This thesis focuses on the analysis of heavy noble gases (argon, krypton and xenon) and halogens (chlorine, bromine and iodine) in Martian meteorites. In the absence of a sample-return mission, Martian meteorite analysis is essential for establishing evidence for an active fluid system, evaluating the potential for life and understanding the formation and evolution of Mars. Noble gas analysis has multiple applications for Martian meteorite study, as described in this thesis. The noble gas isotopic signatures of Earth’s atmosphere, Martian atmosphere and Martian interior are sufficiently different that they can be distinguished through noble gas analysis. Analysis of bulk and mineral separates of shergottites showed that Martian atmospheric Xe was distributed evenly amongst samples, whilst terrestrially weathered samples contained elevated concentrations of terrestrial atmospheric Xe. Both atmospheric components were introduced by weathering. Shock redistribution is responsible for the distribution of Martian atmosphere into more retentive sites. Crustal contamination may be responsible for the presence or absence of detectable 129Xe from the Martian atmosphere. Halogen abundances can be determined as an extension of the Ar-Ar dating technique. As the halogen system on Earth acts as a tracer for important fluid related processes, Martian halogen abundances in meteorites may provide a tracer for the Martian fluid system. Analysis of bulk and mineral separates of nakhlites showed that halogens are distributed amongst minor phases and clear variation of Br/Cl and I/Cl ratios was observed amongst samples. Elevated I concentrations in low temperature releases of finds NWA 998 and MIL 03346 are consistent with terrestrial contamination. Analysis of Nakhla, (a meteorite fall), showed a trend of elevated Br/Cl and I/Cl ratios in crush and low temperature releases, consistent with Br/Cl ratios observed in Martian rocks, soils and weathering products. In contrast, high temperature releases had lower I/Cl and Br/Cl ratios, which are broadly comparable to the terrestrial mantle. This trend may represent mixing of hydrothermal fluids (low Br/Cl and I/Cl) and surface brines (high Br/Cl and I/Cl). An impact-induced hydrothermal system may provide a mechanism for mixing of both fluid types. The crystallisation ages of nakhlite meteorites were determined using the Ar-Ar dating technique. The apparent ages measured were similar to previous Ar-Ar analysis, and older than reported for other chronometers. Previously unrecognised components were observed, including evidence for a trapped hydrous fluid. This Cl-rich component showed strong correlation with 40Ar and had 40Ar/36Ar and 40Ar/129XeXS ratios consistent with Martian atmosphere. As this component was released during crush and low temperature analysis, fluid inclusions formed by percolation of brines from the Martian surface are likely hosts. Both finds showed clear evidence of a trapped component with 40Ar/36Ar ratios similar to either terrestrial atmosphere or the Martian interior. A further component observed in olivine phases had low 40Ar/36Ar ratios, and likely formed by the release of 36Ar formed by cosmic-ray spallation reactions on iron.

[pt] A necessidade da determinação do comportamento tensão-deformação de solos sob carregamento para fins de projeto de Engenharia exige o conhecimento prévio do estado natural de tensões ao que o solo está imposto. Quando se trata de solos residuais tropicais, este desafio amplia-se ainda mais devido à ação do intemperismo e variação de umidade. O estado natural do solo é usualmente expresso pelo coeficiente de empuxo no repouso (K0). Para a determinação de K0 três classes de métodos são utilizadas: métodos de correlação, de determinação in situ e em laboratório. Neste estudo, é utilizada uma célula rígida com sistema de controle de sucção para a obtenção de K0 em laboratório. Foram analisadas três amostras de solo residual de Gnaisse com diferentes graus de intemperismo, provenientes de São Conrado, Rio de Janeiro, denominadas: solo residual jovem (SRJ); solo residual de transição (SRT); e solo residual maduro (SRM). Para a análise da influência da sucção no valor do coeficiente de empuxo, cada amostra de solo foi ensaiada sob três diferentes condições de umidade, que tentaram representar as seguintes condições: mais úmida, com sucção de 10 kPa; intermediária, com 40 kPa de sucção; e mais seca, com 100 kPa. Os valores de K0 obtidos nos ensaios variaram de 0,50 a 0,65. Os resultados seguiram, em parte, a tendência esperada. Entretanto, devido à heterogeneidade do material estudado, é necessário realizar repetições dos ensaios a fim de obter dados representativos. / [en] The necessity to determine the stress-strain behavior of soils under loading for the purpose of engineering projects requires early knowledge of the natural state of stress that acting on the mass of soil. When it comes to tropical residual soils, this challenge is even greater due to weathering and moisture variation. The natural state of the soil is usually expressed by the coefficient of earth pressure at rest (K0). For the determination of K0 three classes of methods can be used: correlation meth-ods, in situ determination and laboratory tests. On this research, one rigid cell with system of suction control is used to obtain values of K0 in laboratory tests. Were analyzed three samples of Gneiss residual soil with different degrees of weathering. The samples were provenient to São Conrado, Rio de Janeiro and namely: young residual soil (SRJ), transition residual soil (SRT) and mature residual soil (SRM). To evaluate the influence of suction on the value of coefficient of earth pressure at rest, each sample of soil were tested into three different levels of moisture which correspond of following conditions: more humid, with suction of 10 kPa; interme-diate, with 40 kPa of suction; and more dry, with 100 kPa. The K0 values obtained in the tests ranged from 0,50 to 0,65. In general, the results attended the expected trend. However, due to the great heterogeneity of the studied material, it is neces-sary to perform repetitions of tests in order to obtain representative data.

This work deals with the influence of atmospheric corrosion on high-cycle fatigue properties of a weathering steel ATMOFIX B. New experimental data on fatigue strength of a steel exposed for 20 years to an atmospheric corrosion were compared to those characterizing the base material. Reduction of the fatigue lifetime of the exposed material compared with the base material was predicted on the basic of fractographic examination of fracture surfaces and the influence of surface notches on fatigue strength. The predicted results agree well with the experimental results.

L'objectif principal de cette thèse est de restituer l'évolution passée des moussons asiatiques au cours du Quaternaire et d’en évaluer leurs impacts sur l’érosion continentale et les transferts sédimentaires terre-mer, à partir de l’étude de carottes marines collectées dans la Baie du Bengale, l'ouest de la mer des Philippines et la mer d'Arabie. La stratégie scientifique mise en œuvre implique des analyses minéralogiques (argiles), sédimentologiques (granulométrie laser) et géochimiques (⁸⁷Sr/⁸⁶Sr et εNd) afin de restituer les zones sources sédimentaires, les conditions d’érosion et de transfert sédimentaires à l’océan. Les analyses de la concentration en élément des terres rares et des valeurs de l’εNd ont également été faites sur des échantillons d’eau de mer et de foraminifères collectés dans la Baie du Bengale afin de contraindre l’utilisation de ce traceur dans un contexte de très forts changements saisonniers de débit des fleuves Himalayens. Cette stratégie nous a permis, entre autre, de restituer les précipitations de mousson du domaine ouest tropical Pacific au cours du Quaternaire et d’établir un lien avec l’évolution à long terme de la dynamique de circulation méridienne de type ENSO. Nous avons également apporté de nouvelles contraintes sur l’utilisation du traceur εNd dans les foraminifères de la Baie du Bengale en vue d’en restituer la dynamique passée de l’érosion himalayenne. / The main objective of this PhD study is to reconstruct the evolution of the Asian monsoons during the Quaternary and their impacts on the continental erosion and sedimentary transfers from land to sea by the investigation of sediments cores collected in the Northern Bay of Bengal, the western Philippines Sea and the Arabian Sea. The implemented scientific strategy involves mineralogical (clay size fraction), sedimentological (grain-size laser) and geochemical (⁸⁷Sr/⁸⁶Sr and εNd) analyses in order to establish sedimentary sources, conditions of erosion and transfer of sediments to the Ocean. The analyses of the concentration of Rare Earth Elements (REE) and εNd were also made on seawater and foraminifera samples to better constrain the εNd as a proxy of weathering in a context of strong seasonal variations of sediment discharges by Himalayan rivers. Clay mineralogy and laser grain-size analyses have been conducted on sediments from core MD06-3050 collected on the Benham Rise (Philippines Sea). Siliciclastic grain-size results indicate variations of the relative proportion of three grain-size sub-populations corresponding to eolian dusts (EM2 about 9-11 μm) and Luzon rivers inputs (EM1 about 2-5 μm and EM3 about 19-25 μm). The long-term evolutions of the EM1/EM2 and smectite/(illite+chlorite) ratios permit to reconstruct variations of the contribution of detrital material deriving from the volcanic arc of Luzon and rainfall intensity of this tropical region. At long time scale, periods of intensification of monsoon rainfall on Luzon are associated to a reduction of precipitation on central China. These periods are also associated to an increase of the zonal gradient of sea surface temperatures on the equatorial Pacific Ocean suggesting a strengthening of El Niña conditions. These results highlight for the first time a strong role of the dynamics of the meridian circulation of ENSO on the long-term changes of rainfall of the tropical western Pacific during the Quaternary. In the Arabian Sea, clay mineralogy, siliciclastic grain-size, ⁸⁷Sr/⁸⁶Sr ratio and εNd were analysed on Quaternary sediments of the IODP site U1457. Our results suggest a change in the relative proportions of sediments from the Deccan Trapps (smectite) and the Indus river (mainly illite and chlorite). Variability of sedimentary sources and sediment transport (turbidites activity) to the Indus Fan have been reconstructed and attributed to monsoon rainfall and the sea level variations. The concentrations of REE combined with εNd were analysed on seawater samples collected in June 2012 along a North-South cross section in the Bay of Bengal. We highlighted from normalized REE patterns that the contributions of dissolved REE from the Ganges-Brahmaputra river system was the main source of the dissolved REE of surface waters of the Bay of Bengal, whereas the desorption of lithogenic particles dominate the dissolved REE of the intermediate and deep waters masses. We then revalued the residence time of the dissolved REE in the Bay of Bengal. A comparison of εNd, obtained just before the increase of the Ganges-Brahmaputra river discharge inferred by Indian monsoon rainfall, with the results obtained by Singh and al. (2012) for seawater samples collected after the peak of river discharge, allowed us to highlight for the first time a seasonal variability of seawater εNd of the Bay of Bengal. εNd have been analysed on planktonic foraminiferas of core MD77-176 located at 1375 m water depth to reconstruct for the first time the seawater εNd record of the intermediate waters masses of northern Bay of Bengal for the last 27 kyr. This new seawater εNd record of the Northern Bay of Bengal give us new constrain for this proxy already used to reconstruct past changes of the Himalayan weathering.

