Reduced sulfur compounds in the bottom sediments of meromictic lakes

Abstract

This paper presents data on the content of reduced sulfur compounds in the bottom sediments of two meromictic reservoirs: Mogilnoe Lake (Barents Sea) and Lake Trekhtsvetnoe (White Sea). A distinctive feature of both reservoirs is the high content of hydrogen sulfide in the anaerobic monimolimnion. The total content of reduced sulfur compounds, characterized by the ƩSH2S parameter, averaged 0.500% for Mogilnoe Lake and 0.994% for Lake Trekhtsvetnoe. The main form of sulfur for both lakes was pyrite (more than 60% for Mogilnoe Lake and up to 80% for Lake Trekhtsvetnoe). Significant amounts of sulfur associated with organic matter were noted in the surface layers. The contents of acid-soluble monosulfides and elemental sulfur were not significantly different (no more than 10% of ƩSH2S). This distribution of forms in the composition of ƩSH2S makes the bottom sediments of the studied lakes similar to sea sediments. The high level of accumulation of reduced sulfur compounds in sediments is due to their provision of a sufficient amount of organic matter, which comes mainly from the chemocline zone.