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Automatic Chamber Measurements of Methane and Carbon Dioxide
Fluxes and Isotopologues of CH4 in a sub-Arctic Mire
Ryan D.
1*
Lawrence ,
Carmody K.
2
McCalley ,
Patrick M.
3
Crill ,
Ruth K.
4
Varner ,
Scott R.
2
Saleska
1Department
of Chemistry, Geology, and Physics, Elizabeth City State University, Elizabeth City, NC 27909, USA. (*[email protected])
2Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85719, USA.
3Department of Geological Sciences, University of Stockholm, Svante Arrhenius Va ̈g 8 C, SE-10691 Stockholm, Sweden.
4 Climate Change Research Center, Institute for the Study of Earth, Oceans and Space, Morse Hall, University of New Hampshire, Durham, NH 03824, USA.
INTRODUCTION
METHODOLOGY
 Northern peatlands currently store ~30% of the world’s soil carbon and are the largest
single natural source of atmospheric methane (CH4)
 Since 2000, the Swedish sub-Arctic mean annual temperature has crossed the significant
0 C threshold1
 Individual automated chamber measurements were conducted using two 5 minute interval lid
closures, under two different light conditions:
I. Ambient light [transparent chamber] (Figure 5*)
II. Darkened [shrouded chamber] (Figure 6)
 Methane isotopic composition derived from Keeling regressions of isotope and
concentration data from automated chamber flux measurement
 the atmospheric concentrations of both greenhouse gases2
 cryospheric and ecological processes1
Table I. Automated Chamber Ecosystem
Chamber #
Ecosystem
1, 3, 5
2, 4, 6
palsa
Sphagnum
7, 8, 9
Eriophorum
 Methane has 62 times the global warming potential (GWP) of CO2 at 20 year timescales3
 In wetland systems, CH4 emissions are highly variable (both spatially and temporally)4,5
 In terrestrial freshwater systems, CH4 is formed by two main pathways:
CH3COOH → CH4 + CO2
Fig. 6 Darkened chamber
*chamber lid open in photo
Equation I: Acetate Fermentation;
dominates freshwater systems 6 / Eriophorum sites 7
II. 2CH2O + 2H2O → 2CO2 + 4H2
CO2 + 4H2 → CH4+ 2H2O
III. 2CH2O → CH4 + CO2
Fig. 5 Ambient light chamber
Time
Equation II: Reduction of CO2 with Hydrogen;
dominates Sphagnum sites 7
Equation III: Overall reaction encompassing both
pathways of CH4 production
# of Sampling Days
7
2
4
09:00 – 15:00
12:00 – 18:00
21:00 – 03:00
Table III. Automated Chamber Measurements
Measurement Type
Table II. Sample Time Period
* In addition, entire automated chamber system was calibrated
every 90 minutes.
* One complete cycle (Chamber 1-9) is three hours.
 As the landscape transitions from a dry palsa, underlain by permafrost, to a
predominately wet site dominated by Eriophorum spp.
I. Sequestration of CO2
II. Increasing amount of CH4 to the atmosphere
 δ13C-CH4 was determined using a Quantum Cascade Laser Spectrometer (QCL)
 As the climate warms, possible positive feedbacks driven by changes in peatland carbon
dioxide (CO2) and CH4 cycling could have major impacts on
I.
CONCLUSION
Light Condition
Ambient Dark
NEE
Respiration
✓
✓
✓
CH4 Exchange
✓
✓
δ13C-CH4
✓
✓
 The average carbon isotope composition of emitted CH4 was -68 ‰ at the Sphagnum
site compared to -62 ‰ at the Eriophorum site
I.
Depicts relative shift from CO2-reductive towards acetate fermentation 6
 Isotopic signature of derive CH4 appears to not be affected by light conditions
FUTURE WORK
 More measurements should be conducted, especially during the 21:00 – 03:00 time
period
 larger data sets will begin to offset the the high variability of CH4 emissions
 provide more information about potential impact of light on δ13C-CH4
 Collect active layer depth8, water table depth4,9, chamber plant species composition by
percent cover8,6, and pH8 if suitable for site
 Aforementioned variables shown to affect CH4 exchange and CO2 dynamics
 Further analyze data using a statistical package, such as SPSS or SAS
 Example : paired t-test of average day vs. night δ13C-CH4 to determine if
isotopic composition of derived CH4 source is affected by light
 Examine CH4 exchange
Flux measurements
Eriophorum
palsa
-20
NEE
-65
Respiration
-25.93
-44.83
-110
GPP
-78.41
-77.39
-200
-150.77
First and foremost, I would like to thank God for without him truly none of this would have been possible.
6
4
2
1.17
0.02
Figure 7) GPP was calculated using the equation
GPP = NEE – respiration. From permafrost to
Eriophorum, more plants result in overall uptake of
CO2.
-62
-64
-70
-68.61
-67.95
-72
-74
-66.98
-67.65
All Measurements
Day (0900-1500)
Night (2100-0300)
Eriophorum Site δ13C-CH4
Dark
-56
-57
-58
-59
All Measurments
Day (0900-1500)
Night (2100-0300)
-60
-61
-62
-63
-72.33
-61.49
-60.87
-61.63
-62.26 -62.48
-64
-76
-65
-78
-66
-63.27
Figure 9 & 10) The averages of all δ13C-CH4 within each cover type are similar; however, measurements conducted
during the hours of 09:00 – 15:00 vs. 21:00 – 03:00 may potentially be significantly different. Yet, CH4 high variability
may heavily influence results of small sample size (n = 24).
Fig. 2)
Fig. 3)
Fig. 4)
Thanks to Mr. E. Froburg, NERU collaborators, and NSF for making this research experience possible.
To Ms. Kaitlyn Steele, I most graciously appreciate the selflessness actions and contributions to the overall success of the NERU 2012.
Figures 1- 4 provided by Maria Paula (MP) Mugnani..Figures 5 & 6 provided by Dr. Ruth K. Varner.
This research was supported through the Northern Ecosystems Research for Undergraduates (NERU) program (NSF REU site
EAR#1063037).
Ambient Light
-60
-67.18
0.00
Figure 8) Methane flux measurements were made
under ambient light and shrouded conditions.
Differences in CH4 emission occur; however, high
variability and small sample size may reason that
result in observed change.
Dark
-66
Ambient Flux
Dark Flux
0
Sphagnum Site δ13C-CH4
Ambient Light
1.56
-4
-219.38
-290
-68
ACKNOWLEDGEMENT
6.33
-2
-245
 Measure δ13C-CH4 of
emitted CH4
5.51
33.23
25
-155
Sphagnum Eriophorum
8
69.23
51
70
δ13C-CH4 (‰)
Elevated, dry palsa underlain by
permafrost) (Figure 2)
II. Intermediate moisture site
dominated by Sphagnum spp.
(Figure 3)
III. Completely thawed wet site
dominated by Eriophorum spp.
(Figure 4)
Sphagnum
Average CH4 Exchange by Site
mg CH4 m-2 h-1
 Net ecosystem
exchange (NEE)
 Respiration
 Gross Primary
Production (GPP)
I.
Carbon Dioxide Dynamics by Site
palsa
 Examine the dynamics of
CO2
 Primarily composed of three different
ecosystems:
RESULTS
δ13C-CH4 (‰)
 Stordalen Mire near Abisko, Sweden
(68°21' N, 19°03' E) (Figure 1, shown below)
RESEARCH
OBJECTIVES
mg C m-2h-1
RESEARCH FIELD SITE
REFERENCES
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