Level and origin of iodine-129 in the Baltic Sea

Environmental samples, such as seawater, seaweed, lake water, lake sediment and grass collected from the Baltic Sea area were analyzed for 129I and 127I by radiochemical neutron activation analysis. In 2000, the concentration of 129I in the seawater from Borholm and M?en in the Baltic Sea has reached 6.0 x 10(-13) and 16 x 10(-13) g/l, respectively, these are more than two orders of magnitude higher than the global fallout level. The highest value of 270 x 10(-13) g/l being found in the seawater from the Kattegat. By comparison of the level of 129I in the lake water and precipitation in this region, it is estimated that more than 95% of 129I in the Baltic Sea originates from reprocessing emissions, especially from the French nuclear fuel reprocessing plant at La Hague. More than 30% of 129I in the south Baltic and 93% in the Kattegat directly originates from the marine discharges of the European reprocessing plants.     

Iodine-129 in the environment of a nuclear fuel reprocessing plant: I. 127I and 127I contents of soils,food crops and animal products

Concentrations of ¹²⁹I and ¹²⁷I in soils, food crops and animal products collected in the environment of the small Karlsruhe nuclear fuel reprocessing plant (WAK) were determined by neutron activation analysis. ¹²⁹I levels in all samples were found to be elevated by several orders of magnitude above current average biospheric background values. Resultant thyroid doses from consumption of food produced at locations in the vicinity of the Karlsruhe reprocessing plant are, however, small relative to the natural background dose.     

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.     

Iodine-129 in the environment of a nuclear fuel reprocessing plant: II. Iodine-129 and iodine-127 contents of soils,forage plants and deer thyroids

Concentrations of ¹²⁹I and ¹²⁷I in soils, forage plants and deer thyroids collected in the environment of the small Karlsruhe nuclear fuel reprocessing plant (WAK) were determined by neutron activation analysis. Levels of ¹²⁹I in all samples were found to be elevated by several orders of magnitude above current average biospheric background values. In particular, deer thyroids were found to have very high ¹²⁹I levels and corresponding high ¹²⁹I/¹²⁷I ratios.Using all the analytical data for ¹²⁹I and ¹²⁷I concentrations in plants it seems probable that there is a correlation between the ¹²⁹I and the natural ¹²⁷I concentrations in plants.     

127I and 129I/127I isotopic ratio in marine alga Fucus virsoides from the North Adriatic Sea

The only stable iodine isotope is 127I and the natural 129I/127I ratio in the biosphere has increased from 10(-15)-10(-14) to 10(-10)-10(-9), mainly due to emissions from nuclear fuel reprocessing plants. In Europe they are located at La Hague (France) and Sellafield (England), where the ratio of 129I/127I is up to 10(-4). The marine environment, i.e. the oceans, is the major source of iodine with average concentrations of around 60 mirogL(-1) iodine in seawater. Brown algae accumulate iodine at high levels of up to 1.0% of dry weight, and therefore they are an ideal bioindicator for studying the levels of 127I and 129I in the marine environment. A radiochemical neutron activation analysis (RNAA) method, developed at our laboratory, was used for 129I determination in the brown alga Fucus virsoides (Donati) J. Agardh, and the same technique of RNAA was used for total 127I determination. The samples were collected along the coast of the Gulf of Trieste and the West coast of Istria in the North Adriatic Sea in the period from 2005 to 2006. Values of the 129I/127I ratio up to 10(-9) were found, which is in agreement with the present average global distribution of 129I. The levels of stable iodine found were in the range from 235 to 506 microg g(-1) and the levels of 129I from 1.7 to 7.3 x 10(-3)Bq kg(-1) (2.6-10.9 x 10(-7) microg g(-1)), on a dry matter basis.     

Studies with natural and anthropogenic iodine isotopes: iodine distribution and cycling in the global environment

Iodine is an important trace element in geological and biological processes. We summarize here recent results and new data of experiments and observations carried out to improve the understanding of concentration levels and behavior of natural and anthropogenic iodine nuclides in the global environment. The distribution of stable iodine in the Earth's crust was estimated using concentration data in a suite of representative samples and the influence of subduction on the marine iodine cycle was investigated using (129)I systematics on iodine-rich brines from Japan. The importance of microorganisms for the natural iodine cycle is shown in recent studies of iodine sorption on soil and of iodine volatilization from terrestrial and marine environments. Levels of anthropogenic (129)I were measured in samples collected around a spent fuel reprocessing plant in Japan.     

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.     

