Greg Carmichael
Department of Chemical & Biochemical Engineering
Center for Global & Regional Environmental Research (CGRER)
University of Iowa
Iowa City, Iowa 52240
319-335-1399
Fax 319-335-3332
gcarmich@icaen.uiowa.edu

V. H. Grassian
University of Iowa

The primary objectives are to: (i) Evaluate the extent to which heterogeneous chemistry affects the photochemical oxidant cycle, particularly, tropospheric ozone formation; and (ii) conduct laboratory studies on heterogeneous reactions involving NO_x and VOCs on aerosol surfaces. These objectives are being pursued through a multidisciplinary approach that combines modeling and laboratory components. The modeling activities provide a means to rapidly evaluate the significance of the new laboratory findings and help guide the laboratory studies to those areas that have high sensitivity and importance. The laboratory studies provide a molecular level understanding of the mechanism of adsorption and reaction of atmospheric gases on aerosol surfaces and the identification of saturation effects and product species, which are then accounted for in new model formulations.

Laboratory Studies:

• continue to improve our efforts in measuring heterogeneous reaction kinetics on particle surfaces;
• investigate heterogeneous reactions of atmospheric gases, especially nitrogen oxides and VOCs, on mineral oxides, mineral dust and soot in greater detail as a function of relative humidity and temperature;
• determine the effects of aerosol aging on the heterogeneous reactivity;
• determine the effects of solar light (hv) and increased complexity of reactant mixtures (VOCs, NO_x and other trace atmospheric cases such as O₃ together);
• use microscopic techniques such as atomic force microscopy, transmission and scanning electron microscopy coupled with energy dispersive x-ray analysis to study changes in particle morphology;
• use transmission and scanning electron microscopy coupled with energy dispersive x-ray analysis for single particle analysis of authentic mineral dust samples.

Modeling Studies:

• continue to investigate the uptake of VOCs on aerosol surfaces;
• further evaluate the relative importance of various surfaces and reaction pathways;
• perform three-dimensional modeling analysis to provide a more realistic representation of heterogeneous interactions under a broad-range of chemical regimes (which vary both in space and time) and to test hypothesis in and aid the analysis of ACP field studies.

Some further information can be found in the viewgraphs from a presentation at the Atmospheric Sciences Program Annual Meeting held in February 2001. Additional information can be found in the viewgraphs from a presentation at the Atmospheric Sciences Program Annual Meeting held in March 2002.