Vertical distributions and gamma dose rates of 40K, 232Th, 238U and 137Cs in the selected forest soils in Izmir, Turkey

This paper presents the results obtained from a radioecological study carried out in the selected forest sites of Izmir, Turkey. The levels of gamma-emitting radionuclides, 40K, 232Th, 238U and 137Cs, in soils were determined using gamma spectroscopy. The activity profile for 40K, 232Th and 238U exhibits a uniform distribution with respect to depth. The depth distribution of 137Cs activity was established by fitting the experimental points to an exponential or a Gaussian function. About 42-97% of the 137Cs deposition was found in the first 10 cm of soil even after 18 y from Chernobyl accident. The dose-rate and annual-effective dose received from external irradiation were quantified. It is indicated that 137Cs from the fallout plays a less role in external radiation exposures in forest sites of Izmir than in potential exposures from naturally occurring radionuclides accounted for by soil.     

Natural and artificial radioactivity distribution in soil of Fars Province, Iran

Fars province is a large populated large province located in the southwest of Iran. This work presents a study of natural and radioactivity levels in soil samples of this province. For this purpose, 126 samples were gathered from different regions of the province and analysed by gamma spectroscopy to quantify radioactivity concentrations of radionuclides using a high-purity germanium detector and spectroscopy system. The results of this investigation show the average concentrations of 271 ± 28 Bq kg(-1), 6.37 ± 0.5 Bq kg(-1), 14.9 ± 0.9 Bq kg(-1) and 26.3 ± 1.9 Bq kg(-1) for (40)K, (137)Cs, (232)Th and (238)U in soil, respectively. Finally, baseline maps were established for the concentrations of each of the radionuclides in different regions. The absorbed dose rate and the annual effective dose (AED) were also calculated for the radionuclides according to the guidelines of UNSCEAR 2000. The average AED from the radioactivity content of soil in this province was found to be 39.9 ± 1.8 μSv.     

Radioactivity concentrations and dose assessment in surface soil samples from east and south of Marmara region, Turkey

The activity concentrations of 137Cs, 40K, 232Th, 238U and 226Ra were measured in surface soil samples from East and South of Marmara region, Turkey. The physico-chemical parameters (organic matter, CaCO3 contents and pH-value) of the soil samples were determined in the samples collected from 100 sampling stations. The average activity concentrations of 137Cs, 40K, 232Th, 238U and 226Ra were found to be 27.46+/-21.84, 442.51+/-189.85, 26.63+/-15.90, 21.77+/-12.08 and 22.45+/-13.31 Bq kg(-1), respectively. The mean value of total annual external gamma radiation dose equivalent for the natural radionuclides was calculated to be 54.86 microSv. The current data were compared with those found in the other locations of Turkey and different countries.     

Gis predictive mapping of terrestrial gamma radiation in the Northern state, Sudan

This study presents the evaluation of absorbed dose in air due to gamma-emitting nuclides from (238)U and (232)Th series, (40)K and (137)Cs and the corresponding geographical information system (GIS) predictive mapping for the Northern State. Activity concentration of (238)U, (232)Th , (40)K and (137)Cs in soil samples collected from different locations have been measured using high-resolution gamma spectrometry. On average, activity concentrations were 19±4 ((238)U), 47±11 ((232)Th), 317±65 ((40)K) and 2.26 Bq kg(-1) for (137)Cs. Absorbed dose rate in air at a height of 1 m above ground surface was calculated using seven sets of dose rate conversion factors (DRCFs) and the corresponding annual effective dose was estimated. On average, the values obtained fall within a narrow range of 44 and 53 nGy h(-1), indicating that the variation in absorbed dose rate is insignificant for different DRCFs. The corresponding annual effective dose ranged from 53 to 65 μSv y(-1). Using GIS, prediction maps for concentrations of (238)U, (232)Th, (40)K and (137)Cs were produced. Also, a map for absorbed dose rate in air at a height of 1 m above the ground level was produced, which showed a trend of increasing from the west towards south-east of the State.     

