NATURAL RADIOACTIVITY AND RADON CONCENTRATION IN INTRUSIVE ROCK FORMATION AREA IN KEDAH, MALAYSIA

NATURAL RADIOACTIVITY AND RADON CONCENTRATION IN INTRUSIVE ROCK FORMATION AREA IN KEDAH, MALAYSIA

 

ABSTRACT

 

Natural radioactivity, radon concentration and heavy metals measurements in virgin and agriculture soil and radon concentrations in water samples collected from Sungai Petani, Baling and Kulim, Malaysia, comprising the levels of natural radioactivity and radon concentration in virgin and agriculture soil and radon concentration in water obtained from different sources were conducted. This study was conducted using High Purity Germanium (HPGe) to measure natural radioactivity, CR-39 and Continuous Radon Monitor (CRM) to measure radon concentration in soil, Rad-7 to measure radon concentration in water and Atomic Absorption Spectrometer (AAS) to measure the level of heavy metals in soil and water samples. The average activity concentrations of 226Ra, 232Th and 40K were found higher in agriculture soil and to be within those reported for other countries worldwide. Based on the investigated activity concentrations of 226Ra, 232Th and 40K, outdoor hazard indices (such as Gamma index, Radium equivalent activity, External hazard index and outdoor external dose), indoor hazard indices (such as Alpha index, internal hazard index and indoor external dose) and annual effective doses (such as outdoor effective dose and indoor effective dose) from soil samples were calculated to assess to health risk. All the virgin and agriculture soil samples have radium equivalent activities within the recommended level 370 Bq/kg reported by OECD, except samples of sites B2, SPB4, SPC2, BB1, BC1, BC2 and KB4. Outdoor and indoor absorbed doe’s rates were found higher than safety limit 70 nGy h-1 and 51 nGy h-1, respectively reported by UNSCEAR. The average values of Hex, Hin, Iα and Iγ in virgin and agriculture soil were found lower than unity, except agriculture soil of Baling where the average values of Hin, Iγ were slightly higher than unity. The values of indoor annual effective dose and outdoor annual effective dose were found below the safety limits 20 mSv y-1 for radiation workers and 1 mSv y-1 for general public recommended by ICRP. The results obtained for

radon concentration in virgin soil having different grain size show that radon exhalation rate increase with the increase in grain size. The values of radon exhalation rate from virgin and agriculture soil were found lower than safety limit 57.600 Bq/m2/h. The maximum value of waterborne radon was found in well water and minimum was found in tap water. The concentrations of heavy metals in soil collected from chili farms were found higher than palm oil and banana farms, while in case of water samples, the concentrations were found higher in stream water and lower in tap water. However, all the soil and water samples have heavy metals concentration below the safety limits recommended by different agencies.