3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item An assessment of spatial and temporal variations of nitrogen dioxide over Mpumalanga highveld(2017) Malaza, Lucky SamuelHigh concentrations of nitrogen containing compounds are a growing concern in the Mpumalanga Highveld with satellite measurements confirming high NO2 in different hotspots around the globe including Mpumalanga Highveld. Nitrogen oxides are produced from the eight coal fired power stations in Mpumalanga Highveld, a petrochemical industry in Secunda, steel processing plants in Middelburg and Emalahleni and tail emissions from traffic in the Mpumalanga Highveld. Monitoring of these trace gases is important to estimate an impact that they cause to human health and the environment and also to implement air quality emission standards by government Authorities. A 2008 data from Elandsfontein monitoring station and seven other monitoring stations in the Mpumalanga Highveld have been compared with the 2008 satellite data taken from Ozone Monitoring Instrument (OMI) overpass over the Mpumalanga Highveld. Elandsfontein monitoring station is situated on the highly industrialized Mpumalanga Highveld and its purpose is to monitor impacts of stack emissions on air quality. The study focuses on a 2008 nitrogen dioxide dataset which was taken from Elandsfontein monitoring station. An analysis of data from other monitoring stations located in Ermelo, Bulfour, Hendrina, two stations in Middelburg, Emalahleni, Standerton and Secunda have been undertaken to indicate temporal variation and spatial distribution of nitrogen dioxide in the Mpumalanga Highveld. Temporal variability and spatial distribution of nitrogen dioxide in the Mpumalanga Highveld were estimated by analyzing the ground based measurements and satellite data sets. Smoke stacks emit NO into the atmosphere where it reacts with atmospheric oxygen to form NO2. Subsequent reactions of NO2 result in the formation of ozone. The satellite derived data has been modelled and compared with the ground measured data. Meteorological factors including diurnal and temporal variations of the NO2 concentrations have been analyzed to establish differences and similarities between the two data sets. Vertical column densities of nitrogen oxides from satellite measurements with high resolution are presented in mole x (1015)/cm2 and together with ground measured data from other eight air quality monitoring stations have been converted into μg/m3. Analysis of both data sets have been done on the same units, μg/m3 . Seasonal and diurnal variations between the two data sets seem to form the same graphical trends by showing high concentrations during winter than in summer. Ground measured and satellite born datasets do not agree because clouds, air mass factor, aerosols and surface albedo create retrieval errors on the satellite data.Item The atmospheric nitrogen budget over the South African Highveld(2010-03-15T10:28:33Z) Ferguson, Kirsten SheenaMolecular nitrogen is a highly abundant element in the atmosphere; it is stable and not very reactive. Anthropogenic activities have caused greater concentrations of nitrogen-containing compounds that are highly reactive and ultimately toxic. Reactive nitrogen concentrations have become a growing concern on the South African Highveld, with satellite images indicating very high nitrogen dioxide concentrations in the region. This study investigates the nitrogen budget on the Highveld through the analysis of the nitrogen species emitted into the atmosphere on a temporal scale as well as the atmospheric conversion, transport and removal of these species. Data was collected at Elandsfontein monitoring site, which is centrally located on the industrialised Highveld. The formation and interaction of nitric oxide (NO), nitrogen dioxide (NO2), and nitrate (NO3) are a major focus in the study. NOx concentrations are higher in winter (6.5 to 8.5 μg.m-3) as a result of stable atmospheric conditions. NO3 concentrations also peak during winter (3.5 to 5.5 μg.m-3), with a distinct biomass burning peak during July and August. Diurnally, NOx concentrations indicate a tall-stack industrial source, with concentrations peaking at midday. NO3 concentrations are higher at night and lower during the day, as during the day the NO3 radical is rapidly photolysed and nitrates cannot be produced. Case studies indicate that the conversion rate of NO to NO2 is highly variable as a result of varying atmospheric factors. These rates range from 11% to 59% per hour. Rates of dry deposition of NO, NO2 and NO3 are generally higher during winter as a result of higher concentrations and increased atmospheric stability, which prevents transport out of the region. Nitrogen is predominantly deposited as NO2 throughout the year, except during spring when NO3 deposition dominates. The total amount of nitrogen deposited to the Mpumalanga Highveld region is in the range of 6.7 to 13.1 kg ha-1 yr-1, which is well below the stipulated critical load value. Such deposition therefore does not pose significant threats to the natural environment on the Highveld. Between 4% and 14% of the total emitted nitrogen on the Highveld is deposited to the surface via wet and dry deposition. The remainder stays in the atmosphere and is advected out of the region.