云南省部分地区环境放射性水平调查及居民所受外照射剂量估算

目的 探讨云南省部分地区的环境放射性水平及所致居民外照射剂量。方法 通过对表层土壤、近地面空气气溶胶和水中放射性核素的γ能谱测量分析,利用卫生系统全国土壤调查中选用的模式,估算环境中²³⁸U、²²⁶Ra、²³²Th、⁴⁰K和¹³⁷Cs所致居民的受照剂量。利用美国航空管理局的CARI-6软件,估算了调查地区居民的宇宙辐射剂量。 结果 调查地区近地面空气气溶胶和水样中各核素比活度都低于探测下限。土壤中放射性核素所致居民人均外照射年有效剂量为0.5206 mSv/年,其中,0.52 mSv/年来自土壤中天然放射性核素,0.6 μSv/年来自土壤中¹³⁷Cs。宇宙辐射所致居民剂量为0.61 mSv/年。结论 宇宙辐射和土壤中天然辐射对居民所受外照射剂量贡献为99.95%,人工放射性核素¹³⁷Cs所致居民的外照射剂量贡献仅为0.05%。     

Radioactivity levels of recent sediments in the Butrint Lagoon and the adjacent coast of Albania.

Sediment samples have been collected in the Butrint area, located in the south-west Albania to determine the radioactivity levels of (40)K, (137)Cs, (212)Bi, (212)Pb, (214)Bi, (214)Pb, (226)Ra and (228)Ac on the bed of the lagoon and adjacent sea, using direct counting gamma spectroscopy. The concentration of (137)Cs and (40)K varied from 2.8 to 37.5 Bq/kg and from 266 to 675 Bq/kg dry weight (dw), respectively (central values). The average concentrations of (238)U and (232)Th daughter products varied from 8 to 27 Bq/kg and from 13 to 40 Bq/kg dw, respectively. The measured (235)U activity ranged from 0.7 to 2.5 Bq/kg dw. Samples of different sedimentary properties, studied for the radioactivity concentration, revealed an inversely proportional relation between grain size and a linear combination of measured specific activities of (226)Ra, (232)Th ((228)Ac, (212)Bi and (212)Pb), (40)K and (137)Cs.     

Environmental radioactivity measurements in Kastamonu region of northern Turkey.

Located in the north-western part of Turkey, the province of Kastamonu has lately been receiving national attention because of its cultural and touristic attractions. This study assesses the environmental radioactivity levels of the region through measurements of indoor radon concentrations and indoor/outdoor gamma absorbed dose in air and radionuclide activities in surface soil and drinking water. The indoor (222)Rn activity concentration was found to be 98.4 Bq/m(3) equivalent to an annual effective dose of 2.48 mSv. The indoor and outdoor gamma absorbed doses were measured as 54.81 and 48.03 nGy/h, respectively, corresponding to a total gamma radiation level (of terrestrial and cosmic origin) of 0.33 mSv/y. The activity concentrations in the soil samples collected from the study area were determined as 32.93, 27.17, 431.43 Bq/kg for the natural radionuclides (238)U, (232)Th and (40)K, respectively, and 8.02 Bq/kg for the fission product (137)Cs. These natural radioactivity sources result in a terrestrial gamma level of 60 microSv/y. The water samples collected from the region carry an average of 0.0089 Bq/l of gross alpha and 0.271 Bq/l of gross beta activities which together cause an annual effective dose of 1.83 microSv. The measurement results obtained in this study indicate that the region has a background radiation level that is within the natural limits and shows no significant departure from the other parts of the country.     

Calibration of a field-portable gamma detector to obtain in situ measurements of the 137Cs inventories of cultivated soils and floodplain sediments.

Over the past 10 years, a number of studies have exploited the potential for using measurements of fallout 137Cs inventories to document rates and patterns of soil erosion on cultivated land and to estimate rates of overbank sedimentation on river floodplains. Traditional procedures for applying the 137Cs technique involve the collection of soil or sediment cores from a study site and their subsequent transfer to the laboratory for preparation and analysis by gamma spectrometry. Such procedures are time consuming and there may be a considerable delay before the results are available. It is therefore difficult to obtain preliminary results, which could be used to guide the development of an ongoing sampling programme. The use of in situ gamma spectrometry measurements to quantify 137Cs inventories in soils and sediments offers a number of potential advantages over traditional procedures. However, in order to derive a reliable estimate of the 137Cs inventory for a measurement point, it is necessary to take account of the attenuation of 137Cs gamma rays by the soil matrix and information on the depth distribution of 137Cs in the soil or sediment is therefore required. In the present study, empirical relationships between in situ measurements of 137Cs activity and total 137Cs inventories have been established for soils from a cultivated field and for floodplain sediments, based on information on the vertical distribution of 137Cs in the soils and sediments provided by the forward scattering ratio derived from the field measured spectra. These relationships have been used to estimate 137Cs inventories from in situ measurements of 137Cs activity at other locations.     

