Scielo RSS <![CDATA[South African Journal of Science]]> http://www.scielo.org.za/rss.php?pid=0038-235320140003&lang=pt vol. 110 num. 5-6 lang. pt <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Dealing with 'open access' demons</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000300001&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>The unknown underworld: Understanding soil health in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000300002&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>Climate change, biodiversity and extinction risk</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000300003&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>Protected but vulnerable</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000300004&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>Anything but simple: Inappropriate use of euclidean distance in Govinder et al. (2013)</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000300005&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>On taking the transformation discourse for a ride: Rejoinder to a response (Govinder et al. 2014)</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000300006&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>Some thoughts about the future of food and agriculture</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000300007&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>Ubiquitous modelling: In honour of Tony Starfield's 70th anniversary</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000300008&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>Further response to Govinder et al. (2014): Flaws in the equity index</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000300009&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>Ecological consequences of global climate change for freshwater ecosystems in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000300010&lng=pt&nrm=iso&tlng=pt Freshwater resources in South Africa are under severe pressure from existing anthropogenic impacts and global climate change is likely to exacerbate this stress. This review outlines the abiotic drivers of climate change, focusing on predicted changes in temperature and precipitation. The consequences of global climate change for freshwater ecosystems are reviewed, with effects grouped into those related to water quantity, water quality, habitat and aquatic biological assemblages. Several guiding principles aimed at minimising the potential impact of climate change on freshwater ecosystems are discussed. These guidelines include those focused on water quantity and the maintenance of appropriate environmental flows, integration of global climate change into water quality management, conservation planning for freshwater biodiversity, the promotion of ecosystem resilience, and extending climate change science into policy and public discourse. Proactive assessment and monitoring are seen as key as these will allow for the identification of ecological triggers and thresholds, including thresholds of vulnerability, which may be used to monitor and inform decisions, as well as to improve the ability to forecast based on this knowledge. <![CDATA[<b>A review on opportunities for the development of heat pump drying systems in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000300011&lng=pt&nrm=iso&tlng=pt Recently, it has been discovered that heat pump drying is an efficient method of drying for drying industries. Heat pumps deliver more heat during the drying process than the work input to the compressor. Heat pump drying is a more advanced method than the traditional South African industrial and agricultural drying methods, such as direct/indirect sunlight, wood burning, fossil fuel burning, electrical heating and diesel engine heating. Heat pump dryers provide high energy efficiency with controllable temperature, air flow and air humidity and have significant energy-saving potential. In the last decade the market for heat pump systems for water heating and space cooling/heating has grown in South Africa, but the development of heat pumps for industrial and agricultural drying is very slow. As a result of high increases in fossil fuel prices and electricity in South Africa, as well as the problem of CO2 emissions, green energy, energy saving and energy efficiency are imperative. The development of heat pump drying systems in South Africa is an efficient way to solve energy problems in drying applications as this technology is still in its infancy. We review studies on heat pump drying and compare the methods therein with the most common methods of drying in South Africa <![CDATA[<b>Review of carbon dioxide capture and storage with relevance to the South African power sector</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000300012&lng=pt&nrm=iso&tlng=pt Carbon dioxide (CO2) emissions and their association with climate change are currently a major discussion point in government and amongst the public at large in South Africa, especially because of the country's heavy reliance on fossil fuels for electricity production. Here we review the current situation regarding CO2 emissions in the South African power generation sector, and potential process engineering solutions to reduce these emissions. Estimates of CO2 emissions are presented, with the main sources of emissions identified and benchmarked to other countries. A promising mid-term solution for mitigation of high CO2 emissions, known as CO2 capture and storage, is reviewed. The various aspects of CO2 capture and storage technology and techniques for CO2 capture from pulverised coal power plants are discussed; these techniques include processes such as gas absorption, hydrate formation, cryogenic separation, membrane usage, sorbent usage, enzyme-based systems and metal organic frameworks. The latest power plant designs which optimise CO2 capture are also discussed and include integrated gasification combined cycle, oxy-fuel combustion, integrated gasification steam cycle and chemical looping