Evolution of aqSOA from the Air–Liquid Interfacial Photochemistry of Glyoxal and Hydroxyl Radicals
The effect of photochemical reaction time on glyoxal and hydrogen peroxide at the aqueous surface is investigated using in situ time-of-flights Secondary ion mass spectrometry (ToF-SIMS) enabled by a system for analysis at the liquid vacuum interface (SALVI) microreactor. Carboxylic acids (i.e., glyoxylic acid, oxalic acid, malonic acid, tartaric acid) are observed in the initial reactions (i.e., < 3 h.), more oligomers, cluster ions, and water clusters formed in the long ultraviolet (UV) aging period (i.e., = 3 h). Our results provide the direct evidence that water clusters could promote proton transfer and facilitate the formation of oligomers and cluster ions in the aqeous environment as photochemical aging continues. Furthermore, new chemical reaction pathways are proposed to expand existing understanding. The temporal evolution shows that oxidation products such as carboxylic acids reach a maximum in 1 h, whereas oligomer yields peak in 3 to 4 h. Glyoxal not only undergoes oxidation to form carboxylic acids (mainly occurred in the aging time less than 3 h), but also takes part in radical reactions, hemiacetal, oligomerization, polymerization, esterification, and anhydride reactions to form higher molecular weight species. Our in situ findings verify that the air-liquid interfacial reactions are important pathways for aqueous secondary organic aerosol (aqSOA) formation.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- Grant/Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1572949
- Report Number(s):
- PNNL-SA-135488; TRN: US2001150
- Journal Information:
- Environmental Science and Technology, Vol. 53, Issue 17; ISSN 0013-936X
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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