Occurrence of Perfluoroalkyl Acids Including Perfluorooctane

Dec 19, 2012 - Sulfonate Isomers in Huai River Basin and Taihu Lake in Jiangsu ... of Monitoring and Analysis for Organic Pollutants in Surface Water,...
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Occurrence of Perfluoroalkyl Acids Including Perfluorooctane Sulfonate Isomers in Huai River Basin and Taihu Lake in Jiangsu Province, China Nanyang Yu,† Wei Shi,† Beibei Zhang,‡ Guanyong Su,† Jianfang Feng,† Xiaowei Zhang,† Si Wei,*,† and Hongxia Yu*,† †

State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, People’s Republic of China ‡ State Environmental Protection Key Laboratory of Monitoring and Analysis for Organic Pollutants in Surface Water, Jiangsu Provincial Environmental Monitoring Center, Nanjing, People’s Republic of China S Supporting Information *

ABSTRACT: The spatial distribution of 10 perfluoroalkyl acids including linear and branched (six monotrifluoromethyl isomers) perfluorooctane sulfonate (PFOS) in surface water was investigated in Huai River Basin and Taihu Lake in Jiangsu Province, China. In the water samples from Huai River Basin, perfluorooctanoic acid (PFOA) and PFOS were the predominant compounds (mean 18 ng/L and 4.7 ng/L, respectively), while in samples from Taihu Lake, PFOA, perfluorohexanoic acid (PFHxA), and PFOS were the predominant compounds (mean 56 ng/L, 19 ng/L, and 15 ng/L, respectively). Branched PFOS (Br-PFOS) isomers accounting for 48.1% to 62.5% of total PFOS were enriched in all samples from Taihu Lake, compared to technical electrochemical fluorination (ECF) PFOS (Br-PFOS ∼30.0%), while the similar phenomena were not found in samples from Huai River Basin (Br-PFOS 29.0−35.0%). Principal component analysis (PCA) on the percentages of the individual isomer showed that the first two components accounted for 78.4% and 15.3% of the overall observed data variance. Samples from Huai River Basin were grouped together with the ECF PFOS standard suggesting the profiles were similar, while samples from Taihu Lake were grouped by themselves, suggesting that isomer profiles in these samples were different from that of Huai River Basin. The obvious difference in isomer profiles probably results from the different environmental behaviors of PFOS isomers and/or unknown sources (PFOS or PFOS precursors).

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INTRODUCTION Perfluoroalkyl acids (PFAAs) have been used as an additive in commercial products and industries, such as fire fighting foams, photolithography, textile industries, paper mills, and plating plants1,2 for more than 50 years. PFAAs have been identified as global pollutants and detected in rivers,3 oceans,4 sediment,5 wildlife,6 and human blood.7 Perfluoroalkane sulfonates (PFSAs) and perfluoroalkyl carboxylates (PFCAs) are two major classifications of PFAAs. Generally, PFSAs and PFCAs are extremely persistent in environment.1,6 Contrarily, the neutral perfluoroalkyl and polyfluoroalkyl substances (PFASs), such as fluorotelomer alcohols (FTOHs) and perfluorooctane sulfonamide (FOSA), can be transformed to PFSAs or PFCAs by abiotic8−10 and biotic11,12 processes. Toxicological studies on animals have revealed that perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), recognized as the predominant PFAAs in environmental matrices, can cause liver toxicity, developmental toxicity, immunotoxicity, and endocrine disrupting effects.13,14 These results suggest that © 2012 American Chemical Society

PFSAs and PFCAs could be accumulated in the environment and could be a potential risk to human health and ecosystem. PFAAs are mainly produced by two manufacturing processes including electrochemical fluorination (ECF) and telomerization (TM). The ECF products are typically a mixture of linear and branched isomers,15 while the TM products are linear (LTM) or isopropyl isomer (iso-TM).15,16 From 1950 to 2002, PFOS was mainly produced via ECF process by 3 M Co.17 Generally, ECF PFOS consists of ∼70% linear PFOS (LPFOS) and ∼30% branched PFOS (Br-PFOS).18 Other manufacturing sources of PFOS are unknown. The manufacturing origin of PFOA in seawater may include ECF PFOA, L-TM PFOA, or iso-TM PFOA. It is shown that iso-TM PFOA can be identified in coastal seawater from Japan19 and some Atlantic Received: Revised: Accepted: Published: 710

