Norsk institutt for luftforskning
NORACIA: IMPACT OF CLIMATE CHANGE ON TRANSPORT AND
DISTRIBUTION OF PERSISTENT ORGANIC POLLUTANTS (POPS) IN THE
ARCTIC ENVIRONMENTS
Contributing authors
Norwegian Institute for Air Research (NILU)
Georg H. Hansen (NILU)
Roland Kallenborn (NILU),
Henrik Kylin (NILU),
Sabine. Eckhardt (NILU).
John Burkhart (NILU),
Andreas Stohl (NILU)
David Hirdman (NILU)
Harald Sodemann (NILU)
Vladimir Pavlov (Norwegian Polar Institute)
With support from
Hayley Hung (Environment Canada),
Sara Becker (Lancaster University, UK),
Et institutt i Miljøalliansen
NILU
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Table of Contents
Glossary ............................................................................................................................................... 3
Highlights ............................................................................................................................................ 4
Aim of the work ................................................................................................................................... 5
Acknowledgement ............................................................................................................................... 5
Scientific Background ......................................................................................................................... 6
Relevant scientific findings – a literature survey ................................................................................ 7
Atmospheric transport and distribution ........................................................................................... 7
Marine and terrestrial environments .............................................................................................. 11
Transport pathways and source elucidation....................................................................................... 14
Atmospheric transport ................................................................................................................... 14
Model characterisation .............................................................................................................. 14
Calculation baseline ................................................................................................................... 15
Transport climatologies for selected Arctic stations ................................................................. 15
Modelled anthropogenic influence ............................................................................................ 18
Transport of biomass burning emission into the Arctic ............................................................ 21
Is direct atmospheric transport the dominant mechanism? ....................................................... 23
Oceanic transport ........................................................................................................................... 24
Ocean currents in the Arctic ...................................................................................................... 24
Investigations of oceanic and ice transport................................................................................ 25
Numerical studies ...................................................................................................................... 25
Consequences and perspectives ......................................................................................................... 28
International research on climate and contaminants in the Arctic ................................................. 29
Consequences and scenarios .......................................................................................................... 29
Atmospheric transport ............................................................................................................... 30
Ocean current transport ............................................................................................................. 30
Ice coverage - Sea ice scenarios ................................................................................................ 31
Glacial ice coverage................................................................................................................... 31
Industrial activities and infrastructures ...................................................................................... 31
Accessibility for transportation and tourism ............................................................................. 32
New contaminant sources .......................................................................................................... 32
The way ahead ................................................................................................................................... 33
Scenario descriptions ..................................................................................................................... 33
Present knowledge gaps................................................................................................................. 33
Conclusions ....................................................................................................................................... 33
References ......................................................................................................................................... 34
3
Glossary
AMAP :
AO:
BFR:
CACAR:
CO:
DDT:
DF
DHR
ECMWF:
EU:
HCH:
HCB:
IPCC:
IUPAC:
LRT:
NAO:
NCP:
POP:
PCB:
UNEP:
Arctic Monitoring and Assessment Programme
Arctic Oscillation
Brominated Flame Retardants
Canadian Arctic Contaminants Assessment Report
Carbon monoxide
IUPAC name: 1-chloro-4-[2,2,2-trichloro-1-(4-chlorophenyl)ethyl]benzene
Digital filtration
Digital harmonised Regression
European Centre for Medium-range Weather Forcast
European Union
Hexzachlorocyclohexane
Hexachlorobenzene
Interngovernmental Panel on Climate Change
International Union for Pure and Applied Chemistry
Long-range transport
North Atlantic oscillation
Northern Contaminants Program (Canada)
Persistent Organic Pollutants
Polychlorinated biphenyls
United Nations Environmental Program
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Highlights
An updated (per 2008) scientific review on climate related influences on the fate and distribution of
contaminants in the Arctic environment has been conducted. The following highlights summarize
the overall finding of the study:
1.) The Arctic region is identified as a sentinel for climate related effects on contaminant longrange transport.
2.) Positive trends for selected POPs (in particular HCB and PCB) in the Svalbard atmosphere
have been found in ambient air samples from the Zeppelin Station (Ny-Ålesund).
3.) A correlation has been found between the atmospheric -HCH levels (concentration
variations) in samples from the Zeppelin station and the North Atlantic Oscillation (NAO)
index, indicating some influence of direct atmospheric transport.
4.) There is new scientific evidence that the continuously ice-covered water masses of the
Arctic Ocean accumulated α-HCH while technical HCH was still used and at present act as
secondary sources of these pollutants.
5.) There is strong observational evidence that also biotic processes are of utmost importance
for transformation of POPs in the marine environment.
6.) Meridional gradient studies in Scandinavia indicate that α-HCH accumulates continuously
during the lifetime of spruce needles in boreal Arctic forests and can be released via forest
fires or aging of the plants.
7.) Based upon model calculation (FLEXPART) the anthropogenic influence on contaminant
loadings is calculated lowest at Alert (Canada) and highest at Zeppelin (Svalbard).
8.) Severe forest fire events in the boreal sub-Arctic forests could be directly associated with
elevated contaminant levels in the Svalbard region and at other Arctic sites.
9.) Comparison of atmospheric model calculations with observations on a climatological basis
indicates that direct atmospheric transport of pollutants is an explanation of high pollution
episodes in the Arctic, but fails in explaining longer-time-scale variability such as seasonal
variation.
10.) Model studies of marine transport of pollution indicate that the geographical spreading
critically depends on the source location: while emissions from the Kara Sea remain in the
same area, releases from Eastern Siberia and North American Coast are spread widely in
the Arctic Basin.
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Aim of the work
The Norwegian ACIA follow-up programme NorACIA (Norwegian Arctic Climate Impact
Assessment) has the goal to study climate change (CC) and its effects on ecosystems as well on
other processes connected to CC and ecosystems such as pollution transport in the Norwegian
Arctic, especially the Barents Sea and the Svalbard region. One of the first studies in the frame of
NorACIA investigated the pollution situation at Bear Island as monitored in biota samples there in
the period 1998-2005 and its possible relation to atmospheric transport. There were indications, but
no clear proof of that atmospheric transport changes were responsible for the large year-to-year
variations found in samples from glaucous gulls.
As Bear Island has been found to be a special case in terms of POP contamination, it was initiated
to put this study into a larger context, with a focus on comparative studies both in time, space, and
media/compartments. The present evaluation, which is the result of this extended study, is based on
a combination of direct expert contributions and literature surveys aiming at summarizing the state
of the science on relevant knowledge within the research topic ”Climate influences on transport and
fate of persistent organic pollutants in the Arctic”.
Acknowledgement
The report could not have been completed in the present form without the help of many colleagues.
The Norwegian Ministry of the Environment, through the Norwegian Pollution Control Authority
(SFT), supported the study financially.
The Norwegian Polar Institute coordinated the NorACIA program.
The Norwegian Institute for Air Research (NILU) provided information on the ongoing POP
monitoring at the Zeppelin station.
AMAP provided information on circumarctic POP distribution.
ECMWF provided the meteorological data for the model assessment presented.
The crew of the Swedish ice certified research vessel ”R/V Oden” supported the field work
reported by Henrik Kylin.
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Scientific Background
Persistent anthropogenic pollutants including Hg and radionuclides are transported via the
atmosphere, ocean currents and rivers into the Arctic. After entering the Arctic, the chemicals are
immediately redistributed within the region by the same transport pathways, and, in addition,
transpolar ice transport as well as incorporation into biological systems through accumulation in the
food web (figure 1).
Figure 1: The Arctic region, a sentinel area for global climate change processes. (with kind permission from UNEP,
GRID Arendal)
Every step along the transport and redistribution pathways to and within the Arctic can be
influenced by climate change processes because reactivity and adsorption processes, as well as
accumulation, are temperature dependent processes. At the same time, transport means such as
atmospheric motion and ocean currents are expected to change, sea and land ice is expected to
change (and in fact is already doing so), and so is the extent and composition of potential
intermediate storages of pollutants, such as forests and soils in sub-Arctic areas. Summing up all
these processes, changes in global climate and the associated environmental change in the Arctic
are expected to have significant consequences for contaminant pathways (Macdonald et al. 2005).
During the past decade, circum-Arctic national and international scientific and monitoring
programs including the Arctic Monitoring and Assessment Program (AMAP) have delivered a
wealth of evidence for the presence and distribution of xenobiotics (e.g., contaminants originating
from anthropogenic sources) in the Arctic environment. The first report in 2003 on potential impact
of global change processes on contaminant transport pathways and fate paved the way for new
ideas and studies on consequences of global change for Arctic pollution pathways (Macdonald et al
2003, 2005) As a consequence, numerous research activities were initiated in order to elucidate the
consequences of global change processes on occurrence, transport and fate of anthropogenic
pollutants in remote Arctic regions. However, the “state-of-the-science” is still far from complete
and needs comprehensive assessment. Such an assessment must be based upon a strong
international and interdisciplinary scientific co-operation. A combination of long-term monitoring
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(both atmosphere, ocean and terrestrial environment monitoring), regional campaign based studies
(e.g., impact of new emerging chemicals), modeling (e.g., air- and sea-borne, food-web
accumulation etc.) and ecotoxicological risk evaluation (e.g., laboratory studies and modeling) is
needed in order to tackle this challenge.