Outdoor radioactivity and health risks in Balikesir, northwestern Turkey

External irradiation from radionuclides naturally present in the environment or released from man-made practices or events is usually an important component of the exposure of human populations. These exposures derive primarily from gamma radiation arising from the decay of these radionuclides at locations outside the human body. The main objective of this study is to evaluate the radioactivity levels and health risks due to terrestrial radionuclides in the soil of Balikesir, one of the largest cities of the country, northwestern Turkey. For this purpose, activity concentrations of radionuclides in soil and outdoor gamma dose rates (terrestrial and cosmic) have been investigated in the city of Balikesir. In addition, maps for the radionuclide activity concentrations of soil and the outdoor gamma dose rate distributions have been plotted for the region. The average activities of radionuclides, (238)U, (232)Th, (40)K, (235)U and (137)Cs in the soil were determined to be 37.6 ± 10.8, 54.7 ± 15.1, 674.5 ± 203.2, 3.6 ± 1.6, 3.4 ± 2.2 Bq kg(-1), respectively, in the region. The average outdoor gamma dose rates due to terrestrial and cosmic radiations were found to be 78.5 ± 12.4 and 48.9 ± 5.8 nGy h(-1) with the total of 127.4 ± 18.9 nGy h(-1) in the region. Annual effective dose due to environmental outdoor gamma radiation exposures was determined to be 156.3 nSv. The mean estimated cancer risk values were found to be 0.063 × 10(-2) for the region using risk factors of ICRP 103. The results of the study were discussed with the studies done in other cities of Turkey and the worldwide averages.     

Distribution, enrichment and principal component analysis for possible sources of naturally occurring and anthropogenic radionuclides in the agricultural soil of Punjab state, India

Enrichment factor (EF) of elements including geo-accumulation indices for soil quality and principal component analysis (PCA) were used to identify the contributions of the origin of sources in the studied area. Results of (40)K, (137)Cs, (238)U and (232)Th including their decay series isotopes in the agricultural soil of Mansa and Bathinda districts in the state of Punjab were presented and discussed. The measured mean radioactivity concentrations for (238)U, (232)Th and (40)K in the agricultural soil of the studied area differed from nationwide average crustal abundances by 51, 17 and 43 %, respectively. The sequence of the EFs of radionuclides in soil from the greatest to the least was found to be (238)U > (40)K > (226)Ra > (137)Cs > (232)Th > (228)Ra. Even though the enrichment of naturally occurring radionuclides was found to be higher, they remained to be in I(geo) class of '0', indicating that the soil is uncontaminated with respect to these radionuclides. Among non-metals, N showed the highest EF and belonged to I(geo) class of '2', indicating that soil is moderately contaminated due to intrusion of fertiliser. The resulting data set of elemental contents in soil was also interpreted by PCA, which facilitates identification of the different groups of correlated elements. The levels of the (40)K, (238)U and (232)Th radionuclides showed a significant positive correlation with each other, suggesting a similar origin of their geochemical sources and identical behaviour during transport in the soil system.     

Accuracy of field spectrometry in estimating 137Cs contamination in high altitude alpine soils

In situ gamma ray spectrometry is an attractive method for providing information on the concentrations of radionuclides in the soil. This method requires separate knowledge of the soil density and of the radioactivity distribution relative to soil depth. In-field gamma spectrometry measurements were performed together with sampling of the soil at the same site for subsequent gamma spectrometry analysis in the laboratory. Results of 137Cs concentration were compared in order to: (i) verify the effectiveness of in situ gamma spectrometry in averaging local inhomogeneties in the soil; and (ii) quantify the sensitivity of the gamma ray spectrometry soil radioactivity evaluation with respect to the variability of the depth profiles obtained from a single site sampling. The site of study is a high altitude pasture, in the Alpine environment.     

