Distribution Of Thorium Research Articles

Radioactivity distribution of thorium in sediment core of the Sabah-Sarawak coast

Thorium activity concentrations were measured in seven marine sediment cores taken from Sabah-Sarawak coast on 2004 by using a gravity box corer. Collected sediments were generally homogenous mud which contained much more mixture of silt and clay compared to sand and relatively low content of organic carbon (i.e. less than 5% at all sampling stations). The results found that activity concentrations of 230Th, 232Th and ratios of 230Th/232Th were ranged from 6.5–20.4 Bq/kg dry wt., 6.8–27.8 Bq/kg dry wt. and 0.69–0.92, respectively. It seem that, 232Th activity concentrations are slightly higher than 230Th at all sampling stations and both radionuclides were generally high at Sabah compared to Sarawak coastal waters. 230Th activity concentrations in sediment core appear to be correlated with the activity concentrations of 232Th at some sampling station. These indicating both radionuclides were supplied from the same of environment and source origin of detrital from terrestrial and shallower water. The low 230Th/232Th activity ratio which is less than unity suggesting that 232Th was actively and rapidly regenerated compared to 230Th from 234U. It also can be attributed to less efficiently scavenge of 230Th onto particles prior deposited at the marine sediment bed.

Distribution of lithogenic radionuclides in soils of the Belgrade region (Serbia)

An assessment of environmental radioactivity in the area of Belgrade, the capital of Serbia, was performed using gamma-ray spectrometry. The concentration, distribution and mutual correlations of uranium, thorium and potassium in 135 soil samples from 45 locations were determined. The mean elemental concentrations of uranium, thorium and potassium were found to be 2.52 ± 0.73 mg kg − 1 , 9.40 ± 2.86 mg kg − 1 and 1.60 ± 0.40%, respectively. The results obtained were compared with equivalent values from other studies conducted worldwide.

Geo-neutrino flux calculation

Observation of terrestrial antineutrinos provides information on the origin, composition, and thermal evolution of the earth. Comparing the measured flux of terrestrial antineutrinos with the modeled flux constrains the quantity and distribution of uranium and thorium, the main heat-producing elements within the earth. Because the flux is dominated by nearby crustal material, detailed studies of the local geology are essential to a refined understanding of the bulk earth. This contribution outlines the calculation of the terrestrial antineutrino flux.

Spatial distribution of uranium and thorium in the surface soil around proposed uranium mining site at Lambapur and its vertical profile in the Nagarjuna Sagar Dam

The understanding and evaluation of the possible interactions of various naturally occurring radionuclides in the world's third largest man-made dam, Nagarjuna Sagar located in Andhra Pradesh, India and built on river Krishna assumed significance with the finding of uranium deposits in locations near the dam. For the present work, surface soil samples from the mineralized area of Lambapur, Mallapuram, Peddagattu and sediment core samples from the Nagarjuna Sagar dam were analyzed for naturally occurring radionuclides namely uranium and thorium using gamma spectrometric technique. Also toxic elements lead and chromium were analysed by the Energy Dispersive X-ray Fluorescence Spectrometer (EDXRF) technique. Surface soil samples show a variation from 25 to 291 Bq/kg (2.02–23.5 mg/kg) for 238U and 32–311 Bq/kg (7.9–76.9 mg/kg) for 232Th. U/Th concentration ratio in surface soil samples ranged from 0.19 to 0.31 and was found comparable with the nation wise average of 0.26. The study of sediment core samples reflected higher U/Th concentration ratio of 0.30–0.33 in the bottom section of the core as compared to 0.22–0.25 in the upper section. The concentration ratio in the upper section of the core was similar to the ratio 0.23 found in the western Deccan Basalt region through which the river originates. A higher concentration of lead and chromium was observed in the upper section of the core compared to bottom section indicating the impact of river input on the geochemical character of dam sediment.