September 18, 2012 December 17, 2012 December 19, 2012 December 19, 2012 dx.doi.org/10.1021/es3037803 | Environ. Sci. Technol. 2013, 47, 710−717

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Figure 1. Sample sites in Huai River Basin (upper, HR, red) and Taihu Lake (below, TL, blue) in Jiangsu Province of China.

seawater samples.20 Recently, it has been reported that exposure to the technical ECF PFOS altered the expression of more transcripts than that in the exposure to L-PFOS in cultured chicken embryonic hepatocytes.21 In addition, branched PFOA was less toxic than the linear PFOA in rats and mice.22 Thus, the risk of PFAAs to human and wildlife is likely to be affected by their isomer profiles in environment. PFOS, its salts, and perfluorooctyl sulfonyl fluoride (PFOSF) were listed in Annex B of the Stockholm Convention on Persistent Organic Pollutants in May 2009.23 Because of the demand for PFASs and current restrictions in developed countries, the PFAS manufacturing industry has been transferred to China. Before 2003, the annual production of PFOS was less than 100 tons in China; however, the average annual increasing rate was 130% during 2004−2006.24 Jiangsu is a province in the middle-east of China, which is also an important manufacturing base for chemical industries, textile industries, electronics, and metal refining. The downstream region of Huai River Basin is situated in the north of Jiangsu Province with a catchment area of 39 700 km2, the watershed of which covers highly industrialized and dense regions in the north of Jiangsu Province. Taihu Lake lies in the south of Jiangsu Province and is the second largest freshwater lake in

China. Taihu Lake has been recognized for its highly eutrophicated water and regularly has algae blooms.25 To our knowledge, this is the first reported data on distributions of PFOS isomers in freshwater of China. PFOS is still being manufactured and used in China. These data are especially valuable because the PFOS isomer profiles in freshwater better reflect the current ECF PFOS manufacturing in China. Benskin et al.19 have reported PFOS isomer profiles in the costal seawater of Shanghai and Hangzhou, China, which appeared to be similar to 3 M ECF PFOS. However, the freshwater data of PFOS isomers not only provide exposure information relevant to ecological species but also represent the isomer profiles in drinking water, which is critical for human exposure assessment. The aim of this study was to detect short chain and long chain PFAAs and PFOS isomers in Huai River Basin and Taihu Lake in Jiangsu Province and to investigate factors that affect PFOS isomer profiles in surface waters using principal component analysis.

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MATERIALS AND METHODS Standards and Reagents. Target PFAAs in this study included 10 PFCAs (C5−14), PFHxS, and 7 PFOS isomers (detailed in the Supporting Information). Sodium perfluoro-1711

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(Thermo Scientific, U.S.A.). Detailed instrument parameters are shown in the Supporting Information. QA/QC. Information about quality assurance and quality control is detailed in the Supporting Information. PFTrA and PFTeA were not reported in this study due to the recoveries out of the range 70−120% (Table S2, Supporting Information). Under the current UPLC/MS-MS condition, the PFOA isomers were separated into two peaks. In order to analyze the relative level of branched PFOA isomers (Br-PFOA) among samples, Br-PFOA was quantified by its linear isomer, assuming branched isomers and the linear isomer with equal response factors. Individual PFOS isomers in the PFOS-TCI standard and samples were identified by comparing the ratio of monitored ions and retention time with corresponding standards. The determination of PFOS isomers in the PFOSTCI standard was performed using a five point internal standard calibration curve (13C4−PFOS) with corresponding standards. Because we did not obtain diperfluoromethyl branched PFOS isomer standards, we cannot identify and quantify diperfluoromethyl branched PFOS isomers in PFOSTCI and samples. The procedural recovery (n = 3) of individual PFOS isomers ranged from 84% to 106%, and the matrix spike recovery (n = 3) of individual PFOS isomers ranged from 80% to 97%. Data analysis. For samples with concentrations of one PFAA below the LOQ, a value of half of the LOQ was accepted. Concentrations of PFOS isomers were based on results of GC/MS, because individual PFOS isomers were not separated by our UPLC-MS/MS method. The concentration of total PFOS (ΣPFOS) was equal to the sum of L-PFOS and 1− 6m-PFOS, and the concentration of branched PFOS (BrPFOS) was equal to the sum of 1−6m-PFOS. Because we only obtained 1−6m-PFOS and L-PFOS isomer standards, other branched PFOS isomers (B1 and B2 in Figure S4, Supporting Information) were not included in ΣPFOS and Br-PFOS. However, these two isomers (B1 and B2) did not contribute more than 7% to total concentrations of 1−6m-PFOS and LPFOS (Table S9, Supporting Information). The percentages of PFOS isomers and the ratios of individual branched isomers relative to L-PFOS were calculated as parameters to describe the isomer profile of sample or ECF PFOS. To accurately compare samples with ECF PFOS, the data on compositions of ECF PFOS in references19,27 was calculated again, only considering 1−6m-PFOS and L-PFOS. The data analysis was conducted by SPSS statistical software (SPSS Inc., U.S.A.). Ratios of individual branched isomers relative to L-PFOS of samples and ECF PFOS were analyzed using one-way analysis of variance (ANOVA), which was successfully applied to identification of the difference of PFAAs isomer profile.19,20 Principal component analysis was based on the percentages of PFOS isomers in samples and ECF PFOS. The degree of difference in PFOS isomer profile between samples and ECF PFOS was evaluated by the ratios of corresponding percentages of individual PFOS isomer, Ri, which is defined by eq 1.