Today, it becomes more and more clear that a thorough science based understanding of temporal as
well as spatial distribution patterns including comprehensive source elucidation for selected
compounds is mandatory for an adequate assessment of all factors influencing chemical transport
processes (air and ocean- and ice-borne transport) as well as regional pathways leading to the
accumulation of selected persistent chemicals in the Arctic ecosystem.
Relevant scientific findings – a literature survey
According to the conclusions drawn from recent scientific studies (ACIA 2004; AMAP 2004,
Macdonald et al. 2005) climate change is expected to influence contaminant composition, sources,
pathways and distribution processes within the Arctic. This research area has developed into an
important multi-disciplinary research endeavour during the 6 years, since AMAP concluded that
significant changes have to be expected for the Arctic people and the environment within the
coming generation (Macdonald et al. 2003). Already today, the Arctic and Arctic environmental
monitoring programs serve as sentinel for the detection of indications for global climate change.
The most recent IPCC report (2007) concluded that the largest climate related environmental
changes have to be expected in Arctic regions. In the following chapters, published results are
presented confirming that already today influences of climate change on persistent organic pollutant
(POP) transport and distribution processes are evident.
Atmospheric transport and distribution
Atmospheric transport is believed to be the major transport pathway for volatile and semi-volatile
persistent pollutants into the Arctic (AMAP 2004). Thus, long-term monitoring programs at several
national research stations performed under the umbrella of the Arctic Monitoring and Assessment
Programme (AMAP) have continuously delivered level and pattern information on persistent
organic pollutants (POPs), trace metals and other types of human-made pollution in Arctic air
samples. For many of the stations, weekly/monthly concentration data are available for more than a
decade. The longest Arctic data series exist for the monitoring stations Alert (Ellesmere Island,
Canada) and the Zeppelin Atmospheric Research Station in Ny-Ålesund (Svalbard, Norway) dating
back to the early 1990s.
When discussing persistent organic pollutants (POPs) most of the scientific investigations cited are
based on scientific studies of either polychlorinated biphenyls (PCB) or hexachlorocyclohexane
isomers (HCH). HCH was used as insecticide until it was banned in most of the western world
during the 1990s. Originally the technical mixture as such was used for agricultural application
until the 1970s. Because of international application restrictions, the technical mixture was
successively replaced by pure -HCH (lindane), which is the only HCH isomer with insecticidal
effect. Nevertheless, technical HCH is the insecticide that was produced and used in largest
quantities worldwide from the 1940s until the 1970s as a replacement for DDT (Breivik et al.
1999). -HCH is dominating the technical HCH mixture (> 60%), while the insecticidal isomer, HCH (lindane), constitutes only 10-15% of the technical product, -HCH 5-12%, and the remaining
isomers are minor products. The isomer that accumulates most in biota and is most persistent in the
environment is -HCH. Because of their respective properties, dominance in the technical product,
insecticidal activity, and persistence, these three isomers are dominating environmental
investigations compared to other HCH isomers. HCHs have gained interest in the past as indicator
chemicals to understand the processes involved in the global environmental fate of a specific semivolatile, POP-like chemical.
8
An added benefit, when using α-HCH to investigate environmental processes, is that this isomer is
a chiral molecule as the only of 8 possible HCH isomers. Due to its unique molecular structure, HCH exists as two mirror images (enantiomers) which are not superimposable. The ratio of the
enatiomers can provide important scientific information about, e.g., biotic degradation and transport
processes because chirality is preserved during biological processes and thus enatiomers act as two
separate chemicals. The enantiomeric composition is described by the enantiomer fraction (EF:
Harner et al. 2000b) or the enantiomer ratio (E1/E2). A comprehensive summary about enantiomer
selective analytical methods and their scientific applicability can be found in a comprehensive
monograph (Kallenborn & Hühnerfuss 2001).
For all circum-Arctic atmospheric monitoring sites reporting to the AMAP data atmospheric
contaminants data centre at NILU (Kjeller, Norway), except for Zeppelin, negative temporal trends
are reported for all major POPs. At Zeppelin, significant decreasing trends are only reported for
hexachlorocyclohexane isomers (- and -HCH); this is shown in Figure 2.
Figure 2: Concentration distribution (pg/m3) of -HCH (hexachlorocyclohexane) in weekly collected Zeppelin air
samples from 1993 until 2005
A comparison of the available annual arithmetic means for the first and last year of sampling
periods for Alert (Canada) and Zeppelin (Svalbard) reveals a reduction of α-HCH of 26% and
39%, and γ-HCH of 13% and 15% for Zeppelin and Alert, respectively (Becker et al. 2008).
The HCH ratio (-HCH) is also an important indicator of potential emission sources. In
general, the ratios are lower at Zeppelin than at Alert, with the proportion of γ-HCH (i.e. γ/(γ +
α)*100) at Zeppelin ranging from 13 to 26%, compared to 8 - 26% at Alert. This is an indication of
the stronger influence of Eurasian source regions on the HCH levels determined at the Zeppelin
station compared to Alert (Becker at al. 2008).
Climate change is likely to influence contaminant transport pathways and transfer processes to, and
within, the Arctic as already postulated earlier (Macdonald et al., 2005). The North Atlantic
Oscillation (NAO) and Arctic Oscillation (AO) are today considered as two manifestations of the
primary circulation pattern in the Northern Hemisphere. These circulations are parameterized by
fluctuations in atmospheric sea-level pressures (SLP). In particular, the AO describes wind
speed/direction and precipitation rates at a Pan-Arctic scale (Becker et al. 2008). The correlation of
negative and positive phases of the AO to HCH concentrations was investigated in a recently
published study (Becker et al. 2008). The Dynamic Harmonic Regression (DHR) model fit was
applied on the respective datasets available from Alert and Zeppelin (Becker et al. 2008). A
correlation to AO fluctuations was found in the α-HCH time-series at Zeppelin, but not at Alert
(figure 3).
9
Model plot: alpha-HCH
R2=0.94525
2.5
Since 2000 the Arctic
Oscillation has been
predominantly in the
‘negative’ phase.
2
log pg/m3
1.5
1
0.5
During the 1990s the
Arctic Oscillation was
predominantly in the
‘positive’ phase
model uncertainty
model
data
0
1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
Figure 3: Influence of AO on the atmospheric distribution of -HCH in Zeppelin air data. The DHR model fit is
represented by the R2 and uncertainty is to within 95% confidence limits. Dashed lines represent the expected
differences between summer and winter concentrations assuming a constant decline (According to Becker et al. 2008).
The differences in intra-annual pattern distributions indicate that much larger concentration
variations between the summer and winter months are occurring during the years when AO is in the
negative phase (after year 2000). During positive AO years (before year 2000) the concentration
difference between summer and winter is much less pronounced. The dashed lines in Figure 3 show
the predicted variation in summer maxima and winter minima assuming a constant decline in
α−HCH air concentrations throughout the time series (Becker et al. 2008).
Although the method of Becker et al. (2008) is very intriguing, there are further aspects to be
considered. On one side, the AO/NAO index was relatively stable and positive for several years
until 1995, but much more variable and on an average neutral since, while the -HCH annual
variability signature has emerged in the latter period of AO variability. Another aspect to be
considered is the fact that the NAO/AO has a distinct but delayed impact on sea ice cover and
dynamics in the Arctic Ocean. It is hypothesized (e.g., Stroeve et al., 2008) that the period of
persisting high positive NAO/AO in the early 1990s triggered a massive export of multi-year ice
out of the Arctic Basin through the Fram Strait and thus influenced the recent dramatic summer sea
ice extent in the region decisively. The change in the sea ice regime may have promoted the reemission of HCH from intermediate storages (the ocean) to become the most important source of
HCH nowadays, which shows a more pronounced annual variation in accordance with sea ice
extent; this is discussed further below.
During the final evaluation of temporal and spatial trends for atmospheric POP levels in the Arctic
(3rd AMAP assessment), a comprehensive evaluation of long-term temporal trends in the POP data
available for several Arctic monitoring sites incl. Zeppelin (Svalbard) and Alert (Canada) was
conducted (Hung et al 2009). This information was also used for the first UNEP assessment on the
effectivity of the Stockholm convention on global POP distribution and reported to the Western
10
Europe and other countries group (WEOG) as a part of the AMAP-EMEP Programme summary
(October 2008).
A statistical trend analysis was performed using the Digital Filtration (DF) technique, which is a
sophisticated distribution independent statistical time series tool used in modeling of environmental
data sets to provide long term trend information and forecast scenarios (Hung et al. 2009).
For hexachlorobenzene (HCB), formerly used as a fungicide, but today released into the
environment as by-product of various industrial chemical processes, generally negative trends were
reported for all monitoring programs and stations. However, during the past 4 years the levels for
the Zeppelin station (Spitsbergen) have been increasing again (figure 4).
Figure 4. Temporal trend analysis for hexachlorobenzene (HCB) in Zeppelin air using statistical digital filtration (DF).
Please note: concentration values are given in a logarithmic scale (ln)
This feature is only observed at the Zeppelin station; no similar trends are reported from other
Arctic atmospheric monitoring sites including Alert. These increasing concentrations at Zeppelin
may be explained by increased evaporation of previously deposited HCB from open ocean along
the western coast of Spitsbergen which has been ice-free since from 2005 to 2008, including the
winter seasons. Although there has been a dramatic decrease in sea ice also in other parts of the
Arctic, a permanently ice-free state at 80º N is fairly unique, so that this signature could be
interpreted as a possible influence of regional climate change on the POP distribution in the Arctic
environment. Similar trends were seen at Zeppelin for middle chlorinated polychlorinated
biphenyls (penta- to hexa-chlorinated CBs) and dichlorodiphenyltrichloroethane derivatives (DDT).
