Radium contamination in the Nizzana-1 water well, Negev Desert, Israel

In a search for fresh groundwater reserves in the northwestern Negev Desert of Israel, the Nizzana-1 water well drilled into the Judea Group aquifer encountered water that exhibits an anomalously high 226Ra activity of 2.4 Bq/l, along with 133 Bq/l 222Rn. The exploited well water is a mixture of the original Judea Group aquifer water and the underlying more saline artesian water of the Kurnub Group (or Nubian Sandstone) aquifer that is currently intruding via faults. Both aquifers elsewhere contain intrinsically low radioactivity. A study of the sedimentary sequence transected by the borehole revealed that much of the bituminous sequence of the Mount Scopus Group of Upper Cretaceous age is substantially depleted in 226Ra. During its ascent, the Nubian Sandstone water flushes the moderately uranium enriched bituminous sediments, selectively leaching radium and/or receiving alpha-recoil additions of radium. These bituminous chalks and marls are regionally widespread. It is thus suggested that radium should be monitored where faulting allows for inter-aquiferial connections across uranium enriched bituminous sections.