The neotropical semi-woody perennial shrub Chromolaena odorata (L.) King and Robinson (Asteraceae: Eupatorieae) has become a serious invasive weed in the sub-tropical regions of southern Africa, resulting in the initiation of an insect biocontrol research programme at Cedara in the KwaZulu-Natal province. The programme has experienced difficulties in growing and maintaining healthy potted C. odorata plants for research, for almost ten years. In an attempt to identify possible causes of mortality, plants were grown on elevated grids in two trials; (winter-spring 2003) and (autumn-winter 2004) in Durban (subtropical region, within the natural range of C. odorata) and Cedara (temperate region, outside its natural range). Plants that established at all sites, in Trials 1 and 2, did not display any visual symptoms associated with mortality; however, results from Trial 1 indicated that plants grown in a tunnel at Cedara were physiologically stressed evidenced by lower transpiration rates despite higher vapour pressure deficits, compared with plants grown in a tunnel in Durban. Environmental stress was further indicated by the chlorophyll fluorescence ratio and a change in allocation of total non-structural carbohydrate (TNC) within Cedara-grown plants compared with Durbangrown plants. An attempt to relate mortality symptoms of unhealthy C. odorata plants with TNC content of the roots was unsuccessful but unhealthy plants had lower levels of N, P and K than healthy plants. Although mortality seem to be exacerbated by pathogenic fungi in saturated soil, infection was reduced by treating the soil with Previcur N and Benlate drench. Morphological adaptations of plants exposed to waterlogged soils include hypertrophied lenticels and new lateral roots; these were observed on the stem base of unhealthy C. odorata plants placed on the ground, that had reached a critical stage of die-back or had died back and re-sprouted. Examination of the root anatomy of C. odorata plants indicated an absence of cortical aerenchyma (interconnected system of air spaces), which may explain plant mortality in waterlogged pots wherein levels of oxygen in the soil may be reduced. C. odorata stock plants at Cedara have been placed on elevated grids since August 2004 and two years later plant mortality has been significantly reduced. Presently, the only feasible option is to grow potted C. odorata plants on elevated grids at Cedara because this allows for adequate drainage, aeration of soil and air-nipping of roots, and spacing plants on the grids also improves penetration of light. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2007.

An orthophoto map is made from a combination of different geospatial datasets such as relief, imagery, powerlines and annotation. These data sets are usually generated by different divisions within national mapping agencies. Often, when an orthophoto mapping project is to be undertaken, other functions within and outside the system, are actuated. Examples of such functions include; photogrammetric scanning, digital elevation capturing, aerial triangulation, ancillary data and imagery acquisition and map compilation. This research is underpinned by the hypothesis that different components that supply data required for generating orthophoto maps do not work as a coherent whole. This behaviour impacts negatively on the production of orthophoto maps as well as the quality of the end product and can have spill over effects on service delivery. In this research, systems analysis, client satisfaction survey and SWOT (Strengths, Weaknesses, Opportunities and Threats) analysis are used as a collective set of tools to analyze an orthophoto mapping system (OMS) in order to mitigate this unwanted behaviour. The case of orthophoto map production at the Chief Directorate of Surveys and Mapping (CDSM) in South Africa is used. First, systems analysis, which uses the Data Flow Diagram (DFD) technique, is employed to depict the system‘s data stores, processes and data flows. This approach helps to show how the current system works thereby assisting to pin point areas that require improvement. After presenting the system ‘s processes, data stores and data flows, a client satisfaction survey, built on the criteria of; accuracy, completeness, correctness and accessibility of geospatial datasets, is conducted on one of the data stores – the Topographical Information System (TIS) database. Finally, a SWOT analysis is then done on the whole OMS to evaluate the internal and external environment under which the current system operates in. Gaps are identified and recommendations suggested. Although in this case, the recommendations are built based on the CDSM case study, it is believed they can benefit other OMS’s in similar operating conditions elsewhere. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

