Heavy metals (Cd, Pb, Cu, Zn) in mudfish and sediments from three hard-water dams of the Mooi River catchment, South Africa

Abstract

Fish tissue from Labeo capensis and sediment core samples from three dams in the Mooi River catchment area were collected and analysed for Cd and Pb by electro-thermal AAS, and for Cu and Zn by flame AAS. The highest Cd concentrations were found in the clay fractions in all three dams, with a range between 66.0 µg·g -1 and 107 µg·g -1 . Lead concentrations below 34 µg·g -1 were found in all six sediment types from Klerkskraal Dam, while Potchefstroom Dam had the highest lead levels (range: 34 -62 µg·g -1 ) for the six sediment fractions and also for all the fish tissue types (range: 38 -79 µg·g -1 ). Lead alkyls from motorboat exhausts were probably responsible for the high lead concentrations in the sediment of Potchefstroom Dam and in the mudfish tissues. The mean zinc concentrations from five of the six fractions in Boskop Dam were significantly higher compared to the other dams, with a range between 25 µg·g -1 to 59 µg·g -1 . The combined six fractions were between five and 100 times lower in concentration when compared to the pelitic sediment samples from sediments at the Lebanon and West Driefontein mines in the Mooi River catchment. Copper concentrations in dam sediment from the six fractions for the three dams, ranging between 11µg·g -1 to 36 µg·g -1 , were higher when compared with copper levels worldwide. The kidneys, gills and liver had the highest levels of Cd, Pb and Cu respectively compared to other tissues from L. capensis, while the gills had the highest concentration of Zn. In conclusion, higher than normal metal concentrations were found in Boskop Dam sediments, which could be linked to gold mine operations inside the Mooi River catchment area. Lead, Cd, Cu and Zn concentrations in L. capensis tissues were much lower compared to reported data on South African fish, but on par with world levels. The percentage of uranium present in sediment samples (analysed by energy dispersive X-ray spectrometry) from the three dams was 9.0 % (SD 2.1%). In sediment it was found that cation exchange capacity measurements and the dolomitic hard water and high pH of the Mooi River water effectively 'detoxified' Cd and Pb, forming insoluble complexation products buried in the sediment.

Determination of heavy metal levels in Oreochromis niloticus and Chrysichthys nigrodigitatus from Ogun River, Nigeria

“…The high concentrations of Cd above 0.1 mg/kg threshold were considered to be harmful to fish and other fish predators (FAO, 1983). The concentrations of Cd in flesh and bone of O. niloticus and C. nigrodigitatus were lower than what was found in previous findings (El-Nemr, 2003;Mwashot, 2003;Van Aardt and Erdman, 2004;Khaled, 2004).…”

Heavy metal levels in mud crabs (Scylla spp.) from East Bataan Coast

“…Copper is an essential component of hemolymph (Yilmaz 2005;Van Aardt and Erdman 2004) and is essential in eye development and maintenance of cytochrome activity (Gupta and Mathur 1983;Guvan et al 1999). Though grow-out sites have significantly lower levels of heavy metals, the use of the same polluted water from the Bay replenishes heavy metal levels in the system.…”

Geospatial analyses in support of heavy metal contamination assessments of soil and grass along highways at Mafikeng, South Africa

“…The Molopo River drains through the Mafikeng area, and it is quite possible that negative impacts in the aquatic ecosystem could result from heavy metals being washed by surface runoff into the river. In a river whose catchment is just east of the Molopo's head waters, Van Aardt & Erdmann (2004) reported Cd, Cu, Pb and Zn concentrations in fish. In the predominantly agriculture area of Mafikeng meat livestock graze near the highways, and could accumulate the heavy metals in their organs.…”

“…Studies have highlighted detrimental effects of heavy metals on aquatic organisms in terrestrial water bodies in South Africa (e.g. Van Aardt & Erdmann, 2004;Retief et al, 2006). The metals have also been detected in estuaries and the coastal marine environment (Binning & Baird, 2001;Jackson et al, 2005;Bosch et al, 2016).…”