Investigation into the metal contamination of the Plankenburg and Diep Rivers, Western Cape, South Africa

Investigation into the metal contamination of the Plankenburg and Diep Rivers, Western Cape, South Africa VA Jackson1, AN Paulse1, JP Odendaal2 and W Khan3* 1 Department of Biomedical Sciences, Faculty of Health and Wellness Sciences, Cape Peninsula University of Technology, Bellville 7535, South Africa 2 Department of Environmental and Occupational Studies, Faculty of Applied Sciences, Cape Peninsula University of Technology, Cape Town 8000, South Africa 3 Department of Agricultural and Food Sciences, Faculty of Applied Science, Cape Peninsula University of Technology, Cape Town 8000, South Africa 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·ℓ-1 (water – Week 18, Site B) and 15 018 mg·kg-1 (sediment – Week 1, Site C) for Al, and 48 mg·ℓ-1 (water – Week 43, Site A) and 14 363.8 mg·kg-1 (sediment – Week 1, Site A) for Fe. The highest concentrations recorded in the Diep River were 4 mg·ℓ-1 (water – Week 1, Site A) and 19 179 mg·kg-1 (sediment – Week 1, Site C) for Al, and 513 mg·ℓ-1 (water – Week 27, Site A) and 106 379.5 mg·kg-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 ‘world average’. 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. Keywords: ICP-AES, metal contamination, Plankenburg- and Diep River water, sediment, water and sediment quality guidelines Introduction 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, however, 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). In addition, population increases in South Africa are expected to lead to an increase in agricultural development, which will in turn lead to an increased demand for irrigation water (FAO, 2007). Point- and non-point source pollution contributes to a decline in water quality when leaching occurs into the surrounding environment (Hills et al., 1998; Ho et al., 2003). Agricultural contamination arises from the discharge of pesticides into rivers (ATSDR, 2000). In addition, pollutants such as microorganisms, metals, oils and other toxic substances contribute to decreases in water quality (Pegram et al., 1999). Metals are present in the environment in trace amounts and certain metals, such as iron (Fe), copper (Cu) and zinc (Zn), are * To whom all correspondence should be addressed.  +2721 460 3175; fax: +2721 460 3193; e-mail: Received 28 October 2008; accepted in revised form 9 March 2009. Available on website http://www.wrc.org.za ISSN 0378-4738 = Water SA Vol. 35 No. 3 April 2009 ISSN 1816-7950 = Water SA (on-line) essential for a variety of functions in organisms. It is important though to ensure that these metals do not exceed normal concentrations, as they may then have detrimental long-term effects on human health (Wright and Welbourne, 2002). Excessive consumption of cadmium (Cd) and lead (Pb) could result in neurological, bone and cardiovascular diseases, renal dysfunction and various cancers, even at relatively low levels (Calderon, 2000; Jarup, 2002). The short-term effects of high Cd concentrations also include diarrhoea, nausea, vomiting, renal failure, muscle cramps, salivation, sensory disturbances, convulsions, shock and liver injury (Hazards Centre and People’s Science Institute, 2005). Short-term exposure to Cu fumes causes irritation of the eyes, nose and throat, and a flu-like illness called metal fume fever. Symptoms of metal fume fever include: fever, muscle aches, nausea, chills, dry throat and cough (US Department of Health and Human Services, 1978). Iron is an essential element, but ingestion of Fe at concentrations above permissible levels may cause many gastrointestinal disturbances, including vomiting, diarrhoea and abdominal pain. The prolonged intake of high doses of Fe can result in liver damage and kidney failure (Hazards Centre and People’s Science Institute, 2005). High concentrations of metals usually deposit on and then integrate in the river sediment. The sediment comprises organic or inorganic materials removed by erosion and transported by fluid flow to different locations (Prange and Dennison, 2000; Marchand et al., 2006). The highest metal content available for transport between sites is that which is stored in the sedimentwater interface (Maanan et al., 2004). Increased levels of heavy metals were reported in the sediment of the Mooi River, South 289 Africa (Wade et al., 2000). These increased levels of toxic metals in both the water and sediment presumably resulted from the release of mine water from a nearby goldmine into a tributary of the Mooi River. The levels of heavy metals reported did not differ appreciably from those found by a previous study conducted by Witmann and Förstner (1977), where concentrations recorded for water and sediment for Cu were 5.4 mg·ℓ-1 and 484 mg·kg-1 and for Zn were 26.0 mg·ℓ-1 and 6440 mg·kg-1, for water and sediment respectively. The authors concluded that the high concentrations could be due to the fact that the slimes dams receive discharges with high acidity from the mines. Mzimela et al. (2003) conducted a study investigating the aluminium (Al), Fe, Mn, Zn, chromium (Cr), Cu, Pb, Cd and mercury (Hg) bioaccumulation patterns in sediment, water and fish samples collected on a quarterly basis from the Mhlathuze Estuary, South Africa.. The highest concentrations for Al (26 200 mg·ℓ-1 and 13 928.6 mg·kg-1), Fe (23 500 mg·ℓ-1 and 16 035.71 mg·kg-1) and Mn (266 mg·ℓ-1 and 182.8 mg·kg-1) in water and sediment respectively, were recorded in December, which coincided with an extremely high freshwater inflow from the Mhlathuze (...truncated)