High upward fluxes of formic acid from a boreal forest canopy

Siegfried Schobesberger, Felipe D. Lopez-Hilfiker, Ditte Taipale, Dylan B. Millet, Emma L. D'Ambro, Pekka Rantala, Ivan Mammarella, Putian Zhou, Glenn M. Wolfe, Ben H. Lee, Michael Boy, Joel A. Thornton

Research output: Contribution to journalArticlepeer-review

32 Scopus citations


Eddy covariance fluxes of formic acid, HCOOH, were measured over a boreal forest canopy in spring/summer 2014. The HCOOH fluxes were bidirectional but mostly upward during daytime, in contrast to studies elsewhere that reported mostly downward fluxes. Downward flux episodes were explained well by modeled dry deposition rates. The sum of net observed flux and modeled dry deposition yields an upward “gross flux” of HCOOH, which could not be quantitatively explained by literature estimates of direct vegetative/soil emissions nor by efficient chemical production from other volatile organic compounds, suggesting missing or greatly underestimated HCOOH sources in the boreal ecosystem. We implemented a vegetative HCOOH source into the GEOS-Chem chemical transport model to match our derived gross flux and evaluated the updated model against airborne and spaceborne observations. Model biases in the boundary layer were substantially reduced based on this revised treatment, but biases in the free troposphere remain unexplained.

Original languageEnglish (US)
Pages (from-to)9342-9351
Number of pages10
JournalGeophysical Research Letters
Issue number17
StatePublished - Sep 16 2016

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  • biogenic emissions
  • boreal forest
  • chemical ionization mass spectrometry
  • eddy covariance fluxes
  • formic acid


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