Articles | Volume 14, issue 22
Atmos. Chem. Phys., 14, 12143–12153, 2014
Atmos. Chem. Phys., 14, 12143–12153, 2014

Research article 19 Nov 2014

Research article | 19 Nov 2014

Reactivity of stabilized Criegee intermediates (sCIs) from isoprene and monoterpene ozonolysis toward SO2 and organic acids

M. Sipilä1, T. Jokinen1,2, T. Berndt2, S. Richters2, R. Makkonen1,3, N. M. Donahue4, R. L. Mauldin III1,5,6, T. Kurtén7, P. Paasonen1, N. Sarnela1, M. Ehn1, H. Junninen1, M. P. Rissanen1, J. Thornton1, F. Stratmann2, H. Herrmann1,8,9, D. R. Worsnop1, M. Kulmala1, V.-M. Kerminen1, and T. Petäjä1 M. Sipilä et al.
  • 1Department of Physics, University of Helsinki, 00014 Helsinki, Finland
  • 2Leibniz Institute for Tropospheric Research, TROPOS, 04318 Leipzig, Germany
  • 3Department of Geosciences, University of Oslo, 0316 Oslo, Norway
  • 4Center for Atmospheric Particle Studies, Carnegie-Mellon University, Pittsburgh, PA 15213, USA
  • 5Department of Atmospheric and Oceanic Sciences University of Colorado – Boulder, Boulder, Colorado 80309, USA
  • 6Institute for Arctic and Alpine Research, University of Colorado – Boulder, Boulder, Colorado 80309, USA
  • 7Department of Chemistry, University of Helsinki, 00014 Helsinki, Finland
  • 8Department of Applied Physics, University of Eastern Finland, 70211 Kuopio, Finland
  • 9Aerodyne Research Inc., Billerica, Massachusetts 01821, USA

Abstract. Oxidation processes in Earth's atmosphere are tightly connected to many environmental and human health issues and are essential drivers for biogeochemistry. Until the recent discovery of the atmospheric relevance of the reaction of stabilized Criegee intermediates (sCIs) with SO2, atmospheric oxidation processes were thought to be dominated by a few main oxidants: ozone, hydroxyl radicals (OH), nitrate radicals and, e.g. over oceans, halogen atoms such as chlorine. Here, we report results from laboratory experiments at 293 K and atmospheric pressure focusing on sCI formation from the ozonolysis of isoprene and the most abundant monoterpenes (α-pinene and limonene), and subsequent reactions of the resulting sCIs with SO2 producing sulfuric acid (H2SO4). The measured total sCI yields were (0.15 ± 0.07), (0.27 ± 0.12) and (0.58 ± 0.26) for α-pinene, limonene and isoprene, respectively. The ratio between the rate coefficient for the sCI loss (including thermal decomposition and the reaction with water vapour) and the rate coefficient for the reaction of sCI with SO2, k(loss) /k(sCI + SO2), was determined at relative humidities of 10 and 50%. Observed values represent the average reactivity of all sCIs produced from the individual alkene used in the ozonolysis. For the monoterpene-derived sCIs, the relative rate coefficients k(loss) / k(sCI + SO2) were in the range (2.0–2.4) × 1012 molecules cm−3 and nearly independent of the relative humidity. This fact points to a minor importance of the sCI + H2O reaction in the case of the sCI arising from α-pinene and limonene. For the isoprene sCIs, however, the ratio k(loss) / k(sCI + SO2) was strongly dependent on the relative humidity. To explore whether sCIs could have a more general role in atmospheric oxidation, we investigated as an example the reactivity of acetone oxide (sCI from the ozonolysis of 2,3-dimethyl-2-butene) toward small organic acids, i.e. formic and acetic acid. Acetone oxide was found to react faster with the organic acids than with SO2; k(sCI + acid) / k(sCI + SO2) = (2.8 ± 0.3) for formic acid, and k(sCI + acid) / k(sCI + SO2) = (3.4 ± 0.2) for acetic acid. This finding indicates that sCIs can play a role in the formation and loss of other atmospheric constituents besides SO2.

Final-revised paper