Thesis advisor: Paul Davidovits / Aerosol particles are an important component of the Earth-Atmosphere system because of their influence on the radiation budget both directly (through absorption and scattering) and indirectly (through cloud condensation nuclei (CCN) activity). The magnitude of the raditaive forcing attributed to the direct and indirect aerosol effects is highly uncertain, leading to large uncertainties in projections of global climate change. Real-time measurements of aerosol properties are a critical step toward constraining the uncertainties in current global climate modeling and understanding the influence that anthropogenic activities have on the climate. The objective of the work presented in this thesis is to gain a more complete understanding of the atmospheric transformations of aerosol particles and how such transformations influence the direct and indirect radiative effects of the particles. The work focuses on real-time measurements of aerosol particles made with the Aerodyne Aerosol Mass Spectrometer (AMS) developed in collaboration with the Boston College research group. A key feature of the work described is the development of a lightscattering module for the AMS. Here we present the first results obtained with the integrated light scattering – AMS system. The unique and powerful capabilities of this new instrument combination are demonstrated through laboratory experiments and field deployments. Results from two field studies are presented: (1) The Northeast Air Quality Study (NEAQS), in the summer of 2004, conducted at Chebogue Point, Nova Scotia and (2) The Megacity Initiative: Local and Global Research Observations (MILAGRO) field campaign conducted in and around Mexico City, Mexico in March of 2006. Both field studies were designed to study the transformations that occur within pollution plumes as they are transported throughout the atmosphere. During the NEAQS campaign, the pollution plume from the Northeastern United States was intercepted as it was transported towards Europe. In this study, particles were highly processed prior to sampling, with residence times of a few days in the atmosphere. The MILAGRO campaign focused on the evolution of the Mexico City plume as it was transported north. During this study, regional and locally emitted particles were measured with residence times varying from minutes to days in the atmosphere. In both studies, the light scattering – AMS system provided detailed information about the density and composition of single particles, leading to important insights into how atmospheric processing transforms the particle properties. In Mexico City, the light scattering-AMS system was used for the first time as a true single particle mass spectrometer and revealed specific details about the atmospheric processing of primary particles from combustion sources.To quantify the radiative effects of the particles on climate, the processing and ultimate fate of primary emissions (often containing black carbon or soot) must be understood. To provide a solid basis for the interpretation of the data obtained during the field studies, experiments were conducted with a well characterized soot generation-sampling system developed by the Boston College research group. The laboratory soot source was combined with the light scattering – AMS system and a Cloud Condensation Nuclei Counter (CCNC) to measure the change in cloud-forming activity of soot particles as they are processed in the atmosphere. Because of the importance of black carbon in the atmosphere, several instruments have been developed to measure black carbon. In July of 2008, an intercomparison study of 18 instruments was conducted in the Boston College laboratory, with soot particles produced and processed to mimic a wide range of atmospherically-relevant conditions. Transformations in the physical, chemical, and optical properties of soot particles were monitored with the combined suite of aerosol instrumentation. Results from the intercomparison study not only calibrated the different instruments used in the study, but also provided critical details about how atmospheric processing influences the radiative effects of primary combustion particles. / Thesis (PhD) — Boston College, 2008. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Mit Untersuchungen auf dem Gebiet der trockenen Desagglomeration konnte nachgewiesen werden, dass mit Strahlmühlen unter bestimmten technischen Voraussetzungen Materialagglomerate aus der Produktklasse Nanopartikelfocken auf Partikelgrößen kleiner 1 µm bei maximal möglicher Beladung stabil desagglomerierbar sind. Dabei zeigt sich vor allem, dass mit sinkender spezifischer Oberfläche des Ausgangsmaterials eine höhere Dispersität bei vergleichbarem Input an Desagglomerationsenergie möglich ist. Voraussetzung hierfür ist die speziell auf die Desagglomerationsaufgabe angepasste Versuchsanlage. Mit der zur Bestimmung der Dispersität entwickelten Online-Messstrecke sind Partikelgrößen von 10 nm bis hin zu ca. 42 µm in einem Körnungsband erfassbar. Mit den gegebenen Möglichkeiten der Prozessanalyse zu wesentlichen Einflussparametern wird eine Überwachung der Prozessstabilität ermöglicht. Die Variation der Transportstrecke bei den verschiedenen Produktaerosolen mit maximaler Dispersität zeigt, dass technisch sinnvolle und kurze Wege bis 1 m die Einleitung stabiler Aerosole hoher Dispersität bis in den Bereich der Materialaggregate bei 100 nm bis 200 nm in einen Folgeprozess (z.B. Coating) ermöglichen.

