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

Abstract

Abstract. In this study a long-term volatile organic compounds (VOCs) data set, measured at the SMEAR II (Station for measuring Ecosystem–Atmosphere Relations) boreal forest site at Hyytiälä, Finland during the years 2006–2011, was investigated. VOC mixing ratios were measured using proton transfer reaction mass spectrometry. Four-day backward trajectories and the Unmix 6.0 receptor model were used for source area and source composition analysis. Two major forest fire events, one in Eastern Europe and one 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, e.g. acetonitrile and aromatic VOCs, related to forest fires were observed. Ten major source areas for long-lived VOCs (methanol, acetonitrile, acetaldehyde, acetone, benzene and toluene) were identified at the SMEAR II site. The main source areas for all the targeted VOCs were Western Russia, Northern Poland, Kaliningrad and 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 both the VOCs studied and with other trace gases (CO, SO2 and NOx) than areas of Eastern and Western Continental Europe, Western Russia and Southern Fennoscandia.

Plant volatiles as cues and signals in plant communication

“…Depending on the day‐night cycle, plants release VOCs in a different manner, which indicates the importance of periodic cues (Barrios‐Collado et al, 2016). A clear periodic pattern of changes in VOC release has been observed through diurnal as well as seasonal studies (Patokoski et al, 2015). Periodic changes in VOC emissions could provide a reliable signal for surrounding plants.…”

The effect of clouds and precipitation on the aerosol concentrations and composition in a boreal forest environment

“…In SMEAR II, the gas-phase precursors from biogenic sources are dominated by monoterpenes especially during warm months (e.g. Hakola et al, 2012;Patokoski et al, 2015;Barreira et al, 2017;Heikkinen et al, 2021).…”

“…6c and d), the air masses are likely to have more anthropogenic influences and thus a different VOC profile (e.g. Patokoski et al, 2015), but the formation of aqSOA is still negligible when the total Org mass is investigated in this area of northern Europe. It has also been suggested that water soluble SOA (originating from other sources than aqueous-phase processing) in the cloud droplets can become oxidised to form more volatile compounds leading to evaporation.…”

Precursor apportionment of atmospheric oxygenated organic molecules using a machine learning method

“…The unnegligible proportion of anthropogenic OOMs in Hyytiälä are also reported in a previous PMF results on OOMs by Yan et al 9 . They may come from distant anthropogenic sources or from local wood combustion sources [26][27][28] .…”