Measuring self-pollution in school buses using a tracer gas technique

Behrentz, Eduardo; Fitz, Dennis R.; Pankratz, David; Sabin, Lisa D.; Colome, Steven D.; Fruin, Scott; Winer, Arthur M.

doi:10.1016/j.atmosenv.2004.04.007

Cited by 64 publications

(40 citation statements)

References 17 publications

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“…Results for the trap-outfitted diesel bus were generally in between the conventional diesel buses and the CNG bus, although diesel-related pollutant concentrations on board our specific trap-outfitted bus appeared to be higher than expected, based on emission data reported for other trap-equipped diesel vehicles (Johnson, 2001). Differences between buses with windows closed were at least in part due to self-pollution, as demonstrated by onboard measurements of SF 6 , added to each bus's exhaust (Behrentz et al, 2004a). Self-pollution was detected in all buses, with higher rates for older buses.…”

Section: Discussionsupporting

confidence: 42%

“…In order to determine if a significant amount of a bus's own exhaust entered the cabin during commutes, sulfur hexafluoride (SF 6 ) tracer gas was injected into the bus exhaust system during each run (Behrentz et al, 2004a). SF 6 concentrations were then measured inside the cabin at the front and rear, and just outside the cabin at the front of the bus, with an AeroVironment Model CTA 1000 real-time analyzer using electron capture detection.…”

Section: Instrumentationmentioning

confidence: 99%

“…A detailed description of the measurements of a bus's own exhaust inside the cabin using an SF 6 tracer gas, including the method used to calculate this self pollution, is published in Behrentz et al (2004a). In summary, (Figure 4), all buses exhibited a degree of self-pollution during every commute; for each bus, the amount of the bus's own exhaust inside the cabin was substantially higher with windows closed compared with open; and compared with newer buses, older buses showed a larger percentage (up to 10 times) of their own exhaust entering the cabin.…”

Section: Self-pollutionmentioning

confidence: 99%

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Characterizing the range of children's air pollutant exposure during school bus commutes

Sabin

Behrentz

Winer

et al. 2004

J Expo Sci Environ Epidemiol

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Real-time and integrated measurements of gaseous and particulate pollutants were conducted inside five conventional diesel school buses, a diesel bus with a particulate trap, and a bus powered by compressed natural gas (CNG) to determine the range of children's exposures during school bus commutes and conditions leading to high exposures. Measurements were made during 24 morning and afternoon commutes on two Los Angeles Unified School District bus routes from South to West Los Angeles, with seven additional runs on a rural/suburban route, and three runs to test the effect of window position. For these commutes, the mean concentrations of diesel vehicle-related pollutants ranged from 0.9 to 19 mg/m 3 for black carbon, 23 to 400 ng/m 3 for particle-bound polycyclic aromatic hydrocarbon (PB-PAH), and 64 to 220 mg/m 3 for NO 2 . Concentrations of benzene and formaldehyde ranged from 0.1 to 11 mg/m 3 and 0.3 to 5 mg/m 3 , respectively. The highest real-time concentrations of black carbon, PB-PAH and NO 2 inside the buses were 52 mg/m 3 , 2000 ng/m 3 , and 370 mg/m 3 , respectively. These pollutants were significantly higher inside conventional diesel buses compared to the CNG bus, although formaldehyde concentrations were higher inside the CNG bus. Mean black carbon, PB-PAH, benzene and formaldehyde concentrations were higher when the windows were closed, compared with partially open, in part, due to intrusion of the bus's own exhaust into the bus cabin, as demonstrated through the use of a tracer gas added to each bus's exhaust. These same pollutants tended to be higher on urban routes compared to the rural/suburban route, and substantially higher inside the bus cabins compared to ambient measurements. Mean concentrations of pollutants with substantial secondary formation, such as PM 2.5 , showed smaller differences between open and closed window conditions and between bus routes. Type of bus, traffic congestion levels, and encounters with other diesel vehicles contributed to high exposure variability between runs.

