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Journal of Radioanalytical and Nuclear Chemistry
Authors: M. Alrakabi, G. Singh, A. Bhalla, S. Kumar, S. Kumar, A. Srivastava, B. Rai, N. Singh, J. Shahi, and D. Mehta

Abstract  

The elemental concentration of uranium in the samples collected from the ground water and the canal water in the Bathinda district of Punjab state, India, have been investigated using X-ray fluorescence technique. The residues obtained after drying the water samples were analysed using the energy dispersive X-ray fluorescence spectrometer consisting of Mo-anode X-ray tube equipped with selective absorbers as an excitation source and an Si(Li) detector. The uranium concentration values in significant fraction of the shallow ground water samples from the hand pumps is found to be above the permissible level of 15 ppb recommended by World Health Organisation for the drinking water, and its values in the canal water samples are below 5 ppb. To investigate the flyash from the coal-fired thermal power plants as a possible source of ground water contamination, the water samples collected from the surroundings of the power plants and the flyash samples were also analyzed. The results rule out flyash as a source of uranium contamination. Agrochemical processes occurring in the calcareous soils in the region are the favoured potential source of uranium contamination of the ground water.

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Abstract  

A brief study on dissolved radionuclides in aquatic environment, especially in ground water, constitutes the key aspect for assessment and control of natural exposure. In the present study the distribution of natural uranium and 226Ra concentration were measured in ground water samples collected within a 10 km radius around the Narwapahar uranium mine in the Singhbhum thrust belt of Jharkhand, India in 2007–2008. The natural uranium content in the ground water samples in this region was found to vary from 0.1 to 3.75 μg L−1 with an average of 0.87 ± 0.73 μg L−1 and 226Ra concentration was found to vary from 5.2 to 38.1 mBq L−1 with an average of 13.73 ± 7.34 mBq L−1. The mean annual ingestion dose due to intake of natural uranium and 226Ra through drinking water pathway to male and female adults population was estimated to be 6.55 and 4.78 μSv y−1, respectively, which constitutes merely a small fraction of the reference dose level of 100 μSv y−1 as recommended by WHO.

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Abstract  

An analytical methodology has been developed for the separation of arsenic from ground water using inorganic material in neutral medium. The separation procedure involves the quantitative retention of arsenic on hydrated manganese dioxide, in neutral medium. The validity of the separation procedure has been checked by a standard addition method and radiotracer studies. Neutron activation analysis (NAA), a powerful measurement technique, has been used for the quantitative determination of arsenic.

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Abstract  

The possible sources analyzed up to now for the neutron flux background at the Gran Sasso National Laboratory are the natural radioactivity in the rock, the concrete, as well as the induced part coming from interaction of cosmic ray muons with the rock or the detector material itself. Water was considered only as moderator in concrete, due to its variable concentration and its radioactivity as additional source for neutron flux modulation. Therefore, the water–rock interaction and its spatial-temporal variation induced by hydrological pattern of the Gran Sasso aquifer are taken into account.

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Abstract  

Speciation of technetium in ground water has been studied for understanding the migration behaviour of this radionuclide in deep geological formations. A combination of free-liquid electromigration, ion exchange, solvent extraction, coprecipitation and dialysis methods has been applied. Both oxic and anoxic conditions have been employed. Systems studied include leaching of sodium borosilicate glass spiked with99Tc and95mTc followed by its passage through glauconitic sand columns, and dialysis of TcO2 with ground water, sodium chloride, and humic acid solutions. Results indicate the presence of the pertechnetate, TcO 4 , ion as the dominating species.

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Abstract  

A new screening method is proposed for the determination of alpha-radioactivity in ground water. Natural alpha-emitters of Po, Ra, Th and U are precipitated from solution with sulphuric acid and ammonia. Ba2+ and Fe2+ are used as carriers. The overall yield for all emitters is greater than 80%. This method is faster than the evaporation technique, less dependent on the water composition and a better sensitivity can be achieved by using a large volume sample.

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Preliminary application of low-background gamma-spectrometry to volcanic ground water

Low-levels of 7Be, 22Na, 137Cs and radium isotopes as new geochemical tracers in a ground water flow system

Journal of Radioanalytical and Nuclear Chemistry
Authors: M. Inoue and K. Komura

Abstract  

To enrich cosmogenic 7Be and 22Na, artificial 137Cs and natural radium isotopes, three chemical methods were applied to large volumes (100–300 l) of ground water from Daisen Volcano, Japan. The co-precipitation method using BaSO4, Fe(OH)3 and AMP, yielded 7Be, 137Cs and radium isotope levels of nearly 100%. An ordinary ion-exchange column method, selectively recovered 22Na (77%) through two continuous column operations. 40K was satisfactorily removed in both, the co-precipitation and column methods. In addition, the simple batch method was suitable for rapid treatment even on the slope of a volcano without sacrificing yields. Low-background γ-spectrometry combined with these chemical treatments enabled the determination of extremely low-levels of 7Be, 22Na, 137Cs and radium isotopes (0.01–4 mBq/l) in ground water samples. The measurement of these nuclides of Daisen ground water provide new information on the flow system of volcanic water, including residence time, the mixing of precipitation, and the aquifer’s environment.

