Efficient decomposition of environmentally persistent perfluorocarboxylic acids by use of persulfate as a photochemical oxidant

Photochemical decomposition of persistent perfluorocarboxylic acids (PFCAs) in water by use of persulfate ion (S2O8(2-)) was examined to develop a technique to neutralize stationary sources of PFCAs. Photolysis of S2O8(2-) produced highly oxidative sulfate radical anions (SO4-), which efficiently decomposed perfluorooctanoic acid (PFOA) and other PFCAs bearing C4-C8 perfluoroalkyl groups. The major products were F- and CO2; also, small amounts of PFCAs with shorter than initial chain lengths were detected in the reaction solution. PFOA at a concentration of 1.35 mM (typical of that in untreated wastewater after an emulsifying process in fluoropolymer manufacture) was completely decomposed by a photochemical system with 50 mM S2O8(2-) and 4 h of irradiation from a 200-W xenon-mercury lamp. The initial PFOA decomposition rate was 11 times higherthan with photolysis alone. All sulfur-containing species in the reaction solution were eventually transformed to sulfate ions by this method. This method was successfully applied to the decomposition of perfluorononanoic acid contained in a floor wax solution.     

Efficient electrochemical oxidation of perfluorooctanoate using a Ti/SnO2-Sb-Bi anode

The electrochemical decomposition of persistent perfluorooctanoate (PFOA) with a Ti/SnO2-Sb-Bi electrode was demonstrated in this study. After 2 h electrolysis, over 99% of PFOA (25 mL of 50 mg·L(-1)) was degraded with a first-order kinetic constant of 1.93 h(-1). The intermediate products including short-chain perfluorocarboxyl anions (CF3COO-, C2F5COO-, C3F7COO-, C4F9COO-, C5F11COO-, and C6F13COO-) and F- were detected in the aqueous solution. The electrochemical oxidation mechanism was revealed, that PFOA decomposition first occurred through a direct one electron transfer from the carboxyl group in PFOA to the anode at the potential of 3.37 V (vs saturated calomel electrode, SCE). After that, the PFOA radical was decarboxylated to form perfluoroheptyl radical which allowed a defluorination reaction between perfluoroheptyl radical and hydroxyl radical/O2. Electrospray ionization (ESI) mass spectrum further confirmed that the oxidation of PFOA on the Ti/SnO2-Sb-Bi electrode proceeded from the carboxyl group in PFOA rather than C-C cleavage, and the decomposition processes followed the CF2 unzipping cycle. The electrochemical technique with the Ti/SnO2-Sb-Bi electrode provided a potential method for PFOA degradation in the aqueous solution.     

Efficient photochemical decomposition of long-chain perfluorocarboxylic acids by means of an aqueous/liquid CO2 biphasic system

Photochemical decomposition of persistent and bioaccumulative long-chain (C9-C11) perfluorocarboxylic acids (PFCAs) with persulfate ion (S2O8(2-)) in an aqueous/liquid CO2 biphasic system was examined to develop a technique to neutralize stationary sources of the long-chain PFCAs. The long-chain PFCAs, namely, perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), and perfluoroundecanoic acid (PFUA), which are used as emulsifying agents and as surface treatment agents in industry, are relatively insoluble in water but are soluble in liquid CO2; therefore, introduction of liquid CO2 to the aqueous photoreaction system reduces the interference of colloidal PFCA particles. When the biphasic system was used to decompose these PFCAs, the extent of reaction was 6.4-51 times as high as that achieved in the absence of CO2. In the biphasic system, PFNA, PFDA, and PFUA (33.5-33.6 micromol) in 25.0 mL of water were 100%, 100%, and 77.1% decomposed, respectively, after 12 h of irradiation with a 200-W xenon-mercury lamp; F- ions were produced as a major product, and short-chain PFCAs, which are less bioaccumulative than the original PFCAs, were minor products. All of the initial S2O8(2-) was transformed to SO42-. The system also efficiently decomposed PFCAs at lower concentrations (e.g., 4.28-16.7 micromol of PFDA in 25.0 mL) and was successfully applied to decompose PFNA in floor wax.     

