PFAS

Science of the Total Environment 447 (2013) 46–55

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Transport of Perfluoroalkyl substances (PFAS) from an arctic glacier to downstream locations: Implications for sources Karen Y. Kwok a, b, c, Eriko Yamazaki c, Nobuyoshi Yamashita c,⁎, Sachi Taniyasu c, Margaret B. Murphy a, b, Yuichi Horii d, Gert Petrick e, Roland Kallerborn f, Kurunthachalam Kannan g, Kentaro Murano h, Paul K.S. Lam a, b,⁎⁎ a

State Key Laboratory in Marine Pollution, Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong SAR, China Research Centre for the Oceans and Human Health, Room 801, City University of Hong Kong (Shenzhen) Research Institute Building, 8 Yuexing 1st Road, Shenzhen Hi-tech Industrial Park, Nanshan District, Shenzhen, PRC c National Institute of Advanced Industrial Science and Technology (AIST), 16–1 Onogawa, Tsukuba, Ibaraki 305–8569, Japan d Group of Chemical Substances, Center for Environmental Science in Saitama, 914 Kamitanadare, Kisai-machi, Saitama 347–0115, Japan e Leibniz-Institute of Marine Sciences, Department of Marine Chemistry, Düsternbrooker Weg 20, D-24105 Kiel, Germany f Department of Chemistry, Biotechnology and Food Science (IKBM), Norwegian University of Life Sciences (UMB), Christian Magnus Falsen vei, P.O. Box 5003, NO-1432 As, Norway g Wadsworth Center, New York State Department of Health, Department of Environmental Health Sciences, State University of New York at Albany , Empire State Plaza, P.O. Box 509, Albany, NY, 12201–0509 USA h Department of Chemical Science and Technology, Faculty of Bioscience and Applied Chemistry, Hosei University, 3-7-2 Kajino-chou, Koganei, Tokyo 184–8584, Japan b

H I G H L I G H T S

G R A P H I C A L

A B S T R A C T

► To quantify individual PFCs in ice cores, surface snow and waters from Svalbard. ► To reconstruct the timeline of PFC inputs into the European Arctic using ice cores. ► To compare the degree of PFC contamination in the Arctic ice cores. ► To study the fate of PFCs from the glacier to downstream locations in Svalbard. ► To determine the sources of PFC contamination by using correlation analyses.

a r t i c l e

i n f o

Article history: Received 14 June 2012 Received in revised form 17 October 2012 Accepted 24 October 2012 Available online 31 January 2013

a b s t r a c t Perfluoroalkyl substances (PFAS) have been globally detected in various environmental matrices, yet their fate and transport to the Arctic is still unclear, especially for the European Arctic. In this study, concentrations of 17 PFAS were quantified in two ice cores (n=26), surface snow (n=9) and surface water samples (n=14) collected along a spatial gradient in Svalbard, Norway. Concentrations of selected ions (Na+, SO42−, etc.) were also determined for tracing the origins and sources of PFAS. Perfluorobutanoate (PFBA), perfluorooctanoate (PFOA) and

⁎ Correspondence to: N. Yamashita, National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba West, 16–1 Onogawa, Tsukuba, Ibaraki 305–8569, Japan. Tel.: +81 29 861 8335; fax: +81 29 861 8335. ⁎⁎ Correspondence to: P.K.S. Lam, Department of Biology and Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR, China. Tel.: +852 2788 7681; fax: +852 2788 7406. E-mail addresses: [email protected] (N. Yamashita), [email protected] (P.K.S. Lam). 0048-9697/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.scitotenv.2012.10.091

K.Y. Kwok et al. / Science of the Total Environment 447 (2013) 46–55 Keywords: Perfluoroalkyl substances (PFAS) Svalbard European Arctic ice cores source determination

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perfluorononanoate (PFNA) were the dominant compounds found in ice core samples. Taking PFOA, PFNA and perfluorooctane-sulfonate (PFOS) as examples, higher concentrations were detected in the middle layers of the ice cores representing the period of 1997−2000. Lower concentrations of C8–C12 perfluorocarboxylates (PFCAs) were detected in comparison with concentrations measured previously in an ice core from the Canadian Arctic, indicating that contamination levels in the European Arctic are lower. Average PFAS concentrations were found to be lower in surface snow and melted glacier water samples, while increased concentrations were observed in river water downstream near the coastal area. Perfluorohexanesulfonate (PFHxS) was detected in the downstream locations, but not in the glacier, suggesting existence of local sources of this compound. Long-range atmospheric transport of PFAS was the major deposition pathway for the glaciers, while local sources (e.g., skiing activities) were identified in the downstream locations. © 2012 Elsevier B.V. All rights reserved.

