Natural radioactivity in cultivated land in the vicinity of a phosphate fertilizer plant in Nigeria

Natural radioactivity in soil and vegetable samples in cultivated land in the vicinity of an active phosphate fertilizer plant in Kaduna, Nigeria was carried out to assess the potential radiological impact of the plant on its immediate environment. The activity counting was carried out using sodium iodide gamma spectrometry. The annual committed effective dose for two vegetables in the farmlands due to uranium (²³⁸U) and thorium (²³²Th) was assessed. The mean activity concentration of radionuclides in the soil samples ranges from 20.5±7.3 to 31.6±4.1 Bq kg^?1 for ²²⁶Ra, 19.6±1.6 to 53.2±3.7 Bq kg^?1 for ²³²Th and 203.9±6.3 to 253.6±9.5 Bq kg^?1 for ⁴⁰K. The annual intake of ²³⁸U and ²³²Th from consumption of okra were 1.9 Bq kg^?1 and 5.22 Bq kg^?1 and for tomatoes 2.66 Bq kg^?1 and 5.1 Bq kg^?1 respectively. The committed effective doses from consumption of okra and tomatoes were 0.1 μSv y^?1 and 0.12 μSv y^?1 respectively.     

Radon exhalation and natural radiation exposure in low ventilated rooms

In the first part of this paper, the influence of radon (²²²Rn) exhalation rate from walls and air exchange upon its concentration in room air was considered using a simple mathematical room model. The exhalation rates have been determined in ten low ventilated rooms of ten villas in Jeddah city (Western Province) of Saudi Arabia. An electroprecipitation method has been applied for the determination of the ²²²Rn gas concentration in these rooms. The mean ²²²Rn gas concentration was found to be 46.80±8.80 Bq m^?3. The mean ²²²Rn exhalation rate was estimated to be 20.11±6.90 Bq m^?2 h^?1. The mean inhalation dose due to the exposure to ²²²Rn gas was calculated to be 1.18±2.30 mSv y^?1.The second part of this paper deals with a study of natural radionuclide contents of samples collected from the building materials of these rooms under investigations in part one. Analyses were performed in Marinelli beakers with a gamma spectroscopy system to quantify radioactivity concentrations. The collected samples revealed the presence of the uranium–radium (²²⁶Ra) and thorium (²³²Th) radioisotopes as well as ⁴⁰K. The mean activity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K was determined to be 48.30±5.08, 43.90±5.63 and 223.90±7.55 Bq kg^?1, respectively. These activities amount to a radium equivalent (Ra_eq) of 125.96±15.90 Bq kg^?1 and to a mean value of external hazard index (H_ex) of 0.34±0.04.     

Radioactivity level of soil around Baqiao coal-fired power plant in China

Natural radioactivity level of soil around Baqiao coal-fired power plant in China was determined using gamma ray spectrometry. The concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in the studied soil samples range from 27.6 to 48.8, 44.4 to 61.4 and 640.2 to 992.2 Bq kg^?1 with an average of 36.1, 51.1 and 733.9 Bq kg^?1, respectively, which are slightly higher than the average values of Shaanxi soil. The radium equivalent activity, the air absorbed dose rate and the annual effective dose rate were calculated and compared with the internationally reported or reference values. The radium equivalent activities of the studied samples are below the internationally accepted values. The air absorbed dose rate and the annual effective dose rate received by the local residents due to the natural radionuclides in soil are slightly higher than the mean value of Xi'an and worldwide.     

