Browsing by Subject "Environmental Geochemistry"

Now showing 1 - 20 of 33
  • Thumbnail Image
    Item
    Open Access
    Arsenic dispersion associated with the Barbrook gold mine in the Mpumalanga Province of South Africa
    (1997) Lanyon, Ruth; Fey, Martin V
    Arseniferous sulphide-hosted gold deposits associated with the Barberton greenstone belt, located in the Mpumalanga province of South Africa, have been mined on various scales since late last century. The Barbrook mine is located close to the Swaziland border in an area of the Barberton mountainlands which forms part of the Kaap subcatchment of the Crocodile River. Scattered small communities depend on local streams and boreholes in the area for drinking and irrigation water. Hence, the prime motivation for this study was the potential risk to human health associated with enhanced As mobility as a result of the sulphide mineral weathering which accompanies gold mining and processing. Sampling of local waters, soils and sediments, as well as the ore and waste rock at Barbrook was undertaken during a week of fieldwork in August 1996. A range of chemical analyses were performed on the various samples, including As analysis by hydride generation-atomic absorption spectroscopy and inductively coupled plasma - mass spectrometry. The Barbrook ore bodies are structurally controlled and hosted by banded iron formation, carbonaceous shales and carbonate-bearing schists. Within these ore bodies, As is mainly associated with auriferous arsenopyrite (FeAsS), although minor amounts also occur within pyrite (FeS₂) and ullmannite (NiSbS). Of the streams which flow through the mining lease, those at most risk of As contamination are Barbrook Creek, Low's Creek and Crystal Stream. Low's Creek flows through the main mine area, adjacent to the level 1O mine adit entrance, and past the processing plant before converging with Barbrook Creek. The latter receives water from the Shiyalongubo Dam which is the main water source for the area. Immediately downstream of the level 10 mine adit entrance, the steep eastern bank of Low's Creek is lined for several hundred metres with waste rock containing low grade ore. Tailings material from the processing plant is pumped to two tailings dams located about 5 km to the northwest of the plant and close to Crystal Stream.
  • Thumbnail Image
    Item
    Open Access
    Assessment of the suitability of composted sewage sludge as an adsorbent for the treatment of heavy-metal contaminated wastewater, with special reference to cadmium
    (1995) Schwegler, Frank Rudolf; Fey, Martin V; Willis, James P
    A large proportion of sewage sludge in South Africa contains heavy metal concentrations which are deemed to be above threshold limits for its use as a fertiliser. Furthermore, sewage sludge has a high affinity for heavy metals. Until the sources of heavy metal contamination of municipal sewage sludge are considerably reduced the contaminated sewage sludge must either be disposed of or used for some other purpose. The use of contaminated sewage sludge as an adsorbent for treating heavy metal-contaminated wastewaters may provide an alternative and practical use for this material. The objective of this study was to assess the potential of composted sewage sludge (which is more stable and has a higher permeability than ordinary sewage sludge), produced from municipal sewage sludge in Milnerton, as an adsorbent for the extraction of heavy metals from contaminated wastewaters. The study was conducted with specific reference to cadmium since it is one of the most toxic of the heavy metals and occurs in many types of wastewaters.
