Articles | Volume 15, issue 7
Atmos. Chem. Phys., 15, 3687–3701, 2015

Special issue: Amazonian Aerosol Characterization Experiment 2008...

Atmos. Chem. Phys., 15, 3687–3701, 2015
Research article
02 Apr 2015
Research article | 02 Apr 2015

Submicron particle mass concentrations and sources in the Amazonian wet season (AMAZE-08)

Q. Chen1,*, D. K. Farmer2,**, L. V. Rizzo3, T. Pauliquevis3, M. Kuwata1,***, T. G. Karl4,****, A. Guenther4,*****, J. D. Allan5, H. Coe5, M. O. Andreae6, U. Pöschl6, J. L. Jimenez2, P. Artaxo7, and S. T. Martin1 Q. Chen et al.
  • 1School of Engineering and Applied Sciences & Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA
  • 2Department of Chemistry and Biochemistry & Cooperative Institute for Research in Environmental Science, University of Colorado, Boulder, CO, USA
  • 3Department of Natural and Earth Sciences, Federal University of São Paulo, Diadema, Brazil
  • 4National Center for Atmospheric Research, Boulder, CO, USA
  • 5National Centre for Atmospheric Science & School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, UK
  • 6Biogeochemistry and Multiphase Chemistry Departments, Max Planck Institute for Chemistry, Mainz, Germany
  • 7Applied Physics Department & Atmospheric Science Department, University of São Paulo, São Paulo, Brazil
  • *now at: State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, China
  • **now at: Department of Chemistry, Colorado State University, Fort Collins, CO, USA
  • ***now at: Earth Observatory of Singapore, Nanyang Technological University, Singapore
  • ****now at: Institute of Meteorology and Geophysics, University of Innsbruck, Austria
  • *****now at: Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, WA, USA

Abstract. Real-time mass spectra of the non-refractory species in submicron aerosol particles were recorded in a tropical rainforest in the central Amazon Basin during the wet season from February to March 2008, as a part of the Amazonian Aerosol Characterization Experiment (AMAZE-08). Organic material accounted on average for more than 80% of the non-refractory submicron particle mass concentrations during the period of measurements. There was insufficient ammonium to neutralize sulfate. In this acidic, isoprene-rich, HO2-dominant environment, positive-matrix factorization of the time series of particle mass spectra identified four statistical factors to account for the 99% of the variance in the signal intensities of the organic constituents. The first factor was identified as associated with regional and local pollution and labeled "HOA" for its hydrocarbon-like characteristics. A second factor was associated with long-range transport and labeled "OOA-1" for its oxygenated characteristics. A third factor, labeled "OOA-2," was implicated as associated with the reactive uptake of isoprene oxidation products, especially of epoxydiols to acidic haze, fog, or cloud droplets. A fourth factor, labeled "OOA-3," was consistent with an association with the fresh production of secondary organic material (SOM) by the mechanism of gas-phase oxidation of biogenic volatile organic precursors followed by gas-to-particle conversion of the oxidation products. The suffixes 1, 2, and 3 on the OOA labels signify ordinal ranking with respect to the extent of oxidation represented by the factor. The process of aqueous-phase oxidation of water-soluble products of gas-phase photochemistry might also have been associated to some extent with the OOA-2 factor. The campaign-average factor loadings had a ratio of 1.4:1 for OOA-2 : OOA-3, suggesting the comparable importance of particle-phase compared to gas-phase pathways for the production of SOM during the study period.

Short summary
Submicron particle mass concentration in the Amazon during the wet season of 2008 was dominated by organic material. The PMF analysis finds a comparable importance of gas-phase (gas-to-particle condensation) and particle-phase (reactive uptake of isoprene oxidation products, especially of epoxydiols to acidic haze, fog, or cloud droplets) production of secondary organic material during the study period, together accounting for >70% of the organic-particle mass concentration.
Final-revised paper