Levels and effects of natural radionuclides in soil samples of Garhwal Himalaya

Distribution of natural radionuclide gives significant parameter to assess the presence of gamma radioactivity and its radiological effect in our environment. Natural radionuclides are present in the form of ²²⁶Ra, ²³²Th and ⁴⁰K in soil, rocks, water, air, and building materials. Distribution of natural radionuclides depends on the type of minerals present in the soil and rocks. For this purpose gamma spectrometer is used as tool for finding the concentration of these radionuclides. The activity concentration of naturally occurring radionuclides ²²⁶Ra, ²³²Th and ⁴⁰K in these soil samples were found to vary from of 8 ± 1 Bq/kg to 50 ± 10 Bq/kg with an average 20 Bq/kg, 7 ± 1–88 ± 16 Bq/kg with an Average 26 Bq/kg and 115 ± 18–885 ± 132 Bq/kg with an average 329 Bq/kg, respectively. In this paper, we are presenting the radiological effect due to distribution of natural radionuclide present in soil of Garhwal Himalaya.     

Natural radioactivity of some local building materials in the middle Euphrates of Iraq

People are exposed to ionizing radiation from the radionuclides that are present in different types of a natural sources, of which building materials is one of the most important sources. Radionuclides in building materials belonging to ²³⁸U, ²³²Th series as well as radioisotope of Potassium ⁴⁰K are the major contributors of outdoor terrestrial natural radiation. This study is the first ever in Iraq. In order to estimate the radiological impact to the dweller, the activity concentration of radionuclides present in various Iraqi building materials were analyzed using Gamma-spectrometry. The radiation hazard indexes were calculated based on the above results. The results showed that the activity concentration of ²³⁸U, ²³²Th and ⁴⁰K was between 32.9 Bq/kg (Najaf gypsum)–179.32 Bq/kg (Karbala cement), 1.98 Bq/kg (Najaf sand)–17.43 Bq/kg (Qadisiya brick) and 108.73 Bq/kg (Karbala sand)–977.79 Bq/kg (Najaf brick), respectively. All values of Radium equivalent activities were found to be less than the maximum permissible limit and the internal hazard indexes (except Karbala cement) were less than unity for the radiation hazard. Some samples have external annual dose and external hazard index values greater than unity.     

Radioactive Contamination of Lichens and Mosses Collected in South Shetlands and Antarctic Peninsula

Samples belonging to two species of lichen and one of moss collected on the Antarctic seashore (King George Island, Deception, Antarctic Peninsula) were analysed for gamma-emitters using HPGe gamma-spectrometry, and for alpha-emitters using alpha-spectrometry with silicon detectors. Observed ¹³⁷Cs activities show large variations: from 4.1±0.4 to 74±3 Bq/kg. Total activity of ²¹⁰Pb changed from <2 to 125±35 Bq/kg. The ^2391240Pu activity ranged from 0.07±0.02 to 2.95±0.16 Bq/kg. The activity of ²³⁸Pu ranged from <0.02 to 0.64±0.04 Bq/kg. Maximum ²³⁸U and ²³⁴U activity was 7 Bq/kg, respectively, and 0.3 Bq/kg for ²³⁵U, whereas minimum activities were below 0.5 Bq/kg for ²³⁴U and ²³⁸U and about 0.02 Bq/kg for ²³⁵U. The ²³⁵U to ²³⁸U activity ratio for most of the samples was natural. Thorium activities were about two times lower than those for uranium. The activities of ¹⁴⁷Sm ranged from 0.014±0.002 to 1.0±0.2 Bq/kg. One sample had relatively high activity of ²⁴¹Am: 3.38±0.11 Bq/kg, another did not exceeded 1 Bq/kg. Observed activity ratios confirmed differences between mosses and lichen accumulation properties for radionuclides. Lichens are more selective for plutonium accumulation. Some radiocesium and probably also americium can be leached from them.     

