Browsing by Subject "environment"

Now showing 1 - 10 of 10
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    Aeolian dust emission dynamics across spatial scales: landforms, controls and characteristics
    (2018) von Holdt, Johanna R C; Eckardt, Frank; Wiggs, Giles; Hipondoka, Martin
    Variable erodibility (surface characteristics) and erosivity factors (meteorological conditions) result in dust emission dynamics being complex in both space and time. Accounting for localscale surface variability is critical to our understanding of dust emitting processes. This study identifies mineral dust using remote sensing, establishes emission thresholds through field measurements and identifies particle chemistry for major dust sources in the Central Namib Desert. Examining over 2000 Landsat images over a period from 1972 to 2016, identified 40 days of visually detectable dust, originating from sub-km scale point sources. The observations suggest that dust sources can be identified at the landform scales which particularly include ephemeral river valleys and saline pan surfaces. These persist throughout the 25-year record; however, a gradual shift in source point clusters is noted through time, which can be tentatively attributed to anthropogenic modification of the hydrological systems. A PI-SWERL (Portable In-Situ Wind ERosion Lab) wind tunnel was used to measure the emission potential of the Landsat derived targets. The most emissive sources were paleostockpiles of alluvial silt deposits and associated degraded nebkhas within the Kuiseb River Delta. These had a geometric mean emission flux of 0.076 mg m-2 s -1. In comparison, the active channel had a geometric mean emission flux of 0.008 mg m-2 s -1, undisturbed desert pavement 0.007 mg m-2 s -1, pan surfaces 0.001 mg m-2 s -1 and wadis within the gravel plains 0.030 mg m-2 s -1. The emission thresholds were augmented with site-specific field measurements such gravel cover (%), moisture content (%), particle size (µm), elemental composition (%) and shear and compressive strength (kg cm-2). A Boosted Regression Tree (BRT) machine-learning algorithm identified the most important surface and sediment characteristics determining dust emission from the measured surfaces. The model explained 70.8% of the deviance in the measured dust flux with the top predictor variables and their relative importance (%) as follows: gravel cover, 16%; moisture content, 14%; kurtosis, 13%; very coarse silt, 13%; very fine sand, 11%; fine sand, 8%; compressive strength, 7%, calcium, 7% and magnesium, 6%. Such an analysis can be used to identify critical thresholds for dust emission and standardise testing protocols. Linking landforms with such emission measurements allow for the assessment of two existing dust emission schemes: the Preferential Dust Scheme (PDS; Bullard et al. 2011) and the Sediment Supply Map (SSM; Parajuli et al. 2017). Although these schemes represent a major advance in our representation of dust emission source areas and erodibility, this study shows that these schemes still need to be improved to accurately depict dust emission potential. For the PDS this would include producing a global rasterised output with quantified dust emission potential and for the SSM, a more accurate classification of the highly emissive geomorphic units. Landsat source point sediments were subjected to physical and geochemical analyses and compared to samples obtained from passive collectors such as the Big Spring Number Eight (BSNE) and active PI-SWERL exhaust emissions, using an auto-SEM (QEMSCAN). This provided individual particle mineralogy (>2 µm resolution) for a total of approximately 10000 to 60000 particles per sample which enabled a comparison of particle size, shape and mineralogy. The samples consist of a mixture of minerals reflecting the varied metamorphic geology and consists predominantly of feldspar, quartz, mica, other aluminosilicates such as the alteration products epidote and chlorite and low to medium grade metamorphics such as amphibole and pyroxene, iron oxihydroxides, titanium minerals, carbonates and clay minerals.
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    Cleaner energy cooler climate: developing sustainable energy solutions for South Africa
    (2011) Winkler, Harald
    For South Africa, finding a policy approach which balances the increasing demand for energy with the need for sustainability, equity and climate change mitigation is a particular challenge. Energy and climate change are issues of critical importance for shaping a sustainable future, both in South Africa and globally. This book provides an innovative and strategic approach to climate policy, with local development objectives as its starting point.
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    Energy and environmental challenges in Southern Africa: The case of South Africa
    (1995) Mammon, Nisa; Simmonds, Gillian; van Horen, Clive
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    HI in group interactions: HCG 44
    (2017) Hess, Kelley M; Cluver, M E; Yahya, Sahba; Leisman, Lukas; Serra, Paolo; Lucero, Danielle M; Passmoor, Sean S; Carignan, Claude
    Extending deep observations of the neutral atomic hydrogen (H I) to the environment around galaxy groups can reveal a complex history of group interactions which is invisible to studies that focus on the stellar component. Hickson Compact Group 44 (HCG 44) is a nearby example, and we have combined H I data from the Karoo Array Telescope, Westerbork Synthesis Radio Telescope, and Arecibo Legacy Fast ALFA survey, in order to achieve high column density sensitivity (N _{H {I}}
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    International Environmental Justice and the Climate Change Challenge
    (2012-12) Lawhon, Mary; Ziervogel, Gina;
    This course module is one section of a larger course called Geography, Development and Environment that runs as a first year course in the Department of Environmental and Geographical Science at the University of Cape Town. The course work provided here is one of 3 modules including 1) the global economic environment, 2) regional dynamics of development, and 3) the North-South debates on environmental problems. This module falls under the theme of North-South debates on environmental problems. The courses use theories of underdevelopment and climatic change to explain global and regional inequalities and environmental problems. Key concepts in the course are: trade, foreign aid, regional integration, and climatic change. The objectives of this section of the course are to begin understanding: 1. the concepts of environmental justice and climate change, 2. the relationship between environmental change and development, and 3. the international politics of global environmental change, This topic provides the scope for debate among students because of the contentious nature of the subject, and the lack of clear answers. Importantly this course focuses on presenting multiple explanations and diverse viewpoints and is intended to provide context, history and structure for students’ thinking. Students are not provided with solutions, but instead encouraged to develop their own explanations and responses to climate change and justice. This 4 week module, supported by powerpoint slides, uses climate change to explore key environmental and geographical issues including: justice, scale, international equality, global political processes, and environmental change. We begin by examining the foundation and principles of the environmental movement, distinguishing between different types of environmentalism and articulating early environmental conflicts between the North and South (presentations 1, 2, 4). We then develop ideas of environmental justice (presentation 3) and how it applies to climate change.
