Since the UK industrial revolution, coal combustion, ore smelting and other industrial activities have resulted in a marked increase in emissions of potentially toxic elements (PTEs) such as antimony (Sb), lead (Pb), arsenic (As), copper (Cu) and zinc (Zn), along with polycyclic aromatic hydrocarbons (PAHs), to the atmosphere. Although stricter environmental regulation and improved technology has led to a notable decline for some contaminant emissions in recent decades, this has not been observed for all elements, e.g. Sb, where only a modest reduction in emissions have been recorded. Once emitted, Sb along with Pb, As, Cu, Zn and PAHs may persist in the environment for considerable periods of time after their release; although their chemical associations may change, elements are not broken down over time and organic contaminants may break down slowly. Above all, PTEs and PAHs are detrimental to human and environmental health, with chemical forms of Sb, Pb, As and PAHs categorised as carcinogenic. Understanding their behaviour and fate in the environment is therefore an important step towards evaluating their likely impact on both ecosystem and human health. Consequently, this study focuses on the release, behaviour and fate of contaminants from current and past anthropogenic sources in the urban and rural environment, with a specific interest in Sb and PAHs, where emissions originate from similar anthropogenic sources, with Pb, As, Cu and Zn also included for comparison purposes. Current and past industrial activity was identified as the dominant source of PTEs and PAHs to the urban environment, with emissions from vehicle, coal combustion and metal smelting identified as main contributors to total contaminant concentrations. Using road dust collected from Edinburgh at five high- and low-traffic roads at a distance of 10 and 50 m from the closest road junction, concentrations of Sb, Pb, Cu, Zn, PAHs and Pb isotope ratios were determined, with road dust undergoing further characterisation using chemical (sequential extraction) and spectroscopic (X-ray diffraction, SEM-EDX) techniques. No consistent trend for the element concentrations released from vehicles braking at 10 and 50 m from the closest road junction was observed. Mean concentrations for Sb, Cu and Zn were 5.3 ± 2.8 mg kg-1, 91.4 ± 48 mg kg-1 and 237 ± 144 mg kg-1, respectively, and were similar to road dust sampled from five high- and five low-traffic locations in Glasgow (Sb 4.5 ± 2.1 mg kg-1; Cu 117 ± 71.9 mg kg-1; Zn: 283 ± 146 mg kg-1). This was in contrast to mean concentrations for Pb and Σ16PAHs obtained from Glasgow (Pb 250 ± 283 mg kg-1, Σ16PAH 7.7 ± 4.3 mg kg-1) where values were approximately double and two-thirds greater than those found in Edinburgh (Pb 135 ± 129 mg kg-1, Σ16PAH 4.7 ± 2.9 mg kg-1), respectively. Lead isotopic analysis of Glasgow road dust (206Pb/207Pb range of 1.140-1.174) showed a strong influence of past emissions from coal combustion and metal smelting, and was in agreement with Glasgow's industrial history. For Edinburgh, the isotopic signature was considerably lower (206Pb/207Pb range of 1.116-1.151), and was influenced moreso by emissions of Australian sourced Pb in leaded fuel. Isotopic signatures in Edinburgh were lowest at easterly locations within 5 km of Edinburgh airport (206Pb/207Pb ~ 1.12), and corresponded with past vehicle emissions from leaded petrol use, and to a lesser degree, emissions from avgas, which was consistent with the mean annual wind direction for Edinburgh. The mobility of elements from the road dust to the aqueous phase were assessed by sequential extraction, and by using road surface water samples which showed mobility decreased in the order of Zn > Cu > Pb > Sb. Road dust characterised by XRD and SEM-EDX had a high proportion of quartz present (~55%), whilst the presence of less abundant minerals such as calcite were found to increase Pb mobility through ease of dissolution into the aqueous phase. For the rural environment, the behaviour and fate of elemental pollution originating from two former mining sites, an Sb mine at Glendinning, SW Scotland, and a Pb mine at Tyndrum in central Scotland was examined. Under specific environmental conditions, Sb was found to be both mobile and immobile in the environment. The chemical weathering of stibnite found in spoil heaps at Glendinning Sb mine demonstrated that ~3% of total Sb can be mobilised during the chemical weathering process, while hydrous Fe oxides and organic matter in the surrounding soil favoured its retention. The retention of Sb, along with Pb, was similarly observed in Loch Tay sediment downstream of Tyndrum Pb mine, where upon deposition, Sb and Pb remained immobile in sediment and allowed the construction of deposition chronologies for two sediment cores to be established. Excellent agreement between the sediment core deposition chronologies was observed, with both chronologies identifying atmospheric deposition as the primary source of Sb to Loch Tay sediment, whilst the dominant source of Pb was from Tyndrum Pb mine ~25 km upstream of Loch Tay. Relative to Sb and Pb, As had the greatest mobility, with its geochemical behaviour and partial retention by the solid phase influenced by the presence of Fe. This was evident in the surrounding soil at Glendinning Sb mine, where As was associated with hydrous Fe oxides present in the solid phase, while at Loch Tay, the redox cycling of Fe resulted in the post-depositional mobility of As in sediment. The use of ombrotrophic peat bogs for this study provided an effective means to assess atmospheric deposition of contaminants over past centuries; they continually accumulate and receive all their nutrients and contaminants exclusively by deposition from the atmosphere. The deposition archives of Sb and Pb from two Scottish peat cores sampled from Great Moss, Cairngorms Mountains, and, Auchencorth Moss, Midlothian, were used to construct chronologies for historic and contemporary emissions, particularly in relation to current and historic anthropogenic activities observed in urban and rural environments. At Great Moss, the deposition of Sb and Pb during the 19th century increased by a factor of 10 and 4, respectively, as a result of the industrial revolution and emissions from the combustion of coal and metal smelting. The trend continued into the 20th century where Sb and Pb deposition peaked ~1950, followed by a decline towards the early 21st century by a factor of 5 and 11, respectively. Over this period of time, the contribution from coal combustion and metal smelting towards total anthropogenic emissions was on the decline, while emissions from the combustion of leaded fuel increased until the ~1980s. Although deposition chronologies before 1970 for Sb and Pb at Auchencorth Moss were generally in agreement with those from Great Moss, several differences were observed after 1970, or more specifically, in the top ~10 cm of the peat core. This was a result of sub-surface perturbations for Ti, Sb, Pb and 210Pb concentrations, and indicated once deposited, elements were susceptible to post-depositional mobility brought about from a change in environmental conditions. The thicker acrotelm layer present at Auchencorth Moss, and the vertical movement of the peat water-table within this layer, resulted in a change in redox conditions and led to the redox cycling of Mn and Fe, which in turn, influenced vertical concentrations of Ti, Sb, Pb and 210Pb. While Sb and Pb are usually found immobile in peat systems, the post-deposition mobility of Sb and Pb at Auchencorth Moss was comparable to a peat core sampled from Flanders Moss, and indicated that under specific environmental conditions, both elements can become mobile in ombrotrophic peat bogs. It is worth bearing in mind however, that these results are the exception, and in all other cases ombrotrophic peat bogs remain a reliable archival material to use.

