The studies of ¹³⁷Cs content in the seawater surrounding Peninsular Malaysia had been carried out as part of the Malaysia Marine Radioactivity Database Project. The results of the measurement will serve as the baseline data and reference level to Malaysia. A numbers of sampling locations, including coastal and offshore at the East Coast (South China Sea) and West Coast (Straits of Malacca) of Peninsular Malaysia had been selected for the study. From each location at the coastal area, water samples were collected from the surface of the seawater. Meanwhile, for the offshore area, water samples have been collected at three different depths. Due to usual low concentration of ¹³⁷Cs in the marine environment, large volumes of seawater were collected and the co precipitation technique was employed to concentrate the ¹³⁷Cs. The activity of ¹³⁷Cs was determined by measuring the peak area under photo peak of the gamma spectrum at 661 keV, which is equivalent to the gamma intensity corrected to the HpGe detection efficiency and percentage of gamma ray abundance of the ¹³⁴Cs. At each study location, there were no significant differences for ¹³⁷Cs activities at 95% confidence interval. The activities of ¹³⁷Cs found to be quite uniformly distributed in the range of 2.33 to 5.00 Bq/m3and 1.76 to 4.76 Bq/m3for the South China Sea and the Straits of Malacca, respectively.
Natural radionuclides such as 210 Po and 210 Pb were analyzed in soft part of cockle (Anadara granosa) obtained from Kuala Selangor in the west coast Peninsular of Malaysia. The activity levels of both nuclides fluctuated within the size of cockles from 41.3 ± 2.5 Bq/kg to 114 ± 7 Bq/kg and 12.9 ± 1.7 Bq/kg to 96.8 ± 5.3 Bq/kg in dry weight (dwt) for 210 Po and 210 Pb, respectively. The level activity in wet weight (wwt) also varied from 8.60 ± 0.52 Bq/kg to 25.70 ± 1.63 Bq/kg and 2.47 ± 0.40 Bq/kg to 19.27 ± 1.05 Bq/kg for 210 Po and 210 Pb, respectively, probably related to the different of metabolic rate and growth of cockles. Activity ratio of 210 Po/ 210 Pb in dry weight also fluctuated from 0.93 to 6.41 with not related to the decay of 210 Pb.
Concentration of Ra-226 and Ra-228 activities in water and sediment samples were measured using the Liquid Scintillation Counter (LSC) and High Purity Germanium Gamma Spectrometry (HPGe). respectively. Concentrations of Ra-226 activity in sediment samples range from 18.93 Bg/ kg to 236.06 Bq/kg and for Ra-228 activity range from 12.59 Bg/kg to 410.60 Bq/kg. Meanwhile, concentrations of Ra-226 activity obtained in water samples range from 0.064 Bg/L to 0.199 Bq/L. These data indicate, that the distribution of Ra-228 and Ra-226 in the study area were varied from one sampling stations to another and is probably related to the contents of suspended particles.
Penentuan kepekatan aktiviti Ra-226 dan Ra-228 dalam sampel air dan sedimen dilakukan masing-masing dengan Pembilang Sintilasi Cecair (LSC) dan Spektrometri Gamma Germanium Lampau Tulen (HPGe). Kepekatan aktiviti Ra-226 dalam sampel sedimen adalah berjulat dari 18.93 Bg/kg hingga 236.06 Bq/kg dan kepekatan aktiviti Ra-228 berjulat dari 12.59 Bg/kg hingga 410.60 Bq/kg. Kepekatan aktiviti Ra-226 dalam sampel air yang diperolehi pula berjulat dari 0.064 Bg/L hingga 0.199 Bq/L. Ini menunjukkan taburan Ra-228 dan Ra-226 di kawasan kajian adalah berubah mengikut lokasi kajian dan berkemungkinan dipengaruhi oleh sifat kandungan bahan terampai.
The determination technique for U (238U, 235U, 234U) and Th (232Th, 230Th, 228Th) isotopes using alpha spectrometry was developed. The developed technique involved digestion, dissolution, coprecipitation, solvent extraction and electrodeposition methods. The NBS River Sediment and Rocky Flats Soil Standard Reference Materials were analysed to determine the accuracy of the technique. A good accuracy and high percentage recovery of the carrier (70 - 90%) indicated that the developed technique was suitable for U and Th isotopes determination. The technique was used to determine the U and Th concentration in monazite, xenotime and zircon samples. The results showed that the U and Th total concentrations were in the range of 21.03 to 171.25 Bq/g and 27.48 to 242.87 Bq/g respectively.
Kaedah penguraian, pemelarutan, pemendakan bersama, ekstraksi pelarut dan pemendapan elektrik telah dikaji dan digunakan untuk mendapatkan suatu teknik yang terbaik dalam penentuan isotop uranium 234U, 235U & 238U) dan torium 228Th, 230Th & 232Th) menggunakan sistem spektrometri alfa. Kepekatan isotop U dan Th dalam bahan rujukan piawai River Sediment dan Rocky Flats Soil (NBS) telah dianalisis untuk menentukan kejituan teknik yang dibangunkan. Kajian ini mendapati kepekatan isotop yang diperolehi adalah menghampiri nilai teraku (sijil) dan peratus perolehan semula pembawa yang besar (70-90%). Ini menunjukkan teknik yang dibangunkan sesuai digunakan untuk penentuan isotop uranium dan torium. Seterusnya teknik yang dibangunkan telah digunakan untuk menentukan kandungan uranium dan torium dalam sampel monazit, xenotim dan zirkon tempatan. Kepekatan jumlah isotop uranium yang diperolehi didapati berada dalam julat 21.03 - 171.25 Bq/g manakala kepekatan jumlah isotop torium pula terletak antara 27.48 - 242.87 Bq/g.
Kajian ini dijalankan bagi mengenalpasti kepelbagaian nisbah 234U/238U yang wujud di dalam jumlah pepejal terampai (TSS) pada lapan stesen yang berbeza di Kuala Selangor, Selangor. Prosedur kajian ini melibatkan proses persampelan, pemendakan, resin penukaran anion, pemendakan elektrik dan teknik pengiraaan spektrometer alfa. Nisbah 234U/238U adalah paling tinggi di Stesen 8 (234U/238U = 2.98) dan Stesen 2 (234U/238U = 3.34) pada persampelan pertama. Manakala pada persampelan kedua julat nisbah 234U/238U adalah lebih luas iaitu antara 1.29 (Stesen 4) hingga 11.57 (Stesen 6). Ini disebabkan oleh berlakunya pergerakan 234U bersama-sama mikroorganisme di dalam fasa terampai dan berlaku proses penurunan U(VI) kepada U(IV) yang akan memendakkan uranium daripada air ke dalam sedimen.
Analyses activities of 226 Ra and 228 Ra were conducted at ten stations of Pulau Redang, Malaysia. Dissolved radium isotopes such as 226 Ra and 228 Ra had shown enrichment at coastal area stations. Meanwhile, activities of both nuclides in the suspended particle matters were slightly in equilibrium with the activity ratio ranging from 0.88 – 1.86. The calculated distribution coefficient values (Kd) of 226 Ra and 228 Ra were in the range of 0.78 x 10 5 L g -1 to 5.56 x 10 5 L g -1 and 0.21 x 10 5 L g -1 to 1.86 x 10 5 L g -1 , respectively, indicate that most of the radium nuclides in the study area are strongly absorbed into the particulate phases. Therefore, low concentrations of suspended particles matter in the water column (< 10 mg L -1 ) have insignificant effects on the Kd values.