A conduit dilation model of methane venting from lake sediments

Scandella, Benjamin P.; Varadharajan, Charuleka; Hemond, Harold F.; Ruppel, Carolyn D.; Juanes, Rubén

doi:10.1029/2011gl046768

Cited by 96 publications

(135 citation statements)

References 34 publications

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“…This is in stark contrast to the homogenous, cohesive fine-grained estuarine sediment that fills the nearshore basins in the north temperate pockmark fields. Coarser-grained channel fill could promote fluid migration and diffusion along the channel, rather than vertical migration of fluids that occurs in fine-grained sediment (e.g., Jain and Juanes, 2009;Scandella et al, 2011), resulting in gas spatially coincident with paleochannels and minimal seafloor disturbance (Hill et al, 1992).…”

Section: Pockmarks' Relation To Stratigraphymentioning

confidence: 99%

Shallow stratigraphic control on pockmark distribution in north temperate estuaries

et al. 2012

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Pockmark fields occur throughout northern North American temperate estuaries despite the absence of extensive thermogenic hydrocarbon deposits typically associated with pockmarks. In such settings, the origins of the gas and triggering mechanism(s) responsible for pockmark formation are not obvious. Nor is it known why pockmarks proliferate in this region but do not occur south of the glacial terminus in eastern North America. This paper tests two hypotheses addressing these knowledge gaps: 1) the region's unique sea-level history provided a terrestrial deposit that sourced the gas responsible for pockmark formation; and 2) the region's physiography controls pockmarks distribution. This study integrates over 2500 km of high-resolution swath bathymetry, Chirp seismic reflection profiles and vibracore data acquired in three estuarine pockmark fields in the Gulf of Maine and Bay of Fundy. Vibracores sampled a hydric paleosol lacking the organic-rich upper horizons, indicating that an organic-rich terrestrial deposit was eroded prior to pockmark formation. This observation suggests that the gas, which is presumably responsible for the formation of the pockmarks, originated in Holocene estuarine sediments (loss on ignition 3.5-10%), not terrestrial deposits that were subsequently drowned and buried by mud. The 7470 pockmarks identified in this study are non-randomly clustered. Pockmark size and distribution relate to Holocene sediment thickness (r 2 =0.60), basin morphology and glacial deposits. The irregular underlying topography that dictates Holocene sediment thickness may ultimately play a more important role in temperate estuarine pockmark distribution than drowned terrestrial deposits. These results give insight into the conditions necessary for pockmark formation in nearshore coastal environments.Published by Elsevier B.V.

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Section: Pockmarks' Relation To Stratigraphymentioning

confidence: 99%

Shallow stratigraphic control on pockmark distribution in north temperate estuaries

et al. 2012

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“…The prevailing paradigm is that microbial methanogenesis occurs primarily in anoxic environments (3,4). A commonly observed paradox is methane accumulation in well-oxygenated waters (2,5), which is often assumed to be the result of physical transport from anoxic sediment and water (6)(7)(8) or in situ production within microanoxic zones (9)(10)(11). Two recent studies challenged this paradigm and suggested that microbes in oligotrophic ocean can metabolize methylated compounds and release methane even aerobically (12,13).…”