Distribution of natural and anthropogenic radionuclides in soil and beach sand samples of Kalpakkam (India) using hyper pure germanium (HPGe) gamma ray spectrometry.

Pre-operational survey at Kalpakkam coast, indicated elevated gamma background radiation levels in the range of 100-4000 nGy h(-1) over the large tracts of the coastal sands due to the presence of pockets of monazite mineral in beach sands. In view of the prevalence of monazite, a systematic gamma spectrometric study of distribution of natural radionuclides in soil and beach sand samples collected from the terrestrial and coastal environment of Kalpakkam was performed and concentrations of primordial radionuclides such as 238U, 232Th and 40K and anthropogenic radionuclide 137Cs were determined. The concentrations of 238U, 232Th and 40K in soil samples were 5-71, 15-776 and 200-854 Bq kg(-1) dry, respectively. In beach sand samples, 238U, 232Th and 40K contents varied in the range of 36-258, 352-3872 and 324-405 Bq kg(-1) dry, respectively. The total absorbed gamma dose rate in air due to the presence of 238U, 232Th and 40K in Kalpakkam soil samples varied between 24 and 556 nGy h(-1) with a mean of 103 nGy h(-1). The contribution to the total absorbed gamma dose rate in air in the decreasing order was due to the presence of 232Th (76.4%), followed by 40K (16.9%) and 238U (6.7%) in Kalpakkam soils. However, in beach areas of Kalpakkam, the presence of 232Th in beach sand contributed maximum (94.0%) to the total absorbed gamma dose rate in air followed by 238U (4.7%) and minimum contribution was by 40K (1.3%). 137Cs in Kalpakkam soils ranged from < or = 1.0 to 2.8 Bq kg(-1) dry, which was 1-3 order of magnitude less than the concentration of primordial radionuclides in soil.     

Distribution pattern of 90Sr and 137Cs in the Nile delta and the adjacent regions after Chernobyl accident.

Strontium and cesium contents in surface soil samples across the Nile Delta and the north coast of Egypt after the Chernobyl accident have been investigated. The concentration of 137Cs and 90Sr was determined using a high resolution gamma spectrometer based on hyperpure germanium detector (HPGe) and a liquid scintillation counter (LSC) respectively. 90Sr was determined through its decay product 90Y using Cerenkov counting. The determination of 90Sr was based on tributylphosphate (TBP) extraction of yttrium from nitric acid extract of ashed samples. The radioactivity of soils ranged between 18.5 and 2175 Bq/m2 with a mean of 652 Bq/m2 and 234 and 3129 Bq/m2 with a mean of 760 Bq/m2 for 137Cs and 90Sr respectively. An estimated absorbed dose equivalent due to the measured deposit of 137Cs was found to be 0.062 murem/h.     

Distribution of radionuclides in the river sediments and coastal soils of Chittagong, Bangladesh and evaluation of the radiation hazard

The concentrations and distribution of natural and anthropogenic radioactive materials in sediments and soils from around the two major rivers and coastal area of Chittagong, Bangladesh were investigated with an aim of evaluating the environmental radioactivity and radiation hazard. In the sediment and soils in general, the concentration of ²³²Th was found to be higher than that of the ²³⁸U and the activities of ²³²Th and ²³⁸U in this area are higher than the world average. ¹³⁷Cs was observed in all the samples, ranging from 0.4 to 3.88 Bq kg⁻¹. The radium equivalent activities, emanation coefficients and radon exhalation rates were estimated for the sediment and soils; the emanation coefficients, radon exhalation rates and dose rates were found to be higher than the world average values.     

Classification of soil samples according to geographic origin using gamma-ray spectrometry and pattern recognition methods.

Multivariate data analysis methods were used to recognize and classify soils of unknown geographic origin. A total of 103 soil samples were differentiated into classes, according to regions in Serbia and Montenegro from which they were collected. Their radionuclide (226Ra, 238U, 235U, 40K, 134Cs, 137Cs, 232Th and 7Be) activities detected by gamma-ray spectrometry were then used as the inputs in different pattern recognition methods. For the classification of soil samples using eight selected radionuclides, the prediction ability of linear discriminant analysis (LDA), k-nearest neighbours (kNN), soft independent modelling of class analogy (SIMCA) and artificial neural network (ANN) were 82.8%, 88.6%, 60.0% and 92.1%, respectively.     

