A comparison of new measurements of total monoterpene flux with improved measurements of speciated monoterpene flux A. Lee1, G. W. Schade2, R. Holzinger1, and A. H. Goldstein1 1Department of Environmental Science, Policy, and Management, University of California, Berkeley, 151 Hilgard Hall # 3110, Berkeley, CA 94720-3110, USA 2Institute of Environmental Physics, University of Bremen, NW1, Otto-Hahn-Allee 1, D-28359 Bremen, Germany
Abstract. Many monoterpenes have been identified in forest emissions using gas
chromatography (GC). Until now, it has been impossible to determine whether
all monoterpenes are appropriately measured using GC techniques. We used a
proton transfer reaction mass spectrometer (PTR-MS) coupled with the eddy
covariance (EC) technique to measure mixing ratios and fluxes of total
monoterpenes above a ponderosa pine plantation. We compared PTR-MS-EC
results with simultaneous measurements of eight speciated monoterpenes,
β-pinene, α-pinene, 3-carene, d-limonene, β-phellandrene,
α-terpinene, camphene, and terpinolene, made with an
automated, in situ gas chromatograph with flame ionization detectors
(GC-FID), coupled to a relaxed eddy accumulation system (REA). Monoterpene
mixing ratios and fluxes measured by PTR-MS averaged 30±2.3% and
31±9.2% larger than by GC-FID, with larger mixing ratio
discrepancies between the two techniques at night than during the day. Two
unidentified peaks that correlated with β-pinene were resolved in the
chromatograms and completely accounted for the daytime difference and
reduced the nighttime mixing ratio difference to 20±2.9%.
Measurements of total monoterpenes by PTR-MS-EC indicated that GC-FID-REA
measured the common, longer-lived monoterpenes well, but that additional
terpenes were emitted from the ecosystem that represented an important
contribution to the total mixing ratio above the forest at night.
Citation: Lee, A., Schade, G. W., Holzinger, R., and Goldstein, A. H.: A comparison of new measurements of total monoterpene flux with improved measurements of speciated monoterpene flux, Atmos. Chem. Phys., 5, 505-513, doi:10.5194/acp-5-505-2005, 2005.