International Research Journal of Environment Sciences________________________________ ISSN 2319–1414Vol. 3(3), 55-58, March (2014) Int. Res. J. Environment Sci. International Science Congress Association 55 Identification of Radio Nuclides in Soil Samples from selected Locations in Kerala, IndiaRamsiya M. and Antony Joseph Department of Physics, University of Calicut, Kerala-673635, INDIAAvailable online at: www.isca.in, www.isca.me Received 29th November 2013, revised 7th January 2014, accepted 21st March 2014 AbstractEnvironmental radioactivity is an unavoidable phenomenon and is definitely harmful to all living organisms. It is non uniformly distributed in earth’s crust and Kerala is considered as one of the high back ground radiation areas. The present study is initiated with the objective of detecting various radio nuclides present in the soil from five different places in the districts of Thrissur and Malappuram in Kerala, using Scintillation detector Nay(Tl), connected to multi channel analyzer. The samples were analyzed using gamma ray spectroscopic method and the photo peaks from the spectrum indicates the presence of lead (212Pb, 214Pb), actinium (228Ac), bismuth(214Bi) and potassium (40K). Keywords: Environmental radio activity, soil sample. IntroductionHuman beings are continuously exposed to natural radiation coming from cosmic ray sources and terrestrial sources such as 238U and 232Th series, and singly occurring 40K. The radio nuclides in the two series have short half lives, they are still important because they are continuously produced by their long lived parents through many decay modes. It is non uniformly distributed on earth's crust. Some areas of world are known as High Back Ground Radiation Areas where radiation levels are more than the other parts of world due to the presence of radio active minerals present in natural sources such as rock, soil, minerals. The well documented data regarding high natural background radiations are obtained in places like Guarapari in Brazil, Yangjiang in Chin, Chavara and Manavalakurichi in India, and Ramsar in Iran. There has been an increasing interest in understanding the natural radiation levels present in natural sources and building materials since the last few year. It is necessary for evaluating the risk due to low level radiations exposed to public with the increased concern over radiation safety. Material and MethodsThe samples were selected from the regions near Thrissur and Malappuram which are located near the northern zone of kerala. The sample type and regions are listed: i. Beach Sand Sample -Kottapuram Kota (Thrissur), ii. The Laterite Soil -Kottappuram (Thrissur), iii. Soil Sample-Ponnani (Malappuram), iv. Soil Sample-Puthu ponnani (Malappuram), v. Soil Sample-.Kodungalloor (Thrissur). Collected samples were from about one meter beneath the ground. Archaeological studies by State Archaeological Department is now going on at Kottapuram Kota, Thrissur (Pattanam excavation) for estimating the age of historical monuments found at that site. The samples collected were dried in an oven at a temperature of about 100°C for five hours to remove the moisture content in it. Dried samples were then finely powdered in a mortar. Finely powdered samples are packed in a polythene bags and were sealed using Araldite to prevent the escape of radon from the sample. All samples were stored for about four weeks before gamma analysis is performed. This is to allow 226Ra and its short lived progenies to reach secular equilibrium. 226Ra is an intermediate member of the decay series whose half life is shorter than its parent nuclide. Natural radio activity in the selected samples were studied using scintillation detector (NaI(Tl)) and it is more often used for gamma ray spectroscopy . The detector system consists of a single crystal of thallium activated sodium iodide NaI(Tl) and a photo multiplier tube, amplifier and a multichannel analyser. Collected samples were subjected to analysis with the help of PHAST PC- 8K software. The detector is shielded using lead blocks to minimise the background radiation effects. The samples were counted for a period of 18000s. The spectrum was analysed by gamma ray spectroscopic method. Each gamma ray photon has descrete energy, and this energy is characteristic of source isotope. We can determine the source of radiation by measuring the energies of gamma ray photon. For Gamma rays of natural terrestrial origin and for matter comprising rock, water and air, compton scattering is dominant interaction process. The main gamma energy peak recorded in a detector is called photo peak which results in full absorption of the gamma photon energy in the crystal. Any source whose peaks are known can be used to do energy calibration. From the calibration graph, the gamma ray energies of radionuclides present in the samples are found out. These energy values are compared with the standard values