extremely toxic form of mercury—methylmercury will accelerate with a loss of the
arctic ice cover by a larger penetration of sunlight (Point et al. 2011).
3.3 Oxygen Concentration, pH and Redox Conditions
Changes in pH and redox conditions strongly influence chemical forms of radionuclides (e.g. Pu, Cs) and heavy metals (e.g. Hg). Their different forms—oxidation
states—influence distinct affinity to suspended particulate matter. For instance, in
reducing environment (low pH, low redox, low oxygen) plutonium exists at IV of V
oxidation state (Mitchell et al. 1991; Choppin and Morgenstern 2001). Reduced
plutonium is highly particle reactive and is readily scavenged from the water column to sediments. In oxidizing environment, the Pu is exist in form of PuO 2
+ and is
very soluble in the water column. In that form it may be transported for the long
distances and its elimination to marine sediments is very limited.
Usually oxygen is present only in surface most sediment layers and contaminants deposited in deeper layers many years ago are immobile. However, mixing
processes caused by animals (bioturbation) or physical processes (bottom currents),
allow the oxygen enter to the lower sediment layers. Sediment mixing may facilitate
re-mobilization of contaminants and their re-introduction to sediment pore waters
and then water column (Thibodeaux and Bierman 2003) and may induce changes of
chemical form from less to more bioavailable.
The possible effects of global changes: the increase of bottom fauna population
and the higher intensity of physical processes (storms) may facilitate contaminant
re-introduction to marine environment. Thus, bottom sediments that have been a
sink for contaminants for the last century may now become their sources (Vintró
et al. 2002).
3.4 Change in Salinity
The salinity changes in the Arctic depend on the global change scenario, but the
future trends of salinity is poorly constrained. With the higher influence of Atlantic
waters the warmer, more saline waters will penetrate larger Arctic areas. However,
the actually observed temperature rise initiates glaciers and ice cover melting, thus
the arctic marine environment will receive the enormous influx of freshwater.
Most of the studies indicate that toxicity of inorganic contaminants increases
with decreasing salinity (Hall and Anderson 1995; Ytreberg et al. 2011). Heavy
metals (e.g. Cd, Hg, Zn) are more bioavailable in lower salinity due to presence of
free metal ions. Increasing salinity decreases the dissolved concentrations of metal
ions due to the precipitation of the metal ions. Thus in consequence in more saline
waters the toxicity of metals to organisms is reduced (Park et al. 2014).
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A. Pouch and A. Zaborska
arctic ice cover by a larger penetration of sunlight (Point et al. 2011).
3.3 Oxygen Concentration, pH and Redox Conditions
Changes in pH and redox conditions strongly influence chemical forms of radionuclides (e.g. Pu, Cs) and heavy metals (e.g. Hg). Their different forms—oxidation
states—influence distinct affinity to suspended particulate matter. For instance, in
reducing environment (low pH, low redox, low oxygen) plutonium exists at IV of V
oxidation state (Mitchell et al. 1991; Choppin and Morgenstern 2001). Reduced
plutonium is highly particle reactive and is readily scavenged from the water column to sediments. In oxidizing environment, the Pu is exist in form of PuO 2
+ and is
very soluble in the water column. In that form it may be transported for the long
distances and its elimination to marine sediments is very limited.
Usually oxygen is present only in surface most sediment layers and contaminants deposited in deeper layers many years ago are immobile. However, mixing
processes caused by animals (bioturbation) or physical processes (bottom currents),
allow the oxygen enter to the lower sediment layers. Sediment mixing may facilitate
re-mobilization of contaminants and their re-introduction to sediment pore waters
and then water column (Thibodeaux and Bierman 2003) and may induce changes of
chemical form from less to more bioavailable.
The possible effects of global changes: the increase of bottom fauna population
and the higher intensity of physical processes (storms) may facilitate contaminant
re-introduction to marine environment. Thus, bottom sediments that have been a
sink for contaminants for the last century may now become their sources (Vintró
et al. 2002).
3.4 Change in Salinity
The salinity changes in the Arctic depend on the global change scenario, but the
future trends of salinity is poorly constrained. With the higher influence of Atlantic
waters the warmer, more saline waters will penetrate larger Arctic areas. However,
the actually observed temperature rise initiates glaciers and ice cover melting, thus
the arctic marine environment will receive the enormous influx of freshwater.
Most of the studies indicate that toxicity of inorganic contaminants increases
with decreasing salinity (Hall and Anderson 1995; Ytreberg et al. 2011). Heavy
metals (e.g. Cd, Hg, Zn) are more bioavailable in lower salinity due to presence of
free metal ions. Increasing salinity decreases the dissolved concentrations of metal
ions due to the precipitation of the metal ions. Thus in consequence in more saline
waters the toxicity of metals to organisms is reduced (Park et al. 2014).
84
A. Pouch and A. Zaborska