Substrate role in the accumulation of heavy metals in sporocarps of wild fungi

The distribution of neodymium, lead, thorium and uranium was investigated in about 100 samples of 12 different species of common, edible and non-edible mushrooms collected in unpolluted areas in the province of Ciudad Real, Central Spain. The quantitative analysis of heavy metals was performed by X-ray fluorescence spectrometry (a simple, accurate and non-destructive method). The concentration of these elements was related to three factors: mushroom specie, life style/substrate and study area. The results reveal considerable amounts of the four metals in all species analyzed as well as significant differences on the capability to accumulate these elements. The maximum absorption of Nd and Pb was found in the ectomycorrhizal Cantharellus cibarius, reaching values of 7.10 and 4.86 microg g(-1), respectively. Thorium and uranium were mainly accumulated (3.63 and 4.13 microg g(-1), respectively) in Hypholoma fasciculare although it is an epiphyte species, isolated from the mineral particles of soil. The distribution patterns of these metals in sporocarps of different habitats and locations showed no significant differences, except for thorium, mainly accumulated in mushrooms living on wood regarding these living on soil organic matter. The species-specific is therefore the determining factor for accumulation of Nd, Pb, Th and U, more than substrate, in this study.

Behavior and Distribution of Rare Earth Elements, Thorium and Uranium in Soil Environment

Consequently, the following matters have been mainly clarified. (1)REEs in soils mainly exists in the form of F(rd)fraction(i.e., silicate), although F(om) or F(fm) was relatively large proportion fraction(F(om):8-28%; F(fm):6-20%); while U in soils may be present as the fraction bound to carbonate (15%) in addition to as F(rd)(60-70%). (2)The total concentrations of U in soil in agricultural field is remarkably larger (about 2 times) than that in non-agricultural field, although the concentrations of REEs and Th are not greatly varied regardless of soil utilizations(i.e., paddy field, upland field or no plow). (3)The value of pH(H2O)-pH(KCl) in soil of the upland field is smallest. Moreover, EC(electric conductivity) in soil of the upland field is much higher than that of the paddy field or of the non-agricultural field. (4)REE pattern of the crops and fertilizers is generally similar to that of soils, although the order of the concentration of REEs is “soils” > “fertilizers” > “crops”.

An Impact Model of the Imbrium Basin for Distribution of Thorium on Lunar Surface

We consider the thorium distributions that are coincident with the distribution of ejecta after the Mare Imbrium impact occurs on the lunar surface and derive a simple model on the spherical target to predict the thickness of Imbrium ejecta deposits as a function of distance from the centre of the Imbrium basin. Then we use the result of Lunar Prospector's gamma ray experiment to test the hypothesis that the distribution of thorium on the lunar surface has an origin from the Mare Imbrium.

GRS evidence and the possibility of paleooceans on Mars

The Gamma Ray Spectrometer (Mars Odyssey spacecraft) has revealed elemental distributions of potassium (K), thorium (Th), and iron (Fe) on Mars that require fractionation of K (and possibly Th and Fe) consistent with aqueous activity. This includes weathering, evolution of soils, and transport, sorting, and deposition, as well as with the location of first-order geomorphological demarcations identified as possible paleoocean boundaries. The element abundances occur in patterns consistent with weathering in situ and possible presence of relict or exhumed paleosols, deposition of weathered materials (salts and clastic minerals), and weathering/transport under neutral to acidic brines. The abundances are explained by hydrogeology consistent with the possibly overlapping alternatives of paleooceans and/or heterogeneous rock compositions from diverse provenances (e.g., differing igneous compositions).

