Search Results

You are looking at 1 - 10 of 11 items for

  • Author or Editor: G. Shaw x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract  

The influence of background electrolytes (KCl, NH4Cl, CTABr) in different concentrations on the sorption ability of radiocesium by measuring the distribution coefficient has been studied. Sorption isotherms of cesium for characterization of soil sorption ability were used. Sorption of cesium depends on its concentration and at least three different sorption sites are active in the sorption process. In the case of low cesium concentration, two very selective sites with high distribution coefficients are responsible for the sorption. With increasing cesium concentration in the aqueous phase, distribution coefficient is decreasing. Frayed edge sites of illite in soil and exchangeable potassium are probably responsible for nonlinear isotherms at low cesium concentrations. From sorption isotherms and determination of potassium by activation analysis, it was found that the capacity of very selective sites for different concentrations of background electrolyte was up to 7 mmol·kg–1.

Restricted access

Abstract  

Neutron activation analysis has been used to assay the trace elements Co, Fe, Sc, Rb and Zn in pollen and derived sporopollenins. The method is capable of high precision and avoids the necessity for sample ashing and the introduction of reagent contamination. Rubidium was completely removed during the chemical isolation of sporopollenins and the remaining elements which survived chemical treatment were found in reduced amounts. The ratio of Sc: Fe in pollen and in several derived sporopollenins was found to be approximately constant. Results are discussed with reference to the possibilities of anomalous chemical behaviour of the elements resulting from irradiation.

Restricted access

Abstract  

The movement of85Sr,137Cs,54Mn and60Co in the 50 cm soil profile was studied with and without the presence of plant roots (triticum aestivum) in order to investigate the influence of roots and depth contamination upon the migration of radionuclides. The water table was maintained manually at 3 cm from the bottom. The physiochemical characteristics (Eh Fe–2, NH 4 + , pH and moisture content) as well as the total and extractable radioactivity were investigated. In the discrete contamination, where the location of contamination varied within the soil profile (0–5, 25–30 or 45–50 cm from the top), the influence of location upon the movement of these radionuclides was also studied. It was found that the changes in the soil physicochemical characteristics influenced the mobility of the four radionuclides. The extractability of54Mn and60Co was significantly increased in the reducing region of the soil, whereas that of85Sr,137Cs was not. Plant roots excerted significant effects upon the soil characteristics, via, reducing the Eh pH and moisture content of the soil; increasing the extractability of both54Mn and60Co from the depth of 35 cm downwards. Radionuclide migration occurred via physicochemical and biological transport. The biological transport via plant roots was of particular importance for137Cs. Location of contamination had a significant influence upon the mobility of radionuclides. The migration of radionuclides was in the sequence of contamination in middle>bottom>top. The degree of the influence varied with radionuclides concemed. In the top layer contamination, the rank of the migration from the contamination layers, on the other hand54Mn,60Co and137Cs were more mobile and the movement was:85Sr 54Mn 60Co>137Cs. In the middle and bottom contamination layers, on the other hand,54Mn and60Co and137Cs were more mobile and the movement was85Sr 54Mn 60Co>137Cs. The results provide evidence conceming the soil-root interaction influencing the transfer efficiency of radionuclides from below the soil surface into the human food chain.

Restricted access

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.

Restricted access

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.

Restricted access

Abstract  

Following the accident at the nuclear reactor at Chernobyl, in the Soviet Union on April 26, 1986, we performed a variety of measurements to determine the level of the radioactive fallout on the western United States. We used gamma-spectroscopy to analyze air filters from the areas around Lawrence Livermore National Laboratory (LLNL), California, and Barrow and Fairbanks, Alaska. Milk from California and imported vegetables were also analyzed. The levels of the various fission products detected were far below the maximum permissable concentration levels.

Restricted access

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.

Restricted access

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.

Restricted access