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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-394
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
01 Jun 2017
Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Atmospheric Chemistry and Physics (ACP).
Temporal variation of VOC fluxes measured with PTR-TOF above a boreal forest
Simon Schallhart1, Pekka Rantala1, Maija K. Kajos1, Juho Aalto2, Ivan Mammarella1, Taina M. Ruuskanen1, and Markku Kulmala1 1Department of Physics, University of Helsinki, Finland
2Department of Forest sciences, University of Helsinki, Finland
Abstract. Between April and June 2013 fluxes of volatile organic compounds (VOCs) were measured in a Scots pine and Norway spruce forest using the eddy covariance (EC) method with a proton transfer reaction time of flight (PTR-TOF) mass spectrometer. The observations were performed above a boreal forest at the SMEAR II site in Southern Finland. We found a total of 25 different compounds with exchange and investigated their seasonal variations from spring to summer. The majority of the net VOC flux was comprised of methanol, monoterpenes, acetone and butene. The VOC emissions followed a seasonal trend, the released amount increased from spring to summer. Only a three compounds were emitted in April while in June emissions of some 19 VOCs were observed. During the measurements in April, the emissions were dominated by butene, while in May and June methanol was the most emitted compound. The main source of methanol is likely the growth of new biomass. During a 21-day period in June, the net VOC flux was 2.3 nmol m−2 s−1. This is on the lower end of PTR-TOF flux measurements from other ecosystems, which range from 2 to 10 nmol m−2 s−1. The EC flux results were compared with surface layer profile measurements, an indirect method using a proton transfer reaction quadrupole mass spectrometer, which is permanently installed at the SMEAR II site was used. For most of the compounds the fluxes, measured with the two different methods, agreed well

Citation: Schallhart, S., Rantala, P., Kajos, M. K., Aalto, J., Mammarella, I., Ruuskanen, T. M., and Kulmala, M.: Temporal variation of VOC fluxes measured with PTR-TOF above a boreal forest, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-394, in review, 2017.
Simon Schallhart et al.
Simon Schallhart et al.
Simon Schallhart et al.

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Short summary
Emissions of volatile organic compounds (VOCs) have impact to air quality, human health and climate. We investigated the development of VOC exchange in a boreal forest between April and June 2013. VOC exchange and diversity increased towards summer, however, 80 % of the exchange was driven by four compounds only, methanol, monoterpenes, acetone and butene. The boreal forest emitted just 0.2 % carbon in form of VOCs in relation to the carbon uptake.
Emissions of volatile organic compounds (VOCs) have impact to air quality, human health and...
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