Organophosphate Esters in Canadian Arctic Air: Occurrence, Levels

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Organophosphate Esters in Canadian Arctic Air: Occurrence, Levels and Trends Roxana Sühring, Miriam L. Diamond, Martin Scheringer, Fiona Wong, Monika Pu#ko, Gary Stern, Alexis Burt, Hayley Hung, Philip Fellin, Henrik Li, and Liisa M. Jantunen Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.6b00365 • Publication Date (Web): 16 Jun 2016 Downloaded from http://pubs.acs.org on June 21, 2016

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Environmental Science & Technology

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Organophosphate Esters in Canadian Arctic Air: Occurrence, Levels and Trends

Roxana Sühring 1+, Miriam L. Diamond 1, Martin Scheringer 2,3, Fiona Wong4, Monika Pućko5, Gary Stern5, Alexis Burt5, Hayley Hung4, Philip Fellin6, Henrik Li6, Liisa M. Jantunen* 7,1 1

Department of Earth Sciences, University of Toronto, 22 Russell Street, Toronto, Ontario, Canada M5S 3B1 2 RECETOX, Masaryk University, 625 00 Brno, Czech Republic 3 ETH Zürich, 8093 Zürich, Switzerland 4 Air Quality Processes Research Section, Environment and Climate Change Canada, Toronto, Ontario, Canada, M5H 5T4 5 Centre for Earth Observation Science, University of Manitoba, 586 Wallace Building, Winnipeg, Manitoba, Canada R3T 2N2 6 AirZOne, Mississauga, Ontario, Canada, L4Z 1X1 7 Air Quality Processes Research Section, Environment and Climate Change Canada, Egbert, Ontario, Canada L0L 1N0 +

Current Address: Centre for Environment, Fisheries and Aquaculture Science (Cefas), Lowestoft, Suffolk NR33 0HT, United Kingdom

* Corresponding Author: Liisa M. Jantunen, Air Quality Processes Research Section, Environment and Climate Change Canada, Egbert, Ontario, Canada L0L 1N0 Email: [email protected]

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1 ACS Paragon Plus Environment


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Abstract

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Fourteen organophosphate esters (OPEs) were measured in the filter fraction of 117 active air

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samples from yearly ship-based sampling campaigns (2007–2013) and two land-based stations in the

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Canadian Arctic, to assess trends and long-range transport potential of OPEs.

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Four OPEs were detected in up to 97% of the samples, 7 in 50% or less of the samples, and 3 were

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not detected. Median concentrations of ΣOPEs were 237 and 50 pg m-3 for ship- and land-based

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samples, respectively. Individual median concentrations ranged from below detection to 119 pg m–3

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for Ethanol, 2-chloro-, phosphate (3:1) (TCEP). High concentrations of up to 2340 pg m–3 were

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observed for Tri-n-butyl phosphate (TnBP) at a land-based sampling location in Resolute Bay from

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2012, whereas it was only detected in one ship-based sample at a concentration below 100 pg m–3.

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Concentrations of halogenated OPEs seemed to be driven by river discharge from the Nelson and

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Churchill Rivers (Manitoba) and Churchill River and Lake Melville (Newfoundland and Labrador). In

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contrast, non-halogenated OPE concentrations appeared to have diffuse sources or local sources

42

close to the land-based sampling stations. Triphenyl phosphate (TPhP) showed an apparent temporal

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trend with a doubling-time of 11 months (p = 0.044).

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The results emphasize the increasing relevance of halogenated and non-halogenated OPEs as

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contaminants in the Arctic.


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1. Introduction

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Organophosphate esters (OPEs) are synthetic chemicals used in many polymer-based consumer and

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industrial products in order to comply with flammability standards (1). Non-chlorinated alkyl and aryl

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phosphates are also used as plasticizers, as well as antifoaming agents in lacquers, hydraulic fluids,

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floor polishes (2) and nail polish (3). OPEs have been in use for decades (4), however their use has

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increased significantly since the listing of several brominated flame retardants (BFRs) as persistent

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organic pollutants (POPs) under the Stockholm Convention (5). In 2013 the estimated market volume

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of OPEs was 620 kt, accounting for 30% of the global total of flame retardants (5).

