Dissertations / Theses on the topic 'Weathering'

Weathering of biotite supplies nutrients such as K+ and weathers into vermiculite/montmorillonite or kaolinite, which have varying influences on soil properties and characteristics. This study was conducted to determine if the weathering mechanisms of biotite are controlled by temperature, or if other factors, such as vegetation or leaching intensity dominantly influence the weathering process. A column study investigation was conducted to assess the influence of different acids, simulated rainfall rates, surface horizons, and temperature on the weathering and cation release of biotite. A field investigation was also conducted on the clay mineral fraction of soils in Grayson County, VA formed above biotite granite. Selected acid leachates did show a greater Al+3, Fe+2, and Si+4 release with organic acids (ascorbic, citric, and fulvic) than that with hydrochloric acid treatment at high leachate rates. Loss of K+ is greater with ascorbic acid than all other acids at high leachate rates. Leachate rate interaction with low temperature was an influencing factor in cation release. Field investigations revealed a greater weathering intensity at high elevations evidenced by; (i) higher clay content, (ii) a dominance of 2:1 minerals, (iii) greater surface area in the upper horizons, (iv) minerals indicative of later stages in the biotite weathering mechanism, and (v) precipitation of halloysite in the C horizon at the high elevation site where temperature is lower and a suspected higher leaching intensity occur.
Master of Science

The aim of this thesis was to further the knowledge on microbial weathering, by looking at the effect of model organisms (AcidithiobacilIus ferrooxidans and Geobacter metallireducens) to natural microbial communities (from basaltic glass). It was found that the medium water-rock ratio (50: I) provided the optimum conditions for A. ferrooxidans growth, whilst the low water-rock ratio (1: I) had a lower release of iron because of pH. The pH affected the release of iron and REEs, with less released the higher the pH. In addition, it was found that, though localised areas of hematite were found on the treated rocks, there were also oxidised layers that did not correspond to specific mineralogy. The lack of specific mineral signatures on the rock surface, but the apparent oxidation of the surface, suggested that the surface had been passivated with Fe3+ binding to the mineral surface. In contrast, G. metallireducens did not affect the production of Fe2+ from basalt glass when compared to controls. However, when low water-rock ratios and hematite were tested, a difference was observed between abiotic and biotic flasks. It was suggested the low water ~rock ratio possibly allowed G. metallireducens to obtain the iron more easily by affecting the pH of the solution which in turn affected the stability of the bound iron. In terms of studying microbial communities on rocks, it was found that community structure in Icelandic basaltic glass changed over time, becoming more diverse, with a switch from r- to K-selected microorganisms over the course of the year, similarly to results obtained in the field. DGGE results showed each flask had a distinctive population - with no correlation between ratios, and replicates different in composition to each other. It is suggested that, though community does change over time (as shown by the clone libraries), the ratios do not have an effect and each flask is developing with its own 'microbial island'. However, the results of the chemistry of the flask solutions indicated that the biological experiments showed differences in pH and elemental release between ratios. Elemental release rates were faster in the biological experiments. 'the natural communities affected mineral dissolution, possibly through -- the release of organic acids, which would also account for the drop in pHs observed in the biological experiments. It was noted that there were differences in dissolution rates between the results reported in this thesis and previous literature. It is suggested that these are caused by the rock surface area as in previous studies the rocks have typically been crushed into powder and fine particles. This crushed powder would have provided fresh rock surface for the microorganisms and also greater surface area for reactions to take place, accounting for generally higher weathering rates in previous literature per unit weight of material.

Plastics glazing materials have properties which allow their widespread use in construction, for example as rootlights. However, they are more susceptible than is glass to degradation by weathering, notably the combined effects of ultraviolet light, heat and moisture. Examples of unacceptable durability have been seen in practice, particularly when high operating temperatures occur in sunlight. Artificial weathering tests are used to assess plastics glazing materials in a reasonably short time, two main types being utilised in this study. The applicability of ultra-fast methods of accelerated degradation has been shown to depend on the extent to which the mechanisms of degradation simulate practical weathering, since different procedures were found to promote different mechanisms in the materials tested. Misleading information was obtained when the full spectrum of solar UV and much of the visible was not adequately reproduced in the accelerated tests. In particular an established grade of PVC-U performed unexpectedly poorly under fluorescent lamps. Procedures based on xenon arc sources were found to be the most generally applicable because they better reproduce the full solar spectrum range and, hence, the typical effects observed in plastics materials in practice. Several analytical techniques were used to characterise the virgin polymers and to assess the weathered materials. Two commercial grades of each polymer type (poly[vinylchloride], polycarbonate and poly[methylmethacrylate]) were studied, and measured changes explained in terms of initial polymer properties. Profiling of chemical (e.g. carbonyl index measured by photo-acoustic fourier transform infrared), physical (e.g. molecular weight, surface gloss/roughness), optical (e.g. colour, light transmission) and mechanical properties (e.g. impact resistance) as a function of exposure period and environmental conditions enabled degradation rates and mechanisms to be established for each material. In conducting these tests particular attention was given to the control and effects of sample temperature during weathering, and to the wavelength range of the light source used. Poly(vinylchloride) was affected much more by weathering at higher temperatures, and by exposure to short wavelength radiation, than was polycarbonate, with acrylic being the most durable overall. Practical applications of this work are through Standards committees primarily. in particular with plastics rootlights (B/542/8 and CEN/TCI28/SC9).

