Natural Radioactivity, Radon Concentration And Heavy Metals In Soil And Water In Kedah, Malaysia
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Date
2015-09
Authors
Ahmad, Nisar
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Abstract
Natural radioactivity, 222Rn concentration and heavy metals (Pb, Ni, Cr, Cd and As) were determined in 31 uncultivated soil, 42 cultivated soil and 51 drinking and irrigated water to investigate the effects of human activities in Sungai Petani, Baling and Kulim in the state of Kedah, Malaysia. This study was conducted using High Purity Germanium (HPGe) to measure natural radioactivity, CR-39 NTDs and Continuous Radon Monitor (CRM) to measure 222Rn concentration in soil, Rad-7 to measure 222Rn 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 cultivated 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 (Iγ), radium equivalent activity (Raeq), external hazard index (Hex) and outdoor external dose (Dout)), indoor hazard indices (such as alpha index (Iα), internal hazard index (Hin) and indoor external dose (Din)) and annual effective doses (such as outdoor effective dose (Eout) and indoor effective dose (Ein)) from soil samples were found. All the uncultivated and cultivated soil samples have radium equivalent activities within the recommended level 370 Bq kg-1 reported by OECD, except samples collected from Taman Desa Anggerik, Baling, Kampong Guar Station, Kampong Kepala Bukit, Kampong Tandop, Kampong Dalam Wang, Kampong Janjung Merbau and Kampong Bagan Sena. Outdoor and indoor absorbed dose rates were found higher than the safety limits of 70 nGy h-1 and 51 nGy h-1, respectively reported by UNSCEAR. The average values of Hex, Hin, Iα and Iγ in uncultivated and cultivated soil were found lower than unity, except cultivated 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 limit 1 mSv y-1 for general public recommended by ICRP. The results obtained for 222Rn concentration in uncultivated soil having different grain size show that 222Rn concentration increase with the increase in grain size. The values of radon exhalation rate from uncultivated and cultivated soil were found lower than safety limit 57.6 Bq m-2 h-1. The maximum value of waterborne radon was found 20.0±2.2 Bq/L in well water and minimum was found 1.4±0.27 Bq/L in tap water. The maximum values of Pb, Ni, Cr, Cd and As in cultivated soil were found in chili farms with the highest values of 2.29±0.05 mg kg-1, 2.76±0.045 mg kg-1, 2.05±0.029 mg kg-1, 0.52±0.044 mg/kg and 0.58±0.042 mg- kg-1, respectively and minimum were found in palm oil farms with the lowest values of below detection limit, 0.21±0.022 mg kg-1, below detection limit, 0.03±0.024 mg kg-1 and 0.04±0.006 mg kg-1, respectively. The maximum values of Ni, Pb, Cd, Cr and As in water were found in stream water with the highest values of 12.2±1.2 μg/L, 9.74±1.14 μg/L, 4.82±0.72 μg/L, 5.4±1.16 μg/L and 7.2±0.8 μg/L, respectively and minimum were found in tap water with the lowest values of 0.28±0.1 μg/L for Ni and 0.64±0.14 μg/L, 0.1±0.04 μg/L, 0.28±0.06 μg/L and below detection limit for Pb, Cr, Cd and As, respectively. However, all the soil and water samples have heavy metals concentration below the safety limits recommended by different agencies.
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Physics (General)