Sains Malaysiana 39(4)(2010): 599–605

Statistical Prediction of Environmental Gamma Radiation Doses, in Perak, Malaysia

(Ramalan Statistik Dos Sinar Gama Sekitaran, Perak, Malaysia)

Zalina Rahmat*, Ismail Bahari, Muhammad Samudi Yasir,  Redzuwan Yahaya & Amran Ab. Majid

School of Applied Physics, Faculty of Science and Technology

Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia

Diserahkan: 30 April 2009 / Diterima: 29 Januari 2010

ABSTRACT

The concentrations of Naturally Occurring Radioactive Material (NORM) and their corresponding terrestrial gamma radiation have been shown to be associated with certain lithology and soil types. A possible relationships among gamma radiation levels, and the lithology and soil types make it possible to predict ionizing radiation level of an area that cannot be directly measured. A study was carried out to statistically predict and validate environmental gamma radiation dose rates based on actual field measurements using a sodium iodide detector. Results obtained showed that the predicted dose rate (Dp) may be determined using a multiple correlation regression equation, Dp = 0.35DL + 0.82 Ds – 0.02, that integrates dose rates contributed by different lithological structures (DL) and soil types (Ds). Statistical analysis on 32 different lithology and soil type combinations showed that more than 50% of the predicted data were not significantly different from the data measured in the field. A predicted isodose map was subsequently plotted base on 4 dose rate classes ranging from 0.1 – 0.3 μSv h^-1.

Keywords: GIS; isodose map; Malaysia; NORM

ABSTRAK

Kepekatan bahan radioaktif tabii (NORM) yang terdapat dalam tanih dan aras gama terestrial berkaitan dipengaruhi oleh litologi dan jenis tanih. Kemungkinan wujudnya perhubungan antara aras sinar gama dan litologi serta jenis tanih ini memungkinkan ia digunakan untuk meramal aras sinaran mengion sesuatu kawasan yang tidak boleh diukur aras sinarannya secara langsung. Satu kajian telah dilakukan untuk meramal dan mengesahkan secara statistik kadar dos sinar gama sekitaran berdasarkan bilangan pengukuran sebenar di lapangan dengan menggunakan pengesan natrium iodid. Hasil kajian mendapati bahawa kadar dos ramalan (Dp) boleh ditentukan melalui persamaan regresi korelasi berganda, Dp = 0.35DL + 0.82 Ds – 0.02, yang menyepadukan kadar dos sumbangan struktur litologi (DL) dan jenis tanih (Ds) yang berlainan. Analisis statistik terhadap 32 kombinasi litologi dan jenis tanih yang berlainan mendapati lebih daripada 50% data ramalan adalah tidak berbeza secara signifikan dengan data yang diukur di lapangan. Sebuah peta isodos ramalan telah dibangunkan berdasarkan 4 kelas kadar dos antara 0.1 – 0.3 μSv h^-1.

Kata kunci: GIS; Malaysia; NORM; peta isodos

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*Pengarang untuk surat-menyurat; email: zalinarahmat@gmail.com