Environ. Sci. Technol. 2003, 37, 4841-4847
Investigation of NH3 Emissions from New Technology Vehicles as a Function of Vehicle Operating Conditions TAO HUAI, THOMAS D. DURBIN,* J. WAYNE MILLER, JOHN T. PISANO, CLAUDIA G. SAUER, SAM H. RHEE, AND JOSEPH M. NORBECK Bourns College of Engineering, Center for Environmental Research and Technology (CE-CERT), University of California, Riverside, California 92521
The objective of this study was to measure ammonia (NH3) emissions from modern technology vehicles since information is scarce about this important source of particulate matter (PM) precursors. Test variables included the emission level to which the vehicle was certified, the vehicle operating conditions, and catalyst age. Eight vehicles with low-emission vehicle (LEV) to super-ultralowemission vehicle (SULEV) certification levels were tested over the Federal Test Procedure (FTP75), a US06 cycle, a hot running 505, a New York City Cycle (NYCC), and a specially designed Modal Emissions Cycle (MEC01v7) using both as-received and bench-aged catalysts. NH3 emissions in the raw exhaust were measured by tunable diode laser (TDL) absorption spectroscopy. The results show that NH3 emissions depend on driving mode and are primarily generated during acceleration events. More specifically, high NH3 emissions were found for high vehicle specific power (VSP) events and rich operating conditions. For some vehicles, NH3 emissions formed immediately after catalyst light-off during a cold start.
1. Introduction Understanding the relationship between emissions and mode of vehicle operation is complex but also one of the most critical aspects of accurately quantifying vehicle emissions. In recent years, there has been an increased effort to develop more extensive databases of real-time vehicle emissions and subsequently utilize these data for model development. Using real-time data, Jimenez-Palacios et al. showed that emissions were a function of vehicle specific power (VSP) (1). The United States Environmental Protection Agency (EPA) is also developing a new Multi-Scale Motor Vehicle and Equipment Emissions System (MOVES) model that will utilize real-time data for emissions estimates (2). In a preliminary modeling “shootout,” EPA concluded that approaches using both binning of data by operational mode as well as VSP were promising for modeling emissions (2, 3). While there have been considerable efforts to characterize and understand real-time emissions of regulated pollutants, fewer data are available for emissions of unregulated mobilesource emissions such as ammonia (NH3). NH3 contributes to the production of secondary particulate matter (PM) as * Corresponding author phone: (909)781-5794, fax: (909)781-5790; e-mail:
[email protected]. 10.1021/es030403+ CCC: $25.00 Published on Web 10/03/2003
2003 American Chemical Society
ammonium nitrate (NH4NO3) and ammonium sulfate ((NH4)2SO4), and some recent studies have indicated that NH3 emission rates from automobiles may be higher than previously estimated, although a wide range of NH3 emissions estimates (from
