Ouring this symposium, various aspects of research into the recultivation of open-cast minesites were discussed. As a prime example, the symposium focussed on the recultivation reclamation of post-mining landscapes in the Lusatian lignite mining district of the former German 2 Oemocratic Republic GOR.
Therefore, the research into recultivation has a long tradition in Lusatia, going back to the 's. Oue [0 the scientific isolation of the former GOR, most of the research results were not available to an international audience until now.
This situation holds also true for other eastern countries. Hence, this special volume is a first step to fill this gap. The papers by Pietsch, Heinsdorf, and Katzur and Haubold-Rosar detail the Lusatian lignite mining district presenting an overview of recultivation research results and practical experiences related to the establishment of terrestrial and aquatic ecosystems in this region after mining.
In particular, the amelioration and reforestation of extremely acid, sulfurous mine soils, the fertilization of forest stands under different mine site conditions and the site-specific recolonization and re vegetation strategies are described. Ihr Name:. Folgen Sie uns beck-shop.
Quaternary substrates do not contain lignite or pyrite and, thus, there is usually no acid drainage developing from these substrates.
They are therefore often used to cover Tertiary substrates or mixes of Tertiary and Quaternary substrates that have been deposited at the base of the recultivation site. The Quaternary substrates are mostly sandy and have comparatively high concentrations of calcium carbonate Stock et al. Substrates with cohesive properties can only be found in areas of former terminal and ground moraines and in smaller and isolated lenses.
With the excavators and stackers used in Lusatia, it is generally not feasible to separate cohesive material from the sandy substrates for systematic formation of an upper layer suitable for agriculture or forestry. The Quaternary sandy substrates used to cover lignitic and pyritic substrates and to create a surface suitable for agricultural and forestal recultivation tend to severe hard setting Stock Due to increasing pore water suction during dry periods, mechanical stability of the soil can be so high that penetration of the soil by plant roots or soil tillage operations is restricted and sometimes impossible.
This hard-setting behaviour is attributed to soil particle size texture ; the fine sand and silt allow quite high tensile stresses to be transferred between mineral soil particles by concave water menisci. Another reason for the very high mechanical stability in a dry state is cementation of coarser soil particles with calcium carbonate and silt and clay particles.
Quaternary and Tertiary substrates have very low mechanical stabilities in a wet state. Stock et al. Until the beginning of the s, the substrates used for recultivation of post-mining landscapes were very heterogeneous mixtures of Tertiary and Quaternary substrates. Due to the high contents of pyrite in Tertiary substrates, they tended to be severely acidic.
Bio-Geotechnologies for Mine Site Rehabilitation - 1st Edition
The lignite- and pyrite-containing substrates and substrates free of those materials mostly have a sandy texture, low recent organic matter content and low nutrient status Wilden Stock showed that the technical processes described above led to modification of the original coherent structure of the substrates before they were excavated to a single grain structure. The single mineral particles are far more movable than before when they had a cohesive structure. Due to drying processes and increasing forces transferred by water menisci, soil particles rearrange spatially, which enhances mechanical stability of the matrix.
The hard-setting behaviour of a soil or substrate is enhanced by intense drying. In contrast with the behaviour of the soil or substrate under dry conditions, Stock et al. Similar behaviour is reported for typical hard-setting soils in Australia and Africa Mullins et al. This behaviour is attributed to textural composition of the substrate, which contains swelling and shrinking clay too small to induce crack and structure formation. However, the silt and clay particles, which fit into the voids between the sand grains, are high enough to cement the sand grains without forming a continuous fine-textured matrix.
Due to the processes of substrate formation by mining described above, the recultivation sites display very heterogeneous physical properties. Depending on substrate water content during excavation, transport, deposition and levelling and the number of wheelings passes with machinery during surface levelling, the mechanical forces induced are spatially very heterogeneous. They found that especially on reclaimed anthropogenic post-mining sites, bulk density did not explain precompression stress, saturated hydraulic conductivity and air permeability.
The varying physical properties lead to heterogeneous water-holding and infiltration capacity. Thus, preferential flow patterns developed with known effects on ground water recharge and ground water pollution Buczko They even found a negative correlation between bulk density and precompression stress in some cases. Construction of recultivation sites in Lusatia includes heaping dam-like structures with heights up to 4 m, which are later levelled with heavy crawlers. Bulk densities up to 1.
In Lusatia, recultivation practices include deep ploughing or deep ripping 50 cm soil depth to reduce the compaction induced by dumping and levelling the substrate Katzur and Haubold-Rosar The very low mechanical stability of the recultivation substrates, especially under wet conditions Stock et al.
The fact that Gunschera recommends a second deep ploughing after approximately 3 yr in addition to the primary deep ploughing clarifies the low persistence of such loosening actions. Significant recompaction occurred in soils and substrates with lower clay contents. Recultivation substrates containing pyrite have acidic pH and require chemical amelioration to increase pH and to prevent percolation of acidic water into ground water and lakes. Based on field research, ameliorative methods were developed for forestal reclamation even on substrates with high pyrite concentrations Weber et al.
In this context the acid-base balance introduced by Illner and Katzur and Illner and Lorenz is of great importance.
Bio-Geotechnologies for Mine Site Rehabilitation
For amelioration of sulphuric substrates, lime, and, until , brown coal ash, by-products of combustion of lignite for energy and heat production, have been used Illner and Lorenz The thickness of the upper, ameliorated layer, which consists of either Tertiary substrate with additions of lime or ashes or of Quaternary substrates determines the depth of the rooting zone.
