What the bubble knows: Lake methane dynamics revealed by sediment gas bubble composition
TLDR
In this paper, the authors presented a method to quantify basin-wide hypolimnetic CH4 fluxes at the sediment level based on measurements of bubble gas content and modeling of dissolved pore water gases.Abstract:
Atmospheric methane (CH4) concentrations have more than doubled in the past ~ 250 yr, although the sources of this potent greenhouse gas remain poorly constrained. Freshwaters contribute ~ 20% of natural CH4 emissions, about half attributed to ebullition. Estimates remain uncertain as ebullition is stochastic, making measurements difficult, time consuming, and costly with current methods (e.g., floating chambers, funnel gas traps, and hydroacoustics). We present a novel approach to quantify basin‐wide hypolimnetic CH4 fluxes at the sediment level based on measurements of bubble gas content and modeling of dissolved pore‐water gases. We show that the relative ebullition flux pathway can be resolved by knowledge of only bubble gas content. As sediment CH4 production, diffusion, and ebullition are interrelated, the addition of a second observation allows closing the entire sediment CH4 balance. Such measurements could include bubble formation depth, sediment diffusive fluxes, ebullition, sediment CH4 production, or the hypolimnetic CH4 mass balance. The measurement of bubble gas content is particularly useful for identifying local ebullitive hotspots and integrating spatial heterogeneity of CH4 fluxes. Our results further revealed the crucial effect of water column depth, production rates, and hypolimnetic dissolved CH4 concentrations on sediment CH4 dynamics. Although we apply the model to cohesive sediments in an anoxic hypolimnion, the model can be applied to shallow, oxic settings by altering the CH4 production rate curve to account for oxidation. Utilizing our approach will provide a deeper understanding of in‐lake CH4 budgets, and thus improve CH4 emission estimates from inland freshwaters at the regional and global scales.read more
Citations
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Journal ArticleDOI
Influence of water column stratification and mixing patterns on the fate of methane produced in deep sediments of a small eutrophic lake
TL;DR: In this article, a small eutrophic lake (Soppensee, Switzerland) was sampled for CH4 concentrations profiles and emissions, combined with water column hydrodynamics to investigate the fate of CH4 produced in hypolimnetic sediments.
Journal ArticleDOI
Clumped Isotopes Link Older Carbon Substrates With Slower Rates of Methanogenesis in Northern Lakes
Peter M. J. Douglas,Peter M. J. Douglas,Regina Gonzalez Moguel,Katey M. Walter Anthony,Martin Wik,Patrick M. Crill,Katherine S. Dawson,Katherine S. Dawson,Derek Smith,Derek Smith,Ella Yanay,Ella Yanay,Max K. Lloyd,Max K. Lloyd,Daniel A. Stolper,John M. Eiler,Alex L. Sessions +16 more
TL;DR: In this paper, the authors apply methane clumped isotope (Δ₁₈) and ¹⁴C measurements to test whether rates of methanogenesis are related to carbon substrate age.
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Exploring the Sources of Unexpected High Methane Concentrations and Fluxes From Alpine Headwater Streams
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High methane emissions from thermokarst lakes on the Tibetan Plateau are largely attributed to ebullition fluxes
Lei Wang,Zhiheng Du,Zhiqiang Wei,Qian Xu,Yaru Feng,Penglin Lin,Jiahui Lin,Shengyun Chen,Yongping Qiao,Jianzong Shi,Cunde Xiao +10 more
TL;DR: In this article, Wang et al. investigated the magnitude and regulation of two CH4 pathways, ebullition and diffusion, in 32 thermokarst lakes on the Tibetan Plateau during the summer of 2020.
Journal ArticleDOI
iAMES: An inexpensive, Automated Methane Ebullition Sensor.
TL;DR: The widespread deployment of low cost automated ebullition sensors such as the iAMES described here will help constrain one of the largest uncertainties in the global methane budget.
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