octanesulfonate (L-PFOS, >98%), sodium perfluoro-1-methylheptanesulfonate (1m-PFOS), sodium perfluoro-2-methylheptanesulfonate (2m-PFOS), sodium perfluoro-3-methylheptanesulfonate (3m-PFOS), sodium perfluoro-4-methylheptanesulfonate (4m-PFOS), sodium perfluoro-5methylheptanesulfonate (5m-PFOS), sodium perfluoro-6methylheptanesulfo na te (6m-PFOS), per fluoro-n[1,2,3,4-13C4]octanoic acid (13C4−PFOA), and sodium perfluoro-1-[1,2,3,4-13C4]octanesulfonate (13C4−PFOS) were purchased from Wellington Laboratories (Guelph, ON, Canada). Perfluorooctane sulfonate (PFOS-TCI, >98%) was purchased from Tokyo Chemical Industry (Kita-ku,Tokyo, Japan) and used as a standard for PFOS isomer analysis with GC/MS, which was identified and determined by 1−6m-PFOS and LPFOS. Water Sampling. Water samples were collected from Huai River Basin and Taihu Lake in March 2011 and July 2011, respectively. Nine sites (HR1−9) were along Huai River Basin, and eight sites (TL1−8) were in Taihu Lake (Figure 1). Water samples were transported to the laboratory in 24 h and were stored at 4 °C in polypropylene containers before analysis. Sample Extraction and Cleanup. All water samples were extracted by solid phase extraction (SPE) without prefiltration according to a previously reported method that described by Taniyasu et al.26 with some modifications. Prior to preconcentration, 1 L water sample was spiked with 2 ng mass labeled internal standards, including 13C4−PFOA and 13C4−PFOS. The Oasis WAX cartridges (6 cc, 150 mg, 30 μm, Waters, Milford, MA) were cleaned and conditioned with 4 mL of 0.1% NH4OH in methanol, 4 mL of methanol, and 4 mL of Milli-Q water. Cartridges were washed with 4 mL of buffer (25 mM acetic acid/ammonium acetate, pH 4) and centrifugated for 3 min at 3000 r/min to remove residual water. Target compounds were then eluted with 4 mL of methanol and 4 mL of 0.1% NH4OH in methanol, respectively. The latter fraction was concentrated under nitrogen to 0.5 mL and passed through a polypropylene-membrane syringe filter (Acrodisc GHP, 13 mm, 0.2 μm, Waters). A volume of 100 μL of filtrate and 100 μL of Milli-Q water was transferred into a polypropylene vial for PFCs analysis. Extract Preparation for PFOS Isomer Analysis. Preparation of the extracts for PFOS isomer analysis was based on the method of Chu and Letcher27 with some modifications. Briefly, 5 μL 10% TBAH solution and 4 mL MTBE were added to a polypropylene tube, mixed by vortex mixer, and then sonicated for half an hour. A volume of 250 μL of methanol filtrate from SPE process was evaporated to dryness under nitrogen. A volume of 250 μL of TBAH in MTBE solution was added and mixed for 1 min; subsequently, 750 μL of MTBE was added, and the solution was mixed again. The sample solution was evaporated to dryness, reconstituted in 100 μL MTBE, and transferred to a polypropylene vial for GC/MS analysis. Instrument Analysis for PFAAs and PFOS Isomers. PFAAs analysis was performed using with Waters ACQUITY UPLC system (Waters, Milford, MA) equipped with a Waters ACQUITY TQD triple quadrupole mass spectrometer (Waters, Milford, MA). A PFC isolator column was placed in-line between the solvent mixer and the injector to reduce the instrument background. PFOS isomer analysis was performed using with Trace Ultra gas chromatograph system coupled to Trace DSQ II quadrupole mass spectrometer detector

