Atmospheric mixing ratios and emissions of sulfuryl fluoride (SO2F2) in China

Abstract

As a substitute for methyl bromide (CH3Br), sulfuryl fluoride (SO2F2) is widely used and shows an increasing trend in global atmospheric mixing ratio. Long-term measurements of SO2F2 were conducted at 10 stations of the China Meteorological Administration. The SO2F2 mixing ratios of background events at five observation sites with long sequences (9 or 10 years) showed a similar increasing trend, which was also similar to the measurements at Mace Head in Ireland, a global background station of the Advanced Global Atmospheric Gases Experiment (AGAGE) network. The background mixing ratios of SO2F2 increased from 1.8 ppt in 2011 to 2.6 ppt in 2019. From 2010 to 2016, the enhanced mixing ratios above background of all the 10 stations exhibited an increasing trend before 2017, while there are no obvious trends from 2017 to 2019. The highest enhanced mixing ratios appeared at Lin'an (LAN) and Jiangjin (JGJ) in all years, mainly due to production and application of SO2F2 in the Yangtze River Delta and the Sichuan Basin. Also, the two stations are closer to sources than other stations. The Concentration Weighted Trajectory (CWT) was applied to identify the possible source areas associated with SO2F2 pollution events. The potential source areas identified at the 10 stations covered the main economic zones of China. Additionally, the total SO2F2 emissions of China and key emission regions from 2011 to 2019 were estimated by a tracer-ratio method, using carbon monoxide (CO) as a reference tracer. The estimated total SO2F2 emission of China was 0.49 ± 0.49 Gg yr−1 during 2011 to 2016 and 0.32 ± 0.32 Gg yr−1 during 2017 to 2019, and China's per capita SO2F2 emissions were lower than global averages during 2011-2019.