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Published April 15, 1998 | public
Journal Article

Detection of Excess Ammonia Emissions from In-Use Vehicles and the Implications for Fine Particle Control


The emission rate for ammonia from in-use vehicles is calculated based on measurements made inside a Los Angeles roadway tunnel. Using fleet distributions by vehicle age and type, known catalyst distributions, and fuel economy by model year and vehicle type and attributing all ammonia to vehicles equipped with three-way catalysts or three-way catalysts plus oxidizing catalysts (dual-bed catalysts), we estimate an average ammonia emission rate of 72 mg km^(-1) for these vehicles, or 61 mg km^(-1) driven by the vehicle fleet as a whole. These emissions can emanate from vehicles running under rich air−fuel conditions, with three-way catalytic converters designed to reduce NO_x to N_2 and O_2 in addition forming NH_3. Resulting calculations estimate ammonia emissions of 24−29 t of NH_3 day^(-1) from the vehicle fleet for the South Coast Air Basin (SoCAB) that surrounds Los Angeles. This represents an increase in the daily emissions of ammonia attributable to motor vehicles in the SoCAB from 2% of basin wide emissions before the introduction of catalyst-equipped automobiles to 15% based on the current experiment. The air basin wide emission rate of ammonia from motor vehicles is compared to ammonia emissions from livestock waste decomposition at local dairies, and the implications for control of fine particle ammonium nitrate concentrations are discussed.

Additional Information

© 1998 American Chemical Society. Received for review April 29, 1997. Revised manuscript received December 18, 1997. Accepted January 6, 1998. Publication Date (Web): March 6, 1998. We thank Michael Hannigan and Claudine Butcher, who assisted with the field experiment; R. A. Rasmussen of the Oregon Graduate Institute, who anaylzed the canister samples for CO, CO_2, CH_4, NMHC, and SF_6; and William Ray (formerly of the U.S. Environmental Protection Agency), who identified the vehicles in the tunnel according to type and model year. This research was supported by the Electric Power Research Institute under Agreement RP3189-03 and by the Caltech Center for Air Quality Analysis.

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August 19, 2023
October 19, 2023