  • Thumbnail Image
    Item
    Open Access
    Chemical characterisation of landfill leachate and its potential mobility through the Cape Flats sand
    (1996) Harraway, Trevor John; Fey, Martin V; Willis, James P
    Researchers have expressed concern about pollution of groundwater at Coastal Park, a large, general waste landfill situated on the False Bay coastline above the Cape Flats Aquifer. The landfill was constructed without a liner, but with an average 2m separation of calcareous sand providing a "buffer" zone between the waste pile and the water table. Water balance studies and application of a model, FLOW, have predicted that leachate will be generated seasonally. This study was initiated as a result of uncertainties about hydrological and geochemical aspects, such as the hydraulic conductivity of the soil in the buffer zone and the degree of leachate attenuation occurring in this zone. The Coastal Park soil was classified as an aeolian, calcareous, medium quartzitic sand with negligible organic carbon content. Extreme clay-depletion would render the soil almost incapable of leachate attenuation, although calcite and aragonite, found by X-ray diffractometry, would impart a significant pH buffering capacity to the soil. The solid phase of a locally-derived landfill leachate (sampled from Vissershok landfill, about 35 km NW of Cape Town) was found to contain amorphous sulfides of iron and heavy metals, and green rusts which are mixtures of Fe²⁺ - Fe³⁺ hydroxides, in addition to organic matter. The solid phase was isolated by centrifugation, freeze-dried, and analyzed by XRF and XRD. Distribution coefficients of heavy metals in the leachate (at pH 7.7) demonstrated the high affinity of heavy metals, such as Cu, Zn, Cr, Ni and Pb, for the solid phase. The leachate solid phase consists of amorphous solids, with high Ca and Cl concentrations in the liquid phase leading to halite and calcite formation upon evaporation of the liquid phase. According to locally specified requirements by Department of Water Affairs and Forestry, a landfill liner material must have a hydraulic conductivity (K) not higher than 1 x 10⁻⁷cm.s⁻¹. Air dried samples of Coastal Park soil were treated with various amendments to test their efficacy as landfill liners. An 8 % kaolinite plus 4 % gypsum treatment was the most effective, maintaining a minimum K of 10⁻⁴⁵ cm.s⁻¹, which, however, is still higher than the local requirement. Amendment with 8 % Na-bentonite initially achieved a minimum K of 10⁻⁷·⁸ cm.s⁻¹, but the high electrical conductivity (EC) of the leachate (26.8mS.cm⁻¹) caused shrinking and severe side-wall seepage, which rapidly enhanced hydraulic conductivity, reaching a maximum K of about 10⁻⁴·⁷ cm.s⁻¹. Both treatments of the sand do show promise as possible liners, although the use of higher percentage concentrations of clay should be investigated further. LEACHW (the water regime submodel of LEACHM) was used to predict leachate discharge from the Coastal Park landfill, assuming a hypothetical capping system of 1 or 2 m soil depth with 0, 50, 70, or 90 % vegetation cover (Acacia cyclops), and based on the assumption that drainage from this layer into the waste pile contributes directly to leachate generation. The model predicted that under average rainfall conditions the landfill, with a 2 m soil depth and 0 % vegetation cover, would not generate leachate. However, under the wettest conditions not even a 90% vegetation cover and 2 m soil cover would be sufficient to prevent the landfill from generating leachate, suggesting that, under such conditions, a more effective leachate management strategy, such as leachate collection sumps, should be implemented. This exercise demonstrated the use of LEACHM as an alternative means of predicting leachate discharge from landfill sites.
  • Thumbnail Image
    Item
    Open Access
    The chemical response of deep, leached and weathered soils of the Mpumalanga Highveld, South Africa, to irrigation with saline mine water
    (2000) Campbell, Ross; Abanda, Peter Azah; Smith, Meris
    Coal mining in the Highveld region of Mpumalanga Province, South Africa generates between 14 and 30 million litres of waste water per day. Much of the water is saline (TDS> 2500 mg/I) and has high concentrations of dissolved SO₄²⁻, Ca²⁺ and Mg²⁺. Crop irrigation has been proposed as a useful way to dispose of saline mine water and enhance agricultural productivity in this low rainfall (˂800 mm/year) region. In order to avoid undesirable salinization of the regional groundwater, it is necessary that soils immobilize, at least partially, the dissolved salt load of irrigation water.
  • Thumbnail Image
    Item
    Open Access
    Chemical, physical and mineralogical properties associated with the hardening of some South African fly ashes
    (1999) Campbell, Alex E; Fey, Martin V; Willis, James
    Coal combustion for power generation is relied on heavily in South Africa. The main residue from the combustion process is fly ash, with about 22 million tons being produced in 1994, of which only about 1 million tons is utilised, the remainder requiring disposal as waste. Various environmental impacts are associated with the disposal of fly ash in surface impoundments, including loss of usable land, contamination of groundwater, and production of wind-blown particulates, effects on vegetation and aesthetic impacts. Ultimately the disposal of fly ash in the mined-out underground workings is highly sought after, as it may limit many of the impacts which fly ash induces on the environment. The main purpose of this study was to assess the degree of hardening of four South African fly ashes from power stations at Kriel, Lethabo, Matla and Sasol in terms of their chemical, physical and mineralogical properties. Samples were taken of fresh and unweathered ashes from each power station. Unweathered ash samples analysed by XRFS were found to have high contents of Si0 2 (49.9-56.3%), Al 2 0 3 (27.2-31.5%), CaO (4.2-8.6%Y and Fez03 (3.1-3.9%) with varying contributions from loss on ignition (L.O.I.) (0.4-4.4%) and MgO (1.1- 2.2%). The major mineral phases detected in unweathered ash by XRD include quartz, mullite and glass, with smaller contributions from hematite and lime. Laser particle size analysis and liquid limit determination (Atterberg tests) were also conducted. The exceptionally high L.O.I of Sasol ash (4.4%) was attributed to the presence of partially burned coal, based on DTA and TGA investigation. Modulus of rupture experiments were conducted on briquettes (dimensions 7.0 x 3.5 x 1.0 em) of unweathered ash from Kriel, Matla, Lethabo and Sasol, which were wetted to their liquid limit and cured for 24 h under ambient conditions. The tests indicated that there is a strong linear relationship between total Ca content and the modulus of rupture for 3 of the 4 unweathered ashes. The fly ash from Kriel deviates from this relationship, providing evidence that other chemical (e.g. form of Ca) and physical factors (e.g. particle size) may also play a role in hardening.