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    Jet lag and environmental conditions that may influence exercise performance during the 2010 FIFA World Cup in South Africa
    (2010) Schwellnus, Martin; Derman, Elton
    The 2010 FIFA World Cup will be held in South Africa in June/July 2010. This is the largest international sports event ever to be held in this country. At this time 32 international football teams, with their management and supporters, will travel to South Africa. These players and visitors will be exposed to changes in time zones (those travelling from continents in the East and West) as well as different environmental conditions. In particular, for the players, the achievement of peak sporting performance during this event is most important. It is well established that, in order to achieve peak exercise performance, many variables need to be optimised. These variables include physical and mental training, rest, nutrition, team dynamics and tactics. However, adjustments to differences in time zones as well as environmental factors on and around the playing field can also have a significant impact on exercise performance. In this review, the potential effects of “jet lag”, as well as several important environmental conditions, on exercise performance will be discussed. The climatic, atmospheric and weather conditions that are likely to be prevalent in each of the South African host cities at the time of the 2010 FIFA World Cup will be reviewed. Finally, practical recommendations to deal with the effects of jet lag, as well as guidelines to optimise performance under different environmental conditions that are expected during the 2010 FIFA World Cup, will be provided.
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    The Impact of Aid on Human Development Indices in Sub-Saharan Africa
    (2020) Tsokodayi, Jade Takudzwa; Gossel, Sean
    This study investigates the relationship between official development assistance (ODA) and human development indicators (HDIs) in 49 sub-Saharan African countries over the period of 1995 to 2017 using 3-stage least squares (3SLS). The four key sub-classes of HDIs considered for this research include education, health, government and civic society, as well as environmental indicators. Of all these HDIs, the results of the analysis show that health aid is the most effective form of aid, significantly reducing the incidence of HIV, the infant mortality rate and the maternal mortality rate, as well as leading to improved life expectancy. Education aid has a significant effect on the progression to secondary school followed by adult literacy rates. Government and civil society aid significantly affects the ability of girls to access education at primary, secondary and tertiary levels while environmental aid is found to increase the carbon efficiency of production. Hence, this study demonstrates that aid is most effective on the health, education and environmental human development indicators.
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    The void galaxy survey: photometry, structure and identity of void galaxies
    (2017) Beygu, B; Peletier, R F; Hulst, J M van der; Jarrett, T H; Kreckel, K; Weygaert, R van de; van Gorkom, J H; Aragon-Calvo, M A
    We analyse photometry from deep B-band images of 59 void galaxies in the Void Galaxy Survey (VGS), together with their near-infrared 3.6 μm and 4.5 μm Spitzer photometry. The VGS galaxies constitute a sample of void galaxies that were selected by a geometric-topological procedure from the Sloan Digital Sky Survey Data Release 7 data release, and which populate the deep interior of voids. Our void galaxies span a range of absolute B-magnitude from MB = -15.5 to -20, while at the 3.6 μm band their magnitudes range from M3.6 = -18 to -24. Their B-[3.6] colour and structural parameters indicate these are star-forming galaxies. A good reflection of the old stellar population, the near-infrared band photometry also provide a robust estimate of the stellar mass, which for the VGS galaxies we confirm to be smaller than 3 × 1010 M⊙. In terms of the structural parameters and morphology, our findings align with other studies in that our VGS galaxy sample consists mostly of small late-type galaxies. Most of them are similar to Sd-Sm galaxies, although a few are irregularly shaped galaxies. The sample even includes two early-type galaxies, one of which is an AGN. Their Sérsic indices are nearly all smaller than n = 2 in both bands and they also have small half-light radii. In all, we conclude that the principal impact of the void environment on the galaxies populating them mostly concerns their low stellar mass and small size.
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    Vulnerability to environmental change
    (2014-08-22) Ziervogel, Gina
    The material is presented in the form of powerpoint presentations for 6 sections. Activities to accompany the slides are presented here. The slides form the basis of presenting the theory and linking it to key literature. Examples are provided in many places of how the theory is applied in case studies, often from work that the lecturer has been involved in and relevant to the southern African region. It is suggested that teachers who use this material in other contexts draw on local examples to support the theoretical discussions. Course objectives: 1. understand theoretical concepts of vulnerability 2. overview of what methods to use to assess vulnerability 3. understanding of the concept and application of adaptation to climate change. This 4 week module on vulnerability to environmental change is part of a third year course called Sustainability and the Environment (EGS 3021F) in the Department of Environmental and Geographical Science , University of Cape Town. The course introduces the concept of vulnerability and explores its origin, drawing on three different conceptual approaches namely Risk/hazard, Political economy/ecology and Ecological resilience. It then looks at different methods for undertaking vulnerability assessments. Building on the theory and method sections it focuses on why the concept of vulnerability is important in the field of environmental change with a focus on climate change. The international process of assessing the science is explored followed by material addressing adaptation to climate change and examples of vulnerability and adaptation in practice in South Africa.