Airborne Observations of CFCs Over Hebei Province, China in Spring 2016
Sarah E. Benish, R. J. Salawitch, Xinrong Ren, Hao He, Russell R. Dickerson
Abstract
Abstract In Spring 2016, 27 whole air samples were collected from an aircraft ∼500–∼3,500 m over Hebei Province, China and analyzed for 16 halocarbons, including chlorofluorocarbons (CFCs). Mixing ratios (median, 25th–75th percentiles) of CFC‐11 (281, 255–318 ppt), CFC‐12 (546, 473–591 ppt), CFC‐113 (79, 73–85 ppt), CFC‐114 (22, 19–25 ppt), HCFC‐22 (345, 308–432 ppt), and CCl 4 (88, 75–104 ppt) were often observed to be higher than their global tropospheric background levels. The significantly elevated mixing ratios of ozone depleting substances (ODSs) combined with strong correlations with anthropogenic tracers known to have substantial use and emission in this region (HCFC‐22 and CH 2 Cl 2 ) suggest continuing emissions of multiple Montreal Protocol‐controlled gases at the time of measurement. We use HYSPLIT trajectory clusters and potential source contribution function methods to identify principal transport pathways of CFCs. We find the highest mixing ratios of ODSs in air originating from Inner Mongolia, Hebei, and Shandong. The strong correlations between CFC‐11 and CFC‐12 with the feedstock CCl 4 suggest new production is prevalent in all three regions. We find no evidence for new production of CFC‐113, but the strong correlation of CFC‐114 with the feedstock C 2 Cl 4 suggests new production of CFC‐114 from the southeast of China. The findings of this study confirm high mixing ratios of ODSs over Hebei in Spring 2016 and suggest new production and use (rather than release from banks), which is in conflict with the Montreal Protocol agreement that bans the production of CFCs.