70
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
bottom topography of the Laptev Sea and water circulation (Figure 4) which determine the
location of errosion and deposition zones. Some increased values in the coastal zone are the
result of the transport of the radionuclides by rivers and of the sedimentation of the
radionuclides, released during fast ice melting.
Some increase of the 90Sr and 137Cs concentrations in the surface water of the coastal zone
of the Laptev Sea may be attributed to resuspension of radionuclides from the upper layer of the
sediments by waves and bottom currents which velocities can reach critical values in this
region.
Atmospheric precipitations
Radionuclides are deposited from the atmosphere onto land and water surfaces, upper surface
of the drifting and fast ice. On the ice surface radionuclides remain and accumulate, increasing
radioactive contamination of the ice cover.
In accordance with the data of Rosgidromet (for the Kara Sea), about 2.1 Bq/m2 year of
137Cs and 1.4 Bq/m2 year of 90Sr fell out with precipitations in 1993.
Rivers
There are no sources of anthropogenic radionuclides in the water catchment area of the rivers of
the Laptev Sea basin. The only source is the global fallout onto the territory of the water
catchment area and subsequent transport by the rivers into the sea. Thus, the contribution of the
rivers to the radioactive contaminants in the Laptev Sea is quite small at the present time. The
rivers influence the level of radioactive contaminants only near the river mouths.
Discussion and conclusions
During the joint Russian-German expedition in summer 1993 water samples and samples from
the upper layer of the bottom sediments were collected to analyse the contents of the
anthropogenic radionuclides Discussion and conclusions 137Cs and 90Sr for the first time. So
far the Laptev Sea has been considered less polluted by radioactivity than the Kara Sea,
therefore the results of the analysis were rather unexpected.
Results from the expedition "Tundra Ecology-94" in summer 1994 confirmed the enhanced
levels of the radioactive contamintion of the Laptev Sea. Obtained in summer 1994 in the
Laptev Sea fewness data of the 137Cs concentration are at the same level and a similar spatial
distribution as formed in 1993. Moreover, the 137Cs concentration in the Vil'kitsky Strait was
relatively high (10.6 Bq/m3) (Josefsson et aI., 1995).
The spatial distribution of the 137Cs concentration has a good agreement with the spatial
distributions of the water temperature and salinity and with the general water circulation in the
Laptev Sea. The coefficient of correlation between the water salinity and 137Cs concentration is
equal to 0.95. Therefore the main cause of the enhanced levels of the 137Cs concentration in the
water of the Laptev Sea in 1993 and 1994 is the transport of the radionuclides by the currents
and the drifting ice from the Kara Sea and the Arctic Basin.
The relation of the 90Sr concentration to the salinity is not so close and the coefficient of
correlation is equal to -0.32. Therefore the possible causes of the enhanced levels of the 90Sr
concentration in the water of the Laptev Sea in 1993 is not only the transport of the
radionuclides by the currents and the drifting ice from the Kara Sea and the Arctic Basin, but
also the runoff by rivers.
Some higher level of the 90Sr and 137Cs concentrations in the surface water of the coastal
zone of the Laptev Sea may be attributed to resuspension of radionuclides from the upper layer
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
bottom topography of the Laptev Sea and water circulation (Figure 4) which determine the
location of errosion and deposition zones. Some increased values in the coastal zone are the
result of the transport of the radionuclides by rivers and of the sedimentation of the
radionuclides, released during fast ice melting.
Some increase of the 90Sr and 137Cs concentrations in the surface water of the coastal zone
of the Laptev Sea may be attributed to resuspension of radionuclides from the upper layer of the
sediments by waves and bottom currents which velocities can reach critical values in this
region.
Atmospheric precipitations
Radionuclides are deposited from the atmosphere onto land and water surfaces, upper surface
of the drifting and fast ice. On the ice surface radionuclides remain and accumulate, increasing
radioactive contamination of the ice cover.
In accordance with the data of Rosgidromet (for the Kara Sea), about 2.1 Bq/m2 year of
137Cs and 1.4 Bq/m2 year of 90Sr fell out with precipitations in 1993.
Rivers
There are no sources of anthropogenic radionuclides in the water catchment area of the rivers of
the Laptev Sea basin. The only source is the global fallout onto the territory of the water
catchment area and subsequent transport by the rivers into the sea. Thus, the contribution of the
rivers to the radioactive contaminants in the Laptev Sea is quite small at the present time. The
rivers influence the level of radioactive contaminants only near the river mouths.
Discussion and conclusions
During the joint Russian-German expedition in summer 1993 water samples and samples from
the upper layer of the bottom sediments were collected to analyse the contents of the
anthropogenic radionuclides Discussion and conclusions 137Cs and 90Sr for the first time. So
far the Laptev Sea has been considered less polluted by radioactivity than the Kara Sea,
therefore the results of the analysis were rather unexpected.
Results from the expedition "Tundra Ecology-94" in summer 1994 confirmed the enhanced
levels of the radioactive contamintion of the Laptev Sea. Obtained in summer 1994 in the
Laptev Sea fewness data of the 137Cs concentration are at the same level and a similar spatial
distribution as formed in 1993. Moreover, the 137Cs concentration in the Vil'kitsky Strait was
relatively high (10.6 Bq/m3) (Josefsson et aI., 1995).
The spatial distribution of the 137Cs concentration has a good agreement with the spatial
distributions of the water temperature and salinity and with the general water circulation in the
Laptev Sea. The coefficient of correlation between the water salinity and 137Cs concentration is
equal to 0.95. Therefore the main cause of the enhanced levels of the 137Cs concentration in the
water of the Laptev Sea in 1993 and 1994 is the transport of the radionuclides by the currents
and the drifting ice from the Kara Sea and the Arctic Basin.
The relation of the 90Sr concentration to the salinity is not so close and the coefficient of
correlation is equal to -0.32. Therefore the possible causes of the enhanced levels of the 90Sr
concentration in the water of the Laptev Sea in 1993 is not only the transport of the
radionuclides by the currents and the drifting ice from the Kara Sea and the Arctic Basin, but
also the runoff by rivers.
Some higher level of the 90Sr and 137Cs concentrations in the surface water of the coastal
zone of the Laptev Sea may be attributed to resuspension of radionuclides from the upper layer