TiO2-induced heterogeneous photodegradation of a fluorotelomer alcohol in air

Degradation of C4F9C2H4OH in air over TiO2 particles was examined in this first report of gas-solid heterogeneous photochemical degradation of fluorotelomer alcohols (FTOHs), which may be precursors of perfluorocarboxylic acids (PFCAs) in the environment. Photoirradiation (>290 nm) of C4F9C2H4OH in air flowing over TiO2 produced CO2, via C4F9CH2CHO, C4F9CHO, CnF(2n+1)COF (n=2 and/or 3), and COF2, in that order. X-ray photoelectron spectroscopy of the Ti02 surface showed a decrease in the amount of fluorine bonded to carbon and an increase in the amount of F- as the degradation of C4F9C2H4OH in air proceeded. Of the carbon content in the initial C4F9C2H4OH (78.8 ppmv), 90.7% was transformed to CO2, and the predominant fluorine species produced on the TiO2 surface was F-. Fluorotelomer unsaturated acids, which are considered to be toxic and have been observed in the biodegradation of FTOHs, did notform. Increased relative humidity in the air accelerated the decomposition of the reaction intermediates, which led to increased CO2 and F- formation. This result indicates that humidity is a key factor for counteracting FTOHs in indoor air. Although perfluoroalkyl substances such as PFCAs in water reportedly undergo little photodegradation over TiO2, our data show that mineralization of C4F9C2H4OH in air can be achieved with TiO2.     

Decomposition of environmentally persistent perfluorooctanoic acid in water by photochemical approaches

The decomposition of persistent and bioaccumulative perfluorooctanoic acid (PFOA) in water by UV-visible light irradiation, by H202 with UV-visible light irradiation, and by a tungstic heteropolyacid photocatalyst was examined to develop a technique to counteract stationary sources of PFOA. Direct photolysis proceeded slowly to produce CO2, F-, and short-chain perfluorocarboxylic acids. Compared to the direct photolysis, H2O2 was less effective in PFOA decomposition. On the other hand, the heteropolyacid photocatalyst led to efficient PFOA decomposition and the production of F- ions and CO2. The photocatalyst also suppressed the accumulation of short-chain perfluorocarboxylic acids in the reaction solution. PFOA in the concentrations of 0.34-3.35 mM, typical of those in wastewaters after an emulsifying process in fluoropolymer manufacture, was completely decomposed by the catalyst within 24 h of irradiation from a 200-W xenon-mercury lamp, with no accompanying catalyst degradation, permitting the catalyst to be reused in consecutive runs. Gas chromatography/mass spectrometry (GC/MS) measurements showed no trace of environmentally undesirable species such as CF4, which has a very high global-warming potential. When the (initial PFOA)/(initial catalyst) molar ratio was 10: 1, the turnover number for PFOA decomposition reached 4.33 over 24 h of irradiation.     

Efficient decomposition of environmentally persistent perfluorooctanesulfonate and related fluorochemicals using zerovalent iron in subcritical water

Decomposition of perfluorooctanesulfonate (PFOS) and related chemicals in subcritical water was investigated. Although PFOS demonstrated little reactivity in pure subcritical water, addition of zerovalent metals to the reaction system enhanced the PFOS decomposition to form F-ions, with an increasing order of activity of no metal approximately equal Al < Cu < Zn < Fe. Use of iron led to the most efficient PFOS decomposition: When iron powder was added to an aqueous solution of PFOS (93-372 microM) and the mixture was heated at 350 degrees C for 6 h, PFOS concentration in the reaction solution fell below 2.2 microM (detection limit of HPLC with conductometric detection), with formation of F-ions with yields [i.e., (moles of F- formed)/(moles of fluorine content in initial PFOS) x 100] of 46.2-51.4% and without any formation of perfluorocarboxylic acids. A small amount of CHF3 was detected in the gas phase with a yield [i.e., (moles of CHF3)/(moles of carbon content in initial PFOS) x 100] of 0.7%, after the reaction of PFOS (372 microM) with iron at 350 degree C for 6 h. Spectroscopic measurements indicated that PFOS in water markedly adsorbed on the iron surface even at room temperature, and the adsorbed fluorinated species on the iron surface decomposed with rising temperature, with prominent release of F- ions to the solution phase above 250 degrees C. This method was also effective in decomposing other perfluoroalkylsulfonates bearing shorter chain (C2-C6) perfluoroalkyl groups and was successfully applied to the decomposition of PFOS contained in an antireflective coating agent used in semiconductor manufacturing.     

