Measurements of ⁸¹Kr/Kr in deep groundwater from the Nubian Aquifer (Egypt) were performed by a new laser‐based atom‐counting method. ⁸¹Kr ages range from ∼2 × 10⁵ to ∼1 × 10⁶ yr, correlate with ³⁶Cl/Cl ratios, and are consistent with lateral flow of groundwater from a recharge area near the Uweinat Uplift in SW Egypt. Low δ²H values of the ⁸¹Kr‐dated groundwater reveal a recurrent Atlantic moisture source during Pleistocene pluvial periods. These results indicate that the ⁸¹Kr method for dating old groundwater is robust and such measurements can now be applied to a wide range of hydrologic problems.

Due to heightening concern about radiation hazards protection, activity concentrations of ²²⁶Ra, ²³²Th, ⁴⁰K in forty soil samples collected from Shoubra El Kheima in the South Nile Delta were measured using gamma-ray spectrometry. The mean activity concentrations of ²²⁶Ra and ⁴⁰K were higher in 20% of the considered samples than the world average values. A comprehensive comparison with up-to-date data was carried out. Spatial distribution maps of the measured radionuclides and radiological parameters were generated. The distributions of natural radionuclides were influenced by the soil organic matter, clay content, and scavenger metals oxides, as well as differences in the physical and chemical attributes and solubility of these radionuclides. The results revealed that industrial activity and agricultural practices in the study area caused an incremental increase in ²²⁶Ra and ⁴⁰K activity concentrations. It can be deduced that although there are intensive industrial activities in this area, the natural radiation that comes from the soil is normal and does not pose a significant radiological hazard to the public. The natural radioactivity of soil in this area needs to be monitored periodically to prevent unnecessary radiation exposure to inhabitants.

Electron microprobe analysis (EMPA) and microscopic investigations were performed on monazite grains from the black sand deposits of northern Sinai beach. Electron microprobe backscattered electron images, X-ray mapping and wavelength dispersive spectroscopy line scans showed some grains with sector zoning and others with thorite inclusions. Based on the EMPA data, the studied monazite is grouped into monazite-(Ce) and Th-rich monazite. Monazite-(Ce) is enriched in REE and P, whereas Th-rich monazite is enriched in Th, U, Ca, Y, Si and Fe. The compositional variations of monazite are governed by the substitution of REE by Th, U, Ca and Y. The monazite grains show enriched chondrite-normalized REE patterns represented mainly by LREE and only Gd from the HREE. These patterns demonstrate negative Nd and Euanomalies. The floods associated with the pluvial periods which prevailed in Egypt during the Pleistocene, were able to erode the source rocks and liberate heavy minerals including monazite. The mineral grains were transported through several wadis and tributaries to the main channel of the River Nile. At the confluence sites, these heavy minerals were mixed with Ethiopian and central African heavy mineral assemblages. The grains continued to move together downriver until being deposited in their current locations. The analytical results suggest that pegmatites and granites of the Eastern Desert are the most likely source of the monazite. However, due to the large area of the Nile watershed, other undiscovered sources are possible.

Stream sediments and groundwater samples were collected from the vicinity of El Allouga uranium mine in southwestern Sinai and analyzed for their radionuclides to explore the geochemical dispersion and environmental impact. The radioactivity measurements were performed using γ-ray spectrometry and UV-photometry. Most stream sediments samples have eU concentrations more than the background level. The significant correlations between eU, clay, and organic matter contents reflect possible adsorption of U to the surface of clay and organic matter. The high radionuclide concentrations in the stream sediment are mainly due to contamination from the mining process, and, in some locations, due to rock outcrops weathering. The measured concentrations of U in groundwater samples exceed the Maximum Contamination Level of groundwater U (30 ppb). The lack of correspondence of U concentrations in the country rocks and associated groundwater indicates the high mobility of U and reflects absence of a simple rock/water equilibration. Water resources in the study area have ²³⁴U/²³⁸U activity ratios with obvious deviations from secular equilibrium. The U isotopic data support that uranium ore body could be locally forming within the rock aquifer at El Allouga area. The calculated external hazard parameter values are higher than the worldwide average in 30% of the studied stream sediment samples; this indicates that people who are exposed to that level of radiation for a lifetime would have an elevated cancer risk. The Annual Effective Dose resulting from U activity concentrations in the studied drinking water is significantly higher than the recommended limit for children and adults. Therefore, the available water resources in the study area are considered unsafe for human consumption.