Includes bibliographical references (leaves 84-88). / 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.

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.

Includes bibliographical references. / The term atmospheric haze is a condition of reduced visibility, caused by the presence of fine particulate matter in the atmosphere, which can originate from natural or anthropogenic sources. The "Brown Haze" is a phenomenon that is associated with Cape Town and can be described as brown coloured smog. It occurs over the winter months, mainly May to September, due to the strong temperature inversions and windless conditions that can occur during these months. These conditions lead to the build-up of pollutants emitted into the atmosphere. The Cape Town Brown Haze Phase Two study was used to obtain a detailed analysis of the atmosphere in a programme of lateral and vertical profiles through the Brown Haze. The field campaign took place from the 29th July 2003 to the 26th August 2003 around the Cape Town metropolitan region.

Includes bibliographical references. / 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.

Summary in English. / Bibliography: leaves 70-75. / Recent research on the platinum-group elements (PGE) has shown increased concentrations in environmental samples, probably as a result of the widespread use of PGE (Pt, Pd and Rh in particular) as catalysts in the chemical and car industry. Most of the recent research on PGE focuses on the analysis of concentrations in environmental samples exposed to anthropogenic sources of PGE, but there are very few studies that have investigated sorption behaviour of PGE in soils.

Includes bibliographical references. / Large quantities of water are available in the Cape Flats sandy aquifer in the Western Cape. Local industrial, agricultural, domestic and urban development activities are known to be potential polluters of this water through infiltration of wastewater, because of the unconfined nature of the aquifer. In order to determine the potential of the water in the aquifer, fifteen water samples from the Cape Flats were analysed and geochemically assessed prior to their qualify being evaluated in terms of future use in domestic, irrigation and industrial activities.

No description available.

No description available.

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.

Bibliography: pages 135-145. / 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.