However for DDT, the re-introductions as insecticide in the tropic regions for Malaria control
purposes and the related increased frequency of transport episodes from primary sources (direct
application in agriculture) in low-latitude source regions may also contribute to the currently
increasing levels in the North.
Also polychlorinated biphenyl (PCB) concentrations seem to have increased in air sampled at
Zeppelin during the past 4 years (after 2004). Sum concentrations (sum of the 10 PCBs in the
AMAP monitoring program) show a slightly positive trend (Hung et al. 2009). However, the
strongest contribution to this trend in PCB concentrations, based on reported levels of 33 individual
congeners, is derived from medium-chlorinated PCBs (penta- and hexa-chlorinated congeners), in
particular those congeners which are known to accumulate effectively in lipid-rich tissues of toppredating organisms in the Arctic like PCB 153 (figure 5).
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ln C (PCB 153)
2
1,5
1
0,5
0
-0,5
-1
-1,5
-2
-2,5
-3
1998
1999
2000
2001
2002
Seasonal Cycle
2003
Trend
2004
2005
2006
2007
Measured
Figure 5: Temporal trend analysis for PCB 153 (2,2’4,4’,5,5’-Hexa-CB) in Zeppelin air using statistical digital
filtration (DF). Please note: concentration values are given in a logarithmic scale (ln)
The reasons for this regionally limited significant increase of ”legacy” POPs monitored for more
than 15 years in the Svalbard region are currently under investigation. However, the influence of
local climate variations, including the predominant inflow of ”warm” Atlantic waters into the west
coast region of Svalbard and the resulting lack of ice coverage during the past 4 years may play an
important role. The marked increase of penta- and hexachloro-PCBs during the past years which
are characterized as semi-volatile with relatively low water solubility (Log KOW = 6.8) cannot be
solely explained by increased evaporation due to their relatively low volatility. A substantial
contribution from increased forest fire events from boreal regions and related Arctic haze events
may be considered as an important additional mechanism (Eckhardt et al. 2007).
Marine and terrestrial environments
The central Arctic is characterized by a marine environment, and the most pronounced effects of
long-range transport of pollutants are found in marine ecosystems and human societies depending
on these ecosystems. It is, therefore, natural to put special focus on conditions in the marine
environment. Data from three expeditions of the Swedish Research vessel “RS ODEN” to the
Central Arctic and the North Atlantic in 2001, 2002, and 2005 have been synthesised for this report,
with emphasis on the fate of organochlorines in the marine environment.
One must, however, not forget that the Arctic Ocean mostly is surrounded by vast landmasses,
which may also have an important – though presently very poorly understood - influence on the
poleward transport of pollutants. For this reason, also data from the terrestrial environment based
on large data sets from vegetation and lake sediments collected in northern Scandinavia have been
evaluated.
There is new scientific evidence that the water masses of the Arctic Ocean which are continuously
ice covered, accumulated α-HCH while technical HCH was still used as an insecticide in the
industrialised world. Today, the application of technical HCH as agricultural chemical is banned in
most of the western countries. Thus, there is no new input of α-HCH from primary application
sources in this part of the world. As a consequence, air concentrations of -HCH have continuously
decreased (see atmospheric data described earlier) so that the Arctic Ocean today is considered as
“oversaturated” with α-HCH relative to the atmosphere. Therefore, it is expected that the central
Arctic Ocean will serve as a direct source for this type of contaminants if the ice cover disappears
on a seasonal basis (as predicted in various climate change scenarios)
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One illustrative example for this effect, besides the long-term atmospheric monitoring programs at
Zeppelin and Alert, is shown in Figure 6 for Resolute Bay in the Canadian Archipelago (Jantunen
et al. 2008). While the sea was still ice-covered, the concentrations of α-HCH in the air were
relatively constant and the enantiomeric composition essentially racemic (the EF close to 0.5;
racemic mixture = the same amount of both enantiomers). This racemic distribution indicates that
α-HCH only had undergone long-range transport and no biotic degradation. But as soon as the ice
cover disappeared, the concentrations in the air rose and the EF changed towards the signature of
the surrounding waters. The shift in EF is considered as clear evidence that the origin of the α-HCH
in the air shifted from long-range transport to a more local secondary source in which biotic
degradation has taken place (aging processes).
A
B
Figure 6: Average air concentrations (A) and enantiomer fractions (B) at Resolute Bay before and after ice breakup.
After Jantunen et al. 2008.
In earlier scientific studies on the fate of organic pollutants in the Arctic it was presumed that the
degradation of POPs in the Arctic Ocean was dominated by abiotic processes. It was assumed that,
due to the low temperatures, biotic degradation was too slow to be of any significance. However,
when studying the enantiomeric signal of α-HCH it became clear that biotic processes were of
utmost importance. Furthermore, it became evident that the microbial communities in the Arctic
environments are adapted to the cold environments and are highly involved in biodegradation
processes, resulting in enantio-selective transformation patterns for chiral environmental pollutants.
In-depth studies of the EF at different depths in the Arctic Ocean made it possible to provisionally
calculate the degradation rates of the individual enantiomers (Kallenborn & Hühnerfuss 2001).
However, this calculation was based on a hypothetical calculation of the ventilation age of the
water mass, i.e., how long ago the water at a specific depth had been in contact with the atmosphere
and was loaded with racemic α-HCH.
During the Oden expeditions 2001 (Arctic Ocean NE and N of Svalbard), 2002 (Storfjorden, Fram
Strait, East Greenland Current to central Norwegian Sea), and 2005 (transect across the North Pole)
sampling was performed in co-operation with oceanographers using chlorofluorocarbons (CFCs) to
calculate the ventilation age of water masses at different depths. These data were used to refine the
calculation of the degradation rate of the α-HCH enantiomers with greater precision than would
have been possible without the CFC-data. An even more interesting point that can be drawn from
these calculations is that the degradation rates seem to be fairly constant in the Atlantic water mass,
irrespective of the latitude. A tentative conclusion to be drawn from this experiment is that Arctic
microorganism communities seem to be well adapted to the low ambient temperatures in the water
column (-1,8 - + 1 °C). Thus, slight variations (increase) of the water temperatures are not expected
to affect the degradation rates substantially, at least not if the increase is within the temperature
range found in the water masses investigated during the described field experiments (Kylin,
personal communication 2008).
13
The Arctic is surrounded by boreal forests. The effect of the boreal forests on the transport of
hydrophobic organic compounds to the Arctic has been discussed for many years (e.g., Su et al.
2007) and the views vary depending on the background of the individual researcher and the design
of the studies reported in the literature. The boreal forests constitute a large amount of biomass “in
the air” that could potentially affect/disturb long-range atmospheric transport of compounds that are
prone to partitioning to lipids. The green parts of vascular plants are covered by a hydrophobic
cuticle comprising waxes and cutin, the latter essentially a polymeric lipid that will adsorb
hydrophobic compounds from the air.
The models that have gained most interest (Czub et al 2008) indicate that compounds with physicochemical properties similar to HCHs will not accumulate to great extent in the vegetation. Typical
examples of such compounds are the HCHs and HCB that have a vapour pressure sufficiently low
to be mainly transported in the gas phase at most environmentally relevant temperatures with very
little binding to airborne particles. An interesting and illustrative compound for this discussion is
again α-HCH.
After the official ban of technical HCH, the air concentrations of α-HCH in Europe are more or less
the same all year round with negative trends all over Europe including the Arctic. A compound
with these properties should, according to the models, attain higher concentrations in the vegetation
during winter, when low temperatures favour deposition, than during summer when the
volatilization is more rapid. In a three year long study on the uptake of airborne POPs into Scots
pine needles performed at Stockholm University, Sweden, it was shown that instead of the modelpredicted seasonal concentration variation, α-HCH accumulates continuously during the lifetime of
the needles (figure 7). Furthermore, most of the accumulation took place during the spring and
summer when volatilization, according to the model, should prevail over deposition, while very
little concentration change took place during the cold season when deposition should prevail.
(Kylin, personal communication 2008).
Figure 7. Seasonal accumulation of α-HCH in Scots pine needles at Stockholm in comparison with a schematic
presentation of the seasonal variation in air concentrations (not quantitative). Red curve: approximation of the seasonal
variation in needle concentrations predicted by the models.
That the above-mentioned model does not describe the uptake process very well becomes obvious
when one compares the accumulation of α-HCH with the accumulation of -HCH. The main part of
the field sampling was performed when -HCH (lindane) was still used extensively in Southern
Europe. This was reflected in a prominent spring concentration peak of -HCH in the air which
appeared significantly higher than the air concentrations measured at other times of the year. In
spite of the very different seasonality pattern between α-HCH and -HCH, the uptake patterns in the
needles are surprisingly similar. The continuous accumulation of both compounds throughout the
14
lifetime of the needles is similar. The uptake rate of -HCH during spring and early summer is
slightly more rapid than that of α-HCH, coinciding with the peak in the air concentrations during
the spring. It is, therefore, assumed that biological uptake and internal distribution factors influence
the properties of the needles in such a way that the partitioning of the HCHs between air and plant
surface cannot be explained solely by physical chemistry alone.
