Emissions of Size-Segregated Aerosols from On-Road Vehicles in the Caldecott Tunnel Jonathan O. Allen SCOS97 -- NARSTO Data Analysis Conference15 February 2001 Environmental Engineering Science Department, California Institute of Technology School of Earth and Atmospheric Science, Georgia Institute of Technology Glen R. Cass Civil and Environmental Engineering Department, Arizona State University Chemistry Department, University of California, Riverside Paul R. Mayo, Lynn G. Salmon Lara S. Hughes

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 NO x, NH 3, SO 2, organic compounds Actual on-road vehicle fleet emissions can be measured in tunnels including –high emitters –non-tailpipe emissions

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 –3:30 to 6:30 p.m. Caldecott Tunnel Study HDV - Heavy Duty Vehicles LDV - Light Duty Vehicles

Aerosol Measurements Mass Trace Metals (V,Fe,Br,Mg,…) Carbon (Elemental, Organic) Ions (NO 3 -, SO 4 =, Cl -, NH 4 + ) HNO 3, HCl, NH 3 Organic Tracers (PAHs, Hopanes, …) Fine Particle Filters PM 10 Filters Impactors  m < 0.10 SamplersAnalytes Reactive Gases Electronic Particle CountersParticle Size Distribution

PM 1.9 Concentrations Unidentified Cl - Na + SO 4 = NH 4 + NO 3 - Organic Compounds Elemental Carbon Metals and Metal Oxides Carbonaceous emissions are most important Higher emissions in HDV than LDV Tunnel Bore

Emissions Calculations Gas phase carbonaceous species (CO 2, CO, CH 4, NMHC) measured Calculate aerosol emissions based on fuel consumption as E C,i =  C i   C C,j  C i Concentration increase in species i E C,i Emission of species i on carbon consumption basis   C C,j Sum of carbon emissions in tunnel

PM 1.9 Emissions Unidentified Cl - Na + SO 4 = NH 4 + NO 3 - Organic Compounds Elemental Carbon Metals and Metal Oxides

Size-Segregated Emissions in Bore 1 (HDV and LDV) Unidentified Cl - Na + SO 4 = NH 4 + NO 3 - Organic Compounds Elemental Carbon Metals and Metal Oxides

Size-Segregated Emissions in Bore 2 (“LDV Only”) Unidentified Cl - Na + SO 4 = NH 4 + NO 3 - Organic Compounds Elemental Carbon Metals and Metal Oxides

LDV and HDV Fleet Emissions Estimate emission rates of LDV and HDV fleets by linear regression E C,ik =  k E C,i (HDV) + (1-  k ) E C,i (LDV) +  ik  k Fraction of carbon emitted by HDV fleet in experiment k  k calculated from vehicle counts fuel consumption estimates fuel properties

Linear Fit of Mass Emissions Fraction Carbon Emitted by HDVs,  Mass Emissions (mg kgC )

PM 1.9 Emissions by HDV and LDV Fleets HDV emissions  25 times greater than LDV emissions Unidentified Cl - Na + SO 4 = NH 4 + NO 3 - Organic Compounds Elemental Carbon Metals and Metal Oxides

Size-Segregated HDV Emissions Size-segregated LDV emissions are indistinguishable from zero Maximum LDV emissions are those for Bore 2 Unidentified Cl - Na + SO 4 = NH 4 + NO 3 - Organic Compounds Elemental Carbon Metals and Metal Oxides

Emission Source Measurements Kleeman, Schauer, and Cass (Environ. Sci. Technol., 34:1578–1587, 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

Medium Duty Diesel Emissions Unidentified Cl - Na + SO 4 = NH 4 + NO 3 - Organic Compounds Elemental Carbon Metals and Metal Oxides

Catalyst-Equipped Gasoline Vehicle Emissions Unidentified Cl - Na + SO 4 = NH 4 + NO 3 - Organic Compounds Elemental Carbon Metals and Metal Oxides

Noncatalyst-Equipped Gasoline Vehicle Emissions Unidentified Cl - Na + SO 4 = NH 4 + NO 3 - Organic Compounds Elemental Carbon Metals and Metal Oxides

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  m — 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

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

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.