mentioning

confidence: 99%

Microbial methane production in oxygenated water column of an oligotrophic lake

Grossart

Frindte

Dziallas

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

273

326

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The prevailing paradigm in aquatic science is that microbial methanogenesis happens primarily in anoxic environments. Here, we used multiple complementary approaches to show that microbial methane production could and did occur in the well-oxygenated water column of an oligotrophic lake (Lake Stechlin, Germany). Oversaturation of methane was repeatedly recorded in the well-oxygenated upper 10 m of the water column, and the methane maxima coincided with oxygen oversaturation at 6 m. Laboratory incubations of unamended epilimnetic lake water and inoculations of photoautotrophs with a lake-enrichment culture both led to methane production even in the presence of oxygen, and the production was not affected by the addition of inorganic phosphate or methylated compounds. Methane production was also detected by in-lake incubations of lake water, and the highest production rate was 1.8-2.4 nM·h −1 at 6 m, which could explain 33-44% of the observed ambient methane accumulation in the same month. Temporal and spatial uncoupling between methanogenesis and methanotrophy was supported by field and laboratory measurements, which also helped explain the oversaturation of methane in the upper water column. Potentially methanogenic Archaea were detected in situ in the oxygenated, methane-rich epilimnion, and their attachment to photoautotrophs might allow for anaerobic growth and direct transfer of substrates for methane production. Specific PCR on mRNA of the methyl coenzyme M reductase A gene revealed active methanogenesis. Microbial methane production in oxygenated water represents a hitherto overlooked source of methane and can be important for carbon cycling in the aquatic environments and water to air methane flux. epilimnic methane peak | methanogens A lthough methane makes up <2 parts per million by volume (ppmv) of the atmosphere, it accounts for 20% of the total radiative forcing among all long-lived greenhouse gases (1). In the aquatic environments, methane is also an important substrate for microbial production (2). The prevailing paradigm is that microbial methanogenesis occurs primarily in anoxic environments (3, 4). A commonly observed paradox is methane accumulation in well-oxygenated waters (2, 5), which is often assumed to be the result of physical transport from anoxic sediment and water (6-8) or in situ production within microanoxic zones (9-11). Two recent studies challenged this paradigm and suggested that microbes in oligotrophic ocean can metabolize methylated compounds and release methane even aerobically (12, 13). These claims are not without caveats, because the amounts of methylated compounds added [1-10 μM methylphosphonate (12) and 50 μM dimethyl sulfoniopropionate (13)] were far higher than their environmental concentrations, and therefore, the ecological relevance remains obscure. Moreover, dissolved oxygen (DO) was not monitored during the long incubation (5-6 d), and the possibility that the experimental setups had become anoxic before methane production could not be dismissed.* Despite the unce...

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“…The ebullition rate, E CH 4 ,s becomes non-zero when bulk CH 4 concentration exceeds a critical value, defined by the hydrostatic load of the water column and sediments layer above at a given depth, z s , as well as by nitrogen concentration at the sediments top Walter et al, 1996). Retention of bubbles in a sediment's skeleton (Scandella et al, 2011) is neglected so that the CH 4 ebullition flux at the sediment's top of the kth column, F B,1,k , is calculated as…”

Section: Methane In Sedimentsmentioning

confidence: 99%

“…This situation is complicated by high vertical and sometimes horizontal variability of gas concentrations in a given lake (Schilder et al, 2013;Blees et al, 2015). Third, when considering gas dynamics in lakes, new physical processes become crucial such as diffusion through the water surface (Donelan et al, 2002), vertical diffusion in metalimnion and hypolimnion, bubble interactions with sediments skeleton (Scandella et al, 2011), and others. Many of these have not been addressed enough so far in both theoretical and experimental studies.…”

Section: Introductionmentioning

confidence: 99%

LAKE 2.0: a model for temperature, methane, carbon dioxide and oxygen dynamics in lakes

et al. 2016

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Abstract. A one-dimensional (1-D) model for an enclosed basin (lake) is presented, which reproduces temperature, horizontal velocities, oxygen, carbon dioxide and methane in the basin. All prognostic variables are treated in a unified manner via a generic 1-D transport equation for horizontally averaged property. A water body interacts with underlying sediments. These sediments are represented by a set of vertical columns with heat, moisture and CH 4 transport inside. The model is validated vs. a comprehensive observational data set gathered at Kuivajärvi Lake (southern Finland), demonstrating a fair agreement. The value of a key calibration constant, regulating the magnitude of methane production in sediments, corresponded well to that obtained from another two lakes. We demonstrated via surface seiche parameterization that the near-bottom turbulence induced by surface seiches is likely to significantly affect CH 4 accumulation there. Furthermore, our results suggest that a gas transfer through thermocline under intense internal seiche motions is a bottleneck in quantifying greenhouse gas dynamics in dimictic lakes, which calls for further research.

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A conduit dilation model of methane venting from lake sediments

Cited by 96 publications

References 34 publications

Shallow stratigraphic control on pockmark distribution in north temperate estuaries

Shallow stratigraphic control on pockmark distribution in north temperate estuaries

Microbial methane production in oxygenated water column of an oligotrophic lake

LAKE 2.0: a model for temperature, methane, carbon dioxide and oxygen dynamics in lakes

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