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An argument often used in favor of OPEs as replacements for banned BFRs is that OPEs, in general,

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are less persistent in the environment and do not bioaccumulate to the extent shown by BFRs (6).

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Persistence and bioaccumulation potential are key criteria used under the Stockholm Convention for

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evaluating the environmental hazard of a chemical (7). However, several OPEs, such as 2-Ethylhexyl

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diphenyl phosphate (EHDPP), Tris(2-butoxyethyl) phosphate (TBEP), Tris(cresyl) phosphate (TCP), and

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Triphenyl phosphate (TPhP) have a persistence similar to that of the BFRs they are replacing (8,9).

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A third criterion for the evaluation of chemicals and classification as POPs is the potential to undergo

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long-range transport (LRT) into remote environments such as polar regions (7, 10). Polar regions are

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sentinels for contaminants because of their remote geographical location and minimal local sources

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(10). However, recent studies have reported OPEs in remote areas, such as the Arctic and Antarctic, at

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concentrations exceeding those of BFRs by orders of magnitude (11-14).

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In this study, we present the results of ship- and land-based observations of 14 OPEs in high-volume

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air samples from the Canadian Arctic between 2007–2013. Through the observation of OPEs over

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seven years and the comparison of land- and ship-based sampling results, we have suggested

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geographic and temporal trends, as well as indications of the factors contributing to the observed

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OPE patterns. This paper follows from Sühring et al. (2016) (15), who presented data and estimates of

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the gas-particle partitioning of OPEs, which is relevant to atmospheric transport and LRT in particular. 3 ACS Paragon Plus Environment


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2. Materials and Methods

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2.1 Sampling

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Shipboard-based sampling was conducted between 2007–2013 from the CCGS Amundsen as a part of

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ArcticNet (see Figure S1 for sampling locations and cruise tracks). In August 2007, as a part of the

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International Polar Year (IPY), samples were taken in the Labrador Sea, eastern Canadian Archipelago and

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Hudson Bay. In 2008, also during IPY, samples were collected in May–June off Banks Island in the western

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archipelago. In 2010 and 2011, the cruises departed from Kugluktuk (Northwest Territories) and

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terminated in Iqaluit (Northwest Territories) and Quebec City, respectively, and sampled in the central

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and eastern Archipelago. In 2013, the ship left Resolute Bay in the central Archipelago, headed west to

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the Beaufort Sea and returned to Resolute Bay (Figure S1).

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Shipboard air sampling was performed on the tip of the bow to minimize contamination from the ship’s

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smoke stack. Further details of sampling can be found in Jantunen et al. (2015) (16). Land-based samples

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were collected at Resolute Bay (Cornwallis Island, Nunavut, 74.70oN, 94.83oW) in 2012 and Alert,

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Nunavut (82.50oN, 62.34oW) in 2008–9 and 2012.

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Air samples of 500–1500 m3 were collected using a sampling train of a glass fiber filter (GFF, 100 mm

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diameter, Whatman, >99% collection of particles >0.3 mm, baked at 400oC prior to use) to retain

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particulate compounds followed by a polyurethane foam (PUF, Sigma Aldrich, 7.8 cm diameter x 7.5 cm)

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and XAD-2 (Supleco, pre-cleaned polystyrene-divinylbenzene copolymer, 20–60 mesh, 18 g) sandwich

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to trap the gaseous fraction.

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2.2 Extraction and Cleanup

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Filter and PUF-XAD samples were extracted separately except for the Alert samples, which were

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extracted as composite samples. Screening of previous samples indicated that the OPEs were

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primarily on the filter and below the detection limit in the PUF-XAD samples; therefore, we report the

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methods for the GFFs only. GFFs were Soxhlet extracted in dichloromethane (DCM) overnight, except


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the Alert samples, which were extracted by accelerated solvent extraction. A mixture of deuterated

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and carbon-13 labelled surrogates were added prior to extraction (see Tables S2a,b for details). Blank

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samples (one in six samples) and spikes of native compounds were also analyzed. Extracts were

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volume reduced by rotary evaporation under a gentle stream of nitrogen to 0.5 mL. The extracts

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required no further cleanup.

