OpenUCT :: Browsing by Author "Willis, James"

Browsing by Author "Willis, James"

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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
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
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
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.
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
Effects of waste disposal on soil and water chemistry at an industrial complex near Somerset West, South Africa
(1997) Doel, Sean Laurens; Willis, James; Fey, Martin
The estimated total annual production of waste in South Africa is 318 million metric tons. Of this waste, 3.8%, approximately 12 million metric tons, arises from the chemical manufacturing industry. Although increasing attention is being given to methods of land treatment for waste disposal waste is still disposed of by dumping/stockpiling. This study focuses on the effects of such waste disposal on soil and water chemistry at an industrial complex near Somerset West, South Africa. Since 1903 a multitude of industrial activities have occurred on the site including manufacture of explosives, chemicals, fertilizers and vinyl coated products: Decommissioning of the industrial complex is presently in progress. The overall objective of this study was to conduct an investigation of the water and soils in an area termed the Dead Tree Area. The area was considered of particular interest due to the presence of a sulphur stockpile, gypsum waste dumps and fertilizer wastewater evaporation site located immediately adjacent to the area. Four key objectives were addressed in the study, namely: (i) to chemically characterise the water and soils in the Dead Tree Area, (ii) to assess the degree of contamination of the water and soils in the area, (iii) to question whether tree mortality in the area could have resulted from toxicy or deficiency effects, and (iv) to determine the potential of gypsum application as a means of remediating dispersed, sodic soils.
Open Access
Factors influencing the mobility of uranium, thorium and rare earth elements at the Steenkampskraal monazite, North Western Cape
(1997) Glendinning, John Edward; Willis, James
It is well known that the release of long-lived radionuclides to the water path is probably the most relevant radiological risk originating from an underground repository. Transuranic elements (ie. all elements with an atomic number greater than 92 (U)) do not have any non-radioactive isotopes and are very rare in natural materials. The long term geochemical behaviour of these elements must thus be derived from chemical analogues such as the rare earth elements (REE), Th and U. Steenkampskraal monazite mine, situated 350 km north of Cape Town, has been found to be an excellent locality for the study of these elements, due to the high concentration of these elements in the ore as well as the ideal geology, which consists of low permeability rocks with groundwater flow governed by fractures. The ore body consists of a monazite [(REE, Th, U)P04], apatite [Ca₃P0₄)₂], chalcopyrite [CuFeS] and magnetite [FeP₄] veindeposit. Water was sampled from six boreholes in the vicinity of the mine and five wi.ndpumps on the surrounding farm Nabeep and Brandewynskraal. Surface water samples were taken from the slimes dam, an ephemeral stream on the western side of the mine, as well as from the surface of a road shortly after rain, below the tailings. Four water samples were taken from within the underground mine workings (Mainshaft, Main shaft extension, Sump on level 3 and Inclined shaft). Colloids were sampled from three of the boreholes and a precipitate was taken from the surface of the main shaft water. Soils were sampled along two transects away from the mine on the eastern and western side of the ore body. Due to the topography of the area, surface contamination could only occur on these two sides. Stable isotopes of oxygen (8 180) and hydrogen ((8 180) indicated the presence of two distinct groups of waters within the vicinity of the mine. One group is composed of unevaporated waters and includes all borehole sand the water sampled in the inclined shaft. The water moving through the inclined shaft is in contact with the ground water. A second group of highly evaporated waters was present in the slin1es dam samples as well as the underground water samples not directly in contact with groundwater. Groundwater contamination by REE-bearing phosphate minerals has resulted in measurable concentrations of U, Th and REE in all mine waters and boreholes in the near vicinity of the mine. The chondritenormalized REE patterns of the water samples are sin1ilar to those displayed by monazite, with a distinctive Eu depletion and an obvious enrichment in LREE with respect to HREE. Monazite-normalized REE patterns for the selected borehole waters show a marked fractionation between LREE and HREE, with the HREE strongly enriched in the aqueous phase. Heavy REE have been shown to have a greater tendency for complexatioi1 and a greater affinity for mineral surfaces. In the present study, the three boreholes in which colloids were found had high concentrations of U, Th and REE. It is likely that colloidal transport of these elements is the dominant mechanism of transport.
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 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 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
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
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
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.
