Date of Thesis

Spring 2023

Description

Most particles in the atmosphere take up water when exposed to increasing relative humidity (RH), and this behavior is described and quantized by a hygroscopicity parameter, kappa. Hygroscopic Tandem Differential Mobility Analysis (HTDMA) can be used to measure the physicochemical properties of aerosol particles and study phenomena that lead to size changes in submicron aerosol particles. Specifically, HTDMA measures how aerosol particles of different initial dry sizes grow or shrink when exposed to changing RH. HTDMA uses two differential mobility analyzers (DMAs) and a humidification system to make these measurements. One DMA selects a narrow size range of dry aerosol particles which are exposed to varying RH conditions. The second humidified DMA scans the particle size distribution after the particles have been conditioned by the humidification system. Scanning a wide range of particle sizes enables the second DMA to measure changes in size or growth factor (growth factor = humidified size/dry size) due to water uptake by the particles. The kappa can then be calculated from the growth factor. A new HTDMA system was designed for a set of RH conditions with user-friendly data-analyzing software. The software can determine the theoretical distribution of dry particles and accurately captures multiple peaks even when two peaks are close in diameter. The designed HTDMA system was calibrated by pure ammonium sulfate, a well-characterized salt that can be used to calibrate these systems. The hygroscopic behavior of a few pure amino acids and aerosol mixtures of amino acids and ammonium sulfate was investigated.

Keywords

aerosol, hygroscopicity, particles, environment, atmosphere

Access Type

Honors Thesis

Degree Type

Bachelor of Science in Chemical Engineering

Major

Chemical Engineering

Minor, Emphasis, or Concentration

Studio Art

First Advisor

Timothy M. Raymond

Second Advisor

Dabrina D Dutcher

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