Aqueous secondary organic aerosol (aqSOA) are among the most ubiquitous environmental systems and their impacts on the climate and overall environment can be far reaching. The secondary organics within aqSOA significantly influence their formation, structure, and characteristics. However, much of this influence remains poorly understood due lack of knowledge about the aqueous phase processing these organics undergo after partitioning into the aerosol phase. In particular, small atmospheric dicarbonyls that contribute to aqSOA formation can further react in the aqueous phase to form hydrated species and oligomers. The vast number of potential reaction pathways resulting from this means that the molecular nature of many of the organics at aerosol interfaces is largely unknown. A prime example of this is pyruvic acid (PA), which despite being better known for its biological significance, is also an abundant atmospheric secondary organic. Literature studies have revealed that in aqueous solutions, PA has two populated hydration species, the unhydrated alpha-keto acid form and a singly hydrated triol form. Previous studies by the Richmond lab have shown that that such an hydration equilibrium can be depth dependent and can potentially affect the interfacial properties of the system. Interestingly, the neat-PA systems revealed higher than anticipated surface activity and VSF spectra provided significant evidence of surface-active oligomeric species at the interface. The experimental VSF spectra contain strong responses arising from vibrational modes of functional groups not found in the monomeric forms, establishing the presence of oligomers. The presence of favorable oligomeric reaction products in the bulk are well documented for PA, but the relative surface affinity of such species has not been previously studied. As these larger molecular weight species can have substantial impacts on aerosol properties, these are significant findings for the atmospheric community.

Evidence for surface-active pyruvic acid oligomers products at the air-water interface: Combined experimental and computational VSFS study

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.