Geochemistry and health burden of radionuclides and trace metals in shale samples from the North-Western Niger Delta

Organic sedimentary rock samples were collected from three Oil Wells in the North-Western Niger Delta, Nigeria in order to determine their natural radioactivity and elemental geochemistry, with the aim of determining the concentrations of major radionuclides and their radiological and environmental health implication. The PIXE method of IBA technique and an accurately calibrated Si(Li) detector system was used to measure the elemental concentration of the sediment samples. The radionuclides identified belong to the decay series of naturally occurring radionuclides headed by ²³⁸U and ²³²Th along with the non-decay series radionuclide, ⁴⁰K. The activity concentrations of the radionuclides and their derived dose were then calculated. The average activity concentrations of ⁴⁰K were 248 Bq/kg for Well A, 261 Bq/kg for Well B and 273 Bq/kg for Well C. For ²³²Th the activity concentrations were 1,043 Bq/kg for Well A, 1,400 Bq/kg for Well B, 1,434 Bq/kg for Well C. ²³⁸U activity concentrations were 2,210, 3,508 and 250 Bq/kg for the Oil Wells A, B, C, respectively. The equivalent dose ranges from 8.5 ± 1.1 to 24.3 ± 2.1 mSv/year with a mean of 14.5 ± 2.2 mSv/year for Oil Well A, 2.4 ± 0.1–75.0 ± 1.2 mSv/year with a mean of 21.5 ± 1.1 mSv/year for Oil Well B and 3.7 ± 0.2–10.7 ± 0.6 mSv/year with a mean of 9.4 ± 2.5 for Oil Well C. The detected trace metals were majorly V, Ni, Pb, Fe, Cr, Cu, Zn, Co and their concentrations together with those of the radionuclides are compared with the relevant world standard limits. The results obtained were high, and hence, the radioactivity level and trace element content of the sediment samples from the North-Western Niger Delta Oil province could constitute health hazard to occupationally exposed workers, and to the public if not properly disposed. However, despite the careful disposal practice claims by the Oil industries, and given the high concentrations, the sediments could still pose an intrinsic health hazard considering their cumulative effects in the environment.     

NORM activity concentration in sediment cores from the Peninsular Malaysia East Coast Exclusive Economic Zone

Study for distribution of Naturally Occurring Radioactive Materials (NORM) i.e. ²²⁶Ra, ²²⁸Ra and ⁴⁰K in the east coast of Peninsular Malaysia Exclusive Economic Zone (EEZ) was carried out as part of the national marine environment project. Sixteen marine sediment cores from selected locations within the EEZ were collected for determination of NORM activity concentrations using high-purity germanium (HPGe) gamma spectrometer. From the measurement, the activity concentration of ²²⁶Ra, ²²⁸Ra and ⁴⁰K is ranged from 16 ± 4 Bq/kg to 46 ± 6 Bq/kg (total mean 30), 28 ± 7 Bq/kg to 87 ± 11 Bq/kg (total mean 56) and 171 ± 33 Bq/kg to 690 ± 89 Bq/kg (total mean 420), dry wt., respectively. The activity concentrations of radionuclides in most of the core were quite uniform suggesting that there were thorough vertical mixed of sediment throughout the core. The results obtained were also in good agreement with those previous reported from other countries in the region and therefore can be used to enhance present radioactivity database. The calculated external hazard values were ranged from 0.25 to 0.51 with the mean of 0.38 (less than unity) showed little risk of external hazard to the workers handling the sediments and it was likely low level of the mainland natural gamma-radiation in the east coast of Peninsular Malaysia.     

90Sr and239+240Pu238Pu241Am in some samples of mushrooms and forest soil from Poland

Strontium-90, plutonium and americium activity concentrations in a few samples of forest soils, some species of mushrooms and fern leaves have been determined. These results are compared with cesium activity concentrations in the same materials obtained in a previous work. Radiochemical procedures are described. The origin of the contamination (Chernobyl accident or nuclear test explosion release) is discussed. The⁹⁰Sr activity concentration ranges from 0.6 Bq/kg (mushroom samples) to 48.4 Bq/kg (fern leaves). For^239+240Pu, it ranges from not detected above background (mushrooms, fern) to 10.8 Bq/kg (humus layer of forest soil). The maximum concentration of²⁴¹Am is found to be 2.4 Bq/kg (humus sample) and for²³⁸Pu it is 0.85 Bq/kg (also in the humus sample).     

