Photochemistry of biogenic emissions over the Amazon forest
Article first published online: 21 SEP 2012
Copyright 1988 by the American Geophysical Union.
Journal of Geophysical Research: Atmospheres (1984–2012)
Volume 93, Issue D2, pages 1477–1486, 20 February 1988
How to Cite
1988), Photochemistry of biogenic emissions over the Amazon forest, J. Geophys. Res., 93(D2), 1477–1486, doi:10.1029/JD093iD02p01477., and (
- Issue published online: 21 SEP 2012
- Article first published online: 21 SEP 2012
- Manuscript Accepted: 23 JUN 1987
- Manuscript Received: 18 DEC 1986
The boundary layer chemistry over the Amazon forest during the dry season is simulated with a photochemical model. Results are in good agreement with measurements of isoprene, NO, ozone, and organic acids. Photochemical reactions of biogenic isoprene and NOx can supply most of the ozone observed in the boundary layer. Production of ozone is very sensitive to the availability of NOx, but is insensitive to the isoprene source strength. High concentrations of total odd nitrogen (NOy,) are predicted for the planetary boundary layer, about 1 ppb in the mixed layer and 0.75 ppb in the convective cloud layer. Most of the odd nitrogen (≈70%) is present as PAN-type species, which are removed by dry deposition to the forest. The observed daytime variations of isoprene are explained by a strong dependence of the isoprene emission flux on sun angle. Nighttime losses of isoprene exceed rates of reaction with NO3 and O3 and appear to reflect dry-deposition processes. The 24-hour averaged isoprene emission flux is calculated to be 38 mg m−2 d−1. Photooxidation of isoprene could account for a large fraction of the CO enrichment observed in the boundary layer under unpolluted conditions and could constitute an important atmospheric source of formic acid, methacrylic acid, and pyruvic acid.