Investigation of the nighttime decay of isoprene

Julia M. Hurst, Dennis J. Barket, Orlando Herrera-Gomez, Tara L. Couch, Paul B. Shepson, I. Faloona, D. Tan, W. Brune, H. Westberg, B. Lamb, T. Biesenthal, V. Young, Allen Goldstein, J. W. Munger, T. Thornberry, M. A. Carroll

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37 Scopus citations


A rapid nighttime decay of isoprene (2-methyl-1,3-butadiene) has been observed at several forest sites. Data from the Program for Research on Oxidants: PHotochemistry, Emissions, and Transport (PROPHET) have been carefully examined with respect to this phenomenon. Essentially every evening (at PROPHET), isoprene concentrations fall from several ppb to levels below 100 ppt, with an average lifetime of 2.7 hours. Since this decay rate exceeds that expected from established nighttime chemistry, other possible mechanisms are suggested and discussed. Reaction with ozone will not occur at a rate consistent with the observed decay. Calculations of nitrate radical concentrations reveal that this oxidant only becomes an important sink for isoprene after the majority of the isoprene decay has taken place. The isoprene flux data were not consistent with dry deposition playing a significant role in nighttime forest loss. On the basis of ambient measurements of OH radical concentrations at the PROPHET site, calculated isoprene decay rates were compared with observations. For some nights the observed decay can be fit strictly by OH consumption; however, the reported OH data overpredict the isoprene loss rate on most nights. We estimate that vertical mixing with isoprene-depleted air probably contributes to the fast isoprene decay observed; however, the measurements needed to support this suggestion have yet to be made.

Original languageEnglish (US)
Article number2000JD900727
Pages (from-to)24335-24346
Number of pages12
JournalJournal of Geophysical Research Atmospheres
Issue numberD20
StatePublished - Oct 27 2001

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Materials Chemistry
  • Polymers and Plastics
  • Physical and Theoretical Chemistry


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