Deposition History of Brominated Flame Retardant Compounds in an

Sep 14, 2010 - University Center on Svalbard, N-9171 Longyearbyen, Norway, ... BFR deposition history on Svalbard, Norway, we analyzed 19. BFRs ...
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Environ. Sci. Technol. 2010, 44, 7405–7410

Deposition History of Brominated Flame Retardant Compounds in an Ice Core from Holtedahlfonna, Svalbard, Norway M A R K H . H E R M A N S O N , * ,† ELISABETH ISAKSSON,‡ ¨ M,‡ SANJA FORSSTRO CAMILLA TEIXEIRA,§ DEREK C. G. MUIR,§ VEIJO A. POHJOLA,| AND RODERIK S. V. VAN DE WAL⊥ University Center on Svalbard, N-9171 Longyearbyen, Norway, Norwegian Polar Institute, N-9296 Tromsø, Norway, Environment Canada, Burlington, Ontario L7R 4A6, Canada, Department of Earth Sciences, Uppsala University, Uppsala, Sweden, and Institute for Marine and Atmospheric Research, Utrecht University, Utrecht, The Netherlands

Received May 15, 2010. Revised manuscript received August 20, 2010. Accepted August 30, 2010.

Brominated flame retardants (BFRs) have been found in Arctic wildlife, lake sediment, and air. To identify the atmospheric BFR deposition history on Svalbard, Norway, we analyzed 19 BFRs, including hexabromocyclododecane (HBCD), 1,2-bis(2,4,6tribromophenoxy)ethane (BTBPE), decabromodiphenyl ethane (DBDPE), pentabromoethylbenzene (PBEB), and 15 polybrominated diphenyl ether congeners (PBDE) in the upper 34 m of an ice core (representing 1953-2005) from Holtedahlfonna, the westernmost ice sheet on Svalbard. All of the non-PBDE compounds were detected in nearly continuous profiles in the core. Seven PBDEs were not observed above background (28, 47, 66, 100, 99, 154, 153), while 4 were found in 1 or 2 of 6 segments (17, 85, 138, 183). BDEs-49, 71, 190, 209 had nearly continuous profiles but only BDE-209 in large amounts. The greatest inputs were HBCD and BDE-209, 910, and 320 pg cm-2 yr-1 from 1995-2005. DBDPE, BTBPE, and PBEB show nearly continuous input growth in recent core segments, but all were 75% of atmospheric flow to Holtedahlfonna coming from Eurasia during haze periods (March and April).

Introduction Brominated flame retardants (BFRs) are a class of compounds used to slow the spread of flame in residential and commercial indoor fabric, foam, and electronic products in the industrialized world (1). Most BFRs are “additive” and are mixed directly into, but do not react with, materials during production and are easily emitted to the environment during * Corresponding author phone: (Norway) 47 79 023351; (USA) (267)207-7895; e-mail: [email protected]. † University Center on Svalbard. ‡ Norwegian Polar Institute. § Environment Canada. | Uppsala University. ⊥ Utrecht University. 10.1021/es1016608