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2.3 Instrumental Analysis

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A full list of the targeted analytes including IUPAC name and CAS number is presented in Supporting

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Information Table S1.

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All analyses were performed by gas chromatography with a mass-selective detector operating in

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electron-impact (GC-EI-MS) and electron-capture negative ion modes (GC-ECNI-MS) using an Agilent

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6890 GC-5973 or 5975 Mass Selective Detector (MSD). Quantitative analysis was performed on a DB-5

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column (J&W, Agilent Technologies, 30 m, 0.25 mm i.d., 0.25 µm film thickness). Mirex was added to

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extracts prior to injection as the internal standard (100 ng). Random samples were checked for native

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Mirex/dechlorane and found negative. Ions monitored for each compound and surrogates are presented

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in Tables S2a,b and S3.

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2.4 QA/QC

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Sampling media, procedural and field blanks were collected at every step in the sampling process.

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Samples were field-blank corrected. For a compound to be positive, the sample must have exceeded

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the limit of detection (LOD), defined as the LOD = mean blank + 3*SD of the blank. Where there were no

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peaks in the blanks, the instrumental detection limits (IDLs) were used (see Table S3 for IDLs). Blank

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values for all compounds ranged from below detection to 3359 pg per sample; since the sample

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volumes varied, this translated to below detection to 6.7 pg m-3 (based on a 500 m3 sample) and

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below detection to 2.2 pg m-3 (based on a 1500 m3 sample).

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Recovery of native compounds ranged from 88–117% (n = 5) and average surrogate recoveries ranged

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from 79–116%. Samples were surrogate-recovery corrected on an individual basis. 5 ACS Paragon Plus Environment


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2.5 Statistical Analysis and Graphical Representation

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Basic statistical tests including tests for normality, F-test and t-test were performed using Microsoft

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Excel 2013. Concentrations below the LOD were treated as “0” for statistical analysis. For details on

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statistical methods and graphical representation, see supporting information (S3).

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Temporal trends were tested using the PIA statistical application (17), a robust regression-based

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analysis to detect trends in time-series datasets (18). Only data from ship-based sampling campaigns

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were included for temporal trends because the land-based sampling was either just one year

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(Resolute Bay) or did not consistently include all analytes. Temperature (and thereby latitude) was

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used as adjustment variable in the regression analysis to control for variability in OPE concentrations

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based on geographic location.

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Ocean Data View (version 4.7.4) (19) was used for geographic representation of OPE concentrations

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(Figures 2, 3, S1-3), as well as for plotting concentration against temperature and year (Figures S4a,b).

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The OECD POV and LRTP screening tool (“The Tool”) (20) (S4) was used to predict characteristic travel

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distances (CTD) and persistence (POV) of OPEs in air and water. The input data used and underlying

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methods were described by Zhang and Sühring et al. (8). In short, POV and CTD were estimated using

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partition coefficients (octanol-water and air-water) obtained from EPI Suite (21) (including literature

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data and estimates from the US EPA PBT profiler), Absolv (22) and SPARC (23). Environmental

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degradation half-lives were obtained from EPISuite (21), SPARC (23) and CATALOGIC (24). Data points

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with a value below Q1 – 1.5 IQR or above Q3 + 1.5 IQR were defined as outliers and removed from

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the input dataset, with Q1 = the first quartile or 25th percentile, Q3 = the third quartile or 75th

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percentile, and IQR being the interquartile range defined as Q3 – Q1.

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3. Results and Discussion

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3.1 Patterns of OPEs in the Canadian Arctic

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Fourteen OPEs were analyzed for this study, including three chlorinated OPEs (Cl-OPEs) and 11 non-

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chlorinated OPEs (non-Cl OPEs) (Table S1, we followed the OPE nomenclature of Bergman et al.

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(2012) (25)). Four of the 14 target analytes were detected in 50-97% of the samples, seven in ≤50%,

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and three were not detected.

