Seasonality of Formic Acid (HCOOH) in London during the ClearfLo Campaign

Thomas J. Bannan, A. Murray Booth, Michael Le Breton, Asan Bacak, Jennifer B.A. Muller, Kimberley E. Leather, M. Anwar H. Khan, James D. Lee, Rachel E. Dunmore, James R. Hopkins, Zoë L. Fleming, Leonid Sheps, Craig A Taatjes, Dudley E. Shallcross, Carl J. Percival*

*Corresponding author for this work

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

12 Citations (Scopus)
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Following measurements in the winter of 2012, formic acid (HCOOH) and nitric acid (HNO3) were measured using a chemical ionization mass spectrometer (CIMS) during the Summer Clean Air for London (ClearfLo) campaign in London, 2012. Consequently, the seasonal dependence of formic acid sources could be better understood. A mean formic acid concentration of 1.3 ppb and a maximum of 12.7 ppb was measured which is significantly greater than that measured during the winter campaign (0.63 ppb and 6.7 ppb, respectively). Daily calibrations of formic acid during the summer campaign gave sensitivities of 1.2 ion counts s-1 parts per trillion (ppt) by volume-1 and a limit of detection of 34 ppt. During the summer campaign, there was no correlation between formic acid and anthropogenic emissions such as NOx and CO or peaks associated with the rush hour as was identified in the winter. Rather, peaks in formic acid were observed that correlated with solar irradiance. Analysis using a photochemical trajectory model has been conducted to determine the source of this formic acid. The contribution of formic acid formation through ozonolysis of alkenes is important but the secondary production from biogenic VOCs could be the most dominant source of formic acid at this measurement site during the summer.

Original languageEnglish
Pages (from-to)12488-12498
Number of pages11
JournalJournal of Geophysical Research: Atmospheres
Issue number22
Early online date24 Nov 2017
Publication statusPublished - 14 Dec 2017


  • Air quality
  • Chemical ionization mass spectrometry
  • Clean Air for London
  • Criegee intermediate
  • Formic acid
  • Ozonolysis

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