<p>U okviru ovog istraživanja ispitani su: (1) Procesi koji se odvijaju prilikom &nbsp;bioremedijacije zemlji&scaron;ta zagađenog naftom i derivatima nafte, koje je bilo izloženo&nbsp;spontanim abiotičkim i biotičkim procesima degradacije u toku 8 godina, tehnikama&nbsp;biogomila i povr&scaron;inske obrade na poluindustrijskoj (pilot) skali uz optimizaciju&nbsp;tehnolo&scaron;kih parametara sa ciljem povećanja efikasnosti i efektivnosti biodegradacije&nbsp;ugljovodonika; (2) Uticaj starenja, koncentracije, biodsotupnosti i strukture zagađujućih&nbsp;materija na procese biodegradacije i biotransformacije u kontrolisanim laboratorijskim&nbsp;uslovima. Tokom dve godine bioremedijacionog tretmana sadržaj mineralnih ulja opao&nbsp;je za 52% (od 27,8 g/kg do 13,2 g/kg) i 53% (od &nbsp;23,2 g/kg do 10,8 g/kg), dok je sadržaj&nbsp;ukupnih ugljovodonika opao za 43% (od 41,4 g/kg do 23,4 g/kg) i 27% (od 35,3 g/kg do&nbsp;25,8 g/kg) u biogomili i povr&scaron;inskoj obradi respektivno. Efikasnost uklanjanja&nbsp;mineralnih ulja iz zemlji&scaron;ta u dva posmatrana bioremedijaciona tretmana je praktično&nbsp;ista. Međutim, u pogledu sadržaja ukupnih ugljovodonika u biogomili uklonjeno je dva&nbsp;puta vi&scaron;e ukupnih ugljovodonika (gledajući &nbsp;apsolutnu količinu ukupno uklonjenih&nbsp;ugljovodonika). Kinetika biodegradacije mineralnih ulja i ukupnih ugljovodonika u toku&nbsp;tretmana u biogomili u saglasnosti je sa kinetičkim modelima lnC=lnC_0-kt i lnC=lnC_0-kt^0,5. Kinetika biodegradacije mineralnih ulja u toku povr&scaron;inske obrade relativno se&nbsp;dobro može opisati sa dva pomenuta kinetička modela, međutim, znatno bolju&nbsp;korelaciju pokazao je linearni model (C=C_0-kt) primenjen na prvih 92 i poslednjih 200&nbsp;dana eksperimenta. Promena sadržaja ukupnih ugljovodonika u toku povr&scaron;inske obrade&nbsp;zagađenog zemlji&scaron;ta relativno je u dobroj korelaciji samo sa kinetičkim modelom&nbsp;lnC=lnC_0-kt^0,5. Laboratorijska ispitivanja pokazala su da biodegradabilnost i sudbina&nbsp;ugljovodonika u životnoj sredini jako zavise od tipa, starosti i koncentracije zagađujućih&nbsp;materija. Naime, u slučaju zemlji&scaron;ta sveže kontaminiranog dizel uljem, već pri&nbsp;<br />koncentracijama od 20 mg/g uočen toksičan efekat koji je prevaziđen nakon dve nedelje&nbsp;tretmana kao posledica smenjenja prekomerne koncentracije rastvorenih ugljovodonika&nbsp;biotičkim i abiotičkim putem i adaptacije prisutne mikroflore. U slučaju većih&nbsp;koncentracija ovaj efekat je bio jo&scaron; izraženiji. Kod zemlji&scaron;ta kontaminiranog sirovom&nbsp;naftom isti efekat se javlja tek pri koncentraciji od 35 mg/g, kao posledica toga da&nbsp;sirova nafta sadrži manju količinu lako rastvornih ugljovodonika. Za razliku od sveže&nbsp;kontaminiranog zemlji&scaron;ta, na biodegradaciju starog naftnog zagađanja u zemlji&scaron;tu&nbsp;koncentracija nije imala uticaj, u ovakvom zemlji&scaron;tu respiracija je bila na veoma niskom&nbsp;nivou pri svim ispitivanim koncentracijama, ali ne kao posledica toksičnosti, već kao&nbsp;posledica činjenice da se degradabilni deo zagađujućih materija degradirao tokom&nbsp;procesa starenja, tako da su u zemlji&scaron;tu zaostali visokomolekularni &nbsp;te&scaron;ko rastvorni&nbsp;ugljovodonici (smole, asfaltne komponente i dr.) sekvestrovani u zemlji&scaron;tu. Merenja biodostupnosti ugljovodonika (ekstrakcijom sa Tween80) pokazala &nbsp;su da je u zemlji&scaron;tu sveže kontaminiranom dizel uljem i sirovom naftom i starim naftnim zagađenjem oko 95%, 85% i 40% ugljovodonika biodostupno, respektivno. Koncentracija rezidualne frakcije mineralnih ulja i ukupnih ugljovodonika dobijena nakon 48 dana laboratorijskog tretmana u skoro svim probama je veća od predviđenih, &scaron;to je posledica bifaznog pona&scaron;anja ugljovodonika u zemlji&scaron;tu, gde se jedan deo uklanja biodegradacijom, dok drugi deo difunduje u pore zemlji&scaron;ta i kompleksira se sa zemlji&scaron;nom organskom materijom. Količina ugljovodonika iz starog naftnog zagađenja zemlji&scaron;ta koja može da pređe u vodenu fazu je mala reda veličine nekoliko mg/l, međutim, u prirodnim uslovima usled spiranja ugljovodonika sa zemlji&scaron;ta ki&scaron;om, postoji verovatnoća da ovi ugljovodonici dospeju u podzemnu vodu iznad maksimalno dozvoljene koncentracije za vodu za piće (MDK = 10 &mu;g/l) i na taj način degradiraju njen kvalitet. Zbog nemogućnosti daljag uklanjanja zagađenja bioremedijacijom, preostala količina zagađujućih materija koja može dospeti u vodenu fazu bi trebalo da se ukloni nekim drugim remedijacionim tehnikama pre njegovog konačnog bezbednog odlaganja u životnu sredinu.