Cycling of Molecular Hydrogen in Subarctic Sweden
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Cycling of Molecular Hydrogen in Subarctic Sweden Victoria Ward¹, Ruth K. Varner¹, Kaitlyn Steele¹, Patrick Crill² ¹Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH ²Department of Geological Sciences, Stockholm University, Stockholm, Sweden Introduction • Over the past decade, significant warming has caused organic-rich permafrost to thaw, increasing the amount of soil carbon available for decomposition (Callaghan et al., 2010). • It is expected that the release of greenhouse gases, including methane (CH₄), will increase. •Little is known, however, about the effect of permafrost thaw on the release of molecular hydrogen (H 2 ) from wetland ecosystems. Research Question Does an increase in soil moisture impact the behavior of H 2 in permafrost thaw microhabitats? Fig. 1: Stordalen Mire (N 68°21’ E19°02’), a research site near the Abisko Scientific Research Station in the discontinuous permafrost region of Sweden. Methods Data were collected across 4 different sub-habitats at Stordalen Mire (Fig. 1): frozen palsa (Fig. 2a), mesic Sphagnum (Fig. 2b), and fully thawed Carex (Fig. 2c) and Eriophorum (Fig. 2d) sites. Acknowledgements: Dr. Varner for serving as my advisor, Kaitlyn Steel for serving as a mentor and Sophie Burke for runnin many of my samples for methane. This research was supported through the Northern Ecosystems Research for Undergraduates program (NSF REU site EAR#1063037) and the UNH Hamel Center for Undergraduate Research. Depth Profiles Fig. 13: Photo of Stordalen Mire showing thawing of permafrost that has already occurred Fig. 7: Depth Profile of CH₄ at Sphagnum 1 SGS site Fig. 6: Depth profile of H₂ at Sphagnum 1 SGS site Fig. 9: Depth Profiles of CH₄ over time at Eriophorum 1 SGS site Fig. 8: Depth Profiles of H₂ over time at Eriophorum 1 SGS site Fig. 11: Depth Profiles of CH₄ at Carex SGS site Fig. 10: Depth profiles of H₂ at Carex SGS site Fig. 12: Fluxes of H₂, CH₄, and NEE from Eriophorum, Sphagnum, Palsa, and Hummock sites, showing Tukey Kramer connecting letters report Conclusions •Methane and H₂ concentrations decrease during the storm due to a flushing of the system by the large influx of freshwater. •After a certain amount of time, the system begins to recover from this resetting of its biogeochemistry, and the concentrations build back up toward pre-precipitation levels. •It is believed the hydrology and vegetation coverage of each site also produce differences in the behavior of soil H₂. •By considering the fluxes to the atmosphere (Fig. 12), an additional understanding of the relationship between all gases studied is gained. Fig. 4: H₂ and precipitation over time at the Carex sipper site Fig. 3b: Collecting Sipper Data at the Palsa site. Photo by Ryan Lawrence. Fig. 3a: SGS array before insertion in July 2011. Photo by Kaitlyn Steele. Fig. 3c: Autochamber at which measurements were taken to determine fluxes to the atmosphere. Photo by Niklas Rakos Fig. 2b: mesic Sphagnum Fig. 2d: fully thawed Eriophorum Fig. 2c: fully thawed Carex Fig. 2a: frozen Palsa The region experienced record precipitation on July 14 th and 15 th (Fig. 4). Across all depths and vegetation types, there was a drop in concentrations directly following the storm. Eventually, the systems began to recover. The recovery was quickest at the Sphagnum site and slowest at the Carex site. This is attributed to differences in hydrologic flow regimes (Fig. 5). Autochamber fluxes Analysis of CH₄, carbon dioxide (CO₂), and H₂ fluxes to the atmosphere (Fig. 12) shows that the Eriophorum site was both the greatest source of CH₄ and the greatest sink of H₂. These data provide insight into the behavior of H₂ and CH₄ in the soil. Fig. 5: Conceptual diagram of water table response to precipitation event Carex Eriophorum H 2 C oncentration (nM ) 0 10 20 30 40 50 D epth (cm ) -50 -40 -30 -20 -10 0 Before R ain D uring Rain 1 D ay AfterR ain 7+ D ays AfterR ain H 2 