Browsing by Author "Altieri, Katye"
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- ItemOpen AccessAn analysis of the potential socio-economic impacts of shale gas development in South Africa(2016) Tukwayo, Yonela; Altieri, Katye; Caetano, Tara HelenaThe South African government is in the process of considering shale gas exploration applications in the Karoo basin. There are conflicting views on whether the development of the resource will be to the detriment or benefit of the South African economy. This paper makes use of a dynamic Computable General Equilibrium (CGE) model adapted for the South African energy sector to analyse the potential socio-economic impacts of the development of shale gas. Simulation results indicate potential negative impacts on GDP contribution by all the sectors simulated, except the natural gas sector and the Gas-to-Liquid petroleum sector, as well as potential negative impacts on employment. The negative impacts on growth and employment are likely to worsen poverty and inequality. Potential impacts on trade are negative as the trade deficit increases. In terms of environmental impacts, the uptake of gas would decrease CO2 emissions. All results are compared to the baseline scenario. Based on these results, it is recommended that the decision on whether the development should go ahead or not ought to take into account the potential socio-economic costs, and potential ways to hedge against them.
- ItemRestrictedAnalysis of the quantity and cost of modelled nitrate deposition to the Vaal River from power station emissions with insights for cost-benefit analysis and policy recommendations(2019) Ras, Anna; Sparks, Debbie; Altieri, KatyeAnthropogenic processes have led to high levels of reactive nitrogen entering freshwater ecosystems. This increase in reactive nitrogen levels has caused several adverse environmental and health effects and has resulted in higher deposition rates of nitrates to freshwater ecosystems. The costs and benefits associated with nitrate deposition have been analysed by the European Nitrogen Assessment (ENA) for European countries. However, no studies similar to this have been done for the South African context. The aim of the study was to present a cost analysis of nitrate deposition originating from power station NOx emissions. The objectives were: to examine the changes in nitrate deposition for the years 1980, 2005, 2006 and 2014; to determine the costs associated with nitrate deposition to freshwater ecosystems for the South African context; to calculate the costs of power station emissions to the Vaal River; to consider how European costs differ from South African costs; to consider the impact of the NEMAQA of 2004 and finally, to evaluate the likelihood of these costs being incurred. The years that were selected for this study were chosen due to availability of data, which were supplied by EScience Associates. Three scenarios were considered for each of these years: Scenario 1 was a case in which Eskom operated as usual without any retrofits of power stations, Scenario 2 considered the implementation of the Eskom air quality management strategy and Scenario 3 considered full compliance with the minimum emissions standards set out in the NEMAQA of 2004. The costing method followed the ENA approach, whilst considering the South African context by consulting the relevant literature. The monetized annual costs for the South African context were: mitigation options for improving water quality; increased coal consumption due to power station interventions; agricultural costs; water purification and waste treatment; health impacts and loss of biodiversity as a result of acidification and eutrophication. Power station interventions were found to be the only capital expenditure. The nitrate deposition per unit of electricity generated was expected to decrease, due to changes within the electricity mix of Eskom during this period. Furthermore, the least costly option was expected to be a scenario in which no intervention was made by Eskom to reduce emissions, due to the high capital cost associated with retrofitting low NOx burners in the older power stations. The final expected outcome was that the National Environment Management: Air Quality Act (NEMAQA) of 2004 would have led to a significant decrease in the emissions and, therefore, nitrate deposition to the Vaal River. The costs that were calculated for the South African context differed greatly from the costs in the ENA, indicating that the European costs could not be used directly for the South African context. Furthermore, the results showed that the costs of nitrate deposition increased between 1980 and 2005, decreased between 2005 and 2006 and increased again between 2006 and 2014. Between 1980, 2005 and 2006, a clear link is seen between electricity generated and nitrate deposition. Even though electricity generation increased from 2006 to 2014, the 2014 emissions data show that emissions decreased over the same period. The cost of a fine for non-compliance to emission limits is R10 million. The lowest cost calculated for each year and scenario was found to be Scenario 1 for 1980, and was approximately R 70 million of costs arising from nitrate deposition from power station emissions. The R 70 million, therefore, does not include mitigation options for water quality, increased coal consumption and power station interventions. Therefore, the fines associated with non-compliance, which occur in Scenario 1 and Scenario 2, should be increased to force compliance. The total cost associated with Eskom’s air quality strategy, calculated as part of scenario two, was the lowest cost option for 1980, 2006 and 2014. In 2005, the lowest cost option was scenario 1, where no retrofits were done by Eskom. This indicated that there was a trade-off between capital expenditure for low NOx burners and the annual costs, listed previously. This study concluded that when air quality policies, such as the NEMAQA of 2004 are implemented without stringent enforcement, the desired result is not achieved. The findings in this study show that no significant decrease in nitrate deposition occurred between 2005, when the NEMAQA of 2004 was released, and 2014, which was almost 10 years after the policy was implemented. This study makes a valuable contribution to informing policy makers on the impact of reactive nitrogen addition to the environment. Future research should be done on the cost of agricultural nitrate deposition to the Vaal River, considering that these inputs to the Vaal River are several times larger than those of deposition from power station emissions and could, therefore, have costs of a larger scale associated with them.