</p> / <p>The aims of this study were to examine: (1) the processes that occur during bioremediation of soil contaminated by oil and oil derivatives, which was exposed to spontaneous abiotic and biotic degradation processes over 8 years, using pilot scale biopiles and landfarming techniques to optimise technological parameters with the aim of increasing the efficiency and effectiveness of hydrocarbons biodegradation. (2) the effect of contaminants weathering, concentration, bioavailability and structure on the biodegradation and biotransformation process under controlled laboratory conditions. Over the two years of bioremediation treatment by biopiles and landfarming, the mineral oil content decreased by 52% (from 27.8 g/kg to 13.2 g/kg) and 53% (from 23.2 g/kg to 10.8 g/kg),&nbsp; and the total hydrocarbon content decreased by 43% (from 41.4 g/kg to 23.4 g/kg) and 27% (from 35.3 g/kg to 25.8 g/kg), respectively. The efficiency of mineral oil removal from soil in these two applied bioremediation treatments was practically the same. However, in terms ofthe absolute amount of total hydrocarbons, twice as many total hydrocarbons were removed in the biopile. The mineral oil and total hydrocarbons biodegradation kinetics in the biopile were in good agreement with&nbsp; the kinetic models lnC = lnC0-kt and lnC = lnC0-kt0.5. The mineral oil biodegradation&nbsp;kinetics during the landfarming treatment is relatively well described with those two kinetic models, however, significantly better correlation is obtained by the linear model (C = C0-kt) applied to the first 92 and last 200 days of the experiment. The change in total hydrocarbons content during the landfarming treatment is in relatively good correlation only with the kinetic model lnC = lnC-kt0.5. The laboratory biodegradation investigation showed that hydrocarbon biodegradability and its fate in the environment strongly depend upon the structure, concentration and weathering of the hydrocarbons. Thus, in the case of diesel contaminated soil, as a consequence of&nbsp; its structure, i.e. the presence in a higher concentration of the soluble and toxic midrange n-alkanes, a toxic effect is detected at a diesel oil concentration of 20 mg/g, although this effect is overcome after two weeks, as a consequence of the decreasing&nbsp; concentration of soluble hydrocarbons in biotic and abiotic processes and microbial adaptation. This effect was more pronounced in the case of the soil withthe highest diesel oil concentration. In crude oil contaminated soil, a toxic effect was observed at a much higher hydrocarbon concentration (35 mg/g) than in the diesel oil contaminated soil, which corresponds to the fact that crude oil contains significantly less soluble hydrocarbon. In contrast to these two freshly contaminated soils, the weathered contaminated soil contaminant concentration did not have an effect on hydrocarbon biodegradation, with biodegradation in this soil actually at a low level at all concentrations, not as a consequence of toxicity, but because the degradable part of the contaminant was already degraded during the weathering process, leaving behind only highly condensed hydrophobic organic contaminants (asphaltenes, resins, etc.) sequestered in the soil. The data obtained for hydrocarbons bioavailability (by Tween80 extraction) showed that the bioavailable hydrocarbon fraction from soils freshly contaminated with diesel oil and crude and weathered oil contamination were approximately 95%, 85% and 40%, respectively. The concentration of residual mineral oil fractions and total hydrocarbons obtained after 48 days of laboratory biodegradability treatment in almost all batches was greater than predicted, as a result of the biphasic behaviour of hydrocarbons in the soil, where some were degraded or lost from the soil and some transformed into the recalcitrant fraction. The amount of hydrocarbons from the weathered soil contamination that can be transferred into the water phase is small, of the order of a few mg/l in magnitude, however, under natural conditions, due to hydrocarbons leaching by rainfall, it is possible that these hydrocarbons infiltrate groundwater above&nbsp; the maximum permissible concentration for drinking water (MAC = 10 &mu;g/l) and thus degrade its quality. As it is not possible to achieve further contamination degradation by bioremediation, the remaining amount of pollutants which can be transferred into the water phase should be removed by some other remediation techniques before its final safe disposal in the environment.</p>

