BIOGEOCHEMICAL PARTITIONING BETWEEN THE LIQUID WATER AND ICE PHASES DURING FREEZE-DOWN IN ANTARCTIC AND ARCTIC LAKES Santibáñez, P., A. Michaud, T. Vick, A. Chiuchiolo, K. Hell, H. Adams, J. Dore, J. D’Andrilli and J.C. Priscu Field Sampling: Samples were collected during the 2009-2010 field seasons from Barrow (BAR II), AK and the 6m depth of Lake Fryxell (FRX), Taylor Valley, Antarctica. Barrow lakes are seasonally ice covered (~1 m) and Lake Fryxell is permanently ice covered (4 m). Experimental Design: A 75 L tank was lined with Teflon and 50 L of lake water was added (Fig. 1). The system was incubated for ~4 days at -10°C with a “cold sky” set at -50°C to simulate a cold night sky. A clean drill bit was used to penetrate the ice cover and liquid samples were taken over time. The ice phase was sampled after freezing was complete by band-saw layer separation. Sample Analysis: Ions, stable isotopes of water, nutrients, TOC, and biological samples were collected at 4-7 time points throughout the experiment from both the liquid and ice phases. Concentrations from the two phases were compared and a segregation coefficient computed for each analyte. METHODS RESULTS ABSTRACT Photo background courtesy of Alex Michaud Acknowledgements The authors would like to thank Deb Leslie, Kathy Welch, and Berry Lyons for isotope and ion chemistry data; Raytheon Polar Services for logistical support in Antarctica; and Petroleum Helicopters Inc. for air support in the Dry Valleys. This work was supported by NSF-OPP grants to JP; an NSF IGERT fellowship and Montana Space Grant Consortium fellowship to AM; and a Fulbright-Conicyt Scholarship to PS. The thick ice covers on polar lakes play a major role in the physical, chemical and biological properties of these lakes. Of particular importance is the partitioning of chemical and biological constituents between the water and ice, which can produce highly concentrated brines beneath the overlying ice and influence the biogeophysical properties of the ice itself. As water molecules freeze they create a crystalline lattice that repels most of the solutes and particulate matter that was in the water. The materials that are trapped in the ice typically concentrate in localized inclusions or concentrate between the ice grains. Despite much contemporary interest in the habitability of icy systems at Earth’s poles, little is known about how constituents partition between the liquid and solid phase. We conducted a series of controlled freezing experiments using water from selected Arctic and Antarctic lakes to investigate chemical and biological fractionation between ice and water as the lake water freezes. Conclusions OBJECTIVES AND HYPOTHESES Overarching objective: To define the biogeochemical dynamics of ice and liquid phase changes during formation and growth of ice covers of Antarctic and Arctic Lakes. Hypotheses: 1. Solutes will be incorporated into the ice based on their respective affinities: Cl − > F − ~ NH 4 + > NO 3 − > Na + ~ K + > Ca 2+ > SO 4 2− (Eichler et al., 2001). 2. The relative magnitude of segregation coefficients (Mg 2+ > Ca 2+ ) is attributed to interstitial incorporation (coupled with HCO 3 - ) in the ice lattice, and controlled by ion size (Killawee et al., 1998) 3. The relative evolution of water and ice chemistry during freezing will depend on the partitioning process at the ice-water interface and on the redistribution of the solutes under diffusional and convective processes in the water reservoir (Lock et al., 1990). Figure 1. The simulated lake experimental setup Figure 4. Conductivity at the bottom of the simulated lake over the course of the FRX and BAR freeze-down experiments (Freezing rate for BAR = 2.7 mm hr -1 ; FRX = 2.2 mm hr -1 ) Montana State University, Land Resources and Environmental Sciences, Bozeman, MT 59717, USA. 1. Solutes incorporated into the ice phase for BAR II: Stage 2: Ca 2+ > Cl − > Na + and in stage 3: Cl − ~ Na + > Ca 2+ (relative magnitude of segregation coefficients). 2. Solutes incorporated into the ice phase for FRX: K+ > Cl− ~ Na+> Mg 2+ > SO 4 2− > > Ca 2+ > F 3. More conservative species in BAR II liquid phase: Mg 2+ > K + > Ca 2+ > Na + ~ Cl − > SO 4 2− > > F − 4. More conservative species in FRX liquid phase: Mg 2+ ~ K + > Na + ~ Cl − > SO 4 2− >F − >Ca 2+ 5. BAR II segregation coefficients: Stage 2: Ca 2+ = 0,0029, Cl − = 0,0012, Na + =0,0006. 