- ItemOpen AccessBiogeochemical controls on ammonium accumulation in the surface layer of the TD: Southern Ocean(2022) Smith, Shantelle; Altieri, Katye; Fawcett, SarahThe production and assimilation of ammonium (NH₄⁺) are essential upper-ocean nitrogen (N) cycle pathways. However, in the Southern Ocean where the alternation between biological nitrate drawdown in summer and physical nitrate resupply in winter is central for setting atmospheric CO2, the active cycling of NH₄⁺ in the seasonally-varying mixed layer remains poorly understood. On a cruise from Cape Town (33.9°S) to the Marginal Ice Zone (MIZ; 61.4°S) in winter 2017, surface samples were collected and analysed for nutrient concentrations, planktonic community composition, size-fractionated rates of net primary production and N (as NH₄⁺, urea, and nitrate) uptake, and rates of NH₄⁺ oxidation. NH₄⁺ concentrations, measured every four hours, were five-fold higher than is typical for summer, and lower north than south of the Subantarctic Front (SAF; 0.01–0.26 µM versus 0.19–0.70 µM). Thus, showing that NH₄⁺ accumulates in the Southern Ocean's winter mixed layer, particularly in polar waters. NH₄⁺ uptake rates were highest near the Polar Front (PF; 12.9 ± 0.4 nM day-1 ) and in the Subantarctic Zone (10.0 ± 1.5 nM day-1), decreasing towards the MIZ (3.0 ± 0.8 nM day-1) despite the high ambient NH₄⁺ concentrations, likely due to the low temperatures and limited light. By contrast, rates of NH₄⁺ oxidation were higher south than north of the PF (16.0 ± 0.8 versus 11.1 ± 0.5 nM day-1), perhaps due to the lower light and higher iron concentrations characteristic of polar waters. Additional NH₄⁺ concentration measurements spanning the 2018/2019 annual cycle suggest that mixed-layer NH₄⁺ accumulation south of the SAF is due to sustained heterotrophic NH₄⁺ production in late summer through winter that outpaces NH₄⁺ removal by temperature-, light, and iron-limited microorganisms. The contribution by heterotrophic prokaryotes is supported by observations from winter 2017, where lower ratios of photosynthetic-to-heterotrophic cells were associated with maxima in NH₄⁺ concentrations. These observations imply that the Southern Ocean 27 becomes a biological source of CO₂ to the atmosphere in autumn and winter, not only because nitrate drawdown is weak, but also because the ambient conditions favour net heterotrophy and NH₄⁺ accumulation. High wintertime surface NH4 + concentrations, and the drivers of biological NH4 + cycling, may also have implications for nitrate uptake, through inhibition, and for the air-sea flux of ammonia gas, with the latter influencing the formation of aerosols, clouds, and climate.
