Halocarbons are hot topics in atmospheric environment and climate change research. Combining observational data from six field campaigns at the summit of Mount Taishan (36.25°N, 117.10°E, 1534 m above sea level) with backward trajectory and receptor source analyses, this study analyzed the long-term trends and major emission sources of halocarbons in the regional background atmosphere of the North China Plain (NCP) from 2003 to 2018. The results showed that the volume fraction of species eliminated by the Montreal Protocol (MP) showed a significant downward trend; however, the MP-controlled and unregulated species showed an overall upward trend. Meanwhile, the median volume fraction of the MP-controlled and unregulated species at Mount Taishan were significantly higher than the mid-latitude median background values in the northern hemisphere. Mount Taishan air was mainly affected by four types of air masses, of which the air mass originating from NCP accounted for the highest proportion (41%). The major sources of halocarbons were biomass/biofuel burning (38.1%), refrigeration (26.2%), industrial and domestic solvent use (21.7%), solvent use in the electronic industry (8.7%), and leakage of chlorofluorocarbon (CFCs) banks (5.3%). This study fully demonstrates that MP has been effectively implemented in China and provides evidence and recommendations to further reduce and control the volume fraction of halocarbons.
Keywords: Montreal Protocol; Mount Taishan; halocarbons; long-term trends; source apportionment.