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

The atmospheric degradation of three chlorofluorocarbon (CFC) replacement c ompounds, namely HFC-134a, HCFC-123, and HCFC-124, results in the formation of trifluoroacetic acid (TFA). Concentrations of TFA were determined in pr ecipitation and surface water samples collected in California and Nevada du ring 1996-1997. Terminal lake systems were found to have concentrations 4-1 3 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 wi th significantly higher concentrations in fogwater (median = 689 ng/L) over rainwater (median = 63.7 ng/L). Elevated levels of TFA were observed for r ainwater collected in Nevada (median = 136 ng/L) over those collected in Ca lifornia (median = 49.5 ng/L), indicating continual uptake and concentratio n as clouds move from a semiarid to arid climate. Thus several mechanisms e xist, including evaporative concentration, vapor-liquid phase partitioning, lowered washout volumes of atmospheric deposition water, and dry depositio n, which may lead to elevated concentrations of TFA in atmospheric and surf ace waters above levels expected from usual rainfall washout.