- ItemOpen AccessChemical composition and pH of marine aerosols in the summer-time marine boundary layer of the Atlantic sector of the Southern Ocean(2023) Xokashe, Sive; Altieri, KatyeAerosol acidity is a fundamental parameter of aqueous chemistry that impacts the lifetime of pollutants, biogeochemical cycles, human health, and climate. However, despite this importance, the effects of aerosol pH on these processes are difficult to constrain, in part because there are no direct methods to measure aerosol pH. The lack of observations in the remote clean atmosphere makes quantification of aerosol pH even more challenging. This dissertation aims to predict the spatial and temporal variation of aerosol pH and its drivers in the marine boundary layer of the summertime Southern Ocean. Results are presented from Ambient Ion Monitor (online method) and high volume sampler (offline method) based chemical analysis of aerosol species sampled during a cruise from Cape Town (34.11°S, 18.03°E) to Antarctica (70°S, 2.11°W). In addition, a thermodynamic model, ISORROPIA-II, is used to predict the pH of aerosol. The thermodynamically predicted aerosol pH from both the online and offline methods are generally acidic (i.e., <7). The modelled pH of particles with a diameter less than 1 µm (submicron) from the offline method ranged from -0.67 to 4.37 with an average value of 0.27, while the pH of particles with a diameter greater than 1 µm (supermicron) ranged from 1.67 to 4.68 with an average value of 2.98. For the online method, which only sampled particulate matter with a diameter less than 2.5 µm in size (PM2.5), the pH ranged from -0.68 to 4.46 with an average value of 2.07. The variation in predicted submicron pH was best explained by the sodium to sulfate (Na+ /SO4 2- ) ratio, while no relationship was observed with temperature or relative humidity. For both supermicron and the PM2.5 aerosols measured online, the pH was best explained by the molar ratio of the inorganic aerosol species. In addition, the supermicron pH varied as a function of relative humidity while for the PM2.5 did not. Using a combination of aerosol concentration, windspeed, and sea ice concentration data, along with air mass back trajectories, it was found that generally, aerosol samples that originated from the open ocean were relatively more acidic compared to those that had air mass back trajectories originating from sea ice covered surface ocean. This was attributed to the partitioning of hydrogen chloride (HCl). One of the major limitations in this study was a lack of aerosol gas concentrations to constrain the model (e.g., ammonia (NH3), nitric acid (HNO3), HCl). Therefore, to improve the predicted aerosol pH, measurements of aerosol gas species is highly recommended. Additionally, it was found that when an offline method is used, an online method proves useful for validation of possible sampling artefacts that may be occurring in the offline method.
- ItemOpen AccessInfluence of environmental parameters on atmospheric aerosol size distributions in a South African coastal zone(2023) February, Faith; Altieri, KatyeAerosols are microscopic solid or liquid particles suspended in the atmosphere, which impact and are impacted by many physicochemical processes related to climate. By scattering and absorbing solar radiation and acting as cloud condensation nuclei, they have both a direct effect and indirect effect on Earth's radiative budget. The Intergovernmental Panel on Climate Change (IPCC) recognizes aerosols as an important component of climate change, and as such the estimation of their impacts on climate remains an important scientific challenge. Atmospheric aerosol sources include natural and anthropogenic emissions, and these are both present in coastal areas. Marine aerosols are a major contributor to total aerosols in coastal regions, and these aerosols can interact with other gases and molecules, and influence biogeochemical cycles, air quality, and human health. Due to the complex nature of aerosols in coastal areas and the importance of aerosols to climate change, there is a need for in-situ observational aerosol data from data poor regions, which is the case for most of the Southern Hemisphere. To that aim, this thesis presents an extensive series of measurements of aerosol properties (concentrations, sizes, and types) at the coastal location of Simon's Town in False Bay, to characterize these properties for the first time in a coastal region of South Africa. The study site provides the opportunity to measure these aerosol properties in pristine marine conditions exclusively, as well as mixed conditions typical of a coastal site. With these geographical advantages and long-term, unbiased measurements, the aerosol processes of generation, transport, dispersion, mixing, and deposition have been investigated under unique natural conditions. The data analyses focus on evaluating changes in the average particle size distributions with changes in meteorological parameters. An increase in aerosol concentrations with an increase in wind speed during clean marine conditions resulted in the identification of sea spray generation and long-range transport as the dominant natural aerosol processes with the type of aerosol being predominantly marine. For the NW conditions, a decrease in aerosol concentrations with an increase in wind speed led to the identification of dispersion as the dominant process. A mixture of aerosol types emerged, but the higher aerosol concentrations for the pure continental conditions compared to the pure marine conditions indicated that non-marine aerosols dominate around 0.4 μm and 10 μm. The main conclusions of this thesis focus on the behavior of natural sea spray aerosols in the absence of continental or anthropogenic sources. This highlights the pure marine influence of the Southern Ocean at this location and the unique opportunity to explore understudied natural aerosol processes absent from anthropogenic influence.
