This document summarizes a master's thesis project studying methane production and carbon cycling in Georgetown Lake, Montana. Previous work found the lake to be eutrophic with anoxic conditions below 6 meters depth. The current study aims to identify and quantify methane in the lake water and sediments using GC-MS and CRDS analysis. Depth profiles show increasing methane and reducing conditions near the redox boundary. Preliminary calculations estimate 109 moles of methane released from the lake during spring ice-off.

1. Methanogenesis, Redox and Carbon
Isotope Biogeochemistry: Georgetown
Lake, Montana
Master Thesis Project, Tyler Johnston
Department of Chemistry and Geochemistry, Montana Tech

2. Overview
• Field Area and History
• Previous Work
– Conclusions Made
– Concerns
• Objective of Current Work
• Methods
– Methane Identification
• GC-MS
• CRDS
• Results
– Water Column
– Sediment
– C speciation
• Conclusions
• Recommendations

3. Google Earth image of the Georgetown Lake area showing the Pintlar & Flint
Creek ranges, Discovery Ski Area and Anaconda, MT

4. Comers
Pt Site
Adapted from Gammons et al. in press

5. History of Georgetown Lake
• Flint Creek dammed
in 1899 - power for
mining operations in
Philipsburg,
Anaconda, and the
surrounding areas.
• The new dam flooded
the Georgetown flats,
which was primarily
grazing pasture,
creating Georgetown
Lake.

6. Previous Work
• In 1977 EPA report classified
Georgetown Lake as an eutrophic
(excess nutrient loads)
• 9th out of 15 lakes studied (15
being most eutrophic)
• Analysis determined lake water
was nitrogen limited
• Estimated 4250 kg/year
phosphorus loading
• Several more studies have been
conducted in order to determine
sources of nutrient loading
– Groundwater, septic tanks, surface
run off (fertilizers, detergents),
surface and submarine springs,
lake sediment

7. So, what is eutrophication?
• Eutrophication - a water
body becomes loaded in
excess nutrients causing
blooms of algae and plant
growth.
• Decay of excess organic
matter via respiration,
lowers dissolved oxygen to
levels lethal to aquatic life.

8. Previous Work cont.
• Deep water and sediment become anoxic during
winter ice cover.
• Apparent redox boundary allows for the
formation of reduced species.
• NH4
+ found in large quantities in bottom water
(up to 3.3 mg/L)
• H2S gas produced by sulfate reducing bacteria
(up to1.2 mg/L)
SO4
2- + 2 CH2O + 2 H+  H2S + 2 CO2 + 2 H2O
Org C

9. Previous Work Cont.
• A more recent study by Stafford of the U of M
(2013) found Georgetown Lake is becoming
less eutrophic.
• Nutrient loading had greatly decreased since
last comprehensive study in 1980’s
– Phosphorus has now become a limiting nutrient
• Suboxic conditions are still present even with
decreased nutrient loading

10. Adapted from NSF proposal in review (S. Parker, C. Gammons, J. Dore, E. Boyd)
Transition from open water to ice-cover is accompanied by
a dramatic change in geochemical structure.
• Persistent anoxic conditions threaten GTL fisheries
• High potential for release of toxic and greenhouse gases during ice break up
and spring turnover

11. Reason for this study
A: GT-1
Dam
DIC concentration, mmol/L
0 1 2 3 4 5
13
C-DIC,‰
-9
-6
-3
0
3
Nov 2010
Jan 2011
Feb 2011
March 2011
April 2011
May 2011
June 2011
Aug 2011
B: GT-2
Comer's
DIC concentration, mmol/L
0 2 4 6 8 10
Nov 2010
Jan 2011
March 2011
April 2011
May 2011
June 2011
Aug 2011
From Henne, 2011
Produces isotopically light CH4
and heavy CO2

12. Objectives
• To identify and quantify
methane production in the
waters of GTL.
• Use carbon stable isotopes to
identify carbon cycling in GTL.
• Estimate quantity of CH4
released from GTL to the
atmosphere with ice-off.

