Continuous Measurements of PM 2'5 and Black Carbon Mass: The GasDiesel Split Project

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Continuous Measurements of PM 2.5 and Black
Carbon Mass The Gas/Diesel Split Project
By Pat Arnott, John Walker, Hans Moosmüller,
Desert Research Institute, Reno NV. pat_at_dri.edu
775-674-7023. Dave Campbell of DRI provided the
filter data comparison. Eric Fujita of DRI is the
chief architect. DOE/NREL Doug Lawson supports
this portion of the project.

• Outline
• Overview Instruments and how/where they are
  being used.
• Preliminary comparison with filter data - Unified
  driving cycle and gasoline vehicles.
• Example of detailed driving cycle PM fora. A
  common vehicle.B. A smoker.C. A diesel
  automobile.
• Preliminary impressions.

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TSI DustTrak for Total PM
Sample air is enclosed in a sheath of filtered
air to keep the optics clean. Aerosol light
scattering at 90 degrees from the 780 nm laser
diode is measured. The manufacturer empirically
calibrates the instrument using Arizona Road
Dust. Simple, reliable, portable, sensitive
instrument Are the results really particle
mass? (Dynamic range 1 ug/m3 to 260,000
ug/m3). Source http//www.tsi.com/partsamp/appnot
e/iti_036.shtml
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DustTrak Calibration
Frequently Asked Questions DUSTTRAK Aerosol
Monitor Q What are the traceability
specifications? There is no National Institute
of Standards and Technology (NIST) standard for
optical mass measurements. Calibration of the
DUSTTRAK is performed by TSI using Emery oilmist
aerosol and nominally adjusted to the respirable
mass of standard ISO 12103-1, Al test dust
(formerly called Arizona test dust).
http//www.particletechnology.com/testdust.html ht
tp//www.tsi.com/partsamp/faq/dusttrak/answers/dus
t9.htm
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DRI Photoacoustic Instrument for Black Carbon
Mass Measurement

• Basic principles
• Laser light is power modulated by the chopper, or
  with a TTL signal.
• Light absorbing aerosols convert light to heat -
  a sound wave is produced.
• Microphone signal is a measure of the light
  absorption.
• Light scattering aerosols don't generate heat.
• Aerosol light absorption is proportional to
  aerosol mass concentration.
• Dynamic range 0.2 to 200,000 ug/m3).

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Optical Surrogates forTotal PM 2.5 and the Black
Carbon Fraction.

• Uses
• Gasoline and Diesel vehicle PM emission
  measurements (dyno), both direct and from
  secondary dilution,
• Get a preliminary emission estimate during the
  BAR dyno evaluation - use as a guide for filter
  sampling.
• On-road sampling from a mobile laboratory on an
  RV,
• Ambient sampling at fixed sites.

• Provide continuous data at intervals of 1 to 10
  seconds
• 1. Can refine the understanding of PM emission
  during various parts of the driving cycle
• Can be quickly averaged to obtain PM emission
  rates for parts of, or the entire driving cycle
• BE SURE YOU DRY THE AEROSOL (RH lt 40)!! PM2.5
  CAN BE BIASED LARGE DUE TO WATER CONTENT.

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Some Images of the Photoacoustic Instrument in
Operation
Mobile sampling from an RV. (Dave Campbell left,
and Eric Fujita right.)
Sampling a vehicle (dyno) during a unified
driving cycle.
PA and dusttrak installed in the Univ. West
Virginia trailer for sampling from their dilution
tunnel.
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Preliminary emission rates from vehicles operated
on the Unified Cycle Phases 1 and 2, Cold, soak,
then Repeat Phases 1 and 2 PM 2.5
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Black Carbon Fraction of Total Emission
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Fraction of Vehicles with Various Emission Rates
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Emission Example from 3 Typical vehicles
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PM 2.5 During the Modified UC Test
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BC During the Modified UC Test
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BC / Total PM 2.5 from DT During the Modified UC
Test
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Modified Unified Driving Cycle Phases 3 and 4
are a warm repeat of phases 1 and 2 Evaluate
the cold versus warm start PM and BC emission.
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Emission Rates on Cold and Warm Start
Note the cold start phase 1 bias towards more
emission Phases 2 and 4 are similar.
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Example From Class 3 Heavy Duty Diesel Truck
Tests 3 Load Settings on the CSR. Load doesnt
seem to influence PM emission.
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Preliminary Impressions

• We found measurable PM and Black Carbon emission
  from all vehicles.
• Gasoline powered smokers can rival diesel cars
  in PM emission rates.
• The EC/TC (optical surrogate BC/DT) ratio for
  gasoline vehicles varies with driving cycle,
  vehicle 1/10 to 1/5. For diesels, 1/5 to
  1/2.
• Ambient measurements, and some mobile, often show
  BC/PM2.5dt ratios of 1/20. BC is likely a
  local vehicle tracer. What causes the drop in
  the ratio for ambient samples? Gas to particle
  conversion on existing PM2.5? Other sources of
  PM2.5?