Distribution of radionuclides in soil samples from a petrified wood forest in El-Qattamia,Cairo, Egypt

The concentrations and distribution of radionuclides in a petrified wood forest in El-Qattamia have been determined using high-resolution gamma spectrometry to evaluate the environmental radioactivity. The mean activity concentrations of ²³⁸U, ²³²Th and ⁴⁰K were 65.26±12.99, 23.66±0.95 and 146.33±1.50 Bq kg⁻¹, respectively.Data of the soil samples show evidence of possible deposition and accumulation of ¹³⁷Cs. The mean activity concentration of ¹³⁷Cs in the soil samples was 4.37±0.16 Bq kg⁻¹ with a range of 0.00–35.70 Bq kg⁻¹. The measured activity concentration range of ¹³⁷Cs was compared with reported ranges in the literature from some of the other locations in the world. The radium-equivalent, dose rate in air and annual effective dose rate were evaluated. The mean activity concentrations of the γ-ray emissions from radionuclides in El-Qattamia petrified wood forest region were relatively low.     

Distribution and uptake of (137)Cs in relation to alkali metals in a perhumid montane forest ecosystem.

We determined the content of radiocesium ((137)Cs) and alkali metals in soils, plants (2 ferns, a shrub and moss) and rainwater collected in an undisturbed forest ecosystem. The (137)Cs activity and the isotopic ratio of (137)Cs/Cs in the samples were used to interpret the distribution and uptake of (137)Cs and the alkali metals in plants. As a whole, the (137)Cs in plants was assimilated together with K but was not dependent on Cs. Different adaptations of fern species collected in ecological niches cause them to have different (137)Cs/Cs ratios. Diplopterygium glaucum is distributed at the edges of the forest; it usually has shallow organic layers, and the root takes up more stable Cs from mineral layers, leading to lower (137)Cs/Cs ratios than that in the understory Plagiogyria formosana and Rhododendron formosanum species. The steady supply of stable Cs through the uptake by D. glaucum from deep soils may gradually dilute the (137)Cs concentration and thus explain the lower (137)Cs/Cs ratio in the fern samples. The (137)Cs is predicted to be proportional to the Cs content across plant species in the biological cycle once isotopic equilibrium is attained.     

云南芒市地区野生食用蘑菇中137Cs、40K含量及所致居民剂量估算

目的 检测可食用野生蘑菇中人工放射性核素¹³⁷Cs和天然放射性核素⁴⁰K的含量及分布特点,计算野生蘑菇中放射性核素水平及其所致剂量。方法 采集了产自云南省芒市的18类33份可食用野生蘑菇样品,用实验室低本底高纯锗（HPGe）γ谱仪分析了其中放射性核素¹³⁷Cs、⁴⁰K的含量。结果 33份样品中,仅1份样品¹³⁷Cs的含量在探测限之下,其余32份样品中均可检测出¹³⁷Cs,比活度范围值为0.45~339.58 Bq/kg（干重）,平均值25.47 Bq/kg（干重）。所有样品均检测出天然放射性核素⁴⁰K,核素比活度最小值和最大值分别为453.4、1 882.6 Bq/kg（干重）,平均值为815.1 Bq/kg（干重）。当去除只有1个样品数的蘑菇种类后,毛钉菇、美味牛肝菌、白牛肝菌、锈盖粉孢牛肝菌、香菇、茶褐牛肝菌6个种类蘑菇间¹³⁷Cs含量差异有统计学意义（F=21.13,P<0.05）,而⁴⁰K含量差异无统计学意义。结论 6类不同蘑菇中¹³⁷Cs含量不同,其中毛钉菇、香菇中人工放射性核素¹³⁷Cs含量相对较高。但食入此类蘑菇对成人所致待积有效剂量极其微小,不会影响健康。     

Natural radionuclide distribution in soils of Gudalore, India.

The concentration of primordial radionuclides in soil samples of Gudalore Taluk in the Udagamandalam district has been measured from the gamma ray spectrum of the soil. The mean activities of 232Th, 238U and 40K are 75.3 +/- 44.1, 37.7 +/- 10.1 and 195.2 +/- 85.1 Bq kg-1 dry weight, respectively. The average outdoor absorbed dose rate in air at a height of 1 m above ground is 74.3 +/- 27.8 nGy h-1, corresponding to an annual effective dose equivalent of 455.6 microSv. The dose equivalent ranges from 168.3 to 1250.5 microSv. The results have been compared with other global radioactivity measurements and evaluations.     

