AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Determination of Setschenow Constants of Organic Compounds in Ammonium Sulfate Solutions and the Salt Effect on Air-Water Partitioning
CHEN WANG, Ying Duan Lei, Frank Wania, University of Toronto
Abstract Number: 678 Working Group: Aerosol Chemistry
Abstract The presence of salts significantly influences the partitioning behavior of organic compounds between the gas phase and environmentally relevant aqueous phases such as sea water and aqueous aerosol. The change in the activity of organic chemicals in aqueous solutions caused by inorganic salts is quantified with empirical Setschenow constants. Atmospheric water (cloud, fog and aqueous aerosol) contains a mixture of various inorganic salts, of which ammonium sulfate is often the most abundant. As a result, Setschenow constants for ammonium sulfate are required for accurate atmospheric phase distribution assessments of organic compounds, including those implicated in secondary organic aerosol (SOA) formation. However, Setschenow constants for ammonium sulfate are available only for a very limited number of chemicals. One reason for this lack of data might be that their determination traditionally requires highly precise measurements of aqueous solubility at different ionic strength. In the present study, the suitability of three methods for determining Setschenow constants in a relatively simple, reliable and inexpensive way is explored. They are a shared headspace passive dosing method, a negligible-depletion solid phase micro-extraction (SPME) technique, and a headspace gas chromatography method. The objective of this project is to make measurements of the Setschenow coefficients for diverse organic compounds (especially SOA relevant substances) in ammonium sulfate solutions and then develop a predictive model for estimating Setschenow coefficients from chemical structure.