Gold mine tailings material facilities are characterized by sparse vegetation and an
abundance of dust. Mine tailings facilities are examples of extreme geotechnical and
geochemical conditions which make it almost impossible for higher plants to establish and
grow without rehabilitation intervention. In most cases higher plants such as grasses and
trees are the focus areas for rehabilitation, but, having a look at something a little smaller
such as biological crusts, it is seen that these micro-organisms play very important roles in
any ecosystem.
Various studies have shown that biological crusts, consisting of micro-organisms such as
lichens, algae and cyanoprokaryotes enhance the soil quality by binding soil particles
together, forming aggregates which counteract the erosive forces of wind and water. They
play a part in nitrogen and carbon fixation, increase the soil surface temperature and
increase the water retention of the soil. Thus, these organisms improve the overall health of
the soil, which will in time encourage the successful establishment of higher plants.
The aim of this study was to investigate the presence of cyanoprokaryotes and soil algae on
mine tailings storage facilities that have been rehabilitated for different periods of time as
well as to correlate the presence of these species with the physical and chemical
characteristics of the mine tailings material. Chemical, physical and biological analyses of
soil samples were done. Some of the ecologically important and dominant species were
isolated and protocols were developed in order to identify the most successful manner in
which to re-inoculate the organisms to a chosen substrate and how to measure biomass.
Due to the immense cost of standard rehabilitation practices there is a need for a more cost
effective, sustainable manner in which to protect the tailings material against the erosive
forces of wind and water with as little input as possible. The influence of an organism
cultured in normal Bold’s Basal medium (BBM) growth medium, BBM growth medium with
half the phosphate concentration and BBM growth medium with half the nitrate concentration
on the establishment of a biological soil crust (BSC) was tested. To test the influence of the
inoculums already present in the tailings material and in the air, trials with mulch, water and
nutrients without the addition of an organism was also investigated. This was done in the
controlled environment of a glasshouse, as well as in field conditions. The biomass of the
cyanoprokaryotes and algae, as well as the soil surface strength was also tested.
The results show that the time of rehabilitation did not have an influence on the
cyanoprokaryotes as well as algal species that occurred on the tailings material. Chlorella
sp., Chlorococcum sp. and Klebsormidium sp. were present on all six sites, except on the fresh material and 15 year old material where no rehabilitation has been done. As for
dominance; Chlamydomonas sp., Chlorococcum sp., Klebsormidium sp. and Phormidium
sp. were dominant on all six sites except for the fresh material, where nothing grew.
An array of methods exists for measuring algal biomass as a measure of growth. During the
development of protocols for further use in investigating the growth of algae, the extraction
solvent ethanol, for use in chlorophyll a extraction, was identified as the most sufficient. The
re-inoculation of cyanoprokaryotes and soil algae onto a chosen substrate is most
successful when pouring the organisms, cultured in growth medium and 0.1% agar, over the
substrate.
During the glasshouse trials the influence of the growth medium and growth medium with
half the nitrate and half the phosphate concentrations showed that Chlamydomonas sp.
produced the highest biomass when cultured in BBM. With Nostoc sp. the highest biomass
occurred with culturing in BBM and BBM with half the phosphate concentration. Microcoleus
vaginatus showed no significant difference when cultured in the three different growth
mediums (BBM, BBM with half the nitrate concentration and BBM with half the phosphate
concentration). Overall Nostoc sp. produced the highest biomass (34.33 μg/g), followed by
Microcoleus vaginatus (17.05 μg/g) and Chlamydomonas sp. (6.12 μg/g).
Soil surface strength, measured with a hand held penetrometer showed that
Chlamydomonas sp. cultured in BBM growth medium produced the most stable crust (2.58
kg/cm2), although it had the lowest biomass measurements (6.12 μg/g). Nostoc sp. produced
the highest biomass (34.44 μg/g), but had the lowest soil surface strength results (1.75
kg/cm2). Microcoleus vaginatus proved to be the species with high biomass production
(17.05 μg/g), as well as high soil surface strength (2.08 kg/cm2). M. vaginatus is also a
pioneer species and is therefore a good choice as primary inoculum on bare tailings
material.
It was decided to use Nostoc sp. in the field trials due to its high biomass and Microcoleus
vaginatus due to the high soil surface strength produced. Despite the occurrence of a severe
thunder storm on the afternoon of application and poor water management during the field
trials the significance of water on the establishment of soil algae and cyanoprokaryotes on
tailings material was determined. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/11928 |
| Date | January 2014 |
| Creators | Orlekowsky, Tanya |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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