Based upon these studies (and other scientific results not presented here), it can be concluded that
for the deposition effectivity of semivolatile organic compounds from the gas phase onto pine
needles the determining factor is the length of the vegetation period which usually coincides with
“high” temperature and sun light radiation season also in Arctic regions. It seems that the
deposition process of hydrophobic compounds to vegetation and soil surfaces (terrestrial
environment) is more complex than presumed in the models available for the evaluation of the
global distribution of hydrophobic semivolatile organic compounds. This type of POP deposition
and storage is obviously largely underestimated when estimating persistence and transport
properties of POPs and need, thus, further in-depth research also with respect to potential climate
change influences.
Terrestrial ecosystems in the North seem less contaminated with POPs compared to the marine
environment due to ecosystem specific uptake and accumulation processes. However, newly
detected, “emerging” environmental pollutants like perfluorinated alkylated chemicals (PFAS)
seem to accumulate in greater extend into the terrestrial food webs (including the Arctic: Gamberg
et al. 2005). Therefore, the introduction of new “emerging” chemicals into the Arctic environment
and potentially more local sources due to increased industrial activities, ore pronounced
contamination of the local and regional terrestrial environments have to be expected in the wake of
climate change.
Transport pathways and source elucidation
Atmospheric transport
For source elucidation and atmospheric transport, modern meteorological complex dynamic
transport models are frequently used for scientific assessments. In the present case, for
investigations of pollutant transport and distribution with emphasis on climatology the Lagrangian
particle dispersion model FLEXPART (Stohl et al., 1998; Stohl and Thomson, 1999; Stohl et al.,
2005) was applied (see http://zardoz.nilu.no/~andreas/flextra+flexpart. html). FLEXPART was
validated with data from continental-scale tracer experiments (Stohl et al., 1998). The model was
previously used to study the transport of biomass burning emissions into the Arctic (Stohl 2006,
Stohl et al., 2007), as well as the transport of anthropogenic emissions between continents (Stohl et
al., 2003) and into the Arctic (Eckhardt et al., 2003).
Model characterisation
FLEXPART is based on analyses of meteorological data from the European Centre for MediumRange Weather Forecast (ECMWF) with 1°×1° resolution. In addition to the analyses at 00:00,
06:00, 12:00 and 18:00 UTC, 3-hour forecasts at 03:00, 09:00, 15:00 and 21:00 UTC were used.
There are 23 ECMWF model levels below an altitude of 3000 m (91 throughout the atmosphere).
The model was used for the interpretation of in-situ point measurements similar to simple trajectory
models (Seibert and Frank, 2004). With this model approach it is possible to map quantitatively the
sensitivity of the pollutant concentration at the monitoring site to emission input as a function of
space and time. This is possible for inert species and substances with first-order loss processes (e.g.,
radioactive decay, dry deposition, wet scavenging, or linear chemical conversion).
15
Calculation baseline
For every receptor (receiving station), 40000 particles are released in a small box at the
measurement location and during the measurement interval (see below) and followed backward in
time for around 20 days. The cloud of particles forms a so-called retro-plume, in analogy to the
plume forming downwind of a point source in a forward simulation. The model output is a threedimensional potential emission sensitivity (PES) distribution, The word ”potential” shall remind the
user of that the sensitivity is based on transport calculations for an inert substance, ignoring
removal processes that would reduce the sensitivity. The value of the PES (in units of s kg−1) in a
particular grid cell is proportional to the particle residence time in that cell. It is a measure for the
simulated mixing ratio at the receptor that a source of unit strength (1 kg s−1) in the respective grid
cell would produce. The PES output is made on a three-dimensional grid of typically 1° longitude ×
1° latitude resolution and global or hemispheric coverage. Results show the footprint layer which
refers to the lowest 100 m, and the uppermost layer covering the rest of the atmosphere. Model
output is produced every 24 hours. To reveal the potential contribution from anthropogenic
pollution sources, we fold (i.e., multiply) the PES footprint with the emission flux densities (in
units of kg m−2 s−1) taken from an appropriate emission inventory (see below). Spatial integration
gives the simulated total mixing ratio at the receptor. For species that are conserved on the time
scales considered here (e.g., carbon monoxide), this total mixing ratio should be quantitatively
comparable to the measured enhancement over an eventual background. In addition, the
contributions from the different continents, obtained by regional integration, are also listed on the
plot. Emissions are taken from the global EDGAR 3.2 Fast Track 2000 dataset (Olivier et al., 2001)
and blended with higher-resolution regional inventories where available.
Transport climatologies for selected Arctic stations
A comparison of the climatology for five Arctic monitoring sites has been performed. All
simulations were performed and analyzed for the stations listed in Table 1 below and are shown in
figures 8 to 11. Except for Bear Island and Summit (Greenland) a 10-year record of retro-plume
calculations was available for the stations
16
0.1
DJF
MAM
JJA
SON
0.5
0.7
1
5
7.5
[ps/kg]
10
50
75
100
Figure 8: Average potential emission sensitivity (PES) footprint map (0-100 m altitude) for air arriving at Zeppelin for
the different season based on the whole climatology.
DJF = December, January, February
MAM = March, April, May
JJA = June, July, August
SON = September, October, November
Table 1: Coordinates and time periods used for analysis for the five arctic measurement stations.
Station
Alert
Barrow
Summit
Zeppelin
Bjørnøya
Coordinates
82.5 N, 62.5 W
71.3 N 156.6 W
72.6 N 38.5 W
78.9 N 11.9 E
74.3 N 19 E
available data
1996-2007
1998-2007
2000-2007
1997-2007
2000-2004
The Zeppelin station is located on top of a mountain close to the research municipality of NyÅlesund, 478 m above sea level on the island Spitsbergen (Svalbard, Norway). The potential
emission sensitivity (PES) decreases from the station in all directions but the decrease is slowest
towards Europe and Siberia, especially in winter. This indicates that emissions from these regions
are most likely to reach the Zeppelin observatory. On the other hand, in the summer months, the
region of maximum PES moves to the Arctic Ocean, the North Atlantic and the northernmost areas
of the American continent, i.e., very clean regions.
17
0.1
DJF
MAM
JJA
SON
0.5
0.7
1
5
7.5
[ps/kg]
10
50
75
100
Figure 9: same as figure 8, but for Alert (N-Canada).
Alert is the most northerly of the discussed stations. So the highest emission sensitivities are
restricted to the polar region. However, even for that station located much further west in the Arctic
than Zeppelin Station, transport from Siberia is favored in winter. Europe appears to play a smaller
role as potential source region compared to Zeppelin. The shift of pattern in summer is similar to
Zeppelin, but there is a stronger influence from the Bering region.
0.1
DJF
MAM
JJA
SON
0.5
0.7
1
5
7.5
[ps/kg]
10
50
75
100
18
Figure 10: Same as figure 8, but for Point Barrow (Alaska).
The research station Point Barrow (Alaska, USA) is located further south at about 71 N and much
further west than Alert and shows, therefore, a quite different pattern with respect to source regions.
In winter, the Asian continent plays an important role also for this station, but in summer high PES
values can also be found over northern Canada and Alaska (in addition to Siberia), all regions with
frequent occurrence of boreal forest fires. In all seasons, the North Pacific contribution is
considerably larger than at the other sites.
0.1
DJF
MAM
JJA
SON
0.5
0.7
1
5
7.5
[ps/kg]
10
50
75
100
Figure 11: Same as figure 8, but for Summit
The GEO Summit station (Greenland) is located on top of the Greenlandic ice sheet at an elevation
of 3200 m above sea level. The highest residence times (above 75ps) are in a limited region over
Greenland itself and are not changing significantly during the change of the seasons. However,
there is a noticeably larger part of the Northern hemisphere contributing (to a smaller degree),
which mirrors the fact that this high-elevation site is exposed to more dynamic free-troposphere
conditions than the low-elevation sites. The northern Atlantic and eastern Canada are the main
influence regions. During wintertime, northwestern Europe can also be important as a potential
source region.
Modelled anthropogenic influence
The following analysis was performed to achieve scientific information on potential anthropogenic
sources for POP pollution at the respective Arctic stations. The source contributions were derived
by folding the above PES maps with carbon monoxide (CO) emissions taken from the EDGAR
inventory. Furthermore, the globe was divided into 3 longitudinal “boxes” (American, European
and Asian box), crudely describing the origin of the emissions (see Figure ). As the influence of
source region varies considerably during the year, the seasons are indicated separately.
19
Zeppelin
80 Barrow
Alert
70
Bjoernoeya
60
Summit
50
40
-150
-100
-50
0
50
100
150
Figure 12: Source regions definition for the American, European and Asian region and the location of the four
measurement stations.
ZEP
ALT
30
20
average CO [ppb]
average CO [ppb]
25
20
15
10
15
10
5
5
0
all
ame
asi
0
eur
all
SUM
eur
20
20
average CO [ppb]
average CO [ppb]
asi
BRW
25
15
10
5
0
ame
all
ame
asi
eur
DJF
MAM
JJA
SON
15
10
5
0
all
ame
asi
eur
Figure 13: Modeled average CO contribution for the four arctic stations and for the 4 seasons (DJF, MAM, JJA,
SON), the results are once for all source regions and then spitted to different regions (for details see text).
Abbreviations: Seasons as in Figure 8; ZEP = Zeppelin, ALT = Alert; SUM = Summit; BRW = Point Barrow.
ame = America; asi = Asia; eur = Europe
Anthropogenic influence is calculated lowest at Alert and highest at Zeppelin. At all stations the
highest emissions occur in winter and the lowest in summer. The seasonal variation is highest at
Zeppelin and Alert. At Zeppelin in winter nearly twice as much anthropogenic CO as during the
rest of the year can be expected. Spring and fall are quite similar for all stations. Zeppelin is clearly
dominated by European emissions, but also Asian emissions play a role in winter (figure 13). For
Alert and Barrow the inflow from the different boxes is less variable. As this study focuses on the
20
Norwegian Arctic, the time series of monthly averaged CO anthropogenic emission is analysed
below.
