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ATMOSPHERIC CHEMISTRY AND PHYSICAL FATE OF HCFCS AND HFCS AND THEIR DEGRADATION PRODUCTS
Citation:
Edney, E. ATMOSPHERIC CHEMISTRY AND PHYSICAL FATE OF HCFCS AND HFCS AND THEIR DEGRADATION PRODUCTS. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/R-92/222 (NTIS PB93131449).
Description:
Laboratory experiments were conducted to determine the fate of the proposed CFC substitutes HCFC-22, HCFC-123, HCFC-124, HCFC-141b, HCFC-142b, HFC-125, HFC-134a, and HFC-152a. he program consisted of photochemical oxidation experiments to identify stable oxidation products and measure their yields; deposition studies to measure the extent oxidation products are absorbed into aqueous media; and experiments to determine the fate of hydrolysis products during droplet evaporation. roduct studies showed that acid halides, including COF2, COFC1, CF3CF0, HFCo, and CF3CC10, are major oxidation products of HCFCs and HFCs. he deposition studies were compatible with significant uptake of the acid halides to HC1, and CF3C00H. odel results, obtained using laboratory derived lower limits estimates for aqueous depoistion velocities and assuming a well mixed atmosphere, suggest the uptakes rates to cloudwater and oceans are sufficiently fast such that significant buildup of gas phase products is unlikely. owever, for a global emission rate of 10-5 tonnes yr-1, precipitation concentrations as high as 20 pmol m1-1 of the apparently long lived species CF3C00 are possible. he laboratory studies suggest that product accumulation in aqueous media could be affected by losses during evaporation. irect loss by evaporation of halogenated acids and/or production of volatile compounds after further reactions of the dissolved acids could return halogenated compounds to the atmosphere.