Increased barium levels in recent marine sediments from the Norwegian and Barents Seas suggest impact of hydrocarbon drilling and production.

Barium (Ba) in recent marine sediments can originate from natural and anthropogenic sources including discharges from the oil and gas industry. In this study, we use data from the Norwegian and Barents Seas to assess whether Ba in recent marine sediments has increased due to these discharges. To account for Ba in detrital material, we normalise all samples with respect to aluminosilicate by calculating an enrichment factor. We use statistical modelling to control for parameters related to sedimentation. We present results that suggest increased Ba levels in recent sediments that coincide with the timing of hydrocarbon drilling and production. This is supported by geographical differences on a large scale that relate to proximity to hydrocarbon drilling and production. Among 243 sampling stations, we identify 73 locations exhibiting enrichment of Ba in the upper 6 of sediment. At these locations, Ba is 1.55 to 3.55 times higher than the levels that can be expected from the shale average when Ba in detrital matter is accounted for. Excess Ba is reported in sediment surface samples in areas important to fisheries like the Lofoten area and the western Barents Sea.

Understanding source terms of anthropogenic uranium in the Arctic Ocean - First 236U and 233U dataset in Barents Sea sediments.

This work reports the first dataset of 236U and 233U in sediment cores taken from the Barents Sea, with the aim to better understand the source terms of anthropogenic uranium in the Arctic region. Concentrations of 236U and 233U along with 137Cs, and 233U/236U atomic ratio were measured in six sediment profiles. The cumulative areal inventories of 236U and 233U obtained in this work are (3.50-12.7) × 1011 atom/m2 and (4.92-21.2) × 109 atom/m2, with averages values of (8.08 ± 2.93) × 1011 atom/m2 and (1.08 ± 0.56) × 1010 atom/m2, respectively. The total quantities of 236U and 233U deposited in the Barents Sea bottom sediments were estimated to be 507 ± 184 g and 7 ± 3 g, respectively, which are negligible compared to the total direct deposition of 236U (6000 g) and 233U (40-90 g) from global fallout in the Barents Sea. The integrated atomic ratios of 233U/236U ranging in (0.98-1.57) × 10-2 reflect the predominant global fallout signal of 236U in the Barents Sea sediments and the highest reactor-236U contribution accounts for 30 ± 14 % among the six sediment cores. The reactor-236U input in the Barents Sea sediments is most likely transported from the European reprocessing plants rather than related to any local radioactive contamination. These results provide better understanding on the source term of anthropogenic 236U in the Barents Sea, prompt the oceanic tracer application of 236U for studying the dynamics of the Atlantic-Arctic Ocean and associated climate changes. The 236U-233U benchmarked age-depth profiles seem to match reasonably well with the reported input function history of radioactive contamination in the Barents Sea, indicating the high potential of anthropogenic 236U-233U pair as a useful tool for sediment dating.

Natural and anthropogenic radionuclides in Norwegian farmed Atlantic salmon (Salmo salar).

Norway is one of the main producers of farmed fish and the world's second-largest exporter of seafood. Farmed Atlantic salmon (Salmo salar) represents the most exported species. This is the first comprehensive survey of anthropogenic (137Cs, 90Sr, 238Pu, 239,240Pu and 241Am) and natural (40K, 226Ra, 228Ra, 210Pb, 210Po) radionuclides in farmed salmon and manufactured fish feed from Norway. The only anthropogenic radionuclide detected in salmon and fish feed was 137Cs. The levels were low with arithmetic means in salmon and feed of 0.13 and 0.30 Bq/kg fresh weight (fw), respectively. The natural radionuclide 40K exhibited the highest levels with arithmetic means in salmon and feed of 115 and 239 Bq/kg fw, respectively. The arithmetic means of 210Po and 210Pb in salmon were 0.013 and 0.044 Bq/kg fw, respectively, with a mean 210Po:210Pb activity ratio of 0.32. For fish feed, the situation was reversed: the arithmetic means of 210Po and 210Pb were 3.8 and 0.67 Bq/kg fw, respectively, with a mean 210Po:210Pb activity ratio of 5.7. The radionuclide levels found in farmed salmon in the present study are comparable to or lower than the levels found in other fish species in the North Atlantic Ocean. A highly conservative dose estimate for consumption showed that doses were no higher than 1.2 µSv/year for toddlers and 4.0 µSv/year for adults. This suggests that the risk associated with radioactivity in farmed salmon is very low even when considering individuals with high consumption and the highest radionuclide levels found in this study.