70
60
CO average [ppb]
50
40
30
20
10
0
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
Figure 14: Monthly averaged simulated CO-concentration [ppb] at Zeppelin station. The light blue dots show the
winter (DJF) averages, the green dots the summer (JJA) average and the orange dots the annual average.
10
5
0
-5
-10
-15
-20
2000
2001
2002
2003
2004
2005
2006
2007
2008
Figure 15: Monthly average hourly temperature (° C) measured at Zeppelin, the green and blue dots mark summer and
winter months used for further analyses.
According to the data presented in figure 14, a high seasonal and interannual variability is obvious.
In order to highlight these differences, the average values for winter and summer are indicated
(figure 14) with different colors. The year-to-year variability is highest in winter. The years 1999,
2005, and especially 2006 show the highest concentrations. The comparison with the average
temperature measured at the Zeppelin station (figure 15) revealed that 2006 was also the warmest
winter on the record. In the years 2001 and 2002 it seems as if the atmospheric transport into the
Arctic was minimal.
21
Transport of biomass burning emission into the Arctic
Recent satellite and ground-based LIDAR (Light Detection and Ranging) measurements observed
substantial amounts of forest fire smoke in the tropopause region and lower stratosphere at high
latitudes and in the Arctic (e.g. Waibel et al., 1999; Fromm et al., 2000; Damoah et al, 2004).
Especially over snow/ice surfaces the short-wave (visible light) reflectivity to space can be
considerably reduced by forest fire smoke, which may have important implications for the radiative
energy budget in the polar region (Hsu et al., 1999). Episodically, the fires also pollute large
regions in the lower troposphere at high latitudes (Forster et al., 2001). Presumably, the deposition
of substances like black carbon (soot) from such fires will ultimately decrease the reflectivity
(albedo) of ice and snow and lead to enhanced melting of Arctic glaciers and sea ice (Kim et al.,
2005).
Climate change is today considered as an accepted reality, and observed and forecast impacts are
expected to become most significant at northern latitudes and over land, particularly over the
continental regions of Russia, Canada and Alaska. These are areas where large fires have been
common since the last Ice Age, and recent research (e.g. Stocks et al. 1998; Flannigan et al. 2003)
indicates that more frequent and severe fires are expected as a possible outcome of the described
climate change scenarios. This will have a significant impact on the age class structure and carbon
budget of the boreal/Arctic zone in particular and the globe in general. Boreal fires consume large
quantities of wood as fuel and spread quickly, creating high energy release rates that are often
sustained for long burning periods. This frequently results in convection columns with strong
vertical development that reach into the stratosphere (up to 18 km altitude). Long-range smoke
transport from large boreal fires is already common, with smoke loads from Siberian fires often
reinforcing smoke from North American fires. This phenomenon is expected to become even more
common with more frequent and severe fires in the future, increasing the likelihood that smoke
from boreal fires will provide a positive feedback to climate change (Kurz and Apps 1994).
Soils and forests in the boreal region of the northern hemisphere are recognized as large capacity
storage compartments for air-borne long range transported POPs, such as polychlorinated biphenyls
(PCBs) and HCHs. This postulation is also supported by the results previously presented by Becker
et al. and H. Kylin’s report on POP uptake in scots pine needles (see above). Following reductions
of primary emissions of various legacy POPs, there is an increasing interest and debate about the
relative importance of secondary emissions from intermediate storages on the atmospheric levels of
POPs.
Figure 16: Potential emission sensitivity (PES) footprint map (0-100 m) for air arriving at Zeppelin between 1 May
2006 at 10:14 UTC and 3 May 2006 at 8:38 UTC 2006. Black dots show MODIS _re detections on days when the
footprint emission sensitivity in the corresponding grid cell on that day exceeded 2 ps kg -1.
22
In July 2004, about 5.8 million hectare of boreal forest burned in North America, emitting a
pollution plume which reached the Zeppelin station after a travel time of 3-4 weeks (Stohl 2006).
12 PCB congeners were elevated above the long-term mean by more than two standard deviations,
with the less chlorinated congeners being most strongly affected. During an extreme event in spring
(early May) of 2006, biomass burning emissions from agricultural fires in Eastern Europe were
transported poleward and recorded at the Zeppelin station, with record-high levels of many air
pollutants (Stohl et al., 2007), including PCBs. 21 out of 32 PCB congeners were enhanced by
more than two standard deviations above the long-term mean concentrations. It is, thus, proposed
that these abnormally high concentrations were caused by biomass burning emissions. Based on
enhancement ratios with carbon monoxide and known emissions factors for this species, it is
estimated that 130 and 66 µg PCBs were released per kilogram dry matter burned, respectively. To
our knowledge, this is the first study relating atmospheric PCB enhancements with biomass
burning. The strong effects on observed concentrations far away from the sources, suggest that
biomass burning is an important source of PCBs for the atmosphere.
b) PCB 28
a) Temp
30
0
20
-20
10
o
C
20
0
-40
d) PCB 101
c) PCB 52
3
8
pg/m3
6
2
4
1
2
0
0
f) PCB 138
e) PCB 118
3
2
pg/m3
1.5
2
1
1
0.5
0
0
g) PCB 153
h) PCB 180
6
0.8
0.6
pg/m3
4
0.4
2
0
2002
0.2
2003
2004
2005
2006
0
2007 2002
2003
2004
2005
2006
2007
i) PCB 28
-22
ln(P)
-23
-24
-25
-26
0.0035
0.0036
0.0037
0.0038
0.0039
0.0040
0.0041
0.0042
1/T
Figure 17: Time series of temperature (a) and the seven most important PCBs (b-h) for the time period January 2002
till 8 May 2006 measured at the Zeppelin station. Crosses represent the individual concentrations, the blue line was
derived by a running mean over 4 months, the green dots indicate the sample from 26 to 28 July 2004 and the orange
dots the sample from 1 to 3 May 2006. Clausius-Clapeyron plot (i) relating the natural logarithm of the partial pressure
(Pa) of PCB 28 to the inverse temperature (K). The partial pressure is calculated as P=log(PCB 28/m*R*T), where m is
the molar weight of PCB 28.The red lines in (i) indicate the residuals from the regression with temperature.
23
Is direct atmospheric transport the dominant mechanism?
The previous sections show that both direct atmospheric transport from source regions at lower
latitudes and re-mobilization of intermediate storages at higher latitudes are found in the in-depth
study for pollution levels and transport patterns. A crucial question, not least with respect to the
future development of pollution levels, is which of these two processes is dominant in the Arctic
and whether it is different from the picture at lower latitudes.
To this purpose, the levels of PCB-28, based on FLEXPART model calculations and a standard
source inventory, were compared with measured values at Zeppelin over the whole time period of
2003 – 2007. The result is shown in figure 18.
Figure 18: Modeled (blue) and measured PCB-28 tracer concentrations at Zeppelin. Red: temperature measured at
Zeppelin Station.
From this, it is obvious that the correlation is rather poor. Only in isolated events, e.g., in early
2005 and early 2006 (the biomass burning event in Eastern Europe described above), measured
concentration maxima coincide with modeled maxima. Most striking is the mismatch at a seasonal
scale: While the model clearly indicates frequent high-concentration episodes during the winter
half-year and generally low levels in summer, the measurements show, on average, higher levels
during summer and only occasional high concentration episodes in winter. The duration of the
period with elevated levels in summer tends to correlate with the (local) air temperature: e.g., it was
rather short in 2004, but considerably longer in 2005. Possible mechanisms here may be the melting
of sea ice (although this should imply a delay in time between temperature maximum and pollution
levels, which is not seen in the data), or increased re-evaporation from soils and vegetation (but
then it should not correlate with local temperature).
In any case, this pattern indicates that the direct atmospheric transport of pollutants is not the
primary explanation of Arctic pollution levels. This is underlined by comparison with the same
study at Birkenes in Southern Norway, which is summarized in Figure 19: Here, one finds a
qualitatively much better consistence between the modeled and measured PCB-28 levels.
24
Figure 19. As Figure 16, but for Birkenes Station, Southern Norway.
Oceanic transport
Ocean currents in the Arctic
The Arctic Ocean is the smallest of the four oceans on the globe and lies almost entirely north of
the Arctic Circle (66.6º N latitude). Almost completely surrounded by land, its only outlets are the
Bering Strait between Alaska and Russia, Davis Strait between Greenland and Canada, and
Denmark Strait and the Norwegian Sea between Greenland and Europe. The Arctic Ocean has the
largest share of continental shelf areas of all the oceans. The major large-scale features of the
general water circulation at the surface are anticyclonic: the Beaufort Gyre and the Transpolar Drift
starting in the East-Siberian and Laptev Seas and ending in the Fram Strait (Coachman and Barnes
1961). The Fram Strait has largest water exchange with the Arctic Basin (AB). Cold and fresh
surface polar water leaves the AB in the western part of the Fram Strait with the East Greenland
current, while in the eastern part of the Fram Strait warm and salty water of Atlantic origin enters
the AB with the West Spitsbergen current. This branch is a continuation of the Norwegian Atlantic
Current which flows northwards parallel to the Norwegian Coast (Hansen and Østerhus 2000).
