Constraining Emission Estimates of CFC-11 in Eastern China Based on Local Observations at Surface Stations and Mount Tai

Abstract

While observations at global background sites in east Asia suggested unexpectedly increased emissions of trichlorofluoromethane (CFC-11) after 2012 in eastern China, particularly in Shandong province, there is a lack of local monitoring data to constrain the emission estimates. Here we report observations of ambient CFC-11 during 2012–2018 in Shandong province at five sites, including three rural sites and two background sites [one at Tuoji Island (TJI) in the Bohai Sea and the other at Mount Tai (MT), 1534 m above sea level]. The mixing ratios of CFC-11 at rural sites were 17–23% above the global background levels at Mauna Loa, Hawaii, and observations at MT and TJI revealed larger enhancements occurring in air masses traveling through the polyurethane foam industry region of the Shandong Peninsula. On the basis of the ratios of CFC-11 to tracers such as carbon monoxide (CO), chloroform (CHCl3), and carbon tetrachloride (CCl4) at the MT and TJI sites, the estimated emissions of CFC-11 in eastern China ranged from 12.0 ± 1.6 to 20.8 ± 3.9 Gg year–1 with an average of 14.7 ± 4.3 Gg year–1 in 2014 and 2017–2018. These tracer-based estimates may represent the upper limits due to relatively higher ratios of CFC-11 to tracers in the hot spot province.

Observations and emission constraints of trichlorofluoromethane (CFC-11) in southeastern China: first-year results from a new AGAGE station

“…The ISC method was applied to estimate CFC-11 emissions (E CFC−11 ) from southeastern China [11,12,17,22,31,[38][39][40][41][42][43][44][45][46][47][48]. This method derives the emission of a trace gas of interest by correlating its enhanced mixing ratios above the baseline with that of a reference compound (tracer).…”

“…Contrary to the expectations of declining emissions from banks and effective implementation of the MPA agreement, recent studies reveal an unexpected increase in global and regional emissions of CFC-11 since 2013 [7,8]. Inverse modeling [9,10] and tracerbased estimates [11,12] identify unexpected production and use of CFC-11 from eastern China, which contributes 64 ± 32% of the total global CFC-11 emission increases estimated by the Advanced Global Atmospheric Gases Experiment (AGAGE) and 41 ± 20% of that by the National Oceanic and Atmospheric Administration (NOAA). Other regions in China or other countries may be responsible for the remaining increase in emissions.…”

“…Southeastern China has undergone significant economic and industrial growth over the past decades, thus holding great importance in investigating CFC-11 emissions. However, ambient levels of CFC-11 in southeastern China have been poorly quantified [12,[15][16][17][18][19][20][21]. Previous studies allow emission estimates only based on short-term campaigns [18,22].…”

Constraining Trifluoromethane (HFC‐23) Emission in Eastern China Based on Two‐Year Online Measurements

“…The emissions of HFC-23 can be estimated from its enhanced mixing ratios to that of a tracer. The tracer used should have a good correlation with HFC-23 and available emission estimates (Huang et al, 2021;Zhang et al, 2014). The mixing ratios of HFC-23 and tracers are subtracted with their annual means observed at the regional background station SDZ as reported by Yi et al (2023) to calculate the enhanced ratio of ΔHFC-23/Δtracer.…”

“…Air mass back trajectories were calculated using the The back trajectories were then clustered by HYSPLIT according to the change of the total spatial variance of the individual trajectories about their cluster-mean (Stein et al, 2015), for which the smaller value indicates that all objects in the cluster have consistent patterns. We selected the clustering with the least spatial variance among the clustering results from HYSPLIT (Huang et al, 2021).…”