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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Pulmonary inflammatory effects of environmental and surrogate environmental particulates and their components

Wilson, Martin Robert January 2003 (has links)
No description available.

Statistical analysis of particle distributions in composite materials

Mucharreira de Azeredo Lopes, Sofia January 2000 (has links)
No description available.

Evaluation and development of numerical algorithms for multi component aerosol modelling in London

Bowsmer, Jason Paul January 2001 (has links)
No description available.

Atmospheric ammonia measurements and implications for particulate matter formation in urban and suburban areas of Texas

Gong, Longwen 16 September 2013 (has links)
In order to improve the current understanding of the dynamics of ammonia (NH3) in the Greater Houston and Dallas-Fort Worth (DFW) areas and to examine the effects of NH3 on local and regional air quality with respect to particulate matter formation, intensive field investigations were made. A 10.4-μm external cavity quantum cascade laser based-sensor employing conventional photo-acoustic spectroscopy was used to conduct real-time and continuous measurements of atmospheric NH3 in this work. Results from the Houston campaign indicate that the mixing ratio of NH3 ranged from 0.1 to 8.7 ppb with a mean of 2.4±1.2 (1σ) ppb in winter and ranged from 0.2 to 27.1 ppb with a mean of 3.1±2.9 ppb in summer. The larger levels in summer probably are due to higher ambient temperature. A notable morning increase and a mid-day decrease were observed in the diurnal profile of NH3 mixing ratios. Motor vehicles were found to be major contributors to the elevated levels during morning rush hours in winter. However, changes in vehicular catalytic converter performance and other local or regional emission sources from different wind directions governed the behavior of NH3 during morning rush hours in summer. There was a large amount of variability, particularly in summer, with several episodes of elevated NH3 mixing ratios that could be linked to industrial facilities. A considerable discrepancy in NH3 mixing ratios existed between weekdays and weekends. During the simultaneous high-time-resolution measurements of gaseous and aerosol species in summer, elevated NH3 levels occurred around mid-day when NH4+ (0.5 ± 1.0 μg m-3) and SO42- (4.5 ± 4.3 μg m-3) also increased considerably, indicating that NH3 likely influenced aerosol particle mass. NH4+ mainly existed in the form of (NH4)2SO4 and NH4HSO4; by contrast, the formation of NH4NO3 and NH4Cl was suppressed. Power plant plumes were found to be potential contributors to the enhancements in NH3 at the urban sampling site under favorable meteorological conditions. Increased particle number concentrations were predicted by the SAM-TOMAS model downwind of a large coal-fired power plant when NH3 emissions (based on these measurements) were included, highlighting the potential importance of NH3 with respect to particle number concentration. Measurements also show the role of NH3 in new particle formation in Houston under low-sulfur conditions. Results from the DFW campaign indicate that the mixing ratio of NH3 ranged from 0.1 to 10.1 ppb, with a mean of 2.7 ± 1.7 ppb. The diurnal profile of NH3 exhibited a daytime increase, likely due to increasing temperatures affecting temperature-dependent sources in the study region. Automobiles might be potential sources of NH3 on Sundays based on the Pearson’s correlation coefficient between NH3 and carbon monoxide, but the relationship did not exist on weekdays and Saturdays, probably due to decreased traffic volume and different traffic composition. According to the results from the EPA PMF 3.0 model, biogenic (primarily vegetation and soil) emissions were major contributors to gas-phase NH3 levels measured at the suburban site during the campaign. In addition, agriculture (especially livestock-related activities) also was expected to be a potentially significant source of NH3 based on the nature of the region. Inorganic aerosol components of submicron particles (PM1) (4.41 ± 2.13 μg m-3) were dominated by SO42- (1.25 ± 0.66 μg m-3), followed by NH4+ (0.44 ± 0.24 μg m-3) and NO3- (0.12 ± 0.11 μg m-3). Pearson’s correlation coefficients between NH4+, SO42-, and NO3- imply that particulate NH4+ mainly existed as (NH4)2SO4 and that NH4NO3 was not formed during most of the study period, likely due to high temperatures (30.15 ± 4.12 oC) over the entire campaign. Ambient aerosols tended to be nearly neutral. Theoretical calculations of thermodynamic equilibrium were performed to consider the formation of NH4NO3 and NH4Cl. When relative humidity (RH) was lower than deliquescence relative humidity (DRH), the partial pressure products of PNH3PHNO3 and PNH3PHCl were smaller than the associated equilibrium constants, indicating the lack of NH4NO3 and NH4Cl formation. When RH was above DRH, higher levels of NO3- often were observed. A strong relationship between NO3- and SO42- at higher RH suggests that NH4NO3 might be formed on the moist surface of pre-existing sulfate aerosols. In the particle mixture, (NH4)2SO4 reduces the equilibrium constant, making the aqueous system a more favorable medium for NH4NO3 formation. In addition, measured particle number size distributions showed that an aerosol nucleation and growth event was coincident with humid periods characterized by substantially increased concentrations of particulate NH4+, NO3-, and SO42-. Excess NH4+ also was found to be correlated closely with NO3- during this episode when elevated PM1 levels imply aqueous NH4NO3 formation.

