The Impact of Methane Seepage on the Pore-Water Geochemistry across the East Siberian Arctic Shelf

• Published in: Water
• Main Authors: Natalia Guseva, Yulia Moiseeva, Darya Purgina, Elena Gershelis, Evgeniy Yakushev, Igor Semiletov
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2021
• Subjects: pore-water; methane seep; trace elements; East Siberian Arctic Shelf; global warming; Hydraulic engineering; TC1-978; Water supply for domestic and industrial purposes; TD201-500; Arctic; East Siberian Sea; Laptev Sea; Global warming; laptev
• Online Access: https://doi.org/10.3390/w13040397; https://doaj.org/article/019ef3b81b16404c9f877b5cada8254f

East Siberian Arctic Shelf, the widest and the shallowest shelf of the World Ocean, covering greater than two million square kilometers, has recently been shown to be a significant modern source of atmospheric methane (CH 4 ). The CH 4 emitted to the water column could result from modern methanogenesis processes and/or could originate from seabed deposits (pre-formed CH 4 preserved as free gas and/or gas hydrates). This paper focuses primarily on understanding the source and transformation of geofluid in the methane seepage areas using ions/trace elements and element ratios in the sediment pore-water. Six piston cores and totally 42 pore-water samples were collected in the East Siberian Sea and the Laptev Sea at water depths ranging from 22 to 68 m. In the active zones of methane release, concentrations of vanadium, thorium, phosphorus, aluminum are increased, while concentrations of cobalt, iron, manganese, uranium, molybdenum, copper are generally low. The behavior of these elements is determined by biogeochemical processes occurring in the pore-waters at the methane seeps sites (sulfate reduction, anaerobic oxidation of methane, secondary precipitation of carbonates and sulfides). These processes affect the geochemical environment and, consequently, the species of these elements within the pore-waters and the processes of their redistribution in the corresponding water–rock system.