Aerosols play important roles in atmospheric and environmental processes. Not only do they impact human health, they also affect visibility and climate. Despite recent advances made to under their sources and fate, there remains a limited understanding of the mechanisms that lead to the formation of aerosols and their ultimate fate in the atmosphere. These knowledge gaps provide the crux of the research reported herein, which has focused on identifying novel sources of atmospheric aerosol, characterizing its physical and optical properties, and rationalizing these properties using an in-depth knowledge of the molecular level mechanisms that led to its formation. Upon mowing, turfgrasses emit large amounts of green leaf volatiles which can then be oxidized by ozone to form SOA. Overall, the mowing of lawns has the potential to contribute nearly 50 µg SOA per square meter of lawn mowed. This SOA contribution is on the same order of magnitude as other predominant SOA sources (isoprene, monoterpenes, sesquiterpenes). Turfgrasses represent an interesting and potentially meaningful SOA source because they contribute to SOA and also because they cover large land areas in close proximity to oxidant sources. Another related SOA precursor is sugarcane, which is in the same family as turfgrass and is among the largest agricultural crops worldwide. Globally, the ozonolysis of sugarcane has the potential to contribute 16 Mg SOA to the atmosphere, compared to global estimates of SOA loading that range from 12-70 Tg SOA. In order to fully understand the role of atmospheric SOA on the radiative budget (and therefore climate), it is also important to understand its optical properties; its ability to absorb vs scatter light. Turfgrass and sugarcane produced SOA that was weakly absorbing while its scatter efficiency was wavelength and size-dependent. Interestingly, SOA formed under both dry (10% RH) and wet (70% RH) conditions had the same bulk chemical properties (O:C), yet significantly different optical properties, which was attributed to differences in molecular-level composition. The work presented herein represents a unique, inclusive study of SOA precursors. A complete understanding of the chemistry leading to SOA formation is used to understand its physical and optical properties and evaluate these large-scale effects of SOA from these precursors.

Organic aerosol (OA) is a ubiquitous component of atmospheric particulate that influences both human health and global climate. A large fraction of OA is secondary in nature (SOA), being produced by oxidation of volatile organic compounds (VOCs) emitted by biogenic and anthropogenic sources. Despite the integral role of SOA in atmospheric processes, there remains a limited scientific understanding of the chemical and physical changes induced in SOA as it ages in the atmosphere. This thesis describes work done to increase the knowledge of processes and properties of atmospherically relevant SOA. In the work presented in this thesis, I have worked on improving an existing innovative, soft ionization aerosol mass spectrometer and utilized it to establish chemical mechanisms for oxidation of atmospherically relevant organic precursors (i.e., Green Leaf Volatiles). I discovered that SOA formation from cis-3-hexen-1-ol is dominated by oligomer and higher molecular weight products, whereas the acetate functionality in cis-3-hexenylacetate inhibited oligomer formation, resulting in SOA that is dominated by low molecular weight products. One of the most important factors contributing to uncertainties in our estimations of SOA mass in the atmosphere, remains our basic assumption that atmospheric SOA is liquid-like, which we have found to be untrue. Hence, I developed a methodology to estimate the phase state of SOA and identified new parameters that can have significant influence on the phase state of atmospheric aerosol. This simplified method eliminates the need for a Scanning Mobility Particle Sizer (SMPS) and directly measures Bounce Factor (BF) of polydisperse SOA using only one multi-stage cascade Electrostatic Low Pressure Impactor (ELPI). The novel method allows for the real time determination of SOA phase state, permitting studies of the relationship between SOA phase, oxidative formation and chemical aging in the atmosphere. I demonstrated that SOA mass loading (CSOA) influences the phase state significantly. Results show that under nominally identical conditions, the maximum BF decreases by approximately 30% at higher CSOA and suggests that extrapolation of experiments not conducted at atmospherically relevant SOA levels to simulate the chemical properties may not yield results that are relevant to our natural environment. My work has provided a better understanding of the mechanisms of aerosol formation at atmospheric concentrations, which is necessary to understand its physical properties. This improved understanding is fundamental to accurately model aerosol formation in the atmosphere, and subsequently evaluate their large-scale effect on human health and environment.

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Studies focused on developing a semiochemical-based monitoring system for Plutella xylostella (L.) using sex pheromone and Z3-hexenyl acetate. A commercially available pheromone trapping system was used to capture male moths at sites in Alberta in 2007 and 2008. Larval sampling occurred every two weeks after the first males were captured. Male moth capture was predictive of larval density on individual sample dates during the growing season. The predictive capability of pheromone-baited trap capture was not in direct proportion to population density and was inconsistent. Modifications to the trapping system were tested to improve attractiveness. Adding Z3-hexenyl acetate at various doses to pheromone did not improve the attractiveness to males over pheromone alone and did not attract significant numbers of females when tested at various times during the flight season. Trap height and colour did not influence male capture. Pheromone dose and lure type did influence male moth capture in traps. / Plant Science