| Abstrakt: |
Halocarbons are emitted by various anthropogenic activities to the atmosphere, where they contribute to global warming and stratospheric ozone-depletion. To determine national halocarbon emissions, the so-called "top-down" approach relies on atmospheric observations, at sites that reflect emissions on a country level, and combines these observations with inverse modelling methods. In this study, we present 12 months (September 2019 to September 2020) of continuous atmospheric observations of 28 halocarbons from a measurement campaign at the Beromünster tall tower in Switzerland. The site is sensitive to the most densely populated area of Switzerland, the Swiss Plateau, thus the measurements were well suited to derive Swiss halocarbon emissions. Emissions were calculated by two different top-down methods, a tracer-ratio method (TRM) with carbon monoxide (CO) as the independent tracer, and a Bayesian inversion (BI), based on atmospheric transport simulations using FLEXPART-COSMO. The results were compared to previously reported top-down emission estimates, based on measurements at the high-Alpine site Jungfraujoch, and to the "bottom-up" Swiss national greenhouse gas (GHG) inventory, as annually reported to the United Nations Framework Convention on Climate Change (UNFCCC). We observed ongoing outgassing from existing foams and refrigerators for the ozone-depleting, banned chlorofluorocarbons (CFCs) and the regulated hydrochlorofluorocarbons (HCFCs), confirming their large historical use. For the major hydrofluorocarbons (HFCs) HFC-125 (CHF2CF3) and HFC-32 (CH2F2), our calculated emissions of 99 ± 29 Mg yr-1 and ± 13 Mg yr-1 were in good agreement with the national Swiss inventory values, whereas for HFC-134a (CH2FCF3) our result of 300 ± 85 Mg yr-1 was about 30 % lower than the UNFCCC reported value. For the other investigated HFCs, perfluorocarbons (PFCs), SF6 and NF3, emissions were small and in agreement with the inventory. Finally, we report the first country-based emission estimates of a total of 50 Mg yr-1 for three recently phased-in, unregulated hydrofluoroolefins (HFOs), HFO-1234yf (CF3CF=CH2), HFO-1234ze(E) ((E)-CF3CH=CHF) and HCFO-1233zd(E) ((E)-CF3CH=CHCl). [ABSTRACT FROM AUTHOR] |