Norwegian monitoring (1990-2015) of the marine environment around the sunken nuclear submarine Komsomolets.

Norway has monitored the marine environment around the sunken Russian nuclear submarine Komsomolets since 1990. This study presents an overview of 25 years of Norwegian monitoring data (1990-2015). Komsomolets sank in 1989 at a depth of 1680 m in the Norwegian Sea while carrying two nuclear torpedoes in its armament. Subsequent Soviet and Russian expeditions to Komsomolets have shown that releases from the reactor have occurred and that the submarine has suffered considerable damage to its hulls. Norwegian monitoring detected 134Cs in surface sediments around Komsomolets in 1993 and 1994 and elevated activity concentrations of 137Cs in bottom seawater between 1991 and 1993. Since then and up to 2015, no increased activity concentrations of radionuclides above values typical for the Norwegian Sea have been observed in any environmental sample collected by Norwegian monitoring. In 2013 and 2015, Norwegian monitoring was carried out using an acoustic transponder on the sampling gear that allowed samples to be collected at precise locations, ∼20 m from the hull of Komsomolets. The observed 238Pu/239,240Pu activity ratios and 240Pu/239Pu atom ratios in surface sediments sampled close to Komsomolets in 2013 did not indicate any releases of Pu isotopes from reactor or the torpedo warheads. Rather, these values probably reflect the overprinting of global fallout ratios with fluxes of these Pu isotopes from long-range transport of authorised discharges from nuclear reprocessing facilities in Northern Europe. However, due to the depth at which Komsomolets lies, the collection of seawater and sediment samples in the immediate area around the submarine using traditional sampling techniques from surface vessels is not possible, even with the use of acoustic transponders. Further monitoring is required in order to have a clear understanding of the current status of Komsomolets as a potential source of radioactive contamination to the Norwegian marine environment. Such monitoring should involve the use of ROVs or submersibles in order to obtain samples next to and within the different compartments of the submarine.

The impact of tidal and mesoscale eddy advection on the long term dispersion of 99Tc from Sellafield.

In the present work, numerical models are used to study the fate of the 99Tc discharges from Sellafield with a specific focus on the role of mesoscale eddy and tidal advection on the transport and dispersion of this radionuclide. Transport estimates are made with an ocean model that resolves a large part of the ocean mesoscale eddy field and also includes tides. Equivalent estimates are also computed with another model in which these processes are either absent or parametrized. Comparison with field observations shows that the coarse-resolution model can reproduce the general features of the observed time-space 99Tc distribution if the diffusivity in its eddy parametrization scheme is suitably chosen. However, the eddy-permitting simulations capture regional details better and show an overall higher prediction skill, with the model predictions agreeing with the observations within a factor of two to four. The importance of tidal advection is investigated by comparing transport in the eddy-permitting model when this is run either with tides included or with tides filtered out. The results point to systematic Lagrangian tidal drift in the Irish Sea and the North Sea that eventually impacts the 99Tc activity concentration levels also far downstream.

Main results of the 2012 joint Norwegian-Russian expedition to the dumping sites of the nuclear submarine K-27 and solid radioactive waste in Stepovogo Fjord, Novaya Zemlya.