Estimation of annual effective dose due to natural and man-made radionuclides in the metropolitan area of the Bay of Cadiz (SW of Spain)

In order to investigate the radiological hazard of naturally occurring radioactive material (NORM) and man-made (137)Cs radionuclide in the Bay of Cádiz, 149 samples of sediments have been analysed. Activity concentration in all the samples was determined using a HPGe detection system. Activity concentrations values of (226)Ra, (232)Th, (40)K and (137)Cs in the samples were 12.6±2.6 (2.5-40.6), 18.5±4.0 (2.8-73.4), 451±45 (105-1342) and 3.2±1.3 (0.2-16.0) Bq kg(-1), respectively. Outdoor external dose rate due to natural and man-made radionuclides was calculated to be 35.79±1.69 (4.71-119.16) nGy h(-1) and annual effective dose was estimated to be 43.89±2.27 (5.78-146.14) μSv y(-1). Results showed low levels of radioactivity due to NORM and man-made (137)Cs radionuclide in marine sediments recovered from the Bay of Cádiz (Spain), discarding any significant radiological risks related to human activities of the area. Furthermore, the obtained data set could be used as background levels for future research.     

Natural radioactivity in tap waters of Eastern Black Sea region of Turkey

In this study, the activity concentrations of some radionuclides in tap water samples of the Eastern Black Sea region of Turkey were measured. The activity concentrations of radionuclides (214)Pb, (214)Bi, (40)K, (226)Ra and (137)Cs were determined using high resolution gamma ray spectrometry. Furthermore, (222)Rn activity concentrations in tap water samples were measured using Liquid Scintillation Counting. The mean specific activities of (214)Pb, (214)Bi, (226)Ra, (40)K, (137)Cs and (222)Rn in tap water samples were 6.73, 6, 19.16, 168.57, 5.45 mBq l(-1) and 10.82 Bq l(-1), respectively. These values are comparable with concentrations reported for other countries. The effective doses were determined due to intake of these radionuclides as a consequence of direct consumption of tap water samples. The estimated effective doses were 6.878 x 10(-4) microSv y(-1) for (214)Pb, 4.800 x 10(-4) microSv y(-1) for (214)Bi, 3.916 microSv y(-1) for (226)Ra, 0.763 microSv y(-1) for (40)K, 0.052 microSv y(-1) for (137)Cs and 5.848 microSv y(-1) for (222)Rn.     

Environmental gamma radiation measurement in district Swat, Pakistan

External exposure to environmental gamma ray sources is an important component of exposure to the public. A survey was carried out to determine activity concentration levels and associated doses from (226)Ra, (232)Th, (40)K and (137)Cs by means of high-resolution gamma ray spectrometry in the Swat district, famous for tourism. The mean concentrations for (226)Ra, (232)Th and (40)K were found to be 50.4 +/- 0.7, 34.8 +/- 0.7 and 434.5 +/- 7.4 Bq kg(-1), respectively, in soil samples, which are slightly more than the world average values. However, (137)Cs was only found in the soil sample of Barikot with an activity concentration of 34 +/- 1.2 Bq kg(-1). Only (40)K was determined in vegetation samples with an average activity of 172.2 +/- 1.7 Bq kg(-1), whereas in water samples, all radionuclides were found below lower limits of detection. The radium equivalent activity in all soil samples is lower than the limit set in the Organisation for Economic Cooperation and Development report (370 Bq kg(-1)). The value of the external exposure dose has been determined from the content of these radionuclides in soil. The average terrestrial gamma air absorbed dose rate was observed to be 62.4 nGy h(-1), which yields an annual effective dose of 0.08 mSv. The average value of the annual effective dose lies close to the global range of outdoor radiation exposure given in United Nations Scientific Committee on the Effects of Atomic Radiation. However, the main component of the radiation dose to the population residing in the study area arises from cosmic ray due to high altitude.     

