The use of mosses as indicators of airborne radionuclides near a major nuclear installation

Samples of naturally growing moss (mainly Pseudoscleropodium purum and Hypnum cupressiforme ) were used to investigate the distribution of photon-emitting radionuclides, notably 129I , 137Cs, 144Ce and 241Am, at distances up to 12 km from the nuclear fuel reprocessing plant at Sellafield in West Cumbria . The relative activities of the naturally occurring radionuclides, 7Be and 210Pb, in moss and air indicated that the removal half-time of these radionuclides on moss is very long (best estimate of half-time, corrected for radioactive decay, was 240 days) and that the mosses are very efficient collectors of airborne particulates (product of deposition velocity and interception factor was 2.4 X 10(-2) ms-1). Hence the activities of artificially-produced radionuclides on the mosses present an effective record of local airborne radionuclide pollution integrated over a number of years. The activity of 210Pb in each sample was used to standardize the activities of artificial radionuclides in the samples. It was found that the activity ratio of 129I /210Pb, 137Cs/210Pb and 144Ce/210Pb declined with distance from Sellafield indicating that the major local source of these radionuclides has been material discharged to air from the site. The activity ratio of 241Am/210Pb declined with distance from the site and also with distance from the sea confirming that the resuspension of material originally discharged to sea is an important local source of 241Am.     

Mesoscale variability of vertical profiles of environmental radionuclides (40K, 226Ra, 210Pb and 137Cs) in temperate forest soils in Germany

Vertical profiles of environmental radionuclides (40K, 226Ra, 210Pb and 137Cs) were investigated in several temperate forest soils in Germany to estimate heterogeneity of the soil horizon of interest. Absolute values of the activity concentrations of these nuclides varied to a large extent depending on the properties of individual forests as well as local geology. Several trends were generally observed independent of the location: (1) Activity concentrations of 40K increased with increasing soil density reflecting that most potassium is contained in mineral components of the soil. The variations in the 40K activity with depth may relate to biological activities in subsoil, such as root uptake of the nutrients. (2) Profiles of 226Ra with depth could be an indicator for evaluating soil heterogeneity within a horizon of interest. They are also useful to estimate anthropogenic 210Pb (210Pbexc) derived from the atmosphere via dry fallout or wet deposition. In several forests, there appeared surface enrichment of 210Pb down to a depth of approximately 10 cm, in which the 210Pb would have come from the atmosphere by combustion of fossil fuels. (3) Depth profiles of 137Cs were roughly divided into three types in which (a) the activity concentration decreased exponentially with soil depth, (b) small amounts of 137Cs existed only in the upper-most layer of the soil (0-5 cm) and (c) 137Cs disappeared at certain depths and appeared again at deeper portions of the soil. Consequences of bioturbation could be deduced from variability in vertical profiles of the environmental radionuclides. It is probable that a site showing an exponential decrease of the 137Cs activity with depth and also having a surface enrichment of 210Pb is not significantly influenced by bioturbation.     

Distribution of artificial radionuclides in deep sediments of the Mediterranean Sea

Artificial radionuclides enter the Mediterranean Sea mainly through atmospheric deposition following nuclear weapons tests and the Chernobyl accident, but also through the river discharge of nuclear facility effluents. Previous studies of artificial radionuclides impact of the Mediterranean Sea have focussed on shallow, coastal sediments. However, deep sea sediments have the potential to store and accumulate pollutants, including artificial radionuclides. Deep sea marine sediment cores were collected from Mediterranean Sea abyssal plains (depth > 2000 m) and analysed for ^239,240Pu and ¹³⁷Cs to elucidate the concentrations, inventories and sources of these radionuclides in the deepest areas of the Mediterranean. The activity — depth profiles of ²¹⁰Pb, together with ¹⁴C dating, indicate that sediment mixing redistributes the artificial radionuclides within the first 2.5 cm of the sedimentary column. The excess ²¹⁰Pb inventory was used to normalize ^239,240Pu and ¹³⁷Cs inventories for variable sediment fluxes. The ^239,240Pu/²¹⁰Pb_xs ratio was uniform across the entire sea, with a mean value of 1.24 × 10^− 3, indicating homogeneous fallout of ^239,240Pu. The ¹³⁷Cs/²¹⁰Pb_xs ratio showed differences between the eastern (0.049) and western basins (0.030), clearly significant impact of deep sea sediments from the Chernobyl accident. The inventory ratios of ^239,240Pu/¹³⁷Cs were 0.041 and 0.025 in the western and eastern basins respectively, greater than the fallout ratio, 0.021, showing more efficient scavenging of ^239,240Pu in the water column and major sedimentation of ¹³⁷Cs in the eastern basin. Although areas with water depths of > 2000 m constitute around 40% of the entire Mediterranean basin, the sediments in these regions only contained 2.7% of the ^239,240Pu and 0.95% of the ¹³⁷Cs deposited across the Sea in 2000. These data show that the accumulation of artificial radionuclides in deep Mediterranean environments is much lower than predicted by other studies from the analysis of continental shelf sediments.     