Terrestrial absorbed dose rate measurement in the Jhangar valley of Pakistan

Specific activity of natural radionuclides; ²²⁶Ra, ²³²Th and ⁴⁰K were measured in the agricultural soil of eastern salt range of Pakistan using gamma ray spectrometry. The soil samples were collected within the ploughing region (up to 12 cm depth) and processed before analysis. The average specific activities of different radionuclides in the dry mass of soil samples were: ⁴⁰K, (666 Bq/kg), ²²⁶Ra (51 Bq/kg), and ²³²Th (59 Bq/kg). The average outdoor terrestrial absorbed dose rate in air from gamma radiation one meter above ground surface was found to be 93 nGy/h.     

Comparison of analytical methods used to determine <Superscript>235</Superscript>U, <Superscript>238</Superscript>U and <Superscript>210</Superscript>Pb from sediment samples by alpha,beta and gamma spectrometry

An intercomparison of the methodology (alpha, beta and gamma spectrometry) used for ²³⁸U, ²³⁵U and ²¹⁰Pb determination was carried out based on 38 sediment samples. The activity range of the samples varied from 10–700 Bq/kg for ²¹⁰Pb, 1–35 Bq/kg for ²³⁵U and 10–800 Bq/kg for ²³⁸U. Results obtained using the three methods were not statistically different at high activity levels, but agreement between the results decreased at lower sample activity levels. For ²¹⁰Pb, the smallest difference was found between alpha and gamma spectrometry. A good correlation between results from alpha and gamma spectrometry was observed over the whole activity range. In beta spectrometry, the results were slightly higher than those obtained by alpha or gamma spectrometry due to the impurity of ²²⁸Ra. In ²³⁸U analysis, good correspondence was observed between ²³⁸U determined by gamma and alpha spectrometry, particularly at higher ²³⁸U activity concentrations over 100 Bq/kg. In ²³⁵U analysis, attention needs to be paid to interference from ²²⁶Ra and its reduction.     

Determination of technetium-99 from the aspect of environmental radioactivity

A radioanalytical procedure has been developed for the determination of⁹⁹Tc in environmental samples. The procedure consists of precipitation, solvent extraction, ion exchange, electrodeposition and radiation measurement. Rhenium was used as a non-isotopic carrier of⁹⁹Tc. On the basis of 3σ counting error, the detection limits were 4.9·10^?5 Bq/l, 7.4·10^?3 Bq/kg wet and 7.4·10^?2 Bq/kg dry for water, biota and soil samples, respectively. Sea water, seaweeds (brown algae) and soils were collected to evaluate the present levels of⁹⁹Tc in Japan. The level of⁹⁹Tc in sea water was ca. 1·10^?4 Bq/l around Japan. Among the seaweeds (brown algae), Ishige okamurai showed the highest concentration of 5.8·10^?2 Bq/kg wet tissue and the highest concentration factor of 583. The level of⁹⁹Tc in the organic rich surface soil was ca. 1 Bq/kg dry soil in Fukuoka.     

Separation of strontium from calcium by the use of sodium hydroxide and its application for the determination of long-term background activity concentrations of <Superscript>90</Superscript>Sr in 100 km area around Kozloduy Nuclear Power Plant (Bulgaria)

The method for the determination of ⁹⁰Sr which employs sodium hydroxide for the separation of strontium from calcium was further improved introducing the use of elevated temperatures. The results from 11-year study of background activity concentrations of ⁹⁰Sr in different environmental objects in 100 km zone around Kozloduy Nuclear Power Plant (Bulgaria) are presented as an application of the analytical method. The measured mean values are as follows: air precipitation − 0.0015±0.0009 Bq(m^2.d), tap water − 0.0017±0.0012 Bq/L, soil − 1.90±1.26 Bq/kg, grass − 1.54±0.80 Bq/kg, milk − 0.023±0.012 Bq/L and for the Danube river: water − 0.0046±0.0026 Bq/L, bottom sediments − 0.64±0.60 Bq/kg, algae − 1.99±1.56 Bq/kg. The calculated transfer coefficients (soil-grass) are in the range of 0.33–0.84. Between 2 and 5 times reduction in actual background activities of ⁹⁰Sr is observed compared to 1972–1974.     