R i = wi ,sample/wi ,ECF

(1)

where wi,sample and wi,ECF are the percents of PFOS isomer i in samples and the ECF PFOS, respectively. 712

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Figure 2. PFAAs compositions of surface water sample from Huai Rive Basin (HR) and Taihu Lake (TL) are shown along with the total PFAAs concentrations. (Corresponding half of the LOQ values were used if the concentrations of the samples were below LOQ.)

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RESULTS AND DISCUSSION PFAAs Distribution in Huai River Basin and Taihu Lake. Ten PFAAs, including C6 and C8 PFSAs and C5−12 PFCAs were quantified in water samples (Table S4 (Supporting Information) and Figure 2). At least one of PFAA congeners was detected at the level over its LOQ at each sample site (Table S4, Supporting Information). For the surface water samples from Huai River Basin, total PFAA (as a sum of PFCAs and PFSAs) concentrations ranged from 11 ng/L to 79 ng/L with a mean of 28 ng/L (Table S4, Supporting Information). PFOA and ΣPFOS (including branched isomers) were predominant compounds in the surface waters of Huai River Basin and contributed to 64.1% (53.9−80.2% of total PFAA) and 12.8% (6.4−32.1% of total PFAA) of total PFAA, respectively (Figure 2). PFOA and PFOS have been identified as the predominant compounds in surface water from different regions, such as Yangzi River and Pearl River in China28 and Korea29 and Tennessee River in United States.3 PFHpA and PFNA were detected in all of surface waters, but with a lower concentration (1.4 ng/L and 0.84 ng/L, respectively, Table S4, Supporting Information) than PFOA and ΣPFOS. The other PFAAs were detected in most surface waters, except PFDoDA, which was detected in only one sample. The total PFAA concentrations of the downstream Huai River Basin (HR6−9, 22−79 ng/L, Table S4, Supporting Information) were higher than those of the upstream Huai River Basin (HR1−5, 11−27 ng/L, Table S4, Supporting Information) in Jiangsu Province. The Huai River Basin in Jiangsu Province flows through several industrial cities, such as Yangzhou, Taizhou, and Yancheng, and contains textile industries, paper mills and plating plants, which are possible PFAAs sources.1,2 The total PFAA concentrations of water from Taihu Lake (62−126 ng/L, Table S4, Supporting Information) were higher than that of Huai River Basin. Similar to the case of the Huai River Basin, PFOA and ΣPFOS were also the major compounds in samples from Taihu Lake and contributed to 54.8% (38.5−61.3%) and 14.6% (9.7−20.6%) of total PFAA, respectively (Figure 2). PFHxA was present at a high proportion of total PFAA (mean 19.6%, range 15.8−29.0%) in all samples from Taihu Lake, while PFHxA in Huai River Basin only contributed to 2.6% of total PFAA (Figure 2). This result suggests that specific sources for PFHxA likely exist

