Investigation into metal contamination of the Berg River, Western Cape, South Africa

Va Jackson,W Khan,T Van Stormbroek,Jp Odendaal,An Paulse Paulse

doi:10.4314/wsa.v33i2.49057

Abstract

A recent decline in water quality of the Berg River, Western Cape, South Africa, has led to the investigation into the degree of metal pollution in the river system. This study was conducted over a period of one year, from May 2004 to May 2005. The nitric acid digestion technique was used to extract metals from water, sediment and biofilm samples collected at various points (Site A . agricultural area, Site B . informal settlement and Site C . Newton pumping station) along the Berg River. Metal concentrations were determined using inductively coupled plasma atomic emission spectrometry (ICP-AES). The highest mean metal concentrations recorded were as follows; water samples, 6 mgE.-1 for Al, 14.6 mgE.-1 for Fe and 18.8 mg..-1 for Mn; sediment samples, 17 448.8 mgEkg-1 for Al and 26 473.3 mgEkg-1 for Fe; biofilm samples, 876.8 mgE.-1 for Al and 1 017.5 mgE.-1 for Fe. The increased availability, or noteworthy incidence of Al and Fe, could be due to the leaching of metals into the river water from waste and household products associated with the informal settlement and the subsequent settling on sediment. No guidelines were available for metals in biofilms. The highest recorded concentrations in water were for Site C (agricultural area). Recorded concentrations in water fluctuated throughout the study period for most of the metals analysed, but Al and Fe were consistently above the recommended guidelines as stipulated by the Department of Water Affairs and Forestry and the Canadian Council of Ministers of the Environment.

Highlights

Metals occur in less than 1% of the earth’s crust, with trace amounts generally found in the environment (Alloway, 1995a)
The objective of this study was to identify the predominant metals, which occur within the river water, sediment and the biofilm samples isolated from the Berg River (Paarl) in the Western Cape, South Africa
This study proved that biofilms are effective in the accumulation of metals from the environment

Summary

Introduction

Metals occur in less than 1% of the earth’s crust, with trace amounts generally found in the environment (Alloway, 1995a). Micro-organisms will generally form a biofilm on any surface exposed to an aqueous environment These biofilms can be defined as a community of attached microbial cells organised within extracellular polymer matrices (EPS). Biofilms are advantageous in that they encapsulate toxic molecules, such as metals (Costerton et al, 1978), by providing a substrate for them to adhere to, thereby limiting the diffusion of biocides and other toxic molecules across the EPS (De Beer et al, 1994; Huang et al, 1995) This implies that the attached biofilm communities may be employed in the removal of toxins from aqueous systems, as the biofilms are able to concentrate and bind ions from the passing water (Neu et al, 1992)

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Conclusion