Major and trace metal loading to mountains in the western US depends on dust sources, intensity of storms and their availability for transport during snowmelt and runoff. Previous work has been conducted on dust production, composition, and its affect on solar radiation and timing of snow melt. This study was conducted to 1) examine temporal and spatial variability in dust chemistry; 2) evaluate form and availability of major and trace elements in dust; and 3) identify potential dust sources affecting mountains in Utah and Nevada. Spring and summertime dust was collected across northern Utah over the course of three years (2013-2015). Additional dust samples were collected from eastern Nevada for comparison. All samples were analyzed for mineralogy. The spring dust samples were also leached with 1 M acetic acid, 0.8 M nitric acid, and aqua regia and analyzed for 87Sr/86Sr ratios and concentrations of 40+ trace and major elements. Nearly all dust samples were enriched in playa-associated elements (U, Mg, Li, Ca, Sr, As) and anthropogenic elements (Sb, Mn, Zn, Cu, Pb, Se, Cd) relative to average upper continental crust. Leachate results showed that nearly 60% Ca, Sr, and Cd mass is potentially available for transport during snowmelt and that the rare earth elements could be mobilized under lower pH conditions in the soil zone. A major dust event on 17 March 2014 that was sampled across the study area showed spatially variable trace element concentrations and 87Sr/86Sr ratios, indicating that dust deposited to mountain snowpack originated from multiple upwind desert dust source areas. The NOAA HYSPLIT model was used to calculate back trajectories for this dust event and showed potential dust sources ranged from the Sevier, West and Great Salt Lake deserts in Utah and the Snake River Plain in Idaho. In contrast, multivariate statistical analysis showed that over the course of the study samples had unique geochemical signatures within each sample area. These findings suggest that spatial variability is more important than temporal variability in terms of the chemistry of dust deposition. With increasing populations and land use change in the western US, the short and long term effects of aeolian dust deposition to mountain environments need to continual monitored and constrained.

Mon travail de thèse a porté sur la simulation numérique du comportement dynamique de poussières et de petits corps autour d’étoiles, appliqué à deux grands domaines de localisation : les disques de débris et les exozodis.Concernant les disques de débris, je me suis plus particulièrement intéressé aux arches mouvantes observées sur une période de 15 ans au sein du disque d’AU Mic. En supposant qu’elles proviennent toutes d’un corps parent unique et que les grains composant les arches ont la même dynamique que les arches elles-mêmes, j’ai montré que le corps parent doit être plus interne que la ceinture de planétésimaux (<25 UA) et qu’il peut être sur une orbite circulaire ou fixe par rapport à l’observateur. Afin d’expliquer la vitesse apparente des arches, il est nécessaire que les grains les composant soient submicrométriques pour être suffisamment sensibles à la pression du vent stellaire. Le champ magnétique à grande échelle de cette étoile est suffisant pour expliquer l’élévation verticale des arches, mais l’interaction des grains avec ce champ nécessite des études plus approfondies.D’autre part, j’ai développé un code numérique permettant de tester l’origine dynamique des poussières constituant les exozodis, en comparant les résultats de mes simulations aux observations. J‘ai montré que le scénario classique de migration par PR-drag de grains provenant d’une ceinture externe froide produit trop de flux dans le moyen infrarouge en regard du proche infrarouge, et cet effet n’est pas suffisamment contrebalancé par l’accumulation proche de la distance de sublimation. En revanche, le scénario cométaire, avec un apport de matière au plus près de l’étoile, permet de modérer le flux en moyen infrarouge. Les observations peuvent être reproduites avec une dizaine de comètes kilométriques autour de chaque étoile. Le code que j’ai conçu est capable d’appréhender de nombreux effets physiques, et il est possible de tester l’influence du DDE, de la pression du vent stellaire ou encore du champ magnétique.Par mon travail, j’ai montré que la prise en compte de la dynamique des grains de poussière permet de contraindre les propriétés physiques des grains, et j’ai développé des outils numériques adaptables à de nombreux cas de figures afin de pouvoir caractériser la diversité et la complexité de la poussière observée autour des étoiles. / During my thesis, I numerically simulated the dynamical behaviour of dust and small grains around stars, applied to two ranges of stellar distance : debris disks and exozodis.Concerning debris disks, I focused on the fast moving arch-like structures observed over 15 years inside the disk of AU Mic. Supposing that they all come from a single parent body and that the dust composing the arches have the same dynamics, I showed that the parent body must be closer-in than the planetesimal belt (<25 au), on a circular orbit or static with respect to the observer. Grains must be submicronic in order to explain the apparent velocity of the arches, gained by means of stellar wind pressure. Large-scale magnetic field of the star is large enough to explain the vertical extent of the arches, but require further investigations.I also developped a numerical code in order to test the dynamical origin of dust composing exozodis, to compare its results to the observations. I showed that the classical PR-drag scenario involving grains drifting inward from a distant cold parent belt produce an excess flux in mid-infrared compared to the near-infrared, unbalanced by the pile-up. The cometary scenario, by producing dust very close to the star, emits less in mid-infrared. A ten of kilometric comets can reproduce the flux levels observed around all stars. This numerical code is also able to handle the DDE, the stellar wind pressure or the magnetic field.During my work, I showed that taking into account the dust dynamics can constrain the dust physical properties. I developped adaptative numerical tools that can handle the variety and complexity of dust observed around stars.

I study a dusty plasma produced in a DC glow discharge device. The chamber is a stainless steel cylinder 0.6 m in diameter and 0.9 m long. A stainless steel disk 3.2 cm in diameter acts as the anode and the walls act as the cathode. The discharge current is set between 1 - 10 mA and the voltage at the anode between 250 - 300 V. Dust is initially on a tray beneath the anode, and becomes trapped in the anode glow naturally with high discharge current. A secondary cloud can be made at a different location using a biased mesh. I make experimental observations of the dynamics of the secondary cloud as well as the unique interaction of the dust with a wire loop near the anode. First, I describe the interaction of the secondary cloud with a wire when it the cloud is released to flow back to the primary cloud. A detached bow shock is observed as the cloud encounters an obstacle, and an elongated teardrop shaped void is formed downstream of the obstacle. Second, a continuous flow is set up using at biased ring. The potentials of the ring and anode create a converging-diverging electrostatic potential structure which accelerates dust particles into a thin stream in the diverging section. The interaction of this stream and a wire obstacle is described. Finally, the potentials of the mesh and anode are suddenly switched to float simultaneously to observe the secondary cloud expansion in the afterglow plasma. The rate of expansion is shown to depend inversely on the background pressure in the range of 100-200mTorr. The expansion shows a separation in the cloud and possible Yukawa-like expansion where the center of the cloud does not respond initially to the removal of confinement.