129I/127I, 129I/137Cs and 129I/99Tc in the Norwegian coastal current from 1980 to 1998

Discharges of the nuclides 129I, 137Cs and 99Tc from the nuclear reprocessing facilities at Sellafield (UK) and La Hague (France) are very useful as oceanic tracers. On the basis of 129I/127I, 137Cs and 99Tc measurements in archived seaweeds, the ratios of 129I/127I, 129I/137Cs and 129I/99Tc have been estimated in seawater at two locations (Utsira and Kiberg) in the Norwegian Coastal Current from 1980 to 1998. These ratios, which vary up to two orders of magnitude over this period, are potentially very interesting for determining "transit times" in the Arctic and North Atlantic oceans. While the long-term trends in these ratios are quite clear, measurements in monthly and bimonthly samples show considerable structure. Further studies are required to determine the exact origin of this structure, which may be a limiting factor in the time resolution that can be obtained with these parameters.     

Areal distribution of 129I in west cumbrian solis

¹²⁹I has been released during operations at the BNFL nuclear fuel reprocessing plant at Sellafield in west Cumbria over the past thirty years with about 95% being discharged into the sea and 5% into the atmosphere. Soil samples have been taken within a 40 km radius of Sellafield to determine the extent to which the ¹²⁹I is deposited in the immediate vicinity of the plant. The ¹²⁹I content has been determined by a sensitive neutron activation technique and levels in soil were found to be elevated above global levels in all samples. The areal distribution of ¹²⁹I was consistent with direct deposition following release to the atmosphere from Sellafield and the relationship between ¹²⁹I activity and the distance from Sellafield was of a form predicted by atmospheric dispersion models. The absence of any observable return of ¹²⁹I from the sea has implications for assessments of dose.     

Carbon-14 transfer into rice plants from a continuous atmospheric source: observations and model predictions

Carbon-14 ((14)C) is one of the most important radionuclides from the perspective of dose estimation due to the nuclear fuel cycle. Ten years of monitoring data on (14)C in airborne emissions, in atmospheric CO(2) and in rice grain collected around the Tokai reprocessing plant (TRP) showed an insignificant radiological effect of the TRP-derived (14)C on the public, but suggested a minor contribution of the TRP-derived (14)C to atmospheric (14)C concentrations, and an influence on (14)C concentrations in rice grain at harvest. This paper also summarizes a modelling exercise (the so-called rice scenario of the IAEA's EMRAS program) in which (14)C concentrations in air and rice predicted with various models using information on (14)C discharge rates, meteorological conditions and so on were compared with observed concentrations. The modelling results showed that simple Gaussian plume models with different assumptions predict monthly averaged (14)C concentrations in air well, even for near-field receptors, and also that specific activity and dynamic models were equally good for the prediction of inter-annual changes in (14)C concentrations in rice grain. The scenario, however, offered little opportunity for comparing the predictive capabilities of these two types of models because the scenario involved a near-chronic release to the atmosphere. A scenario based on an episodic release and short-term, time-dependent observations is needed to establish the overall confidence in the predictions of environmental (14)C models.     

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.     

Environmental radioactivity around tokai-works after the reactor accident at chernobyl

Following the reactor accident at Chernobyl, environmental samples of air, rain water and agricultural and marine products were collected and analyzed by gamma- and alpha-spectrometry. The highest concentrations of ¹³¹I in the environmental samples were as follows: 1·0×⁻¹ Bqm⁻³ (aerosol-associated in air); 3·0×10⁻¹ Bqm⁻³ (gaseous in air); 2·1×10² bq kg⁻¹ (plants); 1·4×10¹ Bq litre⁻¹ (milk). Other nuclides such as ⁹⁵Zr, ⁹⁵Nb, ¹⁰³Ru, ¹⁰⁶Ru, ¹²⁵Sb, ^129mTe, ¹³²I/¹³²Te, ¹³⁴Cs, ¹³⁷Cs, ¹⁴⁰Ba/¹⁴⁰La, ¹⁴¹Ce and ¹⁴⁴Ce were also observed in various environmental samples. ^110mAg was only detected in marine products such as cephalopoda and shellfish, ^239,240Pu and ²⁴¹Am originating from the accident were not identified.Based on the monitoring results at one dairy farm, we have derived an equation to model the transport of ¹³¹I from pasture grass to milk. This equation was then applied to the data from two other farms around Tokai-Works and the calculated ¹³¹I activities in milk were compared with those measured. The equation shows good predictive capabilities for quantification of the peak concentrations of ¹³¹I in milk but underestimates longer-term activities.     

