DEVELOPMENT AND EVALUATION OF SAMPLING AND ANALYTICAL TECHNIQUES FOR INVESTIGATING AIR-WATER EXCHANGE OF CHEMICALS

Gas exchange across the air-water interface is one of the three major transport pathways for atmospheric inputs of organic pollutants in the Great Lakes. It is essential to advance our knowledge of the air-wate r exchange processes to improve our understanding of the environmental pathways and fate of a variety of persistent and toxic chemicals. Two complementary prototype devices were developed and tested for direct characterization of air-water exchange processes. One was a sparger de vice which was used to determine the (truly) dissolved concentration o f a given chemical in water, and hence its potential for diffusive tra nsfer at the air-water interface. The other was a flux chamber with wh ich the chemical mass transfer rate from the water surface to the atmo sphere (or vice versa) was determined. Ambient air and air from the sp arger and flux chamber were collected/concentrated on multi-bed adsorb ent tubes, followed by thermal desorption GC-MS analysis. Collected wa ter samples were filtered and then concentrated on adsorbent tubes whi ch were subject to similar thermal desorption GC-MS analytical procedu res. The combination of these techniques provides a useful means for t he estimation of the mass transfer rates of chemicals across the air-w ater interface.