Gas-phase alkylamines in a boreal Scots pine forest air

Abstract

Alkylamines are highly reactive volatile nitrogen compounds that may take part in aerosol formation and growth in the atmosphere in boreal forests. We measured alkylamine concentrations from May to October 2011 in a boreal forest at the SMEAR II station in Hyytiälä, southern Finland. The weekly air samples were collected in phosphoric acid-impregnated fiberglass filters through a polytetrafluoroethylene (PTFE) filter and analyzed with a high performance liquid chromatography electrospray ionization ion-trap mass spectrometer.Ethylamine (EA) and dimethylamine (DMA), propylamine (PA) and trimethylamine (TMA), and diethylamine (DEA) were observed on levels above the detection limits, while butylamine and triethylamine were under the detection limits. The highest concentrations for EA + DMA (157 ± 20 pptV) and PA + TMA (102 ± 61 pptV) were observed from September to October. For DEA the seasonal course was different and the highest concentrations were measured during the summer (max 15.5 ± 0.5 pptV, early July).The amine concentrations were compared with those of ambient air ions, other trace gases (O3, NO, NOx and CO and monoterpenes), and with soil and air temperatures and litterfall. Positive and negative cluster ions did not correlate with the amine concentration measured. However, peaks in the positive and negative intermediate ions showing similar concentrations occurred simultaneously with peaks in EA + DMA and DEA during the summer. The number of new particle formation days followed the sum of the alkylamine concentrations observed during the autumn. The autumnal monoterpene emissions from the forest floor and litterfall maxima coincided with the elevated or peaked EA + DMA and PA + TMA concentrations. Similar to the monoterpene concentrations in the forest air, amine concentrations seem to be linked with vegetation, soil activity, and litterfall, and rather than with other trace gases in the atmosphere.