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Cl-OPEs had the highest overall concentrations and detection frequencies with average

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concentrations over the entire sampling period and at all sites (excluding samples from Quebec City

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and the St. Lawrence River) of ΣCl-OPEs of 209 ± 242 pg m–3 and a detection frequency of 97%. TCEP

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had the highest average concentration of 173 ± 172 pg m–3 and 87% detection frequency. The high

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variability in concentrations was a result of including data from all years and all sites. Tris(2-

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chloroisopropyl)phosphate (TCIPP) had a lower average concentration of 86 ± 101 pg m–3 with

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detection in 89% of the samples. Tris(2,3-dichloropropyl) phosphate (TDCPP) was the least abundant

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Cl-OPE with an average concentration of 5.3 ± 8.3 pg m–3 and 75% detection frequency (Table 1,

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Figure 1; average and median concentrations per sampling year are presented in Table S4 and all data

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are presented in Tables S5 and S6).

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Most non-Cl OPEs were detected in significantly lower concentrations than Cl-OPEs (Student’s t-test

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at p< 0.05) (Tables 1 and S4, Figure 1). One exception was the high concentrations of TnBP from the

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land-based sampling site at Resolute Bay of up to 2340 pg m–3, for which no indications of sampling

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or analysis related contamination were apparent. The other exception was TPhP, the most abundantly

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detected non-Cl OPE, with a detection frequency of 90% and concentrations from below detection to

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1930 pg m–3, with higher concentrations from ship-based samples (median 4.7 pg m–3) (Tables 1, S4-

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S6, Figure 1). EHDPP was detected in 36% of the samples with concentrations ranging from below

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detection to 40 pg m–3. All other non-Cl OPEs were detected in less than 25% of the samples with

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detected concentrations between 1.7 pg m-3 (Tris(2-isopropyl phenyl) phosphate or TPPP) and 157 pg 7 ACS Paragon Plus Environment


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m–3 (TBEP) (Table 1, S4-S6, Figure 1). Tris-ortho-(cresyl) phosphate (ToCP), Tris(3,5-dimethyl phenyl)

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phosphate (TDMPP), and Tris(4-tert-butylphenyl) phosphate (TTBPP) were not detected in any of the

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samples (Table 1, S4-S6).

172 173 174 175

Figure 1: Concentrations (pg m–3) of OPEs in the filter fraction of air samples from the Canadian Arctic (2007–2013). The black horizontal line inside each box represents the median, the boxes represent the 25th and 75th percentiles of concentrations above the LOD, and the dots represent outliers.

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OPE concentrations were of the same order of magnitude as those reported by Salamova et al. (12)

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and Möller et al. (11). They found median OPE concentrations from 9 pg m–3 (Tris(2-ethylhexyl)

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phosphate (TEHP)) to 85 pg m–3 (EHDPP) in the Norwegian Arctic (12), and from 1 pg m–3 (TEHP) to

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289 pg m–3 (TCEP) in the Arctic Ocean north of Alaska (11).

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The higher concentrations of Cl-OPEs compared to non-Cl OPEs are not surprising. Cl-OPEs are

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generally more persistent in the environment than non-halogenated OPEs (26) and have, historically,

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been produced and used in larger quantities (1).

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The high concentrations and detection frequency of TCEP reflects its continued use in North America

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and Asia. Whereas use and production of TCEP have been restricted under the REACH legislation in

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Europe (27) and thus TCEP has been replaced by TCIPP in many applications (26). TCEP has, to this


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day, consistently been found in higher concentrations than TCIPP in samples from North America (28),

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the North Pacific and Arctic Ocean (11).

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In contrast to patterns of Cl-OPEs, patterns of some non-Cl OPEs were highly dependent on whether

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samples were taken from land- or ship-based sampling (Tables 1, S5 and S6, Figure 2).

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TPhP had the highest detection frequencies of 100 and 86% in both land- and ship-based samples,

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respectively, as well as the highest concentrations of non-Cl OPEs in ship-based samples with an

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average concentration similar to those of Cl-OPEs (84 ± 264 pg m–3) (Table 1). However, TPhP was not

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the predominant non-Cl OPE in land-based samples where its average concentration was 22 ± 26 pg

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m–3 (Table 1). The high contribution of TPhP to ship-based air concentrations matched observations

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made by Möller et al. (11), who reported TPhP as the predominant non-Cl OPE in ship-based samples

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from the North Pacific and Arctic Ocean. Similarly, TPhP dominated in ship-board samples taken in

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the Great Lakes (29).