Natural and anthropogenic radionuclides in rocks and beach sands from Ezine region (Canakkale), Western Anatolia, Turkey.

This paper represents the first reports on the natural and anthropogenic radionuclides in Kestanbol granitic pluton and surrounding rocks, and coastal region of the Ezine town. To assess the radiological hazard of the natural radioactivity, the radium equivalent activity, the absorbed dose rate and the external hazard index were calculated, and in situ gamma dose rates were measured. The high-activity concentrations were measured in the pluton and sands, which was originated mainly from the pluton, due to the presence of zircon, allanite, monazite, thorite, uranothorite and apatite. The average activity concentrations of (238)U, (232)Th and (40)K are 174.78, 204.69 and 1171.95 Bq kg(-1) for pluton, and 290.36, 532.04 and 1160.75 Bq kg(-1) for sands, respectively. (137)Cs in Ezine region ranged from 0-6.57 Bq kg(-1). The average absorbed dose rate for the granitic and sand samples were calculated to be 251.6 and 527.92 nGy h(-1), respectively. The maximum contribution to the total absorbed gamma dose rate in air was due to the (232)Th (52.3% for pluton and 67.1% for sands). The Raeq activities of the pluton and sands are higher than the recommended maximum value of 370 Bq kg(-1) criterion limit of Raeq activity for building materials.     

Effect of lower grain sized particles on natural radiation level of the Ponnaiyar river sediments

River sediment depositions on the bottom of rivers most frequently consist of sand and gravel particles with different grain sizes, which make them particularly valuable for the building construction. Knowledge of radioactivity present in building material enables one to assess any possible radiological hazard to mankind by the use of such materials. The natural radionuclide (²³⁸U, ²³²Th and ⁴⁰K) contents have been analyzed for the sediment samples of Ponnaiyar River with an aim of evaluating the radiation hazard nature. To know the radiological characteristics of the sediment, dose rate is calculated and are compared with recommended values. Mineral characteristics of the sediments have been analyzed through FTIR and XRD techniques. Extinction coefficient and Crystallinity index is calculated to know the relative distribution of major minerals and crystalline nature of quartz, respectively. Multivariate statistical analyses were carried to find the relationship between the radioactivity characteristics and minerals, the results obtained in the study suggest that the level of natural radioactivity of the present sediments mainly depends upon the amount of kaolinite (clay). Mineral characterization of various grain sized sediments show clay and magnetic minerals are rich in lower grain sized (≤120 μm) samples. The level of radioactivity has also been measured for >120 μm sediments and results show that both activity concentrations and dose rate are considerably lowered when compared with the respective values of the bulk samples. The removal of ≤120 μm particles from the sediments of the river make it safer to use these materials for building construction.     

On line gamma-ray spectrometry at open sea.

Set up and application of a stationary monitoring network for measuring specific gamma- activities in the Aegean Sea are described. Three NaI scintillator based spectrometers have been used to detect the gamma rays. The gross counting rate of each system was found to be nearly constant, when there was no rainfall. The volumetric activity of the natural gamma-ray emitter 40K in open sea varied from 12,200 to 13,000 Bq/m3. The counting rate for 1461 keV 40K radiation was measured by intercalibration with an appropriate salinity sensor mounted close to the NaI-detector system. A simple relation between the counting rate and the salt concentration has been observed. The amount of the artificial radioactivity from 137Cs was increased up to seven times higher after strong rainfall, compared to the radiation level as given in literature (3.5-5.5 Bq/m3), while the 214Bi counting rate was increased up to ten times compared to the data without rainfall.     

Uptake of radioactivity by marine surface sediments collected in Ghazaouet, west coast of Algeria

Samples of surface marine sediments of different grain sizes collected in Ghazaouet, a small bay on the western coast of Algeria, have been examined to measure concentrations of natural and artificial gamma-emitting radionuclides. The aim of this study is to determine the level of radioactivity and its repartition in the sedimentary area. The samples analyzed by direct counting gamma spectrometry, showed relatively high activities for natural radioactivity and revealed measurable quantities of ¹³⁷Cs, ranging from 0.66–8.47 Bq kg⁻¹ dry weight. In addition, some of the samples of different nature were sieved in different grain-sizes, to study the uptake of radioactivity. It is found that the sediments of less than 100 μm grain-size have the highest level of uptake of radioactivity.     

