OpenUCT :: Browsing by Author "Fey, Martin V"

Browsing by Author "Fey, Martin V"

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Open Access
The amendment of acid soil with an ettringitic waste and its effects on plant growth
(1995) Tomlinson, Ian Rory; Fey, Martin V; Willis, James
Associated with ESKOM's ash water beneficiation programme is the precipitation of an ettringitic waste from highly alkaline, saline water. The waste is dominated by ettringite (CauAJ4(OH)24(S04) 6.52H20) with calcite (CaC03) as a minor phase (17.7% for the sample used in this study). Apart from the presence of calcite, the ettringite itself is alkaline due to the presence of OH ions. Following a submission that the waste had potential as an ameliorant of acid soil, research into this possibility was initiated. Following the determination of a calcium carbonate equivalent (HCl-CCE) value of 78% using the HCl back titration method of Horwitz (1980), an incubation experiment was initiated using three acid soils of contrasting characteristics: a so-called Silvermine sand, Kranskop A and Kranskop B soils. The effects on soil acidity of ettringitic waste were compared with analytical grade calcite. Soils (50g samples) were incubated with the two alkaline amendments for two weeks, following which pH(KCl), pH(H20) and KCl-extractable acidity were determined. Ettringitic waste led to apparently lower levels of acidity neutralization for corresponding treatments set on an HCl-CCE basis. This difference was minimized with the highly buffered, sesquioxide and organic-rich Kranskop A soil which could be attributed to the greater reactivity of the ettringitic waste with organically-complexed acidity together with the "self-liming" effect of so4 in sesquioxide-rich soils (sensu Reeve & Sumner, 1972). The waste showed progressively less neutralization with Kranskop B and Silvermine soils apparently in response to a decline in buffering capacity of these soils.
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.
Open Access
Assessment of long-term air pollution impacts on soil properties in the vicinity of Arnot power station on the South African highveld
(1997) Van Tienhoven, Anne Mieke; Fey, Martin V; Willis, James
Atmospheric pollution on the South African high veld is perceived as a concern because of the combination of heavy industry and climatic features that prevail in the region. The frequent occurrence of surface inversions (80 - 90 % of days in the winter months), permits the accumulation of pollutants near ground level. Although industrial stacks, and those of power stations in particular, are generally able to emit gaseous and particulate pollutants above the boundary layer, looping and fumigation of plumes may occur under convective conditions. Under such circumstances, the concentration of pollutants at ground level may be high, especially within 4 km of the stack. Since considerable damage to European and North American ecosystems has occurred as a result of atmospheric pollution, concerns were first raised in a report by Tyson, Kruger and Louw in 1988, that similar effects may be taking place on the eastern highveld region of South Africa. The current study was prompted in direct response to these concerns. The first major objective was to establish long-term monitoring sites whereby changes in the pedosphere in response to atmospheric inputs could be detected. The second objective was to characterise the soil collection and to determine whether any impacts are detectable at this early stage. Arnot power station was selected as the focal point of the study as it is a base-load power station, is the most distant from the industrial centres of Witbank, Middelburg and Gauteng and has been in operation for over twenty years. Fifteen sampling sites located in an arc ranging ENE to SE downwind of the power station were selected. Both topsoil and subsoil were sampled at each site. Details of geographical co-ordinates and site features were noted to enable reproducible resampling. Sampling took place in August 1996, but three sites were visited again in October and resampled to test the reproducibility of sampling. Although not statistically comparable, the soils of each site showed similar results for key analyses, which included EC, pH, organic carbon and acid neutralising capacity.
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.
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.
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.
Open Access
The effect of industrial practices on stream sediments, and the impact of these sediments on the geochemistry of a wetland
(1997) Lake, James Andrew; Willis, James; Fey, Martin V
The objective of this study was to characterise the impact that a major industrial operation, situated at Somerset West and involved in the manufacturing of a diverse range of chemicals, has had on the sediments of the drainage system that drains the site on which these activities occur. Furthermore, the impact of these sediments on the geochemistry of a wetland, Wagenveldt vlei, situated downstream of the complex, has been investigated. Sediment cores and water samples were collected at a number of locations down the length of the drain . The water samples were analysed to determine which constituents were present in solution. The cores were separated into a top and bottom layer which were analysed separately to determine their geochemical composition. In some instances a lack of time resulted in some of the analyses being performed on only a select number of samples. An experiment was performed on the sediments collected from the bottom layer to determine what would happen if the sediments became oxic and the sulphides and organic matter in the sediments were oxidised.
