Scielo RSS <![CDATA[South African Journal of Science]]> vol. 111 num. 5-6 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>Women, productivity and progress</b>]]> <![CDATA[<b>#RhodesMustFall: No room for ignorance or arrogance</b>]]> <![CDATA[<b>The role of intellectuals in the state-society nexus</b>]]> <![CDATA[<b>Professor Benito Makhala Khotseng (1948-2015): A passionate, humanitarian educationist</b>]]> <![CDATA[<b>Professor Patricia Berjak (1939-2015): World-renowned plant scientist and exceptional mentor</b>]]> <![CDATA[<b>Ghosts</b>]]> <![CDATA[<b>Ancient DNA comes of age</b>]]> <![CDATA[<b>Transdisciplinarity within South Africa's global change research: How (well?) are we doing?</b>]]> <![CDATA[<b>Fruit waste streams in South Africa and their potential role in developing a bio-economy</b>]]> Current and previous studies on bio-based (fruit) wastes and wastewaters, with a particular emphasis on research in South Africa, were reviewed. Previous studies have focused predominantly on the beneficiation and application of fruit waste as a feedstock for renewable energy. A definite gap in knowledge and application of fruit waste streams with regard to enzyme production as a value-added product is identified. The characteristics and composition of each type of fruit waste are highlighted and their potential as feedstocks in the production of value-added products is identified. The conversion of agri-industrial wastewaters to bioenergy and value-added products is discussed, with special mention of the newly published South African Bio-Economy Strategy, and the potential production of biofuels and enzymes from waste streams using recombinant Aspergillus strains. Finally, to maximise utilisation of waste streams in South Africa and abroad, a conceptual model for an integrated system using different technologies is proposed. <![CDATA[<b>Unearthing a hidden treasure: 60 years of karst research in the Far West Rand, South Africa</b>]]> Karstified dolomitic formations situated in the Far West Rand goldfield of the Witwatersrand Basin constitute a significant groundwater resource in semi-arid South Africa and would be of strategic importance for alleviating the increasing water stress in nearby metropolitan areas. The deep-level gold mines operating below the dolomites have suffered from large volumes of dolomitic groundwater flowing into the mine voids, rendering mining both expensive and hazardous. In order to secure safe and economical mining, the overlying dolomites were dewatered. Here we review research over 60 years, conducted in three of the four major dolomitic compartments affected by dewatering. After more than six decades of research, these aquifers are arguably the most investigated karst systems in South Africa, and possibly worldwide. The data generated are, in many respects, unique, as many measurements can never be repeated, covering stochastic events such as a major water inrush into mine workings and some of the most catastrophic sinkhole developments ever recorded. Given the potential value for improving the understanding of general and local karst hydrogeology, our main goal for this paper is to alert the scientific community to the existence of this resource of mostly unpublished data and research. A no less important aim is to support a systematic collation of these studies which are in danger of being irretrievably lost as mines increasingly close down. Ecological and economic impacts of the flooding of mines in and around Johannesburg emphasise the lack of reliable historical mine data to optimally address the matter. We provide the first comprehensive, yet not exhaustive, overview on the existing studies, briefly discussing scientific content as well as obstacles for utilising the scattered, and often non-peer reviewed, information sources. <![CDATA[<b>Spatial soil information in South Africa: Situational analysis, limitations and challenges</b>]]> Soil information is vital for a range of purposes; however, soils vary greatly over short distances, making accurate soil data difficult to obtain. Soil surveys were first carried out in the 1920s, and the first national soil map was produced in 1940. Several regional studies were done in the 1960s, with the national Land Type Survey completed in 2002. Subsequently, the transfer of soil data to digital format has allowed a wide range of interpretations, but many data are still not freely available as they are held by a number of different bodies. The need for soil data is rapidly expanding to a range of fields, including health, food security, hydrological modelling and climate change. Fortunately, advances have been made in fields such as digital soil mapping, which enables the soil surveyors to address the need. The South African Soil Science fraternity will have to adapt to the changing environment in order to comply with the growing demands for data. At a recent Soil Information Workshop, soil scientists from government, academia and industry met to concentrate efforts in meeting the current and future soil data needs. The priorities identified included: interdisciplinary collaboration; expansion of the current national soil database with advanced data acquisition, manipulation, interpretation and countrywide dissemination facilities; and policy and human capital development in newly emerging soil science and environmental fields. It is hoped that soil information