Chemistry and Photochemistry of Pyruvic Acid at the Air-Water Interface.

Interfacial regions are unique chemical reaction environments that can promote chemistry not found elsewhere. The air-water interface is ubiquitous in the natural environment in the form of ocean surfaces and aqueous atmospheric aerosols. Here we investigate the chemistry and photochemistry of pyruvic acid (PA), a common environmental species, at the air-water interface and compare it to its aqueous bulk chemistry using two different experimental setups: (1) a Langmuir-Blodgett trough, which models natural water surfaces and provides a direct comparison between the two reaction environments, and (2) an atmospheric simulation chamber (CESAM) to monitor the chemical processing of nebulized aqueous PA droplets. The results show that surface chemistry leads to substantial oligomer formation. The sequence begins with the condensation of lactic acid (LA), formed at the surface, with itself and with pyruvic acid, and LA + LA - H