This paper assesses the role of biological geotextiles on non-agricultural erosion environments, based on studies in the mine tailings Gauteng Province (South Africa) and urban area of São Luis City (Brazil). Gauteng Province (South Africa) has suffered immense problems related to sustainable rehabilitation of mine dumps. This is a huge challenge, as wastes are highly susceptible to both water and wind erosion. Establishing a grass cover to reduce erosion is the dominant reclamation method. Covering the slopes with biological geotextiles might constitute another option for mining companies to reduce erosion and aid natural re-vegetation. The objective of the waste part of this study was to determine the beneficial effect of palm mat cover on erosion control, using rainfall simulation. Results clearly illustrated that application of palm-mats more than halved the sediment load in runoff, thereby having the potential to effectively stabilize tailing dam slopes. Covering tailings with palm-mats did not reduce runoff or improve water infiltration, however. In São Luis City, biological geotextile mats were constructed from palm leaves which are an effective, sustainable and economically-viable soil conservation technique. At Sacavém Community biological geotextile mats were used in association with barriers of wooden stakes and the construction of terraces along contour lines. The aim is to minimize soil erosion, by intercepting rainfall, retarding runoff velocity and sediment loss.
Rehabilitation of mine tailings dams is often a challenge due to a lack of nutrients and a poor humus reservoir prevailing in tailings soils. This is especially true for establishing longer lived species such as trees. For these reasons the effects of different soil ameliorants (woodchips compost, vermicompost, mature sewage sludge), added to the root system of Karee (Searsia lancea) saplings were tested in pot trials. Those pots were filled with platinum and gold tailings substrate as well as red clay soil, respectively. For three months plants remained in a greenhouse and were subsequently moved to a test field outside. Throughout the test period regular chl a fluorescence measurements were taken and subjected to JIP-test quantifying changes in photosynthetic vitality status. Additionally, growth measurements and one-off leaf analysis were carried out. Test plants growing on mine tailings experienced an up to 35% higher average photosynthetic vitality (PI(ABS)) and improved nutrient supply, when treated with mature sewage sludge. Consequently, sewage sludge treated plants showed a higher biomass build-up rate and an up to 55% higher diameter growth, compared to control. In summary the experiments present a low cost alternative for reforestation enterprises on platinum and gold tailings dams in South Africa.
Local work on selected environmental impacts on soil quality and the role of soils in the attenuation of environmental pollution is reviewed. Examples of negative impacts from mining, industries, urbanization, agriculture and forestry abound. The safe and sustainable use of various waste products may impact positively, but norms and standards are needed. Soil nutrient deficiencies or excesses give rise to nutrition-related disorders in humans and animals. Through bioremediation, soil becomes an ally in restoring environmental health. Harmonization of agricultural production and the environment is a political target towards which science must provide effective decision support. The development and application of a national environmental monitoring and evaluation system is needed for incorporating environmental data, information, norms and standards into a holistic picture. There is a need for improved cross-linking and synergy between various sectors impacting on the environment. The local government level is becoming critical to environmental management. The safe and sustainable use of sewage sludge/fly ash combinations on agricultural soils is suggested to be a highly promiSing future avenue of environmental R&D.
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