Relative influence of 129I sources in a sediment core from the Kattegat area

Reconstructing atmospheric 129I deposition over 170 years with the varved sediment in the Sihailongwan Maar Lake, northeast China

Long-term deposition of atmospheric radioactive iodine-129 (129I) is important for assessing the impact of human nuclear activities (HNAs), but still not well understood in East Asia. In this study, we quantitatively reconstructed the deposition history of airborne 129I using varved sediment from Sihailongwan Maar Lake (SHLW) in northeast China. Our results revealed significant increases in 129I concentrations and 129I/127I atomic ratios since the 1950s, indicating the influence of HNAs on the environment and marking the onset of the Anthropocene. The variation of 129I in the investigated site can be primarily attributed to the global fallout of ANWT as well as nuclear fuel reprocessing in Europe, Russia and the USA. Notably, neither the Chernobyl nor the Fukushima nuclear accidents have had any discernable impact on the SHLW Lake. Over the past 170 years (1846-2021), the reconstructed fluxes indicate a rapid increase in 129I deposition from the early 1950s until the 1970s followed by dramatic changes thereafter. The measured 129I fluxes range between (1.26-349) × 109 atoms m-2 yr-1 in the SHLW Lake, which are consistent with similar latitude zones across East Asia, but differ significantly from those observed in high-elevation glaciers within the Northern Hemisphere due to prevailing atmospheric circulation patterns. The total 129I inventory was calculated to be 11.9 × 1012 atoms m-2, with natural and anthropogenic 129I accounting for 2.86 % and 97.1 %, respectively, suggesting an overwhelming artificial contribution. The reconstructed fluxes and inventory of atmospheric 129I deposition quantitatively distinguish the natural and artificial contributions, and provide a novel insight into the historical environmental impact of HNAs in East Asia and the characteristics of the Anthropocene.

Sediments as sinks and sources of marine radionuclides: Implications for their use as ocean tracers

A Lagrangian transport model for the North Atlantic has been applied to simulate the historical releases of 137Cs, 129I and 236U from the European nuclear fuel reprocessing plants. Advection by currents, mixing and decay are included, as radionuclide interactions between water, sediments and suspended matter. The model was validated comparing predictions with measured radionuclide concentrations in water and sediments in several areas. 129I and 236U signals entering the Arctic Ocean have been compared with the input terms: the 236U signal is distorted, but the 129I signal preserves its shape. In the first moments after the releases, the sediments act as sinks for 236U, but not significantly for 129I and ultimately they become sources of 236U to the open sea. This results in a weaker correlation between input and output signals for 236U than for 129I. The same effects as for 236U have been found for 137Cs signal into the Arctic.

The behaviour of 236U in the North Atlantic Ocean assessed from numerical modelling: A new evaluation of the input function into the Arctic

A numerical model, previously validated with other radionuclides, was applied to simulate the dispersion of ²³⁶U released from European nuclear fuel reprocessing plants in the North Atlantic and Shelf Seas using a published reconstruction of Sellafield and La Hague releases. Model results are in better agreement with observations if the lowest estimation of such releases are used. This implies that approximately 40kg of ²³⁶U has been discharged from Sellafield. It was found that adsorption of ²³⁶U on bed sediments of the shallow European Shelf Seas plays an essential role in its dispersion patterns. This contrasts strongly with the more conservative behaviour of ¹²⁹I in the same area. This has two important implications in the use of ²³⁶U as oceanographic tracer; i) special care must be taken in coastal areas, as sediments might act as sinks and sources of ²³⁶U; ii) the annual input function of ²³⁶U into the Arctic is not directly controlled by the annual discharges from Sellafield and La Hague, since sediments from the Irish, Celtic and North Sea modulate and smooth the signal. Only 52% of the total releases enter into the Arctic Ocean.

