2.5. pm2.5 composition, sources, and air 2.5. pm2.5 composition, sources, and air concentrations...
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30 June 2004 | State of SOS-3: 1995 - 2003 | 79
2.5. PM2.5 Composition, Sources, and Air Concentrations
Composition of PM
Industrial emissions Major sources
Composition of ultrafines Motor vehicles and elemental
carbon Secondary vs primary aerosol
Local vs distant sources Exceedances in SE
Diurnal and seasonal variability
Radiative and optical properties
Internal mixing of constituents
Urban plumes under stagnation conditions
Urban plumes under advective conditions
Ozone transport from urban to rural areas
2.5. PM2.5 COMPOSITION, SOURCES, AND AIR CONCENTRATIONS Paul Solomon and David Allen
SOS was selected by EPA’s Office of Air Quality
Planning and Standards (EPA/OAQPS) to establish the
first of two initial Supersites. The other initial Supersite
was in Fresno-Bakerfield, CA. Both sites were part of
EPA's effort under the leadership of Paul Solomon and
Richard Scheffe to increase the nation's capacity to
monitor both coarse (PM10) and fine (PM2.5) fractions in
a reliable way in various parts of the United States.
The Atlanta Supersite Experiment was established
under the leadership of SOS' Chief Scientist, Bill
Chameides. SOS brought together in Atlanta during
August 1999, the most comprehensive array of
particulate-matter measurement instruments ever
assembled in the US and about 150 of the nation’s most
competent aerosol research scientists and a few from
David Allen of the University of Texas in Austin, TX and Matt Fraser of Rice University in
Houston, TX also were selected by EPA/OAQPS to lead the Houston Supersite, one of eight
EPA Supersites around the United States that are part of EPA’s PM Supersite Program – a
cooperative endeavor with other carefully selected public-health and regional-haze investigators.
Here very detailed, chemical and physical characterization measurements of ambient coarse and
fine aerosols were made in all months of the year (2001-2002) at multiple, carefully selected
urban and rural locations in southeast Texas.
The objectives of both the Atlanta and Houston Supersite programs were to “advance
scientific understanding of atmospheric processes regarding formation and accumulation of PM.”
The Atlanta Supersite Experiment was located on Jefferson Street in Atlanta, GA at a mixed
commercial and industrial area about 8 km west of the city center. Here detailed PM
characterization measurements had been made routinely as a part of EPRI’s and the Southern
Company’s SEARCH and ARIES programs for more than a year. An extraordinarily diverse
30 June 2004 | State of SOS-3: 1995 - 2003 | 80
variety of instruments were assembled at this site for comparison purposes and to determine the
mass, particle size distribution, chemical composition of individual particles, and chemical
composition of hourly-collected filter samples collected on all days of the week, and
simultaneous gas and particle measurements.
Scientific findings are summarized below – mainly from the Atlanta Supersite Experiment in
August 1999, year-round, rural and urban measurements at the Houston Supersite in southeast
Texas, and both January and July measurements at a rural site near Anderson, SC.
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2.5.1. Composition of PM in the Southeastern US The major components of total PM mass on average for the urban Atlanta Supersite study
[and both rural and urban locations within the Houston Supersite program] were: organic
material (~35%) [25-30%], sulfate (~34%) [30-40%]; ammonium (~12%) [7-10%], elemental
carbon (~3%) [2-5%], nitrate (~2%) [1-4%], and crustal material (~3%) [
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• Sulfate, ammonium ion (which neutralizes the sulfate ion), organic carbon, and elemental carbon are the major constituents of PM2.5; the annual average concentrations of these major components were spatially homogeneous across southeast Texas.
• Nevertheless, localized events with high mass fractions of sulfate or carbon occurred frequently at many monitors in this region.
• Concentrations of sulfate were slightly higher in the spring and late fall than in the summer; carbon concentrations were highest in the late fall.
• High organic-carbon to elemental-carbon ratios suggest that much of the carbonaceous material in PM2.5 in southeast Texas is not emitted directly, but is formed in the air through reactions involving both gaseous biogenic and anthropogenic VOC emissions.
KEY CITATIONS: Husain, H. and C. Christoforou. 2003. Concentration and Chemical Composition of PM2.5 Particles at a Rural Site
in South Carolina. SOS Final Report. Clemson University. 35 pp. Modey, W.K., E.J. Eatough, Y. Pang, and N.L. Eatough. 2004. Performance and evaluation of the PC-BOSS for
fine PM2.5 sampling during the summer EPA Supersite Program in Atlanta. J. Air Waste Manage. Assoc. (in press).
