Tracking volatile organic compounds

It is well-known that vegetation, and forests in particular, play an important role in the carbon cycle. Researchers have now become interested in other chemical compounds produced by plants which play an important role in atmospheric pollution and even in climate change: these are volatile organic compounds (VOCs). More than two thousand of these compounds have been identified. Some of them, such as isoprene, for example, which are emitted by forests in large quantities, are currently being studied by scientists. A recent study compiled 28 measuring programs which were conducted virtually all over the world in order to compare the modeling of isoprene emissions with actual emissions in nature in accordance with climate and the natural environment (tundra, temperate forests etc.). The measurements carried out by Bernard Heinesch and his collaborators at the Unit of Biosystems Physics at Gembloux Agro-Bio Tech (University of Liege) in the forest of Vielsalm have been included in this study. They have thus been able to demonstrate outside the laboratory that the production of isoprene is linked to photosynthesis and therefore to the quantity of carbon absorbed by the plant.

VOC measuring towerThe method used could be loosely compared with that of an elevated blind used by hunters except that the top of the structure extends above the forest canopy and reaches a height of ten meters above the forest of Vielsalm, the “Grand Bois” site. Right at the top of this structure, some fifty meters high, the researchers from the Unit of Biosystems Physics at Gembloux Agro-Bio Tech (University of Liege) installed their measuring equipment with a view to understanding what happens on a chemical level where vegetation meets the atmosphere. They discovered a lot of things…

Vegetation certainly exchanges carbon dioxide (CO2) with the atmosphere. The type of scientific equipment used makes it possible to have a better understanding of the natural carbon cycle and to answer this important question: are the forests carbon sinks? Also, to what extent are they involved in the fight against global warming? For quite a few years now, these “scientific hunting blinds” have also been used to track volatile organic compounds (VOCs) in order to understand their impact on the chemistry of the atmosphere. (1). “Laboratory equipment for measuring these emissions exists”, explains Bernard Heinesch, a lecturer at Gembloux Agro-Bio Tech and a researcher at the Unit of Biosystems Physics. “In simple terms, it consists in placing a plant under a bell and measuring at the exit of this bell what the plant releases into the air. This is a useful but somewhat simplistic method. A forest is much more complex than a potted plant. This is why it was important to take real-time measurements in the natural environment.”

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