The Investigation of Secondary Particle Formation Initiated by Non-Prototypical Sources and the role of Amines in the Atmosphere

• Main Author: Burrell, Emily
• Format: Others
• Published: BYU ScholarsArchive 2019
• Subjects: Secondary Particle Formation; Amines; Carboxylic Acids; Nucleation Theory; Atmospheric Chemistry; Peroxy Radicals; Ab-initio Calculations
• Online Access: https://scholarsarchive.byu.edu/etd/8634; https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=9634&context=etd

This dissertation is a collection of works that investigate non-prototypical sources leading to new particle formation in the atmosphere. Particles play a major role in atmospheric chemistry. For example, particles are a component of smog and are commonly found in high concentrations under conditions of atmospheric inversions. In order to reconcile the difference between measured and modeled particle concentrations new mechanisms from non-prototypical sources for particle formation need to be determined. Formation of particles has frequently been modeled using classical nucleation theory (CNT). The first step in CNT is the nucleation step where molecular clusters form. In a second step, these clusters grow into particles through coagulation or condensation. First, this research aims to improve the modeling of equilibrium constants for the formation of peroxy radical-water complexes. Failure of the harmonic approximation in the partition function for describing the low frequency vibrational modes of the complexes was explored. Instead the dissociative hydrogen bond mode using a Lennard-Jones 6-3 potential and the other low frequency vibrational modes using one- and two-fold hindered rotors was modeled. It was determined that the contribution of the two-fold hindered rotors is more important than the long-range dipole-dipole potentials and of vibration-rotation coupling. In related work, the hydroperoxy radical was investigated as a non-prototypical source of particles using high level ab initio calculations. The results indicate that the addition of an amine to the dimer increased the overall stability of complex through the increased number and strength of the hydrogen bonds. When compared to prototypical systems, sulfuric acid and methane sulfonic acid, the strength of the complex was found to be similar to the peroxy radical system. Finally, carboxylic acids, formic acid and acetic acid, were investigated as a source for new particle formation using computational and experimental techniques. Using a slow flow reactor cell particle formation was enhanced by the addition of trimethylamine. High level ab initio calculations indicate like the peroxy radicals, carboxylic acids may act as a molecular cluster in particle formation