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Ambient Elemental Signatures of Diesel and Automotive Particulate Matter by Size, Time, and Composition. 1 Thomas A. Cahill, 1 Earl Withycombe, Steven S. Cliff, Michael Jimenez-Cruz, Lee Portnoff, and 2 Kevin D. Perry, DELTA Group, University of California, Davis, ,

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Ambient Elemental Signatures of Diesel and Automotive Particulate Matter by Size, Time, and Composition.

1Thomas A. Cahill, 1Earl Withycombe, Steven S. Cliff, Michael Jimenez-Cruz, Lee Portnoff, and 2Kevin D. Perry,

DELTA Group, University of California, Davis,,

1The Health Effects Task Force, American Lung Association, Sacramento-Emigrant Trails,

2Dept. of Meteorology, University of Utah

sources of information joint studies with the delta group
Sources of information – joint studies with the DELTA Group
  • Laboratory studies – NREL/U. Minnesota/DRI diesels; UCD S-XRF analysis –(Lawson, Watts, Zielenska et al.), plus DRI Lube oil (Fujita)
  • Prior field studies – prior ARB/UC Davis work; HEI/DRI Tuscarora Tunnel (Gertler et al 2002)
  • Quasi-ambient and ambient applications
    • Interstate 5 on downtown Sacramento and Watt Ave School – (Lung Assoc – Sacramento Emigrant Trails)
    • Fresno FACES studies (ARB)
    • Highway 50 in South Lake Tahoe – TRPA (Tahoe Regional Planning Agency)
summary of laboratory tests
Summary of laboratory tests
  • Most diesel mass lies below 0.25 µm (very fine/ultra fine)
  • Sulfur correlates with emitted very fine/ultra fine mass, and is associated with the diesel fuel
  • Diesel tracers, some ultra-fine, comes from combustion of lubricating oil stabilized with zinc thiophosphate and CaCO3 ; the amounts are highly variable (factor of 3)
  • Ultra fine diesel particles have much more massive and less volatile organic components than coarser diesel components, as required by the Kelvin effect.
  • Lubricating oil for spark ignition vehicles has more and heavier PAHs than lubricating oil for diesels
  • Diesel particles are highly light absorbing at all wavelengths, 350 nm – 820 nm

PM 0.25 ?

PM 10

PM 2.5

Average Zn to mass, all DRI tests, 1800  1300

summary for prior field tests
Summary for prior field tests
  • Diesel truck have roughly 10 (PM2.5) to 18 (PM10) times the mass emission rate of light duty vehicles
  • Diesels and light duty vehicles emit species seen in the laboratory tests, plus others in the PM2.5 mode.
  • There are a number of possible tracers that separate diesels from gasoline powered vehicles, including a few heavy PAHs
  • Gross emitting light duty vehicles, a few percent of all vehicles, can be as bad or worse per vehicle than the average heavy duty diesel.
current ambient quasi ambient studies
Current ambient/quasi-ambient studies
  • Interstate 5 in downtown Sacramento
    • urban
  • Watt Avenue on Arden Middle School
    • suburban
  • Highway 50 in South Lake Tahoe
  • The Fresno Super-site
    • suburban

Lung Assoc. Sacramento Transect Study Site Map and PM2.5 aggregated data

#1, #3 - light blue = rain, yellow = “clear”, rest = fogs, wet and dry






sacramento a highway nexus i 5 i 80 hwy 50 hwy 99 and close to violations of pm 2 5 standards
Sacramento – a highway nexus, (I-5, I-80, Hwy 50, Hwy 99) and close to violations of PM2.5 standards
interstate 5 in sacramento
Interstate 5 in Sacramento
  • Impact of I-5 on Downtown Sacramento
    • 10,500 light duty, 1125 heavy duty (> 5 axel) vehicles/hr,
    • 10 traffic lanes, nearest 100 m to Crocker Art Museum site
    • Sound wall; some trees but not a barrier
    • Prevailing wind in daytime from southwest, across I-80; stagnation low winds from southeast
    • Cut section freeway; complex terrain prevents direct line source modeling; use very fine diesel tracers

DELTA Group slotted 8 DRUM Impactor

  • 8 size ranges:
    • Inlet ( ~ 12) to 5.0 μm
    • 5.0 to 2.5 μm
    • 2.5 to 1.15 μm
    • 1.15 to 0.75 μm
    • 0.75 to 0.56 μm
    • 0.56 to 0.34 μm
    • 0.34 to 0.26 μm
    • 0.26 to 0.09 μm
  • 10.4 l/min, critical orifice control, ¼ hp pump
  • 6.5 x 168 mm Mylar strips
  • For 42 day run, 4 mm/day,

time resolution = 3 hr.

  • Field portable
    • 10 kg, 43 × 22× 13 cm

43 cm


Crocker Art Museum site

Predict 4.3  2.9µg/m3 diesel mass (U. Minn.)