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For land-based samples, TnBP had a 70% detection frequency at Resolute Bay and a high average

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concentration of 747 ± 876 pg m–3 (Table 1, Figure 2). In comparison, TnBP was only detected in one

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of the ship-based samples at a considerably lower concentration (97 pg m-3) (Table 1). TnBP is used in

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various hydraulic fluids and is a principal component in Skydol 500B-4, a commercial airline fire-

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resistant hydraulic fuel (30). A potential source for the high levels of TnBP at Resolute Bay could be

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the local airport, which is an important transportation center and refueling stop for aircraft travelling

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towards the high Arctic (31). High levels of TnBP have previously been linked to emissions from

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airports (32).



207 208 209

Figure 2: Distribution of total non-Cl OPEs [pg m-3] in in the filter fraction of air samples from the Canadian Arctic from 2007 to 2013 (Map from (19)).

210 211

Similarly to TnBP, EHDPP and TmCP were detected in most (77% and 69%, respectively) of the land-

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based samples (Figure 2, Table 1), whereas they were only detected in 16% and 10%, respectively, of

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the ship-based samples. In contrast to TnBP, EHDPP and TmCP have no known, unique use that could

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explain the high detection frequencies at land-based sampling stations compared to ship-based

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samples. These results suggest that TnBP, EHDPP and TmCP primarily originate from local sources

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such as airports, harbors and settlements, rather than from long-range transport. The high

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abundance of both TnBP and EHDPP in air samples from land-based sampling was also reported for

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the Norwegian Arctic by Salamova et al. (12).

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Other non-Cl OPEs (TBEP, TpCP, TEHP and TPPP) could only be detected in air samples from the ship-

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based sampling at detection frequencies below 20% (Tables 1, S4 and S5).

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Table 1: Average ± standard deviation and median concentrations (range) in pg m–3 as well as N = the number of samples the compound was sought in, detection frequency (Det.) [%] for individual OPEs, ∑OPEs, ∑Cl-OPEs and ∑non-Cl OPEs from ship-based (left) and land-based (right) filter fraction of samples. Ship-based

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Land-based Det. [%]

N

55 (n.d.-660) 128 (n.d.-856)

92 85

2.7 ± 2.9

1.7 (n.d. -13)

72

74

84 ± 264

4.7 (n.d.-1930)

EHDPP TmCP

51 51

1.2 ± 2.9 0.27 ± 1.1

TEHP TnBP

51 42

TpCP TBEP

N

Average

Median

Temp. [oC]

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1.5 ± 6.3

1.5 (-12-12)

TCIPP TCEP

74 74

85 ± 105 187 ± 181

TDCPP

74

TPhP

Det. [%]

Average

Median

43

-8.7 ± 13

-4.7(-35-16)

18 18

92 ± 88 118 ± 120

54 (n.d.-276) 72 (n.d.-433)

78 94

43

10 ± 12

4.8 (n.d.-46)

81

86

26

22 ± 26

12 (1.2-96)

100

n.d. (n.d.-11) n.d. (n.d.-7.0)

16 10

26 16

11 ± 13 0.60 ± 0.48

3.7 (n.d.-40) 0.78 (n.d.-1.7)

77 69

0.56 ± 1.4 2.3 ± 15

n.d. (n.d.-7.5) n.d. (n.d.-97)

18 2

0 10*

n.a. 747 ± 876*

n.a. 416 (n.d.-2340)*

n.a. 70*

42 5

0.22 ± 0.86 n.a.

n.d. (n.d.-4.8) n.d. (n.d.-157)

7.1 20

0 10

n.a. n.d.

n.a. n.d.

n.a. 0

TPPP ToCP

42 51

n.a. n.d.

n.d. (n.d.-1.7) n.d.

2.4 0

0 13

n.a. n.d.

n.a. n.d.

n.a. 0

TDMPP TTBPP

42 42

n.d. n.d.

n.d. n.d.

0 0

0 0

n.a. n.a.

n.a. n.a.

n.a. n.a.

