Date of Award
December 2024
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Mechanical Engineering
First Advisor
Hallie B. Chelmo
Abstract
Atmospheric aerosol processes regulate our climate through light scattering and cloud formation, which are governed by their physicochemical properties. Despite their climate impacts, important individual particle properties are difficult to measure at controlled temperatures relevant to the troposphere. This study presents the Low-Temperature Dual Balance Electrodynamic Trap (LT-DBET), a commercial DBET from MicroLev LLC, modified with a copper tubing network and a recirculating chiller to achieve temperature control as low as -5 ⁰C, which is suitable for heterogenous freezing using AgI. Aerosol microdroplet growth via water uptake is indirectly measured using a feedback loop, which continuously applies balancing voltages proportional to the droplet’s changing mass due to water uptake and release in response to varying relative humidity (RH) and temperature. Atmospherically relevant aerosol microdroplet solutes (NaCl, (NH4)2SO4, sucrose, and 2-methyltetrols) are studied. NaCl is observed to exhibit faster water uptake than (NH4)2SO4, and both electrolyte solutions favor dependence on RH for condensational growth over temperature. The presence of 2-methyltetrols in (NH4)2SO4 solution hampers water uptake compared to the single solute (NH4)2SO4 solution. Lowered temperatures decrease the rate of water uptake for sucrose solutions, suggesting that temperature influences organic hygroscopicity more than electrolytes. Heterogenous freezing with AgI is demonstrated at -4.6 ⁰C under controlled RH. This study demonstrates that the LT-DBET potentially provides a robust platform for investigating temperature dependence on other aerosol physicochemical properties, such as surface tension, viscosity, and hygroscopicity, which would improve our understanding of complex aerosol properties and their impact on climate. The sub-zero temperatures enable studies of processes such as ice nucleation and ice aggregation, using the dual balance.
Recommended Citation
Ojo, Victor Oyebamiji, "Low-Temperature Dual Balance Electrodynamic Trap (LT-DBET) For Single Microparticle Aerosol Studies" (2024). Theses and Dissertations. 6555.
https://commons.und.edu/theses/6555