À la recherche de traces de frigorigène dans l'atmosphère (en anglais)

Les chercheurs du Laboratoire fédéral d'essai des matériaux et de recherche (Empa) viennent de publier les premiers résultats de mesures attestant de la présence et de la propagation de la 4e génération des fluides frigorigènes et des produits moussants halogénés (fluoroolefins).
The Swiss Federal Laboratories for Materials Science and Technology (Empa) researchers have now published first measurements on the atmospheric distribution and abundance of the 4th generation halogenated coolants and foaming agents. (fluoroolefins)

Fluoroolefins, such as R1234yf, R1234ze(E) and R1233zd(E), decay more quickly in the atmosphere hence their lifetimes are considerably shorter. That is why they do not add nearly as much to the greenhouse gas effect as their stable predecessors. These new substances, like, are now more frequently used, as evidenced by the first measurements made by Empa at the Jungfraujoch and in Dübendorf.

Researchers have been tracing the distribution of the latest refrigerants in the atmosphere since their introduction onto the market. What is interesting is that the substance R1234yf did not appear at the start of the test series at the Jungfraujoch. It is evident that the substance is anthropogenic – it is man-made. It took two years until the concentrations of the new substances in the atmosphere were high enough to be detected at Jungfraujoch.

These investigations could be a fully functioning early warning system. As soon as a new substance is on the market, researchers can monitor it and identify precisely when the substances appear in the atmosphere for the first time - and how long they persist. While, for example, the first generation of coolants remain in the atmosphere for decades (and even now traces of them can still be detected), the new coolants «survive» for only a few days or weeks before decaying in the atmosphere.

According to Empa, this degradation poses new problems for science. R1234yf, for example degrades faster in the air than its predecessor. However it decomposes into a new harmful substance: trifluoroacetic acid, an extremely stable molecule that does not naturally degrade any further. It accumulates in water and living organisms, and it is also toxic for certain plants, especially certain types of algae. So in terms of the atmosphere the problem is solved, but now other kinds of ecosystems face new challenges – and so does research. It is increasingly important for researchers to consider not only the half-life of the new substances in the atmosphere, but also the effects of their decay products.

The measurements and models from Switzerland not only show whether and to what degree certain substances are present in the region, but also give indications on their source regions. In the case of the foaming agent R1234ze(E), the «epicentre» of the emissions lies on the border between Belgium and the Netherlands. Empa's researchers identified this by combining their data with meteorological data on air movement.