∑ OPE

74

363 ± 409

237 (n.d.-2445)

97

43

291 ± 591

50 (2.7-2588)

100

∑ Cl-OPE 74 274 ± 259 187 (n.d.-1172) ∑ non-Cl OPE 74 89 ± 279 5.4 (n.d.-1944) *only analyzed at Resolute Bay for land-based sampling

96 92

43 43

97 ± 158 194 ± 524

27 (2.7-720) 7 (n.d.-2397)

100 60

227 228

3.2 Apparent Geographic and Temporal Trends

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Geographic and temporal trends discerned here were calculated from a compound’s median

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concentration taken from each year’s cruise track that varied geographically from year-to-year

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whereas sampling and analytical methods remained the same (Figure S1). Jantunen et al. (16) also

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assessed apparent geographic and temporal trends of pesticides in Arctic air measured in the same

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samples. We say “apparent” trends to acknowledge the variations in locations of samples taken year-

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to-year.

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Ship-based OPE concentrations showed some interesting geographic patterns. Unsurprisingly, the

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highest overall OPE concentrations and most individual OPEs were detected furthest south in the

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Saint Lawrence River close to Quebec City (Table S5). Since OPEs are predominantly used in consumer



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products, furniture and building materials (1, 2, 5), high concentrations around cities are expected

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and have been repeatedly documented (1, 3, 28, 33).

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Interestingly, Cl-OPEs appeared to have contamination “hotspots” around mouths of major rivers,

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notably the Nelson and Churchill Rivers (with a drainage basin of over 1,000,000 km2 in the provinces

242

of Alberta, Saskatchewan and Manitoba) as well as the Churchill River and Lake Melville that

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discharge at the Labrador coast (with a drainage area of 80,000 km2 in Labrador) (significant outliers

244

based on 25th and 75th percentile) (S3, Figure 3). Apart from these “hotspots” and excluding the

245

sampling stations at Quebec City, concentrations of Cl-OPEs decreased significantly with increasing

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latitude (degree north [oN]) (Tables S5 and S7). In contrast, non-Cl OPEs did not show a significant

247

decreasing trend towards northern regions (r = –0.4, p > 0.05) (Figures 2, Tables S5 and S7).

248 249 250

Figure 3: Geographic distribution of total Cl-OPEs [pg m-3] in the filter fraction of air samples from the Canadian Arctic from 2007 to 2013 (Map from (19)).

251 252

Table 2 summarizes apparent temporal trends reported as the percentage increase or decrease in

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annual median concentrations between 2007 and 2013 from ship based sampling only (excluding

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samples from Quebec City and the St Lawrence River). Concentrations of Cl-OPEs and most non-Cl

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OPEs did not change significantly over time, apart from a significant annual increase from 2007–2013 12 ACS Paragon Plus Environment

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of TPhP by 109% (p = 0.044, r2 = 0.65) (Table 2, Figures S4a and S5). This 7-year trend suggests a

257

doubling time in TPhP concentrations of 335 days (11 months). The only non-Cl OPE with a tendency

258

to decrease (not statistically significant, but p = 0.075, r2 > 0.5) was TEHP with a 31% annual decrease

259

(Table 2). TPhP was the driving force behind the significant increase in the Σnon-Cl-OPEs.

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None of the Cl-OPEs showed any significant apparent temporal trend. TCEP and TDCPP

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concentrations appeared to decrease slightly (Figure S4b), whereas TCIPP was the only Cl-OPE with

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slightly increasing concentrations (27% annual increase, p = 0.11, r2 = 0.51) (Table 2). An increasing

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trend of TCIPP concentrations would be consistent with increasing use due to restrictions placed on

264

TCEP as discussed in Section 3.1.

265 266 267 268 269

Table 2: Median concentrations [pg m–3] (range) for all ship- and land-based samples (excluding samples from the Quebec City and St. Lawrence River), number of values (N), annual increase/decrease in concentration from 2007–2013 from ship-based sampling [%], r2 and p value of the observed trend as well as confidence interval [%]; statistically significant trends are marked with*, trends with r2 > 0.5 are marked with +. Bold indicates a significant p-value.

