Methane Seeps and Records of AOM in the Lake Baikal Freshwater Environment
Abstract
Anoxic oxidation of methane is an important mechanism in removing methane seeping to the sea. In freshwater wetland environment, sulfate is usually low in concentration and hence could not act as an important mechanism in removing methane in the aqueous environment and its subsequent emitting into the atmosphere. In polar and deep freshwater, e.g., Lake Baikal, environment, low temperature condition favor methane exist as gas hydrate. However, methane seeps are frequently observed in the Lake Baikal and could release high amount of methane into the atmosphere. The purpose of this research is to unravel role of sulfate in controlling methane in the freshwater Lake Baikal. A set of 15 gravity cores was collected. In addition, we have also collected river water and hot spring waters (18 sites) in order to characterize source(s) of sulfate entering the Lake. Our results show that gas hydrate existed in sediments in the Lake Baikal. In addition, methane is actively releasing into water column. However, unusually high concentrations of authigenic pyrite also existed in sediment, which indicating AOM (anaerobic oxidation of methane) is also an important process in this freshwater environment. Lake water sulfate and chloride remain low concentrations throughout the entire lake water. Existence of authigenic pyrite, higher concentrations of pore water sulfate and chloride demonstrated that deep source of sulfate from gas venting could be another source of sulfate which facilitate AOM in sediments. The result indicated that AOM is an important process in the freshwater lake environment with extra source of sulfate.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.B33G0559L
- Keywords:
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- 0414 BIOGEOSCIENCES Biogeochemical cycles;
- processes;
- and modeling;
- 0428 BIOGEOSCIENCES Carbon cycling;
- 0488 BIOGEOSCIENCES Sulfur cycling;
- 0454 BIOGEOSCIENCES Isotopic composition and chemistry