Determination of Uranium and Thorium in Soil and Plant Parts around Abandoned Lead–Zinc–Copper Mining Area

This study reports distribution of uranium (U) and thorium (Th) in soil samples and the roots and shoots of some plants grown around an abandoned lead (Pb)–zinc (Zn)–copper (Cu) mining area. The plants Euphorbia macroclada, Verbascum cheiranthifolium Boiss, and Astragalus gummifer were examined. The determinations of U and Th were carried out by inductively coupled plasma‐mass spectrometry (ICP‐MS). Uranium and Th levels of the studied soil samples were found to be in the range of 1.1–70.3 mg kg−1 and 2.1–62.1 mg kg−1, respectively. Some results obtained from this study were higher than the mean U and Th concentrations of soils reported around the world. Uranium and thorium concentrations in studied plant roots were in the range of 0.04–16 and 0.08–14.57 mg kg−1, whereas in plant shoots they were 0.02–2.76 and 0.07–12.3 mg kg−1, respectively. It was concluded that the shoots of Astragalus and roots of Euphorbia and Verbascum can be used as both a biomonitor for environmental pollution and biogeochemical indicator because of their higher U and Th concentrations.

Extraction of thorium with tributyl phosphate from chloride solutions

Thorium distribution was studied in relation to concentration of Th, HCl, and metal chloride in aqueous solutions, the nature of the diluent, and the tributyl phosphate concentration in the extractant. Thorium extraction from salt solutions increases in the order NaCl < CaCl2 < AlCl3. The fact that introduction of up to 30% of benzene or dodecane into tributyl phosphate has virtually no effect on the Th extraction is important for industrial application. The results obtained are discussed.

The distribution of uranium and thorium in samples taken from different polluted marine environment

Concentrations of uranium and thorium in seawater, sediment and some marine species taken from along the coastal areas of Malaysia were determined spectrophotometrically. The uranium and thorium concentrations in seawater were found to vary ranging from 1.80 to 4.1 and 0.14 to 0.88 μg/L, respectively. The concentration of uranium in sediment samples was reported to range from 3.00 to 6.60 μg/g while those of thorium were slightly lower ranging from 0.01 to 0.68 μg/g. The uptake of uranium and thorium in marine species was found to be rather low. Similar variations in total alpha activities in samples were also observed with the total alpha activities relatively lower than the beta activities in most samples.

Refined thorium abundances for lunar red spots: Implications for evolved, nonmare volcanism on the Moon

We have used improved knowledge of the spatial distribution of thorium (Th) on the lunar surface, in conjunction with a forward modeling analysis of Lunar Prospector gamma ray data, to estimate the thorium abundances of lunar red spots. The results from this study can be combined with preexisting compositional and morphologic evidence to suggest that Hansteen Alpha, the Gruithuisen domes, and the Lassell massif are silicic, nonmare, volcanic constructs, similar in nature to terrestrial rhyolite domes. We propose that either silicate liquid immiscibility or, more likely, basaltic underplating could have produced lunar rhyolite domes. Thus the Lunar Prospector data presented in this study provide new information about the full range of volcanic and crustal processes that could have occurred on the Moon.

Distribution of uranium and thorium in Irtysh River and the upriver wastewater from a rare metal mine impact on it

lag/g) was about 3 times higher than in the control (0.60 lag/g). Conclusions: This study indicated that smelters in a Chinese mercury mine were exposed to extremely high levels of Hg0 vapor, and that miners were estimated to be also exposed to higher levels of MeHg than those in controls. Further study is needed to determine the origin of such the comparatively high hair MeHg concentrations in the exposed group.

Impact of the Mediterranean Outflow Water on particle dynamics in intermediate waters of the Northeast Atlantic, as revealed by 234Th and 228Th

