Search

Disasters related to climate change regarding water resources are on the rise in terms of scale and severity. Therefore, predicting groundwater levels (GWLs) is a crucial means to aid adaptive capacity towards disasters related to climate change in water resources. In this study, a Gradient Boosting (GB) regression modelling approach for GWL prediction as a function of rainfall and antecedent GWL is used. A correlation analysis carried out from 2011 to 2020 demonstrated that monthly GWLs can be predicted by antecedent GWLs and rainfall. The study also sought to understand the long-term effects of climate events on groundwater levels over the study area through a Mann–Kendall (MK) trend analysis. A total of 50% of the groundwater stations revealed declining trends, while 25% had no trends and the other 25% showed an increasing trend. Again, the correlation analysis results were used in justifying the trends. The GB predictive model performed satisfactorily for all groundwater stations, with the MSE values ranging from 0.03 to 0.304 and the MAE varying from 0.12 to 0.496 in the validation period. The R2 ranged from 0.795 to 0.902 for the overall period. Therefore, based on projected rainfall and antecedent groundwater levels, future GWLs can be predicted using the GB model derived in this study. [ABSTRACT FROM AUTHOR]

The issue of hydraulic fracturing in the onshore Karoo Basin has triggered an intense political, social and environmental debate in South Africa. This research paper proposes the relatively under-explored F–O tight gas field in South Africa as a demonstration site that can shed light on the ongoing debate on the use of hydraulic fracturing in the Karoo Basin. By combining petrographic and geomechanical analyses with critical velocity experiments and rock mechanics testing, a step-by-step guide for assessing the hydraulic fracturing potential of tight gas reservoirs was presented. K-Means clustering was used to improve the sampling strategy and to capture reservoir heterogeneity. The results obtained showed that K-Means clustering improves reservoir characterisation by revealing heterogeneous intervals, thus optimising petrographic and geomechanical analyses. In addition, the hydraulic fracturing fluid was found not to cause formation damage in the reservoir at a critical velocity of 0.155 ml/min. The elastic properties also showed that the F–O Tight Gas Field has a high degree of brittleness with good hydraulic fracturing potential. Finally, the characterisation of the fractures shows that partially open fractures are prevalent, which can dilate under the high differential stresses in the reservoir. Although further investigation is required, this study has shown that the F–O gas field is a promising candidate for hydraulic fracturing. • Hydraulic fracturing of a tight gas field located in the Bredasdorp Basin in South Africa is investigated. • K-means clustering improves reservoir characterisation • Under high differential stress, partial fractures tend to propagate [ABSTRACT FROM AUTHOR]

The via media technique of characterisation in private international law, as proposed by the Canadian author Falconbridge, was – over a period of three decades – gradually adopted by the courts in Lesotho, South Africa, Zimbabwe, and, more recently, Eswatini. In a particular dispute, which is used as angle of incidence for the discussion below, the High Court of Swaziland (now Eswatini) applied the rules of the lex fori pertaining to liberative prescription (the limitation of actions) against the background of the via media technique. The decision was overruled by the Supreme Court of Eswatini, which – using the same technique – applied the proper law of the contract in this regard. In this contribution, the Canadian doctrine and its application by the Eswatini and other Southern African courts is critically discussed. The scenario in the Eswatini cases provides an example of what the author calls the phenomenon of dual cumulation. He attempts to provide guidance for the development of Southern African private international law in this regard beyond the via media technique. [ABSTRACT FROM AUTHOR]

Previous research in South Africa has identified gaps in wastewater quality characterisation and remediation. Wastewater quality indicators need to be known in order to reuse, recycle, and/or recover resources, but are poorly reported for wastewater streams. Formal and relational approaches were used to access wastewater quality information. Relational approaches included building relationships with industry partners through telephone calls, emails and meetings, while formal approaches included requests for public documents and legal applications using the Promotion of Access to Information Act. Published data were another source of information. The following industries were identified as major wastewater generating industries: pulp and paper, fish processing, power generation, mining and petroleum. Seven parameters were commonly used to indicate quality: pH, volume, electrical conductivity, nitrogen, sulphate, sodium and chemical oxygen demand. Calcium was not measured, even though discharge limits are required in environmental licenses. The accessed wastewater quality data ranged from qualitative to quantitative. The number of parameters used varied within and between industries. Although wastewater information is non-confidential, in practice it is not readily available. There are opportunities to improve wastewater management and resource recovery; however, this needs to happen in an environment of trust and transparency. This is currently lacking between industry, government, and research bodies. [ABSTRACT FROM AUTHOR]

