Distribution of uranium and thorium radioelements in subsurface pleistocene-holocene sediments of the Nile Delta, Egypt

الملخص EN

Collaborative techniques were used to investigate the textural and mineralogical characteristics as well as uranium and thorium contents of the Pleistocene-Holocene subsurface sediments of the onshore area of northern Nile Delta.

Fluctuation of water flow during the formation of these sediments resulted in particle sizes variability over time.

Approximately 25 % of the samples are classified into sand, 20 % clayey silt, 18 % silty sand, 15 % sandy silt and 15 % sand-silt-clay.

The average uranium content of these sediments is 3.7 ppm and that of thorium is 7.83 ppm.

The ranges of Th / U ratio (1.03-4.74) possibly reflect vertical variability based on changes in textures, mineralogical composition and organic matter contents.

This variation points to interactions between fluvial, brackish and freshwater regimes, which would be expected to typify a delta setting.

Geochemical behavior of both uranium and thorium is regarded as the essential factor controlling the distribution of the two elements.

Zircon, monazite and apatite are the main accessory minerals hosting uranium and thorium.

However sportive uptake of uranium by sediments of relatively high organic matter contents have also played a significant role in uranium adsorption to the sediments.