Date of Thesis

Spring 2025

Description

Aerosols, defined as suspensions of liquid or solid particles in a gaseous medium, are ubiquitous in both indoor and outdoor environments. They have significant impacts ranging from public health concerns to climate dynamics. In laboratory settings, aerosols are most often generated through a technique known as atomization. The atomization or nebulization is from dilute, aqueous solutions of various chemical compositions. This process typically produces a unimodal, lognormal particle size distribution with exceedingly rare exceptions. Colleagues in a different laboratory (Dr. Freedman’s Group at Pennsylvania State University), however, mentioned they observed a bimodal size distribution, a distribution with more than one distinct peak, in a system of ammonium sulfate (AS) and succinic acid (SA) combined aqueous solutions. They chose not to pursue this finding further and allowed Drs. Dutcher and Raymond’s research group at Bucknell University to explore it. We hypothesize the bimodal particle size distributions of AS and SA aerosol systems arise from acid/base interactions between AS-derived ammonium ions (NH₄⁺) and SA’s carboxylic acid groups, which enhance SA’s volatility. These interactions cause destabilized crystal structure from decreased coulombic forces. This causes an increase in structural disorder, and thus an increase in Gibbs free energy. This undergraduate honors thesis systematically investigates this hypothesis through a series of controlled laboratory experiments, utilizing advanced aerosol characterization techniques, including scanning mobility size analysis, to elucidate the evaporation and deposition mechanisms driving the bimodal particle size distributions. Implications of this mechanism include aerosol behavior in the atmosphere and an unforeseen source of contaminated laboratory equipment.

Keywords

aerosols, atmospheric, chemistry, chemical engineering

Access Type

Honors Thesis

Degree Type

Bachelor of Arts

Major

Chemistry

Second Major

Environmental Science

Minor, Emphasis, or Concentration

Women's and Gender Studies

First Advisor

Dabrina Dutcher

Second Advisor

Molly McGuire

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