Air Quality Impacts of Atmospheric Particles & Trace Gases: Field Studies in Diverse Environments
Mwaniki, George Ruchathi
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Air pollution impacts occur at all scales, meaning that policies and air quality management practices must be implemented and coordinated at the local, regional, national, and global scales. This dissertation is part of a continuing effort to improve our understanding of various air quality related issues in different environments. The dissertation consists of four studies. In the first study, wintertime chemical composition of water-soluble particulate matter with aerodynamic diameter less than 2.5 µm (PM2.5) was monitored in the Treasure Valley region near Boise, Idaho. This study was aimed at understanding the major drivers of wintertime PM2.5 within the locality of Boise and its suburbs. From this study, organics and particulate nitrate were the dominant contributors to the PM2.5 mass during wintertime. In the second study, particle size distribution, light scattering coefficient, speciated water soluble PM2.5, and cloud condensation nuclei (CCN) concentration were monitored in a mixed deciduous forest in Northern Michigan during the Community Atmosphere-Biosphere Interactions Experiment (CABINEX-2009). The overall goal of this study was to understand on how emissions of biogenic volatile organic compounds (BVOC) affect the gas-phase and particle-phase chemistry in the near-canopy environment, and the implications on local and regional air quality. From this study aerosol derived from the oxidation of BVOCs exhibited reduced hygroscopicity and CCN activation potential compared to aerosols derived from anthropogenic activities. The third study employed the eddy covariance (EC) technique to understand source-sink interactions of carbon dioxide (CO2), methane (CH4), carbon monoxide (CO) and nitrous oxide (N2O) in Xi'an, China. In this study urban vegetation were found to play a major role in regulating CO2 emissions within the city while vehicular activities were a major driver for CO and CH4 fluxes. In the fourth study, visibility degradation effects of nitrogen oxide (NO) and nitrogen dioxide (NO2) emissions from a natural gas compressing facility in southern Idaho were evaluated and quantified. In addition, several retrofit technologies were evaluated based to their ability to reduce NOx (NO + NO2) emissions. From this study selective catalytic reduction (SCR) was found to be the most appropriate technology to reduce NOx emissions from the facility.