Overall the activity concentrations of such radionuclides as 99Tc, 137Cs, 90Sr, 239+240Pu, 241Am, 226Ra and 228Ra in the Barents Sea are similar, or slightly lower than have been observed in recent years. Presently,a general tendency to decrease is indicated. for all the radionuclides.
The issue of present and potential radioactive contamination in the Barents Sea has received considerable attention in recent years. In the late 1980s several accidents and incidents involving nuclear-powered submarines demonstrated that the risk of releases of radionuclides into the Barents Sea should be considered more carefully.
In the early 1990s, information concerning the dumping of nuclear waste emerged through bilateral environmental cooperation between Norway and Russia (NRPA, 2008b). In the years that followed, concern grew regarding the safety of military and civil nuclear installations in the northwest of Russia. In addition, the long-range transport of radionuclides originating from nuclear weapons fallout, the Chernobyl accident (1986) and from spent nuclear fuel reprocessing are still the main contributors to anthropogenic radionuclides (99Tc, 137Cs, 90Sr, 239+240Pu, 241Am) in the northern marine environment (Figure 4.4.12).
In 1994 and 1995, the discharge of 99Tc from the reprocessing facility at Sellafield in the UK increased sharply as a result of commencement of operations at the Enhanced Actinide Removal Plant (EARP). There has been much public concern about the consequences of such kinds of releases, as radionuclides discharged to the Irish Sea are transported by ocean currents via the North Sea, into the Norwegian coastal current and to the Barents Sea. From 2004 the discharge of 99Tc was substantially reduced, but it takes 3-4 years before it will be observable in Norwegian waters (NRPA, 2008b).
In 2005-2008 surface water, sediment samples and fish species from the Barents Sea were collected by the Norwegian Radiation Protection Authority (NRPA) and the Institute of Marine Research (IMR) to be analyzed for anthropogenic and naturally-occurring radionuclides (NRPA, 2007c and 2008b).
Sediments and seawater
During 2005, 99Tc activity concentrations in seawater water from the Barents Sea ranged from 0.13 to 0.72 Bq m-3 (Figure 4.4.13), ), whereas in seawater samples collected around the Svalbard archipelago 99Tc activity ranged from 0.10 to 0.20 Bq m-3. Comparison of these values with earlier observations (Gwynn et al., 2004) indicated that seawater activity concentrations for 2005 were generally lower than those reported for same region in 2000 and 2001, but comparable with values for 2004 (NRPA, 2006b). In 2006, the average activity concentration of 99Tc in seawater from the Barents Sea was slightly lower (0.1-0.2 Bq m-3) than that reported in 2005 (NRPA, 2008b; IMR, 2009). Due to the reduction in discharge of 99Tc from Sellafield since 2003, the levels of this radionuclide are expected to continue to decrease.
239+240Pu activity concentrations of in seawater from the Barents Sea collected in 2005 ranged from 1.8 to 20 mBq m-3 (Figure 4.4.14), with the highest values observed in seawater collected off the coast of Scotland, showing that Sellafield is a source to plutonium in the North Sea, where part of the 239+240Pu comes from remobilised plutonium from contaminated Irish Sea sediments (NRPA, 2007c). The values of 239+240Pu observed in 2005 were generally lower than those observed in 2001 (Gafvert et al., 2003).
Activity concentrations of 241Am in seawater from the Barents Sea in 2005 ranged from 0.8 to 19 mBq m-3 (Figure 4.4.14.). The 241Am found in the water column today, can be due to both the present discharge from Sellafield of 241Am and from the decay of 241Pu resulting from earlier discharges and global fallout. In 2006 the activity concentrations of 241Am in seawater from the Barents Sea ranged from 1.3 to 19 mBq m-3. With the exception of two samples, the activity concentrations of 241Am in the Barents Sea were similar to those observed in 2002 (NRPA, 2008b).
(a) (b)
Figure 4.4.13. Activity concentration (Bq m-3) of 99Tc (a) and 137Cs (b) in seawater samples collected in the Barents Sea in 2005 (NRPA, 2007).
The activity concentration of 137Cs in the Barents Sea surface water in 2005 (Figure 4.4.13) and 2006 varied from 1.4 to 4.4 and 0.6 to 3.7 Bq m-3, respectively (NRPA, 2007c; IMR, 2009). In 2005 137Cs activity concentration in sediment samples ranged from 0.4 to 9.9 Bq kg-1 (d.w.). Activity concentrations of 137Cs in surface water and sediments were similar to values observed in 2003 (NRPA, 2007c). 137Cs in sediments from open Barents sea and the fjords in Troms and Finnmark provinces measured in 2007 varied from below detection limits up to 14,0 Bq kg-1 (d.w.) Values were highest in the fjords, probably as a result of draining from land (IMR, 2009).
Activity concentrations of 90Sr in surface water from the Barents Sea in 2005 ranged from 1.0 to 2.7 Bq m-3, which is similar to the levels observed in 2002 (NRPA, 2007c).
239+240Pu activity concentrations of in seawater from the Barents Sea collected in 2005 ranged from 1.8 to 20 mBq m-3 (Figure 4.4.14), with the highest values observed in seawater collected off the coast of Scotland, showing that Sellafield is a source to plutonium in the North Sea, where part of the 239+240Pu comes from remobilised plutonium from contaminated Irish Sea sediments (NRPA, 2007c). The values of 239+240Pu observed in 2005 were generally lower than those observed in 2001 (Gafvert et al., 2003).
Activity concentrations of 241Am in seawater from the Barents Sea in 2005 ranged from 0.8 to 19 mBq m-3 (Figure 4.4.14.). The 241Am found in the water column today, can be due to both the present discharge from Sellafield of 241Am and from the decay of 241Pu resulting from earlier discharges and global fallout. In 2006 the activity concentrations of 241Am in seawater from the Barents Sea ranged from 1.3 to 19 mBq m-3. With the exception of two samples, the activity concentrations of 241Am in the Barents Sea were similar to those observed in 2002 (NRPA, 2008b).
a) (b)
Figure 4.4.14. Activity concentration (Bq m-3) of 239+240Pu (a) and 241Am (b) in surface water samples from the Barents Sea and along the coast in 2005 (NRPA, 2007).
As reported earlier, produced water from offshore oil production may contain elevated concentrations of especially naturally occurring 226Ra and 228Ra (NRPA (2005a). Activity concentrations of 226Ra in seawater from the Barents Sea in 2005 ranged from 0.4 to 2.3 Bq m-3 (Figure 4.4.15) which is close to the reported typical activity concentrations of 226Ra in Atlantic surface water - around 1.3 Bq m-3 (IAEA, 1990). Activity ratios of 228Ra/226Ra were generally below 1, with the lowest ratios found in arctic water. In 2004 Norwegian data concerning produced water discharges from installations in the Norwegian sector of the Norwegian Sea was used to determine any potential impact of 226Ra and its daughter products 210Pb and 210Po on biota in the Barents Sea. Modelled calculations demonstrated that contributions to dose from these radionuclides were minor and could not be separated from natural variations of naturally occurring concentrations of the same radionuclides (Brekken et al., 2004).
Seafood
In 2005 the activity concentrations of 137Cs in different fish species from the Barents Sea varied between 0.1 and 0.31 Bq kg-1 (w.w.). In cod from the Barents Sea the activity concentration of 137Cs have been analyzed annually since 1992. All obtained values have been lower than 1 Bq kg-1 w.w. (with most values lower than 0.5 Bq kg-1 w.w), with a slight decreasing trend observed over the period 1992 - 2005(NRPA, 2007c; IMR, 2009).
