Abstract
M.Sc.
Sediments within riverine systems act as sinks for metals. Aquatic organisms which are
associated with sediments are therefore at risk of being exposed to metals that can be taken
up, resulting in adverse biological responses. Due to the processes of bioconcentration and
bioaccumulation, all organisms within a food web are thus potentially exposed. Different
sediment characteristics can alter the concentrations of metals which are bioavailable to
organisms, as well as their impact upon the effected organism. The bioavailability of
sediment-bound metals is determined by complex interactions amongst various
environmental, biological, physical and chemical parameters. The effects of metals on
aquatic organisms are associated with the type and duration of exposure, the concentration
and bioavailability of the pollutants, and the sensitivity of the organisms to the toxic effects of
the contaminants. Rivers such as the Olifants in Mpumalanga River contain high
concentrations of metals. This is due to increased levels of mining activities within the
catchment area, which impact directly upon the system. The river has also has an increased
siltation load resulting from amplified agricultural, mining and afforestation activities.
Following their introduction to aquatic systems, metals from mining effluents adsorb to
sediments and suspended particles within the aquatic environment. These metals are then
available for uptake by aquatic organisms.
The aim of this study is to determine whether acid-volatile sulphides (AVS) influence the
availability of sediment-bound metals to benthic dwelling fish species. The study was
undertaken in the Olifants River Kruger National Park. At the 5 selected Sites sediment and
the bottom dwelling Leaden mudfish (Labeo molybdinus) (Sites 1, 2 and 3) were sampled
during a low flow period. Bioavailable metal concentrations in sediments were determined
using the Community Bureau of Reference (BCR) soil extraction protocol. As certain
characteristics influence metal uptake and bioavailability within sediment, the concentrations
of AVS and total organic carbon (TOC) within the sediment were also analysed. Liver tissue
samples of L. molybdinus were analysed for Cr, Cu, Ni, Pb and Zn using ICP-OES and
ICP-MS techniques.
Water nutrient and anion analysis and characterisation of dissolved and suspended metal
concentrations were assessed using a Merck Spectroquant Photometer SQ 118, and the
Thermofisher x-series ICP-MS, respectively. Analysis revealed high concentrations of Total
Dissolved Solids (TDS) and SO4
2- within the water column, with high metal concentrations
within analysed Total Suspended Solids (TSS).