13. Methods
• Sampling of the vertical water column
was conducted from Jan. 2013 to
March 2014.
• Measured: pH, Temp, Conductivity,
ORP and DO
• Water was pumped to the surface
from ~2ft intervals for analysis
– Alkalinity, Ammonia, Sulfide, Anions,
Methane, DIC/DOC, Carbon isotopes,,
TPC, and Water isotopes.
• Sediment cores were taken in Sept.
and Dec. 2013
• Gas samples were gathered from
ebullition by disturbance of sediment

15. CH4 Methods
• CH4 analysis by GC-MS (EI) or CRDS
analyzer
• Samples were gathered vertically
throughout water column
• Water was pumped to the surface and
collected in125 mL glass serum bottles.
• Analysis by CRDS was done on septum
capped vial.
Analyze CH4 in gas
bubble

16. Methane Identification by GC-MS
• Initial column did not resolve
methyl cation peak (m/z 15
CH3
+)
• Switched to mole sieve
column which resolved methyl
cation peak.
• Sample precision in duplicate
samples was poor, ranging
between 5-20%
CH4 ( mol)
0.00 0.04 0.08 0.12
Peakarea
0.0
5.0e+5
1.0e+6
1.5e+6
2.0e+6
y=(4.615·105
)·ln(x)+2.683·106
R2
=0.999
Sample calibration curve
Peak area for m/z 15, CH3
+

17. Sample GC-MS results
RT: 0.00 - 9.08
0 1 2 3 4 5 6 7 8 9
Time (min)
0
50
100
0
50
100
0
50
100
0
50
100
0
50
100
2.80
4.27
5.792.97 5.451.48 3.98 7.81 8.146.52 7.120.26 2.00
RT: 5.79
MA: 437457
5.83
6.432.79 4.29 8.12
RT: 2.80
MA: 5243006
1.48 4.003.05 4.32 6.634.95 7.156.25 7.960.18 8.762.68
RT: 4.27
MA: 6116147
2.97 5.454.54 6.89 7.826.522.78 8.380.17 0.77 3.41
RT: 7.81
MA: 114691
8.04
8.31
2.81
4.24 4.312.970.36 2.281.38 7.126.135.65
NL:
1.95E6
TIC MS
mix_std-1-02-
14_10
NL:
9.65E4
m/z=
14.50-15.50
MS
mix_std-1-02-
14_10
NL:
1.89E6
m/z=
31.50-32.50
MS
mix_std-1-02-
14_10
NL:
1.42E6
m/z=
27.50-28.50
MS
mix_std-1-02-
14_10
NL:
7.20E3
m/z=
43.50-44.50
MS
mix_std-1-02-
14_10
CH4 as CH3
+
ion
O2
N2
CO2
TIC; 20 μL of standard mixture
(A)
(B)
(C)
(D)
(E)

18. CH4 using CRDS
• CH4 using Cavity Ring-Down
Spectrometer.
• CH4 measured for
interference correction with
CO2 for δ13C.
• Original CH4 calculated based
temperature, cavity volume &
pressure, molar volume
CH4 ( M)
0 500 1000 1500
CH4peakarea
0
10000
20000
30000
40000
y=20.2*x+48.7
R2
=0.9998
All points are duplicate determinations
Calibration of CRDS for CH4 analysis

19. Results
Date
Jan Mar May Jul Sep Nov Jan Mar
CH4(M)
0
300
600
900
1200
1500
GC-MS
CRDS
2013 2014
ice ice
CH4 concentration over the sampling visits to the GT-2 site

20. Results
Date
Jan Mar May Jul Sep Nov Jan Mar
ORP(mV)
-150
0
150
300
450
DO(mg/L)
0
2
4
6
ORP
DO
2013 2014
ice ice
Dissolved oxygen near bottom at GT-2 and oxidation-reduction potential

