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Article
Multi-year measurements of flame retardants and organochlorine pesticides in air in Canada’s Western sub-Arctic Yong Yu, Hayley Hung, Nick Alexandrou, Pat Roach, and Ken Nordin Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.5b01996 • Publication Date (Web): 22 Jun 2015 Downloaded from http://pubs.acs.org on June 25, 2015
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Multi-year measurements of flame retardants and
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organochlorine pesticides in air in Canada’s Western sub-
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Arctic
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Yong Yu 1*, Hayley Hung 1*, Nick Alexandrou 1, Pat Roach 2, Ken Nordin 3
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Air Quality Processes Research Section, Environment Canada, Toronto, ON, M3H 5T4, Canada
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2
Aboriginal Affairs and Northern Development Canada, Whitehorse, YT, Y1A 2B5, Canada
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3
Laberge Environmental Services, Whitehorse, YT, Y1A 2S5, Canada
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Corresponding authors:
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*Tel: 1-416-739-4770; e-mail:
[email protected] 16
*Tel: 1-416-739-5944; fax: 1-416-739-4281; e-mail:
[email protected] 17 18
Abstract:
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Fourteen polybrominated diphenyl ethers (PBDEs), 14 non-BDE flame retardants (FRs) and 25
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organochlorine pesticides (OCPs) were analyzed in air samples collected at Little Fox Lake (LFL)
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in Canada’s Yukon Territory from August 2011 to December 2014. LFL is a long term
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monitoring station operated under the Northern Contaminants Program (NCP) and one of only a
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few stations that contribute to the assessment of air pollution levels and pathways to the sub-
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Arctic region. BDE-47 was the most abundant congener among the 14 PBDEs, followed by
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BDE-99. Non-BDE FRs pentabromotoluene (PBT) and dechlorane plus (DP) were detected in all
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the
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hexabromobenzene (HBB), and 2-ethylhexyl 2,3,4,5-tetrabromobenzoate (EH-TBB) were also
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detected in > 75% of all samples. PBDEs have shown decreasing tendency as of 2013, which
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may reflect the phase out of penta- and octa-BDE mixtures has led to significant decline in the
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atmosphere. The highest concentrations of OCPs were observed for hexachlorobenzene (HCB),
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with a median concentration of 61 pg/m3, followed by α-hexachlorocyclohexane (α-HCH) and α-
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endosulfan. Potential source contribution function (PSCF) highlights Northern Canada, Pacific,
samples.
Dechlorane
602,
2,3-dibromopropyl-2,4,6-tribromophenyl
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(DPTE),
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and East Asia as potential sources in warm seasons; while in cold seasons, the chemicals mainly
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came from the Pacific Rim.
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Introduction
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Polybrominated diphenyl ethers (PBDEs) and organochlorine pesticides (OCPs) are two
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classes of persistent organic pollutants (POPs) which have attracted much public and scientific
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attention [1]. They were widely used in the world and most of them have been banned or
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restricted in increasing numbers of countries. Due to their persistence and bioaccumulation
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potential, they are ubiquitous in various environmental matrices. These trace organic compounds
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have been detected in wastewater treatment plants (WWTPs), aquatic environment, mammals,
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and human [2, 3]. However, fewer studies have reported about their occurrence in the
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atmosphere of remote regions, especially in the western Arctic [4].
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Long-range atmospheric transport (LRAT) is the most rapid pathway for semi-volatile
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organic compounds (SVOCs) to travel to remote locations. The occurrence of SVOCs in the
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Arctic atmosphere has been investigated under the Canadian Northern Contaminants Program
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(NCP), which is Canada’s National Implementation Plan for the Arctic Monitoring and
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Assessment Programme (AMAP), to assess LRAT of pollutants. Since 2002, NCP has conducted
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air monitoring of SVOCs at Little Fox Lake (LFL), in Canada’s Yukon Territory, including
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measurements of PBDEs, OCPs and polycyclic aromatic hydrocarbons (PAHs) [4].
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In a previous study, Westgate et al. [5] investigated the occurrence of PBDEs and OCPs
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from August 2007 to October 2009 at LFL using a super-high-volume air sampler (SHV).
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However, this type of sampling is expensive and requires high maintenance and is therefore not
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suitable for long-term monitoring at a remote site like LFL. Xiao et al. [6, 7] developed a flow-
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through sampler (FTS) for SVOCs in air, which can sample air in the absence of power.
