Summary and Future Work
1
Methane Concentrations and Biogeochemistry in Lake Sediments from Stordalen Mire in Sub-Arctic Sweden Madison Halloran¹ , Joel DeStasio², Lance Erickson³ , Joel E. Johnson 4 , Ruth K.Varner², Jacob B. Setera 4 , Martin Wik 5 , Florencia Meana-Prado 4 , Patrick Crill 5 ¹ Department of Environmental Studies, Carleton College, Northfield, MN ² Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH ³Department of Geology, Gustavus Adolphus College, St Peter, MN 4 Department of Earth Sciences, University of New Hampshire, Durham, NH 5 Department of Geological Sciences, Stockholm University, Stockholm, Sweden Summary and Future Work • Maximum TOC, TS, and CH 4 is in the upper 40 cm of the lake sediments. Methane is diffusing away from this maximum zone. •Core sites with known high lake surface methane fluxes from bubble trap measurements also show high methane concentrations in the sediment, high DIC concentrations in the pore fluids, and δ 13 C signatures of DIC ranging from 0 to 10, consistent with methanogenesis. •Future work, including 14 C dating, microbial community profiling, and δ 13 C signatures of CH 4 will yield more insight into the biogeochemical mechanisms that regulate sediment methane distributions. Core Analysis Method 1 CHNS and grain size • split core • take 1 cm 3 sample every 5 cm down the core • bulk TOC, TC, TN, TS, and CaCO3 (by difference) using a CHNS Elemental Analyzer • Grain size fractions using a laser particle size analyzer 2 CO 2 and CH 4 production rates • 2 cm 3 sample “plug” of sediment taken every 5 cm of length • Duplicates from three depths in the core stored at +5⁰C and +20⁰C • 10 mL samples of headspace collected daily for 5 days • 5 mL sample run on GC • 1 mL sample (with duplicates) run on IRGA 3 CH 4 sediment concentrations • 2 cm 3 sample plug taken every 5 cm of length • GC 4 Dissolved Inorganic Carbon (DIC) • Rhizons used to extract 10mL of porewater, then added to 0.2mL 30% phosphoric acid (H 3 PO 4 ) in vials flushed with N 2 gas • Samples degassed CO 2 • 1.0 mL sample of vial headspace run on IRGA References: 1. Downing et al., 2008; 2. Gorham, Eville. "Northern Peatlands: Role in the Carbon Cycle and Probable Responses to Climatic Warming." Ecological Applications 1.2 (1991): 182-95. Print; 3. Gore, A.J.P., editor. 1983. Ecosystems of the world. Mires: swamp, bog, fen and moor. 4A, General studies, and 4B, Regional studies. Elsevier, Amsterdam, The Netherlands. Figure 1. Map of shallow and deep coring sites in Inre Harrsjön (IS1 and ID1) and Mellan Harrsjön (MS1 and MD1) as well as coing transects in Villasjön (VM1-6, VP1-6). Site IS1 is approximate, all other locations were plotted using GPS waypoints. Images courtesy of Google Earth, 2013. Figure 4b. Lance and Joel coring on Villasj ön Figure 4a. The AMS soil coring kit, which was adapted using only one piece of the stainless barrel, duct taped a plastic core liner 4a . 4b . 4c . Figure 4c. Taking a sediment sample to analyze methane concentrati on Villasjön Inre Harrsjön Mellan Harrsjön Site Map Introduction •Lake sediments are an important global carbon sink, storing carbon from both allochthonous and autochthonous inputs 1 . •The burial of organic carbon in natural lake sediments globally is estimated in the range of 30 to 70 Tg C/a 1 .This organic carbon can be mobilized into the atmosphere through the movement of gases, particularly methane (CH 4 ) 2 . •Although freshwater lakes cover a large area in northern peatlands 3 , few studies have quantified their contribution of greenhouse gas emissions to the atmospheric carbon budget. •In July of 2013 we took 48 cores at 16 sites throughout three lakes in the Stordalen Mire, Abisko, Sweden to characterize the sedimentology and geochemistry of the lake sediments in order to understand the production, distribution,and flux of CO 2 and CH 4 from these lakes. These sites differed in water depth and ebullition (bubbling) rates. Concentrations of dissolved