The formation and common occurrence of riparian wetlands within the semi-arid Highveld interior of South Africa, a landscape setting undergoing extensive long-term fluvial incision, is an enigma and the underlying controls on the formation and hydrogeomorphological dynamics of these wetlands has not been widely investigated. Wakkerstroom Vlei is one such enigma in that it is a large (~ 1000 ha) Highveld system comprising extensive reaches of unchanneled valley-bottom wetland with considerable (up to 2 m deep) peat deposits. Accommodation space for wetland formation is thought to be controlled by the superimposition of the main (Wakkerstroom/Thaka) river upon an erosion-resistant Karoo dolerite sill at the toe of the system, which forms a stable local base-level along the rivers course. As a result, the river has carved broad (up to 1300 m), gently sloping (average slope ~ 0.17 %) valleys along softer shale valley reaches upstream of the dolerite barrier. Examination of the valley fill along these valley-bottom wetland reaches, together with analysis of historic aerial photography, reveals that continuous tracts of meandering river and floodplain wetlands formerly existed, and that the wetland experienced an abrupt shift to valley-bottom wetland conditions where surface flow of water is diffusive. Following the creation of accommodation space along the main river valley, lateral tributary streams began to deposit substantial amounts of course sediment into the main valley via alluvial fans. Several of these fans have coalesced to form multiple coalescing alluvial fan complexes that historically were able to extend far across the floodplain from either side of the valley, resulting in main river valley impoundment. This has promoted flood-out formation, along the main valley which, together with the denser growth of vegetation across the floodplain, has created conditions suitable for organic sedimentation and peat accumulation. The formation and evolution of Wakkerstroom Vlei has thus been controlled by the complex interaction between geological, geomorphological and biotic processes. Understanding the role of these factors in shaping both the short- and long-term hydro-geomorphic dynamics of the system is essential in implementing effective management and conservation strategies both within Wakkerstroom Vlei and other large valley-bottom wetlands within the South African Highveld interior. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2009.

<p>Well known dynamic models for air and stormwater quality typically involve the application of deterministic differential equations (DDEs) or random differential equations (RDEs) that apply Monte Carlo simulation. An alternative to RDEs are stochastic differential equations (SDEs), which are DDEs that incorporate random noise. In this thesis, we develop air and stormwater quality models that employ DDEs, RDEs and SDEs numerically solved by finite difference methods. The numerical results of the model variants are compared to each other and empirical data. The outcome demonstrates the utility of the SDE approach. The stormwater model is based on a one-dimensional advection-diffusion partial differential equation (PDE) that simulates the stream transport of copper in a small area within Los Angeles. Two air models are implemented, an ordinary differential equation model based on the continuity equation and a two-dimensional advection-diffusion PDE. The models approximate carbon monoxide levels in Costa Mesa and the Coachella Valley in California. The numerical PDEs are solved with the Strang splitting method, where the Lax-Wendroff and Crank-Nicolson methods are employed for the advection and diffusion subproblems respectively. For the SDE case the Euler-Maruyama method is applied to the source term subproblem. </p>

<p> Pinyon-juniper (<i>Pinus monophylla &ndash; Juniperus osteosperma</i>) woodlands have expanded and infilled over the last 150 years to cover more than 40 million ha in the Great Basin. Many land managers seek to remove Pinyon-juniper trees using a variety of treatments. This thesis looks at six different Pinyon-juniper removal projects in Central and Eastern Nevada. We established a total of 73 vegetation and soil monitoring plots (38 treated, 35 adjacent untreated) across six Pinyon-juniper removal projects in Central and Eastern Nevada to look at the effects of fire, hand thinning, and chaining. The four burns examined together in Chapter 1 had similar elevation, precipitation, and pre-treatment vegetation communities in the untreated areas, but the treated areas had significantly different responses to treatment. With nonmetric multidimensional scaling (NMS), we found a useful 3-axis ordination of the plots (stress=7.1, R²=.966). Within ordination space, the treated plots were well grouped by parent material. These results informed a Poisson generalized linear model that found parent material factorized explained 86.5% of the deviance in cheatgrass (<i>Bromus tectorum</i>) cover at the treated plots. The projects on soils derived from welded tuff had very little cheatgrass while soils derived from limestone or mixed limestone/volcanics were dominated by cheatgrass. Parent material should be considered an important factor when planning Pinyon-juniper removal treatments. Chapter 2 examined the effects of a hand thinning. The hand thinning significantly reduced tree cover [F(1,10) = 7.43, p = 0.027] to less than 2%. Perennial grasses on the site are slightly higher in the treated area. There was a significant increase in perennial grass cover from 2013 to 2014 [F(1,10) = 14.5, p = 0.003]. The hand thinning did not have significant effects on shrubs, annual grasses, annual forbs, perennial forbs, ground cover, stability, species richness, diversity, infiltration, or gap structure. Because hand thinning does not remove the shrubs or other perennials, site resistance can be maintained. With sufficient understory vegetation to maintain resistance post treatment (as in phase I or early phase II Pinyon-juniper woodlands), nonnative annual grasses are less likely to dominate after treatment. Chapter 3 examined the effects of a chaining. The effects of the 40-year old chaining are still significant even though Pinyon-juniper trees are reinvading and make up >5% of the cover in the treated area. The treated areas still have a much more productive understory than adjacent untreated areas. Perennial grass cover, frequency, and density was 2-5 times greater in the chained area. The treated area had fewer large gaps (>100 cm). However, interspace infiltration times were slower in the treatment (t(4)=-2.14, p=0.09). Surface and subsurface soil aggregate stability remained significantly lower in the treatment for vegetation-protected and unprotected samples (t(4)=3.53, p=0.024; t(4)=3.10, p=0.036). Chainings have long-term benefits for vegetation, but also long term impacts on soils and hydrologic ecosystem processes. When planning Pinyon-juniper removal treatments, land managers should consider the plant community, temperature and precipitation regime, and soils at the potential treatment location to better achieve desired outcomes.</p>