C oncentration (nM ) 0 10 20 30 40 50 D epth (cm ) -25 -20 -15 -10 -5 0 5 10 Before R ain D uring Rain 1 D ay AfterR ain 7+ D ays AfterR ain CH 4 C oncentration ( M) 0 20 40 60 80 100 D epth (cm ) -25 -20 -15 -10 -5 0 1 D ay AfterR ain 7+ D ays AfterR ain CH 4 C oncentration ( M) 0 100 200 300 400 500 D epth (cm ) -50 -40 -30 -20 -10 0 D uring R ain 1 D ay AfterR ain 7+ D ays AfterR ain H 2 C oncentration (nM ) 0 10 20 30 40 50 D epth (cm ) -30 -20 -10 0 10 20 Before R ain D uring R ain 1 D ay AfterR ain 7+ D ays AfterR ain Sphagnum CH 4 C oncentration ( M) 0 50 100 150 200 250 D epth (cm ) -30 -20 -10 0 10 20 D uring R ain 1 D ay AfterR ain 7+ D ays AfterR ain Date 7/8 7/12 7/16 7/20 7/24 Precipitation (cm ) 0 10 20 30 40 50 H 2 Concentration (nM) 0 20 40 60 80 Precipitation -30 cm -40 cm -10 cm -20 cm -60 cm Samples of dissolved gases within the soil were collected using Soil Gas Sampling (SGS) arrays (Fig. 3a) and sipper devices (Fig. 3b) several times per week. Fluxes to the atmosphere were determined by collecting manual samples from autochambers (Fig. 3c). All samples were collected with and stored in syringes before being analyzed for H 2 using a reduced gas detector and CH 4 using a flame ionization detector. Niklas Rakos Sphagnum Palsa Eriophorum Carex N Response to Precipitation Event References: Callaghan, T.V., F. Bergholm, T.R. Christensen, C. Jonasson, U. Kokfelt, and M. Johansson. 2010. A new climate era in the sub-Arctic: Accelerating climate changes and multiple impacts. Geophysical Research Letters. 37, doi:10.1029/2009GL042064
description
Cycling of Molecular Hydrogen in Subarctic Sweden. Sphagnum . Victoria Ward¹, Ruth K. Varner¹ , Kaitlyn Steele¹, Patrick Crill² ¹Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH - PowerPoint PPT Presentation
Transcript of Cycling of Molecular Hydrogen in Subarctic Sweden
Cycling of Molecular Hydrogen in Subarctic SwedenVictoria Ward¹, Ruth K. Varner¹, Kaitlyn Steele¹, Patrick Crill²
¹Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH ²Department of Geological Sciences, Stockholm University, Stockholm, Sweden
Introduction• Over the past decade, significant warming has caused organic-rich permafrost to thaw, increasing the amount of soil carbon available for decomposition (Callaghan et al., 2010).
• It is expected that the release of greenhouse gases, including methane (CH₄), will increase.
•Little is known, however, about the effect of permafrost thaw on the release of molecular hydrogen (H2) from wetland ecosystems.
Research QuestionDoes an increase in soil moisture impact the behavior of H2 in permafrost thaw microhabitats?
Fig. 1: Stordalen Mire (N 68°21’ E19°02’), a research site near the Abisko Scientific Research Station in the discontinuous permafrost region of Sweden.
MethodsData were collected across 4 different sub-habitats at Stordalen Mire (Fig. 1): frozen palsa (Fig. 2a), mesic Sphagnum (Fig. 2b), and fully thawed Carex (Fig. 2c) and Eriophorum (Fig. 2d) sites.
Acknowledgements:Dr. Varner for serving as my advisor, Kaitlyn Steele for serving as a mentor and Sophie Burke for running many of my samples for methane. This research was supported through the Northern Ecosystems Research for Undergraduates program (NSF REU site EAR#1063037) and the UNH Hamel Center for Undergraduate Research.
Depth Profiles
Fig. 13: Photo of Stordalen Mire showing thawing of permafrost that has already occurred
Fig. 7: Depth Profile of CH₄ at Sphagnum 1 SGS site
Fig. 6: Depth profile of H₂ at Sphagnum 1 SGS site
Fig. 9: Depth Profiles of CH₄ over time at Eriophorum 1 SGS site
Fig. 8: Depth Profiles of H₂ over time at Eriophorum 1 SGS site
Fig. 11: Depth Profiles of CH₄ at Carex SGS site
Fig. 10: Depth profiles of H₂ at Carex SGS site
Fig. 12: Fluxes of H₂, CH₄, and NEE from Eriophorum, Sphagnum, Palsa, and Hummock sites, showing Tukey Kramer connecting letters report
Conclusions•Methane and H₂ concentrations decrease during the storm due to a flushing of the system by the large influx of freshwater.
