Sources of long-lived atmospheric VOCs at the rural boreal forest site, SMEAR II

Abstract

Abstract. In this study a long-term volatile organic compound (VOCs) concentration data set, measured at the SMEAR II (Station for Measuring Ecosystem–Atmosphere Relations) boreal forest site in Hyytiälä, Finland during the years 2006–2011, was analyzed in order to identify source areas and profiles of the observed VOCs. VOC mixing ratios were measured using proton transfer reaction mass spectrometry. Four-day HYSPLIT 4 (Hybrid Single Particle Lagrangian Integrated Trajectory) backward trajectories and the Unmix 6.0 receptor model were used for source area and source composition analysis. Two major forest fire events in Russia took place during the measurement period. The effect of these fires was clearly visible in the trajectory analysis, lending confidence to the method employed with this data set. Elevated volume mixing ratios (VMRs) of non-biogenic VOCs related to forest fires, e.g. acetonitrile and aromatic VOCs, were observed. Ten major source areas for long-lived VOCs (methanol, acetonitrile, acetaldehyde, acetone, benzene, and toluene) observed at the SMEAR II site were identified. The main source areas for all the targeted VOCs were western Russia, northern Poland, Kaliningrad, and the Baltic countries. Industrial areas in northern continental Europe were also found to be source areas for certain VOCs. Both trajectory and receptor analysis showed that air masses from northern Fennoscandia were less polluted with respect to both the VOCs studied and other trace gases (CO, SO2 and NOx), compared to areas of eastern and western continental Europe, western Russia, and southern Fennoscandia.

Anthropogenic and biogenic influence on VOC fluxes at an urban background site in Helsinki, Finland

“…However, this was probably related to advection from distant sources (e.g. Patokoski et al, 2015). Generally, the average acetonitrile fluxes were really small being still above the detection limits except in winter (Table 4 and Fig.…”

“…Finally, spectral corrections were applied. The low frequency losses for the fluxes were corrected based on theoretical corrections (Rannik and Vesala, 1999), whereas the high-frequency losses were experimentally determined. Finally, the 30 min fluxes were quality checked for stationarity with a limit of 0.3 (Foken and Wichura, 1996), and the periods with u * < 0.2 m s −1 were removed from further analysis.…”

“…Generally, acetonitrile is used as a marker for biomass burning as it is released from those processes (e.g. Holzinger et al, 1999;De Gouw et al, 2003;Patokoski et al, 2015).…”

“…Long-lived compounds, such as anthropogenically emitted benzene, also contribute to the VOC concentrations in rural areas (e.g. Patokoski et al, 2014Patokoski et al, , 2015.…”

Long-term sub-micron aerosol chemical composition in the boreal forest: inter- and intra-annual variability

“…Other evident nearby sources of anthropogenic pollution are the town of Orivesi (population approximately 9 200) 19 km south of SMEAR II and the nearby village of Korkeakoski with two saw mills and a pellet factory 6-7 km to the south east from SMEAR II (Liao et al, 2011;Äijälä et al, 2017). Nonetheless, the dominating source of air pollutants are air masses advected from industrialized areas over southern Finland, St. Petersburg region in Russia and continental Europe (Kulmala et al, 2000;Patokoski et al, 2015;Riuttanen et al, 2013). The anthropogenic emissions are minor at the station.…”