2.3 Riverine Runoff
The mean annual riverine discharge to Arctic Ocean was estimated recently to
3,588 km
3 (Syed et al. 2007). The largest rivers discharging freshwater to the Arctic
Ocean are Yenisei (*620 km
3 year
−1 ) and Lena (*530 km
3 year
−1 ) and Ob
(*404 km
3 year
−1 ). However the suspended matter discharge to the Arctic Ocean
is highest at Mackenzie (124 × 10
6 t year
−1 ), Yukon (54 × 10
6 t year
−1 ) and Lena
(21 × 10
6 t year
−1 ) (Stein 2008). The freshwater run-off and the suspended matter
influx to the Arctic Ocean is largest in May and June.
The Siberian rivers catchment areas include many diffuse contaminant sources
such as agricultural runoff loaded with pesticides and discharges of municipal and
industrial sewage from heavily populated and industrialized areas. Other polluting
activities that pollute rivers are mining, gas exploitation (Harms et al. 2000), and
radioactive contamination from the Mayak Production Association in the Urals, the
Siberian Chemical Combine, and the Krasnoyarsk Mining and Chemical Combine
(KMCC) (Melnikova et al. 2003; Lind et al. 2006; Skipperud et al. 2004, 2009).
Rivers transport contaminants for long distances from southern parts of their
catchment but there are also important point sources of contaminants located within
Arctic. Particularly large mines and industrial processing plants in the Kola Peninsula, Pechora Basin, Urals, Noril’sk and Yakutsk introduce contaminated waters
into the rivers system (Clarke and Harris 2003; Karcher et al. 2010).
The Arctic Ocean interior is characterized by a strong vertical haline stratification. Due to its low density, the major portion of the inflowing river water from the
shelves stays in the upper tens of meters. Dissolved contaminants may reach deeper
water layers only through vertical mixing or convective overturning in well-mixed
shelf areas. The situation is different for particle bound contaminants (e.g. some
organic contaminants, heavy metals and radionuclides). Up to 90 % of the suspended organic matter settle in the estuaries in contrast to 20–40 % of riverine
dissolved organic components (Stein 2008).
Simulations have shown that annual river discharge will increase by 20 % for
main arctic rivers (Arora and Boer 2001; Macdonald et al. 2005; Stein 2008). The
increase of river runoff from riverine drainage basins into the Arctic Ocean may
lead to increased inputs of contaminants from Siberian rivers. The peatlands covering Arctic and sub-Arctic areas over thousands of years have accumulated contaminants strongly associated with organic matter, such as mercury (Hg) (Biester
et al. 2003; Bindler et al. 2004) and persistent organic pollutants, e.g., DDT and
PCB (Turetsky et al. 2004). Most of peatlands are underlain by permafrost (Gorham
1991), constituting about 24 % of terrestrial surface in Northern Hemispere (Stein
2008). Due to actual temperature increase, permafrost have currently started
thawing (Smith and Frey 2005; Fronzek et al. 2006; IPCC 2013; Turetsky et al.
2007). The rain water will now be able to penetrate soils containing contaminants
and flush them into rivers. Higher riverine run-off coupled with intense permafrost
melting will have increasing significance contaminants transport in the Arctic.
80
A. Pouch and A. Zaborska
The mean annual riverine discharge to Arctic Ocean was estimated recently to
3,588 km
3 (Syed et al. 2007). The largest rivers discharging freshwater to the Arctic
Ocean are Yenisei (*620 km
3 year
−1 ) and Lena (*530 km
3 year
−1 ) and Ob
(*404 km
3 year
−1 ). However the suspended matter discharge to the Arctic Ocean
is highest at Mackenzie (124 × 10
6 t year
−1 ), Yukon (54 × 10
6 t year
−1 ) and Lena
(21 × 10
6 t year
−1 ) (Stein 2008). The freshwater run-off and the suspended matter
influx to the Arctic Ocean is largest in May and June.
The Siberian rivers catchment areas include many diffuse contaminant sources
such as agricultural runoff loaded with pesticides and discharges of municipal and
industrial sewage from heavily populated and industrialized areas. Other polluting
activities that pollute rivers are mining, gas exploitation (Harms et al. 2000), and
radioactive contamination from the Mayak Production Association in the Urals, the
Siberian Chemical Combine, and the Krasnoyarsk Mining and Chemical Combine
(KMCC) (Melnikova et al. 2003; Lind et al. 2006; Skipperud et al. 2004, 2009).
Rivers transport contaminants for long distances from southern parts of their
catchment but there are also important point sources of contaminants located within
Arctic. Particularly large mines and industrial processing plants in the Kola Peninsula, Pechora Basin, Urals, Noril’sk and Yakutsk introduce contaminated waters
into the rivers system (Clarke and Harris 2003; Karcher et al. 2010).
The Arctic Ocean interior is characterized by a strong vertical haline stratification. Due to its low density, the major portion of the inflowing river water from the
shelves stays in the upper tens of meters. Dissolved contaminants may reach deeper
water layers only through vertical mixing or convective overturning in well-mixed
shelf areas. The situation is different for particle bound contaminants (e.g. some
organic contaminants, heavy metals and radionuclides). Up to 90 % of the suspended organic matter settle in the estuaries in contrast to 20–40 % of riverine
dissolved organic components (Stein 2008).
Simulations have shown that annual river discharge will increase by 20 % for
main arctic rivers (Arora and Boer 2001; Macdonald et al. 2005; Stein 2008). The
increase of river runoff from riverine drainage basins into the Arctic Ocean may
lead to increased inputs of contaminants from Siberian rivers. The peatlands covering Arctic and sub-Arctic areas over thousands of years have accumulated contaminants strongly associated with organic matter, such as mercury (Hg) (Biester
et al. 2003; Bindler et al. 2004) and persistent organic pollutants, e.g., DDT and
PCB (Turetsky et al. 2004). Most of peatlands are underlain by permafrost (Gorham
1991), constituting about 24 % of terrestrial surface in Northern Hemispere (Stein
2008). Due to actual temperature increase, permafrost have currently started
thawing (Smith and Frey 2005; Fronzek et al. 2006; IPCC 2013; Turetsky et al.
2007). The rain water will now be able to penetrate soils containing contaminants
and flush them into rivers. Higher riverine run-off coupled with intense permafrost
melting will have increasing significance contaminants transport in the Arctic.
80
A. Pouch and A. Zaborska