Efficient photocatalytic decomposition of perfluorooctanoic acid by indium oxide and its mechanism

Perfluorooctanoic acid (C(7)F(15)COOH, PFOA) has increasingly attracted worldwide concerns due to its global occurrence and resistance to most conventional treatment processes. Though TiO(2)-based photocatalysis is strong enough to decompose most organics, it is not effective for PFOA decomposition. We first find that indium oxide (In(2)O(3)) possesses significant activity for PFOA decomposition under UV irradiation, with the rate constant about 8.4 times higher than that by TiO(2). The major intermediates of PFOA were C(2)-C(7) shorter-chain perfluorocarboxylic acids, implying that the reaction proceeded in a stepwise manner. By using diffuse reflectance infrared Fourier transform spectroscopy, (19)F magic angle spinning nuclear magnetic resonance, and electron spin resonance, we demonstrate that the terminal carboxylate group of PFOA molecule tightly coordinates to the In(2)O(3) surface in a bidentate or bridging configuration, which is beneficial for PFOA to be directly decomposed by photogenerated holes of In(2)O(3) under UV irradiation, while PFOA coordinates to TiO(2) in a monodentate mode, and photogenerated holes of TiO(2) preferentially transform to hydroxyl radicals, which are inert to react with PFOA. PFOA decomposition in wastewater was inhibited by bicarbonate and other organic matters; however, their adverse impacts can be mostly avoided via pH adjustment and ozone addition.     

Fluorotelomer alcohol biodegradation yields poly- and perfluorinated acids

The widespread detection of environmentally persistent perfluorinated acids (PFCAs) such as perfluorooctanoic acid (PFOA) and its longer chained homologues (C9>C15) in biota has instigated a need to identify potential sources. It has recently been suggested that fluorinated telomer alcohols (FTOHs) are probable precursor compounds that may undergo transformation reactions in the environment leading to the formation of these potentially toxic and bioaccumulative PFCAs. This study examined the aerobic biodegradation of the 8:2 telomer alcohol (8:2 FTOH, CF3(CF2)7CH2CH2OH) using a mixed microbial system. The initial measured half-life of the 8:2 FTOH was approximately 0.2 days mg(-1) of initial biomass protein. The degradation of the telomer alcohol was monitored using a gas chromatograph equipped with an electron capture detector (GC/ECD). Volatile metabolites were identified using gas chromatography/ mass spectrometry (GC/MS), and nonvolatile metabolites were identified and quantified using liquid chromatography/ tandem mass spectrometry (LC/MS/MS). Telomer acids (CF3(CF2)7CH2COOH; CF3(CF2)6CFCHCOOH) and PFOA were identified as metabolites during the degradation, the unsaturated telomer acid being the predominant metabolite measured. The overall mechanism involves the oxidation of the 8:2 FTOH to the telomer acid via the transient telomer aldehyde. The telomer acid via a beta-oxidation mechanism was furthertransformed, leading to the unsaturated acid and ultimately producing the highly stable PFOA. Telomer alcohols were demonstrated to be potential sources of PFCAs as a consequence of biotic degradation. Biological transformation may be a major degradation pathway for fluorinated telomer alcohols in aquatic systems.     

Isomer distribution of perfluorocarboxylates in human blood: potential correlation to source

Detection of perfluorocarboxylate anions (PFCAs), such as perfluorooctanoate (C7F15COO-, PFOA), at ng/g levels in human tissues has engendered public scrutiny of industrial fluorochemicals. Routes of PFCA exposure for the general human population are likely diverse given direct (industrially produced) and indirect (production from precursor organofluorines) sources. Major industrial production of organofluorines, including PFCAs, stems from either electrochemical fluorination (ECF) or telomerization. ECF products are a mixture of structural isomers (linear and branched perfluoroalkyls) and telomerization products are assumed to have one perfluorocarbon arrangement, typically linear. The objective of this research was to investigate structural isomer patterns of PFCAs in human blood. Volatile derivatives of PFCAs in human blood were analyzed by GC-(NCI)-MS for quantitation and isomers. PFOA was the dominant PFCA (mean 4.4 ng/g). Blood serum isomer profiles consisted of predominantly (mean approximately 98%) the linear isomer for each PFCA (C8-C11). There were similarities in branched isomer patterns of an ECF PFOA standard with both PFOA and PFNA in blood. Direct exposure to ECF PFOA, which has a legacy of production for uses in fluoropolymer industries, is postulated to be a source of the observed branched isomer pattern. Predominance of linear PFCA isomers and the [even PFCA] > [odd PFCA] concentration trend in blood is suggestive of additional input from a strictly linear perfluoroalkyl source.     

