Determination of the Petro-physical and Natural Radioactivity Properties of Nubian Sandstone Aquifer at the Area of Northwest El Ain Village, Sharq El-Oweinat Area, Southwestern Desert, Egypt

The Nubian sandstone aquifer's hydrogeophysical and natural radioactivity parameters at the Northwestern part of El Ain village, Sharq El Oweinat, Southwestern desert, Egypt are resolved using geophysical well logging and natural radioactivity techniques. The study aims to monitor the phenomenon of appearing an unusual high gamma-ray at a zone of high resistivity record. A nest of well logs is collected to assess how the phenomenon is widespread. Results of correlated well logs are clarified that this phenomenon at zone between 80 and 100 m and zone of 200 and 230m depth is noticed. The petro-physical properties are estimated from the recorded well logs. The results showed that the percentage of the average of effective porosity % varies between 20 and 28.2%, while average vary from 2 to 12.5 %, which indicates that the aquifer of Nubian Sandstone is classified as a clean aquifer. The natural radioactivities of the studied area in the rock samples were evaluated using high-purity germanium (HPGe) detector. The results indicated that the average value of Th-232 is (51.32 ±4.92%) Bq/kg, Ra-226 is (29.03 ± 4.68%) Bq/kg while the radioactivity concentration of K-40 exists only in one sample with low concentration.

Geoelectrical Exploration of Groundwater by Using Vertical Electrical Sounding Technique at Wadi Morra, South Sinai, Egypt

Wadi Morra area is one of the most important areas targeted by the government for sustainable development. This development depends mainly on groundwater occurrences. This research aims to explore groundwater in this region, which depends on groundwater for its needs. To achieve this aim, the geoelectrical resistivity method was used, represented by Schlumberger Vertical Electrical Soundings (VESs). Seventeen VESs have been carried out with a maximum half current electrode spacing (AB/2) of 700m. The measured VESs are interpreted qualitatively and quantitatively to construct a geoelectrical model. To detect the water-bearing layers and their extensions, three geoelectric cross-sections in addition to a one-panel diagram were constructed using all the available data. Also, both true resistivity and isopach contour maps of waterbearing layers were created based on these data. The interpretation results indicate that there are five geoelectric layers (A, B, C, D, and E), two of them (C and D) are water-bearing layers. The first water-bearing layer is layer C, which represents the Nubian sandstone aquifer, and the second layer is layer D, which represents the fractured basement aquifer. These two aquifers were observed along the northern part of the Saint Catherine - Nuweiba road that dissects the Wadi Morra basin, while it is absent at the southern part of this road. It is due to the presence of a few faults. According to groundwater occurrences, the study area was divided into two zones. The first zone is zone (A) where the groundwater is present, either in the Nubian sandstone aquifer or in the fractured basement aquifer and the second zone is zone (B) where there is no groundwater at all due to the presence of basement rocks at a few depths. This research also recommends that the best places for drilling productive wells be at zone A.

Exploitation of Geological Resources

Nubia is well endowed with the geological resources needed to supply a succession of ancient cultures and kingdoms. Igneous and metamorphic rocks of the region’s Basement Complex provided most of the materials, including gold, copper, gemstones, and a variety of ornamental stones. Overlying the Basement Complex are sedimentary rocks and among these is the Nubian Sandstone Formation, which supplied the material used to build Nubia’s many temples and pyramids. This formation also provided the oolitic ironstone that was the raw material for Kushite iron production as well as two unusually hard varieties of sandstone—iron oxide-cemented ferricrete and quartz-cemented quartzite—that were used in buildings where extra strength was needed and also for many ornamental applications. Surficial sediments deposited by the Nile River and desert wadis were important sources of gold, gemstones, and, for ceramics, clay. A total of 117 ancient mines and quarries have been identified in Nubia with twenty-three for sandstone, seven for ornamental stones, four for quartzite, seventy-six for gold, five for copper, one each for iron and lead, and three for gemstones.

Elevated radium levels in Nubian Aquifer groundwater of Northeastern Africa

The Nubian Sandstone Aquifer System in Northeast Africa and the Middle East is a huge water resource of inestimable value to the population. However, natural radioactivity impairs groundwater quality throughout the aquifer posing a radiological health risk to millions of people. Here we present measurements of radium isotopes in Nubian Aquifer groundwater from population centers in the Western Desert of Egypt. Groundwater has 226Ra and 228Ra activities ranging from 0.01 to 2.11 and 0.03 to 2.31 Bq/L, respectively. Most activities (combined 226Ra + 228Ra) exceed U.S. EPA drinking water standards. The estimated annual radiation doses associated with ingestion of water having the highest measured Ra activities are up to 138 and 14 times the WHO-recommended maxima for infants and adults, respectively. Dissolved Ra activities are positively correlated with barium and negatively correlated with sulfate, while barite is approximately saturated. In contrast, Ra is uncorrelated with salinity. These observations indicate the dominant geochemical mechanisms controlling dissolved Ra activity may be barite precipitation and sulfate reduction, along with input from alpha-recoil and dissolution of aquifer minerals and loss by radioactive decay. Radium mitigation measures should be adopted for water quality management where Nubian Aquifer groundwater is produced for agricultural and domestic consumption.