Isoprene and its oxidation products methyl vinyl ketone, methacrolein, and isoprene related peroxides measured online over the tropical rain forest of Surinam in March 1998

C Warneke*, R Holzinger, A Hansel, A Jordan, W Lindinger, U Poschl, J Williams, P Hoor, H Fischer, PJ Crutzen, HA Scheeren, J Lelieveld

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

Airborne measurements of volatile organic compounds (VOC) were performed over the tropical rainforest in Surinam (0-12 km altitude, 2 degrees -7 degrees N, 54 degrees -58 degrees W) using the proton transfer reaction mass spectrometry (PTR-MS) technique, which allows online monitoring of compounds like isoprene, its oxidation products methyl vinyl ketone, methacrolein, tentatively identified hydroxy-isoprene-hydroperoxides, and several other organic compounds. Isoprene volume mixing ratios (VMR) varied from below the detection limit at the highest altitudes to about 7 nmol/mol in the planetary boundary layer shortly before sunset. Correlations between isoprene and its product compounds were made for different times of day and altitudes, with the isoprene-hydroperoxides showing the highest correlation. Model calculated mixing ratios of the isoprene oxidation products using a detailed hydrocarbon oxidation mechanism, as well as the intercomparison measurement with air samples collected during the flights in canisters and later analysed with a GC-FID, showed good agreement with the PTR-MS measurements, in particular at the higher mixing ratios.

Low OH concentrations in the range of 1-3 x 10(5) molecules cm(-3) averaged over 24 hours were calculated due to loss of OH and HO(2) in the isoprene oxidation chain, thereby strongly enhancing the lifetime of gases in the forest boundary layer.

Original languageEnglish
Pages (from-to)167-185
Number of pages19
JournalJournal of Atmospheric Chemistry
Volume38
Issue number2
Publication statusPublished - Feb-2001

Keywords

  • isoprene
  • isoprene oxidation products
  • tropical forest boundary layer
  • box model
  • methylvinylketone
  • methacrolein
  • VOLATILE ORGANIC-COMPOUNDS
  • TROPOSPHERIC CHEMISTRY
  • NONMETHANE HYDROCARBONS
  • EMISSION
  • OZONE
  • PHOTOSYNTHESIS
  • TEMPERATURE
  • IMPACT
  • PPTV

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