title: Changes in the levels and variability of halocarbons and the compliance with the Montreal Protocol from an urban view.
abstract: Ambient levels and variability of major atmospheric halocarbons, i.e. CFC-12, CFC-11, CFC-113, CCl4, CH3CCl3, C2HCl3, and C2Cl4 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 CCl4 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, C2HCl3, and C2Cl4 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.
authors.affiliation: Department of Chemistry, National Central University, Taoyuan 32001, Taiwan; Department of Atmospheric Sciences, National Central University, Taoyuan 32001, Taiwan.
authors.forename: Chang-Feng
authors.initials: CF
authors.lastname: Ou-Yang
authors.affiliation: Research Center for Environmental Changes, Academia Sinica, Taipei 11529, Taiwan. Electronic address: joechang@rcec.sinica.edu.tw.
authors.forename: Chih-Chung
authors.initials: CC
authors.lastname: Chang
authors.affiliation: Department of Chemistry, National Central University, Taoyuan 32001, Taiwan.
authors.forename: Shen-Po
authors.initials: SP
authors.lastname: Chen
authors.affiliation: Research Center for Environmental Changes, Academia Sinica, Taipei 11529, Taiwan.
authors.forename: Clock
authors.initials: C
authors.lastname: Chew
authors.affiliation: Research Center for Environmental Changes, Academia Sinica, Taipei 11529, Taiwan.
authors.forename: Bo-Ru
authors.initials: BR
authors.lastname: Lee
authors.affiliation: Research Center for Environmental Changes, Academia Sinica, Taipei 11529, Taiwan.
authors.forename: Chih-Yuan
authors.initials: CY
authors.lastname: Chang
authors.affiliation: Global Monitoring Division, Earth Systems Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305, United States.
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Montzka
authors.affiliation: Global Monitoring Division, Earth Systems Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305, United States; Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, United States.
authors.forename: Geoffrey S
authors.initials: GS
authors.lastname: Dutton
authors.affiliation: Global Monitoring Division, Earth Systems Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305, United States.
authors.forename: James H
authors.initials: JH
authors.lastname: Butler
authors.affiliation: Global Monitoring Division, Earth Systems Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305, United States.
authors.forename: James W
authors.initials: JW
authors.lastname: Elkins
authors.affiliation: Department of Chemistry, National Central University, Taoyuan 32001, Taiwan. Electronic address: cwang@cc.ncu.edu.tw.
authors.forename: Jia-Lin
authors.initials: JL
authors.lastname: Wang
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D001272:Atmosphere / Q000737:chemistry; D002947:Cities; D004784:Environmental Monitoring; D019983:Guideline Adherence / Q000706:statistics & numerical data*; D006846:Hydrocarbons, Halogenated / Q000032:analysis*; D007391:International Cooperation; D010126:Ozone / Q000737:chemistry; D013624:Taiwan
chemical_list: D000393:Air Pollutants; D006846:Hydrocarbons, Halogenated; D010126:Ozone
keywords: Halocarbons; Montreal Protocol; Ozone-depleting substances (ODS); Variability