Natural and anthropogenic radionuclides in the granitic region of Kapidag peninsula, Western Anatolia, Turkey

Naturally occurring radionuclides of terrestrial origin (also called primordial radionuclides) are present in various degrees in all media in the environment. This study represents the reports on the natural and anthropogenic radionuclides in the Kapidag granitic region. For this purpose, activities of radionuclides in soil, beach sands and rocks of the region have been investigated to assess the radiological hazard of the natural radioactivity. The radium equivalent activities, the absorbed dose rates and the external hazard indexes have been calculated, and also in situ gamma dose rates have been measured in the region. The mean activities of (238)U, (232)Th and (40)K with the ranges were determined as 31.1±15.7 (12.1-71.9), 42.5±15.9 (19.7-94.9), 590.3±192.2 (184.7-892.5), in the soil, as 16.5±9.5 (4.9-40.8), 67.1±106.9 (18.5-433.0), 569.2±212.6 (162.0-821.1) in the sand and as 25.4±12.8 (4.8-50.7), 37.8±21.5 (4.5-96.7), and 592.4±285.5 (62.4-1121.6) Bq kg(-1) in the rocks, respectively. It was also observed that the average activities of (137)Cs were ranged 0-27.8 Bq kg(-1) in the soil and 0.6-3.8 Bq kg(-1) in the beach sands. The mean Ra(eq) activities of the rocks, sands and soil were found to be 125.1±59.5, 156.3±157.2 and 137.3±48.8 Bq kg(-1), respectively, lower than the recommended maximum value of 370 Bq kg(-1) with some exceptions. The maximum contributors to the total absorbed gamma dose rates in air were determined as (238)U (45%) for the beach sands, (238)U (40%) for the soil and (40)K (41%) for rocks. The average outdoor gamma dose rates for the soil due to terrestrial and cosmic radiations were found to be 64.6±22.7 and 47.1±9.6 nGy h(-1), respectively, with the total of 111.7±29.5 nGy h(-1) outdoor gamma exposure rate and the annual average effective outdoor gamma dose was calculated as 137±36.2 μSv for the region. The results of the study were discussed with similar studies in close regions and the worldwide averages.     

Radioactivity concentration in soil samples in the southern part of the West Bank, Palestine

The activity concentrations of naturally occurring radioactive materials such as (238)U, (232)Th and (40)K were measured for 38 soil samples collected from diverse zones in the southern area of West Bank, Palestine using gamma-ray spectroscopy. The measured activities of (238)U, (232)Th and (40)K were found to range from 32.9 to 104.7, 14.5 to 76.6 and 297 to 962 Bq kg(-1) with averages value of 68.7, 48.0 and 630 Bq kg(-1), respectively. The obtained values of activity concentrations are higher than the world average of 35, 30 and 500 Bq kg(-1) for (238)U, (232)Th and (40)K, respectively. The measured (137)Cs activity concentration was found to range from 1.8 to 36.1 Bq kg(-1) with an average value of 8.5 Bq kg(-1). The detected activities were attributed to the fallout of (137)Cs, which is the only man-made radionuclide. The calculated average of the total gamma-radiation dose rate of natural radionuclides, (137)Cs and cosmic radiation is 121.4 nGy h(-1). The radium equivalent activity (R(aeq)), dose rate (D(r)), external hazard index (H(ex)) and radioactivity level index (I(gamma)) in all samples are presented. Some values were found to be in the range of worldwide values, whereas others were above the worldwide values.     

Natural and artificial radioactivity measurements in Eastern Black Sea region of Turkey

In the present work, naturally occurring radionuclides of ²²⁶Ra, ²³²Th and ⁴⁰K were measured in soil samples collected from the Eastern Black Sea region of Turkey. It was found that the activity concentrations ranged from 12 to 120 Bq kg⁻¹ for ²²⁶Ra, from 13 to 121 Bq kg⁻¹ for ²³²Th and from 204 to 1295 Bq kg⁻¹ for ⁴⁰K. Besides naturally occurring radionuclides, ¹³⁷Cs activity concentration was measured in soil, lichen and moss samples and it was found that ¹³⁷Cs activity concentration ranged from 27 to 775 Bq kg⁻¹ with for soil, from 29 to 879 Bq kg⁻¹ for lichen and from 67 to 1396 Bq kg⁻¹ for moss samples. Annual effective doses due to the naturally occurring radionuclides and ¹³⁷Cs were estimated. Ecological half-lives of ¹³⁷Cs in lichen and moss species were estimated. The decrease of the activity concentrations in the present measurements (2007) relative to those in 1993 indicated ecological half-lives between 1.36 and 2.96 years for lichen and between 1.35 and 2.85 years for moss species.     

