Abstract. We measured amines in boreal forest air in Finland both in gas and particle
phases with 1 h time resolution using an online ion chromatograph
(instrument for Measuring AeRosols and Gases in Ambient Air – MARGA)
connected to an electrospray ionization quadrupole mass spectrometer (MS).
The developed MARGA-MS method was able to separate and detect seven different
amines: monomethylamine (MMA), dimethylamine (DMA), trimethylamine (TMA),
ethylamine (EA), diethylamine (DEA), propylamine (PA), and butylamine (BA).
The detection limits of the method for amines were low
(0.2–3.1 ng m−3), the accuracy of IC-MS analysis was 11–37 %, and
the precision 10–15 %. The proper measurements in the boreal forest
covered about 8 weeks between March and December 2015. The amines were found
to be an inhomogeneous group of compounds, showing different seasonal and
diurnal variability. Total MMA (MMA(tot)) peaked together with the sum of
ammonia and ammonium ions already in March. In March, monthly means for MMA
were < 2.4 and 6.8 ± 9.1 ng m−3 in gas and aerosol phases,
respectively, and for NH3 and NH4+ these were 52 ± 16 and
425 ± 371 ng m−3, respectively. Monthly medians in March for
MMA(tot), NH3, and NH4+ were < 2.4, 19 and 90 ng m−3,
respectively. DMA(tot) and TMA(tot) had summer maxima indicating biogenic
sources. We observed diurnal variation for DMA(tot) but not for TMA(tot). The
highest concentrations of these compounds were measured in July. Then,
monthly means for DMA were < 3.1 and 8.4 ± 3.1 ng m−3 in gas
and aerosol phases, respectively, and for TMA these were 0.4 ± 0.1 and
1.8 ± 0.5 ng m−3. Monthly medians in July for DMA were below the
detection limit (DL) and 4.9 ng m−3 in gas and aerosol phases,
respectively, and for TMA these were 0.4 and 1.4 ng m−3. When relative
humidity of air was > 90 %, gas-phase DMA correlated well with
1.1–2 nm particle number concentration (R2=0.63) suggesting that it
participates in atmospheric clustering. EA concentrations were low all the
time. Its July means were < 0.36 and 0.4 ± 0.4 ng m−3 in gas
and aerosol phases, respectively, but individual concentration data
correlated well with monoterpene concentrations in July. Monthly means of PA
and BA were below detection limits at all times.
Amines in boreal forest air at SMEAR II station in Finland