Huge changes in climate occurred at the end of the last Quaternary glaciation. The end of this glaciation corresponds with the end of Pleistocene with its repeated glacial cycles and the start of the current geological epoch, the Holocene interglacial. The climate at this time was characterized by increasing temperatures and an increase in rainfall. This project focuses on understanding and examining these changes in climate using loess deposits from south-western England. Loess is an aeolian sediment and covers around 10 % of the Earth’s land surface and these deposits are excellent archives of past climate. Investigating loess can give understanding of past regional and local wind circulation patterns, atmospheric dustiness as well as weathering conditions. Studying paleoclimate is important since studying and understanding trends in past climate can increase our understanding of how the climate will change in the future. This study examined loess from two sites in south-western England, Porth Cressa and Lowland Point. These are relatively thin deposits; Lowland Point has a thickness of 180 cm and Porth Cressa has a thickness of 97 cm. England lacks the thick loess deposits that can be found in other parts of the world and thus the study of English loess has mostly been neglected. These deposits thus could contain unutilized information about paleoclimate. The elemental composition of the samples was examined using X-Ray Fluorescence (XRF). With the measured elemental composition, it’s possible to use weathering indices to see trends in postdepositional weathering. Low weathering intensities indicate a colder and drier climate, while higher weathering intensities indicate a warmer and more humid climate. The results from the weathering indices were plotted against depth at the two sites to identify changes in weathering and hence climate over time. Compared with the results from previous studies the results from some weathering indices seemed credible. Previous studies have indicated that the Chemical Proxy of Alteration (CPA) is the most appropriate weathering index for loess and the results from this study supports that theory. The results from the CPA show a trend with decreasing weathering intensities followed by a trend with increasing weathering intensities This implies that there was a period with decreasing temperatures/humidity followed by a period with increasing temperature humidity sometime at the end of the last glaciation. The geochemical data also showed support for a previous archaeological theory that there has been human reworking in the upper horizons at Lowland Point. / Slutet av den sista kvartära glaciationen var en tid med stora klimatförändringar. Denna tid sammanfaller med slutet av Pleistocene och dess glaciära cyklar samt starten på den nuvarande geologiska epoken, Holocen. Klimatet vid den här tiden karaktäriserades av ökande temperaturer och ökande nederbörd. Det här projektet fokuserar på att granska och förstå dessa klimatförändringar med hjälp av lössjordar från sydvästra England. Löss bildas av vindburet sediment och täcker ungefär 10 % av jordens landyta, dessa avlagringar är utmärkta arkiv för historiskt klimat. Att undersöka lössjordar kan ge information om historiska regionala och lokala vindcirkulations-mönster, vittringsförhållanden samt mängden damm i atmosfären. Att undersöka paleoklimat är viktigt då förståelse för trender i tidigare klimat kan ge oss förståelse för hur klimatet kommer förändras i framtiden. Den här studien undersökte löss från två platser i sydvästra England, Lowland Point och Porth Cressa. Dessa avlagringar är relativt tunna; Lowland Point har en tjocklek på 180 cm och Porth Cressa har en tjocklek på 97 cm. England har inte de tjocka lössavlagringarna som går att hitta i andra delar av världen och därför har lite forskning utförts på brittiskt löss. Dessa avlagringar kan alltså innehålla oanvänd