1. Introduction Perfluoroalkyl substances (PFAS) are environmental contaminants that have received worldwide attention due to their ubiquitous environmental distribution. All PFAS found in the environment are anthropogenic, and they have been manufactured and used for more than 60 years (Giesy and Kannan, 2002). Owing to their high chemical and thermal stability and surface active properties, PFAS can be useful in a wide range of industrial and commercial applications like surface treatment, paper protection and as performance chemicals (Kissa, 2001; U.S. EPA, 2000). Widespread occurrence of PFAS has also been documented globally in various environmental matrices, even in remote areas including the Arctic (Giesy and Kannan, 2001; Kannan et al., 2004; Butt et al., 2010), yet, the fate and transport pathways of this class of contaminants to the Arctic are still not well understood. Long-range atmospheric transport of volatile and semi-volatile PFAS precursors (Vésine et al., 2000; Ellis et al., 2004; D'eon et al., 2006; Wallington et al., 2006; Butt et al., 2009; Young et al., 2008) such as fluorotelomer alcohols (FTOHs), fluorotelomer olefins (FTOs), fluorotelomer acrylates (FTAcs) and fluorosulfonamido alcohols (FSAs) and degradation of these volatile precursors into ionic perfluorocarboxylates (PFCAs) and perfluoroalkylsulfonates (PFSAs) are suggested as potential sources of PFAS in remote areas. Volatile precursors, with sufficient atmospheric lifetime and persistence, can be transported by wind/air movements. FTOHs and FSAs have been reported to occur in the Arctic atmosphere at approximately five times lower concentrations than those measured in urban regions (Shoeib et al., 2006; Stock et al., 2007). Besides atmospheric pathways, PFAS released directly into the aquatic environment can reach the Arctic via oceanic currents (Prevedouros et al., 2006). Perfluorobutanesulfonate (PFBS), perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) have been found in sea surface and deep water samples collected from the Labrador Sea in the North Atlantic Ocean (Yamashita et al., 2005). In addition, local sources of PFAS in the Arctic cannot be ignored. A recent study showed high concentrations of perfluorohexanesulfonate (PFHxS), PFOS, perfluoroheptanoic acid (PFHpA) and PFOA in an Arctic lake receiving sewage and wastewater discharge and from the use of aqueousfilm-forming foam (AFFF) in a nearby residential area and airport (Stock et al., 2007). Skiing activities in some parts of the Arctic can also result in the release of PFAS used in products such as jackets and waxes applied on skiing equipment (Freberg et al., 2010; Nilsson et al., 2010; Langford et al., 2011). To date, many PFAS monitoring studies have been carried out in the Canadian Arctic (e.g., Martin et al., 2004; Shoeib et al., 2006; Butt et al., 2007a, 2007b; Stock et al., 2007; Young et al., 2007; Kelly et al., 2009), but limited information is available for other areas of the circumpolar Arctic, including the European Arctic (Butt et al., 2007a; Muir and de Wit, 2010). In the present study, Svalbard, Norway was chosen as the site of investigation. Svalbard is located in an area characterized by shifting boundaries of both atmospheric and oceanic currents (Hisdal, 1998; Kang et al., 2001; Isaksson et al., 2003), and 60% of this island is covered by glaciers. It is remote

from major pollution sources with the exception of local coal mines; however, previous studies have shown that Svalbard is experiencing long-range transport of contaminants from industrialized areas in Europe (Gjessing, 1977; Staebler et al., 1999; Goto-Azuma and Koerner, 2001). In order to further understand the transport pathways and sources of PFAS to the Arctic, there is a need to examine PFAS concentrations in abiotic environmental compartments for which little information is available (Muir and de Wit, 2010). Recently, we developed a sensitive and selective method for the analysis of PFAS in environmental samples from remote marine locations (Yamashita et al., 2004, 2008). We applied this method for the trace analysis of PFAS in ice core, surface snow and water samples collected from glaciers and downstream/ coastal areas of Svalbard. Glaciers are formed by the compression of fallen snow over many years. The glacier sampled in the present study is expected to receive PFAS contamination mainly from atmospheric pathways, and therefore ice cores in this location can be used to trace the global transport of PFAS. Analysis of glacial ice cores can also provide information on the temporal trends of atmospheric concentrations of contaminants. Only a few earlier studies reported on persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs), pesticides and brominated flame retardants (BFRs) in glacial ice cores (Gregor et al.;, 1995; Hermanson et al., 2005, 2010). Melted glacier water may reflect atmospheric and local PFAS contamination over several years, while surface snow and water samples represent recent sources from both local and global sources. The samples collected from glaciers to downstream locations can also be used for source determination in the European Arctic.