Pollutant emission rates from indoor combustion appliances and sidestream cigarette smoke

Particulate and gaseous emissions from indoor combustion appliances and smoking can elevate the indoor concentrations of various pollutants. Indoor pollutant concentrations resulting from operating one of several combustion appliances, or from sidestream tobacco smoke, were measured in a 27-m³ environmental chamber under varying ventilation rates. The combustion appliances investigated were gas-fired cooking stoves, unvented kerosene-fired space heaters, and unvented natural-gas-fired space heaters. Results showed elevated levels of carbon dioxide, carbon monoxide, nitric oxide, nitrogen dioxide, formaldehyde, and suspended particles from one or more of the pollutant sources investigated. Our findings suggest that, of the sources examined in this study, nitrogen dioxide from combustion appliances and particles from sidestream cigarette smoke are the most serious contaminants of indoor air, if we use existing standards and guidelines as the criteria. An emission rate model was used to quantify the strengths of the pollutant sources, which are reported in terms of the mass of pollutant emitted per energy unit of fuel consumed (in the case of gas and kerosene appliances) and per mass of tobacco combusted (in the case of smoking).     

129I in the environment of the La Hague nuclear fuel reprocessing plant--from sea to land

In recent years, particular attention was paid to the long-lived radionuclides discharged with authorized low-level radioactive liquid and gaseous effluents by the nuclear spent fuel reprocessing plants of La Hague and Sellafield. The knowledge of (129)I (half-life=15.7 x 10(6) a) distribution in the environment is required to assess the radiological impact to the environment and population living in the area under the direct influence of La Hague NRP discharges. Measurement difficulties of (129)I in environmental matrices, where it is usually present at trace level, limited data published on (129)I activity levels in the European and more particularly in the French territory. Studies conducted to qualify a new alternative measurement method, direct gamma-X spectrometry with experimental self-absorption correction, led to test samples collected in the La Hague marine and terrestrial environment : seaweeds, lichens, grass, bovine thyroids, etc. All these results, often already published separately for analytical purposes and treated for intercomparison exercises, are presented here together in a radioecological manner. The levels of (129)I activity and (129)I/(127)I ratios in these samples show the spatial and temporal influence of the La Hague NRP in its local near-field environment as well as at the regional scale along the French Channel coast.     

Health risk assessment of emissions of dioxins and furans from a municipal waste incinerator: comparison with other emission sources

The aim of this study was to calculate the incremental lifetime-risk to dioxins and furans (PCDD/Fs) for the population living in the surroundings of a municipal solid waste incinerator (MSWI), as well as to establish the potential reduction on human health risks as a consequence of the adaptation to the EU legislation on pollutant emissions from the MSWI stack. Analytical and modelled results were obtained. PCDD/F concentrations in environmental media were determined by means of a simple-compartment-multimedia model (air-soil-vegetation model). Predicted and measured PCDD/F concentrations in soils and vegetation were compared, and the effects of MSWI emissions in the environmental media were determined. Human health risks due to PCDD/F emissions from the MSWI were also estimated based on I-TEQ measured and modelled in various environmental media. Cancer risks due to PCDD/F emissions of the plant were 1.07E-07 and 3.08E-09, before and after installation of the clean air system, respectively. On the other hand, cancer risks due to other PCDD/F emission sources in the area were 5.54E-06 and 1.86E-06. Total PCDD/F cancer risks (including those from diet) for the population living in the vicinity of the MSWI were 1.3E-04 and 4.25E-05, respectively (67.6% of reduction). Hazard ratio for total PCDD/F exposure (including diet) decreased during the last 5 years from 1.16 to 0.38. The above data show that other emission sources of PCDD/Fs also have a notable environmental impact on the area under direct influence of the MSWI.     

The transfer of radionuclides from saltmarsh vegetation to sheep tissues and milk

Radionuclides released into the Irish Sea by the Sellafield reprocessing plant are deposited onto tide-washed pastures along the western coast of the United Kingdom. Many of these pastures are grazed by sheep or cattle. This paper describes a controlled feeding study, in which saltmarsh vegetation harvested from close to the Sellafield plant, was fed to lambs and adult female sheep for a period of 8 weeks. Activity concentrations of (60)Co, (95)Nb, (106)Ru, (134)Cs, (137)Cs, (238)Pu, (239,240)Pu and (241)Am were determined in edible tissues and transfer parameters estimated. The activity concentrations of some of the radionuclides will not have been in equilibrium with those in the diet. Nevertheless, the study was reasonably realistic in terms of agricultural management as the period of the study was similar to that for which lambs graze on the saltmarshes. A field study to determine the activity concentrations of (137)Cs and (239,240)Pu in the milk of ewes grazing a saltmarsh close to Sellafield is also described.     

