Constraining Anthropogenic and Biogenic Emissions using Chemical Ionization Mass Spectrometry

Citation

Spencer, Kathleen Marie (2011) Constraining Anthropogenic and Biogenic Emissions using Chemical Ionization Mass Spectrometry. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/XRFJ-2Q92. https://resolver.caltech.edu/CaltechTHESIS:05262011-132849976

Abstract

Numerous gas-phase anthropogenic and biogenic compounds are emitted into the atmosphere. These gases undergo oxidation to form other gas-phase species and particulate matter. Whether directly or indirectly, primary pollutants, secondary gas-phase products, and particulate matter all pose health and environmental risks. In this work, ambient measurements conducted using chemical ionization mass spectrometry are used as a tool for investigating regional air quality.

Ambient measurements of peroxynitric acid (HO₂NO₂) were conducted in Mexico City. A method of inferring the rate of ozone production, P_O3, is developed based on observations of HO₂NO₂, NO, and NO₂. Comparison of this observationally based P_O3 to a highly constrained photochemical box model indicates that regulations aimed at reducing ozone levels in Mexico City by reducing NO_x concentrations may be effective at higher NO_x levels than predicted using accepted photochemistry.

Measurements of SO₂ and particulate sulfate were conducted over the Los Angeles basin in 2008 and are compared to measurements made in 2002. A large decrease in SO₂ concentration and a change in spatial distribution are observed. Nevertheless, only a modest reduction in sulfate concentration is observed at ground sites within the basin. Possible explanations for these trends are investigated.

Two techniques, single and triple quadrupole chemical ionization mass spectrometry, were used to quantify ambient concentrations of biogenic oxidation products, hydroxyacetone and glycolaldehyde. The use of these techniques demonstrates the advantage of triple quadrupole mass spectrometry for separation of mass analogues, provided the collision-induced daughter ions are sufficiently distinct. Enhancement ratios of hydroxyacetone and glycolaldehyde in Californian biomass burning plumes are presented as are concentrations of these compounds at a rural ground site downwind of Sacramento.

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