image: Interpolation of deuterium-excess values in the study area. Elevated values (red) occur in the proximity of the area down gradient of local Nubian Sandstone outcrops, also shown in red. Gray lines represent water table levels and dotted arrows perpendicular to them are anticipated flow directions. Data point size indicates depth. view more
Credit: Reika Yokochi
Researchers demonstrate the use of krypton-81 as a groundwater tracer to uncover different sources of water to an aquifer in Israel. In arid regions, the emplacement of groundwater corresponds to periods of regional humidity. Reika Yokochi, Zheng-Tian Lu, Eilon Adar, and colleagues used a long-lived radioisotope, krypton-81, to trace the origins of the water in the Nubian Sandstone Aquifer in Israel's Negev Desert. The authors analyzed samples from across the aquifer for krypton-81 and stable isotopes. The analysis suggested 2 sources of water: one source delivered less than 38,000 years ago from the Mediterranean and another source delivered around 361,000 years ago from the Atlantic Ocean. The long residence time of the oldest water is likely due to a fault zone that serves to impede groundwater flow and retain water in the aquifer for an extended time. The recent groundwater was likely emplaced around the time that Mediterranean cyclone tracks shifted southward during the Last Glacial Maximum, whereas the older, Atlantic groundwater was likely delivered by tropical plumes during a relatively cold climate. According to the authors, the results demonstrate how krypton-81 can enable old groundwater to serve as a proxy of paleoclimate and subsurface water storage.
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Article #19-04260: "Radiokrypton unveils dual moisture sources of a deep desert aquifer," by Reika Yokochi et al.
MEDIA CONTACT: Reika Yokochi, University of Chicago, IL; tel: 312-316-8783; e-mail: <yokochi@uchicago.edu>
Journal
Proceedings of the National Academy of Sciences