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

Abstract

Emissions rates of ammonia (NH 3) 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. NH 3 measurements were performed using Fourier transform infrared spectroscopy and the federal test procedure (FTP) driving cycle. The FTP NH 3 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, NH 3 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. NH 3 emissions showed a strong cycle dependence, with increased emissions under more aggressive driving conditions. These results show that NH 3 emissions formed during more aggressive driving conditions should be considered in the development of NH 3 emission factors. The onset of NH 3 emissions typically occurred after catalyst light-off, near when the catalyst reached its equilibrium temperature. Initial studies showed that NH 3 emissions increased as the sulfur content in the fuel was decreased.