Solubility data requirements and new experimental methods in atmospheric aerosol research

The uptake of trace gases by atmospheric aerosols and cloud droplets plays a critical role in the atmospheric chemistry of both the troposphere and stratosphere. The transfer of gaseous species through the interfacial boundary layer and into the liquid phase involves a number of closely entwined processes, including: gas phase diffusion, mass accommodation, evaporation, Henry's law solubility, liquid phase diffusion, and, in some cases, chemical reaction at the gashquid interface or in the bulk liquid. In the atmosphere or in the laboratory these physical processes are seldom isolated and must be addressed together for many trace gases of interest. Mathematical parameterizations of trace gas uptake for cloud droplets and aerosols will be discussed. During the past decade several new experimental approaches have been developed to investigate trace gas uptake by aqueoudacid liquid and ice surfaces and to distinguish and quantify the physical and chemical parameters governing the uptake process. Here, particular emphasis is on three techniques: the droplet train/flow reactor, the bubble column reactor, and the bubble train reactor, all jointly developed in our laboratories. Examples of measured temperature dependent kinetic uptake parameters and their dependence on the measured Henry's law solubility will be presented for trace species important in stratospheric ozone depletion, tropospheric ozone production and tropospheric sulfate aerosol formation.