Biogeochemical
Research
At Lake Baikal
Beat Müller, Lawrence Och
EAWAG
Federal Institute of Science and Technology of the Environment, Kastanienbaum, Switzerland
Michael Sturm
EAWAG
Federal Institute of Science and Technology of the Environment, Dübendorf/Switzerland
Elena G. Vologina
IEC
Institute of the Earth‘s Crust, Russ.Acad.Sci., Irkutsk/Russia
Focus of Scientific Interest
Element budgets and fluxes:
How is the lake influenced by changing loads?
How do they affect the ecosystem?
Quantify the loads in and out of the lake, and quantify the
fluxes between reservoirs
Sediment formation:
Investigation of the biogeochemical processes and rates
that determine the formation of the ‘young sediment’ so that
the climate signals in the ‘old sediment’ can be interpreted
Fluxes between reservoirs and the cycling of elements
Import
Precipitation/Deposition
Export
BPrimary
I O LProduction
OGY
Turbulence/
Advection
Export from Epilimnion
(New production)
P H Y S IMineralization
CS
Mineralization/
Dissolution
CHEMISTRY
Gross Sedimentation
GEOLOGY
Net Sedimentation
Particle Fluxes: Sedimentation
Sediment traps:
•Export from Hypolimnion
•Degrad. in water column
•Gross sedimentation
Sinking
particle
s
The Large Moorings
Mooring Instruments
sequencing
trap
T-logger
(10 min. intervals)
(24 cups,
2 weeks interval)
current
meter
(30 min. intervals)
Acoustic
releaser
integrating
trap
(2 cups)
Particle Fluxes: Sedimentation
Sediment cores:
•Net sedimentation
•Mineralization/Dissolution
sediments
Processes at the Sediment-Water Interface
•Mineralization of organic matter
•Consumption of oxidants
•Release of nutrients
water
sediments
Mineralization and Dissolution
mm
O2
concentration
profiles
Mineralization and Dissolution
In average: 3 mmol O2 m-2Od-1
2
=> 1.1 mio t O2 a-1
mm
concentration
profiles
=> 92 km3 of water
(a layer of 3m thickness)
i.e. Mineralization of
=> 880’000 t algae a-1
Fluxes in the water column
Advection:
Estimation of annual coldwater intrusions into the
deep water of the Lake
Turbulent mixing:
Determination of vertical
diffusivity with temperature
microstructure measurements
and inertial diffusivity
eg. Sibio
N
P
Upwelling
Cold
water
intrusion
s
Fluxes in the water column
CDT Probe
Temp.
logger
Fluxes of Phosphorus (South Basin)
50
10
P flux
Water column
P in
Sed. traps
80
40
30
difference
P in
Sed. traps
50
P flux
Porewater
kt P yr-1
20
25
25
difference
P in
Sediments
Fluxes of Phosphorus (South Basin)
50
kt P yr-1
Monitoring of Tributaries
Selenga is the main tributary discharging
50 % of the water load
75 % of the particle load
50 % of terrestrial organic carbon
Reliable monitoring data of
hydrology
major elements, nutrients
suspended particles
are essential to estimate
element budgets
long term changes
Sediment Formation
Sediment formation:
Investigation of the biogeochemical processes and rates
that determine the formation of the ‘young sediment’ so that
the climate signals in the ‘old sediment’ can be interpreted
Early diagenetic processes in the sediment
Formation at the redox
interface
Upper layer moves up with
sedimentation
Lower layer stays in place
Observed in layers of
up to 65’000 years
What causes the detachment?
Indicators of changes in the
catchment (climate?)
What happens here?
Early diagenetic processes in the sediment
Early diagenetic processes in the sediment
Diagenetic Processes of the Fe/Mn layer
O2
Oxidation of Mn(II) by O2
Reduction of
Mn(IV) by Corg, Fe
Reduction of
Fe(III) by Corg
Diffusion of Mn(II)
Diffusion of Fe(II)
Fe(II) reduces Mn-oxide
Diffusion Fe(II)
Oxidation by Fe-oxide
Diffusion CH4
Methanogenesis
Development of Fe/Mn layers
Mn
Fe
Thank you
Summary Nutrient Budgets
New Production
Net Sedimentation
SB
20.8
2.6
NB
14.6
1.5
gC m-2 yr-1
gC m-2 yr-1
Fluxes of N, P and Sibio were 30% smaller in the NB than in the SB.
Denitrification rates 37 (SB) and 52 (NB) mmol m-2 yr-1.
(cf. 57 mmol m-2 yr-1 for oceans (Middleburg et al., 1996))
10.6 and 6.0 mmol P m-2 yr-1 were transferred to the deep water in the
SB and NB where 26% and 42% P were retained in the sediments.
Structure of the buried crust: Micro-XRF Profiles
Peeper Plate after Exposition
Fluxes of Organic Carbon (South Basin)
O2 flux
Water column
20.8
difference
7.2
Corg in
20.8
Sed.
traps
6.2 difference
sum
13.6
14.6
O2 flux
Porewate
r
11.0
12.0
gCm-2yr-1
Corg in
2.6 Sedimens
Corg in
Sed.
traps
difference
SILIKAT
im SedimentPorenwasser
Rücklösung:
0.56 mmol/m2 d
bei 31’500 km2…
180’000 t Si/Jahr
Jährlicher Eintrag
aus dem Einzugsgebiet:
250’000 t Si/Jahr