Comparison of Different Normalisers for Identifying Metal Enrichment of Sediment: A Case Study from Richards Bay Harbour, South Africa

Abstract

AbstractSouth Africa’s ecosystems are challenged in various ways by anthropogenic effects, such as land-use change, leading to soil erosion in concert with industrial or agricultural pollution, leading to an increase in pollutants in final depositional systems. Here we focus on metals in the marine environment of Richards Bay Harbour. The use for Al, Fe, Rb, Ti and the silt fraction of the sediment as normalisers of Cr, Cu, Co and Pb concentrations in sediment is compared to determine if they provide the same understanding on the enrichment. Baseline metal concentration models were defined and Enrichment Factors calculated to quantify the magnitude of enrichment.Exceedingly high Cr and Cu concentrations in defined parts of the harbour lead to similar trends rather than a similar effectiveness of the normalisers. Probable biogeochemical processes hinder the effectiveness of Fe and geological background or hydrodynamic properties hinder the effectiveness of Ti as normaliser. Differences in the spatial extent of sediment identified as enriched and the area where metal concentrations exceed guidelines detracts from fully appreciating the extent of metal contamination of sediment using guidelines, with management implications. Furthermore, in the case of Cu, the guidelines for this metal might be underproductive.