Iodine-129, Iodine-127 and Cesium-137 in seawater from the North Sea and the Baltic Sea.

In this study, new data are presented for the iodine isotopes (127I, 129I and their isotopic ratios) and Cesium (137Cs) in water samples of the North Sea and the Baltic Sea in 2005 and 2009. This study supplements and extends the study of Michel et al. (2012). Iodine isotopes were separated from their matrix by using an anion exchange method and were determined by applying ICP-MS and AMS. 137Cs in seawater was determined after cesium ion exchange procedure enrichment by gamma-spectrometry. The concentrations of 127I in seawater of the North and Baltic Sea are fairly constant in each Sea with averages of (44 ± 2) and (21 ± 1) ng g-1, respectively, depending on the salinity. However, large variations of 129I concentrations in these areas were detected, which decreased along the French, Belgian, Dutch, German, and Danish shores. 129I/127I isotope ratios in the Baltic Sea are about 10 times lower than in the North Sea in 2009. The highest isotopic ratios (2.7 × 10-6) was detected in the English Channel east of the nuclear reprocessing plant at Cap de la Hague. The results confirm the result of our early study that the sources of 129I in the North Sea are primarily the nuclear reprocessing facilities at Sellafield (UK) and La Hague (F), and that in the Baltic Sea the inflow of water from North Sea through the Danish Straits dominates the occurrence of 129I. In 2009, the activity concentration of 137Cs was at least 6 times higher in the Baltic Sea (37 Bq m-3) than in the North Sea (5.9 Bq m-3), due to release of 137Cs from sediments in the Baltic Sea, which were contaminated by the Chernobyl accident and - to a minor degree - the atmospheric explosions of atomic bombs. The results are discussed by comparing the results of our previous work and the current study demonstrating the continuing disequilibrium of 129I/127I atomic ratio in the environmental compartments.

Retrospective dosimetry of Iodine-131 exposures using Iodine-129 and Caesium-137 inventories in soils--A critical evaluation of the consequences of the Chernobyl accident in parts of Northern Ukraine.

The radiation exposure of thyroid glands due to (131)I as a consequence of the Chernobyl accident was investigated retrospectively based on (129)I and (137)Cs inventories in soils in Northern Ukraine. To this end, soil samples from 60 settlements were investigated for (129)I, (127)I, and (137)Cs by AMS, ICP-MS and gamma-spectrometry, respectively. Sampling was performed between 2004 und 2007. In those parts of Northern Ukraine investigated here the (129)I and (137)Cs inventories are well correlated, the variability of the individual (129)I/(137)Cs ratios being, however, high. Both the (129)I and (137)Cs inventories in the individual 5 samples for each settlement allowed estimating the uncertainties of the inventories due to the variability of the radionuclide deposition and consequently of the retrospective dosimetry. Thyroid equivalent doses were calculated from the (129)I and the (137)Cs inventories using aggregated dose coefficients for 5-year old and 10-year-old children as well as for adults. The highest thyroid equivalent doses (calculated from (129)I inventories) were calculated for Wladimirowka with 30 Gy for 5-years-old children and 7 Gy for adults. In 35 settlements of contamination zone II the geometric mean of the thyroid equivalent doses was 2.0 Gy for 5-years-old children with a geometric standard deviation (GSD) of 3.0. For adults the geometric mean was 0.47 Gy also with a GSD of 3.0. In more than 25 settlements of contamination zone III the geometric means were 0.82 Gy for 5-years old children with a GSD of 1.8 and 0.21 Gy for adults (GSD 1.8). For 45 settlements, the results of the retrospective dosimetry could be compared with thyroid equivalent doses calculated using time-integrated (131)I activities of thyroids which were measured in 1986. Thus, a critical evaluation of the results was possible which demonstrated the general feasibility of the method, but also the associated uncertainties and limitations.

Iodine-129, iodine-127 and caesium-137 in the environment: soils from Germany and Chile.

