Baseline monitoring of mercury levels in environmental matrices in the Limpopo Province

Abstract

Mercury (Hg) speciation and bioavailability were studied in surface water, surface sediment and freshwater fish samples collected upstream and downstream of the Medupi (currently under construction) and Matimba power stations in the Waterberg area, Limpopo Province. The initial survey was conducted in May 2010 and continued periodically/seasonally until October 2014. This study was designed to provide an overall description of the levels of Hg in areas potentially impacted by emissions from the coal-fired power station and provide the necessary information to enhance the understanding of the factors regulating the fate and transport of Hg in the environment. Percent loss on ignition (LOI) and ancillary water quality measurements were also carried out. In this study, the total mercury (TotHg) concentrations ranged between 0.92 and 29.13 ng/L, and 0.13 and 8.00 ng/L for methylmercury (MeHg) in water. Total Hg concentrations ranged between 0.50 and 28.60 ng/g, while the MeHg concentration ranged between 0.08 and 2.22 ng/g in sediments. Mercury concentrations in fish ranged between 40 and 1200 ng/g for TotHg, and 13.42 and 600 ng/g for MeHg. Methylmercury concentrations in freshwater fish sampled exceeded the United States Environmental Protection Agency criteria (300 ng/g) in 10% of the total fish sampled and 5% exceeded the WHO guideline (500 ng/g).