M.Sc. (Geography) / Severe Aeolian deposition of windblown dust from mine tailings storage facilities (TSFs) is a common phenomenon on the Witwatersrand, especially during the spring windy season. For communities around tailings storage facilities, this poses health and environmental challenges. This dissertation estimates the risk of adverse health effects resulting from human exposure to hazardous elements in particulate matter (sub 20 μm diameter) for selected tailings storage facilities: East Rand Gold and Uranium Company (ERGO); East Rand Proprietary Mine (ERPM); Crown Gold Recoveries (CGR) and Durban Roodepoort Deep (DRD). Samples of surface material from these TSFs were analysed for heavy metal content using the ICP-MS method. Other than the expected gold, five heavy metals (arsenic, cadmium, chromium, lead and uranium) exhibited enrichments in the tailings material significantly above average (greater than a factor of 2) crustal composition. These elements were selected for comprehensive risk assessment through airborne exposure routes. The mean ambient particulate concentration in air of 540 μg m-3 (used in the risk calculations) was based on a conservative worst-case exposure scenario. U.S. Environmental Protection Agency (US EPA) risk assessment methods were used to determine the inhalation and ingestion hazard quotient and hazard indices for adults and children. The sum of the hazard indices was below the non-cancer benchmark (hazard indices 1.0) considered to be acceptable for a lifetime exposure. The risk cancer included the excess life cancer risk for the inhalation and the ingestion risk. The total risk for both exposures was within the range of 1 in 1 000 000 to 100 in 1 000 000 - taken as “acceptable risk” by the U.S. Environmental Protection Agency for adults and children.

M.Sc. (Geography) / Gold mine tailings deposits in the Witwatersrand are subjected to intensive wind and water erosion the combination of factors responsible for air and water pollution. Numerous efforts to alleviate this problem through vegetation have succeeded in establishing soil cover, although the surviving species are not representative of original indigenous vegetation and longer-term soil establishment has been poor. Contributing to these difficult conditions for establishing stable soil and plant communities are: low pH values; low surface stability; deficient organic matter and nitrogen; and high levels of heavy metal in the tailings. Although the role of cryptogams on nutrient cycling and positive impacts on growth of plants is well documented, their potential use in the planning of rehabilitation programmes of gold mine tailings has not been explored. In this study, the abundance and diversity of cryptogams and their impact on the chemical properties of Tailings Storage Facilities (TSF) surface material were investigated on three selected tailings dams: Fleurhof (2L3), Rand Leases (2L8), and Durban Roodepoort Deep DRD (2L24). On the third TSF, DRD (2L24), the original vegetation on the northern half has been entirely covered by wind- eroded material from the southern half the current surface represents a fresh un-vegetated surface. Field investigation was conducted to determine the abundance, diversity and coverage of cryptogams and their effect on the surface stability of the selected tailings. Bacteria, cyanobacteria and fungi were isolated and identified to evaluate the diversity and abundance of these organisms in the study area. In addition, electron microscopy observations were performed to understand the formation of the TSF crust. Chemical analyses of pH, electrical conductivity and the nutritional level of cryptogams TSF material were conducted to determine the effects of cryptogams on the chemical properties of the TSF material and predict the suitability of the substrate for the establishment of other microbes and vegetation. Abundant cryptogams, with diversified growth and morphological features, were found within the sampled areas. The cryptogam diversity proved similar to those across the three tailings dams, and was dominated by mosses and lichens. The abundance and growth of these mosses and lichens was dependent on the presence of vegetative cover and the direction of solar radiation. On undisturbed sites, cryptogams covered as much as 30% on DRD, 70% on RL, and 80% on FL. It was observed that the TSF surfaces covered by cryptogams were more stable than the bare ones. Ten genera of cyanobacteria were isolated from samples for the three tailings and identified, based on their morphology and growth characteristics, as: Aphanocapsa sp., Chromonas sp., Chroococcus sp., Cyanothece sp., Microcystis aeruginosa; Microcoleus sp., Nostoc sp., Oscillatoria sp, Scytonema sp. and Stigonema sp. Five fungal (Trichoderma gamsii, Phoma sp., Hypocrea lixii, Lecythophora sp, and Ascomycota) and four bacterial species (Bacillus subtilis, Arthrobacter aurescens, A. histidinolovorans, and A. sulfonivorans), representing the most abundant isolates from each group, iv were identified using DNA sequencing. Under the electron microscope, it was observed that the cryptogams being examined constituted diversified groups of organisms. Mycelia mats and sheathe produced by filamentous cyanobacteria and fungi played a major role in the formation of the crust by binding the TSF particles. The substrate had very low pH, EC, organic matter and nutrients essential for plant growth. However, the presence of cryptogams altered the acidity of the surface material into almost neutral and significantly improved the level of the essential nutrients and organic matter. It was concluded that the diversity of cryptogams in the TSF material was comparable to the diversity reported on other (different) soils. In addition, the cryptogams’ role in ameliorating the chemical properties of the surface material of the TSF is a clear indication that these organisms can play a positive role in stabilising the tailings material surface and promoting the growth of other microbes and higher plant forms.

D.Phil. / Over a century gold exploration and extraction on the central Witwatersrand has left a legacy of mine residue deposits. Although there have been numerous complaints and claims of health effects associated with dust from these residue deposits, mostly these have been dismissed as mere nuisance. This study hypothesized that gold mine tailings on the Witwatersrand pose significant health risks to the nearby communities due to respirable airborne tailings material. Preliminary review of information on the tailings led to the insight that tailings source material and atmospheric properties at receptor sites are poorly characterized from the point of view of particle size-mass distributions. For years, routine monitoring of emissions from tailings storage facilities has been limited to sampling of dust fallout (settlable particles ≥ 30 μm). A suite of fifty four source samples (thirty-six slime, six newer slime and twelve sand) were collected from tailings storage facilities along the mining corridor covering deposits in the Carltonville area through to Springs. Size class characterization of source material was performed in the diameter range 0.05 μm to 900 μm using a Malvern® MS-14 Particle Analyser with 64 channels, from which the respirable (dp< 5 μm) and thoracic (dp < 10 μm) components were measured. Secondly, source materials were sieved (using a sieving cloth) in dp < 5 and < 10 μm fractions and the data derived was used in validating the size class results from the Malvern® MS-14 Particle Analyser before subjecting the samples to chemical analyses (elemental, mineralogical and radioactivity). Two years of continuous dust fall samples were collected in two different residential areas close to selected tailings storage facilities and subjected to similar size class characterization with the Malvern® MS-14 Particle Analyser. Further, continuous size-mass characterization of airborne aerosols was conducted in two different locations in the vicinity of tailings storage facilities with the Grimm® aerosol particle counter, in the diameter range 0.25 μm to 32 μm. The Grimm® aerosol particle counter was collocated with the MicroVol® PM10 filter sampler ambient monitor. The risk zones around selected tailings storage facilities were established by conducting dispersion modeling with American Meteorological Society/Environmental Protection Agency Regulatory Model (AERMOD). The spatial evolution of tailings storage facilities and built-up areas is assessed using multiple aerial photographic images, covering four periods from 1952 to 2008. Overall, detailed spatial analysis was conducted and human inhabitants are now at greater risk than before. We have quantified the number of inhabitants living within the high-risk zone surrounding selected tailings storage facilities. The combined areas occupied by tailings storage facilities have increased from ~4 km2 (1952) to 10 km2 (2002); and residential areas ~4 km2 (1952) to 27 km2 (2002) within a buffer of 2 km. Population grew between 1952 and 2002 by a factor x29 at Crown Gold Recoveries; x43 at Durban Roodepoort Deep (from 1976); and x25 at East Rand Proprietary Mines.