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CC BY-NC-ND V4.0, Open Access
Dissertation
Methane flux from lacustrine sediments: Advancing methodologies, determining drivers, and characterizing variability across spatiotemporal scales
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2022
DOI:
https://doi.org/10.7273/000004345
Handle:
https://hdl.handle.net/2376/118859
Abstract
The sediments of lakes and reservoirs produce significant amounts of the powerful greenhouse gas methane (CH4). Characterizing the rate, timing, and controls on the transport of CH4 from sediments is critical for understanding emissions from lacustrine ecosystems. In this dissertation, we explore environmental and anthropogenic drivers of CH4 flux from lake sediments at multiple spatiotemporal scales and address several methodological challenges to measuring CH4 transport into lake water columns.In the first chapter, we examine rates of sediment CH4 production and consumption (oxidation) in a global dataset of lakes and reservoirs. Sediment CH4 production rates positively correlated with lake biological productivity, and systems with greater sediment CH4 production rates had less efficient oxidation. Together, our findings indicate eutrophication may increase emissions from lake and reservoir surfaces by driving greater transport of CH4 from sediments into the water column.
The second chapter presents a novel approach for measuring flux a short distance above sediments. The flux gradient method provides a non-invasive, in situ measurement of flux at an hourly temporal resolution. We apply this method in a eutrophic reservoir and suggest that significant changes in CH4 fluxes observed within hours may be linked to fluctuations in CH4 oxidation and/or near-bed turbulence. Although CH4 fluxes increased from spring to summer, we report that most CH4 was oxidized in the hypolimnion. Our results are the first to examine CH4 flux variability and controls on hourly and seasonal time scales. In addition, the developed method is a promising future tool for quantifying other solute fluxes.
Finally, the third chapter is a critical review of common approaches available for measuring CH4 flux from lake sediments. We highlight important caveats to consider when comparing fluxes across studies, such as some methods disturbing microbial activity, excluding sediment surface processes, or ignoring CH4 dynamics in deeper sediment. We argue that the coarse spatiotemporal resolution and ex situ nature of most techniques have resulted in a poor understanding of the sub-daily variability and controls on CH4 transport from sediments. Lastly, we identify future methodological advancements needed, such as eddy correlation techniques, modeling approaches, and explicit method comparison studies.
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Details
- Title
- Methane flux from lacustrine sediments
- Creators
- Sofia Louise D'Ambrosio
- Contributors
- John A. Harrison (Advisor)Stephen M. Henderson (Committee Member)Kevan B. Moffett (Committee Member)David E. Butman (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- School of the Environment (CAHNRS)
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 191
- Identifiers
- 99900882929401842
- Language
- English
- Resource Type
- Dissertation