Abstract
Metal contamination in the Plankenburg and Diep Rivers (Western Cape) was investigated over a 12 and 9 month period, respectively. Aluminium (Al), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), nickel (Ni) and zinc (Zn) concentrations were determined using the nitric acid digestion method and analysed by inductively coupled plasma atomic emission spectrometry (ICP-AES). For both rivers the Al and Fe concentrations were higher than that for all the other metals analysed for in sediment and water samples. The highest concentrations recorded in the Plankenburg River were 13.6 mgE.-1 (water . Week 18, Site B) and 15 018 mgEkg-1 (sediment . Week 1, Site C) for Al, and 48 mgE.-1 (water . Week 43, Site A) and 14 363.8 mgEkg-1 (sediment . Week 1, Site A) for Fe. The highest concentrations recorded in the Diep River were 4 mgE.-1 (water . Week 1, Site A) and 19 179 mgEkg-1 (sediment . Week 1, Site C) for Al, and 513 mgE.-1 (water . Week 27, Site A) and 106 379.5 mgEkg-1 (sediment . Week 9, Site C) for Fe. For most of the metals analysed the concentrations were higher than the recommended water quality guidelines as stipulated by the Department of Water Affairs and Forestry, the Canadian Council for the Ministers of the Environment and the accepted eworld averagef. Point sources of pollution could not be conclusively identified, but runoff from both industrial and residential areas could have contributed to the increased concentrations. Metal concentrations should be routinely monitored and the guidelines should be updated and revised based on the current state of the rivers and pollution sources.
Highlights
South Africa’s major water sources are primarily used for agricultural activities (52%), followed by industry, mining and power generation (12.5%), domestic and municipal uses (12%), with a further 15% needed to maintain estuaries and rivers (Schutte and Pretorius, 1997; Holtzhausen, 2002)
Plankenburg River Comparisons of the mean metal concentrations in water samples collected at Sites A, B, C and D along the Plankenburg River over time are presented in Tables 1, 2 and 5
Aluminium and Fe concentrations were higher than the concentrations of all the other metals analysed for in the water samples collected from the Plankenburg River, and exceeded the guidelines stipulated by DWAF and the CCME (Al and Fe) and the ‘world average’ (Fe)
Summary
South Africa’s major water sources are primarily used for agricultural activities (52%), followed by industry, mining and power generation (12.5%), domestic and municipal uses (12%), with a further 15% needed to maintain estuaries and rivers (Schutte and Pretorius, 1997; Holtzhausen, 2002). The quality of the water resources is, steadily declining due to an increase in urbanisation and industrialisation, with the major sources of pollution including industrial and agricultural effluents and domestic and commercial sewage (DWAF, 2004). Agricultural contamination arises from the discharge of pesticides into rivers (ATSDR, 2000). Pollutants such as microorganisms, metals, oils and other toxic substances contribute to decreases in water quality (Pegram et al, 1999)
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