North of the Lofoten Islands at approximately 72° N one branch turns northwest and flows along
the Barents Sea margin. Southwest of Spitsbergen, a part of the Atlantic water re-circulates
westward and southward around the deep Greenland Basin and meets the East Greenland Current
flowing southward, before part of the current turns eastward, first into the Iceland Sea and then into
the Norwegian Sea north of Iceland.
The second branch of Atlantic Norwegian Current, the North Cape branch, enters the Barents Sea
through the Bear Island Trough (the Barents Sea opening) and flows northwards along Novaya
Zemlya before it enters the Arctic Ocean between Franz Josef Land and Novaya Zemlya, flowing
parallel to the northern branch around the Eurasian Basin (Rudels et al. 1999). The major part of the
Atlantic water as West Spitsbergen Current enters the Arctic north of Spitsbergen, where it
submerges under the surface, turns to the east and continues below polar surface waters, forming
the core of the Atlantic layer which lies approximately 200-600 m (Rudels et al. 1999). After
several cyclonic recirculations along major ridges and continental slopes in the Canadian and
Eurasian basins, these waters finally return into the Fram Strait on the Greenland side as Arctic
Intermediate Waters at depths of 500-900 m. This deep and cold water mass turns east north of Jan
25
Mayen, and follows the same circulation system as the surface water along the Spitsbergen Shelf
slope. Atlantic waters entering through Fram Strait play a key role in the climatic system of the
Arctic Ocean.
Investigations of oceanic and ice transport
The geographical position and climatic features of the Arctic seas mean that their ecological
balance is sensitive to disturbance by inputs of man-made pollutants. The Arctic seas represent
zones where pollutants naturally accumulate and pollutants are transported between regions where
there is active exploitation of natural resources and pollution, and the ecologically clean regions of
the central Polar Basin. The processes involved in the transport, transformation and accumulation
of contaminants from different possible sources are important in assessing whether we are to
forecast the fate of potential pollutant releases. Ocean currents and drifting ice are among the most
important mechanisms of pollutant transport (Nürnberg et al. 1994; Emery et al. 1997; Pfirman et
al. 1997; Rigor and Colony 1997; Pfirman et al. 2004; Pavlov et al. 2004, Pavlov 2007).
Severe natural conditions and the year-round presence of drifting ice make direct full-scale
observations of currents difficult and expensive. Numerical modeling, supported and validated by
in situ field observations, is therefore the only practical possibility for gaining an understanding of
water circulation in the Arctic Ocean on different spatial and temporal scales. Many models
describing transport and transformation of various pollutants in the water environment of the Arctic
have appeared in recent years, inspired by increasing anthropogenic effects, especially in coastal
zones (Preller and Cheng 1995; Pavlov et al. 1995, 2004; AMAP 1998; Harms and Karcher 1999;
Harms et al. 2000; and others). In these papers, modeling results for the spreading of contaminants
from individual sources, mostly located in the Nordic seas and Kara Sea, were discussed.
For example Harms et al. (2000) investigated the role of Siberian river runoff for the transport of
possible river contaminants in the Arctic Ocean. 3-D coupled ice-ocean models of different
horizontal resolution were applied to simulate the dispersion of river water from the Ob, Yenisei
and Lena. Circulation model results explain the main pathways and transit times of Siberian river
water in the Arctic Ocean. Kara Sea river water (Ob, Yenisei) clearly dominates in the Siberian
branch of the Transpolar Drift, while the water from the Lena dominates in the Canadian Branch.
The model confirms that contaminant transport through sediment laden sea ice offers a short and
effective pathway for pollutant transport from Siberian rivers to the Barents and Nordic seas.
Pavlov (2007) discusses the results of the simulation of the transport of passive non-conservative
tracers by currents from a number of possible sources in the Arctic Ocean and Nordic seas. For
simulation vectors of ocean currents he used a 3-D baroclinic ocean model which is documented in
Pavlov (1995) and Pavlov and Pavlov (1999).The annual cycle of all forcing and boundary
conditions was not changed during the simulations and as a result after about 30 years we obtained
a stable annual cycle of the 3-D water circulation in the Arctic Ocean. Harms et al. (2000) using a
similar approach achieved a stable seasonal cycle in the ice and the upper ocean circulation after
35-years running their coupled ice-ocean model of the Arctic Ocean. The annual cycle of the water
circulation obtained is used in the integration of the diffusion-advection equation.
Numerical studies
Numerical experiments simulating the transport of contaminants from possible sources in different
parts of the Arctic Ocean have been performed using calculated 3-D current fields (Pavlov 2007).
For these simulations potential pollutant sources have been located in the vicinity of river-mouths
of major rivers flowing into the Arctic Ocean, as well as in the Bering Strait, in the bottle-neck of
the White Sea and in the Faeroe-Shetland Channel. What is the reason of such chooses?
26
The Faeroe-Shetland Channel is the main gate for a potential pollutant penetration from the coastal
zone of Western Europe to the Norwegian Sea. The Kara Sea is distinguished from the other
Siberian shelf seas by the strong influence of continental discharge. It receives about 55 % (1290
km3/year) of the total river runoff discharged to the entire Siberian Arctic. The annual discharge
from the Ob river is 400 km3 and from the Yenisei river it is 630 km3 (Soviet Arctic 1970; Pavlov
and Pfirman 1995). As at the other sites, there is a risk of contaminated water migrating into the
rivers (AMAP 1998).
The large rivers of Siberia such as Lena and Kolyma, and Mackenzie in Canada transport large
amounts of water over long distances and on their way to the Arctic seas. The annual discharge of
the Lena and Kolyma is 525 km3 and 132 km3, respectively, and the Mackenzie runoff is 333
km3/year (AMAP 1998). These areas include agricultural and industrial regions, and also regions of
mining, and oil and gas exploration in Siberia and Canada. So, these rivers are expected to be a key
source for considerable quantities of several different contaminants.
About 1 Sv enters the Arctic Ocean from the Pacific Ocean with the Pacific current through the
Bering Strait (Pavlov and Pavlova 1999). These waters wash the industrial regions of the Russian
Far East and Northern America, where possible sources of contamination are located, such as the
large industrial areas near Vladivostok, and the regions of drilling activity in Alaska.
The bottle-neck of the White Sea was chosen because the city of Severodvinsk lies in the delta of
the Dvina river, close to Archangelsk, and has one of the largest shipyards for nuclear-powered
submarines in the former Soviet Union. This area is also not far from the sites of the oil and gas
exploration in the Barents Sea.
A
B
NORWAY
NORWAY
R
R
U
U
S
S
GREENLAND
GREENLAND
10
S
S
7.5
I
I
CA
NA
A
A
DA
5
USA
2.5
USA
1
D
C
NORWAY
NORWAY
R
R
0.5
0.1
U
U
0.01
S
S
GREENLAND
GREENLAND
0.001
S
S
0
I
I
A
A
USA
USA
27
Figure 20. Distributions of pollutant concentration in the surface layer of the Arctic Ocean after 15 years of
release from sources in the river-mouths of the major rivers: A - Ob and Yenisei rivers, B - Lena river, C Kolyma river, and D - Mackenzie river. The scale shows % of pollutant in relation to its concentration at
source. - source location.
Information about contaminant levels at the potential sources mentioned above is fragmental or
practically absent. However, even if we do not have information about contaminants from these
regions, the selected sources could release large amounts of contaminants in the future. For
example, release of contaminants can occur in case of accidents during production, transport, waste
disposal and storage in connection with oil and gas exploration and exploitation. Potential
contaminant release that may occur in the Arctic in the future and source related assessments of
potential release are well documented in AMAP (1998). In lack of realistic numbers, pollutant
concentration in all these sources has been set to 100 arbitrary units in the model runs.
Distributions of the pollutant concentration from all the permanently acting sources in the rivermouths of major rivers in the surface layer of the Arctic Ocean after 15 years from the beginning of
the release are presented in Fig. 20. Depths of the sources near the river-mouths have been set equal
to 5 m.
Pollutant spreading from sources in the river mouths of the Siberian shelf is directed predominantly
to the north-west. Pollutants from the source in the Kara Sea in the region of the Ob-Yenisei river
mouth (Fig. 20a) cover a greater part of the Nordic seas, the Laptev Sea and the area near the
northern coast of Greenland. However, pollutant concentrations exceeding 5% of the source
concentration in the surface layers of the ocean are only observed within the Kara Sea area. The
most rapid spreading of the pollutant is observed from the source near the Lena river mouth (Fig.
20b). The pollutants entering the Transpolar Drift are transported to the coast of Greenland,
spreading later over the region of the Nordic seas. Pollutant concentrations of 5% are observed in
the Fram Strait and near the northern coast of Greenland.
The structure of the pollutant transportation from the source near the Kolyma river mouth (Fig.
20c) is in many ways similar to the previous one. However, in this case contamination of the
Nordic seas significantly decreases, and contamination of the coastal zone of the East Siberian and
Chukchi seas increases. As this takes place, concentrations exceeding 5% are registered along the
continental slope and in the south-eastern part of the Laptev Sea and in the coastal zone of the East
Siberian Sea. Pollutants from the source near the Kolyma river mouth are transported also along the
continental slope to the east in the sub-bottom layer. They reach the sea surface in the Chukchi Sea
to the north of Wrangel Island and near the northeast coast of Alaska. A pollutant concentration of
5% of the source is registered in this region, whereas on the surface of the northern part of the East
Siberian Sea, along the transportation route of the pollutants, their concentration is less than 3%. A
completely different situation occurs in the case where the pollutant spreads from a source located
in the Mackenzie river mouth (Fig. 20d). The pollutants in this case essentially fill the region of the
anticyclonic gyre, and only an insignificant part of them enters the Laptev Sea and Nordic seas.
