2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 4
Presentation Time: 8:55 AM

Isotopic Tracers (Ra, Sr, O, H) for Elucidating the Sources of High Naturally Occurring Radioactive Groundwater from the Disi Aquifer, Jordan


VENGOSH, Avner1, HIRSCHFELD, Daniella2, VINSON, David S.3, RIMAWI, Omar4, AL ZOUBI, Abdallah4, MARIE, Amer5, GANOR, Jiwchar6 and DWYER, Gary7, (1)Division of Earth and Ocean Sciences, Nicholas School of the Environment, Duke University, Durham, NC 27708, (2)Division of Earth & Ocean Sciences, Nicholas School of the Environment and Earth Sciences, Duke University, Box 90227, Durham, NC 27708, (3)Division of Earth & Ocean Sciences, Nicholas School of the Environment, Duke University, Durham, NC 27708, (4)Al-Balqa’ Applied University, Salt, 19117, Jordan, (5)3Department of Applied Earth and Environmental Sciences, Al Quds Univ, P.O.Box 89, east Jerusalem, 69978, Palestine, (6)Geological and Environmental Sciences, Ben Gurion University, P.O. Box 653, Beer Sheva, 84105, Israel, (7)Division of Earth & Ocean Sciences, Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC 27708, N/A

The Nubian sandstones basins of the Middle East and northeastern Africa host several important aquifers with high-quality, yet fossil, groundwater that is becoming an essential water source in the region. In Jordan, fossil groundwater from the Paleozoic Disi (Saq) aquifer is part of a new large-scale water project in which water will be transferred to the capital Amman to compensate water shortage in Jordan. Here, we investigate the geochemical (major and trace elements), radium, strontium, oxygen, and hydrogen isotope compositions of groundwater from the Disi aquifer in southern Jordan. We have identified three groundwater types: (1) low-saline from the unconfined Rum Group; (2) low-saline from the confined Rum Group; and (3) saline from the Khreim Group. The Khreim saline water has a distinguished high 87Sr/86Sr (0.70117), low Ra content, and low δ18O values relative to the Rum aquifer (0.70854). This suggests negligible leakage between the aquifer systems. The Ra activities in the low-saline groundwater from the Rum Group are high and largely exceed international drinking water standards. The 228Ra/226Ra ratios in groundwater from the unconfined (1.8) and confined zones (2.8) are higher than sandstone rocks (~1.5), while their 224Ra/223Ra ratios (32-25) are consistent with theoretical 224Ra/223Ra ratios ratios emitted by recoil from sandstone rocks. The high ratios of the short-lived 224Ra and 223Ra to the long-lived 226Ra and 228Ra isotopes indicate that Ra mobilization is controlled by recoil process from the aquifer solids combined with rapid Ra adsorption. We propose that contents of efficient radium scavenging minerals (e.g., clays, Fe- and Mn-oxides) in sandstone aquifers would determine the Ra retardation and thus the Ra activity levels in groundwater. These findings could have implications for high radium anomalies in low-saline groundwater from similar Nubian Sandstone basins in the region and exacerbate the water crisis in the Middle East.