Enigmatic stable isotope dynamics of deep peat methane

Waldron, Susan; Hall, Anthony; Fallick, Anthony E.

doi:10.1029/1998gb900002

Cited by 52 publications

(47 citation statements)

References 43 publications

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“…Major effects on δ 13 C in CO 2 should thus be due to methanogenic activity (Whiticar, 1999). A residual enrichment of 13 C in CO 2 as observed in this study is consistent with prior investigations (Hornibrook et al, 2000a;Lansdown et al, 1992;Waldron et al, 1999) and is typical for methanogenic environments, due to strong fractionation during methanogenesis (Conrad, 2005;Whiticar, 1999). Therefore, it was frequently found that δ 13 C CO 2 does Fig.…”

Section: Respiration and Methanogenesissupporting

confidence: 78%

“…The isotopic composition of methane in W-V was in accordance with δ 13 C CH 4 reported in other studies, particularly if sedges were present. Values observed in DW-V and DW-D were considerably lighter in isotopic composition than previously reported (Chasar et al, 2000;Lansdown et al, 1992;Popp et al, 1999;Waldron et al, 1999). In the wet treatment W-V, concentrations of methane and total dissolved carbon dioxide reached a steady state and were high enough to sustain measurable emission.…”

Section: Respiration and Methanogenesismentioning

confidence: 49%

“…energy could be gained from this process according to the thermodynamic calculations. Contrarily, G hm is mostly positive for hydrogenotrophic methanogenesis using measured hydrogen concentrations but again negative using the fractionation factor α C (see also not match δ 13 C of the solid phase (Hornibrook et al, 2000a;Waldron et al, 1999). At greater depths in W-V, δ 13 C CO 2 reached values of around −15‰ compared to a δ 13 C SOM of −28‰.…”

Section: Respiration and Methanogenesismentioning

confidence: 99%

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Fluxes and <sup>13</sup>C isotopic composition of dissolved carbon and pathways of methanogenesis in a fen soil exposed to experimental drought

2008

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Abstract. Peatlands contain a carbon stock of global concern and significantly contribute to the global methane burden. The impact of drought and rewetting on carbon cycling in peatland ecosystems is thus currently debated. We studied the impact of experimental drought and rewetting on intact monoliths from a temperate fen over a period of ~300 days, using a permanently wet treatment and two treatments undergoing drought for 50 days. In one of the mesocosms, vegetation had been removed. Net production of CH4 was calculated from mass balances in the peat and emission using static chamber measurements. Results were compared to 13C isotope budgets of CO2 and CH4 and energy yields of acetoclastic and hydrogenotrophic methanogenesis. Drought retarded methane production after rewetting for days to weeks and promoted methanotrophic activity. Based on isotope and flux budgets, aerobic soil respiration contributed 32–96% in the wet treatment and 86–99% in the other treatments. Drying and rewetting did not shift methanogenic pathways according to δ13C ratios of CH4 and CO2. Although δ13C ratios indicated a prevalence of hydrogenotrophic methanogenesis, free energies of this process were small and often positive on the horizon scale. This suggests that methane was produced very locally. Fresh plant-derived carbon input apparently supported respiration in the rhizosphere and sustained methanogenesis in the unsaturated zone, according to a 13C-CO2 labelling experiment. The study documents that drying and rewetting in a rich fen soil may have little effect on methanogenic pathways, but result in rapid shifts between methanogenesis and methanotrophy. Such shifts may be promoted by roots and soil heterogeneity, as hydrogenotrophic methanogenesis occurred locally even when conditions were not conducive for this process in the bulk peat.

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Section: Respiration and Methanogenesissupporting

confidence: 78%

Section: Respiration and Methanogenesismentioning

confidence: 49%

Section: Respiration and Methanogenesismentioning

confidence: 99%

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Fluxes and <sup>13</sup>C isotopic composition of dissolved carbon and pathways of methanogenesis in a fen soil exposed to experimental drought

2008

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“…For example, Waldron et al (1999) reported  13 C values for CH 4 at Ellergower Moss (near New Galloway, UK) substantially different (up to ~10‰) to results later reported by Clymo and Bryant (2008) from similar depths in the same peatland, only 75 m away. Alternatively, given the extreme difference in  13 C values for both the CO 2 and CH 4 components of peat gases, it would only take a small amount of carbon from 1 fraction contaminating the other (during sample processing) to cause a shift in the measured  13 C value.…”

Section: Test Of Sampling and Laboratory Methods On Field Samplesmentioning

confidence: 95%

“…Waldron et al 1999;Steinmann et al 2008). Clymo and Bryant (2008) review some of these studies in the context of their own results, showing general agreement that  13 C values of dissolved CO 2 increase with depth to between +5‰ to +10‰ at depths below several meters.…”