The use of 210Pb and 137Cs in the study of sediment pollution in the Lagoon of Venice

The activity of 137Cs per unit area in sediments of the central part of the Lagoon of Venice was determined with the aim of identifying boundaries of homogeneous depositional zones. The 210Pb dating technique was used to date vertical profiles of cores from the same area. A comparison of the total amounts of 137Cs and non-supported 210Pb present in each core and the atmospheric input allows us to identify different depositional areas inside the basin and to outline the possible drainage effect of industrial solid wastes used in past reclaiming operations.     

Recent sedimentation rates and 210Pb fluxes in Georgian Bay and Lake Huron

The ²¹⁰Pb and ¹³⁷Cs profiles are determined at five locations in Georgian Bay and Lake Huron. Compaction-corrected recent sedimentation rates are derived for all locations using the ²¹⁰Pb data. The rates range from 0.13 ± 0.03 mm y^?1 (2.2 ± 0.4 mg cm^?2 y^?1) to 0.78 ± 0.06 mm y^?1 (14.5 ± 1.1 mg cm^?2 y^?1). Except for one location, the rates show marginal to good agreement with those estimated from palynological measurements at four of the five study locations. ¹³⁷Cs profiles at study locations suggest that the top portions of the sediment cores were satisfactorily retrieved during coring and sectioning operations. However, considerable downward migration of ¹³Cs is noted at three locations. The fluxes of excess ²¹⁰Pb vary between 0.06 and 0.27 pCi cm^?2 y^?1. The average depositional flux is found to be considerably lower than the flux of atmospheric ²¹⁰Pb. It is postulated that the deposition of atmospheric ²¹⁰Pb in Lake Huron and Georgian Bay sediments is limited by the supply of scavenging particulates.     

The particulate Be/Pbxs and Th/Pbxs activity ratios as tracers for tidal-to-seasonal particle dynamics in the Gironde estuary (France): Implications for the budget of particle-associated contaminants

The short-lived natural radionuclides ⁷Be (T_1/2 = 53 days), ²³⁴Th_xs (T_1/2 = 24.1 days) and ²¹⁰Pb_xs (T_1/2 = 22.3 years), i.e. ²³⁴Th and ²¹⁰Pb in excesses of that supported within particles by the decay of their parent isotopes, were analysed in suspended particulate matter (SPM) to study the particle dynamics in the Gironde fluvial estuarine system (France), strongly impacted by heavy metal pollution. From surveys of this land-ocean interface in 2006 and 2007, we established a times series of these radioisotopes and of their activity ratios (⁷Be/²¹⁰Pb_xs and ²³⁴Th/²¹⁰Pb_xs ARs) in particles sampled under different hydrological conditions.The particulate ⁷Be/²¹⁰Pb_xs AR varies along the fluvial estuarine system mainly due to variations in ⁷Be activities, controlled by riverine, oceanic and atmospheric inputs and by resuspension of old ⁷Be-deficient sediments. These processes vary with river discharge, tidal cycle and season. Therefore, seasonal particle transport processes can be described using variations of the SPM ⁷Be/²¹⁰Pb_xs ARs.During high river discharge, the SPM ⁷Be/²¹⁰Pb_x ARs decrease from river to the ocean. The turbidity maximum zone (TMZ) is dispersed and the particles, and the associated contaminants, are rapidly transported from river to coastal waters, without significant retention within the TMZ. During low river discharge, the TMZ intrudes into the fluvial estuary, and the lowest ⁷Be/²¹⁰Pb_x ARs are observed there due to resuspension of ⁷Be-deficient sediments. Away from the TMZ, from the middle to lower estuary, SPM ⁷Be/²¹⁰Pb_x ARs increase, indicating that the particles have been recently tagged with ⁷Be. We explain this trend as being caused by marine input of dissolved radionuclides, as traced by SPM ²³⁴Th/²¹⁰Pb_xs ARs, followed by scavenging in the estuary. This result indicates that particle transport models based on ⁷Be and trace-metal budgets must consider oceanic dissolved inputs as an additional source of ⁷Be and, possibly, of contaminants to estuaries.     