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Meanwhile, the phase out of penta-, octa-, and deca-BDE has led to the increased use of
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alternative flame retardants (FRs) in different products. In recent years, various studies explored
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the presence of non-BDE FRs in air samples [8-10].
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In this study, we investigated the atmospheric concentrations of OCPs, PBDEs and
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emerging non-BDE FRs at LFL by FTS. This is the first report of multi-year measurements of
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non-BDE FRs in air in the western sub-Arctic region. The aim of this study is to examine the
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monthly variation and time trend of these chemicals and to assess and map the possible source
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regions of these contaminants at LFL.
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Experimental
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Chemicals. Fourteen PBDEs (BDE-17, -28, -49, -71, -47, -66, -100, -99, -85, -154, -153, -138,
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-183, and -190), 14 non-BDE FRs, allyl-2,4,6-tribromophenyl ether (ATE), 2-bromoallyl-2,4,6-
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tribromophenyl
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hexabromobenzene (HBB), hexabromocyclododecane (HBCD), 1,2-bis(2,4,6-tribromophenoxy)
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ethane (BTBPE), pentabromotoluene (PBT), pentabromoethylbenzene (PBEB), 2-ethylhexyl
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2,3,4,5-tetrabromobenzoate
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dechlorane 602 and 604, syn- and anti- dechlorane plus (DP), and 25 OCPs, α-, β-, γ-, δ-
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hexachlorocyclohexane (HCH), hexachlorobenzene (HCB), aldrin, dieldrin, endrin, heptachlor,
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heptachlor epoxide, trans- and cis-chlordane, trans-nonachlor, α- and β-endosulfan, endosulfan
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sulfate, o,p’-DDE, o,p’-DDD, o,p’-DDT, p,p’-DDE, p,p’-DDD, p,p’-DDT, methoxychlor,
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oxychlordane, and photomirex, were measured in 42 air samples. Details on these compounds
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are provided in Table S1.
ether
(BATE),
2,3-dibromopropyl-2,4,6-tribromophenyl
(EH-TBB),
ether
bis(2-ethylhexyl)tetrabromophthalate
(DPTE),
(TBPH),
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Sampling. The sampling site is located in a sub-Arctic environment in the Yukon Territory
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near LFL (61°21’ N, 135°38’ W, and 1128 m above sea level), about 85 km north of the city of
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Whitehorse, YT, Canada. The population density of this area is very low, < 0.1 person/km2 [11].
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Details of the air sampling procedure are described elsewhere [6, 7]. Briefly, the sampling media
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consist of two 3-inch and one 1-inch polyurethane foam (PUF) plugs, housed in an FTS
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described previously in Xiao et al. [7]. The FTS turns into the wind with the help of vanes and
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the air volume collected by the FTS during a 1-month period depends on wind speed and ranged
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from 1025 m3 to 10,500 m3. Forty-two monthly air samples were collected from August 2011 to
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December 2014 at LFL with FTS for this study. Details on sampling time and air volume are
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provided in Table S2. Air monitoring for SVOCs at LFL is continuous and on-going.
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Analytical Procedure. Each PUF in the FTS sample was individually Soxhlet extracted for
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24 h with 480 mL of acetone and petroleum ether (PE) 1:1 v/v. The extracts were dehydrated 4 ACS Paragon Plus Environment
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with 5 g of sodium sulfate (J.T. Baker, Center Valley, PA), solvent exchanged to 2 mL of
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isooctane, and 100 ng of mirex was added to each sample for volume correction. All samples
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were reduced in volume with a Turbovap 500 (Biotage, Charlotte, NC) to 0.5 mL, the volume
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was brought to 1.0 mL with isooctane, then transferred into a vial.
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PBDEs and non-BDE FRs were analyzed by gas chromatography- mass spectrometry (GC-
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MS) using an Agilent 5975 MSD (Mississauga, ON) in negative chemical ionization (NCI) mode
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with methane as the reagent gas by selected ion monitoring (SIM). Using a DB-5 column (30 m×
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0.25 mm i.d. × 0.25 µm film thickness, Agilent Technologies, Mississauga, ON), the oven
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temperature program was as follows: 110 °C for 2 min, increased by 15 °C/min to 160 °C, held
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for 0 min, increased by 2.5 °C/min to 260 °C, held for 4 min, increased by 2.5°C/min to 285 °C,
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and then held for 15 min. The source was at 150 °C and the transfer line at 280 °C. The injector
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was held at 200 °C in pulsed splitless mode.
