Chemistry Reference
In-Depth Information
devastated land to ensure agricultural or forest productivity of the areas
affected. Returning these areas to agricultural production after mining ceases
is referred to as 'recultivation'. Recultivation in Germany, to a wide extent,
does not rely on natural succession of the devastated area.
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The problems of
the post-mining areas are varied; natural conditions are modified on the
landscape scale. To enable mining, the groundwater has to be lowered below
the brown-coal seam (between ca. 50 and 400 m below the surface). The impact
of ground-water lowering continues for decades after site reclamation, which
changes the water balance of whole landscapes. Settlements are moved and
finally trees cut. Then the soil material covering the brown-coal deposit is
excavated and transported to the other side of the mine with conveyor belts.
Excavators are used to spread the substrate as dam-like structures. Thereafter,
the recultivation sites are levelled.
Chemical and biological substrate limitations, such as very low or very high
pH values
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and lack of macro and micro nutrients and recent organic matter,
can be ameliorated by the application of lime, mineral and/or organic
fertilisers, topsoil, and potentially soil microbes. The physical functionality and
mechanical stability of the reclamation substrates is generally poor. This is
partly because of the substrate properties themselves, but also due to the
technical processes of site construction. Substrates excavated from deep in the
mine are unstructured and devoid of recent organic carbon.
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The lack of
structure and organic carbon in these soils makes them very susceptible to
compaction,
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especially at high water contents. These natural properties are
affected by excavating, depositing and levelling the substrates with large-scale
heavy machinery, which impart strong mechanical stresses to soils (Figure 5).
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Figure 5
Levelling of stockpiled topsoil during the recultivation of a mine in Eastern
Germany. The weight of machinery and degradation of the soil in the
stockpile presents challenges to physical conditions for crop production if
land is returned to agricultural production.
