Eddy covariance VOC emission and deposition fluxes above grassland using PTR-TOF 1Institute of Ion Physics and Applied Physics, University of Innsbruck, Innsbruck, Austria
20 Jan 2011
2Ionicon Analytik, Innsbruck, Austria
3Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, CO 80307, USA
4Institute of Ecology, University of Innsbruck, Innsbruck, Austria
*current address: Division of atmospheric Sciences, Department of Physics, University of Helsinki, Helsinki, Finland
**current address: UMR 5256, IRCELYON CNRS, Université Lyon 1, Lyon, France
***current address: Chemical Sciences Division, NOAA Earth System Research Laboratory, Boulder, CO, USA
Received: 17 August 2010 – Published in Atmos. Chem. Phys. Discuss.: 02 September 2010 Abstract. Eddy covariance (EC) is the preferable technique for flux measurements since
it is the only direct flux determination method. It requires a continuum of
high time resolution measurements (e.g. 5–20 Hz). For volatile organic
compounds (VOC) soft ionization via proton transfer reaction has proven to
be a quantitative method for real time mass spectrometry; here we use a
proton transfer reaction time of flight mass spectrometer (PTR-TOF) for 10 Hz EC measurements of full mass spectra up to m/z 315. The mass resolution
of the PTR-TOF enabled the identification of chemical formulas and
separation of oxygenated and hydrocarbon species exhibiting the same nominal
mass. We determined 481 ion mass peaks from ambient air concentration above
a managed, temperate mountain grassland in Neustift, Stubai Valley, Austria.
During harvesting we found significant fluxes of 18 compounds distributed
over 43 ions, including protonated parent compounds, as well as their
isotopes and fragments and VOC-H+ – water clusters. The dominant BVOC
fluxes were methanol, acetaldehyde, ethanol, hexenal and other C6 leaf
wound compounds, acetone, acetic acid, monoterpenes and sequiterpenes.
Revised: 13 December 2010 – Accepted: 21 December 2010 – Published: 20 January 2011
The smallest reliable fluxes we determined were less than
0.1 nmol m−2 s−1, as in the case of sesquiterpene emissions from freshly cut grass.
Terpenoids, including mono- and sesquiterpenes, were also deposited to the
grassland before and after the harvesting. During cutting, total VOC
emission fluxes up to 200 nmolC m−2 s−1 were measured. Methanol
emissions accounted for half of the emissions of oxygenated VOCs and a third
of the carbon of all measured VOC emissions during harvesting.
Citation: Ruuskanen, T. M., Müller, M., Schnitzhofer, R., Karl, T., Graus, M., Bamberger, I., Hörtnagl, L., Brilli, F., Wohlfahrt, G., and Hansel, A.: Eddy covariance VOC emission and deposition fluxes above grassland using PTR-TOF, Atmos. Chem. Phys., 11, 611-625, doi:10.5194/acp-11-611-2011, 2011.