Natural radionuclides and radiological risk assessment in the stream and river sediments of a high background natural radiation area Kanyakumari, India.

The Kanyakumari coast is known to be a high background natural radiation area due to the placer deposits of heavy minerals such as ilmenite, monazite, and rutile. The Kanyakumari river sediments that could be the source of the elevated amounts of natural radionuclides in the coastal sands have been studied in this paper. The activity concentrations of primordial radionuclides 226 Ra, 232 Th, and 40 K were determined using high-purity germanium (HPGe) gamma-ray spectrometry. The mean activity concentrations of 226 Ra, 232 Th, and 40 K were found to be 75 Bq kg-1 , 565 Bq kg-1 , and 360 Bq kg-1 , respectively. The mean absorbed dose rate was 395 nGy h-1 . Radiological hazard parameters were studied and compared with the world average values. The contribution of 232 Th to the total dose rate was found to be higher than that of the two other radionuclides. The high mean ratio of 232 Th/226 Ra suggested an enrichment of 232 Th and the occurrence of 226 Ra leaching due to an oxidizing environment. Principal component analysis (PCA) was carried out for the radionuclides in order to discriminate the source of the sediments. This study provides new insights into the distribution of natural radionuclides in sediments of rivers and streams.