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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113, D09303, doi:10.1029/2007JD009426, 2008

Formation of secondary organic aerosol from irradiated α-pinene/toluene/NO_x mixtures and the effect of isoprene and sulfur dioxide

Mohammed Jaoui

Alion Science and Technology, Research Triangle Park, North Carolina, USA

Edward O. Edney

National Exposure Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA

Tadeusz E. Kleindienst

National Exposure Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA

Michael Lewandowski

National Exposure Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA

John H. Offenberg

National Exposure Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA

Jason D. Surratt

Departments of Environmental Science and Engineering, Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, USA

John H. Seinfeld

Departments of Environmental Science and Engineering, Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, USA

Abstract

Secondary organic aerosol (SOA) was generated by irradiating a series of α-pinene/toluene/NO _x mixtures in the absence and presence of isoprene or sulfur dioxide. The purpose of the experiment was to evaluate the extent to which chemical perturbations to this base-case (α-pinene/toluene) mixture led to changes in the gas-phase chemistry which strongly influences mass and composition of SOA and secondary organic carbon (SOC) formed. The chemical composition was examined by gas chromatography-mass spectrometry (GC-MS) and laser desorption ionization-mass spectrometry (LDI-MS). The results showed that the addition of isoprene to the base-case mixture significantly lowered the amount of toluene reacted, and thereby lowered the amount SOC produced. Simultaneous measurement of the organic NO _y showed that reactions of isoprene effectively sequester NO₂ by producing gas-phase organic nitrates. The addition of SO₂ to the base-case mixture, while having little effect on the gas-phase chemistry, formed sulfuric acid which led to a modest enhancement of the SOC through acid-catalyzed or sulfur-incorporating reactions of α-pinene. The contribution of each hydrocarbon to the composition of the SOA was estimated using an organic tracer method. SOC from the tracer technique tended to underpredict the measured SOC, although the underprediction was especially pronounced with SO₂ present. A comparison of the chromatographic results from samples of the irradiation of the α-pinene/toluene/isoprene/NO _x /SO₂ mixture and ambient PM_2.5 showed the presence of two unique peaks that were associated with reactions of isoprene and SO₂.

Received 27 September 2007; accepted 6 February 2008; published 10 May 2008.

Keywords: α-Pinene; isoprene; toluene; mixtures; SOA; SO₂.

Index Terms: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801, 4906); 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0365 Atmospheric Composition and Structure: Troposphere: composition and chemistry; 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions (0426, 1610).

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 575810 bytes)

Citation: Jaoui, M., E. O. Edney, T. E. Kleindienst, M. Lewandowski, J. H. Offenberg, J. D. Surratt, and J. H. Seinfeld (2008), Formation of secondary organic aerosol from irradiated α-pinene/toluene/NO_x mixtures and the effect of isoprene and sulfur dioxide, J. Geophys. Res., 113, D09303, doi:10.1029/2007JD009426.

Copyright 2008 by the American Geophysical Union.