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| Titel |
Impact of ground water - surface water interactions on pore-water and solid sediment phase composition of an acidic mining lake |
| VerfasserIn |
J. Beer, C. Neumann, J. Fleckenstein, S. Peiffer, C. Blodau |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250030793
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| Zusammenfassung |
| Biogeochemical processes in lake sediments are influenced by diffusive and advective supply
of solutes from lake and ground water. It has been demonstrated that the pore-water pH in
lake sediments characterized by low pH and high concentrations of iron and sulfur (e.g.
acidic mining lakes) are significantly affected by exchange flows with moderately acidic or
near-neutral ground water (Blodau 20041). The resulting pore-water pH is a master variable
which controls many biogeochemical processes such as mineral transformations, the
reduction of iron and sulfate, etc.
The aim of this study was to investigate whether inflow of ground water into an acidic
mining lake leads to a shift from acidic, iron-reducing to near-neutral, sulfate-reducing and
pyrite-precipitating conditions within the lake sediment. Therefore, we investigated
ground-water advection rates among different sites and related them to concentration-depth
profiles of relevant chemical species, and the composition of the solid sediment
phase.
We observed a heterogeneous pattern of ground water - surface water exchange within the
lake. In shallow areas, ground water inflow occurred in the northern part (up to
7Â LÂ m-2Â d-1) of the lake and outflow (up to 3Â LÂ m-2Â d-1) in the southern part. In
deeper areas, ground water generally infiltrated into the lake with rates of up to 6
 L m-2 d-1except one site (> 200  L m-2 d-1). Advective transport affected pore-water
concentrations of ferrous iron and sulfate which both ranged from 5 to 30Â mmol
L-1. Additionally, concentration-depth profiles of these dissolved species were
altered by other processes such as schwertmannite transformation, and iron and
sulfate reduction. Ground water – surface water exchange flows caused apparent
differences in the pore-water pH: under outflow or low inflow conditions the pore
water was more acidic (below pH 3.5) compared to the other sites (pH up to 6).
Since sulfate reduction is pH-controlled the observed differences in the pore-water
pH should have an effect on the sequestration of total reduced inorganic sulfur
(TRIS); and this is supported by the preliminary results of the solid sediment phase
analysis.
1 Blodau, C. (2004). "Evidence for a hydrologically controlled iron cycle in acidic and
iron rich sediments." Aquatic Sciences 66(1): 47-59. |
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