31
Chapter 6
The Effects of Climate Change on Contaminant Pathways
ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ
This chapter considers how the changes described in
connections remain intact. Air transport from eastern
the previous chapters will affect specific groups of con-
North America and Western Europe strengthens under
taminants ญ heavy metals, radionuclides, organochlor-
strong AO+ conditions, especially in winter, due to the
ine compounds (OCs), and hydrocarbons. For each
intensification and extension northward of the Icelandic
group, the significance of the recent shift to high Arctic
Low. Air mass trajectory changes, while probably shift-
Oscillation (AO) index will be discussed and then con-
ing the pathway and rate of transport between temper-
sideration will be given to the more general, long-term
ate sources and Arctic sinks, will probably not change
changes thought likely. To avoid repetition, direct, un-
the net delivery of airborne contaminants substantially.
supported statements are made for which the argu-
This hypothesis could be tested by running transport
ments and citations have been provided in previous
models (e.g., see Akeredolu et al., 1994) under AO+ and
chapters. Connections in the contaminant pathways
AOญ conditions.
(Figure 1ท2) will be emphasized, such as: 1) mobiliza-
The greatest leverage for change with aerosol met-
tion from global primary or secondary contaminant
als resides in the wet and dry removal processes within
sources and/or a change in delivery pathways to Arc-
the Arctic for which present knowledge is relatively in-
tic ecosystems; 2) entry into the base of the food web
complete. Because the Arctic is a poor trap for atmos-
from water, snow pack, ice, soil, and runoff; 3) shifts in
pheric metals associated with aerosols and particulates,
the relative importance of the source of primary pro-
sequestering < 10% of the emissions that pass through
ductivity in aquatic systems (ice versus aquatic or
it (Akeredolu et al., 1994; Pacyna, 1995), there is con-
coastal versus deep ocean); 4) change in food web struc-
siderable scope to enhance the deposition of airborne
ture affecting the degree of biomagnification (bottom-
contaminants to surfaces by altering location and in-
up effects); 5) change in the feeding ecology of key
tensity of precipitation (Figures 3ท4 a and 3ท4 b) and/or
higher order consumers (top-down effects); and 6) change
by changing the balance between snow and rain (see, for
in the age structure of higher trophic order populations
example, Sherrell et al., 2000). Under AO+ conditions,
where contaminant concentrations in tissue are age-
the atmospheric corridor from eastern North America
dependent.
and Western Europe will become a more efficient trap
for particulates, raining them out in the Nordic Seas
and in the southern portion of the Eurasian Basin. Par-
6.1. Heavy metals
ticle scavenging will generally increase wherever higher
6.1.1. Lead, cadmium, zinc
precipitation prevails, such as over northern Europe
Lead (Pb), cadmium (Cd) and zinc (Zn) are common-
and the Eurasian Basin in general. Contaminants de-
ly released to the atmosphere through high-tempera-
posited on the eastern side of the Nordic Seas will then
ture processes or, in even greater quantities, to water
enter the Barents Sea and the Eurasian Basin via ocean
through runoff, municipal discharges and dumping (Pa-
currents. Contaminants deposited to the west will be
cyna et al., 1995). In addition, anthropogenic Pb has
delivered back into the North Atlantic via the East
had a unique, predominant source in leaded gasoline
Greenland Current. Given this scenario, it seems likely
combustion. Although leaded gasoline has been largely
that under AO+ conditions, metal-contaminated aero-
phased-out in North America and Europe, it is still used
sols entering the Arctic near the prime meridian will be
in other regions, including much of Russia. Due to the
subject to enhanced scavenging en route. Larger areas
strong atmospheric connection in winter between Eura-
of open water (Figure 3ท8) mean that scavenging will
sia and the High Arctic (Figures 3ท2 a and b), long rec-
tend to place a greater proportion of these airborne
ognized in events such as Arctic haze (Hileman, 1983)
contaminants directly into the surface ocean rather
and brown snow (Welch et al., 1991), much attention
than on the sea ice. The decline of aerosol metal con-
has been focused on the atmosphere as a means of
centrations at Alert after about 1991, ascribed by Sir-
transporting contaminant metals to the Arctic (Ak-
ois and Barrie (1999) to the collapse of industry fol-
eredolu et al., 1994; AMAP, 1998; Boutron et al., 1995;
lowing the break-up of the former Soviet Union, could
Pacyna, 1995; Rosman et al., 1993; Sirois and Barrie,
also be explained partly by changes in wind and precip-
1999; Sturges and Barrie, 1989). Based on back trajec-
itation patterns at the end of the 1980s (Figures 3ท2
tories, models, and stable lead isotope composition, the
and 3ท4). Enhanced loadings to sea-ice surfaces under
sources of atmospheric metals have been established
AO+ conditions are most likely to occur over the south-
primarily as Eurasia, including the industrialized areas
ern Eurasian Basin and this ice would then be exported
of Western and Eastern Europe and the Urals (in partic-
back into the Greenland Sea.
ular Norilsk), and secondly North America ญ each of
The focus on the atmosphere as a pathway for the
which supplies air masses to the Arctic at particular
transport of metals from anthropogenic sources to the
times during the year (Figure 3ท2). The shift between
Arctic has to some degree diverted attention from the
AOญ and AO+ conditions alters mean wind fields
ocean. Sediment cores collected along the margins of the
thereby effecting change in the balance and timing of air
Eurasian and Canadian Basins (Figure 6ท1) suggest that
movement from these various source regions, but the
a major route for contaminant Pb to the Arctic Ocean

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32
AMAP Assessment 2002: The Influence of Global Change on Contaminant Pathways
1.18
Russia / Eastern Europe
Major sources of lead
R U S S I A
Atlantic water in
boundary currents
1.14
1.14
Generalized ice drift
and surface-water circulation
Kara
Front
Sea
Ice cover:
Laptev
summer minimum,
Sea
Barents Sea Branch W
winter maximum
1.18
a
2-3 yr
te
5
r
Lead
Barents Sea
depositional flux,
0
mg/m2
S C A N D I N A V I A
3000
T
Bold figures
Stable lead isotope ratio
ran
Time taken for water
7- 8 yr
sp
Italic figures
to transport from
ola
the North Sea
r D
F
Western
13 yr
r
r
i
a
ft
m S
1000
1.12-1.155
S I B E R I A
13 yr
tr
200
ai
Norwegian Sea
t B
Europe
1000
r a nch Water
3000
2 yr
Fram
2000
180ฐ
0ฐ
Strait
Chukchi Sea
+15 yr
Beaufort Gyre

1.165-1.178
Bering Strait
1000
+15 yr
1.14
Beaufort Sea
Denmark
A L A S K A
3000
200
1000
Strait 1000
2000
G R E E N L A N D
2000
C A N A D I A N
1000
A R C T I C A R C H I P E L A G O
2000
90ฐW
Figure 6ท1. The major sources of contaminant lead transported to the Arctic are indicated by the stable lead isotope composition of sediment
cores as being either Western Europe (indicated by a 206Pb : 207Pb ratio of 1.14) or Eurasia (indicated by a 206Pb : 207Pb ratio of 1.18) (adapted
from Gobeil et al., 2001a).
has been the same ocean current that transports ra-
tion of anthropogenic Pb in the Arctic sediments, these
dionuclides northward from the European reprocessing
authors proposed a transport scheme wherein Pb from
plants (Gobeil et al., 2001a). The residence time of Pb in
these source areas enters the Arctic Ocean via the Laptev
surface water, which is relatively short (< 5 years), is still
Sea, either entrained in ice or, perhaps more likely, in
long enough to permit transfer of contaminant Pb from
water carried in the Transpolar Drift (TPD) (Gobeil et
the North Atlantic and Nordic Seas into the Arctic
al., 2001a). The observation that anthropogenic Pb was
(Gobeil et al., 2001a). Under AO+ conditions an even
conspicuous in the Eurasian Basin margins but not in the
more efficient transfer of metals may be expected from
Canadian Basin, led these authors to conclude that
Western Europe to the Arctic either via rainout in the air
ocean and ice transport pathways during the peak Pb
transport corridor to the northwest of Europe (Figures
emission years (~ the last 60 years) must have been
3ท2 and 3ท4) or via coastal discharges to the North or
predominantly those associated with AOญ conditions.
Baltic Seas. Lead comprises four stable isotopes: 204Pb
Under AO+ conditions, pathways for ice, ocean currents
(1.48%), 206Pb (23.6%), 207Pb (22.6%) and 208Pb
and runoff change dramatically (Figures 3ท2, 3ท5, 3ท14)
(52.3%), with the composition varying between geolog-
such that contaminant metals entering the Russian
ical reservoirs (Sangster et al., 2000). This variation has
shelves (atmospherically or by runoff) would be diverted
provided an incisive means of determining the sources
to the east into the Canada Basin and toward the Cana-
of contaminant Pb in global environmental media, in-
dian Arctic Archipelago (Gobeil et al., 2001a; Mysak,
cluding Arctic aerosols and ice (Rosman et al., 1993;
2001). The pathways indicated by Pb contamination are
Sturges and Barrie, 1989; Sturges et al., 1993). Accord-
probably relevant for other particulate-bound contami-
ingly, Gobeil et al. (2001a) were able to relate the con-
nants ญ for example some of the more highly chlorinated
taminant Pb accumulating in sediments along the Bar-
polychlorinated biphenyls (PCBs).
ents Sea margin to a western European source (206Pb :
Atmospheric aerosols of Cd and Zn will to some de-
207Pb ~ 1.14) with ocean currents acting as the major
gree behave like Pb, except that the predominant source
transporting mechanism (Figures 3ท17 and 6ท1). Anthro-
of anthropogenic Pb is leaded gasoline as opposed to
pogenic Pb in sediments near the North Pole, however,
metallurgical industries and stationary combustion for
had an Eastern European or Russian composition
Cd and Zn. Time series of aerosol composition at Alert
(206Pb :207Pb ~1.18) (Figure 6ท1). Based on the distribu-
(Sirois and Barrie, 1999) and records from ice cores

