In this work, the radioactivity in the gold bearing samples collected from the artisanal mining sites in Birnin Gwari Local Government Area, Kaduna State have been determined, experimental measurements of 226Ra, 232Th and 40K activities concentration in the gold bearing samples have been carried out using a NaI(Ti) gamma ray spectrometer. The measured activity concentration for 226Ra have been found to lie in the specific ranges from 1.0545±0.4983Bq/Kg to 3.8355± 0.3476Bq/Kg while the  mean concentration is 2.383±0.4415Bq/Kg for 232Th, the activity concentration ranges from 9.3501±1.0260Bq/Kg to 66.7047±0.5700Bq/Kg, while the mean activity concentration of 232Th is 32.3644±9.3440Bq/Kg, for 40K,the activity concentration ranges from 120.9953±6.5319Bq/Kg to 815.8631±10.504Bq/Kg, while the mean activity concentration is 383.7924±72.5436Bq/Kg. The mean absorbed dose rate in the study area is 35.7334nGy/hr; while the mean annual effective dose rate is 0.032mSv/year which is lower when compared with tolerable limits of 1mSv/year. Keywords; Natural Radionuclides,Aactivity Concentrations, Absorbed Dose

Abdulkarim, M. S.

Abdullahi, M .A.

Aliu, S. O.

English

International Institute for Science, Technology and Education (IISTE): E-Journals

Journal of Natural Sciences Research                                                                                                                                                www.iiste.org ISSN 2224-3186 (Paper)   ISSN 2225-0921 (Online) Vol.4, No.24, 2014  31 Gamma Ray Spectrometric Analysis of Naturally Occurring Radioactive Materials (NORMS) in Gold Bearing Soil using NaI (Tl) Technique  M .A. Abdullahi       S. O. Aliu      M. S. Abdulkarim Department of Applied Science, College of Science and Technology ,Kaduna Polytechnic P.M.B 2021-8000 Kaduna Nigeria *Email of Corresponding Author : ariftahir64@gmail.com  Abstract In this work, the radioactivity in the gold bearing samples collected from the artisanal mining sites in Birnin Gwari Local Government Area, Kaduna State have been determined, experimental measurements of 226Ra, 232Th and 40K activities concentration in the gold bearing samples have been carried out using a NaI(Ti) gamma ray spectrometer. The measured activity concentration for 226Ra have been found to lie in the specific ranges from 1.0545±0.4983Bq/Kg to 3.8355± 0.3476Bq/Kg while the  mean concentration is 2.383±0.4415Bq/Kg for 232Th, the activity concentration ranges from 9.3501±1.0260Bq/Kg to 66.7047±0.5700Bq/Kg, while the mean activity concentration of 232Th is 32.3644±9.3440Bq/Kg, for 40K,the activity concentration ranges from 120.9953±6.5319Bq/Kg to 815.8631±10.504Bq/Kg, while the mean activity concentration is 383.7924±72.5436Bq/Kg. The mean absorbed dose rate in the study area is 35.7334nGy/hr; while the mean annual effective dose rate is 0.032mSv/year which is lower when compared with tolerable limits of 1mSv/year. Keywords; Natural Radionuclides,Aactivity Concentrations, Absorbed Dose.    1.0 Introduction Naturally Occurring Radioactive Materials (NORMS) are present in several types of materials, these are   materials which may contain any of the primordial radionuclides or radioactive elements as they occur in nature, such as radium, uranium, thorium, potassium, and their radioactive decay products, that are disturbed as a result of human activities. However the  concentration of NORM in most natural substances is so low that the risk is generally regarded as negligible. Higher concentrations may arise as a result of human activities. In most NORM, several or all of the radioactive isotopes of the three primordial decay series (235U, 238U and 232Th) are present in small concentrations in the natural matrix.(Darko and Faanu 2007, Faanu et al 2010)  Irradiation of the human body from external sources is mainly by gamma radiation from radionuclides of the 235U, 238U and 232Th decay series and from 40K. These radionuclides may be present in the body and irradiate various organs with alpha and beta particles as well as gamma rays [Cember, 1996; UNSCEAR, 2000; IAEA; 2005].  Mineral ores in the naturally undisturbed environments, the radionuclides in the decay series are more or less in radiological equilibrium. However, this equilibrium becomes disturbed through human activities such as mining and mineral processing, resulting in either an enrichment or depletion of some of the radionuclides concentrations compared to the original matrix. This disequilibrium is as a result of differences in the properties of the radionuclides in the series, due to geochemical migration processes and differences in their half-lives [Cember, 1996; UNSCEAR, 2000; Sato and Endo, 2001] The International Basic Safety Standards (BSS) for protection against ionizing radiation and the safety of radiation sources [IAEA, 1996] specify the basic requirements for the protection of health and the environment from ionizing radiation. These are based on the latest recommendations of the International Commission on Radiological Protection [ICRP, 2007] on the regulation of Practices and Interventions. The BSS is applied to both natural and artificial sources of radiation in the environment and the consequences on living and non-living species. The mining activities is capable of enhancing the NORMS .NaI(Tl) gamma ray spectrometry was used to determined  the activity concentration of natural occurring radionuclides (40K 232Th and 226Ra) the absorbed and annual effective  doses  were also determined.  2.0.  Materials and Methods 2.1. Sampling locations Six samples were collected from 6 gold pits at different depth  in the study area which comprised of the following artisanal gold mining sites: Kakini, Farinruwa and Tsohowar Gwari. Global Position System (GPS) was used to determine the location of each pit and a tape rule was used to determine the depth of each pit. Table 1 shows the location, depth and elevation of each pit where samples were collected.   Journal of Natural Sciences Research                                                                                                                                                www.iiste.org ISSN 2224-3186 (Paper)   ISSN 2225-0921 (Online) Vol.4, No.24, 2014  32 2.2 Sample Preparation:  The samples collected were taken to the Laboratory of Mineral Resources Engineering Department of Kaduna Polytechnic where they were crushed and sieved to tiny bits of 38 µm (Kogo et al., 2009 and El-Taher et al., 2003). The crushed samples were dried at about 100°C to a constant weight. The samples were kept in a container for 30 days and then taken to Centre for Energy Research and Training Ahmadu Bello University Zaria, Nigeria for NaI( Tl)Gamma ray Spectrometry analysis.  3. Results and Discussion The result of the activity concentration of 40K 226Ra and 232 Th is as indicated  in the table 2 below: The annual effective dose is  calculated using   HE = D (nGy/hr) TF where,  H E = Annual effective dose.  D = Absorbed dose rate (10-9 Gy/hr).   T= Coefficient factor (0.2)  F = Conversion coefficient (0.7 Sv/Gy)  For BG2   HE = D (nGy/hr) TF.    .			.		.				         = 0.019mSV  The annual effective dose of the other samples as calculated above are shown in the table 4. below:  3.1. Discussion 3.1.1Potassium:K-40 The mean activity concentration of 40K is 383.79±72.54Bq/Kg with the highest value of 815.86±10.50Bq/Kg in BG4 and the lowest value of 120.99±6.53Bq/Kg at BG1 as shown in fig 1.   3.1.2  Radium Ra-226  The mean activity concentration of 226Ra is 2.383±0.44Bq/Kg with highest concentration of 3.856±0.34 Bq/Kg at BG1 and the lowest at BG4 with value 1.054±0.498 Bq/Kg as shown in fig :2. 3.1.3 Thorium Th-232 The mean activity concentration of 232Th is 32.36±9.34Bq/Kg with highest concentration of 66.70±0.57Bq/Kg at BG6 and  lowest value of 13.45±1.25 Bq/Kg at BG.3 as shown in fig :3. The result also indicated that in all location the activity concentration of 40K is higher followed by 232Th while 226Ra has the lowest concentration in all location as shown in fig :4 3.1.4 Absorbed and Annual Effective Doses The mean absorbed dose rate was calculated to be 3.73nGy/hr with the highest value of 65.17 nGy/hr at BG6 and lowest value of 12.46 nGy/hr at BG 1 as shown in table :3. The mean annual effective dose was calculated to be 0.032 mSv/year with the highest value of 0.079mSv/year at BG 6  and the lowest value of  0.015mSv/year at BG.6 as shown in table:4.     4  Conclusion The mean activity concentration of  40K,226Ra and 232Th in the samples analysed were 383.79±72.54Bq/Kg , 2.38±0.44 Bq/Kg and 32.36±9.34Bq/Kg respectively. The result obtained in this work show that the activity concentration of 40K and 232Th  are slightly lower  than the world average value of 420 Bq/Kg and 45Bq/Kg for  40K and 232Th while the activity concentration of 226Ra obtained  in this work is by far less than 33Bq/Kg world average value for 226Ra . the mean absorbed dose rate of 35.73nGy/hr  calculated in this study is less than the world average value of 59nGy/hr while the mean annual effective dose 0.032mSv/year calculated in this work is also lower than 1mSv/year tolerable limit recommended by ICRP. This therefore suggested   that the level of exposure  to radiation  in the study area is within the tolerable limit .  REFERENCES Cember, H. (1996). Introduction to Health Physics. 3rd Edition McGraw – Hill, New York.  Darko, E.O., and Faanu A., (2007)., Baseline Radioactivity measurement in the vicinity of a gold Treatment plants, Journal of Applied Science and Technology, Vol. 10, Ghana El-Taher, A., Kratz K.L., Nossair, A. Azam A.H., (2003): Determination of gold in two Egyptian gold ores using instrumental neutron activation analysis; Science Direct. Radiation Physics and Chemistry 68, 751 - 755. Faanu, A., Darko, E. O., and Ephraim, J. H., (2010): Assessment of public Exposure to naturally occurring Journal of Natural Sciences Research                                                                                                                                                www.iiste.org ISSN 2224-3186 (Paper)   ISSN 2225-0921 (Online) Vol.4, No.24, 2014  33 radioactive materials from mining and processing activities of Tarkwa Gold mine in Ghana J. Environ. Monit Assess 180: 15-29 IAEA (1996) International Basic Safety Standard for protection against ionising radiation and for the safety of radiation sources, safety series No 115, IAEA Vienna.  IAEA (2005). Naturally occurring Radioactive Materials (iv), Proceedings of an International Conference held in Szezyrk, IAEA TEC DOC-1472, Poland.  ICRP (2007). 2006 Recommendations of the International commission on Radiological protection, ICRP publication 103, pergamon press, oxford Kogo, B.E. Gajere, E.N. Ogunmola J.K and Ogbole J.O (2009), Neutron Activation Analysis of Soil samples from different parts of Abuja metropolis Middle -East J. Scientific Research 4 (4) 254 - 262. Sato, J and Endo, M., (2001). Activity ratios of Uranium Isotopes in Volcanic Rocks from Izumariana Island-Arc volcanoes, Journal of Nuclear and Radiochemical Sciences Vol. 2 Japan. UNSCEAR (2000). Exposures from Natural Sources of Radiation 2000 Report to General Assembly Annex B, New York.  Table 1: Sampling Locations   SAMPLE CODE DEPTH LOCATION N   E ELEVATION  KAKINI  F/RUWA   TSBG KANO   TSBG JINEER   TS.BG KASTINA   TS.BG ABUJA BG1  BG2   BG3   BG4   BG5   BG6  2.70M  7.00M   19.00M   28.00M   24.00M   10.20M  110.10” 25’  110 04” 14’   100 59” 45’   110 00” 43’   110 01” 14’   100 59” 19’  060 58” 0’  060 47” 34’   060 48” 27’   060 48” 28’   060 48” 20’    060 48” 31’  663M  595M          560M   547M   550M   558M   Table 2. Activity concentration of 40K, 226 Ra and 232 Th (Bq/kg) S/No Sample Code 40K (Bq/kg) 226Ra 232Th 1. BG1 120.9953±6.5319 3.8355±0.3476 17.6739±1.0260 2. BG2 226.283, ±3.7325 1.2167±0.1391 9.3501±1.3680 3. BG3 376.9828±9.978 3.1286±0.3592 13.4549±1.2540 4. BG4 815.8631±10.504 1.0545±0.4983 50.1710±1.02562 5. BG5 492.8460±6.0653 2.6188±0.2202 36.0319±1.5960 6. BG6 569.8289±8.3791 2.4218±0.2433 66.7047±0.5700 Mean   383.7924±72.5436 2.383±0.4415 32.3644±9.3440       Table 3. Absorbed dose rate (10-9Gy/hr S/NO Sample Code Absorbed dose rate (10-9Gy/hr due to 40K, 226Ra, 232Th). 1. BG1 12.46 2. BG2 15.64 3. BG3 25.29 4. BG4 52.30 5. BG5 43.52 6. BG6 65.17    Mean 35.7334         Journal of Natural Sciences Research                                                                                                                                                www.iiste.org ISSN 2224-3186 (Paper)   ISSN 2225-0921 (Online) Vol.4, No.24, 2014  34   Table 4. Annual Effective Dose in mSv/year  Location  Annual Effective Dose mSv/year (40K,226 Ra,232 Th) BG1  0.015 BG2  0.019 BG3  0.031 BG4  0.064 BG5  0.053 BG6  0.079 Mean  0.032   Fig. 1: Plot of concentration of 40K against location.   Fig.2: Plot of concentration of 226Ra against location  0100200300400500600700800900BG 1 BG 2 BG 3 BG 4 BG 5 BG 6Concentration  of 40k (Bq/kg )Location40K00.511.522.533.544.5BG 1 BG 2 BG 3 BG 4 BG 5 BG 6Concentration of 226Ra (Bq/Kg)Location226 RaJournal of Natural Sciences Research                                                                                                                                                www.iiste.org ISSN 2224-3186 (Paper)   ISSN 2225-0921 (Online) Vol.4, No.24, 2014  35  Fig. 3: Plot of Concentration of 232Th against location   Fig: 4: Plot of Concentration of 40K,226Ra, 232Th against location    01020304050607080BG 1 BG 2 BG 3 BG 4 BG 5 BG 6Concentration of 232 Th (Bq/Kg)Location 232Th0100200300400500600700800900BG1 BG2 BG3 BG4 BG5 BG6Concentration of 40K,226Ra,232Th (Bq/kg)Location 40K226Ra232ThThe IISTE is a pioneer in the Open-Access hosting service and academic event management.  The aim of the firm is Accelerating Global Knowledge Sharing.  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Gamma Ray Spectrometric Analysis of Naturally Occurring Radioactive Materials (NORMS) in Gold Bearing Soil using NaI (Tl) Technique

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Gamma Ray Spectrometric Analysis of Naturally Occurring Radioactive Materials (NORMS) in Gold Bearing Soil using NaI (Tl) Technique

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