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Acid mine drainage as a global problem
There is no doubt that mining and its environmental impact has caught global attention, with the continued drive and awareness in research (Warhurst and Noronha, 2000). The exposed surface area of sulfur-bearing rocks is increased during mining, and this causes the generation of excess acid beyond the natural buffering capabilities found in host rock and water resources. AMD has become a universal environmental problem that adversely affects both surface and ground waters. This is characterized by the formation of several soluble iron sulphates, the production of acidity due to the presence of hydrogen ions, and subsequent metal dissolution and leakage, following the oxidation and hydrolysis of metal sulphides (pyrites) in water permeable strata. AMD, as a complex pollutant, has a high concentration of iron and sulphate, a low pH and an assortment of elevated concentrations of a variety of metals (Parsons, 1977; Gray, 1997; Kelly, 1988; Heath and Eksteen, 2005). AMD is not only a problem emanating from active, abandoned and liquidated mines: waste rocks and mine tailings are prone to generating more AMD (Younger and Robins, 2002). If not mitigated, the environmental and ecological, human health and economic consequences of AMD have longlasting effects. A number of factors are responsible for controlling AMD; first is the production of the acids (the oxidation reaction involving the metal sulphides), the second is the control of the products resulting from the oxidation reactions (which may react with other minerals or potentially neutralize the acids) and lastly, factors that are associated with managing the waste generated (Ferguson and Erickson, 1988), as effective waste management is crucial to reducing environmental pollution. Worldwide, mine effluents affect an estimated 19 300 km of streams and river and 72 000 ha of lakes and reservoirs causing serious damage (Johnson and Hallberg, 2005). Management options in Alaska involve water treatment measures that encompass physical and chemical methods. Neutralization methods using lime or other suitable alkaline agents are the preferred choice of chemical treatment method employed. Other methods incorporate the use of suitable wetlands and bioreactors that aim to reduce surface bacteria, allowing for precipitation of metals as metal sulfides (NSCEP, 2006).
In vitro cytotoxicity and genotoxicity
Freshney (2001) defined cytotoxicity as ―adverse effect(s) observed in a cell that affects the structural and/or functional processes essential for survival and proliferation following exposure to exogenous chemicals‖. Cytotoxic effects are expressed as basal, selective or functional cytotoxicity. Basal cytotoxicity is seen when cellular structures and/or functions are attacked and commonly observed effects affect energy metabolism, plasma membrane and ion regulation (Ekwall, 1983; Ekwall and Ekwall, 1988). Selective cytotoxicity is seen with chemicals exhibiting preferential toxicity to particular cell types; an example is seen in biotransformation potential found in specific cell types (Seibert, 1996). Functional toxicity results in interference with cellular processes, threatening the survival of a particular organ or even the organism as a whole (Mothersill and Austin, 2003). The reaction of cells challenged with xenobiotics may follow patterns such as sequestration as the cells concentrate the assault in a subcellular compartment (Sheehan et al., 1995). Detoxification of the chemical by non-enzymatic reactions may likewise occur, as is seen with antioxidants conjugation of Reactive Oxygen Species (ROS). Some proteins such as metallothioneins actively bind metallic xenobiotics preventing them from binding to other sites, and lastly, xenobiotics may become enzymatically detoxified by specialized systems such as the CYP450 systems for ease of excretion (Mothersill and Austin, 2003).
CHAPTER 1: Introduction
1.1 Background information
1.2 Properties of acid mine drainage
1.3 Problem statement and motivation
1.4 Hypothesis
1.5 Study aim and objectives
1.6 Thesis structure
CHAPTER 2: Literature review
2.1 Drivers of change in aquatic ecosystem
2.2 Coal mining in South Africa
2.3 Acid mine drainage as a global problem
2.4 Chemistry and formation of AMD
2.5 Treatment technologies for AMD
2.6 South African water resources and water quality
2.7 Monitoring and biomonitoring of South African aquatic systems
2.8 In vitro techniques
2.9 Effects of coal derived pah‘s on fishes
CHAPTER 3: Characteristics of the study sites and water quality
3.1 The Witbank coalfield
3.2 Site selection within the Witbank coalfield
3.3 Materials and Methods
3.4 Discussion
3.5 Conclusion
3.6 Conclusion
CHAPTER 4: Generation of reactive oxygen species in species relevant cell lines as a bioindicator of the safety of treated acid mine water
4.1 Introduction
4.2 Materials and Methods
4.3 Data analysis
4.4 Results
4.5 Discussion
4.6 Acknowledgements
CHAPTER 5: Assessing the potential of cell lines as tools for the cytotoxicity testing of acid mine drainage effluent impacting a natural water resource
5.1 Introduction
5.2 Materials and Methods
5.3 Results
5.4 Discussion
5.5 Conclusion
CHAPTER 6: Induction of 7-ethoxyresorufin-O-deethylase activity by B[a]P in primary culture of gill epithelial cells from Tilapia (Oreochromis mossambicus)
6.1 Introduction
6.2 Materials and Methods
6.3 Results
6.4 Discussion
6.5 Conclusion
CHAPTER 7: Evaluation of the genotoxic potential of water impacted by acid mine drainage from a coal mine in Mpumalanga, South Africa using the Ames test and comet assay
7.1 Introduction
7.2 Methodology
7.3 Results
7.4 Discussion
7.5 Conclusion
CHAPTER 8: GENERAL DISCUSSION AND CONCLUSIONS
CHAPTER 9: REFERENCES
