Levels and Trends of Radioactive Contaminants in the Greenland Environment

Science of the Total Environment 331 (2004) 53–67

Levels and trends of radioactive contaminants in the Greenland environment

Henning Dahlgaarda, *, Mats Erikssona,1a , Sven P. Nielsen , Hans Pauli Joensen b

aRisø National Laboratory, Radiation Research Department, NUK-204, DK-4000 Roskilde, Denmark bUniversity of the Faroe Islands, Noatun,´´ FO-100 Torshavn, ´ Faroe Islands, Denmark

Accepted 1 March 2004

Abstract

Levels of radioactive contaminants in various Greenland environments have been assessed during 1999–2001. The source of137 Cs, 90 Sr and 239,240 Pu in terrestrial and fresh water environments is mainly global fallout. In addition, the Chernobyl accident gave a small contribution of137 Cs. Reindeer and lamb contain the largest observed137 Cs concentrations in the terrestrial environment—up to 80 Bq kgy1 fresh weight have been observed in reindeer. Due to special environmental conditions,137 Cs is transferred to landlocked Arctic char with extremely high efficiency in South Greenland leading to concentrations up to 100 Bq kgy1 fresh weight. In these cases very long ecological half- lives are seen. Concentrations of99 Tc, 137 Cs and 90 Sr in seawater and in marine biota decrease in the order North- East Greenland and the coastal East Greenland current)South-West Greenland)Central West Greenland and North-West Greenland)Irmiger Sea;Faroe Islands. The general large-scale oceanic circulation combined with European coastal discharges and previous contamination of the Arctic Ocean causes this. As the same tendency is seen for the persistent organic pollutants (POPs) DDT and PCBin marine biota, it is suggested that long-distance oceanic transport by coastal currents is a significant pathway also for POPs in the Greenland marine environment. The peak99 Tc discharge from Sellafield 1994–1995 has only been slightly visible in the present survey year 2000. The concentrations are expected to increase in the future, especially in East Greenland. The Bylot Sound at the Thule Airbase (Pituffik) in North-West Greenland was contaminated with plutonium and enriched uranium in a weapons accident in 1968. Biological activity has mixed accident plutonium efficiently into the new sediments resulting in continued high surface sediment concentrations three decades after the accident. Transfer of plutonium to benthic biota is low—and lower than observed in the Irish Sea. This is supposed to be caused by the physico–chemical form of the accident plutonium. A recent study indicates that ‘hot particles’ hold considerably more plutonium than previously anticipated and that the Bylot Sound sediments may account for the major part of the un-recovered plutonium after the accident, i.e. approximately 3 kg. ᮊ 2004 Elsevier B.V. All rights reserved.

Keywords: Caesium-137; Strontium-90; Technetium-99; Plutonium-239-240; Polonium-210; Greenland; Environmental radioactivity

*Corresponding author. Tel.: q45-4677-5314; fax: q45-4677-5330. E-mail address: [email protected] (H. Dahlgaard). 1 Present address : Institute for Transuranium Elements, JRC European Commission, P.O. Box 2340, D-76125 Karlsruhe, Germany

1. Introduction the exception of a new discharge of99 Tc to the Irish Sea peaking in 1995 and transported to the Artificial radionuclides have been monitored in Arctic along the Norwegian Coastal Current the Greenland environment since the 1960s. The (AMAP, 2003). Danish data have been reviewed in Arctic Moni- toring and Assessment (AMAP) reports (Aarkrog 2. Materials and methods et al., 1997a; Strand et al., 1998) and further by Aarkrog et al. (1999, 2000). The present data from The sampling regions are given in Fig. 1. A 1997–2001 are published in new AMAP reports sampling campaign was carried out to determine (AMAP, 2003; Hoydal and Dam, 2003; Riget et the deposition of137 Cs and 239,240 Pu from four al., 2003a). No new man-made radioactive con- different regions in Greenland. The aim was to get tamination of the Greenland environment of sig- area-representative soil samples from relatively flat nificance has been detected. As compared to the regions split in 10 cm depth sections. Three soil previous assessment, the levels measured are thus profiles were taken from different areas in each mainly influenced by environmental redistribution region. The samples from the four regions were and continued decay and dilution with time with taken by four different NERI (National Environ-

