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

Sustained Increases in Hydrofluorocarbon Emissions from China and Implications for Global Emissions

Hydrofluorocarbons (HFCs), which are potent greenhouse gases and widely used as replacements for ozone-depleting substances, are controlled under the Montreal Protocol. China is considered an emission hot region of HFCs, however, the observations and emission quantifications are still insufficient. In this study, we report new high-frequency in situ observations of HFC-125, HFC-134a, and HFC-143a at the Changdao (CHD) station, whose emission sensitivity to northern China is higher than those of previously used stations to better quantify emissions. Combining these observations at CHD with an inverse modeling approach, we present the most recent emission estimates for northern China and reveal the distinct spatial distributions of HFC emissions that have not been previously uncovered, facilitating different priorities of provinces in future controls for HFCs. Subsequently, we show that the combined CO2-equivalent emissions of these HFCs in China increased rapidly from 7.1 ± 2.5 Mt CO2-equivalent yr-1 (2.2 ± 0.8% of global totals) in 2005 to 206.4 ± 15.9 Mt CO2-equivalent yr-1 (20.3 ± 1.8% of global totals) in 2022. Finally, we reveal that in terms of per area, per capita, and per gross domestic product, CO2-equivalent emissions of HFCs in China were increasing fast and becoming larger than the global average level. Our new high-frequency in situ observations of HFCs and ongoing observations are crucially important to assess the historical and future emission evolution of HFCs under the Montreal Protocol.

Atmospheric observation and emission estimation of HFC-125 and HFC-32 in China from four representative cities

HFC-125 and HFC-32 are fluorinated greenhouse gases of great concern due to their high GWPs and increasing background atmospheric concentrations. Long-term atmospheric observations of HFC-125 and HFC-32 were carried out in four representative cities of China (Beijing, Guangzhou, Hangzhou, and Lanzhou) from January 2012 to October 2019. Overall, the annual mean atmospheric concentrations of HFC-125 and HFC-32 both showed increasing trends, with average rates of 4.8 ppt yr-1 and 7.9 ppt yr-1. The average concentrations of HFC-125 and HFC-32 in urban areas were significantly higher than those in suburban areas. Significant differences in atmospheric concentrations of the two HFCs were observed among the four cities. HFC-125 and HFC-32 emissions were estimated accordingly, averaging 6.2 Gg yr-1 (23.6 Mt. CO2-eq) and 5.7 Gg yr-1 (4.3 Mt. CO2-eq) during 2012 and 2019 and growing at rates of 0.8 Gg yr-1 (3.1 Mt. CO2-eq) and 0.8 Gg yr-1 (0.6 Mt. CO2-eq), respectively, with an increasing contribution to global radiative forcing. The bottom-up inventories of HFC-125 and HFC-32 in the four cities increased annually from 2012 to 2019, with the highest emissions in Beijing, while the top-down emissions fluctuated during the research period. SYNOPSIS: The atmospheric concentrations of HFC-125 and HFC-32 were measured from 2012 to 2019 in four representative cities of China. Both HFC emissions at national and city levels were estimated using observation-based and inventory methods.

Trends of halocarbons in the Himalayan atmosphere and implications

Halocarbons are the primary driver behind ozone depletion and global warming. There is a vast observation gap in the Himalayan region. We report the field observations of thirty-four halocarbons at Nepal Climate Laboratory-Pyramid station and near the Mt. Qomolangma (Everest) base camp in the high Himalayas, including their atmospheric abundance and related changes over time. The dominant ozone depleting substances (ODSs) exhibited a declining trend, reflecting the effectiveness of the Montreal Protocol. However, a larger increase in HFCs and a higher abundance of unregulated chlorocarbons (e. g., CH3Cl) in this region compared to the global and North-Hemisphere values were found. It underscores that more attention is needed, not only for knowing where and how much HFCs and unregulated chlorocarbons are being emitted, but also for understanding its complicated role in climate change.

Long-Term Halocarbon Observations in an Urban Area of the YRD Region, China: Characteristic, Sources Apportionment and Health Risk Assessment

To observe the long-term variations in halocarbons in the Yangtze River Delta (YRD) region, this study analyzes halocarbon concentrations and composition characteristics in Shanxi from 2018 to 2020, exploring their origins and the health effects. The total concentration of halocarbons has shown an overall increasing trend, which is driven by both regulated substances (CFC-11 and CFC-113) and unregulated substances, such as dichloromethane, chloromethane and chloroform. The results of the study also reveal that dichloromethane (1.194 ± 1.003 to 1.424 ± 1.004 ppbv) and chloromethane (0.205 ± 0.185 to 0.666 ± 0.323 ppbv) are the predominant halocarbons in Shanxi, influenced by local and northwestern emissions. Next, this study identifies that neighboring cities in Zhejiang Province and other YRD areas are potentially affected by backward trajectory models. Notably, chloroform and 1,2-dichloroethane have consistently surpassed acceptable thresholds, indicating a significant carcinogenic risk associated with solvent usage. This research sheds light on the evolution of halocarbons in the YRD region, offering valuable data for the control and reduction in halocarbon emissions.