(70h) Investigation of Hygroscopic and Morphological Properties of Atmospheric Aerosols

The first objective of this research was to examine the hygroscopic and morphological nature of various substances through the use of an Environmental Scanning Electron Microscope (ESEM). The hygroscopic growth and changes in morphology for pure-component aerosols were studied for particles greater than two microns in size. Hygroscopic growth was observed through changes in relative humidity (RH) and hygroscopic growth curves were created for ammonium sulfate, ammonium chloride, sodium chloride, calcium chloride, glutaric acid, and malonic acid. The ESEM system is advantageous over the Hygroscopic Tandem Differential Mobility Analysis (HTDMA) system becuase it offers a in-situ view of changes in morphology as particles experience water uptake.
The second objective of this research, the hygroscopic growth of multi-component aerosol mixtures, was studied using Hygroscopic Tandem Differential Mobility Analysis (HTDMA). The size distribution for an aerosol stream was determined before and after the stream was subjected to an increase in relative humidity. The complex mixtures examined contained combinations in equal mass amounts of adipic acid, glutaric acid, maleic acid, aspartic acid, tartaric acid, succinic acid, malonic acid, phthalic acid, and azelaic acid. Pure solutions of sodium chloride, ammonium sulfate, ammonium chloride, ammonium nitrate, calcium chloride, maleic acid, tartaric acid, malonic acid, and phthalic acids were also run through the HTMDA system. Understanding the hygroscopic growth and morphology of aerosols are essential for understanding cloud formation and climate change. This research will provide insight into the physical morphological changes that atmospheric particles exhibit when experiencing changes in humidity.