 2010 American Chemical Society

Published on Web 09/14/2010

manufacture, use, and disposal (2). As a result, BFRs have been observed in environmental matrices in most parts of the world, including the Arctic, where they were never produced and used only in small urban areas (3). Their appearance in Arctic organisms shows that they are persistent and bioaccumulative (4, 5). Many BFRs have vapor pressures (VP) too low to be found in the gas phase at ambient temperatures (6) so BFR transport in the atmosphere may be governed by movement of particles (7, 8). Generally, particle transport has been thought to have a more limited spatial range than gas phase long-range atmospheric transport (LRAT). Early application of steadystate LRAT models suggested that low VP BFRs sorbed to particles would not be transported over long distances (6). However, in the dry Arctic atmosphere, particles are considered to have a longer atmospheric lifetime (9), and, in some cases, particle transport there is known to be rapid (10). There are indications that particle-sorbed contaminant LRAT is underestimated (11). The earliest class and, until 2008, the most widely used modern BFRs were the polybrominated diphenyl ethers (PBDEs) made into commercial mixtures known as pentaBDE, octaBDE, and decaBDE. PentaBDE and decaBDE together made up ∼93% of the global PBDE commercial trade in 2001. DecaBDE itself accounted for ∼83% of the PBDE market that year (12). Bans on the pentaBDE and octaBDE mixtures were enacted in Europe in 2004, and in the USA, the manufacture of these products was voluntarily ended by industry at that time (12). Regulatory action since then has been swift: by 2008 decaBDE, or, more specifically, BDE209, had been banned throughout Europe (13) in part because of concern about possible formation of more toxic oxidation and/or debromination residues. In North America, a phase-out of decabromodiphenyl ether is expected by 2013 (14). It is already banned by some U.S. states (13). The Stockholm Convention on POPs includes tetra-, penta-, hexa-, and heptaBDEs, covering many of the major congeners of pentaBDE and octaBDE commercial products, as of August 2010. Since the 1980s, the BFR industry has introduced compounds that are considered to be less persistent and toxic than PBDEs or their decomposition products. These PBDE alternatives include hexabromocyclododecane (HBCD), introduced as an early replacement for pentaBDE in Europe and more recently in the USA (15). A replacement for octaBDE is 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE) (15). Both are high production chemicals (16). Decabromodiphenyl ethane (DBDPE) is a replacement product for decaBDE that will not form the toxic residues noted above (17). It now is considered to be a low production chemical in Europe (ecb.jrc.ed.europa.eu/esis.index.php?PGM)ein). Pentabromoethylbenzene (PBEB), an apparent pentaBDE replacement, was not produced in the USA after 1986 but continued to be made in France until at least 2002 (3, 18). While all four of these replacement compounds have been in commerce in the USA and Europe at some time during the last ∼25 years, only HBCD has been reported in the Arctic, including Svalbard (3, 19). Many BFRs have been found in wildlife, lake sediment, and air in the Arctic (3, 11), with particularly high concentrations in female polar bears from eastern Greenland and Svalbard (5, 20). More recent studies have also shown BFRs (almost exclusively PBDEs) in other marine mammals around Svalbard where there are likely very few local, direct sources (5, 19). Sea ice near Svalbard contains low levels of some PBDEs (4). Knowing that Svalbard is being impacted by BFRs, VOL. 44, NO. 19, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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FIGURE 1. Map of Svalbard showing major towns and the Holtedahlfonna sampling site. we decided to quantify the net historic atmospheric inputs of these compounds to remote, high-elevation, permanent ice on Svalbard to identify if the atmosphere could be a source to the region. In addition, we are interested in knowing if the delivery of these contaminants on particles is related to the Arctic haze which is believed to originate largely in Eurasia (9).

Methods Methods are summarized here. Additional sampling and laboratory analytical method information appears in the Supporting Information. In April 2005 we drilled a 105 mm diameter, 125 m deep ice-core at Holtedahlfonna (79.13° N, 13.27° E at 1150 m above sea level (masl)) about 40 km northeast of Ny-Ålesund on the west coast of Spitsbergen, the largest island on Svalbard (Figure 1). The retrieved core sections were approximately 50-60 cm long. In the field they were packed in plastic bags and kept in insulated boxes at temperatures below freezing until transported to cold room facilities at the Norwegian Polar Institute (NPI), Tromsø, Norway. Estimated age of this core using glacialogical modeling is 400 years at 150 m - the maximum ice depth. Tritium analyses were performed on samples from 5 cm intervals, and the 1963 peak level was identified at about 28.4 m core depth (21). This gives an annual water equivalent (weq) accumulation rate of 0.52 m during the period 1963-2005, which compares well with the results from a core drilled at the same site in 1992 (22) showing that the 2005 core is representative of accumulation conditions in the area. Core subsampling for BFR analysis included combining contiguous sections of the core from the upper 34 m into 6 distinct samples with liquid volumes 11-15 L each. This depth covered the entire BFR use period from 1953 to 2005. Core segments forming an individual sample were placed into stainless steel cans and melted to a final temperature not >5 °C. Contaminants were separated from the melt by pumping 200-250 mL min-1 through Teflon-walled extraction columns filled with polymeric Amberlite XAD-2 resin which adsorbed compounds of interest from the dissolved phase. Particles were trapped by glass wool which held the XAD-2 in place inside the tube. Particle and dissolved phases were not separated. The XAD-2 was precleaned by sequential solvent 7406

