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Bioaccumulation of metals in freshwater crabs (potamonautes perlatus) of the Lourens River, Western Cape, South Africa
Author(s)
Van Stormbroek, Tim
Date Issued
2007
Type
Thesis
Publisher
Cape Peninsula University of Technology
Abstract
Urban rivers are the most utilised and yet degraded rivers worldwide. The urban
rivers of the Western Cape are no different. The Lourens River flows through the
agricultural and urban areas of Somerset West in the Western Cape and as a
result is subjected to a variety of pollution sources. In the upper reaches this river
flows through two large farms where metal containing pesticides are used.
Further downstream it passes through an urban area where a variety of pollution
sources could contribute to the contamination of the river. The extent to which
the Lourens River, and the ecosystem it supports, is affected by metal pollutants
is not known. The aim of this study was to determine the concentrations of
metals in the Lourens River as well as the contribution of agricultural and urban
activities to metal contamination of the river. Sediment and crab (Potamonautes
perlatus) samples were collected over a period of one year from seven sites over
the length of the river. Sediment samples were also collected from a
sedimentation pond on the bank of the river where orchard run-off water is remediated.
Preliminary analysis of samples was done for ten metals (AI, Cd, Co,
Cu, Cr, Fe, Mn, Ni, Pb and Zn). Results from these analyses determined the
selection of six metals (AI, Cr, Cu, Fe, Mn and Zn) for further investigation in this
study. The concentrations of metals detected in collected samples varied
significantly throughout the sampling period. This can be attributed to various
factors such as rainfall patterns, the fact that pesticide application varies
throughout the year and other urban activities. AI, Cr, Fe and Zn were found in
significantly higher concentrations in the urban areas. These higher levels of
contamination, relative to the upper parts of the river, can probably be attributed
to various urban activities contributing to the contamination of run-off into the
river. The sedimentation pond results revealed high concentrations of AI and Fe,
while Cu, Cr, Mn, and Zn were found in lower concentrations. All six metals
however followed the same pattern where the first four sampling occasions
showed higher concentrations than the last three occasions. It can be concluded
that agricultural and urban activities do contribute significantly to the metal
contamination of the Lourens River.
rivers of the Western Cape are no different. The Lourens River flows through the
agricultural and urban areas of Somerset West in the Western Cape and as a
result is subjected to a variety of pollution sources. In the upper reaches this river
flows through two large farms where metal containing pesticides are used.
Further downstream it passes through an urban area where a variety of pollution
sources could contribute to the contamination of the river. The extent to which
the Lourens River, and the ecosystem it supports, is affected by metal pollutants
is not known. The aim of this study was to determine the concentrations of
metals in the Lourens River as well as the contribution of agricultural and urban
activities to metal contamination of the river. Sediment and crab (Potamonautes
perlatus) samples were collected over a period of one year from seven sites over
the length of the river. Sediment samples were also collected from a
sedimentation pond on the bank of the river where orchard run-off water is remediated.
Preliminary analysis of samples was done for ten metals (AI, Cd, Co,
Cu, Cr, Fe, Mn, Ni, Pb and Zn). Results from these analyses determined the
selection of six metals (AI, Cr, Cu, Fe, Mn and Zn) for further investigation in this
study. The concentrations of metals detected in collected samples varied
significantly throughout the sampling period. This can be attributed to various
factors such as rainfall patterns, the fact that pesticide application varies
throughout the year and other urban activities. AI, Cr, Fe and Zn were found in
significantly higher concentrations in the urban areas. These higher levels of
contamination, relative to the upper parts of the river, can probably be attributed
to various urban activities contributing to the contamination of run-off into the
river. The sedimentation pond results revealed high concentrations of AI and Fe,
while Cu, Cr, Mn, and Zn were found in lower concentrations. All six metals
however followed the same pattern where the first four sampling occasions
showed higher concentrations than the last three occasions. It can be concluded
that agricultural and urban activities do contribute significantly to the metal
contamination of the Lourens River.
Additional information
Thesis (MTech (Environmental Health))--Cape Peninsula University of Technology, 2007
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