Vertical distributions of dissolved methane into bottom sediments from background areas of Lake Baikal

Abstract

Vertical distributions of dissolved methane and this flux into bottom sediments (up to 3 m thickness) from background (undisturbed sedimentation) areas of the Southern, Middle and Northern basins of Lake Baikal were obtained and characterized. Vertical methane profiles at all stations are similar characteristics: low concentrations in the near-surface layers (≤ 1–2 µM) and a steady increase with depth. The highest concentrations of methane into sedimentary were observed in the Middle basin, followed by somewhat lower levels in the Southern, and concentrations an order of magnitude lower in in the Northern basin. The exponential decrease in methane concentrations toward to the bottom–water interface to equally low values, regardless of its content within the sediment, indicates its significant oxidation and consequently minimal influence on methane concentrations at the near-bottom water interface. The obtained results fill a gap in knowledge concerning the vertical distribution of methane into baikalian bottom sediments and are important for assessing the stability and functioning of hydrocarbon systems in a cold and deep freshwater reservoir.