2. Materials and methods 2.1. Sample collection All samples were collected from the Longyearbreen glacier, along a river and around the coastal area of Longyearbyen, Svalbard Archipelago, Norway in May 2006 (Fig. 1). Longyearbyen is a sparsely populated (around 2000 inhabitants) administrative centre of Svalbard, and is located west of Spitsbergen, the largest island of Svalbard; the local industry is coal mining. Two glacial ice cores (n = 26) up to a depth of 6–7 m, which were 2 m apart, were collected using a custom-made ice core sampler (Hand Auger I; Chikyu Kogaku Kenkyujo Co., Japan) with a diameter of 10 cm, which is comprised of only stainless steel and nylon to avoid contamination by PFAS during sampling. Cores were then cut into layers (approx. 0.2–0.3 m/layer) and transferred to pre-cleaned polypropylene (PP) bottles for storage after thawing. Volumes of 400–800 mL water equivalents were collected from each depth. Consecutive layers from the same year were combined to a sample volume of more than 1 L for trace analysis of PFAS. Surface snow (n = 10) and surface water samples (i.e., glacial water, river water, seawater and lake water, n = 14) were collected from both the glacier and downstream locations. Details on the sampling locations (Figs. S1) and

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Svalbard

U.S.A

Canada

Longyearbyen

Google map

North Pole Devon Island (Young et. al., 2007)

Greenland

Longyearbyen (Our study, 2010) Svalbard

Russia

Norway

Fig. 1. Map of sampling in the Arctic.

sampling collection (Tables S1–2) are given in the Supporting Information (SI). 2.2. Chemical extraction Details of chemicals and reagents are provided in the SI. Unfiltered samples were extracted using Oasis® WAX cartridges following recent published methods (Taniyasu et al., 2005, 2008; ISO25101, 2009). The cartridges were preconditioned by passage of 4 mL of 0.1% NH4OH in methanol followed by 4 mL of methanol and 4 mL of MilliQ water. Ice core, surface snow and surface water samples (approx. 1000 mL) were passed through the pre-conditioned cartridges at a rate of 1 drop/sec. The cartridges were then washed with 4 mL of 25 mM ammonium acetate buffer at pH 4. Before elution, water remaining in the cartridges was removed by centrifugation at 3000 rpm for 2 mins. The target analytes were eluted into two fractions by 4 mL of methanol and 4 mL of 0.1% NH4OH in methanol, respectively. A modified step (i.e. bottles were each washed with 2 mL MeOH three times and used for elution of the first fraction) was added to improve the recoveries of the long-chain PFAS. The two fractions were then concentrated to 0.5 mL under a gentle stream of high-purity nitrogen. If particulates/suspension appeared in the final solution, samples were centrifuged at 3000 rpm for 1 min before being transferred to vials for instrumental analysis. For ion measurement, four milliliters of samples were passed through PP disposable syringe filters, pore size: 0.45 μm; diameter: 13 mm, (Iwaki Glass, Japan) to remove particulate present in the samples. The first 2 mL of the samples were discarded in order to wash

the filter, and the remaining filtrate was collected in screw-cap PP bottles and stored at 4 °C until analysis. The filtered samples were then transferred to vials for instrumental analysis for both cations (i.e., Na+, NH4+, K+, Mg2+, Ca2+) and anions (i.e., Cl-, NO3-, SO42-). 2.3. Instrumental analysis Separation of the target analytes was performed using an Agilent HP1100 liquid chromatograph (Agilent, Palo Alto, CA) interfaced with a Micromass Quattro Ultima Pt mass spectrometer (Waters Corp., Milford, MA) that was operated in electrospray negative ionization mode. A 10-μL aliquot of the extract was injected onto an ion exchange column, RSpak JJ-50 2D (2.0 mm i.d. × 150 mm length, 5 μm; Shodex, Showa Denko K.K., Kawasaki, Japan), with 50 mM ammonium acetate and methanol as the mobile phase, for the quantification of the C2–C4 PFAS. Further quantification of C5–C18 PFAS was conducted by injecting the same extracts onto a Keystone Betasil C18 column (2.1 mm i.d. × 50 mm length, 5 μm, 100 Å pore size, end-capped), with 2 mM ammonium acetate and methanol as the mobile phase, and operated with an initial condition of 10% methanol, followed by a increment to 75% at 7 min, and finally 100% at 10 min; the gradient was then kept until 13 min before reversion to normal conditions. The desolvation gas flow and temperature were kept at 610 L/h and 450 °C, respectively. The collision energies, cone voltages, and MS/MS parameters for the instrument were optimized for individual analytes and were similar to those reported elsewhere (Taniyasu et al., 2005, 2008). Determination of cations (i.e., Na +, NH4+, K +, Mg 2 +, Ca 2+) and anions (i.e., Cl -, NO3-, SO42-) were performed by ion chromatography (ICS–1100, Dionex Corp., Sunnyvale, CA). A 25-μL aliquot of the

K.Y. Kwok et al. / Science of the Total Environment 447 (2013) 46–55

filtered sample was injected onto an ion exchange column, the Ion Pac CS 12A (4 mm i.d. × 250 mm length, 8.0 μm, Dionex Corp., Sunnyvale, CA), with 10 mM methanesulfonate as the mobile phase for quantification of the cations. Quantification of anions were done by injecting the same filtered sample onto an Ion Pac AS 12A (4 mm i.d. × 200 mm length, 9.0 μm, 2000 Å pore size; Dionex Corp., Sunnyvale, CA), with 2.7 mM sodium carbonate and 0.3 mM sodium hydrogen carbonate as the mobile phase. The flow rate and column oven temperature were kept at 1.0 mL/min and 35 °C, respectively.