21. Results
DO (mg/L)
0 2 4 6 8 10 12
Depth(m)
0
1
2
3
4
5
6
Temp (o
C)
0 1 2 3 4 5
SC ( S/cm)
150 225 300 375
pH
6.0 6.5 7.0 7.5
ORP (mV)
100 200 300 400 500
NH3-NH4
+
(N-mg/L)
0 1 2 3 4 5 6
CH4 ( M)
0 200 400 600 800
Sulfide (S-mg/L)
0.0 0.2 0.4
C-DIC (‰)
-6 -5 -4 -3 -2 -1 0
13
C-DOC (‰)
-32 -30 -28 -26
DIC (mg/L)
0 25 50 75 100125150
Depth(m)
0
1
2
3
4
5
6
DOC (mg/L)
2.0 2.2 2.4 2.6
ICE ICE ICE ICE ICE ICEA B C D E F
Temp
DO
SC
pH
NH3
ORP
Sulfide
CH4
DOC
DIC DIC
DOC
Depth profiles for the GT-2 site in Feb. 2013

22. Microbe populations under ice cover (from Apr. 2013); densities increase near the
redox boundary.
Adapted from NSF proposal in review (S. Parker, C. Gammons, J. Dore, E. Boyd)
Possibly a result of increase spectrum of nutrients allowing broader range of
“niches” for greater species diversity and ecological success.

23. Results
DO (mg/L)
4 6 8
Depth(m)
0
2
4
6
Temp (o
C)
17.8 17.9 18.0
Temp
DO
pH
7.0 7.5 8.0 8.5
SC ( S/cm)
176 180 184 188
ORP (mV)
0 100 200 300 400
SO4
2-
(mg/L)
3.0 3.2 3.4
pH
SC
SO4
2-
ORP
13
CDIC (‰)
-4.0 -3.5 -3.0 -2.5
13
CDOC (‰)
-29.6 -28.8 -28.0 -27.2
DOC
DIC
DIC (mg C/L)
20 22 24 26
DOC (mg C/L)
2.0 2.4 2.8
CH4 ( M)
0 20 40 60
DOC
DIC
CH4
18
OH2O (‰)
-13.8 -13.5 -13.2 -12.9
Depth(m)
0
2
4
6
dDH2O (‰)
-114.4 -113.6 -112.8
A B C D E F G
Depth profiles for the GT-2 site in Sep. 2013

24. Results
Depth profiles in shallow sediment cores from the GT-2 site.
A to C are from Sep. 2013
Organic C concentration at top of core is less than deeper. Suggests
processing of C and return to lake (atmosphere?).
Org C (mmol/g)
28 32 36 40
Sedimentdepth(cm)
0
4
8
12
Inorg. C (mmol/g)
0 2 4 6
OC
IC
13
C (‰)
-32 -28 -24 -20 -16
13
C-OC
13
C-IC
Lodge pole
Kinickinick
A B
N/P
0 10 20 30 40
Sedimentdepth(cm)
0
4
8
12
N/S
0.0 0.6 1.2 1.8
N/P
N/S
C
Limestone
-0.41
Bottom plants
-9.6 & -11.7

