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Biomonitoring of metal contamination in the lower Diep River, Milnerton, Western Cape

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dc.contributor Snyman, R.G.
dc.contributor Odendaal, J.P.
dc.contributor Cape Peninsula University of Technology. Faculty of Applied Sciences. Department of Environmental and Occupational Studies.
dc.creator Shuping, Likentso Sylvia
dc.date 2012-09-17T10:43:06Z
dc.date 2012-09-17T10:43:06Z
dc.date 2008
dc.date.accessioned 2017-05-10T10:21:27Z
dc.date.available 2017-05-10T10:21:27Z
dc.identifier http://hdl.handle.net/11189/412
dc.identifier.uri http://hdl.handle.net/11189/412
dc.description Thesis (MTech (Environmental Health))--Cape Peninsula University of Technology, 2008.
dc.description The lower Diep River is a major freshwater ecosystem in the Western Cape. The river is surrounded by many possible sources of metal pollution such as an oil refinery, industries, a sewage treatment plant and a landfill site. However, metal contamination levels have not been monitored in this river. The aim of the study was therefore to monitor the degree of metal pollution in the lower Diep River, over a period of one year, and to investigate the use of the sedge Bolboschoenus maritimus, as biomonitor species. Three sampling sites were used. Site I was located in the vicinity of landfill sites and farm areas. Site 2 was located I km upstream from a wetland reserve, surrounded by heavy industrial activity and continuous residential developments. Site 3 was located downstream of the wetland reserve, 2 km from the river mouth. The following metals were investigated: aluminium, cadmium, chromium, cobalt, copper, iron, lead, manganese, nickel and zinc. Water and sediment samples were collected every two months for a period of one year. Plant specimens (roots, leaves and stems) were collected seasonally from site I and site 3. Samples were acid digested and metal analysis was done using an ICP - AES (Inductively Coupled Plasma- Atomic Emission Spectrophotometer). Statistical analyses were done to investigate possible differences between the sites, sampling occasions and various plant components. The results showed that the water of the lower Diep River is contaminated in terms of aluminium, copper, zinc, manganese and iron, as their concentrations were higher than the DWAF guidelines for aquatic ecosystems at all sites. The high levels of these metals could pose a threat to the health of the ecosystem. The metals that were below detectable levels may also pose a similar threat, even if present in minute quantities. They may possibly be highly bioavailable to freshwater organisms and could lead to toxic effects at various levels of biological organisation. Metal concentrations in sediments were generally significantly higher at site 2 and significantly lower at site 3, compared to the other sites. The concentrations in the sediment of site 2 were generally high, compared to the Canadian Sediment Quality Guidelines (CSQG) and other South African studies. It seems that metals. originating from surrounding metal sources (e.g. industries), settle into the sediments at a faster rate than they are washed downstream. Closer to the mouth of the river, large concentrations of metals have already been accumulated by plants such as Bolboschoenus maritimus, lessening the threat to the estuary. However, these accumulated metals have of course not been taken out of the ecosystem and, with decomposition of plants, and via food chains, these metals still pose a threat to the ecosystem. Plant results revealed greater metal bioaccumulation by plants from site 3. This indicates higher bioavailability of metals at this site, which was probably influenced by salinity levels. Sediment clay content at site I probably played a major role in making metals less available to plants. The results showed that B. maritimus is a root accumulator, as higher concentrations of metals were found in roots than in above-ground tissues. The distribution of metals from the roots to other plant parts was probably mainly influenced by factors such as seasonality and translocation of metals, as a result of a demand for essential micronutrients in the above-ground parts, limited storage capacity of the roots, saline river conditions and the presence of other metals in the plant. Seasonal variations in metal concentrations in B. maririmlls roots were observed, as well as some concentration peaks, but these did not follow similar patterns between the different metals or between the two sites. Neither did the results correspond with seasonal sediment concentrations. Again, the significance of bioavailability was highlighted. Although root concentrations mostly did not indicate the actual level of contamination in the environment (sediment), or changes in contamination levels over time, using B. maritimlls as test species in this study did provide additional information, that soil analyses alone could not have provided, namely the bioavailability of the metals in the sediment and water. With such mixed results it is therefore not possible to make final conclusions about the effective use of B. maritimus as biomonitor species in an environment such as the lower Diep River. More extensive research is needed.
dc.language en
dc.publisher Cape Peninsula University of Technology
dc.rights http://creativecommons.org/licenses/by-nc-sa/3.0/za/
dc.subject Water pollution -- South Africa
dc.subject Diep River (South Africa)
dc.title Biomonitoring of metal contamination in the lower Diep River, Milnerton, Western Cape
dc.type Thesis

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