S. Mishra

Estimation of 210Po and its risk to human beings due to consumption of marine species at Mumbai, India

(210)Po was estimated in the edible muscle and soft tissue of 15 different marine species (fish, crab, prawn and bivalve) collected from Trans-Thane Creek area (Trombay) and Thane. Potential risks associated with consumption of marine organisms due to (210)Po collected from this particular area to human beings were assessed. Estimation of (210)Po was carried out using radiochemical separation and alpha spectrometric technique. The concentration of (210)Po was found to vary from 0.18 to 10.9 Bqkg(-1) wet wt in different biota species and maximum concentrations were observed in bivalves. The variations in (210)Po concentration in different species are mainly due to difference in metabolism and feeding habits. The daily intake and individual dose of (210)Po to human beings through biota consumption was calculated and found to be 31.89 mBqd(-1) and 19.44 microSvyr(-1), respectively. An assessment of the risk on human beings due to consumption of marine organism was undertaken using carcinogenic slope factor for (210)Po. 5th, 50th and 95th percentile of life time risk was calculated to be 9.74E-06, 4.39E-05 and 2.12E-04, respectively.

Distribution and retention of Cs radioisotopes in soil affected by Fukushima nuclear plant accident

PurposeThere was a large release of radio-cesium (134Cs and 137Cs) to the atmosphere during the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, and contaminated the soil, over a vast area, due to fallout activity. Therefore, studies on the behaviour of radio-cesium especially migration in soil and its retention on soil particles is very important for external dose assessment and root uptake.Materials and methodsWe have determined the sorption coefficient (Kd) for Cs using the laboratory batch method in soil samples collected from a contaminated area affected by the FDNPP accident, and the effect of various soil parameters on the Kd value has been studied.Results and discussionWe have noticed that Cs sorption is mostly influenced by cation exchange process and Cs is sorbed on the surface of clay particles. From vertical depth profile of Cs in soil, it is found that most of it is retained on the top layer within a 5-cm thickness.ConclusionsSequential extraction of soil using various reagents may be helpful to understand better the mechanism of Cs retention.

Estimation of distribution coefficient of natural radionuclides in soil around uranium mines and its effect with ionic strength of water

The distribution coefficient, K(d) in soil is an important parameter to predict the migration of contaminants. In this study, uranium (U) and its decay products thorium (Th), radium (Ra), bismuth (Bi), lead (Pb) and polonium (Po), which may contaminate the soil and ground water around uranium mining areas, have been considered. Soil and ground water samples were collected from a proposed uranium mining site in India. The soil samples were characterised for different parameters affecting the K(d) values. The batch sorption method was employed to measure the K(d) of different radionuclides. The important factors affecting the batch method for K(d) estimation were identified and optimised. The variation of K(d) was observed with different ionic strength water samples. Results showed high K(d) values for Th(IV), Po(IV) and Pb(II) (log K(d) ∼4) and low K(d) (log K(d) ∼2-3) for U(VI), Ra(II) and Bi(III) in all three types of water with different ionic strength.

Variability of radiocaesium inventory in Fukushima soil cores from one site measured at different times

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident has resulted in the deposition of radioactive contamination of soils mainly by (134)Cs and (137)Cs. The contaminated areas are of a great concern since external radiation may lead to significant long-term doses to humans and animals. External dose rate above ground will decrease with physical decay of the radionuclides and as they migrate deeper into the soil with time. In the present study, depth profiles of Cs radioisotopes have been studied at different times over a period of 1 y. Radiocaesium inventories for (134)Cs and (137)Cs down to a depth of 10 cm at the four measurement times varied from 2.09 to 4.14 MBq m(-2) with coefficient of variation (CV): 27.4 %, n = 4 and from 2.13 to 4.23 MBq m(-2) with CV: 27.3 %, n = 4, respectively. The activity ratio for (134)Cs/(137)Cs decreased from 0.62 to 0.46 during 1 y of measurement i.e. July 2012 to June 2013. However, the ratio with decay correction (15 March 2011) was found to be constant ∼1, indicating contamination from FDNPP origin. In order to understand the radiocaesium distribution in soil profile, physico-chemical characterisation of soil has been carried out.

Distribution coefficients of radionuclides around uranium mining area and effect of different analytical parameters on their determination

Macroscopic batch sorption study has been carried out to measure distribution coefficient (Kd) of uranium, thorium and their daughter products, radium and polonium, on soil samples collected from a proposed uranium mining site in India. Results showed high Kd values for Th(IV) and Po(IV) (log Kd ~4), while lower Kd values were obtained for U(VI) with the site ground water as aqueous medium compared to the synthetic water. Ra(II)–Kd has been found dependent on soluble Ca(II) content of the water samples. Determination of Kd values in an inter-comparison manner involving different estimation methodology produced a consistent data set.

Estimation of Distribution Coefficient of Uranium and Its Correlation with Soil Parameters Around Uranium Mining Site

Distribution coefficient of uranium and its daughter products are very important for migration study around uranium mining sites. Since the distribution coefficient depends very much on the soil chemistry, generation of site specific Kd is very important. The present study emphasizes on the estimation of distribution coefficient for uranium and its correlation with various soil parameters. The distribution coefficient of uranium in top and one meter depth soil samples from above locations were estimated using laboratory batch method. The distribution coefficient of uranium varies from 69 to 5524 l/kg. No significant difference in uranium Kd values was observed for top and one meter depth soil samples. A good correlation was observed between distribution coefficient of uranium and soil parameters like pH and concentration of CaCO3.

Study of Extraction of Co(II) Ions using the Synthesized Polyacrylonitrile-Manganese Dioxide Composite Beads

Extraction of cobalt ions from aqueous medium has been studied, using macroporous polyacrylonitrile-manganese dioxide composite beads. Polyacrylonitrile, synthesized by γ-radiation induced polymerization of saturated aqueous solution of acrylonitrile monomer, has been employed, to produce polyacrylonitrile-manganese dioxide composite beads. Results of the extraction study indicate efficient adsorption of cobalt ions from neutral, or slightly acidic, aqueous solutions. The cobalt ions, adsorbed on the composite beads, can be leached out with 0.1 M HNO3 solution. The effect of various experimental parameters, such as concentration of cobalt ions, pH of the aqueous solution, etc., on the adsorption process and its kinetics has been studied. Further, adsorption capacity of the beads for cobalt ion, as well as their reusability for multiple adsorption-desorption of the cobalt ions, have also been evaluated. SEM and BET techniques have been used to determine the porous nature of the beads. IR spectroscopy has been used to understand the interaction of the polyacrylonitrile-manganese dioxide composite beads with cobalt ions.