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

J Patokoski,J Aalto,T M Ruuskanen,H Hakola,R Taipale,J Rinne,P Rantala,T Nieminen,M K Kajos,T Ryyppö

doi:10.5194/acp-15-13413-2015

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.

Highlights

Volatile organic compounds (VOCs) in the atmosphere have several sources, both biogenic and anthropogenic
This study has focused on identifying the source areas of the long-lived VOCs measured at the SMEAR II site in southern Finland, and to investigate the relative influences of biogenic and anthropogenic sources to compounds arriving to southern Finland from areas outside of the country
The analysis is based on a data set which consisted of several years (2006–2011) of volume mixing ratios (VMRs) measurements of VOC

Summary

Introduction

Volatile organic compounds (VOCs) in the atmosphere have several sources, both biogenic and anthropogenic. On a global scale the biogenic emissions are estimated to be an order of magnitude higher than the anthropogenic ones (Guenther et al, 1995). The main biogenic sources are forests (Simpson et al, 1999), to a lesser degree, crops (Guenther et al, 1995), and algae in aquatic ecosystems (Fink et al, 2007). The most important non-biogenic VOC sources are traffic, biomass burning (especially forest fires), extraction and refining of fossil fuels, and evaporation of solvents (Blake et al, 2009). The main oxidants for VOCs in the atmosphere are ozone (O3), and the hydroxyl (OH) and Published by Copernicus Publications on behalf of the European Geosciences Union

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