Regional distribution of trifluoroacetate in surface waters downwind of urban areas in Northern California. USA

Trifluoroacetate (TFA), a breakdown product of the hydrofluorocarbons (HFCs ) and hydrochlorofluorocarhons (HCFCs), has been found at higher concentrat ions in surface waters near urban areas compared to globally remote sires, but the scale of the urban enrichment, namely local or regional, is unknown . To determine the scale of urban enrichment of TFA in Northern California, a series of streams were sampled in 1998 along a transect upwind and downw ind of the San Francisco and Sacramento metropolitan areas. In addition, 17 remote sites were sampled in British Columbia and the Yukon Territory, Can ada and in Alaska, U.S.A. to determine the baseline TFA concentrations in N orthern Hemisphere surface waters. The results showed elevated TFA concentr ations in surface waters around and immediately downwind of urban areas. Th e enrichment was approximately 5-6 times higher than the concentrations in upwind sites. The northern remote sites showed a median TFA concentration o f 21 ng/L, which was statistically indistinguishable from the upwind coasta l sites of the Californian transect. The mechanism for the urban enrichment was unknown, but it may have been the result of additional sources of TFA other than the HFC/HCFCs or faster formation of TFA due to higher HFC/HCFC and hydroxyl radical concentrations.