Compound

Median [pg m ]

N

Increase/ decrease [%]

r

p

confidence interval [%]

∑OPEs

148 (2.7-2588)

84

24

0.38

0.188

95

∑ Cl-OPEs ∑ non-Cl OPEs

135 (2.7-1172) 6.4 (0.54-2397)

84 84

-3.5 164*+

0.01 0.73

0.8 0.031

95 95

TEHP TBEP

n.d. (n.d.-7.5) n.d. (157)

50 58

-31 6.6

0.59 0.01

0.075 0.86

95 95

EHDPP TPhP

n.d. (1.1-40) 7.3 (0.37-1930)

55 81

1.8 109*+

0 0.65

0.89 0.044

95 95

TnBP TCIPP

n.d. (n.d.-2340) 55 (n.d.-660)

59 81

67 27+

0.29 0.51

0.27 0.11

95 95

TCEP TDCPP

119 (5.3-856) 2.9 (n.d.-46)

74 67

-10 -3.8

0.26 0.03

0.301 0.72

95 95

-3

+

2

270 271

3.3 Driving factors for OPE contamination in the Canadian Arctic

272

The apparent geographic distribution and temporal trends of the OPEs presented here suggest

273

differences in emissions, sources and transportation pathways to the Canadian Arctic and/or

274

degradation of Cl- and non-Cl OPEs.



275

The higher concentrations around river mouths are consistent with river discharge of dissolved Cl-

276

OPEs and subsequent volatilization. The higher water solubility of Cl-OPEs compared to non-Cl OPEs,

277

and therefore primary partitioning into the water phase, has been reported previously (34-37).

278

Increased rates of volatilization are expected at the river mouth as Cl-OPEs are “salted-out”, i.e. their

279

solubility decreases in salt water compared to fresh water (38, 39). Moreover, the OECD POV and LRTP

280

Screening Tool (the Tool) predicts that Cl-OPEs have a longer characteristic travel distance (CTD) in

281

water enabled by their higher persistence (POV) in water (due to resistance to neutral hydrolysis (2))

282

compared to air (Table 3).

283

In contrast, for non-Cl OPEs the Tool yields low POV and CTD in water because of the potential for

284

hydrolysis. Interestingly, the most frequently detected non-Cl-OPEs or those with the highest

285

concentrations, namely TPhP, TnBP, TCP and EHDPP, have a similar or greater POV in water than POV in

286

air or, in case of TnBP, comparably low POV in air. All other non-Cl OPEs had significantly lower POV in

287

water than POV in air (Table 3). This suggests a potential combination of water-based and atmospheric

288

transport in addition to the local sources of TnBP and EHDPP discussed above (Section 3.1) (Table 3,

289

highlighted).

290 291 292

Table 3: Characteristic travel distance (CTD) [km] and persistence (POV) [h] of OPEs in air and water predicted by the OECD POV and LRTP Screening Tool; POV in water exceeding POV air (EHDPP, TCP, TPhP) and low POV air of TnBP are bolded. CTD air [km]

CTD water [km]

POV [h]

air

POV water [h]

TCIPP

117

338

1464

4704

TDCPP TCEP

107 179

445 225

13800 864

6240 3120

TTBPP

2853

121

8160

6240

TPPP TDMPP

2739 1968

62 75

2724 2136

1320 1320

TEHP EHDPP

1475 234

22 80

1176 900

336 1128

TCP TPhP

179 437

225 82

864 168

3120 1128

TnBP TBEP

67 41

21 47

12 1512

288 648

293 14 ACS Paragon Plus Environment

Page 14 of 20

Page 15 of 20


294

These results suggest that the contamination of Cl-OPEs in the Canadian Arctic is a result of their use

295

within those watersheds in Canada and the subsequent discharge into rivers, similarly to the

296

transport to the Arctic of nutrients (40, 41) and radioisotopes (42). The observed lack of an apparent

297

temporal trend for Cl-OPEs (Section 3.3) could be either a result of stable emissions, or could be an

298

artifact of increasing emissions in combination with an increase in water discharge and therefore

299

dilution of the OPE concentration in the watersheds. For example, the water discharge of the

300

Winnipeg River, which discharges into the Nelson River, has increased by 80% compared to the

301

beginning of the 20th century (43). High reported concentrations of OPEs in surface waters (44–46)

302

and their limited retention in wastewater treatment facilities (32) could thus be a significant source of

303

the Cl-OPE concentrations in the Canadian Arctic. Legislative actions taken in Canada, similar to those

304

taken by the EU, could therefore have a significant impact on the concentrations of these compounds

305

in the Arctic environment.

