Regional distribution of trifluoroacetate in surface waters downwind of urban areas in Northern California, U.S.A.

Trifluoroacetate (TFA), a breakdown product of the hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs), has been found at higher concentrations in surface waters near urban areas compared to globally remote sites, 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 downwind of the San Francisco and Sacramento metropolitan areas. In addition, 17 remote sites were sam pied in British Columbia and the Yukon Territory, Canada and in Alaska, U.S.A. to determine the baseline TFA concentrations in Northern Hemisphere surface waters. The results showed elevated TFA concentrations in surface waters around and immediately downwind of urban areas. The enrichment was approximately 5-6 times higher than the concentrations in upwind sites. The northern remote sites showed a median TFA concentration of 21 ng/L, which was statistically indistinguishable from the upwind coastal 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.