Nguyen Dinh Chau

Natural radioactivity in groundwater – a review

The issue of natural radioactivity in groundwater is reviewed, with emphasis on those radioisotopes which contribute in a significant way to the overall effective dose received by members of the public due to the intake of drinking water originating from groundwater systems. The term ‘natural radioactivity’ is used in this context to cover all radioactivity present in the environment, including man-made (anthropogenic) radioactivity. Comprehensive discussion of radiological aspects of the presence of natural radionuclides in groundwater, including an overview of current regulations dealing with radioactivity in drinking water, is provided. The presented data indicate that thorough assessments of the committed doses resulting from the presence of natural radioactivity in groundwater are needed, particularly when such water is envisaged for regular intake by infants. They should be based on a precise determination of radioactivity concentration levels of the whole suite of radionuclides, including characterisation of their temporal variability. Equally important is a realistic assessment of water intake values for specific age groups. Only such an evaluation may provide the basis for possible remedial actions.

Determination of radium isotopes in mine waters through alpha- and beta-activities measured by liquid scintillation spectrometry

This paper presents a method for the determination of radium isotopes in mineralised mine waters, based on the separation of alpha- and beta-intensities measured in the precipitate by a liquid scintillation spectrometer in two time intervals (1 day and 7 days) after radium precipitation. The count rates of α-particles give not only the concentration of alpha emitters (226Ra and224Ra), but also make possible to find the β-counting efficiency of the system and through that-to determine the concentration of the β-emitting radium isotope (228Ra) with higher accuracy. An improved chemical procedure was elaborated. By this method radium isotopes in different water samples were determined, in wide range of concentrations, from about 0.06 Bq/dm3 in potable water to more than 100 Bq/dm3 in some mine brines. As an example some analytical results are given. The detection limit, defined as three standard deviations, is-for both radium isotopes −0.03 Bq/dm3 (for intial volume of water sample equal to about 1 dm3 and for counting time of each measurement not longer than 1 hour).

Radium isotopes in the Polish Outer Carpathian mineral waters of various chemical composition

The paper presents the activity concentrations of radium isotopes ((226)Ra, (228)Ra) and chemical compositions of above 70 mineral water samples collected from several dozens of springs and boreholes localized in the Polish Outer Carpathians. The activity concentrations of both radium isotopes clearly increase with the increase of water TDS, but decrease when the SO(4)(2-) content increases. These concentrations vary in the broad interval from a few to near 1000 mBq/L. The coefficient of the linear correlation between concentrations of these isotopes amounts to 0.85, and the activity ratio (226)Ra/(228)Ra is >1 for chloride-sodium waters, being ≈1 for hydrogen-carbonate and <1 for the sulfate ones.

Uranium in mining waters of kaolin open pit in arów (Lower Silesia); methodology of determination and genetic remarks

In this paper, a method of determination of uranium 238 and 234 in mining waters of Andrzej kaolin open pit in Zarów (Lower Silesia) is presented. The method is based on independent measurements of alpha and beta radiation intensities by means of a liquid scintillation spectrometer alpha/beta. The initial volume of water sample was 3 dm3, then it was diminished by chemical preparation to 6 cm3, and then 12 cm3 of scintillator was added. The lower limit of detection (for the measurement time of 8 h) for both 234U and 238U amounted to 0.02 Bq/dm3. For determination of the uranium content in ferruginous sediments precipitating from mining waters of the above-mentioned open pit, gamma ray spectrometry was used. The obtained results may be viewed as a contribution to studies on anomalous uranium concentration within this kaolin deposit. The elevated uranium content, in comparison with its average concentration in the Earth crust, is characteristic for parent rocks of Andrzej kaolin deposit, which are granitoids of Strzegom-Sobótka massif. In connection with it, the high uranium content can be observed not only in kaolin and weakly kaolinised granitoids from the deposit in question, but also in mining waters genetically related with them.