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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.

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A differential optical absorption spectrometer for measurements of low-level sulfur dioxide (SO2) emissions from vehicles in real time was developed and employed. With a time resolution of 3 s and an optical path length of 19.6 m, a minimum detection limit of 75 ppbv SO2 (three times the standard deviation) was achieved. The wavelength region covered, UVB, was chosen to include the major SO2 absorption feature at 300 nm, while avoiding wavelength regions in which other components of vehicle exhaust are known to absorb. However, formaldehyde was found to be present in vehicle exhaust in high enough concentrations to be a major interferent. The analysis software was modified to account for the formaldehyde interferent using a two-dimensional fitting routine. The application of the instrument to real vehicle exhaust demonstrated that it was capable of measuring the contribution to SO2 emissions from lubricant oil sulfur over the range of current and future oil sulfur levels.

The LASIR system ofinstruments provide a way ofmeasuring specific pollutants with no interferences from other gases. Since they are based on laser diodes operating in the communication region ofthe near infrared, they are rugged, easy to operate and relatively small and inexpensive. The instrument can be located in any desired location where it is free of environmental constraints and is readily available for servicing ifrequired. The monitoring beam is transmitted to the measuring location by fiber optics. In some configurations the delivery optics contain no electrical components and can be placed in explosive or hazardous locations. These measurement locations can be up to several kilometers distant from the control. Three versions ofthe LASIR are available,-the LASIR-R for perimeter or area ambient air monitoring, the LASIR-P for point source measurements and the LASIR-S for in stack monitoring. Multiplexing can be used to operate, simultaneously, a combination ofa number ofthese versions from the same instrument at a number oflocations and, if desired, with a variety of different lasers.Examples ofthe application of these systems for measuring HF in aluminum smelters have shown that there is ample sensitivity to measure I-IF both in the stacks and in the pot-rooms ofthese smeltersThe increasing availability oftunable diode lasers which operate in the near infrared have opened up a number of possibilities for emission monitoring. Although absorption coefficients in this wavelength region are several orders of magnitude weaker than in the fundamental mid-infrared regions, the quality ofthese lasers permit the use ofvery high frequency modulation to improve the sensitivity. Since they operate at close to ambient temperatures small thermoelectric coolers can be used for temperature control. . Mother advantage ofoperating in the near-infrared is that pressure broadening does not present as large a problem as it does at the longer wavelengths which makes it suitable for remote sensing at atmospheric pressure. These features makes it possible to reduce both the size and cost ofthe instrument.The response of the system for most gases is in the range of a few parts per million per meter which is more than adequate for most industrial applications. Some ofthe gases which absorb in this spectral region include HF, HC1, CH, , H2S, CO. CO2 , CO,NH3, C2H2, C2H, NO2Unisearch has developed a series of instruments designed to exploit these advantages.' One application to the real time onroad measurements of CO and CO2 has been described in a previous publication.2 In this paper the system will be briefly described and some examples of their use in the monitoring of HF in the aluminum industry will be presented. INSTRUMENT DESCRIPTIONThree basic versions of instrument have been developed, -the LASIR-R for remote sensing, the LASIR-S for stack monitoring and the LASIR-P for point source monitoring. All three versions use a common control unit and laser housing as shown schematically in Figure 1. The control unit contains: 198 ...