Laboratory Studies of the Chemical and Physical Properties of Internally Mixed Organic/Sulfate Aerosols
Margaret A. Tolbert
University of Colorado
CIRES, Campus Box 216
Boulder, CO 80309
303-492-3179
Fax 303-492-1149
tolbert@spot.colorado.edu
It has recently become apparent that tropospheric aerosols play an important role in the global climate system and may also be important for heterogeneous chemistry. While many studies of the impact of aerosols on chemistry and climate have focussed on sulfate particles, new studies have revealed that most sulfate particles in the troposphere are internally mixed with organics. The impact of these organics on the chemical and physical properties of the aerosol are not known. This makes inclusion of aerosols into chemistry and climate models speculative at best.
We are performing laboratory studies of mixed organic/sulfate aerosols. Specifically, we are studying the deliquescence, efflorescence and water uptake of mixed ammonium sulfate/organic aerosols. We perform studies using both water-soluble and water-insoluble organics internally mixed with ammonium sulfate. These studies are performed using a flow tube apparatus similar to that used in our previous studies of pure ammonium sulfate aerosols.
We are also performing laboratory studies of heterogeneous NOy chemistry on mixed ammonium sulfate/organic films. Currently, the only heterogeneous reaction to be widely included in global tropospheric models is the nighttime hydrolysis of N2O5. Because the rate of this reaction depends strongly on particle phase, it is essential to measure its rate on surfaces relevant to the troposphere. We are thus studying this reaction on ammonium sulfate films containing both water-soluble and water-insoluble organics. We also plan to study the uptake of NO2 and HNO3 on ammonium sulfate/organic films. Finally, we plan investigating reactions that may recycle HNO3 back to NOx on mixed organic/salt films.
For more information on this and other projects in the Tolbert group, please see http://cires.colorado.edu/people/tolbert.group/ The presentation made at the Atmospheric Sciences Program Annual meeting held in February 2001 can be found by clicking on "Professor Tolbert" and then on the "DOE Annual Meeting, Feb. 2001." Additional information can be found in the viewgraphs from a presentation at the Atmospheric Sciences Program Annual Meeting held in March 2002.