around Taihu Lake. Recently, PFHxA was identified as a major compound in Hun River30 and Haihe River31 in China. The effluent of wastewater treatment plant was reported to be an important source for PFASs in surface water,32−34 and PFHxA was identified as a major compound in municipal wastewaters in Taipei.35 Finishing agents containing PFOS and PFOA are largely used in the textiles industry, which is an important industry in Jiangsu Province. It was reported that textiles industry consumed 100t PFOS in China.24 Under current restrictions for PFOS and PFOA in the world, short-chain perfluorinated alternatives (C6 or shorter chain) are produced and used as additives. Manufacturers, such as Clariant, Asahi Glass, and Dakin, have produced new textile finishing agents containing C6 perfluoroalkyl or polyfluoroalkyl substances, which could be PFHxA or PFHxA precursors. Using these new textile finishing agents in textile industry around Taihu Lake could be a reason for the higher PFHxA in Taihu Lake than Huai River Basin. Our results are consistent with the widespread use of short-chain perfluorinated compounds. Recently, it was reported that short-chain PFCs (C ≤ 6) may have a different toxic mechanism,36 although they are thought to have a lower bioaccumulation potential37and a lower toxicity.38 Further research is necessary to identify the PFHxA sources around Taihu Lake. PFOS Isomer Profiles in Huai River Basin and Taihu Lake. In order to exactly compare two isomer profiles, the ratios of individual branched isomers relative to L-PFOS and the percentages of individual PFOS isomers were not calculated for samples with two or more PFOS isomers below the LOQ. Howerver, for samples with only one isomer below the LOQ, the nondetected PFOS isomer was assigned by a value of half of the LOQ. Because diperfluoromethyl branched PFOS was not included, the ΣBr-PFOS and ΣPFOS for samples and standard were under-reported. It should be noted that 1m-PFOS and 2m-PFOS in most samples were confirmed without m/z 400, which was not detected at a low 1m-PFOS and 2m-PFOS concentration in samples (details in the Supporting Information). For Huai River Basin, 2m-PFOS was below its LOQ in most water samples, but 1m-PFOS was detected above LOQ in all samples. HR-2, HR-6, HR-8, and HR-9 were contained most PFOS isomers. The content of L-PFOS in Huai River Basin (HR-2, HR-6 and HR-8−9, mean 68.6%, 65.0−71.0%, Table 713

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L-PFOS and 1−6m-PFOS were detected in all lake water samples in Taihu Lake, and enrichment of branched PFOS isomers was observed in Taihu Lake (Figure 3, Table 1). The Br-PFOS content (mean 54.9%, 48.1−62.5%) in Taihu Lake was higher than ECF PFOS (mean 29.1%, 21.8−33.7%). Enrichment of branched PFOS isomers in Taihu Lake was similar to observations in the Lake Ontario,39 Mississippi River,19 and the seepage water near a fire-drill area,40 the BrPFOS content of which were 43−57%, 51.9% and 39−42% of total PFOS, respectively. The previous work on the coastal seawater did not find enrichment of branched PFOS isomers in Shanghai and Hangzhou, China.19 Ratios of each branched isomer relative to L-PFOS in Taihu Lake were higher than ECF PFOS (Table S6, Supporting Information), especially for 2− 6m-PFOS with a statistically significant difference, which indicated that the isomer profiles of Taihu Lake were different from ECF PFOS. The enrichment of 2−6m-PFOS and the deficiency of LPFOS were found in Taihu Lake (Table 1). The degree of enrichment of 2−6m-PFOS in Taihu Lake relative to ECF PFOS, which was evaluated by Ri, followed the order 3m > 2m > 4m > 5m > 6m in the most samples. The enrichment of 1mPFOS relative to ECF PFOS was found in most samples from Taihu Lake, but the degree of enrichment of 1m-PFOS was more variable than for other PFOS isomers (Table 1). The fractionation of PFOS isomers in Taihu Lake may result from the biotransformation of PFOS precursors and the different behaviors of PFOS isomers in aquatic environment. Principal Component Analysis of the PFOS Isomer Profiles. Two components were extracted from the

S5, Supporting Information) is similar to ECF PFOS (mean 70.9%, 66.3−78.2%, Table S5, Supporting Information) based on our results and the other references.19,27 It was also found that PFOS isomer profiles appeared similar to 3 M ECF PFOS in the coastal seawater of Shanghai and Hangzhou, China.19 The enrichment of 1m-PFOS and the deficiency of 2m-PFOS, 4m-PFOS, 5m-PFOS were found in Huai River Basin (Table 1). However, the PFOS isomer profile of Huai River Basin was not significantly different from ECF PFOS. Table 1. Ratios of Percentages of Individual PFOS Isomer between Samples and the ECF PFOS, Ri, in Huai River Basin (HR) and Taihu Lake (TL)a PFOS-isomers