In situ radiometric mapping as a proxy of sediment contamination: assessment of the underlying geochemical and -physical principles.

Correlations between sediment contaminants like heavy metals or organic micro-compounds and natural or anthropogenic radionuclides ((40)K, (238)U, (232)Th, (137)Cs) facilitates in situ mapping of the contaminated sediment using gamma-ray detectors. These maps can be made quickly and economically using surveys with towed underwater gamma-ray detectors and based on the fundamental correlation of contaminants with radioactivity. This paper aims at an assessment of the geochemical and -physical principles underlying these correlations. This assessment uses multivariate analysis of a data base containing information on radionuclides and contaminants for a large number of sediment samples used to derive radionuclide-contaminant correlations in radiometric mapping projects in freshwater bodies of the Netherlands. More specifically, the aims of this study are to test if these correlations are valid for the entire Dutch freshwater environment and to investigate the validity of the thesis that these correlations are mainly due to the presence of clay.     

Accumulation and potential dissolution of Chernobyl-derived radionuclides in river bottom sediment.

Areas contaminated with radionuclides from the Chernobyl nuclear accident have been identified in Pripyat River near the Chernobyl Nuclear Power Plant. The river bottom sediment cores contained 137Cs (10(5)-10(6) Bq/m2) within 0-30 cm depth, whose concentration is comparable to that in the ground soil in the vicinity of the nuclear power plant (the Exclusion Zone). The sediment cores also accumulated 90Sr (10(5) Bq/m2), (239,240)Pu (10(4) Bq/m2) and 241Am (10(4)Bq/m2) derived from the accident. Several nuclear fuel particles have been preserved at 20-25 cm depth that is the peak area of the concentrations of the radionuclides. These inventories in the bottom sediments were compared with those of the released radionuclides during the accident. An analysis using a selective sequential extraction technique was applied for the radionuclides in the sediments. Results suggest that the possibility of release of 137Cs and (293,240)Pu from the bottom sediment was low compared with 90Sr. The potential dissolution and subsequent transport of 90Sr from the river bottom sediment should be taken into account with respect to the long-term radiological influence on the aquatic environment.     

云南省部分地区大米和玉米放射性核素水平调查

目的 调查云南省部分地区大米和玉米放射性核素水平,充实云南地区食品放射性水平基线数据,评估其对居民产生的健康风险。方法 依据国家标准《生物样品中放射性核素的γ能谱分析方法》《高纯锗γ能谱分析通用方法》《食品中放射性物质检验总则》《土壤中放射性核素的γ能谱分析方法》,对云南省20个县（区）大米和玉米样品进行放射性核素检测,对检测结果进行处理与分析。结果 大米样品中²³⁸U、²³²Th、²²⁶Ra、⁴⁰K和¹³⁷Cs活度浓度均值分别为（0.416±0.403）、（0.045±0.034）、（0.030±0.013）、（28.4±18.8）和（0.014±0.019）Bq/kg,玉米样品中²³⁸U、²³²Th、²²⁶Ra、⁴⁰K活度浓度均值分别为（0.308±0.230）、（0.035±0.031）、（0.053±0.072）、（56.8±38.6）Bq/kg,¹³⁷Cs的活度浓度低于探测下限。结论 云南省20个县（区）大米和玉米中²³⁸U、²³²Th、²²⁶Ra、⁴⁰K和¹³⁷Cs的放射性水平均在国家标准正常范围内,食入后不会对居民的健康造成影响。     

中日γ能谱分析土壤样品中放射性核素的比对

目的 通过开展γ能谱测量分析比对活动,检验比对样品的采集、制备、测量和分析全过程,以促进放射性核素γ能谱测量分析技术的发展。方法 由中国疾病预防控制中心辐射防护与核安全医学所采集和制备环境土壤样品,比对各方分别对两个土壤样品中的²¹⁴Pb、²¹⁴Bi、²⁰⁸Tl、²²⁸Ac、⁴⁰K和¹³⁷Cs 6个核素进行测量和分析。根据3个实验室约定测量结果的评定标准,利用各实验室上报的活度浓度和总不确定度数据计算测量结果评价变量(En)值。结果 每两个实验室间计算的En值均小于1,3个实验室的结果均为可接受的结果。结论 各比对方的测量结果在一定范围内是一致的。本次比对既检验了比对方实验室的核素分析水平,又促进了本实验室样品制备中均匀性检验能力的提高。