Trifluoroacetic acid from degradation of HCFCs and HFCs: A three‐dimensional modeling study

Abstract

In this paper we present the global distribution of TFA in the gas phase and in precipitation produced by the degradation of HFC-134a, HCFC-124, and HCFC-123 using a coarse grid chemical transport model (CTM), but including synoptic scale weather patterns, diurnal boundary layers, and wet and dry convective plume mixing processes derived from a general circulation model (GCM). Observed climatological values of 5747

Rainwater trifluoroacetic acid (TFA) in Guangzhou, South China: Levels, wet deposition fluxes and source implication

“…Rainwater TFA levels TFA levels in collected rainwater samples ranged from 45.8 to 974 ng L −1 with a median concentration of 166 ng L −1 and an average of 225 ng L −1 (Fig. 2), exceeding annual average levels of about 120 ng L −1 as predicted for the year 2010 (Kotamarthi et al, 1998).…”

“…Similarly, a study in Switzerland reported an average TFA level of 151 ng L −1 in rainwater, but calculated rainfall-weighted average was 116 ng L −1 using their rainfall and TFA data (Berg et al, 2000). It should be noted that Kotamarthi et al (1998) for the year 2010, and higher rainwater TFA levels with a range from 150 to 200 ng L −1 occurred in the northern middle latitudes due to CF 3 COF converting to TFA with so short lifetime that production of TFA maximizes in these areas. In this study, the annual rainfallweighted average TFA level of 152 ng L −1 in Guangzhou fell within the range predicted by Kotamarthi et al (1998) for the year 2010 in the northern middle latitudes.…”

“…It should be noted that Kotamarthi et al (1998) for the year 2010, and higher rainwater TFA levels with a range from 150 to 200 ng L −1 occurred in the northern middle latitudes due to CF 3 COF converting to TFA with so short lifetime that production of TFA maximizes in these areas. In this study, the annual rainfallweighted average TFA level of 152 ng L −1 in Guangzhou fell within the range predicted by Kotamarthi et al (1998) for the year 2010 in the northern middle latitudes. Due to the accumulation of CF 3 COX or TFA in non-raining days, TFA levels should be the highest at the beginning of a rain event and then decrease with time.…”

“…However, previous studies showed that the degradation of these halocarbons cannot explain well the observed TFA in precipitation Jordan and Frank, 1999). As model predicted, in the year of 2010 the global average of HCFC-123, HCFC-124 and HFC134a would reach 1.1 pptv, 9.8 pptv and 80 pptv, respectively, resulting in a global average of 120 ng L −1 TFA in rainwater (Kotamarthi et al, 1998). However, many studies around 1995 (e.g.…”

“…Higher concentrations of oxidants like OH radical in this subtropical/ tropical region (Prinn et al, 1995) should also promote the degradation of precursors to produce TFA. The abundance of rainfall in PRD (~1900 mm, annual) would facilitate TFA removal from the atmosphere through wet precipitation as the major pathway for final removal of TFA in the atmosphere (Kotamarthi et al, 1998). China government implemented one compulsory policy since 2002 to convert previously CFC-12 based MACs to HFC-134a based MACs.…”