---

The Effects of Climate Change on Contaminant Pathways
33
(Boutron et al., 1991, 1995) and glacial snow (Sherrell
chemical cycle and exhibits a strong correlation with
et al., 2000) reveal contamination due to industrial ac-
phosphate (Boyle, 1988; de Baar et al., 1994). The inter-
tivity in Asia, Europe and North America. Like Pb, Cd
action between the biogeochemical cycle and circulation
and Zn are poorly captured within the Arctic (<15%;
of the world ocean results in sub-surface water of the
Akeredolu et al., 1994; Pacyna, 1995) and changes in
North Pacific containing naturally higher Cd concentra-
precipitation patterns probably have the greatest poten-
tions than that of the North Atlantic (by a factor of
tial to change metal delivery to surfaces.
about 5 ญ see Bruland and Franks, 1983) which in turn
Of these three heavy metals, Cd provides the greatest
makes the Pacific inflow through Bering Strait by far the
risk to wildlife and human health, as a result of bioac-
dominant source of Cd to surface waters of the Arctic
cumulation and biomagnification (Figure 6ท2), espe-
Ocean (Macdonald et al., 2000a). Reduced Bering in-
cially into liver and kidney of marine and terrestrial
flow since the 1960s (Figure 3ท20 a) probably entails a
mammals (Braune et al., 1999; Muir et al., 1999). Ob-
similar (15%) reduction of the supply of Cd to the Arc-
served high concentrations of Cd in Arctic biota, how-
tic Ocean from that source. The encroachment of At-
ever, appear to be natural and not obviously related to
lantic water into the surface of the Makarov Basin, seen
human activities except, possibly, at locations close to
under recent AO+ conditions, will further reduce the do-
sources (<100 km). In consequence, significant changes
main of Cd-rich water within the Arctic (Figures 3ท13
in Cd exposure are likely to occur through changes in
and 3ท15). The accompanying increased stratification
the natural cycle of Cd and not by changes in anthro-
and recycled production in the smaller Pacific domain of
pogenic Cd pathways. An exception to this rule may
the Canada Basin will, however, tend to maintain Cd
occur locally when Cd contamination is accompanied
from runoff or atmospheric deposition at the surface.
by, or followed by, system changes that alter Cd biogeo-
It is noteworthy that the Canadian Arctic Archipelago
chemistry. Croteau et al. (2002) provide a clear example
is the downstream recipient of water from the Pacific
of where reductions in Cd loadings to a contaminated
Ocean and, therefore, the recipient of Cd and nutrients
lake were accompanied by increases in pH with the con-
from that source.
sequence that organisms actually exhibited increasing
Recent work on metal-impacted lakes near a copper-
Cd uptake.
smelting center in Quebec, Canada, shows that metal
In the Arctic Ocean, natural cycles completely domi-
loadings (Cd, Cu, Zn) can alter ecosystem structure,
nate Cd fluxes and budgets (Macdonald et al., 2000a).
causing the demise of medium to large benthic inverte-
Cadmium follows soft body parts in the marine biogeo-
brates and producing fish populations shifted to smaller
sizes (Sherwood et al., 2000, 2001). This suggests the
Cadmium, biomagnification factors
strong possibility that contamination by these heavy
metals could interact with the accumulation and bio-
Plankton
Epontic
Plankton
magnification of other contaminants like mercury (Hg)
(>509 ตm)
algae
(25-215 ตm)
and OCs, potentially reducing concentrations of the lat-
ter in apex feeders.
2.4-3.4
1.9-5.6
6.1.2. Mercury
0.15-0.22
Pelagic
amphipods
Due to its volatility and tendency to undergo biogeo-
chemical transformation, Hg must be considered sepa-
0.01-0.02
rately from other heavy metals (see, for example, Fitz-
gerald et al., 1998; Mason and Fitzgerald, 1996; Mason
et al., 1994). Particular attention must be given to
Arctic cod
aquatic environments because it is there that Hg poses
0.5 -1.0
its greatest threat through biomagnification (Atwell et
al., 1998; Evans and Lockhart, 1999; Muir et al., 1999).
To a certain extent, processes leading to enhanced Hg
concentration in the environment can be considered as
either `solvent switching' or `solvent depletion' (Mac-
Narwhal
Beluga
Ringed
seal
donald, et al., 2002c). In the former, Hg moves between
phases such as air, water and particles based simply on
0.1- 0.25
0.4 -80
partition coefficients, whereas in the latter Hg may
achieve high fugacity through the loss of surfaces or
through chemical reactions mediated by photons or mi-
Glaucous
Gammarid
Polar bear
gull
amphipods
crobes (see, for example, processes described by Lind-
berg et al., 2002; Malcolm and Keeler, 2002). The natu-
ral Hg cycle has been enhanced by human activities such
Figure 6ท2. Pathways and biomagnification factors for cadmium in
the Arctic marine food web. Biomagnification factors are based on
that two to three times as much Hg is presently cycling
dry weight concentrations in whole organisms for biomagnification
through the atmosphere and upper ocean than before
to invertebrates and fish, and on wet weight concentrations for fish
the rise of industry (Lamborg et al., 2002; Mason and
34
to muscle in top predators (for polar bear, liver was used instead of
Fitzgerald, 1996; Mason et al., 1994; Pacyna and Keeler,
muscle) (from Muir et al., 1999). In the case of the biomagnification
1995). Because atmospheric Hg is almost entirely gas-
factors from ringed seal to polar bear, the lower value is for seal
eous (Hg0), it is tempting to assume that the polar re-
blubber to polar bear liver, and the higher value is for ringed seal
liver to polar bear liver.
gions might be global sinks simply due to low tempera-

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34
AMAP Assessment 2002: The Influence of Global Change on Contaminant Pathways
h
BrCl + h
Brท/Clท

Atmospheric
Atmospheric
transport
Br2 + h
2Brท

transport
into the Arctic
out of the Arctic
Br/Cl + O3
BrO/Cl O + O

2
Hg0
BrO/Cl O + Hg0
Brท/Clท + Hg O

Hg0
}
2Brท/Clท + Hg0
HgBr

RGM
2/Hg Cl2
Hg0
Br2, Cl2
Hg2+ (particulate) + RGM
Hg0
h
h
Hg0
Hg0
Snow
Runoff
Hg2+
Hg2+
Advection from
Hg2+
Hg0
Advection to
oceans to the south
oceans to the south
HgP
CH
Food web
3MeHg
Surface mixed layer
Particle removal
Figure 6ท3. A schematic diagram illus-
trating how atmospheric mercury is
Sediment
scavenged after polar sunrise and sub-
sequently enters surface waters.
ture and, accordingly, to make projections of the effects
ble, because it here that sea salt (and therefore bromine)
of climate change based on this fact alone. In fact, ther-
can most easily interact with snow through aerosols or
mal forcing for Hg0 to Arctic aquatic systems, either by
frost flower formation associated with flaw leads or
rain or by airญwater exchange, is weak due to a rela-
first-year ice. With spring warming, about two-thirds of
tively high Henry's Law constant (Macdonald et al.,
the Hg deposited in snow is estimated to re-volatilize
2000a; Mason et al., 1994). Nevertheless, the Arctic
(Brooks, pers. comm., 2001) with the remaining third en-
may be especially vulnerable to Hg because of an ex-
tering aquatic environments through meltwater.
traordinary set of circumstances at polar sunrise that re-
Before projecting the impact of global change on the
sults in the deposition of reactive (and bioavailable) Hg
Hg cycle in the Arctic, it is necessary to understand how
to the surface (Figure 6ท3; Lindberg et al., 2002; Lu et
the invasion of Hg to global aquatic reservoirs via wet
al., 2001; Schroeder et al., 1998). A relatively long resi-
and dry deposition of reactive forms is balanced by
dence time for Hg0 of one to two years in the atmos-
gaseous evasion of reduced forms of Hg such as Hg0 or
phere (Lamborg et al., 2002) ensures that winds can
methylmercury (MeHg) (Mason et al., 1994). Dissolved
transport Hg to the Arctic from sources throughout the
Hg or Hg associated with suspended particulates in melt-
Northern Hemisphere. With the increase of UV radia-
water and runoff can drain into surface water below the
tion at polar sunrise, Hg0 is converted to reactive gase-
ice cover whereas the evasion of Hg0 is partly or com-
ous mercury (RGM) through reaction sequences in which
pletely blocked by ice cover. Indeed, this set of circum-
bromine, chlorine and ozone, and compounds like BrO
stances may provide the foundation for the elevated Hg
and ClO appear to have prominent roles (Figure 6ท3 and
levels which have been observed in Arctic biota (Evans
see Lindberg et al., 2002; Lu et al., 2001). The RGM thus
and Lockhart, 1999; Macdonald et al., 2000a; Muir et al.,
formed is very effectively removed from the atmosphere
1999; Wagemann et al., 1995, 1996). Unfortunately, ap-
by particles/snow, with this process estimated to account
propriate geochemical studies investigating the cycling
for the deposition of ~50 t (> 90% of the annual total)
of Hg in Arctic aquatic systems have not yet been con-
on the Arctic Ocean and Hudson Bay during spring (Lu
ducted and this is only speculation at the present time.
et al., 2001) and perhaps as much as 150 to 300 t/yr
The vulnerability of the Arctic to global Hg emis-
(Lindberg et al., 2002). Using an air transport model,
sions, therefore, probably lies in the mismatch between
Christensen et al. (AMAP, 2003a) estimated Hg deposi-
invasion and evasion processes. Climate change can af-
tion north of the Arctic Circle at 180 t when mercury de-
fect both the invasion and evasion routes for Hg. Spring-
pletion event (MDE) chemistry was included in the model,
time depletion of atmospheric Hg depends on the avail-
as opposed to ca. 80 t in the absence of MDEs. Based on
ability of sea salt, calm weather, a temperature inver-
snow samples, and the BrO distribution as determined
sion, the presence of sunlight and sub-zero temperatures
from satellite measurements, reactive or particulate Hg
(Lindberg et al., 2002; Lu et al., 2001). Initially with cli-
is probably deposited mainly in areas subject to marine
mate change, it is likely that increased amounts of first-
influence (marine aerosol being the source of the bro-
year ice around the polar margins will contribute to gen-
mine/chlorine compounds involved in MDEs). The mar-
erally saltier ice and snow in spring which will enhance
ginal seas of the Arctic appear to be especially vulnera-
the production of BrO/ClO. Depending on what con-