Radiometric dating of sediment cores from a hydrothermal vent zone off Milos Island in the Aegean Sea

Sediment cores from a hydrothermal vent zone off Milos Island in the Aegean Sea were dated using the 210Pb method. The average unsupported 210Pb inventory in the cores was calculated to be 3256 Bq m(-2). The corresponding mean annual 210Pb flux of 105 Bq m(-2) year(-1) is comparable to estimates of the atmospheric flux given in the literature. 210Pb fluxes calculated from the unsupported 210Pb inventories in cores are also comparable with the 210Pb vertical fluxes determined from settling particles off the coast of Milos Island. The highest unsupported 210Pb concentrations (89 Bq kg(-1)) were measured in the sediments nearest to the hydrothermal vent area suggesting that the sedimentation rate is lowest at this site. Direct gamma measurements of 210Pb were used to date three sediment cores that are located at different distances from the vent zone: one is in the immediate vicinity of the vent; and others are outside the zone. Sedimentation rates for these cores, calculated using the CRS and CIC models, ranged from 0.088+/-0.008 cm year(-1) to 0.14+/-0.01 cm year(-1). Where both models were applicable, the results given by the two methods were in good agreement. 137Cs concentrations in all three cores generally declined with depth but showed no clear signal of either the period of maximum fallout from weapons testing or the Chernobyl accident. 210Po activities were also measured and the maximum 210Po concentration was in the sediment surface layer (166 Bq kg(-1)).     

Radiocaesium and natural gamma emitters in mushrooms collected in Spain

Mushrooms can accumulate heavy metals in general, including radionuclides found in the nature. However, little attention has been paid to the radioactive content of mushrooms collected in Spain and the dose for the population due to their ingestion. To address this, we analysed the contents of 137Cs, 40K, 226Ra and 7Be present in different species of mushrooms, according to their genus and nutritional mechanism. We observed that mycorrhizal mushrooms accumulate 137Cs more than saprophytes, and vice versa for 7Be. 40K and 226Ra are accumulated to the same degree by the two groups of mushrooms. We estimated the dose due to ingestion of mushrooms in Spain to be 2 microSv/year, and the contribution of 40K and 226Ra to be generally greater than that of 137Cs. The contribution of 137Cs to the dose was calculated by taking into account the results of an experiment carried out under the controlled laboratory conditions, which showed that approximately 98% of 134Cs was associated with the readily digestible fraction of the mushrooms.     

Distribution,cycling and mean residence time of 226Ra, 210Pb and 210Po in the Tagus estuary

Results for dissolved and particulate ²²⁶Ra, ²¹⁰Pb and ²¹⁰Po in the Tagus river, estuary and coastal sea system show different distribution and chemical behaviour patterns for these radionuclides in the three aquatic environments. ²²⁶Ra from riverborne particles dissolves in the estuary and contributes to increased concentrations of dissolved ²²⁶Ra in estuarine water. In the estuary, dissolved ²¹⁰Pb and ²¹⁰Po from river discharge and atmospheric deposition are scavenged by suspended matter, which in turn becomes enriched in these nuclides in comparison with riverborne particles. As a result of these processes, the estuarine water flowing into the coastal sea contains enhanced concentrations of dissolved ²²⁶Ra, but is depleted in dissolved ²¹⁰Pb and ²¹⁰Po. Under average river flow conditions, mass balance calculations for dissolved ²¹⁰Po and ²¹⁰Pb in the estuary allowed their mean residence times to be estimated as 18 and 30 days, respectively. Due to the rapid sorption of these radionuclides on to settling particles, bottom sediments in the estuary represent a sink for ²¹⁰Pb and ²¹⁰Po from both natural sources and industrial waste releases. Results also suggest that partial re-dissolution of these radionuclides from bottom sediments and intertidal mudflats is likely to occur in the mid- and low-estuary zones. Nevertheless, box-model computations indicate that the discharge of ²¹⁰Pb and ²¹⁰Po into the coastal sea takes place mainly with the transport of sediment, whereas the discharge in the dissolved fraction can only account for one third of the activities entering the estuary in the soluble phase. Implications of these results to the cycling of radionuclides in phosphate waste releases into estuarine environments are discussed.     

