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A new method for studies of volatile organic acids in the forest air

A new method for studies of volatile organic acids in the forest air

An in situ method for studying gas phase C2-C7 monocarboxylic volatile organic acids (VOAs) in ambient air has been developed and evaluated at the Finnish Meteorological Institute.

Organic acids comprise a large fraction of the non-methane hydrocarbons in the atmosphere, but knowledge of especially volatile organic acids is poor. This is at least partly due to the lack of sensitive enough measurement methods for detecting concentrations in ambient air. These acids potentially play a role in the atmospheric chemistry and production of secondary organic aerosols and therefore they have effects also on air quality and climate.

In this method samples are collected directly into the cold trap of the thermal desorption unit and analyzed in situ using a gas chromatograph coupled to a mass spectrometer. The method was validated in the laboratory and tested on the ambient air of a boreal forest in June 2015. The highest mixing ratios were found for acetic acid and the highest relative variations for hexanoic acid.

This novel method will allow us to study diurnal and seasonal variations of VOAs in ambient air and produce new data on, which will benefit atmospheric chemistry and new particle formation studies.

More information:

Academy Research fellow Heidi Hellén,

Hellén, H., Schallhart, S., Praplan, A. P., Petäjä, T., and Hakola, H.: Using in situ GC-MS for analysis of C2–C7 volatile organic acids in ambient air of a boreal forest site, Atmos. Meas. Tech., 10, 281-289, doi:10.5194/amt-10-281-2017, 2017.


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