PDF(Pubmed)
Abstract：
Aromatic carbonyls have been mainly probed as photosensitizers for aqueous secondary organic aerosol (aqSOA) and light-absorbing organic aerosol (i.e., brown carbon or BrC) formation, but due to their organic nature, they can also undergo oxidation to form aqSOA and BrC. However, photochemical transformations of aromatic carbonyl photosensitizers, particularly in multicomponent systems, are understudied. This study explored aqSOA formation from the irradiation of aromatic carbonyl photosensitizers in mixed and single systems under cloud/fog conditions. Mixed systems consisting of phenolic carbonyls only (VL + ActSyr + SyrAld: vanillin [VL] + acetosyringone [ActSyr] + syringaldehyde [SyrAld]) and another composed of both nonphenolic and phenolic carbonyls (DMB + ActSyr + SyrAld: 3,4-dimethoxybenzaldehyde [DMB], a nonphenolic carbonyl, + ActSyr + SyrAld) were compared to single systems of VL (VL*) and DMB (DMB*), respectively. In mixed systems, the shorter lifetimes of VL and DMB indicate their diminished capacity to trigger the oxidation of other organic compounds (e.g., guaiacol [GUA], a noncarbonyl phenol). In contrast to the slow decay and minimal photoenhancement for DMB*, the rapid photodegradation and significant photoenhancement for VL* indicate efficient direct photosensitized oxidation (i.e., self-photosensitization). Relative to single systems, the increased oxidant availability promoted functionalization in VL + ActSyr + SyrAld and accelerated the conversion of early generation aqSOA in DMB + ActSyr + SyrAld. Moreover, the increased availability of oxidizable substrates countered by stronger oxidative capacity limited the contribution of mixed systems to aqSOA light absorption. This suggests a weaker radiative effect of BrC from mixed photosensitizer systems than BrC from single photosensitizer systems. Furthermore, more oxygenated and oxidized aqSOA was observed with increasing complexity of the reaction systems (e.g., VL* < VL + ActSyr + SyrAld < VL + ActSyr + SyrAld + GUA). This work offers new insights into aqSOA formation by emphasizing the dual role of organic photosensitizers as oxidant sources and oxidizable substrates.
摘要：
芳香族羰基化合物主要被用作水性二次有机气溶胶（aqSOA）和光吸收有机气溶胶的光敏剂（即，棕色碳或BrC)形成，但是由于它们的有机性质，它们还可以经历氧化以形成aqSOA和BrC。然而,芳香羰基光敏剂的光化学转化，特别是在多组分系统中，研究不足。这项研究探索了在云/雾条件下，混合和单一系统中芳族羰基光敏剂辐照的aqSOA形成。仅由酚醛羰基组成的混合系统（VLActSyrSyrAld：香兰素[VL]乙酰丁香酮[ActSyr]丁香醛[SyrAld]）和另一个由非酚醛和酚醛羰基组成的系统（DMBActSyrSyrAld：3,4-二甲氧基苯甲醛[DMB]，一种非酚羰基，+ActSyr+SyrAld)与VL(VL*)和DMB(DMB*)的单一系统进行比较，分别。在混合系统中，VL和DMB的较短寿命表明它们触发其他有机化合物氧化的能力减弱(例如，愈创木酚[GUA],非羰基苯酚）。与DMB*的缓慢衰减和最小的光增强相反，VL*的快速光降解和显着的光增强表明有效的直接光敏化氧化(即，自我光敏化)。相对于单一系统，氧化剂可用性的增加促进了VLActSyrSyrAld中的功能化，并加速了DMBActSyrSyrAld中早期aqSOA的转化。此外，可氧化底物的可用性增加与更强的氧化能力相反，限制了混合系统对aqSOA光吸收的贡献。这表明来自混合光敏剂系统的BrC的辐射效应比来自单一光敏剂系统的BrC更弱。此外，随着反应系统复杂性的增加，观察到更多的氧化和氧化的aqSOA(例如，VL*