Measurement of radioactivity levels of the Sirt gulf,Libya

The paper presents the results of measurements on air and soil samples collected for their natural and artificial radioactivity content. The radionuclides studied under this programme are ⁷Be and ¹³⁷Cs. Average activity concentrations in surface air of ⁷Be and ¹³⁷Cs were found to be 1920 and 2.1 μBq m^‐3, respectively. ¹³⁷Cs activity concentration in surface soil is found to be 450m Bq kg^‐1. Estimated effective doses to adult from inhaled ⁷Be and ¹³⁷Cs were found to be 1 and 0.13 nSvy^‐1, respectively.

The average outdoors absorbed dose rate in air, 1 m above the ground level was found to be (48 ± 4.0 nGy h^‐1), based on the analysis of thermoluminescence dosimeters data collected.     

Anthropogenic and natural radionuclides in caribou and muskoxen in the western Alaskan Arctic and marine fish in the Aleutian Islands in the first half of 2000s

A number of caribou and muskoxen samples from the western Alaskan Arctic and fish samples from the Aleutian Islands were collected between 1998 and 2006 and analyzed for anthropogenic (⁹⁰Sr and ¹³⁷Cs) and natural radionculides (⁴⁰ K, ²¹⁰Pb and ²²⁶Ra), as part of the radiological assessment for the regional subsistence hunting communities in the first half of 2000s. We examined the relationship between the activities of these nuclides with the size of the fish. In caribou samples, concentration of ⁹⁰Sr in muscle was below the detection limit of 0.14 Bq kg^− 1 and ¹³⁷Cs concentration in bones was below the detection limit of 0.15 Bq kg^− 1.¹³⁷Cs activity varied over an order of magnitude in caribou muscle samples with an average value of 2.5 Bq/kg wet wt. Average ¹³⁷Cs activity in muskoxen muscle was found to be 9.7 Bq/kg wet wt. However, there were a little variation (less than 60%) in ²¹⁰Pb, ⁴⁰ K, and ²²⁶Ra in both muscle and bone of both caribou and muskoxen. The activities of total ²¹⁰Pb in caribou and muskox bones were found to be 1-2 orders of magnitude higher than that of parent-supported ²¹⁰Pb indicating the potential for dating of bones of terrestrial mammals (time elapsed since the death of the animal) based on the excess ²¹⁰Pb method exists. In fish muscle samples, ¹³⁷Cs activity varied from below detection limit to 154 mBq/kg wet wt. and its content increased with the size of the fish due to its transfer through the food chain. Among the seven fish species investigated, ²¹⁰Pb activities varied almost an order of magnitude; however, ⁴⁰K and ²²⁶Ra activities varied less than a factor of two. Total annual effective dose due to ⁹⁰Sr and ¹³⁷Cs from the ingestion of those terrestrial and marine meats was estimated to be negligible (ca. 9 μSV/a) compared to the natural radionuclides present thus posing negligible radiological threat to humans.     

Multitracer study of anthropogenic contamination records in the Camargue, Southern France

Contaminants are supplied to the coastal zone by the atmosphere, rivers and point sources like wastewaters or industrial area. Wetlands retain many of these contaminants and can be used to reconstruct sources and magnitudes of contaminant inputs. Radionuclides ((137)Cs, (210)Pb, (239)Pu and (240)Pu) and stable lead isotope ((206)Pb, (207)Pb) profiles were investigated in two cores collected in wetlands of the Rh?ne River delta, south of France (Camargue), to estimate the recent sediment accumulation rates and reconstruct the deposition of pollutants during the last century. One site was affected by storm or flood deposition from the Rh?ne river and showed the influence of Marcoule reprocessing plant releases on the plutonium isotopic ratios. The other site appears suitable for the reconstruction, even if mixing is evidenced at the surface by the radionuclides profiles. Plutonium isotopic ratios are characteristic of global fallout and the (210)Pb inventory of 4240 Bq m(-2) is approximately 30% higher than atmospheric deposit estimation. The pollutant lead inventory is 139 microg cm(-2), slightly higher than previous estimation from direct fallout. This difference can be partly due to an over-collection at this site (due to canopy cover) but also to variations with time in the deposition.     