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.
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.
Open Access
A geochemical investigation of the aquatic sediments, groundwater and surface water of the Verlorenvlei coastal lake, with special reference to nitrate transformations
(1995) Harck, Terry Richard; Willis, James P; Fey, Martin V
The incorporation of nitrogen in living cells gives rise to cycling between atmospheric, inorganic and organic forms of nitrogen. Nitrogen cycling is largely controlled by microbial respiration and metabolism. In aquatic systems, N-cycling occurs dominantly in sediments. Removal of nitrogen from aquatic sediments occurs through the successive Ntransformation processes of mineralisation (organic N -> NH4+), nitrification (NH4+ -> NO3-) and denitrification (NO3- -> N2). Denitrification, mineralisation and also immobilisation of inorganic N (NO3-, NH4+ ) to organic N occur under reducing conditions. Build-up of the nitrate (NO3- ) concentration in groundwater is a widely-recognised phenomenon. Groundwater nitrate may contribute significantly to the N input to aquatic bodies that receive groundwater flow. The Verlorenvlei coastal lake on the arid south-west coast of South Africa is an important ecological habitat and also a valuable agricultural water resource. Analyses conducted in this study indicate that the groundwater, which flows towards the lake, has a significantly higher NO3- concentration than the lake water. The difference in NO3- concentration is due to: 1. Dilution of groundwater by a larger quantity of low-nitrate water in the lake, and/or, 2. Removal of nitrate from groundwater through microbial processes in the lake sediments. Insufficient information is available concerning the magnitude of groundwater flow into the lake to investigate the importance of option 1. Experiments were conducted on two lake sediments (high organic content and low organic content) to determine the relevance of option 2. Sediment subsamples were incubated under reducing conditions and amended with 25mg/l and 100mg/l NaNO3-N solutions with and without the addition of 40mg/l glucose and with and without irradiation. After 10 days incubation, a period chosen to simulate the residence time of groundwater in the sediments, the added NO3- had all been removed through denitrification or immobilised as organic N. The exact removal pathway could not be determined. The high organic content sediment was found to remove nitrate more efficiently. It was concluded that the decrease in nitrate concentration as high-nitrate groundwater flows into the Verlorenvlei lake can probably be ascribed to denitrification or immobilisation processes under reducing conditions in the sediment lining of the lake.
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.
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.
Open Access
A geochemical investigation of the water and sediments of Barber's Pan, North West Province
(1996) Knesl, Oliver; Willis, James P; Fey, Martin V
Pans comprise a large proportion of southern African wetlands and yet remain poorly classified. Very little data is available on the aqueous chemistry of southern African saline systems, and with the exception of a few publications dealing, in part, with the soil and associated materials of pan floors and margins, soil and sediment information on pans is similarly limited. Barber's Pan is a shallow, alkaline lake situated in the North West Province of South Africa. It is a unique system in several respects, but is considered most valuable from the aspect of bird conservation, since it is perennial in an area characterized by shallow, seasonally filled pans. Its perennial state is the consequence of anthropogenic intervention in the early part of this century which resulted in the diversion of the Harts River back along its fossil course. The biogeographical importance of Barber's Pan is emphasised by its designation as the only RAMSAR site in the North West Province. The overall objective of this study was to provide a geochemical characterization of Barber's Pan. This was approached by reviewing pertinent literature on the origin and geochemical characteristics of pans and saline lakes through an investigation of the water and sediments of Barber's Pan. The study focused on four aspects of the pan geochemistry, namely: the levels of certain nutrients and potential pollutants in the pan; gaining an understanding of the dynamics of phosphorus, as well as other nutrients, in the pan; geochemically characterizing the sediments; and investigating the impact of evaporative concentration of the pan water on the overall geochemistry of the system. Comparative investigations were carried out on the sediments of the Harts River diversion and Leeupan, a neighbouring, actively deflational, ephemeral pan.