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in standard ocean water (Brewer, 1975), the SS-component of an ion concentration was calculated as: h i þ SS−X ¼ Na

sample

 h i þ ½Xsea = Na



sea

while the NSS-component of an ion concentration was calculated as: h i þ NSS−X ¼ ½Xsample − Na

sample

 h i þ ½Xsea = Na

 sea

2.4. Quality control and quality assurance The quality assurance and control measures including background contamination, limits of quantification (LOQs), calibration curves, procedural blanks and matrix spike recoveries are provided in the SI. Generally, concentrations found in procedural blanks were below the corresponding LOQs (5–25 pg/L). The matrix spike recoveries of PFAS in ice core samples ranged from 71 to 108%. The overall procedural recoveries of the target PFAS and the surrogate standards (i.e., 13C-labelled standards) were between 60%–100% (Table S3). As only single measurement was performed in each sample, surrogate standards were used as a reference to check for the negative effects (i.e., matrix effect or ion suppression). PFAS concentrations were quantified using an external calibration curve and were not corrected for the recoveries of the internal standards (for details, see the SI).

where [X]sample = ion concentration in the sample [X]sea = ion concentration in standard ocean water (Table S4)

3. Results and discussion 3.1. Ion analysis in ice core samples

Fluxes of PFAS were calculated using the concentrations in each core layer and the sample volume during the time interval/year (Hermanson et al., 2010). Flux (fg/cm2) = Concentration of sample (fg/L) x Total volume (L) / Inner area of the corer (cm 2)

Concentrations of certain ions in aqueous samples have been used for tracing the origin of source waters. Concentrations of cations (i.e., Na+, NH4+, K+, Mg2+, Ca2+) and anions (i.e., Cl−, NO3−, SO42−) were measured in each layer (i.e., 0.2–0.3 m/layer) of the two ice cores. Vertical profiles of the ions in ice cores are shown in Fig. 2. Concentrations of Na+ and Cl− were found to be higher than those of other ions. Ca2+ had the highest contribution to the NSS-component of all the ion concentrations (87% and 90% for ice cores 1 and 2, respectively, refer to Table S5), followed by K+. Rock-surrounded valley glaciers are the major type of glaciers found in the Longyearbyen region, and Ca2+ may be originating from the earth's crust, though local dust from the surrounding rocks was another possible source. NSS-K + may be sourced from plants. High percentages of the SS-component (> 75%) were found for other ions (i.e., Mg 2 +, Cl − and SO42 −), suggesting that the major sources of these ions are oceanic. Correlation analyses were performed among individual ions in ice core samples for source determination (Table S6). Na + and Cl − were strongly correlated with each other (ice core 1: r = 0.961; ice core 2: r = 0.981, p b 0.0001), reflecting their uniform sea-salt source. Consistent with a previous study of Svalbard snow samples (Kang et al., 2001), SO42 − showed significant correlations (p b 0.01) with Mg 2 +, Ca 2 +, Cl − and NO3−. A positive association was found between SO42 − and NO3− (p b 0.01), indicating that these ions may share similar anthropogenic sources of sulphur dioxide (SO2) and nitrogen oxides (NOx) from mid-latitude continental areas (Joranger and Ottar, 1984; Kang et al., 2001).

2.7. Statistical analyses

3.2. PFAS in ice core samples

Normality tests (Kolmogorov-Smirnov) were performed before statistical analyses. Non-parametric Mann–Whitney Rank Sum test was used to assess significant differences between the mean concentrations of PFAS in surface snow and water samples collected from the glacial and downstream region of Svalbard. Furthermore, non-parametric Spearman Rank correlation analyses were used for the examination of significant correlations among different PFAS and ions in ice core, surface snow and surface water. The significance level was set at α = 0.05. All statistical analyses were carried out using statistical software SigmaStat 3.5 (Systat Software Inc, Chicago, USA).

