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.

Includes bibliographical references. / The precipitation of iron from aquifer water in boreholes is a problem in the Klein Karoo region of South Africa. The precipitation causes boreholes to clog and limits full use of well fields in the area. The iron is naturally occurring and this project sets out to identify the lithological source of the iron and in what form the iron is presented. The Table Mountain Group (TMG) aquifer is a fractured rock aquifer situated in the TMG and rock samples were taken from the various lithologies in the area.

Includes bibliographical references (leaves 99-105). / Trace elements have received increased attention since the mid-1900's. Although some studies have investigated trace element accumulation as a result of urban expansion in the Western Cape, South Africa, few have catalogued the accumulation and behavior of trace elements resulting from agricultural practices. This study investigates the distribution and behavior of trace elements for the Olifants and Berg river catchments by focusing on the sediments of the estuaries. The dominant industry in both catchments is agriculture and there exists relatively little urban sprawl. Two sediment samples taken from the offshore mud belt in the vicinity of the two river mouths were also analyzed. The sediments were analyzed for trace elements using inductively coupled plasma mass spectrometry (ICP-MS), major elements using X-ray fluorescent spectroscopy (XRF), total sulfur using XRF, total and organic carbon using a C:H:N analyzer, and grain size analysis was performed (>62 μm, 38-63 μm, 2-38 μm, <2μm). The mud belt cores were dated using 14C dating. Estuarine surface waters were analyzed for trace elements, pH, dissolved oxygen (DO), electrical conductivity (EC), and temperature. The trace elements arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) were focused on. The trace element concentrations in the sediments were compared with those of soils that occur in the study area, as well as their parent materials, to determine background concentrations. The concentration profiles of elements with respect to depth are compared with natural deposition rates to recognize signs of recent enrichment of individual trace elements. Inter-element comparisons are made in an attempt to determine speciation. Comparison between the estuarine and mud belt sediments were made to assess the estuaries ability to filter fluvial trace elements, as well as to determine the sediment contributions of the Olifants and Berg rivers to the mud belt. Statistical analysis was performed to"group sediment populations Trace element and organic matter concentrations showed strong positive correlations with fine-sized particles. The mud belt sediments displayed considerably more OC than the estuarine sediments. The trace elements appear to associate predominantly with clay minerals (alumino-silicates), Fe/Mn oxides, and organic matter. Trace element correlations with S and carbonate carbon were also observed. Comparison with estimates of natural deposition rates and compositions of soils occurring in the catchments did not suggest an anthropogenic pollution input. From the data available the estuarine and Mud Belt sediments appear enriched in Cd, Cu and Zn in comparison to the background soils. The estuaries seem to effectively trap Zn and Pb, but do not capture As well. Statistical analysis suggest that, of the rock types considered, the sediments of the Olifants and Berg river estuaries and those of the off shore mud belt are most similar to sediments derived from the Malmesbury and Ecca Groups. The Olifants and Berg rivers are important sources of water for the farming community, as well as for municipal use in the Western Cape. Based on this investigation of the estuarine waters and sediments the rivers appear to be in good health in regards to trace element concentrations.

Includes bibliographical references. / 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.

Bibliography: leaves 84-91. / 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.

Bibliography: leaves 183-189. / 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.

Summary in English. / Includes bibliographical references. / 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.

Bibliography: pages 123-137. / 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.

Bibliography: leaves 57-62. / 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.

Includes bibliography. / 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.