Background monitoring and long-range transport of atmospheric CFC-11 and CFC-12 at Kosan, Korea

The background concentrations of atmospheric CFC-11 and CFC-12 were monitor ed to assess their impact on stratospheric ozone depletion and global warmi ng from September 1995 to March 1999 at Kosan, Korea, located at eastern ma rgin of the Asian Continent. The concentrations of atmospheric CFC-11 at Ko san have decreased slightly, at a rate of -2.5 pptv yr(-1), over the period in response to the Montreal Protocol. The CFC-12 mixing ratio at Kosan con tinues to increase in the atmosphere at a rate of 5.7 pptv yr(-)1 despite i nternational regulations, because of its extreme atmosphere persistence. Re cent trends of these two chlorofluorocarbons at Kosan, Korea were concordan t with those of the northern hemispheric background monitored unit at Mauna Loa, Hawaii. The maximum seasonal mean mixing ratios of CFC-11 and CFC-12 at Kosan, Korea, were 270 +/-4 pptv in the spring and 538 +/-9 pptv in the winter, and the corresponding seasonal minima were 267 +/-7 and 529 +/- 12 pptv. This occurred in the summer and was due to southeasterly winds from t he northwestern Pacific Ocean. By performing a three-day isentropic backwar d trajectory analysis, it was shown that air masses at Kosan, and with the exception of summer, mainly originated from central and northern China. In particular, the mixing ratios of these two contaminant species are closely related with their air mass trajectories.