The direct and indirect effects of aerosols on the hurricane ‘Katrina’ have been investigated using the WRF model with a two-moment bulk microphysical scheme and modified Goddard shortwave radiation scheme. Simulations of the hurricane ‘Katrina’ are conducted under the three aerosol scenarios: 1) the clean case with an aerosol number concentration of 200 cm-1, 2) the polluted case with a number concentration of 1000 cm-1, and 3) the aerosol radiative effects (AR) case with same aerosol concentration as polluted case but with a modified shortwave radiation scheme. The polluted and AR cases have much larger amounts of cloud water and water vapor in troposphere, and the increased cloud water can freeze to produce ice water paths. A tropical cyclone in dirty and dusty air has active rainbands outside the eyewall due to aerosol indirect effects. The aerosol direct effect can lead to the suppressing of convection and weakening of updraft intensity by warming the troposphere and cooling the surface temperature. However, these thermal changes in atmosphere are concerned with the enhanced amounts of cloud hydrometeors and modification of downdraft and corresponding the low level winds in rainband regions. Thus, the AR case can produce the enhanced precipitation even in the weakest hurricane. When comparing the model performance between aerosol indirect and direct effect by ensemble experiments, the adjustment time of the circulation due to modification of the aerosol radiative forcing by aerosol layers may take a longer time than the hurricane lifetime, and the results from the simulated hurricane show that it is more sensitive to aerosol indirect effects which are related to the cloud microphysics process changes. From this aerosol study, we can suggest that aerosols can influence the cloudiness, precipitation, and intensity of hurricanes significantly, and there may be different results in the meso-scale convective clouds cases. The hurricane system is a large and complex convective system with enormous heating energy and moistures. Moreover, relationships between various hydrometeors in hurricane systems are difficult to isolate and thus, it needs further study with more realistic cloud microphysical processes, aerosol distributions, and parameterizations.

Organic aerosols represent one of the main sources of uncertainty affecting attempts to quantify anthropogenic climate change. The diverse physical and chemical properties of organic aerosols and the varied pathways involved in their formation and aging form the basis of this uncertainty, preventing extensive and accurate representation within regional and global scale models. This inability to constrain the radiative forcings produced by organic aerosols within the atmosphere consequently acts as a limitation to the wider objective of providing reliable projections of future climate. Biomass burning constitutes one of the main anthropogenic contributions to the global atmospheric organic aerosol (OA) burden, particularly in tropical regions where the potential for perturbations to the climate system is also enhanced due to higher average levels of solar irradiance. Emissions from biomass burning have been the subject of an intense research focus in recent years, involving a combination of field campaigns and laboratory studies. These experiments have aimed to improve the limited understanding of the processes involved in the evolution of biomass burning organic aerosol (BBOA) and contribute towards the development of more robust parameterisations for climate and chemical transport models. The main objective of this thesis was to use datasets acquired from several different global regions to perform a broad analysis of the BBOA fraction, with the extensive temporal and spatial scales provided by such measurements enabling investigation of a number of key uncertainties, including regional variability in emissions and the role of secondary organic aerosol (SOA) formation in aging smoke plumes. Measurements of BBOA mass concentration obtained using Aerodyne Research Inc. Aerosol Mass Spectrometers (AMS) were used to calculate characteristic ΔOA/ΔCO ratios for different environments, accounting for the effects of dilution and contrasting fire sizes to give a proportional representation of OA production. High levels of variability in average ΔOA/ΔCO were observed both between and within different regions. The scale of this variability consistently exceeded any differences between plumes of different ages, while a widespread absence of any sustained increase in ΔOA/ΔCO with aging indicates that SOA formation does not provide a net increase in OA mass. Despite this lack of OA enhancement, increasing proportions of oxygenated OA components in aged plumes highlight the chemical transformations occurring during the evolution of BBOA, and the additional influence of OA loss through evaporation or deposition. Potential drivers of variability in ΔOA/ΔCO at source, such as changes in fuel types and combustion conditions, were investigated for controlled fires carried out within a combustion chamber. These laboratory experiments revealed a number of complex relationships between BB emissions and source conditions. Although ΔOA/ΔCO was shown to be influenced by both fuel properties and transitions between flaming and smouldering combustion phases, the extent of these effects was limited, while variability between fires exceeded levels observed for ambient measurements. These findings emphasise the complexity of the BBOA lifecycle and the need to address the extensive uncertainties associated with its various constituent processes, in order to improve understanding of eventual climate impacts from biomass burning.

