『Abstract
Acid mine drainage is a widespread environmental problem in Lusatia
in the eastern part of Germany, where extensive brown coal and
lignite mining was carried out during the last century. As a result
of oxidation of pyrite in strip mine dumps of this region, numerous
mine drainage lakes have pH values ＜3 and are characterized by
high concentrations of dissolved sulphate and ferrous iron. Using
chemical and isotopic techniques, we tested in laboratory bottle
experiments the extent to which the addition of degradable organic
carbon to acid lake water and sediments could stimulate bacterial
(dissimilatory) sulphate reduction. The overall goal was to evaluate
whether bacterial sulphate reduction, and subsequent formation
of sedimentary sulphide minerals, could generate enough alkalinity
to potentially neutralize the acid lakes in Lusatia.
Pyruvate, glucose, succinic acid, lactate, ethanol, acetate,
and various industrial by-products were added in various concentrations
to original lake water and sediments in glass bottles and incubated
between 4 and 12 weeks in darkness. The extent of bacterial sulphate
reduction was determined by analyzing the concentrations and the
isotopic compositions of sulphate in the water column, and the
contents and δ34S values of various sedimentary sulphur
compounds at the beginning and the end of the experiments. Bacterial
sulphate reduction was significantly enhanced after addition of
pure substances (lactate, pyruvate, acetate, and ethanol) resulting
in elevated pH values (4.5 to 6.0) in the bottle water at the
end of the experiments. Cheap industrial by-products (whey, molasses,
Pfezi-granules, and Carbokalk) as organic carbon source were also
shown to be effective in enhancing bacterial sulphate reduction,
thereby increasing the pH value of the bottle water. In general,
the addition of selected organic carbon compounds enhanced sufficiently
bacterial sulphate reduction and the formation of sedimentary
sulphur minerals, generating enough alkalinity for raising the
pH of the bottle water to near-neutral values. Further research
in enclosures and under field conditions is needed to determine
whether this technique constitutes a feasible remediation strategy
for the acid lakes in Lusatia.
Keywords: Acid mine drainage; Bacterial sulphate reduction; Sulphate;
Sulphur isotopes; Oxygen isotopes』
1. Introduction
2. Materials
3. Experiments
4. Analytical methods
4.1. Water samples
4.2. Sediment samples
5. Results
5.1. Water
5.2. Sediments
6. Discussion
7. Conclusions
Acknowledgements
References