Changes in the levels and variability of halocarbons and the compliance with the Montreal Protocol from an urban view
2015
Abstract Ambient levels and variability of major atmospheric halocarbons, i.e. CFC-12, CFC-11, CFC-113, CCl 4 , CH 3 CCl 3 , C 2 HCl 3 , and C 2 Cl 4 in a major metropolis (Taipei, Taiwan) were re-investigated after fourteen years by flask sampling in 2012. Our data indicates that the variability expressed as standard deviations (SD) of CFC-113 and CCl 4 remained small (2.0 ppt and 1.9 ppt, respectively) for the 10th–90th percentile range in both sampling periods; whereas the variability of CFC-12, CFC-11, C 2 HCl 3 , and C 2 Cl 4 measured in 2012 became noticeably smaller than observed in 1998, suggesting their emissions were reduced over time. By comparing with the background data of a global network (NOAA/ESRL/GMD baseline observatories), the ambient levels and distribution of these major halocarbons in Taipei approximated those at a background site (Mauna Loa) in 2012, suggesting that the fingerprint of the major halocarbons in a used-to-be prominent source area has gradually approached to that of the background atmosphere.
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