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Section: Discussionsupporting

confidence: 42%

Section: Instrumentationmentioning

confidence: 99%

Section: Self-pollutionmentioning

confidence: 99%

See 1 more Smart Citation

Characterizing the range of children's air pollutant exposure during school bus commutes

Sabin

Behrentz

Winer

et al. 2004

J Expo Sci Environ Epidemiol

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“…Furthermore, the density and frequency of people's movements in a bus are much higher than in offices, day care centres and homes, and may be more comparable to school classrooms, for which high concentrations of coarse particles have also been reported (Stridh [16]). Particle concentrations in buses most likely reflect high outdoor concentrations, often in busy traffic [1], the effects of self-pollution from exhausts (Behrentza et al [4]), and re-suspension from activities within the bus, but previous studies have not clearly distinguished the contribution of these different sources to in-bus concentrations.…”

Section: Discussionmentioning

confidence: 99%

Size distribution of commuters' exposure to airborne particulate matter in buses in the UK

Song¹,

Ashmore²

2007

WIT Transactions on Ecology and the Environment, Vol 101

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Traffic is an important source of particle emissions which contribute to urban air pollution around the world. In transport microenvironments particles of various sizes, which can be inhaled and cause serious health effects, are generated from fuel combustion. In this study, the size distribution of commuters' exposure to particles inside public buses was examined in the city of York, UK. Measurements were conducted during the winter, inside different types of buses. Particle number concentrations were measured in four main size classes: 0.3-10µm, 1.0-3.0µm, 3.0-7.5µm, and 7.5-15µm. The correlation coefficients between particle number concentrations for these different size ranges differed for each type of bus. Statistical analysis showed that the different size classes of particles were influenced by different factors. Particles in size class 0.3-1.0µm were affected by the duration at bus stops, number of people active, and outdoor concentrations, but the effect of numbers and activities of passengers in re-suspending particles was the dominant factor for coarse particles.

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“…A number of studies has been conducted to assess children's exposure to diesel pollutants during school bus commutes, some of which address potential exposures during loading/unloading (3)(4)(5)(6)(7)(8)(9)(10)(11). In 2002, both Wargo and Brown (10) and Sabin et al (4) found significantly higher concentrations of black carbon (BC) inside idling buses as compared to those measured in buses while in motion.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Fine Particle and Gaseous Emissions during School Bus Idling

Kinsey

Williams

Dong

et al. 2007

Environ. Sci. Technol.

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The particulate matter (PM) and gaseous emissions from six diesel school buses were determined over a simulated waiting period typical of schools in the northeastern U.S. Testing was conducted for both continuous idle and hot restart conditions using a suite of on-line particle and gas analyzers installed in the U.S. Environmental Protection Agency's Diesel Emissions Aerosol Laboratory. The specific pollutants measured encompassed total PM-2.5 mass (PM ≤2.5 μm in aerodynamic diameter), PM-2.5 number concentration, particle size distribution, particle-surface polycyclic aromatic hydrocarbons (PAHs), and a tracer gas (1,1,1,2,3,3,3-heptafluoropropane) in the diluted sample stream. Carbon monoxide (CO), carbon dioxide, nitrogen oxides (NO x ), total hydrocarbons (THC), oxygen, formaldehyde, and the tracer gas were also measured in the raw exhaust. Results of the study showed little difference in the measured emissions between a 10 min post-restart idle and a 10 min continuous idle with the exception of THC and formaldehyde. However, an emissions pulse was observed during engine restart. A predictive equation was developed from the experimental data, which allows a comparison between continuous idle and hot restart for NO x , CO, PM-2.5, and PAHs and which considers factors such as the restart emissions pulse and periods when the engine is not running. This equation indicates that restart is the preferred operating scenario as long as there is no extended idling after the engine is restarted.

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Measuring self-pollution in school buses using a tracer gas technique

Cited by 64 publications

References 17 publications

Characterizing the range of children's air pollutant exposure during school bus commutes

Characterizing the range of children's air pollutant exposure during school bus commutes

Size distribution of commuters' exposure to airborne particulate matter in buses in the UK

Characterization of Fine Particle and Gaseous Emissions during School Bus Idling

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