Spatial distribution of radionuclides in soil around a coal-fired power plant: 210Pb, 210Po, 226Ra, 232Th, 40K emitted with the fly ash and 137Cs from the worldwide weapon testing fallout

To determine the effect of airborne emissions of radionuclides from coal-fired power plants on the environment, the concentrations of the most important radionuclides were measured in soil samples from the local environments (0.4–5.2 km) as well as in fly ash. The spatial distribution of the radionuclides in the soil did not indicate any significantly increased concentrations in the area downwind of the plant compared to other areas; the ratios ²¹⁰Pb/²²⁶Ra and ²¹⁰Po/²²⁶Ra were within the range observed for unaffected soils. The emissions from the plant, though present, are obviously too small to significantly change the natural local distribution pattern of the radionuclides in the soil. A highly significant correlation between ⁴⁰K and ²³²Th was observed which was independent of the different types of soils found in this area. The concentration of ¹³⁷Cs in topsoil, which is the result of worldwide fallout from nuclear weapons testing, varied at some places even within a small distance (～ 2 km) by up to one order of magnitude. Furthermore, it was observed that the concentration of ¹³⁷Cs in soils from cropland was on average a factor of 2 less than in those from grassland. This variability has to be considered in planning monitoring programs around nuclear power plants, which may also release this radionuclide.     

Atmospheric deposition and migration of artificial radionuclides in Alpine soils (Val Piora, Switzerland) compared to the distribution of selected major and trace elements

Artificial radionuclides (¹³⁷Cs, ⁹⁰Sr, Pu, and ²⁴¹Am) are present in soils because of Nuclear Weapon Tests and accidents in nuclear facilities. Their distribution in soil depth varies according to soil characteristics, their own chemical properties, and their deposition history. For this project, we studied the atmospheric deposition of ¹³⁷Cs, ⁹⁰Sr, Pu, ²⁴¹Am, ²¹⁰Pb, and stable Pb. We compared the distribution of these elements in soil profiles from different soil types from an alpine Valley (Val Piora, Switzerland) with the distribution of selected major and trace elements in the same soils. Our goals were to explain the distribution of the radioisotopes as a function of soil parameters and to identify stable elements with analogous behaviors. We found that Pu and ²⁴¹Am are relatively immobile and accumulate in the topsoil. In all soils, ⁹⁰Sr is more mobile and shows some accumulations at depth into Fe-Al rich horizons. This behavior is also observed for Cu and Zn, indicating that these elements may be used as chemical analogues for the migration of ⁹⁰Sr into the soil.     

Monitoring of air radioactivity at the Jungfraujoch research station: test of a new high volume aerosol sampler

The Swiss Federal Office of Public Health (SFOPH) is responsible for the surveillance of environmental radioactivity in Switzerland and for the protection of the public from ionizing and non-ionizing radiation. In order to improve the Swiss radioactivity monitoring network, a new high volume air sampler (DIGITEL DHA-80) was tested in Fribourg and at the Jungfraujoch High Altitude Research Station at 3454 m. The filters are analyzed in the laboratory by a high purity coaxial germanium detector. In the test period natural radio nuclides and traces of 137Cs, due to the Chernobyl accident of April 1986, were measured and are in good agreement with values from Germany and Poland. Albeit, the main purpose of this radioactivity monitoring network is to detect rapidly any input of artificial radioactivity, it is also helpful to understand transport of natural radio nuclides in the atmosphere, as for example the cosmogenic 7Be and the long-lived radon daughter 210Pb. The DIGITEL sampler proved to be sufficiently reliable for aerosol radioactivity monitoring even in extreme meteorological conditions at Jungfraujoch. A detection limit for artificial 137Cs of 2 microBq/m3 is obtained.     

