High Radioactivity in Fossil Groundwater in the Middle East:
A New Challenge for Water Management
 
Avner Vengosh
Duke University
vengosh@duke.edu

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. In my talk I will present the geochemical (major and trace elements), radium, strontium, oxygen, and hydrogen isotope compositions of groundwater from the Disi aquifer in southern and central Jordan. The radium 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 confined zone (2.8) are higher than sandstone rocks (~1.6), while their ²²⁴Ra/²²³Ra ratios (32-25) are consistent with theoretical ²²⁴Ra/²²³Ra 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. Based on compilation of radium and radon data from worldwide groundwater and sandstone rocks, we propose that radium levels in groundwater resources are depend on the contents of efficient radium scavenging minerals (e.g., clays, Fe- and Mn-oxides) in sandstone aquifers that control Ra retardation. These findings could have implications for high radium anomalies in low-saline groundwater from similar Nubian Sandstone basins in the region and exacerbate the already severe water crisis in the Middle East.