inorganic carbon (DIC), dissolved CH 4 and potential production rates of CO 2 and CH 4 were determined, and are linked to bulk TOC, TC, TN, TS, and CaCO 3 , as well as grain size fractions. Upper layer: organic rich sediment Middle layer: transition of mixed organic and lithogenic materials Deep layer: grey lithogenic clay with less organic carbon Core Site: VM1 Core Stratigraphy Results Villasj ön Inre Harrsjön Mellan Harrsjön TO C TO C W eight% 0 10 20 30 40 50 D epth (cm ) 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 TS TS W eight% 0.0 0.2 0.4 0.6 0.8 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 VM1 VM2 VM3 VM4 VM5 VM6 VP1 VP2 VP3 VP4 VP5 VP6 G rain Size M edian G rain Size (m icrons) 0 20 40 60 80 100 120 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 Methane ug C H 4 g-1ds 0 25 50 75 100 225 250 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 TO C Weight% 0 5 10 15 20 25 30 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 TS Weight% 0.0 0.2 0.4 0.6 0.8 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 G rain Size M edian G rain Size (m icrons) 10 20 30 40 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 Methane ug C H 4 g-1ds 0 50 100 150 200 250 300 350 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 del 13 C -6 -4 -2 0 2 4 6 8 10 12 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 D IC (m M) 0 1 2 3 4 5 Inre D eep Site del13C Inre Shallow Site del13C Inre D eep Site D IC Inre Shallow Site D IC Inre D eep Site (ID 1) Inre Shallow Site (IS1)
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Methane Concentrations and Biogeochemistry in Lake Sediments from Stordalen Mire in Sub-Arctic Sweden
Madison Halloran¹ , Joel DeStasio², Lance Erickson³ , Joel E. Johnson4, Ruth K.Varner², Jacob B. Setera4, Martin Wik5, Florencia Meana-Prado4, Patrick Crill5
¹ Department of Environmental Studies, Carleton College, Northfield, MN ² Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH ³Department of Geology, Gustavus Adolphus College, St Peter, MN 4 Department of Earth Sciences, University of New Hampshire, Durham, NH 5 Department of Geological Sciences, Stockholm University, Stockholm, Sweden
Summary and Future Work
• Maximum TOC, TS, and CH4 is in the upper 40 cm of the lake sediments. Methane is diffusing away from this maximum zone.
•Core sites with known high lake surface methane fluxes from bubble trap measurements also show high methane concentrations in the sediment, high DIC concentrations in the pore fluids, and δ 13C signatures of DIC ranging from 0 to 10, consistent with methanogenesis.
•Future work, including 14C dating, microbial community profiling, and δ13C signatures of CH4 will yield more insight into the biogeochemical mechanisms that regulate sediment methane distributions.
Core Analysis Method
1CHNS and grain size
• split core• take 1 cm3 sample every 5 cm down the core• bulk TOC, TC, TN, TS, and CaCO3 (by difference) using a CHNS Elemental Analyzer• Grain size fractions using a laser particle size analyzer
2CO2 and CH4 production rates
• 2 cm3 sample “plug” of sediment taken every 5 cm of length • Duplicates from three depths in the core stored at +5⁰C and +20⁰C• 10 mL samples of headspace collected daily for 5 days • 5 mL sample run on GC• 1 mL sample (with duplicates) run on IRGA
3 CH4 sediment concentrations• 2 cm3 sample plug taken every 5 cm of length • GC
4 Dissolved Inorganic Carbon (DIC)
• Rhizons used to extract 10mL of porewater, then added to 0.2mL 30% phosphoric acid (H3PO4) in vials flushed with N2 gas• Samples degassed CO2
• 1.0 mL sample of vial headspace run on IRGA
References: 1. Downing et al., 2008; 2. Gorham, Eville. "Northern Peatlands: Role in the Carbon Cycle and Probable Responses to Climatic Warming." Ecological Applications 1.2 (1991): 182-95. Print; 3. Gore, A.J.P., editor. 1983. Ecosystems of the world. Mires: swamp, bog, fen and moor. 4A, General studies, and 4B, Regional studies. Elsevier, Amsterdam, The Netherlands.
