Wadi el Natrun depression, Egypt

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Main saline lakes in the Wadi Natrun sump

Wadi El Natrun (‎ "Valley of Natron") is an endoheic depression in the Sahara Desert of northern Egypt. The lower parts of the valley are up to 23 m below sea level and 38 m below the level of the Rosette branch of Nile River. The valley contains seven large alkaline lakes accumulating natron-rich salt deposits, as well as salt marshes and freshwater marshes (oases). Water is supplied by underground seepage from the Nile Valley and occasional winter precipitation. The depth of the lakes ranges between 0.5 and 2 m and is regulated by seasonal changes in influx seepage and evaporation.

Natrun, a mixture of bedded and displacive capillary evaporite salts, is dominated by sodium carbonate minerals, and accumulates as shallow layers and crusts in several sumps in the Wadi el Natrun depression (e.g. Lake Natrun, while similar sodium bicarbonate assemblages also occur at Behiera in the nearby Libyan desert). Natrun has been mined and traded from these localities for thousands of years. Writings as old as the reign of Rameses III (1198-1166 B.C.) refer to these natural deposits. These natrun beds (aka historical natron) are not just composed of the mineral natron, but also contain varying amounts of burkeite, gaylussite, trona, halite, northupite, pirssonite and thenardite. In the lowest lake in the Natrun chain, there is a massive 1-m-thick thenardite bed located below the 0.5 m halite bed. All lakes are spring-fed depressions, with an ultimate source in Nile waters (see Warren, 2016; Chapter 12 for detailed literature compilation).

High evaporation rates in and arid climatic conditions, especially during the summer months, mean salinities rise above 300‰ in the more saline lakes, with pH values between 9.5 and 11. The main ionic components in the brines are sulphate, chloride, carbonate and sodium. Traces of magnesium are also present. Waters in the lakes are classified as Cl to SO4−Cl types. Increased Cl levels in Wadi El Natrun brines are thought to increase metal solubilities in the lake brines, due to the formation of soluble chloro-complexes with trace elements. The metal concentrations in the brine decrease in the order: Pb>Cu>Cd>Ni>Zn >Fe>Mn.

Historically, natrun was harvested directly as a salt mixture from the dry lake beds and used for thousands of years as a cleaning product for both the home and body. Blended with oil, it was an early form of soap. It softens water while removing oil and grease. Undiluted, natron was used as a cleanser for the teeth and an early mouthwash. The mineral was mixed into early antiseptics for wounds and minor cuts. Natron can be used to dry and preserve fish and meat. It was also an ancient household insecticide and was used for making leather as well as a bleach for clothing.

The mineral was used during mummification ceremonies in ancient Egypt because it absorbs water and behaves as a drying agent. Moreover, when exposed to moisture, the carbonate in natron increases pH (raises alkalinity), which creates a hostile environment for bacteria. In some cultures, natron was thought to enhance spiritual safety for both the living and the dead. Natron was added to castor oil to make a smokeless fuel, which allowed Egyptian artisans to paint elaborate artworks inside ancient tombs without staining them with soot. Natron (sodium carbonate) from the region was also used in the manufacture of Egyptian faience and in glass manufacture by the Ancient Romans

….More infomation on mummification

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Nam El-Hamra, Wadi Natrun, Egypt

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