Dose rate associated with activity of radium-226 in Canadian soils

Background levels of²²⁶Ra on non-cultivated soils in Canada (in southern and northern Quebec and in the North-West Territories) are presented. The activity of²²⁶Ra was measured at 34 sites. The specific activity levels ranged from 4.4 to 56.4 Bq/kg with an overall mean of 19.1±12.8 Bq/kg. This activity generates an annual absorbed dose in air of 0.07 mGy. The activities were found to be approximately lognormally distributed with the median activity equal to 15.4 Bq/kg. The activity of²²⁶Ra in the soil does not change with the depth. There is a significant difference between Ra concentrations in soils in all three regions studied.     

Determination of a strong organic ligand dissolved in seawater: Thorium-complexing capacity of oceanic dissolved organic matter

Studies have been made of loose water tritium (LWT) distribution and behavior in the soil samples taken from the region within a radius of 2 km to the HWRR stack of CIAE. The analytical results show that the LWT concentrations in most soil samples of the region are in the range from 24.8 Bq/l (3.6 Bq/kg) to 116 Bq/l (16.0 Bq/kg) with an average value of 58.1±24.8 Bq/l (10.3±4.5 Bq/kg). There are two areas with a higher LWT content; the first one (4.61 · 10⁴ m²) is located near HWRR with ahighest LWT concentration of 287 Bq/l (55.8 Bq/kg) and the second one (3.27 ·10⁵ m²) is located near Lab. A with a highest LWT concentration of 2.35 · 10⁴ Bq/l (2.56 · 10³ Bq/kg). It is estimated that the LWT inventories deposited in soil of the two areas are about 1.52 · 10⁹ Bq and 1.42 · 10¹⁰ Bq, respectively. The analytical results have been evaluated by comparing the possible tritium intake of the human body with the annual limit of intake recommended by ICRP, it can be concluded that the operations of all the nuclear facilities releasing tritium in CIAE are safe without causing any notable tritium contamination.     

Radiological status of Rongelap Island in 1999

A radiological survey and whole body counting of ¹³⁷Cs were carried out in Rongelap Island (main island) of Rongelap Atoll in July 1999. The maximum values of ¹³⁷Cs contamination and of g-ray dose rate were 39 kBq/m² and 0.033 mSv/h, respectively. The maximum a and b gross counting rates on the surface of ground were 1 cpm and 182 cpm in active area of 72 cm², respectively. Activity of ^239,240Pu for soil was 80 Bq/kg in the top 5 cm and aerial deposition was 3.4 kBq/m² in Rongelap Island in 1999. The body burden of ¹³⁷Cs was observed to be 27±11 Bq/kg for 6 workers. Assessment of external and internal annual doses (0.1 and 0.07 mSv/y) indicates that as of 1999 there is no large risk to the inhabitants of Rongelap Island from a radiological point of view. The radiological status of Rongelap Island, which was severely contaminated by the radiological fallouts of nuclear testings carried out in 1954, has improved year by year as shown by the decrease of ¹³⁷Cs. The effective halftime of ¹³⁷Cs, which is estimated to be 6.6 y is much shorter than the physical half-life of ¹³⁷Cs. Radioactive contamination in Kaballe Island, (a part of the northern islands used for farming) which is located 25 km northeast of Rongelap Island, was still high in 1999. One site nearby a beach was highly contaminated with ¹³⁷Cs, where the maximum activity of ¹³⁷Cs was 3.4 MBq/m², a-ray of 2 cpm, b-ray of 1205 cpm and g-ray of 0.73 mSv/h. Activity of ^239,240Pu in soil (n = 1) was 294 Bq/kg (top 5 cm) and 16 kBq/m².     