Russell, M.M. and D.T. Allen. 2004. Seasonal and spatial trends in primary and secondary organic carbon concentrations in southeast Texas. Atmos Environ. 38:3225-3239.
Russell, M.M., D.T. Allen, D.R. Collins, and M.P. Fraser. 2004. Daily, seasonal and spatial trends in PM2.5 mass and composition in southeast Texas. Aerosol. Sci. Technol. 38(S1):14-26, doi:10.1080/02786820390229138.
Solomon, P.A., W. Chameides, R. Weber, A. Middlebrook, C.S. Kiang, A.G. Russell, A. Butler, B. Turpin, D. Mikel, R. Scheffe, E. Cowling, E. Edgerton, J. St. John, J. Jansen, P. McMurry, S. Hering, and T. Bahadori. 2003b. Overview of the 1999 Atlanta Supersite project. J. Geophys. Res. 108(D7), 8413, doi:10.1029/2001JD001458.
Weber, R., D. Orsini, A. Sullivan, M. Bergin, C.S. Kiang, M. Chang, Y.N. Lee, P. Dasgupta, J. Slanina, B. Turpin, E. Edgerton, S. Hering, G. Allen, P. Solomon, and W. Chameides. 2003. Transient PM2.5 aerosol events in metro Atlanta: Implications for air quality and health. J. Air Waste Manage. Assoc. 53:84-91.
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2.5.2. Sources of Fine Particles in Houston, TX Fresh hydrophobic ultrafine particles are emitted by industrial sources in the Ship Channel
area of Houston; they grow in size and become more hydrophilic as they grow.
Particle growth within the VOC-rich ship channel plume exceeded that expected solely from
SO2 oxidation. But particle growth within the plume of the Parish power plant was generally
consistent with condensation of the oxidation products of SO2 when the plume did not pass over
substantial sources of VOCs.
There are five major sources of primary PM2.5 emissions in southeast Texas. They include:
1) mobile sources, 2) cooking of foods, 3) point sources, 4) geological sources, and 5) wild fires
and open burning.
• Primary mobile-source emissions are significant; evidence suggests that these emissions account for about 25-35% of PM2.5 mass in SE Texas. In fact, diesel engines in heavy duty trucks, trains, and farm or construction equipment, and gasoline engines in cars, trucks, boats, and hand tools, as well as jet-fueled aircraft, account for most primary emissions of PM2.5 in southeast Texas.
• Primary emissions from cooking of foods are significant in all urban areas; evidence suggests that these emissions account for about 10-15% of PM2.5 mass in urban areas.
• Point sources of primary PM10 particles are significant, but point-sources of primary PM2.5 particles have not yet been quantified. Thus, additional research is needed to determine the importance, size distributions, and chemical compositions of these PM2.5 primary emissions.
• Geological sources (wind-blown dust) are a relatively minor contributor to the total mass of PM2.5.
• Fires are a sporadic, but significant source of primary PM2.5 emissions in Texas. On an annual average basis, they contribute about 1-2% of the total mass of fine particles in the Houston-Galveston area; but these emissions tend to be concentrated on specific days with fire events.
KEY CITATIONS: Allen, D.T. 2002. Particulate Matter Concentrations, Compositions, and Sources in Southeast Texas: State of the
Science and Critical Research Needs. Report to the Texas Environmental Research Consortium. 93 pp. http://www.harc.edu/harc/Projects/AirQuality/Projects/Status/Reports.aspx
Brock, C.A., M. Trainer, T.B. Ryerson, J.A. Neuman, D.D. Parrish, J.S. Holloway, D.K. Nicks, Jr., G.J. Frost, G. Hübler, F.C. Fehsenfeld, J.C. Wilson, J.M. Reeves, B.G. Lafleur, H. Hilbert, E.L. Atlas, S.G. Donnelly, S.M. Schauffler, V.R. Stroud, and C. Wiedinmyer. 2003. Particle growth in urban and industrial plumes in Texas. J. Geophys. Res. 108(D3), 4111, doi:10.1029/2002JD002746.
NOAA Aeronomy Laboratory. 2003. Texas 2000 Air Quality Study - Phase II Analysis of NOAA Data. Final Report to Texas Commission on Environmental Quality Houston/Galveston Air Quality Science Evaluation. 158 pp.
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ftp://ftp.tnrcc.state.tx.us/pub/OEPAA/TAD/Modeling/HGAQSE/Contract_Reports/Data_Analysis/TexAQS200 0_NOAA_Data_Analysis.pdf 2.5.3.