Constraining Anthropogenic Emissions of Fugitive Dust with Dynamic Transportable Fraction and Measurements

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Constraining Anthropogenic Emissions of Fugitive
Dust with Dynamic Transportable Fraction and
Measurements
Daniel Tong1,2, Daewon Byun1, George Pouliot3,
David Mobley3, Prakash Behave3, Rohit Mathur3,
Tom Pierce3, Tom Pace4, Shaocai Yu3, Tianfeng
Chai1,2, Heather Simon3
1 US NOAA Air Resources Laboratory, Silver
Spring, MD 2 Science Technology Corp., Silver
Spring, MD 2 U.S. EPA National Exposure Research
Laboratory, RTP, NC 4 US EPA OAQPS, RTP, NC
Chapel Hill, NC October 22, 2009
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Fugitive Dust Emissions
Anthropogenic Fugitive Dust
Natural Fugitive Dust
Unpaved Road Paved Road
Construction
Mining
Tilling
Wind-blown dust from barren or disturbed land
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Anthropogenic Fugitive DustMajor Sources
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Chemical Profiles of Fugitive Dust
(Source SPECIATE Database)
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Concept of Transportable Fraction

• Direct use of emission inventories results in
  severe PM2.5 over-prediction (Pace 2005)
• The model assumes emissions are mixed across a
  grid cell (100 to 1000 km2) instantaneously and
  evenly
• In reality, 75 of emitted dust particles are
  deposited within 1 km from the source

Transportable Fraction (TF) (Cowherd and Pace
2002) The fraction of particle emissions that
remains airborne after near source enhanced
deposition and is available for transport away
from the vicinity of the source.
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Methods of Determining Transportable Fraction (TF)

• In the mid 1990s, the US EPA OAQPS used an ad
  hoc divide-the-inventory-by-four approach to
  adjust the fugitive dust emission estimates (Pace
  2005)
• Since 2003, the Pace conceptual model was used
  to determine the adjustment factor (Static TF)

Transportable Fraction (TF) 1 Capture
Fraction (CF)
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Proposed Dynamic Transportable Fraction (TF)

• The dynamic TF Derived based on land cover,
  vegetation growing season, and changing
  atmospheric conditions.

• TF1 above-canopy effect

Vd dry deposition parameterized after Slinn
(1982), Minvielle et al. (2002).
N -- number of LU types u -- friction
velocity fi Land use fraction

• TF2 Land use based capture fraction

TF2 1 CF
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Static vs Dynamic Transportable Fraction (TF)
TF2 - Obstruction Impact
TF1 Above Canopy
TF Pace Model
TF1 x TF2
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Applying new TF to SMOKE and AQ modeling
Applying new TF

• The TF1 and TF2 values are calculated using land
  use data (BELD), surface wind, friction velocity
  and roughness (from the MET model) and parameters
  from literature
• Dynamic cropland fraction is calculated based on
  27 major crop growing seasons so both TF1 and
  TF2 change with time
• TF1 and TF2 are applied to each grid cell to
  adjust the original fugitive dust emission
  estimates

CMAQ Modeling

• CMAQ (v4.6) runs with three emission datasets
  Fugitive dust without TF with Pace TF with the
  new TF

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Effect of TF on Fugitive Dust Emissions
Before
After
PMFINE
POC
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Fugitive Dust Emissions and CMAQ PM Conc.
PM2.5 (13)
PM10 (18)
A25 (42)
AORGPA (9)
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Potential Effects of TF on CMAQ Performance
Percentage of dust AORGPA
CMAQ vs. Obs.
(source Mathur et al., 2008)

• The transportable fraction brings down both A25
  and POA concentrations in CMAQ
• Help with A25 over-prediction, and the effect on
  POA is limited.

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Conclusion

• Proposed a dynamic transportable fraction to
  adjust fugitive dust emissions
• The dynamic TF takes consideration of land use,
  crop growth, and meteorological parameters both
  TF1 and TF2 change with time
• The TF effect is most significant in the
  forested eastern US, and less so over the barren
  land
• Applying the TF brings down CMAQ prediction of
  PM2.5, mostly A25, and primary OC Reducing A25
  over-prediction and having a limited effect on OC
  prediction.

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Future work
1. Study the forces controlling enhanced near
source removal

• Impaction by surface obstructions
• Particle agglomeration

• Electrostatic forces
• Thermal deposition

2. Compare model results with the adjusted
emissions with measurements of dust fingerprint
constituent (crustal)
3. Examine temporal profiles of fugitive dust
emissions
IMPROVE measurements show a clear weekly pattern
in all crustal elements (source Murphy et al,
ACP, 2008)