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Pollution of air represents the contamination with matter that can affect both humanhealth and the environment. Road dust has been recognized as a dominant source ofparticulate matter and one of the factors that contributes to its development is the useof gritting sand. Gritting sand is being used during snowy winter conditions as atraction control method. During spring season, when snow and ice melt and surfacesdry out, and the influence of traffic, asphalt surface wear, particle ejection from tires,etc; under the effect of their interaction, cause the formation of particulate matter.A general aim of this study was to perform analysis of factors which can be consideredresponsible generating road pollution, with resistance to abrasion of gritting sandbeing a potential key problem. The correlation between the use of studded tires andparticulate matter formation has been considered to be one of major issues in urbanareas.In order to carry out this investigation, an individual study case was considered,measurements indicated that levels of pollution increased even after studded tires werebanned.The literature review revealed important knowledge gaps regarding the quantificationof particulate emissions from non-exhaust sources, most importantly, emissions due tolow quality gritting sanding. At this point, very little information is available thatcould be used for determining the resistance to abrasion of gritting sanding material.This is further supported by numerous institutions and companies, all suggesting thatquality of gritting sand is not taken into consideration. Gritting sand is part of abigger problem which also involves types of pavement, types of tires, weather,background pollution, etc. Furthermore, there is no practical method to characterizewear of resistance of gritting sand.

Chronic respiratory diseases such as asthma and chronic bronchitis have significantly increased in prevalence in Africa over the past 10 years. Recent studies have demonstrated that exposure to air pollution may be associated with an increased risk of chronic respiratory diseases. However, such studies have predominantly been conducted in western societies or often used urbanicity as a proxy for exposure to air pollution. Therefore, we evaluated the association between PM2.5 exposure and asthma/chronic bronchitis in Senegal. A cross-sectional study was conducted for the time period of 3 October 2010 to 28 April 2011 using annual concentrations of PM2.5 measured via multiple satellite instruments, and asthma/chronic bronchitis, which was self-reported at baseline via a health survey questionnaire. We used mixed model logistic regression to evaluate the relationship between PM2.5 exposure and asthma/chronic bronchitis risk while adjusting for lifestyle factors, location, and other air pollutants. Sex was evaluated as an effect modifier. The adjusted association between PM2.5 and asthma/chronic bronchitis was 1.03 (95%CI: 0.99 – 1.06). In males the adjusted odds ratio was 1.09 (95%CI: 1.03-1.15), compared to females (aOR 1.01 (95%CI: 0.97 – 1.05). Our results suggest that increasing levels of exposure to PM2.5 puts individuals at a higher risk for chronic respiratory diseases, especially men. These findings have significant policy implications and should be built upon in future research.

<p> Pollution problems have drawn worldwide awareness and become significantly important now. Particulate matter (PM) emission is one of the key pollution issues. Particulate matter has a significant impact on the environment and human health, especially particle sizes that range below lOJJ.m. Researches continuously work an improvement of fine particulate matter collections emitted from all kinds of sources, such as automobiles, industrial combustion, etc. Governments in many countries are planning to regulate the PM emission from the existing PM10 (particle diameter<10μm) to new limits PM2.5 (particle diameter<2.5μm) within the next few years. For this reason, present PM control system needs to be improved. </p> <p> The objective of this work is to develop a dust flow separator type electrostatic precipitator (DFS-ESP) for the effective control of fine particulate matter emission from natural gas combustions. The characteristic of PM emitted from natural gas combustion is studied, and the performance of a DFS-ESP is evaluated by experiments and numerical predictions. </p> <p> An experiment was conducted for natural gas combustion exhaust flow rates from 2.5 to 9 Nm^3/h, ESP applied voltages from 0 to 30kV, and gas temperature from 80 to 160°C. A series of particle measurements were conducted at upstream, downstream and middle of the DFS-ESP system by an optical particle counter for particle mass density, and by condensation nucleate particle counter for particle size distributions and particle number density. Particle sampled from the natural gas combustion system was also analyzed by an environmental scanning electron microscope (ESEM) technique. Flow velocity profile and pressure drop of the DFS-ESP were measured by a Pitot tube and diaphragm type pressure transducer, respectively. </p> <p> The experimental results show that the particle size emitted from natural gas combustion ranges from 17 to 300nm in diameter, and the volume density is approximately from 5 x 10^8 #pt/m^3 to 5 x 109 #pt/m^3 depending on the combustion conditions. The dust flow separator can concentrate 90% of fine particles in 1 to 3% of the gas flow and divert it from the main flow to the ESP section where the particles can be removed. In terms of overall particle collection efficiency, the DFS-ESP system can remove up to 90% of the particles based on the number density. The pressure drop across the DFS-ESP is observed to be lower than lPa for the present range of flow rate, which is within acceptable limits for industrial applications. </p> / Thesis / Master of Applied Science (MASc)

