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
Site Map
Introduction
Mellan
Harrsjön
Inre Harrsjön
Villasjön
• 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
few
studies have quantified their contribution of greenhouse gas emissions to
the atmospheric carbon budget.
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CO2 and CH4 production rates
CH4 sediment concentrations
Dissolved Inorganic Carbon (DIC)
Figure 4a. The AMS soil
coring kit, which was
adapted using only one
piece of the stainless
barrel, duct taped to a
plastic core liner
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Figure 4b.
Lance and
Joel coring
on Villasjön
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Figure 4c. Taking
a sediment
sample to
analyze for
methane
concentration
from holes drilled
into a plastic
core liner
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Inre Shallow Site del13C
Inre Deep Site DIC
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Methane
DIC (mM)
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CHNS and grain size
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• 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
• 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
• 2 cm3 sample plug taken every 5 cm of length
• GC
• 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
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Core Analysis
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Figure 1. Map of shallow and deep coring sites in Inre Harrsjön (IS1 and ID1) and
Mellan Harrsjön (MS1 and MD1) as well as coring 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.
Methane
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peatlands3,
• 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.
Core
Stratigraphy
Grain Size
TS
TOC
Depth (cm)
• Lake sediments are an important global carbon sink, storing carbon from
both allochthonous and autochthonous inputs1.
Results
1
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Middle layer:
transition of
mixed organic
and lithogenic
materials
Deep layer:
grey lithogenic
clay with less
organic carbon
Mellan Deep Site del13C
Mellan Shallow Site del13C
Mellan Deep Site DIC
Mellan Shallow Site DIC
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del13C
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.
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.