In Situ Observations of Halogenated Gases at the Shangdianzi Background Station and Emission Estimates for Northern China.

ABSTRACT

Halogenated gases include ozone-depleting substances and greenhouse gases, such as chlorofluorocarbons, halons, hydrochlorofluorocarbons, hydrofluorocarbons, and perfluorinated gases. In situ atmospheric observations of major halogenated gases were conducted at the Shangdianzi (SDZ) background station, China, from October 2020 to September 2021 using ODS5-pro, a newly developed measurement system. The measurement time series of 36 halogenated gases showed occasional pollution events, where background conditions represented 25% (CH2Cl2) to 81% (CF3Cl, CFC-13) of the measurements. The annual mean background mole fractions of most species at SDZ were consistent with those obtained at the Mace Head station in Ireland. The background conditions were distinguished from pollution events, and the enhanced mole fractions were used to estimate the emissions of four categories of fluorinated gases (F-gases) from northern China using a tracer ratio method. The CO2-equivalent (CO2-equiv) emission of F-gases from northern China reached 181 ± 18 Tg year-1 during 2020-2021. Among the four categories of F-gases estimated, SF6 accounted for the highest proportion of CO2-equiv emissions (24%), followed by HFC-23 (22%), HFC-125 (17%), HFC-134a (13%), NF3 (10%), CF4 (5.9%), HFC-143a (3.9%), HFC-32 (3.4%), and HFC-152a (0.2%).