Nanoparticulate atmospheric soot particles are complex in their shape, size and chemical composition. They can be variably observed as fractal aggregates composed of elemental carbon (EC- in graphitic or graphene structures), or organic carbon compounds (OC - hydrocarbons with oxidized or other attached heteroatom moieties). Other aerosol materials potentially embed or enmesh, in either internal or external mixing states, such soot particles as they age in the ambient atmosphere. Our limited knowledge of relationships between soot mixing state, soot morphology, and soot optical properties, remains a major source of uncertainty in evaluating the optical and radiative contribution of carbonaceous aerosols to direct radiative) climate forcing. Researchers will undertake a series of combined laboratory and computational studies to better characterize the formation of soot particles with different mixing states, and to investigate associated structural and optical properties in relation to the particle initial state and aerosol aging.
Mixing states and morphology of soot aggregates will be determined from a combination of mass-mobility measurements and environmental scanning electron microscopy imaging. Optical calculations constrained by the experimentally measured mixing states and morphologies will provide a closure with directly determined light absorption and scattering by this range of carbonaceous soot.
One broader impact of this work will be the promotion of collaboration between faculty at a PhD-granting and a primarily undergraduate teaching university.