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Abstract  

The paper presents a survey of the contamination level of the Danube river sediments along its course, between 849 km and 1162 km, during the period 1985–1988. Sampling was performed on several locations in the seasons with extreme hydrological conditions (spring, autumn).

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Summary  

Radioactivity of water and sediments from the Danube river in its course through Serbia during 2001-2003 years has been tested by alpha- and gamma-ray spectrometry. Except for cesium originating from Chernobyl, the radioactivity level of water and sediment coincide with the content of natural radionuclides in the environment of rivers basin. No increase in the radioactivity of sediments, due to slowing down of the water flow, was observed. The obtained results were analyzed in accordance with the model which considers only naturally occurring radionuclides originating in river sediment. The distribution coefficients for natural radionuclides are determined.

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Abstract  

The concentrations of137Cs were determined by in 11 sediment samples, collected along the Romanian sector of the Danube river and the Black Sea coast during 1994 γ-ray spectrometry. The concentrations of90Sr in the same sediment samples were determined by β-counting of the90Y oxalate, precipitated after strontium separation using a strontium extraction chromatography column. The concentration distributions of137Cs and90Sr are compared with the238Pu and239,240Pu concentration distributions in the same samples, reported in a previous paper. The accumulation potential of137Cs,90Sr and plutonium isotopes in the river and sea sediments analysed is discussed.

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Abstract  

The concentrations of90Sr,238Pu,239,240Pu and241Am were determined in 12 sediment samples, collected from the bed of the Romanian sector of the Danube river and the Black Sea coast during 1996–1997. The samples were dissolved using a microwave digestion technique which left the refractory part of the samples undissolved. Part of the samples were also dissolved totally by alkaline fusion. The results obtained after radiochemical separations and measurement of the radionuclides by the two dissolution methods were compared recommending the optimum method. The radioactive contamination of the investigated sector in 1996–1997 is compared with the results obtained for the same locations in 1994–1995 reported in previous papers.

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Abstract  

The concentrations of238Pu,239,240Pu and241Am were determined in eight sediment samples, collected from the bed of the Romanian sector of the Danube river and the Black Sea coast during 1994 and 1995. Fusion with potassium carbonate was used to achieve complete dissolution of the samples. Tracers,242Pu and243Am, were added and the separation of plutonium from americium, uranium and thorium was performed by anion exchange. Americium was separated from uranium in two steps, using a conventional anion exchange resin and an extraction chromatographic resin for transuranics. After electrodeposition on stainless steel discs the nuclides were counted with -spectrometry with -PIPS detectors. The total plutonium concentrations obtained by this method were compared with the acid leachable plutonium concentrations reported for the same samples in a previous paper.

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Abstract  

The concentrations of238Pu and239, 240Pu were determined in 12 sediment samples collected from the bed of the Romanian Danube river and Black Sea coast during June–September 1994. After the sample material has been properly prepared and242Pu tracer added, plutonium was separated from americium and curium by anion exchange. After electrodeposition on stainless steel discs the elements were counted with an -spectrometry system with silicon surface-barrier detectors. The239, 240Pu concentrations range between 150 and 800 mBq kg–1 dry, while the238Pu concentrations rise up to max 150 mBq kg–1 dry. Although the chemical yields are rather low (51%) we appreciate the results as valuable since they report for the first time the distribution of the plutonium contamination along the Danube river and the Black Sea coast-Romanian sector.

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Abstract  

The concentrations of210Po have been determined in 12 sediment samples collected from the bed of the Romanian Danube river and the Black Sea coast during June–September 1994. After the sample preparation and the addition of the208Po tracer, polonium was coprecipitated with manganese dioxide, the precipitate was dissolved in hydrochloric acid and the polonium isotopes deposited on silver planchettes were counted by -spectrometry. The resolution of the subsequent -spectra was typically 40 to 60 keV full-width-half-maximum with 450 mm2 silicon surface-barrier detectors at 30% counting efficiency. The procedure is quite fast, giving chemical yields between 60 and 80%. The210Po concentrations range between 5 and 73 Bq kg–1 dry, showing for the first time the polonium contamination distribution along the Romanian sector of the Danube river and the Black Sea coast.

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Abstract  

The concentrations of238U and232Th were determined by neutron activation analysis using epithermal irradiation in 12 sediment samples, collected along the Romanian sector of the Danube river and the Black Sea coast during 1994. The concentrations of226Ra were determined by the emanation method in the same sediment samples. The concentration ranges obtained were compared also with the210Po concentration range for the same sector, reported in a previous paper. The accumulation potential of -emitting radionuclides in the analysed sediments is discussed.

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Abstract  

The concentration distributions of U and Th nuclides in some sediment and algae samples from the Romanian sector of the Danube river and the Black Sea coast are presented. Data are obtained by neutron-induced fission activation analysis, epithermal instrumental neutron activation analysis and radiochemical separation using tracers followed by -spectrometry counting of stainless steel discs after electrodeposition. The analysing time, the working steps, the necessary equipment, the information and quality of the obtained results are discussed.

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Abstract  

The trend of variation of sediment radiocontamination, expressed as a function of space and time, and specific accumulation of particular radionuclides in some investigated localities, are discussed on the basis of experimental results of gamma spectrometric analyses of artificial radionuclide contents.

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