Jabulani Gumbo

By Kudakwashe K. Shamuyarira and Jabulani R. Gumbo

Trace metals including nanosilver in our aquatic environment are on the increase in part due to discharge from municipal sewage and indirectly from leaching from abandoned mine tailings and from sludge spread on farmland. The presence of the trace metals will likely impact negatively on the aquatic environment in excess of background levels. This review reports on the concentration of trace metals in municipal sewage in Limpopo province and the impact on fish and human health. Human health risks associated with the consumption of contaminated fish are discussed. The presence of silver is also highlighted and the remedial actions that are available in reducing the health risks including positive outcomes are discussed. The source of silver may be from the use of silver nanoproducts. There is a need for a paradigm shift of zero effluent discharge and start with harvesting of metals from the sewage effluent and sludge in order to protect the environment.

Part of the book: Sewage

By John M. Mokgoebo, Tibangayuka A. Kabanda and Jabulani R. Gumbo

Dams have been associated with various impacts on downstream river ecosystems, including a decrease in stream flow, species biodiversity, water quality, altered hydrology and colonisation of the area by invasive alien plant species. The impacts normally interfere with the ecosystem functioning of riparian and aquatic environments, thereby leading to decreased biodiversity. This study aims to assess the impacts of dams on downstream river ecosystems, using data from aerial photographs and orthophotos, supplemented by field work. Five dams in Limpopo Province, South Africa, were selected (Albasini, Damani, Mambedi, Nandoni and Vondo), and photographs from different years were used. The area devoid of trees of certain species both downstream and upstream of the dams was calculated using grids of predetermined square sizes on each available photograph. Aerial photographs and orthophoto data were supplemented by field work. The nearest-individual method was used in the field to determine tree density of particular tree species. The environments downstream of the dams show a loss of obligate riparian vegetation and an increase of obligate terrestrial vegetation (Acacia Karroo, Acacia Ataxacantha and Bauhinia galpinii). Treeless area increased in all cases, especially in the case of Mambedi and Vondo dams, indicating lower resilience and higher fragility there.

Part of the book: Environmental Risks