Download - Biogeochemical Research At Lake Baikal
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Biogeochemical ResearchAt Lake Baikal
Beat Müller, Lawrence OchEAWAGFederal Institute of Science and Technology of the Environment, Kastanienbaum, Switzerland
Michael SturmEAWAGFederal Institute of Science and Technology of the Environment, Dübendorf/Switzerland
Elena G. VologinaIECInstitute of the Earth‘s Crust, Russ.Acad.Sci., Irkutsk/Russia
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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
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Fluxes between reservoirs and the cycling of elements
Import
Export
Precipitation/DepositionPrimary
ProductionExport from
Epilimnion(New production)
Gross Sedimentation
Net Sedimentation
Mineralization/
Dissolution
Turbulence/
Advection Mineralization
BIOLOGY
GEOLOGY
CHEMISTRY
PHYSICS
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Sediment traps: • Export from Hypolimnion
• Degrad. in water column
• Gross sedimentation
Sinking
particles
Particle Fluxes: Sedimentation
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The Large Moorings
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current meter(30 min. intervals)
Acousticreleaser
T-logger(10 min. intervals)
sequencingtrap(24 cups,2 weeks interval)
integratingtrap
(2 cups)
Mooring Instruments
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Sediment cores:• Net sedimentation
• Mineralization/Dissolution
sediments
Particle Fluxes: Sedimentation
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• Mineralization of organic matter
• Consumption of oxidants• Release of nutrients
water
Processes at the Sediment-Water Interface
sediments
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O2 concentration
profiles
Mineralization and Dissolution
mm
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O2 concentration
profiles
Mineralization and Dissolution
mm
In average: 3 mmol O2 m-
2d-1 => 1.1 mio t O2 a-1
i.e. Mineralization of => 880’000 t algae a-1
=> 92 km3 of water (a layer of 3m thickness)
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Advection:Estimation of annual cold-water 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
Upwel- ling
Cold water
intrusions
Fluxes in the water column
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Fluxes in the water column
CDT ProbeTemp.logger
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kt P yr-1
50 10
P fluxWater column 40 80 P in
Sed. traps
50
25
20P fluxPorewate
rP inSediments
25 difference
30 difference
P inSed. traps
Fluxes of Phosphorus (South Basin)
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kt P yr-1
50Fluxes of Phosphorus (South Basin)
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Selenga is the main tributary discharging50 % of the water load75 % of the particle load50 % of terrestrial organic carbon
Monitoring of Tributaries
Reliable monitoring data ofhydrologymajor elements, nutrientssuspended particles
are essential to estimateelement budgetslong term changes
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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
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Formation at the redoxinterface
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
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Early diagenetic processes in the sediment
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Early diagenetic processes in the sediment
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Diagenetic Processes of the Fe/Mn layer
O2
Oxidation of Mn(II) by O2
Reduction of Mn(IV) by Corg, Fe
Diffusion CH4
Methanogenesis
Oxidation by Fe-oxide
Fe(II) reduces Mn-oxide
Diffusion Fe(II)
Diffusion of Mn(II)
Diffusion of Fe(II)
Reduction of Fe(III) by Corg
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Development of Fe/Mn layers
MnFe
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Thank you
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SB NB New Production 20.8 14.6 gC m-2 yr-1
Net Sedimentation 2.6 1.5 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.
Summary Nutrient Budgets
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Structure of the buried crust: Micro-XRF Profiles
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Peeper Plate after Exposition
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O2 fluxWater column 20.
820.8
Corg inSed.
traps
14.6
2.611.0
O2 fluxPorewa
ter Corg inSedimens
12.0
difference
6.2 difference7.2
difference
Corg inSed.
traps
gCm-2yr-
1
13.6
sum
Fluxes of Organic Carbon (South Basin)
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im Sediment-Porenwasser
Rücklösung:0.56 mmol/m2 d
SILIKAT
Jährlicher Eintrag aus dem Einzugsgebiet:
250’000 t Si/Jahr
bei 31’500 km2… 180’000 t Si/Jahr