Analysis for perfluorocarboxylic acids/anions in surface waters and precipitation using GC--MS and analysis of PFOA from large-volume samples

The presence of perfluorocarboxylates (PFCAs) in the environment is of increasing concern, following the discovery of perfluoroalkyl acids (PFAs) in wildlife and human samples. Here we report a method forthe determination of (C2-C9) PFCAs by preparing the 2,4-difluoroanilides of the acids and analyzing by using GC-MS. Detector response was linear over the range 0.1 -1000 pg of each perfluoroalkyl anilide. A complete suite of PFCAs can be analyzed in an individual sample with the PFCAs detected at levels similar to or lower than those determined by other methods. For a comparison between the present method and the more common LC-MS/MS method, 10 replicates of a sewage treatment plant discharge were analyzed for perfluoro-octanoic acid (PFOA) using both methods. Results were nearly identical with low standard deviation (GC-MS 30.9 +/- 1.88 ng/L; while the LC-MS/MS 34.7 +/- 3.05 ng/L). PFCA concentrations for water samples collected from depth profiles in mid-Lake Ontario were analyzed by GC-MS with most PFCAs (C2-C8) present above the detection limit (0.5 ng/L). Major PFCAs were trifluoroacetate (TFA) (100 ng/L) and perfluorobutanoate (PFBA) (> 5 ng/L). Results for PFOA (2.5 ng/L) were in good agreement with recent analyses by LC-MS/MS. PFCAs were also detected in the precipitation samples at concentrations lower than those of the samples from the lake profiles or sewage treatment plants (STPs) effluent. Since PFOA levels may be less than the lower detection limit (<0.5 ng/L) in 1 L samples, a method for large volumes using XAD-7 resin was developed that allows detection to 0.01 ng/L. This method was applied to Lake Superior samples which produced good agreement for C6-C9 PFCAs between regular analysis (GC-MS) and the XAD-7 followed by GC-MS analysis.     

Analysis of a homologous series of perfluorocarboxylates from American Red Cross adult blood donors, 2000-2001 and 2006

The purpose of this study was to determine the concentration trends of a nine-target-analyte homologous series of perfluorocarboxylates from six American Red Cross adult blood donor centers. A total of 645 serum and 600 plasma samples were obtained in 2000-2001 and 2006, respectively, with samples stratified for each 10-year (20-69) age- and sex-group per each location. Samples were extracted by protein precipitation and quantified by using tandem mass spectrometry. The nine perfluorocarboxylates were perfluorobutanoate (PFBA, C(3)F(7)CO(2)(-)), perfluoropentanoate (PFPeA, C(4)F(9)CO(2)(-)), perfluorohexanoate (PFHxA, C(5)F(11)CO(2)(-)), perfluoroheptanoate (PFHpA, C(6)F(13)CO(2)(-)), perfluorooctanoate (PFOA, C(7)F(15)CO(2)(-)), perfluorononanoate (PFNA, C(8)F(17)CO(2)(-)), perfluorodecanoate (PFDA, C(9)F(19)CO(2)(-)), perfluoroundecanoate (PFUnA,C(10)F(21)CO(2)(-)), and perfluorododecanoate (PFDoA, C(11)F(23)CO(2)(-)). The majority of measurements were less than the lower limit of quantitation for PFPeA, PFHxA, and PFDoA. For the remaining targeted analytes, the geometric mean serum and plasma concentrations (ng/mL) for 2000-2001 and 2006 were, respectively, as follows: PFBA 2.61 vs 0.33, PFHpA 0.13 vs 0.09, PFOA 4.70 vs 3.44, PFNA 0.57 vs 0.97, PFDA 0.16 vs 0.34, and PFUnA 0.10 vs 0.18. Estimates of the 95th percent tolerance limits (ng/mL) were as follows: PFBA 5.3 vs 1.4, PFHpA 0.4 vs 0.4, PFOA 12.3 vs 7.7, PFNA 1.4 vs 2.2, PFDA 0.4 vs 0.8, and PFUnA 0.3 vs 0.5. Important observations were the decline in PFBA and increase in PFNA, PFDA, and PFUnA concentrations between 2000-2001 and 2006. The longer chain length perfluorocarboxylates were also highly correlated with each other.     

