High frequency measurements of HFCs at a remote site in east Asia and their implications for Chinese emissions

High frequency monitoring of hydrofluorocarbons (HFCs) and some other halocarbons in the atmosphere has been performed at Hateruma Island (lat. 24.1 degrees N, long. 123.8 degrees E), a background site in east Asia. The observed concentrations showed occasional short-term enhancement events over hours to days as well as a clear seasonal variation, being lower in summer than in other seasons. We found that HFC-23 enhancements were closely related to the air transport from China. Using a tagged simulation from three-dimensional transport model and a tracer-ratio technique, the emission rate of HFC-23 from China was estimated to amount to 10 Gg (= 10 000 metric tonnes) per year with an uncertainty of 50%, which could account for two thirds of the total global emission. HFCs emitted from Japan, Korea, and Taiwan were characterized by a predominance of HFC-134a with very little contribution of HFC-23.