HR-2 HR-6 HR-8 HR-9 TL-1 TL-2 TL-3 TL-4 TL-5 TL-6 TL-7 TL-8

LPFOS

1mPFOS

2mPFOS

3mPFOS

4mPFOS

5mPFOS

6mPFOS

BrPFOS

1.00 0.96 0.99 0.92 0.56 0.73 0.57 0.70 0.66 0.73 0.53 0.60

2.70 4.61 2.79 7.47 5.39 1.05 2.34 1.74 2.07 1.98 1.98 1.56

1.02 0.64 0.68 0.88 2.97 2.27 2.04 2.73 2.43 2.10 2.89 2.81

0.94 0.99 0.92 1.01 3.19 2.74 3.05 3.09 3.05 2.36 3.91 3.78

0.74 0.79 0.85 0.72 1.98 1.92 2.27 2.16 2.13 1.81 2.82 2.50

0.81 0.78 0.78 0.82 1.40 1.41 1.80 1.29 1.54 1.30 1.77 1.47

1.00 0.97 1.07 0.76 1.46 1.36 1.72 1.20 1.36 1.49 1.42 1.38

1.00 1.09 1.02 1.20 2.06 1.65 2.04 1.72 1.83 1.65 2.15 1.97

a

Ri > 1 indicates enrichment of isomer i; Ri < 1 indicates deficiency of isomer i.

Figure 3. PFOS isomers compositions of surface water sample from Huai River Basin (HR) and Taihu Lake (TL) and technical ECF PFOS (ECF PFOS) are shown along with the PFOS concentrations. (* from ref 19 without reporting 2m-PFOS content; # from ref 27). 714

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influenced by different species, environmental processes, and sources. In addition, the variation of 1m-PFOS concentrations may reflect that enrichment effects and deficiency effects for 1m-PFOS coexistence, depending on the sample sites. Thus, further study is needed to discriminate PFOS isomers in environmental processes, and to determine the sources for PFOS isomers. Samples from Huai River Basin were grouped together with ECF PFOS, and samples from Taihu Lake were grouped by themselves (Figure 4). These results suggested the PFOS isomer profiles of Huai River Basin were similar to ECF PFOS, while the samples from Taihu Lake were unique. The biomass in Taihu Lake, which regularly has algae blooms,25 is larger than the Huai River Basin. This may be an important reason for the difference on PFOS isomer profiles between Taihu Lake and Huai River Basin, because biological processes affect the isomer profile. There are textile industries, semiconductor production, and plating plants, which could use PFOS, around Taihu Lake. In addition, a pesticide factory around Taihu Lake is known to produce sulfluramid containing N-ethyl perfluorooctane sulfonamide (NEtFOSA), a PFOS precursor. Contrarily, no information on industries manufacturing PFOS or PFOS precursors along Huai River Basin was found. Therefore, isomer profile in water samples from Taihu Lake may be influenced by the PFOS and/or PFOS precursors released from these industries. The effluent treated by biological processes in WWTP may contain large amount of PFASs and degradation products,which may largely contributed to the isomer profile in the water samples. The region around Taihu Lake with a higher population density could consume more water than Huai River Basin. Although isomer profiles in Huai River Basin were similar to the ECF PFOS, there was a slight difference between them (Table1 and Figure 3). We speculated that PFOS as manufactured in China may contain a different isomer profile than that of ECF PFOS, although we referred to reported results on PFOS manufactured in China.19 Certainly, the atmospheric deposition may affect isomer profiles in samples. McMurdo et al.46 speculated that the discrimination of linear and branched isomers could occur in partitioning of PFCs to the atmosphere via marine aerosols. Branched PFOA in Huai River Basin and Taihu Lake. The peaks of Br-PFOA were detected in all of samples. As mentioned above, the percentages of PFOA and Br-PFOA in samples were calculated semiquantitatively in the present study to compare the relative level of Br-PFOA among samples. The percentages of Br-PFOA in Huai River Basin and Taihu Lake were 9.5% (8.5−10.6%) and 7.6% (6.2−8.8%, Table S7, Supporting Information), with a significant difference between two basins by student t-test. There was not a significant difference between the upstream and downstream of Huai River Basin in Jiangsu Province. The percentage of Br-PFOA is lower than the reported ECF PFOA (17.8% Br-PFOA) using the similar LC/MS-MS method. Environmental processes of PFOA isomers and different manufacture sources can affect branched isomer percentages in water. Similar to the case of PFOS, biological processes42,43,47 could result in enrichment of Br-PFOA in water. L-TM manufacturing source could result in deficiency of Br-PFOA in water, while iso-TM manufacturing source could result in enrichment of Br-PFOA in water. Therefore, we speculated that the manufacturing and using of L-TM PFOA or PFOA precursor is the major reason for the deficiency of Br-PFOA in Huai River Basin and Taihu Lake in Jiangsu Province.