Fig. 1. Sampling regions. H. Dahlgaard et al. / Science of the Total Environment 331 (2004) 53–67 55 mental Research Institute) employees working in ratory (cf. Ballestra et al., 1992). The quality of the regions. The comparability of the samples is 99Tc data was assessed by Dahlgaard et al. (1995). reduced as no standard soil profilers were used and as the sampling depth varied. Large seawater 3. Results and discussion samples have been obtained by various means— mostly from ships pumps or with buckets from 3.1. The terrestrial environment small boats. Fresh water samples were taken from land. Biological samples were all from NERI The data on137 Cs in soil showed a large programmes, i.e. the same samples are used for variation: in most profiles, only the top 5 or 10 metal and POP analysis (cf. Riget et al., 2003b). cm were above detection limit, whereas other Cesium-137 was analysed by high resolution profiles had137 Cs distributed to 50 cm. It should gamma spectrometry of its meta-stable daughter be expected that a fraction of the137 Cs and maybe 137mBa (2.55 min) on low-background high-purity the239,240 Pu have been washed out to streams, semiconductor detectors (HP–Ge) shielded with lakes and fjords. The results above detection limits 10 cm low-active lead.137 Cs in water samples have been summed up in Table 1. In spite of the were preconcentrated on ammonium-dodeca-mol- variability, the data gives a picture similar to what ( ) ybdo-phosphate (AMP) after adjusting to pH 2. was seen earlier Aarkrog et al., 1997a , i.e. highest fallout to the South parallel to high precip- Biota samples were dried and partly ashed at 450 239,240 137 8C to reduce volume. Technetium-99 is concen- itation rates. The Puy Cs activity ratio in integrated global fallout has been estimated to trated by anion exchange directly from seawater ( or after wet-ashing of biota samples. The metasta- 0.0116 without decay correction Beck and Ben- nett, 2002). Decay correcting from 1962 to 2002 ble isotope99m Tc (6.0 h) is used as a yield changes this ratio to approximately 0.029, which determinant.99 Tc is measured on a GM gas flow is relatively close to the measured values. Due to b-counter after decay of the yield determinant limitations described above, the values given in (Chen et al., 1994, 2001). Strontium is separated 85 Table 1 do not represent the total integrated fallout. from ashed samples by co-precipitation with Sr The239,240 Pu 137Cs ratios from Zackenberg are 90 y as a yield determinant. Sr is determined from it apparently higher than for the other sites and 90 daughter Y after precipitation with gravimetric higher than in the samples taken in 1994 (Aarkrog yield determination and measurement on a GM et al., 1997a), where Zackenberg was not included. gas flow -b-counter (Chen et al., 2002b). The The low239,240 Puy 137Cs ratios at Pituffik indicates q plutonium oxidation state is adjusted to Pu4 , that the three sampled sites near the Thule Airbase which is coprecipitated with Fe-hydroxides and had not been affected by the Thule weapons cleaned further by anion exchange.242 Pu is used accident in 1968. This is in accordance with the as a yield tracer. Plutonium was measured by alpha finding that no accident plutonium could be detect- spectrometry after electroplating (Chen et al., ed in the lakes to the North and East of the Thule 2001, 2002a). Several plutonium samples from Airbase (Eriksson et al., 2001). Thule were analysed by a sector-field ICPMS. For Table 2 gives137 Cs concentrations in various analysis of210 Po, samples are spiked with 208 Po, terrestrial plants. As expected, lichen and moss q wet digested with HNO3 HCl and further with samples show the highest levels as the concentra- H22 O in HCl followed by spontaneous deposition tions obtained from the global fallout and the on a silver disc and alpha spectrometry (Chen et Chernobyl contamination is retained and only al., 2001). slowly diluted due to a slow growth rate. The The quality of137 Cs, 90 Sr and 239,240 Pu data relatively high level in the grass samples indicates have been assessed in several international inter- root uptake. comparisons, mainly arranged by the International Table 3 gives137 Cs concentrations in meat from Atomic Energy Agency’s (IAEA) Monaco labo- lamb, reindeer and grouse. In 1997, a special 56 H. Dahlgaard et al. / Science of the Total Environment 331 (2004) 53–67

Table 1 137Cs and 239,240 Pu in soil samples from four Greenland regions (cf. Fig. 1)