Natural radioactivity measurements in the granite rock of quarry sites,Johor, Malaysia

This study was conducted to determine the concentration of natural radionuclides in the granite rocks of selected quarry sites in Johor state, Malaysia and their possible radiological effects. The activity concentrations of ²³⁸U, ²³²Th and ⁴⁰K in the areas of study indicated varying values of ²³⁸U, ²³²Th and ⁴⁰K. The highest values of ²³⁸U and ²³²Th concentrations (67±1 and 85±2 Bq kg^?1, respectively) were observed at Kamad Quarry (IJM), whereas the highest value of ⁴⁰K concentration (722±18 Bq kg^?1) was detected in Kim Seng Quarry, while the values of activity concentration are lower in Hanson Quarry Products (Kulai) (25±0.5 for ²³⁸U, 24±0.5 for ²³²Th and 429±11 for ⁴⁰K). Overall, ⁴⁰K has the highest concentration in the granite rocks of the quarry sites, followed by ²³²Th and the least for ²³⁸U. The radium equivalent activity concentration was found in the range between 94 and 239 Bq kg^?1, the absorbed dose rate was found to be in the range between 47 and 112 nGy h^?1, and effective dose ranged from 58 to 137 μSv h^?1. Moreover, the internal and external hazard index values were given in results lower than unity.     

Natural radioactivity investigations in soil samples obtained from phosphate hills in the Russaifa region,Jordan

The specific activity, hazard index, and the annual effective dose of the terrestrial naturally occurring radionuclides (²³⁸U, ²³²Th, and ⁴⁰K) were determined in soil samples obtained from 20 sites of phosphate hills in the Russaifa region using an HPGe-detector of 50% relative efficiency. The resolution is 2 keV for the 1.33 MeV ⁶⁰Co. The soil activity ranged from 5.3 to 1201.1 Bq kg^?1 for ²³⁸U, 2.2 to 31.2 Bq kg^?1 for ²³²Th, and 19.4 to 288.4 Bq kg^?1 for ⁴⁰K. Annual effective dose was found in the range 0.03–0.69 mSv. The external hazard index ranged from 0.15 to 3.29 Bq kg^?1, while the global value given in UNSCEAR, 2000 publications is 1 Bq kg^?1. The average values of the radium equivalent activities were determined for all sites and they were found to be approximately 319 Bq kg^?1. This value is below the limit of 370 Bq kg^?1 recommended by . The average value of the radium equivalent activities for certain locations (sample numbers: 2, 3, 4, 9, 10, and 14) is above the same limit.     

Natural radioactivity and radiological hazards of building materials in Xianyang,China

Common building materials collected from Xianyang, China were analyzed for the natural radioactivity of ²²⁶Ra, ²³²Th and ⁴⁰K using γ-ray spectroscopy. The average activity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K in the studied building materials ranges from 13.4 to 69.9, 13.1–99.1 and 124.7–915.1 Bq kg^?1, respectively. The measured activity concentrations for these radionuclides were compared with the reported data of other countries and with the worldwide average activity of soil. To assess the radiation hazard of the natural radioactivity in all samples to the people, the radium equivalent activity, external hazard index, internal hazard index, indoor absorbed dose rate and total annual effective dose were estimated. The radium equivalent activities of the studied samples are below the internationally accepted values. The external hazard index and internal hazard index of all analyzed building materials are less than unity. The mean values of indoor absorbed dose rate for all building materials except for lime are higher than the world population-weighted average of 84 nGy h^?1 and the total annual effective dose values of building materials are lower than 1 mSv y^?1 except for some cyan brick samples. The study shows the measured building materials do not pose significant source of radiation hazard and are safe for use in the construction of dwellings.     

Radon concentration in hot springs of the touristic city of Sarein and methods to reduce radon in water

The aim of this research was to measure the efficiency of various simple methods to decrease the concentration of radon in hot springs of the touristic city of Sarein (a touristic city in northwest Iran). With the aid of “RAD7” radon detector, concentrations in water varied from 212 Bq m^?3 to 3890 Bq m^?3. Using 250 mL vials half-filled with water samples, our research showed that when the temperature of the water increased from 17 °C to 27 °C, the radon concentration decreased from 3230 Bq m^?3 to 745 Bq m^?3. The mixing of the sample at a speed of 500 rpm for 12 min led to a radon reduction of about 70%. Aerating the water sample with 0.2 L min^?1 of ambient air resulted in a 90% decrease in radon concentration in 6 min. Strong exponential correlations (>95%) were reported, which verified that the effectiveness of these methods in reducing dissolved gas in the waters used would be high.     

