Recent tropospheric growth rate and distribution of HFC-134a (CFCHF)

Air samples collected at Cape Grim, Tasmania (41°S) between 1978 and 1995, and at Mace Head, Ireland (53°N) between July 1994 and May 1995, have been analysed by GC-MS to determine recent trends of HFC-134a, an important CFC replacement, in the background atmosphere. Until 1990, the concentration of HFC-134a at Cape Grim was below detection limits, the first quantifiable level (0.01 pptv) appearing in May 1990. Between 1992 and mid-1995 the concentration grew exponentially at -200 % yr. with the concentration at the end of 1994 reaching 0.43 pptv. At Mace Head, HFC-134a grew at a rate of 1.24±0.11 pptv yr between July 1994 and May 1995, with the concentration at the end of 1994 being 1.48 pptv. In the absence of industrial production and release estimates for HFC-134a, the observations have been used in conjunction with a 2-D global model to estimate recent emissions. The model indicates that significant emissions (250 tonnes) began in 1991, increasing rapidly to a level of ~8 ktonnes in 1994.