Radioactivity concentrations in soil and dose assessment for Samsun City Centre, Turkey

In this study, natural gamma radioactivity levels were determined in the soil samples of the Samsun city centre by using the gamma ray spectrometry method. The analysis carried out with the high-purity germanium gamma spectrometry system has shown that average activity concentrations of (238)U, (232)Th, (40)K and (137)Cs were 19±2, 22±4, 521±23 and 15±1 Bq kg(-1), respectively. From the gamma analysis of soil samples, the average value of the absorbed gamma dose rates in air and the average value of the external annual effective dose rates were calculated as 45±4 nGy h(-1) and 55±5 μSv y(-1), respectively. The external hazard index has also been calculated and it has been found that the radiation hazard in Samsun is insignificant.     

Environmental contamination and external radiation dose rates from radionuclides released from the Fukushima nuclear power plant

To evaluate the environmental contamination and contributory external exposure after the accident at the Fukushima Nuclear Power Plant (FNPP), the concentrations of artificial radionuclides in soil samples from each area were analysed by gamma spectrometry. Six artificial radionuclides ((131)I, (134)Cs, (137)Cs, (129m)Te, (95)Nb and (136)Cs) were detected in soil samples around FNPP. Calculated external effective doses from artificial radionuclide contamination in soil samples around FNPP were 1.9-2.9 μSv h(-1) (8.7-17.8 mSv y(-1)) in Fukushima city on 22 March 2011. After several months, these calculated external effective doses were 0.25-0.88 μSv h(-1) (2.2-7.6 mSv y(-1)) in Fukushima city on 29 June 2011. The present study revealed that the detected artificial radionuclides around FNPP mainly shifted to long-lived radionuclides such as radioactive caesium ((134)Cs and (137)Cs) even though current levels are decreasing gradually due to the decay of short-lived radionuclides such as (131)I, (129m)Te, (95)Nb and (136)Cs. Thus, radiation exposure potency still exists even though the national efforts are ongoing for reducing the annual exposure dose closer to 1 mSv, the public dose limit. Long-term environmental monitoring around FNPP contributes to radiation safety, with a reduction in unnecessary exposure to the residents.     

Radioactivity in soil from the city of Kavadarci (Republic of Macedonia) and its environs

The activity concentrations and distribution of natural and anthropogenic radionuclides in soils from the city of Kavadarci, Republic of Macedonia, and its environs were investigated. The purpose of the study, the first of this kind in this region was to evaluate the environmental radioactivity and radiological health hazard, as well as to determine the connection between the concentration of natural radionuclides and the geology of the terrain. A total of 45 surface soil samples were collected from evenly distributed sampling sites. Gross alpha and gross beta activity measurements were made using a gas flow proportional counter, while the activity concentrations of gamma emitting radionuclides were measured using a high purity germanium detector. The average activity concentrations of ??K, 22?Ra, 232Th and 13?Cs were found to be 546±118, 38.8±14.6, 43.7±18.4 and 41.5±40 Bq kg?1, respectively. The mean values of gross alpha and gross beta activities were 522±192 and 681±146 Bq kg?1. The mean total absorbed dose rate in air calculated from the concentration of the natural radionuclides was 67.1±20.9 nGy h?1, and the corresponding annual effective dose rate outdoors was 0.082±0.026 mSv y?1. The results of the analysis show strong correlation between the abundance of the natural radionuclides in soils and their geological origin.     