Evaluation of radiological hazards in the sediments of Ogun river, South-Western Nigeria

The concentrations of natural radionuclides in the sediments of Ogun river in South Western Nigeria have been measured and determined using gamma-ray spectrometry. The mean activity concentrations of ⁴⁰K, ²²⁶Ra, and ²³²Th at different locations along the course of the river were found to vary from 370.99±19.26 Bq/kg (at Olopade) to 608.02±24.66 Bq/kg (at Owere), 5.57±2.34 (at Ekerin) to 20.40±4.52 Bq/kg (at Sokori) and 5.04±2.24 Bq/kg (at mile 12-Maidan) to 23.10±4.81 Bq/kg (at Sokori) respectively. The overall calculated mean of the total indoor absorbed dose rates was 64.46±9.16 nGy/h with corresponding annual indoor effective dose of 0.32±0.05 mSv/y. Radium equivalent activity (Ra_eq), external hazard index (H_ex), internal hazard index (H_in) and representative gamma index (I_γr) were calculated in order to assess the radiation hazards associated with the use of these sediments in the construction of dwellings. The overall estimated values for the radium equivalent activity, external hazard index, internal hazard index and the representative gamma index were 67.96±10.74 Bq/kg, 0.18±0.03, 0.22±0.05 and 0.54±0.08, respectively. These values obtained for the river sediments were less than the recommended safe and criterion limits by UNSCEAR and also, they compared well with the values from other countries of normal radiation areas. It suffices to say therefore that sediments from Ogun river are safe and can be used for construction of buildings without undue radiological health concerns. Results of the study could serve as an important baseline radiometric data for future epidemiological studies and monitoring initiatives in the study area.     

Advantages of low-background liquid scintillation alpha-spectrometry and pulse shape analysis in measuring222Rn, uranium and226Ra in groundwater samples

Liquid scintillation counting (LSC) and pulse shape analysis (PSA) was used in measuring radon and gross alpha- and beta-activities in groundwater. We used conventional LSC counters for the measurement of radon in water, but low-background LSC spectrometers for the gross activity measurements. The lower limit of detection (LLD) for radon in water is 0.6 Bq/l for a 60 min count with a conventional counter, but 0.1 or 0.2 Bq/l, with the two types of low-background LSC spectrometers equipped with a pulse shape analyser (PSA). The gross alpha and beta activity measurements are made using a simple sample preparation method, PSA of a low background LSC and spectrum analysis. The LLD recorded for gross alpha and beta with the two spectrometers are 0.02 and 0.03 Bq/l and 0.2 and 0.4 Bq/l, respectively, for a 180 minutes count and a 38 ml sample volume. The method also enable the calculation of the U and²²⁶Ra contents in water and indicates the presence of some other long-lived radionuclides (²¹⁰Pb,²²⁸Ra or⁴⁰K). The LLD for U recorded with both spectrometers is 0.02 Bq^–1 and for²²⁶Ra 0.01 Bq·1^–1. The LLDs attained by this LSC method are two orders of magnitude lower than the maximum permissible concentrations set for U and²²⁶Ra.     

Radioactivity of plutonium isotopes, <Superscript>137</Superscript>Cs and their ratio in sediment,seawater and biota from the east coast of Peninsular Malaysia

This study with sampling expeditions of marine sediment, seawater and biota were performed at 30 stations within Malaysian Exclusive Economic Zone (EEZ). A total of >400 samples were collected to determine the activity concentration of anthropogenic radionuclides (^239+240Pu, ¹³⁷Cs) and their activity ratio (^239+240Pu/¹³⁷Cs) in sediments, seawater and biota. The purpose of this study was to determine the concentration levels for these radionuclides and to evaluate any occurrence of radioactive contamination. Sediment cores were obtained using multicorer device, while water samples via co-precipitation techniques and biota was purchased from local fishermen. The activity concentrations of ^239+240Pu in sediment, seawater and biota were ranged 0.21–0.45 Bq/kg dry wt., 2.33–7.95 mBq/m³ and <0.008 Bq/kg fresh wt., respectively. Meanwhile, the values of ¹³⁷Cs were ranged <1.00–2.71 Bq/kg dry wt. in sediment, 3.40–5.89 Bq/m³ in seawater and <0.05–0.41 Bq/kg fresh wt. in biota, respectively. Activity ratios of ^239+240Pu to ¹³⁷Cs obtained seem to confirm that these artificial radioactivities were mainly due to global nuclear fallout.     