Open Access
An investigation into the use of smectitic clay soil for the containment and treatment of petrochemical waste
(1996) Huntsman, Philippa Rose; Fey, Martin V; Willis, James
The manufacture, transport, use and disposal of organic chemicals may result in the release of significant quantities of organic substances into soil, from which they are subject to possible transport into underlying groundwater. Many of these organic chemicals are potentially toxic (Wilson et al., 1981). Information is required concerning the chemical and physical behaviour of organic chemicals in the soil environment in order to implement measures that will protect groundwater but also permit reasonable usage of soil for waste containment. This study deals with the interactions of a smectitic clay soil of the Rensburg form and two petrochemical wastes, which were sampled from storage dams, adjacent to a petrochemical plant at Secunda, South Africa. There is growing interest at the plant in utilizing soil for cost-effective waste containment and treatment. The objectives of this study were twofold: firstly, to determine the permeability of the Rensburg soil with respect to the two waste liquids (BPlO- aqueous and phenolic, and BP2- non-aqueous); and, secondly, to investigate the sorptive capacity of the clay fraction of the soil for two common groundwater contaminants, benzene and phenol, in the context of the potential for using treated clays for decontaminating BP10 and other organic wastes. The Rensburg soil was compared with a commercial bentonite for containing and treating petrochemical waste.
Open Access
Land treatment of grape-processing effluents near Robertson, Western Cape
(2000) Papini, AG; Fey, Martin V; Willis, James
Land treatment is the predominant disposal method of effluents generated by distilling, wine making and grape juice production in the Western Cape. Primary settling and treatment in aerobic and anaerobic lagoons typically precede disposal to land. Land treatment can effectively remove COD and also benefit the soil by increasing organic matter, cation exchange capacity and moisture retention capacity. Adverse effects can include salinisation of soils and groundwater, soil structural degradation and odours generated by anaerobic conditions.
Open Access
Mineralogy and geochemistry of the carbonaceous mudstones and coal petrogenesis of the Grootgeluk formation in the Waterberg coalfield, South Africa
(1993) Faure, Kevin; Willis, James
The Grootegeluk Formation in the Waterberg Coalfield consists of coal and mudstone layers that were deposited during the Late Permian. In the south-central part of the Waterberg Basin rapid subsidence resulted in the formation of strata (-70 m thick) which consist of relatively thin coal beds interbedded with a multitude of mudstone and carbonaceous mudstone layers. Mudstones from the Grootegeluk Formation, the underlying upper Vryheid Formation and the base of the overlying Beaufort Group were obtained predominantly from borehole cores. The thesis integrates thin-section petrography, mineralogy, maceral composition, maximum vitrinite reflectivity and geochemical analyses to investigate: (1) the source of the sediments and the palaeo-environment of formation of the coal and mudstone layers; (2) the stratigraphical correlations of some South African coal formations and the formation of coal, on a continental scale, during the Late Permian and Triassic times; (3) the possibility of contamination to the environment by the waste products of coal-mining ( carbonaceous mudstones) and coal-burning in a local power-station (fly ash and bottom ash). The lower portion of the Grootegeluk Formation is dominated by kaolinite, quartz and minor amounts of anatase, and the upper parts of by quartz, kaolinite and minor amounts of montmorillonite-illite and microcline. These minerals are predominantly allogenic. Mineralogical evidence from the mudstones suggests that the base of the Grootegeluk Formation was relatively more distal and the upper portions more proximal to the source of the sediments. The maceral variation of the coal seams and the organic matter in the mudstones reveal that conditions for the preservation of organic matter were more suitable during the deposition of the sediments in the upper (vitrinite-rich) rather than the lower (inertinite-rich) Grootegeluk Formation. At the base of the Grootegeluk Formation a 2 m thick carbo-tonstein occurs that is dominated by kaolinite, organic matter (-40 weight %), siderite, calcite and minor proportions of apatite. The carbo- tonstein has mineralogical, maceral and chemical characteristics distinctive from the other mudstones. Syn-depositional calcite lenses occur predominantly in the upper-half of the Grootegeluk Formation. Early diagenetic globular pyrite and spherulitic siderite occur in the coals and organic rich-mudstones of the Grootegeluk Formation. Globular pyrite and granular siderite are present predominantly in the organic-poor mudstones of the Grootegeluk Formation and Beaufort Group. Marcasite sometimes occurs along bedding planes and calcite is generally present as deat-filling in the coal seams. Based on their geochemistry, the Grootegeluk