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In order to integrate necessary interdisciplinary complexity, sustainability, defined targets and endpoints for reclamation progress, the objective of this research is to advance reclamation knowledge on (i) international scale and (ii) national scale, taking Nigeria as an example. On the international scale (i), a systematic reclamation threshold scale for assessing, evaluating, documenting, and monitoring reclamation progress was developed. The threshold stages begin from the initial state I0 down to degraded state D0 (depending on the type of mining). Reclamation starts with soil reconstruction R-2 up to revegetation R-1 (red zones) to reach minimum threshold R0 (amber zone). Beyond R0 are the green zones R1, R2, and R3 representing soil/abiotic condition, biological and improved threshold respectively. Adaptation of the threshold model to degraded ecosystems in national and international laws is recommended. On the national scale with Nigeria (ii), endowed with over 34 solid minerals and abundant crude oil, findings show that almost all mine sites are below the minimum threshold scale R0. The sites are adversely affected by Artisanal and Small Scale Mining (ASM), whereby, contamination and soil lithology disturbances are the state-of-the-art discussions. However, bioremediation (phytoremediation) is the most feasible remediation technique. Therefore, for the crude oil contaminated sites, this study highlights typical cogitation for large in-situ implementation and potential species for remediation. For the mineral resources, gold mining was the typical example. As a practical approach, experimental areas on an abandoned mining site (Site 1), an active mining site (Site 2) and an undisturbed vegetation site (Control) in southwestern Nigeria were mapped out to represent its mining and farming activities. On the sites, (a) the impacts of the ASM activities on the floristic association were assessed. (b) the potential of 2D Electrical Resistivity Tomography (ERT) was explored to characterize the horizontal and vertical landscape homogeneity of the mine sites, and lastly, (c) the study identified native high-accumulating plants growing on the sites that can be employed for phytoremediation. Thus, the results show that (a) the floristic association of the mine sites have been stressed and disturbed. (b) the resistivity structure of the sites shows that ASM has greatly impaired the lithological status of the sites. (c) out of the 9 considered species, Crinum jagus has the highest accumulation factor of 8.71, 37.47, 1.08 and 29.38 for Pb, Cd, Fe and Cu respectively. It is a recommendable novel plant in the tropics. However, future studies must verify its hyperaccumulator potentials, identify other high accumulating species and develop effective approaches and policies to curb ASM activities and enhance remediation in Nigeria.
Soils deposited can undergo a sudden change in the structure when they are inundated with water resulting decrease in the volume. This process is known as water induced compaction. The decrease in volume occurs without any change in external loads and is only caused by the water, which results in the settlement of soil surface having a resultant potential to damage the structures. The water induced compaction process is characterized by sudden change in the voids or pores of the soil that are loaded at their natural water content and flooded. The objective of this thesis work was to understand the water induced consolidation process at agriculturally used reclaimed soils. The approach was to reproduce the situation occurring when the soil was subjected to water induced compaction at defined loads typical in the top soil (0 kPa to 20 kPa). The glacial till used for the experiments was sampled in the Lusatian lignite-mining district located about 100 km southeast of Berlin, Germany. Sediment samples for different investigations were taken from the pre-cut section at 1500 m west of the eastern end from 3 m depth till 10 m depth. The glacial till used for the experiments derived from the sediment layer of Warthe sub-stage of the saalian glaciation. To characterize the soil properties at the pre-cut section, parameters like grain size distribution, soil bulk density, calcium carbonate content (CaCo3) and water retention characteristics were measured. The stability of the glacial till was evaluated using parameter pre-consolidation load. This was done in three sub-steps. The first step was determination of the stress-strain behaviour under natural conditions. In the second step the stress-strain behaviour of disturbed dry samples was simulated, which would be the situation in summer when the glacial till dries during transport. In the third step we saturated the disturbed dry samples which were subjected to different preloads to simulate the effect of saturation and re-compaction by precipitation. This work was exemplarily done for undisturbed samples and also for disturbed dry samples from 4 depths (4 m, 6 m, 8 m, and 10 m). Disturbed dry and saturated conditions were tested for samples from depths 4 m and 8 m. i) It was found from the grain size distribution that the soil profile is uniformly distributed with different particle sizes. High soil bulk density was recorded, which were in the range of 1.9 g cm-3 to 2.0 g cm-3. We observed that the carbonate content increased with the depths, in our observation it increased up to 5.4 %. From the water retention characteristics we observe that the samples from 4 m and 10 m depth do not have coarse pores where as 6 m and 8 m depth samples have coarse pores. ii) We observed that the undisturbed samples showed a flat curve having the initial void ratio and final void ratio values within a small range (between 0.2 and 0.4), where as the disturbed dry and the disturbed saturated curves showed a huge difference in the initial and final void ratio values. The difference was decreasing with the increase in pre-loads. We found that pre-consolidation stress values obtained were not increasing with the increase in depth. The disturbed saturated samples from the 4 m depth showed over-estimation of the results, where as the disturbed saturated samples from 8 m appeared to be realistic. We found that the magnitude of water induced compaction increased with the increase in preloads and a decrease with respect to the depths