Location Year 137Cs 239,240Pu Ratio Depth Bq kgy1 Bqmy2 S.D.% Bq kgy1 Bqmy2 S.D.%239,240 Puy cm dry dry137 Cs Zackenberg (Salix) 1999 0–10 1.10 122 14.5 0.054 6.0 12.4 0.049 Zackenberg (Cassiope) 1999 0–10 0.32 27 36.7 0.014 1.2 37.8 0.045 Zackenberg (Dryas) 1999 0–10 1.57 146 11.0 0.071 6.6 10.9 0.045 Isortoq, profile 1 1999 0–10 74.4 2034 0.6 2.120 58.0 5.8 0.028 Isortoq, profile 2 1999 0–10 16.6 1113 1.5 0.541 36.2 6.4 0.033 Isortoq, profile 3 1999 0–10 14.2 1423 1.7 0.438 44.0 6.7 0.031 Itinnera, profile 1 1999 0–7 28.5 320 2.0 1.001 11.2 15.1 0.035 Itinnera, profile 2a 1999 0–7 103 276 0.8 2.53 6.8 5.5 0.025 Itinnera, profile 3b 1999 0–5 76 114 1.2 4.4 6.6 5.5 0.058 Pituffik, profile 1 2000 0–10 -0.7 DL 0.012 30.3 Pituffik, profile 2c 2000 0–10 16.7 3.7 0.391 7.5 0.023 Pituffik, profile 3 2000 0–10 0.62 25.6 0.013 31.0 0.021 aData 0–7 cm, 137 Cs detected to 17 cm. bData 0–5 cm, 137 Cs detected to 32 cm. cData 0–10 cm, 137 Cs detected to 50 cm.

Table 2 Cs-137 (Bq kgy1 dry weight) in various terrestrial plants

Species Location Region Year 137Cs S.D. n 137Cs S.D. n Bqkgy1 Bqmy2 d.w. Lichenymoss Faroe Islands FR 1999 708 1 Moss Faroe Islands FR 1999 196 147 2 Grass Faroe Islands FR 1999 11 14 3 Cetraria nivalis Zackenberg NE 1999 59 29 3 Lichen Scoresbysund NE 1999 189 71 2 Vaccinium uligonosum Scoresbysund NE 1999 70 1 Lichen Isortoq SW 1999 292 175 5 Grass Isortoq SW 1999 80 144 5 826 1160 2 Grass Itinnera CW 1999 39 21 3 4 2 3 Lichen Pituffik NW 2000 90 14 3 Region acronyms for this and following tables: see Fig. 1.

Table 3 Cs-137 (Bq kgy1 fresh weight) in meat from lamb, reindeer and grouse

Species Location Region Year 137Cs S.D. n Bqkgy1 fr.w. Lamb Bøur (Faroe Islands) FR 1999 5.10 2.00 2 Lamb Sandur (Faroe Islands) FR 1999 4.90 0.10 2 Lamb Narssaq SW 1999 19 18 3 Reindeer Isortoq SW 1999 79 6 3 Reindeer Akia (Lichen rich) CW 1997 65 9 5 Reindeer Itinnera (Lichen poor) CW 1997 59 13 10 Grouse Godhavn CW 1999 0.76 0.33 6 H. Dahlgaard et al. / Science of the Total Environment 331 (2004) 53–67 57 sampling of reindeer was performed to evaluate Table 5 ( y1 ) the effect of lichen-rich and lichen-poor areas on Cs-137 Bq kg freshweight in landlocked Arctic char 137 the level of Cs. This was initiated because the Species Location Region Year 137Cs S.D. n 137 food chain transfer of Cs from lichen to reindeer Bqkgy1 is known to be important for137 Cs (Ahman et al., fr.w. ) 2001 . The levels observed in Greenland are inter- Arctic char Zackenberg NE 1999 0.77 0.71 3 mediary between the low Icelandic levels, Arctic char Isortoq SW 1999 79 18 9 explained by a low frequency of lichens, and the Arctic char Itinnera CW 1999 21 6 2 Norwegian pre-Chernobyl values (Palsson et al., 1994). There was no significant difference between the two groups of reindeer sampled. The test is highest. This is concurrent with the highest precip- weakened by the fact that the two groups of itation rates in these areas. The global fallout reindeer were shot 16–17 September 1997, which showed137 Csy 90Sr activity ratios approximately is before the main lichen-grazing period. Although 1.5. For the Faroe Islands and South Greenland, lower than in reindeer, the transfer of caesium to this ratio was further increased with137 Cs from lamb in South Greenland is high. As seen in the Chernobyl in 1986. The lower ratios observed in Faroe Islands, high levels in lamb are explained fresh water is due to the larger mobility in the not only by a high fallout, but also by long drainage area and the lower association with sedi- ecological half-lives and high transfer parameters menting particles of Sr. The present Greenlandic due to special environmental conditions, especially levels vary between 0.03 and 0.46 indicating a acidity and high content of organic matter (Joen- large variability in drainage area and lake charac- sen, 1999). This phenomenon deserves further teristics. As an example of this variability, the study in Greenland. highest concentration of90 Sr in freshwater was observed in North-West Greenland where the fall- 3.2. Freshwater out and the137 Cs concentration is lowest (Table 4). Tables 4 and 5 and Fig. 2 present average By comparing137 Cs concentrations in land- concentrations of137 Cs and 90 Sr in fresh water, locked Arctic char and fresh water from the same sampled in four Greenland regions and the Faroe sites, bioaccumulation factors approximately 2800, Islands, and137 Cs in landlocked Arctic char (Sal- 37 000 and 12 000 Bq kgy1 fresh char meatyBq velinus alpinus) caught in North-East and South- ly1 water (or l kgy1) for Zackenberg, Isortoq and West Greenland. The data indicate a large Itinnera, respectively, were calculated. A relatively geographical variability, but reproduce the same high bioaccumulation factor and a long environ- trends as seen in the previous AMAP assessment: mental half-life for radiocaesium is expected (Uge- the highest concentrations of137 Cs in water are dal et al., 1995; Rowan et al., 1998; Jonsson et found in South and South-West Greenland and in al., 1999), but the extremely high bioaccumulation the Faroe Islands, where the global fallout was factors in South and South-West Greenland are