---

The Effects of Climate Change on Contaminant Pathways
35
trols the rate of supply of Hg to the Arctic, increased
Mercury, biomagnification factors
BrO/ClO will either enhance scavenging or maintain it
at present levels, possibly extending the area of spring-
Plankton
Epontic
Plankton
(>509 ตm)
algae
(25-215 ตm)
time Hg depletion beyond that implied by recent satellite
measurements of the distribution of BrO/ClO (see Lu et
al., 2001). Considering that global emissions of Hg have
generally decreased over the last 20 years, Lindberg et
a
al. (2002) proposed that the recent increases observed in
Pelagic
Hg levels in Arctic biota in some areas are, in fact, evi-
amphipods
dence that MDEs may be a recent phenomenon associ-
ated with change in sea-ice climate and atmospheric
chemistry over the past decade or two. However, the en-
tire Hg cycle must be considered before linking MDEs
with Hg concentrations in apex aquatic feeders. Larger
Arctic cod
areas of open water in spring, either for ocean or lakes,
will enhance exchange allowing gaseous forms of Hg to
escape back into the atmosphere (Figure 6ท3). With fur-
32
29
11
ther warming, parts of the Arctic will become more tem-
perate in character implying that atmospheric Hg deple-
Narwhal
Beluga
Ringed
tion would decrease and evasion from the water increase
seal
leading eventually to lower Hg concentrations in water.
Aquatic food webs have strong leverage for change
50-100
12-3000
in Hg exposure in the Arctic because MeHg biomagni-
fies, exhibiting a concentration increase of about 1000-
to 3000-fold from particulate organic matter to apex
Glaucous
Gammarid
Polar bear
gull
amphipods
predators (Figure 6ท4; Atwell et al., 1998; Kidd et al.,
1995a; Muir et al., 1999). Mercury concentration also
increases with age/size in predatory fish, such that large,
old fish often exceed thresholds considered safe for un-
Log10 [Hg], ตg/g
restricted human consumption (Lockhart and Evans,
1
Mammals
b
2000), containing anywhere from two to five times the
Birds
Hg concentration of smaller fish of the same species.
Fish
Therefore, adding an extra step in the food web could
Invertebrates
reasonably be expected to enhance Hg concentrations
POM
0
in higher trophic levels by a factor of about five. Like-
wise, altering the population distribution of fish in a
lake could produce a change rivaling or exceeding any
change caused by alteration of physical pathways.
With warming (Figure 3ท3) will come the loss of per-
ญ 1
mafrost (Figure 3ท24) causing altered hydrology, poten-
tially more wetland, and enhanced fluxes of soil and or-
ganic carbon to rivers, lakes and estuaries. Warming of
drainage basins in the Arctic, therefore, would appear to
provide a widespread mechanism to increase Hg fluxes
ญ 2
Log
to northern aquatic environments and to the atmos-
10 [Hg ] = 0.20 ( 15 N) ญ 3.33
phere. A recent study of the pathway of Hg from snow-
4
10
16
22
covered land to streams in Vermont (Stanley et al., 2002)
15N ()
showed that Hg export from soils correlated with partic-
Figure 6ท4. Biomagnification of mercury in Arctic food webs. This
ulate organic carbon, and that Hg concentrations in
figure illustrates a) biomagnification factors for a simplified food
runoff increased with flow ญ unlike most solutes (see
web (based on dry weight concentrations in whole organisms (in-
also Bishop et al., 1995). These two factors together
vertebrates and fish) and on a wet weight concentration for fish to
suggest that episodic, large releases of organically-bound
muscle in top predators. For polar bear, liver was used instead of
Hg (of both anthropogenic and natural origin) may be-
muscle) (Muir et al., 1999) and b) biomagnification as a function of
trophic level based on 15N measurements (adapted from Atwell et
come a dominant feature accompanying permafrost de-
al., 1998). In the case of the biomagnification factors from ringed
gradation. Clearly, Arctic lakes would be most vulnera-
seal to polar bear, the lower value is for seal blubber to polar bear
ble to this process, but enhanced input of terrestrial car-
liver, and the higher value is for ringed seal liver to polar bear liver.
bon is projected to occur to Arctic seas as well (Kabat et
al., 2001), suggesting that Hg loadings there may, simi-
concentrations of Hg in snow are observed generally in
larly, be increased. In the ocean, Hudson Bay would
that region (Lu et al., 2001) and that a recent increase in
seem especially vulnerable, partly due to its large drain-
Hg flux to Hudson Bay sediments has, likewise, been
age basin, already affected by reservoir flooding (Bodaly
observed (Lockhart et al., 1995).
and Johnston, 1992), and partly due to the likelihood of
Historical records from dated sediment cores have
permafrost melting within that drainage basin (Gough
been used to infer Hg fluxes increasing by factors of 3 to
and Wolfe, 2001). It seems noteworthy that enhanced
7 in some Arctic lakes during the past two centuries

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36
AMAP Assessment 2002: The Influence of Global Change on Contaminant Pathways
(Bindler et al., 2001; Landers et al., 1995; Lockhart et
sediments is remobilized through reduction to As(III),
al., 1998). What is not so clear is whether such increases
which then diffuses upward to re-precipitate through re-
are due to increased atmospheric deposition or to alter-
actions with nitrate, oxides of manganese or oxygen
ation of processes that transfer Hg from wetlands to at-
(Figure 6ท5). This natural redistribution of As in sedi-
mosphere or from the drainage basin into lakes or trans-
ments makes it exceptionally precarious to infer contam-
fer Hg from the water to the sediments. In regard to the
ination from sediment surface As enrichments (Loring et
latter, Gajewski et al. (1997) have shown major in-
al., 1995, 1998; Siegel et al., 2001). However, strong
creases in diatom fluxes to varved sediments from a lake
sediment-surface enrichments serve as a warning that al-
on Devon Island which they attribute to climate change
teration of the organic geochemistry of aquatic sedi-
(i.e., longer, ice-free summers). Not only could such a
ments by enhanced organic carbon fluxes may have
mechanism explain enhanced Hg fluxes to Arctic lake
unanticipated consequences for As mobility (cf. Figures
sediments but it could also have the non-intuitive result
6ท5 a and b).
of reducing the exposure of higher trophic levels to Hg
A geochemical study of a temperate, seasonally ice-
through bloom dilution at the algal stage (Pickhardt et
covered lake contaminated by As, Cu, nickel and Zn is
al., 2002).
especially instructive (Martin and Pedersen, 2002). When
Mercury depletion events leading to the production
action was taken to reduce metal loadings, the lake's re-
of bioavailable Hg have been confirmed at Barrow, Al-
sponse was enhanced phytoplankton production which
aska (Lindberg et al., 2002). Given that this region re-
then invigorated carbon fluxes to sediments. Through
ceives airborne contaminants from Asia (Li et al.,
metabolism in sediments, the enhanced carbon fluxes
2002; Wilkening et al., 2000), that China is increasing
then reduced oxygen, thus mediating the conversion of
its reliance on coal for energy, and that coal is a leading
solid-phase As(V) to dissolved-phase As(III) which then
source of anthropogenic Hg (Nriagu and Pacyna, 1988),
diffused back into the bottom water. The unanticipated
it seems likely that the Bering/Chukchi Sea region may
result of decreasing metal loadings to the lake was to
be especially vulnerable to further increased Hg load-
produce higher As concentrations. If one of the re-
ings. In general, the pathways of anthropogenic Hg
sponses to change in Arctic aquatic environments is en-
might be expected to change as a result of shifts in
hanced aquatic productivity or enhanced organic carbon
major sources, for example, as European and North
loadings, release of solid-phase As, especially from sedi-
American emissions decrease and Asian emissions in-
ments with high natural or anthropogenic contaminant
crease.
burdens (e.g., see Loring et al., 1995, 1998; Siegel et al.,
2001) is a likely response.
6.1.3. Arsenic
6.2. Radionuclides
The sediment geochemistry of arsenic (As) can, like Hg,
be altered by changing the carbon cycle. Mining and
Previous assessments have outlined the atmospheric and
smelting have been major sources of As to the environ-
oceanic pathways that transport artificial radionuclides
ment (Nriagu, 1989), where it may accumulate in aquatic
to the Arctic (AMAP, 1998; Macdonald, et al., 2000).
sediments (Martin and Pedersen, 2002). In the Arctic, it
Atmospheric artificial radionuclides derive mainly from
has also been suggested that underwater nuclear weap-
atmospheric weapons testing predating the mid 1960s,
ons testing may have provided a significant anthropo-
and the Chernobyl accident in 1986. Accordingly, pre-
genic As source to the Pechora Sea (Loring et al., 1995).
dominant food web contamination from the atmosphere
Large natural surface sediment enrichment of As is often
has occurred to terrestrial systems through fallout
produced by diagenesis; solid-phase As(V) at depth in
(AMAP, 1998) and there appears little opportunity for
a
Water
b
Water
C org
C org
Oxic
Diffusion
Diffusion
NO ญ
3 , MnO 2
Fe (III) = As (V)
Fe (II) = As (III)
NO ญ
3 , MnO 2
Suboxic
(solid )
(dissolved )
Fe (III) = As (V)
Fe (II) = As (III)
C
(solid )
(dissolved )
org
C org
Burial
Precipitation
Burial
Precipitation
Sediment
Sediment
Figure 6ท5. A schematic diagram showing how arsenic cycles in sediments (modified from Sullivan and Aller, 1996). The solid-phase form of
arsenic (As(V)) is released to pore water through reduction to As(III) which may then diffuse back out of sediments. Enhanced fluxes of organic
carbon to sediments, shown in the right-hand panel, are reflected by enhanced diffusion of dissolved arsenic back into bottom waters.

