Date of Award

December 2018

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Advisor(s)

Tara Kahan

Subject Categories

Physical Sciences and Mathematics

Abstract

Condensed phases in the environment are often chemically complex. Reactivity can differ significantly depending on the physical state (i.e. solid or liquid) and composition. Many laboratory studies that investigate reaction kinetics in condensed phases are done under simplified conditions that do not accurately reflect the complexity found in the environment. I have measured photolysis rate constants of the aromatic pollutants toluene, ethylbenzene, xylenes (TEX) and anthracene under environmentally-relevant conditions in order to improve fate predictions. The photolysis kinetics of TEX in water, ice and at ice surfaces were investigated using environmentally-relevant wavelengths. Previously, photolysis has not been considered a viable degradation pathway for these compounds in the environment because their absorbance spectra in water does not overlap with wavelengths that reach the Earth’s surface. However, I observed photolysis in ice granules, suggesting direct photolysis could be an important removal pathway for TEX in snow-covered environments.

Sodium chloride (NaCl) and organic matter (OM) are common constituents of condensed phases in the environment. However, the combined effects of salt and organic matter on anthracene photolysis rate constants have previously not been investigated. Therefore, I measured anthracene photolysis rate constants in water, octanol, and phase-separated aqueous-organic mixtures containing varying concentrations of sodium chloride. In aqueous-organic mixtures, anthracene photolysis rate constants were largely explained by a salting-out effect. However, these results are complicated by turbulence, as evidenced by different kinetics observed in stirred and stagnant mixtures. My results suggest that anthracene photolysis kinetics in the environment may not be well described by simple matrices.

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Open Access

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