Recent evolution of 129I levels in the Nordic Seas and the North Atlantic Ocean

Most of the anthropogenic radionuclide ¹²⁹I released to the marine environment from the nuclear fuel reprocessing plants (NFRP) at Sellafield (England) and La Hague (France) is transported to the Arctic Ocean via the North Atlantic Current and the Norwegian Coastal Current. ¹²⁹I concentrations in seawater provides a powerful and well-established radiotracer technique to provide information about the mechanisms which govern water mass transport in the Nordic Seas and the Arctic Ocean and is gaining importance when coupled with other tracers (e.g. CFC, ²³⁶U). In this work, ¹²⁹I concentrations in surface and depth profiles from the Nordic Seas and the North Atlantic (NA) Ocean collected from four different cruises between 2011 and 2012 are presented. This work allowed us to i) update information on ¹²⁹I concentrations in these areas, required for the accurate use of ¹²⁹I as a tracer of water masses; and ii) investigate the formation of deep water currents in the eastern part of the Nordic Seas, by the analysis of ¹²⁹I concentrations and temperature-salinity (T-S) diagrams from locations within the Greenland Sea Gyre. In the Nordic Seas, ¹²⁹I concentrations in seawater are of the order of 10⁹ at·kg^-1, one or two orders of magnitude higher than those measured at the NA Ocean, not so importantly affected by the releases from the NFRP. ¹²⁹I concentrations of the order of 10⁸atoms·kg^-1 at the Ellet Line and the PAP suggest a direct contribution from the NFRP in the NA Ocean. An increase in the concentrations in the Nordic Seas between 2002 and 2012 has been detected, which agrees with the temporal evolution of the ¹²⁹I liquid discharges from the NFRPs in years prior to this. Finally, ¹²⁹I profile concentrations, ¹²⁹I inventories and T-S diagrams suggest that deep water formation occurred in the easternmost area of the Nordic Seas during 2012.

A 60-year record of 129I in Taal Lake sediments (Philippines): Influence of human nuclear activities at low latitude regions

The influence of human nuclear activities on environmental radioactivity is not well known at low latitude regions that are distant from nuclear test sites and nuclear facilities. A sediment core collected from Taal Lake in the central Philippines was analyzed for ¹²⁹I and ¹²⁷I to investigate this influence in a low-latitude terrestrial system. A baseline of ¹²⁹I/¹²⁷I atomic ratios was established at (2.04-5.14) × 10^-12 in the pre-nuclear era in this region. Controlled by the northeasterly equatorial trade winds, increased ¹²⁹I/¹²⁷I ratios of (20.1-69.3) × 10^-12 suggest that atmospheric nuclear weapons tests at the Pacific Proving Grounds in the central Pacific Ocean was the major source of ¹²⁹I in the sediment during 1956-1962. The ¹²⁹I/¹²⁷I ratios, up to 157.5 × 10^-12 after 1964, indicate a strong influence by European nuclear fuel reprocessing plants. The East Asian Winter Monsoon is found to be the dominant driving force in the atmospheric dispersion of radioactive iodine (¹²⁹I) from the European nuclear fuel reprocessing plants to Southeast Asia, which is also important for dispersion of other airborne pollutants from the middle-high to low latitude regions. A significant ¹²⁹I/¹²⁷I peak at 42.8 cm in the Taal Lake core appears to be the signal of the Chernobyl accident in 1986. In addition, volcanic activities are reflected in the iodine isotope profiles in the sediment core, suggesting the potential of using iodine isotopes as an indicator of volcanic eruptions.

Concentrations of iodine isotopes ((129)I and (127)I) and their isotopic ratios in aerosol samples from Northern Germany