can play a critical role in the establishment of a national Natural Agricultural Information System. <![CDATA[<b>Real-time measurement of outdoor worker's exposure to solar ultraviolet radiation in Pretoria, South Africa</b>]]> The city of Pretoria in South Africa receives considerable solar ultraviolet radiation (UVR) because of its low latitude (22-35°S) and relatively clear skies. Certain meteorological factors affect the amount of solar UVR that reaches the ground; the most dominant factors being stratospheric ozone, cloud cover and solar zenith angle. It is known that overexposure to solar UVR may lead to the development of adverse health conditions, the most significant being skin cancer. Outdoor workers spend a significant amount of time outside and are thus susceptible to this risk. In this case study, we estimated, for the first time, the realtime solar UVR exposure of an outdoor worker in Pretoria. Measurements were made on 27 and 28 May 2013 using a handheld ultraviolet index (UVI) meter calibrated against a science-grade biometer at the South African Weather Service in Pretoria. Personal exposure estimation was used to discern the pattern in diurnal and annual sunburn risk for the outdoor worker. Ambient UVR levels ranged from 0 UVI to 4.66 UVI and the outdoor worker's potential exposure estimates regularly exceeded 80% of these levels depending on the time of day. The risk of sunburn was evident; however, actual incidents would depend on individual skin photosensitivity and melanin content, as well as sun protection used. Further research is needed to determine the personal exposure estimations of outdoor workers in other provinces in which solar UVR levels may be equally high, or higher than those in Pretoria. <![CDATA[<b>Monitoring and evaluating astronomy outreach programmes: Challenges and solutions</b>]]> A number of tools exist to guide the monitoring and evaluation of science, technology, engineering and mathematics (STEM) education and outreach programmes. Fewer tools exist for evaluating astronomy outreach programmes. In this paper we try to overcome this limitation by presenting a monitoring and evaluation framework developed for the International Astronomical Union's Office of Astronomy for Development (OAD). The mandate of the OAD is to stimulate sustainable development at an international level and to expand astronomy education and outreach globally. The broad assumptions of this programme are that astronomy has the potential to contribute to human development by means of the transferable nature of its science discoveries, as well as its potential to activate feelings of wonderment, inspiration and awareness of the universe. As a result, the programme potentially embodies a far broader mix of outcomes than conventionally considered in STEM evaluation approaches. Towards this aim, we operationalise our monitoring and evaluation approach by first outlining programme theories for three key OAD programmes: a programme for universities and research, another one for schools, and one for public outreach. We then identify outcomes, indicators and measures for each one of these programmes. We conclude with suggestions for evaluating the global impact of astronomy for development. <![CDATA[<b>Particle boards produced from cassava stalks: Evaluation of physical and mechanical properties</b>]]> We investigated the potential use of cassava stalks for the production of bonded particle boards. Particle boards were produced from cassava stalks using urea-formaldehyde as a binder. Water absorption and thickness swelling tests were carried out to determine dimensional stability of the boards while modulus of rupture and modulus of elasticity tests were carried out to assess the mechanical strength of the boards. Particle boards produced using an adhesive-cassava stalk ratio of 3:1 gave the best results in terms of the lowest mean values of water absorption (20%) and thickness swelling (6.26%), as well as the highest values of modulus of rupture (4x10(6) N/m²) and modulus of elasticity (2366.74x10(6) N/m²). The particle boards produced met the ANSI/A208.1-1999 standard for general-purpose boards. The results of analyses of variance carried out revealed that the adhesive-cassava stalk ratio had a marked influence (p<0.05) on the physical properties (water absorption and thickness swelling) but not on the mechanical properties (modulus of rupture and modulus of elasticity). <![CDATA[<b>A Rasch analysis of a Grade 12 test written by mathematics teachers</b>]]> There is much concern in South Africa about the low levels of mathematics achievement amongst learners. Aligned to this issue is that of mathematics teachers' proficiency in mathematics. The purpose of this study was to explore mathematics teachers' proficiency in the mathematics that they teach. A sample of 253 teachers' responses to a shortened Grade 12 examination was analysed using the Rasch model. When the teachers' proficiency and item location are represented on one scale, as is the case in Rasch measurement theory, it is expected that the teachers should be located beyond the difficulty level of the items as they teach the content to their learners. However, in this study, the teachers' proficiency was located close to the mean of the item locations. Furthermore, the levels of almost one-third of the group were below that of all the Level 3 and Level 4 items in the