Laboratory Studies of Main Component Composition of Hyperhaline Lakes

Abstract

Introduction. Composition of water is an important hydrochemical characteristic of a salt water body. It is very important in shaping the conditions for the ecosystem functioning. This factor should be taken into account in determining water salinity since salinity measurements carried out by the standard oceanographic equipment using electrical conductivity in the water where the ion ratio is different from that in the oceanic water results in significant errors. Data and methods. The present paper describes the analytical methods for laboratory determining the chlorides, sulfates, calcium, magnesium and total dissolved inorganic carbon concentrations using potentiometric titration, the potassium contentby the gravimetric method. These methods are adapted for hyperhaline waters having the different ion-salt composition as compared with the oceanic one. The method's error (relative deviation) did not exceed 1.7% for halogens, 4% for sulfates, 1.5% for carbonate ions, 0.7% for bicarbonate ions, 4% for calcium ions, 3.2% for magnesium and 1.3% for potassium. Results. The components of main chemical composition of the hyperhaline reservoirs, namely the Aral and Dead seas, and Lake Urmia were obtained. Salinity of these water bodies represented by total amount of the basic ions were determined. Discussion and conclusion. The natural basins under study represent the terminal lakes characterized by high water salinity, which is many times higher than that of the ocean water. The ratios of the main ions in the sources under study differ from each other significantly as well as from the similar ratios in the world ocean.

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“…The potentiometric titration method was employed to measure the concentration of Ca 2+ and Mg 2+ as an indication of sample degradation. [ 66 ] In this regard, an automatic potential titrator (ZDJ‐5, Shanghai Rex Electric Chemical Co., Ltd.) equipped with a Ca 2+ ‐selective electrode and a calomel reference electrode (232‐01) was used. Tris(hydroxymethyl)aminomethane (Tris, ACS, T110600, Aladdin) and acetylacetone (HACAC, AR, A110367, Aladdin) were dissolved together in the deionized water to serve as the auxiliary complexing agent.…”