| dc.description.abstract | The purpose of this research was to learn more about the release, transport, dispersal, and fate
of metal species emitted by mine tailings storage facilities (MTSFs) on the Sabie River system.
Analytical techniques and geochemical modelling were used to evaluate the chemical reactions
that occur after metals are released from gold mine tailings in the Sabie Goldfield. MSTFs, a
rainwater runoff pond and the Sabie River system were all considered as potential metal
contaminants flow paths. Seasonal variation was taken into account to learn more about the
effects on metal dispersion during the wet (summer) as well as dry (winter) seasons.
Very high concentrations of metal species were found in the tailings from the Nestor MTSF when
compared to concentrations found in stream sediments. There was no substantial difference in
metal (loid) distribution, specifically, cobalt (Co), nickel (Ni), lead (Pb), chromium (Cr), zinc (Zn),
copper (Cu) and arsenic (As) between the summer and winter seasons. In addition, no indication
of metal species dispersal was observed from the Nestor MTSF to the nearby water bodies,
namely, the Klein Sabie and the Sabie River respectively. This is because the majority of the
metal pollution is detached from the system over a short distance. When compared to
concentrations found in stream sediments, the tailings from the Nestor MTSF had elevated
concentrations of metal species. Acid producing minerals such as pyrite and secondary iron
minerals, which are commonly found in mine wastes, were discovered to be possible polluters to
the Sabie River system. Furthermore, the mineral capable of neutralizing acid dolomite present
in the sediments may function as a critical buffer.
Using traditional acid base accounting (ABA) criteria, gold mine tailings from the Nestor MTSF
are classified as potential acid forming (PAF), whereas gold tailings from the Glynns Lydenburg
MTSF are classified as non-acid forming (NAF) but may still produce alkaline drainage.
Furthermore, tailings from these two sites were mixed, and ABA was performed to determine
whether the alkaline tailings could neutralize the acid from the Nestor (MIX25 and MIX75). The
results indicated that materials from the Glynns Lydenburg are capable of neutralizing the acid
from the Nestor mine tailings. Therefore, materials from the Glynns Lydenburg MTSF can be an
economically viable option to treat potential acid-generation from the Nestor MTSF by forming a
base cover system in which vegetation will grow.
To characterize the solid phase speciation of metal species in the vicinity of the Sabie River
system, a four-stage sequential extraction procedure was performed on mine waste, soil and
stream sediment samples. Organics and sulphides-bound fractions, as well as Fe and Mn-bound
fractions were considered bioavailable, with metals in these phases being possibly remobilised
under varying environmental settings. Aluminium and iron were discovered to achieve maximum
bioavailability in mine waste, followed in decreasing order by manganese (Mn), As, Zn, Cr, Cu,
Co, and Pb. Adsorption into Mn, Al, and Fe-hydroxide precipitates observable in the drainage
path flowing towards the Klein Sabie River is the crucial process for this geochemical scavenging.
The PHREEQC modelling code was used in conjunction with sequential extraction to characterize
the chemical reactions that transform metals. According to the results of PHREEQC modelling,
cation exchange played a substantial part in regulating the chemistry of surface water in the Sabie
River system. The obtained results can be used to guide environmental management of gold mine
tailings. | en_US |