This study reports the presence, concentration, and characteristics of microplastics (MPs) in tap water in three suburbs in Gauteng Province in South Africa. Physical characterisation was conducted using stereomicroscopy and scanning electron microscopy following staining of MPs with the Rose Bengal dye. The concentrations of MPs in all samples ranged from 4.7 to 31 particles/L, with a mean of 14 ± 5.6 particles/L. Small-sized (<1 mm) and fibrous-shaped MPs were most abundant in all samples. Fibers accounted for 83.1% of MPs in samples from all the three areas, followed by fragments (12.4%), pellets/beads (3.1%), and films (1.5%), with a minor variation in the distribution of shapes and sizes in samples from each area. Raman microspectroscopy was used for chemical analysis, and five polymers were identified, namely: high-density polyethylene, polyurethane, polyethylene terephthalate, poly(hexamethylene terephtalamide), and poly(acrylamide-co-acrylic acid). C.I Pigment Red 1, C.I. Solvent Yellow 4, Potassium indigotetrasulphonate, and C.I Pigment Black 7 were the colourants detected. These colourants are carcinogenic and mutagenic and are potentially toxic to humans. The prevalence of MPs in tap water implies their inadequate removal during water treatment. For instance, the presence of poly(AM-co-AA) suggests that drinking water treatment plants may be a potential source of MPs in tap water. Other polymers, e.g., high-density polyethylene may be released from pipes during the transportation of drinking water. The estimated daily consumption of MPs from tap water was 1.2, 0.71, and 0.50 particles/kg.day for children, men, and women, respectively. The findings of this study provide evidence of the presence of MPs in drinking water in South Africa, thus giving some insights into the performance of treatment plants in removing these contaminants and a benchmark for the formulation of standard limits for the amount of MPs in drinking water. [Display omitted] • Tap water from three suburbs in the Gauteng Province, South Africa contained MPs. • Fibrous microplastics less than 1 mm were most prevalent in tap water samples. • The presence of poly(AM-co-AA) polymer suggests that DWTPs could be a potential source of MPs in tap water. • The estimated daily intake pointed to an increased likelihood of exposure of children to MPs in tap water. [ABSTRACT FROM AUTHOR]

Inquiry-based science education has been incorporated in science curricula internationally. In this regard, however, many teachers encounter challenges. The challenges have been characterised into those linked to the personal characteristics of these teachers (intrinsic challenges) and others associated with contextual factors (extrinsic challenges). However, this level of characterisation is inadequate in terms of appreciating the complexity of the challenges, tracking of their development, and discovering knowledge within specific categories. Against this background, the purpose of the research presented here was to characterise extrinsic challenges linked to the design and implementation of inquiry-based practical work. In order to do so, we used a conceptual framework of teaching challenges based on Bronfenbrenner's ecological theory of human development. The data gathered using a multi-method case study of practical work in two South African high schools, was analysed by combining the data-driven inductive approach and the deductive a priori template of codes approach in thematic analysis. On this basis, the extrinsic challenges linked to the design and implementation of inquiry-based practical work that participants are confronted with, were found to consist of macrosystem challenges (such as a restrictive curriculum) and microsystem challenges. At the latter level, the challenges are material-related (e.g., lack of science education equipment and materials) or non-material-related (such as time constraints and the lack of access to interactive computer simulations). We have discussed the theory-, practice- and research-based implications of these results in relation to the design and implementation of inquiry-based practical work in South Africa and internationally. [ABSTRACT FROM AUTHOR]

