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....HYPOX kickoff: Site introduction
Swiss lakes introduction
Carsten Schubert & Mathias Kirf (Eawag)
....HYPOX kickoff: introduction to Swiss lakes
Part 1: Introduction to the sites
Carsten Schubert (Eawag)
....HYPOX kickoff: introduction to Swiss lakes
Locations of Swiss lakes with available
long time-series of temperature, O2 and
nutrients
Greifensee
Lower Lake Zurich
Upper Lake Zurich
Lake of Walenstadt
Lake Neuchatel
Lake Zug
Aegerisee
Lake Lugano
....HYPOX kickoff: introduction to Swiss lakes
Lake „Rotsee“
Famous rowing lake near Lucerne (0.5 km2 surface)
16 m maximal depth, mixes in winter
Oxic (0-9 m) and anoxic water layer
Oxygen (mg/l)
Oxygen (mg/l)
0
2
4
6
8
0
2
2
4
4
6
6
Depth (m)
Depth (m)
0
8
10
14
14
16
4
8
12
16
20
Transmission (FTU)
24
4
6
8
Lake mixed over the weekend !
10
12
0
2
8
12
16
0
80
70
60
50
40
30
Transmission (%)
20
....HYPOX kickoff: introduction to Swiss lakes
Lago di Lugano
Three basins (artificial dam), Hypox conc. on N-basin
Max. depth of 288 m, 4.7 km2, 12.3 y residence time
Lake had an anoxic layer below a chemocline (100m)
however, in 2004-2005 and 2005-2006 lake mixed
completely
Thereafter a warm winter was responsible for an only
80m deep mixing
....HYPOX kickoff: introduction to Swiss lakes
Lake Zürich
Max. depth of 136 m, 88 km2, oxygenated water column
....HYPOX kickoff: introduction to Swiss lakes
Lake Zürich time series example
Time-series of temperature, oxygen concentration and nutrient
concentrations are available from Lake Zurich (mesotrophic, 136 m deep) at
monthly intervals from June 1936 to the present.
Usual sampling depths:
0, 1, 2.5, 5, 7.5, 10, 12.5, 15, 20, 30, 40, 60, 80, 100, 110, 120, 130, 135 m.
Time-series of oxygen concentration in Lake Zurich at 80 m (red) and 135 m (blue)
11
10
9
8
7
6
135 m
80 m
5
4
3
2
1
0
2/1/34
2/1/44
2/1/54
2/1/64
2/1/74
2/1/84
2/1/94
2/1/04
2/1/14
....HYPOX kickoff: introduction to Swiss lakes
Rationale: Changes & problems
connected to global change
....HYPOX kickoff: introduction to Swiss lakes
Impact of unusually mild winters (‘88,89,90)
Lake Zurich:
Mixing suppressed, so deep-water O2 falls.
Recovery during mixing events in 1990
(mild, but high deep-water temperature allows
mixing to occur) and 1991 (cold).
Lake Neuchâtel:
Wind-exposed, so always mixes.
Almost no impact on deep-water O2.
Lake Geneva:
As Lake Zurich, but only slight recovery in
1991 (deep-water volume very large).
Lake Zug:
Meromictic, so O2 concs. always low.
Situation exacerbated by mild winters. Abrupt
but slight recovery in 1991.
Livingstone (1997) Verh. Internat. Verein. Limnol., 26(2): 822-826.
....HYPOX kickoff: introduction to Swiss lakes
Impact of ice cover
The presence or
absence of ice
cover, which
depends on the
severity of winter,
has a determining
influence on
profiles of
temperature and
oxygen
concentration.
Winter of 1978/79:
- mild winter
-no ice cover
- homothermy and
mixing
- deep-water well
oxygenated
Winter of 1980/81:
- cold winter
-ice cover
- O2 uptake and
mixing inhibited
Example: Aegerisee - low O2 in deep
water
(83 m deep,
oligotrophic)
Livingstone (1993) Internat. Rev. ges. Hydrobiol., 78(4): 465-480.
....HYPOX kickoff: introduction to Swiss lakes
Aim of the HYPOX work at the site,
suggested key parameters to measure
We will measure biomarkers like alkanes and sterols and more
specific markers like lycopane/C31 ratios and isorenieratene
(pigment) in the sediment cores recovered from different water
depths
Oxygen and nutrient measurements are ongoing
Noble gases at sediment cores will reveal paleo oxygen conc.
