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Atmospheric Sciences - Graduate Student Presentations

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Monday, April 3, 2023, 4 pm– 5 pm

This is a past event.

Please join this week's Atmospheric Sciences Graduate Student presenters Shreya Joshi (ATM) and Thusitha Divisekara (Chemistry) for their in-person presentations Monday, April 3rd at 4 PM - Fisher Hall 101.


Effects of Cloud-Aerosol Interactions on Absorbing Aerosols
Shreya Joshi [Advisor: Dr. Claudio Mazzoleni]

Atmospheric light-absorbing aerosols, such as particles containing black carbon (BC), have a significant impact on the Earth’s radiation budget. These particles interact with solar radiation, scattering, and absorbing light, as well as with clouds. However, changes in the morphology of BC particles and their internal mixing with other materials, like organic coatings, can affect their ability to scatter and absorb light and interact with clouds. While previous studies have explored these processes, the effects of these interactions of BC with clouds have received less attention, and important questions remain open. Light-absorbing aerosol-cloud interactions is a project designed to investigate these processes in the Michigan Tech cloud chamber (the Pi-Chamber). We used BC and BC surrogates and coating surrogates to understand better the effects of aging on aerosol-cloud interactions. Cloud experiments employed a Pumped Counterflow Virtual Impactor to investigate changes in the morphology, optical and chemical properties of the BC particle aggregates and coated BC upon cloud activation and evaporation in the PI chamber. During these experiments, we study the changes in optical and cloud condensation nuclei properties of interstitial and residual particles compared to the aerosols before they are injected into the Pi chamber. We also studied the changes in the properties of liquid smoke upon activation, which was used as a surrogate for BC coating. We also developed a coating method to coat surrogate BC. We will provide an overview of the project and some preliminary results.



Liquid Smoke as a Surrogate for Biomass Combustion Organic Aerosol
Thusitha Divisekara (Chemistry) [Advisor: Dr. Lynn Mazzoleni]

Biomass burning organic aerosol (BBOA) significantly impacts the earth's climate and human health. Laboratory studies of BBOA frequently generate fresh smoke, however, it lacks the molecular complexity of ambient BBOA and is impractical for many laboratory situations. Commercial liquid smoke, a food flavor, produced by wood pyrolysis, offers a viable inexpensive alternative for BBOA that can be chemically altered. In this study, commercial liquid smoke was photo-oxidized in the presence of several aerosol relevant species. The molecular formulas obtained in each sample were compared with an ambient biomass combustion aerosol sample which included a 90% of tar ball composition by number. Using chemical additives and photo-oxidation we simulated the organic composition of 92% of the ambient BBOA sample with respect to total mass spectral abundance measured using ultrahigh resolution Fourier transform mass spectrometry. This confirms the successful use of commercial liquid smoke as a surrogate for biomass combustion organic aerosol and its transforming environmental products.

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