test. If such a result holds across other groups of teachers, it may explain why higher levels of passes in mathematics are not achieved. A second aim of this study was to illustrate how the application of the Rasch model can be used to contribute to a more informative and fair assessment. In line with Rasch measurement theory, the test was subjected to various analyses and the results were used to improve the fit of the items and the test. <![CDATA[<b>Quantifying the catchment salt balance: An important component of salinity assessments</b>]]> Soil and stream salinisation is a major environmental problem because it reduces the productivity of landscapes and degrades water quality. The Berg River (South Africa) has been exhibiting a trend of increasing salinity levels, which has primarily been attributed to the manifestation of dryland salinity. Dryland salinity occurs as a result of changes in land use (indigenous vegetation to agriculture and/or pasture), which cause a change in the water and salt balance of the landscape, consequently mobilising stored salts. The quantification of salinity fluxes at the catchment scale is an initial step and integral part of developing dryland salinity mitigation measures. The objective of this study was to quantify the salinity fluxes in the Sandspruit catchment, a tributary catchment of the Berg River. This included the quantification of salt storage, salt input (rainfall) and salt output (in run-off). The results of the catchment salt balance computations indicate that the Sandspruit catchment is exporting salts, i.e. salt output exceeds salt input, which may have serious implications for downstream water users. Interpolated regolith salt storage generally exhibited increasing storage with decreasing ground elevation. A salinity hotspot was identified in the lower reaches of the catchment. It is envisaged that the data presented in this study may be used to classify the land according to the levels of salinity present; inform land management decisions; and provide a guide and framework for the prioritisation of areas for intervention and the choice and implementation of salinity management options. The data which were generated may also be used to calibrate hydrosalinity models. <![CDATA[<b>Eutrophication and cyanobacteria in South Africa's standing water bodies: A view from space</b>]]> Satellite remote sensing can make a significant contribution to monitoring water quality in South African standing water bodies. Eutrophication, defined as enrichment by nutrients, and toxin-producing cyanobacteria (blue-green algae) blooms pose a significant threat to the quality of South African surface water bodies. The status and trends of chlorophyll a (chl-a, a proxy for eutrophication), cyanobacterial blooms and cyanobacterial surface scum were determined for South Africa's 50 largest water bodies between 2002 and 2012, using a recently developed algorithm and 10 years of data from the Medium Resolution Imaging Spectrometer (MERIS) satellite. The majority (62%) of the 50 water bodies were highly nutrient enriched or hypertrophic, while 26 had cyanobacterial blooms which posed a high health risk from surface scums. This study is the first of its kind to provide quantitative water quality information for South Africa's water bodies from a time series of satellite remotely sensed data. We demonstrate the pivotal role that satellite remote sensing can play in greatly supplementing in-situ monitoring efforts such as the National Eutrophication Monitoring Programme. The finding that many water supply bodies are severely impacted by eutrophication and cyanobacterial blooms confirms that these remain issues of critical concern for water security and supply in South Africa. <![CDATA[<b>Characteristics of potential gasifier fuels in selected regions of the Lake Victoria Basin</b>]]> All countries in the Lake Victoria Basin depend mostly on hydroelectric power for the provision of energy. Gasification technology has a high potential for reducing biomass energy consumption whilst increasing access to modern energy services. The key aspect for the failure of gasification operations in the Lake Victoria Basin is inadequate adaptation of gasification equipment to fuel characteristics, lack of fuel specification and inappropriate material choice. We therefore investigated the thermo-chemical characterisation of six biomass fuels, namely Pinus caribaea, Calitris robusta, Cupressus lusitanica, Eucalyptus grandis, Pinus patula and sugarcane bagasse from selected regions of the Lake Victoria Basin. Ultimate analysis was done using a Flash 2000 elemental analyser. Moisture content, ash content and volatile matter were determined in oven and muffle furnaces while heating values were determined using a Gallenkamp calorimeter. The mean percentage levels obtained indicate that all six biomass fuels had a mean range for nitrogen of 0.07±0.2-0.25±0.07%, for carbon of 40.45±0.61-48.88±0.29%, for hydrogen of 4.32±0.13-5.59±0.18% and for oxygen of 43.41±1.58-51.1±0.64%. Moisture content ranged between 25.74±1.54% and 56.69±0.52%, ash content between 0.38±0.02% and 2.94±0.14%, volatile matter between 74.68±0.49% and 82.71±0.19% and fixed carbon between 14.35±0.33% and 24.74±0.27%. Heating values ranged between 16.95±0.10 MJ/kg and 19.48±0.42 MJ/kg. The results suggest that all six biomass fuels are potential biomass gasification materials.