New data about (129)I, (127)I concentrations and their isotopic ratios in aerosol samples from the trace survey station of the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig, Northern Germany, are presented and discussed in this paper. The investigated samples were collected on a weekly basis during the years 2011 to 2013. Iodine was extracted from aerosol filters using a strong basic solution and was separated from the matrix elements with chloroform and was analysed by accelerator mass spectrometry (AMS) for (129)I and by inductively coupled plasma mass spectrometry (ICP-MS) for (127)I. The concentrations of (127)I and (129)I in aerosol filters ranged from 0.31 to 3.71 ng m(-3) and from 0.06 to 0.75 fg m(-3), respectively. The results of (129)I/(127)I isotopic ratios were in the order 10(-8) to 10(-7). The (129)I originated directly from gaseous emissions and indirectly from liquid emissions (via sea spray) from the reprocessing plants in Sellafield and La Hague. In comparison with the results of (131)I after the Fukushima accident, no contribution of (129)I from this accident was detectable in Central Europe due to the high background originating from the (129)I releases of the European reprocessing plants. (129)I atmospheric activity concentrations were compared with those of an anthropogenic radionuclide ((85)Kr). We did not find any correlation between (129)I and (85)Kr, both having nuclear reprocessing plant as the main source.

Pre- and post-accident (129)I and (137)Cs levels, and (129)I/(137)Cs ratios in soil near the Fukushima Dai-ichi Nuclear Power Plant, Japan

To evaluate the deposition density and extent of subsurface infiltration of (129)I and (137)Cs in the restricted area that was highly contaminated by the accident of Fukushima Dai-ichi Nuclear Power Plant, cumulative inventories of (129)I and (137)Cs, concentrations of (129)I and (137)Cs, and (129)I/(137)Cs ratio in 30-cm-long soil columns were compared with pre-accident levels from the same area. The cores were collected before and after the accident from locations of S-1 (4 km west of FDNPP) and S-2 (8 km west of FDNPP). Deposition densities of (129)I and (137)Cs in the soil following the accident were 0.90-2.33 Bq m(-2) and 0.80-4.04 MBq m(-2), respectively, which were 14-39 and 320-510 times larger than the pre-accident levels of (129)I (59.3-63.3 mBq m(-2)) and (137)Cs (2.51-7.88 kBq m(-2)), respectively. Approximately 90% of accident-derived (129)I and (137)Cs deposited in the 30-cm soil cores was concentrated in the surface layer from 0 to 44-95 kg m(-2) of mass depth (0-4.3-6.2 cm depth) and from 0 to 16-25 kg m(-2) of mass depth (0-1.0-3.1 cm depth), respectively. The relaxation mass depths (h0) of 10.8-11.2 kg m(-2) for (129)I estimated in the previous study were larger than those of 8.1-10.6 kg m(-2) for (137)Cs at both sites, owing to the larger infiltration depth of radioiodine mainly by the gravitational water penetration in the surface soil in our study sites. Approximately 7-9% of the accident-derived (129)I was present in the lower layer from 44 to 100 kg m(-2) (4.3-8.6 cm depth) at S-1, and from 95 to 160 kg m(-2) (6.2-10.2 cm depth) at S-2. Approximately 1% of (137)Cs seems to infiltrate deeper than (129)I in the lower layer at each site in contrast to the surface layer.

Distribution and source of (129)I, (239)(,240)Pu, (137)Cs in the environment of Lithuania

Fifty five soil samples collected in the Lithuania teritory in 2011 and 2012 were analyzed for (129)I, (137)Cs and Pu isotopes in order to investigate the level and distribution of artificial radioactivity in Lithuania. The activity and atomic ratio of (238)Pu/((239,24)0)Pu, (129)I/(127)I and (131)I/(137)Cs were used to identify the origin of these radionuclides. The (238)Pu/(239+240)Pu and (240)Pu/(239)Pu ratios in the soil samples analyzed varied in the range of 0.02-0.18 and 0.18-0.24, respectively, suggesting the global fallout as the major source of Pu in Lithuania. The values of 10(-9) to 10(-6) for (129)I/(127)I atomic ratio revealed that the source of (129)I in Lithuania is global fallout in most cases though several sampling sites shows a possible impact of reprocessing releases. Estimated (129)I/(131)I ratio in soil samples from the southern part of Lithuania shows negligible input of the Chernobyl fallout. No correlation of the (137)Cs and Pu isotopes with (129)I was observed, indicating their different sources terms. Results demonstrate uneven distribution of these radionuclides in the Lithuanian territory and several sources of contamination i.e. Chernobyl accident, reprocessing releases and global fallout.