Pollutant concentrations exceeding 5% are observed in the surface layers in the anticyclonic gyre in
the Canadian Basin.
In the second set of numerical experiments, pollutants with 100% concentration are released in the
bottle-neck of the White Sea, in the Faeroe-Shetland Channel and in the Bering Strait in the streams
of the Atlantic and Pacific currents, respectively, at a depth 5 m. The pollutant-spreading from
these sources 15 years after their release is shown in Fig. 21.
The pollutants from the source in the surface layer near the bottleneck of the White Sea (Fig. 21a)
spread to the East along the coasts of the Barents and Kara seas and to the North along the western
coast of Severnaya Zemlya. Having entered the Transpolar Drift Stream in the northern part of the
28
Kara Sea, the pollutants subsequently reach the Greenland Sea. Pollutant concentrations exceeding
5% are registered in the eastern and southeastern parts of the Barents Sea, in the Kara Sea and in
the stream of the Transpolar Drift.
A
B
NORWAY
R
R
R
NORWAY
NORWAY
U
U
U
S
S
S
GREENLAND
GREENLAND
GREENLAND
S
S
S
I
I
I
A
A
A
USA
USA
USA
C
NORWAY
10
R
7.5
U
5
2.5
S
GREENLAND
1
S
0.5
0.1
I
0.01
A
0.001
USA
0
Figure 21. The spread of a pollutant with ocean currents, 15 years after the beginning of a hypothetic
pollutant release, from sources located in the following regions: A - the bottle-neck of the White Sea, B - the
Faeroe-Shetland Channel in the stream of the Atlantic current and C - the Bering Strait. The scale shows %
of pollutant in relation to its concentration at source. - source location.
The pollutants from the possible source in the stream of the North Atlantic Current in the FaeroeShetland Channel (Fig. 21b) spread predominantly in the Norwegian and Barents seas and in the
northern part of the Kara Sea. A region with concentrations higher than 5% in the surface layer is
observed in the Norwegian Sea, in the western part of the Barents Sea and near the southern and
western coasts of Spitsbergen.
The pollutants from the possible source in the Bering Strait (Fig. 21c) spread mainly to the west.
The zone of possible contamination covers the Chukchi Sea, the northern part of the East Siberian
Sea, the greater part of the Laptev Sea and the region of the Transpolar Drift Stream. Pollutant
concentrations exceeding 5% are registered in the Chukchi Sea and in the north-eastern part of the
East Siberian Sea. Concentrations of 10% and above are located in the Bering Strait and in the
Chukchi Sea near the coasts of Alaska and Chukotka.
Consequences and perspectives
After the first AMAP report on ”the influence of global change on contaminant pathways in the
Arctic” (AMAP, 2002), international research has been focusing on this research topics within
Arctic environmental chemistry. A recently published study on modeling climate impact on the
distribution of persistent organic pollutants (POPs) in the Arctic, concluded that all of the
29
parameters that have been shown to strongly influence the Arctic contamination behavior of
persistent organic chemicals are predicted to undergo considerable change over the next few
decades (Meyer & Wania 2007). It is thus assumed that the global transport and distribution
behavior of many persistent organic chemicals, and in particular their accumulation in polar marine
ecosystems, will be significantly influenced by global climate change. Based on both experimental
and modelling evidence available today, it is expected that climate fluctuations may have impact on
the atmospheric transport and distribution of persistent organic pollutants (POP) in the Arctic.
International research on climate and contaminants in the Arctic
The international research in the research area ”climate influences on atmospheric POP transport
and distribution” is today mainly performed in the Canadian and Western European (Norwegian)
sector. The first studies were summarized in an AMAP summary report (Macdonald et al 2003).
Under the auspice of AMAP also two comprehensive international research projects located in the
Western European Arctic are currently under way, aiming at elucidating changing contaminant
pathways and potential exposure risk for the indigenous people of the North:
1. EU-project ArcRISK: 7th Framework Programme, Theme 6: environment (including climate
change).
2. Nordic Council of Ministers (NMR) project: Effects of climate change on transport, levels
and effects of contaminants in northern areas.
In conjunction with already ongoing research activities within the Canadian Northern Contaminants
Program (NCP) as well as international research activities during the International Polar Year
(IPY), it is expected that after 2009, additional comprehensive science based information will be
available on the influence of climate change on contaminant transport to and within the Arctic. In
the frame of IPY, the following projects address contaminants:
 Intercontinental Atmospheric Transport of Anthropogenic Pollutants to the Arctic
(INCATPA),Canada: http://www.msc-smc.ec.gc.ca/arqp/incatpa/incatp0_e.cfm.
 Contaminants in Polar Regions: Dynamic range of contaminants in polar marine ecosystems
(COPOL), Norway: http://www.copol.net/
 Atmospheric monitoring of pollutants in the polar regions (ATMOPOL), Norway:
http://classic.ipy.org/development/eoi/proposal-details.php?id=76
 Ocean - Atmosphere - Sea Ice - Snowpack (OASIS) program studies, Italy:
http://www.oasishome.net/.
In addition to the above mentioned international research initiatives, a suit of national and/or
institute funded research activities are already ongoing. It is, thus, assumed that new scientific
contributions and findings will be important input to shape and prioritize future international
research efforts on the relationship between climatology and the fate of POPs and new emerging
contaminants in arctic environments.
Consequences and scenarios
Not only transport pathways, distribution and accumulation processes of pollutants will be
influenced by environmental/climate change (as outlined above). Also source structures and
increased local/regional human activities (e.g., industry, tourism, transportation, infrastructures)
due to increasing accessibility will impact the contaminant status in the Arctic (if the described
scenarios come true).
The following scenarios are, thus, selected in order to illustrate potential scientific and social
challenges the Arctic will encounter, and proper mitigation actions have to be considered when the
Arctic environment is changing as predicted.
30
Atmospheric transport
The temperature-driven ”polar front” system in the North is today considered as an important
meteorological barrier, preventing to a large degree atmospheric transport of polluted air masses
into the Arctic during summer. Thus, today, for many anthropogenic pollutants, seasonal
distribution patterns with increased LRT episodes during winter are reported from Arctic long-term
atmospheric monitoring (see above).
Based upon climate change scenarios as used in ACIA 2004, it is expected that the temperature
difference between the cold Arctic sink region and the mid-latitude source regions will be reduced
considerably. Therefore, the extension of the ”Polar front” during winter time is expected to be
larger as today, sometimes also including possible source regions in Western and Eastern Europe
and North America. As a direct consequence, present seasonal patterns for selected chemicals will
be replaced by a more evenly distributed transport of contaminants throughout the year.
The extreme pollution event in May 2006 also revealed another possible mechanism: This episode
was preceded by an extreme temperature anomaly during April with temperatures on average 12
degrees above the long-term mean. As a consequence, the polar dome, the lense of cold air near the
surface which largely prevents warmer polluted air from entering the arctic boundary layer, was
removed so that the polluted air from Central Europe could move in. Such episodes are expected to
become much more frequent in case of a massive warming in the Arctic.
Ocean current transport
The numerical experiments performed and described above revealed that the anticyclonic gyre zone
in the Canadian Basin would be the least polluted area of the Arctic Ocean for the contamination
sources located in the coastal zone of the Siberian shelf seas, the Barents and Norwegian seas.
There are some regions that would become contaminated in nearly all possible variants of location
of the possible sources in the coastal zone of the Arctic seas. Among these are the Laptev Sea and
the northern and eastern coasts of Greenland.
During the past years increased inflow of North Atlantic waters has been registered by
oceanographic monitoring along the west coast of Spitsbergen and the east coast of Greenland
(Fram Strait). Recent studies (Pavlov and Pavlova 2007, 2008; Hakkinen et al. 2008) showed an
increase of the sea ice drift velocities in the Arctic Ocean during the last three decades. It leads to
an intensification of the surface currents, induced by drifting ice. Thus a higher contamination risk
is associated to this feature, since water masses previously moving along the potential source
regions of western industrialized countries are now reaching the high North. The ocean waters are
considered today as a major storage reservoir and transport medium for water soluble POPs. Sea ice
throughout the central Arctic Ocean may be important in transporting POPs and other contaminants
from coastal sediments during the winter, and from deposition from the atmosphere, with
subsequent redistribution during ice melt. At the same time, ice functions as a sealing of the ocean,
inhibiting re-evaporation of super-saturated pollutants. In northern Norwegian marine areas, PCBs
and DDT levels are considered highest in the eastern part of the Barents Sea. In general, there is a
clear global trend towards declining concentrations of persistent organic pollutants, which is
following the worldwide international regulation policies resulting in the ban of several
compounds, such as PCB, DDT and HCH. Nevertheless, for some PCBs the observed changes are
small, while for others the concentrations are even increasing. Therefore, it can be concluded that
there are insufficient time-series measurements to unambiguously show the effects of global
measures within the Arctic Ocean and the adjacent oceans and/or that the processes influencing
contaminant levels in the marine compartment are not understood satisfactorily.
