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1.
Rohit Mehra Sandeep Kumar Rajendra Sonkawade N. P. Singh Komal Badhan 《Environmental Earth Sciences》2010,59(5):1159-1164
The activity concentration and the gamma-absorbed dose rates of the terrestrial naturally occurring radionuclides (232Th, 226Ra and 40K) were determined in soil samples collected from ten different locations of Sirsa district of Haryana, using HPGe detector
based on high-resolution gamma spectrometry system. The range of activity concentrations of 226Ra, 232Th and 40K in the soil samples from the studied areas varies from 19.18 Bq kg−1 (Moriwala) to 40.31 Bq kg−1 (Rori), 59.43 Bq kg−1 (Pipli) to 89.54 Bq kg−1 (Fatehpur) and 223.22 Bq kg−1 (Moriwala) to 313.32 Bq kg−1 (SamatKhera) with overall mean values of 27.94, 72.75 and 286.73 Bq kg−1 respectively. The absorbed dose rate calculated from activity concentration of 226Ra, 232Th and 40K ranges between 8.84 and 18.58, 37.02 and 55.78, and 9.24 and 12.97 nGy h−1, respectively. The total absorbed dose in the study area ranges from 60.40 to 82.15 nGy h−1 with an average value of 70.12 nGy h−1. The calculated values of external hazard index (H
ex) for the soil samples of the study area range from 0.36 to 0.49 with an average value of 0.42. 相似文献
2.
Alpha-spectrometric technique is described as an independent method for determining micro-contents of U238 and Th232. It is based on the comparison of alpha spectral activity of U238 and Th232 in geological samples with that contributed by the U232·Th228 spike of known concentration. The experiment procedure consists of dissolving fine powdered samples with acid and adding a given amount of U232-Th228 spike. Uranium and thorium are then separated by ion exchange. After purification, each aliquot is mounted onto a separate stainless steel disk for measurement by alpha spectrometer, which consists essentially of a silicon surface barrier detector and a low noise amplification system connected to a multi-channel analyzer. After corrections for the background, tail and other factors, the desired U232 and Th232 concentrations can be calculated. The data obtained by the alpha-spectrometric method using U232-Th228 spike are compared with colorimetric determinations. Excellent agreement is obtained between the two sets of results. The coefficients of correlation are about 0.98 for U238 and 0.97 for Th232. The accuracy of uranium and thorium analyses by this method depends primarily upon the counting statistics of U232, U238 and Th228 and, to a certain extent, upon the calibration of U232-Th228 spike. Errors in uranium and thorium concentrations obtained by this method are generally within 2 to 5%. 相似文献
3.
《International Geology Review》2012,54(10):1548-1557
Thickness of consolidated crust, depth of the magmatic differentiation, and partial pressure of oxygen during the differentiation are found to be the principal factors on which the ultimate concentrations of U and Th depend, in the Siberian traprocks. Enrichments of both U and Th in late differentiates of the magma develop at about the same rate, if PO2 remains unchanged during the process, i.e. as long as U remains essentially tetravalent. The oxidation of U to hexavalent state at increasing PO2, and hence the increase in its mobility, leads to a dissipation of uranium and lowers its concentration in the late fractions of the magma, while the concentrations of thorium remain unaffected therein. 相似文献
4.
The determination of rare earth elements (REEs), Th and U in seaweeds of various species and in ambient surface seawater were performed by inductively coupled plasma mass spectrometry. The seaweeds and the seawater samples were collected at 10 different coastal areas of Niigata Prefecture in Japan twice a year (spring and autumn) in 2004 and 2005. Results showed that concentration of REEs in seaweed species from Niigata Prefecture were about 103 times higher than those in seawater, and the enrichment factors of REEs were larger in heavy REE than light REE. A significant concentration difference of REEs, Th and U was found among species even in the same phylum. Undaria pinnatifida had the highest concentration of U. Considering that U. pinnatifida has low concentrations of REEs among typical brown algae, different REEs and U uptake mechanisms are suggested. The concentration of REEs, Th and U did not vary remarkably between sampling points and/or seasons. 相似文献
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6.
G.L. Cumming 《Chemical Geology》1974,13(4):257-267
Delayed neutron measurements of U and Th in three meteorites yield the following values:
Bruderheim | U (ppb) | Th(ppb) |
Bruderheim | ||
Peace River | ||
Stannern |