Spatial Distribution and Lifetime Cancer Risk Due to Gamma Radioactivity in Yelagiri Hills, Tamilnadu, India
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egyptian journal of basic and applied sciences xxx (2014) 1e11 Available online at www.sciencedirect.com ScienceDirect journal homepage: http://ees.elsevier.com/ejbas/default.asp Full Length Article Spatial distribution and lifetime cancer risk due to gamma radioactivity in Yelagiri Hills, Tamilnadu, India A. Chandrasekaran a, R. Ravisankar b,*, G. Senthilkumar c, K. Thillaivelavan d, B. Dhinakaran e, P. Vijayagopal f, S.N. Bramha f, B. Venkatraman f a Global Institute of Engineering & Technology, Vellore 632509, Tamilnadu, India b Post Graduate and Research Department of Physics, Government Arts College, Thiruvanamalai 606603, Tamilnadu, India c Department of Physics, University College of Engineering Arni, Arni 632317, Tamilnadu, India d Department of Physics, Periayar Arts College, Cuddalore 607 001, Tamilnadu, India e Department of Physics, Government Arts College, Chidambaram 608102, Tamilnadu, India f Radiation Safety Section, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamilnadu, India article info abstract Article history: The spatial distribution of natural radioactivity due to uranium, thorium and potassium Received 23 October 2013 was investigated in soils from the undisturbed areas in Yelagiri Hills, Tamilnadu, India by Received in revised form Isodose map. The radiological hazards due to natural radionuclides content such as 27 December 2013 representative level index (RLI), activity utilization index (AUI), excess lifetime cancer risk Accepted 6 February 2014 (ELCR) and internal radiation hazards (Hin) of the soil samples in this area were calculated. The calculated radiological hazard parameters are compared with different countries of À À the world. The calculated range of ELCR is 0.326 Â 10 3 to 1.067 Â 10 3 with an average of À Keywords: 0.700 Â 10 3 for soils. This average value of ELCR is more twice than the world average À Soil (0.290 Â 10 3). A correlation analysis was made between measured dose rate and individual Gamma ray spectrometry radionuclides, in order to delineate the contribution of the respective nuclides toward the Excess lifetime cancer risk dose rate. The U/Th concentration ratio in surface soil samples ranged from 0.05 to 1.72 Statistical analysis with an average of 0.43 which is more higher (80%) than the world average of 0.26. The Spatial distribution application of cluster analysis (CA) and principal component analysis (PCA), coupled with Pearson correlation coefficient analysis, were utilized to analyze the data, identify and clarify between the radiological parameters to know the existing relations. The CA and PCA results showed that the former method yielded three distinctive groups of the soil variables * Corresponding author. Tel.: þ91 9443520534/þ91 9840807356; fax: þ91 4175 236553. E-mail address: [email protected] (R. Ravisankar). Peer review under responsibility of Mansoura University Production and hosting by Elsevier http://dx.doi.org/10.1016/j.ejbas.2014.02.001 2314-808X/Copyright 2014, Mansoura University. Production and hosting by Elsevier B.V. All rights reserved. Please cite this article in press as: Chandrasekaran A, et al., Spatial distribution and lifetime cancer risk due to gamma radioactivity in Yelagiri Hills, Tamilnadu, India, Egyptian Journal of Basic and Applied Sciences (2014), http://dx.doi.org/10.1016/ j.ejbas.2014.02.001 2 egyptian journal of basic and applied sciences xxx (2014) 1e11 whereas the latter one yielded the number of variables into two factors with 94.47% vari- ance explanation. Copyright 2014, Mansoura University. Production and hosting by Elsevier B.V. All rights reserved. condition. The ability of hydrogenous migration falls in the 1. Introduction order U > Ra > Th. Uranium is able to remain in soluble state for a long time and gets migrated by flow of streams or river to a The radioactivity level from the natural radionuclides is long distance. Horizontal transfer of uranium and thorium is termed as background radiation which will depend on the dominated by interchange of sorption and desorption [5]. Un- amount of the radioactive materials in the environment. The fortunately rapid increasing of population and usage of fertil- background radiation can be high if the environment is izers for agriculture day by day contaminate the soils. Due to polluted either from man-made or natural activities. Mate- one of the main tourism places in Tamilnadu, point and rials from the deposit may be brought to the surface soil nonpoint pollution sources are dominated in study area. Hence through processes such as weathering of rocks and soil for- it is necessary to determine the concentration levels of the 238U mation. They can also leach into the groundwater system, and 232Th as well as 40K in the soil from Yelagiri hills, Tamil- contaminate it, and