31
Ice coverage - Sea ice scenarios
In 2007, the world has seen the most dramatic loss of Arctic sea ice coverage since satellite-based
pan-arctic sea ice observations started in 1979. This is generally interpreted as a sign that the area
of ice coverage is shrinking at a pace faster than expected, e.g., from model simulations. The loss in
sea ice volume is probably even larger, but this is uncertain because of a lack of data on sea ice
thickness. These trends, which are severely underestimated by all global climate models, suggest
that global warming is likely to further reinforce in the Arctic and may push the Arctic system into
a seasonally ice-free state not seen for more than one million years (Stroeve et al. 2008) in the near
future.
This development will have considerable consequences for the availability of previously stored
contaminants in the central Arctic water masses. As outlined above, chemicals previously stored
under the ice sealing of the central Arctic basin are expected to re-evaporate into the atmosphere
(HCH, HCB) and are, thus, available again for uptake and bioaccumulation into the Arctic food
webs.
On the other hand, the transpolar ice drift is considered an important motor driving the transport of
contaminated multi-year ice from the eastern Siberian shores (with huge amounts of fresh water
draining from the large Russian rivers) in to the Marginal Ice zones (MIZ) of the Barents Sea
(presently located between Bjørnøya and Svalbard). The loss of seasonal ice coverage will
consequently lead to a reduced volume of ice drifting across the central Arctic Basin, and the
movement of the MIZ into the central Arctic. Therefore, the transpolar ice drift, currently blamed to
be a major reason for high pollutant (POP) levels in the European Arctic, will probably be of minor
importance for contaminant transport and the overall contamination due to ice transport of the
South-Eastern Arctic (around Bear Island and Svalbard) is expected to decrease with a shrinking
ice coverage.
More local ”hot-spot” like contamination patterns are expected to occur in the coastal ecosystems
along the Arctic margins because the ”ice linkage” serving as transport belt for contaminants will
disappear during the Arctic summer.
Glacial ice coverage
The land fast ice coverage (ice caps and glaciers) is changing rapidly. On Greenland, the ice cap is
loosing mass on the margins whereas the central ice cap has been growing during the past years
(ACIA 2004); overall, there has been observed an increasingly negative ice mass balance in the
most recent decade. The Svalbard glaciers and ice caps are decreasing continuously. Recent
temporal trend studies conclude that the land fast ice contains considerable amounts of POPs
(including currently used pesticides, Hermanson et al. 2005). These chemicals will be released
through the increased melting of the glacial surface ice during the summer melting periods and,
thus, will be available for up-take into the sensitive Arctic food web afterwards.
Industrial activities and infrastructures
Reduced ice coverage and increased annual mean temperatures (sea and atmosphere) will make it
economically feasible to explore minerals (eg., Mn) and off-shore petroleum resources in the deep
sea areas of the central Arctic Basin. In addition, a considerable reduction of glacial and ice cap
coverage (e.g., on Greenland) will provide space for new settlements and industrial activities (e.g.,
mining etc.). As a consequence, the increased presence of human industrial facilities in
combination with infrastructure support, maintenance and transportation of products can be
considered as a potential new local/regional contamination source for both POPs and new
”emerging” chemicals. In addition, substances which are today considered as less persistent and not
transported into the Arctic regions through the ”traditional” transport pathways may enter the
sensitive Arctic ecosystems through this type of local contamination.
32
Accessibility for transportation and tourism
The expected reduction or even lack of seasonal ice coverage during the Arctic summer will allow
the passage of large transport vessels from the western industrial countries to the rapidly growing
Asian markets and vice versa. Shipping from/to Asia through the Northwest or Northeast passage is
economically very attractive for shipping agencies both with respect to shipping time and
associated shipping cost (expected passage and harbor fees etc.) and for security reasons.
Tourist activities in central Arctic regions (including cruise ships and on-shore activities) are
expected to increase due to increased accessibility of remote sites within the central Arctic. Due to
off-shore and on-shore industrial activities in the Arctic, maintenance and product transportation to
the consumers and/or refining facilities will significantly increase.
As a consequence, the expected increase of shipping activities (transportation, industry, tourism)
and the lack of adequate national and international security plans will potentially lead to a
considerably higher risk for accidents and environmental contamination in the region.
New contaminant sources
As a consequence of the interconnection of the contamination scenarios described above, a
significant increase of potential local contamination sources is expected. Today, the Arctic is
considered as an important region for monitoring of background contamination levels. In case the
above scenarios come true, this value is about to change within the next century. Ultimately, the
increased human activities in the Arctic will be accompanied with new potential environmental
pollutants hitherto not considered as relevant for the Arctic environment.
The increased density of human populations in the North in association with increased ambient
temperatures and not well adapted hygienic systems (pipes and Sewage treatment facilities) will
consequently lead to a significant increase of (infectious) diseases and the associated application of
pharmaceuticals during medical treatment. Since usually a large proportion of the medical agents is
leaving the organism unchanged, local contamination of the aquatic environment can be expected.
The environmental stability, half-life and bio-accessibility for these substances are expected to be
considerably prolonged under Arctic conditions (Kallenborn et al. 2008). Therefore, a higher risk
for adverse environmental and human-related effects is associated to these compounds in the still
relative cold Arctic aquatic environments with water temperatures close to 0 °C. The development
of resistant strains in the Arctic microbial communities close to growing human settlements due to
local, but continuous release of antibacterial agents cannot be excluded.
Through the increased inflow of warm Atlantic currents into the central Arctic Ocean, the transport
of legacy POPs into Arctic waters may be enhanced.
New commercially exploited fish species (Atlantic cod, mackerel, etc.) will and are already
entering the Arctic waters. These species will move their spawning grounds into the Arctic. Thus,
the Arctic food web, especially the marine top- predators (marine mammals including whales and
sea birds) will adapt to these changes in new food available in their hunting grounds. These new
species are known to be carriers of substantial loads of lipophilic contaminants. The consumption
of these new prey species may, thus, lead to an increased exposure for top predating species
(including humans) to POPs stored in the lipid-rich tissues of these formerly mid-latitude species.
33
The way ahead
Scenario descriptions
The scenario descriptions in the concluding reports of the Arctic Climate Impact Assessment
(ACIA, 2004) and the Intergovernmental Panel for Climate Change (IPCC, 2007) allow a firstapproximation assessment of the future challenges associated to pollutant transport and distribution
related with climate change in the Arctic (Macdonald et al 2005). However, these scenarios have
proven to be rather conservative compared to the real-world development in recent years and
should, therefore, be updated, before further comprehensive studies of the effects on contaminant
loads in the Arctic are performed. The breathtaking technological developments within analytical
chemistry leading to new instrumentation allowing the quantitative detection of ultra-trace levels of
hitherto unknown contaminants, will inevitably lead to the identification and quantification of many
new Arctic contaminants not yet known today.





Increased industrial activity, transport across the Arctic Ocean and off-shore activities in the
Arctic will lead to significantly more potential local sources than registered today.
The reduction of sea ice coverage in the central Arctic Ocean will lead to an increased
summer evaporation of (semi)-volatile POPs
New marine species (fish, crustacean, other invertebrates etc.) will invade the Central Arctic
basin and will serve as contaminant carrier and potential POP source for top predating
animals.
The human population in the circum-arctic regions will increase due to new working
opportunities. In combination with increased temperatures new challenges with respect to
hygiene and increased occurrence of infectious diseases will emerge. New chemicals
(hitherto not identified as relevant in the North) will enter the Arctic environment.
The development of new highly sensitive instrument will allow ultra trace detection and
monitoring of new “emerging chemicals on long time series in virtually all environmental
compartments of the Arctic
Present knowledge gaps
The following research areas are identified to require future research focus:
 The role of increasing forest fire events in boreal forests as a source and transport
mechanism of pollutants into the Arctic;
 Sea surface –atmosphere exchange processes for pollutants in the light of a changing
climate, especially sea ice;
 Monitoring of new emerging contaminants in Arctic environments (biota, atmosphere,
sediments, soil);
 New pathways and exposure risks for the Arctic terrestrial environment (biota, vegetation
etc.);
 Migrating marine species as contaminant carriers;
 Invading species in the Arctic as contaminant sources;
 Increased ships traffic and the risk for introducing alien species and contaminants into the
Arctic ecosystems;
 Future local source evaluation (off-shore activities, on-land and coastal installations).
Conclusions
Based upon the scientific studies described above, it seems already today evident that levels and
distribution patterns of contaminants including POPs and volatile chemicals are influenced by longterm and rapid changes of the local and regional climate.
34
Previous sinks, especially the Arctic Ocean, are today identified as important sources for legacy
contaminants (enantioselectivity).
The diminishing ice coverage is resulting in an increased evaporation and increased atmospheric
POP burden in Central Arctic environments; a changing redistribution pattern in the Arctic Basin
may be expected as well.
Model based calculations of atmospheric POP transport clearly indicate influences of climatology,
but also a strong influence indirect transport pathways
.
Increased forest fire events in the Sub-Arctic result already today in increased levels of particlebound semi-volatile POPs including hexachloro-PCBs.
Due to the substantial increase of human activities in the Arctic (incl. off-shore industry, growing
settlements, on-land exploration of minerals, etc.) in the future, it is expected that new, short lived
chemicals are introduced and primary sources are moving closer to the Arctic.
Therefore, additional studies with intensive collection of data in long time-series and with a better
geographical coverage are necessary to shed light on these expected climate change related
challenges.
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Pavlov VK, Kulakov MYu, Stanovoy VV (1995) Modeling of the transport and transformation of
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