The Dust Community

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Intercontinental Dust and Smoke over North
AmericaQuantitative Tools an Results
July Dust
??
10
5
Local
Sahara Dust
0

• The Dust Community

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Observational Tools Establishing Aerosol Origin
(Egen, 1835)

• Modern Methods similar to century-old
  approaches but with more data
• Direct Evidence. Photographic, satellite or
  compelling visual evidence of origin
• Aerosol Composition. Chemical fingerprinting of
  different source types (speciation, traces)
• Temporal pattern. Chemical Physical property
  analysis (satellite, ASOS, PM2.5)
• Spatial Pattern. Chemical
• Transport Pattern. Forward, backward trajectory,
  residence time analysis
• Chemistry with Transport. Combining chemical
  fingerprinting and transport (CATT)
• Dynamic modeling. Simulation model (forward,
  inversion) quantifying origin/transport

• Historical Methods
• Source attribution methods have been used for the
  past 2 centuries
• A list of methods was given my Egen, 1835. See
  paper and PPT

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Origin of Fine Dust Events over the US
Gobi dust in spring Sahara in summer
US-scale fine dust events are mainly from
intercontinental transport
Fine Dust Events, 1992-2003
ug/m3
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Sahara and Local Dust Apportionment Annual and
July
The Sahara and Local dust was apportioned based
on their respect
ive Al/Si ratios.

The maximum annual Sahara dust

In July the Sahara dust contributions are 4
-
m
m
contribution is about 1
g.m
3
8
g.m
3

In Florida, the local and Sahara dust

Throughout the Southeast, the Sahara dust
contributions are about equal but at Big
exceeds the local source contributions by
Bend, the Sahara contribution is lt 25.
w wide margin (factor of 2
-
4)
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Combined Aerosol-Trajectory Tool (CATT)

• High dust concentration (gt7 ug/m3) in July all
  originate from Sahara
• Lower concentration form local sources

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Seasonal Average Fine Soil (VIEWS database,
1992-2002)
Sahara

• Fine soil concentration is highest in the summer
  over Mississippi Valley, lowest in the winter
• In the spring, high concentrations also exists in
  the arid Southwest (Arizona and Texas)
• Evidently, the summer Mississippi Valley peak is
  Sahara dust while the Spring peak is from local
  (and Asian) sources

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Sahara Dust Impact EventsAIRS PM10 Concentration
June 30, 1993
July 5 1992
June 21, 1997
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Eastern US PM25 Event Composition

• The largest EUS PM25 events (as RCFM) are
  simultaneously events in sulfate, organics and
  soil!
• Some EUS PM25 events are single species events
• Some PM25 events are not events in any species
  their reinforcing combination causes the PM25
  event

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Aerosol Event Catalog Web pages

• Catalog of generic web objects pages, images,
  animations that relate to aerosol events
• Each web object is cataloged by location, time
  and aerosol type.

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Summary of Quantification Techniques

• Intercontinental Transport Analysis Methods
• Direct evidence satellite images
• Chemical tracers of Sahara, Gobi Local dust
  (Al, Si, Fe, K)
• Temporal analysis spikes are IC transport
  events
• Spatial analysis excess dust in the dust
  transport path
• Spatio-temporal-chemical analysis with
  backtrajectories
• Results
• The chemical, temporal and spatial analyses
  indicate a consistent estimate of 0.3 ug/m3 (2
  ug/m3 in July) of fine dust over the SE US.