Chromium is used in many processing applications, which has led to the formation of
chromium(VI) waste. Cr(VI) is an unstable, mobile carcinogen, which is interchangeable
with Cr(III) under certain environmental conditions. Management of this waste, however, is
often not considered. Mine under investigation is an example of such historic
mismanagement. During the second World War, Cr(VI) waste was transferred to the study
site from areas where leather products were made for the war effort. This waste was not
managed appropriately in the past and with time Cr(VI) leached into the groundwater and
possibly surface water resources. As these water resources are used for domestic and
agricultural water supply, this may have serious effects on the human and environmental
health in the area.
Some of the major Cr(VI) effects on human and animal health include malignant tumours,
skin irritation, respiratory and reproductive system damage. Lung cancer is of concern when
Cr(VI) is inhaled and stomach tumours occur when this chemical pollutant is ingested. The
effects of Cr(VI) on plants include the disruption of shoot and root elongation, and if it
accumulates enough within the plant can cause ingested health problems for humans and
animals.
Water quality guidelines state that the Target Water Quality Range for Cr(VI) in drinking
water should not exceed 0.05 mg/L. Prolonged exposure of values higher than this target
value has adverse health effects and may result in cancer. The study site has a scarcity in
water sources and therefore requires good quality water resources.
This study aims to identify and use biomarkers to assist in the hydrological characterization
of the mine. Available mitigation options can be implemented once it is known how the
water in the area moves and distributes Cr(VI) pollution. A biomarker is an indicator of a
biological state, which in turn can be used to assist in characterizing the chemical conditions
of the sub-surface. Bacteria can aid as environmental biomarkers as they are sensitive and
specific to the environmental conditions in which they flourish. In this way they give a good
indication of the environmental condition and any possible pollution. Due to the fact that
ground- and surface water are integrated resources, it is likely that if one is impacted by
pollution, it will indirectly impact the other one. Therefore, the biomarkers identified can be
used to characterize water pollutants that are present in ground- and some surface water resources. A description of the study site is provided, wherein the climate, elevation, geology, land use,
geohydrology, hydrochemistry and surface water are documented. These factors help to
identify and clarify the sources and pathways that water and the pollution would follow.
Ten water samples, from surface and groundwater, were obtained in two separate sampling
opportunities. The first analysis of the water samples included the determination of the
chemical constituents. Two of these constituents analyzed were the total Cr and individual
Cr(VI) levels. Six water samples had excessively high Cr values (exceeding the Water
Quality Target Range of drinking water and water agricultural use). These values ranged
from 0.1 – 3.9 mg/L. The 6 samples with excessive Cr(VI) values were used for the
microbial analyses.
The microbial analyses consisted of DAPI (4’,6-diamidino-2-phenylindole ) staining, for cell
enumeration, and molecular analyses. The molecular analyses included polymerase chain
reaction (PCR), denaturing gradient gel electrophoresis (DGGE) and sequencing
applications concluded in the laboratory. Fifteen bands, representing different organisms,
were removed from the DGGE polyacrylamide gel and processed for sequencing.
The organisms that were present in the sample were uncultured Cyanobacterium,
Sediminibacterium salmoneum, uncultured Bacteroidetes bacterium, uncultured betaproteobacterium,
uncultured actinobacterium, uncultured Rhodocyclaceae, uncultured
Chloroflexi bacterium and uncultured delta-proteobacterium. According to literature most of
these organisms may adapt the ability to either reduce Cr(VI) or resist any effect of Cr(VI) in
the environment. Two of the bands were highly unidentified organisms, which means that
these organisms have not yet been cultured or identified in any sense. The reason for this is
that most microorganisms have not yet been documented. This also makes it difficult to
identify the exact bacterial strain present within the samples. The deoxyribonucleic acid
(DNA) sequences of the different organisms were very different from each other, when
compared by a dendrogram. This means that there was a diverse community present within
the samples.
Electrical conductivity profiles were conducted in the monitoring boreholes to identify
possible fracture positions. The total chromium and chromium(VI) levels were documented
and compared.
Other chemical factors were analysed and those of high value, such as chloride, nitrate and
chromium measurements, were used for statistical analyses and comparison with the
biomarkers present in the sample. A positive correlation was found between the sample
sites and the organisms present within each. It was noted that different communities have different metabolic activities related to
susceptibility and will therefore differ under specific environmental conditions. The
microorganisms that were present in the 6 water samples all have the ability to either resist
or reduce Cr(VI). This means that in Cr(VI) polluted areas they are more likely to flourish
than organisms that do not possess this ability. Such susceptible, non-resistant organisms
would otherwise occur naturally in a non-polluted environment. From the obtained results it
was noted that microorganisms could aid as biomarkers when determining the
environmental condition (with respect to Cr(VI) pollution). The bacteria analysed in the
samples all indicate a level of chromium pollution, and aided in the determination of pollution
sources. These biomarkers can therefore be used to determine the location of other
chromium deposits not yet located. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2013
| Identifer | oai:union.ndltd.org:NWUBOLOKA1/oai:dspace.nwu.ac.za:10394/10508 |
| Date | January 2013 |
| Creators | McIntyre, Maaike Josette |
| Source Sets | North-West University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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