Tropospheric air samples have been collected over Japan (24-44°N, 128-144°E) since 1978, and analyzed for CCl
2F
2 and CCl
3F using GC-ECD.
Mean volume mixing ratios in the troposphere were 453 ppt for CCl
2F
2 and 272 ppt for CCl
3F as of January 1990, and increased at almost constant rates, i.e., 16.2±3.5 ppt/year for CCl
2F
2 and 10.3±2.0 ppt/year for CCl
3F between 1978 and 1990. Since 1990, the growth rate of CCl
3F mixing ratios has clearly slowed, while that of CCl
2F
2 mixing ratios seems to have decreased after 1993. These are presumably in response to their reduced emission.
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