Flowing suspensions of solid particles in gas can be found in various industrial applications, as a method for transporting powdered solids (known as "pneumatic conveying"). The problem of measuring the mass concentration of the solid fraction has not yet been satisfactorily resolved. This thesis explores acoustic techniques to measure the particle concentration. Controlled suspensions -- both flowing and quasi-static - were generated in cylindrical tubes, and their acoustic properties were measured over three frequency ranges, requiring a variety of different measuring techniques: Plane wave region (200 -4 kHz): the attenuation of plane waves travelling along the flow tube was measured. A simple method of measuring the characteristic impedance of the suspension was also devised and preliminary measurements were made. Reverberant region (4 - 20 kHz). Three parameters were measured: the decay rate of the reverberant field in certain frequency bands; the level of actively-excited steady state sound; and the frequency of transverse resonant modes of the pipe. Ultrasonic region (40 - 75 kHz): the attenuation of ultrasound was measured across the pipe diameter. The measurements were compared with theoretical predictions. They showed the predicted linearity of acoustic attenuation with concentration, although the frequency dependence was less well predicted. In general, the larger particle sizes produced the greatest discrepancy; an explanation is proposed. Ultrasonic measurements showed significant differences from the predicted frequency dependence. A method of isolating acoustic transducers from the flow with a column of clean air is described. However, measurements may be complicated by interactions at the orifice into the flow pipe. Further work is needed in this area. It is concluded that acoustic methods could be used to measure particle concentration. However, to remain insensitive to changes in the properties of the particles - size in particular - measurements must be made at more than one frequency.

No description available.

We interpret satellite, aircraft, and ground-based measurements using the GEOS-Chem Chemical Transport Model (CTM) to better understand the global transport and distribution of fine aerosol (PM2.5). Using satellite retrievals of Aerosol Optical Depth (AOD) from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Multiangle Imaging Spectroradiometer (MISR), we estimate an annual growth in Chinese sulfur emissions of 6.2-9.6% between 2000-2006, in agreement with bottom-up inventories. Using aircraft measurements from the Intercontinental Chemical Transport Experiment (INTEX-B) with a CTM, we calculate that 56% of measured sulfate between 500-900 hPa over British Columbia is due to East Asian sources. We find evidence of a 72-85% increase in the relative contribution of East Asian sulfate to the total burden in spring off the northwest coast of the United States since 1985. We interpret retrievals AOD from MODIS and MISR using GEOS-Chem to estimate global long-term (2001-2006) mean PM2.5 concentrations at a resolution of 0.1° x 0.1°. Evaluation of the satellite-derived estimate with ground-based in-situ measurements indicates significant spatial agreement with North American measurements (r = 0.77, slope = 1.07, n = 1057) and with non-coincident measurements elsewhere (r = 0.83, slope = 0.86, n = 244). The one standard deviation uncertainty in the satellite-derived PM2.5 is 25%, inferred from the AOD retrieval and aerosol vertical profiles errors and sampling. The global population-weighted mean uncertainty is 6.7 µg/m3. We find a global population-weighted geometric mean PM2.5 concentration of 20 ?g/m3. The World Health Organization Air Quality PM2.5 Interim Target-1 (35 µg/m3 annual average) is exceeded over central and eastern Asia for 38% and 50% of the population, respectively. Annual mean PM2.5 concentrations exceed 80 µg/m3 over Eastern China. We test the capability of remotely-sensed PM2.5 to capture extreme short-term events by examining the major biomass burning event around Moscow in summer 2010. We find good agreement (r2=0.85, slope=1.06) between daily estimates of PM2.5 from in-situ and satellite-derived sources in the Moscow region during the fires. Both satellite-derived and in-situ values have peak daily mean concentrations of approximately 600 ?g/m3 on August 7, 2010 in the Moscow region.

No description available.

The aerosol diluter characteristics of three different systems, the single-stage and the two-stage TSI 379020A rotary disk thermodiluters and Dekati FPS-4000 ejector diluter, were tested using gases and particles over a range of dilution ratios. The upstream and downstream gas and particle concentrations of the diluters were measured in real-time to compute the actual dilution ratio achieved by the three systems. Dilution ratios from approximately 15 to 100 were found to fall within the expected operating error margin of ± 10% for CO2 and CH4. Dilution ratios covering a similar range were also achieved to within ± 10% for particles with diameters from 9.3 to 200 nm. However, when engine exhaust was sampled, significant loss of particles smaller than 29.4 nm occurred during the dilution process. As the dilution ratio increased, the deviation from the expected value increased due to an increase in measurement uncertainty.

The aerosol diluter characteristics of three different systems, the single-stage and the two-stage TSI 379020A rotary disk thermodiluters and Dekati FPS-4000 ejector diluter, were tested using gases and particles over a range of dilution ratios. The upstream and downstream gas and particle concentrations of the diluters were measured in real-time to compute the actual dilution ratio achieved by the three systems. Dilution ratios from approximately 15 to 100 were found to fall within the expected operating error margin of ± 10% for CO2 and CH4. Dilution ratios covering a similar range were also achieved to within ± 10% for particles with diameters from 9.3 to 200 nm. However, when engine exhaust was sampled, significant loss of particles smaller than 29.4 nm occurred during the dilution process. As the dilution ratio increased, the deviation from the expected value increased due to an increase in measurement uncertainty.

No description available.

From June 2006 to March 2007, the concentrations of water soluble inorganic particulates and their associated precursor gases were semi-continuously measured adjacent to a high traffic street in downtown Toronto, Canada. Measurements underwent extensive quality assurance and control protocols. Seasonal and diurnal variations in HNO3 and NH3 partitioning to NH4NO3 were observed. Long range transported air masses from southwest of Toronto were the predominant source of measured SO4 2- for all seasons. The contributing sources of PM2.5 nitrate mass fluctuated between seasons: pNO3- was predominantly locally derived in the summer and resulted from long range transport in the winter. Comparison between measurements and ISORROPIA thermodynamic model predictions identified model weaknesses and was used to explore the effect of modulating primary gas concentrations on consequent particulate levels. SO2 emissions reductions were the most influential and direct method to reduce overall PM2.5 concentrations; however, limiting ammonia emissions was also another successful strategy.

From June 2006 to March 2007, the concentrations of water soluble inorganic particulates and their associated precursor gases were semi-continuously measured adjacent to a high traffic street in downtown Toronto, Canada. Measurements underwent extensive quality assurance and control protocols. Seasonal and diurnal variations in HNO3 and NH3 partitioning to NH4NO3 were observed. Long range transported air masses from southwest of Toronto were the predominant source of measured SO4 2- for all seasons. The contributing sources of PM2.5 nitrate mass fluctuated between seasons: pNO3- was predominantly locally derived in the summer and resulted from long range transport in the winter. Comparison between measurements and ISORROPIA thermodynamic model predictions identified model weaknesses and was used to explore the effect of modulating primary gas concentrations on consequent particulate levels. SO2 emissions reductions were the most influential and direct method to reduce overall PM2.5 concentrations; however, limiting ammonia emissions was also another successful strategy.

Hohenheim, Univ., Diss., 2008.