HR: 10:35h
AN: A21F-02    [PDF]
TI: Ozone Oxidation of Monoterpenes, Sesquiterpenes, and Oxygenated Terpenes: Product Yields and Relevance to Field Observations and Atmospheric Chemistry
AU: * Lee, A
EM: alee@nature.berkeley.edu
AF: Department of Environmental Science, Policy, and Management, University of California at Berkeley, Berkeley, CA 94720-3110 United States
AU: Goldstein, A H
EM: ahg@nature.berkeley.edu
AF: Department of Environmental Science, Policy, and Management, University of California at Berkeley, Berkeley, CA 94720-3110 United States
AU: Keywood, M
EM: melita@cheme.caltech.edu
AF: Departments of Chemical Engineering and Environmental Science and Engineering, California Institute of Technology, Pasadena, CA 91125 United States
AU: Varutbangkul, V
EM: tomtor@its.caltech.edu
AF: Departments of Chemical Engineering and Environmental Science and Engineering, California Institute of Technology, Pasadena, CA 91125 United States
AU: Bahreini, R
EM: broya@its.caltech.edu
AF: Departments of Chemical Engineering and Environmental Science and Engineering, California Institute of Technology, Pasadena, CA 91125 United States
AU: Gao, S
EM: sgao@caltech.edu
AF: Departments of Chemical Engineering and Environmental Science and Engineering, California Institute of Technology, Pasadena, CA 91125 United States
AU: Flagan, R
EM: flagan@caltech.edu
AF: Departments of Chemical Engineering and Environmental Science and Engineering, California Institute of Technology, Pasadena, CA 91125 United States
AU: Seinfeld, J
EM: seinfeld@caltech.edu
AF: Departments of Chemical Engineering and Environmental Science and Engineering, California Institute of Technology, Pasadena, CA 91125 United States
AB: Measurements conducted in a ponderosa pine plantation in the Sierra Nevada, CA have shown that the reaction of ozone with gas-phase compounds dominates summertime ozone deposition to the ecosystem, with an exponential dependence on temperature that is similar to monoterpene emissions. Monoterpene fluxes measured above the forest canopy represent the monoterpenes that have effectively "escaped" the canopy, whereas measurements of ozone deposition due to chemistry provide an estimate of the compounds "missing" from the ecosystem scale flux due to within-canopy reactions with ozone. To be lost within the canopy, these "missing" compounds must have short lifetimes, on the order of a few minutes, compared to those that escape. Longer-lived, less reactive terpenes are widely measured, and are typically the compounds included in global inventories to assess impacts of biogenic emissions on tropospheric ozone production and secondary organic aerosol formation. The shorter-lived, highly reactive terpenes, however, are more difficult to observe and rarely measured, and thus the impacts of these compounds are likely inadequately represented. To better characterize the ozone-initiated oxidation of a range of terpenes, including those that escape the forest canopy and those oxidized within the canopy, we conducted laboratory measurements at the Caltech Indoor Chamber Facility to characterize the gas and particle phase yields from terpene + ozone reactions. These measurements were made to provide a guide to the oxidation products we expect to observe within a forest canopy, and to expand the knowledge of the impacts of these terpenes (both "missing" and "escaped") on atmospheric chemistry. The terpenes studied included several monoterpenes: $\alpha$- and $\beta$-pinene, $\alpha$-terpinene, terpinolene, myrcene, and 3-carene, two sesquiterpenes: $\beta$-caryophyllene and $\alpha$-humulene, and two oxygenated terpenes: linalool and methyl chavicol, many of which have been observed at our field site. The terpenes were each reacted singly with ozone, in the dark, in the presence of ammonium sulfate seed aerosol and an OH scavenger. A Proton Transfer Reaction Mass Spectrometer was used to measure the gas-phase yields of many low molecular weight oxidation products, including formaldehyde, acetaldehyde, formic acid, acetic acid, and acetone, as well as yields of larger oxidation products, including nopinone, pinonaldehyde, and many currently unidentified compounds which were observed according to their mass to charge ratios. Secondary organic aerosol yields, and yields of small carbonyls and larger oxidation products varied widely between the different terpene species tested. In general, terpenes with high aerosol yields had low yields of small carbonyls, including the sesquiterpenes and $\alpha$-terpinene, while terpenes with low aerosol yields had high yields of small carbonyls, including linalool, methyl chavicol, myrcene, and terpinolene.
DE: 0315 Biosphere/atmosphere interactions
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting