International Conference on Environmental Research ...

International Conference on Environmental Research and Technology (ICERT 2012)

238

U, 232Th AND 40K CONCENTRATIONS EVALUATION FOR SOIL AND WATER SAMPLES IN NORTHERN MALAYSIAN PENINSULAR B.A. Almayahi*, A.A. Tajuddin and M.S. Jaafar School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia *Corresponding author email: [email protected]

ABSTRACT This paper highlights a study of top soil and water samples from Northern Malaysian Peninsular (NMP), comprising the states of Penang, Kedah, Perlis and Perak using a NaI (Tl) detector (7.8 cm x 7.8 cm ) and an Exploranium GR-135, which contains a 3.8 cm x 5.5 cm spectrometer NaI (Tl) detector. Concentrations of 238U, 232 Th and 40K have been determined in ppm and % wt. Soil samples were collected from the top surface until 10 cm deep of the soil, whereas water samples were collected from the sea, waterfall, river and rain. Concentrations measured by NaI (Tl) detector are higher than concentrations measured by an Exploranium GR-135. The radionuclides concentrations in some studied sites exceed the norm. The data are then compared with results obtained from other regions. Keywords: Exploranium GR-135; environmental radionuclides; water; soil. INTRODUCTION Radionuclides such as 40K and 226Ra that occur naturally in soil are incorporated metabolically into plants and ultimately find their way into food and water. The terrestrial sources of γ-radiation are 40K and nuclides of the 238U and 232Th series. If the concentrations of 40K, 238U and 232Th in soil are known, the γ-dose can be estimated, using equations developed [1]. 40K, 238 U and 232Th are a major (2.3 %), minor (3 ppm) and minor (12 ppm) components, respectively of the Earth’s crust.

Study area The study was conducted at NMP, comprising the states of Penang, Kedah, Perlis and Perak as shown in Figure 1. The geological description of NMP has been reported elsewhere [2]. Table 1 shows geographical coordinates of sampling sites.

Fig. 1: The geological map of West Malaysia with sampling sites [3]

Green Tech & Engineering

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SC *110 *031 *881 *099 *111 *016 *196 *211 *233 *259

Table 1: Geographic site of sampling sites. Sampling site N Gelugor, Penang 05022’20.0" Bayan Lepas, Penang 05016’50.4” Batu Feringghi, Penang 05028’02.2" Pantai Kerachut, Penang 05027’39.5” Penang Hill, Penang 05025’39.5" Kg.Lubok Peringgi, Kedah 6° 7'43.20" Forest Research Complex, Perlis, Malaysia-Thailand border 6°39'15.40" Kg.Telaga Baru, Kedah 6°21'4.70" Pulai Kedah 5°39'26.80" Kg. Bukit Sapi, Lenggong, Perak 05°09'3.50"

E 100018’56.8" 100017’24.5” 100015’04.6" 100012’15.5” 100016’09.6" 100°21'54.00" 100°14'30.60" 100°21'21.20" 100°53'31.20" 101°04'17.80"

METHODS Materials Twenty samples are collected from NMP. Ten soil samples collected from topsoil 0-10 cm and ten water samples collected from the sea, waterfall, river and rain near soil sample about 300 m to 1000 m in NMP. The soil samples have been prepared as reported elsewhere [2] and counted using NaI(Tl) a 7.68 cm x 7.68 cm spectroscopy (Ortec, USA) and a portable handheld a 3.8 cm x 5.5 cm spectrometer NaI (Tl) detector (GR-135 Exploranium, Canada) as shown Figure 2. Sites coordinates were determined using the GPS Garmin Model 60 CSX [4] global positioning system, with accuracy of < 10 m Figure 2. Water samples 500 ml collected in plastic bottle, stored, and counted using GR-135 spectrometer.

Fig. 2: Na I (Tl) spectroscopy, a lead shielding with Marineli beaker, balance, GR-135 spectrometer with water samples and GPS used in this study The NaI(Tl) detector had an energy resolution of 56 keV (FWHM) for the 662 keV γ-transition of 137Cs is 8.4%. The detector was connected to a multichannel analyser PC board (MAESTRO-32) with 16,384 channels, high power supply of operating voltage of 920 volt as shown Figure 3, enables data acquisition, storage, and display of the acquired spectra. The detector is surrounded by a lead shielding, that is 5 cm in thickness, 9.5 cm in diameter, and 20 cm in high as shown Figure 2 to reduce the gamma ray background [5]. A constant counting time for calibration sources (241Am, 137Cs, 60Co, and 152Eu), for the background spectrum, and for measuring samples of 36,000 s was adopted. The background gamma-ray spectrum of the detection system was determined with an empty Marinelli beaker with the same geometrical conditions and the counting time as the samples, and was strip from the spectra of each sample. The radioactivity concentrations of 238U and 232Th in ppm were determined from the photopeaks of 214Pb (295 keV) and 212Pb (238 keV) respectively, whereas 40K was determined in % wt from the 1460 keV photopeak. The absolute detection efficiency of the NaI (Tl) detector was determined using 241Am,


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International Conference on Environmental Research and Technology (ICERT 2012) 137

Cs, 60Co, and 152Eu sources from the International Atomic Energy Agency (IAEA). The absolute efficiency of the detector for each γ-ray energy was then calculated from the formula

(1) where n is the net area under the full energy peak of gamma-ray energy E, t is the counting time, Pγ (E) is the gamma-ray emission probability at energy E, No is the activity of the source (Becquerel), λ is the decay constant = ln 2/T1/2. T1/2 is the half-life of the radionuclide, and td is the decay time. The efficiency calibration curve for the NaI (Tl) detector is shown in Figure 4. The 238U, 232Th and 40K concentrations measurements in ppm and % wt were done using GR-135. The spectrum analysis of soil and water samples was performed for 5400 s in the laboratory as shown in Figure 2. The GR-135 Exploranium system was calibrated aginst a 137Cs with FWHM= 7%.

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Fig. 3: The operating voltage of NaI (Tl) detector . 0.08

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Fig. 4: The efficiency calibration curve for the NaI (Tl) detector.


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RESULTS AND DISCUSSION Figure 5 shows the γ-ray spectra of two typical samples and detector calibration with MAESTRO software.

Fig. 5: A detector calibration and two typical samples spectrums with software. The results of the radioactivity analysis of soil samples and water samples in NMP were shown in Figures 5, 6 and 7 using NaI (Tl) and GR-135. The concentration obtained for 238U and 232Th of soil samples using GR-135 ranged from 0.6 ppm to 1.9 ppm and 2.3 ppm to 8.7 ppm, respectively, whereas the concentration of 40K ranged from 0.1 ppm to 0.6 ppm as shown in Figure 5. The 238U and 232Th concentration obtained of soil samples using NaI (Tl) ranged from 0.5 ppm to 9.8 ppm and 18.8 ppm to 90 ppm, respectively, whereas the concentration of 40K ranged from 0.3 ppm to 5.6 ppm as shown in Figure 6. The 238U and 232Th concentration of water samples obtained using GR-135 ranged from 0.3 ppm to 0.7 ppm and 1.4 ppm to 2 ppm, respectively, and the higher 238U and 232Th concentrations at Kg.Telaga Baru, Kedah, whereas the 40K concentration was not detected as shown in Figure 7.

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Fig. 5:

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Fig. 6: 238U, 232Th and 40K concentrations of soil samples in NMP using NaI (Tl) spectroscopy.

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Fig. 7:

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A comparison between NaI (Tl) spectroscopy and GR-135 spectrometer results of soil samples in laboratory shown in Figure 6. 50 40

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Fig. 8: Comparison between concentrations (40K, 238U, 232Th) by NaI(Tl) spectroscopy and GR-135 spectrometer of soil samples


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Tables 4 shows comparisons between studies conducted around the globe.

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K concentrations measurements in soil with different

Table 2: Comparison of gamma ray activity concentrations (Bq Kg-1) of top soil samples with the values reported for other countries of the world. Countries Serbia France Hungary Jordan Nigeria Norway Malaysia

Depth (cm) 5 5-10 0-20 2 10-15 3 0-10

40 K 332-925 348-802 176-567 179-307 69-530 31-564 97-1772

238 U 25-174 28-53 ND-1346 62-660 11-40 17-134 6-124

232 Th 26-70 22-42 15-41 18-25 12-46 4-52 76-366

References [6] [7] [8] [9] [10] [11] Present study

CONCLUSIONS In NMP, the higher and lower soil 238U concentrations occurred at Gelugor, Penang and Kg.Telaga Baru, Kedah, respectively. The higher and lower soil 238Th concentrations occurred at Penang Hill, Penang and Forest Research Complex, Perlis, respectively. Whereas, the higher and lower soil 40K concentrations occurred at Bayan Lepas and Penang Hill, Penang, respectively and the higher water 238U and 232Th concentration at Kg.Telaga Baru, Kedah. Concentrations measured by NaI (Tl) detector higher than concentrations measured by GR-135. The radionuclides concentrations in some studied sites exceed the norm.

ACKNOWLEDGMENT The authors are grateful to the Director General of Geological Survey, Malaysia. Financial support was provided by the School of Physics, Universiti Sains Malaysia through research grant no. 1001/PFPFIZIK 844085. REFERENCES [1] Eisenbud, M., Gesell, T., 1997. Environmental Radioactivity. 4th Edition. USA. [2] Almayahi, B. A., Tajuddin, A. A., Jaafar, M.S., 2012. 210Pb, 235U, 137Cs, 40K and 222 Rn Concentrations in Soil Samples After 2010 Thai and Malaysian Floods Advances in Biomedical Engineering Journal vol.6, 593-598. [3] Map of Geological of Peninsular Malaysia based on 8th. Edition Geological Map, 1985. [4] Garmin International Inc. GPS Garmin Model 60 CSX. Operator’s manual & Reference. 1200 East 151st street, Olathe, Kansas 66062, USA, 2007. [5] Tsoulfanidis, N., 1995. Measurement and Detection of Radiation. Taylor & Francis. [6] D. Popovic, D. Todorovic, M. Frontasyeva, J. Ajtic, M. Tasic, and S. Rajsic, Radionuclides and heavy metals in Serbia, Environmental Science and Pollution Research, vol.15, 509-20, 2008. [7] J. Perrina, F. Carrier, and L. Guillot, Determination of the vertical distribution of radioelements (K, U, Th, Cs) in soils from portable HP-Ge spectrometer measurements: A tool for soil erosion studies. Applied Radiation and Isotopes, vol.64, p.p 830-843, 2006. [8] Z. Papp, Z. Dezso, and S. Daroczy, Significant radioactive contamination of soil around a coal fired thermal power plant, Journal of Environmental Radioactivity,vol.59, p.p 191-205, 2002. [9] S. Al-Kharouf, I. Al-Hamarneh, and M. Dababneh, Natural radioactivity, dose assessment and uranium uptake by agricultural crops at Khan Al-Zabeeb, Jordan, Journal of Environmental Radioactivity, vol.99, p.p 1192-1199, 2008. [10] Agbalagba, E. O., Onoja, R. A., Evaluation of natural radioactivity in soil, sediment and water samples of Niger Delta (Biseni) flood plain lakes, Nigeria. Journal of Environmental Radioactivity 102 (2011) 667-671. [11] M. Dowdall, S. Gerland, and B. Lind, Gamma emitting natural and anthropogenic radionuclides in the terrestrial environment of Svalbard. The Science of the Total Environment,vol.305, p.p 229-40, 2003.


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