Table 4 Average concentrations of137 Cs and 90 Sr in fresh water sampled in the five regions

Location Region Year 137Cs S.D. 90Sr S.D. n Bqmy3 Bqmy3 Faroe Islands FR 1999 2.41 1.55 2.96 1.96 3 Zackenberg NE 1999 0.27 0.07 1.62 0.17 3 Isortoq SW 1999 2.10 0.16 4.57 0.45 4 Itinnera CW 1999 1.73 0.14 5.02 0.11 3 Lake Crescent, Pituffik NW 1999 0.16 0.01 5.17 0.38 3 58 H. Dahlgaard et al. / Science of the Total Environment 331 (2004) 53–67

Fig. 2.137 Cs and 90 Sr in lake water and 137 Cs in landlocked Arctic char. noteworthy. Caesium is transferred preferentially water, low-ionic oligotrophic lakes from areas with via food and is biomagnified along food chains. a high precipitation. This deserves further study. The accumulation in fresh water fish is enhanced The concentrations of137 Cs in fresh water fish due to several ecological reasons, e.g. low ionic are of no serious radiological concern. However, content, slow growth rates, food choice, age and the annual consumption of 10 kg of the Isortoq size (Ugedal et al., 1995; Rowan et al., 1998). char will cause an annual radiation dose of 10 The levels at Isortoq and Itinnera are similar to mSv corresponding to a radiological risk which is observations in the previous AMAP assessment considered to be at the limit of regulatory concern (Aarkrog et al., 1997a), where it could be con- (EU, 1996). cluded that only 10% of the Isortoq value was due 3.3. Levels of137 Cs, 99 Tc, 90 Sr and 239,240 Pu in the to Chernobyl derived137 Cs, i.e. the high levels are marine environment originating in global fallout from the 1950s and 1960s. As large variations between individuals and Table 6 gives average radionuclide concentra- between different lakes can be expected, it is likely tions observed in 1999 in surface seawater sam- that other lakes in South Greenland will show even ples. Further data from 2000 and 2001 are shown higher137 Cs levels in Arctic char, especially clear- in Figs. 3 and 4. H. Dahlgaard et al. / Science of the Total Environment 331 (2004) 53–67 59

Table 6 Average radionuclide concentrations observed 1999 in surface seawater samples

Region* 137Cs S.D. n 99Tc S.D. n 90Sr S.D. n Salinity S.D. n 239,240Pu S.D. n Bqmy3 Bqmy3 Bqmy3 ‰mBqmy3 FR 1.7 0.1 2 0.020 0.000 2 1.1 0.1 2 34.8 0 2 4.6 0.4 2 IRM 1.7 – 1 -0.01 – 1 1.0 – 1 35.1 – 1 Ice 2.8 0.1 2 0.031 0.003 2 1.1 0.0 2 34.7 0.0 2 NE 4.5 0.6 4 0.082 0.009 4 1.8 0.3 4 29.2 2.9 4 2.5 0.1 3 EGC 5.4 0.3 7 0.078 0.012 7 2.0 0.4 7 32.2 1.5 7 SW 4.3 0.4 4 0.071 0.008 4 1.6 0.1 4 31.3 0.5 4 7.1 0.5 3 CW 2.8 0.8 3 0.052 0.017 3 1.5 0.1 3 31.8 2.0 3 2.1 0.8 3 NW 2.9 0.1 4 0.024 0.003 4 1.1 – 1 31.5 – 1 * IRM: Irmiger Sea; Ice: Iceland Sea; EGC: the East Greenland Current in the Denmark Strait (cf. Fig. 1).

