The reaction of Criegee intermediate CH2OO with water dimer: primary products and atmospheric impact

Leonid Sheps, Brandon Rotavera, Arkke Eskola, David Osborn, Craig Taatjes, Kendrew Au, Dudley Shallcross, Anwar Khan, Carl Percival

Research output: Contribution to journalArticle (Academic Journal)peer-review

47 Citations (Scopus)
379 Downloads (Pure)


The rapid reaction of the smallest Criegee intermediate, CH2OO, with water dimers is the dominant removal mechanism for CH2OO in the Earth’s atmosphere, but its products are not well understood. This reaction was recently suggested as a significant source of the most abundant tropospheric organic acid, formic acid (HCOOH), which is consistently underpredicted by atmospheric models. However, using time-resolved measurements of reaction kinetics by UV absorption and product analysis by photoionization mass spectrometry, we show that the primary products of this reaction are formaldehyde and hydroxymethyl hydroperoxide (HMHP), with direct HCOOH yields of less than 10%. Incorporating our results into a global chemistry-transport model further reduces HCOOH levels by 10 – 90%, relative to previous assumptions, which indicates that the reaction CH2OO + water dimer by itself cannot resolve the discrepancy between the measured and predicted HCOOH levels.
Original languageEnglish
Pages (from-to)21970-21979
Number of pages10
JournalPhysical Chemistry Chemical Physics
Issue number33
Early online date4 Aug 2017
Publication statusPublished - 7 Sep 2017

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