Deployment of a ground-based CIMS apparatus for the detection of organic gases in the boreal forest during the QUEST campaign

Measurements of atmospheric volatile organic compounds were performed in the Finnish Boreal forest atmosphere during spring 2003, as part of the project QUEST (Quantification of Aerosol Nucleation in the European Boundary Layer), using a ground-based Chemical Ionization Mass Spectrometer (CIMS) instrument. Based on the study of their hydrate distribution, Methanol, Acetonitrile, Acetaldehyde, Dimethyl Amine (DMA), Ethanol/Formic Acid, Acetone, Trimethyl Amine TMA, Propanol/Acetic Acid, Methyl Vinyl Ketone (MVK) and Metacrolein (MaCR), Monoterpenes, Cis-3-hexenyl Acetate and Monoterpene Oxidation Products (MTOP) are proposed as candidates for masses 33, 41, 44, 45, 46, 58, 59, 60, 70, 136, 142 and 168 amu, respectively. It would be, to our knowledge, the first time DMA, TMA, MTOP and Cis-3-hexenyl Acetate are measured with this method. A compound with mass 68 amu, which could be Isoprene has also been identified. Most compounds show a clear diurnal variation with higher concentrations at night, starting at the onset of the nocturnal inversion and in agreement with independent measurements of CO. Biogenic compounds are highly correlated with each other and the ratio monoterpene/oxidation product shows a typical daily pattern of nighttime maxima. Cis-3-hexenyl Acetate has a diurnal variation similar to the ones of Isoprene and Monoterpenes, and especially close to the diurnal variation of their oxidation products.