<p> Increasingly stringent legislation governing the emissions of diesel engine particulate matter (DPM) has required the development of technological improvements to diesel engines, fuels and exhaust treatments. A main focus of diesel particulate matter abatement is on exhaust after treatment, that consists of the removal of particulate matter from the exhaust gas after it exits the engine. This is currently accomplished with regenerative diesel particulate traps that are effective at removing DPM, but are costly and introduce a significant pressure drop in the exhaust flow.</p> <p> The objective of this study was to evaluate the potential of a novel particulate removal system consisting of a particulate flow separator combined with electrostatic precipitators (ESPs). Previous application of this system to natural gas emissions resulted in collection efficiencies larger than 90% with negligible pressure drop.</p> <p> The ESPs used in the proposed flow separator-ESP were characterized and have collection efficiencies of up to 99% at the flow rates studied. The flow separator-ESP was characterized with a straight inlet section and an expanding inlet section. The collection efficiency of the flow separator-ESP configured with the expanding inlet section was up to 60% for a flow rate of 2.5 kg/hr, that corresponded to laminar flow with Reynolds number of 1100. Collection efficiencies on the order of 20% were obtained for exhaust flow rates of 3.75 kg/hr (Re = 1500) and 5.0 kg/hr (Re = 2100) for both inlet configurations, and 2.5 kg/hr with the straight inlet. The effectiveness of the current design is limited by exhaust flow rate.</p> <p> The diesel exhaust gas was sampled using a partial flow dilution tunnel developed specifically for this study. The dilution ratio for this system can be estimated to within ±10% using volumetric flow measurements. It was found that changes in the dilution and sampling velocity ratios for diesel exhaust have some effect on measured particulate matter mass concentrations.</p> / Thesis / Master of Applied Science (MASc)

Air quality management strategies in the US are developed largely from estimates of emissions, some highly uncertain, rather than actual measurements. Improved knowledge based on measurements of real-world emissions is needed to increase the effectiveness of these strategies. Consequently, the objectives of this research were to (1) quantify relationships among urban emissions sources, land use, and demographics, (2) determine the spatial and temporal variability of emissions, and (3) evaluate the accuracy of official emissions estimates. These objectives guided three field campaigns that employed a unique mobile laboratory equipped to measure pollutant fluxes by eddy covariance. The first campaign, conducted in Norfolk, Virginia, represented the first time fluxes of nitrogen oxides (NO_x) were measured by eddy covariance in an urban environment. Fluxes agreed to within 10% of estimates in the National Emissions Inventory (NEI), but were three times higher than those of an inventory used for air quality modeling and planning. Additionally, measured fluxes were correlated with road density and increased development. The second campaign took place in the Tijuana-San Diego border region. Distinct spatial differences in fluxes of carbon dioxide (CO₂), NO_x, and particles were revealed across four sampling locations with the lowest fluxes occurring in a residential neighborhood and the highest ones at a port of entry characterized by heavy motor vehicle traffic. Additionally, observed emissions of NO_x and carbon monoxide were significantly higher than those in emissions inventories, suggesting the need for further refinement of the inventories. The third campaign focused on emissions at a regional airport in Roanoke, Virginia. NOx and particle number emissions indices (EIs) were calculated for aircraft, in terms of grams of pollutant emitted per kilogram of fuel burned. Observed NO_x EIs were ~20% lower than those in an international databank. NO_x EIs from takeoffs were significantly higher than those from taxiing, but relative differences for particle EIs were mixed. Observed NO_x fluxes at the airport agreed to within 25% of estimates derived from the NEI. The results of this research will provide greater knowledge of urban impacts to air quality and will improve associated management strategies through increased accuracy of official emissions estimates. / Ph. D.