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extraction and then packed into extraction columns in a clean room (positively pressured HEPA and carbon filtered air) at the National Water Research Institute (NWRI), Burlington, ON, Canada. These XAD columns were then shipped to NPI in Tromsø, Norway, where the ice was melted and pumped. After sample pumping, the XAD columns were shipped back to the NWRI clean room laboratory where they were sequentially extracted in CH3OH and CH2Cl2 after addition of surrogate standard (1,3,5-tribromobenzene). These extracts were combined and washed with 3% NaCl and dried on anhydrous Na2SO4. The extract was volume-reduced and added to a small column of 10% H2O-deactivated silica-gel and eluted with 10% CH3OH/CH2Cl2 and then exchanged to CH3COCH3/C8H18. We analyzed the core for 15 polybrominated diphenyl ethers (PBDEs), including congeners 17, 28, 49, 71, 47, 66, 100, 99, 85, 154, 153, 138, 183, 190, and 209. These congeners are characteristic of those found in pentaBDE, octaBDE, and decaBDE (BDE-209) commercial products. We also analyzed non-PBDE BFRs including HBCD, reported as ΣHBCD, BTBPE, PBEB, and DBDPE. To account for possible background contamination from transport, storage, and other handling, including in the laboratory in Tromsø, we analyzed two deeper ice core segments representing the pre-BFR period from about 1900 to 1914 at depths of 52.3 to 59.2 m. The largest BFR concentration in these deep samples represented our procedural detection limit, or background, which was subtracted from amounts in the upper 34 m of the core. These detection limits are reported in Table S1 (Supporting Information). The result was no reported data for 7 PBDE congeners (28, 47, 66, 100, 99, 154, 153) and no data for all but 1 or 2 samples for 4 other congeners (17, 85, 138, 183) clearly showing the vulnerability of sample collection, transport, and storage to BFR contamination, even in remote areas. The analysis yielded net ng L-1 units. They were converted to a flux (pg cm-2 yr-1) by dividing the amount of BFR by the surface area of the core (86.6 cm2) and the years represented in the core segments analyzed. Our earlier work on pesticides in ice cores from Svalbard indicated that event-based, rapid (>50 km h-1 average velocity) movements of air masses over long distances (∼1000 km) was possible (23). For this work we decided to investigate the longer-term temporal and geographic trends of air mass movements as a way of identifying possible source regions. Since atmospheric BFRs likely are associated with particles, we decided to emphasize the major atmospheric particle period throughout the Arctic known as the “haze” season, generally occurring during March and April. The haze results from enhanced transport and prolonged atmospheric residence time of particles as the polar front moves poleward from agricultural and urban areas at temperate latitudes (9, 24). We prepared air mass trajectories in 2 10-year periods from 1986-2005 approximately corresponding to the upper two segments of the ice core. Daily trajectories reaching back 5 days and ending at Holtedahlfonna location and altitude were calculated using NCEP/ NCAR reanalysis fields. We divided the trajectory year into two general parts, the haze season (March - April) and the rest of the year (May - February). The trajectories were grouped into 6 clusters using the built-in clustering algorithm in HYSPLIT (25).

Results The two most abundant BFRs in the Holtedahlfonna ice core were HBCD and BDE-209 (Figure 2). HBCD has a generally increasing input from 1962, with no detection from 1971-1980 and a small drop in flux from 1988-1995 relative to 1980-1988. Its peak input is 910 pg cm-2 yr-1 in the surface

