Monitoring Chlorofluorocarbons in Potential Source Regions in Eastern China

Abstract

Recent studies have indicated that Eastern China might be a potential source region of increased atmospheric chlorofluorocarbons (CFCs). To investigate this possibility, a field measurement was carried out from October to December 2017 for identifying the ambient concentration levels of representative trichlorofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12), trifluorotrichloroethane (CFC-113), and tetrafluorodichloroethane (CFC-114) at the residential and municipal solid waste (MSW) landfills and industrial sites in Eastern China. The ambient mixing ratios of CFCs at residential sites were almost within 20% enhancement of the global background sites. The highest levels of CFCs were observed at the MSW landfill sites. Moreover, CFC-11 and CFC-113 concentrations at MSW landfills, which were in service, were two times higher than that at completed MSW landfills. Mean concentrations of 322 pptv for CFC-11, 791 pptv for CFC-12, 91 pptv for CFC-113, and 16 pptv for CFC-114 at various industrial sites were higher than that at residential sites, but they were obviously lower than that at MSW landfills in use. A poor intercorrelation between the CFCs indicated that they did not come from the same sources. Higher concentrations measured in this study compared with background sites indicates that MSW landfills could be an unintentional emission source and there are still substantial amounts of CFCs being stored in banks that may discharge CFCs into the atmosphere in Eastern China.

Concentrations and emissions of trichlorotrifluoroethane (CFC-113) from eastern china inferred from atmospheric observations

“…Therefore, the mean concentration of CFC-113 at the ZJU station in 2021 (73 ppt) was lower than that recorded at Lin'an station in 2011−2012 (80 ppt) [24] mainly because of the decrease in background concentration. China's CFC-113 concentrations reported in this study and previous studies [13,14,[22][23][24] were higher than the global mean concentrations after 2007, suggesting that there were CFC-113 emissions in China after 2007.…”

“…There were no evident diurnal variations of atmospheric CFC-113 concentrations, although the highest concentrations (76 ppt) were observed at 11:00 local time, and the lowest concentrations occurred at 15:00 (73 ppt) and 21:00 (73 ppt) (Figure S3). As shown in figure 2, the CFC-113 concentrations in this study were compared to those of previous studies for eastern China [13,14,[22][23][24], and concentrations of the Trinidad Head station (a global background site is at a similar latitude to ZJU) from the AGAGE (http://agage.mit.edu/) [16]. According to the fitting line based on all observed data in eastern China, CFC-113 concentrations in eastern China decreased from 2001 to 2021 (figure 2).…”

“…Chlorotrifluoroethylene, TFA) after 2007 in eastern China [27]. As high CFC-113 concentrations were observed in some landfills in eastern China [14], landfills might be potential sources of CFC-113.…”

“…Based on the top-down method, China's CFC-113 emissions were higher than 0.80 Gg/yr in 2007 [10], 2008 [11], and 2009 [12]. According to recent studies, there were still CFC-113 emissions in eastern China due to the observed higher concentrations (during 2017-2018) compared to the global background [13,14]. However, studies of atmospheric CFC-113 in eastern China in recent years are still lacking.…”