Assessment of Persistent Organic Pollutant accumulation in Sediments of the Klip River Wetland, Johannesburg

Abstract The accumulation of Polyaromatic Hydrocarbons (PAHs) and Polychlorinated Biphenyls (PCBs) was investigated in sediments of the Klip River wetland Johannesburg South Africa. The wetland serves as an important source of potable water to the Vaal Dam Johannesburg and purifier of contaminants from different anthropogenic activities at the Witwatersrand basin. In this study, PCBs and PAHs were found to be spatially distributed in surface and core sediments of the two major tributaries entering into the wetland. The total concentration of PAHs and PCBs found in the surface sediments ranged from 45–95 mg/kg and 0.2–5.3 mg/kg respectively. Highlights of the distribution of PAHs indicated the upstream sites of both tributaries to be more polluted and were attributed to the proximity of these sites to heavy traffic and industrial complexes. Conversely, the downstream sites were more polluted with residues of PCBs and were attributed to anthropogenic activities from the residential settlements of Soweto and Lenasia. The total amount of PAHs and PCBs found in the sediment core site were 2.4 − 6.3 mg/kg and 0.17–0.80 mg/kg respectively, which is significantly lower than the concentrations found in the surface sample sites. Risk characterization of the sites indicated that about 60% of the investigated sites could be classified as moderately to highly polluted sites with potential ecological risk. A further investigation is therefore required for comprehensive ecotoxicological risk assessment.