No description available.

Thesis (M.S. in biological systems engineering)--Washington State University, December 2007. / Includes bibliographical references (p. 41-45).

Thesis (M.S.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (February 7, 2007) Includes bibliographical references.

Because the bulk optical properties of dust are largely dependent on their chemical composition, published reports from numerous dust field studies enabled us to compile observation data sets to derive the effective complex refractive indices of Saharan and Asian dust. We considered the individual mineral components as aggregates and used the Bruggeman approximation to derive the effective refractive indices. Using the results, we calculated the single-scattering properties, including phase matrix, single-scattering albedo and asymmetry factor, with a combination of the T-matrix method and an improved geometric optics method (IGOM). The single-scattering properties were averaged by the measured particle size distribution to provide bulk optical properties for radiative transfer simulations. Using a Rapid Radiative Transfer Model (RRTM), the radiative forcing of mineral dust was computed at both the top of the atmosphere and the surface. By analyzing samples from various in-situ measurements, we assumed the Saharan and Asian dust to have average volume compositions and average aspect ratios. The effective refractive indices for Saharan and Asian dust were derived based on the assumed composition models. Bulk optical properties were integrated using the modified log-normal particle size distributions. The aspect ratio assumed in this study is 1.6 for both Saharan and Asian dust. The longwave radiative (IR) forcings at the top of the atmosphere (TOA) and at the surface were found to be positive and sensitive to wavelength. The shortwave (solar) radiative forcing at TOA, was also positive, but may possibly have been due to the strong absorption components considered in the composition models.

No description available.

A special challenge posed by mineral dust aerosols is associated with their predominantly nonspherical particle shapes. In the present study, the scattering and radiative properties for nonspherical mineral dust aerosols at violet-to-blue (0.412, 0.441, and 0.470 μm) and red (0.650 μm) wavelengths are investigated. To account for the effect of particle nonsphericity on the optical properties of dust aerosols, the particle shapes for these particles are assumed to be spheroids. A combination of the T-matrix method and an improved geometric optics method is applied to the computation of the single-scattering properties of spheroidal particles with size parameters ranging from the Rayleigh to geometric optics regimes. For comparison, the Mie theory is employed to compute the optical properties of spherical dust particles that have the same volumes as their nonspherical counterparts. The differences between the phase functions of spheroidal and spherical particles lead to quite different lookup tables (LUTs) involved in retrieving dust aerosol properties. Moreover, the applicability of a hybrid approach based on the spheroid model for the phase function and the sphere model for the other phase matrix elements is demonstrated. The present sensitivity study, employing the Moderate Resolution Imaging Spectroradiometer (MODIS) observations and the fundamental principle of the Deep Blue algorithm, illustrates that neglecting the nonsphericity of dust particles leads to an underestimate of retrieved aerosol optical depth at most scattering angles, and an overestimate is noted in some cases. The sensitivity study of the effect of thin cirrus clouds on dust optical depth retrievals is also investigated and quantified from MODIS observations. The importance of identifying thin cirrus clouds in dust optical depth retrievals is demonstrated. This has been undertaken through the comparison of retrieved dust optical depths by using two different LUTs. One is for the dust only atmosphere, and the other is for the atmosphere with overlapping mineral dust and thin cirrus clouds. For simplicity, the optical depth and bulk scattering properties of thin cirrus clouds are prescribed a priori. Under heavy dusty conditions, the errors in the retrieved dust optical depths due to the effect of thin cirrus are comparable to the assumed optical depth of thin cirrus clouds. With the spheroidal and spherical particle shape assumptions for mineral dust aerosols, the effect of particle shapes on dust radiative forcing calculations is estimated based on Fu-Liou radiative transfer model. The effect of particle shapes on dust radiative forcing is illustrated in the following two aspects. First, the effect of particle shapes on the single-scattering properties of dust aerosols and associated dust direct radiative forcing is assessed, without considering the effect on dust optical depth retrievals. Second, the effect of particle shapes on dust direct radiative forcing is further discussed by including the effect of particle nonsphericity on dust optical depth retrievals.