Abstract
The present paper describes a detailed study on the distribution of radionuclides along Chavara – Neendakara placer deposit, a high background radiation area (HBRA) along the Southwest coast of India (Kerala). Judged from our studies using HPGe gamma spectrometric detector, it becomes evident that Uranium (238U), Thorium (232Th) and Potassium (40K) are the major sources for radioactivity prevailing in the area. Our statistical analyses reveal the existence of a high positive correlation between 238U and 232Th, implicating that the levels of these elements are interdependent. Our SEM-EDAX analyses reveal that titanium (Ti) and zircon (Zr) are the major trace elements in the sand samples, followed by aluminum, copper, iron, ruthenium, magnesium, calcium, sulphur and lead. This is first of its kind report on the radiation hazard indices on this placer deposit. The average absorbed dose rates (9795 nGy h−1) computed from the present study is comparable with the top-ranking HBRAs in the world, thus offering the Chavara-Neendakara placer the second position, after Brazil; pertinently, this value is much higher than the World average. The perceptibly high absorbed gamma dose rates, entrained with the high annual external effective dose rates (AEED) and average annual gonadal dose equivalent (AGDE) values existing in this HBRA, encourage us to suggest for a candid assessment of the impact of the background radiation, if any, on the organisms that inhabit along this placer deposit. Future research could effectively address the issue of the possible impact of natural radiation on the biota inhabiting this HBRA.
Highlights
Natural radiation is largely caused by the presence of primordial radionuclides and their decay products
Monazite sands have been found to be the source of such high background radiation levels in certain parts of Brazil, China, Egypt and India [1,3,12] while in parts of Southwest France, uranium minerals form the source of natural radiation [13], and in Ramsar, the very high amounts of 226Ra and its decay products brought to the surface by hot springs [11,12] have been found to be the source
The varying results on the natural radioactivity obtained by the previous investigations from the same locality [20,21] have prompted us to undertake a study focusing on the Chavara – Neendakara placer deposits situated along the Southwest coast of India (Kerala), one of the very well known high background radiation area (HBRA) in the world
Summary
Natural radiation is largely caused by the presence of primordial radionuclides and their decay products. Ullal in Karnataka [14], Kalpakkam [15] in Tamilnadu, and coastal parts of Kerala state, and the Southwestern coast of India are known to be HBRAs [10] Research in these places has generated considerable interest primarily due to geological reasons inasmuch as monazite, the rich source of radioactive uranium and thorium, becomes an important component in the sand from HBRAs [16]. The varying results on the natural radioactivity obtained by the previous investigations from the same locality [20,21] have prompted us to undertake a study focusing on the Chavara – Neendakara placer deposits situated along the Southwest coast of India (Kerala), one of the very well known HBRAs in the world. The types of trace elements in the soil sample have been computed using EDAX, and are presented in this paper
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