Determination of radionuclides in the environment using gamma-spectrometry

Summary Seventy nine samples, including soil and rock, were collected from the agrestic region of the State of Pernambuco, Brazil. The activity concentrations of ²³⁸U and ²²⁶Ra in the samples were determined by gamma-spectrometry using an HPGe detector. The concentrations of ²³⁸U were 22 Bq ^. kg^-1 to 22 kBq ^. kg^-1. The concentrations of ²²⁶Ra were 14 Bq ^. kg^-1 to 17 kBq ^. kg^-1. The ²³⁸U/²²⁶Ra ratios in the soil were 0.7 to 3.4 (arithmetic mean 1.7). The radiometric data were evaluated to explain ²³⁸U and ²²⁶Ra migration in the soil and the possible consequences to the environment.     

Heavy elements concentrations,physiochemical characteristics and natural radionuclides levels along the Saudi coastline of the Gulf of Aqaba

This paper represents the first work on the concentrations of heavy elements, physiochemical characteristics and activity levels of the naturally occurring radionuclides in the Saudi Arabian coastline of the Gulf of Aqaba. Concentrations of 19 heavy elements were measured, namely: Ag, Al, As, Ba, Be, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Se, V and Zn. The radioactivity levels of ²³⁸U, ²³²Th and ⁴⁰K were estimated to be: 17 ± 1.7, 22.5 ± 3.7 and 649.6 ± 64.2 Bq kg^?1, respectively. The measurements were carried out using inductively coupled plasma-mass spectrometry (ICP-MS). In addition, physiochemical characteristics of 19 sediment samples (i.e., saturation percentage, pH, electrical conductivity, organic matter, cation exchange capacity and content of clay, silt and sand) have been determined. Indications for high correlation between most heavy elements are found. The correlation between heavy elements and the radionuclides ²³⁸U, ²³²Th and ⁴⁰K was generally significant.     

Natural radioactivity levels in mineral,therapeutic and spring waters in Tunisia

Radioactivity measurements were carried out in 26 groundwater samples from Tunisia. Activity concentrations of uranium were studied by radiochemical separation procedures followed by alpha spectrometry and that for radium isotopes by gamma-ray spectrometry.The results show that, the concentrations in water samples range from 1.2 to 69 mBq/L.1, 1.3 to 153.4 mBq/L, 2.0 to 1630.0 mBq/L and 2.0 to 1032.0 mBq/L for ²³⁸U, ²³⁴U, ²²⁶Ra and ²²⁸Ra, respectively. The U and Ra activity concentrations are low and similar to those published for other regions in the world. The natural radioactivity levels in the investigated samples are generally increased from mineral waters through therapeutic to the spring waters.The results show that a correlation between total dissolved solids (TDS) values and the ²²⁶Ra concentrations was found to be high indicating that ²⁶⁶Ra has a high affinity towards the majority of mineral elements dissolved in these waters. High correlation coefficients were also observed between ²²⁶Ra content and chloride ions for Cl^?–Na⁺ water types. This can be explained by the fact that radium forms a complex with chloride and in this form is more soluble.The isotopic ratio of ²³⁴U/²³⁸U and ²²⁶Ra/²³⁴U varies in the range from 0.8 to 2.6 and 0.6 to 360.8, respectively, in all investigated waters, which means that there is no radioactive equilibrium between the two members of the ²³⁸U series. The fractionation of isotopes of a given element may occur because of preferential leaching of one, or by the direct action of recoil during radioactive decay.The annual effective doses due to ingestion of the mineral waters have been estimated to be well below the 0.1 mSv/y reference dose level.     