....HYPOX kickoff: introduction to Swiss lakes
atmospheric noble gases
eighth column
Helium
Introduction: Why noble gases in aquatic
systems? A plea for simplicity
3,4He
• production ('dating')
• accumulation ('origin')
air contamination ?
• gas exchange
environmental conditions
Ù
(He), Ne, Ar, Kr, Xe
entering water by gas exchange
Ci,water = ki(T, S, ∆air,...)*pi,gas /'air'
• secondary gas exchange: Ci,water ≠Csat
• climate indicator: T, ∆air
• Deep high-intensity 'gas seeps' associated
with mud volcanoes at the sea floor.
Gas escaping from the bottom of Black Sea
(courtesy of Dr. Lyobomir Dimitrov, Inst. of
Oceanography, Varna, Bulgaria)
EC project EVK-2-CT-2002-00162
Example Black Sea (1)
CH4 gas seeps from mud volcanos
www.crimea-info.org
....HYPOX kickoff: introduction to Swiss lakes
Example Black Sea (2)
CH4 gas seeps from mud volcanos
• Seeps of ~ 1000 m height were detected
by echo sounding.
• Two deep water sites:
•
•
mud volcano
reference site
1 km
ª New mud volcano Vodyanitskiy.
ª Reference site in the open water.
EC project EVK-2-CT-2002-00162
www.crimea-info.org
....HYPOX kickoff: introduction to Swiss lakes
....HYPOX kickoff: introduction to Swiss lakes
Example Black Sea (3) When gases meet:
CH4 bubbles on the rise
Concept: CH4 flare / bubble plume affect the
noble gas abundance in the water
• Noble gas free CH4 bubbles
emanate from the sediment.
• Gas exchange between
ascending bubbles and
water.
ª CH4 dissolution & gas stripping.
ª ª NG Î bubbles.
ª ª NG depletion in the water.
Õ
Õ
Î
Õ
Ístripping
Í
Ö dissolution
Í
....HYPOX kickoff: introduction to Swiss lakes
Noble gases in pore water of sediments
from lakes and oceans
Experimental break through (UI, L&O, 2003)
The (old) idea
solubility
preparing
coring
age
T, Sal
centrifugation
sampling
....HYPOX kickoff: introduction to Swiss lakes
Lacustrine sediments Lake Issyk-Kul
(closed lake, Kyrgyzstan)
The data
Conclusion (Ci = Ci(h)))
307 m
291 m
Other recent applications:
i. Quantification CH4 ebulation (UI, EPSL, 2005)
ii. Terrestrial He degassing & transport
Lake level drop of 300 m 8 kyr ago
....HYPOX kickoff: introduction to Swiss lakes
Lacustrine sediments
Lake Van: He emanation
Lake Van
morphometry
Fault zone?
Caldera?
Turkey
Lake Van
Facts:
• largest lake in Turkey
(~ 3700 km2, ~ 440 m)
• soda lake (pH 10, S ~ 22-23
g/kg)
• enclosed basin:
(+ lake level: - deep water
mixing)
• tectonically active region:
Æ mantel He injection,
but how & where?
....HYPOX kickoff: introduction to Swiss lakes
Lacustrine sediments
Lake Van: Results
'3H input' (M)
'hot spot' (H)
Heex: 300%
'strong gradient'
(C,D,E,F,G,J,K,L)
'low gradient' (A,B,I)
•
•
•
13 cores with He (plus Ne, Ar, Kr, Xe)
3 types of He emanation
3He/4He constant (+ tritiogenic 3He?)
....HYPOX kickoff: introduction to Swiss lakes
Lacustrine sediments
Lake Van: Summary & Outlook
So far ...
• He release heterogeneous within km
• Caldera sediments constrains He
input (mixture of mantle & crustal He)
The next steps ...
• Coring specific 'seismic' structures
• Noble gases as proxy for paleoclimatic
changes in lakes? (Lake level
fluctuations in core M?)