Many local authorities are major polluters and are ignoring each and every rule in the book. Raw sewerage is dumped in to rivers and the Vaal River is already a national health threat. Pollution of land, air and water is a common consequence by large corporations capable of causing harm to humans and other living organisms. Research on the pollution of these key natural resources is required to understand cumulative impacts, so as to take measures of precaution to minimize such pollution and reduce its consequences. Risk Assessments are therefore encouraged to identify and explore in quantitative terms, the types, intensities and likelihood of undesired consequences related to the risk of pollution. This study has identified a potential risk from creosote bleedings at Eskom pole yards and aims to explore the probability of such occurrences cumulatively so as to identify precautionary measures at the forefront of this problem to develop effective contingency plans. Soil samples were collected systematically and analysed for polycyclic aromatic hydrocarbons (PAH), a component of creosote that preserves wood. Studies have indicated that concentrations of this preservative beyond acceptable limits can impact negatively on natural resources especially water and soil. The laboratory analysed data indicates that the soil samples collected from the Howick Pole Yard were contaminated with PAH beyond the threshold values. The severity of the contamination, as determined by the application of the Risk Assessment tool, indicates that mitigation measures are essential. / Thesis (M.Sc.)-University of KwaZulu-Natal, 2008.

Spatial and temporal patterns of semi-volatile organic contaminant (SVOC) concentrations in air and precipitation were investigated at the urban scale in order to improve our understanding of emission sources and factors affecting intra-urban variability. Toronto, Canada was used as a case study. Advances were made in two methods used to examine intra-urban variability, namely passive air sampling and land use regression analysis. The study showed that these methods are useful for assessing local-scale variability, and that passive air sampler concentrations are most reliable when using homologue-specific sampling rates obtained from a co-located low volume sampler. The results of the spatially and temporally distributed sampling demonstrated that the highest atmospheric concentrations of SVOCs were associated with the highest density regions of the urban area. Temporal patterns of elevated concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and polycyclic aromatic hydrocarbons (PAHs) in warm seasons were consistent with temperature-related emission processes such as volatilization and/or ventilation of indoor air. Spatial patterns in air concentrations were influenced by local sources on a scale of <5 km and were explained by factors related to human population activities such as building volume (PBDEs), population density (polycyclic musks, or PCMs), residential, commercial and transportation infrastructure (PAHs), and chemical inventory (PCBs). Industrial activities were not important factors. The link between elevated environmental concentrations and the in-use stock of banned chemicals, such as PCBs and PBDEs, suggest that efforts to control emissions and reduce environmental concentrations must address the removal of current use products, in addition to the bans on new uses of the SVOCs.

Spatial and temporal patterns of semi-volatile organic contaminant (SVOC) concentrations in air and precipitation were investigated at the urban scale in order to improve our understanding of emission sources and factors affecting intra-urban variability. Toronto, Canada was used as a case study. Advances were made in two methods used to examine intra-urban variability, namely passive air sampling and land use regression analysis. The study showed that these methods are useful for assessing local-scale variability, and that passive air sampler concentrations are most reliable when using homologue-specific sampling rates obtained from a co-located low volume sampler. The results of the spatially and temporally distributed sampling demonstrated that the highest atmospheric concentrations of SVOCs were associated with the highest density regions of the urban area. Temporal patterns of elevated concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and polycyclic aromatic hydrocarbons (PAHs) in warm seasons were consistent with temperature-related emission processes such as volatilization and/or ventilation of indoor air. Spatial patterns in air concentrations were influenced by local sources on a scale of <5 km and were explained by factors related to human population activities such as building volume (PBDEs), population density (polycyclic musks, or PCMs), residential, commercial and transportation infrastructure (PAHs), and chemical inventory (PCBs). Industrial activities were not important factors. The link between elevated environmental concentrations and the in-use stock of banned chemicals, such as PCBs and PBDEs, suggest that efforts to control emissions and reduce environmental concentrations must address the removal of current use products, in addition to the bans on new uses of the SVOCs.

Thesis (M. S.)--Oklahoma State University, 2004. / Vita. Includes bibliographical references (p. 79-86).

Thesis (Ph.D.)--Drexel University, 2009. / Includes abstract and vita. Includes bibliographical references (leaves 205-220).