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This study presents atmospheric N2O mole fractions measured from discrete air samples from 2001 to 2018 at Mt. Waliguan (WLG) station (36°17′N, 100°54′E, 3816 m asl) in China, which is a global background station of the World Meteorological Organization/Global Atmosphere Watch Programme (WMO/GAW) in central Eurasia. Observed N2O characteristics of annual means, interannual variability, and seasonal cycles were investigated. Our results show that N2O at WLG possess a distinct increasing trend and a statistically significant seasonal cycle, with an average growth rate of 0.9±0.01 ppb yr−1 (1σ)(1ppb=10−9), which is close to the global mean. The detrended seasonal cycle shows a trough of −0.25±0.04 (1σ) ppb in June and a peak of 0.13±0.07 (1σ) ppb in September, with an amplitude of 0.38 ppb. The pattern is due to combined effects of variation in surface sources, vertical convection within the boundary layer and stratosphere to troposphere transportation (STE). The interannual variability in growth rate was partly driven by quasi-biennial oscillation (QBO) of tropical zonal wind through stratospheric transport into the troposphere. According to a cluster analysis of back trajectories and the corresponding average N2O load, most air masses cover arid and semi-arid areas in inner Asia with low N2O emissions, indicating that the atmospheric N2O at the WLG represents the background N2O level in central Eurasia. [ABSTRACT FROM AUTHOR]

As a substitute for methyl bromide (CH 3 Br), sulfuryl fluoride (SO 2 F 2) is widely used and shows an increasing trend in global atmospheric mixing ratio. Long-term measurements of SO 2 F 2 were conducted at 10 stations of the China Meteorological Administration. The SO 2 F 2 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 SO 2 F 2 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 SO 2 F 2 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 SO 2 F 2 pollution events. The potential source areas identified at the 10 stations covered the main economic zones of China. Additionally, the total SO 2 F 2 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 SO 2 F 2 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 SO 2 F 2 emissions were lower than global averages during 2011-2019. • The long-term atmospheric mixing ratios of sulfuryl fluoride in China were reported for the first time. • Sulfuryl fluoride emissions of key regions and Chinese totals were estimated by trace ratio method. • Both enhanced sulfuryl fluoride mixing ratios in Eastern China and the national emissions have declined in recent years. [ABSTRACT FROM AUTHOR]