The measurement of ambient particulate concentration (PM10 and PM2.5) using active monitors requires expensive or labour-intensive apparatus or both. Although PM is a priority pollutant, this has precluded widespread or intensive ambient particulate monitoring networks to be set up in South Africa, except in some priority areas. In this study, locally manufactured passive PM monitoring devices (samplers), based on a design initially published by researchers at the University of North Carolina (UNC), were calibrated for the measurement of PM10-2.5. Duplicate samplers of each type (local and UNC) were co-located at eight reference stations equipped with TEOM (Tapered element oscillating microbalance) or BAM (Beta radiation attenuation monitor) particulate monitors in three networks. Imaging of the substrate was carried out using an optical microscope to limit the cost of analysis. The images (10 to 49 per sample) were analysed using both proprietary (Zeiss AxioVision®) and open-source (ImageJ) software at 100X and 200X magnification. Considerable variation exists between the four co-located local and UNC samplers at all stations, although the latter show lesser discrepancies when analysed using the AxioVision software. Greater agreement of the local samplers and the continuous monitors is noted at a 200X and 100X magnification using the AxioVision software with R2 = 0.81 and R2 = 0.79 respectively. The precision of PM10-2.5 measured with the passive samplers was highly variable with calculated CVs ranging from 10.4% to 73.3%. 82% of the CVs were less than 40%. The average CV for all samplers was 34.6%. Passive samplers analysed using the AxioVision software recorded smaller average discrepancies of 45.3% at 100X and 37.3% at 200X magnification. Samplers analysed using ImageJ at 100X magnification exhibited the highest percentage difference from the reference values (81.2%). Using a two factor ANOVA we can show that (at 95% confidence) the analysis software and the imaging magnification have the most significant effect on the calculated sampler concentration results. A disadvantage of passive samplers is large number of days (2-7) required to produce statistically significant values hence disqualifying it for use as a reference method. The device is, therefore, more suitable for screening-level, high spatial density sampling, but some non-regulatory applications are pointed out. / Dissertation (MEng)--University of Pretoria, 2019. / Chemical Engineering / MEng (Environmental Engineering) / Unrestricted

Thesis (M. Sc.)--University of Hong Kong, 1993.

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

Active travel can provide short-term and long-term health benefits and has the ability to reduce the negative externalities of vehicular traffic, for example, congestion, land consumption, and air pollution. However, exposure to air pollution is higher for pedestrians and cyclists than other road users when considering inhalation rate and travel distance. Route choice for active travel is a potential strategy to reduce the adverse impact of exposure to air pollution. Multi-use trails could be an effective way to reduce health impacts as the pollutant concentration is typically lower on trails, however, proximity to nearby roadways can deteriorate the air quality in multi-use trails. The goal of this study is to investigate the air pollutant concentrations on multi-use trails adjacent to different roadway classification and identify the factors that influence air quality in multi-use trails. I collected pollutant concentrations of PM2.5, particle number, and black carbon using mobile monitoring on an e-bike. I identified five trail routes that run parallel to an interstate highway, principal arterial, and local roads for this study and collected pollutant concentrations during morning, afternoon, and weekend afternoon peak hours. The average concentration of PM2.5, particle number, and black carbon was 15.62 µg/m3, 9,857 pt/cc, and 595.36 ng/m3 respectively among all the trail routes used for this study. I observed higher pollutant concentrations during morning peak hours than afternoon peak hours. Also, concentrations were lower on weekends than weekdays. The pollutant concentrations were different among multi-use trails based on their proximity and characteristics of nearby roadways. The pollutant concentrations significantly declined when the trail segment was 50-100 meters away as compared to segments within 50 meters of nearby interstates, freeways, or collectors. Concentrations increased significantly for trail segments having a nearby road Annual Average Daily Travel (AADT) of more than 32,000. The regression models explain 65%, 59%, and 52% of variability in the PM2.5, particle number, and black carbon concentrations respectively. Nearby road AADT and road density were found to be significant for PM2.5, particle number, and black carbon concentrations. Cooking place (rest areas with barbeque grills) and construction sites were significant and positively associated with PM2.5 concentrations. Airport and construction sites near trails showed a positive relation to the particle number concentration. Parking spaces near trails increase the concentration of black carbon along trails. This study shows the impact of roadway proximity on the air quality of trails which should be considered by municipalities while planning for multi-use trail network to mitigate health risks of pedestrians and bicyclists on trails. / Master of Urban and Regional Planning / Traffic related pollutants such as PM2.5, particle number, and black carbon can cause short and long terms health impacts. Exposure to these pollutants varies by travel mode, duration, route selection, etc. People who bike or walk have higher exposure than other users when taking the inhalation rate and travel duration into account. Hence, route choice is important in active travel. Multi-use trails could be effective to reduce exposure as the pollutant concentrations are typically lower on multi-use trails. However, multi-use trails are often in close proximity to pollution sources (i.e. roadways). This study focuses on identifying the impacts of road proximity and other determinants of air quality along multi-use trails. I selected five multi-use trails based on the classification of adjacent roadway and collected air quality data. I found that air quality differs along trails based on the proximity of nearby roadway and the trail route along interstate highway had the highest concentration of pollutants. The concentrations of pollutants were higher during morning than afternoon and also, it was higher during the weekdays than weekends. Trail segments within 0-50m distance of a nearby interstate or freeway had the highest concentration which decreased as the distance from the interstate or freeway increased. Construction site, airport, and BBQ place along trails also worsened air quality on multi-use trails. This study demonstrates the importance of selecting trail locations when planning for the trail network to improve the air quality on multi-use trails that will further improve the benefits of active travel.

Thesis (M. Sc.)--University of Hong Kong, 2001. / Includes bibliographical references (p. [84-85]).

No description available.

Thesis (M.S.)--University of Texas at El Paso, 2008. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (M. Sc.)--University of Hong Kong, 1995. / Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 226-244). Available also in a digital version from Dissertation Abstracts.

No description available.