Measurement of activity concentration of primordial radionuclides in the soil samples of Tiruchirappalli, Tamil Nadu , India *A. Sadiq Bukhari, M. Saiyad Musthafa, H.E.Syed Mohamed, R.Krishnamoorthy M.M. Shahul Hameed and P. Shahul Hameed 1 Environmental Research Laboratory, P.G. Dept. of Zoology, Jamal Mohamed College, Tiruchirapalli, Tamil Nadu, India – 620 020. 1 Environmental Research Centre, J.J. College of Engineering & Technology, Tiruchirappalli, Tamil Nadu, India – 620 009. Abstract Radioactive minerals such as uranium (238U), thorium (232Th) and potassium (40K) are considered to be Primordial radionuclides which are widely distributed in the earth’s crust. Gamma-radiation from these radionuclides represents the main external source of irradiation for the human body. Human beings are exposed outdoors to the natural terrestrial radiation that originates predominantly from the upper 30 cm of the soil. A pilot project was therefore initiated aiming at systematically measuring the terrestrial gamma radiation in Tiruchirappalli city, Tamil Nadu, South India and to establish baseline data on the terrestrial background radiation level determining its contribution to the annual effective dose equivalent to the human population. The natural radioactivity concentrations were studied in soil samples collected from 50 locations in Tiruchirappalli city. The concentration varies significantly over different soil types and the highest radioactivity was measured over soil types of granite 232 238 origin followed by red soil and alluvial loam. The mean activity concentrations of Th, U 40 -1 -1 -1 and K in soil samples are found to be 81.78 Bq.kg , 32.62 Bq.kg , and 551.35 Bq.kg -1 respectively. The calculated gamma dose from the soil is in the range between 38.86nGy.h and 240.59 nGy.h-1 with a mean value of 89.76 nGy.h-1. The mean annual effective dose to the population from outdoor terrestrial gamma radiation was estimated to be 0.11mSv.y-1 which is low as compared with the maximum permissible effective dose equivalent of 1mSv.y-1 (ICRP,1991). In the present study it is observed that the major sources of gamma radiation in soils are mainly derived from rocky area with granite basement. Key words : Primordial radionuclides, Gamma-radiation, Annual effective dose * Presenting Author : [email protected] Table 1. Concentration activity of Primordial radionuclides in soil samples (Bq.Kg-1 dry weight) and absorbed dose rates and annual effective dose to population in Tiruchirappalli city Location Sampling 232Th 238U 40K Absorbed dose Annual effective -1 Code location rate (nGy.h-1) effective dose (mSv.y ) S1 Srirangam 33.05 12.55 387.72 44.28 0.05 S2 Thiruvanikkovi 20.82 19.94 367.42 38.86 0.05 S3 Mambalachalai 47.01 14.13 345.70 51.68 0.06 S4 Chinthamani 60.42 30.34 450.15 71.89 0.09 S5 Mutharasanallore 320.26 96.18 BDL 240.59 0.30 S6 Ibrahim park 106.40 20.71 655.05 106.11 0.13 S7 Gandhi Market 82.30 26.43 612.44 91.53 0.11 S8 Palakarai 86.34 30.33 323.42 82.04 0.10 S9 Railway Colony 85.27 47.62 355.09 90.25 0.11 S10 Ramji Nagar 98.56 32.51 711.12 110.20 0.14 S11 Annamalai Nagar 53.83 29.61 442.43 67.11 0.08 S12 Thillai Nagar 67.63 29.23 459.82 76.36 0.09 S13 Makkal Mandram 64.19 28.51 400.35 71.10 0.09 S14 Puthur 67.96 29.16 477.52 77.38 0.09 S15 Vayalore 42.82 14.89 478.26 55.66 0.07 S16 Somarasam Pettai 58.94 20.57 360.77 62.56 0.08 S17 Govt.Hospital 94.39 44.56 563.07 104.46 0.08 S18 Contonment 87.53 27.47 646.93 96.86 0.12 S19 Thennur 86.72 18.50 548.32 87.87 0.11 S20 Vekaliyaman Kovil 49.72 21.50 595.84 68.34 0.10 S21 Woriur 59.96 21.63 471.08 63.89 0.08 S22 Ramalinga Nagar 80.54 31.59 632.90 93.61 0.12 S23 Collector Office 108.19 50.17 928.60 132.74 0.16 S24 Periyamilaguparai 68.54 36.53 778.01 95.10 0.12 S25 Karumandabam 159.90 12.57 523.27 129.74 0.16 S26 Kirappatti 74.69 BDL 529.36 71.57 0.09 S27 Edamalaipattai Puthur 73.58 33.92 693.95 93.14 0.11 S28 Mannarpuram 68.65 33.35 505.81 80.93 0.10 S29 K.K. Nagar 70.21 62.83 910.13 113.62 0.14 S30 Kajamalai 90.40 47.02 664.18 107.82 0.13 S31 Anna Stadium 89.99 31.86 983.20 116.17 0.14 S32 Subramaniyapuram 113.49 34.18 556.33 111.61 0.14 S33 Central Jail 64.33 41.17 663.87 89.06 0.11 S34 Airport 66.86 62.53 603.51 96.90 0.12 S35 Anna Nagar 82.93 31.49 344.64 81.42 0.10 S36 Police Colony 64.31 23.18 411.41 69.43 0.10 S37 Ponmalaipatti 114.46 103.71 419.48 135.43 0.17 S38 Ponmalai 74.83 48.72 542.06 93.06 0.11 S39 Palpannai 66.51 28.62 633.86 83.64 0.10 S40 Ariyamangalam 65.42 14.64 862.24 87.79 0.11 S41 Kamaraj Nagar 59.73 26.21 703.63 81.68 0.10 S42 Kattur 71.63 21.94 510.13 78.13 0.10 S43 Thiruverumbur 66.17 25.75 455.82 73.78 0.10 S44 Melakalkondarkottai 62.87 33.11 441.64 74.78 0.10 S45 Kelakalkondarkottai 76.80 23.36 547.09 83.70 0.10 S46 Uyyakondthirumalai 52.95 13.83 551.18 64.97 0.10 S47 Kambarasampettai 77.80 14.02 439.68 75.26 0.10 S48 Thiruvalar Solai 136.97 29.69 303.10 112.35 0.14 S49 Senthaneerpuram 78.73 31.34 605.86 91.09 0.10 S50 Melapulivar 133.28 14.61 455.26 110.8 0.14 Mean (81.78 ± (32.62 ± (551.35 ± (89.76 ± (0.11 ± 42.75) 18.43) 160.30) 30.50) 0.04) Minimum 20.82 12.57 303.10 38.86 0.05 Maximum 320.26 103.71 983.20 240.59 0.30 A map of Tiruchirappalli city showing the sampling locations .