Depth and temporal variability of organic carbon, total nitrogen and their isotopic compositions of sinking particulate organic matter and POC flux at SEATS time-series station, northern South China Sea

Liang, Yu-jen 08 September 2008 (has links)
This study investigates depth and temporal variability of organic carbon (POC), total nitrogen (TN) and their isotopic compositions in sinking particulate organic matter collected at station KK (18¢X15¡¦N; 115¢X5¡¦E), northern South China Sea. Sinking particles collected from two separate sediment trap moorings conducted from August 8, 2004 to February 16, 2005 (KK-3) and from April 1, 2005 to October 10, 2005 (KK-4). Results show that their variations respond closely to the strong seasonality in the surface layer, but are modified considerably by subsequent remineralization and large terrigeneous input in the deep water. The highest of Al concentrations at 3500m is equivalent approximately to 58% of lithogenic material. Sinking particles of terrestrial origins has lower £_13C values of POM. Terrigeneous input should make the £_13C values increase but decrease from 600m to 3500m. Based upon data measured in this study, a C/N increase rate of 0.21 unit per 1 km of water depth. The C/N ratio of POM collected in the winter is significantly higher than those collected in the rest of the year (9.05 vs. 7.02). With this regard, cyanobacteria, which have been reported as an important N2-fixer may attribute to the insufficiency in new production sources. The £_15N values prove the occurrence of nitrogen fixation in the surface water of the South China Sea in summer.

Assessment of Particulate Matter Exposure in Franklin County, Ohio: A Comparison of Static and Dynamic Approaches

Sineri, Jaclyn R. 25 August 2010 (has links)
No description available.