Fog and haze



Observe  6  1 µg/m3 mass

impact of watt avenue on arden middle school
Impact of Watt Avenue on Arden Middle School
  • 3800 light duty, 53 heavy (> 5 axel) vehicles/hr
  • Stop light at NW corner of school grounds
  • 9 traffic lanes, nearest 15 m to school buildings
  • Prevailing wind in daytime from southwest, across Watt Avenue; stagnation winds weak from southeast
  • No wall or vegetation barrier; line source modeling easy from Tuscarora PM2.5 data

Watt Ave


Arden Way

Sebastian Way site

application of tuscarora data
Application of Tuscarora data
  • Sliding box model on roadway
  • Upwind regional PM2.5 data (CARB)
  • Regional meteorology (NOAA’s ARL HYSPLIT 4)
  • PM2.5 inlet (IMPROVE); 3 stage rotating DRUM impactor at 1.15, 0.34, and <0.15 μm diameter
  • Line source model, neutral stability
  • Soft beta gauge PM2.5 mass ~ 7.0 ± 1.5 µg/m3 ( ~8µg/m3 with uf correction)
  • Calculated mass, 3.7 µg/m3 light, 1.7 µg/m3 trucks, for 5.4 µg/m3; with literature values, 7.7 µg/m3
summary of watt avenue impacts
Summary of Watt Avenue impacts
  • Mass numbers calculated are in fair to good agreement with observed values, car and truck
  • About 1/3 of the mass is diesel, even through diesels were only about 1.5% of the average vehicle mix
  • Very fine aerosols at the downwind school site have many of the elements predicted from the laboratory and Tuscarora studies,
  • Very fine aerosols 300 m upwind (Sebastian Way) are much lower that downwind at the school, and much lower than downtown Sacramento.
very fine aerosols characteristic of diesels smoking cars in fresno 1 km from freeways
Very fine aerosols characteristic of diesels/smoking cars in Fresno > 1 km from freeways

Predicted diesel vf/uf mass 11/25 – 12/17, 9 ± 6 µg/m3


Nov 25 – Dec. 17, measured mass = 4.8 ± 1.0, predicted mass = 6.6 ± 4.8,

estimated total very fine mass = 8.8 μg/m3

persistence of very fine ultra fine particles
Persistence of very fine/ultra fine particles
  • We find high concentrations of very fine particles near freeways in periods of stagnation,
  • We also find significant concentrations (6 µg/m3) over large areas of downtown Sacramento well away (> 400 m) from the nearest freeway source
  • Even higher levels are seen in Fresno in winter, in a residential neighborhood > 1 km away from the nearest freeway.
  • Recent work in Los Angeles finds ultra fines falling off from freeways roughly as rapidly as diffusion-limited CO, so coagulation appears to be limited and lifetimes long (for the non H2SO4 fraction).
study of ultrafine particles near a major highway with heavy duty diesel traffic zhu et al 2002
Study of ultrafine particles near a major highway with heavy-duty diesel traffic Zhu et al (2002)
study of ultrafine particles near a major highway zhu et al 2002 lead from cahill et al arb 1974
Study of ultrafine particles near a major highway Zhu et al (2002); Lead from Cahill et al (ARB, 1974)

BC, number -diesels

CO, Pb - cars

  • Diesel exhaust mass lies almost entirely in the very fine mode < 0.25 µm; ultra-fine mode misses ~ ½ of the diesel mass.
  • Laboratory and field studies are consistent in composition and particle size, allowing calculation of diesel impacts.
  • Separation of diesel and smoking car exhaust is difficult, organic tracers unstable and uncertain, and costs high.
  • Smoking car exhaust appears to be as toxic as diesel exhaust per unit mass.
  • Diesel and smoking car exhaust represents most of the very fine mass in Sacramento and Fresno, even well away from freeways.
  • Diesel and smoking car exhaust must be measured in ambient urban and sub-urban sites where it is a significant and toxic fraction of PM2.5 mass.
proposals for california
Proposals for California
  • We propose getting automobile smoke listed as a Toxic Air Contaminant (TAC) under California Prop 65, joining diesel
    • Diesel is presently 70% of the cancer risk of all current California TACs, combined.
  • We have initiated PM0.25 mass measurements in the CA Central Valley, using High Schools and air district support.
    • We have deployed robust, simple and inexpensive monitors to begin generating data on possible PM0.25 – health associations
  • We propose that these urgent but unmet needs can be addressed via a new California PM0.25 mass standard
    • It would include diesels, smoking cars, and other high temperature processes (coal fired power plants, smelting, welding, ….) that generate very fine and ultra fine particles of suspected health impacts.
    • It avoids the difficulty and expense of routinely resolving the diesel-smoking car overlap, since it appears both are toxic and both must be controlled
    • It could in the future allow the possibility of US EPA re-evaluating the PM2.5 standard if it turns out that 2.5 μm – 0.25 μm mode aerosols prove less harmful to human health.
  • American Lung Association – Sacramento Emigrant Trails Health Effects Task Force – many volunteers, modest funding, excellent oversight
  • National Renewable Energy Laboratory – DRI diesel tests
  • Health Effects Institute – Tuscarora Tunnel studies
  • California Air Resources Board – Fresno FACES study
  • Tahoe Regional Planning Agency and CalTrans – Tahoe Studies
  • Department of Energy - Lawrence Berkeley NL and the Advanced Light Source – S-XRF capabilities
  • National Science Foundation – ACE-Asia DRUM samplers
ultra fine particles near a busy road gramotnev and ristovski atm env 2003
“…ultra-fine particles near a busy road” – (Gramotnev and Ristovski Atm. Env. 2003)