Mean PFAS concentrations in ice core are summarized in Table S7, and concentrations are expressed on the basis of water volume (pg/L). The topmost layer of each core was excluded because this was considered to be surface snow rather than ice. An overview of PFAS concentrations in each layer of the ice core samples is shown in Figs. S2. Among the 17 PFAS analyzed, nine individual PFAS (i.e., PFOS, C4–C6, C8–C12 PFCAs) were detected. PFOS was the only PFSA detected, and interestingly, PFHpA, which has been found in precipitation samples worldwide, was not detected in the ice core samples (Kwok et al., 2010; Kim and Kannan, 2007). Total PFAS concentrations (sum of arithmetic mean of each PFAS from all layers of the core) were 94.8 pg/L and 165.8 pg/L in ice core 1 and 2, respectively. Consistent patterns were observed between the vertical profiles of PFOS and total PFCAs in both ice cores (Figs. S3). Similar PFAS composition profiles were found in each layer of the ice core, with PFBA (39%), PFOA (17%) and PFNA (11%) as the major PFAS (Figs. S4). PFOA and PFNA were also the dominant PFAS found in precipitation samples from Japan and the USA

2.5. Dating of the ice core Visual inspection and measurements of ion concentrations were used in the determination of age of the ice cores. Tentative age was estimated based on the observation of seasonal and annual markers such as bubbles and clearness in digital photos (3968 × 2976 pixels) taken of the core (Lemieux-Dudon et al., 2010). Measured concentrations of major ions were further used to confirm the assigned year of deposition of the ice core (Young et al., 2007). The two ice cores collected in our study represented deposition from 1990 to 2005. 2.6. Flux calculation

2.8. Sea-salt and non-sea-salt component calculation The non-sea-salt (NSS) component of the ice core samples was calculated to understand the atmospheric origin in the samples (Zhang et al., 2002). All of the Na + in an ice core sample was assumed to come from sea salt (SS). According to the ratio of the ions and Na +

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Fig. 2. Vertical profiles of ion concentrations in ice cores from Svalbard, Norway.

(Kwok et al., 2010; Kim and Kannan, 2007), suggesting worldwide atmospheric contamination by these two compounds. Glacial ice cores can provide information on temporal trends of atmospheric pollutant concentrations, since accumulated snow layers remain relatively undisturbed, although there will be slow movement/drift of the ice. Each layer of an ice core represents a corresponding time period of deposition, reflecting the atmospheric input during that period. Vertical profiles of long-chain (i.e., PFOS, PFOA and PFNA) and short-chain PFAS (i.e., PFHxA, PFPeA and PFPrA) in ice cores are shown in Figs. S5. Year-to-year variation in concentrations of PFAS was observed among the layers of the cores. The reasons may be due to many different factors, such as meteorological conditions (i.e., temperature, wind direction and precipitation amount) (Kwok et al., 2010), atmospheric PFAS concentrations, contamination sources, environmental transformation, weathering processes and melting and freezing cycles. Over the 14 years reflected in the ice core, all detected PFAS except PFHxA, showed specific and comparable trends in their vertical profiles in each of the ice cores. In general, consistent patterns were observed for the long-chain PFAS, while short-chain PFAS showed a more fluctuating pattern of concentrations among layers. Higher concentrations of PFOA, PFNA and PFOS were detected in the middle layers of both ice cores representing 1997–2000 (Fig. 3), which coincides with the peak production periods of these compounds (Prevedouros et al., 2006). The reduced levels of PFOA, PFNA and PFOS in the surface layers after 2000 may be due to the phase-out of PFOS and PFOA-related compounds (Prevedouros et al., 2006), though atmospheric breakdown of PFAS precursors are likely

to be a source for these compounds in recent years. In addition, vertical profiles of PFHxA varied from those of other PFAS in both ice cores, with the highest concentration detected in 1993–1995. Strong positive correlations were found between PFNA and PFOA (r = 0.782, p b 0.01) and between PFOS and PFOA (r = 0.794, p b 0.01) in surface snow (Fig. 4). However, no significant correlation was found between PFOA and PFHxA (Fig. 4), suggesting different contamination sources for PFHxA. Hence, the correlation results in surface snow explained the different vertical profile observed for PFHxA in both of the ice cores when compared to other PFAS. Annual fluxes of individual PFAS in the European Arctic were also estimated from the concentration in each layer of the ice core, and the results correspond with the vertical profiles of PFAS concentrations (Fig. 5). Since some layers in the ice cores represent a two-year period (Ice core 1: 2001–2002 and 2003–2004; Ice core 2: 2003–2004), and in these cases average values were used for estimation. Annual fluxes of each PFAS were comparable between the two ice cores. Elevated annual fluxes of PFAS were found in 1997, especially in ice core 1, with the exception of PFHxA, which was measured as its highest levels during 1994–1995 (500–600 fg/cm2). Similar annual fluxes of PFAS were measured after 1999, except for PFHxA, which showed an approximately two- to three-fold decrease. Furthermore, a two-fold increase in annual PFAS fluxes was detected in ice core 2 in 2005. Lower annual fluxes were calculated for PFOS (arithmetic mean: 170 fg/cm2/year) compared to C4–C6, C8 and C9 PFCAs (>250 fg/cm2/year), which may be attributed to the physicochemical properties of PFOS, such as lower water solubility (570 mg/L; OECD, 2002) and higher predicted log Kow (5.25; Arp et al., 2006).