Characterisation of carbonaceous particulate matter in Edinburgh

Hammonds, Mark David January 2012 (has links)
Airborne particulate matter (PM) has important harmful effects on human health, as well as a number of other important atmospheric effects. Although progress has been made in understanding the sources and effects of PM, there remains considerable uncertainty on a number of issues, including the nature of a lot of the carbonaceous material, which comprises 30{50% on average of PM mass. This project aims to compare different methods of PM measurement, and contribute understanding to the nature and origin of the carbonaceous fraction of PM. Daily samples of PM10 were collected from three sites in the Edinburgh area using Partisol-Plus 2025 Sequential Air Samplers: 1) Urban Background (20 August 2008 until 21 April 2010); 2) Rural (25 February 2009 until 21 April 2009); and 3) Roadside (10 September 2009 until 21 April 2010). These localities provided PM that was, respectively, representative of: 1) city-wide background air; 2) air at a location distanced from population centres, roads and industrial areas; and 3) air influenced by the emissions associated with traffic. Gravimetric PM10 concentration (µgm-3) was determined for each daily filter sample, after a blank correction to compensate for the relative humidity (RH)-influenced change in filter mass over time. The correction was successful, with good agreement attained between the Partisol and a PM10 Tapered Element Oscillating Microbalance Filter Dynamics Measurement System (TEOM-FDMS) co-located at the Urban Background site. The general levels of PM10 measured in this monitoring campaign indicate that the air in Edinburgh was relatively clean. The main factor causing exceedance of the daily European Union (EU) limit value was shown to be transport of PM10 from areas of mainland Europe. High PM10 concentrations were also strongly associated with calm weather conditions in Edinburgh, which allowed the build-up of particulate pollution over time. Aethalometer-equivalent daily concentrations of black carbon (BC) were determined by measuring the optical reflectance of the PM10 filters from the Partisol samplers. The conversion of reflectance values to BC concentrations relied on a number of correction factors, which may have impacted on the accuracy of the results with time and location. The concentration of BC in Edinburgh was shown to be relatively low, with the daily variation being controlled by local emissions and meteorology. BC as a proportion of PM10 increased with sampling location in the order: Rural < Urban Background < Roadside. Predominantly traffic-related BC concentrations increased during periods of low wind speed and were not greatly influenced by long-range transport of aerosol. Daily water-soluble organic matter (WSOM) concentrations were obtained by aqueous extraction of the filter samples and measurement of the dissolved organic carbon (DOC). About 11% on average of the Edinburgh PM10 was WSOM. The majority of this WSOM seemed to have originated from air masses outside of the city, although there was a minor contribution from urban traffic sources. A solid phase extraction (SPE) procedure was used to isolate about one-third of the WSOM as hydrophobic compounds and this revealed a relative increase in the amount of less oxygenated material from traffic sources. Higher than average WSOM concentrations were strongly associated with calm weather conditions that allowed the transient build-up of particle concentrations. Some of the peaks in WSOM concentration were related to the transport of air masses from areas of mainland Europe where biogenic secondary organic aerosol (SOA) and biomass burning were likely sources. Analysis of the WSOM samples by UV-Vis absorption spectroscopy showed clear seasonal trends in the composition of hydrophobic watersoluble organic matter (HWSOM), interpreted as predominance of lower molecular weight aliphatic compounds in summer but predominance of larger aromatic and polyconjugated compounds in winter. Raman spectra were obtained for different carbonaceous reference materials. The results of curve fitting for these spectra gave D1 band full width at half maximum (FWHM) values that distinguished between diesel exhaust particles from a local bus and a humic acid sample. Analysis of Edinburgh PM10 samples using Raman microspectroscopy (RM) showed a variation in the structural order of the carbon compounds present between that of soot and HUmic-LIke Substances (HULIS), with a tendency towards more soot-like material being present. There was no strong relationship between carbonaceous order and BC concentration, showing that coloured organic compounds have the potential to influence reflectance measurements. The combination of these measurement approaches has yielded insights into the nature and variation in carbonaceous PM material with time and sampling location.

The Effect of Building Construction and HVAC Systems on PM Concentration from Outdoor Sources