---

The Effects of Climate Change on Contaminant Pathways
37
present or future climate changes to have much impact
water motion and, although they will reflect recent
on historical atmospheric sources which are decaying
changes in that motion, they will continue to provide al-
with half-lives of about 30 years (137Cs and 90Sr, pre-
most no risk to Arctic marine biota (Macdonald and Be-
dominantly). The distribution of fallout from Chernobyl
wers, 1996).
was very much controlled by wind and rainfall patterns
The ice and surface water pathway changes forced by
(see Figures 8.4 and 8.5 in AMAP, 1998), and these
the AO (Figures 3ท10 and 3ท14) strongly suggest that ra-
pathways are clearly subject to climate change. An im-
dionuclides discharged to the Russian shelves may,
portant lesson to be learned from the Chernobyl acci-
under AO+ conditions, enter the Canadian Basin and
dent is that climate patterns can predispose the Arctic
subsequently find their way into the Canadian Arctic
in how it will receive contaminants from such accidents
Archipelago. The estimated total release of radionu-
and, for example, wetter conditions in the Nordic Seas
clides to the Kara Sea via river water (Ob, Yenisey) is
and Northern Europe during AO+ conditions (Figure
about 1.1 1015 Bq (90Sr and 137Cs) (Paluszkiewicz et al.,
3ท4 b) would favour deposition of 137Cs fallout in that
2001), or about an order of magnitude less than the fall-
region.
out and reprocessing plant sources to the Arctic Ocean
In the ocean, the predominant artificial radionuclides
(Aarkrog, 1994). It seems likely, therefore, that diver-
(137Cs, 90Sr, 239+240Pu) do not biomagnify sufficiently (ex-
sion of Russian river runoff from the Eurasian Basin
cept perhaps for plutonium (Pu) in brown macroalgae;
to the Canadian Basin under AO+ conditions will be
see Berrow et al., 1998; Fisher et al., 1999) to contribute
matched by a diversion of associated radionuclides (see
significantly to the radiation dose for humans (Layton et
Cooper et al., 1999) which, nevertheless, will provide
al., 1997; Macdonald and Bewers, 1996). This suggests
little threat to ecosystems there.
that, in order to find pathway changes that might be
Ice drift, the remaining transport pathway, provides
cause for concern, it is the ice and surface water motion
a distinct, but difficult to quantify risk. Sediments from
of the Arctic Ocean that must be considered, both of
the Russian shelves, known to have been contaminated
which exhibit variability resulting from the AO/NAO
by weapons testing and accidental and deliberate ra-
(Figures 3ท9 and 3ท14).
dioactive waste discharges, have been found to be heav-
Clearly, the enhanced northward transport of water
ily contaminated at several locations (Josefsson, 1998;
in the Nordic Seas under the AO+ conditions of the
Matishov et al., 1999; Smith et al., 2000). Suspension
1990s (Figure 3ท15) strengthened the delivery to the Arc-
freezing provides an efficient mechanism to entrain fine
tic of radionuclides discharged by the European nuclear
sediments into newly-formed ice in the Russian seas
reprocessing plants where they continued to spread into
(Eicken et al., 2000) and ice has been shown to carry ra-
the surface waters of the Makarov Basin (Figures 3ท13
dioactive sediments (Dethleff et al., 2000a; Landa et al.,
and 3ท15; Smith et al., 1998).
1998; Meese et al., 1997). High radioactivity has been
The transport routes for radionuclides in the Nordic
found in ice-entrained sediments in the Canada Basin
Seas are generally known (Figure 3ท17). A shift in the cli-
(> 70 Bq/kg; Cooper et al., 1998) and in the Canadian
mate regime toward increased NAO index and stronger
Arctic Archipelago (Darby, pers comm., 2001) but the
wind fields will probably lead to radionuclides undergo-
origin of the sediment in the ice, based on mineralogy,
ing a faster transport closer to the Norwegian coast,
has not been assigned to Russian shelves. Given the very
with a larger proportion entering the Barents Sea. It is
few samples together with their uncertain provenance, it
expected that other contaminants entering the North Sea
is impossible to quantify risks to biota in the Canada
and southern Norwegian Sea from sources in Europe
Basin and the Canadian Arctic Archipelago from con-
will encounter similar change in their oceanic transport
taminated ice, except to say that the AO+ conditions of
route as that proposed for radionuclides.
the early 1990s appear to produce ice transport path-
The enhanced coupling between release points for
ways conducive to carrying sediment and surface water
European reprocessing plant nuclear wastes and the Arc-
from the Russian shelves into the Archipelago.
tic Ocean will be more than offset by reduction in re-
Perhaps the most significant increase in radioactivity
leases of the major radionuclides that have occurred
exposure to northern residents will come from the natu-
since the 1970s (Macdonald et al., 2000a), and input of
ral 226Ra decay series that supports 222Rn, 210Pb and
tracers such as 137Cs to the Arctic Ocean should con-
210Po. 210Pb in aquatic systems derives partly from in-
tinue to decline. Recent increased discharges of tech-
situ production supported by 226Ra and partly from
netium, however, provide a reminder that not all ra-
222Rn which has diffused out of soils and, with a short
dionuclide discharges from European reprocessing
(3.8 day) half-life, decays to 210Pb which is scavenged by
plants are declining (AMAP, 2003c). Extensive data col-
particles. This latter component, called excess 210Pb,
lection under the Arctic Nuclear Waste Assessment Pro-
often exceeds the `supported' 210Pb in aquatic sediments.
gram (ANWAP; Layton et al., 1997) and from icebreak-
Presently, excess 210Pb tends to be very low in the Arctic
ers (Smith et al., 1998) has provided sufficient informa-
because 222Rn remains trapped in the soil by permafrost
tion on the distribution of artificial radionuclides in Arc-
and snow/ice cover. With warming, 222Rn evasion will
tic surface waters to show that they pose little risk to hu-
increase as will excess 210Pb activity matched by the ac-
man or ecosystem health. The conclusion of the
tivity of 210Po, its granddaughter. Since 210Po and 222Rn
ANWAP assessment was that the largest radiation doses
together account for about 75% of the radiation dose to
to individuals living on the Alaskan coast and consum-
native northern residents (Layton et al., 1997; Macdon-
ing subsistence seafoods were, in order of importance,
ald and Bewers, 1996) any substantive increase in 222Rn
210Po (a natural radionuclide), followed by 137Cs and
evasion due to warming/permafrost melting would have
90Sr from atmospheric fallout. It seems that the nuclear
a widespread and substantial (doubling or tripling) ef-
reprocessing radionuclides have made elegant tracers of
fect on the radiation dose.

---

38
AMAP Assessment 2002: The Influence of Global Change on Contaminant Pathways
toplankton or small zooplankton strictly according to
6.3. Organochlorine compounds
thermodynamic forcing.
Of all the contaminants, the organochlorines (OCs) pro-
Solvent depletion, however, is a very different pro-
vide the greatest challenge to predict consequences of
cess in that it can lead to concentrations in selected
change because they have been so widely released, com-
media that exceed thermodynamic equilibrium (i.e., fu-
prise so many compounds and exhibit such a wide range
gacity is increased), which requires a source of energy.
of physical chemical properties. Furthermore, the impor-
Perhaps the clearest example of solvent depletion occurs
tant chemical properties ญ volatility, phase partitioning,
in the food web where lipid transfers, going from one
and degradation kinetics ญ are all sensitive to tempera-
trophic level to a higher one, are inefficient. Metabolism
ture and hydrological change. Efforts to determine
effectively burns much of the lipid, leaving the contami-
where in the environment these compounds end up have
nant to accumulate in a decreasing volume of stored fat.
improved the understanding of global pathways enor-
This process can lead to OC concentrations in aquatic
mously, but new surprises give an indication that intu-
apex feeders that are well above thermodynamic equilib-
ition often fails due to an incomplete grasp of environ-
rium with the water, and the situation can be exacer-
mental processes (Macdonald et al., 2000b; Oreskes et
bated by starvation cycles during which individuals re-
al., 1994; Schindler, 1997). Recent OC budgets under-
duce their fat content further. Arctic and other cold envi-
score the importance of the atmosphereญocean coupling
ronments offer several solvent depletion processes by
in the transfer of OCs to the Arctic from their temperate
which contaminants can be ramped up above thermody-
and tropical release points (Li et al., 2002; Macdonald et
namic equilibrium (Macdonald et al., 2002c). In partic-
al., 2000a,b). These same budgets show that the relative
ular, a POP can be scavenged by adsorption onto snow
importance of atmosphere versus ocean in transporting
and thence transported to the ground. The initial large
contaminants will vary widely among the OCs and over
snow surface (0.1 m2/g) can be reduced by a factor of
time. Therefore, change forced by the AO or by general
over 100 and, indeed, during melting, the snow surface
global change will have a similarly varied impact de-
can disappear entirely effectively removing the solvent
pending on the particular OC and the time period in
(the snow's surface) from under the contaminant. The
question. All the OCs of concern (DDT, toxaphene, chlor-
fugacity can be increased enormously during snow sin-
dane, PCBs, hexachlorocyclohexanes (HCHs)) have tran-
tering/melt with the consequence that the OC is forced
sient emissions: that is, they were first released in the
to diffuse back into the atmosphere, enter the meltwater
1930s to 1940s, emissions peaked sometime in the
or adsorb onto other particles. Similarly, fog water drop-
1970s to 1990s, after which they have generally declined
lets can provide a temporarily large surface area which is
or ceased. Continued declines, or possibly increases, will
thermodynamically attractive ญ upon coalescence, most
depend on bans, further controls, or new use following
of the surface is lost and contaminant fugacity increases
invigorated assaults by pests linked to climate change.
in the remaining large water droplets. Finally, cryo-con-
As a general rule, particularly with transient releases of
centration may occur in shallow lakes or seas that form
chemicals that partition strongly into water, the atmos-
a thick ice cover. The withdrawal of water into the ice,
phere is initially the dominant transporting medium, but
leaving behind most of the POPs, can easily increase
as aquatic reservoirs (lakes, rivers, upper ocean) become
concentrations in the water beneath the ice to values
loaded, these then contain the important if not domi-
that exceed thermodynamic equilibrium with the atmos-
nant budget and flux terms (Li et al., 2002; Macdonald
phere by factors of 2 to 5. Due to the ice cover, diffusion
et al., 2000a,b) and it is dominant budget terms that
back into the atmosphere is not an option.
posses the greatest leverage for change.
Under change scenarios, the solvent-switching pro-
Before discussing how climate change is likely to im-
cesses can be modeled by taking into account changes in
pact upon OCs, it is important to understand the man-
partition coefficients and vapour pressures with temper-
ner in which OCs become concentrated in the environ-
ature. However, changes in the solvent-depletion pro-
ment. Building on earlier perspectives developed by
cesses are much harder to project especially since the el-
Wania (1999), Macdonald et al. (2002c) suggest there to
evated fugacities imply transports that will be sensitive
be two fundamental concentrating processes which they
to time. For example, the effect of snow on contami-
termed solvent switching and solvent depletion. The dis-
nants entering an Arctic lake will depend on when the
tinction between these two processes is particularly im-
snow accumulates, how long it sinters, how porous and
portant in the context of change. Solvent switching is a
how deep the snow is, how and when snow melt occurs,
natural process wherein a particular contaminant dis-
and how quickly snow melt enters the lake. None of
tributes itself between various phases (solid, liquid, gas)
these transfer processes have been investigated in suffi-
according to well-described thermodynamic rules. This
cient detail to provide guidance for modellers.
process can lead to elevated concentrations ญ for exam-
ple, the partitioning of HCH into cold water will pro-
6.3.1. The influence of the Arctic Oscillation
duce concentrations in the water that far exceed those in
the air, and indeed this process alone can cause non-in-
There appear to be several consequential ways that
tuitive divergence of chemicals over large scales (Li et
physical pathways could change in response to the AO.
al., 2002). But this process cannot cause concentrations
In the Nordic Seas, especially under AO+ conditions, the
to exceed thermodynamic equilibrium (that is, solvent
atmospheric coupling of eastern North America and
switching does not increase fugacity). Another very im-
Western Europe with the Arctic becomes more intense,
portant solvent-switching process is the transfer of a
in particular during winter/spring (Figures 3ท2 a and b)
POP from water to lipid at the bottom of the food web;
suggesting that spraying pesticides in these regions will,
again, this process enhances POP concentrations in phy-
if anything, intensify `events' such as those seen at Alert