Natural radioactivity in different commercial ceramic samples used in Yemeni buildings

In this work we calculated the radioactivity concentrations of the natural radioactive nuclides ²³⁸U, ²³²Th, ²²⁶Ra and ⁴⁰K for 10 commercial samples collected from 10 different companies which are used in the construction of Yemeni buildings. Gamma ray spectroscopy was used to analyze the samples and the concentrations of radioisotopes were determined using a hyper-pure germanium (HPGe) detector in Bq/kg dry-weight. The average concentrations of ²³⁸U, ²³²Th, ²²⁶Ra and ⁴⁰K were found to be 131.4, 83.55, 131.88 and 400.7 Bq/kg respectively. Different hazard indices were also determined. The results showed that the average radium equivalent activity (Ra_eq), the absorbed dose rate (D_r), the annual effective dose equivalent (AEDE), the external hazard index (H_ex) and representation level index (I_γ) were: 307.52 Bq/kg, 139.31 nGy/h, 1.40 mSv/yr, 0.83 and 2.15 respectively. The mean value of (Ra_eq) obtained in this study is in good agreement with that of the international value while the mean values of the other indices are found to be higher than the international reference values. The measured activity concentrations for these radionuclide were compared with the reported data obtained from similar materials used in other countries.     

Radioactivity measurements and radiation dose assessments due to natural radiation in Karabük (Turkey)

In this work, the radionuclide activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in surface soils and radon levels in dwellings of Karabük, Turkey were determined in order to evaluate the environmental radioactivity. Concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K radionuclides were determined using gamma spectrometry with using HPGe detector. The etch track detectors (CR-39) were used to determine the distribution of radon concentrations. The average activity concentrations for ²²⁶Ra, ²³²Th and ⁴⁰K were found as 21.0, 23.5 and 363.5 Bq kg⁻¹, respectively. The calculated average annual effective dose equivalent from the outdoor terrestrial gamma radiation from ²²⁶Ra, ²³²Th and ⁴⁰K is 53.5 μSv y⁻¹. The average radon concentration and annual effective dose equivalent of ²²²Rn in Karabük dwellings were obtained 131.6 Bqm⁻³ and 3.32 mSv y⁻¹, respectively. The evaluated data were compared with the data obtained from different countries.     

Evaluation of 222Rn and 226Ra concentrations in cement and limestone of Sheikh Buddin Hill,Pezu, Pakistan using different techniques

Lucky Cement Factory, Pezu is using limestone of Sheikh Buddin Hills as a raw material in cement. Workers of the factory have direct and general public have indirect exposure to radiological hazard due to natural radionuclides present in limestone. To address the radiological hazards, limestone, mixed (limestone+clay) and cement samples were evaluate for concentrations of ²²²Rn and ²²⁶Ra using CR-39, RAD7 and HPGe detectors. Maximum mean values of ²²²Rn using CR-39 and RAD7 detectors were found 1447 ± 198 and 1416 ± 74 Bq.m^?3 in cement samples and minimum were found in 536 ± 122 and 525 ± 45 Bq.m^?3 limestone samples, respectively. Maximum mean value of radon exhalation rate of 12.28 ± 1.68 Bq.m^?2 h^?1 in cement samples was found below the world average value of 57.6 Bq.m^?2 h^?1. Maximum mean values of ²²⁶Ra measured by CR-39 and HPGe detectors were found 24.25 ± 3.35 and 23.6 ± 0.70 Bq.kg^?1 in cement samples and minimum were found in 8.98 ± 2.02 and 9.19 ± 0.40 Bq.kg^?1 limestone samples, respectively. A positive correlations (R² = 0.9714) using CR-39 and RAD7 detectors and (R² = 0.9573) using CR-39 and HPGe detectors were obtained for the concentrations of ²²²Rn and ²²⁶Ra, respectively. Maximum mean value of annual effective dose of 347.78 ± 47.58 µSv.y^?1 in cement samples was found below the world average value of 1100 µSv.y^?1.     

