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 physiochemica 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 TotHgsed and DOC concentrations were identified as important factors controlling TotHgaq, while TotHgsed were correlated to TotHgaq. This result is indicative of the combined effects of sediment settling and resuspension in the aquatic environment. In contrast, MeHgaq was not correlated to DOC. MeHginvert were correlated to MeHgsed, while MeHgfish were correlated to MeHgaq 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.