  • No Thumbnail Available
    Item
    Open Access
    Coal mine waters in South Africa: Their Geochemistry,quality and classification. Volume one and two
    (2002) Azzie, Bernadette Ann-Marie
    South Africa is thought to be one of the few water-scarce countries in the world in which coal mining has been, and still is, extensively performed. Parts of Australia and the U.S.A. (specifically Wyoming and Montana) are also water-scarce coal-mining regions. In the past, mining has impacted heavily on the South African environment (Funke, 1983). In recent years, however, individual mines have been striving to ensure that the negative impacts of their operations are kept within acceptable limits, especially in terms of water conservation. Numerous problems are known to exist specifically in the coal mining industry where water is required for underground and surface operations. In these operations it is used for drilling, dust suppression, environmental cooling, as an energy source in hydropower and as a transport medium for backfilling. In addition, potable water is required for drinking purposes. Large volumes of water are affected by chemical contaminants in the coal mines (Azzie, 1999). These contaminants vary significantly depending on the coal seam mined, the mining method employed, the area, size and purpose of the infrastructure used. The water management structures in place around the seam, the chemistry of the rock sequence in which the coal is found and the quality and quantity of the natural groundwater also play a role (Kempe, 1983).
  • Thumbnail Image
    Item
    Open Access
    Crushed rock and clay amelioration of a nutrient decifient, sandy soil of Maputaland
    (1999) Ceruti, Portia Odessyl; Willis, James
    Various studies have suggested the possibility that food derived through subsistence agriculture in the Mseleni region of Maputaland contributes to malnutrition within the local community, particularfy within the high proportion of the population which suffers from a severe, disabling form of osteoarthritis. This study was conducted to determine if the application of local crushed rock or black clay to these nutrient deficient, sandy soils would increase available nutrient concentrations and improve the growth of plants in the ameliorated soil.
  • Thumbnail Image
    Item
    Open Access
    Economic structural adjustment programmes in the Southern African development community : an analysis of impact and policy considerations with special reference to Zambia and Zimbabwe
    (1999) Gumede, Nyawo Basirio Simbi; Kuye, Jerry O
    This study is primarily aimed at examining the impact of World Bank / IMF, structural adjustment programmes in the SADC region. However, the main focus of the study was on Zimbabwe and Zambia. These World Bank / IMF-influenced perestroikas, are believed to be viable panacea, for the state of economic malaise prevalent in the SADC region. In undertaking this research, various methods were utilised to acquire data. A case study approach was used. However, the main method of data collection which was heavily relied upon was document study. The collected data was analysed and presented in both graphical and tabular form. This study, inter alia, established that the implementation of IMF / WB structural adjustment programmes in the SADC region has precipitated a plethora of insurmountable socio-economic problems for the citizenry of both Zimbabwe and Zambia. Furthermore, the research has revealed that IMF / WB influenced structural adjustment programmes have culminated in large-scale unemployment, retrenchments, an acute decline in educational and health standards, ever-skyrocketing food prices, rents, taxes, mass exodus of qualified human resources to greener pastures, big debts, inflation and labour strikes in Zimbabwe and Zambia.
  • Thumbnail Image
    Item
    Open Access
    Environmental consequences associated with ash-stabilisation of organic sludges from the synthol process
    (2002) Makhathini, S. C.
    Worldwide increases in environmental awareness have led to the development of new innovative technologies aimed at site remediation and hazardous waste treatment. Solidification/Stabilisation (S/S) is one of such technologies and it has emerged as an environmentally acceptable treatment option for hazardous waste. Initially applied to inorganic wastes, S/S is now being investigated for the treatment of organic wastes and sludges. Challenges facing this venture into the SIS of organic wastes include the lack of technical information on waste-binder interactions, the uncertainty regarding an appropriate method to evaluate the performance of CPS systems, as well as evaluation of the long-term stability of stabilised material. This paper attempts to expand the understanding of chemical and micro-structural waste-binder interactions. Also addressed is the weathering behaviour of stabilised/ solidified organic waste when exposed to two different leaching media, distilled water and the US EPA's Toxicity Characteristic Leaching Procedure (TCLP) solution. Addressed to a minor extent is the effect of stabilised/solidified organic waste on biomass production of sweetcorn maize. The focus in this study was the stabilisation of the synthol sludge (synthol gunk) using a pozzolan system. This was done by preparing stabilised waste forms from synthol gunk and fine ash (ash obtained from the slimes dams, hence has hydrated to some extent). A particle size fraction less than 2 mm of these waste forms were leached with the two leaching solutions. Some of the material was pressed into pellets, which were subsequently leached in the same leaching solutions. The pellets were analysed under SEM-EDS for micro-structural analysis. In a separate set of experiments fine ash, synthol gunk and the stabilised waste forms were mixed with soil in the range 0% to 30% waste addition, after which sweetcorn maize was planted to study the effects on biomass production. Other instrumental techniques used in this study include WDXRF, ICP-MS, FTIR, IC as well as the analysis of dissolved organic carbon (DOC). The study showed that the trace metal speciation of the pozzolanic binder is affected by the presence of the organic waste, with a possible threat of turning the binder into a hazardous material. Elements that were leachable by TCLP on the stabilised product include B, Mn, Ni, Fe, and Br. The addition of lime in the system appears to lower the leachability of B, Mn, and Br while worsening the leachability of Fe, Ba, and Zn. However, addition of lime increases the leachability of B, Cr, Mn, Fe and Br in distilled water. The most likely source of B, Fe, Br and Ba is fine ash. Plant growth studies showed that the toxicity threshold of synthol gunk in the stabilised material on biomass production appears to be lowered from about 2.5% in unstabilised synthol gunk to about 1.2% either due to synergy or the additive effect of ash and synthol gunk. Furthermore, it is likely that some of the toxicity of synthol gunk is due to the hydrophobic coating of roots resulting in inadequate water intake by the plant.
  • Thumbnail Image
    Item
    Open Access
    Experimental improvement of flyash as a growth medium for plants through addition of selected solid wastes
    (1997) Webster, Glen Robert; Fey, Martin V
    Large quantities of coal are consumed in South Africa as a result of the generation of electricity and the manufacture of automotive fuel. A consequence of this was the production of more than 15 Mt of ash and associated coal combustion by-products in 1987 alone. This poses a large scale waste-disposal problem. Flyash, the major waste product is from South African coal sources, an alkaline, saline material the pozzolanic nature of which results in the formation of massive, compacted and cemented ash deposits which have significant environmental impacts. Efforts made to limit this impact by revegetation, in many locations throughout the world, have had limited success due to the mobility of phytotoxic concentrations of some elements, including As, B, Cr, Cu, Mo, Ni, S and Se. Flyash also has limited quantities of bioavailable Fe, Mn, P and Zn and these elemental limitations are associated with the alkaline nature of the flyash. Another element that is deficient, is N, it is unavailable in flyash as it is lost from coal during combustion. Aside from the chemical limitations to plant growth, the compacted nature results in low porosity which can limit plant available moisture. Plant root penetration is also impeded which limits nutrient uptake. The basis of this study was to incorporate other selected waste materials into the flyash to produce, by co-disposal, a combined waste material that is geochemically inert and a satisfactory plant growth medium. The ameliorants selected for inclusion in this study included interphase sulphur, a Vcontaminated waste sulphur product from the sulphur recovery plant at the SASOL' s Secunda petrochemical production facility and Catpoly, a spent catalyst consisting of phosphoric acidimpregnated diatomaceous earth, also obtained from SASOL's Secunda operation.
  • Thumbnail Image
    Item
    Open Access
    Geochemical and limnological aspects of phosphorous contamination in the Noordhoek Valley, Cape Peninsula
    (1999) Gassner, Anja; Willis, James; Fey, Martin V
    The Noordhoek Valley is situated on the Atlantic coast of the Cape Peninsula, South Africa (34°07'S, 18°22'E). Towards the east, the valley hosts numerous townships, while to the west it opens into a lowland marsh area, bordered by a five-kilometre beach. The wetland is subjected to various forms of anthropogenic pollution; the two most important being the discharge of urban runoff and treated effluent from the local sewage works. During the period of the study (Jan-Oct 1998), the occurrence of toxic cyanobacteria of the species Microcystis aeruginosa was reported for the two main water bodies within the wetland. The objective of this study was to conduct an investigation of geochemical and limnological aspects of phosphorus contamination within the wetland. The investigation concentrated on the two main water bodies of the wetland: The Lake and Wildevoëlvlei.
  • Thumbnail Image
    Item
    Open Access
    A geochemical investigation of ground water and soils affected by evaporation pond seepage, at the Namakwa Sands Mineral Seperation Plant(MSP)
    (2004) Petersen, Jacques R; Roychoudhury, Alakendra N
    Evaporation ponds are used for treating wastewaters in arid regions worldwide. Namakwa Sands an Anglo American plc operation, mines heavy minerals along the semi arid West Coast of South Africa. An acid effluent is generated during treatment of these heavy minerals. The effluent is neutralized and disposed of into unlined evaporation ponds. Seepage from the ponds affects the surrounding environment as well as the subsurface waters. The main objective of this study was to investigate the effects of the seepage on the groundwater resources and potential implications for contaminant migration in the subsurface environment.
  • Thumbnail Image
    Item
    Open Access
    A geochemical investigation of the Lake Sibiya system, Northern Zululand
    (1999) Whyte, Stewart Rodney; Willis, James; Fey, Martin V
    Lake Sibaya (27°15'-21'25'S; 32°32'-32°44'E) is situated in the northern region of the Zululand coastal plain, and is remarkable in that it embodies a near-pristine· freshwater coastal lake preserving clear residual signs of its former estuarine origin. Despite the· fact that the lake constitutes perhaps the most intensively studied of all freshwater bodies in South Africa, little is known .of its geochemical character. The objective of this study was therefore to conduct an investigation of the waters and sediments of the lake system, which might then provide a chemical baseline against which the future environmental quality of the system could be gauged, and in terms of which the current functioning of the ecosystem can be better understood. In line with this rationale, water and sediment samples were collected from each of fourteen sampling sites located along three transects running, variously, S-N, SW-NE and W-E across peripheral arms of the lake. Waters in direct contact with the sediments were thoroughly agitated with the sediments and thereafter decanted for analysis. Since the lake is purported to be fed almost exclusively by groundwater flow, water samples were collected from three groundwater . . wells located north-west of the lake. The Department of Water Affairs (DW AF) databases for groundwater chemistry, and for lake level and chemistry over the period 1980 to 1998, were used to supplement this data, and to provide an indication of any medium-term parameter changes. A water sample was also· collected from the non-perennial Mseleni River, although the river is known to contribute minimally to the lake volume. The majority of laboratory analyses were conducted within the Department of Geological Sciences at the University of Cape Town, adhering to standard analytical methods wherever possible.
  • Thumbnail Image
    Item
    Open Access
    A geochemical investigation of the sediments in Small Bay, Saldanha Bay, with special reference to the mobility of Cd, Cu, Pb and Zn
    (1999) Scott, Diane Lesley; Willis, James; Fey, Martin V
    Saldanha Bay is a natural deep-water harbour situated on the Cape West Coast, approximately 100 km north of Cape Town. The bay is not an estuary, since there are no rivers or streams entering the inlet. Saldanha Bay covers a total area of approximately 9.61 x 107 m2 and consists of three interconnected water bodies: Langebaan Lagoon, Big Bay and Small Bay. The latter two are separated from each other by a causeway and a series of jetties. At present, Small Bay is the most developed of the water bodies, supporting activities such as commercial and industrial fishing, the mariculture of mussels, and the exportation of iron ore and metal concentrates. Conflicting demands are being placed on the system, and the sediments are known to be contaminated with a range of trace metals. The handling of ore and metal concentrates in particular, have been identified as a threat to the survival of the mariculture industries. The overall objective of this study was to provide a geochemical characterisation of the sediments in Small Bay. It focused on identifying the factors which have the greatest influence on the mobilities of Cd, Cu, Pb and Zn in the sediments. This was achieved through a geochemical interpretation of the results obtained from analyses of sediment solid phase samples and pore water samples. Factors affecting the metal mobilities were identified by investigating the statistical relationships between calculated partition coefficients (Kp) and the characteristics of the sediment solid and aqueous phases.
  • Thumbnail Image
    Item
    Open Access
    A geochemical investigation of the waters and sediments of De Hoop Vlei, Bredasdorp district, South Africa
    (1997) Lanz, Johann; Willis, James; Fey, Martin V
    De Hoop Vlei is a saline coastal lake situated 53 kilometres north-east of Cape Agulhas in the Western Cape Province of South Africa. It is probably of estuarine origin but is now separated from the sea by mobile sand dunes and, therefore, has no surface outflow. Inflow to the vlei is from a catchment area of approximately 1200 km2 in which intensive grain farming is practised. The vlei is situated within the De. Hoop Nature Reserve and its ecological value, particularly as a breeding ground for water birds, has been recognised in its designation as an international RAMSAR conservation site. Agricultural practices in the catchment have been identified as a potential threat to the ecology of the vlei. The overall objective of this study was to provide a geochemical characterisation of De Hoop Vlei. It focused on identifying the geochemical factors and processes which control the water chemistry of the vlei and attempted to identify any influence of agricultural activities on water quality. This was achieved through a geochemical interpretation of the results obtained from analyses of water and sediment samples collected during the study. Use was also made of Department of Water Affairs and Forestry monitoring data in order to examine long term behaviour of the system, particularly with respect to the effect of evaporative concentration on water composition. Furthermore, chemical equilibrium was modelled, using the geochemical model MINTEQA2, in order to give an indication of processes likely to occur in the water as well as the behaviour of certain possible pollutants in the vlei. Water and sediment core samples, collected during two separate sampling trips, were taken along the entire length of the vlei and some water samples were taken in the catchment. Interstitial waters were obtained by suction from sediment cores. Samples of secondary precipitates, found along the edge of the vlei, were also taken. The following laboratory analyses were performed on water samples: pH, EC, alkalinity, major cations and anions, dissolved P, fluoride, and the trace metals Fe, Mn, Al, Ni, Cu, Zn, and Pb. The following laboratory analyses were performed on sediment samples: pH of wet and dried sediments, organic C content, carbonate content, total elemental concentrations of major and trace elements, mineralogy, clay percentage and extractable P, Zn and K. Scanning electron microscopy and mineralogical analyses were performed on samples of secondary precipitates.
  • Thumbnail Image
    Item
    Open Access
    Geochemical study of soil salinity in a toposequence near Riebeeck West, South Africa
    (2005) Folefoc, Asongbecap Daniel; Smith, Meris; Fey, Martin V
    A geochemical investigation of salt distribution in soils of the semi-arid of Western Cape, South Africa, was carried out following a pilot study which revealed widespread soil salinity in the Berg River catchment. The present study looks at the distribution of the salts along a toposequence in a subcatchment of the Berg River underlain by Malmesbury Group shale. The objectives were: to investigate salt distribution in relation to landscape topography; to identify potentially harmful trace elements associated with the salinity; and to determine the processes responsible for salt distribution. Ten soil profiles were dug to a depth of 200 cm at points along a slope of angle 10.20 along and 367 m long. The profiles at the crest of the toposequence are underlain by silcrete and alluvium while Malmesbury shale parent material underlies the rest of the profiles. Contour drains disrupt the natural shape of the slope. The soil texture is loamy sand to clay loam at the crest and loamy to sandy-clay loam in the midslope. Mineralogy at the crest is quartz dominated and kaolinite occurs in the mid and lower slope.
  • Thumbnail Image
    Item
    Open Access
    Geochemistry of ferruginous clogging of Karoo wells
    (2000) Miller, Sarah Jane; Willis, James; Fey, Martin V
    The main source of potable water in the Karoo is groundwater and thus any problems resulting from the abstraction of water or from diffifulties in abstractions of water are important. The iron clogging of screens, pumps and filter packs in supply wells is a worldwide problem and the consequences can be severe, leading to costly and harsh rehabilitation measures or even loss of the well. A study was undertaken in order to determine the chemistry and morphology of the precipitates found in relation to the water chemistry, in several wells in the Albertinia-Oudtshoorn-Calitzdorp area of South Africa.
  • Thumbnail Image
    Item
    Open Access
    Geochemistry of the fynbos ecosystem in a Table Mountain Group sub catchment of the Olifants River, Western Cape, South Africa
    (2003) Soderberg, Keir
    This study gives a first-order estimation of the chemical composition of the recharge, discharge, and ground waters, along with the bedrock, soil, and vegetation of the Olifants River Valley around Citrusdal. The valley occurs in a synclinal fold with the main aquifers, the Table Mountain Group (MG) sandstones of the Peninsula Formation and the Nardouw Subgroup, folded beneath the central valley.
  • Thumbnail Image
    Item
    Open Access
    Groundwater redox conditions at a petroleum contaminated site, Kuils River, South Africa : pathways for BTEX biodegradation
    (2003) Merrett, Greg Lee; Roychoudhury, Alakendra N
    A shallow sandy aquifer, contaminated by petrol from an underground storage tank, was studied to determine if intrinsic bioremediation of the hydrocarbons is taking place. Groundwater samples taken from 32 monitoring wells were analysed for NO₃-,NH₄+, Mn²+, Fe²+, SO₄²-, and ΣH₂S. Portable electrodes were used to make field measurements of electrical conductivity, redox potential, and pH. The variation and distribution of these redox-sensitive groundwater constituents show that bioremediation via NO₃- reduction, Fe³+ reduction, and SO₄²- reduction (and possibly methanogenesis in the most reduced part of the plume) is occurring. In some cases redox processes are taking place simultaneously resulting in redox zones that overlap. Iron and sulphate reduction are the dominant processes taking place.
  • Thumbnail Image
    Item
    Open Access
    Impact of pine plantations on the form and mobility of nitrogen in soils of the eastern escarpment region of South Africa
    (2000) Echeverría, Marietta Elena; Willis, James; Fey, Martin V
    Recent research in the eastern escarpment area of South Africa has documented enhanced NO₃- concentrations in soil solution and stream water resulting from afforestation. There has been much research in the Northern Hemisphere regarding the qualitative and quantitative causes and consequences of N saturation in forest ecosystems. In order to assess the significance of local observations of afforestation-induced NO₃- enhancement in a global context, a study was conducted to evaluate the influence of forest plantations (Pinus spp.) on N form and mobility in soils in the eastern escarpment area of South Africa. Twenty soil samples were taken, half in grassland and half in forest, in the Graskop and Kaapsehoop areas of the eastern escarpment. Forest samples were taken as composites of approximately five individual samples in each stand from the top 20-25 em of soil, combining partially decomposed organic litter layer with the subjacent upper mineral soil horizon. Grassland samples were taken, again as composites, consisting of the upper mineral soil horizon (an organic litter layer was for the most part absent). Approximately three-quarters of each sample was air-dried, and crushed to pass through a 2-mm sieve and stored for analysis. The remaining quarter of each sample was passed through a 2-mm sieve and refrigerated at about 4°C in order to maintain field-moist conditions and to inhibit microbial transfornlations. Refrigerated samples were used for KCI-extractable NO₃- and NH₄+ analyses and N mineralisation experiments. The remaining analyses were performed on the air-dried samples. This study included two facets: physical and chemical characterisation of soil samples; and a series of laboratory experiments. The solid phase of the soils was analysed for organic carbon, total nitrogen and particle size distribution. The soil solution was investigated by making saturated paste extracts which were analysed for major ions, trace elements, electrical conductivity (EC) and pH. Extractable base cations, acidity and inorganic nitrogen (NH₄+ and NO₃-) were also analysed after extraction with NH₄OAc or KCl solutions. The laboratory experiments, intended to investigate the apparent differences in soil N transformations and mobility resulting from vegetation, consisted of both aerobic and anaerobic incubation to assess N mineralisation, a NO₃- sorption experiment and a soil to extract ratio dilution experiment.