Tropospheric Concentrations and Distributions of CCl₂F₂ and CCl₃F over Japan since 1978

Abstract

   Tropospheric air samples have been collected over Japan (24-44°N, 128-144°E) since 1978, and analyzed for CCl₂F₂ and CCl₃F using GC-ECD.
   Mean volume mixing ratios in the troposphere were 453 ppt for CCl₂F₂ and 272 ppt for CCl₃F as of January 1990, and increased at almost constant rates, i.e., 16.2±3.5 ppt/year for CCl₂F₂ and 10.3±2.0 ppt/year for CCl₃F between 1978 and 1990. Since 1990, the growth rate of CCl₃F mixing ratios has clearly slowed, while that of CCl₂F₂ mixing ratios seems to have decreased after 1993. These are presumably in response to their reduced emission.