published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

Among the most ubiquitous and persistent air quality problems facing urban areas are high concentrations of gas phase oxidants and fine particulate matter. Ozone and particulate matter concentrations in urban areas are significantly influenced by other factors in addition to local emissions, such as regional transport spanning distances as large as 1000 kilometers. Despite the importance of regional transport in meeting air quality standards, to date most analyses of regional transport have focused only on short duration episodes, or semi-quantitative assessments. The development and evaluation of seasonal, quantitative assessments of regional pollutant transport, based on modeling calculations and observational data is the topic of this dissertation. The observational data available through the Texas Air Quality Studies in 2000 and 2006 provide a unique opportunity to develop, evaluate, and improve methods for characterizing regional air pollutant transport. Measurements collected during these studies are used as the primary observational basis for characterizing regional ozone transport and to evaluate the performance of photochemical models. Results suggest that measurements (from aircraft and surface monitors) and the photochemical model provide consistent estimates of the magnitude of ozone transport. On this basis, photochemical modeling is used to determine potential impacts of regional ozone transport in Texas, under varying meteorological and photochemical conditions, as well as to characterize the dominant chemical and physical processes within urban plumes. While qualitative studies and limited quantitative analyses have been performed to assess regional ozone transport, this work includes the first detailed quantitative characterization of the importance of ozone transport over the course of an entire ozone season using both photochemical modeling and ambient data. Results demonstrate that urban plumes in Texas are capable of transporting significant amounts of ozone over distances spanning hundreds of kilometers. Furthermore, on a seasonal basis, there are a number of days characterized by high contributions from inter-city transport coinciding with high total ozone concentrations, suggesting that the role of inter-city transport will remain significant for many areas to demonstrate attainment of the NAAQS for ozone. Results also indicate that reductions in the impacts of inter-city transport are possible by decreases in emissions from source regions. / text

When modelling pollutants in the atmosphere, it is nearly impossible to get perfect results as the chemical and mechanical processes that govern pollutant concentrations are complex. Results are dependent on the quality of the meteorological input as well as the emissions inventory used to run the model. Also, models cannot currently take every process into consideration. Therefore, the model may get results that are close to, or show the general trend of the observed values, but are not perfect. However, due to the lack of observation stations, the resolution of the observational data is poor. Furthermore, the chemistry over large bodies of water is different from land chemistry, and in North America, there are no stations located over the great lakes or the ocean. Consequently, the observed values cannot accurately cover these regions. Therefore, we have combined model output and observational data when studying ozone concentrations in north eastern North America. We did this by correcting model output at observational sites with local data. We then interpolated those corrections across the model grid, using a Kriging procedure, to produce results that have the resolution of model results with the local accuracy of the observed values. Results showed that the corrected model output is much improved over either model results or observed values alone. This improvement was observed both for sites that were used in the correction process as well as sites that were omitted from the correction process.

Commercial aviation is a vital part of the United States economy. It generates over $1 trillion annually, which is more than 5% of the U.S. GDP, and produces approximately 10 million jobs. Every year there is an increase in commercial air traffic. This is attributed to expanding trade between states and other countries, which requires larger amounts of cargo aircraft in operation, and also catering to the growing number of middle and upper class passengers who travel for business and pleasure purposes. A rise in commercial aviation leads to the use of more aviation fuel on a monthly and annual basis. This in turn leads to escalated levels of combustion by-products from jet and turbofan engines into the atmosphere. The negative effects of these by-products range from producing poor air quality and consequent health hazards to contributing to global warming. This study is aimed at assessing the impacts of aircraft emissions on the local air quality in Corpus Christi using the Emissions and Dispersion Modeling System. Flight data for the study was obtained from the Department of Transportation's Research and Innovative Technology Administration. Analyses of the emissions were compared on monthly, annual, engine type and airline provider bases. Climatic, economic and anthropogenic factors were identified in the analyses.

The relationship between deteriorated outdoor air quality and human health is one of the most studied environmental health issues. The concept of exposure, the link between environmental status and human health, has emerged in the late 1970's, recognizing that fixed monitoring stations do not represent concentrations at the places where persons spend time. Many advances have been made since. Characterizing the individual's exposure reduces uncertainty in links with health, but it implies a question about how exposure (as opposed to directly using concentrations) can be used in the regulatory process. This thesis addresses exposure assessment from several perspectives, with the aim to address its role in air quality management. We are interested in how to use exposure information for policy- and decision making, we investigate if a European-level subgroup-based exposure estimate can provide useful information for designing differentiated measures to protect specific groups, we design an exposure estimate for risk assessment in a specific situation with limited health and air pollution data, and we describe the challenges of the inherent inter-disciplinarity and suggest how to deal with them. We introduce the "full chain" approach to environmental health that links policy - pollution source -...

The purpose of this study was to investigate whether the sampling points for measuring airborne dust deposition in the Aitik copper mine - the largest, most effective opencast copper mining in Europe - are well located regarding efficiency to collect monitoring data. Issues that were addressed, among others, include background levels, weather impacts and possible external influence. The study was carried out by analyzing monitoring data covering a seven-year period (2010–2016). Dust-and copper levels, precipitation patterns, wind direction and wind speed were the parameters analyzed. A further look into the sampling points and their actual location in terrain was also made. The result of the study indicates, according to different aspects, on decreasing dust fall levels even though the production has increased. For instance, many of the 19 sampling points shows to have lower dust and copper levels according to a comparison of measurement data from 2010 to 2016. A correlation test showed that precipitation and wind does not have a strong connection to dust levels. On the other hand, wind speed showed to have a strong impact on dust fall levels under periods when the highest dust amounts were measured. Many of the sampling points also showed to have a strong connection to each other. The study concludes that a better dust control programme can be obtained if sampling points are reorganized along with a better method for calculating the dispersion of airborne dust.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2016. / Global methane (CH4) emissions are divided mostly into three sources; biogenic, thermogenic and pyrogenic. The sources can be anthropogenic or natural in origin. Anthropogenic sources include emissions associated with agriculture (rice paddies and ruminants), waste (landfill and waste water), biomass burning and fossil fuels. Landfills have been implicated as one of the largest anthropogenic sources of atmospheric CH4 globally and as a significant contributor to global warming. According to the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report anthropogenic sources account for 304 – 368 TgCH4/year and methanogenesis in landfills and waste contributes between 67 and 90 TgCH4/year to this amount (between 22 and 24% of emissions). / GR2016