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Persistent Organic Pollutants in the East Antarctic Atmosphere: Inter-Annual Observations from 2010-2015 Using High-Flow-Through Passive Sampling Susan Bengtson Nash, Sean Wild, Darryl W. Hawker, Roger Cropp, Hayley Hung, Frank Wania, Hang Xiao, Pernilla Bohlin Nizzetto, Anders Bignert, and Sara Broomhall Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b04224 • Publication Date (Web): 09 Nov 2017 Downloaded from http://pubs.acs.org on November 12, 2017
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Persistent Organic Pollutants in the East Antarctic Atmosphere: Inter-
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Annual Observations from 2010-2015 Using High-Flow-Through Passive
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Sampling
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Susan M. Bengtson Nash*a; Sean J. Wilda; Darryl W. Hawkerb; Roger A. Croppb; Hayley
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Hungc; Frank Waniad; Hang Xiaoe; Pernilla Bohlin-Nizzettof; Anders Bignertg Sara
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Broomhallh
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a
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170 Kessels Road, Nathan, QLD 4111, Australia
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c
The Environmental Futures Research Institute, bSchool of Environment, Griffith University,
Air Quality Processes Research Section, Environment and Climate Change Canada, Ontario
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M3H 5T4, Canada
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d
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Ontario MIC 1A4, Canada
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e
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Environment Chinese Academy of Sciences, Xiamen 361021, China
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Department of Physical and Environmental Sciences, University of Toronto, Scarborough,
Centre for Excellence in Regional Atmospheric Environment, Institute of Urban
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NILU - Norwegian Institute for Air Research, 2027 Kjeller, Norway
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g
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h
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2600, Australia
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*Corresponding Author: Susan Bengtson Nash, Email:
[email protected] Swedish Museum of Natural History, 11418 Stockholm, Sweden Chemicals Management, The Australian Department of the Environment and Energy, ACT
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Table of Content Art
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Abstract
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In the first multi-year sampling effort for POPs in the eastern Antarctic atmosphere, 32 PCBs
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and 38 organochlorine pesticides were targeted in air collected with a high-flow-through
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passive sampler. Agricultural chemicals were found to dominate atmospheric profiles, in
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particular HCB and endosulfan-I, with average concentrations of 12,600 and 550 fg/m3,
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respectively. HCB showed higher concentrations in the austral summer, indicative of local,
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temperature-dependent volatilisation, whilst endosulfan-I appeared to show fresh, late-
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austral-summer input followed by temporally decreasing levels throughout the year. The
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current-use herbicide, trifluralin, and the legacy pesticides mirex and toxaphene, were
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detected in Antarctic air for the first time. Trifluralin was observed at low but increasing
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levels over the five-year period and its detection in the Antarctic atmosphere provides
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evidence of its persistence and long-range environmental transport capability. Whilst a time-
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frame of five years exceeds the duration of most Antarctic air monitoring efforts, it is
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projected that continuous monitoring at the decadal scale is required to detect an annual 10%
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change in atmospheric concentrations of key analytes. This finding emphasizes the
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importance of continuous, long term monitoring efforts in polar environments that serve a
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special role as sentinel environments of hemispheric chemical usage trends.
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Introduction
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Persistent Organic Pollutants (POPs) are ubiquitous contaminants in the global environment.
