Masters Thesis

Infrared Measurements of Atmospherically Relevant Compounds: Applications to Spectral Composition Determination.

Aerosol particles are a ubiquitous, yet not well understood, component of the atmosphere. The composition of aerosol particles directly affects air quality and climate. In order to better understand the effects of aerosol globally, it is necessary to have global composition measurements. Given that infrared spectroscopy is a robust technique and already on satellite platforms, this work focuses on infrared measurements of short chain (C2- C5), α-ω dicarboxylic acids in aqueous solutions, and mixtures thereof. Pure dicarboxylic acid solutions and dicarboxylic acid mixtures were measured with concentrations between 0.01-3.26 M, which represents a particle under different relative humidity conditions. The infrared spectra of dicarboxylic acids are unique and follow Beer’s Law, with the exception of oxalic acid, which shows a shift in peak position due to the different protic species present across the measured pH range. Similarly, results showed that the pH and the amount of solute in water affects the absorbance of water. To account for these effects, representative eigenspectra for water and acid species were created. Using eigenspectra, models of pure and mixture dicarboxylic acid spectra can be determined. Based on coefficients of the eigenspectra, concentration information can be determined from measured infrared spectra within 20% error. This information is invaluable to climate modelers to better understand how dicarboxylic acids interact with infrared light and for those who make field measurements to better quantify the amount of dicarboxylic acids in their measurements.

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