The behaviour of ¹²⁹I released from nuclear fuel reprocessing factories in the North Atlantic Ocean and transport to the Arctic assessed from numerical modelling

A quantitative evaluation of the fate of (129)I, released from the European reprocessing plants of Sellafield (UK) and La Hague (France), has been made by means of a Lagrangian dispersion model. Transport of radionuclides to the Arctic Ocean has been determined. Thus, 5.1 and 16.6 TBq of (129)I have been introduced in the Arctic from Sellafield and La Hague respectively from 1966 to 2012. These figures represent, respectively, 48% and 55% of the cumulative discharge to that time. Inventories in the North Atlantic, including shelf seas, are 4.4 and 13.8 TBq coming from Sellafield and La Hague respectively. These figures are significantly different from previous estimations based on field data. The distribution of these inventories among several shelf seas and regions has been evaluated as well. Mean ages of tracers have been finally obtained, making use of the age-averaging hypothesis. It has been found that mean ages for Sellafield releases are about 3.5 year larger than for La Hague releases.

New insights on the role of sea ice in intercepting atmospheric pollutants using (129)I

Measurements of (129)I carried out on sea ice samples collected in the central Arctic Ocean in 2007 revealed relatively high levels in the range of 100-1400×10(7) at L(-1) that are comparable to levels measured in the surface mixed layer of the ocean at the same time. The (129)I/(127)I ratio in sea ice is much greater than that in the underlying water, indicating that the (129)I inventory in sea ice cannot be supported by direct uptake from seawater or by iodine volatilization from proximal (nearby) oceanic regimes. Instead, it is proposed that most of the (129)I inventory in the sea ice is derived from direct atmospheric transport from European nuclear fuel reprocessing plants at Sellafield and Cap La Hague. This hypothesis is supported by back trajectory simulations indicating that volume elements of air originating in the Sellafield/La Hague regions would have been present at arctic sampling stations coincident with sampling collection.

Influence of releases of (129)I and (137)Cs from European reprocessing facilities in Fucus vesiculosus and seawater from the Kattegat and Skagerrak areas

(129)I is a very long-lived radionuclide (T1/2=15.7×10(6) years) that is present in the environment because of natural and anthropogenic sources. Compared to the pre-nuclear era, large amounts of (129)I have been released to the marine environment, especially as liquid and gaseous discharges from two European reprocessing facilities located at Sellafield (England) and La Hague (France). The marine environment, i.e., the oceans, is the major source of iodine. Brown seaweed accumulates iodine at high levels up to 1.0% of dry weigh, and therefore they are ideal bioindicators for studying levels of (129)I. In this work, (129)I concentrations have been determined in seaweed Fucus vesiculosus and seawater collected in the Kattegat and Skagerrak areas in July 2007. The resulting data were evaluated in terms of (129)I concentrations and (129)I/(137)Cs ratios. (129)I concentrations were found to be in the order of (44-575)×10(9) atoms g(-1) in seaweed and (5.4-51)×10(9) atoms g(-1) in seawater, with an enhancement in the Skagerrak area in comparison to the Kattegat area. Iodine-129 concentrations in both seaweed and seawater were used to determine the concentration factor of iodine in brown seaweed F. vesiculosus. The high levels of (129)I and (129)I/(137)Cs ratios in the Skagerrak area and their gradually decreasing trend to the Kattegat indicates that the most important contribution to the (129)I inventory in those areas comes from Sellafield and La Hague reprocessing plants.