Formation of C7F15COOH (PFOA) and other perfluorocarboxylic acids during the atmospheric oxidation of 8:2 fluorotelomer alcohol

Calculations using a three-dimensional global atmospheric chemistry model (IMPACT) indicate that n-C8F17CH2CH2OH (widely used in industrial and consumer products) degrades in the atmosphere to give perfluorooctanoic acid (PFOA) and other perfluorocarboxylic acids (PFCAs). PFOA is persistent, bioaccumulative, and potentially toxic. Molar yields of PFOA depend on location and season, are in the range of 1-10%, and are of the correct order of magnitude to explain the observed levels in Arctic fauna. Fluorotelomer alcohols such as n-C8F17CH2CH2OH appear to be a significant global source of persistent bioaccumulative perfluorocarboxylic acid pollution. This is the first modeling study of the atmospheric chemistry of a fluorotelomer alcohol.     

Quantitation of gas-phase perfluoroalkyl surfactants and fluorotelomer alcohols released from nonstick cookware and microwave popcorn bags

Fluoropolymer dispersions are used for coating certain cookware products and food-contact packaging to impart oil and water repellency. Since salts of perfluorooctanoic acid (PFOA) are used as a processing aid in the manufacture of many fluoropolymers, it is necessary to determine if these compounds are still present as residuals after the process used to coat nonstick cookware or packaging, and could be released during typical cooking conditions. In this study, we identified and measured perfluoroalkyl carboxylates (PFCAs), particularly PFOA, and fluorotelomer alcohols (FTOHs; 6:2 FTOH and 8:2 FTOH), released from nonstick cookware into the gas phase under normal cooking temperatures (179 to 233 degrees C surface temperature). PFOA was released into the gas phase at 7-337 ng (11-503 pg/cm2) per pan from four brands of nonstick frying pans. 6:2 FTOH and 8:2 FTOH were found in the gas phase of four brands of frying pans, and the sources of FTOHs released from nonstick cookware are under investigation. We observed a significant decrease in gas-phase PFOA following repeated use of one brand of pan, whereas the other brand did not show a significant reduction in PFOA release following multiple uses. PFOA was found at >5 ng during the fourth use of both brands of pans. FTOHs were not found after the second use of either brand of pans. PFOA was found at 5-34 ng in the vapors produced from a prepacked microwave popcorn bag. PFOA was not found in the vapors produced from plain white corn kernels popped in a polypropylene container. 6:2 FTOH and 8:2 FTOH were measured in the vapors produced from one brand of prepacked microwave popcorn at 223 + 37 ng and 258 +/- 36 ng per bag, respectively, but not measured at >20 ng (LOQ) in the other two brands. On the packaging surface of one brand of microwave popcorn several PFCAs, including C5-C12, 6:2 FTOH, and 8:2 FTOH, were found at concentrations in the order of 0.5-6.0 ng/cm2. This study suggests that residual PFOA is not completely removed during the fabrication process of the nonstick coating for cookware. They remain as residuals on the surface and may be off-gassed when heated at normal cooking temperatures.     

Poly and perfluorinated carboxylates in North American precipitation

Although perfluorocarboxylates (PFCAs) have been detected in a number of environmental matrices, there are very few reports on concentrations in precipitation. In this study PFCAs, fluorotelomercarboxylates (FTCAs), and fluorotelomer-unsaturated carboxylates (FTUCAs), were determined in wet only precipitation samples from nine sites in North America. The analytical method involved derivatization of the carboxylates and measurement of the 2,4-difluoroanilide by GC-MS. Samples from three remote sites in Canada had low concentrations of perfluorooctanoate (PFOA) (<0.1-6.1 ng/L). Significantly higher concentrations of PFOA were found at 4 northeastern United States and 2 southern urban Canadian sites, with Delaware having the highest levels (85 ng/L PFOA, with a range of 0.6-89 ng/L) and a maximum flux of 13 000 ng/m2. 8:2- and 10:2 FTCAs and FTUCAs were detected at all 4 U.S. sites and 2 urban Canadian sites (<0.07-8.6 ng/L), most frequently at the Delaware site. Longer chained PFCAs (deca-, undeca-, and dodeca-perfluorocarboxylates) were detected (<0.07-5.2 ng/L) at 2 urban Ontario sites but not determined in other samples. Air mass back trajectory results for 3 U.S. sites indicate highly populated urban areas in the New York to Washington corridor as the main sources of PFOA, although low PFOA levels associated with air masses coming off the Atlantic Ocean imply multiple sources.     

