Activity and isotopic ratios of natural radium in marine sediment and sea water from west coast of India
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Activity and isotopic ratios of natural radium in marine sediment and sea water from west coast of India R. C. Bhangare1 · S. K. Sahu1,2 · P. Y. Ajmal1 · M. Tiwari1 · T. D. Rathod1,2 · A. Vinod Kumar1,2 Received: 28 January 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract The processes of material transport in oceans and their exchange with the land mass are complex and are a concern of interest to many researchers. Seawater and surface sediment samples from Tarapur, Mumbai and Goa from west coast of India were collected and analysed for 226Ra and 228Ra. The activity levels of 226Ra ranged from 19 to 36 Bq/kg while the levels of 228 Ra ranged from 25 to 55 Bq/kg in sediments. While the 226Ra and 228Ra activity levels ranged between 1.2–3.7 mBq/L and 3.1–7.1 mBq/L respectively. The activity ratios for the two isotopes were also calculated and were found to range between 0.4 and 2.3. The analyses were carried out using gamma spectrometry. Keywords Radium activity · Activity ratio 228Ra/226Ra · Sediments · Seawater · Gamma spectrometry · MnO2 co-precipitation
Introduction Radium, a naturally occurring radionuclide has four radioactive isotopes which are the daughters of radioactive decays of 238U and 232Th series. Similar to the parent nuclei, radium also is present everywhere. Since most of the earth’s crust is under the oceans, large amount of radium is produced there, which is approximately 2 × 1016 Bq every year [1]. The four naturally occurring Ra isotopes are used for studying various oceanic processes [2]. The activity analyses of the two long lived isotopes of radium (226Ra and 228Ra) are helpful for determining the impacts of exchange of materials from the continental mass with the oceans and also from the oceans to atmosphere and the biosphere. The isotopic ratios of these two nuclides and also their isotopic ratios with their parent radionuclide can be useful for the determination of various chemical and physical processes of elemental exchanges between the sediment bed and water and can also throw light on the disequilibria in the U and Th radioactive decay series at particular locations.
* S. K. Sahu [email protected] 1
Environmental Monitoring and Assessment Division, Bhabha Atomic Research Center, Mumbai 400085, India
Homi Bhabha National Institute, Mumbai 400094, India
2
The global biogeochemical cycle is influenced mainly by the processes governing the exchange and transport of material between the continental mass and ocean. The processes of mixing of the natural and anthropogenic input materials in the estuaries and coastal oceans lead to dispersion of these land-based materials such as various minerals as well as pollutants, various blooms of algae and transports of spilled and discharged materials in the oceans [3]. The mixing processes like advection and diffusion, are important for knowing the exchange and transport of material at the land–water interface. The rates of Eddy diffusion and advection velocity are very important in the study of physical processes in oceanograph
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