Using Stable Isotopes to Determine Dominant Methane Production Pathways of Thaw Ponds in a Subarctic Peatland
Arctic and subarctic ecosystems are currently warming faster than any other region of the globe, accelerating seasonal permafrost thaw. As thaw progresses, small water bodies can form due to slumping of the peatland surface. These ponds emit methane (CH4), a strong, radiatively important trace gas,...
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ftuninhampshire:oai:scholars.unh.edu:thesis-2453 2023-05-15T15:16:34+02:00 Using Stable Isotopes to Determine Dominant Methane Production Pathways of Thaw Ponds in a Subarctic Peatland Bennett, Kathryn Ann 2020-12-01T08:00:00Z application/pdf https://scholars.unh.edu/thesis/1414 https://scholars.unh.edu/cgi/viewcontent.cgi?article=2453&context=thesis unknown University of New Hampshire Scholars' Repository https://scholars.unh.edu/thesis/1414 https://scholars.unh.edu/cgi/viewcontent.cgi?article=2453&context=thesis Master's Theses and Capstones methane permafrost stable isotopes thaw text 2020 ftuninhampshire 2023-01-30T21:58:04Z Arctic and subarctic ecosystems are currently warming faster than any other region of the globe, accelerating seasonal permafrost thaw. As thaw progresses, small water bodies can form due to slumping of the peatland surface. These ponds emit methane (CH4), a strong, radiatively important trace gas, predominantly through ebullition (bubbling). Two different types of methanogenic Archaea present in these systems produce CH4 through their respective production pathways: acetoclastic and hydrogenotrophic methanogenesis. The acetoclastic pathway forms CH4 using CH3COOH, an organic carbon (C) source while hydrogenotrophic methanogenesis uses CO2, an inorganic C source. Stable isotopes can be used to characterize the relative contribution of these two pathways in overall CH4 production and to better constrain the global CH4 budget and improve modeling of future emission scenarios. We used stable isotopes, carbon-13 (13C) of CH4 and CO2, deuterium (D) of CH4, and calculated apparent fractionation factors to determine the relative contribution of acetoclastic versus hydrogenotrophic pathways of methanogenesis in thaw ponds in a subarctic peatland located in the discontinuous permafrost region of northern Sweden. Isotopic analysis was performed on porewater samples (n = 310) and gas captured from ebullition (n = 177). Samples were collected from nine ponds over seven years (2012 to 2019) during the ice-free months (June to September). We tested important physical attributes of the ponds that were related to their formation and CH4 production pathways. Results indicated that δ13C-CH4 of ebullition (-86.3‰ to -49.2‰) and porewater (98.2‰ to -42.9‰) and the inferred contribution of hydrogenotrophic vs. acetoclastic methanogenesis differed significantly between certain ponds and pond types. Over the course of this study dissolved and ebullitive δ13C-CH4 remained relatively constant between years but varied significantly between months. Alternatively, δD-CH4 of ebullition (-397.0‰ to -199.4‰) and porewater (-383.4‰ to -184.8‰) ... Text Arctic Ice Northern Sweden permafrost Subarctic University of New Hampshire: Scholars Repository Arctic |
institution |
Open Polar |
collection |
University of New Hampshire: Scholars Repository |
op_collection_id |
ftuninhampshire |
language |
unknown |
topic |
methane permafrost stable isotopes thaw |
spellingShingle |
methane permafrost stable isotopes thaw Bennett, Kathryn Ann Using Stable Isotopes to Determine Dominant Methane Production Pathways of Thaw Ponds in a Subarctic Peatland |
topic_facet |
methane permafrost stable isotopes thaw |
description |
Arctic and subarctic ecosystems are currently warming faster than any other region of the globe, accelerating seasonal permafrost thaw. As thaw progresses, small water bodies can form due to slumping of the peatland surface. These ponds emit methane (CH4), a strong, radiatively important trace gas, predominantly through ebullition (bubbling). Two different types of methanogenic Archaea present in these systems produce CH4 through their respective production pathways: acetoclastic and hydrogenotrophic methanogenesis. The acetoclastic pathway forms CH4 using CH3COOH, an organic carbon (C) source while hydrogenotrophic methanogenesis uses CO2, an inorganic C source. Stable isotopes can be used to characterize the relative contribution of these two pathways in overall CH4 production and to better constrain the global CH4 budget and improve modeling of future emission scenarios. We used stable isotopes, carbon-13 (13C) of CH4 and CO2, deuterium (D) of CH4, and calculated apparent fractionation factors to determine the relative contribution of acetoclastic versus hydrogenotrophic pathways of methanogenesis in thaw ponds in a subarctic peatland located in the discontinuous permafrost region of northern Sweden. Isotopic analysis was performed on porewater samples (n = 310) and gas captured from ebullition (n = 177). Samples were collected from nine ponds over seven years (2012 to 2019) during the ice-free months (June to September). We tested important physical attributes of the ponds that were related to their formation and CH4 production pathways. Results indicated that δ13C-CH4 of ebullition (-86.3‰ to -49.2‰) and porewater (98.2‰ to -42.9‰) and the inferred contribution of hydrogenotrophic vs. acetoclastic methanogenesis differed significantly between certain ponds and pond types. Over the course of this study dissolved and ebullitive δ13C-CH4 remained relatively constant between years but varied significantly between months. Alternatively, δD-CH4 of ebullition (-397.0‰ to -199.4‰) and porewater (-383.4‰ to -184.8‰) ... |
format |
Text |
author |
Bennett, Kathryn Ann |
author_facet |
Bennett, Kathryn Ann |
author_sort |
Bennett, Kathryn Ann |
title |
Using Stable Isotopes to Determine Dominant Methane Production Pathways of Thaw Ponds in a Subarctic Peatland |
title_short |
Using Stable Isotopes to Determine Dominant Methane Production Pathways of Thaw Ponds in a Subarctic Peatland |
title_full |
Using Stable Isotopes to Determine Dominant Methane Production Pathways of Thaw Ponds in a Subarctic Peatland |
title_fullStr |
Using Stable Isotopes to Determine Dominant Methane Production Pathways of Thaw Ponds in a Subarctic Peatland |
title_full_unstemmed |
Using Stable Isotopes to Determine Dominant Methane Production Pathways of Thaw Ponds in a Subarctic Peatland |
title_sort |
using stable isotopes to determine dominant methane production pathways of thaw ponds in a subarctic peatland |
publisher |
University of New Hampshire Scholars' Repository |
publishDate |
2020 |
url |
https://scholars.unh.edu/thesis/1414 https://scholars.unh.edu/cgi/viewcontent.cgi?article=2453&context=thesis |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic Ice Northern Sweden permafrost Subarctic |
genre_facet |
Arctic Ice Northern Sweden permafrost Subarctic |
op_source |
Master's Theses and Capstones |
op_relation |
https://scholars.unh.edu/thesis/1414 https://scholars.unh.edu/cgi/viewcontent.cgi?article=2453&context=thesis |
_version_ |
1766346856480112640 |