Distribution of 137Cs, 238Pu and 239+240 Pu in sediments of the southeastern Brazilian shelf-SW Atlantic margin

In this work levels of 137Cs, 238Pu and 239+240 Pu as well as activity ratios of anthrophogenic radionuclides in sediment samples from the southeastern Brazilian shelf are presented. Instrumental gamma spectrometry was used to determine 137Cs and alpha spectrometry to determine 238Pu and 239+240 Pu after a radiochemical procedure. The levels ranged from 0.30 to 1.79 Bq kg(-1) for 137Cs, from 15 to 150 mBq kg(-1) for 238Pu and, from 18 to 117 mBq kg(-1) for 239+240 Pu. There was a bathymetric differentiation in the radionuclides distribution. 137Cs values were generally higher in the samples collected at water depths of less than 100 m. On the other hand, plutonium isotopes exhibit higher values at greater depths. The mean ratio of 239+240 Pu/137Cs obtained was 0.112+/-0.072 which is in agreement with the value reported for the Atlantic from atmospheric fallout of nuclear explosions in the past. The 238Pu/230+240 Pu ratios varied widely (from 0.339 to 2.088) and showed the influence of the SNAP-9A accident in the 238Pu levels for this area. The main goal of this work was to present unpublished anthropogenic radionuclide levels and activity ratios related to the contamination of the southeastern Brazilian shelf.     

Background radioactivity in sediments near Los Alamos, New Mexico

River and reservoir sediments have been collected annually by Los Alamos National Laboratory since 1974 and 1979, respectively. These background samples are collected from five river stations and four reservoirs located throughout northern New Mexico and southern Colorado. Analyses include 3H, 90Sr, 137Cs, total U, 238Pu, 239,240Pu, 241Am, gross alpha, gross beta, and gross gamma radioactivity. Surprisingly, there are no federal or state regulatory standards in the USA that specify how to compute background radioactivity values on sediments. Hence, the sample median (or 0.50 quantile) is proposed for this background because it reflects central data tendency and is distribution-free. Estimates for the upper limit of background radioactivity on river and reservoir sediments are made for sampled analytes using the 0.95 quantile (two-tail). These analyses also show that seven of ten analytes from reservoir sediments are normally distributed, or are normally distributed after a logarithmic or square root transformation. However, only three of ten analytes from river sediments are similarly distributed. In addition, isotope ratios for 137Cs/238Pu, 137Cs/239,240Pu, and 239,240Pu/238Pu from reservoir sediments are independent of clay content, total organic carbon/specific surface area (TOC/SSA) and cation exchange capacity/specific surface area (CEC/SSA) ratios. These TOC/SSA and CEC/SSA ratios reflect sediment organic carbon and surface charge densities that are associated with radionuclide absorption, adsorption, and ion exchange reactions on clay mineral structures. These latter ratio values greatly exceed the availability of background radionuclides in the environment, and insure that measured background levels are a maximum. Since finer-grained reservoir sediments contain larger clay-sized fractions compared to coarser river sediments, they show higher background levels for most analytes. Furthermore, radioactivity values on reservoir sediments have remained relatively constant since the early 1980s. These results suggest that clay contents in terrestrial sediments are often more important at concentrating background radionuclides than many other environmental factors, including geology, climate and vegetation. Hence, reservoirs and floodplains represent ideal radionuclide sampling locations because fine-grained materials are more easily trapped here. Ultimately, most of these differences still reflect spatial and temporal variability originating from global atmospheric nuclear weapons testing and disintegration of nuclear-powered satellites upon atmospheric reentry.     

210Po and 210Pb cycling in a hydrothermal vent zone in the coastal Aegean sea.

To quantify the potential enhancement of naturally-occurring 210Po and 210Pb that may result from the high sulfur-reducing and sulfur-oxidizing regimes associated with hydrothermal vents, sinking particles from both inside and outside vent areas and benthic molluscs grazing on or living near bacterial mats in the vent zone were collected off Milos Island (Aegean Sea) and analyzed for their 210Po and 210Pb content. There was no significant difference in the range of 210Po specific activities measured in particulate material collected by sediment traps in a control area and in the vent area; the resultant 210Po levels were of the same order of magnitude as literature values reported for other Mediterranean coastal areas. 211Pb levels in sinking particles from the control site tended to be higher than those measured in the vent zone, as demonstrated by the lower 210Po/210Pb ratios observed in particles from the control site. Nevertheless, these 210Pb levels were also comparable with similar 210Pb data reported for the northwestern Mediterranean Sea. The 210Po and 210Pb vertical particulate fluxes were, on average, higher in the vent zone as a consequence of the higher particle flux. This observation indicates that vents can indirectly control the flux of these natural radionuclides by affecting the types and amount of particles produced in hydrothermal areas. The 210Po levels measured in a gastropod and a bivalve living on or near the microbial mat in the vent zone were higher than values reported for non-vent gastropods and bivalves from the NW Mediterranean Sea, an observation which suggests that an enhanced food chain transfer of 210Po may occur in the vicinity of vents off Milos Island. Nevertheless, the lack of a general enhancement of 210Po and 210Pb in the marine particulate samples collected indicates that any input of these radionuclides through venting activity may have a minimal effect in the surrounding environment.     

