Atmospheric Chemistry and Physics Discussions
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3
2004
10.5194/acpd-4-2991-2004
http://www.atmos-chem-phys-discuss.net/4/2991/2004/
http://www.atmos-chem-phys-discuss.net/4/2991/2004/acpd-4-2991-2004.html
http://www.atmos-chem-phys-discuss.net/4/2991/2004/acpd-4-2991-2004.pdf
2991
3011
2004-06-03
Carbonyl compounds in boreal coniferous forest air in Hyytiälä, Southern Finland
H. Hellén
heidi.hellen@fmi.fi
H. Hakola
A. Reissell
T. M. Ruuskanen
Finnish Meteorological Institute, Sahaajankatu 20 E, 00880 Helsinki, Finland
University of Helsinki, Department of Physical Sciences, Finland
University of Helsinki, Department of Chemistry, Finland
A variety of C<sub>1</sub>-C<sub>12</sub> carbonyl compounds were measured in the air of
a boreal coniferous forest located in Hyytiälä, Southern Finland.
24-h samples were collected during March and April in 2003 using DNPH
(2,4-dinitrophenyl hydrazine) coated C<sub>18</sub>-cartridges and analyzed by
liquid chromatography-mass spectrometry (LC-MS).
<br><br>
Altogether 22 carbonyl compounds were quantified. The most abundant
carbonyls were acetone (24-h average 1340 ng/m<sup>3</sup>), formaldehyde
(480 ng/m<sup>3</sup>) and acetaldehyde (360 ng/m<sup>3</sup>). In contrast, scaling of
concentrations against reactivity with the hydroxyl (OH) radical
significantly increased the contribution of larger aldehydes and ketones
(e.g. decanal, octanal and 6-methyl-5-hepten-2-one). Concentrations of
monoterpene reaction products nopinone (9 ng/m<sup>3</sup>) and limona ketone
(5 ng/m<sup>3</sup>) were low compared to the most abundant low molecular weight
carbonyls. The total concentration of carbonyl compounds in Hyytiälä
in April/March 2003 was much higher than the concentration of aromatic
hydrocarbons and monoterpenes in April 2002.
<br><br>
Lifetimes of the measured carbonyls with respect to reactions with OH
radicals, ozone (O<sub>3</sub>), and nitrate (NO<sub>3</sub>) radicals as well as
photolysis were estimated. The main sinks for most of the carbonyl compounds
in Hyytiälä in springtime are expected to be reactions with the OH
radical and photolysis. For 6-methyl-5-hepten-2-one and limona ketone also
reactions with ozone are important. The sources of carbonyl compounds are
presently highly uncertain. Due to the relatively short lifetimes of
aldehydes and ketones, secondary biogenic and anthropogenic sources, that is
oxidation of volatile organic compounds, and primary biogenic sources are
expected to dominate in Hyytiälä.