Date of Thesis

Summer 2020

Description

Water soluble organic compounds (WSOCs) and secondary organic aerosols (SOAs) play a major role on climate. Exploring the water affinity of these organic compounds can enhance our understanding of their impact on cloud formation, and consequently, improve our current climate models. In this study, the subsaturated and supersaturated droplet growth of 1) four WSOCs: sucrose, levoglucosan, raffinose, and trehalose and 2) α-pinene and β-caryophyllene SOAs generated under four different conditions: dry, humid, seeded, and unseeded. The water uptake of these compounds, in collaboration with Pennsylvania State University and Maryland University, were evaluated using three different techniques: cloud condensation nuclei (CCN) counting, hygroscopic tandem differential mobility analyzer (HTDMA), and cavity ring-down spectroscopy (CRD). Using these techniques, the growth factor (Gf) and κ-values were reported, for each aerosol system, and evaluated within the context of theoretical values and current literature. We showed that the Gf and κ-values obtained from the three techniques were comparable within error. In addition, the hygroscopicity of WSOCs was revealed to be correlated with molecular weight. With regards to SOAs generated from α-pinene and β-caryophyllene, this study showed α-pinene SOAs had higher water affinity than β-caryophyllene SOAs, regardless of condition. This outcome highlights the importance of composition in association to hygroscopicity. No hygroscopic growth was seen in the SOA that was seeded with ammonium sulfate, despite its strong affinity for water. This could possibly be explained by the SOA forming a layer around the ammonium sulfate that prevents it from water uptake. This study allowed for a comprehensive analysis, through the use of three different techniques, of water uptake in WSCOs and SOAs aiding our understanding of these organic molecules and their impact on climate.


Keywords

Hygroscopicity, Kappa, CCNC, Aerosols, SOA, WSOC

Access Type

Masters Thesis (Bucknell Access Only)

Degree Type

Master of Science

Major

Chemical Engineering

First Advisor

Dabrina Dutcher

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