information om paleoklimat. Provernas grundämnessammansättning undersöktes med X-Ray Fluorescence (XRF). Med den uppmäta grundämnessammansättningen är det möjligt att använda vittringsindex för att se trender i vittring efter deposition. En låg vittringsintensitet indikerar ett kallare och torrare klimat medan en högre vittringsintensitet indikerar ett varmare och fuktigare klimat. Resultaten plottades mot djup för att visuellt identifiera förändringar i klimatet över tid. Vid jämförelse med tidigare studier verkade resultaten från vittringsindexen trovärdiga. Tidigare studier har föreslagit att CPA (Chemical Proxy of Alteration) är det mest lämpliga vittringsindexet för lössjordar och resultaten från denna studie stödjer den teorin. Resultaten från CPA visade på en trend med minskade vittringsintensitet följt av en trend med ökande vittrings intensitet. Detta antyder att det var en period med minskande temperatur/fuktighet följt av en period med ökande temperatur/fuktighet runt slutet av den senaste istiden. De geokemiska resultaten stödde också den tidigare arkeologiska teorin att mänsklig aktivitet har påverkat de övre horisonterna vid Lowland Point.

Indiana University-Purdue University Indianapolis (IUPUI) / This dissertation focuses on quantification of submicroscopic iron of different sizes, mineral abundance and grain size of lunar soils using Hapke's radiative transfer model. The main objective is to explore implications of these results for assessing the relative importance of solar wind implantation versus micrometeorite impacts for lunar space weathering as well as three hypotheses (solar wind deflection, comet impact and dust transport) for swirl formation on the Moon. Results from this study can help to make connections between ordinary chondritic meteorites and asteroids, and put physical and chemical constraints on heating processes in the early solar system.

Wood is a renewable resource and versatile material used in tasks ranging from tools and furniture to advanced engineering structures. Although wood is light, mechanically robust, environmentally friendly, and abundant, some inherent properties of wood, such as degradation due to moisture and UV radiation from sunlight, are less desirable for extended service life and dimensional stability. In this dissertation, a novel surface modification of wood is explored by depositing nano-sized titania particles on wood veneers and cross-laminated timber (CLT) blocks by liquid-precursor flame spray pyrolysis to confer reversible wettability switching and enhanced durability to UV irradiation. The reaction between a flame source and a titanium precursor in isopropyl alcohol under controlled air pressure created a micrometer-scale thin TiO2 coating on wood that turns the treated wood superhydrophobic with a water contact angle (WCA) of >=150°. Morphological studies suggest the coating is comprised of sub-100 nm TiO2 individual and aggregated particles, creating a very porous microstructure. The coating consists of TiO2 rich in the anatase phase (>60%) with an average crystal size of 18 and 32 nm for the anatase and rutile phases, respectively. The wettability switching characteristics of the surface of TiO2-wood veneers from superhydrophobicity to superhydrophilicity (WCA ~0°) and again back to superhydrophobicity are examined through UV exposure (0.0032 W/m2), WCA measurements, and vacuum drying at ~0.14 mbar. The color and gloss spectrometry results of the TiO2-treated CLT samples indicate that the coating offered better resistance to discoloration and gloss change than the uncoated samples during the 8-week accelerated weathering conditions. The data shows that the FSP-treated CLT samples were more than two times more effective in preventing discoloration and changes in natural luster, as evidenced by the significant differences in L*, a*, b*, and gloss values. Moreover, the FSP treatment might have played a role in preventing weathering defects, such as splits and cracks. In addition, the FSP-treated CLT specimens were able to reduce variability in the samples more effectively than the control group. Overall, the findings of the study indicate that liquid-precursor FSP has the potential to serve as a facile, economically viable, and less energy-intensive approach to modify wooden surfaces for improved hydrophobicity, as well as to provide shielding against the deteriorating impacts of UV radiation and moisture exposure. Keywords: wood modification, flame spray pyrolysis, titania coating, superhydrophobic coating, particle deposition, wettability switching

