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Dr. Andrew P. Ault
Postdoctoral Scholar
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Atmospheric Chemistry Research
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Marine Aerosols: The chemical and physical properties of marine aerosols play an important role in the Earth's climate, yet many of their fundamental chemical and physical properties are poorly understood. My research collaborating with the Center for Aerosol Impacts on the Environment (CAICE) is focused on increasing our understanding of marine aerosols using state-of-the-art microscopy and spectroscopy techniques.
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Urban Aerosols: Densely populated areas with large numbers of sources have extremely complicated interactions between aerosols and traces gases. Since inhaled aerosols have negative health effects, it important to understand the temporal and spatial patterns in aerosol physicochemical properties. At Iowa we are currently collaborating with Prof. Tom Peters in the Dept. of Occupational and Environmental Health to understand the properties of iron-containing particles, a subset of particles that may have enhanced negative health effects. Through the use of computer controlled scanning electron microscopy (CCSEM) with energy dispersive x-ray analysis (EDX) and elemental mapping via SEM-EDX the role of anthropogenic and natural iron-containing aerosols is being probed.
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Chemical Mixing State: The mixing of secondary species (i.e. nitrate, sulfate, and organic carbon) with primary particles (elemental carbon, sea salt, mineral dust) has important implications for the scattering of light through the Earth's atmosphere, yet is poorly understood. This occurs both through direct scattering and absorption by these particles and indirect scattering due to aerosol impacts on the lifetime and reflectivity of clouds. Microscopy and single particle mass spectrometry are complementary techniques ideally suited to study how these primary and secondary species are mixed. Developing methods to extract detailed single particle data from microscopy and combine it with the high statistics and real-time capabilities of single particle mass spectrometry is an important step towards reducing uncertainties in climate forcing due to aerosols.
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Heterogeneous Reactions on Particle Surfaces: The surfaces of mineral dust and other atmospheric particles have been a focus of the Grassian Group for years. These surfaces can serve and sinks and sources of trace gases in the atmosphere, such as NOx, N2O, HONO, H2SO4, through reactions that allow reactions to proceed that are not kinetically favorable in the purely gas or aqueous phase. We use different forms of infrared spectroscopy to probe these surface reactions on a variety of mineral and particle surfaces.