Atmospheric fallout of (129)I in Japan before the Fukushima accident: regional and global contributions (1963-2005)

Atmospheric (129)I deposition was studied in different locations of Japan (Akita, Tsukuba, Tokyo, and Ishigaki Island) with samples collected between 1963 and 2005 in order to understand the distribution and sources of this nuclide and provide a reference deposition level prior to the Fukushima accident. Over this time period, the deposition pattern of (129)I in Tsukuba and Tokyo (on the Pacific side) differed from that of Akita (on the Japan Sea side). The primary source of deposition in Tsukuba and Tokyo is related to the (129)I discharge from domestic reprocessing in Tokai-mura. In contrast, the time-series pattern of deposition in Akita seems to have been influenced by (129)I discharges from reprocessing facilities in Europe and the transport of this radionuclide by westerly winds to coastlines of the Japan Sea. The (129)I deposition in Ishigaki (one of the southernmost islands in Japan) is influenced primarily by oceanic air masses (easterly winds), and deposition was 1 order of magnitude lower than that observed in Tsukuba and Tokyo. Cumulative (129)I deposition in Tokyo before the Fukushima accident was estimated at 13 mBq/m(2). The results of this study on deposition contribute to understanding the deposition levels of (129)I prior to the accident.

Pre- and post-Chernobyl accident levels of 129I and 137Cs in the Southern Baltic Sea by brown seaweed Fucus vesiculosus

(129)I is a very long-lived radionuclide (T(1/2) = 15.7 × 10(6) years) that is present in the environment both because of natural and anthropogenic sources. In this work (129)I concentration and (129)I/(127)I ratio have been determined in seaweed Fucus vesiculosus collected in the Southern Baltic Sea during 1982 and 1986 (post-Chernobyl accident). The resulting data were evaluated in terms of (129)I concentrations, (129)I/(127)I and (129)I/(137)Cs ratios. (129)I concentrations were found to be in the order of (0.82-5.89) × 10(9) atoms g(-1) in 1982 and (1.33-38.83) × 10(9) atoms g(-1) in 1986. The (129)I/(127)I ratios ranged from (22.7-87.8) × 10(-10) for seaweed collected in 1982 and from (26.1-305.5) × 10(-10) for seaweed collected in 1986. Also a linear relationship was established for (127)I concentrations in seawater and salinity in this area, enabling the estimation of concentration factors for (127)I in F. vesiculosus. The high levels of (129)I and (129)I/(127)I in the Kattegat and their gradually decreasing trend to the Baltic Sea indicates that the most important contribution to the (129)I inventory in the Baltic Sea area comes from Sellafield and La Hague reprocessing plants. With respect to Chernobyl accident, (129)I concentrations in samples collected in 1986 were not much higher than those expected in less contaminated samples from 1982. This supports the view that the contribution of the Chernobyl accident to (129)I in the Baltic region was not significant.

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.

Partition of iodine (¹²⁹I and ¹²⁷I) isotopes in soils and marine sediments

Natural organic matter, such as humic and fulvic acids and humin, plays a key role in determining the fate and mobility of radioiodine in soil and sediments. The radioisotope ¹²⁹I is continuously produced and released from nuclear fuel reprocessing plants, and as a biophilic element, its environmental mobility is strongly linked to organic matter. Due to its long half-life (15.7 million years), ¹²⁹I builds up in the environment and can be traced since the beginning of the nuclear era in reservoirs such as soils and marine sediments. Nevertheless, partition of the isotope between the different types of organic matter in soil and sediment is rarely explored. Here we present a sequential extraction of ¹²⁹I and ¹²⁷I chemical forms encountered in a Danish soil, a soil reference material (IAEA-375), an anoxic marine sediment from Southern Norway and an oxic sediment from the Barents Sea. The different forms of iodine are related to water soluble, exchangeable, carbonates, oxides as well as iodine bound to humic acid, fulvic acid and to humin and minerals. This is the first study to identify ¹²⁹I in humic and fulvic acid and humin. The results show that 30-56% of the total ¹²⁷I and 42-60% of the total ¹²⁹I are associated with organic matter in soil and sediment samples. At a soil/sediment pH below 5.0-5.5, (¹²⁷I and ¹²⁹I in the organic fraction associate primarily with the humic acid while at soil/sediment pH > 6 ¹²⁹I was mostly found to be bound to fulvic acid. Anoxic conditions seem to increase the mobility and availability of iodine compared to oxic, while subaerial conditions (soils) reduces the availability of water soluble fraction compared to subaqueous (marine) conditions.