Formation and Beaufort Group mudstones have the same provenance, dominantly "granitic", possibly granodioritic in composition (Late Proterozoic Sm-Nd model ages). The provenance of the Vryheid Formation was relatively more mafic (Early Proterozoic Sm-Nd model ages). Smooth, systematic changes in the mineralogy and major element chemistry make major element whole-rod chemistry an ideal stratigraphic-indicator tool for the Grootegeluk Formation. The mudstones had very low concentrations of the alkali and alkaline-earth elements suggesting that the rocks had undergone very high degrees of chemical alteration. Trace elements in the carbonaceous mudstones are predominantly hosted in the mineral fraction. The carbo-tonstein had anomalously high concentrations of all the trace elements except S, Co, As and Zn, which, in addition to its mineralogical character, make the carbo-tonstein an important ( chrono-) stratigraphic marker for local and intra-basinal correlation. Anomalous concentrations of the chalcophile elements in the mudstones from the overlying lower Beaufort Group mudstones are considered to have been concentrated as a result of diagenesis and(or) reduction-oxidation reactions. The concentrations of trace elements and stable isotope data suggest that the sediments were deposited in fresh rather than in marine waters. Evidence from organic 13 C analyses and palynological studies indicates that ~ 13 C values can be used in stratigraphical correlations and as palaeo-ecological indicators. The ~ 13 C values of the Permian and Triassic terrestrial organic matter suggest a change in the atmospheric 13 C/1 2 C ratio during this time. Leachable concentrations of trace elements which may be toxic to plants, animals or humans are too low in coal mining discards to be of any concern. Mudstones that immediately overlie the Grootegeluk Formation coal-mudstones have leachable concentrations of elements that exceed the critical concentrations believed to be harmful to the environment. Experiments on fly ash and bottom ash samples from the Matimba power station revealed that the fly ash had unacceptably high concentrations of leachable elements, such as As, Cd and Mo. Leachates of bottom ash samples had very low concentrations of potentially harmful elements.
Open Access
Nutrient deficiencies in soils of the Mseleni area, Kwazulu-Natal
(1996) Pooley, Justin John; Willis, James
This study constitutes a baseline epidemiological investigation into the nutrient status of soils in the Mseleni district of Kwazulu Natal, where nutrient deficiencies have been implicated in the etiology of an endemic disease. Mseleni Joint Disease (MJD) is a crippling, osteo-arthritic condition which afflicts an unusually high proportion of the inhabitants of this district. Home-grown produce and indigenous plants, which form the basis of the local diet, may be nutritionally inadequate due to soil-related nutrient deficiencies. In spite of this, and the fact that epidemiological studies have been successfully utilized to elucidate the etiology of similar diseases elsewhere, studies to date have not included soil chemical investigations. The main purpose of this study was to assess the nutrient status of soils in the area by means of both chemical analyses and plant growth trials. Water samples were also examined, especially in relation to fluoride levels.
Open Access
Pb and Zn contamination in Zoar Vlei, Cape Peninsula
(1995) Reid, Caroline Emma; Fey, Martin V; Willis, James
The sediments in Zoar Vlei act as a considerable sink for Pb and Zn derived from the adjacent Paarden-Eiland semi-industrial area and the Milnenon-Rugby residential area. Through elemental analysis of 34 sediment samples by WDXRF spectroscopy, the sediments were shown to be significantly enriched in Pb and Zn.Lead and Zn concentrations are highest at the entrance to the southern pan, and decrease nonhwards through the vlei system. Kaolinite, quanz, illite and smectite are present in the clay fraction of the sediment, as was shown by analysis of a clay separate by XRD. The results of the sorption experiments revealed that both Pb and Zn are sorbed by the sediments. The selective affinity of the sediments for Pb exceeds that for Zn, as Pb sorption was shown to displace Zn from (he sediment while Zn sorption did not induce Pb release. The high degree of irreversibility of both Pb and Zn sorption indicates that sorption is specific in nature, and that under the present environmental conditions, the sediments act as a suitable storage facility for these metals. Acidification of the vlei water in equilibrium with the sediments caused Zn release through neutralisation reactions. Total water analyses were performed on 72 vlei water samples using high performance ion liquid chromatography and ICP-AES. Zinc concentrations in the vlei were elevated compared to natural background values, and decrease in a northerly direction through the vlei system, however remain elevated at the outflow into the Milnerton Lagoon. Zinc appears to be entering the vlei via storm water drains from both the industrial and residential areas.

Browsing by Author "Willis, James"

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