The use of chemical and instrumental methods in the study of the forms of occurrence of sulfides in bottom sediments

Institute of Earth Sciences, Southern Federal University, 344090 Rostov-on-Don, Zorge str. 40, Russia

^* Corresponding author: fedorov@sfedu.ru

Abstract

On the example of the estuary of the Mius River - the mouth of the Mius River, the Mius estuary, the Taganrog Bay of the Azov Sea, a complex of chemical and instrumental methods was applied, including those developed by the authors. This made it possible to study the physicochemical parameters, the content of total hydrogen sulphide, the form of occurrence of sulfides, the total content of iron and their behavior in the bottom sediments of early diagenesis. Bottom sediments were formed at negative Eh values. Sulfides in bottom sediments are mainly in the form of molecular hydrogen sulfide and acid-soluble iron sulfides. The content of total hydrogen sulfide varied within wide limits, reaching 3.2 mg/g of wet weight, and of gross iron - from 25.4 to 45.1 mg/g dry weight. A significant relationship was found between the content of sulfide sulfur and gross iron. The presence of hydrotroilite was identified by the typical smell of hydrogen sulfide, black color, oily sludge, lack of magnetic properties and by visual study of its formations using electron microscopy. Under a microscope, images of coacervates (colloidal accumulations) of hydrotroilite of a round-ellipsoidal shape (lenticular), from gray to black, mercury-like, were obtained in a wet preparation. It was established for the first time that hydrotroilite exists in the natural environment as a gel-like substance capable of moving in the bottom of sediments. Upon collision, small formations coalesced into larger globules. The important role of hydrotroilite as a mercury accumulator in the early diagenesis of bottom sediments is shown.