In this project supported by the Environmental Chemical Sciences (ECS) Program of the Division of Chemistry, Professor Ephraim Woods, III and his students at Colgate University will employ molecular probe methods and photo-ionization spectroscopy to characterize the surface environment of model sea spray aerosol particles. In particular, the research will focus on mixtures of sodium chloride with calcium and magnesium salts, which have been shown to be especially important to the surface chemistry, as well as investigating a variety of surfactant coatings as a model of the organic content of seawater. The work will also explore how the composition and morphology of these model particles affects their uptake of gas-phase polycyclic aromatic compounds (PAH's). The overarching goal of the experiments is to apply their methodologies to increasingly complex environments that better approximate real tropospheric aerosol particles, gaining insight into the factors that control the morphology and heterogeneous chemistry of these particles.
In addition to the implications of the research for atmospheric and environmental sciences, a significant broader impact of the proposed research is the training and development of undergraduates. Colgate University is a primarily undergraduate institution (PUI), and the PI's research group is composed entirely of undergraduates. Students appear as coauthors on all of the PI's publications arising from work at Colgate, and they present their work in seminars and national meetings. Professor Woods will participate in broad educational programs including public seminars sponsored by the Odyssey Center for Talented Youth, high school seminars sponsored by Colgate University, and a general education course for Colgate students entitled "Science, the News Media, and You."
Aerosol particles are solid or liquid particles that are small enough to stay suspended in the atmosphere for an appreciable amount of time, ranging from minutes to months. They are an important component of the atmosphere for a number of reasons, many related to their interaction with sunlight. Part of our work focused an important type of atmospheric particle: sea spray. We investigated the conditions of relative humidity under which sea spray particles would lose water and become solid. This relative humidity is known as the efflorescence point. We measured the efflorescence point for particles that are similar in composition to both nascent sea spray and particles that had undergone chemical transformations in the atmosphere. Using our data, we developed a mathematical model that predicts the efflorescence point for sea spray particles with various degrees of atmospheric "aging". The model helps determine the water content of sea spray aerosol particles, which is an important factor in their interaction with sunlight. We published this research in the following article: Woods III, E.; Heylman, K.D.; Gibson A. K.; Ashwell, A. P.; Rossi, S.R., "Effects of NOy Aging on the Dehydration Dynamics of Model Sea Spray Aerosol", J. Phys. Chem. A 2013, 117, 4214-4222. Tropospheric aerosol particles can also have adverse effect on human health. Some atmospheric constituents pose a greater danger when inhaled in the particle phase than in the gas phase, because the lifetime of those compound in the lungs is greater. A second branch our our work studied the efficiency with a specific class of pollutant molecules, polycyclic aromatic hydrocarbons (or PAH) attach to aerosol particles from the air. We developed a kinetic model that describes the partitioning of a specific PAH molecule, pyrene, between the gas phase and aerosol particles. We described this work in the following article: Woods III, E.;Yi, C.; Gerson, J.R.; Zaman, R. A., "Uptake of Pyrene by NaCl, NaNO3, and MgCl2 Aerosol Particles", J. Phys. Chem. A 2012, 116, 4137-4143. One broader impact of our work is the training of undergraduate researchers. Eleven undergraduate students worked in the lab over the course of this award, either during the academic year or during the summer months. Six of the eleven have done both. All the group members participated fully in the collection and analysis of data, and more mature students contribute to the planning of new experiments. Five of the students are coauthors on papers resulting from their work. Of the seven students who have already graduated, five are pursuing a Ph.D. in chemistry (or related fields), and three are preparing for a health science career. Alumni of the PI’s research group are coauthors on 16 papers resulting from their graduate work in the last three years, and one former member was awarded his Ph.D. from Harvard University during the term of this award. Another student presented a poster about his work at the American Chemical Society National Meeting in Dallas, TX.