A global mass balance analysis of the source of perfluorocarboxylic acids in the Arctic Ocean

Whereas the pervasive and abundant presence of perfluorinated carboxylic acids (PFCAs) in the Arctic marine food chain is clearly established, their origin and transport pathway into the Arctic Ocean are not. Either the atmospheric oxidation of volatile precursor compounds, such as the fluorotelomer alcohols (FTOHs), or the long-range oceanic transport of directly emitted PFCAs is seen as contributing the bulk of the PFCA input to the Arctic. Here simulations with the zonally averaged global fate and transport model Globo-POP, in combination with historical emission estimates for FTOHs and perfluorooctanoic acid (PFOA), are used to evaluate the relative efficiency and importance of the two transport pathways. Estimates of the emission-independent Arctic Contamination Potential reveal that the oceanic transport of directly emitted PFCAs is more than 10-fold more efficient than the atmospheric degradation of FTOHs in delivering PFCAs to the Arctic, mostly because of the low yield of the reaction. The cumulative historic emissions of FTOHs are lower than those estimated for PFOA alone by a factor of 2-3, further limiting the contribution that precursor oxidation makes to the total PFCAs load in the Arctic Ocean. Accordingly, when fed only with FTOH emissions, the model predicts FTOH air concentrations in agreement with the reported measurements, but yields Arctic seawater concentrations for the PFOA that are 2 orders of magnitude too low. Whereas ocean transport is thus very likely the dominant pathway of PFOA into the Arctic Ocean, the major transport route of longer chain PFCAs depends on the size of their direct emissions relative to those of 10:2 FTOH. The predicted time course of Arctic seawater concentrations is very similar for directly emitted and atmospherically generated PFCAs, implying that neither past doubling times of PFCA concentrations in Arctic marine mammals nor any future time trends are likely to resolve the question of the dominant source of PFCAs.     

Atmospheric chemistry of perfluoroalkanesulfonamides: kinetic and product studies of the OH radical and Cl atom initiated oxidation of N-ethyl perfluorobutanesulfonamide

Perfluorooctanesulfonamides [C8F17SO2N(R1)(R2)] are present in the atmosphere and may, via atmospheric transport and oxidation, contribute to perfluorocarboxylates (PFCA) and perfluorooctanesulfonate (PFOS) pollution in remote locations. Smog chamber experiments with the perfluorobutanesulfonyl analogue N-ethyl perfluorobutanesulfonamide [NEtFBSA; C4F9SO2N(H)CH2CH3] were performed to assess this possibility. By use of relative rate methods, rate constants for reactions of NEtFBSA with chlorine atoms (296 K) and OH radicals (301 K) were determined to be kCL) = (8.37 +/- 1.44) x 10(-12) and kOH = (3.74 +/- 0.77) x 10(-13) cm3 molecule(-1) s(-1), indicating OH reactions will be dominant in the troposphere. Simple modeling exercises suggestthat reaction with OH radicals will dominate removal of perfluoroalkanesulfonamides from the gas phase (wet and dry deposition will not be important) and that the atmospheric lifetime of NEtFBSA in the gas phase will be 20-50 days, thus allowing substantial long-range atmospheric transport. Liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis showed that the primary products of chlorine atom initiated oxidation were the ketone C4F9SO2N(H)COCH3; aldehyde 1, C4F9SO2N(H)CH2CHO; and a product identified as C4F9SO2N(C2H5O)- by high-resolution MS but whose structure remains tentative. Another reaction product, aldehyde 2, C4F9SO2N(H)CHO, was also observed and was presumed to be a secondary oxidation product of aldehyde 1. Perfluorobutanesulfonate was not detected above the level of the blank in any sample; however, three perfluoroalkanecarboxylates (C3F7CO2-, C2F5CO2-, and CF3CO2-) were detected in all samples. Taken together, results suggest a plausible route by which perfluorooctanesulfonamides may serve as atmospheric sources of PFCAs, including perfluorooctanoic acid.     