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0.43 m 0.90 m 1.40 m 1.87 m 2.09 m 2.85 m 3.34 m 3.89 m 3.97 m 4.32 m 4.85 m 5.42 m 6.87 m 6.16 m 6.59 m

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0.62 m 1.14 m 1.67 m 2.20 m 2.65 m 3.22 m 3.74 m 4.24 m 4.59 m 4.99 m 5.46 m 5.83 m 6.46 m 6.76 m 6.96 m

10

1997 1996 1995 1994 1993 1992

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Ice core 2 depth [m]

Ice core 1 depth [m]

Concentration [pg/L] 0

Fig. 3. Vertical profiles of PFHxA, PFOA, PFNA and PFOS levels in ice core samples from Svalbard, Norway. Dashed line: corresponding LOQ for each compound.

Concentration of PFOS [pg/L]

200 150 100

r = 0.794 m = 0.261 p < 0.01

50 0 0

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r = 0.782 m = 0.568 p < 0.01

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Concentration of PFOA [pg/L] 160 120 80

r = 0.273 m = 0.071 p >0.01

40 0 0

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Concentration of PFOA [pg/L] Fig. 4. Correlations of PFHxA, PFNA and PFOS levels to those of PFOA in surface snow samples.

Long-range atmospheric transport of PFAS and degradation of volatile precursors such as 8:2 FTOH and 10:2 FTOH have been suggested as possible sources of PFCAs in glacial ice cores (Young et al., 2007). Similar concentrations of PFOA and PFNA, as major products from the atmospheric degradation of 8:2 FTOH, were observed in each ice core in the present study, with an average ratio of 1.9 ± 0.7 and 1.3 ±0.4, respectively. Comparable ratios (1.5±0.8) were also found for the Canadian Arctic ice core (Young et al., 2007), providing primary evidence for atmospheric sources. Furthermore, a positive correlation was found between PFOA and PFNA (r= 0.683, p b 0.05) in ice core 1, suggesting that PFOA and PFNA share similar transportation pathways. In addition to FTOHs, atmospheric oxidation of other fluorotelomer compounds like FTIs, FTOs and FTAcs should not be neglected as possible indirect long-range transportation of PFCAs (Young and Mabury, 2010) in glacial ice cores. A previous study examined concentrations of C8–C11 PFCAs and PFOS in an ice core from the Canadian Arctic collected from the Devon Ice Cap (Fig. 1) in the spring of 2005 (Young et al., 2007). PFOS concentrations were comparable between our study and the Canadian study, but a sharp increase (500%) in PFOS measured in the Canadian Arctic ice core during 1998–1999 was not observed in our study. Two- to three-fold lower concentrations of PFOA, PFNA, perfluorodecanoate (PFDA) and perfluoroundecanoate (PFUnDA) were found in the Norwegian ice cores (present study) than in the Canadian Arctic ice core (Young et al., 2007). This result may indicate less contamination in the European Arctic than in the Canadian Arctic. Svalbard is an island surrounded by oceanic air, whereas the Devon Ice Cap is located near Canada and North America where poly- and perfluorinated compounds were widely used, and therefore it is likely that the study locations are experiencing different degrees of PFAS contamination. Furthermore, wind speed in the European Arctic is also generally higher than in the Canadian Arctic (Przybylak, 2003), which may result in volatile precursors of PFAS being more readily trapped in the Canadian Arctic and higher chance that they will be oxidized and deposited in wet precipitation as PFCAs, leading to higher PFCA levels. These results were also consistent with those reported for air samples collected from Svalbard in 2007 (Butt et al., 2010) and Nunavut, Canada (an island near Devon Island) in 2004 (Stock et al., 2007). A three-fold higher mean concentration of PFOA was found in the air masses of Nunavut (1.4 pg/m 3)

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0 92' 93' 94' 95' 96' 97' 98' 99' 00' 01' 02' 03' 04' 05'

90' 91' N.A. 92' 93' 94' 95' 96' 97' 98' 99' 00' 01' 02' 03' 04'

200 0

PFNA

0

90' 91' 92' 93' 94' 95' 96' 97' 98' 99' 00' 01' 02' 03' 04'

0

PFOA

92' 93' 94' 95' 96' 97' 98' 99' 00' 01' 02' 03' 04' 05'

90' 91' N.A. 92' 93' 94' 95' 96' 97' 98' 99' 00' 01' 02' 03' 04'

800

N.A.

Flux [fg/m2/year]

1200

0

PFHxA

0

90' 91' 92' 93' 94' 95' 96' 97' 98' 99' 00' 01' 02' 03' 04'

0

N.A.