lead to pollution far away from the nadu, India and to analyze the spatial distribution of natural source. radionuclides by Isodose map with statistical approach. Natural radioactivity arises mainly from the primordial radionuclides, such as 40K and the radionuclides from 238U and 232Th series and their decay products, which are present at trace levels in all ground formations [1]. Monitoring the 2. Previous work release of gamma radiation from natural radionuclides is important to protect the humans from lung cancer. The main In an earlier work, activity concentration of natural radionu- sources of gamma radiations are due to two major radionu- clide that in different locations of Yelagiri Hills is reported by clide chains: uraniumeradium and thorium. A geological and Ravisankar et al. [4]. They indicated that average activity geographical condition of the study area determine the concentration of 232Th in that study was 1.19 times higher radioactivity and the associated external exposure due to than world median value while the activity of 238U and 40K was gamma radiation at different levels in the soils of each region found to be lower and also major gamma radiation exposure in the world [2e4]. to humans in Yelagiri Hills due to enrichment of 232Th content The data will offer useful and necessary information in the in soils [4]. The present work is a continuation of the previous monitoring of environmental contamination which will pro- research work in Yelagiri Hills, Tamilnadu to study the spatial vide appropriate and better protection guidelines to the distribution of natural radionuclide and the application of public. Multivariate statistical method to analyze the data, identify The distribution of radionuclide concentration reflects and clarify between the radiological parameters to know the migration of uranium and thorium under surface soil existing relations. Fig. 1 e Soil samples collected at different sampling points of Yelagiri Hills, Tamilnadu, India. Please cite this article in press as: Chandrasekaran A, et al., Spatial distribution and lifetime cancer risk due to gamma radioactivity in Yelagiri Hills, Tamilnadu, India, Egyptian Journal of Basic and Applied Sciences (2014), http://dx.doi.org/10.1016/ j.ejbas.2014.02.001 egyptian journal of basic and applied sciences xxx (2014) 1e11 3 Table 1 e Activity concentration, representative level index (RLI), activity utilization index (AUI), annual gonadal dose H equivalent (AGDE), excess lifetime cancer risk (ELCR), internal radiation hazards ( in) of soils of Yelagiri Hills, Tamilnadu, India. À À Sample Locations Activity concentration (Bq kg 1) RLI AUI AGDE ELCR Â 10 3 Internal À1 À1 location Id 238 232 40 (Bq kg ) (mSv y ) radiation U Th K hazards (Hin) YS1 Pavendar bend BDL 24.47 Æ 6.11 2207.3 Æ 50.53 1.57 0.480 795.38 0.876 0.553 YS2 Bharathiyar bend BDL 21.1 Æ 5.59 656.51 Æ 33.29 0.60 0.310 294.34 0.326 0.218 YS3 Thiruvalluvar bend BDL 13.54 Æ 5.23 851.13 Æ 34.90 0.65 0.235 323.85 0.357 0.229 YS4 Ilango bend 18.93 Æ 8.25 83.77 Æ 8.03 1137 Æ 44.30 1.63 1.282 765.67 0.863 0.662 YS5 Kambar bend 25.55 Æ 7.20 36.24 Æ 6.31 913.95 Æ 39.04 1.06 0.750 517.41 0.588 0.468 YS6 Kabilar bend 6.24 Æ 6.63 28.45 Æ 6.12 1391.6 Æ 42.96 1.16 0.517 575.17 0.639 0.433 YS7 Oviyar bend 23.35 Æ 7.12 38.95 Æ 6.34 872.86 Æ 38.28 1.05 0.759 509.04 0.578 0.458 YS8 Paari bend 18.45 Æ 9.04 89.48 Æ 8.82 1025.2 Æ 46.59 1.62 1.337 752.95 0.850 0.658 YS9 Kaari bend 33.39 Æ 9.49 114.75 Æ 9.21 936.11 Æ 45.95 1.91 1.773 876.77 0.998 0.818 YS10 Oori bend BDL 22.81 Æ 5.25 1143.8 Æ 36.54 0.91 0.371 454.50 0.502 0.326 YS11 Aayai bend 21.2 Æ 8.59 100.42 Æ 8.47 1128.8 Æ 44.92 1.81 1.503 839.71 0.948 0.737 YS12 Adiyaman bend 15.76 Æ 7.96 71.31 Æ 7.69 1250.2 Æ 44.83 1.56 1.111 739.34 0.831 0.620 YS13 Nali bend BDL 28.05 Æ 6.41 1455.5 Æ 45.19 1.15 0.460 574.28 0.634 0.411 YS14 Began bend BDL 26.06 Æ 5.88 2165.5 Æ 48.52 1.56 0.495 788.90 0.869 0.551 YS15 Arthanavoor BDL 41.45 Æ 6.72 1137.8 Æ 41.88 1.10 0.596 530.53 0.588 0.397 YS16 Kottaivoor 10.1 Æ 6.45 43.34 Æ 6.10 2105.4 Æ 46.83 1.76 0.792 873.47 0.970 0.660 YS17 Mangalam 13.13 Æ 6.48 29.52 Æ 5.85 1219.1 Æ 39.97 1.11 0.580 546.76 0.612 0.438 YS18 Meatokalli 23.76 Æ 8.95 13.78 Æ 17.21 1263 Æ 72.55 1.04 0.491 527.60 0.594 0.444 YS19 Pothvoor 23.79 Æ 8.38 61.69 Æ 16.44 700.93 Æ 58.66 1.18 1.023 551.47 0.628 0.513 YS20 Kallivoor 34.93 Æ 9.16 46.79 Æ 16.71 2052.8 Æ 76.73 1.91 1.059 948.10 1.067 0.796 YS21 Nilavoor 39.89 Æ 5.64 57.6 Æ 8.64 630.41 Æ 32.08 1.19 1.117 561.98 0.648 0.569 YS22 Meatokanivoor 39.55 Æ 5.55 50.24 Æ 8.31 625.09 Æ 31.46 1.11 1.024 528.49 0.610 0.538 YS23 Pallakanvoor 49.72 Æ 7.00 35.95 Æ 9.85 261.11 Æ 33.06 0.81 0.915 385.89 0.457 0.462 YS24 Thayaloor 20.45 Æ 4.95 44.47 Æ 9.26 983.08 Æ 39.25 1.16 0.808 557.76 0.630 0.487 YS25 Putthoor 53.23 Æ 7.07 89.89 Æ 10.89 557.88 Æ 36.27 1.55 1.624 715.40 0.829 0.751 Average 19.16 48.56 1146.88 1.29 0.857 621.39 0.700 0.528 through thick reserve forests.