HR: 11:50h
AN: A21F-07    [PDF]
TI: PTR-MS and GC-MS Analyses of Sesquiterpenes
AU: * Rasmussen, R A
EM: rei@ebs.ogi.edu
AF: Oregon Graduate Institute, Environmental and Biomoleculr Systems 20000 NW Walker Rd., Beaverton, OR 97006 United States
AU: Geron, C
EM: Geron.Chris@epamail.epa.gov
AF: U.S. Environmental Protection Agency, National Risk Management Research Laboratory Mail Drop E305-02, 109 TW Alexander Dr., Research Triange Par, NC 27711 United States
AU: Goldstein, A H
EM: ahg@nature.berkeley.edu
AF: University of California, Department of Environmental Science, Policy, and Management 151 Hilgard Hall, Berkeley, CA 94720-3110 United States
AU: Holzinger, R
EM: holzing@nature.berkeley.edu
AF: University of California, Department of Environmental Science, Policy, and Management 151 Hilgard Hall, Berkeley, CA 94720-3110 United States
AU: Lee, A
EM: alee@nature.berkeley.edu
AF: University of California, Department of Environmental Science, Policy, and Management 151 Hilgard Hall, Berkeley, CA 94720-3110 United States
AB: Terpene hydrocarbons are ubiquitous compounds in the atmosphere. Frits Went, in 1960 suggested that the volatile organic emissions from plants especially the monoterpenes were responsible for the formation of the atmosphere's `blue haze'. Surveys of plant emissions using a Proton Transfer Reaction - Mass Spectrometer (PTR-MS) have shown that many species emit sesquiterpenes (Ssqt's) independent of emitting monoterpenes or isoprene. It is possible they are a comparable source of the organic micro-aerosols responsible for scattering the blue end of the spectrum, i.e. `blue haze' in addition to the monoterpenes as they have more rapid and complete reactions with ozone resulting in particles. Ambient concentrations of the terpenic hydrocarbons are site dependent, but are typically very low from a few to 1000 pptCv, except for isoprene which has summer mid-day median levels of 3 to 6 ppbCv. The sesquiterpenes are very difficult to measure in the atmosphere by conventional means but cubebene, copaene, bourbonene and alpha- and beta-caryophyllene are common foliage emissions. Direct measurements of isoprene, monoterpenes and sesquiterpenes over plant foliages with a PTR-MS were compared with captive samples of the air from the same plant foliages collected in Summa canisters. None of the biogenic organic emissions stored in the Summa canisters showed any significant losses due to wall effects. Neither did we observe that any of the processing steps were responsible for losses or internal molecular rearrangements. The reason for the stability and 100% recovery of these C5 to C15 olefinic compounds at room temperature is believed to be due to the water layer formed on the electropolished stainless steel walls of the canister under pressure at 30 psig. Ozone added to the test systems was observed to have an immediate effect on the sesquiterpenes at ambient levels. Measurements made this past summer at the Duke and Blodgett Research Forests again confirm that the ambient levels of the Ssqt's were very low and unless made close to the source foliage not measurable. However, Ssqt's were readily measured in branch and leaf enclosures in most of the species surveyed. Some conifer foliages produced Ssqt's at rates comparable to their monoterpenes emission rates, but more typically the rates were 1/50 to 1/100 that of the monoterpenes.
DE: 0315 Biosphere/atmosphere interactions
DE: 0322 Constituent sources and sinks
DE: 0365 Troposphere--composition and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting