Environmental geochemistry of the Waterberg coalfields

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Date
2015-07
Authors
Deysel, Lore-Marie
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University of the Free State
Abstract
English: The Waterberg Coalfields represent the last area in South Africa which contain large quantities of coal resources. The most important issue with economic growth and development is to take measures to minimise the impact on the environment. With the ever increasing demand for energy, the demand for continuous mining of coal increases and thus expands into areas not previously mined. The by-products of coal mining and the production of electricity from the coal leaves an environmental footprint. For this footprint to be minimised, all the risks associated with mining should be available and understood. Since there are still large coal deposits in the Waterberg which can be mined by opencast mining, the risk of the geological units still to be mined was assessed. Acid generation due the oxidation of mainly pyrite is a source of contamination that can impact the groundwater and to a lesser or no extend the surface water from the mining facilities. Another environmental risk is air pollution from mines, includingthat of Medupi Power Station which will commence shortly. It is a very dry area and thus the aquifers must be protected as far as possible. In this study area,coal is mined by the opencast method from the Karoo formation There currently only one active coal mine in the study area, namely the Grootegeluk mine which started operation in 1980. Samples were collected from exploration boreholes in all three areas in the region (partly weathered, Full succession and Middle Ecca). Acid-Base Accounting was done on all 800+ samples and it indicated that the interburden and discards contained the highest AMD potential while the overburden had the highest buffering capacity. The impact is clear on some of the monitoring boreholes on the site. Unlined facilities lead to the contamination of the aquifers to a point where the pH of the water is acidic. The monitoring boreholes close to the ash dump is affected by a raise in the total dissolved solids due to calcium and sulphate leaching from the ash. To get the total impact or toxicity potential of samples, it is necessary to identify the elements that are available in the different wastes that can leach into the environment. All the risks associated with the different geological units should be known so that the best decision and planning of waste facilities for future extensions can be made, and so that the negative footprint on the environment can be minimised.
Afrikaans: Die Steenkoolvelde in die Waterberge verteenwoordig die laaste gebied in Suid-Afrika waar groot hoeveelhede steenkool nog beskibaar is. Die grootste probleem met ekonomiese groei en ontwikkeling is om maatreëls in plek te kry wat die negatiewe impak op die omgewing sal minimaliseer. Met die toenemende behoeftena energie is daar ‗n deurlopende behoefte na die ontginning van steenkool asook die uitbreiding daarvan na voorheen ongemynde gebiede. Die byprodukte wat ontstaan a.g.v. die myn van steenkool en die opwek van elektrisiteit met behulp van steenkool, laat ‗n negatiewe impak op die omgewing. Indien al die risiko‘s wat verband hou met mynbou bekend is en verstaan word, kan dit die effek wat dit op die omgewing het, minimaliseer. Aangesien daar nog steeds groot steenkoolneerslae in die Waterberg is wat ontgin kan word, is die risiko van die ongemynde geologiese eenhede in hierdie studie ondersoek. Suur produksie vind plaas a.g.v. oksidasie deur hoofsaaklik piriet. Hierdie is ‗n bron van grondwater besoedelik by myn fasiliteite. Met die ontstaan van meer myne het lugbesoedeling ook toegeneemen die nuwe Medupi Kragstasie sal ook risiko vir die omgewing inhou. Die steenkoolvelde is in ‗n baie droë streek geleë en die akwifere moet daarom soveel moontlik beskerm word van besoedeling. Die steenkool is in die Karoo formasies geleë en word deur middel van die oopgroef myn metode gemyn. Grootgeluk is tans die enigste aktiewe steenkoolmyn in die area en het sy ontstaan in 1980 gehad. Monsters is vekry vanaf eksplorasie boorgate in al drie areas (gedeeltelik verweer, vol suksessie en die middel Ecca). Gevolglik is Suur Basis Berekeninge gedoen op die 800 monsters wat daarop gewys het dat die tussenlae (interburden) en weggooi (discards) monsters die hoogste suur potensiaal (AMD) bevat. Die boonste lae (overburden) bevat die hoogste buffer kapasiteit. Die invloed van die aktiwiteite is sigbaar in van die moniterings boorgate. Die ongevoerde fasiliteite het gelei tot die besoedeling van sommige akwifere tot by ‗n punt waar dit suur geword het. Die moniterings boorgate by die ashoop word beinvloed deurdat die totale opgeloste stowwe in die grondwater verhoog het a.g.v. kalsium en sulfaat wat van die ashoop af ingesyfer het. Om die totale potensiaal van die toksisiteit van die monsters te bepaal is dit noodsaaklik om die elemente wat beskikbaar is en in die omgewing kan uitloog, te bepaal. Indien al die risiko‘s van die verskillende geologiese eenhede bekend is, kan die beste besluite en beplanning gedoen word om die negatiewe impak op die omgewing tot die minimum te beperk
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Keywords
Coal mines and mining--Environmental aspects--South Africa--Waterberg, Coalfields--South Africa--Waterberg, Thesis (Ph.D. (Institute for Groundwater Studies))--University of the Free State, 2015
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