ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-11-1039-2011 Evidence for a significant proportion of Secondary Organic Aerosol from isoprene above a maritime tropical forest Robinson N. H. 1 Hamilton J. F. 2 Allan J. D. 1 3 Langford B. 4 Oram D. E. 5 Chen Q. 6 Docherty K. 7 8 Farmer D. K. 7 8 Jimenez J. L. 7 Ward M. W. 2 Hewitt C. N. 4 Barley M. H. 1 Jenkin M. E. 9 Rickard A. R. 10 Martin S. T. 6 McFiggans G. 1 Coe H. 1 Centre for Atmospheric Science, School of Earth Atmospheric and Environmental Science, University of Manchester, UK Department of Chemistry, University of York, UK National Centre for Atmospheric Science, University of Manchester, UK Lancaster Environment Centre, Lancaster University, Lancaster, UK National Centre for Atmospheric Science, University of East Anglia, UK School of Engineering and Applied Sciences, Harvard University, USA Department of Chemistry and Biochemistry, and CIRES, University of Colorado at Boulder, CO, USA Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, CO, USA Atmospheric Chemistry Services, Okehampton, UK National Centre for Atmospheric Science, School of Chemistry, University of Leeds, UK 04 02 2011 11 3 1039 1050 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/11/1039/2011/acp-11-1039-2011.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/11/1039/2011/acp-11-1039-2011.pdf

Isoprene is the most abundant non-methane biogenic volatile organic compound (BVOC), but the processes governing secondary organic aerosol (SOA) formation from isoprene oxidation are only beginning to become understood and selective quantification of the atmospheric particulate burden remains difficult. Organic aerosol above a tropical rainforest located in Danum Valley, Borneo, Malaysia, a high isoprene emission region, was studied during Summer 2008 using Aerosol Mass Spectrometry and offline detailed characterisation using comprehensive two dimensional gas chromatography. Observations indicate that a substantial fraction (up to 15% by mass) of atmospheric sub-micron organic aerosol was observed as methylfuran (MF) after thermal desorption. This observation was associated with the simultaneous measurements of established gas-phase isoprene oxidation products methylvinylketone (MVK) and methacrolein (MACR). Observations of MF were also made during experimental chamber oxidation of isoprene. Positive matrix factorisation of the AMS organic mass spectral time series produced a robust factor which accounts for an average of 23% (0.18 μg m<sup>−3</sup>), reaching as much as 53% (0.50 μg m<sup>−3</sup>) of the total oraganic loading, identified by (and highly correlated with) a strong MF signal. Assuming that this factor is generally representative of isoprene SOA, isoprene derived aerosol plays a significant role in the region. Comparisons with measurements from other studies suggest this type of isoprene SOA plays a role in other isoprene dominated environments, albeit with varying significance.

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