Methane and sulfide sulfur in the bottom sediments of lake Baikal

The paper analyzes data on the distribution of methane and sulfide sulfur concentrations in the upper layer of the bottom sediments in different areas of Lake Baikal obtained during expeditions in 2014 and 2015. During the study, concentrations of methane and sulfide sulfur in lake sediments varied from <0.01 to 3.69 μg/g dry sediment (mean 0.34 μg/g) and from 0.002 to 0.830 mg/g dry sediment (mean 0.042 mg/g), respectively. The maximum concentrations of methane were typical of the Northern region, where the waters of the Upper Angara, Kichera rivers flow, and separate stations of profile along the estuary zone of the Selenga River, as well as stations located in the zone of underwater wastewater discharge of Baikalsk and the Baikal pulp and paper mill closed in 2013. A comparison of the distribution of methane and sulfide sulfur concentrations indicates an intense sulfate reduction at the stations with the highest methane concentrations, which suggests the conjugate processes of their generation. Variations of methane and sulfide sulfur concentrations in the studied upper layers of Lake Baikal sediments are caused by the differences in the anthropogenic impact and also by the variability of sedimentation conditions that determine the grain size composition and the content of organic matter, and, as a consequence, the intensity of methanogenesis and sulfate reduction.