combustion. Each CO2 capture technique and plant modification is presented in terms of the conceptual idea, the advantages and disadvantages, and the extent of development and applicability in a South African context. Lastly, CO2 transportation, storage, and potential uses are also presented. The main conclusions of this review are that gas absorption using solvents is currently most applicable for CO2 capture and that enhanced coal bed methane recovery could provide the best disposal route for CO2 emissions mitigation in South Africa. <![CDATA[<b>Climate and the mfecane</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000300013&lng=pt&nrm=iso&tlng=pt The mfecane is thought to be a massive upheaval and devastation of Nguni tribal chiefdoms in the second decade of the 19th century in what is now KwaZulu-Natal and the Eastern Cape of South Africa. Other historians have challenged this extreme interpretation suggesting that the use of the term mfecane be discontinued. We show that pervasive cycles of drought and cold periods in southern Africa are significantly amplified and extended by volcanic eruptions and that, in particular, the eruption of Tambora in 1815 triggered a prolonged and extreme climatic event which bears all of the characteristics ascribed to the mfecane. These findings are supported by a coupled ocean-atmosphere numerical model and by tree-ring rainfall and sea surface temperature analyses, suggesting that the term mfecane is an appropriate description of a singular climatic event. <![CDATA[<b>Water research paradigm shifts in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000300014&lng=pt&nrm=iso&tlng=pt We performed a scientometric analysis of water research publications extracted from four decades of South African related papers to identify paradigms and paradigm shifts within water research in South Africa. Between 1977 and 1991, research publications are dominated by research into technical and engineering solutions, as well as designs and plans to secure water supply. From 1992 to 2001, publications on water pollution, water quality, water resource management and planning are prominent. The second major paradigm is observed from 2001 to 2011 in which the emphasis is on planning, modelling, catchment-scale studies and a multidisciplinary approach to research. Another transition period, towards the end of 2011, is characterised by uncertainty, although it also shows the prominence of key concepts such as participation, governance and politics in water management. The second aim of this study was to identify and prioritise current and future water research questions through the participation of a wide range of researchers from across the country, and to relate these questions to research paradigms, issues and concerns in water in South Africa. Over 1600 questions were collected, reduced in number and then prioritised by specialists in the water sector. The majority (78%) of questions offered by respondents in the South African case study dealt with relatively short- to medium-term research requirements with 47% of questions focused on medium-term issues such as supplying water, service delivery and technical solutions. <![CDATA[<b>A technique to determine the electromagnetic properties of soil using moisture content</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000300015&lng=pt&nrm=iso&tlng=pt Accurate electromagnetic ground constants are required for applications such as modelling of ground wave propagation of radio signals and antennas above a real, imperfect earth and for use in geological surveys and agricultural applications. A simple method to determine the ground parameters (conductivity and relative dielectric constant) for any radio frequency is outlined here. The method has been verified over the 2-30-MHz frequency range but should be applicable up to several GHz. First, a low cost, commercial soil moisture meter using time domain reflectometry techniques is used to determine the soil moisture percentage. Then previously published universal soil models implemented on a programmable calculator or a PC are used to calculate the required constants at the frequency of interest according to the measured moisture percentage. The results obtained by this method compare favourably with those obtained by the input impedance of a low horizontal dipole technique. The received signal strength of a ground wave, HF transmission also compares favourably with that predicted by GRWave using ground constants calculated by the soil moisture technique. This method offers significant advantages in terms of simplicity, speed and cost when compared with current techniques. <![CDATA[<b>Management strategies to curb rhino poaching: Alternative options using a cost-benefit approach</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000300016&lng=pt&nrm=iso&tlng=pt The combination of increasing demand and high black market prices for rhino horn in Asian markets has fueled an escalation in rhino poaching since 2007, particularly in South Africa. This situation has in turn resulted in greatly increased rhino protection costs, loss in confidence by the private sector in rhinos, loss of revenue to conservation authorities and reduced rhino population growth rates. Within current CITES processes, management responses to threats posed by poaching to rhino persistence fall within a mixture of reactive responses of increased protection and law enforcement and some pro-active responses such as demand reduction tactics, along with a parallel call for opening a legal trade in horn. These rhino management strategies carry different risks and benefits in meeting several conservation objectives. An expert-based risk-benefit analysis of five different rhino management strategies was undertaken to assess their potential for delivering upon agreed rhino conservation objectives. The outcomes indicated that benefits may exceed risks for those strategies that in some or other format legally provided horn for meeting demand. Expert risk-benefit approaches are