- ItemOpen AccessVariations of the chemical characteristics and source regions of aerosols at the Cape Point GAW station(2022) Spence, Kurt; Altieri, Katye; Labuschagne, CasperNitrogen is an essential component for life. The natural nitrogen cycle has been greatly disturbed by the production of fertilizer and use of fossil fuels, such that it has doubled the amount of reactive nitrogen (Nr) produced globally. Excessive additions of Nr to the environment can have negative effects, including eutrophication, loss of biodiversity, enhanced greenhouse gas emissions, acidification, increased tropospheric ozone, and damage to human health. Excess ammonia (NH3) and nitrogen oxide (NOx) emissions lead to increased aerosol loading via secondary aerosol formation processes. Increased aerosol loading has impacts on the climate and on human health. Furthermore, the aerosols formed from Nr from continental sources can get deposited to the open ocean, which is usually nitrogen limited. Knowing the concentrations of different aerosol species from a pollution free environment, such as the remote open ocean, can give insights into the natural preindustrial conditions and be used as a baseline for looking into the impacts of anthropogenic activities. This thesis focuses on establishing the Cape Point Global Atmosphere Watch (GAW) station as a site for collecting aerosol samples from pristine marine air masses. The use of a tower site allows for high temporal resolution sampling across multiple seasons and years, which is logistically difficult when relying on ship-based sampling of pristine marine environments. Results are presented from the chemical composition analysis of aerosols sampled at the Cape Point GAW station, including comparisons of two different aerosol sampling systems (tall-tower PM10 and ground-based sizesegregated). Furthermore, the installation and testing of a sector-controlled sampling system designed to reduce continental influence on samples is evaluated. Air mass back trajectories and radon (222Rn) concentrations were used to classify the air masses of each aerosol sample as either marine, modified marine, or continental. We found that continental samples had elevated concentrations of NH4 + , NO3 - , and non-sea-salt SO4 2- , whereas the marine samples had elevated concentrations of Cl- , and Na+ , as expected. A comparison of the tall-tower PM10 and ground-based size-segregated sampling systems showed that the ground-based sampler measured higher concentrations of coarse mode aerosols. This is attributed to the settling of large aerosols within the long sampling intake tube from the tower sampling system. The sector-controlled sampling system based on wind speed and direction was able to remove some of the influence of continental air masses, however some continental influence could not be avoided as the continental air masses circulated over the ocean before being sampled from the marine sector. This system could be improved by having additional cut-off limits defined for sampling, such as particle number, black carbon, or carbon monoxide (CO) concentrations.
- ItemOpen AccessVertical air profiling in False Bay(2019) Maritz, Benita; Altieri, Katye; van Ejik, AMJMarine surface layer micrometeorology mainly constitutes vertical turbulent fluxes of parameters such as momentum, heat, water vapour and aerosols. These turbulent fluxes have been tested in the laboratory and can be applied to the atmospheric changes over the ocean, where wind speed, the air-sea temperature difference (ASTD) and humidity play a major role. Due to the difficulty of actually measuring these changes directly, equations were derived that describe the micrometeorology in terms of actual meteorological observations. The theory of micrometeorology in turn provided the accepted calculations to predict vertical profiles for wind speed, air temperature and humidity. Nevertheless, using micrometeorology theory to predict atmospheric conditions over the ocean proves to be more difficult than over land. This is mainly due to the complex nature of the oceanic environment and its interaction with the atmosphere directly above it. The primary objective of this work was therefore to investigate the potential of deploying a Helikite in order to characterise the lower atmosphere in False Bay. Focus was placed on the methods to correctly measure air profiles over the ocean up to a maximum height of 200 m. A description of the system set-up, data acquisition, deployment parameters and data analysis are discussed. The second objective was to evaluate the micrometeorology theory used in a micrometeorological model for the marine surface layer with False Bay data. This was achieved by using experimental data to run the model. The model output was then compared to the experimental profile measured as part of objective one. The micrometeorological model it aimed to assess is based on the standard bulk meteorological observations of wind speed, temperature, humidity and the turbulent fluxes of momentum, heat and water vapour. Analysis of the various environmental parameters showed a complex oceanographic and atmospheric system. The air profiles recorded for this study were recorded in an area where smaller scale local effects were dominant, which could explain some of the discrepancies encountered when attempting to reproduce the measured profiles using micrometeorology bulk parameterisations. The four profiles described in this thesis were grouped with two profile days showing a good comparison between the predicted and measured profiles. Results also indicated that micrometeorology theory perform better when using the ‘bucket’ Sea Surface Temperature (SST) at 0.5 m below the surface.