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The concentrations of OCPs were analyzed on an Agilent 6890 Gas Chromatograph
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(Mississauga, ON) with electron capture detector (GC-ECD), coupled with a DB-5 column (60
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m × 0.25 mm i.d. × 0.25 µm film thickness, J&W Scientific, Folsom, CA), using a temperature
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program as follows: 80 °C for 1 min, increased by 15 °C/min to 160 °C, and then increased by
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2.5 °C/min to 265 °C and held for 25 min.
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Quality assurance and quality control. The calibration standards were run at the
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beginning and at the end of every batch of 8 samples. The average of the two sets of standards
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were used to quantify the samples analyzed in the batch. Randomly, one 1- or 3-inch PUF was
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collected as field blank for every sample, while solvent blanks were analyzed for every two
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samples. Field blanks and solvent blanks were extracted and analyzed in the same manner as
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PUF samples. Only BDE-47 and -99 were detected in some of the solvent blanks. The other
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chemicals were not detectable in solvent blanks. BDE-47 and -99 were detected in all the field
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blanks, and the other compounds were occasionally detectable (Table S3). The method detection
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limits (MDLs) were calculated from mean of the 12 field blanks + 3 standard deviations. For the
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chemicals not detected in the field blanks, the instrumental detection limit (IDL), set at S/N
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ratios = 3, was used for calculating MDLs. MDLs were expressed as IDL divided by an average
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sampling air volume of 3455 m3. FTS is open to trap both gas and particle phases, and fine
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particles and gas-phase chemicals may breakthrough. Breakthrough was calculated as the ratios 5 ACS Paragon Plus Environment
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of concentrations on the third PUF (1-inch) to those on all 3 PUFs. Breakthrough was on average
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5.8% for PBDEs, 5.7% for non-BDE FRs, and 9.5% for OCPs. Recoveries of target chemicals
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from each group were determined by spiking three clean PUFs with 1 mL working standard (20
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ng/mL) and treating them as real samples. Recoveries ranged from 88% to 119% for PBDEs, 78%
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to 130% for non-BDE FRs, and 63% to 100% for OCPs (Table S3). No blank-correction or
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recovery adjustment was made.
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Back trajectory analysis. Back-trajectories were calculated using the US NOAA Hybrid
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Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model with GDAS one-degree
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archive meteorological data. Ten-day trajectories were calculated for air arriving at 200 m above
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the earth’s surface starting every 6 h backwards in time. The coordinates of the calculated
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trajectory points were recorded at 1 h time intervals. Trajectories were calculated for each
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sampling period. Hierarchical cluster analysis was used to classify the backward air trajectories
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into similar groups. Potential source contribution function (PSCF) for abundant chemicals was
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computed by MetCor [12] v1.0 in 0.2° × 0.2° grid cells for northern hemisphere; monthly
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concentrations were tagged to the back trajectory endpoints. Visualizations of the PSCF were
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mapped using the Matlab 2012a.
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Results and discussion
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PBDEs. As shown in Fig. 1a, the total concentration of 14 PBDEs ranged from 0.42 to 18
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pg/m3, with median value of 1.6 pg/m3. BDE-47 and -99 were the predominant PBDEs,
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accounting for about 65% of total 14 PBDEs detected in the LFL atmosphere, with the median
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concentration of 0.65 and 0.40 pg/m3, respectively. Commercial penta-BDE is a congener
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combination of different PBDEs, with BDE-47 and -99 as the most abundant congeners. The
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high levels of BDE-47 and -99 suggest penta-BDE mixtures to be the major influence on PBDEs
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in air at LFL. BDE-28, -100 and -183 were also detected in most samples. BDE-17, -49, -71, -66,
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-85, -154 and -153 were frequently detected before April 2013.
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The concentrations of individual PBDE congener showed different profiles. The median
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concentrations of BDE-47, -99 and -100 showed sharp decline in 2013 and 2014 (Fig. 1b), with
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annual percent decline of 71 and 38% (BDE-47), 77 and 13% (BDE-99), 75 and 14% (BDE-100),
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respectively. The medians of other PBDEs significantly decreased in 2013 (p 75% of the samples; PBEB was detected in
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60% of the samples (Fig. 2 and Fig. S1); TBPH was detectable in ~40% of the samples and
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frequently detected before 2013; ATE, BATE and BTBPE were detectable in ~25% of the
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samples; HBCD was only found in two samples.