---

The Effects of Climate Change on Contaminant Pathways
39
for - and -HCH (see, for example, Figure 22 in Mac-
Table 6ท1. Russian river loadings for selected organochlorine com-
donald et al., 2000a). Furthermore, re-emission of old
pounds.
OC residues in soils and aquatic reservoirs of Europe or
ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ
Percent of
eastern North America will enter these same air path-
Arctic Ocean
ways to be transported north. In this regard it is worth
Load, t/yr
input budget
Reference
noting that the highest cumulative use of PCBs was in
ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ
Western Europe and eastern North America (see Figure
-HCH
25
13
Alexeeva et al., 2001;
in AMAP 2003b) ญ both of which are source regions for
Macdonald et al., 2000a
air masses entering the Arctic between Greenland and
-HCH
44
51
Alexeeva et al., 2001;
Europe (Figures 3ท2 a and b). The higher precipitation in
Macdonald et al., 2000a
the Nordic Seas and southern Eurasian Basin (Figure
PCBs
15
23
Macdonald et al., 2000b
3ท4) will provide more effective scavenging of particle-
DDT
18
Alexeeva et al., 2001
associated OCs (high molecular weight PCBs, for exam-
ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ
ple) and for OCs with low Henry's Law constants
(HLCs) that partition strongly into water (HCHs, tox-
be felt in the composition of water exiting the Arctic
aphene).
through the Canadian Arctic Archipelago and in the
In the Bering Sea, gas exchange with the ocean or
East Greenland Current and points farther downstream.
washout by rain can provide a mechanism to remove -
The diversion of Russian river inflow toward the east
HCH selectively from the air as it moves northward,
under AO+ conditions (Figure 3ท14) will have a signifi-
simply due to its exceptionally low HLC (Li et al.,
cant effect on OC pathways within the Arctic Ocean. In-
2002). This process does not prevent the entry of this
herent with this diversion is a shift of all the OC load-
contaminant to the Arctic Ocean; rather, it switches the
ings from these Russian rivers out of the Eurasian Basin
mode of delivery from winds to ocean currents and, as a
and into the Canada Basin (Table 6ท1, and see Macdon-
consequence, slows the rate of transport from m/s to
ald et al., 2000a; Sericano et al., 2001). As the Canada
cm/s. Under AO+ conditions, therefore, a more rapid at-
Basin has a longer residence time (10 years, compared to
mospheric transport of OCs into the Arctic from West-
2 years in the TPD), there would be an added conse-
ern Europe is likely, with the delivery shifting toward the
quence of increased contaminant inventories for the Arc-
ocean pathway for OCs that partition strongly onto par-
tic Ocean in general and the Canada Basin in particular.
ticles or have low HLCs. On the Pacific side, OCs will
Instead of tracking across the Eurasian Basin to exit into
continue to enter the Arctic via the atmosphere and
the East Greenland Current, OCs discharged by the
ocean currents (see, for example, Bailey et al., 2000), but
Russian rivers might now exit via the Canadian Arctic
the 15% reduction in Bering Sea inflow over the past
Archipelago (see Figure 3ท14). The changes here are con-
several decades would effect a proportional reduction in
sequential to budgets (Table 6ท1) and to distribution
this pathway. Variation in precipitation over the North
within the water column, keeping in mind that the same
Pacific and Bering Sea (Figure 3ท20 b) will alter the bal-
river water that delivers contaminants also stratifies the
ance between atmosphere and ocean as transport path-
ocean and potentially reduces new production and verti-
ways to the Arctic.
cal particle flux, which together will act to maintain
Larger areas of open water under AO+ conditions or
river-borne contaminants near the surface where they
from general climate change (Figures 3ท6, 3ท7 and 3ท8)
can partition into algae. Although there are few data
will accelerate equilibrium between air and sea by an
from which to evaluate the relative importance of OC
amount equivalent to the expanded open areas. Further-
pathways in the ocean, the findings of Andersen et al.
more, increased numbers of polynyas in winter will en-
(2001) provide a strong warning that there are sources
hance the production of fog over sea ice, acting to scav-
of PCBs in the region around the Kara Sea and Franz
enge and deposit contaminants to surface (Chernyak et
Josef Land, possibly as a consequence of riverine inputs.
al., 1996) at locations known to be important for biota
Water in the Canadian Arctic Archipelago channels,
(Stirling, 1997). Due to the drastic reduction in atmos-
supplied from surface water in the Arctic Ocean (~ 0-
pheric concentrations as a result of emission controls, -
200 m), has the potential to undergo change in its OC
HCH has become oversaturated in ice-covered areas of
content due to alterations in the distribution of water
the Arctic Ocean (Jantunen and Bidleman, 1995; Mac-
masses in the Canada or Eurasian Basins. As shown in
donald et al., 2000b). The opening of the pack and sea-
several studies (Carmack et al., 1997; Li et al., 2002;
sonal clearance of shelves will, in this case, result in eva-
Macdonald et al., 2000a,b), HCHs are not distributed
sion and drawdown of HCH from the upper ocean. In
uniformly within the Arctic Ocean and it is likely that
contrast, PCBs and toxaphene are still loading into the
other OCs are, likewise, not uniformly distributed. For
Arctic Ocean via the atmosphere (Macdonald et al.,
example, -HCH is highest near the surface, decreasing
2000b) and, therefore, the same loss of ice cover will lead
to very low concentrations in water deeper than several
to increased loading of these substances in surface seawa-
hundred meters, and the Canada Basin under the perma-
ter. A PCB budget for the Arctic Ocean (Macdonald et
nent pack ice exhibits much higher HCH concentrations
al., 2000b) estimated a net gas exchange into the ocean of
than are observed in the Chukchi Sea or the Eurasian
about 20 t/yr. The reduced ice cover evident in Figure 3ท8
Basin surface waters. The redistribution of Pacific and
might lead to as much as a doubling of the area of open
Atlantic water masses in surface water of the Arctic
water which would similarly double net exchange. Not
Ocean (Figures 3ท13 and 3ท15) may therefore have been
only does change in ice cover alter the air-sea exchange of
accompanied by change in the composition of water
OC gases, but the consequent loading or unloading of the
flowing into the Canadian Arctic Archipelago. Such
interior Arctic Ocean with such chemicals will later
change could occur in two ways, either by horizontal

---

40
AMAP Assessment 2002: The Influence of Global Change on Contaminant Pathways
Concentration in seawater, pg/L
5000
800
20
150
-HCH
-HCH
HCB
Toxaphene
50 m
1 m
50 m
50 m
4000
120
600
15
1 m
1 m
3000
1 m
90
400
10
50 m
2000
60
200
5
1000
30
Open
Open
Open
Open
water
water
water
water
0
0
0
0
J F M A M J J A S O N D
J F M A M J J A S O N D
J F M A M J J A S O N D
J F M A M J J A S O N D
Figure 6ท6. Time series of organochlorine concentrations measured at Resolute (Canadian Arctic Archipelago) during 1993 at the surface and
50 m water depth for - and -HCH, hexachlorobenzene and toxaphene (source: Hargrave et al., 1997).
displacement of water mass domains or by vertical dis-
6.3.3. The effect of warming
placement of water properties. Although there are few
on organochlorine cycling in lakes
data from which to evaluate how the water composition
in the Archipelago channels might respond to the AO,
Arctic lakes presently tend to retain only a small fraction
an extraordinary set of data collected by Hargrave et al.
of the contaminants they receive, a fact which should in-
(1997) illustrates clearly that change in upstream water
dicate the potential for change. Studies and models
composition can have important consequences for con-
(Helm et al., 2002; Macdonald et al., 2000a) show that
taminant concentrations in water flowing through the
the snowmelt and runoff cycle connects with the lake's
Archipelago. Seasonal measurements of OCs made at
hydrological cycle such that most of the contaminants
Resolute in 1993 (Figure 6ท6) reveal a coherence be-
deposited in the drainage basin throughout winter are
tween the surface and 50 m water depth in contaminant
transported across the lake surface in a low density layer
trends. This coherence, together with patterns differing
under the ice to exit in out-flowing water. The lack of a
for the various OCs, argues strongly that the observed
strong particle flux due to oligotrophic conditions fur-
time trends at Resolute are produced by variation in the
ther decouples deep lake water from contaminants at the
composition of upstream water drawn into the Archipel-
surface. Reduced ice cover and loss of permafrost, lead-
ago from the Canada Basin. The concentration varia-
ing to greater mixing and stronger primary production,
tions in this single season's data exceed a factor of two.
will enhance the ability of Arctic lakes to retain OCs.
How this added retention will be expressed in the food
web is less certain. Enhanced primary production and
6.3.2. The effect of glacial melt back
settling of ungrazed phytoplankton in early spring might
Glacier ice-mass loss and snow melt back due to warm-
draw down contaminant burdens in lake surface water
ing (cyclical or trend) can release archived contaminants
and thereby reduce entry of contaminants into the food
accumulated during years of higher fluxes (Blais et al.,
web or act so as to dilute the OC concentration in algae
1998). Based on the total amount of glacial melt back
as has been shown for Hg (Pickhardt et al., 2002). How-
(Figure 3ท25) and the range in concentration of OC con-
taminants measured in ice and snow during the 1960s to
Table 6ท2. Potential input of selected organochlorine compounds
1990s for the Agassiz Ice Cap (Table 6ท2) the maximum
from glacial melt.
ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ
total inputs are expected to range from about 3 kg for
Flux through
PCBs to as much as 400 kg for DDT. For 1993, the year
Total
Glacial
the Canadian
exhibiting the most substantial melt back on record, the
Concen-
glacial
input
Arctic
maximum inputs of PCBs and DDT were estimated at
tration,
input,
for 1993, Archipelagoa,
0.5 kg and 74 kg, respectively. The HCH and PCB in-
pg/L
kg
kg/yr
kg/yr
puts are minuscule compared to Arctic Ocean budgets
ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ
-HCH b
256
205
39
195 000
(Macdonald et al., 2000b) and are also relatively small
-HCH b
115
92
18
27 900
compared to the flux of these contaminants through the
DDT b
480
384
74
161
Canadian Arctic Archipelago (Table 6ท2). For DDT, how-
Chlordane b
35
28
5
96
ever, glacial melt appears potentially to provide an im-
HCB b
65
52
10
810
portant, climate-modulated source. For Arctic glaciers,
PCBs c
3.5
2.8
0.5
2 700
ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ
most of the melt occurs in zones where old ice of pre-in-
a Flux through the Canadian Arctic Archipelago was estimated as-
dustrial age is emerging. This ice would contain little or
suming a mean flow of 54 000 km3/yr (Macdonald et al., 2000a)
no contaminant burden and, indeed, would act to dilute
and concentration data collected in the Archipelago during 1993
any contaminants released to aquatic environments. For
(HCH, HCB, Chlordane; Hargrave et al., 1997) or Canada Basin
smaller ice caps, more recent layers of snow and ice
in 1997ญ98 (PCB, DDT; Macdonald et al., 2001);
b Concentration data from Franz et al. (1997); samples collected for
might be involved. Thus, glacial melt back appears to be
1987, 1990 and 1992 in snow layers after first year loss;
of significance only for DDT, and even then is likely to
c Concentration data from Gregor et al. (1995); average concentra-
be of only local and short-lived significance.
tion over a 30-year period from 1964/65 to 1992/93 (n = 34).

