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Submicron particle mass concentrations and sources in the Amazonian wet season...

Chen, Q., D. K. Farmer, L. V. Rizzo, T. Pauliquevis, M. Kuwata, T. Karl, A. Guenther, J. D. Allan, H. Coe, M. O. Andreae, U. Pöschl, J. Jimenez-Palacios, P. Artaxo, and S. Martin (2015), Submicron particle mass concentrations and sources in the Amazonian wet season (AMAZE-08), Atmos. Chem. Phys., 15, 3687-3701, doi:10.5194/acp-15-3687-2015.

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 (AMAZE08). 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 longrange 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 gasphase 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.

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Tropospheric Composition Program (TCP)