Sources of anthropogenic radionuclides in the environment: a review

Studies of radionuclides in the environment have entered a new era with the renaissance of nuclear energy and associated fuel reprocessing, geological disposal of high-level nuclear wastes, and concerns about national security with respect to nuclear non-proliferation. This work presents an overview on sources of anthropogenic radionuclides in the environment, as well as a brief discussion of salient geochemical behavior of important radionuclides. We first discuss the following major anthropogenic sources and current developments that have lead, or could potentially contribute, to the radionuclide contamination of the environment: (1) nuclear weapons program; (2) nuclear weapons testing; (3) nuclear power plants; (4) uranium mining and milling; (5) commercial fuel reprocessing; (6) geological repository of high-level nuclear wastes that include radionuclides might be released in the future, and (7) nuclear accidents. Then, we briefly summarize the inventory of radionuclides ⁹⁹Tc and ¹²⁹I, as well as geochemical behavior for radionuclides ⁹⁹Tc, ¹²⁹I, and ²³⁷Np, because of their complex geochemical behavior, long half-lives, and presumably high mobility in the environment; biogeochemical cycling and environment risk assessment must take into account speciation of these redox-sensitive radionuclides.     

A new compilation of the atmospheric 85krypton inventories from 1945 to 2000 and its evaluation in a global transport model

This paper gives the yearly (85)Kr emissions of all known reprocessing facilities, which are the main sources of (85)Kr in the atmosphere since 1945, for the years 1945 until 2000. According to this inventory 10,600 PBq (Peta=10(15)) of (85)Kr have been globally emitted from the year 1945 until the end of 2000. The global atmospheric inventory at the end of the year 2000 amounts to 4800 PBq. These emissions have been incorporated into the ECHAM4 atmospheric general circulation model as point sources. Monthly mean model results are compared with measurements made at different locations and times. The influence of each source on the measured concentrations at various locations is studied. The calculated concentrations are found to give reasonably good agreement with the observations, indicating that the emission inventory is realistic. Although, at all northern hemispheric observation sites the model tends to slightly overestimate the concentrations. A possible reason for this overestimation can be found in model features (coarse resolution in time and space). The most prominent discrepancy that is consistently repeated at all northern hemispheric stations occurs in the early 1990s. This could most likely be related to an overestimate of sources. Possibly, the Russian emissions declined earlier than assumed in the current database. Another discrepancy between observations and simulations indicating an incompleteness of the release data is found at some southern hemispheric sites. The variability of their observations could only be explained by regional sources. However, several spikes occur after 1992 when no reprocessing facility is known to be in operation in the southern hemisphere. Production of isotopes for radiopharmaceuticals like technetium-99m from highly enriched uranium is the most likely explanation.     

Improvements in modeling sagebrush concentrations of radioiodine released from the Hanford site

The Hanford Environmental Dose Reconstruction Project estimated the radiation dose to individuals from historical emissions of radioactive materials from the Hanford Site in Washington State. Project validation studies using predicted activity concentrations of 131I on sagebrush (Artemisia tridentata) showed a systematic underestimation against historical data during cold weather months, indicating a need for sagebrush model improvement. A deposition model for semi-volatile organic materials presented by Komp and McLachlen (Environ. Sci. Tech. 31 (1997) 886-890) is adapted here for gaseous iodine onto sagebrush. The deposition model includes a temperature-dependent term based on an integrated van't Hoff equation. Calibration data for the model are obtained from a release of 131I in 1963. Modeling results for releases in 1946 show a good match between historical data and predicted results using the new model. The new model shows improvement over interception-fraction type models, but requires plant-type-specific calibration data.     

Fukushima fallout in Northwest German environmental media

Traces of short- and long-lived fallout isotopes (¹³¹I, ¹³⁴Cs and ¹³⁷Cs) were found in environmental samples collected in Northwest Germany (rain water, river sediment, soil, grass and cow milk) from March to May 2011, following the radioactivity releases after the nuclear accident in Fukushima, Japan. The measured concentrations are consistent with reported concentrations in air, amount of rainfall and expected values applying simple radioecological models. The [¹³⁴Cs]/[¹³⁷Cs] ratio reported for air (about 1) allows for discrimination between “recent” and “old” ¹³⁷Cs. Expected ¹³⁶Cs values fell below the detection limits of the instrumentation, despite large sample masses and long counting times.