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At least 1,783 records · Page 99Linked to original sources
PubMed1989

Sources for Pu in near surface air.

This paper provides evidence that most of the Pu in the near surface air today is due to resuspension. Vertical and particle size distribution in near surface air over a period of three years were measured. The seasonal variations of Pu in air and the influence of meteorological parameters on these variations are shown. Samples were taken before the Chernobyl accident in an area where only Pu fallout from the atmospheric nuclear tests of the early sixties occurs. The comparison of the behavior of Pu with other trace elements, which were also measured, showed similar behavior of Pu and elements like Ca, Ti and Fe in near surface air. This confirms that most Pu is resuspended because the main source for these elements in air is the soil surface. Resuspension factors and resuspension rate are estimated for all measured elements. A resuspension factor of 0.8 X 10(-8) m-1 and a resuspension rate of 0.09 X 10(-9) s-1 is calculated for Pu.

Air Pollutants↗
PubMed2002

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 Møen 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.

Baltic States↗
PubMed1996

Challenges in developing estimates of exposure rate near the Nevada Test Site.

As one of several dose reconstruction projects, the Off-site Radiation Exposure Review Project needed to develop models that reflect processes and lifestyles of the past and obtain accurate and adequate historical data to drive the models. One of the critical pieces, ultimately used to estimate the potential dose to people in the area surrounding the Nevada Test Site, was the development of exposure rate estimates used as input to the external and internal dose models. The historical data available for making these estimates were collected in manners and for purposes not necessarily consistent with the needs of this task. The Town Data Base is the culmination of the effort to develop those estimates for the Project's Phase I region (or for locations near the Nevada Test Site that were primarily covered by ground monitoring at the time of the nuclear tests). It includes estimates of discernible exposure rate at 353 populated locations in Arizona, California, Nevada, and Utah and for 74 nuclear tests at the Nevada Test Site. Each dose reconstruction effort has similarities with, and variations from, others. This paper describes some of the challenges encountered in creating the Town Data Base and the approaches used to address them. These challenges included collecting historical data, incorporating net exposure rate values of zero into the estimates, defining a discernible fallout level, handling the lack of measurements at some locations and creating dispersion estimates. The approaches were developed to create "best" estimates and to use actual data (as opposed to assumed values) as the primary source where such data were available. A summary of the spatial distribution of these estimates and a comparison of relative levels of fallout by location are also included.

Environmental Exposure↗
PubMed1999

240Pu/239Pu isotopic ratios and 239 + 240Pu total measurements in surface and deep waters around Mururoa and Fangataufa atolls compared with Rangiroa atoll (French Polynesia).

The average values of 240Pu/239Pu mass isotopic ratios of plutonium deposited in Mururoa and Fangataufa atoll sediments by French atmospheric nuclear tests range from 3.5 to 5%. In order to assess the near field and far field influence of those deposits in the open ocean, two water profiles were measured for 239 + 240Pu and 240Pu/239Pu using, for the first time, an Inductively Coupled Plasma Mass Spectrometer which was developed to achieve femtogram detection limits. One site was located at the limit of the French territorial waters, which is 22 km distant from Mururoa. The second site was located close to Rangiroa atoll, at a distance of approximately 1200-km from French nuclear test sites. The sample volumes were approximately 500 litres and plutonium was purified prior to mass spectrometry and alpha spectrometry measurements. In Rangiroa, the 239 + 240Pu profile is comparable with those already determined in world open oceans but the maximum detected activity, 9 mBq/m3 at 500-600 m is a lot lower than those measured in the northern hemisphere. 240Pu/239Pu ratios were measured between 500 and 1000 m and were not statistically different from the typical 0.18 +/- 0.01 ratio which characterises the global fallout. Consequently, any influence of plutonium from the tests in Mururoa and Fangataufa is not apparent at Rangiroa. The vertical distribution of 239 + 240Pu near Mururoa shows similar changes with depth but with a slight increase in concentration. 240Pu/239Pu mass ratios vary with depth, from 7 to 10% in the upper 500 m and in the deep waters (below 1000 m) to 15-16% between 600 and 1000 m. A contribution from plutonium deposited in the sediments at Mururoa and Fangataufa is observed at the limit of territorial waters, especially in surface and deep waters.

Half-Life↗
PubMed2006

International intercomparison of retrospective luminescence dosimetry method: sampling and distribution of the brick samples from Dolon' village, Kazakhstan.

There are still many differences in dose estimates depending on the applied methods of retrospective dosimetry in the areas, which were affected by nuclear tests at the Semipalatinsk nuclear test site (SNTS). In order to provide more correct estimation of radiation doses to population in proximity to the SNTS an International Intercomparison of Retrospective Luminescence Dosimetry (RLD) method had been proposed. It was suggested there be a comparison of the dose estimates for the brick samples from the buildings in the settlement, suffered following nuclear tests at the SNTS. With this purpose, during the September-October 2002 field mission, the team of specialists from Kazakhstan and Japan had collected four whole bricks for RLD International Intercomparison. Three buildings were selected as sampling locations in Dolon' village (Kazakhstan). The slices from these bricks were distributed between six laboratories in Finland, Germany, Japan, Russia, UK and USA for independent estimations by the RLD method of the accumulated dose of external irradiation. The descriptions of sampling, locations, data on geographical coordinates, dates of building construction, mode of cutting of samples for distribution, labeling, condition of transportation, order of the distribution of samples and information concerning 137Cs and 239+240Pu soil contamination density in the village and near sampling locations are presented in the paper.

Air Pollution, Indoor↗
PubMed1997

Plutonium in fish, algae, and sediments in the Barents, Petshora and Kara Seas.

This work contributed to a joint research programme between the Finnish Centre for Radiation and Nuclear Safety and the Murmansk Marine Biological Institute in the Arctic. Radioanalyses for plutonium isotopes were performed on more than 50 sediment samples, 12 algae samples and 19 fish samples. Plutonium concentrations in algae and fish samples, including fish meat, bone and liver, were low or in many cases below detection limits. Some differences in plutonium concentrations of sediments were found between different sampling areas. However, the concentrations were low. The Pu isotopic ratios were similar to those found in environmental samples generally when Pu is derived from global fallout or discharges from reprocessing plants. No local enhancement of plutonium contamination was found in the marine areas studied. However, the sampling locations represent only areas of free access; prohibited military areas of North-west Russia with potential pollution sources were not included.

Animals↗
PubMed2001

Migration of fallout-radionuclides in the soil: effect of non-uniformity of the sorption properties on the activity-depth profiles.

Experimentally observed activity-depth profiles of fallout radionuclides in the soil frequently exhibit a comparatively fast moving tail in soil layers below the peak concentration (tailing). Monte Carlo calculations on the basis of the convection-dispersion model show that this phenomenon can be explained by assuming that either the hydraulic properties of the soil (characterised by the diffusion/dispersion coefficient and pore water velocity) or the sorption properties of the soil (characterised by the distribution coefficient Kd), or both, exhibit a horizontal variability according to a log-normal distribution. Modifications of the activity-depth profile due to a Kd value which decreases linearly with depth were examined by using a random walk approach, based also on the convection-dispersion model. In this case, however, a pronounced tailing effect of the activity-depth profile did not result. Interpretation and realistic modelling of an experimentally observed activity-depth profile which exhibits a tailing effect is thus not unambiguously possible without any additional information on the spatial variability of the hydraulic parameters and, independently, also for the sorption properties.

Absorption↗