Heavy metal concentrations in the water of the Nyl River system, South Africa

The Nyl River floodplain, a Ramsar site that provides habitat for a number of endangered species, is one of the jewels in the arid Limpopo province and thus its conservation and protection are vitally important. Very little work has been done on assessing its water quality and no data have been published on the metal concentrations found in this valuable system. The aim of this project was thus to provide baseline data for metal concentrations in the Nyl River floodplain system and to determine whether there were any point sources of pollution or if its metal levels were natural. Eighteen localities along the course of the Nyl River were selected as sampling sites. Water samples were collected quarterly, between August 2001 and July 2002, and analysed using ICP-MS to determine metal content. Zinc, copper, iron, selenium, cadmium, lead, aluminium, arsenic, chromium and manganese concentrations were determined. Although metal concentrations in the water were greater than target water quality range (TWQR) values for aquatic ecosystems, they remained relatively constant throughout the system and posed little or no potential threat to the system. The results suggest that the metal content originates from natural sources.