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In recognition of the toxicological threat posed by these chemicals, in addition to their shared
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properties of persistence, capacity to bioaccumulate and undergo long-range environmental
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dispersal, the United Nations Environment Programme Stockholm Convention (SC) on POPs
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was implemented in 2004.1 The purpose of the SC is to eliminate or restrict the emission,
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production and use of annexed POPs globally, as well as to provide guidance for their
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management, disposal and storage. Under the SC’s Global Monitoring Plan (GMP), ongoing
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monitoring of POPs in human blood, breast milk, and air is undertaken with the ultimate aim
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of identifying temporal trends, and hence evaluating the effectiveness of the SC in achieving
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its goals.2
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Owing to their semi-volatile and persistent nature, the majority of POPs disperse through
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Long Range Atmospheric Transport (LRAT).3 Volatilised fractions are amenable to
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atmospheric transport away from source regions. As volatility is temperature dependent,
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POPs can deposit at higher latitudes and altitudes, potentially undergoing one or more cycles
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of volatilisation and deposition.4, 5 Prevailing low temperatures in polar environments favour
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their retention by “cold trapping” and further enhance their persistence.6, 7 As regulation has
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reduced emissions in temperate and tropical source regions, with time, an increasing
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proportion of the remaining global burden of more volatile POPs is expected to occur at polar
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latitudes. The circulation systems of the northern and southern hemispheres effectively
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operate as two separate compartments,8 hence the magnitude of Arctic and Antarctic POP
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contamination is principally a function of hemispheric chemical usage and the efficiency with
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which a compound of interest is transported to high latitude environments.9 As such, POP
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concentrations in the polar atmosphere can provide valuable information regarding
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hemispheric emissions of these chemicals, with minimal interference from local sources.10 In
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the context of the GMP, the Earth’s polar regions serve a special role as sentinel
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environments for the evaluation of the effectiveness of global regulatory measures, which are
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offset by the influence of emissions from nations that have not yet ratified the SC (and have
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no national chemical control regulations), as well as those where phase-out of chemicals is
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still underway. In addition, and of increasing importance in the face of escalating global
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chemical usage,11 detection of chemicals in remote regions serves as direct, empirical
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evidence of a candidate compound’s persistence and long-range environmental transport
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potential, identifying criteria for POPs under the SC.12
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Measurements of POPs in the Antarctic atmosphere remain limited, despite their value for
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furthering effective chemical management. Comparison, synthesis and extrapolation of
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available measurements is further impeded by primarily short sampling campaigns,
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significant geographical bias across the continent, as well as a large diversity in sampling
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approaches and targeted compounds.13 Notwithstanding this, to our knowledge, there have
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been nearly thirty published studies aimed at measuring POPs (both legacy and modern) in
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air masses of the Antarctic region, with the first sampling campaign conducted in 1980.
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Seven of these studies have employed land-based, high-volume or super high-volume active
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air sampling methods (Figure S2), with two studies originating from the Ross sea region,14, 15
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two from the Antarctic Peninsula region,16,
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from the Prydz Bay region of Princess Elizabeth Land in the eastern Antarctic sector.19
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Continuous monitoring over several years (2007 onwards) has only been performed at one
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site, the Norwegian Troll station in Queen Maud Land.20 In order to be suitable for robust
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temporal trend analysis, data must satisfy basic quality criteria such as being derived from
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comparable monitoring and analytical methods.21 Further, the monitoring period must extend
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across a sufficiently long time period to enable the detection of trends above seasonal and
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inter-annual noise. The value of such long-term monitoring efforts in furthering our
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one from the Weddell Sea region,18 and one
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understanding of the environmental behaviour of these chemicals has been clearly
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demonstrated in the Arctic through continuous sampling records dating back to the early
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1990s e.g.22-25 With the notable exception of the Norwegian measurements at Troll station,20
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all Antarctic studies to date have been conducted over limited time frames, and are thus
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unsuitable for trend derivation and GMP monitoring efforts.
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Here we report findings from the first five years of atmospheric monitoring for POPs in the
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Eastern Antarctic sector. Measurements were made with a high-flow-through passive
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sampler, developed for measuring trace contaminant levels in remote atmospheres,26 and
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previously deployed on the Tibetan plateau and in the Arctic.27,
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These first inter-annual
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data on atmospheric POP contamination in Eastern Antarctica constitute an important
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baseline for continued spatial and longitudinal monitoring of POPs. Similarly, the data
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provide a foundation for the investigation of the environmental behaviour and toxicological
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threat of POPs in Antarctic ecosystems, as well as empirical evidence for the persistence and
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LRAT capabilities of compounds under consideration by the SC.
