A study of formaldehyde chemistry above a forest canopy

Ann Louise Sumner, Paul B. Shepson, Tara L. Couch, Troy Thornberry, Mary Anne Carroll, Sandy Sillman, Margaret Pippin, Steven Bertman, David Tan, Ian Faloona, William Brune, Valerie Young, Owen Cooper, Jennie Moody, William Stockwell

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Abstract

Gas-phase formaldehyde (HCHO) was measured at a mixed deciduous/coniferous forest site as a part of the PROPHET 1998 summer field intensive. For the measurement period of July 11 through August 20, 1998, formaldehyde mixing ratios ranged from 0.5 to 12 ppb at a height Ο 10 m above the forest canopy, with the highest concentrations observed in southeasterly air masses. Concentrations varied on average from a mid-afternoon maximum influenced by photochemical production of 4.0 ppb, to a late night minimum of 2.2 ppb, probably resulting from dry depositional loss. An analysis of local HCHO sources revealed that isoprene was the most important of the measured formaldehyde precursors, contributing, on average, 82% of the calculated midday HCHO production rate. We calculate that the nighttime HCHO dry deposition velocity is 2.6 times that of ozone, or approximately 0.65 cm/s. In the daytime, photolysis, dry deposition, and reaction with hydroxyl radical (OH) are roughly equally important as loss processes. Explicit calculations of HCHO chemical behavior highlighted the probable importance of transport and surface deposition to understanding the diel behavior of formaldehyde.

Original languageEnglish (US)
Pages (from-to)24387-24405
Number of pages19
JournalJournal of Geophysical Research Atmospheres
Volume106
Issue number20
StatePublished - Jan 1 2001

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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    Sumner, A. L., Shepson, P. B., Couch, T. L., Thornberry, T., Carroll, M. A., Sillman, S., Pippin, M., Bertman, S., Tan, D., Faloona, I., Brune, W., Young, V., Cooper, O., Moody, J., & Stockwell, W. (2001). A study of formaldehyde chemistry above a forest canopy. Journal of Geophysical Research Atmospheres, 106(20), 24387-24405.