Source contributions to the size and composition distribution of urban particulate air pollution

Citation

Kleeman, Michael John (1999) Source contributions to the size and composition distribution of urban particulate air pollution. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/tthv-kf87. https://resolver.caltech.edu/CaltechETD:etd-02082008-161931

Abstract

A mechanistic air quality model is developed that represents the atmospheric aerosol as a source-oriented external mixture of particles. A source-oriented external mixture is created when particles are released to the atmosphere from sources having distinctly different particle size and composition distributions. These particles evolve separately in the atmosphere while interacting with a common gas phase distribution of pollutants. The model represents advection, turbulent diffusion, gas-phase photochemistry, diffusion of reactants and products to and from the particles, aerosol thermodynamics, heterogeneous chemical reactions within fogs, and dry deposition. Calculations track individual particles from specific sources and then quantify the contribution which each source makes to the size and composition distribution of ambient suspended particulate matter at downwind receptor sites. Model results that simulate the August 28, 1987, episode of the Southern California Air Quality Study (SCAQS) experiments show that hygroscopic background particles advected into the Los Angeles area are transformed significantly by secondary chemical reactions in the urban atmosphere in a way that shapes the largest peak in the ambient fine particle (PM2.5) size distribution. Source contributions from more than 50 separate types of primary particle emissions sources also are revealed through a new technique for displaying model outputs.

The air quality model is used to calculate the effects that alternative specific emissions control measures would have on air quality. Calculations show that a control plan which combines nearly all available emissions reduction techniques for gas- and particle-phase pollutants could have cut atmospheric fine particle (PM2.5) concentrations approximately in half at Claremont, CA, on August 28, 1987, in the absence of any other changes.

Source tests are conducted to measure the size and chemical composition distribution of particles released from diesel vehicles, catalyst-equipped gasoline-powered vehicles, non-catalyst-equipped gasoline vehicles, meat cooking, wood burning, and cigarette smoke. These improved emissions data are combined with the air quality model, which then is used to determine the source origin of particulate matter in the Southern California atmosphere during field experiments conducted for purposes of model evaluation in September, 1996.

Thesis Files