---

The Effects of Climate Change on Contaminant Pathways
41
Table 6ท3. Physical parameters sensitive to temperature change.
especially if ice cover is sufficient to hinder exchange
ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ
during lake turnover. It appears that climate change has
Unit
Description/application
the potential to cause substantive physical and biological
ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ
changes in northern lakes that would alter OC path-
Henry's Law
Pa m3/mol Partitioning between air and water
ways, but current knowledge is insufficient to predict
Constant (HLC)
---------------------------------------------------------------------------------------
what these changes might be.
Airญwater unitless
KAW = HLC / RT
partition coef-
ficient (K
6.3.4. The effect of warming
AW)
---------------------------------------------------------------------------------------
on chemical partitioning and degradation
Octanol-air
unitless
Used as a proxy to model parti-
partition coef-
tioning between air and organic
Physicalญchemical properties sensitive to temperature in-
ficient (KOA)
phases such as vegetation, soil,
clude vapour pressure (po), Henry's Law Constant
sediment organic carbon, and
(HLC; alternatively expressed as the air-water partition
particles in air and water
coefficient, KAW), octanol-air partition coefficient (KOA)
---------------------------------------------------------------------------------------
and the octanol-water partition coefficient (KOW) (Table
Vapour
Pa
Describes the tendency of
6ท3). The particle-gas partition coefficient (K
pressure (po)
a chemical to volatilize
PG), which
---------------------------------------------------------------------------------------
depends on both particle composition and chemical
Particle-gas m3/ตg
The ratio of chemical concentra-
composition, also varies with temperature.
partition coef-
tion on atmospheric particles
The extent to which chemicals are associated with
ficient (KPG)
ng /ตg) to concentration in the
aerosols is fundamental to their atmospheric transport
gas phase
to the Arctic. Association with particles may, on the one
ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ
hand, slow or reduce transport to the Arctic through tem-
ever, if a given lake has a very low sedimentation rate
porary or permanent deposition to surfaces; while on the
and most of the organic carbon depositing to sediments
other hand, the association may protect a chemical from
becomes metabolized, it is likely that OCs associated
oxidation during transit to the Arctic. The potential for
with the particle flux will be released to the bottom
temperature to alter partitioning between gas and aerosol
water and re-mixed within the lake as has been observed
phases appears greatest for chemicals that exhibit log
in Lake Superior (Jeremiason et al., 1994). This process
KOA values in the range of 11 to 14 (Figure 6ท7). For ex-
of drawdown and remineralization could slowly ramp
ample, DDT varies from being over 70% particulate-
up water column concentrations below the thermocline,
bound in winter (ญ30ฐC) to occurring almost entirely in
Percent on particles
1,2,3,4,7,8
77 99
100
1,2,3,4,6,7,8
1,2,3,4,7
66 154
PBDEs
47
PCDDs
2,3,7,8
80
154
0ฐC
1,2,3,4
60
ญ 30ฐC
1,2,3,4,6,7,8
99
40
1,2,3,4,7,8
66
28
2,3,7
1,2,3,4,7
17
20
77
1,2,3,4
47
2,3,7,8
17 28
2,3,7
0
100
OCPs
PCNs
69
80
p,p'-DDT
60
59
trans-chlordane
Figure 6ท7. The partitioning of se-
40
-HCH
lected persistent organic pollutants as
a function of KOA. The figure shows
20
Endosulfan
changes in partitioning between win-
-HCH
HCB
52/60
Dieldrin
24
47
ter (ญ30ฐC) and summer (0ฐC). Par-
Oxychlordane
38
0
ticulate fractions were calculated based
on equations developed by Finizio et
100
180
126
al. (1997) from field measurements of
PCBs
105
PAHs
Chrysene
organochlorines. Calculations are based
80
118
on measurements of particulate or-
153
ganic carbon in air at Alert during
60
winter and summer 1998-1999 (Shar-
ma et al., 2002). Temperature-adjust-
40
77
ed KOA values were taken from the lit-
erature (Harner and Bidleman, 1996,
20
Fluoranthene
1998; Harner and Shoeib, 2002; Har-
Phenanthrene
49
ner et al., 2000; Shoeib and Harner,
Fluorene
Pyrene
95
0
2002).
8
10
12
14
16
8
10
12
14
16
log K OA
log K OA

---

42
AMAP Assessment 2002: The Influence of Global Change on Contaminant Pathways
Percent
atmosphere will increase. On the other hand, models sug-
120
gest that temperature contrast between the equator and
the pole will decrease (Figure 2ท1) (Zwiers, 2002). Ac-
100
cordingly, kinetic processes will increase with tempera-
ture rise but the overall thermodynamic forcing toward
80
polar regions will decrease with reduced global thermal

1/ KOA
contrast. KAW also increases significantly (40-70%) under
60
warming conditions, which would favor evasion from
H
surface waters. This would be particularly important for
40
OCs such as the HCHs which are at, or in the case of -
1/KOW
HCH over, saturation in Arctic waters. The predicted in-
20
crease in KAW associated with a 5ฐC increase in water
temperature corresponds to tonnes of HCHs that could
0
be forced back into the atmosphere each year. However,
PCB
PCB
-HCH
HCB
Fluorene
Pyrene
(low)
(high)
temperature increases of 5ฐC are unlikely to occur in par-
tially ice-covered regions where temperatures will be buf-
Figure 6ท8. Predicted percent changes in H, 1/KOA and 1/KOW asso-
fered by melting ice. Nevertheless, recent changes in the
ciated with a 5ฐC increase in temperature for selected chemicals.
`High' and `low' represent the upper and lower values reported for
AO index (Figure 3ท1) and model projections (Figures 2ท1
PCBs. Values are based on HH (enthalpy of phase change associ-
and 2ท2) indicate that a large number of lakes and major
ated with transfer from water to air, kJ/mol), HOA (enthalpy of
areas of Arctic shelves could be subject to such changes.
phase change from octanol to air), and HOW (enthalpy of phase
Loss of chemicals occurs during transport in the at-
change from octanol to water) (Bidleman et al., 2003).
mosphere through reactions with hydroxyl (OH) radi-
the gas phase in summer (0ฐC). Similar changes in parti-
40
cals, nitrate radicals (NO3) or ozone (O3), through pho-
tioning are evident for many of the other OCs illustrated
tolytic oxidation and through sorptive partitioning to
in Figure 6ท7. Chemicals with KOA values at ญ30ฐC of
other phases (e.g., aerosols, precipitation, vegetation)
about 11 to 12, therefore, are most sensitive to change in
with subsequent deposition. Although photolytic reac-
atmospheric transport as a result of temperature rise.
tions do not have a strong dependence on temperature
At 0ฐC most of the chemicals shown in Figure 6ท8
they will be affected by cloud cover which is predicted to
occur in the gas phase, implying that they are easily ad-
increase with global warming (IPCC, 1995). Increased
vected by air but will be prone to photolytic degrada-
cloud cover will also result in lower OH radical concen-
tion. Timing is important: the transport processes that
trations and less chemical removed by this and other
produce Arctic haze in spring may alter substantially if
photolytic pathways.
warming comes earlier in the season, with consequent
The dominant removal processes in soil and water
change to the particleญgas partitioning. Several of the
include hydrolysis, photolysis, redox reactions, micro-
higher molecular weight polybrominated diphenyl ethers
bial degradation and removal through soil-surfaceญair
(PBDEs) and polychlorinated dibenzo-p-dioxins (PCDDs)
partitioning. Of these, only photolysis is not strongly de-
are appreciably associated with particles even at 0ฐC.
pendent on temperature. The influence of temperature
Depending on their susceptibility to photolysis, particle-
on the rate constant, k, is usually described using the Ar-
association may actually protect these compounds dur-
rhenius expression,
ing transport which might explain why the increase in
k = Ae ญEa/RT
Eqn 1
PBDEs in the Arctic closely follows the production and
usage to the south (Ikonomou et al., 2002) ญ which is
where A is a constant, R is the gas constant, T is temper-
not the case for the PCBs and other OCs which are most-
ature, and Ea is the activation energy. Based on hydroly-
ly in the gas-phase during summer. Despite cold winter
sis activation energies of 78 to 85 kJ/mol (Ngabe et al.,
temperatures, many PCB, organochlorine pesticide (OCP)
1993) for -HCH and -HCH respectively, a 5ฐC in-
and polychlorinated naphthalene (PCN) compounds re-
crease would increase removal rates by ~85 to 95%. The
main in the gas phase. Winter warming projected by cli-
increase would be even greater if it is considered that the
mate models may therefore facilitate their transport dur-
dissociation constant for water (KW) (e.g., at pH =8) in-
ing the period of year when reduced sunlight makes
creases with temperature, resulting in more OHญ ions.
them less vulnerable to degradation.
Activation energies associated with redox reactions are
Chemical partitioning between environmental media
not reported for OCs but are usually assumed to be
(air, water, soil, biota) can be described using three parti-
about 50 kJ/mol (Tratnyek and Macalady, 2000) which
tion coefficients ญ KOA, KAW, and KOW (Gouin et al.,
imply about a 50% increase in reaction rate with a 5ฐC
2000). KOW, which is a ratio of two solubilities that both
rise in temperature.
increase with temperature, tends to vary weakly with
Microbial degradation also follows the Arrhenius
temperature, as shown by the modest 20% increase for
equation, but few studies report Ea. As a general rule,
hexachlorobenzene (HCB) in response to a 5ฐC increase
the biological activity in the mesophilic range (5-35ฐC)
(Figure 6ท8; Bahadur et al., 1997). A 5ฐC temperature
doubles for every 10 to 15ฐC temperature rise which im-
rise produces a more substantive (60-100%) increase in
plies an Ea of 30 to 45 kJ/mol (Viessman and Hammer,
1/KOA, which will be manifest as an increase in volatility
1985). Arctic microbial populations exhibit a large di-
and greater potential for atmospheric transport. Under
versity and abundance (Ravenschlag et al., 2001; Sahm
warming conditions, more chemical will partition out of
and Berninger, 1998) and are typically cold-adapted,
surface soils and aerosols to enter the gas phase. Thus, if
being able to maintain efficient rates of organic degrada-
global warming occurs, cycling of chemicals through the
tion and mineralization down to the freezing point of