Tracing anthropogenic nuclear activity with (129)I in lake sediment

This study reports the first data of (129)I fallout in Scandinavia, covering the last 80 years. The investigation is based on sediment sections from a lake in central Sweden. In addition to analysis of (129)I, a combination of several radionuclides ((210)Pb, (137)Cs and (14)C) was used to establish an accurate chronology of the sediment profile. The concentration of (129)I exhibits an increasing trend ( approximately 10(7) to approximately 10(9)atoms/g) during the last 40 years, suggesting a significant atmospheric input from the nuclear reprocessing facilities in Sellafield (UK) and La Hague (France). A peak corresponding to fallout from the Chernobyl accident (1986) is clearly distinguishable, whereas the impact of fallout from the nuclear weapons' tests since the early 1950s is not distinguished.

Trends in the spatial and temporal distribution of 129I and 99Tc in coastal waters surrounding Ireland using Fucus vesiculosus as a bio-indicator

Spatial and temporal trends in (129)I and (99)Tc concentrations around the Irish coastline have been evaluated using Fucus vesiculosus as a bio-indicator. (129)I concentrations in a recent set of seawater samples have also been recorded and reveal an identical spatial pattern. Concentrations of (129)I in Fucus from the northeast coast of Ireland proved to be at least two orders of magnitude higher than concentrations in Fucus from the west coast. The (129)I content of Fucus increased significantly between 1985 and 2003, in line with increases in discharges of (129)I from the Sellafield nuclear reprocessing plant. Similar trends were observed in the case of (99)Tc. (129)I/(99)Tc ratios in Irish seawater were deduced from the Fucus data, and compared to ratios in discharges from Sellafield and from the French reprocessing plant at Cap de la Hague. Levels of (129)I and (99)Tc in Fucus from the west coast were found to be enhanced with respect to levels in seaweeds from other regions in the Northern Hemisphere unaffected by discharges from nuclear installations such as those referred to.

Distribution and sources of (129)I in rivers of the Baltic region

The concentration of (129)I was measured in 54 river waters discharging into the Baltic Sea from Sweden, Finland, Estonia, Latvia, Lithuania, Poland and Germany. Sample collection was performed during a well-bracketed time interval (June-July 1999), thus allowing comparison of the rivers over a wide latitude range without the effect of long temporal spread. Although there is no direct input of anthropogenic (129)I in the watersheds, the concentration of the isotope is about two to three orders of magnitude higher than the expected pre-nuclear era natural values in the rivers of Finland and northern Sweden, and in the rivers of southern Sweden, Lithuania, Estonia, Latvia, Poland and Germany; the (129)I concentration may reach five orders of magnitude higher. Furthermore, there are significant correlations between the (129)I concentration and latitude and/or distance from the North Sea and between (129)I and Cl. These findings suggest seawater as a main source of (129)I to the rivers through atmospheric transport. Of the many chemical parameters investigated, the pH may account for some of the variability in (129)I concentrations of the rivers. The contribution from nuclear weapon tests and the Chernobyl accident to the riverine (129)I is insignificant compared to the releases from the nuclear fuel reprocessing facilities. The total flux of (129)I by rivers to the Baltic Sea and related basins represents minor amounts of the isotope pool in these marine waters. External radioactivity hazards from (129)I are considered to be negligible in the Baltic region. However, as the main (129)I intake to the human body is likely through water, due to the large amount of daily water consumption, more concern should be given to internal radioactivity hazard that may be associated with the isotope's localized elevated concentration in the human organs.

Determination of 129I/127I in aerosol samples in Seville (Spain)

In this work we present results of the (129)I/(127)I ratio in aerosols of Seville, Southwest of Spain (37.4 degrees N,6 degrees W). A radiochemical method is applied to extract the iodine from the aerosols and prepare samples to be measured by accelerator mass spectrometry (AMS) at the ETH facility in Zürich. We have found the possibility of monitoring the (129)I/(127)I isotopic ratio on a two-days basis with sensitivities in the order of 10(4)-10(5) atoms (129)I/m(3), and values of 10(-8)-10(-9) for the isotopic ratio.

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.