The formation and evolution of secondary organic aerosol (SOA) is poorly understood, with current models based on the reversible gas-to-particle partitioning of semi-volatile organics failing to reproduce SOA observations. Recently, it has been suggested that aqueous-phase processing of atmospheric a-dicarbonyl compounds such as methylglyoxal (MG) could constitute an important source of SOA. The uptake of MG to aqueous particles is higher than expected due to the fact that its carbonyl moieties can hydrate to form diols, as well as the fact that MG can undergo aldol condensation reactions to form larger oligomers in solution. MG is known to be surface active but an improved description of its surface behaviour is crucial to understanding MG-SOA formation, in addition to understanding its gas-to-particle partitioning and cloud forming potential. Here, we will present results from our investigations of MG adsorption at the air-aqueous interface. This study employs a combined experimental and theoretical approach involving vibrational sum frequency generation spectroscopy (VSFS), surface tensiometry, bulk vibrational spectroscopies, molecular dynamics simulations, and density functional theory calculations in order to obtain molecular-level information about MG's surface adsorption, orientation and hydration state, in both the presence and absence of salts.

Methylglyoxal at the air-water interface

248th National Meeting (2014)

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