WATER POLLUTION
CONCERNING CHEMICALS
detected in local dams
A study* was conducted to determine the presence and concentrations of per- and polyfluorinated alkyl substances (PFASs) in the Roodeplaat and Hartbeespoort dams – dams that provide water for domestic consumption, irrigation, fishing and recreational activities. By Bulelwa Batayi & Professor Okechukwu Jonathan Okonkwo
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FASs are man-made organic chemicals that are used in the production of industrial and consumer products such as firefighting foams, paints, non-stick cookware and food packaging. PFASs have hydrophilic and hydrophobic properties, are non-degradable in the environment, bio-accumulative and toxic. They are ubiquitous and, therefore, have been found in air, surface water, sediment, fish, wildlife and human blood. High PFAS levels have been linked to increased liver and kidney dysfunction, reduced postnatal survival with impaired growth, cardiac abnormalities, maternal weight loss, mortality, and induced immunological alterations in laboratory animal studies. They also have carcinogenic properties. Consequently, PFASs, particularly perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) and their salts have been listed in the Stockholm Convention as persistent organic pollutants (POPs). Countries have set restrictions and regulations on the use of PFOS and other PFASs to minimise human exposure to these compounds.
Dams Three water treatment plants abstract raw water from Roodeplaat Dam, which is located approximately 24 km north-east of Pretoria, north of the Magaliesberg range. While the dam supplies potable water to three provinces – namely Gauteng, the North West and Limpopo – the quality of the water is a cause for concern. Hartbeespoort Dam is located in the North West province, in the Crocodile River catchment, within the Limpopo River system. It is a storage reservoir primarily providing water for irrigation and domestic consumption, recreation, and compensation flows to downstream portions of the Crocodile River. About 90% of the inflow of the Hartbeespoort Dam is derived from the Crocodile River, which is balanced by inflow generated from the Magalies River watershed. Since the Crocodile River drains a large, highly industrialised and urbanised area, the dam is subject to high levels of pollution. A total of 30 water samples were collected from different points at each dam, using a hosepipe sampler from downstream to upstream during winter and summer months.
Roodeplaat Dam
Results Nine different PFAS compounds were detected in both dams. • Hartbeespoort Dam – PFAS concentrations were in the range of 1.38 to 346.32 nanograms per litre (ng/ℓ), with Point C having the highest recording. This could be due to the dumping of waste at the banks of the Jukskei River, which drains into the Crocodile River. • Roodeplaat Dam – PFAS concentrations were in the range of 2.31 to 262.29 ng/ℓ, with Point B having the highest recording. This could be due to the Hartebeesspruit and Pienaar rivers, as the catchments are located in highly populated and industrialised areas. PFAS concentrations were higher in the summer months. High rainfall in these months may enhance the leaching of waste dumped near the riverbanks into the rivers that drain into the dams. The concentrations of the PFOA and PFOS compounds found in the dams were higher than the recommended lifetime health advisory issued by the US Environmental Protection Agency for drinking water (70 ng/ℓ). However, the level of human exposure to these compounds from drinking water is unknown. This study reported higher concentrations of PFASs than those reported in developing countries such as Uganda, Singapore and Vietnam but lower than levels reported in developed countries like Germany, Japan and China.
*The study was conducted by Professor Okonkwo and his EnvironmentalAnalytical Research in Chemistry group at the Department of Environmental, Water & Earth Science, Tshwane University of Technology.
Sampling points for the Roodeplaat and Hartbeesport dams J A N /F E B 2022
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