Natural radioactivity in soil samples of Yelagiri Hills,Tamil Nadu,India and the associated radiation hazards

The natural radioactivity of soils at Yelagiri hills has been studied in this paper. The radioactivities of 25 samples have been measured with a NaI(Tl) detector. The radioactivity concentrations of ²³⁸U, ²³²Th and ⁴⁰K ranged from ≤2.17 to 53.23, 13.54 to 89.89 and from 625.09 to 2207.3 Bq kg^?1, respectively. The measured activity concentrations for these radionuclides were compared with world average activity of soil. The average activity concentration of ²³²Th in the present study is 1.19 times higher than world median value while the activity of ²³⁸U and ⁴⁰K is found to be lower. In order to evaluate the radiological hazard of the natural radioactivity, the radium equivalent activity Ra_eq, the absorbed dose rate D_R, the annual effective dose rate and the external hazard index (H_ex) have been calculated and compared with the internationally approved values. The study provides background radioactivity concentrations in Yelagiri hills.     

Measurement of activity concentration of primordial radionuclides in soil samples from Thirthahalli taluk and the assessment of resulting radiation dose

The activity concentration of primordial radionuclides ²²⁶Ra, ²³²Th, and ⁴⁰K in soil samples of Thirthahalli taluk were measured systematically by using a low background HPGe detector coupled to 16 K MCA. The measured activity concentration of ²²⁶Ra lies between 5.1?±?0.2 and 79.5?±?1.7 Bq kg^?1with an average activity of 25.99 Bq kg^?1, ²³²Th ranges from 5.1?±?0.3 to 95.3?±?2.2 Bq kg^?1with an average activity of 33.60 Bq kg^?1and that of ⁴⁰K varies from 18.3?±?1.5 to 833.4?±?17.5 Bq kg^?1with an average activity of 175.52 Bq kg^?1. Higher concentration of these radionuclides were found in the soil samples where the regional geology is granites. The consequential gamma dose and the corresponding radiation hazard was also estimated and is found to be within the permissible limits. The possible radiological impact on the public was also determined and these results are presented in this paper.     

Radioactivity mapping of north western areas of Pakistan

Summary A systematic study of natural and fall-out radionuclides was carried out with the environmental samples of soil, vegetation and water from some regions of North West Frontier Province (NWFP) of Pakistan. The pretreatment of the samples was performed in the laboratory using IAEA recommended methods. The analysis of gamma-emitters such as ⁴⁰K, ²²⁶Ra, ²³² Th and ¹³⁷Cs was performed with a high purity germanium detector (HPGe). For the determination of ⁹⁰Sr, a liquid scintillation counting system was used. The average specific activities of ⁴⁰K, ²²⁶Ra, ²³² Th and ¹³⁷Cs have been found to be 307±101 Bq ^. kg^-1, 10.2±3 Bq ^. kg^-1, 24±6 Bq ^. kg^-1 and 2.8±1.3 Bq ^. kg^-1, respectively, in soil samples. Vegetation samples have smaller values of specific activities and even the analysis of water samples showed values less than LLD for earlier reported radionuclides. Other parameters like hazard indices, radium equivalent activities, absorbed dose rates and effective dose equivalents have also been determined. All these parameters have values less than their respective limiting values representing that the surveyed areas have no significant hazard from health point of view. Analysis of ⁹⁰Sr for all the samples showed results below LLD. The present study provides a general background of the detectable radionuclides for the surveyed areas that will be helpful in any radiological emergency.     

