Long-term atmospheric observations of NF3 at eight background stations during 2018-2024 and regional emission estimates in China.

Nitrogen trifluoride (NF3) is a potent and long-lived fluorinated greenhouse gas with rapidly increasing emissions. However, despite being a major source of NF3 emissions, China has few emission estimates based on long-term atmospheric observations. In this study, weekly atmospheric measurements of NF3 were conducted at eight background stations across China from 2018 to 2024, and regional NF3 emissions during 2018-2023 were estimated using the tracer-ratio method, with HCFC-22 and CO as complementary reference tracers. The results showed a continuous increase in NF3 atmospheric mole fractions at all sites, with the national background level increasing from approximately 2.0 pptv in 2018 to 4.0 pptv in 2024. Enhanced NF3 mole fractions at stations influenced by economically developed regions exhibited upward trends, indicating an increase in the frequency and intensity of pollution events. HCFC-22-based estimates showed that NF3 emissions from four major industrial regions increased from 1.06 ± 0.95 Gg yr-1 in 2018/2019-2020 to 1.53 ± 1.14 Gg yr-1 in 2021-2023. These four regions account for 75% and 92% of China's total NF3 emissions and 36% and 44% of global NF3 emissions, respectively, during the two periods. Central China (CC) was identified as the largest contributor to NF3 emissions in China, while the Yangtze River Delta (YRD) exhibited the most rapid increase in its contribution to emissions and emission intensity. The regional differences and temporal evolution of NF3 emissions were closely associated with variations in industrial structure and development. Furthermore, China's emission intensities, normalized by GDP and population, were substantially higher than global averages, highlighting the importance of region-specific mitigation strategies targeting NF3-intensive industries.