Large isotopic variations and similarities in methane ebullition from northern lakes

• Lakes are abundant in northern, high latitude landscapes and considered a substantial source of atmospheric methane (CH4). In spite of this, little is known about how CH4 release mechanisms relate to underlying organic sources and biogenic production pathways in different types of water bodies. Here, we present a substantial, multiyear dataset of the stable isotopes of CH4 ebullition from three interconnected, subarctic post-glacial lakes. The δ13C-CH4 and δD-CH4 vary from -78.4 to -53.1‰ and from -369.8 to -218.8‰, respectively. Overall, these observations suggest predominantly acetoclastic methanogenesis in the shallow zones, possibly fueled by in-situ plant production, and a shift towards a mix with hydrogenotrophy at depth. The bubbles’ δ13C-CH4 are similar to most of those reported from other northern natural systems, but we found differences in δD-CH4, possibly due to evaporation-driven fractionation over summer. Stable isotopes provide valuable information about underlying organic sources and production pathways, however, due to large overlaps they may not be effective in reducing uncertainties in emissions potentials among different water body types, and in general between lakes and wetlands.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences (hsv//eng)

Nyckelord

northern lakes

methane emission

ebullition

stable isotopes

geokemi

Geochemistry

Publikations- och innehållstyp

vet (ämneskategori)

ovr (ämneskategori)