Alas, David 24 September 2012 (has links)
Adverse health effects of human exposure to particulate matter (PM) in indoor environments and the associated costs have been of interest in recent studies conducted outside Canada. It was, therefore, necessary to investigate these effects in a Canadian environment. This study investigated the effects of building construction and Heating, Ventilation, and Air Conditioning (HVAC) systems on the indoor concentration of airborne PM of outdoor origin and the related health impacts and cost savings in Ontario. Due to the complexity of the investigation, the study has been limited to the metropolitan areas of Toronto and Hamilton which represent much of the population of Ontario and a significant portion of all Canada. The main objective of the cost-benefit analysis (CBA) was to analyze and evaluate the effects of pollution in monetary equivalents. The modeling integrated the various models using the Impact Pathway Approach. The approach consisted of four steps: First, identify the sources and emissions of PM. Although the study focused on indoor environments, outdoor sources such as incomplete combustion from rush hour traffic were identified for the geographical areas of the study. Secondly, evaluate the dispersion or the concentration of PM on the site of interest. In order to achieve this goal, building modeling was first established that was applicable to Ontario. There were three homes and two commercial building scenarios: Existing homes (resExist), new homes constructed under minimum building code requirements (resBC), and under R2000 standard (resR2000); commercial buildings with 40% (school40) and 85% (school85) ASHRAE air filters. Air flow rates were calculated from building and HVAC sizing calculations. These flow rates were used to calculate input parameters for well-established mass balanced indoor PM concentration models. In addition, indoor exposure needed to account for time activity in each micro-environment in Ontario. This was accomplished by using time-weighted exposure modeling. Thirdly and lastly in the Impact Pathway Approach, evaluate the health impact and its monetary equivalent, respectively. In order to evaluate the health effects and monetary equivalents, the study considered fourteen retrofit cases which consisted of improving factors such as building construction, distribution system, and air filtration efficiency. Because input parameters were selected from data applicable to Ontario, the study provided a model setup that could be applied to future work in Canada. The study demonstrated that Canadian building construction provided significant protection from time-weighted PM exposure (Toronto, ambient vs. resExist/school40win, PM2.5 10.00 vs. 4.20 μg/m3). For this scenario, the prevented attributable number of cases (ANCs) was 721 for Toronto related to equivalent PM10. Cost savings due to building envelope protection of mortality alone much outweighed costs in investment scenario for new home construction (Toronto, $1,671 million vs. $21.6 million). Therefore, recommendations were made to invest in home construction. Similarly, the morbidity effects were very significant, especially for chronic bronchitis endpoints which were along the same magnitude as mortality for most of the cases. Similar results were obtained for Hamilton in proportion to their relative population at risk. In addition, Canadian building construction and HVAC systems showed larger time-weighted PM exposure in the summer compared to the winter conditions due to the various HVAC operating conditions such as air flow rates (Toronto, resExist/school40sum, PM2.5 5.18 μg/m3 ; resExist/school40win, PM2.5 4.20 μg/m3). Furthermore, cost savings from retrofits from existing home to forced air with air filtration were very significant. It was demonstrated that the cost savings related to reduction of equivalent PM10 exposure due to mortality alone much outweighed costs in retrofit investment scenarios (R2000, Toronto, $574 million vs. $4.96 million). Therefore, the government would be wise to promote more energy efficient homes by offering more incentive programs. Factors such as wall insulation, air flow rate changes of less than 600cfm, and HRV installation type did not played a major role. In addition, the effect of air filtration was more intense in homes compared to commercial buildings. Similarly, the impact of simultaneously retrofitting both, homes and commercial buildings, where children and adults spent most of the daily activities produced the greatest reduction of outdoor PM exposure. Installing high efficient air filtration in both homes and commercial buildings resulted in optimal reduced effects. The cost savings from the retrofit due to mortality alone much outweighed the investment scenario costs justifying the retrofit (Toronto, $470 million vs. $1.8 million). This demonstrated that PM concentration exposure reduction is a collective effort that needed to be regulated not only in ambient air level but in the work environment and in homes as well. It was identified that results were limited to model assumptions and input parameter data used. Since some of the parameters used, such as ambient PM concentrations, were average values, the results may not represent the exact actual conditions. Nevertheless, they provided a starting point since they were tailored to Ontario. Therefore, this study provided model simulation data that related to the Canadian environment having many factors in common such as weather, building construction, building systems, and government regulations. Therefore, the results are part of useful data for policy decisions as well as a starting point for future related work.

A PM10 emission factor for free stall dairies

Goodrich, Lee Barry 16 August 2006 (has links)
Ambient concentration measurements of total suspended particulate (TSP) were made at a commercial dairy in central Texas during the summers of 2002 and 2003. The facility consisted of both open pen housing and free-stall structures to accommodate approximately 1840 head of milking cattle. The field sampling results were used in the EPA approved dispersion model Industrial Source Complex Short Term version 3 (ISCST-v3) to estimate emission fluxes and ultimately a seasonally corrected emission factor for a free-stall dairy. Ambient measurements of TSP concentrations for sampling periods ranging from 2 to 6 hours were recorded during the summer of 2002. The mean upwind concentration was 115µg/m3 with a maximum of 231µg/m3 and a minimum of 41.4µg/m3. The mean net downwind TSP concentration was 134µg/m3 with a maximum of 491µg/m3 and a minimum of 14µg/m3. Field sampling at this same dairy in the summer of 2003 yielded significantly more 2 to 6 hour TSP concentration measurements. The mean upwind TSP concentration was 76µg/m3 with a maximum concentration of 154µg/m3. The mean net downwind TSP concentration was 118µg/m3 with a maximum of 392µg/m3 and a minimum of 30µg/m3. The particle size distributions (PSD) of the PM on the downwind TSP filters was determined using the Coulter Counter Multisizer. The results of this process was a representative dairy PM PSD with 28% of TSP emissions being PM10. The reported PM10 24-hour emission factors were 4.7 kg/1000hd/day for the free-stall areas of the facility and 11.7 kg/1000hd/day for the open pen areas of the dairy. These emission factors were uncorrected for rainfall events. Corrections for seasonal dust suppression events were made for the San Joaquin Valley of California and the panhandle region of Texas. Using historical rainfall and ET data for central California, the seasonally corrected PM10 emission factor is 3.6kg/1000hd/day for the free-stalls, and 8.7kg/1000hd/day for the open pens. For Texas, the seasonally corrected emission factor is 3.7kg/1000hd/day for the free-stall areas and 9.2kg/1000hd/day for the open lot areas.

