Investigating the light-absorbing carbonaceous aerosol lineage: The brown carbon - black carbon continuum

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Over the past two decades, it has been established that black carbon (BC), also known as soot, is a significant light absorber with a climate-warming effect potentially second only to carbon dioxide. However, the climate forcing effect of BC is subject to large uncertainties, and resolution is crucial for constraining the climate sensitivity of combustion carbon. One of the major contributors to this uncertainty is the limited understanding of light absorption by BrC, which is often co-emitted with BC, thus coupling the effects of the two. This project will promote graduate and undergraduate research by constituting a major component of a PhD dissertation and involving undergraduate students in the project. Third, the project will involve an outreach component through the involvement in workshops led by the UGA College of Education aiming at creating spaces where bilingual (Hispanic) middle- and high-school students, their parents and teachers, and researchers can engage in science-learning (STEM) activities. BrC light-absorption properties (the most relevant properties for climate calculations) are poorly constrained, with reported values varying over two orders of magnitude. The source of this variability is largely unknown, posing major challenges to representing BrC in climate models. This work will build on advances in BC formation research in the field of combustion science and recent findings by the PI to understand the effects of BrC. The main hypothesis of the project is that a major fraction of BrC is comprised of organic precursors of BC, and that BrC exhibits a continuum of light-absorption properties that can be correlated with molecular mass and volatility.