Over the last decade 234Th has become increasingly used to study particle transport in the ocean on a timescale of weeks. The application of 234Th is mainly focused on the determination of particle and associated carbon fluxes from oceanic surface water. However, 234Th is also suitable for investigating particle dynamic from the upper ocean down to interface sediments, as illustrated by the present work which reports unexpected behavior of 234Th in intermediate waters associated with the Mediterranean Outflow Water (MOW). Concentration profiles of dissolved 238U and 228Ra, and dissolved and particulate 234Th and 228Th were measured in the Mediterranean Outflow Water (MOW) near the Gibraltar Straits and at two sites (36°30′N–15°35′W, Nicole; 36°27′N–10°35′W, Yseult) which had hydrographic characteristics of Meddies, i.e. MOW that propagates as eddies in the Northeastern Atlantic at intermediate depths. There are marked differences in the distribution of thorium between MOW and the surrounding Atlantic waters. At the youngest Meddy Nicole salinity maximum at 1000 m depth, 234Th(total) : 238U and 228Th(total) : 228Ra activity ratios are significantly lower than radioactive equilibrium, indicating an unusual deficit of short half-life thorium nuclides. This implies an export of thorium, presumably on particles, from intermediate Meddy Nicole waters. This process is supported by an increase of particulate thorium fluxes measured in sediment traps deployed for two weeks above and within Meddy Nicole. In contrast, offshore Meddy Yseult has more typical profiles of both thorium nuclides that are nearly in equilibrium with their parents. These results indicate that at intermediate depths, the presence of MOW affects the exchange of reactive elements between particles and dissolved forms and enhances the downward flux of particles from intermediate waters in the Northeast Atlantic.

Preparation of (U0.55Th0.45)O2 Microspheres by Sol-Gel Process

An internal gelation process has been developed for preparing high density (U0.55Th0.45)O2 microspheres. Parameters such as concentration of gelation agents, total metal concentration etc were standardized to obtain crack free sintered microspheres of 96% theoretical density (TD). The SEM studies of the sintered spheres indicated uniform microstructure with 10-20 μm grain size. SEM-EDAX study indicated uniform distribution of uranium and thorium within the microspheres.

Imaging of Copper, Zinc, and Other Elements in Thin Section of Human Brain Samples (Hippocampus) by Laser Ablation Inductively Coupled Plasma Mass Spectrometry

Laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) was used to produce images of element distribution in 20-microm thin sections of human brain tissue. The sample surface was scanned (raster area approximately 80 mm(2)) with a focused laser beam (wavelength 213 nm, diameter of laser crater 50 microm, and laser power density 3 x 10(9) W cm(-2)) in a cooled laser ablation chamber developed for these measurements. The laser ablation system was coupled to a double-focusing sector field ICPMS. Ion intensities of 31P+, 32S+, 56Fe+, 63Cu+, 64Zn+, 232Th+, and 238U+ were measured within the area of interest of the human brain tissue (hippocampus) by LA-ICPMS. The quantitative determination of copper, zinc, uranium, and thorium distribution in thin slices of the human hippocampus was performed using matrix-matched laboratory standards. In addition, a new arrangement in solution-based calibration using a micronebulizer, which was inserted directly into the laser ablation chamber, was applied for validation of synthetic laboratory standard. The mass spectrometric analysis yielded an inhomogeneous distribution (layered structure) for P, S, Cu, and Zn in thin brain sections of the hippocampus. In contrast, Th and U are more homogeneously distributed at a low-concentration level with detection limits in the low-nanogram per gram range. The unique analytical capability and the limits of LA-ICPMS will be demonstrated for the imaging of element distribution in thin cross sections of brain tissue from the hippocampus. LA-ICPMS provides new information on the spatial element distribution of the layered structure in thin sections of brain tissues from the hippocampus.

Synthesis and characterization of low-temperature precursors of thorium–uranium (IV) phosphate–diphosphate solid solutions