Isolating isomers of perfluorocarboxylates in polar bears (Ursus maritimus) from two geographical locations

The source of involatile, anthropogenic perfluorocarboxylate anions (PFCAs) in biota from remote regions is of heightened interest due to the persistence, toxicity, and bioaccumulation of these materials. Large-scale production of fluorinated compounds is carried out primarily by one of two methods: electrochemical fluorination (ECF) and telomerization. Products of the two processes may be distinguished based on constitutional isomer pattern as ECF products are characteristically comprised of a variety of constitutional isomers. The objective of this research was to develop a method for identifying the constitutional isomer profile of PFCAs in environmental samples and to apply the method to polar bear livers from two different locations. Resolution of constitutional isomers of derivatized PFCAs (8-13 carbons) was accomplished via GC-MS. Seven isomers of an authentic ECF perfluorooctanoate (PFOA) standard were separated. The linear isomer comprised 78% of this standard. Isomer profiles of PFCAs in liver samples of 15 polar bears (Ursus maritimus) from the Canadian Arctic and eastern Greenland were determined by GC-MS. The PFOA isomer pattern in Greenland polar bear samples showed a variety of branched isomers while only the linear PFOA isomer was determined in Canadian samples. Samples of both locations had primarily (>99%) linear isomers of perfluorononanoate and perfluorotridecanoate. Branched isomers of perfluorodecanoate, perfluoroundecanoate, and perfluorododecanoate were determined in the polar bear samples. Unlike the PFOA isomer signature, only a single branched isomer peak on the chromatograms was observed for these longer chain PFCAs. The presence of branched isomers suggests some contribution from ECF sources. However, in comparison to the amount of branched isomers in the ECF PFOA standard, such minor percentages of branched PFCAs may suggest additional input from an exclusively linear isomer source.     

Oxidative conversion as a means of detecting precursors to perfluoroalkyl acids in urban runoff

A new method was developed to quantify concentrations of difficult-to-measure and unidentified precursors of perfluoroalkyl carboxylic (PFCA) and sulfonic (PFSA) acids in urban runoff. Samples were exposed to hydroxyl radicals generated by thermolysis of persulfate under basic pH conditions and perfluoroalkyl acid (PFAA) precursors were transformed to PFCAs of related perfluorinated chain length. By comparing PFCA concentrations before and after oxidation, the concentrations of total PFAA precursors were inferred. Analysis of 33 urban runoff samples collected from locations around the San Francisco Bay, CA indicated that PFOS (2.6-26 ng/L), PFOA (2.1-16 ng/L), and PFHxA (0.9-9.7 ng/L) were the predominant perfluorinated compounds detected prior to sample treatment. Following oxidative treatment, the total concentrations of PFCAs with 5-12 membered perfluoroalkyl chains increased by a median of 69%, or between 2.8 and 56 ng/L. Precursors that produced PFHxA and PFPeA upon oxidation were more prevalent in runoff samples than those that produced PFOA, despite lower concentrations of their corresponding perfluorinated acids prior to oxidation. Direct measurements of several common precursors to PFOS and PFOA (e.g., perfluorooctanesulfonamide and 8:2 fluorotelomer sulfonate) accounted for less than 25% of the observed increase in PFOA, which increased by a median value of 37%. Exposure of urban runoff to sunlight, advanced oxidation processes, or microbes could result in modest, but measurable, increases in concentrations of PFCAs and PFSAs.     

The fate of fluorine and chlorine during thermal treatment of coals

Release behaviors of fluorine and chlorine during thermal treatments of two Chinese coals, DT and JC, were studied in a quartz tube reactor. The thermal treatments included temperature programmed decomposition (TPD, 300-1000 degrees C) in N2 and gasification (800-1100 degrees C) under a H2O or CO2 atmosphere. The TPD results show that F and Cl in the two coals can be classified into three forms of occurrence, evolving in three temperature ranges, 150350 degrees C, 350-750 dgrees C, and >870 degrees C. Fluorine in the coals is significantly more stable than Cl during the TPD process. Both elements in DT coal are more volatile than that in JC coal, which may be attributed to coexisting F or Cl salts with minerals in JC coal. Gasification under a H2O or CO2 atmosphere may promote the release of F and CI. The promotion effect is more significant in a H2O steam, which is due possibly to reactions of H2O with F and Cl salts in the coals. For both coals, the release ratios are close to 94% for F and 98% for Cl at 1000 degrees C in a H2O steam. Under these conditions, the difference in release ability of F and Cl from the two coals diminishes. No clear correlation can be found between the release ratio of F or Cl with the corresponding volatile yield of the coals.