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Open AccessArticle

Composition and Sources of Particulate Matter Measured near Houston, TX: Anthropogenic-Biogenic Interactions

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McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin, TX 78712, USA
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Department of Civil and Environmental Engineering, Rice University, Houston, TX 77005, USA
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Department of Environmental Science, Baylor University, Waco, TX 76798, USA
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Aerodyne Research Inc., Billerica, MA 01821, USA
*
Author to whom correspondence should be addressed.
Academic Editor: Robert W. Talbot
Atmosphere 2016, 7(5), 73; https://doi.org/10.3390/atmos7050073
Received: 6 April 2016 / Revised: 6 May 2016 / Accepted: 17 May 2016 / Published: 23 May 2016
(This article belongs to the Special Issue Air Quality and Source Apportionment)
Particulate matter was measured in Conroe, Texas (~60 km north of downtown Houston, Texas) during the September 2013 DISCOVER-AQ campaign to determine the sources of particulate matter in the region. The measurement site is influenced by high biogenic emission rates as well as transport of anthropogenic pollutants from the Houston metropolitan area and is therefore an ideal location to study anthropogenic-biogenic interactions. Data from an Aerosol Chemical Speciation Monitor (ACSM) suggest that on average 64 percent of non-refractory PM1 was organic material, including a high fraction (27%–41%) of organic nitrates. There was little diurnal variation in the concentrations of ammonium sulfate; however, concentrations of organic and organic nitrate aerosol were consistently higher at night than during the day. Potential explanations for the higher organic aerosol loadings at night include changing boundary layer height, increased partitioning to the particle phase at lower temperatures, and differences between daytime and nighttime chemical processes such as nitrate radical chemistry. Positive matrix factorization was applied to the organic aerosol mass spectra measured by the ACSM and three factors were resolved—two factors representing oxygenated organic aerosol and one factor representing hydrocarbon-like organic aerosol. The factors suggest that the measured aerosol was well mixed and highly processed, consistent with the distance from the site to major aerosol sources, as well as the high photochemical activity. View Full-Text
Keywords: organic aerosol; ambient measurements; diurnal variation; positive matrix factorization organic aerosol; ambient measurements; diurnal variation; positive matrix factorization
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Bean, J.K.; Faxon, C.B.; Leong, Y.J.; Wallace, H.W.; Cevik, B.K.; Ortiz, S.; Canagaratna, M.R.; Usenko, S.; Sheesley, R.J.; Griffin, R.J.; Hildebrandt Ruiz, L. Composition and Sources of Particulate Matter Measured near Houston, TX: Anthropogenic-Biogenic Interactions. Atmosphere 2016, 7, 73.

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