Emissions of Size-Segregated Aerosols from On-Road Vehicles in the Caldecott Tunnel

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Emissions of Size-Segregated Aerosols from
On-Road Vehicles in the Caldecott Tunnel
Jonathan O. Allen
Civil and Environmental Engineering
Department, Arizona State University
Lara S. Hughes
Chemistry Department, University of California,
Riverside
Paul R. Mayo, Lynn G. Salmon
Environmental Engineering Science
Department, California Institute of Technology
Glen R. Cass
School of Earth and Atmospheric Science, Georgia
Institute of Technology
SCOS97 -- NARSTO Data Analysis Conference
15 February 2001
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Motivation

• Vehicle emissions are large contributors to
  ambient aerosol concentrations
• Los Angeles aerosol in September 1996 study was
  composed of
• 9-11 primary particles emitted by vehicles
• 37-65 gas-to-particle conversion products from
  NOx, NH3, SO2, organic compounds
• Actual on-road vehicle fleet emissions can be
  measured in tunnels including
• high emitters
• non-tailpipe emissions

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Caldecott Tunnel Study

• Bore 1 - HDV and LDV
• 5-6 Heavy Duty
• Nov 17 and 18
• noon to 3 p.m.
• Bore 2 - LDV Only
• 0.24 Heavy Duty
• Nov 19 and 20
• 330 to 630 p.m.

HDV - Heavy Duty Vehicles LDV - Light Duty
Vehicles
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Aerosol Measurements
Samplers
Analytes
Organic Tracers (PAHs, Hopanes, )
Electronic Particle Counters
Particle Size Distribution
HNO3, HCl, NH3
Reactive Gases
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PM1.9 Concentrations

• Carbonaceous emissions are most important
• Higher emissions in HDV than LDV Tunnel Bore

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Emissions Calculations

• Gas phase carbonaceous species (CO2, CO, CH4,
  NMHC) measured
• Calculate aerosol emissions based on fuel
  consumption as

EC,i Emission of species i on carbon consumption
basis
D Ci Concentration increase in species i
S D CC,j Sum of carbon emissions in tunnel
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PM1.9 Emissions
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Size-Segregated Emissions in Bore 1 (HDV and LDV)
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Size-Segregated Emissions in Bore 2 (LDV Only)
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LDV and HDV Fleet Emissions
Estimate emission rates of LDV and HDV fleets by
linear regression
EC,ik fk EC,i(HDV) (1-fk) EC,i(LDV) eik
fk Fraction of carbon emitted by HDV fleet
in experiment k

• fk calculated from
• vehicle counts
• fuel consumption estimates
• fuel properties

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Linear Fit of Mass Emissions
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PM1.9 Emissions by HDV and LDV Fleets
HDV emissions ?25 times greater than LDV emissions
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Size-Segregated HDV Emissions
Size-segregated LDV emissions are
indistinguishable from zero Maximum LDV emissions
are those for Bore 2
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Emission Source Measurements

• Kleeman, Schauer, and Cass (Environ. Sci.
  Technol., 3415781587, 2000) measured the
  emissions of
• Catalyst-Equipped Gasoline Vehicles
• Noncatalyst-Equipped Gasoline Vehicles
• Medium Duty Diesel Trucks
• Size-segregated emission profiles agree with
  tunnel measurements
• Note no afterfilter analyses on these source
  samples

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Medium Duty Diesel Emissions
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Catalyst-Equipped Gasoline Vehicle Emissions
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Noncatalyst-Equipped Gasoline Vehicle Emissions
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Comparison of Laboratory and Tunnel Emissions
Measurements

• Medium duty diesel truck emissions profile
  similar to HDV emissions profile
• Relatively more HDV emissions of particles larger
  than 0.2 mm due to
• heavy duty trucks (source sample was medium duty)
  
• non-tailpipe emissions
• Organic compounds emissions in Bore 2 similar to
  profiles for gasoline powered vehicles
• Elemental carbon emissions in Bore 2 due to
• few trucks
• non-tailpipe emissions

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Conclusions

• Emission rates measured were comparable with
  other tunnel studies
• Size-segregated emission profiles are comparable
  to those from source tests possible additional
  emissions from untested sources
• heavy duty trucks
• gasoline powered trucks
• non-tailpipe emissions
• Ammonia emissions were 194 and 267 mg l-1 fuel
  consumed

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Acknowledgement

• This work was supported by the Coordinating
  Research Council, Inc., and the U.S. DOE Office
  of Heavy Vehicle Technologies through the
  National Renewable Energy Laboratory under CRC
  Project No. A-22.