygen (¹O₂) decreases obviously in POA and ambient PM, which could be attributed to photodegradation of precursors of ¹O₂. The combination of optical property, chemical component and reactive oxygen species has an important impact on the air quality. The new insights on COM photodegradation in aerosol reinforce the importance of studying dissolved organic matter (DOM) related with the photochemistry and aerosol aging.

中文翻译：

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大气生色团的光降解：氧化态和光化学反应性的变化

大气发色有机物 (COM) 在光化学和气溶胶老化中起着重要作用。然而，光降解对 COM 的化学成分和光化学反应性的影响仍未得到解决。在这里，我们报告了光降解对气溶胶中碳含量、光学性质、荧光团成分和光化学反应性的潜在影响。光降解7  d后，COM的荧光强度和吸收系数分别下降71.4  %和32.0  %， 分别。光降解对发色团的化学成分和气溶胶老化程度产生影响。低氧化类腐殖质（HULIS）由于光氧化作用转化为高氧化类腐殖质。光降解也会改变光化学反应性。三重态 COM ( ³ COM ^* ) 在环境颗粒物 (环境 PM) 中的生成略有减少，但在光降解后主要有机气溶胶 (POA) 的生成增加。结果强调了光降解对 POA 和环境 PM 中光化学反应性的相反影响。然而，单线态氧（¹ O ₂) 在 POA 和环境 PM 中明显降低，这可能归因于¹ O ₂前驱体的光降解。光学性质、化学成分和活性氧的组合对空气质量有重要影响。关于气溶胶中 COM 光降解的新见解加强了研究与光化学和气溶胶老化相关的溶解有机物 (DOM) 的重要性。