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.
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.
Open Access
Geochemistry and amelioration of a sulphur contaminated environment near Somerset West, South Africa
(2000) Mc Keown, Stephen; Fey, Martin V; Willis, James
The key objectives of this study are, firstly, to determine the extent and effects of the S contamination and secondly, to determine an effective means of ameliorating the site.
Open Access
The geochemistry and phosphorus sorption characteristics of Mgeni catchment sediments
(1995) Hounsome, Robin Simon; Fey, Martin V
The Mgeni River is vital for the continued industrial and social development of Durban and Pietermaritzburg and the river has been impounded in four places to provide a crucial water resource to these areas. The river is highly susceptible to anthropogenic pollution, particularly phosphorus, which may be derived from unsanitised peri-urban areas or run-off from fertilised agricultural lands. Sediments may be sources or sinks of pollution in aquatic systems. Grab samples of the uppermost sediment layer were taken from sites at each of the impoundments and analysed for salient geochemical characteristics, such as major and trace element concentrations, clay mineralogy, organic carbon, P fractionation, and particle size distribution. Batch experiments were also carried out to determine the P sorption desorption characteristics of the sediments under different pH and redox conditions. The sediments are dominated by clay sized material (< 2mm) which is composed of kaolinite, gibbsite, goethite, mica and other undifferentiated· 2: 1 layer silicates and quartz. Kaolinite, gibbsite and goethite are found extensively throughout the catchment area and are the result of intense weathering. These minerals readily sorb cations onto their surfaces. The significant correlations which were found between the clay content and the concentration of trace metals, particularly Mo, Pb, and Zn, most likely result from accumulations of cations on the mineral surfaces. It was suggested, therefore, that the Mgeni sediments are potential sinks for polluting elements.
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.
Open Access
The geohydrology of the Swartkops River Basin : Uitenhage Region, Eastern Cape
(1996) Maclear, Limont Gordon Alexander; Willis, James P; Fey, Martin V
A hydrocensus of all groundwater users in the Swartkops River Basin was conducted in 1992 and 1993 to assess the occurrence and quality of groundwater in the Basin, as well as the characteristics of the various aquifers in the Basin. The extent of pollution of the groundwater reserves was noted. This specialist study was carried out to assist the Department of Water Affairs and Forestry in formulating a water quality management plan for the river basin, and was prompted by concern regarding the deteriorating water quality of the region. It was determined that the only aquifer in the river basin which was severely polluted in places was the Swartkops River Alluvial Aquifer. Following recommendations arising from the initial survey, a groundwater monitoring network of shallow boreholes was installed in the alluvial aquifer in 1994 and groundwater sampling runs commenced in 1995. Groundwater occurs in the region in a shallow alluvial aquifer and a deeper fractured secondary aquifer. These aquifers are separated from one another by an impermeable, confining layer of Cretaceous sediments in the central and eastern parts of the study area, causing artesian conditions in places. The groundwater of the aquifers in the study area has a sodium-chloride character of low salinity in the western high-lying portion of the study area, with mineralisation increasing eastward, as aquifer lithology and distance from recharge sources change. The hydrochemical character of the groundwater is a function of the proximity of the basin to the sea, as well as connate conditions existing in the sediments of marine origin. It is shown that pollution of both the surface and shallow sub-surface water bodies is occurring, mainly in the industrial and residential areas of Uitenhage and Despatch. These polluted zones are not extensive when compared with the whole catchment area but have a definite effect on local conditions. Estimations of pollution load volumes are made based on hydraulic parameters derived from aquifer tests. This study represents an overview of the geohydrology of the Swartkops River Basin, thereby providing a reference tool for water-resource management purposes in the region. It includes a unique study on the geohydrology of the Swartkops River Alluvial Aquifer and the extent of pollution of this aquifer, as well as a detailed account and discussion on the historical and present factors affecting variations in groundwater flow and artesian conditions in the area. A summary of suggested aquifer management practices is given to ensure the long-term sustainability of the groundwater resources of the river basin.
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.