Abundance and sources of atmospheric halocarbons in the Eastern Mediterranean

Abstract

Abstract. A wide range of anthropogenic halocarbons is released to the atmosphere, contributing to stratospheric ozone depletion and global warming. Using measurements of atmospheric abundances for the estimation of halocarbon emissions on the global and regional scale has become an important top-down tool for emission validation in the recent past, but many populated and developing areas of the world are only poorly covered by the existing atmospheric halocarbon measurement network. Here we present 6 months of continuous halocarbon observations from Finokalia on the island of Crete in the Eastern Mediterranean. The gases measured are the hydrofluorocarbons (HFCs), HFC-134a (CH 2 FCF 3 ), HFC-125 (CHF 2 CF 3 ), HFC-152a (CH 3 CHF 2 ) and HFC143a (CH 3 CF 3 ) and the hydrochlorofluorocarbons (HCFCs), HCFC-22 (CHClF 2 ) and HCFC-142b (CH 3 CClF 2 ). The Eastern Mediterranean is home to 250 million inhabitants, consisting of a number of developed and developing countries, for which different emission regulations exist under the Kyoto and Montreal protocols. Regional emissions of halocarbons were estimated with Lagrangian atmospheric transport simulations and a Bayesian inverse modeling system, using measurements at Finokalia in conjunction with those from Advanced Global Atmospheric Gases Experiment (AGAGE) sites at Mace Head (Ireland), Jungfraujoch (Switzerland) and Monte Cimone (Italy). Measured peak mole fractions at Finokalia showed generally smaller amplitudes for HFCs than at the European AGAGE sites except for periodic peaks of HFC-152a, indicating strong upwind sources. Higher peak mole fractions were observed for HCFCs, suggesting continued emissions from nearby developing regions such as Egypt and the Middle East. For 2013, the Eastern Mediterranean inverse emission estimates for the four analyzed HFCs and the two HCFCs were 13.9 (11.3-19.3) and 9.5 (6.8-15.1) Tg CO 2 eq yr −1 , respectively. These emissions contributed 16.8 % (13.6-23.3 %) and 53.2 % (38.1-84.2 %) to the total inversion domain, which covers the Eastern Mediterranean as well as central and western Europe. Greek bottom-up HFC emissions reported to the UNFCCC were higher than our top-down estimates, whereas for Turkey our estimates agreed with UNFCCC-reported values for HFC-125 and HFC-143a, but were much and slightly smaller for HFC-134a and HFC152a, respectively. Sensitivity estimates suggest an improvement of the a posteriori emission estimates, i.e., a reduction of the uncertainties by 40-80 % in the entire inversion domain, compared to an inversion using only the existing central European AGAGE observations.

Hydrolysis of Formyl Fluoride Catalyzed by Sulfuric Acid and Formic Acid in the Atmosphere

“…Formyl fluoride (HFCO) is a key molecule, produced via atmospheric degradation of hydrofluorocarbons (HFCs) − and hydrofluoroolefins (HFOs). − HFCs have been used as a refrigerant instead of CFCs and HCFCs to protect the ozone layer . Here, HFC-134a is one of the highest concentrations of HFCs in the atmosphere, which mainly reacts with the OH radical; this leads to the formation of the dominant intermediate product HFCO. − In recent years, experimental results have shown that the concentration of HCF-134a has been increasing year by year due to anthropogenic emission; ,− this leads to the increase of the concentration of HFCO in the atmosphere. Therefore, it is particularly necessary and important for clarifying the atmospheric lifetime of HFCO to fully estimate atmospheric environmental effects of HFCs and HFOs.…”

Estimate Gaps of Montreal Protocol-Regulated Potent Greenhouse Gas HFC-152a Emissions in China Have Been Explained

“…The HFC-152a emissions from other countries except China changed with an average growth rate of −0.1 ± 0.2 Gg/yr 2 during 2011–2020. Unfortunately, there were no top-down estimates of HFC-152a emissions from other countries or regions except those listed in Figure S6, especially for the non-Annex I parties, where the estimates were only available for certain years (2005, , 2006, 2008, − 2010, 2010–2012, 2013, 2016, and 2017). For example, our top-down estimates trace the HFC-152a emissions in China until 2020, whereas the top-down estimates in the United States have not been estimated since 2012 and the latest top-down estimates from the other countries have become unavailable after 2017 (Figure S6).…”

CFC-11 emissions are declining as expected in Western Europe

“…The Empa (Swiss Federal Laboratories for Materials Science and Technology) Bayesian inverse modelling framework (Henne et al (2016)) has been used e.g., to estimate methane emissions in Switzerland and halocarbon emissions in Europe (e.g., Brunner et al, 2017;Schoenenberger et al, 2018;Simmonds et al, 2020) and eastern Asia (Rigby et al, 2019;Park et al, 2021).…”