of the International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 3(3), 55-58, March (2014) Int. Res. J. Environment Sci. International Science Congress Association 56 radionuclide series given in the table 1 to identify unknown radionuclides. Table-1 238U and 232Th Series and Primordial Gamma linesSeries Nuclide Energy (keV) 238 U ( 226 Ra) 234 Th 63.24 214 Pb 77.11 226 Ra 186.21 214 Pb 351.93 214 Bi 1120.29 214 Bi 1847.42 232 Th 212 Pb 238.63 228 Ac 440.44 208 TI 510.7 228 Ac 651.51 228 Ac 674.16 228 Ac 968.97 228 Ac 1430.95 40 K 40 K 1460.39 Results and Discussion The energy calibration of the counting system helps the identification of unknown radionuclides. The energy calibration is done by analyzing sources emitting photons of known energy and plotting the channel number where the full energy peaks occur against the energy spent by the photons in the detector. The following table lists the sources used for calibration. Table-2 Sources used for the energy calibration of spectrometer Source Energy(E) in keV 133 Ba 356 22 Na 511 137 Cs 662 60 Co 1173 22 Na 1274 60 Co 1332 With the calibration, we found the energy values corresponding to the channel number of the identified photo peaks in the spectrum of the samples analyzed. From the found energy values, the nuclides which are responsible for emitting these gamma lines were identified as given in the reference table-1, which gives various gamma lines in the Uranium and Thorium series. Figure-1 Calibration graph shows relation between channel number and energy International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 3(3), 55-58, March (2014) Int. Res. J. Environment Sci. International Science Congress Association 57 Table- 3 Radio nuclides present in the Beach Sand Sample -Kottapuram Kota(Thrissur) and their parents Channel Energy (keV) True Energy (keV) Nuclide Source 807 242.98 238.63 212 Pb 232 Th 1244 346.42 351.93 214 Pb 226 Ra 2558 657.44 651.51 228 Ac 232 Th 3892 973.19 968.97 228 Ac 232 Th 5896 1447.53 1460.39 40 K 40 K Table -4 Radio nuclides present in the Laterite Soil –Kottappuram (Thrissur) and their parents Channel Energy (keV) True Energy (keV) Nuclide Source 870 255 250 212 Pb 232 Th 2634 675 651.51 228 Ac 232 Th 4609 1150 1120.29 214 Bi 238 U( 226 Ra) 5943 1430 1460.39 40 K 40 K Table -5 Radio nuclides present in the Soil Sample-Ponnani ( Malappuram) and their parents Channel Energy (keV) True Energy (keV) Nuclide Source 842 250 238.63 212 Pb 232 Th 2599 660 651.51 228 Ac 232 Th 3744 930 968.97 228 Ac 232 Th 6013 1450 1460.39 40 K 40 K Table- 6 Radio nuclides present in the Soil Sample Puthuponnani (Malappuram) and their parents Channel Energy (keV) True Energy (keV) Nuclide Source 883 260.77 238.63 212 Pb 232 Th 1273352.74 351.93 214 Pb 238 U( 226 R) 1381378.2 351.93 214 Pb 238 U( 226 R) 2476636.43 651.51 228 Ac 232 Th Table -7 Radio nuclides present in the Soil sample-Kodungalloor (Thrissur) and their parents Channel Energy (keV) True Energy (keV) Nuclide Source 884261.01 238.63 212 Pb 232 Th 2609667.81 674.16 228 Ac 232 Th 3764 940.18 968.97 228 Ac 232 Th 5185 1275.29 1120.29 214 Bi 238 U( 2 26 R) 59201448.63 1460.39 40 K 40 K Conclusion A detailed study generally involves the identification of the elements and the determination of the activity concentrations of the radionuclides in various samples. This study can be considered as the first step towards a detailed study of the radionuclides in the soil. The spectra of five soil samples spectrum were analysed using Gamma ray spectroscopic method and the corresponding radio nuclides were identified. It is seen that 212 Pb and 228Ac are common in all samples. The presence of 214Bi is seen in Thrissur samples especially in Kottappuram and Kodungalloor40. K is found in all samples except that from Puthuponnani. The presence of daughter nuclides of 238U, 232Th series and 40K identified in the samples International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 3(3), 55-58, March (2014) Int. Res. J. Environment Sci. International Science Congress Association 58 of soil show an important significance. The main reason is that the natural radioactivity and its variation in the sources are due to their geological origin. AcknowledgmentThe author (Ramsiya.m) wishes to acknowledge UGC for providing BSR fellowship. References1.Hand book of radioactivity analysis, Second edition, Elsevier Science (USA), (2003)2.Wood environmental 238U and 232Th concentration measurement in an area of high level natural background radiation at Palong, Jojor, Malaysia, J.Environ. Radioact.,80(1), 287–304 (2005) 3.Nuclear radiation detection, measurement and analysis, Muraleedhara Varier K, Narosa publishing house, (2009) 4.Guide lines for Radiological mapping using Gamma ray spectroscopy data, IAEA, Vienna (2003)5.Radiological production principles concerning the natural radioactivity of building materials, European commission-Radiation protection 112, (1999)