Thesis (Ph. D.)--University of Wisconsin--Madison, 1984. / Typescript. Vita. Description based on print version record. Includes bibliographical references (leaves 361-397).

Thesis (M. S.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2009. / Committee Chair: Sokolik, Irina; Committee Member: Curry, Judith; Committee Member: Kalashnikova, Olga; Committee Member: Nenes, Athanasios; Committee Member: Stieglitz, Marc.

Mineral dust both influences and is influenced by climate on many timescales, from seconds to epochs. Its complex interactions with the climate system are still being unraveled. For example, dust fluxes change in tandem with other records of past changes in climate, and dust source is often presumed to change as well, in response to shifts in climate conditions in source regions; changes in wind regimes; or changes in atmospheric transport pathways. In this work, I investigate dust records from the Southern Hemisphere from ice core and marine sediment core climate archives, looking at both flux and provenance in order elucidate the conditions that allowed for those particles to travel from source to sink. Using multiple radiogenic isotope systems as tracers (87Sr/86Sr, εNd(0), 206Pb/207Pb, and 208Pb/207Pb), I geochemically “fingerprint” of dust particles from Southern Hemisphere climate archives over the last glacial cycle. I compare the dust fingerprints to potential source areas (PSA’s) from across the Southern Hemisphere in order to identify the sources of dust found in the WAIS Divide and Taylor Glacier ice cores from West Antarctica, as well as from marine sediment core ELT39.75 in the Tasman Sea. I use endmember mixing theory to determine the relative contribution of different sources to the climate archives over time. In West Antarctica, I geochemically identify specific local volcanoes from Marie Byrd Land as significant particle contributors to the WAIS Divide ice core during the previous glacial period. In the Tasman Sea, I identify a specific region of southeastern Australia as primary the dust source over the past glacial cycle, with the source remaining constant across glacial-interglacial climate transitions. This clarifies that the “fingerprint” of Australian dust is relatively invariant over time and allows a single Australian signature to be used as an endmember for identifying dust provenance in climate archives downwind. I also identify the dust sources in the WAIS Divide during the Last Glacial Maximum and through the early deglacial, identifying southern South America as the predominant source during cold stages. WAIS Divide and Taylor Glacier dust records do not record dust source changes across millennial-scale climate events, suggesting that a) the source regions did not change, b) the transport pathways remained pinned, or c) the proxy is not sensitive to changes in these variables. Contributions from local volcanoes are also inferred from the WAIS dust record using mixing theory. In summary, I find that the radiogenic isotope fingerprint of dust samples from the archives analyzed show subtle or no changes in source over climate transitions, and therefore the strategy of dust particles as a tracer of past atmospheric circulation pathways should be approached cautiously.

Mineral dust is ubiquitous in the atmosphere and represents a dominant type of particulate matter by mass. Despite its well-recognized importance, assessments of dust impacts on clouds and climate remain highly uncertain. This thesis addresses the role of dust as cloud condensation nuclei (CCN) and giant CCN (GCCN) with the goal of improving our understanding of dust-warm cloud interactions and their representation in climate models. We investigate the CCN-relevant properties of mineral dust samples representative of major regional dust sources experimentally in the laboratory conditions to determine their respective affinity to water. Based on the experimental exponent derived from the dependence of critical supersaturation with particle dry diameter, we determine the dominant physics of activation (i.e., adsorption activation theory (AT) or traditional Köhler theory (KT)) for dust particles from different global regions. Results from experimental measurements are used to support the development of a new parameterization of cloud droplet formation from dust CCN for climate models based on adsorption activation mechanism. The potential role of dust GCCN activating by AT within warm stratocumulus and convective clouds is also evaluated.

To this date, estimates of the climate response to mineral dust remain largely uncertain because of our limited capability to quantify dust distribution in the atmosphere. Focusing on the Central and East Asian dust source regions, this thesis aims to develop a coupled regional dust modeling system to provide an improved modeling capability of atmospheric dust as well as to aid the integration of ground-based and satellite observations. The objectives of this study are as follows: 1) evaluate the capabilities of the available data to detect and quantify mineral dust in the atmosphere; 2) develop and test a coupled regional dust modeling system able to simulate size resolved dust concentrations accounting for the regional specifics of Central and East Asia; and 3) outline a methodology for data and modeling integration. The capabilities of ground-based and satellite data to characterize dust in the atmosphere are examined in great details. Based on analysis of MODIS data reflectance and radiances, we found evidence for regional signature of dust in near-IR and proposed a new probabilistic dust-cloud mask that explicitly takes into account the spatial variability characteristics of dust aerosols. We developed a coupled regional dust modeling system (WRF-DuMo) by incorporating a dust emission module (DuMo) into the NCAR WRF model. The WRF-DuMo unique capabilities include explicit treatment of land surface properties in Central and East Asia, a suite of dust emission schemes with different levels of complexity, multiple options for dust injection in the atmosphere and flexible parameters of the initial size distribution of emitted dust. Two representative dust events that originated in East Asia in the springs of 2001 and 2007 have been modeled with WRF-DuMo. Simulations with different initial size distribution of dust, injection and emission parameterizations have been performed to investigate their relative role on the modeled dust fields. We performed an integrated analysis of modeled dust fields and satellite observations by introducing an ensemble model dust index, which used in conjunction with satellite dust retrievals improves the capability to characterize dust fields. Finally, we provide recommendations for the development of an integrated observational and modeling dust framework.