<p>  </p> <p>Secondary organic aerosols (SOA) play an important role in the Earth’s radiative budget due to their potential to either warm or cool the atmosphere through light absorption or light scattering, respectively, and to cool or warm the lower atmosphere by acting as cloud condensation nuclei. SOA are air-suspended liquid and semi-solid droplets that form through multiphase chemical processes. Atmospheric photochemical oxidation of volatile organic compounds (VOCs) in the presence of air pollutants, such as NO_x (NO + NO₂) and the OH radical, promote formation of low volatility organic products that eventually condense to form SOA. To better understand the sources and sinks, formation, and fate of SOA, laboratory studies investigating oxidation of a biogenic VOC as well as anthropogenic emissions of SOA precursors were conducted. The first study (<em>Chapter 3</em>) investigated the OH-initiated oxidation of β-ocimene, a biogenic volatile organic compound (BVOC) released from vegetation, including forests, agricultural landscapes, and grasslands emitted during the daytime. The oxidation of BVOCs in the presence of NO_x leads to the formation of functionalized organic nitrate (RONO₂) compounds and isomers that easily condense to form SOA. To understand their atmospheric fate, the RONO₂ hydrolysis rate constants were quantified and found to be highly pH dependent. The findings of this study provide key insights into the formation and fate of organic nitrates and NO_x cycling in forested environments from daytime monoterpenes that were not previously included in atmospheric models. </p> <p>The second study (<em>Chapters 4 and 5</em>) investigated condensed waste emissions generated during Cured-In-Place-Pipe (CIPP) installations. This installation process is the most popular, least expensive, and most frequently used technology that cures leaking sanitary and stormwater sewers. Waste plumes discharged during pipe manufacture are complex multi-phase mixtures of volatile and semi-volatile organic compounds (VOC and SVOC, respectively), primary organic aerosols and SOA, fine debris of partially cured resin, and direct emission of nanoplastic particles that are all blown into the atmospheric environment at significant concentrations at worksites. This work unveiled a direct emission source of airborne nanoplastic particles as well as substantial concentrations of hazardous compounds and SOA precursors that were previously unrecognized. </p>

The primary focus of this study was to compare the efficiency of six filter samplers in the collection of inhalable soluble platinum (Pt) salts at a South African base metal refinery. Inhalation remains the major route of occupational exposure to platinum groups metals (PGMs). South Africa would benefit from the study since it’s amongst the major countries where PGMs are produced and hence, monitoring of worker exposure with the most efficient sampler is of utmost importance. The IOM is currently being used in routine exposure monitoring although no studies have been carried out to compare its performance to that of the other samplers under the actual base metal refinery conditions. Method: The button, closed face cassette (CFC), Gesamtsstaubprobenhome (GSP), (Institute of Medicine) IOM, PAS-6 and seven hole (SH-sampler) samplers were randomly allocated to six different positions in presumably high exposure areas. The samplers were moved around in the subsequent sampling days and the process repeated 3 times. The average dust mass and Pt concentrations were used as a basis of sampler performance and comparisons from which sampler hierarchies were determined. Results: The average relative humidity ranged between 37% and 43% and the average dry bulb temperature of 22.4°C was measured. Comparison of the dust mass concentrations revealed no statistically significant differences amongst the six filter samplers tested. The SH-sampler and CFC however collected the highest and lowest dust mass and Pt concentrations respectively. Discussion: The SH-sampler was found to be a sampler with more reliability than the the IOM for the collection of dust mass and soluble Pt. The IOM collected 98% of the SH-sampler dust mass and Pt concentrations. This was in spite of the larger variations indicated by the highest relative standard deviations and confidence intervals shown by the IOM than the other samplers. The GSP sampler, however, showed better precision than all the other samplers in the collection of platinum. The seven 4 mm orifices of the SH-sampler sampler allow for uniform distribution of sampled particles onto the filter supporting its better precision than the IOM which has only one 4 mm opening. The worst performing sampler was the CFC sampler since it collected the lowest dust mass and Pt concentrations. The CFC and the PAS samplers have downward facing inlets that are affected by gravity especially in lower wind speeds which, therefore, influences their efficiency. The GSP sampler concentrations placed it as 4th and 3rd best in Pt and dust mass hierarchies respectively even though it showed better precision than SHS in the sampling of Pt. The button sampler did not perform as well as would have been expected considering that its many evenly spaced orifices and the stainless steel are meant to reduce sample losses. Conclusion: The sampler hierarchy according to dust mass concentrations was in the following order: SH-sampler, IOM, PAS, GSP, button and CFC. The hierarchy obtained from Pt concentrations gave the order as SH-sampler, IOM, GSP, button, PAS and CFC. Similar studies have to be undertaken in primary and secondary platinum workplaces to validate the study results. Such studies should compare better performing samplers (SHS, IOM, Button and GSP) as well as incorporate particle size determination and distribution in those areas. / MSc (Occupational Hygiene), North-West University, Potchefstroom Campus, 2014

