Uranium isotopic evidence for groundwater chemical evolution and flow patterns in the eastern Snake River Plain aquifer, Idaho

Research Article| September 01, 2001 Uranium isotopic evidence for groundwater chemical evolution and flow patterns in the eastern Snake River Plain aquifer, Idaho Robert C. Roback; Robert C. Roback 1Environmental Division, M.S. J514, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA Search for other works by this author on: GSW Google Scholar Thomas M. Johnson; Thomas M. Johnson 2Department of Geology, University of Illinois at Urbana-Champaign, 245 Natural History Building, MC-102, Urbana, Illinois 61801, USA Search for other works by this author on: GSW Google Scholar Travis L. McLing; Travis L. McLing 3Idaho National Engineering and Environmental Laboratory, P.O. Box 1625, Idaho Falls, Idaho 83415, USA Search for other works by this author on: GSW Google Scholar Michael T. Murrell; Michael T. Murrell 4Chemistry Division, M.S. J514, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA Search for other works by this author on: GSW Google Scholar Shangde Luo; Shangde Luo 5Department of Earth Sciences, University of Southern California, Los Angeles, California 90089-0740, USA Search for other works by this author on: GSW Google Scholar Teh-Lung Ku Teh-Lung Ku 5Department of Earth Sciences, University of Southern California, Los Angeles, California 90089-0740, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Robert C. Roback 1Environmental Division, M.S. J514, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA Thomas M. Johnson 2Department of Geology, University of Illinois at Urbana-Champaign, 245 Natural History Building, MC-102, Urbana, Illinois 61801, USA Travis L. McLing 3Idaho National Engineering and Environmental Laboratory, P.O. Box 1625, Idaho Falls, Idaho 83415, USA Michael T. Murrell 4Chemistry Division, M.S. J514, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA Shangde Luo 5Department of Earth Sciences, University of Southern California, Los Angeles, California 90089-0740, USA Teh-Lung Ku 5Department of Earth Sciences, University of Southern California, Los Angeles, California 90089-0740, USA Publisher: Geological Society of America Received: 17 Feb 2000 Revision Received: 15 Feb 2001 Accepted: 20 Feb 2001 First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2001) 113 (9): 1133–1141. https://doi.org/10.1130/0016-7606(2001)113<1133:UIEFGC>2.0.CO;2 Article history Received: 17 Feb 2000 Revision Received: 15 Feb 2001 Accepted: 20 Feb 2001 First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Robert C. Roback, Thomas M. Johnson, Travis L. McLing, Michael T. Murrell, Shangde Luo, Teh-Lung Ku; Uranium isotopic evidence for groundwater chemical evolution and flow patterns in the eastern Snake River Plain aquifer, Idaho. GSA Bulletin 2001;; 113 (9): 1133–1141. doi: https://doi.org/10.1130/0016-7606(2001)113<1133:UIEFGC>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 The isotopic composition and concentration of uranium and strontium in groundwater, combined with solute concentration data, provide important details regarding groundwater geochemical evolution and flow-pathways in the eastern Snake River Plain aquifer. The study was conducted in the vicinity of the Idaho National Engineering and Environmental Laboratory (INEEL), Idaho, which has a long history of storing and disposing of radioactive waste, some of which has entered the aquifer.Uranium concentrations in INEEL groundwater range from 0.3 to 3.6 ppb, and 234U/238U atomic ratios range between 0.000085 and 0.000168 (activity ratios of 1.5 to 3.1). All of the samples have natural 235U/ 238U ratios, and 236U was not detected; thus, the trends delineated by the 234U/238U ratios reflect natural variations in the aquifer. Groundwater nearest the valleys that provides focused recharge to the Snake River Plain aquifer from the northwest has high 234U/238U ratios when compared to values of regional groundwater flowing southwestward in the aquifer. Mixing of these water masses can account for the intermediate uranium isotope ratios of some of the samples; however, water-rock interaction must also be invoked to account for the observed trends in isotopic data. Uranium and 87Sr/ 86Sr isotope ratios are positively correlated and define a trend toward isotope ratios of the aquifer host rock. These relations indicate that dissolution and/or ion exchange are more important than alpha recoil or selective leaching in controlling 234U/238U ratios. As a result, 234U/238U ratios decrease along flow pathways toward the secular equilibrium values of the aquifer host rock. Uranium and strontium isotopic modification can be explained by incongruent dissolution of the host basalt.Lateral distributions of 234U/238U ratios indicate elongate zones of high 234U/238U ratios extending southward from the mouths of Birch Creek and the Little Lost River. These elongate zones are interpreted as preferential flow paths. Two isolated pockets of groundwater located in the central and western parts of the study area have lower 234U/238U ratios than the adjacent aquifer water. Both of these zones are interpreted to contain stagnant waters that are relatively isolated from flow in the regional aquifer due to lower permeability. Physical and chemical evidence strongly suggests that the stagnant zones are dominated by water from the Big Lost River that infiltrated via flood control ponds (spreading areas), playas, and the riverbed. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.