---

The Effects of Climate Change on Contaminant Pathways
43
Calanus (copepod)
Themisto (amphipod)
Arctic cod
Black guillemot
Ringed seal
Trophic level
Concentration, ng/ g lipid weight
Glaucous gull
1
2
3
4
5
Polar bear (male)
10000
HCHs
PCBs
1000
Polar bear
Birds
100
Ringed seal
10
Bearded seal
1
Vertebrates
2 2.6 3.6 4.3 4.5 4.6 5.5 Trophic level
Beluga
0.1
Narwhal
0.01
Water
Fish
0.001
Walrus
0.0001
Sunstars
2ฐ amphipods
Decapods
Air
Sea anemones
Invertebrates
Starfish
10000
Chlordane
DDTs
1ฐ amphipods
1000
Mysids
100
Copepods
10
Bivalves
1
Kelp
0.1
Primary
Ice algae
producers
0.01
Particulate organic matter
0.001
0.0001
Figure 6ท9. The marine food web observed during the
Northwater Project. The panels show average con-
centrations of selected organochlorine compounds in
air, water, and various trophic levels (see Fisk et al.,
2001a, 2001b; Hobson and Welch, 1992).
seawater (ญ 2ฐC) (Arnosti, 1998; Sagemann et al., 1998).
an adapted microbial population that was more capable
This suggests that warming may be accompanied by
of degrading organic contaminants. Thus biodegrada-
consequences of adaptation or population change, but
tion of chemical residues in soil and water will be altered
not necessarily that microbial degradation rates will in-
as microbial populations adapt to changing climate. The
crease. For example, reduced degradation of methyl di-
complexity and uncertainty associated with these changes
chlorprop was observed in experiments where field plots
however, does not, at the present time, allow prediction
were warmed to a temperature of 5ฐC above normal for
of whether global warming will enhance or diminish
several years (Peterjohn, 1994).
chemical removal by this pathway.
Harner et al. (1999) found in situ microbial removal
Putting many of these concepts into a numerical
rates for - and -HCH in cold Arctic Ocean waters to
model, McKone et al. (1996) investigated the effect of a
be surprisingly fast (t1/2 for (+) -HCH, 5.9 yr; (ญ) -HCH,
5ฐC temperature rise on the health risk from HCB. They
22.8 yr; -HCH, 18.8 yr). Assuming an Ea of 50 kJ/mol,
found surprisingly little consequence from the projected
a 2 to 5ฐC temperature rise in the upper Arctic Ocean
5ฐC temperature increase. Indeed, their results showed
would imply a reduction of these half-lives by 20 to 50%.
that warming would actually reduce exposure as it
Microbial degradation was estimated to account for over
would enhance degradation and tend to force HCB out
30% of the removal of HCH suggesting that a small tem-
of water and into air. The critical step, controlled by the
perature rise could push this proportion to over 50%.
sensitivity of airญwater partitioning to temperature, acts
Aside from temperature, alterations in other environ-
at the bottom of aquatic food webs which, due to bio-
mental characteristics (e.g., soil moisture, soil and water
magnification, are still of great significance for dietary
pH, nutrient levels, vegetation cover and type) will be
exposure and related health risks.
tied to global warming and will affect the composition
and density of microbial populations. For instance Lewis
6.3.5. The effect of altering food web structure
et al. (1999) found differences in microbial preference
for microbes inhabiting forested versus pasture soils.
Biomagnification can concentrate fat-soluble compounds,
They also showed that the enantioselectivity (preference
such as the OCs, by factors as high as 105 to 109 from
of the microbial population for a + or ญ enantiomer of a
water to apex predators (Fisk et al., 2001a; Kidd et al.,
chiral compound, i.e., a compound exhibiting mirror-
1995b; Muir and Norstrom, 1994; Muir et al., 1999).
image forms) changed with organic nutrient enrichment.
The distribution of contaminants in air, water, and the
Other studies have observed high rates of microbial
first step in the food web (phytoplankton, particulate or-
degradation of HCHs in Arctic lakes (Law et al., 2001)
ganic carbon), can be predicted simply by applying ap-
and watersheds (Helm et al., 2000). Law et al. (2001)
propriate partition coefficients (e.g., KAW and KOW) (Fig-
found that enantioselective degradation of -HCH was
ure 6ท8). Chemical partitioning, which is based solely on
greater in small, High Arctic lakes and streams com-
thermodynamics, provides a crucial platform upon
pared to temperate lakes and wetlands. They concluded
which biomagnification can then operate (Figure 6ท9).
that low nutrient levels in the Arctic systems resulted in
A chemical at equilibrium will have identical fugacity in

---

44
AMAP Assessment 2002: The Influence of Global Change on Contaminant Pathways
the media in question (e.g., air, water, oil) and this makes
compounds like DDTs and highly-chlorinated PCBs ad-
it relatively simple to predict how temperature will alter
sorb onto sinking particles to produce a more homoge-
its distribution.
nous vertical distribution (Tanabe and Tatsukawa,
Biomagnification, however, cannot be explained sole-
1983). Furthermore, most particles transported by sea
ly by thermodynamics, and it requires energetic proces-
ice are not available to epontic biota because they are re-
ses to produce the elevated concentrations in top preda-
leased in the marginal ice zone when the ice melts (Ram-
tors. These processes can be considered in part as a re-
seier et al., 1999) and descend rapidly, carrying the ad-
duction of fat ญ the solvent containing OCs ญ through
sorbed contaminants with them. For OCs that exhibit
metabolism. The processes are complex and can lead to
strong gradients in the upper ocean, the loss of ice and
variability simply due to bio-energetics; the offloading of
hence of epontic fauna can alter the dietary exposure of
contaminants to offspring by nursing mammals is a clas-
higher trophic levels like seabirds and seals.
sic example (Addison and Smith, 1998). It is not the in-
tent here to conduct a thorough review of bioaccumula-
6.3.7. Food deprivation or shifts in diet
tion and biomagnification except to state that the com-
plexity of the process offers the opportunity for climate
Many of the Arctic top predators undergo periods of
change to act in subtle ways. The data shown in the four
fasting forced by lack of food, seasonality of food, or in-
panels of Figure 6ท9 show an almost linear relationship
ability to access food. Perhaps the best documented ex-
between the log (contaminant burden) and trophic level.
ample is the stress to the Hudson Bay polar bear (Ursus
The slope of this relationship indicates the multiplication
maritimus) population deprived of their ability to hunt
factor involved for each step in trophic level so that, for
seals during spring due to change in the spring ice cli-
example, one step would multiply DDT concentration
mate (see Figure 3ท23 and Stirling, 2002; Stirling and
by perhaps as much as 6 (neglecting polar bears) whereas
Lunn, 1997; Stirling et al., 1999). The burning of stored
the other contaminants experience factors of 2 ( HCH),
fat through metabolism results in release of archived fat-
3 ( PCB) and 4 (chlordane). The removal or addition of
soluble contaminants and, potentially, an increase of
trophic levels in the food web mediated by climate
contaminant burden in the remaining fat reservoir.
change, therefore, will not have the same effect for all
Longer periods of starvation due to change in ice or
contaminants; for example, Figure 6ท9 suggests that
change in prey populations could lead to higher doses of
DDT will be the most sensitive to this kind of change.
OCs sequestered in fat ญ usually at a time when the ani-
Another way in which food web structure can effect
mal can least afford it. Although the concern with nour-
change is by bifurcation. For instance, altering the cou-
ishment-deprived polar bears has received much atten-
pling between pelagic and ice production and the ben-
tion, similar circumstances probably apply to other
thos can change the relative proportions of organic car-
species such as common eider (Somateria mollissima;
bon (and contaminant) that enter pelagic or benthic
Olafsdottir et al., 1998) and Arctic char (Salvelinus alpi-
food webs. However, these changes in pathway do not
nus; AMAP, 2003b).
alter the relationship between contaminant concentra-
Species that have dietary flexibility may respond to
tion and trophic level. In this context it can be seen that
ecosystem change by switching to alternate prey, again
walrus (Odobenus rosmarus) feeding on a benthos en-
with consequences on their OC intake. For example, the
riched by strong coupling with primary production will
large variation in OC concentrations in the livers of
be exposed to lower (by factors of 10 or more) OC con-
glaucous gulls (Larus hyperboreus) from the western
centrations than if they switch to predation on seals.
Barents Sea correlates with nitrogen isotopic ( 15N)
composition (AMAP, 2003b). Nitrogen isotopes provide
a well-established, reliable chemical indicator of the
6.3.6. The epontic food web
trophic level of an animal's prey (Hobson and Welch,
and changes in ice climate
1992) therefore implying that much of the variation in
The entry of contaminants to a stratifying surface layer
OC concentration in glaucous gull livers can be ex-
from ice melt in spring offers a mechanism vulnerable to
plained by the dietary choices the birds make ญ or are
climate change. However, recent studies do not appear
forced to make. Recent decreases in PCB concentrations
to show higher concentrations in epontic fauna than in
in Svalbard minke whales (Balaenoptera acutorostrata)
zooplankton (Borgๅ et al., 2002). Organochlorine con-
might superficially be ascribed to the banning of PCB
centrations in epontic amphipods (Apherusa glacialis,
manufacture during the 1970s. However, it seems more
Gammarus wilkitzkii, Onisimus spp.) and zooplankton
likely that this decline reflects a dietary switch from
(Calanus hyperboreus, Thysanoessa inermis, Parath-
capelin (Mallotus villosus), whose stocks collapsed in
emisto libellula, and Chaetognatha) from the marginal
1992 to 1993, to krill which are lower down the food
ice zone near Svalbard could mostly be explained by
chain (AMAP, 2003b). Polar bears also display a range
diet, with habitat (sea-ice underside versus the pelagic
in prey that can explain regional variation in OC bur-
zone) accounting for a smaller part of the variance.
dens. For example, Chukchi and Bering Sea bears feed
Epontic amphipods had higher concentrations of HCB,
more heavily on Pacific walrus which are less contami-
- and -HCH, while DDTs, PCBs and chlordanes did
nated than ringed seals (Phoca hispida) because they are
not differ between epontic and pelagic habitats. This
at a lower trophic level, whereas bears from Svalbard
pattern of uptake can be explained by the vertical distri-
feed on more heavily contaminated harp seals (Phoca
bution of OCs in the water column: higher concentra-
groenlandica). These latter results indicate that climate
tions of HCHs and HCB are found near the sea surface
variables expressed through prey availability and biolog-
(Harner et al., 1999; Jantunen and Bidleman, 1998;
ical condition can have a considerable influence on the
Tanabe and Tatsukawa, 1983) whereas particle reactive
exposure of apex feeders to OCs.

