Evolution of the Isotopic Composition of Uranium and Thorium in Soil Profiles

Research Article| September 01, 1966 Evolution of the Isotopic Composition of Uranium and Thorium in Soil Profiles J. N ROSHOLT; J. N ROSHOLT U. S. Geological Survey, Denver, Colorado Search for other works by this author on: GSW Google Scholar B. R DOE; B. R DOE U. S. Geological Survey, Denver, Colorado Search for other works by this author on: GSW Google Scholar M TATSUMOTO M TATSUMOTO U. S. Geological Survey, Denver, Colorado Search for other works by this author on: GSW Google Scholar Author and Article Information J. N ROSHOLT U. S. Geological Survey, Denver, Colorado B. R DOE U. S. Geological Survey, Denver, Colorado M TATSUMOTO U. S. Geological Survey, Denver, Colorado Publisher: Geological Society of America Received: 09 Jul 1965 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1966, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1966) 77 (9): 987–1004. https://doi.org/10.1130/0016-7606(1966)77[987:EOTICO]2.0.CO;2 Article history Received: 09 Jul 1965 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation J. N ROSHOLT, B. R DOE, M TATSUMOTO; Evolution of the Isotopic Composition of Uranium and Thorium in Soil Profiles. GSA Bulletin 1966;; 77 (9): 987–1004. doi: https://doi.org/10.1130/0016-7606(1966)77[987:EOTICO]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Mass-spectrometric and alpha-spectrometric analyses for the isotopic composition of U238, U235, U234, Th232, and Th230 have been made on several soils and soil profiles in glacial-derived parent material, volcanic rock, and shale. Three deep profiles from Minnesota represent typical well-developed soils on till and loess of Wisconsin age continuously sampled to depths of 6, 7, and 10 feet, respectively. Results on individual soil horizons, in these three profiles, show similar trends in the variation of U234/U238 and Th230/U238 ratios, the predominant features being excess Th230 and deficient U234 compared to U238. The other soils and soil profiles have different variations which can be correlated by use of a model to describe uranium migration.The data collected provided information for interpreting the causes of uranium migration in soils and for constructing a tentative model to explain the isotopic evolution of uranium and thorium in soil profiles. The proposed model indicates that (1) uranium was leached at depth in the profile, (2) preferential leaching of U234 was continuous in the soil, and (3) upward capillary migration of a fraction of the uranium with above-normal U234/U238 ratio tended to make uranium of high U234 ratio available for isotopic exchange in upper soil horizons and for assimilation in organic complexes in surface soils which are rich in organic matter. Thus some of the organic-rich surface soils, which have had considerable time to develop, contain uranium with excess U234 compared to U238. Interpretations from this model suggest that remixing of radioisotopes by geochemical processes contributes significantly, along with the usual physical processes of radioactive growth and decay, toward producing an isotopic composition near radioactive equilibrium. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.