<p>Space weathering refers to the gradual spectral, microstructural, and chemical alteration of airless planetary regoliths due to their exposure to the harsh environment of outer space. Solar wind irradiation and micrometeoroid impacts are the primary space weathering processes at work in our solar system. Although the microstructural and compositional effects of space weathering are small, occurring at the sub-micron scale in individual regolith grains, their collective impact on the spectral signature of planetary surfaces is critical. Space weathering is known to change the slope, albedo, and strength of absorption band features of reflectance spectra acquired by ground- and spacecraft-based instrumentation. In this way, space weathering impedes our ability to determine planetary surface compositions from remote sensing data and pair meteorites with their parent bodies. Thanks to decades of research since the Apollo sample return missions, the planetary science community has developed a comprehensive understanding of how space weathering alters the Moon and silicate-rich asteroids. However, the effects of space weathering on primitive, carbon-rich asteroids—which dominate the outer main belt—are more poorly constrained and very complex. This dissertation aims to improve our understanding of how solar wind irradiation and micrometeoroid bombardment modifies the spectral, microstructural, and chemical properties of carbonaceous asteroidal regoliths. To accomplish this goal, this research experimentally simulates constituent space weathering processes in the laboratory on carbon-rich analog materials. A multi-faceted analytical approach including a variety of electron microscopy and spectroscopic techniques is used to probe the spectral, microstructural, and chemical changes induced by experimental space weathering.</p><p>Chapter 1 of this dissertation provides an introduction to space weathering, including a description of the current state of knowledge in the field as well as the motivation for this research. Similarly, chapter 2 provides an overview of the various experimental simulations and coordinated analytical techniques employed in this work. Chapter 3 initiates the discussion of research accomplished during this doctoral program, presenting a detailed characterization of the spectral, microstructural, and chemical effects derived from simulated solar wind irradiation of a carbonaceous asteroid analog material. More specifically, in chapter 1, I perform high flux (~1013 ions/cm2/s), high fluence (1018 ions/cm2) 1 keV H+ and 4 keV He+ irradiation experiments on the Murchison meteorite. Chapter 2 investigates the role of incident ion flux in solar wind space weathering of carbonaceous asteroidal regolith by performing a set of low flux (~1011 ions/cm2/s) and high flux (~1013 ions/cm2/s) H+ and He+ irradiation experiments on Murchison samples. These experiments are the lowest flux solar wind simulations carried out, to date. Finally, chapter 5 presents results from the first <i>combined</i> ion irradiation and heating experiments performed on a carbon-rich analog using in situ transmission electron microscopy (TEM). In situ TEM is a relatively novel technique in the planetary and geological sciences which allows users to observe the physiochemical changes caused by an external stimuli in <i>real time</i>. The experimental approach used in chapter 5 simulates both solar wind irradiation and micrometeoroid impacts, and, thus, probes the cumulative microstructural and compositional modifications induced by these concurrent space weathering processes. In chapters 3 through 5, I compare my results to previous space weathering simulations and observations of lunar and asteroidal returned samples. Findings from this dissertation advance the existing model of space weathering on carbon-rich asteroids, help inform remote sensing observations from the Hayabusa2 and OSIRIS-REx missions which have rendezvoused with C-complex asteroids Bennu and Ryugu, respectively, and provide experimental ground-truth for analyzing returned samples from these missions.</p>

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