A review of mercury pollution in South Africa: Current status

Abstract

The present paper is a review on the status of mercury (Hg) as a pollutant in South African aquatic ecosystems. Spatial patterns of Hg distribution and bioaccumulation in water resources were investigated by collecting and analyzing multimedia samples for physiochemical and Hg-species determination from 62 sampling sites. The data presented showed a wide range in concentrations, which was expected given the array of environmental parameters, water chemistry and sources of Hg. Generally, higher Hg concentrations were measured in environmental compartments impacted by the major anthropogenic Hg sources which, in South Africa, are largely represented by emissions from coal-fired power stations (i.e. Olifants and Upper Vaal WMAs) and artisanal gold mining (i.e., Inkomati WMA). Ancillary water quality parameters (e.g. pH, temperature, DOC, EC and nutrients) were measured and regressed with the measured Hg concentrations to determine which environmental parameters most influenced regional Hg concentrations. The TotHg _sed and DOC concentrations were identified as important factors controlling TotHg _aq , while TotHg_sed were correlated to TotHg _aq . This result is indicative of the combined effects of sediment settling and resuspension in the aquatic environment. In contrast, MeHg _aq was not correlated to DOC. MeHginvert were correlated to MeHg _sed , while MeHg _fish were correlated to MeHg _aq and water quality variables (chlorides - Cl⁻ and electrical conductivity - EC). A steady progress has been made in Hg research in South Africa. However, despite the substantial knowledge about Hg toxicity, there are still considerable knowledge gaps on the fate and transport of Hg. Hence, further environmental and human health studies are proposed.

Keywords:

• Mercury
• methylmercury
• environmental parameters
• water
• sediment
• invertebrates
• fish
• South Africa

Acknowledgments

This study was funded by grants from the Council for Scientific and Industrial Research (CSIR) Parliamentary Grant (PG), Strategic Research Panel (SRP), Water Research Commission (WRC) and National Research Foundation (NRF), South Africa. We also thank Prof. Robert Mason and Genevieve Bernier from the University of Connecticut, USA, as well as other field and laboratory personnel.