Soil profiles from Bavaria in southern Germany and from Chile were analysed for (129)I by accelerator mass spectrometry (AMS), for (127)I by inductively coupled plasma mass spectrometry (ICP-MS), and for (137)Cs by gamma-spectrometry. The mean deposition density of (137)Cs in soils from Bavaria was (41×1.5(±1)) kBq m(-2) (geometric mean and geometric standard deviation), originating mostly from the Chernobyl fall-out. The deposition density of (129)I in these soils was (109×1.5(±1)) mBq m(-2). The dominant sources of (129)I in Bavaria are, however, the reprocessing plants La Hague and Sellafield and not the Chernobyl fall-out. The (129)I/(127)I isotopic ratios of the Bavarian soils were between 10(-7) and 10(-10), i.e. 10(2)-10(5) times higher than the ratios observed for the samples from Chile. The (129)I integral deposition densities in Chile, Easter Island and Antarctica were between 0.3 mBq m(-2) and 2 mBq m(-2). In these soils, the observed (129)I/(127)I ratios were about 10(-12). The soils from Chile allow the determination of the (129)I fall-out from the atmospheric nuclear weapons explosions undisturbed from contaminations due to releases from reprocessing plants. An upper limit of the integral (129)I deposition density of the atmospheric nuclear weapons explosions on the Southern Hemisphere (27°S) is about 1 mBq m(-2). Finally, the dependence of the migration behaviour of (137)Cs, (127)I and of (129)I on the soil properties is discussed. It turns out that there is a distinctly different behaviour of (127)I, (129)I, and (137)Cs in the soils exhibiting different sorption mechanisms for old and recent iodine as well as for (137)Cs.

Iodine-129 and iodine-127 in European seawaters and in precipitation from Northern Germany.

In order to obtain a comprehensive survey on the consequences of the marine (129)I discharges from the European reprocessing plants La Hague and Sellafield, the distribution of (129)I and (127)I in surface waters of the North Sea, the English Channel, the Irish Sea, and the Northeast Atlantic was studied using accelerator mass spectrometry for (129)I and ICP-MS for (127)I. Samples of seawater were taken in the German Bight in May, September, and November 2005 and in the entire North Sea and the English Channel in August 2005. Further samples were obtained from the Irish Sea in June and August 2006 and from Arctic waters between Spitsbergen and Southern Norway in September 2005. (129)I is a conservative tracer in seawater. The concentrations of (127)I are relatively constant with exceptions of coastal areas with high biological activity and of areas influenced by influx from rivers and the Baltic Sea. The variability of the (129)I/(127)I isotopic ratios is exclusively determined by admixture of (129)I released from the reprocessing facilities Sellafield and La Hague to the seawater. The (129)I/(127)I ratios were between 4 × 10(-9)and 3 × 10(-6): at least 3 orders of magnitude higher than the natural equilibrium isotopic ratio 1.5 × 10(-12). (129)I/(127)I ratios of a few times 10(-10) were only found in seawater from the Indian Ocean and from the Pacific at Hawaii. Comparison of the results obtained for seawater with those of a measurement of airborne iodine species and with iodine isotopes in precipitation in Northern Germany demonstrates the transfer of (129)I and (127)I from the sea into the atmosphere and the dominating role of the marine discharges for the atmospheric fallout of (129)I in Western Europe. The results are discussed with the goal to estimate the relevance of the marine discharges for the contamination of the continental areas.

Ultra-trace analysis of 36Cl by accelerator mass spectrometry: an interlaboratory study.

A first international (36)Cl interlaboratory comparison has been initiated. Evaluation of the final results of the eight participating accelerator mass spectrometry (AMS) laboratories on three synthetic AgCl samples with (36)Cl/Cl ratios at the 10(-11), 10(-12), and 10(-13) level shows no difference in the sense of simple statistical significance. However, more detailed statistical analyses demonstrate certain interlaboratory bias and underestimation of uncertainties by some laboratories. Following subsequent remeasurement and reanalysis of the data from some AMS facilities, the round-robin data indicate that (36)Cl/Cl data from two individual AMS laboratories can differ by up to 17%. Thus, the demand for further work on harmonising the (36)Cl-system on a worldwide scale and enlarging the improvement of measurements is obvious.

