Sulfate Emissions from Vehicles on the Road

Pierson, William R.; Brachaczek, Wanda W.; Hammerle, R. H.; McKee, Douglas E.; Butler, J. W.

doi:10.1080/00022470.1978.10470579

Cited by 25 publications

(26 citation statements)

References 16 publications

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“…Steady Experiments If the anemometer measured the true average air speed and the SF 6 were perfectly mixed across the tunnel, then the concentration of SF 6 would be (5) The measured concentrations C m , normalized by C p , appear in Figure 6. At the tunnel exit, concentrations are slightly higher at the road level than at the tunnel roof (see also Table 1).…”

Section: Resultsmentioning

confidence: 99%

“…The last trip through the tunnel was timed so that the van exited the tunnel about 5 min before the sampling period ended. This ensured that the tunnel and sampling lines were essentially flushed of SF 6 before the period ended. Air samples were taken about a meter below the tunnel roof at the entrance (south end), control booth, and exit (north end).…”

Section: Transient Experimentsmentioning

confidence: 99%

“…Airpollution scientists are typically interested in the emission characteristics of the vehicles in the tunnel and tunnel-ventilation engineers are interested in designing tunnels to minimize pollutant levels. The majority of work of the first type (including the present study) employs a simple mass balance to relate vehicle-emission rates to measured concentrations [6][7][8] in a tunnel. The difference between the pollutant influx and efflux is the sum of the emission rates of the vehicles in the tunnel.…”

Section: Review Of Tunnel-ventilationmentioning

confidence: 99%

“…Transient tracer experiments have been used in roadway studies. 15 The steady SF 6 release technique has been used in earlier studies. 3,16 Several features of the transient and steady tests were the same.…”

Section: Description Of the Tracer Experimentsmentioning

confidence: 99%

“…A stopwatch was used to determine the times at which the SF 6 release started, and the van entered and exited the tunnel. Release of SF 6 was started approximately 10 sec (approximately 250 m) prior to the van entering the tunnel and was shut off when the van exited the tunnel. Considering typical wind conditions and the local topography, we believe that the measured concentrations would not have changed had we started releasing SF 6 earlier in each trip.…”

Section: Transient Experimentsmentioning

confidence: 99%

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Use of Tracer Gas for Direct Calibration of Emission-Factor Measurements in a Traffic Tunnel

Rogak

Green

Pott

1998

Journal of the Air & Waste Management Association

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Pollutant measurements in traffic tunnels have been used to estimate motor-vehicle emissions for several decades. The objective in this type of study is to use the traffic tunnel as a tool for characterizing motor vehicles rather than seeking a tunnel design with acceptably low pollutant concentrations. In the past, very simple aerodynamic models have been used to relate measured concentrations to vehicle emissions. Typically, it is assumed that velocities and concentrations are uniform across the tunnel cross section. In the present work, a vehicle emitting a known amount of sulfur hexafluoride (SF 6 ) was driven repeatedly through a 730-m-long traffic tunnel in Vancouver, Canada. Comparing the measured SF 6 concentrations to the known emission rates, it is possible to directly assess the accuracy of the simple tunnel aerodynamic models typically used to interpret tunnel data. Correction factors derived from this procedure were then applied to measurements of carbon monoxide and other pollutants to obtain gram-per-kilometer emission factors for vehicles. Although the specific correction factors measured here are valid only for the tunnel tested, the magnitude of the factors (up to two or more) suggests that the phenomena observed here should be considered when interpreting data from other tunnels. IMPLICATIONSFor several decades, vehicle emissions have been inferred from traffic-tunnel measurements. Although ratios of pollutants (e.g., CO/NO x ) can typically be measured quite accurately in the tunnel environment, it is often difficult to measure rates in gram per mile or gram per kilometer, partly because of uncertainties in the aerodynamic behavior of the tunnel. In the Cassiar tunnel, aerodynamic factors can bias measured emission factors by up to a factor of 2. The direct calibration technique developed here allows more accurate measurement of g/km emissions. This can make tunnel studies an even more powerful tool for assessing the performance of emission models and air-quality management measures.

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Section: Resultsmentioning

confidence: 99%

Section: Transient Experimentsmentioning

confidence: 99%