6. BAR II shows the three stages of ice formation. The solute-poor ice (stage 2) presents effective segregation coefficients between ice and bulk solution in the range of 0,0006 and 0,0029 for Ca 2+ , Cl − and Na + (Fig. 5). The ice from BAR II was too pure to measure the other chemical species. 7. FRX freeze-down experiment shows only the solute-rich stage 3 ice due to high initial concentration. These data allow us to describe microhabitats in ice and liquid water based on the biogeochemical partitioning observed. BAR II Water T 0 B T A C M BAR II A BAR II B BAR II C BAR II E FRX C FRX D Fluorescence Intensity (CPS) FRX A FRX B FRX Water T 0 B T A C M Figure 8. Dissolved Organic Matter (DOM) characterization. Excitation-Emission Matrix of FRX (Antarctica) and BAR II (Arctic) showing the major fluorescing components of DOM. A and C are humic-like components, M is a marine humic-like signature, and B and T both denote the protein-like fluorescing components tyrosine and tryptophan. The whole water for BAR II and FRX lakes displays specific regions of DOM fluorophores, which describe environments containing labile DOM (microbial origin) and humic-like, recalcitrant DOM (both terrestrial and marine-like). The DOM character differs between liquid phase (bulk water) and the different depths of the frozen phase; frozen lake water samples contain DOM with significant shifts to amino-acid like fluorescing material. Figure 3. Ice section from BAR freeze- down experiments. Figure 2. Conceptual model of ice cover formation. LIQUID WATER ICE BOUNDARY LAYER ICE-WATER INTERFACE Diffusional process Convective process (Spontaneously or Mechanically) HEAT CONDUCTION EVAPORATION LONG WAVE RADIATION Partitioning process (Fractionation or segregation) ICE FRONT Rejection of solutes Figure 9. Effective segregation coefficient (Keff) and concentration factor of bacteria from FRX and BAR II freeze-down experiments. 0 1 2 0 5 10 15 K eff (Cice/Cbw) Depth of ice front (cm) BAR II Total Free-Bacteria Coccoid Rod 0 1 2 0 5 10 15 Concentration factor Depth of ice front (cm) BAR II_Liquid phase Total Free-Bacteria Coccoid Rod Filament 0 4 8 0 5 10 15 Concentration factor Depth of ice front (cm) BAR II_Ice phase Total Free-Bacteria Coccoid Rod Filament 0 1 2 3 4 0 5 10 15 20 K eff (Cice/Cbw) Depth of ice front (cm) FRX Total Free-Bacteria Coccoid Rod Filament 0 1 2 3 4 0 5 10 15 20 Concentration factor Depth of ice front (cm) FRX_Liquid phase Total Free-Bacteria Coccoid Rod Filament 0 1 2 3 4 0 5 10 15 20 Concentration factor Depth of ice front (cm) FRX_Ice phase Total Free-Bacteria Coccoid Rod Filament Figure 6. Concentration factor (T i divided by T 0 concentration) of chemical species in the liquid phase of FRX and BAR freeze-down experiments. 0 1 2 3 4 5 0 2 4 6 8 10 12 14 16 Concentration factor Freezing front position(cm) FRX F Cl SO4 Na K Ca Cl - SO 4 2- Na + Mg 2+ Ca 2+ K + F - 0 1 2 3 4 5 0 2 4 6 8 10 12 14 16 Concentration factor Freezing front position (cm) BAR II F Cl SO Na K Mg Ca Cl - SO 4 2- Na + Mg 2+ Ca 2+ K + F - Figure 7. Concentration factor of total organic carbon and inorganic carbon between the T final liquid phase divided by concentration at T 0 . 0.1 1 10 100 1000 10000 BAR II FRX Concentration factor (T5/T0) Total organic carbon (ppm) Total inorganic carbon (ppm) Figure 5. Variations with depth of effective segregation coefficient (K eff (Cice/Cbw)) in Barrow (BAR II) and Fryxell (FRX) freeze-down experiments.. The relative evolution of liquid water and ice chemistry is illustrated by the variation with depth of the effective segregation coefficient (keff (i)). These changes are primarily related to incorporation of solute in ice. 0 0,1 0,2 0,3 0,4 0 5 10 15 20 K eff (Cice/Cbw) Freezing front position (cm) FRX F mg/L Cl mg/L SO4 mg/L Na mg/l K mg/L Mg mg/L Ca mg/l Cl - SO 4 2- Na + Mg 2+ Ca 2+ K + F - 0,000 0,005 0,010 0 5 10 15 K eff (Cice/Cbw) Freezing front position (cm) BAR II Cl− (µmol/L) Na+ (μmol/L) Ca2+ (μmol/L) Na + Ca 2+ Cl -
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BIOGEOCHEMICAL PARTITIONING BETWEEN THE LIQUID WATER AND ICE PHASES DURING
FREEZE-DOWN IN ANTARCTIC AND ARCTIC LAKES Santibáñez, P., A. Michaud, T. Vick, A. Chiuchiolo, K. Hell, H. Adams, J. Dore, J. D’Andrilli and J.C. Priscu
Field Sampling:
Samples were collected during the 2009-2010 field seasons from Barrow (BAR II), AK
and the 6m depth of Lake Fryxell (FRX), Taylor Valley, Antarctica. Barrow lakes are
seasonally ice covered (~1 m) and Lake Fryxell is permanently ice covered (4 m).