Section: Garnett Et Almentioning

confidence: 99%

Radiocarbon and Stable Carbon Analysis of Dissolved Methane and Carbon Dioxide from the Profile of a Raised Peat Bog

2011

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ABSTRACT. We developed and tested a new method to separate CO 2 and CH 4 from bulk gas samples for radiocarbon and stable-carbon analysis that utilizes a zeolite molecular sieve. To validate the technique, tests were performed using a suite of standard gases, composed of CO 2 and CH 4 of distinctly different isotopic composition. We employed the method to investigate the carbon isotopic composition of samples of dissolved CO 2 and CH 4 collected in situ from the near surface to deep layers of an ombrotrophic raised peat bog. Results showed that the age of both the CO 2 and CH 4 components of the dissolved gases increased with depth from ~0-300 BP at 0.25 m to ~4000 BP at 4 m. CH 4 was mainly similar or slightly older in age compared to CO 2 , with the greatest difference in ages occurring at 1 m depth where CH 4 was older by 430-615 yr. The  13 C values of CO 2 increased with depth from -12.4‰ and -8.0‰ at 0.25 m to +6.9‰ and +8.3‰ at 4 m, whereas the  13 C of CH 4 stayed in the range -58.4‰ to -70.6‰. The 14 C results from the deepest layers are consistent with a similar source for both gases. 14 C ages for the CO 2 component were younger compared to CH 4 , within the shallower depths of the peat bog (1 m) and demonstrate the incorporation of acrotelm-derived respired CO 2 into the catotelm.

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Stable Carbon Isotopes Reveal Soil‐Stream DIC Linkages in Contrasting Headwater Catchments

et al. 2018

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Large CO2 evasion to the atmosphere occurs as dissolved inorganic carbon (DIC) is transported from soils to streams. While this physical process has been the focus of multiple studies, less is known about the underlying biogeochemical transformations that accompany this transfer of C from soils to streams. Here we used patterns in stream water and groundwater δ13C‐DIC values within three headwater catchments with contrasting land cover to identify the sources and processes regulating DIC during its transport. We found that although considerable CO2 evasion occurs as DIC is transported from soils to streams, there were also other processes affecting the DIC pool. Methane production and mixing of C sources, associated with different types and spatial distribution of peat‐rich areas within each catchment, had a significant influence on the δ13C‐DIC values in both soils and streams. These processes represent an additional control on δ13C‐DIC values and the catchment‐scale cycling of DIC across different northern landscape types. The results from this study demonstrate that the transport of DIC from soils to streams results in more than just rapid CO2 evasion to the atmosphere but also represents a channel of C transformation, which questions some of our current conceptualizations of C cycling at the landscape scale.

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Enigmatic stable isotope dynamics of deep peat methane

Abstract: Abstract. The carbon and hydrogen stable isotope ratios of methane and carbon dioxide from Ellergower Moss, a raised peat bog in SW Scotland, were measured to characterize the isotopic composition of peatland gas flux that is not subject to near-surface bacterial oxidation.

Cited by 52 publications

References 43 publications

Fluxes and <sup>13</sup>C isotopic composition of dissolved carbon and pathways of methanogenesis in a fen soil exposed to experimental drought

Fluxes and <sup>13</sup>C isotopic composition of dissolved carbon and pathways of methanogenesis in a fen soil exposed to experimental drought

Radiocarbon and Stable Carbon Analysis of Dissolved Methane and Carbon Dioxide from the Profile of a Raised Peat Bog

Stable Carbon Isotopes Reveal Soil‐Stream DIC Linkages in Contrasting Headwater Catchments

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Enigmatic stable isotope dynamics of deep peat methane

Abstract: Abstract. The carbon and hydrogen stable isotope ratios of methane and carbon dioxide from Ellergower Moss, a raised peat bog in SW Scotland, were measured to characterize the isotopic composition of peatland gas flux that is not subject to near-surface bacterial oxidation.

Cited by 52 publications

References 43 publications

Fluxes and &lt;sup&gt;13&lt;/sup&gt;C isotopic composition of dissolved carbon and pathways of methanogenesis in a fen soil exposed to experimental drought

Fluxes and &lt;sup&gt;13&lt;/sup&gt;C isotopic composition of dissolved carbon and pathways of methanogenesis in a fen soil exposed to experimental drought

Radiocarbon and Stable Carbon Analysis of Dissolved Methane and Carbon Dioxide from the Profile of a Raised Peat Bog

Stable Carbon Isotopes Reveal Soil‐Stream DIC Linkages in Contrasting Headwater Catchments

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Fluxes and <sup>13</sup>C isotopic composition of dissolved carbon and pathways of methanogenesis in a fen soil exposed to experimental drought

Fluxes and <sup>13</sup>C isotopic composition of dissolved carbon and pathways of methanogenesis in a fen soil exposed to experimental drought