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The article discusses a study related to estimations of the hydrogen sulfide, its concentration and genesis in deep basins in the Caspian Sea. It mentions that a Conductivity, Temperature, Depth (CDT) probe Idronaut, was used to characterize the temperature, salinity, density, and dissolved oxygen in water columns. It further states that in the study concentration of oxygen was controlled by the Winkler method and hydrogen sulfide was measured by the iodometric method.

Isotopic compositions of organic (δC-C) and carbonate (δC-C) carbon were analyzed in the particulate matter (hereafter, particulates) and sediments from the North and Middle Caspian basins. Isotopic composition of C was used for assessing proportions of the allochthonous and autochthonous organic matter in the particulates. Difference between the δC-C values in surface sediments and particulates is explained by the aerobic and anaerobic diagenetic transformations. Isotopic composition of C in sediments may be used as a tool for reconstructing the Quaternary transgressive-regressive history of the Caspian Sea. [ABSTRACT FROM AUTHOR]

The article investigates the system of the Caspian Sea through an interdisciplinary expedition aboard the R/V Rift ship. It examines the hydrophysical, hydrochemical, sedimentological, and geological characteristics of the atmosphere, the waters thickness, and the bottom sediments of the sea. It was discovered that the bottom sediments involved liquefied pelitic-silty material based on the samples. An increased content of methane was also noted.

The article focuses on a study that assesses the methane concentration in the water column of the Northern and Middle Caspian Sea, determines the rate of methane production and oxidation processes and investigates its hydrochemical and microbiological characteristics. It notes that data used were collected in November 2008 on an expedition of the Institute of Oceanology in Russia wherein the total microorganism content (TMC) was determined through direct counting on black polycarbonate filters. A radio-isotopic method was also used to determine the rates of methanogenesis methane oxidization.