Abstract
M.Sc.
The increasing demand for water in South Africa arises from a rapid population growth and supporting
industrial development. This demand has to be met from limited water resources that are shared by
competing user groups and neighbouring states. Deteriorating water quality further limits the
sustainable use of water through point and diffuse source pollution of macro constituents, metals and
biocides. Metals in the environment can originate as point sources, including industrial and mining
effluent, or diffuse sources from geological origin, agricultural activities, acid mine draining and
leachate from dumps. Biocides increase crop yields, protect forests and control vectors of serious
human disease, but are in the process also carried to water courses. Bioaccumulation studies have been
identified as a method to monitor pollutants in the environment. The analyses of data from
bioaccumulation studies share a common problem in having to deal with many independent variables,
for example variations in time and space, environmental conditions and biological parameters. The
objectives of this study were to; investigate the metal levels in water and metal and biocide
bioaccumulation in fish tissues from the Berg, Luvuvhu, Olifants and Sabie Rivers; develop a
procedure to predict areas and biocides at risk of causing diffuse source pollution and; evaluate the
available data and procedures to propose more efficient and cost effective bioaccumulation
programmes. The investigation evaluated current and potential contamination of the selected catchments
and identified research needs.
Fish tissues and water grab samples were collected in the Berg, Luvuvhu, Olifants and Sabie Rivers.
The samples were tested for physical variables and analysed for macro constituents and metal levels
according to standard analytical procedures. Fish were caught (gill and seine nets) and larger specimens
were selected for tissue analyses. Species were identified and standard length, mass, gender,
gonadotrophic development index and age indicators were collected. Standard procedures were used
to analyse fish tissues for metal levels with the atomic absorption spectrophotometer (AAS) and biocide
levels with gas chromatographic methods. A flow diagram of a statistical methodology was developed
to incorporate the effects of all biological parameters in the analyses of bioaccumulation data. The
procedures used to calculate human health risks are that of the Risk Assistant package reviewed by the
United States Environmental Protection Agency (EPA). A Geographical Information System (GIS)
model was developed, incorporating the factors affecting runoff of surface water and biocides, to
predict areas and variables that could cause diffuse source pollution.
The pH values of the rivers studied ranged from of 7.2 to 8.7 except for the Klipspruit River before
its confluence with the Olifants River that had a pH of 4.8. Nutrient levels in the Berg River are within
the South African guidelines. Nutrients in the Luvuvhu River mostly exceed the guideline values for
ortho-phosphate, ammonia nitrogen, nitrate nitrogen and total phosphorus. In the Olifants River the
values for ortho-phosphate, total phosphorus, ammonia nitrogen and nitrate and nitrite nitrogen often
exceed the South African guideline values. Nutrients in the Sabie River have low concentrations with
only ammonia nitrogen exceeding the guideline values. TDS values in the Olifants River is the highest, which is an indication of the high salt loads in the river. The concentrations of various metals in water
from the Berg, Luvuvhu, Sabie and Olifants Rivers exceeded the proposed South African and
international guidelines.