A New Natural Source of Methane has been Studied
A senior researcher at the Faculty of Soil Science at Moscow State University took part in a study of methane flows from the floodplains of rivers in Western Siberia. Methane is the second most important greenhouse gas after carbon dioxide. The processes of formation and movement of methane in soil are diverse and are of interest to researchers in many countries. A team of authors studied the origin, metabolic pathways and migration of methane in recently discovered new natural sources of CH4 – seep fields located in the floodplains of many rivers (including the Irtysh and Ob) in the center of the West Siberian Lowland. In the central part of Western Siberia, seep fields are groups of small craters (about 1-10 cm in diameter) or cone-shaped formations (10-50 cm in diameter), from which groundwater and gas bubbles emerge. The results of the study were published in the journal Global Change Biology.
Methane is known to have a global warming potential (over a 100-year time horizon) 23 times higher than carbon dioxide. Understanding the origin, sources and direction of methane flows from terrestrial ecosystems is of not only academic, but also practical interest: modern mathematical models for forecasting climate change require information about how much methane will enter the atmosphere over the period for which the forecast is made. The West Siberian Lowland is one of the most swampy regions, and swamps, as is known, are the most powerful natural source of methane. The authors of the study suggested that the origin of the methane escaping from the seeps may be associated with Cretaceous-age oil deposits, thawing of deep-lying permafrost, or horizontal migration of gas formed in the surrounding Holocene swamps. To test these hypotheses, scientists used several biogeochemical methods, such as studying the composition of light hydrocarbons; determination of stable isotope ratios in methane, carbon dioxide and water, and radiocarbon dating of methane. The study collected gas and water samples from 50 sites in the study area, which stretches over 120,000 square kilometers.
The radiocarbon age of the methane escaping from the seeps ranged from 4.2 to 8.0 thousand years, indicating Holocene sources in the peatlands. The close similarity in the isotopic composition of the methane that comes out of the seeps and that which is formed by methanogenic microbes in the surrounding peat bogs suggests that the gas, along with water, migrates from the high bogs to the seeps located in the floodplains.
“The results show a close connection between peatlands, groundwater and floodplains in the lowlands of Western Siberia in terms of the routes of methane migration from terrestrial to aquatic ecosystems and its possible large emissions into the atmosphere. This pathway in the terrestrial methane cycle may be overlooked in other regions where raised bogs are common. Undoubtedly, further research is needed to identify environmental factors that control the level of methane concentration in seep waters at various spatial and temporal scales, as well as to assess the contribution of methane from seeps of the boreal zone of Western Siberia to the global methane budget and to study the biogeochemistry of carbon transformation in the aquifers of Western Siberia.” , – commented on the results of the study Mikhail Glagolev, senior researcher at the Department of Physics and Soil Reclamation, Faculty of Soil Science, Moscow State University.
Field sampling and laboratory analyzes were supported by a grant from the Russian Science Foundation (project no. 19-77-10074). The logistics of the work was organized with the support of a grant from the Government of the Tyumen Region within the framework of the Program of the World-Class West Siberian Interregional Scientific and Educational Center (national project “Science”).
Information provided by the press service of Moscow State University