•After a certain amount of time, the system begins to recover from this resetting of its biogeochemistry, and the concentrations build back up toward pre-precipitation levels.
•It is believed the hydrology and vegetation coverage of each site also produce differences in the behavior of soil H₂.
•By considering the fluxes to the atmosphere (Fig. 12), an additional understanding of the relationship between all gases studied is gained.
Fig. 4: H₂ and precipitation over time at the Carex sipper site
Fig. 3b: Collecting Sipper Data at the Palsa site. Photo by Ryan Lawrence.
Fig. 3a: SGS array before insertion in July 2011. Photo by Kaitlyn Steele.
Fig. 3c: Autochamber at which measurements were taken to determine fluxes to the atmosphere. Photo by Niklas Rakos
Fig. 2b: mesic Sphagnum
Fig. 2d: fully thawed Eriophorum
Fig. 2c: fully thawed Carex
Fig. 2a: frozen Palsa
The region experienced record precipitation on July 14th and 15th (Fig. 4). Across all depths and vegetation types, there was a drop in concentrations directly following the storm. Eventually, the systems began to recover. The recovery was quickest at the Sphagnum site and slowest at the Carex site. This is attributed to differences in hydrologic flow regimes (Fig. 5).
Autochamber fluxes
Analysis of CH₄, carbon dioxide (CO₂), and H₂ fluxes to the atmosphere (Fig. 12) shows that the Eriophorum site was both the greatest source of CH₄ and the greatest sink of H₂. These data provide insight into the behavior of H₂ and CH₄ in the soil.
Fig. 5: Conceptual diagram of water table response to precipitation event
CarexEriophorum
H2 Concentration (nM)
0 10 20 30 40 50
Dep
th (c
m)
-50
-40
-30
-20
-10
0
Before RainDuring Rain1 Day After Rain7+ Days After Rain
H2 Concentration (nM)
0 10 20 30 40 50
Dep
th (c
m)
-25
-20
-15
-10
-5
0
5
10
Before RainDuring Rain1 Day After Rain7+ Days After Rain
CH4 Concentration (M)
0 20 40 60 80 100
Dep
th (c
m)
-25
-20
-15
-10
-5
0
1 Day After Rain7+ Days After Rain
CH4 Concentration (M)
0 100 200 300 400 500
Dep
th (c
m)
-50
-40
-30
-20
-10
0
During Rain1 Day After Rain7+ Days After Rain
H2 Concentration (nM)
0 10 20 30 40 50
Dep
th (c
m)
-30
-20
-10
0
10
20
Before RainDuring Rain1 Day After Rain7+ Days After Rain
Sphagnum
CH4 Concentration (M)
0 50 100 150 200 250
Dep
th (c
m)
-30
-20
-10
0
10
20
During Rain1 Day After Rain7+ Days After Rain
Date
7/8 7/12 7/16 7/20 7/24
Pre
cipi
tatio
n (c
m)
0
10
20
30
40
50
H2
Con
cent
ratio
n (n
M)
0
20
40
60
80
Precipitation -30 cm -40 cm -10 cm -20 cm -60 cm
Samples of dissolved gases within the soil were collected using Soil Gas Sampling (SGS) arrays (Fig. 3a) and sipper devices (Fig. 3b) several times per week. Fluxes to the atmosphere were determined by collecting manual samples from autochambers (Fig. 3c). All samples were collected with and stored in syringes before being analyzed for H2 using a reduced gas detector and CH4 using a flame ionization detector.
Niklas Rakos
Sphagnum
Palsa
Eriophorum
Carex
N
Response to Precipitation Event
References:Callaghan, T.V., F. Bergholm, T.R. Christensen, C. Jonasson, U. Kokfelt, and M. Johansson. 2010. A new climate era in the sub-Arctic: Accelerating climate changes and multiple impacts. Geophysical Research Letters. 37, doi:10.1029/2009GL042064
