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Journal article

In situ measurements of volatile organic compounds in a boreal forest

Hakola H, Hellen H, Hemmila M, Rinne J, Kulmala M ...see all

ATMOSPHERIC CHEMISTRY AND PHYSICS, vol. 12, issue 23 (2012) pp. 11665-11678

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Abstract

We present biogenic VOC, including sesquiterpenes, measurements at the
SMEAR II station (Station For Measuring Forest Ecosystem-Atmosphere
Relations) in Finland using an in situ gas chromatograph
mass-spectrometer with 2 h time resolution. The measurements were
conducted over the period October 2010-October 2011, at least one week
every month. To our knowledge there are no earlier species-speciated
semi-continuous BVOC data also covering dormant periods. This was also
the first time sesquiterpene mixing ratios were measured in a boreal
forest.
During the winter months, and still in March, the mixing ratios of all
biogenic compounds were very low, most of the time below detection
limits. The monoterpene mixing ratios increased in April and started to
show diurnal variability, with maximum mixing ratio at night and minima
during the day. The diurnal variability continued until October, after
which the mixing ratios decreased and then only occasional episodes took
place. The diurnal variation was affected by boundary layer height.
Sesquiterpene mixing ratios were very low, only a few ppt. The main
sesquiterpenes were longifolene and isolongifolene. The diurnal
variation of isoprene was opposite to the mono-and sesquiterpene diurnal
curve due to isoprene's light dependent emissions. Due to its daytime
maximum mixing ratios, isoprene also dominated hydroxyl radical
reactivity in summer even though our isoprene measurements are
underestimates due to a breakthrough in a cold trap.

Authors

  • H Hakola

  • H Hellen

  • M Hemmila

  • J Rinne

  • M Kulmala

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