Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Hydrogeochemical properties of hypersaline lake Acıgöl (Denizli) and evaluation using remote sensing methods

Hipersalin Acıgöl’ün (Denizli) hidrojeokimyasal özellikleri ve uzaktan algılama yöntemleri ile değerlendirilmesi

Auteur : Karaman, Muhittin

Université de soutenance : Pamukkale Üniversitesi

Grade : Doctoral Thesis 2017

Résumé
Acıgöl is a Na-Cl-SO4 type, tectonic, alkaline, mesotrophic-hypereutrophic, mesosaline-hypersaline lake. The lake, which has semi-arid climate, is directly affected by meteorological events. Some 25% of the lake volume evaporates during the transition period between dry and pluvial periods ; the lake area also shrinks by 55-61%. Evaporative concentration, dissolution and re-precipitation of evaporite are the most important chemical events that affect the chemistry of the lake. Moreover, under the influence of biogeochemical events, precipitation and dissolution of carbonates, growth of secondary carbonates, cation exchange, and silicate weathering have an impact on the geochemistry of the lake. The dynamic equilibrium between the dissolution of evaporites in the lake and the oxidation of sulphide minerals allowing the deposition of sulfate as sediments controls the isotopic composition of the sulfate component. Climate conditions, biogeochemical cycles, change in the physical properties of the water and redox conditions, water feeding the lake, evolution and dissolution of efflorescence on the lake surface as a result of current evaporation, mineral precipitation and dissolution reactions can all lead to differentiation of the hydro-geochemistry of the lake. Evaporative evolution in the cold period of the lake is different from evaporative evolution in the warmtemperate period. Major element geochemistry is controlled by recent lake sediments, which belong to lithologic units surrounding the lake and are formed by chemical sedimentation having an annual sedimentation rate of 0.029 g.cm-2.y-1. Water surrounding the lake has a meteoric origin where dissolution of evaporites and a fresh-bicarbonate water mixture are observed. Water feeding the lake is fed by rainfall and snowmelt waters. REE and trace element enrichment in the sediments is controlled by K-feldspar, Al-silicates and, especially, phyllosilicates. Proba-NDWI may be used for observing dry and pluvial cycle of the lake with hyperspectral satellite images, and besides, ONDLSI can be used for tracking salinity. The salinity effect is apparent in the absorption between 700-788nm ranges of the infrared region of the lake water spectrum, which are obtained from hyperspectral satellite images. Multi-temporal satellite images should be used to research evaporation-dissolution cycle of saline lakes.

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