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Estimating Future NO2 Levels in the Greater Los Angeles Area by Source–Type Contribution
Authors:Yuji Horie  Vince Mirabella
Institution:1. Technology Service Corporation , Santa Monica , California , USA;2. Southern California Edison Company , Rosemead , California , USA
Abstract:Two indicator pollutants, carbon monoxide (CO) for mobile source influence and sulfur dioxide (SO2) for stationary source influence, were used to estimate source-type contributions to ambient NO2 levels in a base year and to predict NO2 concentrations in a future year. For a specific source-receptor pair, the so-called influence coefficient of each of three source categories (mobile sources, power plants, and other stationary sources) was determined empirically from concurrent measurements of CO and SO2 concentrations at the receptor site and CO and SO2 emissions from each source category in the source area. Those coefficients, which are considered time invariant, were used in conjunction with the base year and future year NO x emission values to estimate source-type contribution to ambient NO2 levels at seven study sites selected from the Greater Los Angeles area for both the base year period, 1974 through 1976, and the future goal year of 1987 in which the air quality standards for NO2 are to be attained. The estimated NO2 air quality at the seven sites is found to meet the national annual standard of 5 pphm and over 99.9% of total hours, the California 1-hr NO2 standard of 25 pphm in 1987. The estimated power plant contributions to ambient NO2 levels are found to be considerably smaller than those to total NO x emissions in the area. Providing that reasonably complete air quality and emissions data are available, the present analysis method may prove to be a useful tool in evaluating source contributions to both short-term peak and long-term average NO2 concentrations for use in control strategy development.
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