Environmental Science and Engineering Seminar

Within atmospheric aerosols, multiphase chemical reactions and complex physicochemical properties play a critical role in their ultimate climate and human health effects at a global scale. The interactions of aerosols with solar radiation via absorption and scattering, water vapor that leads to cloud droplet/crystal formation, and our bodies after inhalation, all depend on individual particles chemical properties and behavior, which can be lost when particles are lumped together in ensemble averages. Additionally, particles can range in viscosity from water to oil to amorphous solids (e.g., marble) and exhibit complex morphologies and internal structures, impacting diffusion rates and reaction timescales. Thus, understanding the nanoscale processes that determine the extent and form of aerosol impacts requires detailed measurements at the individual particle level. We focus on using analytical/physical chemistry characterization techniques to probe individual particles ranging in composition from pure, synthesized compounds to chamber generated aerosol to aerosols from the ambient atmosphere. In this seminar, examples of our approach using the aerosol phase chemistry of isoprene oxidation products across that range of complexity will be explored as a function of acidity, cation, relative humidity, and oxidant exposure explored using spectroscopy, microscopy, mass spectrometry, and materials characterization techniques. We identify underappreciated chemical factors that contribute to or limit secondary aerosol formation. In addition, unexpected complexity resulting from continuing chemistry after SOA formation will be shown and the implications for the atmosphere broadly will be discussed.