Carbon Isotopic Composition of Deep Carbon Gases in an Ombrogenous Peatland, Northwestern Ontario, Canada

Aravena, Ramón; Warner, Barry G.; Charman, Dan; Belyea, Lisa R.; Mathur, Shivani; Dinel, H.

doi:10.1017/s0033822200064948

Cited by 67 publications

(54 citation statements)

References 21 publications

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“…Current research efforts focus on process-based modeling which includes the in¯uence of vegetation on CH 4 emission (Cao et al, 1996;Walter and Heimann, 2000). Radiocarbon measurements of CH 4 suggest that methane is produced primarily from recently-®xed carbon (Wahlen et al, 1989;Martens et al, 1992;Aravena et al, 1993;Chanton et al, 1995). Observed correlations between net ecosystem productivity (NEP) and CH 4 emission (Clymo and Reddaway, 1971;Svensson, 1983;Sebacher et al, 1986;Aselmann and Crutzen, 1989;Moore and Knowles, 1990;Whiting and Chanton, 1993;Klinger et al, 1994;Waddington et al, 1996) suggest that recent plant photosynthates may be an important source of carbon for CH 4 emissions.…”

Section: Introductionmentioning

confidence: 99%

A pulse-labeling experiment to determine the contribution of recent plant photosynthates to net methane emission in arctic wet sedge tundra

King

Reeburgh

2002

Soil Biology and Biochemistry

119

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A pulse-labeling experiment to determine the contribution of recent plant photosynthates to net methane emission in arctic wet sedge tundra AbstractWe conducted a 14 C pulse-labeling experiment under ®eld conditions to estimate the contribution of recent photosynthates to methane (CH 4 ) emission in arctic wet sedge tundra dominated by Carex aquatilis and Eriophorum angustifolium. The average CH 4 emission rate from plant±soil mesocosms in this study was 0.45 g C m 22 d 21. Carbon assimilated by plants via photosynthesis during pulse-labeling turned over rapidly and appeared as emitted CH 4 within 24 h. Integration of¯ux measurements made over a 2-week period shows that the contribution of recent photosynthates to mid-season CH 4 emission is relatively low. Less than 1% of the 14 C-labeled carbon dioxide taken up through photosynthesis was emitted as 14 CH 4 during this study. q

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Section: Introductionmentioning

confidence: 99%

A pulse-labeling experiment to determine the contribution of recent plant photosynthates to net methane emission in arctic wet sedge tundra

King

Reeburgh

2002

Soil Biology and Biochemistry

119

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“…In these studies, dissolved CO 2 has consistently been 52 found to be younger than the surrounding peat. For example, in Canadian boreal peatlands 53 Aravena et al (1993) and Charman et al (1994) found peat CO 2 to be between 500 and 2000 54 years younger than the adjacent peat. Another study performed in an oceanic peatland in south-55 west England (Charman et al, 1999) reported that peat CO 2 was younger than the surrounding 56 peat by between ~ 800 and 1500 years.…”

mentioning

confidence: 99%

Isotope (14C and 13C) analysis of deep peat CO2 using a passive sampling technique