Experimental Design:
A 75 L tank was lined with Teflon and 50 L of lake water was added (Fig. 1). The system
was incubated for ~4 days at -10°C with a “cold sky” set at -50°C to simulate a cold night
sky. A clean drill bit was used to penetrate the ice cover and liquid samples were taken over
time. The ice phase was sampled after freezing was complete by band-saw layer separation.
Sample Analysis:
Ions, stable isotopes of water, nutrients, TOC, and biological samples were collected at 4-7
time points throughout the experiment from both the liquid and ice phases. Concentrations
from the two phases were compared and a segregation coefficient computed for each
analyte.
METHODS
RESULTS ABSTRACT
Photo background courtesy of Alex Michaud
Acknowledgements
The authors would like to thank Deb Leslie, Kathy Welch, and Berry Lyons for isotope and ion
chemistry data; Raytheon Polar Services for logistical support in Antarctica; and Petroleum Helicopters
Inc. for air support in the Dry Valleys. This work was supported by NSF-OPP grants to JP; an NSF
IGERT fellowship and Montana Space Grant Consortium fellowship to AM; and a Fulbright-Conicyt
Scholarship to PS.
The thick ice covers on polar lakes play a major role in the physical, chemical and
biological properties of these lakes. Of particular importance is the partitioning of
chemical and biological constituents between the water and ice, which can produce
highly concentrated brines beneath the overlying ice and influence the biogeophysical
properties of the ice itself. As water molecules freeze they create a crystalline lattice that
repels most of the solutes and particulate matter that was in the water. The materials that
are trapped in the ice typically concentrate in localized inclusions or concentrate between
the ice grains. Despite much contemporary interest in the habitability of icy systems at
Earth’s poles, little is known about how constituents partition between the liquid and
solid phase. We conducted a series of controlled freezing experiments using water from
selected Arctic and Antarctic lakes to investigate chemical and biological fractionation
between ice and water as the lake water freezes.
Conclusions
OBJECTIVES AND HYPOTHESES
Overarching objective: To define the biogeochemical dynamics of ice and liquid phase
changes during formation and growth of ice covers of Antarctic and Arctic Lakes.
Hypotheses:
1. Solutes will be incorporated into the ice based on their respective affinities: Cl− > F−
~ NH4+ > NO3
− > Na+ ~ K+ > Ca2+ > SO42− (Eichler et al., 2001).
2. The relative magnitude of segregation coefficients (Mg2+ > Ca2+) is attributed to
interstitial incorporation (coupled with HCO3 -) in the ice lattice, and controlled by
ion size (Killawee et al., 1998)
3. The relative evolution of water and ice chemistry during freezing will depend on the
partitioning process at the ice-water interface and on the redistribution of the solutes
under diffusional and convective processes in the water reservoir (Lock et al., 1990).
Figure 1. The simulated lake
experimental setup
Figure 4. Conductivity at the bottom of the simulated
lake over the course of the FRX and BAR freeze-down
experiments (Freezing rate for BAR = 2.7 mm hr-1;
FRX = 2.2 mm hr-1)
Montana State University, Land Resources and Environmental Sciences, Bozeman, MT 59717, USA.
1. Solutes incorporated into the ice phase for BAR II: Stage 2: Ca2+ > Cl− > Na+ and in stage 3: Cl− ~ Na+>
Ca2+ (relative magnitude of segregation coefficients).
2. Solutes incorporated into the ice phase for FRX: K+ > Cl− ~ Na+> Mg2+ > SO42− > > Ca2+ > F
3. More conservative species in BAR II liquid phase: Mg2+ > K+ > Ca2+ > Na+ ~ Cl− > SO42− > > F−
4. More conservative species in FRX liquid phase: Mg2+ ~ K+ > Na+ ~ Cl− > SO42− >F− >Ca2+
5. BAR II segregation coefficients: Stage 2: Ca2+ = 0,0029, Cl− = 0,0012, Na+=0,0006.
6. BAR II shows the three stages of ice formation. The solute-poor ice (stage 2) presents effective
segregation coefficients between ice and bulk solution in the range of 0,0006 and 0,0029 for Ca2+ , Cl−
and Na+ (Fig. 5). The ice from BAR II was too pure to measure the other chemical species.
7. FRX freeze-down experiment shows only the solute-rich stage 3 ice due to high initial concentration.
These data allow us to describe microhabitats in ice and liquid water based on the biogeochemical
partitioning observed.
