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03-Sep-2016 06:09

Annual production of CFC-11 and CFC-12 peaked in 1987 and that of CFC-113 peaked in 1989.

CFC-11, CFC-12 and CFC-113 concentrations in water can be determined to a detection limit of about 0.3 picograms per kg of water (pg/kg-1) using purge and trap, gas chromatographic techniques with electron-capture detector (GC-ECD; Bullister, 1984; Bullister and Weiss, 1988; Busenberg and Plummer, 1992). Randall and Schultz (1976) also recognised the need for reconstruction of atmospheric mixing ratios of CFCs to improve dating capability, the possibility of detecting both CFC-11 and CFC-12 in the same analysis (at that time, analytical procedures were capable of detecting only CFC-11), and potential for dating using ratios of CFCs.