This paper reports the main results of the 2012 joint Norwegian-Russian expedition to investigate the radioecological situation of the Stepovogo Fjord on the eastern coast of Novaya Zemlya, where the nuclear submarine K-27 and solid radioactive waste was dumped. Based on in situ gamma measurements and the analysis of seawater and sediment samples taken around the submarine, there was no indication of any leakage from the reactor units of K-27. With regard to the radioecological status of Stepovogo Fjord, activity concentrations of all radionuclides in seawater, sediment and biota in 2012 were in general lower than reported from the previous investigations in the 1990s. However in 2012, the activity concentrations of (137)Cs and, to a lesser extent, those of (90)Sr remained elevated in bottom water from the inner part of Stepovogo Fjord compared with surface water and the outer part of Stepovogo Fjord. Deviations from expected (238)Pu/(239,240)Pu activity ratios and (240)Pu/(239)Pu atom ratios in some sediment samples from the inner part of Stepovogo Fjord observed in this study and earlier studies may indicate the possibility of leakages from dumped waste from different nuclear sources. Although the current environmental levels of radionuclides in Stepovogo Fjord are not of immediate cause for concern, further monitoring of the situation is warranted.

Dispersal of the radionuclide caesium-137 ((137)Cs) from point sources in the Barents and Norwegian Seas and its potential contamination of the Arctic marine food chain: coupling numerical ocean models with geographical fish distribution data.

Dispersal of (137)Cs from the nuclear submarine wrecks Komsomolets and K-159, which are resting on the seabed in the Norwegian and Barents Seas, respectively, is simulated using realistic rates and hypothetical scenarios. Furthermore, spatiotemporal (137)Cs concentrations in Northeast Arctic cod and capelin are estimated based on survey data. The results indicate that neither continuous leakages nor pulse discharges will cause concentrations of (137)Cs in cod muscle or whole body capelin exceeding the intervention level of 600 Bq/kg fw. Continuous leakages from Komsomolets and K-159 and pulse discharges from Komsomolets induced negligible activity concentrations in cod and capelin. A pulse discharge of 100% of the (137)Cs-inventory of K-159 will, however, result in concentrations in muscle of cod of above 100 times the present levels in the eastern Barents Sea. Within three years after the release, (137)Cs levels above 20 Bq/kg fw in cod are no longer occurring in the Barents Sea.

Radiological status of the marine environment in the Barents Sea.

This paper presents the results of Norwegian radiological monitoring of the Barents Sea in 2007, 2008 and 2009. Activity concentrations of the anthropogenic radionuclides (137)Cs, (90)Sr, (239,240)Pu and (241)Am in seawater were low and up to an order of magnitude lower than in previous decades. Activity concentrations of (99)Tc in seawater were low but remain elevated compared to levels prior to the increased discharge of this radionuclide from Sellafield in the 1990s. Activity concentrations of the naturally occurring radionuclide (226)Ra in seawater were comparable to expected background values. Activity concentrations of (137)Cs in surface sediments were low, with higher values observed in sediments from coastal areas along the Norwegian mainland than from locations in the open sea. Activity concentrations of (137)Cs and (99)Tc in marine biota were low and up to an order of magnitude lower than in previous decades. Committed effective dose rates to man from anthropogenic radionuclides via the consumption of seafood from the Barents Sea were low and are not a cause for concern. Weighted absorbed dose rates to biota from anthropogenic radionuclides were low and orders of magnitude below a predicted no effect screening level of 10 µGy/h. Dose rates to man from consumption of seafood and dose rates to biota in the marine environment are dominated by the contribution from naturally occurring radionuclides.

Dispersal of the radionuclide caesium-137 (137Cs) from point sources in the Barents and Norwegian Seas and its potential contamination of the Arctic marine food chain: coupling numerical ocean models with geographical fish distribution data.

Dispersal of (137)Cs from Komsomolets and K-159 is simulated using realistic rates and hypothetical scenarios. Furthermore, spatiotemporal (137)Cs concentrations in Northeast Arctic cod and capelin are estimated based on survey data. The results indicate that only pulse discharges from K-159 will cause concentrations of (137)Cs in cod muscle exceeding the intervention level of 600 Bq/kg fresh weight. A discharge of ≥10% of the (137)Cs-inventory will result in concentrations in muscle of cod exceeding the intervention level for approximately two years. In fact, a discharge of 10% of the (137)Cs-inventory results in an overlap of 8-30% between the different size groups of cod and levels that exceed the intervention level during the first year after the discharge. For capelin, individuals less than one year old during the first year after a discharge are more likely to be severely affected by discharges comprising ≥50% of the inventory.