The primary focus of this study was to compare the efficiency of six filter samplers in the collection of inhalable soluble platinum (Pt) salts at a South African base metal refinery. Inhalation remains the major route of occupational exposure to platinum groups metals (PGMs). South Africa would benefit from the study since it’s amongst the major countries where PGMs are produced and hence, monitoring of worker exposure with the most efficient sampler is of utmost importance. The IOM is currently being used in routine exposure monitoring although no studies have been carried out to compare its performance to that of the other samplers under the actual base metal refinery conditions. Method: The button, closed face cassette (CFC), Gesamtsstaubprobenhome (GSP), (Institute of Medicine) IOM, PAS-6 and seven hole (SH-sampler) samplers were randomly allocated to six different positions in presumably high exposure areas. The samplers were moved around in the subsequent sampling days and the process repeated 3 times. The average dust mass and Pt concentrations were used as a basis of sampler performance and comparisons from which sampler hierarchies were determined. Results: The average relative humidity ranged between 37% and 43% and the average dry bulb temperature of 22.4°C was measured. Comparison of the dust mass concentrations revealed no statistically significant differences amongst the six filter samplers tested. The SH-sampler and CFC however collected the highest and lowest dust mass and Pt concentrations respectively. Discussion: The SH-sampler was found to be a sampler with more reliability than the the IOM for the collection of dust mass and soluble Pt. The IOM collected 98% of the SH-sampler dust mass and Pt concentrations. This was in spite of the larger variations indicated by the highest relative standard deviations and confidence intervals shown by the IOM than the other samplers. The GSP sampler, however, showed better precision than all the other samplers in the collection of platinum. The seven 4 mm orifices of the SH-sampler sampler allow for uniform distribution of sampled particles onto the filter supporting its better precision than the IOM which has only one 4 mm opening. The worst performing sampler was the CFC sampler since it collected the lowest dust mass and Pt concentrations. The CFC and the PAS samplers have downward facing inlets that are affected by gravity especially in lower wind speeds which, therefore, influences their efficiency. The GSP sampler concentrations placed it as 4th and 3rd best in Pt and dust mass hierarchies respectively even though it showed better precision than SHS in the sampling of Pt. The button sampler did not perform as well as would have been expected considering that its many evenly spaced orifices and the stainless steel are meant to reduce sample losses. Conclusion: The sampler hierarchy according to dust mass concentrations was in the following order: SH-sampler, IOM, PAS, GSP, button and CFC. The hierarchy obtained from Pt concentrations gave the order as SH-sampler, IOM, GSP, button, PAS and CFC. Similar studies have to be undertaken in primary and secondary platinum workplaces to validate the study results. Such studies should compare better performing samplers (SHS, IOM, Button and GSP) as well as incorporate particle size determination and distribution in those areas. / MSc (Occupational Hygiene), North-West University, Potchefstroom Campus, 2014

Lake Urmia (LU), which once had been the second largest hypersaline lake in the world, and greatest in the Middle East, has undergone severe environmental changes during recent years that have led to widespread desiccation. These changes have converted the lakebed into a significant Aeolian mineral source, which promotes aerosol plumes that can seriously impact downwind regions. A question remains as to how significant emissions are from LU as compared to others impacting the West and East Azarbaijan provinces encompassing LU. This study uses daily Aerosol Optical Depth (AOD) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) between 2001 and 2015 to show that AOD levels are significantly larger in the latter half of the study period (2008-2015) with AOD values in the West consistently being lower but approaching those of the East with time owing to a combination of increasing emissions from the West province and neighboring areas. While the interannual AOD profile over Azarbaijan resembles that of Iraq owing to transported dust, signatures of the local impact of increasing emissions is evident over the 15-year time period, especially in the months outside of the peak dust season (January, February and October) and on the immediate periphery of LU. Consequently, the spatial profile of AOD over Azarbaijan is not uniform but with distinct hot spot. The onset of the spring AOD ramp-up over Azarbaijan is shown to have started earlier (in February) when comparing 2009-2015 versus earlier years. Correlative analysis confirms that AOD is related to factors promoting dust emissions but also reveals that smoke contributes to AOD over Azarbaijan during the summer months.