Studies on radionuclides around Hemavathi river basin of Karnataka,India

The activity concentration and total annual effective dose of the terrestrial naturally occurring radionuclides (²³²Th, ²²⁶Ra and ⁴⁰K) were measured in soil and rock samples collected from various locations of Hemavathi river basin in Karnataka, using HPGe detector. The results revealed that activity concentration of radionuclides ²²⁶Ra, ²³²Th and ⁴⁰K in the soil had geometrical mean values of 16.7 ± 0.6, 33.9 ± 1.2 and 359.9 ± 9.2 Bq kg^?1, respectively. In rock samples activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K had geometrical mean values of 20.2 ± 0.7, 18.0 ± 0.9 and 276 ± 9.6 Bq kg^?1, respectively. The external Hazard index and indoor hazard index were found to be within safety limits prescribed by European commission 1999 report.     

Measurement of natural radioactivity and radiation hazard assessment in the soil samples of Visakhapatnam,Andhra Pradesh,India

The present work aims to measure and estimate radioactivity and hazardous radiation indices of the soil. Soil samples were collected from various locations in the Visakhapatnam district in Andhra Pradesh, India. The measurement of specific activity of ²²⁶Ra, ²³²Th, and ⁴⁰K radionuclides is carried out with the help of HP-Ge based gamma spectrometer system. Activity concentration of radionuclides in the samples ²²⁶Ra, ²³²Th and ⁴⁰K ranged from 20 ± 2 to 91 ± 2 Bq.kg^-1, 45 ± 3 to 365 ± 3 Bq.kg^-1, and 400 ± 9 to 607 ± 8 Bq.kg^-1, and the respective mean values are 53.36 Bq.kg^-1, 203.74 Bq.kg^-1 and 479.19 Bq.kg^-1. The measured mean value of the absorbed dose rate is 171.41 nGy.h^-1, which was beyond the worldwide mean outdoor value of 60 nGy.h^-1. Thus, the annual effective dose estimated from the above value is 1.04 mSv.y^-1. The correlation was done among the measured ²²⁶Ra, ²³²Th, and ⁴⁰K activity concentrations. The estimated radium equivalent dose is 381.60Bq.kg^-1. The estimated health hazard index and annual effective dose rates of dwellers of Visakhapatnam were studied and compared to Indian average values. The study will help to generate the baseline data for assessing hazard indices to the public and geological mapping of natural radiation in India.     

Activity concentrations of 226Ra, 228Ra, 222Rn and their health impact in the groundwater of Jordan

The activity concentrations of ²²⁶Ra, ²²⁸Ra and ²²²Rn were measured in 87 groundwater samples to estimate the activity concentrations of these radionuclides and health impact due to intake of these radionuclides in groundwater of Jordan. The mean activity concentrations of ²²⁶Ra, ²²⁸Ra and ²²²Rn in groundwater were found to be 0.293?±?0.005 Bq L^?1, 0.508?±?0.009 Bq L^?1 and 58.829?±?8.824 Bq L^?1, respectively. They give a mean annual effective dose of 0.481 mSv with mean lifetime risk of 24.599?×?10^?4, exceeding the admissible limit of 10^?4. Most of the received annual effective dose (59.15% of the total) is attributed to ²²⁸Ra.

     

Natural radioactivity levels of limestone rocks in northern Iraq using gamma spectroscopy and nuclear track detector

The activity concentration of radionuclides, such as ²³⁸U, ²²⁶Ra and ⁴⁰K of limestone rocks in northern Iraq was measured using gamma spectroscopy. The radionuclide activities were obtained and discussed. CR-39 nuclear track detector was used to measure the radon exhalation rates as well as the effective radium contents of these samples and are found to correspond with uranium concentration values measured by NaI(Tl) detector in the corresponding limestone rocks samples. The absorbed gamma dose rates in air due to the presence of ²³⁸U, ²²⁶Ra, ⁴⁰K and cosmic ray contribution varied between 105.3 and 223.11 nGy/h. The annual effective dose of each sample has been calculated. The correlation between activities of ²²⁶Ra, ²²²Rn exhalation rates and ²³⁸U is explained. Results show a symmetrical distribution of activity concentrations of primordial of radionuclides in selected samples. The values of all studied radionuclides are considered to be a typical level of natural background and compared with results of similar investigations carried out else where.