25. Depth
under
ice ft
Depth
under
ice m
pCO2
µatm
HCO3
-
µmol/L
CO3
2-
μmol/L
CO2
μmol/L
frac
HCO3
-
fracCO3
2-
fracCO2
ε(CO2-
HCO3
-
)
ε(CO3
2-
-
HCO3
-
) δ13
C-CO2
δ13
C-
HCO3
-
δ13
C-
CO3
2-
δ13
C-DIC
‰ VPDB
COM-17-3 0 0.00 3620 1678 0.9 270 0.86 0.0005 0.14 12.1 0.64 -13.3 -1.2 -1.8 -2.9
COM-17-6 3 0.91 3516 2032 1.5 253 0.89 0.0006 0.11 12.0 0.63 -14.0 -2.0 -2.6 -3.3
COM-17-9 6 1.83 5502 2036 1.0 382 0.84 0.0004 0.16 11.9 0.62 -13.6 -1.8 -2.4 -3.7
COM-17-12 9 2.74 6953 2081 0.8 475 0.81 0.0003 0.19 11.8 0.62 -13.8 -2.0 -2.6 -4.2
COM-17-14 11 3.35 8124 2156 0.8 544 0.80 0.0003 0.20 11.7 0.61 -13.5 -1.7 -2.3 -4.1
COM-17-16 13 3.96 8221 2386 0.9 545 0.81 0.0003 0.19 11.7 0.61 -13.8 -2.1 -2.7 -4.3
COM-17-18 15 4.57 8798 2490 1.0 579 0.81 0.0003 0.19 11.7 0.61 -12.6 -0.9 -1.5 -3.1
COM-17-20 17 5.18 20632 3119 0.7 1332 0.70 0.0001 0.30 11.6 0.60 -8.3 3.3 2.7 -0.17
Speciate inorganic C using [DIC], T, pH
Calculate fraction inorganic species
Calculate isotopic separation based on T & species
Use these to calculate δ13C of each species
What can we learn from the carbon in the lake?
The dissolved CO2 should
look like this isotopically
(assuming equilibrium).
Mar. 2014 data

26. 13
C (‰)
-36 -30 -24 -18 -12 -6
Depth(m)
0
2
4
ice
local
terrestrial plants
aquatic plants
13
C-CO2
Calc
13
C-DOC
Meas
13
C-DOC
Calc
Calculated C fixation
atm CO2
13
C-TPC
Limestone -0.41
Is the dissolved CO2 being used by in lake processes?

27. How much CH4 actually is released from the lake in the
spring when the ice leaves and the lake turns over.
Making some broad assumptions based on
measured CH4, lake area, depth of anoxic layer
we get about 109 moles (0.02 Tg) CH4 released
from the lake at ice-off.
The watershed can oxidize about 107 moles by
normal processes in upland soils.
At the dam outlet, an estimated 106 mole of
methane enter Flint Creek
Climate change may enhance CH4 production
faster than CO2.

28. Conclusions
• CH4 was found at measurable quantities at the
GT-2 site all year round.
• Sediment cores show an active region of
diagenetic processing in the top regions of the
shallow sediment.

29. Conclusions
• Water in the anoxic zone
showed enrichment of δ13C-
DIC due to the production
of isotopically heavy CO2 via
methanogenesis. Organisms
that consume the enriched
CO2 near the redox
boundary appear to
produce enriched δ13C-DOC.
• DOC found in the lake and
sediment cores is consistent
with a large component of
organic carbon from
terrestrial sources. White-stem pond weed from GTL

30. Conclusions
• Based on broad estimations
109 mol of CH4 can escape
GTL when the lake turns
over in the spring. This
number reveals that the
eutrophic nature of GTL is a
source of greenhouse gas.
• The persistent anoxic zone
is not only bad for the
stability of lake ecosystems,
but has the potential of
being a source of
greenhouse contributing to
global climate change.
Image taken from Google, shows trapped
methane in ice being lit on fire.

31. Distance from bottom of ice to 3 mg/L DO level (Stafford,
2013).
3 mg/L is Montana chronic DO minimum for salmonoid
fisheries.
Comer’s Point site

32. Recommendations
• Perform sampling over a broader range of sites across the
lake to better determine extent of methanogenesis.
• Refine the estimate of the amount of CH4 released after the
ice breaks apart.
• Use stable isotopes of carbon to examine diagenic
processes throughout the lake water and sediment.
• Use “peepers” to examine pore water chemistry in detail
and δ13C-CO2 found in pore water.
• Conduct investigations to types of microbial communities
present and how they change with seasonal changes in the
physical/chemical composition of lake waters.

33. Acknowledgements

34. Questions?