The aim of this paper was to determine the extent of contamination by anthropogeneous radionuclides 137Cs and 90Sr in the bottom sediments from the Barents Sea based on the radioactive activity of the samples taken up in August 1991,
among others, from the area close to New Land Island and Francis Joseph Archipelago. The results are based on the phenomenon
of vertical migration, in the bottom sediments which is of significant importance from the natural environment point of view.
The determination of90Sr in large sample of seawater by its daughter product90Y by means of solvent extraction with bis-2-ethylhexyl-phosphoric acid (HDEHP) ini n-heptane leads to234Th contamination. Two methods are described by which the238U daughter product234Th is separated from the Y3+ samples, either by a cation exchanger procedure or by a co-recipitation with Zr3(PO4)4.
To clarify environmental effects of the Chemobyl radionuclides, long-lived Chernobyl radioactivity (239,240Pu,238Pu,241Pu and90Sr) in deposition samples in May 1986 was measured at 11 stations in Japan. Temporal variation of weekly deposition of90Sr differed from that of volatile radionuclides such as131I and137Cs, which may reflect the released process at Chernobyl. On the other hand, the geographical distributions of the monthly deposition of long-lived radionuclides were similar to those of volatile radionuclides, in which maximum deposits of90Sr and plutonium were observed in Akita, a northwestern Japan Sea coast site of Honshu Island. Higher241Pu deposition in most of the stations, as well as high238Pu/239,240Pu activity ratios were observed. The241Pu/238Pu activity ratios in deposition samples were nearly equal to that in the total release, which is clear evidence that Chernobyl-derived plutonium was transported to Japan in May 1986 together with volatile radionuclides although the contribution of Chernobyl Pu was about three orders of magnitude lower than137Cs.
The dispersion of radioactive substances in the environment following nuclear weapon tests in atmosphere since 1954 and accidents to nuclear plants, like that in Chernobyl in 1986, have allowed us to study the migration processes of some radionuclides in complex ecosystems such as lakes are. In the present paper the behavior of 137Cs and 90Sr in different compartments of the Monterosi Lake (central Italy) was assessed. The 137Cs concentration was measured in lake water as well as sediment, stream water, aquatic plant and fish samples. 90Sr concentration in water and sediments was also determined. A total inventory of 4206±76 Bq . m-2 and 958±79 Bq . m-2 (on 27/6/01) has been found for 137Cs and 90Sr, respectively. The experimental data presented here allow to calibrate theoretical models predicting the temporal trend of radionuclide concentration in similar ecosystems. Moreover, information on cesium and strontium migration processes can be extended to other pollutants having similar environmental behavior.
Authors:P. Froidevaux, K. Friedrich-Bénet, and J.-F. Valley
A method is presented for the determination of 90Sr in environmental water samples by direct milking of its daughter product 90Y. An anionic complex between yttrium and dipicolinic acid is formed in situ in the water sample at pH 3. The complex [Y(dipic)3]3– is then extracted by an anionic exchanger (AG 1x4).The procedure is very simple and can be almost completely automatized and processed overnight. Technician working time is less than two hours for 6 samples and results can be obtained in less than 48 hours. The procedure gives yttrium recoveries above 80% for a water sample of one liter volume and needs an yttrium carrier of 10 mg. Very good decontamination factors are obtained and 90Y half-life measured on water samples with 90Sr activities above the detection limit or spiked with 90Sr is closed to 64 hours, indicating a very pure 90Y source. With using a low background gas flow proportional counter, a detection limit of 5·10–3Bq·l–1 has been achieved for one liter of water. If a lower detection limit is required, the volume can be increased up to 5 liters without any decrease in the performance of the method.
Authors:Ž. Grahek, K. Košutić, and M. Rožmarić-Mačefat
reliability of an 90Sr determination method was tested using an Sr
extraction chromatographic resin for strontium isolation. The 90Sr-content
in samples of vegetables, soil and water (obtained from Environmental
Measurement Laboratory, USA) were determined and the results were controlled by
classical methods and by using an anion-exchanger and an alcohol solution of
nitric acid for the strontium isolation. These methods were previously tested
by determining 90Sr in IAEA 326 and 327 samples of soil. It is shown
that the isolation process with Sr resin is simpler and faster than the
classical and mixed solvent anion-exchange methods. The efficiency of isolation
on a Sr column depends on the resin quantity and separation conditions; and is
the highest with a Sr column, compared to the classical and anion-exchange
methods. Experimental data and theoretical models were used to calculate the
parameters that enable the estimation of optimum dimensions of the column for
isolation. A simple relation is proposed for the calculation of breakthrough
volume, which defines the sample and eluent volumes for an optimal strontium
A method is described incorporating the procedures used in the radiochemical assay of Pu, Am and radiostrontium in environmental samples into a single radioanalytical sequential scheme. Sequential schemes have been used for determining the transuranic nuclides (isotopes of Pu and Am) in various types of sample matrices, but do not normally incorporate90Sr within the same scheme. The method offers potential savings in analyst time and reagents for the analyses of these nuclides, and is particularly suitable for small analytical laboratories where manpower resources coupled with a limited working time (8-hour working day) are constraints, and where limited amounts of sample are submitted for the analyses of all 3 radionuclides.
A rapid and reliable method for determination of90Sr in soil and sediment has been developed. The method is based on lithium-borate fusion and extraction chromatography with
a Sr-resin. The samples can be dissolved and separated for Sr in approximately 5 hours of which the fusion and dissolution
requires 20 minutes. The method has been applied to four reference materials, two soils and two sediments, and the results
agree well with the recommended values. The mean recovery of Sr was 71%.
A simple solvent extraction method has been developed for the separation of90Y from90Sr. Crown ether dissolved in chloroform was used as a selective reagent and organic picrate anion was chosen as a counter ion. The effect of various factors on the extraction separation of strontium and yttrium in the system have been studied. The extraction equilibrium constant of strontium logKex=9.15 was obtained from the study of the distribution coefficient versus the crown ether concentration. The separation method was simple, resulted high purity (>99.9%) and quantitative yield, and took less than half an hour.
Authors:T. Hinton, M. Malek, C. Sherony, and S. Clark
The operationally defined bioavailable fraction from a commonly used sequential extraction (SE) procedure was compared to
biological availability represented by plant uptake of137Cs and90Sr. Experiments were conducted at two locations in the Ukraine and at several field locations on the Savannah River Site,
South Carolina. A significant regression existed between plant uptake and the ammonium acetate fraction (r2=0.65), however, ratios of predicted uptake from the SE procedure to observed plant uptake ranged from 0.03 to 5.2 Data suggest
that SE procedure was useful for qualitative interpretations of biological availability but lacked sufficient rigor to be
useful for quantitative predictions.