Observations of Elevated CFC-11 and CFC-12 over Hebei Province, China

Chlorofluorocarbons (CFCs) are ozone-depleting substances (ODS) and potent greenhouse gases that have been declining in the atmosphere since the mid-1980s due to the enforcement of the Montreal Protocol. However, a recent reported slowdown in the rate of decline of CFC-11 suggests global emissions have increased¹, likely from new production originating in East Asia². Here, we evaluate airborne measurements of CFCs over Hebei Province, China as part of the Air chemistry Research In Asia (ARIAs) campaign. This flight campaign supported 11 research flights collecting meteorological, trace gas, and aerosol measurements in Spring 2016. Twenty seven whole air samples (WAS) were collected at altitudes from 400 to 3500 m and analyzed for 54 non-methane hydrocarbons and 28 halocarbons. We characterize enhancements of several ODS, such as CFC-11 (median=283 pptv, ~52 pptv above background), CFC-12 (median=563 pptv, ~51 pptv above background), and CCl₄ (median=89 pptv, ~7 pptv above background), throughout the campaign by comparing mixing ratios to typical Northern Hemisphere background levels. We find strong correlations among CFC-11, CFC-12, and the feedstock CCl₄, suggesting release from new production. Lastly, we use NOAA ensemble backward Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) simulations to characterize air mass source regions of high CFC-11. By applying a conditional probability function called potential source contribution function (PSCF), we identify likely source regions of elevated CFC-11 values to be Inner Mongolia, Shandong Province, as well as the local Hebei Province.

1. Montzka, S. A. et al. An unexpected and persistent increase in global emissions of ozone-depleting CFC-11. Nature 557, 413–417 (2018).
2. Rigby, M. et al. Increase in CFC-11 emissions from eastern China based on atmospheric observations. Nature 546–550 (2019). doi:10.1038/s41586-019-1193-4