No abstract

The objective of this study was to measure ammonia (NH3) emissions from modern technology vehicles since information is scarce aboutthis importantsource 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-ultralow-emission 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.

Abstract-A series of vertical profiles of temperature, relative humidity, N0 2 and 0, were determined in lhe Lower Fraser Valley, British Columbia, as part oClhe PACIFIC '93 field study. Data from one day show very slructured vertical distributions of all parameters in the morning, as expected from the limited vertical mixing under the nocturnal inversion. N0 2 concentrations of 20ppbv were observed 300 m above the surface, while the surface concentrations were -2 ppbv. Ozone and nitrogen oxide chemislry were observed at all altitudes throughout the PBL. Titration of 0, by NO to produce N0 2 was observed in layers above the ground, under the influence of the NBL. An increase in odd oxygen lhroughout lhe PBL, during the morning and early afternoon, shows "smog chemistry" is occurring even though the groundbased 0J measurements suggest this day was not particularly chemically active. However, once the NBL has dissipated, the ground-based measurements seem representative of lhe entire PBL.

No abstract

No abstract