Consequently, the quality of the basic amelioration is crucial for future agricultural and forestal productivity Katzur and Hanschke Gunschera suggests a minimum depth of cm for this arable and rootable layer. This means that to cm of material must be applied, considering settlement of the substrates.
The depth of the arable layer can be reduced to about 60 cm if the material below that zone is of Quaternary origin or has been ameliorated with lime or similar substances. The short-term success of such ameliorative measures can be assessed by drill seeding a test crop, such as forest bush rye wild rye, Secale multicaule L. Typical horizons which develop in a pyritic substrate ameliorated with lime or ashes are amelioration horizon, a horizon with finished pyrite oxidation and a horizon with ongoing pyrite oxidation Neumann The thickness of the ameliorated horizon depends on the amount and depth of liming or application of ashes.
Katzur and Haubold-Rosar recommend incorporating lime fertilizer or brown coal ash to a depth of 60 cm. Compared with the lower horizon, the ameliorated horizon had higher pH and higher potential cation exchange capacity Neumann Gast showed that pyrite oxidation and pH reduction strongly influenced mineral weathering processes and significant differences in solution chemistry between ameliorated and unameliorated horizons developed. Heterogeneity of pH and other chemical properties in the subsoil is greater than in the ameliorated topsoil.
In younger ameliorated horizons Neumann found that secondary iron formations were mainly jarosite and in older ones mainly goethite. The secondary soluble salt was mainly gypsum.
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No relationship between depth of desalinization and soil age was detected. Rumpel et al. In the ameliorated horizon and in the horizon below zone with completed pyrite oxidation no pyrite crystals are left. Acidic conditions lead to a strong feldspar weathering, clay mineral destruction and high gibbsite contents in these zones.
Due to low pH, aluminum becomes mobilized and can reach phytotoxic concentrations. Even after more than 50 yr, lignitic pyritic sites have strong quantitative and qualitative differences in water and element fluxes with imbalances through the system compared with unmined sites. The main amelioration objective is sustainable improvement of soil reaction Katzur and Haubold-Rosar Gast found that lignite-containing recultivation sites were characterized by extraordinary high fluxes of aluminum, iron, calcium and sulphur as SO 4 , which acted as sources of elements.
The elements transferred to deeper soil layers can reach several tons per hectare per year. Soil solution chemistry is very much influenced by liming or application of fly ash and by acidic atmospheric inputs Wilden et al. Schaaf et al. They showed that application of sufficient amounts of alkaline materials to buffer acid production due to pyrite oxidation in the long term is necessary to enable recultivation and reduce the risk of ground water pollution. Neumann showed that sites recultivated with brown coal ashes still displayed a high acid neutralization capacity after 34 yr of recultivation, and explained it with the high buffering capacity of calcium cations from calcium silicates contained in the ashes.
Development of a closed cycling of nutrients such as nitrogen and potassium are thus essential to create a sustainable ecosystem Schaaf et al. The substrates that are used for recultivation require applications of fertilizer with nitrogen, phosphorus and potassium. The amount and type of fertilizer depends on substrate composition and future land use Katzur and Haubold-Rosar ; Weber et al.
Reclamation of Colliery Mine Spoil Founded on Natural Succession
Wilden et al. They showed that application of mineral fertilizer led to an immediate but short-term about 1 mo increase in nitrate, ammonium and potassium concentrations in the soil solution to a depth of cm. Compared with the sites with mineral fertilizer application the nitrate content in the subsoil was significantly lower.
Compost application resulted in a strong longer-term increase of potassium in the soil solution, whereas nitrate concentration did not increase. Phosphate concentration in the soil solution depended strongly on pH and not on the kind of fertilizer applied. As an added benefit, use of these materials will remove them from the waste storage system. In Lusatia, until organic fertilizer applications were not made due to the risk of nitrate and heavy metals leaching in sandy substrates Wilden Emmerling et al.
Soils consisted of Tertiary and Quaternary substrates, which were ameliorated with brown coal filter ash and lime. In the first 2 yr after application a low level of microbial activity was determined. The microbial and substrate-induced respiration and enzyme activities increased significantly with increasing amounts of organic materials. This was attributed to increased organic matter and nutrient concentrations and improved soil physical properties, such as water and nutrient retention capacities.
Constituents of the coal fragments in Tertiary deposits were mineralized or converted by soil microorganisms. Tertiary substrates ameliorated with brown coal ash showed high microbial and enzyme activities after application of nitrogen-rich sewage sludge or very high amounts of mature compost mainly consisting of green waste. The stimulating effects of composted sewage sludge were lower than those from sewage sludge. In forestal recultivation, Fettweis et al. They used a 14 C method to distinguish between recent and geogenic carbon. The content of organic matter increased with stand age, and carbon contents in the substrate were mainly classified as geogenic brown coal fragments.
They found that brown coal with its ability to store water and nutrients could replace some of the recent functions of organic matter. They showed that water-holding capacity increased with increasing contents of geogenic carbon brown coal. The unstructured and mostly sandy substrates used for recultivation in Lusatia are relatively free of recent organic matter; therefore the application of soil organic matter and topsoil on reclaimed sites has been studied.
This process is known as topsoiling.