• 2010: ICDP 'Paleo Van' ! (> 500 m
long core(s))
Æ He (& fluid) transport through
continents
....HYPOX kickoff: Swiss lakes introduction
Part 2: Introduction to the
Profiling Ion-sensitive Analyzer (PIA)
Mathias Kirf (Eawag)
Chemical Eyes:
Imagine the limit
˚˚˚
Eawag: The Swiss Federal Institute of Aquatic Science and Technology
Chemical Eyes:
Imagine the limit
˚˚˚
Oxygen
Eawag: The Swiss Federal Institute of Aquatic Science and Technology
Project description: Chemical Eyes
Introduction
Hardware
Software
Making biogeochemical gradients visible:
Development and deployment of a water column
Profiling Ion-sensitive Analyzer (PIA)
Increasing need for spatial and temporal highresolution data, preferably in-situ, to allow for:
Detailed understanding of the abiotic environment
and biotic factors shaped by and shaping
biogeochemical gradients within the water column
Defined collection of water samples / microbial
communities
Chemical Eyes: Concept (a kid´s view):
Introduction
Hardware
Software
Chemical Eyes: Concept
High resolution allows to:
Introduction
Hardware
Software
- identify zones of production
and consumption
- estimate fluxes
- sample relevant zones
… at true in-situ conditions
… with high frequency
… and online
Chemical Eyes: Hardware
Introduction
Hardware
Software
Chemical Eyes: Hardware
Introduction
Hardware
Software
Components of Profiling Analyzer-System:
Sensor Array (3x O2, H2S, solid contact potentiometric sensors, CTD)
Amplifier
Brain / embedded computing
Watersampler (12 x 60 ml syringes)
(online / offline)
Chemical Eyes: Hardware
Introduction
Hardware
Software
Sensor-Array:
Switchable Total Oxygen Sensor (STOX / LOD 0.01 µmol l-1,
idea: N. P. Revsbech, source: Unisense)
O2-microsensor (Unisense)
O2-optode (LoD: 0.03 µmol / l-1, insensitive to H2S, PreSens)
H2S-microsensor (LoD: 0.3 µmol / l-1, Unisense)
Potentiometric solid contact (SC)-sensors (pH // NO3-, NO2-, NH4+, S2-)
Auxiliary sensors (temperature, conductivity, depth)
Chemical Eyes:
Anode
Hardware
Software
e-
“Guard”
Ag
Ag
Cl
+
O2 reduction current is
proportional to
diffusive oxygen flux
to the cathode:
AgCl
-
buffered
electrolyte
I red ∝ J O
2
Cathode ( -0.8 V )
4 e-
Measurement
-
4 OH
2 H2O + O2
Silicone
Signal (A)
Introduction
Basic Principle of amperometric
Oxygen-sensors
membrane
Time
O2
O2
Chemical Eyes:
Anode
Hardware
Software
e-
“Guard”
Ag
Ag
Cl
+
AgCl
STOX:
Switchable
Total
OXygen
Sensor
-
buffered
electrolyte
Cathode ( -0.8 V )
4 e-
Measurement
-
4 OH
2 H2O + O2
Silicone
Signal (A)
Introduction
Selfreferencing STOX-Sensor *
membrane
Time
O2
O2
* idea: N. P. Revsbech
Chemical Eyes:
Anode
Hardware
Software
e-
“Guard”
Ag
Ag
Cl
+
AgCl
STOX:
Switchable
Total
OXygen
Sensor
-
buffered
electrolyte
Cathode ( -0.8 V )
4 e-
Calibration
-
4 OH
2 H2O + O2
Silicone
Signal (A)
Introduction
Selfreferencing STOX-Sensor *
membrane
Time
O2
O2
* idea: N. P. Revsbech
Chemical Eyes:
Selfreferencing STOX-Sensor
STOX1 vs Time
5
Introduction
Hardware
Software
STOX1 (V)
4
3
2
1
0
0
5
10
Time (min)
15
20
Chemical Eyes:
Selfreferencing STOX-Sensor
STOX vs O2
STOX O 2 (µM l
85
-1
) Downcast2
Introduction
Hardware
90
Software
Depth (m)
95
100
105
110
115
STOX
µ_sensor
STOX sensor
Oxygen µ_sensor
O 2 Sensor
120
0
10
20
-1
2
30
Oxygen (µmol l-1)
40
50
60
Chemical Eyes: Hardware
Introduction
Hardware
Software
Components of PIA-System:
Embedded Computer
(ZBrain / Schmid_Engineering):
A/D-converter
Digital In / Out
UART-Interfaces
Data logger
Low power consumption
Multiplexer:
4 x 4 Channels,
Including
4 x 3 potentiometric Channels
1 x 4 amperometric Channels
Chemical Eyes: LabView Embedded
Introduction
Hardware
Software
Intuitive flow-charts plus convenient architecture:
Strict separation between data acquisition and reduction (on board)
and data analysis (online on ship / host pc)
Facilitated event-based task-management (offline):
e.g. referencing of STOX-sensor if depth is constant for t > 5 min
Chemical Eyes: Setup
Experimental setup:
Calibration of
SC-pH Sensors
Introduction
Hardware
Software
Chemical Eyes
Introduction
Hardware
Software