The Influence of the Solvent Matrix on Physical Properties and Chemical Reactivity in Secondary Organic Aerosol Mimicking Solutions Containing Glyoxal and Ammonium Sulfate

The reactions between small α-dicabonyls, such as glyoxal, and amines, such as ammonium sulfate, represent important model systems with which to study the non-oxidative production of light absorbing compounds in secondary organic aerosols (SOAs). As a particle ages, it has access to hundreds or thousands of airborne chemicals, many of which can enter the particle phase and subsequently affect growth and physical properties. These compounds can also play a role in mediating (or hindering) the chemical transformations that take place in an aerosol aqueous environment, to produce imidazoles and other large and/or light-absorbing brown carbon components. We seek to understand the role small, atmospherically prevalent organic compounds have on the solvent matrix within which SOA-forming chemical reactions take place.

Our research focuses on understanding the effects of organic compounds containing functional groups such as alcohols, nitriles, and ketones on the chemistry and physical properties of bulk-phase SOA-mimicking solutions that contain glyoxal and ammonium sulfate. Results will be presented for solution matrices that contain short-chain alcohols (methanol, ethanol, propanols, and butanols), diols (propanediols and butanediols), acetonitrile, and acetone. We follow the production kinetics of light-absorbing compounds via UV-Vis measurements, bulk solution properties such as viscosity, and changes to intermolecular interactions within the solvent matrix through infrared spectroscopy (IR-ATR). Perturbations to the solvent environment have wide-ranging effects on the reaction between glyoxal and ammonium sulfate and will be presented, including changes to solution viscosity and reaction kinetics as functions of species and concentration added. System thermodynamics will also be discussed.