Heartwater, one of the major tick-borne diseases of some domestic and wild ruminants in Africa, is caused by Ehrlichia ruminantium. The genetic diversity of E. ruminantium isolates renders the available vaccine ineffective against certain virulent isolates. To better understand the E. ruminantium genotypes in South Africa, a total of 1004 Amblyomma hebraeum tick deoxyribonucleic acid (DNA) samples from cattle in three South African provinces were tested by pCS20 Sol1 real-time polymerase chain reaction (qPCR) and characterised by multilocus sequence typing (MLST) using five housekeeping genes. Out of 1004 samples tested, 222 (22%) were positive for E. ruminantium. The occurrence of E. ruminantium in Mpumalanga, KwaZulu-Natal and Limpopo provinces was 19%, 22% and 27%, respectively. The E. ruminantium positive samples were screened for housekeeping genes and sequenced. Phylogenetic analysis revealed three main lineages: clade 1 made up of worldwide isolates (eastern, southern Africa, and Caribbean isolates), clade 2 comprised only West African isolates and clade 3 consisted of Omatjenne, Kümm2 and Riverside. Some study sample sequences were not identical to any of the reference isolates. However, they could all be grouped into the worldwide clade. Genetic variation in the sequenced regions was observed in the form of single nucleotide polymorphisms (SNPs). Using MLST to characterise E. ruminantium field isolates allowed the South African genotypes to be clearly distinguished from the distinct West African isolates.Contribution: Characterisation of E. ruminantium field isolates is important for the control of heartwater and contributes to preliminary knowledge required for the development of a more practical vaccine against heartwater.

Abstract: It is general believed that a sand filter starts its life with new, perfectly clean media, which becomes gradually clogged with each filtration cycle, eventually getting to a point where either head loss or filtrate quality starts to deteriorate. At this point the backwash cycle is initiated and, through the combined action of air and water, returns the media to its original perfectly clean state. Reality, however, dictates otherwise. Many treatment plants visited a decade or more after commissioning are found to have unacceptably dirty filter sand and backwash systems incapable of returning the filter media to a desired state of cleanliness. In some cases, these problems are common ones encountered in filtration plants but many reasons for media deterioration remain elusive, falling outside of these common problems. The South African conditions of highly eutrophic surface waters at high temperatures, however, exacerbate the problems with dirty filter media. Such conditions often lead to the formation of biofilm in the filter media, which is shown to inhibit the effective backwashing of sand and carbon filters. A systematic investigation into filter media cleanliness was therefore started in 2002, ending in 2005, at the University of Johannesburg (the then Rand Afrikaans University). This involved media from eight South African Water Treatment Plants, varying between sand and sand-anthracite combinations and raw water types from eutrophic through turbid to low-turbidity waters. Five states of cleanliness and four fractions of specific deposit were identified relating to in situ washing, column washing, cylinder inversion and acid-immersion techniques. These were measured and the results compared to acceptable limits for specific deposit, as determined in previous studies, though expressed in kg/m3. These values were used to determine the state of the filters. In order to gain greater insight into the composition of the specific deposits stripped from the media, a four-point characterisation step was introduced for the resultant suspensions based on acid-solubility and volatility. Results showed that a reasonably effective backwash removed a median specific deposit of 0.89kg/m3. Further washing in a laboratory column removed a median specific deposit of 1.34kg/m3. Media subjected to a standardised cylinder inversion procedure removed a median specific deposit of 2.41kg/m3. Immersion in a strong acid removed a median specific deposit of 35.2kg/m3. The four-point characterisation step showed that the soluble-volatile fraction was consistently small in relation to the other fractions. The organic fraction was quite high at the RG treatment plant and the soluble-non-volatile fraction was particularly high at the BK treatment plant. [Copyright &y& Elsevier]

Abstract: This investigation is an attempt to analyse some of the current commercial cements and cement blends in South Africa and mortars produced from them (1:3 mixtures of cementitious material with different sands) for a suite of minor and trace elements that will provide a unique fingerprint of the final product. It was found in both the case of the OPC and the blended cements that a suite of such elements can be successfully employed to uniquely characterise the materials. The contribution of such a fingerprint is that it can provide valuable information in the case of a forensic analysis for discrimination purposes. [Copyright &y& Elsevier]