Abstract
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.