400

Year

Fig. 5. Estimated annual fluxes of PFOS, PFNA, PFOA and PFHxA in ice cores from Svalbard, Norway. N.A.: Not analyzed. Average values were used for calculation, with one layer representing a two-year period. Annual flux of PFAS in 1997 in ice core 2 was underestimated due to a missing layer.

compared to Svalbard (0.44 pg/m3). Likewise, concentrations of volatile precursors (i.e. FTOHs and FSAs) measured in the Arctic atmosphere in 2005 were found to be higher in the oceanic air near Devon Ice Cap than near Svalbard, suggesting that Svalbard received less contamination of these compounds both locally and through long-range atmospheric transportation (Shoeib et al., 2006). However, PFAS contamination in glacial ice cores also depends on the production and usage of PFAS in nearby countries (i.e., in North America, Canada and Europe), meteorological conditions and melting and re-freezing mechanisms, and hence further investigation is needed to confirm these findings. 3.3. PFAS in surface snow and water samples Surface snow and surface water samples (i.e., glacier water, river water, sea water and lake water) collected from the glacier to the downstream and coastal areas of Svalbard were analyzed (Figs. 6–7). Mean PFAS concentrations in surface snow and water samples are summarized in Table S7. Among the 17 PFAS, two PFSAs (i.e., PFHxS and PFOS) and nine PFCAs (i.e., C4–C12 PFCAs) were detected, including PFHxS and PFHpA, neither of which was found in the ice core samples (Table S7). PFOA was the major PFAS present in the surface snow samples, while PFBA and perfluoropentanoate (PFPeA) were found to be dominant in the surface water samples. Significant differences were found between the mean concentrations of PFAS in glacial surface snow and downstream surface snow (p=0.022, Mann Whitney rank sum test) and river water samples (p= 0.022, Mann Whitney rank sum test). Approximately 2–3 times higher average PFAS concentrations were detected in both surface snow and water samples collected from the locations downstream of the glacier (Snow: S1, 2, 8, 9; River Water: W6, 7, 2, 14) when compared to those in the glacier (Snow: S5–7; Glacial Water: W9–11). This may be due to the influence of local sources in addition to long-range atmospheric transport. Higher PFAS concentrations were found in the glacier water (W9–11), especially for PFBA and PFPeA, than in glacial surface snow

(S5–7). Meltwater, representative of hundred years of deposition, is likely to have accumulated slowly from all layers of the core due to global climate change (Kohler et al., 2007) in addition to the process of evaporation, leading to elevated concentrations in the glacier water. Glaciers are generally located at relatively high altitudes with less human and industrial activities, and therefore long-range atmospheric transport of PFAS and degradation of volatile precursors is one of their most important sources of contamination. An increasing trend of PFAS concentrations was observed with greater proximity to the coastal settlement area in both surface snow and river water samples (Fig. 6). The settlement area is comprised of different human activities and industrial development, and therefore local input of PFAS related to domestic application, industrial usage and skiing activities is expected to contribute to higher PFAS concentrations in the local environment. Two- to ten-fold increases in the levels of several PFAS (i.e., PFHxS, PFOS, C4– C6 PFCAs) were detected in river water (W2, 6–8, 14) when compared to surface snow (S1–4, 8, 9) collected in downstream locations (Table S7), indicating that there are direct releases of these compounds into the river. These results suggested that PFAS contamination in the downstream locations of Svalbard is more due to local sources than atmospheric transport. Low PFAS concentrations were detected in the seawater around the coast of Longyearbyen, which may be due to oceanic dilution, as PFAS were not detected in seawater from the Norwegian Sea (Ahrens et al., 2010). Different PFAS composition profiles were observed between surface water and surface snow collected from the coastal area of Longyearbyen, indicating the existence of different contamination sources (Fig. 7). Higher proportions of long-chain (C9–C12, C14) PFCAs were found in surface snow, which may be attributed to skiing activities, as ski waxes contain PFCAs (Nilsson et al., 2010; Freberg et al., 2010). A recent study reported that the major PFAS detected in ski waxing powders were PFDoDA and PFTeDA with a mean concentration of 61 μg/L and 9.7 μg/L (Freberg et al., 2010), respectively, contributing to the observation of 50% and 100% increases in the average concentration of PFDoDA and

K.Y. Kwok et al. / Science of the Total Environment 447 (2013) 46–55

600

600

600

600

400

400

400

400

200

200

200

200

600

S3

S8

S1

53

S2

400 200

S9

S4 600

400

400

200

200

400 200

S7 600

600 400 200 0

400 200

PFHxS PFOS PFBA PFPeA PFHxA PFHpA PFOA PFNA PFDA PFUnDA PFDoDA

600

Concentration [pg/L]

S5

S6 Fig. 6. PFAS concentrations in glacial and downstream surface snow collected in Svalbard, Norway. The arrow indicates river flow. Glacial region: S5–7. Downstream locations: S1−4, 8, 9.

