Some remarks on diurnal radon concentration at various locations in Peninsular Malaysia

Abstract

ABSTRACT 

A study was carried out to determine short term diurnal radon concentration at five locations in Malaysia. Two locations (KG & AP) are former tin mining areas that has been converted to housing area and training centre respectively, one a relatively new city (SA), that was formerly a rubber and oil palm plantation area, one older cities (KB) and one housing complex by the sea (LP). The study was carried out in 2005, 2006 and 2007 using a diffused-junction photodiode sensor continuous radon monitor. The monitor is recognized by the USEPA. In each location, measurements were carried out on at least ten sites. Former tin mining areas of KG and AP shows up to seven times higher indoor average than the average in the other three locations. However the indoor average in all locations is still below the action level of 4 pCiL^-1. For outdoor, the former tin mining areas average concentration was higher than the global average of 0.4 pCiL^-1. For the twenty four hours temporal variation the trend indicated that former tin mining areas concentration are always higher, and at time up to six fold higher. The hourly variation of all locations follows an identical trend of high concentration during early to late morning and drop in the afternoon till evening. The outdoor twenty four hour temporal average of former tin mining areas is consistently higher than the outdoor global average of 0.4 pCiL^-1. The strong correlation between indoor and outdoor concentration at AP, indicates that indoor radon might originates from outdoor environment. The study was also extended to estimate the effective dose (mSvyr^-1) of Rn-222 to the public.

 ABSTRAK 

Satu kajian telah dijalankan bagi menentukan kepekatan diurnal radon melalui pengukuran jangka pendek bagi lima lokasi di Malaysia. Dua lokasi (KG & AP) merupakan bekas kawasan lombong bijih timah yang masing-masing telah ditebusguna menjadi kawasan kediaman dan pusat latihan, satu bandaraya baru (SA) yang sebelum ini ialah kawasan ladang getah dan kelapa sawit, satu bandaraya lama (KB) dan yang terakhir sebuah kawasan kompleks kediaman di tepi pantai (LP). Kajian dijalankan dalam tahun 2005, 2006 dan 2007 menggunakan pengesan radon berterusan ( dengan sesor fotodiod simpang-teresap). Alat pengesan ini diiktiraf oleh USEPA. Bagi setiap lokasi, pengukuran sekurang-kurangnya dilakukan di sepuluh tempat. Hasil kajian di lokasi bekas tanah lombong (KG & AP) menunjukkan purata kepekatan radon dalam bangunan mencapai sehingga tujuh kali lebih tinggi berbanding lokasi-lokasi lain. Walau bagaimanapun kepekatan radon dalam bangunan tersebut masih lebih rendah daripada aras bertindak 4 pCiL^-1. bagi kawasan luar, kepekatan purata radon adalah lebih tinggi daripada kepekatan purata global iaitu 0.4 pCiL^-1. Bagi variasi kepakatan untuk tempoh 24 jam trend menunjukkan kepekatan di lokasi bekas tanah lombong sentiasa lebih tinggi. Bagii semua lokasi, trend variasi setiap jam menunjukkan pola seiras di mana kepekatan radon adalah tinggi sewaktu dinihari dan menurun menjelang tengahari dan petang. Untuk kawasan luar bangunan di lokasi bekas lombong, variasi setiap jam bagi tempoh 24 jam sentiasa lebih tinggi daripada 0.4 pCiL^-1. Bagi lokasi AP terdapat korelasi yang kuat anatara kepekatan dalam bangunan dan luar bangunan, yang menunjukkanradon dalam bangunan berkemungkinan berpunca dari luar bangunan. Hasil kajian juga membolehkan pengiraan dos efektif (mSvth^-1) bagi Rn-222 kepada orang awam.