The bi-directional exchange of oxygenated VOCs between a loblolly pine (Pinus taeda) plantation and the atmosphere T. Karl1, P. Harley1, A. Guenther1, R. Rasmussen2, B. Baker3, K. Jardine3, and E. Nemitz4 1National Center for Atmospheric Research, Boulder, Colorado, USA 2Oregon Health and Science University, Oregon, USA 3South Dakota School of Mines and Technology, Rapid City, South Dakota, USA 4Centre for Ecology and Hydrology, Edinburgh, UK
Abstract. Using new in-situ field observations of the most abundant oxygenated VOCs
(methanol, acetaldehyde, acetone, C3/C4 carbonyls, MVK+MAC and
acetic acid) we were able to constrain emission and deposition patterns
above and within a loblolly pine (Pinus taeda) plantation with a sweetgum (Liquidambar styraciflua) understory.
During the day canopy scale measurements showed significant emission of
methanol and acetone, while methyl vinyl ketone and methacrolein,
acetaldehyde and acetic acid were mainly deposited during the day. All
oxygenated compounds exhibited strong losses during the night that could not
be explained by conventional dry deposition parameterizations. Accompanying
leaf level measurements indicated substantial methanol and acetone emissions
from loblolly pine. The exchange of acetaldehyde was more complex.
Laboratory measurements made on loblolly pine needles indicated that
acetaldehyde may be either emitted or taken up depending on ambient
concentrations, with the compensation point increasing exponentially with
temperature, and that mature needles tended to emit more acetaldehyde than
younger needles. Canopy scale measurements suggested mostly deposition.
Short-term (approx. 2 h) ozone fumigation in the laboratory had no
detectable impact on post-exposure emissions of methanol and acetone, but
decreased the exchange rates of acetaldehyde. The emission of a variety of
oxygenated compounds (e.g. carbonyls and alcohols) was triggered or
significantly enhanced during laboratory ozone fumigation experiments. These
results suggest that higher ambient ozone levels in the future might enhance
the biogenic contribution of some oxygenated compounds. Those with
sufficiently low vapor pressures may potentially influence secondary organic
aerosol growth. Compounds recently hypothesized to be primarily produced in
the canopy atmosphere via ozone plus terpenoid-type reactions can also
originate from the oxidation reaction of ozone with leaf surfaces and inside
the leaf. This needs to be taken into account when scaling up very reactive
Citation: Karl, T., Harley, P., Guenther, A., Rasmussen, R., Baker, B., Jardine, K., and Nemitz, E.: The bi-directional exchange of oxygenated VOCs between a loblolly pine (Pinus taeda) plantation and the atmosphere, Atmos. Chem. Phys., 5, 3015-3031, doi:10.5194/acp-5-3015-2005, 2005.