BAR II Water T0
B T A
C
M
BAR II A BAR II B BAR II C BAR II E
FRX C FRX D
Flu
ore
scen
ce In
ten
sit
y (
CP
S) FRX A FRX B FRX Water T0
B T A
C
M
Figure 8. Dissolved Organic Matter (DOM) characterization. Excitation-Emission Matrix of FRX (Antarctica) and BAR II (Arctic) showing the major
fluorescing components of DOM. A and C are humic-like components, M is a marine humic-like signature, and B and T both denote the protein-like fluorescing
components tyrosine and tryptophan. The whole water for BAR II and FRX lakes displays specific regions of DOM fluorophores, which describe environments
containing labile DOM (microbial origin) and humic-like, recalcitrant DOM (both terrestrial and marine-like). The DOM character differs between liquid phase
(bulk water) and the different depths of the frozen phase; frozen lake water samples contain DOM with significant shifts to amino-acid like fluorescing material.
Figure 3. Ice section from BAR freeze-
down experiments.
Figure 2. Conceptual model of ice cover formation.
LIQUID WATER
ICE
BOUNDARY LAYER
ICE-WATER INTERFACEDiffusional process
Convective process
(Spontaneously or Mechanically)
HEAT CONDUCTION EVAPORATIONLONG WAVE RADIATION
Partitioning process
(Fractionation or segregation)
ICE FRONT
Rejection of solutes
Figure 9. Effective segregation coefficient (Keff) and concentration factor of bacteria from FRX
and BAR II freeze-down experiments.
0
1
2
0 5 10 15
Ke
ff(C
ice
/Cb
w)
Depth of ice front (cm)
BAR II
Total Free-Bacteria
Coccoid
Rod
0
1
2
0 5 10 15
Co
nce
ntr
atio
n f
acto
r
Depth of ice front (cm)
BAR II_Liquid phase
Total Free-Bacteria
Coccoid
Rod
Filament
0
4
8
0 5 10 15
Co
nce
ntr
atio
n f
acto
r
Depth of ice front (cm)
BAR II_Ice phaseTotal Free-Bacteria
Coccoid
Rod
Filament
0
1
2
3
4
0 5 10 15 20
Ke
ff(C
ice
/Cb
w)
Depth of ice front (cm)
FRXTotal Free-Bacteria
Coccoid
Rod
Filament
0
1
2
3
4
0 5 10 15 20
Co
nce
ntr
atio
n f
acto
r
Depth of ice front (cm)
FRX_Liquid phase
Total Free-Bacteria
Coccoid
Rod
Filament
0
1
2
3
4
0 5 10 15 20
Co
nce
ntr
atio
n f
acto
r
Depth of ice front (cm)
FRX_Ice phaseTotal Free-Bacteria
Coccoid
Rod
Filament
Figure 6. Concentration factor (Ti divided by T0 concentration) of chemical species in the liquid phase of FRX and BAR
freeze-down experiments.
0
1
2
3
4
5
0 2 4 6 8 10 12 14 16
Co
nce
ntr
atio
n f
acto
r
Freezing front position(cm)
FRX
F
Cl
SO4
Na
K
Mg
Ca
Cl-
SO42-
Na+
Mg2+
Ca2+
K+
F-
0
1
2
3
4
5
0 2 4 6 8 10 12 14 16
Co
nce
ntr
atio
n f
acto
r
Freezing front position (cm)
BAR II
F
Cl
SO
Na
K
Mg
Ca
Cl-
SO42-
Na+
Mg2+
Ca2+
K+
F-
Figure 7. Concentration factor of
total organic carbon and inorganic
carbon between the Tfinal liquid
phase divided by concentration at
T0 .
0.1
1
10
100
1000
10000
BAR II FRXCo
nce
ntr
atio
n f
acto
r (T
5/T
0) Total organic carbon
(ppm)Total inorganic carbon(ppm)
Figure 5. Variations with depth of effective segregation coefficient (Keff (Cice/Cbw)) in Barrow (BAR II) and Fryxell
(FRX) freeze-down experiments.. The relative evolution of liquid water and ice chemistry is illustrated by the variation
with depth of the effective segregation coefficient (keff (i)). These changes are primarily related to incorporation of
solute in ice.
0
0,1
0,2
0,3
0,4
0 5 10 15 20
Kef
f(C
ice
/Cb
w)
Freezing front position (cm)
FRX
F mg/L
Cl mg/L
SO4 mg/L
Na mg/l
K mg/L
Mg mg/L
Ca mg/l
Cl-
SO42-
Na+
Mg2+
Ca2+
K+
F-
0,000
0,005
0,010
0 5 10 15
Kef
f(C
ice
/Cb
w)
Freezing front position (cm)
BAR II
Cl− (µmol/L)
Na+ (µmol/L)
Ca2+ (µmol/L)
Na+
Ca2+
Cl-
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