Over the course of our lives we are exposed to airborne particulate matter in the workplace, home, and environment that results in the deposition of millions of particles in the lung. These exposures may result in disease if they are significant enough. The potential for harmful exposure depends in part on the dust's biodurability and the bioavailability of harmful constituents derived from the particles. A mixed flow reactor was used to evaluate two applications of geochemical methods to characterize the behavior of inhaled particles in the body. Dissolution rates of a well-characterized sample of powdered talc were measured in solvents that mimic fluids found in the human lung. These studies showed that variation of solvent chemistry, including the addition of organic chelators and proteins at intercellular fluid concentrations, does not markedly affect the measured dissolution rate of talc at 37 degrees Celcius and the data further indicate that the dissolution mechanism for talc in aqueous solutions is independent of pH over a range of pH from 2 to 8. The dissolution rate, determined by measuring the silicon release rate per unit surface area of talc is 1.4 (+/- 1.0) x 10-11 mol Si/(m2 -sec). A geometric shrinking particle model using this dissolution rate predicts an estimated lifetime (upper limit) of approximately 8 years for a 1 micron talc particle under pulmonary conditions. Talc dissolves considerably faster than quartz, but slower than chrysotile and olivine in the body. These data can be used to place constraints on the role of particle dissolution in the disease models associated with airborne respirable particulate matter. Secondly, the bioavailability of As and Cr was determined from a sample of coal fly ash from an eastern U.S. power plant. The time-release profiles of As and Cr were determined for these materials in physiologically-based solvents and incorporated into a toxicokinetic model to predict the exposure potential to As and Cr from occupational exposures to the coal fly ash. Predicted occupational exposure contributions from the ash relative to total environmental exposures were insignificant. The exposure predicted from the geochemical approach was compared with results observed in a cohort occupationally exposed to coal fly ash and found to be within one order of magnitude of the response of the occupational cohort. These results support the application of geochemical techniques to evaluate exposures to complex respirable materials. / Ph. D.

The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission provides unique measurements of vertical profiles of aerosols and clouds and their properties during day and night-time over all types of surfaces. This information has the potential to significantly improve our understanding of the properties and effects of aerosol and clouds. This dissertation presents the results of a comprehensive analysis of CALIPSO lidar (version 2 and version 3.01) data in conjunction with A-Train satellite and ground-based observations aimed at characterizing mineral aerosol in East Asia and other major dust sources. The specific objectives were to characterize the spatial distribution and properties of atmospheric dust in the dust source regions using new CALIOP (version 3.01) data in conjunction with satellite MODIS, OMI, and CloudSat data and ground-based meteorological and lidar data; investigate changes in the vertical distribution and properties of dust during mid- and long-range transport; perform a modeling of the optical properties of nonspherical dust particles, and assess the radiative forcing and heating/cooling rates of atmospheric dust by performing radiative transfer modeling constrained by satellite data in major dust source regions.

Mineral dust aerosols play an important role in atmospheric chemistry through photolysis and heterogeneous uptake. Both mechanisms strongly depend on the size and composition of mineral dust. Because of the complex nature of dust, chemistry modeling commonly relies on simplified assumptions about the properties of dust particles relevant to physiochemical processes. The goal of this thesis is to investigate the impact of size-resolved composition of dust aerosols on atmospheric photochemistry. The relative importance of dust characteristics in photolysis and heterogeneous loss and the relative roles of the two mechanisms on atmospheric photochemistry are investigated. A new block of spectral aerosol optical properties was developed and incorporated into the tropospheric ultraviolet and visible radiation transfer code in order to calculate spectral actinic fluxes and photolysis rates, J-values. The Fuchs-Sutugin approximation was employed to compute mass transfer from gas to dust mineral species and heterogeneous loss rate, kloss,j. The J-values and kloss,j were incorporated into a one-dimensional photochemistry model to simulate the diurnal cycle of a vertical profile of photochemical species. Several cases of dust loading were considered in the clean and polluted marine environments. A size-resolved mineralogical composition was constructed by selecting a range of the mass fraction of the three main mineral species such as iron oxide-containing clay minerals, carbonate-containing species, and quartz. This work demonstrates that differences in microphysical and chemical properties of mineral dust lead to the important changes in spectral optical properties, J-values, and kloss,j. It also shows that non-linear relationships of photochemical species with two mechanisms result in various changes in the photochemical oxidant fields and that the most important factor controlling the photochemistry field is the dust size distribution, followed by the amount of mineral species with high uptake coefficients and the amount of iron oxide-clay aggregates. This work demonstrates that accounting for regional differences in microphysical and chemical properties of mineral dust will improve the assessment of the impact of mineral dust on tropospheric photochemistry. In addition, it suggests that the size and composition of mineral dust will lead to a deeper understanding of the impact of mineral dust on the global climate system.