Analysis of 3-year observations of CFC-11, CFC-12 and CFC-113 from a semi-rural site in China |
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| Authors: | Fang Zhang Lingxi Zhou Bo Yao Martin K Vollmer Brian R Greally Peter G Simmonds Stefan Reimann Frode Stordal Michela Maione Lin Xu Xiaochun Zhang |
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| Institution: | 1. College of Environmental Sciences and Engineering, State Key Joint Laboratory of Environmental Simulation and Pollution Control, Peking University, Beijing, PR China;2. Chongqing Environmental Monitoring Center, Chongqing, PR China;3. Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA, USA;1. Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;2. Chinese Academy of Meteorological Sciences (CAMS), China Meteorological Administration (CMA), Beijing 100081, China;3. University of Chinese Academy of Sciences, Beijing 100049, China;4. Nanjing University of Information Science and Technology, Nanjing 210044, China;5. Meteorological Research Institute of Heilongjiang Province, Harbin 150030, China;1. Longfengshan Regional Background Station, China Meteorological Administration (CMA), Heilongjiang, China;2. Meteorological Observation Center (MOC) of China Meteorological Administration (CMA), Beijing, China;3. College of Life and Environmental Sciences, Minzu University of China, Beijing, China;4. Laboratory for Air Pollution and Environmental Technology, Swiss Federal Laboratories for Materials Science and Technology (Empa), Dübendorf, Switzerland;5. State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Chinese Academy of Sciences, Institute of Atmospheric Physics, Beijing, China;6. State Key Laboratory of Severe Weather & Key Laboratory of Atmospheric Chemistry of China Meteorological Administration (CMA), Chinese Academy of Meteorological Sciences (CAMS), Beijing, China;7. Zhejiang Institute of Meteorological Sciences, Hangzhou, China;8. Atmospheric Chemistry Research Group, University of Bristol, Bristol, UK |
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| Abstract: | In-situ measurements of atmospheric chlorofluorocarbons (CFCs) can be used to the assess their global and regional emissions and to check for compliance with phase-out schedules under Montreal protocol and its amendments. The atmospheric mixing ratios of CFC-11 (CCl3F), CFC-12 (CCl2F2) and CFC-113 (CCl2F–CClF2) have been measured by an automated in-situ GC-ECDs system at the regional Chinese Global Atmosphere Watch (GAW) station Shangdianzi (SDZ), from November 2006 to October 2009. The time series for these three principal CFCs showed large episodic events and background conditions occurred for approximately 30% (CFC-11), 52% (CFC-12) and 56% (CFC-113) of the measurements. The mean background mixing ratios for CFC-11, CFC-12 and CFC-113 were 244.8 ppt (parts per trillion, 10?12, molar) 539.6 ppt and 76.8 ppt, respectively, for 2006–2009. The enhanced CFC mixing ratios compared to AGAGE sites such as Trinidad Head (THD), US and Mace Head (MHD), Ireland suggest regional influences even during background conditions at SDZ, which is much closer to highly-populated areas. Between 2006 and 2009 background CFCs exhibited downward trends at rates of ?2.0 ppt yr?1 for CFC-11, ?2.5 ppt yr?1 for CFC-12 and ?0.7 ppt yr?1 for CFC-113. De-trended 3-year average background seasonal cycles displayed small fluctuations with peak-to-trough amplitudes of 1.0 ± 0.02 ppt (0.4%) for background CFC-11, 1.3 ± 2.1 ppt (0.3%) for CFC-12 and 0.2 ± 0.4 ppt (0.3%) for CFC-113. On the other hand, during pollution periods these CFCs showed much larger seasonal cycles of 11.2 ± 10.7 ppt (5%) for CFC-11, 7.5 ± 6.5 ppt (2%) for CFC-12 and 1.0 ± 1.2 ppt (1.2%) for CFC-113, with apparent winter minima and early summer maxima. This enhancement was attributed to prevailing wind directions from urban regions in summer and to enhanced anthropogenic sources during the warm season. In general, horizontal winds from northeast showed negative contribution to atmospheric CFCs loading, whereas South Western advection (urban sector: Beijing) had positive contributions. |
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