Effect of Heterogeneous Interactions on Optical, Hygroscopic, and Cloud Condensation Nuclei (CCN) Properties of Organic Atmospheric Aerosols

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A laboratory program will be carried out to systematically study how cloud condensation nucleating (CCN) and optical properties of organic aerosols of known morphology, size, and composition are affected by controlled transformations via oxidative reactions (using O3, NO3, and OH as oxidants), and by atmospherically relevant coatings formed by deposition. Experiments will be performed under conditions as close as possible to those found in the atmosphere. The experiments will utilize a laboratory apparatus that combines a controlled source of sized particles, a flow reactor, and an aerosol mass spectrometer (AMS) to measure the composition of aerosol particles and their morphology (size, density, shape, and fractal dimension). The instrument also measures optical scattering by aerosols and their hygroscopic properties. An instrument will be added to measure the CCN activity of aerosols. This will result in data on atmospheric oxidation reaction kinetics as a function of particle composition, structure, size, surface properties, and relative humidity, and on information on the effect of transformations on hygroscopicity, CCN activity and optical properties of model particles. This work will contribute to a better understanding of the role of aerosols in air quality and climate. The grant will support the participation of a graduate student.