Estimates of the emission rates of ammonia from light-duty vehicles using standard chassis dynamometer test cycles

Emissions rates of ammonia (NH3) are reported for a fleet of 39 in-use light-duty gasoline-fueled vehicles. The fleet consisted of both light-duty passenger vehicles and light-duty trucks with various levels of emission control technologies, ranging from non-catalyst vehicles to those that were certified at the ULEV standard for California. NH3 measurements were performed using Fourier transform infrared spectroscopy and the federal test procedure (FTP) driving cycle. The FTP NH3 emission rate for this fleet of vehicles averaged 54 mg mi−1 with a range from <4 to 177 mg mi−1. For this fleet of vehicles, NH3 emissions did not decline as significantly as the regulated pollutants with improvements in emission control technology. A subset of 5 vehicles was tested over the US06, the New York City Cycle (NYCC), and a high-speed freeway cycle for comparison with the FTP cycle. NH3 emissions showed a strong cycle dependence, with increased emissions under more aggressive driving conditions. These results show that NH3 emissions formed during more aggressive driving conditions should be considered in the development of NH3 emission factors. The onset of NH3 emissions typically occurred after catalyst light-off, near when the catalyst reached its equilibrium temperature. Initial studies showed that NH3 emissions increased as the sulfur content in the fuel was decreased.