Assessments of radioactivity concentration of natural radionuclides and radiological hazard indices in sediment samples from the East coast of Tamilnadu, India with statistical approach R. Ravisankar a,⇑ , J. Chandramohan b , A. Chandrasekaran c , J. Prince Prakash Jebakumar d , I. Vijayalakshmi e , P. Vijayagopal e , B. Venkatraman e a PG & Research Department of Physics, Government Arts College, Thiruvannamalai 606603, Tamil Nadu, India b Department of Physics, E.G.S. Pillay Engineering College, Nagapattinam 611002, Tamil Nadu, India c Department of Physics, SSN College of Engineering, Kalavakkam, Chennai 603110, Tamil Nadu, India d Coastal and Environmental Engineering, National Institute of Ocean Technology, Pallikaranai, Chennai 600100, Tamil Nadu, India e Radiological Safety Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamil Nadu, India article info Article history: Received 16 April 2015 Revised 15 May 2015 Accepted 21 May 2015 Available online 30 May 2015 Keywords: Natural radioactivity Sediment Gamma ray spectrometry Radiological parameters Multivariate statistical analysis abstract This paper reports on the distribution of three natural radionuclides 238 U, 232 Th and 40 K in coastal sedi- ments from Pattipulam to Devanampattinam along the East coast of Tamilnadu to establish baseline data for future environmental monitoring. Sediment samples were collected by a Peterson grab samples from 10 m water depth parallel to the shore line. Concentration of natural radionuclides were determined using a NaI(Tl) detector based c-spectrometry. The mean activity concentration is 62.21, 14.29 and 360.23 Bq kg 1 for 238 U, 232 Th and 40 K, respectively. The average activity of 232 Th, 238 U and 40 K is lower when compared to the world average value. Radiological hazard parameters were estimated based on the activity concentrations of 238 U, 232 Th and 40 K to find out any radiation hazard associated with the sed- iments. The radiological hazard parameters such as radium equivalent activity (Ra eq ), absorbed gamma dose rates in air (D R ), the annual gonadal dose equivalent (AGDE), annual effective dose equivalent (AEDE), external hazard index (H ex ) internal hazard index (H in ), activity utilization index (AUI) and excess lifetime cancer (ELCR) associated with the radionuclides were calculated and compared with internation- ally approved values and the recommended safety limits. Pearson correlation, principal component anal- ysis (PCA) and hierarchical cluster analysis (HCA) have been applied in order to recognize and classify radiological parameters in sediments collected at 22 sites on East coast of Tamilnadu. The values of radi- ation hazard parameters were comparable to the world averages and below the recommended values. Therefore, coastal sediments do not to pose any significant radiological health risk to the people living in nearby areas along East coast of Tamilnadu. The data obtained in this study will serve as a baseline data in natural radionuclide concentration in sediments along the coastal East coast of Tamilnadu. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction Radioactivity is common in rocks, soil, beach sand, sediment and riverbed soil, in rivers and oceans, and even in our building materials and houses. Naturally occurring radioactive materials generally contain primordial radionuclides, left over since the cre- ation of the earth (UNSCEAR, 1982). The naturally existing radionu- clides like 238 U, 232 Th and 40 K are present everywhere in the Earth’s crust. Radium-226 ( 226 Ra, uranium series progeny), Radium-228 ( 228 Ra, thorium series progeny) and potassium-40 ( 40 K) are of most concern due to theirs high solubility and mobility. The knowledge of the concentrations and distributions of these radionuclides are of interest since it provides useful information in the monitoring of environmental contamination by natural radioactivity (Yii et al., 2009). The activity of natural radionuclides in soil and sedi- ment depends mainly on the types of rocks from which they orig- inate. These radionuclides pose exposure risks externally due to their c-ray emissions and internally due to radon and its progeny (UNSCEAR, 1988). Hence, humans should be aware of their natural environment with regard to the radiation effects due to the naturally occurring and induced radioactive elements. The study of the distribution of primordial radionuclides allows the understanding of the http://dx.doi.org/10.1016/j.marpolbul.2015.05.058 0025-326X/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: ravisankarphysics@gmail.com (R. Ravisankar). Marine Pollution Bulletin 97 (2015) 419–430 Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul