Measurements of nitrous oxide emissions from light-duty motor vehicles: a pilot study

摘要

Dynamometer testing in conjunction with high-resolution FTIR spectroscopy was used to measure exhaust emissions of nitrous oxide (N_2O) from a fleet of 37 light-duty vehicles at the California Air Resources Board. Exhaust emissions were collected for two driving cycles: the Urban Dynamometer Driving Schedule and the Unified Cycle. The vehicles studied, including passenger cars, sport utility vehicles, and light-duty trucks, were a sub-sample of a fleet that represented California's in-use fleet. The highest correlation between the emissions of N_2O and other vehicle-exhaust species was, as expected, between N_2O and nitrogen oxides (r~2 = 0.45). The previously reported impact of catalyst aging on N_2O emissions could not be verified by our data. Type of catalyst, driving cycle, and vehicle were demonstrated to be the main factors determining the magnitude of N_2O emissions from gasoline-powered light-duty vehicles. The average N_2O emissions factor for the 37 vehicles tested was 20 +- 4mg km~(-1), with a factor of 50 difference between the lowest (2mg km~(-1)) and highest (100mg km~(-1)) N_2O emissions. The average value for N_2O/NO_x emissions ratios was 0.095 + -0.035, with a factor of 14 difference between the lowest (0.01) and the highest (0.14) ratios.