Enhancing Surface Methane Fluxes from an Oligotrophic Lake: Exploring the Microbubble Hypothesis

Exchange of the greenhouse gases carbon dioxide (CO2) and methane (CH4) across inland water surfaces is an important component of the terrestrial carbon (C) balance. We investigated the fluxes of these two gases across the surface of oligotrophic Lake Stechlin using a floating chamber approach. The...

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Bibliographic Details
Published in:Environmental science & technology 2015-01, Vol.49 (2), p.873-880
Main Authors: McGinnis, Daniel F, Kirillin, Georgiy, Tang, Kam W, Flury, Sabine, Bodmer, Pascal, Engelhardt, Christof, Casper, Peter, Grossart, Hans-Peter
Format: Article
Language:English
Subjects:
Aquatic ecology
Atmosphere
Carbon
Carbon Cycle
Carbon dioxide
Carbon Dioxide - analysis
Environmental science
Freshwater
Gases
Germany
Greenhouse gases
Lakes - chemistry
Methane
Methane - analysis
Microbubbles
Water Pollutants, Chemical - analysis
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Summary:Exchange of the greenhouse gases carbon dioxide (CO2) and methane (CH4) across inland water surfaces is an important component of the terrestrial carbon (C) balance. We investigated the fluxes of these two gases across the surface of oligotrophic Lake Stechlin using a floating chamber approach. The normalized gas transfer rate for CH4 (k 600,CH4) was on average 2.5 times higher than that for CO2 (k 600,CO2) and consequently higher than Fickian transport. Because of its low solubility relative to CO2, the enhanced CH4 flux is possibly explained by the presence of microbubbles in the lake’s surface layer. These microbubbles may originate from atmospheric bubble entrainment or gas supersaturation (i.e., O2) or both. Irrespective of the source, we determined that an average of 145 L m–2 d–1 of gas is required to exit the surface layer via microbubbles to produce the observed elevated k 600,CH4. As k 600 values are used to estimate CH4 pathways in aquatic systems, the presence of microbubbles could alter the resulting CH4 and perhaps C balances. These microbubbles will also affect the surface fluxes of other sparingly soluble gases in inland waters, including O2 and N2.
ISSN:0013-936X
1520-5851
DOI:10.1021/es503385d