suggested to offer a rational, inclusive and consensus generating means of addressing complex issues such as rhino poaching and augmenting the information used within the CITES decision-making processes. <![CDATA[<b>Modelling new particle formation events in the South African savannah</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000300017&lng=pt&nrm=iso&tlng=pt Africa is one of the less studied continents with respect to atmospheric aerosols. Savannahs are complex dynamic systems sensitive to climate and land-use changes, but the interaction of these systems with the atmosphere is not well understood. Atmospheric particles, called aerosols, affect the climate on regional and global scales, and are an important factor in air quality. In this study, measurements from a relatively clean savannah environment in South Africa were used to model new particle formation and growth. There already are some combined long-term measurements of trace gas concentrations together with aerosol and meteorological variables available, but to our knowledge this is the first detailed simulation that includes all the main processes relevant to particle formation. The results show that both of the particle formation mechanisms investigated overestimated the dependency of the formation rates on sulphuric acid. From the two particle formation mechanisms tested in this work, the approach that included low volatile organic compounds to the particle formation process was more accurate in describing the nucleation events than the approach that did not. To obtain a reliable estimate of aerosol concentration in simulations for larger scales, nucleation mechanisms would need to include organic compounds, at least in southern Africa. This work is the first step in developing a more comprehensive new particle formation model applicable to the unique environment in southern Africa. Such a model will assist in better understanding and predicting new particle formation - knowledge which could ultimately be used to mitigate impacts of climate change and air quality. <![CDATA[<b>Equilibrium ion exchange studies of Ni<sup>2+</sup> on homoionic forms of clinoptilo</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000300018&lng=pt&nrm=iso&tlng=pt ABSTRACT A natural zeolite (clinoptilolite) that is mined in KwaZulu-Natal, South Africa, was evaluated for the removal of Ni²+ from wastewater. In particular, the effect of zeolite modification on Ni²+ removal from synthetic wastewater was investigated. The natural clinoptilolite was pretreated with 2 M metal chlorides for 24 h to yield near homoionic Na+, K+ and Ca2+ forms. A comparison of the isotherms for the Na+-Ni2+, K+-Ni2+, Ca2+-Ni2+ and natural-Ni2+ systems gave insight into how the displaced ion affects the selectivity of the clinoptilolite for Ni2+. The Na+, K+ and natural forms show highly selective convex isotherms whereas the Ca2+ form has a concave graph suggesting that the selectivity series is Ca2+> Ni2+> (Na+, K+, natural). Thermodynamic properties revealed that the Ni²+ sorption capacity increases as the values of the equilibrium constant and Gibbs free energy increase with increasing temperature from 298.15 K to 348.15 K. The enthalpy change was positive for all forms of clinoptilolite; values of 26.00 kJ/mol, 18.72 kJ/mol and 42.05 kJ/mol were obtained for exchange of Ni2+ into Na+, K+ and Ca2+ forms, respectively. The positive changes in enthalpy provide an indication that the sorption reaction is endothermic for Ni(II). The Gibbs free energy values were all negative except for Ca²+-exchanged clinoptilolite at 298.15 K and 308.15 K, for which the values were positive 3.10 kJ/mol and 0.53 kJ/mol, respectively. The entropy values for Ni²+ sorption were also positive; values of 0.12 kJ/mol.K, 0.08 kJ/mol.K and 0.14 kJ/mol.K were obtained for the Na+, K+ and Ca²+ forms, respectively. As expected, the enthalpy obtained from the Van't Hoff plot is dependent not only on the metal ion being adsorbed, but also on the ion being displaced. Pretreatment of the zeolite enhances the removal efficiency provided that monovalent ions are used for the pretreatment. Thus clinoptilolite is an effective low-cost absorbent for the removal of Ni2+ from aqueous solutions. <![CDATA[<b>Rethinking the science-policy interface in South Africa: experiments in knowledge co-production</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000300019&lng=pt&nrm=iso&tlng=pt This article contributes to the increasingly significant discussion about the science-policy interface. The challenge therein is that such a discussion tends to revolve around two seemingly mutually exclusive approaches: the reflexive approach inspired by Maarten Hajer's work that deconstructs the discourses of participatory policymaking, and the more normative transdisciplinary approaches that legitimise researchers as active change agents. With reference to a discussion of three South African case studies characterised by practical involvement of researchers in change processes, it is concluded that both approaches have merit and can improve the other: the reflexive approach could benefit from a better understanding of appropriate research methods for facilitating authentic engagement and participation, and the transdisciplinary approach could benefit from some reflexive caution about the change agent roles of researchers. The dynamics of the case studies and conclusions are significant in light of the fact that the South African research community is being influenced by re-alignments in the global scientific research community, resulting in an increasing emphasis on the need to do transdisciplinary research. For example, the adoption by some of the most significant global scientific associations in the natural and social sciences of the Future Earth platform at the Rio+20 conference in 2012 reflects most clearly this re-alignment. Researchers would be well advised to critically engage this agenda rather than presume it means little more than a rewording of traditional interdisciplinary approaches.