Technetium-99 ((99)Tc) in annual growth segments of knotted wrack (Ascophyllum nodosum).

The distribution of technetium-99 ((99)Tc) in annual growth segments of the brown seaweed Ascophyllum nodosum (Fucales, Phaeophyceae) from the southwestern coast of Norway is examined in samples collected from January to November 2006. A twenty-fold increase in the (99)Tc-concentration from the youngest to the oldest growth segments was found. The concentrations ranged from 42 to 98Bq/kg dry weight (d.w.) and from 964 to 1000Bq/kg d.w. in growth segments formed in 2006 and 1996, respectively. In addition, a seasonal variation in the (99)Tc concentration was observed in the actively growing 2006-segments: concentrations decreased from 98Bq/kg d.w. in April to 54Bq/kg d.w. in June; there was a further reduction from June to August (42Bq/kg d.w.); and, finally there was an increase from August to November (93Bq/kg d.w.). In most of the segments formed between 2000 and 2005, there was a tendency of slightly decreasing (99)Tc-concentrations between June and November but this pattern was not observed for the older growth segments. In order to find an explanation for the non-homogenous distribution of (99)Tc within thalli of A. nodosum, different hypotheses are discussed. Uptake and elimination of (99)Tc appears to be most pronounced in the actively growing segments. To date, such non-homogenous distribution of (99)Tc within thalli of A. nodosum has not been taken into consideration, neither in connection with sample collection nor analysis. This paper shows that special protocols must be followed if A. nodosum is going to be used as a bioindicator for (99)Tc in the marine environment. A sampling strategy is proposed.

Bioaccumulation of 137Cs in pelagic food webs in the Norwegian and Barents Seas.

Knowledge and documentation of the levels of radioactive contamination in fish stocks important to Norwegian fisheries is of major importance to Norwegian consumers and fish export industry. In the present study, the bioaccumulation of caesium-137 ((137)Cs) has been investigated in marine food webs in the Barents and Norwegian Seas. The contents of (137)Cs in the different organisms were generally low (<1 Bq kg(-1) wet weight), but a marked bioaccumulation was apparent: The concentration of (137)Cs was about 10-fold higher in the harbour porpoise Phocoena phocoena, representing the upper level of the food web, than in the amphipod Themisto sp., representing the lower level of the food web. The Concentration Factors (CF=Bq kg(-1) wet weight/Bq l(-1) seawater) increased from 10+/-3 for a mixed sample of krill and amphipods to 165+/-5 for harbour porpoises.

Distribution of selected anthropogenic radionuclides (137Cs, 238Pu, (239,240)Pu and 241Am) in marine sediments with emphasis on the Spitsbergen-Bear Island area.

Measurements of anthropogenic radionuclides in marine sediments can provide good estimates of past and present radioactive contamination of the marine environment. The Barents Sea is one of the world's richest ocean areas, and it is therefore of major interest for Norwegian fisheries to document the levels of radioactive contamination of this and adjacent ocean areas. In this study, concentrations of 137Cs, 238Pu, (239,240)Pu and 241Am were measured in marine sediments collected mainly in the Spitsbergen-Bear Island region. Additional samples collected in the deep Norwegian Sea and near the Greenland ice-edge have been included for comparison. The highest radionuclide levels were found near Spitsbergen, reaching over 50% higher than in adjacent areas. Determinations of the mineral content and particle size distribution indicate a relation between the content of clay minerals and radionuclide levels. The present study confirms earlier observations of elevated levels of 137Cs in sediments in the Spitsbergen-Bear Island area and documents elevated levels of 238Pu, (239,240)Pu and 241Am in these sediments. Using an exponential curve fit based on determinations of unsupported 210Pb in sediment cores, sedimentation rates of 0.28, 0.05 and 0.26 cm year(-1) were calculated at locations south of Spitsbergen, near the Greenland ice-edge and in the deep Norwegian Sea, respectively.