Hydrogen sulfide and other reduced forms of sulfur in oxic waters of Lake Doroninskoe, eastern Transbaikalia

Abstract

Simultaneous occurrence of oxygen and hydrogen sulfide was established by hydrochemical investigations in the waters of the Black and Baltic seas at a depth of more than 50 m (c-layer) [1‐3, 9, and others]. The most probable reason for the appearance of H 2 S and other sulfur species with intermediate oxidation states (thiosulfates and sulfites) is sulfate reduction in situ, i.e., immediately in the c-layer. A great number of publications have been devoted to the problem of the formation of hydrosulfuric, especially underground, mineral waters [6, 11, and others]. However, the presence of H 2 S in the oxic layer was reported only by few authors [8 and others], who believed that hydrogen sulfide can be supplied in part from bottom sediments. Data on other sulfur species (mainly, thiosulfates and sulfites) are rare [4]. The formation of suboxidized sulfur species (thiosulfates and sulfites) in waters during the oxidation of sulfide deposits has been studied in more detail [7]. The distribution of sulfur species in soda waters of Lake Doroninskoe has been studied since 2003. This work has been supplemented by determinations of oxygen since December 2005. The lake (4.5 km 2 in area and up to 6.5 m deep) is located at the bottom of the Mesozoic Chita‐Ingoda intermountain depression in the Ingoda River basin, one of the sources of the Amur River. The lake is underlain by Early Cretaceous sandy‐silty deposits intercalated with intermediate‐ basic effusive rocks. The bottom muddy sediments (up to 10 m thick) contain up to 0.4% iron sulfides [5]. The basin lacks drainage, and its water is characterized by high salinity due to evaporation. Water was sampled from top to bottom using a plexiglas bathometer or peristaltic pump at two stations located in the central and coastal parts of the lake. Dis