Methane Distribution in Lake Baikal Water

Abstract

Data on the distribution of methane concentration in water in the open water area and the northern end of Lake Baikal and in the source of the Angara R. collected in September 2016 and 2019 are analyzed. To apply correlation analysis, in addition to methane, various hydrochemical characteristics were also determined, including the temperature, pH, the concentrations of О2, suspended matter, Corg, Norg, Porg, mineral compounds of nitrogen and phosphorus. Methane concentration in Baikal water in 2016 varied within 0.44–3.41 µL/dm3 (on the average, 0.80 µL/dm3); in 2019, within 0.20–5.19 µL/dm3 (on the average, 1.22 µL/dm3). The maximal methane concentration was recorded in the water mass of the deepest central depression of the lake, and the minimal, in its southern depression. Among shallow areas, minimal methane concentrations were recorded in the coastal zone of Listvenichnyi Bay, and its maximal concentrations, in the northern part of the lake, into which many rivers empty, as well as in Selenginskoe shallows. Most stations, either deep-water or shallow, showed a peak of subsurface maximum of methane concentration at depths of 25–50 m (thermocline zone), after which its concentrations commonly dropped, reaching their minimal values either in the intermediate water mass or in bottom layers. Shallow areas, in addition to higher methane concentrations compared to deep-water areas, also featured a higher contrast in its vertical distribution in the water mass. The analysis of correlation relationships between the examined hydrochemical characteristics revealed significant direct correlations of methane concentration with the concentrations of Corg and Norg and an inverse correlation with O2 concentrations.