Assessment of radionuclide level in topsoil samples for partial areas of Tibet, China

By using high-purity germanium gamma spectroscopy, specific activities of naturally occurring and man-made radionuclides were determined in topsoil samples collected from Nyingch, Lhasa and Xigazê of Tibet Autonomous Region, China. The average activity concentrations of (226)Ra, (232)Th and (40)K were 25.1 ± 0.7, 67.1 ± 2.8 and 608.6 ± 12.9 Bq kg(-1), respectively. The activity concentration of (137)Cs was found to vary from <0.3 (minimum detection concentration) to 46.2 Bq kg(-1) with an average of 4.3 ± 0.5 Bq kg(-1). By using the results of (226)Ra, (232)Th and (40)K in the sampled soils, the average outdoor gamma dose rate in air was calculated as 77.5 ± 23.2 nGy h(-1). Furthermore, the average outdoor annual effective dose from terrestrial radiation was 0.10 mSv. The external hazard index in this work varied from 0.20 to 0.70 with an average of 0.40 ± 0.14. The external exposure from terrestrial radiation will not pose any significant radiological threat to the population resident in the studied areas.     

Natural and artificial radionuclide measurements and radioactivity assessment of soil samples in eastern Sichuan province (China)

The activity concentrations of natural and artificial radionuclides were measured in the eastern region of Sichuan province (China). One hundred and ninety-three soil samples from this region were collected and analysed by high-purity germanium gamma spectrometry. The measured results show that the average radioactivity concentrations of (226)Ra, (232)Th, (40)K and (137)Cs in the soil samples are 26, 49, 440 and 6 Bq kg(-1), respectively. The calculated average radium equivalent activity is 130 Bq kg(-1), which is less than the recommended limit of 370 Bq kg(-1). The absorbed dose rate and annual effective dose are 60 nGy h(-1) and 74 μSv, respectively. This is the first time the absorbed dose rate in the east region of Sichuan has been mapped. Overall, the environmental radiation background is greater in the southern part of the area studied than in the northern.     

Activity concentrations of natural radionuclides in the sediments of Ogun River, Southwestern Nigeria

The concentrations of naturally occurring radionuclides in the sediments of the Ogun River in Southwestern Nigeria were measured using NaI(Tl) gamma-ray spectrometry. The measurements were made in an effort to better understand the spatial distribution of natural radioactivity and to form a database of radioactivity levels of the Ogun River. The total average activity concentrations of (40)K, (226)Ra and (232)Th in the sediment samples representing the whole Ogun River from the upper region through the middle to the lower region of the river were 499.476±59.167, 12.649±3.476 and 11.774±5.126, respectively. The range of the activity concentrations of (40)K, (226)Ra and (232)Th for the Ogun River were found to be from 370.969±19.261 (at Olopade) to 608.023±24.658 (at Owere), 5.567±2.359 (at Ekerin) to 20.395±4.516 (at Sokori) and 5.037±2.244 (at Mile 12-Maidan) to 23.096±4.806 (at Sokori). The values obtained were compared with internationally accepted values. No man-made radionuclides were detected at any of the locations.     

Activity concentrations and mean annual effective dose of foodstuffs on the island of Tenerife, Spain

A total of 26 different food types and 12 elaborated diets were analysed by low-level gamma spectrometry to measure their content of 238U(234Th), 228Ra(228Ac), 226Ra(214Pb), 210Pb, 137Cs and 40K. The concentrations of these radionuclides measured in some imported foodstuffs were compared with those measured in some locally produced ones. Moreover, the concentrations found in the analysed foodstuffs and composite diets were compared with the data available in literature from other locations, such as Egypt, Brazil, Poland and Hong Kong. 40K contributed highest to the daily dose produced by the intake of comestibles. The largest 40K concentrations were measured in the chickpeas and beans with 380 +/- 30 and 380 +/- 20 Bq kg(-1) fresh weights, respectively. The artificial radionuclide 137Cs was measured only above detection limits in the potatoes and sweet potatoes. A mean annual effective dose of 362 microSv with a standard deviation of 110 microSv was calculated from the composite diets.