306

In contrast, occurrence of the non-Cl OPEs (excluding TnBP and EHDPP) reported here was more likely

307

primarily a result of long-range atmospheric transport. The lack of a geographic pattern was

308

consistent with the predicted CTD in air of > 1000 km for many non-Cl OPEs discussed here (Table 3).

309

The very low predicted CTD for TnBP in air and water further supports the hypothesis that its high

310

concentrations measured at Resolute Bay were a result of local sources (Table 3).

311

These hypotheses of local (TnBP), river (Cl-OPEs) and atmospheric transport (e.g., TPhP and other

312

non-Cl-OPEs) were further supported by the analysis of the temperature dependence of the OPE

313

concentrations (Table S8, Figures S4a,b,). Cl-OPEs showed an overall and significant temperature

314

dependence (p < 0.05) (Table S8), supporting the hypothesis of volatilization from water as a

315

potential source. Conversely, non-Cl OPEs, except for EHDPP, did not display significant temperature

316

dependence, even for the frequently detected TPhP (Table S8, Figure S4a).

317

Due to their supposedly low persistence in the environment, non-Cl OPEs have been proposed as

318

“environmentally friendly” alternatives for BFRs and especially the restricted polybrominated



319

diphenylethers (PBDEs) (6). The detection and significantly increasing concentrations of non-Cl OPEs,

320

and especially TPhP in the Arctic Ocean (11), Canadian Arctic (this study), as well as the European

321

Arctic (12), raises the question as to whether non-Cl OPEs are indeed suitable replacements for BFRs

322

from an environmental perspective. This question is especially important since the concentrations of

323

OPEs consistently exceed the concentrations of BFRs (including PBDEs) in Polar Regions (11-14, 47).

324

Moreover, increasing evidence indicates that Cl- as well as non-Cl OPEs have endocrine disruptive

325

properties (48, 49), reproductive or developmental toxicity (50, 51) and, in the case of Cl-OPEs,

326

carcinogenicity (1, 50). Thus, several current use Cl- and non-Cl OPEs could have hazardous properties

327

or behavior similar to the compounds they are replacing and, despite their lower persistence, reach

328

Polar and other remote regions.

329

4. Acknowledgements

330

We thank ArcticNet, Northern Contaminants Program (Indigenous and Northern Affairs Canada) and

331

Chemicals Management Plan (Environment and Climate Change Canada) for financial support.. Support

332

was also provided by the Czech Ministry of Education, Youth, and Sports (LM2015051) and Masaryk

333

University (CETOCOEN PLUS project). Terry Bidleman is thanked for his guidance and support over the

334

years. We thank Martina Koblizkova, Justin Poole, Cecilia Shin, Autur Pajda, Anya Gawor, Charles

335

Geen, Yushan Su, Camilla Teixeira and Derek Muir (Environment and Climate Change Canada) for field

336

and/or laboratory support. We thank the crew of the CCGS Amundsen, the University of Laval, Allison

337

MacHutchson (DFO), Joanne Delaronde (DFO), Alexis Burt (UofM) and Garry Codling (RECETOX, Czech

338

Republic) for help in sampling. We also thank the Canadian Forces Station Alert for supporting data

339

collection, the Centre for Global Science, University of Toronto, and the Northern Science Training

340

Program for supporting Fiona Wong and Tim Papakyriakou, Brent Else and Bruce Johnston (UoM) for

341

meteorological data, field support and data processing.


Page 16 of 20

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342

Supporting Information Available: Details on target compounds, methods, quality control and results

343

per compound and sampling sites. This material is available free of charge via the Internet at

344

http://pubs.acs.org.

345 346

5. References

347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381

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Organophosphate Esters in Canadian Arctic Air: Occurrence, Levels

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