Several compositions of new precursor of thorium–uranium (IV) phosphate–diphosphate solid solutions (Th4−xUx(PO4)4P2O7, called β-TUPD) were synthesized in closed PTFE containers either in autoclave (160°C) or on sand bath (90–160°C). All the samples appeared to be single phase. From XRD data and TEM observations, the diffraction lines matched well with that of pure thorium phosphate–hydrogenphosphate hydrate (TPHPH), Th2(PO4)2(HPO4)·H2O, which confirmed the preparation of a complete solid solution between pure thorium and uranium (IV) compounds. TGA/DTA experiments showed that samples of thorium–uranium (IV) phosphate–hydrogenphosphate hydrate (TUPHPH) prepared at 150–160°C were monohydrated leading to the proposed formula Th2−x/2Ux/2(PO4)2(HPO4)·H2O. The variation of the XRD diagrams versus the heating temperature showed that TUPHPH remained crystallized and single phase from room temperature to 200°C. After heating between 200°C and 800°C, the presence of diphosphate groups in the solid was evidenced. In this range of temperature, the solid was transformed into the low-temperature monoclinic form of thorium–uranium (IV) phosphate–diphosphate (α-TUPD). This latter compound finally turned into well-crystallized, homogeneous and single-phase β-TUPD (orthorhombic form) above 930–950°C for x values lower than 2.80. For higher x values, a mixture of β-TUPD, α-Th1−zUzP2O7 and U2−wThwO(PO4)2 was obtained. By this new chemical route of preparation of β-TUPD solid solutions, the homogeneity of the samples is significantly improved, especially considering the distribution of thorium and uranium.

Mechanisms of Thorium Migration in a Semiarid Soil

Thorium concentrations at Kirtland Air Force Base training sites in Albuquerque, NM, have been previously described; however, the mechanisms of thorium migration were not fully understood. This work describes the processes affecting thorium mobility in this semiarid soil, which has implications for future remedial action. Aqueous extraction and filtration experiments have demonstrated the colloidal nature of thorium in the soil, due in part to the low solubility of thorium oxide. Colloidal material was defined as that removed by a 0.22-microm or smaller filter after being filtered to nominally dissolved size (0.45 microm). Additionally, association of thorium with natural organic matter is suggested by micro- and ultrafiltration methods, and electrokinetic data, which indicate thorium migration as a negatively charged particle or anionic complex with organic matter. Soil fractionation and digestion experiments show a bimodal distribution of thorium in the largest and smallest size fractions, most likely associated with detrital plant material and inorganic oxide particles, respectively. Plant uptake studies suggest this could also be a mode of thorium migration as plants grown in thorium-containing soil had a higher thorium concentration than those in control soils. Soil erosion laboratory experiments with wind and surface water overflow were performed to determine bulk soil material movement as a possible mechanism of mobility. Information from these experiments is being used to determine viable soil stabilization techniques at the site to maintain a usable training facility with minimal environmental impact.

Distribution of uranium, thorium, and isotopic composition of uranium in soil samples of south Serbia: Evidence of depleted uranium

Inductively coupled plasma mass spectrometry and thermal ionization mass spectrom - etry were used to measure concentration of uranium and thorium as well as isotopic composition of uranium respectively in soil samples collected around south Serbia. An analytical method was established for a routine sample preparation procedure for uranium and thorium. Uranium was chemically separated and purified from soil samples by anion exchange resin and UTEVA extraction chromatography and its isotopic composition was measured using a thermal ionization mass spectrometry. There was a little deviation of U/Th ratio from the average values in some soil samples. Presence of 236U as well as depleted uranium was observed in 235U/238U ratio measurement in the same soil sample.

Radioactivity distribution in some Permian sediments from the Iratı́ and Corumbataı́ Formations of the Paraná Basin, Southeastern Brazil

In the city of Limeira, southeastern Brazil, an important exposure of Permian sediments of the Paraná basin was revealed by an open pit mine that exploits limestone for production of soil correction compounds and raw materials for the ceramic industry. The radioactivity of these sediments was investigated in some detail and the results provided a general view of the vertical distributions of uranium, thorium and potassium concentrations and of the element ratios U/K, U/Th and Th/K. In general, the concentrations of the main natural radioactive elements are low, with uranium being enriched in some limestone and shale levels. In addition the results showed that the 238U series is in radioactive disequilibrium in many of the analyzed samples. Although the origin of the observed disequilibrium has not been investigated, the results suggest that it is due to weathering processes and water interaction with the rock matrix.