• Rohit Mehra

      Articles written in Journal of Earth System Science

    • Measurement of soil-gas radon in some areas of northern Rajasthan, India

      Vikas Duggal Asha Rani Rohit Mehra

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      The health hazards of the radioactive gas radon on general public are well known. In order to understand the level and distribution of 222Rn concentrations in soil-gas in Sri Ganganagar district of Rajasthan, a 222Rn survey was carried out for the first time using RAD7, an electronic radon detector manufactured by Durridge Company (USA), at different locations covering a total area of 10,978 km2, having a population of approximately 20 lakh. The measurement of 222Rn concentration in soil-gas was carried out at four different depths (10, 40, 70, and 100 cm). The radon concentration in soil-gas for 10, 40, 70, and 100 cm depths ranged from 0.09–4.25, 0.15–6.30, 0.50–9.18, and 0.72–10.40 kBq m−3, respectively. The minimum value of radon concentration is observed in 33 GB village at 10 cm depth and maximum for Mohanpura village at 100 cm depth. As expected, our data show an increase of soil-gas radon concentration levels with depth. The present results are compared with the available radon data from other studies.

    • Measurement of radon exhalation rate in various building materials and soil samples

      Pankaj Bala Vinod Kumar Rohit Mehra

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      Indoor radon is considered as one of the potential dangerous radioactive elements. Common building materials and soil are the major source of this radon gas in the indoor environment. In the present study, the measurement of radon exhalation rate in the soil and building material samples of Una and Hamirpurdistricts of Himachal Pradesh has been done with solid state alpha track detectors, LR-115 type-II plastic track detectors. The radon exhalation rate for the soil samples varies from 39.1 to 91.2 mBq kg⁻¹ h⁻¹with a mean value 59.7 mBq kg⁻¹ h⁻¹. Also the radium concentration of the studied area is found and it varies from 30.6 to 51.9 Bq kg⁻¹ with a mean value 41.6 Bq kg⁻¹ . The exhalation rate for the building material samples varies from 40.72 (sandstone) to 81.40 mBq kg⁻¹ h⁻¹ (granite) with a mean value of59.94 mBq kg⁻¹ h⁻¹.

    • Structural and luminescent characterisation of uraniferous fluorapatite and haematite associated with phosphatic rocks of the Bijawar group in Sagar District, Madhya Pradesh (India)

      Pragya Pandit Shailendra Kumar Pargin Bangotra Rohit Mehra Manoj Mohapatra Madhuparna Roy Singh A K

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      The structural and spectroscopic characteristics of phosphatic ferruginous shale samples from the Bijawar Group rocks from Sagar District of Madhya Pradesh (India) have been probed for identification of uranium species. Fluorapatite (Ca$_{5}$(PO$_{4}$)$_{3}$F, FAP) and haematite ($\alpha$-Fe$_{2}$O$_{3}$) were identified as the main phases in the separated mineral concentrates. The photoluminescence (PL) and X-ray absorption near edge spectroscopy (XANES) studies pointed to a strong experimental evidence of both U(IV) and U(VI) oxidation states in the mineral concentrate portion obtained from the same parent host rock. The PL spectrum has confirmed the charge transfer (f–d) transition bands in UV and near-UV regions with emission peaks at ca. 290, 313, 336, 399 and 416 nm, which has been attributed to the substitution of Ca$^{2+}$ ions by U(IV) in FAP and broad structureless emission due to stabilisation of U(VI) as UO$_6^{6-}$ in haematite. Time-resolved spectroscopy studies have revealed biexponential decay components lasting 2–5 ns for U(IV) species and 10 $\mu$s for U(VI) species. These characterisations revealed the fundamental information about the oxidation state and form of uranium in this region. Remediation measures for the Bijawar region are also suggested.

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