FIGURE 2. Deposition trends to Holtedahlfonna of high-input BFRs BDE-209 and HBCD. layer (1995-2005). BDE-209 has a smaller but still large flux in this layer, with a peak value of 322 pg cm-2 yr-1, and has a continuous record starting with very low values from 1953-1971. The earliest observations of BDE-209 likely reflect some downward movement caused by effects of summer melting. The peak value for BDE-209 is >75 times greater than the next highest net PBDE input, for BDE-49 (4.2 pg cm-2 yr-1). This is consistent with the global use patterns for PBDEs, which, again, were ∼83% decaBDE in 2001 (12). Other PBDEs with long records in the core, including BDEs 71 and 109, had peak inputs BDE-209 follows the usage trends in Europe (8) where, again, the former compound apparently was used early as a replacement for pentaBDE (15). We can reach this conclusion about usage reflected in our ice core results while admitting that we do not know the fate of any of the BFRs analyzed between source and sink other than that part of the fate is to end up at Holtedahlfonna. VOL. 44, NO. 19, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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FIGURE 4. Burdens of 12 brominated flame retardants found at Holtedahlfonna, arranged from highest to lowest vapor pressure, left to right. PBDE vapor pressures from Mackay et al. (ref 44), those for HBCD, BTBPE, and PBEB from Syracuse Research Corporation (http://www.srcinc.com/what-we-do/ databaseforms.aspx?id)386). The value for DBDPE assumed equal to BDE-209, as suggested by Kirkkegaard et al. (ref 17). The total liquid volume of the core is 88.2 L. The literature regarding environmental distribution of BDE-209 suggests that it will not be found in the Arctic resulting from long-range atmospheric transport. Two investigators noted that BDE-209, in spite of its high use in the industrialized world, would not be widely distributed through the atmosphere because of a low VP and predominance in the particle phase (6, 33). An investigation of BDE-209 deposition to lake sediments noted that concentrations were very low - near to or at detection limits - in lakes north of 55° N (11). Ikonomu et al. (34) analyzed BDE 209 (among other congeners) in ringed seal blubber from the Canadian Arctic but did not report it because it was detected in fewer than 30% of samples. Bezares-Cruz et al. (35) stated that environmental PBDE congener profiles “include very little, if any BDE-209”. In a literature review, Hites (36) noted that BDE-209 is not abundant in environmental samples other than sediment. Some investigations have suggested that photolytic debromination of BDE-209 to other PBDEs (37-39) might account for little or no concentration in environmental samples. However, Raff and Hites (28) show that the particulate materials themselves that are associated with BDE-209 in the atmosphere will reduce likelihood of photolysis and oxidation. Furthermore, long periods of polar darkness would reduce or eliminate both processes. Gouin et al. (7), Hoh and Hites (40), and Cahill et al. (41) identified BDE-209 in atmospheric particle samples collected at various sites in North America and concluded that atmospheric transport of nonvolatile BFRs will be governed by movement of particles, possibly over long distances. Wang et al. (42) found higher average concentrations of various PBDE congeners (dominated by BDE-47 and BDE-209) in air particles in the Arctic (17.3 pg m-3) than in the North Pacific Ocean (12.8 pg m-3) suggesting long distance particle transport. Su et al. (43) found mean atmospheric BDE-209 to be 1.6 pg m-3, the third most concentrated PBDE (behind congeners 99 and 47) during their study period from early 2002 to ∼mid 2004 at Alert in the Canadian Arctic. During winter, however, BDE-209 was often the most abundant congener; it was never donimant during summer. Su et al. (42) concluded that particle transport was responsible for observations of high winter BDE-209, possibly occurring during late winter haze season. The possible Arctic haze movement of BFRs to Holtedahlfonna is shown by seasonal separation of many years of air mass trajectories. Figure 5a shows a 6-cluster average trajectory pattern developed from 508 trajectories 7408

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FIGURE 5. a. HYSPLIT 5-day back trajectories to Holtedahlfonna for the March/April haze season, 1996-2005. b. HYSPLIT 5-day back trajectories to Holtedahlfonna for May - February 19962005. from the Arctic Haze season in March and April over the 10-year period represented by the top layer of the ice core (1996-2005). Flows to Holtedahlfonna originate from the Eurasian sector (to the S, E, and NE from Holtedahlfonna) 77% of the time. During the May - February nonhaze season (Figure 5b) for 1996-2005, the average flows from that region in 2542 trajectories occur an average of 39% of the time or about half as often. The same trajectories for the 1986-1995 period (Figures S1a and S1b, Supporting Information) show a similar result, with a somewhat higher Eurasian contribution (54%) during the May - February period but still lower than the March - April haze season (74%). A comparison of the 1986-1995 and 1996-2005 trajectories shows that during haze season, the three southern and eastern trajectories shifted to the east in later years. Trajectory 2 during the 1986-1995 haze period (Figure S1a) is over the north Atlantic ocean and shifted east to overland in northern Norway and Sweden during the 1996-2005 haze period (trajectory 3, Figure 5a). This may have contributed to changes in the amounts of BFRs observed at Holtedahlfonna between 1986 and 2005, but further study would be required to verify this effect. It is clear from Figure 5a,b that air mass flow from northern Russia and Siberia dominates all year (trajectories 1, 2, and

5 in Figure 5a and trajectories 1 and 6 in Figure 5b). The greatest seasonal change is the southern trajectory (trajectory 3 in Figure 5b) which is off-shore in the north Atlantic during the nonhaze season but moves to the east over land during haze season (trajectory 3 in Figure 5a). This shows that at least part of the change between haze and nonhaze season is movement of one source trajectory from over-ocean to over-land in Europe, suggesting that Europe is an important haze season source. Again, this requires further study. In any case, the Arctic haze season clearly creates the greatest opportunity for particle-associated BFR transport from possible Eurasian source regions to Holtedahlfonna.

Supporting Information Available Additional field and analytical methods, two additional air mass back trajectories (Figures S1a and S1b), and one table (Table S1) containing BFR net concentration data, deepcore background concentrations, and surrogate recovery for samples covering the period 1953-2005. This material is available free of charge via the Internet at http://pubs.acs.org.

Acknowledgments We wish to thank the field and cold laboratory crews that contributed to this work. Funding for the ice core drilling came from the Norwegian Polar Institute, the Dutch Science Foundation (NWO), and the Swedish Science Council (VR).

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