Chirality in Aerosol Chemistry

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The Environmental Chemical Sciences (ECS) program of the Division of Chemistry, the Atmospheric Chemistry program of the Division of Atmospheric and Geospace Sciences and the Office of International Science and Engineering (OISE) will support the collaborative research program of Prof. Franz Geiger of Northwestern University and Prof. Scot Martin of Harvard University. Professor Geiger, Professor Martin, and their students will combine laboratory and field experiments to test the hypothesis that just like the two hands of one person can use string to produce chiral string figures, the oxidation of chiral biogenic volatile organic compounds can produce chiral organic material in atmospheric particles, with important effects on further chemical reactivity and physical properties. The two research groups will use an environmental chamber to synthesize and analyze chiral secondary organic material from mixes of chiral biogenic volatile organic compounds under well-controlled tropospherically relevant conditions. Climate-related properties of the newly formed secondary organic material will be investigated as a function of the stereoisomeric mix in the gas phase and correlated with the chemical composition and chirality of the organic material using nonlinear optical chemical imaging and nonlinear optical laser spectroscopy. Laboratory model studies will be benchmarked against chemical composition, size distribution, and origin of organic aerosol particles collected in the central Amazon Basin, which features pristine conditions with minimal anthropogenic input. Studying chiral aerosol chemistry has the potential to allow for the discovery of fundamentally new aerosol processes, which could help improve the prediction of radiative forcing of the climate system. Chiral atmospheric stereochemistry could also be developed towards a chiral marker to distinguish, for instance, burning fossil fuels from burning forests. This could potentially transform current methods for source apportionment of biogenic vs. anthropogenic emissions, which are commonly based on costly isotope analysis. The project will provide excellent training opportunities to students, including to members of under-represented groups, who wish to pursue a professional scientific career in an area of great societal importance.