Gamma-emitting natural and anthropogenic radionuclides in the terrestrial environment of Kongsfjord,Svalbard

This paper presents results obtained from a radiometric survey, conducted by the Norwegian Radiation Protection Authority, into the levels of gamma-emitting radionuclides, both anthropogenic and natural, in the terrestrial environment of Kongsfjorden, which lies on the North-Western Coast of Spitsbergen in the Arctic archipelago of Svalbard (79 degrees N, 12 degrees E). Samples of terrestrial matrices were taken during field campaigns conducted between 2000 and 2002 and analysed for a range of gamma-emitting radionuclides. The objectives of this study included an assessment of the levels of gamma-emitting radionuclides in the terrestrial environment of the region, identification of processes and activities that influence the accumulation and redistribution of such nuclides within the region and elucidation of the behaviour of such radionuclides within a high arctic environment. Results indicate a quite homogenous spatial distribution of such radionuclides within the study area and highlight the relatively low levels of contamination by the anthropogenic radionuclide, 137Cs, on Svalbard. Average values and ranges of the radionuclides activities in surface soils (0-3 cm) were: 238U 42 Bq/kg (17-134), 226Ra 43 Bq/kg (12-137), 232Th 21 Bq/kg (4-52), 40K 283 Bq/kg (31-564), 137Cs 35 Bq/kg (1-146). Average levels of these nuclides in avian faecal materials were 238U 63 Bq/kg, 226Ra 54 Bq/kg, 232Th 19 Bq/kg, 40K 365 Bq/kg, 137Cs 78 Bq/kg. Enrichment of radionuclides is apparent in soils taken from locations close to bird colonies in the locale, maximum levels of the radionuclides being found in samples associated with such colonies. The results indicate that this is due to concentration of such radionuclides within the faecal material of the birds and subsequent enrichment of the nearby soils either via direct incorporation of the faeces into the soil or by leaching processes. The results indicate that this process may result in contamination of non-related species, such as Svalbard reindeer (Rangifer tarandus playrhynchus), via pathways other than the traditionally accepted route of atmospheric deposition-vegetation-reindeer.     

Plutonium and 137Cs in surface water of the South Pacific Ocean

The present plutonium and 137Cs concentrations in South Pacific Ocean surface waters were determined. The water samples were collected in the South Pacific mid-latitude region (32.5 degrees S) during the BEAGLE expedition conducted in 2003-04 by JAMSTEC. 239,240Pu concentrations in surface seawater of the South Pacific were in the range of 0.5 to 4.1 mBq m(-3), whereas 137Cs concentrations ranged from 0.07 to 1.7 Bq m(-3). The observed 239,240Pu and 137Cs concentrations in the South Pacific were almost of the same level as those in the North Pacific subtropical gyre. The surface 239,240Pu in the South Pacific subtropical gyre showed larger spatial variations than 137Cs, as it may be affected by physical and biogeochemical processes. The 239,240Pu/137Cs activity ratios, which reflect biogeochemical processes in seawater, were generally smaller than that observed in global fallout, except for the most eastern station. The 239,240Pu/137Cs ratios in the South Pacific tend to be higher than that in the North Pacific. The relationships between anthropogenic radionuclides and oceanographic parameters such as salinity and nutrients were examined. The 137Cs concentrations in the western South Pacific (the Tasman Sea) and the eastern South Pacific were negatively correlated with the phosphate concentration, whereas there is no correlation between the 137Cs and nutrients concentrations in the South Pacific subtropical gyre. The mutual relationships between anthropogenic radionuclides and oceanographic parameters are important for better understanding of transport processes of anthropogenic radionuclides and their fate in the South Pacific.