Anthropogenic iodine-129 in the Arctic Ocean and Nordic Seas: numerical modeling and prognoses.

A numerical model simulation has been used to predict extent and variability in the anthropogenic (129)I pollution in the Arctic Ocean and Nordic Seas region over a period of 100 years. The source function of (129)I used in the model is represented by a well-known history of discharges from the Sellafield and La Hague nuclear reprocessing facilities. The simulations suggest a fast transport and large inventory of the anthropogenic (129)I in the Arctic and North Atlantic Oceans. In a fictitious case of abrupt stop of the discharges, a rapid decline of inventories is observed in all compartments except the North Atlantic Ocean, the deep Nordic Seas and the deep Arctic Ocean. Within 15 years after the stop of releases, the model prediction indicates that near-equilibrium conditions are reached in all compartments.

Retrospective search for evidence of the 1957 Windscale fire in NE Ireland using 129I and other long-lived nuclides.

The accident at Windscale in October 1957 resulted in the release to the atmosphere of a large quantity of radioactivity. The presented work is a retrospective search for evidence of contamination from the accident in the northeastern region of Ireland. A lake yielding a high-resolution sedimentary record was identified near the northeast coast of Ireland. This site was used to reconstruct the history of radionuclide input to the region, based on the analysis of a set of cores extracted from the lake. A chronology for sediment accumulation within the lake was established using radioisotopic dating techniques (including 270Pb). High-resolution gamma and alpha spectrometry techniques were used to quantify concentrations of 137Cs, 239,240Pu and 241Am, all of which were released during the accident. The primary radioactive component of the release was 131I (T1/2 = 8 days), but this short-lived isotope has long since decayed. However, 129I (T1/2 = 1.57 x 10(7) years) was also released during the accident, and in a known ratio to 131I. Recent advances in accelerator mass spectrometry now make it feasible to measure 129I at ultra-trace level and thereby retrospectively reconstruct 131I deposition. Clearly resolved concentration profiles for 137Cs, 239,240Pu and 241Am in the lake cores reflect known historical fallout trends. The data suggest that any contamination from the Windscale fire that might have reached this catchment has been overwritten by input from the testing of nuclear weapons in the atmosphere. A time-series for 129I in lake sediment shows that concentrations in recent sediments are approximately 10 times greater than concentrations recorded in strata corresponding to the period of maximum fallout of other radionuclides from atmospheric testing of nuclear weapons (1964). These recent increases in 129I are attributed to increased emissions from the nuclear industry. The study yields no evidence of any enhancement in radioisotope concentrations, over and above global fallout, in strata dated to 1957, and we conclude that contamination from the Windscale fire had negligible impact on the northeastern region of Ireland.

Anthropogenic iodine-129 in seawater along a transect from the Norwegian coastal current to the North Pole.

Variation in the concentrations of iodine-129 (129I, T1/2=15.7 Myr), a low-level radioactive component of nuclear fuel waste, is documented in surface waters and depth profiles collected during 2001 along a transect from the Norwegian Coastal Current to the North Pole. The surface waters near the Norwegian coast are found to have 20 times higher 129I concentration than the surface waters of the Arctic Ocean. The depth profiles of 129I taken in the Arctic Ocean reveal a sharp decline in the concentration to a depth of about 300-500 m followed by a weaker gradient extending down to the bottom. A twofold increase in the 129I concentration is observed in the upper 1000 m since 1996. Based on known estimates of marine transient time from the release sources (the nuclear reprocessing facilities at La Hague, France, and Sellafield, UK), a doubling in the 129I inventory of the top 1000 m of the Arctic Ocean is expected to occur between the years 2001 and 2006. As 129I of polar mixed layer and Atlantic layer of the Arctic Ocean is ventilated by the East Greenland Current into the Nordic Seas and North Atlantic Ocean, further dispersal and increase of the isotope concentration in these regions will be encountered in the near future.