---

The Effects of Climate Change on Contaminant Pathways
45
6.3.8. Altered migration pathways
6.3.9. Organochlorine compounds,
and invading species
disease, and epidemics
Migratory species, including whales, fish, and birds, can
During the past decade or so, there has emerged much
obtain contaminant loadings in one location and release
evidence that mass mortalities in marine mammals may
them in another, and migrating animals can be subject to
occur as a result of a combination of factors including dis-
varied exposure as they feed along their migration path.
ease vectors, population stress and contaminants, each
For one Alaskan lake, the loadings of OC contaminants
of which may be affected by climate change (see Lavigne
returned by anadromous fish exceeded those entering
and Schmitz, 1990; Ross, 2002). The complexity of this
the drainage basin from the atmosphere (Ewald et al.,
interaction provides fertile ground for surprises. Some dis-
1998). The recent expansion in the range of Pacific
ease outbreaks have been observed following migrations
salmon (Oncorhynchus spp.) into rivers farther north in
associated with large-scale ecological change, and some
the Arctic (Babaluk et al., 2000) could, likewise, have an
have derived from the introduction of viruses from domes-
impact on contaminant budgets for the rivers or lakes
tic animals. But it is the addition of immunotoxic chemi-
that they enter. Certainly, these fish provide a new `vec-
cals, such as many of the POPs, that may provide the trig-
tor' for delivering contaminants to species that predate
ger for disease to emerge (Ross et al., 2000; Vos and Lus-
upon them or depend upon a food web supplied by their
ter, 1989). The widespread distribution of the canine dis-
carcasses. Given the higher concentrations of -HCH in
temper virus, or a closely related morbillivirus in seals
the North Pacific Ocean than in the Arctic (Li et al.,
from Greenland led Dietz et al. (1989) to speculate on the
2001) it seems likely that anadromous fish may provide
possibility that large-scale migration of harp seals from
an important, climate-sensitive vector for -HCH into
the Barents Sea to northern Europe in 1986 to 1987 might
Arctic freshwater environments.
have provided a disease vector. The co-factors of a na๏ve
If the spatial distribution of contaminants is con-
marine mammal (seal) population in coastal Europe man-
trolled by processes subject to climate change, then ex-
ifesting suppressed immune systems through high contam-
posure during population migrations can also alter through
inant PCB burdens would then have provided the foun-
climate change. An intriguing example of how such a
dation for the epidemic (Heide-J๘rgensen et al., 1992).
process may operate has recently been described for the
Within the Arctic, top predators would be at greatest
Bering/Beaufort bowhead whale (Balaena mysticetus)
risk due to their high exposure to contaminants, and
migration. The whales reflect in their body burdens the
marine mammals probably face the added stress of
change in - and -HCH composition between the Be-
changes in ice climate. Accordingly, indications of im-
ring and Beaufort Seas (Hoekstra et al., 2002). The ocean
munosuppression have been found in polar bears, north-
composition for the HCHs is probably controlled by
ern fur seals (Callorhinus ursinus) and glaucous gulls
large-scale physical processes (e.g., rainfall and airญsea
(AMAP, 2003b). In particular, the polar bears of the
partitioning ญ see Li et al., 2002) as are migratory routes
Kara Sea, Franz Josef Land, East Greenland and Sval-
(Dyke et al., 1996b; Moore et al., 1995), each of which
bard would seem especially vulnerable. Firstly, these
is sensitive to climate change. Therefore, alteration in
bears exhibit inordinately high contaminant burdens
HCH loading of the ocean caused by change in winds,
(Andersen et al., 2001; Norstrom et al., 1998) and these
ice cover or rainfall pattern, or alteration in the feeding
high burdens may well derive partly from the enhanced
locations of the whales caused by change in ice distribu-
connection between this region and Europe/North Am-
tion, will similarly alter the exposure to HCHs.
erica under the strong AO+/NAO+ conditions of the
Finally, invasions of new species fostered by climate
1990s (Figures 3ท2 and 3ท17). Secondly, as previously
change, overfishing or by introduced exotic species also
discussed, change in ice climate and in marine ecosys-
have the potential to re-structure food webs. An elegant
tems may have provided the added stress of malnourish-
example of how dramatic such change can be, both in tro-
ment. Lastly, it seems that these bears already have suffi-
phic organization and contaminant pathways, was pro-
cient contaminant burdens to exhibit health effects
vided by the invasion of the zebra mussel (Dreissena poly-
(Bernhoft et al., 2000; Skaare et al., 2001).
morpha) into the Great Lakes (Morrison et al., 1998,
2000; Whittle et al., 2000). Following their invasion in
6.4. Hydrocarbons
1988, zebra mussels have led to a decline in phytoplank-
ton and rotifer densities, the water has become clearer
Hydrocarbons in the Arctic derive from combustion and
(by the removal of particulates), and the deposition of
petrogenic sources (Yunker et al., 1995). The pathways
nutrient-rich pseudofeces at the bottom has altered ben-
of these two sources of hydrocarbon differ substantially
thic habitat density and structure. In turn, the zebra mus-
as will their sensitivity to climate change. Hydrocarbons
sels have become an important prey item altering the
of anthropogenic origin pose two kinds of problem;
trophic structure within the lake as reflected by the sta-
polyaromatic hydrocarbons (PAHs) and their oxidation
ble isotopic composition of fish. In another example, de-
products are toxic (Zedeck, 1980), and spilled oil has di-
vastating change in the Black Sea ecosystem has resulted
rect, well-known effects on biota, especially those that
from the population explosions of phytoplankton and jel-
inhabit interfaces between water, air, ice and sediments.
lyfish (Daskalov, 2002). In this case, top-down trophic
(Patin, 1999; Wolfe et al., 1994).
change may have been initiated by overfishing of apex
feeders. Clearly, the migration northward even of a hum-
6.4.1. Combustion PAHs
ble filter feeder or jellyfish, potential products of changing
water properties or organic carbon supply, could have un-
Combustion PAHs are well-known products of natural
expected impact on contaminant cycling in coastal seas.
fires and human-related combustion processes (e.g., au-

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46
AMAP Assessment 2002: The Influence of Global Change on Contaminant Pathways
a
b
AOญ
AO+
North Alaska
1
North Alaska
1
2
2
3
3
Western
Western
Siberia
Siberia
Sverdrup
Sverdrup
Basin
Basin
Barents 4
6
Barents 4
6
Sea 5
Sea 5
Arctic Circle
Arctic Circle
Oil production
Permanent pack ice
Oil development areas
Gas production
Seasonal ice
1 North Alaska (NPRA)
4 Svalis Dome
Ice drift
Oil and gas production
Perennial open water
2 North Alaska (ANWR)
5 Hammerfest Basin
Area of exploration drilling
Arctic oil/gas formations
3 Beaufort-Mackenzie Basin
6 Timan-Pechora Basin
Figure 6ท10. Oil/gas-bearing regions and locations of oil/gas production together with the ice-drift field under a) AOญ conditions and b) AO+
conditions (ice motion based on Rigor et al. (2002) and oil data from Bakke et al. (1998)).
tomobiles, liquid and solid fuel burning, waste incinera-
biomass burning is thus likely, and this increase will
tion, metallurgy, etc.). In the atmosphere, PAHs parti-
probably have an impact on small rivers, e.g., in north-
tion between the vapor phase and particulates (see for
ern Canada, which already receive almost all their PAHs
example Figures 14 and 15 in Macdonald et al., 2000a)
from combustion sources (Yunker et al., 2002). Loss of
and are detected at remote Arctic locations following
permafrost and enhanced erosion of peat may also con-
transport over long distances (Halsall et al., 1997; Mac-
tribute enhanced amounts of relict PAHs to lakes and
donald et al., 2000a; Patton et al., 1991). There is a
rivers (Yunker et al., 1993).
strong seasonality in PAH concentrations in air at Alert
(Ellesmere Island, Canada) with colder months (Octo-
6.4.2. Petrogenic hydrocarbons and oil
ber-April) displaying concentrations about ten times
higher than in warmer months (May-September). This
A leading concern for the Arctic is the risk of oil spills
suggests that the winter haze phenomenon that trans-
from both onshore and offshore exploration and pro-
ports heavy metals across the pole from Eurasia also
duction (Bakke et al., 1998; Patin, 1999). Climate
transports industrial combustion products. Therefore,
change that produces an ocean margin substantially
much of what has been said about aerosol metals and
clear of ice will undoubtedly encourage further offshore
climate change in section 6.1.1 relates directly to PAHs;
exploration, perhaps in more remote locations. Produc-
altered wind patterns (Figure 3ท2) and enhanced preci-
ing oil from the Arctic reserves, especially those on the
pitation (Figure 3ท4) have the potential to change path-
remote shelves, has the associated problem of transport-
ways and to deposit PAH aerosols over parts of the Arc-
ing produced oil to markets in the south, either by ship
tic Ocean especially toward the southern Eurasian Basin.
or pipeline.
Furthermore, temperature increases may shift the equi-
It is clear that changes in the ice drift associated with
librium from particulate to vapor phase for PAHs like
changes in the AO index will have a dramatic influence
pyrene, fluoranthene, phenanthrene and anthracene,
on where spilled oil will go if it enters the ice pack (Fig-
which at Arctic temperatures are partially distributed
ure 6ท10). For example, in the Canadian and Alaskan
between air and solid phase (Figure 6ท7).
sector of the Arctic Ocean during AOญ conditions, the
In addition to the strong seasonal signal of industrial
oil will follow ice into the East Siberian Sea to traverse
PAHs observed in the Arctic, outliers (samples with ab-
the Russian shelves and then exit to the Greenland Sea.
normally high PAH concentrations) are also observed
During AO+ conditions, oil from the same location
during summer months, particularly at Tagish (south-
would tend to remain within the Beaufort Gyre poten-
west Yukon, Canada), and these have been assigned to
tially to return within a few years to where it was spilled.
forest fires (Macdonald et al., 2000a). Forest fires are
Oil spilled over the Russian shelves, or entering their
projected to increase through climate change as a result
coastal seas from spills into rivers, would tend to track
of warmer continental temperatures (Figure 2ท1) and less
directly across the Arctic under AOญ conditions (Figure
precipitation in continental interiors. A general increase
6ท10 a). However, oil spilled under AO+ conditions could
in atmospheric PAHs in the Arctic deriving from such
move more to the east, with a slight chance that it might

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The Effects of Climate Change on Contaminant Pathways
47
reach the Canada Basin and then the Canadian Arctic
sign life, at greater risk. Oil already spilled onto land
Archipelago through which it would then have to pass.
within the Arctic drainage basin may become more mo-
It is uncertain how viable this latter route might be for
bile, entering water courses as the hydrological cycle be-
oil spilled in the Kara or Laptev Seas, but evidence from
comes more vigorous.
tree dendrology suggests that there have been periods
Another connection between spilled oil and climate
during the Holocene when communication from Siberia
change derives from the projected increase in incident
to the Canadian Arctic Archipelago has been mediated
UV radiation (Weatherhead and Morseth, 1998) which
by ice drift (Dyke and Savelle, 2000; Dyke et al., 1997).
could lead to an increase in photo-enhanced toxicity of
Indeed, the transport of trees by Arctic sea ice and the
spilled oil (see, for example Barron and Ka'aihue, 2001;
change in that transport with time provides some of the
Pelletier et al., 1997). Toxicological assessments of oil
best evidence of where oil spilled in Arctic coastal re-
made in the presence of UV light reveal a toxicity of up
gions is likely to travel (see for example, Eggertsson,
to 1000 times greater than that measured under the tra-
1994a,b).
ditional fluorescent light. Furthermore, photo-enhanced
Pipelines transporting oil across land in the Arctic
toxicity of oil can occur at the intensities and wave-
are vulnerable to enhanced permafrost degradation. Re-
lengths measured for UV in aquatic water columns sug-
gions such as the Komi Republic, which experienced
gesting that increased incident UV radiation projected
large oil spills onto the tundra in 1994, exemplify the
for polar regions may, in addition to many other effects
difficulty. Warming and melting of frozen ground will
on ecosystems (Weatherhead and Morseth, 1998), en-
put corroded pipelines, many working beyond their de-
hance damage done by spilled oil.

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