Aerosoler spelar en viktig roll för klimatet genom att växelverka med solstrålningen. Aerosolpartiklar kan absorbera solstrålning med resultatet att atmosfären värms upp. Mer vanligt är att aerosolpartiklar ger upphov till spridning av solstrålningen, delvis tillbaka ut i rymden, med resultatet att jorden kyls av. Den största påverkan på klimatet är dock att aerosolpartiklar verkar som kondensationskärnor vid molnbildning. Det är sedan molnens olika egenskaper som påverkar klimatet. För att bestämma aerosolförhållandet för den molnfria atmosfären på en plats kan man med solfotometrar bestämma det optiska djupet för aerosolpartiklarna vid olika våglängdsband. Aerosolernas optiska djup är ett mått på hur mycket av den direkta solstrålningen som når ner till marken. Med hjälp av de optiska djupen kan sedan våglängdsexponenten och turbiditetskoefficienten bestämmas. Detta har gjort på två platser i södra Sverige, Marsta och Norrköping. Solfotometrarna som används är kalibrerade med en så kallad Langleymetod ett fåtal gånger på WRC (World Radiation Center) i Davos, Schweiz, men för att resultaten ska bli säkrare bör en kalibreringskontroll genomföras. För att kunna göra en sådan kontroll krävs en lång mätperiod med klara atmosfärsförhållanden vilket det tyvärr inte gjort för mätningarna i Marsta (1997-1999), där mätperioden är kortare än i Norrköping (1995-2001). Innan studien av aerosolernas optiska djup, våglängdsexponenten samt turbiditetskoefficienten kan påbörjas måste mätdatan molnfiltreras eftersom molnen påverkar det optiska djupet. Molnfiltreringen sker automatiskt genom en rad olika tester, i vilka gränsvärdena har satts utifrån var mätningarna utförts någonstans. Studien av aerosolernas optiska djup visar på en sjunkande trend sett över hela mätperioderna. De optiska djupen är generellt högre i Marsta än Norrköping vilket troligtvis kan förklaras med omgivningens beskaffenhet. Medelvärdena av aerosolernas optiska djup för våglängdsbanden 368, 500 och 778 nm under hela mätperioderna är i Marsta 0.29, 0.15 samt 0.07. I Norrköping är motsvarande värden 0.17, 0.12 samt 0.07. Det går även att urskilja en tydlig trend av ökande optiskt djup under sommaren, vilket bland annat beror på att cirkulationen avtar samt att konvektionen tilltar. En annan orsak är att på vintern är polar och arktikluftmassor vanligare än på sommaren. Dessa luftmassor innehåller ett relativt litet antal aerosolpartiklar vilket medför ett mindre optiskt djup. Vad gäller våglängdsexponenten så är även den högre i Marsta än Norrköping vilket indikerar att det är fler små partiklar som bidrar till turbiditeten i Marsta än Norrköping. Medelvärdet av våglängdsexponenten, beräknad med medelvärdena av aerosolernas optiska djup för våglängdsbanden 368, 500 samt 778 nm under perioden 1997-1999, är för Marsta 1.9 och för Norrköping 1.3. Resultaten av turbiditetskoefficienten visar en liknande trend som de optiska djupen det vill säga ett högre värde under sommaren. Detta betyder att antalet partiklar ökar under denna period.

This is a study concerning the use of starphotometry to retrieve night-time aerosol optical depths (AODs). In the summer of 2007 a SPSTAR03 starphotometer was installed at a rural site at Egbert, Ontario for the purpose of the nighttime AOD measurements. Two series of daytime / nighttime AODs were acquired using the CIMEL CE 318 sunphotometer and the SPSTAR03 from Aug. 31 to Sept. 19 2007 and from June 30 to July 5, 2008. The measurements were complemented by vertical backscatter coefficient profiles acquired using a pulsed lidar. We found that starphotometer AOD estimates, based on the application of a two star method (TSM) to low and high elevation stars, are susceptible to atmospheric inhomogeneity effects. Starphotometer AOD estimates based on the one star method (OSM) reduce this sensitivity, but require absolute calibration values. A level of continuity was obtained between the daytime sunphotometry and nighttime starphotometry data. A continuity parameter (defined as the average difference between the measured nighttime and interpolated daytime values) was calculated over four distinct periods. It yielded the differences of 0.160, 0.053, 0.139 (total, fine and coarse mode optical depths) for the low star and 0.195, 0.070, 0.149 for the high star. We argue that cloud screening would have reduced the continuity parameter differences for the coarse and total optical depths. For 5 out of , 8 nights of lidar operation, a combination of the Angstrom and Spectral Deconvolution Algorithm (SDA) analysis provided an indication of the nature of the atmospheric features seen in the lidar data. Fine and coarse-mode events were detected during the measurement periods using the SDA. Lidar data was used to better understand complex atmospheric phenomena and was found especially effective for cloud detection and general signal increase/decrease analysis.