The study on radioactive contamination in foodstuffs imported from Japan after the Fukushima accident

During the Fukushima nuclear accident, a large number of radionuclides were released, causing direct radioactive contamination to the environment and the ecosystem, and eventually indirect contamination to the foodstuffs. The Radiation Monitoring Group, Office of Atoms for Peace (OAP) in cooperation with the Food and Drug Administration (FDA), has been monitoring the foodstuffs imported from Japan, especially the Fukushima and nearby areas. This monitoring program covered the potentially contaminated foodstuffs. The measurements were mainly conducted using Gamma spectroscopy systems in order to analyze the radioactive concentration of ¹³¹I, ¹³⁴Cs, and ¹³⁷Cs fission products. From 442 samples collected between after the nuclear accident to the end of September 2012, 28 of contaminated food products of fission isotopes have been found with the contamination ranges of 0.63–15.25 Bq/kg fresh, 1.45–44.70 Bq/kg fresh, and 0.45–51.10 Bq/kg fresh) for ¹³¹I, ¹³⁴Cs, and ¹³⁷Cs, respectively. However, the contamination levels are still well under the Thailand standard of food contaminated with radionuclide and the relevant international standards. Finally, the research also investigated the relationship between the times the samples were collected and the contamination levels.     

Study of natural radionuclides and its radiation hazard index in Malaysian building materials

The main component of most building materials in Malaysia is rock. All rocks are known to contain natural radionuclides such as ²³⁸U and ²³²Th series as well as ⁴⁰K. In order to estimate the radiological impact to the dweller, the level of radionuclides present in various building materials available in Malaysia were analyzed using γ-spectrometry. The radiation hazard indexes were calculated based on the above results. The results showed that the activity concentration of natural radionculides ²³⁸U, ²³²Th, ⁴⁰K was between 19.0–42.2 Bq/kg, 16.5–28.8 Bq/kg and 243.3–614.2 Bq/kg, respectively. On the whole, the radionuclides concentration was still below the global average of 50 Bq/kg, 50 Bq/kg and 500 Bq/kg for ²³⁸U, ²³²Th, and ⁴⁰K, respectively The radiation hazard indexes of the building materials were also lower than the maximum value suggested.     

Natural and Artificial Radionuclides in Selected Lignites from Istanbul

The radioactivity levels of Istanbul environs lignites were determined. The gamma-spectrometric technique has been used for the determination of activity levels of naturally occurring radionuclides ^235+238U, ^228+232Th, ⁴⁰K, ²²⁶Ra and fallout radionuclides ¹³⁷Cs in lignites taken from 7 different parts of Istanbul. Concentration of ²³⁸U, ^228+232Th, ⁴⁰K, ²²⁶Ra ¹³⁷Cs and ²³⁵U were found up to 1.6 ppm, 1.7 ppm, 4.9 ppm, 56.8 Bq/kg, 34 Bq/kg, 1.8 Bq/kg, 1.6 Bq/kg, respectively. In addition total alpha- and beta-activity levels in lignite samples were found to be 7.6 and 15 eps, respectively.     

Natural radioactivity and radiation hazards in some building materials used in Isparta,Turkey

The activity concentrations of uranium, thorium and potassium can vary from material to material and it should be measured as the radiation is hazardous for human health. Thus first studies have been planned to obtain radioactivity of building material used in the Isparta region of Turkey. The radioactivity of some building materials used in this region has been measured using a γ-ray spectrometry, which contains a NaI(Tl) detector connected to MCA. The specific activity for ²²⁶Ra, ²³²Th and ⁴⁰K, from the selected building materials, were in the range 17.91–58.88, 6.77–19.49 and 65.72–248.76 Bq/kg, respectively. Absorbed dose rate in air (D), annual effective dose (AED), radium equivalent activities (Ra_eq), and external hazard index (H_ex) associated with the natural radionuclide are calculated to assess the radiation hazard of the natural radioactivity in the building materials. It was found that none of the results exceeds the recommended limit value.