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The use of expanded perlite for the adsorption of thorium from aqueous solution by batch technique is presented. The effects of particle size, pH of the solution, initial thorium concentration, shaking time, V/m ratio and temperature were determined. It was found that the adsorption capacity increases by the increase in the pH of the suspensions. The rate of thorium adsorption on expanded perlite was observed to be fast in the first hour of the reaction time. Adsorption isotherms were expressed by Langmuir and Freundlich adsorption models and the adsorption experiments conducted at 30 ± 1 °C showed that the adsorption isotherms correlated well with the Langmuir model. From the adsorption data, thermodynamic parameters such as ΔGo, ΔHo and ΔSo were calculated as a function of temperature. 相似文献
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张洪图 《辽宁城乡环境科技》2004,24(2):13-15
介绍了建筑材料放射性污染检测、控制的重要性及其危害。经研究表明:几乎所有的建筑材料都存在不同程度的放射性污染,超限量的放射性会对人体造成危害。同时,还介绍了建筑材料放射性定量控制的两个指标及其限量标准,着重阐述了建筑材料放射性的测量原理和典型测量方法,并对几年来的一些测量结果进行了分析,提出了要有选择性地使用建筑材料的观点。 相似文献
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对新疆中草药大芸中铀、钍、镭、~(90)锶、~(137)铯进行了含量测定,取得数据结果,并与浙江茶叶、宁夏枸杞子中五种核素含量进行了对比,提供有关部分参考。 相似文献
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Uptake of uranium and thorium by native and cultivated plants 总被引:2,自引:0,他引:2
Shtangeeva I 《Journal of environmental radioactivity》2010,101(6):458-6946
Large part of available literature on biogeochemistry of uranium and thorium refers to the studies performed either in highly contaminated areas or in nutrient solutions that have been artificially ‘spiked’ with radionuclides. Effects of background levels of natural radioactivity on soil-grown plants have not been studied to the same extent. In this paper, we summarised results of greenhouse and field experiments performed by the author from 2000 to 2006. We examined some of the factors affecting transfer of U and Th from soil to plants, differences in uptake of these radionuclides by different plants, relationships between U and Th in soil and in plants, and temporal variations of U and Th in different plant species. Concentrations of radionuclides (critical point for experimental studies on biogeochemistry of U and Th - rare trace elements in non-contaminated regions) and essential plant nutrients and trace elements were determined by instrumental neutron activation analysis. 相似文献
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External shell surface (ESS) of bivalve mollusks is known to adsorb various metals dissolved in ambient water in high concentration. It is hypothesized here that the surface microtopography of the thin organic coating layer, periostracum, or calcareous shell (if periostracum was destroyed) plays a major role in the adsorption of actinides on ESS. Thorium (natural alpha-emitter) was used in short-term biosorption experiment with shell fragments of five bivalve mollusks. After a 72 h exposure to Th (∼6 kBq L−1), thorium concentration was measured on ESS using laser ablation inductively coupled plasma mass spectrometry; the distribution and density of alpha tracks were subsequently visualized by α-track autoradiography. A trend in reduced Th concentrations on the ESS was observed depending upon the species tested: (group 1 ∼4000 μg g−1) Chlamys islandica (M.), Mercenaria mercenaria (L.), Dreissena polymorpha (P.) > (group 2 ∼1200 μg g−1) Crassostrea virginica (G.) ? (group 3 ∼150 μg g−1) Mytilus edulis L. The microtopography of ESS was characterized by scanning electron microscopy revealing the high porosity of the calcareous surface of C. islandica and M. mercenaria, lamellate surface of periostracum in D. polymorpha, uneven but a weakly porous surface of periostracum of C. virginica, and a nearly smooth surface of the periostracum of M. edulis. This work has demonstrated, for the first time, the presence of a strong correlation between concentration of adsorbed Th and ESS microtopography, and the role of the periostracum in this process is discussed. 相似文献
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The Geological Survey of Sweden (SGU) has been conducting airborne gamma spectrometry measurements of natural radioactivity in Sweden for more than 40 years. Today, the database covers about 80% of the country’s land surface. This article explores the first step of putting this data into use in radioactive source search at ground level. However, in order to be able to use the airborne background measurements at ground level, SGU data must be validated against terrestrial data. In this work, we compare the SGU data with data measured by a portable backpack system. This is done for three different areas in southern Sweden. The statistical analysis shows that a linear relationship and a positive correlation exist between the air and ground data. However, this linear relationship could be revealed only when the region possessed large enough variations in areal activity. Furthermore, the activity distributions measured show good agreement to those of SGU. We conclude that the SGU database could be used for terrestrial background assessment, given that a linear transfer function is established. 相似文献
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Particle-reactive, naturally occurring radionuclides are useful tracers of the sinking flux of organic matter from the surface to the deep ocean. Since the Joint Global Ocean Flux Study (JGOFS) began in 1987, the disequilibrium between 234Th and its parent 238U has become widely used as a technique to measure particle export fluxes from surface ocean waters. Another radionuclide pair, 210Po and 210Pb, can be used for the same purpose but has not been as widely adopted due to difficulty with accurately constraining the 210Po/210Pb radiochemical balance in the ocean and because of the more time-consuming radiochemical procedures. Direct comparison of particle flux estimated in different ocean regions using these short-lived radionuclides is important in evaluating their utility and accuracy as tracers of particle flux. In this paper, we present paired 234Th/238U and 210Po/210Pb data from oligotrophic surface waters of the subtropical Northwest Atlantic and discuss their advantages and limitations. Vertical profiles of total and particle size-fractionated 210Po and 234Th activities, together with particulate organic carbon (POC) concentrations, were measured during three seasons at the Bermuda Atlantic Time-series Study (BATS) site. Both 210Po and 234Th reasonably predict sinking POC flux caught in sediment traps, and each tracer provides unique information about the magnitude and efficiency of the ocean's biological pump. 相似文献
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Marmolejo-Rodríguez AJ Caetano M Prego R Vale C 《Journal of environmental radioactivity》2008,99(10):1631-1635
Thorium levels and their association with Fe, Sc, Ca, and Particulate Organic Carbon (POC) were researched in sediments of the Vigo Ria in order to assess the influence of radioactive gneisses from the neighbouring continental Gali?eiro Complex. Sediment of 50 surface samples and 1 core was analysed by ICP-MS and the results were validated with certificate reference material from marine sediment. It was found that Th accumulates in the middle Ria zone (9-15 mg kg(-1)) as a result of the terrestrial source. The thorium concentration in the Ria (average: 9.4+/-5.1 mg kg(-1)) is not anthropogenically impacted in accordance with its own regional background level (11.4+/-3.5 mg kg(-1)), which is two times higher than the content in earth's crust. Throughout the relationship Th/Fe, Th may be associated with the iron cycle in the Ria, probably through iron oxy-hydroxide scavenging. 相似文献
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R. H. Higgy M. S. El-Tahawy A. T. Abdel-Fattah U. A. Al-Akabawy 《Journal of environmental radioactivity》2000,50(3)
Studies have been carried out to determine the natural radioactivity in some building materials (bricks, tiles, marble and ceramics) and their associated radiation hazard. The radioactivity concentrations of 226Ra 232Th and 40K were measured using a gamma spectrometer with a Hp–Ge detector. The activities of 238U and 234U were measured using an alpha-spectrometer with a surface barrier detector after applying a radiochemical procedure. The 234U/238U isotopic ratios were calculated. The radium equivalent activities and the radiation hazard index associated with the natural radionuclides were calculated. A computer program was developed and applied to calculate the dose rate a person will receive from the walls of a room constructed from the studied building materials. 相似文献