Table 7 gives average concentrations of137 Cs edible marine products sampled in 1999. The and99 Tc in seaweed taken in 1999, 2000 and 2001 concentrations of99 Tc, 137 Cs and 90 Sr in seawater and Table 8 gives137 Cs concentrations in various are decreasing in the order North-East Greenland

Fig. 3. Tc-99, mBq ly1 , in surface seawater year 2000. 60 H. Dahlgaard et al. / Science of the Total Environment 331 (2004) 53–67

Fig. 4.137 Cs, 99 Tc and 90 Sr, mBq ly1 , in surface seawater observed in 2001. and the coastal East Greenland current)South- should partly be explained by long-distance oce- West Greenland)Central West Greenland and anic transport from West Europe or Siberia by North-West Greenland)Irmiger Sea;Faroe coastal current pathways (Riget et al., 2000). Table Islands. The same tendency is seen for137 Cs and 9 presents concentrations of different radionuclides 99Tc in seaweed and for example 137 Cs in seal and two POPs normalised to concentrations in East from East and West Greenland. This is in accor- Greenland. Large variations are seen—and should dance with long-distance transport patterns from be expected. However, the present data further European coastal waters, which are responsible for support the hypothesis that at least part of the load most of the99 Tc and a large fraction of the 137 Cs of PCBand DDT in the Greenlandic marine (Dahlgaard, 1994, 1995). The Wolstenholme Fjord environment is transported with marine currents seaweed value for137 Cs (Table 7) is so far consid- either from Europe like the radionuclides, espe- ered an unexplained outlier. cially99 Tc and 137 Cs, or from Siberia or the Arctic Certain persistent organic pollutants (POPs) Ocean. show a similar distribution: highest in East Green- There has been some focus on the levels of99 Tc land, lowest in West Greenland (Riget et al., in the marine environment because the British 2003b). It has earlier been suggested, that this nuclear fuel reprocessing plant Sellafield increased H. Dahlgaard et al. / Science of the Total Environment 331 (2004) 53–67 61

Table 7 Average concentrations of137 Cs and 99 Tc, Bq kgy1 dry weight in seaweed in 1999, 2000 and 2001

Species Location 137Cs S.D. n 99Tc S.D. n dry Region Year Bq kgy1 dw Bqkgy1 dw % Fucus Faroe Islands FR 1999 0.47 0.10 3 1.60 0.41 3 19.6 Fucus Scoresbysund NE 1999 2.74 0.81 5 28.60 5.60 5 12.7 Fu.di. Scoresbysund NE 2000 2.06 1.17 4 29.62 9.10 3 Fu.di. Scoresbysund NE 2001 1.42 0.56 3 24.27 9.69 3 21.0 Fucus Isortoq SW 1999 1.83 0.35 3 5.50 0.30 3 19.6 Fu.ve. South Greenland SW 2000 0.29 0.12 3 12.85 1.43 3 Fucus Godhavn CW 1999 0.29 0.06 3 5.80 1.10 3 17.1 Fu.ve. Kronprinsens Ejland CW 2000 0.35 0.16 3 6.29 0.74 3 Fu.ve. Kronprinsens Ejland CW 2001 0.34 0.05 2 5.97 0.08 2 26.0 As.no. Kronprinsens Ejland CW 2001 0.23 1 11.95 0.67 2 29.0 Fucus Pittufik NW 1999 1.23 1 3.80 1 16.0 Fu.ve. Dundas* NW 2000 0.44 0.09 3 4.58 0.19 3 Fu.di. Wolstenholme fjord* NW 2001 3.06 3.25 2 4.30 0.61 2 20.0 Species: Fu.ve.: Fucus vesiculosus, Fu.di.: F. disticus, As.no.: Ascophyllum nodosum. * Cf. Fig. 5. its discharges from 1994 and onwards (AMAP, but it should be brought in mind that the sampled 2003). Based on results from earlier studies (Aark- area is huge and it has not been possible to perform rog et al., 1983; Dahlgaard et al., 1986; Aarkrog a systematic sampling of the various water masses et al., 1987a; Dahlgaard, 1994), the 1994–1995 in the East Greenland current system. The samples peak discharge may be expected off North-East from 1999, 2000 and 2001 are therefore not direct- Greenland from year 2000 and onwards. Seawater ly comparable. Shrimp meat samples from South- data for 2000 actually indicated increased levels West Greenland were analysed in 2000, but all of99 Tc off North-East Greenland (Fig. 3), whereas results were below detection limits. In normal levels in 2001 seemed to be unchanged. The oxygenated seawater,99 Tc appears mainly as increased levels in year 2000 samples are probably anionic pertechnetate with a low affinity to parti- caused by the increased discharges from Sellafield, cles and to most marine organisms except brown