PFTeDA in surface snow compared to the river water in the downstream locations. Higher proportions of PFSAs (i.e., PFHxS & PFOS) were found in surface water in downstream locations. PFHxS was only detected in samples collected from downstream locations ranging from 20 to 30 pg/L in surface snow and from 20 to 500 pg/L in surface water, which suggests the existence of local sources. This result was also consistent with that of a previous study showing PFHxS levels in livers from polar bears (Ursusmaritimus) from Svalbard to be 10 times higher than in other circumpolar locations (Smithwick et al., 2005). 3.4. Source determination Correlation analyses of SS-SO42−, NSS-SO42− and PFAS concentrations were performed for ice core, surface snow and surface water samples to further examine the sources of contamination (Table S8). SO42− originates from both oceanic and anthropogenic sources such as industry and power plants, and hence SO42− can serve as an important indicator of contamination sources in precipitation samples. Low concentrations of some PFAS were detected in ice core samples, and therefore only correlations between PFOA and PFNA levels were assessed. No correlations were found between SS-SO42− and PFAS concentrations in both ice cores (Table S8a), indicating that PFAS contamination sources are not of oceanic origin, which is consistent with the results reported for the Canadian Arctic ice core samples (Young et al., 2007). A significant negative correlation was observed between PFBA and NSS-SO42− in ice core 2, suggesting that both of these compounds originate from mid-latitude continental areas. The presence of common contamination sources in surface snow was reflected by significant positive associations (pb 0.05) among most of the PFSAs and PFCAs except for PFHxA (Table S8b). These contamination sources include long-range atmospheric transport and degradation of volatile PFAS precursors (i.e., FTOHs, FSAs, FTOs, FTIs and FTAcs) (Young and Mabury, 2010), releases of fluorinated polymer products including 8:2 FTOH and 10:2 FTOH (Dinglasan-Panlilio and

Mabury, 2006) and direct local releases of PFAS (i.e., AFFFs and consumer products) (Prevedouros et al., 2006) into the atmosphere. No correlation was found between any of the PFAS and NSS-SO42− in surface snow. However, PFSAs may originate from marine aerosols as levels of PFHxS (r= 0.912, p b 0.0001) and PFOS (r= 0.879, p b 0.0001) were strongly correlated with those of SS-SO42−. Weak correlations were found between PFSAs and PFCAs, indicating that contamination sources of PFSAs and PFCAs in surface water samples are likely to be different. A previous study reported no correlations between PFOS and PFHxA and other PFCAs in polar bear liver tissue (Smithwick et al., 2005), and the same result was found in the present study. Significant positive correlations (pb 0.05) were found in surface water samples (Table S8c) among most of the PFCAs except PFDoDA, indicating similar contamination sources such as direct local input of PFAS into the river. Significant negative correlations (pb 0.05) were observed between long-chain (C8–C12) PFCAs and NSS-SO42−, in contrast to the patterns found for surface snow samples. Overall, these analyses show that surface snow and surface water samples have different PFAS contamination sources such as skiing activities and industrial discharge. Long-range atmospheric transport of PFAS was found to be the major pathway in the glacier, while local inputs of PFAS were suggested to be significant for the downstream locations (Fig. 8). This study provided abiotic time-trend data on PFAS contamination in the European Arctic using ice core samples, while also indicating the importance of local sources in Svalbard. As long-range atmospheric transport is a dominant pathway for PFAS in the European Arctic, continuation of atmospheric monitoring efforts of PFAS is essential, as emissions of their volatile precursors are known to be increasing globally (Muir and de Wit, 2010). There is a need for researchers to study PFAS long-range transport and deposition in the Arctic. Last but not least, further investigations should be carried out in the Russian Arctic (which covers nearly 50% of the circumpolar area) and the North American Arctic, in order to more fully understand the fate and trends of this class of contaminants in the Arctic.

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2000

2000

2000

1000

1000

1000

1000

N.A.

N.A.

2000

W14

W1 (seawater)

2000

W4

W5 (seawater) 2000

1000

W2

1000

2000

River Water

W3 (lake water)

1000 2000

W7

1000

2000 1000

W6

Melted Glacier

W8

2000

1000 N.A.

1500 1000

W9

500

W13

W10

1000

1000

1000 N.A.

W11

N.A.

0

PFHxS PFOS PFBA PFPeA PFHxA PFHpA PFOA PFNA PFDA PFUnDA PFDoDA

Concentration [pg/L]

2000

Fig. 7. PFAS concentrations in surface waters in the glacier and downstream locations of Svalbard, Norway. N.A.: Not Analyzed. The arrow indicates river flow. Glacial region: W9, 10, 11, 13. Downstream locations: W1–8.

Acknowledgements We acknowledge the staff of University of Life Sciences (UMB), Norway for their local support of sample collection. Part of this

study was funded by the Ministry of the Environment, Japan (project number B-1106). The work described in this paper was also supported by a grant from the Hong Kong Research Grants Councils (CityU160408) and a Hong Kong AoE Project (AoE/P-04/2004).

Fig. 8. Schematic of PFAS contamination sources and pathways in Svalbard, Norway. Note: = atmospheric deposition; ➡ = dispersion by water/melting; PFOA and PFOS concentrations were calculated as an average value of their corresponding samples.

= local emission.

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