composition data of Huai River Basin, Taihu Lake, and ECF PFOS (Table S5, Supporting Information) by principal component analysis. In the first principal component (PC1), 2−6m-PFOS had high factor loadings, but L-PFOS had a negative factor loading (Table S8, Supporting Information), which suggests a negative correlation between L-PFOS and PC1. PC1 is likely associated with the environmental behavior of PFOS isomers, which results in enrichment of branched isomer and deficiency of linear isomer in water. This has been found in biological processes. A deficiency of branched PFOS isomers was found in Herring Gull eggs41 and exposure experiments of rodents42,43 and fish,44 which suggests branched PFOS isomers have a lower BCF in the aqueous ecosystem and are more easily excreted into water than L-PFOS. In a study of PFOS precursor metabolism, branched isomers had a more rapid metabolism rate.45 All of these studies suggested that enrichment of branched PFOS isomers in water could occur if biological factors are significant enough to affect the abiotic burden. 1m-PFOS had a high factor loading in the second principal component (PC2), which explained 15.3% of total variance (Table S8). This result suggested that 1m-PFOS has a different behavior from the other PFOS isomers in the aqueous environment and/or 1m-PFOS has a special unknown source, which contains a higher percentage of 1m-PFOS or its precursor than ECF PFOS (Figure 4). The enrichment of

Figure 4. Percentages of individual PFOS isomers to ΣPFOS concentrations from Huai River Basin (blue) and Taihu Lake (green) and technical ECF PFOS (red) plotted using the first two principal components (PCs), PC1 and PC2. The extent of variability explained by PC1 and PC2 is provided.

1m-PFOS was observed in most samples from the Huai River Basin and Taihu Lake, but with a high variation. 1m-PFOS has been found to have a longer half-life in blood and was excreted less efficiently in urine than other PFOS isomers (2−6m and LPFOS) in rat exposure experiments.42,43 It has also been reported that 1m-PFOS had a higher relative absorption efficiency in tissue than other branched PFOS isomers in a rainbow trout exposure experiment.44 These studies imply that the deficiency, or slight enrichment, of 1m-PFOS could occur in water, which is not consistent with our results. However, the behavior of 1m-PFOS in the aqueous environment may be 715

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Implications. The present research shows PFAAs profiles and PFOS isomers profiles in the surface water of Huai River Basin and Taihu Lake in China. Our results show that PFHxA was one of the predominant compounds in Taihu Lake. We also found that the enrichment of Br-PFOS occurred in Taihu Lake but not in Huai River Basin. To our knowledge, this is the first study finding the enrichment of Br-PFOS in surface water of China. The interesting phenomena probably resulted from a higher biomass in Taihu Lake than Huai River Basin. In addition, other factors, such as PFOS or PFOS precursors as manufactured in China, atmospheric deposition, the effluent of WWTP and the metabolism or degradation of PFOS precursors could also affect PFOS isomer profiles in water. However, there is few available data on PFOS isomer profiles in these environmental processes. Therefore, further research on the discrimination of PFOS isomers in the environmental processes is necessary to confirm the reason for enrichment of Br-PFOS in Taihu Lake. It is also necessary to apportion sources of PFOS. Our results indicate that branched PFOS and PFOA isomers widely exist in surface water in China. However, there have been limited data on the toxicity of individual branched PFOS and PFOA isomer. Further research on the toxicity of individual PFOS and PFOA isomers is necessary for the risk assessment of PFAAs.

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ASSOCIATED CONTENT

* Supporting Information S

Addtional information on materials and methods, method optimization, QA/QC, principal component analysis, and the percents of Br-PFOA. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*Phone: +86 25 8968 0356. Fax: +86 25 8968 0356. E-mail: [email protected] (S.W.). Phone: +86 25 8968 0356. Fax:+86 25 8968 0356. E-mail: [email protected] (H.Y.). Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by National Natural Science Foundation of China (Grant No. 21007022), Natural Science Foundation of Jiangsu Province (Grant No. BK2010384), Natural Science Foundation of Jiangsu Province (Key Program, Grant No. BK2010090), Ph.D. Programs Foundation of Ministry of Education of China (Grant No. 20100091120013), and Jiangsu provincial Environmental Monitoring Research Fund (Grant No. 0918).

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REFERENCES

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