Airborne Trifluoroacetic Acid and Its Fraction from the Degradation of HFC-134a in Beijing, China

Abstract

Trifluoroacetic acid (TFA) has been attracting increasing attention worldwide because of its increased environmental concentrations and high aquatic toxicity. Atmospheric deposition is the major source of aquatic TFA, but only a few studies have reported either air concentrations or deposition fluxes for TFA. This is the first study to report the atmospheric concentrations of TFA in China, where an annular denuder and filter pack collection system were deployed at a highly urbanized site in Beijing. In total, 144 air samples were collected over the course of 1 year (from May 2012 to April 2013) and analyzed directly using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) or following derivatization by gas chromatography-mass spectrometry (GC-MS). The annual mean atmospheric concentration of TFA was 1580 ± 558 pg/m(3), higher than the previously reported annual mean levels in Germany and Canada. For the first time, it was demonstrated that maximum concentrations of TFA were frequently observed in the afternoon, following a diurnal cycle and suggesting that a major source of airborne TFA is likely degradation of volatile precursors. Using a deposition model, the annual TFA deposition flux was estimated to be 619 ± 264 μg m(-2) year(-1). Nevertheless, a box model estimated that the TFA deposition flux from the degradation of HFC-134a contributed only 14% (6-33%) to the total TFA deposition flux in Beijing. Source analysis is quite important for future TFA risk predictions; therefore, future research should focus on identifying additional sources.

Challenges in the analytical determination of ultra-short-chain perfluoroalkyl acids and implications for environmental and human health

“…Many studies have applied precautions during sample preparation, but few studies report contamination sources. It is possible that a large contribution of TFA blank contamination originates from the ambient air, and in that case, the contamination might depend on season [22,23] and the diurnal cycle [23]. Other potential sources including solvents, chemicals, laboratory equipment, and consumables must be taken into consideration and careful blank tests should be done prior to analytical determination.…”

“…Higher concentrations of TFA has been observed in surface waters in industrialized areas compared with less industrialized areas [12]. Concentrations of TFA have also been reported in groundwater (< 5 ng/L to 7.5 μg/L) [9,11,12], ocean water (1-250 ng/L) [10,12,15,22], fog water (20 ng/L to 2.2 μg/L) [13,24,33], in municipal (90-600 ng/L) and industrial (< 100 ng/L to 206 μg/L) wastewater effluent [9], in air (10 ng/ L to 6.3 μg/L) [12,23,26], and in drinking water (16 ng/L to 11 μg/L) [9,11,16,27]. Moreover, TFA has been reported in soil (< 0.1-9.4 ng/L) and conifer needles (< 2-420 ng/L) [18].…”

“…Formation of TFA can also occur via oxidation of precursor compounds, such as n:2 fluorotelomer alcohols (FTOHs) [46], that are major raw materials used in surfactant and surface protecting products; perfluoroalkane sulfonamide derivatives having four perfluorinated carbon atoms (e.g., perfluorobutane sulfonamide, FBSA) [2]; and N-methyl perfluorobutane sulfonamidoethanol (N-MeFBSE) [47], which is used as stain protectants for carpets, fabrics, and paper products. Atmospheric concentrations of TFA has been shown to be higher in spring and summer compared with autumn and winter [23,48]. Wu et al [23] showed that the airborne TFA measured in the north of China peaked in the afternoon and reached a minimum during early morning, following a diurnal cycle.…”

“…Atmospheric concentrations of TFA has been shown to be higher in spring and summer compared with autumn and winter [23,48]. Wu et al [23] showed that the airborne TFA measured in the north of China peaked in the afternoon and reached a minimum during early morning, following a diurnal cycle. These findings suggest that degradation of volatile precursors is a major source of airborne TFA.…”

“…Increased attention was paid on TFA after the phaseout of chlorofluorocarbons (CFCs), according to the Montreal Protocol on substances that deplete the ozone layer in 1989 [8], and the subsequent introduction of hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs). TFA has since then been widely studied and reported in various environmental matrices globally [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. Other ultra-short-chain PFAAs have not been well studied and data reporting their sources, fate, and environmental occurrence is scarce.…”