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 0048-9697/04/$ - see front matter ᮊ 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.scitotenv.2004.03.023 54 H. Dahlgaard et al. / Science of the Total Environment 331 (2004) 53–67 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.

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