Particulate Phosphorus Input and Burial Efficiency in the Gaoping Coastal Sea

Yeh, Yu-ching 30 August 2009 (has links)
The purposes of this study are to investigate the sources, distributions, fluxes and phosphorus burial efficiency (PBE) of particulate phosphorus in the Gaoping (GP) coastal sea. The GP River carried about 3.14 ¡Ñ 104 ton yr-1 (1.03 ¡Ñ 109 mol yr-1) particulate P into the GP coastal sea. The total P flux was primarily determined by the river runoff during the May-yu (monsoon) and typhoon seasons. The river P was approximately consisted of 90.8% particulate inorganic-P (PIP), 7.4% particulate organic-P (POP), 1.5% dissolved inorganic-P (DIP) and 0.3% dissolved organic-P (DOP). The particulate-P existed mainly in 10-63 £gm particles. In the GP costal sea, particulate P in surface sediments was found to be 80-90% as PIP and 10-20% as POP. The highest distribution of PIP was located on the flanks of GP Canyon at the upper slope (200-600 m) region. This distribution may be caused by plumes of river sediments or turbidity currents overflowing the canyon. The sedimentation rates of sediments ranged from 0.032 to 1.62 g cm-2 yr-1 in the GP coastal sea and the highest rates were also located on both sides of the GP Canyon. The burial fluxes of total phosphorus (TP) ranged from 0.02 to 0.84 g cm-2 yr-1, consisted approximately by 88% PIP and 12% POP. The burial fluxes of this study area were generally similar to those in other continental margins (Bohai Sea, Yellow Sea, Mississippi Delta). The total depositions of sediment and TP were approximately 6.6 ¡Ñ 106 ton yr-1 and 4227 ton yr-1, respectively, in the study area. The burial TP was equivalent to 0.06% of deposited sediments. The buried TP can be proportionate approximately into 15% in the continental shelf (< 200 m), 69% in the continental slope (200-1000 m), and 16% in the slope basin (> 1000 m). The continental shelf (<200 m) region was apparently influenced by wave and tidal processes and prevented from sediment accumulation. The burial efficiency of TP (PBE) in the GP costal sea is estimated accordingly to PBE (%) = 100 ¡Ñ PBF / (PBF+JP), where PBF is the burial flux of TP and JP is the diffusion flux of TP from porewater. The PBE decreases with the depth of sampling location and the maximum PBE locates on the station of southern canyon (779-1), the station of northern canyon (791-L18) and the station within the canyon (732-38). The PBE(s) are similar to those found in the Nazar&#x00E9; Canyon, showing a high PBE in coastal and/or canyon regions. The budget model shows that the major sources of particulate-P are derived from the GP River and the net ecosystem production (NEP) from the euphotic zone of study area. The annual river load and NEP input to the study area are 1.03 ¡Ñ 109 mol P yr-1 and 1.5 ¡Ñ 108 mol P yr-1, respectively. However, annual TP accumulation in the GP costal sea is just 1.48 ¡Ñ 108 mol P yr-1, corresponding to 12.5% of river load and NEP input. In addition, about 80% of GP River loads do not deposit into GP sediments and may be exported out of the study area.

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