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A first step towards a better understanding of air chemistry in boreal forests

A first step towards a better understanding of air chemistry in boreal forests

FMI implements method that improves current understanding of air chemistry in boreal forests, which will help to improve predictions of global climate models in the future.

The instrument based on the Comparative Reactivity Method (CRM) was originally developed at the Max Planck Institute for Chemistry in Germany. This new instrument has now been build and characterized in FMI´s laboratory. With the instrument long-term studies in the boreal forest will be conducted to investigate in detail what are the unknown chemical compounds in the air of boreal forests and what are their origins.

The instrument was tested in the vicinity of the Finnish Meteorological Institute in Helsinki. The test took place in February 2016. This first test showed that emissions from traffic dominated the air chemistry during that period.

The method allows measurements of the total hydroxyl radical (OH) reactivity. OH is the most important oxidant in the atmosphere. "OH reactivity, also called OH loss rate, is defined as the inverse of the OH lifetime, i.e. how long OH remains in the atmosphere before reacting with other compounds", explains researcher Arnaud Praplan.

Therefore, OH reactivity measurements reveal how much of reactive compounds are present in the air. A higher amount means a higher reactivity and a reduced OH lifetime. Studies found that total OH reactivity values in forests can be high, despite low pollution levels. However, the reactivity cannot be explained by the known compounds emitted by vegetation.

More information:

Arnaud Praplan,

Praplan, A. P.; Pfannerstill, E. Y.; Williams, J. & Hellén, H. OH reactivity of the urban air in Helsinki, Finland, during winter, Atmos. Environ., 2017, 169, 150 - 161, doi: 10.1016/j.atmosenv.2017.09.013.


The Finnish Meteorological Institute is a leading expert in meteorology, air quality, climate change, earth observation, marine and arctic research areas. FMI is in a unique position to study various themes of climate change in the Northern context.


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