Diesel particulate matter (DPM) is comprised of two main fractions, organic carbon (OC) and elemental carbon (EC). DPM is the solid portion of diesel exhaust and particles are submicron in size typically ranging from 10 to 1000 nanometers. DPM is a known respirable hazard and occupational exposure can lead to negative health effects. These effects can range from irritation of the eyes, nose, and throat to more serious respirable and cardiovascular diseases. Due to the use of diesel powered equipment in confined airways, underground mine environments present an increased risk and underground mine works can be chronically overexposed. Current engineering controls used to mitigate DPM exposure include cleaner fuels, regular engine maintenance, ventilation controls, and enclosed cabs on vehicles. However even with these controls in place, workers can still be overexposed. The author's research group has previously tested the efficacy of a novel, fog-based scrubber treatment for removing DPM from the air, in a laboratory setting. It was found that the fog treatment improved DPM removal by approximately 45% by number density compared to the control trial (fog off). The previous work stated thermal coagulation between the fog drops and the DPM, followed by gravitational settling of the drops to be the likely mechanisms responsible for the DPM removal. The current work investigated the efficacy of the fog treatment on a larger scale in an underground mine environment, by using a fogging scrubber to treat the entire exhaust stream from a diesel vehicle. A total of 11 field tests were conducted. Based on measurements of nanoparticle number concentration at the inlet and outlet of the scrubber, the fog treatment in the current work showed an average improvement in total DPM removal of approximately 55% compared to the control (fog off) condition. It was found that the treatment more effectively removed smaller DPM sizes, removing an average of 84 to 89% of the DPM in the 11.5, 15.4, and 20.5 nanometer size bins and removing 24 to 30% of the DPM in the 88.6, 115.5, and 154 nanometer size bins. These observations are consistent with expectations since the rate of coagulation between the DPM and fog drops should be greater for smaller diameters. Further analysis of the DPM removal was aided by the development of a mechanistic model of the fogging scrubber. The model uses the inlet data from the experimental tests as input parameters, and it outputs the outlet concentration of DPM for comparison to the experimental outlet data. Results provided support for the notion that DPM removal relies on DPM-fog drop coagulation, and subsequent removal of the DPM-laden drops as opposed to DPM removal by diffusion or inertial impaction of DPM directly to the walls. The model results suggest that inertial impaction of these drops to the scrubber walls is likely much more important than gravitational settling. Moreover, the ribbed geometry of the tubing used for the scrubber apparatus tested here appears to greatly enhance inertial impaction (via enhancement of depositional velocity) versus smooth-walled tubing. This is consistent with previous research that shows particle deposition in tubes with internally ribbed or wavy structures is enhanced compared to deposition in tubes with smooth walls. / Master of Science / Diesel particulate matter (DPM) describes the solid portion of diesel exhaust. These particles are in the nanometer size range (10-1000nm) and can penetrate deep within the lungs presenting a serious health hazard. Because of the use of diesel powered equipment in confined spaces, DPM presents an occupational hazard for underground mine workers. Even with the use of cleaner fuels, regular engine maintenance, proper ventilation, and enclosed vehicle cabs, workers can still be over exposed. Previous work has shown that a water fog treatment can help to remove DPM from the air in a laboratory setting. This removal is due to the DPM particles attaching to the drops, followed by the drops settling out of the air due to gravity or impacting the walls of a tube. To explore a full scale exhaust treatment, a fogging scrubber was built using a fogger and a long tube, and was tested in an underground mine on vehicle exhaust. Experimental results showed that the fog treatment was effective at removing DPM from the exhaust. On average, the fog improved DPM removal by about 55% compared to when the treatment was not employed (fog off). To better understand the mechanisms responsible for DPM removal in the scrubber, a computer model was generated. The model uses the inlet parameters from the field tests, such as inlet DPM and fog concentration and tube geometry, and predicts the scrubber outlet DPM concentration. The model results suggest that the primary way that DPM is removed from the system is by combining with fog drops, which then hit the scrubber tube walls. This effect is probably enhanced by the ribbed structure of the scrubber tubing used here, which may be important for practical applications.