Interfaces are ubiquitous in the atmosphere, from the tiny surfaces of aerosol particles miles above the ground to the extensive sea ice and snow pack of high latitudes. Aerosol particles can serve as miniature chemical reactors, taking up gases and converting them to different compounds, affecting the concentrations of trace species in the atmosphere. Furthermore, cloud droplets form on aerosol seed particles. Both aerosol and cloud particles absorb radiation and reflect it back to space and/or back to earth, and therefore play an important role in climate. In snow and ice covered regions, organic gases evolve from the snow and appear to affect ozone and mercury chemistry. Such snow-induced chemistry may also occur in cities that experience snowfall, leading to concerns for human health. Our research focuses on laboratory studies that elucidate chemistry and dynamics at atmospheric interfaces and near-interfaces. In particular, three projects are currently being developed. 1) In order to understand the composition of acidic sulfate aerosols, we are investigating the dissolution and speciation (fast reversible reactions) of volatile organic compounds in sulfate solutions. 2) The feasibility of cross-reactions (between different organic compounds) in such solutions under atmospheric conditions will be assessed in an ongoing collaboration with NASA Ames Research Center. 3) We will explore ice surfaces at atmospherically relevant temperature and pressure. We have measured the thickness of liquid brine at the surface of ice. We are developing methods to measure the properties of the ice surface, such as its ability to solvate, and its effective pH.
