Determination of trifluoroacetic acid in 1996-1997 precipitation and surface waters in California and Nevada

The atmospheric degradation of three chlorofluorocarbon (CFC) replacement compounds, namely HFC-134a, HCFC-123, and HCFC-124, results in the formation of trifluoroacetic acid (TFA). Concentrations of TFA were determined in precipitation and surface water samples collected in California and Nevada during 1996-1997. Terminal lake systems were found to have concentrations 4-13 times higher than their calculated yearly inputs, providing evidence for accumulation. The results support dry deposition as the primary contributor of TFA to surface waters in arid and semiarid environments. Precipitation samples obtained from three different locations contained 20.7-1530 ng/L with significantly higher concentrations in fogwater (median = 689 ng/L) over rainwater (median = 63.7 ng/L). Elevated levels of TFA were observed for rainwater collected in Nevada (median = 136 ng/L) over those collected in California (median = 49.5 ng/L), indicating continual uptake and concentration as clouds move from a semiarid to arid climate. Thus several mechanisms exist, including evaporative concentration, vapor-liquid phase partitioning, lowered washout volumes of atmospheric deposition water, and dry deposition, which may lead to elevated concentrations of TFA in atmospheric and surface waters above levels expected from usual rainfall washout.