Date of Award

2008

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Science

First Advisor

Dr. Samir Abu- Eishah

Second Advisor

Dr. Zein Elabidin Rizk

Third Advisor

Dr. Tarek Yousser

Abstract

Coastal Sabkha area of Abu Dhabi extends about 300 km long and 15km wide. It consist of a series of hypersaline (47%0) lagoons surrounded by salt-encrusted flat sabkhas. Temperature there may reach 60°C in the summer. Moreover, the salinity of the lagoons is very high and may reach 70%0.

The objective of this study was to assess the possibility of utilizing salinity gradient in solar ponds and/or production of solar salt along Abu Dhabi coasts. This study was conducted in sabkha area which extends from Al Mafraq-Al Sil’a Highway, near the satellites station (kilo 255, Dy 17 Street) until khor Al-Bazem and Al-Dhabeia area and is bounded approximately by latitudes 22°40’ and 26°10’N and longitudes 51°35’ and 56°25’E. The collected sediment samples were subjected to sedimentological and mineralogical analyses using grain size, X-ray diffraction, petrographic analysis, carbonate content and salts crystals; while the water samples were subjected to chemical analyses.

The results of this study indicated that the sediments of the sabkha area around Abu Dhabi coast are formed a mixture of sand-sized carbonate and evaporite minerals. A major mineral of evaporite that was recorded by X-ray diffraction technology was halite (NaCl); while carbonate mineral was calcite (CaCO3). Results of the petrographic analysis had similar manner of X-ray analysis’s results; all sediment samples are mainly consisting of calcite and halite in addition to quartz minerals. The high carbonate content reflected the origin of the sediments that was marine input and came from the sea. Salts crystals analysis approved the dominance of an isometric crystal. Generally, sediments characterizations approved that Abu Dhabi sabkhas have halite mineral in high quality which encourages crystallizing solar salts and/or building of solar ponds.

The study found that climatic conditions in Abu Dhabi coastal-plain sabkhas, lead to the formation of marine brines sodium-chloride to chloride dominated type with a pH value of (~ 8.0). Due to the evaporation of the groundwater, the evaporite minerals especially halite were precipitated. The present study showed that Abu Dhabi coastal sabkha system is open is open for sodium and chloride and this resulted in an increase in the Na+ and Cl- ion concentration and the formation of halite mainly on sabkha’s surfaces of the supratidal flats. This gives an indicated that the studied area has reasonable amounts of halite mineral essentially to assemble a natural salinity gradient. The study also evaluated the thermal stratification of sabkha’s water in different sites of the study area by measuring various properties (pH, Temp., E. C., TDS. Colour, odour) directly in the field at different times (February, April, and August 2008). The measured temperature, salinity and electrical conductivity of the water samples indicated the possible occurrence of natural gradient in the sabkhas area.

According to the reported sediments and water characterizations results, the suggested area of the studied sabkhas along Abu Dhabi coast have favourable condition to crystallize solar salt and/or build up natural salinity gradient. On the other hand, the reported results can be considered as documentation of the sedimentological, mineralogical and hydrogeochemical characteristics of Abu Dhabi’s sabkhas and could be useful for planners and researchers interested in Abu Dhabi coastal systems.

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