The effects of contaminated sediments of the Blesbok Spruit near Witbank on water quality and the toxicity thereof to Daphnia pulex

Abstract

With the increasing focus on environmental issues, the objective of this study is to evaluate the potential impact of contaminated sediments of the Blesbok Spruit near Witbank - which receives acid mine drainage (AMD) inter alia - on biota. Direct transfer of chemicals from sediments to organisms is considered to be a major route of exposure for many species, and therefore focusing attention on sediment contamination and highlighting the fact that sediments are an important resource. Acute toxicity tests were performed on Daphnia pulex using both extracted sediment interstitial water and surface water. Chemical analyses were also performed on the sediment, interstitial water and surface water samples. The toxicity results suggest that metal toxicity adds significantly to the toxicity of the stream water which is enhanced by the effect of pH. The pH of the stream and interstitial water was consistently below 4.5.

Quantifying and Predicting the Water Quality Associated with Land Cover Change: A Case Study of the Blesbok Spruit Catchment, South Africa

“…Therefore, the relationships obtained by the PLS analysis coincide with and support the findings by previous studies [27][28][29][30][31][32]. Urban build-up, mining as well as cultivated land cover were established to have the greatest negative impact upon the catchment's water quality.…”

“…Due to the noted ecological importance as well as the large scale degradation of the Blesbok Spruit catchment, numerous scientific research have been conducted in an attempt to create an understanding of the extent of the degradation, the possible sources of pollution, impacts and consequences of the degradation of the catchment and lastly to develop effective management plans for the identified areas of concern. Previous research, which has been conducted within this catchment, includes specialized studies focused upon the effects of acid mine drainage on the upper reaches of the catchment [27], the impacts of contaminated soils [28], the extent associated impacts of the degradation of the catchment's water resources [29], and the development of possible strategies to reduce long term liabilities of the Grootvlei gold mine, which is one of the prime sources for the degradation of the Blesbok Spruit wetland and in turn the catchment [30]. Furthermore, an assessment of the health-related microbiological water quality of the Blesbok Spruit has also been completed and it was established that the water is not suitable for drinking or domestic purposes and full contact recreation would pose infection to users [31].…”

“…The extent to which the water has worsened, as well as associated impacts of the degradation of the catchment's water resources have been identified by previous research as point sources such as mine water decants which cause salinity problems, diffuse runoff from mining activities in the north of the catchment on the Witwatersrand, urban runoff from the large numbers of formal and informal settlements resulting in fecal contamination as well as high nutrients due to poor or failing waste infrastructure, discharges from industries such as South African Pulp and Paper Industries (SAPPI) and lastly return effluents from waste water treatment works and mine water decants [27][28][29][30][31]. The consequences of the degradation include high salinity levels, the presence of metals such as arsenic and cyanide, diurnal temperature changes, microbial contamination (potential water borne diseases and high nutrients) and elevated water temperatures.…”