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PBT was detected in all the samples, with concentrations ranging from 0.007 to 0.47 pg/m3,
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with an average of 0.084 pg/m3. The mean concentrations of HBB and PBEB were 0.023 and
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0.013 pg/m3, respectively. They were reported in European Arctic air with median values of 0.12
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and 0.03 pg/m3, respectively [17].
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ATE, BATE, DPTE and BTBPE are usually discussed together, because they are
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synthesized from 2,4,6-tribromophenol (TBP), commercially known as PH-73 FF [18, 19].
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Within this group, DPTE was detected in most samples, with median concentrations of 0.031
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pg/m3, and was previously reported at levels ranging from 0.009 to 1.7 pg/m3 in the East
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Greenland Sea atmosphere [15]. BATE was detected at the lowest concentration and detection 7 ACS Paragon Plus Environment
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frequency, with a maximum of 0.021 pg/m3. BATE was reported in air around the Great Lakes
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ranging from 0.012 to 3.9 pg/m3 [18]. ATE and BTBPE were detected in fewer samples with
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lower concentrations compared to Alert and the Tibetan plateau [14]. These results in our study
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are also lower than those reported for the Arctic Ocean in summer 2010 [20].
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Firemaster 550 and Firemaster BZ-54, as alternative FRs, were used since 2004. Firemaster
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550 consists of about 35% of EH-TBB and about 15% of TBPH. Firemaster BZ-54 consists of
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about 70% of EH-TBB and about 30% of TBPH [21]. In this study, EH-TBB and TBPH were
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detected in 78% and 38% of all samples, with average concentrations of 0.20 and 0.33 pg/m3,
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respectively. The average ratio of EH-TBB/TBPH from LFL air is 0.94, which is lower than 2.3
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in Toronto, Canada [19], but similar to other sites around Great Lakes ranging from 0.70 to 1.2
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[21, 22].
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Four highly chlorinated FRs, dechlorane 602 and 604, syn- and anti-DP, were measured in
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this study. The total concentrations of syn- and anti-DP ranged from 0.01 to 1.8 pg/m3, with
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average of 0.11 and 0.14 pg/m3, respectively. The average proportion of anti-DP of the total DP
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(Fanti) for the first year was 61%, similar to composition of technical DP (65%) [23], the mean
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Fanti decrease to 56 and 51% in the second and third year. Moreover, the concentrations of DPs
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also decreased over the 3 years, indicating that LFL may be more influenced by local emission in
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the first year. These results are similar to the outcomes of Xiao et al. [14] and Moller et al. [24],
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who reported the concentration ranges of < 0.05 to 2.1 pg/m3 at Alert, and 0.05 to 4.2 pg/m3 in
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East Greenland. Dechlorane 602 was detectable in > 75% of the samples with a maximum of
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0.06 pg/m3, while dechlorane 604 was only detected in 2014. As far as the authors are aware, this
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is the first time that dechlorane 602 and 604 are reported in Arctic air.
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PBDEs and OCPs have been detected in East Greenland polar bears for 3 decades [25, 26].
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PBT and HBB have been found in eggs and plasma from glaucous gulls in the Norwegian Arctic
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collected in 2006 [27]. Recently, Vorkamp et al. [28] reported that EH-TBB, TBPH, BTBPE,
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DPTE and DPs were detectable in polar bear, ringed seal, black guillemot and glaucous gull
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from Greenland. HBB and PBEB were also found in polar bears [29], indicating the potential for
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LRAT and bioaccumulation of these novel FRs.
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Pearson correlations between compounds were used to examine if they have similar sources.
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The results showed that BDE-47, -99, and -100 were significantly correlated with one another (r >
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0.9, p < 0.0001, n=3) but not with BDE-183 (r < 0.3, p > 0.1, n=3). BDE-47 was also 8 ACS Paragon Plus Environment
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significantly correlated with dechlorane 602 and EH-TBB (r > 0.45, p < 0.01, n=2), suggesting
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similar sources. For the non-BDEs FRs, syn- and anti-DP were highly correlated (r = 0.967, p
