State-of-the-art mass spectrometer reveals the complex chemical composition of downy birch emissions

Trees emit volatile organic compounds (VOCs) into the atmosphere. The amount and chemical composition of these emissions depend on various external and internal factors, such as the weather, the state of the tree growth, etc. A state-of-the-art mass spectrometer was used to analyse the chemical composition of downy birch emissions in the boreal forest at the end of the growing season, revealing the importance of oxygenated VOCs (OVOCs).

Photo: Pixabay.

Studying the emissions of VOCs from trees at the branch level is important to understand the conditions driving the variations of their chemical composition and amounts. Recent advances in mass spectrometry techniques have enabled the quantification of a larger number of compounds, such as hydrocarbons with up to 20 carbon atoms and oxygenated VOCs (OVOCs) with up to 4 oxygen atoms.

The Vocus proton-transfer-reaction time-of-flight mass spectrometer (Vocus-PTR-ToF-MS) is such an instrument that can be used for monitoring emissions from a branch enclosure with high sensitivity and high time resolution. It was deployed at the Hyytiälä boreal forest research station (SMEAR II) in August 2019 to observe in real-time the emissions from a downy birch branch placed in an enclosure.

Scientists found that up to 90% of the emissions consisted of OVOCs. In particular, high emissions of C₈H₈O₃ (~60% of total) were noteworthy and possibly indicated that the tree suffered from abiotic stress.

While the results are limited to a specific time, location, and circumstances, they highlight the varying quantity and quality of emissions from downy birch, that are currently not represented with high accuracy in global models. In particular OVOCs directly emitted from trees are not considered, while they might contribute to the formation and growth of particulate matter. Additional measurements of this type allowing for a more detailed parametrization of emissions are needed.

Further information:

Senior Scientist Arnaud P. Praplan, Finnish Meteorological Institute, arnaud.praplan@fmi.fi Scientific article is available on Frontiers in Forests and Global Change.

Publication:

Thomas S.J., Li H., Praplan A.P., Hellén H. and Bianchi F. (2022) Complexity of downy birch emissions revealed by Vocus proton transfer reaction time-of-flight mass spectrometer. Front. For. Glob. Change 5:1030348. doi:10.3389/ffgc.2022.1030348.

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