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Total microbial quality assessment and geographical information system were used for evaluating the quality of water and the spatial distribution of diarrhoea cases in Tshikuwi, a rural community in South Africa, during an outbreak of diarrhoea. The water-abstraction points included two groundwater storage tanks, namely Tank 1 and Tank 2 and the Khandanama river. Indicator microbial counts for total coliforms, faecal coliforms, enterococci, and heterotrophic bacteria exceeded the limit for no risk as stipulated by the South African water-quality guidelines for domestic use for Tank 1 and the Khandanama river. Vibrio, Salmonella, and Shigella species were prevalent in the Khandanama river. The spatial distribution of diarrhoea cases showed a hot-spot of diarrhoea cases close to Tank 1 and the Khandanama river. Results of chi-square analysis showed that the proportion of infection from each water source was different or that infection depends on the type of water source (α=0.05). The demonstrated spatial clustering of diarrhoea cases might have been influenced by the poor microbial quality of water used from Tank 1 and the Khandanama river. The results further highlight the urgent need of water-treatment facilities and monitoring of water quality in rural communities of South Africa.

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Adsorption of dissolved phosphate onto synthetic hydrous ferric oxide (HFO) was measured in the laboratory as a function of pH, ionic strength, and phosphate relative concentration. Experimental data were used to constrain optimal values of surface complexation reactions using a geochemical modeling code JCHESS according to the diffuse layer model. The results provide a consistent set of model equilibrium constant (log K) values at 25° C and 100 KPa for the following reactions: These results differ significantly from previously-published estimates of log K 2 int and log K 3 int [1][2][3], and provide a more accurate fit to experimental measurements over a broad range of pH (3-12), ionic strength (0.001-0.1 mol/ℓ) and total relative phosphate concentration (12-500 µmol phosphate/g HFO). The results provide a close fit to the experimental data within a wide range of conditions, and should be adopted in modelling the chemical speciation of phosphate in natural systems containing HFO as a predominant adsorbing material.

Diffusive gradient in thin-films (DGT) technology was used to monitor bio-available metals and the tool was developed for risk-based pollution assessment and liability apportionment in the Witwatersrand Goldfields, South Africa, where there is widespread mine-related pollution. DGT technology is a passive sampling technique whereby metal species are selectively diffused from polluted water through a diffusion layer and trapped by an inner chelating resin, giving rise to time-weighted average concentrations.The results show that the concentrations of most hazardous metals recorded from grab samples are higher than values recorded from DGT samplers, resulting in inaccurate input information to risk assessors, the public and decision makers. DGT samplers deployed along upper, middle and lower reaches of Elsburgspruit, a stream southeast of Johannesburg, provided data which could assist in evaluating the source and evolution of metals along the stream length. DGT samplers deployed in 5 augers at different depths around a tailings dam showed that liming and trenching fails to contain deep seepage of trace metals. The results highlight the potential of using DGT samplers as a monitoring tool for providing accurate metal pollution information, assessing source and evolution of metals in streams or rivers for apportionment of liabilities, and evaluating the success of current contaminant containment methods.

We use new and existing Bouguer gravity data to characterize the long‐term flexural rigidity of the lithosphere beneath East Africa. Four tectonic provinces are characterized by distinct effective elastic plate thicknesses. These are the Tanzanian Craton, the Proterozoic Mobile Belts, the Paleogene rift basins in Sudan and Kenya, and the Cenozoic East African Rift System. Beneath the Tanzanian craton the elastic plate thickness is ∼75 km, while the Pan African Mobile Belts and the Ubendian Belts are ∼55 and ∼65 km, respectively. The Paleogene rift basins exhibit an elastic plate thickness varying between 40 and 45 km. The effective elastic plate thickness within the faulted East African Rift System ranges from 14 km in the north to 33 km in the south. The minimum is found beneath the active rift of the Afar depression. The north to south along‐rift axis variation in effective elastic plate thickness can be attributed to contrasts in the mechanical strength of the lithosphere. This is consistent with the north‐south decrease in extensional velocity and the northward decrease in the focal depths of the earthquakes, reflecting a northward thinning in the brittle layer of the crust. The maximum elastic plate thickness is found beneath the Tanzanian craton, while the surrounding Mobile Belts have relatively moderate elastic plate thicknesses. The high effective elastic plate thickness of the Tanzanian craton suggests that this part of the lithosphere is rheologically competent compared to the surrounding Mobile Belts. The craton effectively resists deformation, even though it is located within a broad zone of an east‐west extensional tectonic regime. Consequently, it has altered the direction of the rift propagation into the warmer and weaker lithosphere of the surrounding Mobile Belts.