The mechanism of 234U 238U activity ratio enhancement in karstic limestone groundwater

dc.contributorUniversidade Estadual Paulista (UNESP)
dc.creatorBonotto, Daniel Marcos
dc.creatorAndrews, J. N.
dc.date2014-05-27T11:17:31Z
dc.date2016-10-25T21:25:32Z
dc.date2014-05-27T11:17:31Z
dc.date2016-10-25T21:25:32Z
dc.date1993-01-05
dc.date.accessioned2017-04-06T09:38:12Z
dc.date.available2017-04-06T09:38:12Z
dc.identifierChemical Geology, v. 103, n. 1-4, p. 193-206, 1993.
dc.identifier0009-2541
dc.identifierhttp://hdl.handle.net/11449/132314
dc.identifierhttp://acervodigital.unesp.br/handle/11449/132314
dc.identifier10.1016/0009-2541(93)90301-X
dc.identifierWOS:A1993KG43500015
dc.identifier2-s2.0-0027449506
dc.identifierhttp://dx.doi.org/10.1016/0009-2541(93)90301-X
dc.identifier.urihttp://repositorioslatinoamericanos.uchile.cl/handle/2250/942855
dc.descriptionExperimental etch/leach of Carboniferous Limestone gravels on a laboratory time-scale has demonstrated that 234U 238U activity ratios (AR's) greater than the radiochemical equilibrium value may be generated on short time-scales. The molar U/Ca and Mg/Ca ratios show that both U and Mg are leached preferentially relative to Ca whereas the molar U/Mg ratio is only slightly greater than that of the rock matrix. The generation of enhanced AR's is attributed to a two-stage process in which the limestone surface is dissolved by zero-order etch and silicate minerals so released are subjected to first-order chemical leach of U and Mg. The implications of these results for the production of enhanced AR's in Carboniferous Limestone groundwater are discussed. It is suggested that chemical leaching or exchange of U between groundwater and its particulate load or at the aquifer fluid-solid interface is an important mechanism controlling AR changes as groundwater migrates beyond a redox boundary. AR's for dissolved U in groundwater are more probably related to chemical equilibria than to groundwater age. © 1993.
dc.languageeng
dc.publisherElsevier B.V.
dc.relationChemical Geology
dc.rightsinfo:eu-repo/semantics/closedAccess
dc.subjectActivity ratio
dc.subjectChemical leaching
dc.subjectEtching
dc.subjectGroundwater
dc.subjectGroundwater chemistry
dc.subjectIsotope activity ratio
dc.subjectKarst
dc.subjectLeaching
dc.subjectLimestone
dc.subjectLimestone aquifer
dc.subjectUranium- 234/uranium-238
dc.subjectUranium-234
dc.subjectUranium-238
dc.titleThe mechanism of 234U 238U activity ratio enhancement in karstic limestone groundwater
dc.typeOtro


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