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Methods
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Sampling. Atmospheric sampling of gaseous and particle-bound POPs was undertaken with a
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high-flow-through sampler described previously.26 The sampling period covered 5 years from
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December 2009 to November 2014. All samples were collected at the abandoned Wilkes
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Station, 3 km north of Australia’s Casey Station (66°16’56”S 110°31’32”E), the largest of
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Australia’s three Antarctic research stations. The prevailing easterly wind direction in this
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coastal region ensured that there was minimal influence on the sampling site from local
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Casey station activities (Figure 1). The sampler consists of a cartridge, containing three
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polyurethane foam (PUF) units in series, mounted horizontally in an aerodynamically shaped
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housing on a post with a rotatable joint (Figure S1 in Supplementary Information (SI)).
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Through quantitative experimentation, Xiao et al. (2007)26 found that the sampler can be
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expected to collect both gaseous semi-volatile organic compounds, and those sorbed to
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atmospheric particles. The sampler is designed to turn towards oncoming wind to maximise
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airflow through the PUF unit, thus capturing significantly greater air volumes than traditional
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passive air samplers, and indeed, volumes comparable to those of active high-volume
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samplers. As sampling rate with the flow-through approach becomes dependent upon wind
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speed, uptake is no longer controlled by molecular diffusion and the accumulation of gas-
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phase compounds and particles is more similar to high-volume air samplers than the
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diffusion-based uptake in other passive air samplers.28 In contrast to active air samplers,
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however, the high-flow-through sampler requires no electricity therefore permitting sampling
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away from power sources and inhabited areas in general.
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Regional map, sampler image and location map of Casey station and the
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Figure 1
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surrounding area, indicating the air-sampling site relative to the station. Location map
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supplied by the Australian Antarctic Division (AAD) Data Management Centre
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A total of 33 sample sets (denoted as samples A to I1) were obtained during the 5-year
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sampling period, with the first six samples being deployed for approximately three months
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each. The sampling interval was subsequently shortened to 4-6 weeks for the remainder of
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the campaign. Details (sample ID, sampling period, sampled air volume) are presented in
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Table S1. The SI also details how the air volumes were derived from ambient wind speed.27,
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was deployed on a post adjacent to the sampler at the same height. Air volume sampled with
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the flow-through sampler was calculated in two steps; Firstly, the speed of air passing
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through the sampler was determined from that outside of the air sampler using the
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relationship previously developed by Xiao et al. (2008)29 (Equation S1). The air speed
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passing through the sampler (m/s) was then multiplied by the cross-sectional area of the
In brief, an anemometer (inspeed.com), connected to a data logger (MadgeTech Pulse 110)
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sampler and sampling duration, thus providing the sampling volumes, which were adjusted
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for ambient conditions (Equation S2).
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The Australian Bureau of Meteorology (BOM) measures local temperature, atmospheric
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pressure as well as wind speed at nearby Casey Station. Surrogate wind data were obtained
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from the local BOM station when data loggers failed to record data for part of, or the whole
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deployment period. Whilst localised wind differences between the BOM station and the
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abandoned Wilkes station were evident, these were not consistent and the BOM site was
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considered an adequate approximation of wind conditions in the area.
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Sample Preparation and Handling. PUF units (P10z polyester PUF, Pinta Foamtec,
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Minneapolis, MN) were pre-cleaned by scrubbing under hot water followed by successive
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24-hour Soxhlet extraction with petroleum ether and acetone, respectively. They were then
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dried in a desiccator under pure N2 flow and sealed in furnaced glass jars with Teflon‐lined
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lids until deployment. All solvents (SupraSolv, Merck, Germany) and gases (BOC, Australia)
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were of the highest purity and selected for their specific application to ultra-trace analysis.
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Each sample-set consisted of three sample PUF units plus two PUF units as travel blanks,
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cleaned and handled in an identical manner to the sample PUFs. Each sample set was
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transported in water-tight Pelican™ cases to and from Antarctica. PUFs were deployed and
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collected by trained personnel using solvent rinsed tongs. Travel blanks were briefly exposed
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to ambient air during deployment and collection of sample PUFs. Collected samples were
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maintained at