Garnett¹,

Hardie²

2009

Soil Biology and Biochemistry

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10 11We developed and tested a new method to collect CO 2 from the surface to deep layers of a 12 peatland for radiocarbon analysis. The method comprises two components: i) a probe equipped 13 with a hydrophobic filter that allows entry of peat gases by diffusion, whilst simultaneously 14 excluding water, and, ii) a cartridge containing zeolite molecular sieve that traps CO 2 passively. 15We field tested the method by sampling at depths of between 0.25 and 4 m at duplicate sites 16 within a temperate raised peat bog. CO 2 was trapped at a depth-dependent rate of between ~ 0.2-17 0.8 ml d -1 , enabling sufficient CO 2 for routine 14 C analysis to be collected when left in place for 18 several weeks. The age of peatland CO 2 increased with depth from modern to ~ 170 BP for 19 samples collected from 0.25 m, to ~ 4000 BP at 4 m. The CO 2 was younger, but followed a 20 similar trend to the age profile of bulk peat previously reported for the site (Langdon and Barber, 21 2005). δ 13 C values of recovered CO 2 increased with depth. CO 2 collected from the deepest 22 sampling probes was considerably 13 C-enriched (up to ~ +9 ‰) and agreed well with results 23 reported for other peatlands where this phenomenon has been attributed to fermentation 24 processes. CO 2 collected from plant-free static chambers at the surface of the mire was slightly 25 * Manuscript Click here to view linked References -2 -14 C-enriched compared to the contemporary atmosphere, suggesting that surface CO 2 emissions 26 were predominantly derived from carbon fixed during the post-bomb era. However, consistent 27 trends of enriched 13 C and depleted 14 C in chamber CO 2 between autumn and winter samples 28 were most likely explained by an increased contribution of deep peat CO 2 to the surface efflux in 29 winter. The passive sampling technique is readily portable, easy to install and operate, causes 30 minimal site disturbance, and can be reliably used to collect peatland CO 2 from a wide range of 31 depths. 32 33

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“…As mentioned before, higher concentrations of dissolved CH 4 were measured at the approximate depth of the esker crest, suggesting that the methanogenesis rates are higher in the vicinity of the esker crest. Younger radiocarbon dates of dissolved organic carbon in deep peat indicate downward transport of labile carbon in other studies (Aravena et al, 1993;Charman et al, 1994;Chanton et al, 1995;Chasar et al, 2000). Computer simulations have also shown permeable mineral lenses to create a downward transport effect in peatlands (e.g., Reeve et al, 2009).…”

Section: Hydrologic Datamentioning

confidence: 67%

“…CH 4 in deep peat has been shown to be radiocarbon enriched compared to the surrounding peat, suggesting anaerobic respiration that is supported by a downward transport of younger dissolved organic carbon (Aravena et al, 1993;Charman et al, 1994;Chanton et al, 1995). estimated that CH 4 in pore waters contained as much as 25 % modern carbon at 2.5 m depths.…”

Section: Methane Production and Consumptionmentioning

confidence: 99%

Using hydrologic measurements to investigate free-phase gas ebullition in a Maine peatland, USA

Bon

Reeve

Slater

et al. 2014

Hydrol. Earth Syst. Sci.

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Abstract. Northern peatlands cover more than 350 million ha and are an important source of methane (CH 4 ) and other biogenic gases contributing to climate change. Free-phase gas (FPG) accumulation and episodic release has recently been recognized as an important mechanism for biogenic gas flux from peatlands. It is likely that gas production and groundwater flow are interconnected in peatlands: groundwater flow influences gas production by regulating geochemical conditions and nutrient supply available for methanogenesis, while FPG influences groundwater flow through a reduction in peat permeability and by creating excess pore water pressures. Water samples collected from three well sites at Caribou Bog, Maine, show substantial dissolved CH 4 (5-16 mg L −1 ) in peat waters below 2 m depth and an increase in concentrations with depth. This suggests production and storage of CH 4 in deep peat that may be episodically released as FPG. Two min increment pressure transducer data reveal approximately 5 cm fluctuations in hydraulic head from both deep and shallow peat that are believed to be indicative of FPG release. FPG release persists up to 24 h during decreasing atmospheric pressure and a rising water table. Preferential flow is seen towards an area of relatively lower hydraulic head associated with the esker and pool system. Increased CH 4 concentrations are also found at the depth of the esker crest, suggesting that the high permeability esker is acting as a conduit for groundwater flow, driving a downward transport of labile carbon, resulting in higher rates of CH 4 production.

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Carbon Isotopic Composition of Deep Carbon Gases in an Ombrogenous Peatland, Northwestern Ontario, Canada

Cited by 67 publications

References 21 publications

A pulse-labeling experiment to determine the contribution of recent plant photosynthates to net methane emission in arctic wet sedge tundra

A pulse-labeling experiment to determine the contribution of recent plant photosynthates to net methane emission in arctic wet sedge tundra

Isotope (14C and 13C) analysis of deep peat CO2 using a passive sampling technique

Using hydrologic measurements to investigate free-phase gas ebullition in a Maine peatland, USA

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