1,720,978 research outputs found
Uranium pollution in South Africa: past research and future needs
No full textExtracting gold for over a century from the Witwatersrand basin in South Africa as the largest known deposit on Earth, inadvertently also brought large amounts of radioactive and chemotoxic uranium (U) into densely populated environments. With well over 6000 million t of tailings, the Witwatersrand goldfields contain more uraniferous mine waste than all other U-producing countries worldwide combined, exposing millions of mainly impoverished residents to contaminated air, water, soil and food. Yet, to date, no systematic effort has been made to quantify reliably the extent of the problem and assess associated health risks for the entire region. Acknowledging that any concerted strategy for addressing the U legacy requires a scientific base, this paper briefly describes how research on U pollution in South Africa developed, which topics were covered and some of the gaps. Based on this, a radio-ecological approach is proposed to be followed for systematically addressing the problem and arriving at a sound scientific understanding of where U originates, how it migrates through the environment and what the associated health risks are
Uranium pollution of the Wonderfonteinspruit, 1997-2008 Part 2: Uranium in water concentrations, loads and associated risks
No full texthttp://www.scielo.org.za/scielo.php?pid=S1816-79502010000300007&script=sci_arttex
Uranium pollution of the Wonderfonteinspruit, 1997-2008. Part 1: Uranium toxicity, regional background and mining-related sources of uranium pollution
No full texthttp://www.scielo.org.za/scielo.php?pid=S1816-79502010000300006&script=sci_arttex
Generating high-resolution digital elevation models for wetland research using Google EarthTM imagery an example from South Africa
No full texthttp://www.scielo.org.za/scielo.php?pid=S1816-79502010000100007&script=sci_arttex
Uranium contaminated drinking water linked to leukaemia - revisiting a case study from South Africa taking alternative exposure pathways into account
No full textThe paper presents results of a follow-up to an earlier study which established a geospatial link between naturally elevated uranium (U) levels in borehole water and haematological abnormalities in local residents serving as a proxy for leukaemia prevalent in the area. While the original study focussed on drinking water only, this paper also explores alternative exposure pathways including the inhalation of dust and the food chain. U-levels in grass and tissue of sheep generally reflect U-levels in nearby borehole water and exceed background concentrations by 20 to nearly 500 times. U-levels in sheep tissue increase with age of the animal. Wool showed the highest U-concentration followed by other non-consumable tissue such as hooves, teeth and bones. Lower levels occur in edible parts such as meat and inner organs. The U-deposition rate in wool is several orders of magnitudes higher than in bone as a known target organ. Wool is an easy-to-sample non-invasive bioindicator for U-levels in meat. Depending on the original water content, dried samples show up to 5 times higher U-levels than identical fresh material. Contaminated drinking water is the main exposure pathway for farm residents resulting in U-uptake rates exceeding the WHO's tolerable daily intake (TDI) limit by up to 900%. This is somewhat mitigated by the fact that U-speciation is dominated by a neutral calcium-uranyl-carbonate complex of relatively low toxicity. Commercially available household filters are able to significantly reduce U-levels in well water and are thus recommended as a short-term intervention. Based on average consumption rates sheep meat, as local staple food, accounts for 34% of the TDI for U. Indoor levels of radon should be monitored, too, since it is linked to both, U and leukaemia. With elevated U-levels being present in other geological formations across South Africa boreholes in these areas should be surveyed
Water sustainability and watershed ecosystem health
No full textClimate change and human activities have unprecedentedly altered the hydrological processes and ecosystem services of watersheds all over the world, causing or exacerbating local and regional water crises, threatening ecosystem integrity, and compromising water sustainability. Understanding the effects of interactions and dynamics of such coupled human and natural systems on eco-hydrological processes at the watershed scale is essential for addressing and adapting to global environmental chang
Unearthing a hidden treasure: 60 years of karst research in the Far West Rand, South Africa
Get PDFKarstified dolomitic formations situated in the Far West Rand goldfield of the Witwatersrand Basin constitute a significant groundwater resource in semi-arid South Africa and would be of strategic importance for alleviating the increasing water stress in nearby metropolitan areas. The deep-level gold mines operating below the dolomites have suffered from large volumes of dolomitic groundwater flowing into the mine voids, rendering mining both expensive and hazardous. In order to secure safe and economical mining, the overlying dolomites were dewatered. Here we review research over 60 years, conducted in three of the four major dolomitic compartments affected by dewatering. After more than six decades of research, these aquifers are arguably the most investigated karst systems in South Africa, and possibly worldwide. The data generated are, in many respects, unique, as many measurements can never be repeated, covering stochastic events such as a major water inrush into mine workings and some of the most catastrophic sinkhole developments ever recorded. Given the potential value for improving the understanding of general and local karst hydrogeology, our main goal for this paper is to alert the scientific community to the existence of this resource of mostly unpublished data and research. A no less important aim is to support a systematic collation of these studies which are in danger of being irretrievably lost as mines increasingly close down. Ecological and economic impacts of the flooding of mines in and around Johannesburg emphasise the lack of reliable historical mine data to optimally address the matter. We provide the first comprehensive, yet not exhaustive, overview on the existing studies, briefly discussing scientific content as well as obstacles for utilising the scattered, and often non-peer reviewed, information sources
Determining hydraulic parameters of a karst aquifer using unique historical data from large-scale dewatering by deep level mining – a case study from South Africa
Get PDFAlthough karst aquifers constitute some of the most important water resources worldwide, generally accepted methods for reliably characterising their hydraulic properties are still elusive. This paper aims at contributing to the discussion by a first-ever attempt to utilise various sets of unique historical data derived from draining a large dolomitic karst aquifer by deep-level gold mines in South Africa. In contrast to conventional pumping tests which only penetrate thick aquifers to a limited extent from surface, this draining took place at the very bottom of the aquifer offering the rare opportunity to capture its entire thickness of nearly a kilometre. The datasets have been treated as analogies to conventional pumping tests applying various types of analytical methods designed for porous media. In order to increase the robustness of the results and to account for specific local conditions a total of four different analytical methods were applied to calculate (horizontal) transmissivity and storage coefficients. The obtained values, in general, compare favourably to previous studies in the area and values reported in literature for similar aquifer types confirming earlier findings that Darcy-based methods can be successfully applied to karst aquifers if the scale of investigation is large enough. Apart from improving the understanding of local karst hydrology the present study also aimed at retrieving and preserving valuable and unique historical datasets that otherwise would have been lost for scientific evaluation and the proactive preparation for mine closure.http://dx.doi.org/10.4314/wsa.v40i3.20http://www.ajol.info/index.php/wsa/article/view/105861/9587
Threats and opportunities for post-closure development in dolomitic gold-mining areas of the West Rand and Far West Rand (South Africa) – a hydraulic view Part 2: Opportunities
Get PDFLargely dependent on gold mines for their economic survival, many mining towns in the Far West Rand fear the effects of the inevitable impact of mine closure, not only on the economy but also on social stability. Large-scale environmental degradation in the form of sinkholes and widespread radioactive pollution exacerbate such fears. Based on an analysis of mining impacts and potential threats for post-mining developments provided in Part I, this 2nd paper in a 3-part series aims to stimulate thought, through the discussion of potential opportunities centred on the rich water resources of the area. This is in full recognition of a subsequent need to assess the economic and technical feasibility of identified opportunities in more detail. Many opportunities are based on the concept that perceived mining liabilities may have the potential to be turned into assets. Examples include the restoration of dewatered karst aquifers and their use for storing large volumes of water, protected from evaporation losses, combined with artificial groundwater recharge and harvesting as well as underground generation of hydropower. This could well be complemented by other water-based developments such as aquaculture, agriculture and different forms of tourism relating to water, karst and mining. Possibilities for using waste land such as sinkhole areas and slimes dams include the establishment of a large game reserve on donated land as well as using tailings for biofuel production and generating solar- and wind-based electricity. Lastly, the re-establishment of a uranium-related industry is explored; this could capitalise on existing infrastructure and former expertise and benefit from the envisaged development of uranium as a strategic resource in SA. In view of the current media attention given to negative environmental and healtheffects, it is, however, questionable whether such development would be acceptable to local residents.Keywords: post-mining development, karst, groundwater storage and harvesting, subterranean hydro-energy generation, tourism, wasteland transformation, uranium industry, research opportunitie
Threats and opportunities for post-closure development in dolomitic gold mining areas of the West Rand and Far West Rand (South Africa) – a hydraulic view Part 1: Mining legacy and future threats
Get PDFhttp://www.scielo.org.za/scielo.php?pid=S1816-79502010000100008&script=sci_arttex
- …