Figure 1. Map of shallow and deep coring sites in Inre Harrsjön (IS1 and ID1) and Mellan Harrsjön (MS1 and MD1) as well as coing transects in Villasjön (VM1-6, VP1-6). Site IS1 is approximate, all other locations were plotted using GPS waypoints. Images courtesy of Google Earth, 2013.
Figure 4b. Lance and Joel coring on Villasjön
Figure 4a. The AMS soil coring kit, which was adapted using only one piece of the stainless barrel, duct taped a plastic core liner4a. 4b. 4c.
Figure 4c. Taking a sediment sample to analyze methane concentration
Villasjön
Inre HarrsjönMellan Harrsjön
Site MapIntroduction• Lake sediments are an important global carbon sink, storing carbon from both allochthonous and autochthonous inputs1.
• The burial of organic carbon in natural lake sediments globally is estimated in the range of 30 to 70 Tg C/a 1.This organic carbon can be mobilized into the atmosphere through the movement of gases, particularly methane (CH4)2.
• Although freshwater lakes cover a large area in northern peatlands3, few studies have quantified their contribution of greenhouse gas emissions to the atmospheric carbon budget.
• In July of 2013 we took 48 cores at 16 sites throughout three lakes in the Stordalen Mire, Abisko, Sweden to characterize the sedimentology and geochemistry of the lake sediments in order to understand the production, distribution,and flux of CO2 and CH4 from these lakes. These sites differed in water depth and ebullition (bubbling) rates. Concentrations of dissolved inorganic carbon (DIC), dissolved CH4 and potential production rates of CO2 and CH4 were determined, and are linked to bulk TOC, TC, TN, TS, and CaCO3, as well as grain size fractions.
Upper layer: organic rich sediment
Middle layer: transition of mixed organic and lithogenic materials
Deep layer:grey lithogenic clay with less organic carbon
Core Site: VM1
Core Stratigraphy
Results
Vill
asjö
nIn
re H
arrs
jön
Mel
lan
Har
rsjö
n
TOC
TOC Weight %
0 10 20 30 40 50
Dep
th (
cm)
0
5
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20
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35
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65
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75
TS
TS Weight %
0.0 0.2 0.4 0.6 0.8
0
5
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VM1 VM2 VM3 VM4 VM5 VM6 VP1 VP2 VP3VP4VP5 VP6
Grain Size
Median Grain Size (microns)
0 20 40 60 80 100 120
0
5
10
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20
25
30
35
40
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50
55
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65
70
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Methane
ug CH4 g-1ds
0 25 50 75 100 225 250
0
5
10
15
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25
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TOC
Weight %
0 5 10 15 20 25 30
0
5
10
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TS
Weight %
0.0 0.2 0.4 0.6 0.8
0
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10
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75
Grain Size
Median Grain Size (microns)
10 20 30 40
0
5
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15
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75
Methane
ug CH4 g-1ds
0 50 100 150 200 250 300 350
0
5
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del13C
-6 -4 -2 0 2 4 6 8 10 12
0
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DIC (mM)
0 1 2 3 4 5
Inre Deep Site del13CInre Shallow Site del13C Inre Deep Site DIC Inre Shallow Site DIC
Inre Deep Site (ID1)Inre Shallow Site (IS1)