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Abstract  

Small volumes of aqueous solutions have been subjected to -radiation from a241Am source. The irradiated solution was separated from the bulk solution by a glass filter serving as a diffusion barrier. The H2O2 concentration in the bulk solution was monitored by a chemiluminescence technique and the overall production of oxidizing species (H2O2/O2) in irradiated ground water was studied by measuring the Fe2+-consumption in ground water initially containing 2·10–6 mol dm–3 Fe2+. H2O2 yields calculated using the computer program CHEMSIMUL are in fair agreement with experimental yields for pure water (pH 8) and aqueous methanol solutions (pH 5). Experimentally G(H2O2)=1.06±0.1 was obtained in pure water. In solutions containing 2·10–3 mol·dm–3 HCO 3 and in ground water G(H2O2) decreased to 0.69±0.03. A corresponding decrease in G(H2O2) was not found in the calculations. The agreement between measured and calculated Fe2+ consumption is fair when slow oxidative reactions in the bulk solutions are taken into account.

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Abstract  

Shallow land burial is routinely used for the disposal of low-level radioactive waste. Natural processes causing leaching of radionuclides can lead to contamination of surrounding ground water and soil by the radionuclides. The comparative leachability of radionuclides U(nat), 226Ra, 228Ra and Th(nat) from the soil of a radioactive waste disposal site, by ground water was evaluated. The probability of leaching was obtained in the following order Ra (≈77%) > U (≈40%) > Th (≈20%). Observed ratios (OR) were calculated to correlate leachability of radionuclides to that of major cations Ca2+ and Mg2+. The leaching of the radionuclides was seen to be dependent on Ca2+ and SO4 2− leached from the soil. This study provides sitespecific leachability of radionuclides, that can be used as indicator of the tendency for migration or retention in soil. It can play an important role during an unforeseen accident like breach of containment at the waste disposal site leading to contamination of soil and ground water and causing hazard to public via drinking water route.

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Abstract  

A system using an ion chromatograph coupled to a flow-cell scintillation detector for rapidly measuring the oxidation states of actinides at low concentrations (<10–6M) in aqueous solutions was evaluated. The key components of the system are a cation–anion separation column (Dionex, CS5) and a flow cell detector with scintillating cerium activated glass beads. The typical procedure was to introduce a 0.5 ml aliquot of sample spiked with actinides in the +III to +VI oxidation states into a 5 ml sample loop followed by 4 ml of synthetic groundwater simulant. Separation was achieved at a flow rate of 1 ml/min using an isocratic elution with oxalic, diglycolic, and nitric acids followed by distilled water. Tests were first conducted to determine elution times and recoveries for an acidic solution (pH 2) and a ground water simulant (pH 8) containing Am(III), Pu(IV), Th(IV), Pu(V), and U(VI). Then, an analysis was performed using a mixture of Pu(IV), Pu(V), and Pu(VI) in the ground water simulant and compared to results using the DBM extraction technique. Approximate elution times were the same for both the acidic solution and the ground water simulant. These were as follows: Pu(V) at 10 min, Am(III) at 15 min, Pu(IV) at 25 min, Th (IV) at 28 min and U(VI) at 36 min. Recoveries for the acidic solution were quantitative for U(VI) and Th(IV) and exceeded 80% for Am(III). Recoveries for the ground water simulant were quantitative for U(VI), but they were generally not quantitative for Th(IV), Pu(IV), and Am(III). For Th(IV) and Pu(IV), less than quantitative recoveries were attributed to the formation of neutral hydroxides and colloids; for Am(III) they were attributed to insoluble carbonates and/or hydroxycarbonates. When applied to the measurement of plutonium in the ground water simulant, the technique provided showed good agreement with the dibenzoylmethane (DBM) extraction technique, but it could not distinguish between Pu(V) and Pu(VI). This was likely due to the reduction of Pu(VI) to Pu(V) in the sample by the oxalic acid eluent. However, in spite of this limitation, the technique can be used to distinguish between Pu(IV) and Pu(V) in aqueous environmental samples within a pH range of 4 to 8 and an E H range of -0.2 to 0.6 V, the predominance region for Pu(III), (IV), and (V). In addition, this technique can be used to corroborate oxidation state analysis from the dibenzoylmethane (DBM) extraction method for environmental samples.

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