Table 8 Cs-137 (Bq kgy1 fresh weight) in various edible products. Except for sculpin (whole fish), the values are for meat

Species Location Region Year 137Cs S.D. n Bqkgy1 w.w. Cod Faroe Islands FR 1999 0.22 0.05 2 Haddock Faroe Islands FR 1999 0.10 1 Mytilus, soft Faroe Islands FR 1999 0.05 1 Sculpin total Faroe Islands FR 1999 0.05 1 Shrimp Faroe Islands FR 1999 0.10 0.01 3 Whale Faroe Islands FR 1999 0.23 0.08 3 Black guillemot Scoresbysund NE 1999 0.35 0.01 3 Sculpin total Scoresbysund NE 1999 0.47 0.10 3 Seal Scoresbysund NE 1999 0.50 0.11 3 Whale Scoresbysund NE 1999 0.47 0.17 3 Black guillemot Godhavn CW 1999 0.21 0.04 5 Sculpin total Godhavn CW 1999 0.26 0.06 3 Seal Godhavn CW 1999 0.19 0.08 3 62 H. Dahlgaard et al. / Science of the Total Environment 331 (2004) 53–67 macroalgae (Fucus, Ascophyllum) and certain Table 10 ( ) 210 y1 crustaceans such as lobster and shrimp. Ringed seal from Disco Fjord CW , PoBqkg wet weight As a pilot study, liver, kidney and meat from five ringed seals caught in Disco Fjord (CW) ID Sex Length BqPokg210 y1 under NERI’s time-trend programme were ana- cm Kidney Liver Muscle lysed for210 Po (Table 10). 210 Po is a naturally occurring alpha-emitter that appears in the238 U 24602 Female 98 98 73 16 226 222 210 24603 Male 95 106 92 29 decay series after Ra, Rn and Pb, and it is 24606 Male 95 84 71 17 bioaccumulated in aquatic organisms. The present 24608 Male 98 107 107 21 levels are high compared to average global values 24616 Female 123 86 59 17 210 y1210y1 of 2.4 Bq Po kg , 15 Bq Po kg and 6 Bq Average 96 81 20 y 210Po kg 1 (wet weight) in fish, molluscs and S.D. 11 19 6 crustaceans, respectively, found in an international Decay corrected to time of catch: 6 May 2001. study (Aarkrog et al., 1997b). That study conclud- 210 ed that Po gives rise to a major component of 3.4. Plutonium in Bylot Sound—the Thule accident the radiation dose to man from consumption of 1968 marine products, but the study did not include marine mammals and doses to Inuits. Consumption On 21 January 1968, a B-52 aircraft from the of 1 kg of kidney, 1 kg of liver and 4 kg of meat US Strategic Air Command crashed on the sea ice with the present average values would each give a of Bylot Sound 12 km West of the Thule Air Base radiation dose approximately 0.1 mSv. It is thus in Greenland. The aircraft disintegrated on impact evident that consumption of fresh seal significantly and an explosion and a fire ensued. The four enhances the natural radiation dose received by nuclear weapons onboard were destroyed and fis- Inuits. Canadian caribou holds even higher con- sionable material—plutonium and uranium—was centrations in liver and kidney and similar concen- dispersed. The benthic marine environment in the trations in meat due to accumulation via lichen 180–230 m deep Bylot Sound was then contami- (Thomas et al., 1994). nated with239,240 Pu. The site was revisited August

Table 9 Relative concentrations of radionuclides in seawater and biota and the POPs SDDT and SPCBin biota (Riget et al., 2003b)

NE SW CW NW FR 137Cs 1999 Water 100 96 62 64 38 137Cs 1999 Fucus 100 67 11 45 17 137Cs 1999 Sculpin 100 55 11 137Cs 1999 Seal 100 38 137Cs 1999 Whale 100 49 137Cs 1999 Black guillemot 100 60 99Tc 1999 Water 100 87 63 29 24 99Tc 1999 Fucus 100 19 20 13 6 90Sr 1999 Water 100 89 83 61 61 SDDT 2000 Sculpin, female, liver 100 103 11 SPCB2000 Sculpin, female, liver 100 126 26 SDDT 1999 Seal, fem.-blubber 100 51 65 SPCB1999 Seal, fem.-blubber 100 44 52 SDDT 2000 Black guillemot, fem. 100 50 SPCB2000 Blackguillemot, fem. 100 82 H. Dahlgaard et al. / Science of the Total Environment 331 (2004) 53–67 63

