The occurrence and bioaccumulation of selected metals and radionuclides in aquatic and terrestrial ecosystems on the Witwatersrand.

Abstract

Ph.D.The investigations reported here conducted during 1990-1994 had the following objectives: Selection of representative localities in impoundments and rivers in wetlands affected by radionuclide- and metal-containing effluents and seepage water from mines and metal-processing industries. To determine the occurrence and concentration of radionuclides and selected metals in mine- and industry-polluted waters and sediments in catchments of the Blesbokspruit, the Klip River and the Crocodile River systems. To establish radionuclide and metal concentrations in some semi-aquatic and aquatic weeds in these mine- and industry-polluted waters with observations on the ability of some plants to accumulate certain metals in their roots and/or shoots. To evaluate some benthic macro-invertebrate organisms as possible indicators of radionuclide and metal pollution in the affected streams. To determine the radionuclide and metal concentrations in selected vegetable crops irrigated with mine- and industry-polluted water. The localities where the investigation took place were mainly in wetland regions on the East and West Rand. Water of polluted streams traverse expansive wetlands containing floating, emergent and submerged aquatic vegetation. These plants play an important role in the recovery from pollution of the affected waters. Pollutants are also available to and accumulated by other aquatic organisms such as crabs, fish and birds. In addition, the same water is often used for the irrigation of vegetable crops, thereby creating potential pathways through which these pollutants may be consumed by humans. All the above objectives have largely been met in as such that potential sources of pollution were identified and pollutants detected in the abiotic (water and sediments) environment. These pollutants were also found in wetland biota as well as agricultural crops irrigated with contaminated water. Potential pathways for the transfer of these pollutants were identified and dose assessment modelling was conducted