Annual cycle of volatile organic compound exchange between a boreal pine forest and the atmosphere

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http://hdl.handle.net/10138/161789

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Rantala , P , Aalto , J , Taipale , R , Ruuskanen , T M & Rinne , J 2015 , ' Annual cycle of volatile organic compound exchange between a boreal pine forest and the atmosphere ' , Biogeosciences , vol. 12 , no. 19 , pp. 5753-5770 . https://doi.org/10.5194/bg-12-5753-2015

Titel: Annual cycle of volatile organic compound exchange between a boreal pine forest and the atmosphere
Författare: Rantala, P.; Aalto, J.; Taipale, R.; Ruuskanen, T. M.; Rinne, J.
Upphovmannens organisation: Department of Physics
INAR Physics
Department of Forest Sciences
The University of Helsinki Centre for Continuing Education
Department of Geosciences and Geography
Ecosystem processes (INAR Forest Sciences)
Datum: 2015
Språk: eng
Sidantal: 18
Tillhör serie: Biogeosciences
ISSN: 1726-4170
DOI: https://doi.org/10.5194/bg-12-5753-2015
Permanenta länken (URI): http://hdl.handle.net/10138/161789
Abstrakt: Long-term flux measurements of volatile organic compounds (VOC) over boreal forests are rare, although the forests are known to emit considerable amounts of VOCs into the atmosphere. Thus, we measured fluxes of several VOCs and oxygenated VOCs over a Scots-pine-dominated boreal forest semi-continuously between May 2010 and December 2013. The VOC profiles were obtained with a proton transfer reaction mass spectrometry, and the fluxes were calculated using vertical concentration profiles and the surface layer profile method connected to the Monin-Obukhov similarity theory. In total fluxes that differed significantly from zero on a monthly basis were observed for 13 out of 27 measured masses. Monoterpenes had the highest net emission in all seasons and statistically significant positive fluxes were detected from March until October. Other important compounds emitted were methanol, ethanol+ formic acid, acetone and isoprene+ methylbutenol. Oxygenated VOCs showed also deposition fluxes that were statistically different from zero. Isoprene+ methylbutenol and monoterpene fluxes followed well the traditional isoprene algorithm and the hybrid algorithm, respectively. Emission potentials of monoterpenes were largest in late spring and autumn which was possibly driven by growth processes and decaying of soil litter, respectively. Conversely, largest emission potentials of isoprene+ methylbutenol were found in July. Thus, we concluded that most of the emissions of m/z 69 at the site consisted of isoprene that originated from broadleaved trees. Methanol had deposition fluxes especially before sunrise. This can be connected to water films on surfaces. Based on this assumption, we were able to build an empirical algorithm for bi-directional methanol exchange that described both emission term and deposition term. Methanol emissions were highest in May and June and deposition level increased towards autumn, probably as a result of increasing relative humidity levels leading to predominance of deposition.
Subject: PROTON-TRANSFER-REACTION
REACTION-MASS-SPECTROMETRY
SCALE MONOTERPENE EMISSIONS
LONG-TERM MEASUREMENTS
PTR-MS
SCOTS PINE
FLUX MEASUREMENTS
METHANOL EMISSION
VOC EMISSIONS
HYDROCARBON FLUXES
114 Physical sciences
1172 Environmental sciences
Referentgranskad: Ja
Licens: cc_by
Användningsbegränsning: openAccess
Parallelpublicerad version: publishedVersion


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