1997, 29 years after the accident (Dahlgaard et al., cores are included in the present estimate, and that 2001; Eriksson, 2002). The plutonium was present a large uncertainty is connected to the result and in an insoluble oxide form and mainly associated to the area integration. Thus the new result can at to particles with a geometric mean diameter of 2 the present state not be considered as significantly mm and a log-normal size distribution (US Air different from the earlier, although it fits better to Force, 1970). The total amount of plutonium the estimate above of the missing 3 kg. dispersed in the accident was 6 kg. Approximately Plutonium concentrations in surface sediments half of this was recovered, i.e. ;3 kg of plutonium vary between fallout levels -2 Bq kgy1 dry and may have entered the environment. After the acci- contaminated levels )1000 Bq kgy1 dry (Dahl- dent, the amount of plutonium in the marine gaard et al., 2001). Average values for the upper- sediments in Bylot Sound has been estimated based most 3 cm sediment layer are given in Fig. 5. on samples taken at six sampling expeditions Plutonium concentrations in biota samples have (1970, 1974, 1979, 1984, 1991 and 1997) These been compared with concentrations in 0–3 cm inventory estimates were in the range 1–1.6 TBq surface sediments from the same sites to give a or approximately 0.5 kg (Aarkrog, 1971, 1977; ‘concentration ratio’, CR, (Bq239,240 Pu kgy1 dry Aarkrog et al., 1984, 1987b, 1994). These esti- biotayBq kgy1 dry 0–3 cm sediment)(Table 11). mates did not take account of hot particles. The It is noted that although the analysed biota is inhomogeneous nature of the plutonium contami- living buried in the sediments or on the sediment nation has been noted for many years, but it was surface, the CR values indicate that the bioavaila- earlier assumed not significantly to influence the bility of the weapons plutonium is low. Most of inventory estimates. The earlier works are solely the observed CR values are in the range 0.01–0.1, based on leaching with aqua-regia and extraction i.e. plutonium concentrations in benthic biota are of plutonium from samples followed by alpha in general 1–2 orders of magnitude lower than in spectrometry. The hot particles may have been surface sediments. Furthermore, a significant part underestimated for two reasons: incomplete disso- of this plutonium is probably not metabolised but lution and extraction of the particles and in some rather associated with particles in the guts and cases inability to quantify heavily contaminated adhering to the surface structure of the animals. samples due to insufficient energy resolution in Higher transfer rates to benthic biota have been the alpha spectrometry system used. An improved observed in the Irish Sea (Ryan et al., 1999), method to determine the total inventory of a probably due to differences in physical and chem- heterogeneously distributed contamination of ical forms of plutonium. One single bivalve sample marine sediments has been introduced (Eriksson, showed a much higher level, which was probably 2002). The estimate is based on gamma spectro- due to a hot particle. metric screening of the241 Am concentration in Average isotope ratios,240 Puy 239Pu atom ratios 450, 1 g aliquots from six sediment cores. The and238 Puy 239,240Pu and 241 Amy 239,240Pu activity 241Am activity is building up as a decay product ratios for sediment samples containing more than of241 Pu (half-life 14.4 year), which is present in 20 Bq239,240 Pu kgy1 dry, i.e. at least an order of weapons plutonium as an impurity. Based on magnitude above the fallout background, are given radiochemical determination of the plutonium con- in Table 12. The reference date is the sampling centration in 20 of these subsamples, the241 Am date, i.e. 1997. By comparison of the241 Amy values are used to estimate the239,240 Pu concentra- 239,240Pu activity ratios for the sediments (Table tions. Results centre on a total inventory approxi- 12) with data for the benthic biota samples (Table mately 9.5 TBq or 3.5 kg239,240 Pu, which is seven 13), it is seen that some of the biota groups seem times higher than earlier estimates (0.5 kg). The to have a higher uptake of americium than of difference is partly explained by the full inclusion plutonium, especially molluscs and brittle stars of hot particles in the present methodology. It (Ophiuroids). A higher affinity for americium than should, however, be noted, that only six sediment for plutonium in some biota groups is not new. 64 H. Dahlgaard et al. / Science of the Total Environment 331 (2004) 53–67

Fig. 5. Thule-1997. Plutonium concentrations in surface 0–3 cm layer of sediments, Bq239,240 Pu kgy1 dry. Location names in italics, concentrations in bold. The point of impact was on the sea ice at the location marked V2.

