| مستخلص: |
There are lots of studies on biogenic volatile organic compound (BVOC) emissions of themain coniferous trees in boreal forests, but the data on deciduous trees is more limited. Herewe have studied downy birch (Betula pubescens) emissions of terpenes, oxygenated VOCs(OVOCs) and green leaf volatiles (GLVs) in a boreal forest at SMEAR II (Station forMeasuring Forest Ecosystem–Atmosphere Relations; 61o51’N, 24o18’E; 181 m a.s.l.) inHyytiälä, southern Finland, using in situ gas chromatographs coupled with massspectrometers (GC-MSs). Sesquiterpenes were clearly the dominating VOC group at the beginning of the growingseason, but in July and August GLVs had the highest contribution. Monthly mean MT andSQT emissions were 3 – 62 and 5 – 298 ng gdw−1 h−1, respectively. Isoprene emissions werevery low (monthly means < 0.3 ng gdw−1 h−1). High emissions of GLVs were detectedwhen leaf damages occurred, leading to monthly means of GLV between 0.5 – 475 ng gdw−1h−1. Emissions were highly variating over the growing season. Of the SQTs, β-caryophyllenehad the highest contribution, when the leaves were growing, but its emission and emissionpotential decreased over the growing season. For fully grown leaves from Juneto Augustα-farnesene was the most emitted compound. Temperature was the significant factorcontrolling the emissions of several compounds. Especially β-caryophyllene emissions werehighly correlated with temperature (R2 > 0.80). However, the variation of the othersignificant SQT, α-farnesene, was not explained by the temperature, especially in June andAugust. Results indicate that downy birch can be a significant contributor for therelatively high SQT concentrations found in the boreal forest air (Hellén et al.,2018). Hellén, H., Praplan, A. P., Tykkä, T., Ylivinkka, I., Vakkari, V., Bäck, J., Petäjä, T.,Kulmala, M., and Hakola, H.: Long-term measurements of volatile organic compoundshighlight the importance of sesquiterpenes for the atmospheric chemistry of a boreal forest,Atmos. Chem. Phys., 18, 13839-13863, doi:10.5194/acp-18-13839-2018, 2018. [ABSTRACT FROM AUTHOR] |
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