Thus IAEA reported higher CF values for Am ecological half-lives are seen because of the special than for Pu in molluscs (IAEA, 1985). environmental conditions. 137Csy 90Sr activity ratios in fresh waters have 4. Conclusions decreased from the fallout level approximately 1.5 to the present levels varying between 0.03 and Reindeer and lamb hold the largest137 Cs con- 0.46. This indicates a large variability in drainage centrations in the terrestrial environment, and long area and lake characteristics. H. Dahlgaard et al. / Science of the Total Environment 331 (2004) 53–67 65

Table 11 Table 12 Thule-1997. Plutonium Concentration Ratios, CR, Bq239,240 Pu Thule-1997. Isotope ratios in sediment samples holding more kgy1 dry biotayBq kgy1 dry sediment between various groups than 20 Bq239,240 Pu kgy1 dry. Reference date: August 1997 of benthic biota and upper 3 cm of sediments Sediments )20 Bq kgy1 dry Mean S.D.% n y1 Class Species CR, Bq kg drybiotay 240 239 y1 Puy Pu atom ratio 0.045 15 30 Bq kg dry sediment 238 239,240 (0–3 cm) Puy Pu activity ratio 0.014 53 223 241Amy 239,240Pu activity ratio 0.13 61 114 Average S.D. n

Mollusc Bivalves 0.025 0.024 13 In the plutonium contaminated Bylot Sound, Mollusc Macoma calcarea 37* 1 Mollusc Snails 0.0033 0.0018 9 biological activity has mixed accident plutonium Mollusc Squid, Rossia sp. 0.00036 1 efficiently into the 5–12 cm recent sediment result- Echinoderm Starfish 0.0094 0.0139 9 ing in continued high surface sediment concentra- Echinoderm Brittle stars 0.013 0.0159 4 tions three decades after the accident. Echinoderm Feather stars 0.0070 0.0060 4 A recent work indicates that ‘hot particles’ Echinoderm Sea Urchins 0.12 0.16 4 Echinoderm Sea cucumber 0.0080 0.0083 4 probably hold considerably more plutonium than Crustacea Shrimp 0.0048 0.0088 4 previously anticipated and that the Bylot Sound Crustacea var. 0.038 0.039 4 sediments may be accounting for the major part Annelida Pectinaria 0.068 0.05234 4 of the un-recovered amount, i.e. approximately 3 Annelida var. 0.023 0.033 10 kg, although this is based on a small number of Annelida Tube 0.28 0.29 6 Fish Liparis sp. 0.00035 1 samples.

* Transfer of plutonium to benthic biota is low— Outlier, probably caused by hot particle. and lower than observed in the Irish Sea. This is considered to be caused by the physico–chemical Due to special environmental conditions,137 Cs form of the accident plutonium. from global fallout is still transferred to landlocked Arctic char with extremely high efficiency in South Acknowledgments Greenland. Concentrations of99 Tc, 137 Cs and 90 Sr in sea- The sampling and analysis was mainly financed water and in marine biota are decreasing in the by Dancea (Danish Co-operation for Environment order North-East Greenland and the coastal East in the Arctic). Please note that the content of this Greenland current)South-West Greenland)Cen- paper does not necessarily reflect the views of the tral West Greenland and North-West Greenland) Irmiger Sea;Faroe Islands. The general Table 13 large-scale oceanic circulation combined with Eur- Thule-1997.241 Amy 239,240Pu activity ratios in various groups opean coastal discharges and previous contamina- of sediment dwelling benthic biota tion of the Arctic Ocean causes this. Type Sub-type 241Amy 239,240Pu activity As the same tendency is seen for DDT and PCB ratio in marine biota, it is suggested that long-distance Mean S.D.% n oceanic transport by coastal currents is a significant pathway also for POPs in the Greenland Benthos All 0.39 76 84 Molluscs All 0.63 62 24 marine environment. Polychaetes All 0.28 77 16 99 The peak Tc discharge from Sellafield 1994– Crustaceans All 0.22 36 5 1995 has only been slightly visible in the present Echinoderms Ophiuroidea 0.55 24 4 survey year 2000. The concentrations are expected Echinoderms Asteroidea 0.41 34 11 to increase in future years, especially in East Echinoderms Echinoidea 0.17 8 5 Echinoderms Holothurioidea 0.13 67 2 Greenland 66 H. Dahlgaard et al. / Science of the Total Environment 331 (2004) 53–67

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