Thesis (M.S.) -- University of Maryland, College Park, 2004.
Thesis research directed by: Dept. of Civil and Environmental Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

This study is the geochemical examination of mineral weathering and its path from hinterland, through sediment deposition and pedogenesis, to its dissolution and eventual uptake into plants or precipitation as carbonate minerals. The three papers examine the rate and character of carbonate and silicate mineral weathering over a wide range of climatic and tectonic regimes, time periods, and lithologies, and focus on very different questions. Examination of the 87Sr/86Sr ratios of architectural ponderosa pine in Chaco Canyon, New Mexico confirms a societally complex style of timber procurement from the 10th to the 12th centuries. In El Malpais National Monument, New Mexico, we measured the 87Sr/86Sr ratios in local bedrock and soils and compared them to the leaf/wood cellulose of four conifers (Pinus ponderosa, Pinus edulis, Juniperus monosperma, Juniperus scopulorum), a deciduous tree (Populus tremuloides), three shrubs (Chrysothamus nauseosus, Fallugia paradoxa, Rhus trilobata), and an annual grass (Bouteloua gracilis) and a lichen (Xanthoparmelia lineola). We found that plant 87Sr/86Sr ratios covaried with variations in plant physiognomy, life history, and rooting depth. In addition, the proportion of atmospheric dust and bedrock mineral contributions to soil water 87Sr/86Sr ratios varied predictably with landscape age and bedrock lithology. On the Himalayan floodplain, soils and paleosol silicate weathering intensities were measured along a climatic transect and through time. Overall, carbonate weathering dominates floodplain weathering. But, periods of more intense silicate weathering between 9 - 2 Ma, identified in soil profile and in the 87Sr/86Sr ratios of pedogenic carbonates, appear to be driven by changes in tectonic, rather than climatic, regime. All three papers are good examples of how 87Sr/86Sr isotopic tracer studies can shed light on pedogenic formation rates and internal processes. The complexity of each system warns against generalizations based on just one locale, one species or lithology, or a few isotopic ratios.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2004.
Includes bibliographical references (leaves 48-49).
Trojan asteroids orbit the Sun at Jupiter's L4 and L5 stability points. They are included in the D-class group of asteroids because of their characteristically steep spectral slope. In accordance with spectra of other asteroid classes, we expected that the larger the diameter is of a D-class asteroid, the redder (visually) the asteroid should be in the visible spectrum. Approximately ninety Trojan asteroids have been examined, fourteen of which come from our own observations, and five of which are small and come from the SMASS I data set. The results did not confirm our original hypothesis. Instead, space weathering appears to affect Trojans in a different way than it does other asteroid classes due to their different composition.
by April A. Russell.
S.M.

L'altération chimique des roches primaires et des minéraux dans les systèmes naturels a un impact majeur sur la formation des sols et leur composition. L'altération chimique est largement pilotée par la dissolution des minéraux. Les éléments chimiques libérés dans les eaux souterraines par la dissolution des minéraux réagissent facilement pour former des minéraux secondaires comme les argiles, zéolites et carbonates. Les carbonates se forment par réaction des cations divalents (Ca, Fe et Mg) avec CO2 dissous tandis que la formation des kaolins et de la gibbsite est attribuée à l'altération des minéraux riches en aluminium, le plus souvent les feldspaths. Le projet Carbfix à Hellisheiði (sud-ouest de l'Islande) a pour but d'utiliser les processus d'altération naturelle pour former des minéraux carbonatés par réinjection dans les roches basaltiques environnantes de CO2 provenant d'une centrale géothermique. Ce processus trouve son origine dans la dissolution des roches basaltiques riches en cations divalents (Ca, Fe et Mg) qui se combinent au CO2 injecté pour former des minéraux carbonatés. Cette thèse est centrée sur la dissolution du basalte cristallin de Stapafell qui est composé essentiellement de trois phases minérales (plagioclase, pyroxène et olivine) et qui est riche en cations divalents. La vitesse de libération des éléments du basalte à l'état stationnaire et loin de l'équilibre a été mesurée dans des réacteurs à circulation à des pH de 2 à 12 et des températures de 5 à 75°C. Les vitesses de libération de Si et Ca à l'état stationnaire présentent une variation en fonction du pH en forme de U avec une diminution des vitesses lorsque le pH augmente en conditions acides et une augmentation avec le pH en conditions alcalines. Les vitesses de libération du silicium par le basalte cristallin sont comparables à celles par le verre basaltique de même composition chimique aux faibles pH et aux températures = 25°C mais elles sont plus lentes aux pH alcalins et aux températures = 50°C. Par contre, les vitesses de libération de Mg et Fe diminuent de manière monotone avec l'accroissement du pH à toutes les températures. Ce comportement a pour cause les variations contrastées, en fonction du pH, des vitesses de dissolution des trois minéraux constitutifs du basalte: plagioclase, olivine et pyroxène. Les vitesses de libération des éléments déduites de la somme des vitesses de dissolution du plagioclase, pyroxène et olivine normalisées à la fraction volumique de ces minéraux sont, à un ordre de grandeur près, les mêmes que celles mesurées dans cette étude. En outre, les résultats expérimentaux montrent que, durant l'injection d'eaux chargées en CO2 de pH proche de 3. 6, le basalte cristallin libère préférentiellement Mg et Fe en solution par rapport à Ca. L'injection de fluides acides chargés en CO2 dans des roches cristallines basaltiques peut donc favoriser la formation de carbonates de Mg et Fe aux dépends de la calcite aux conditions de pH acides à neutres. Le plagioclase, qui est la phase la plus abondante du basalte, influence fortement la réactivité de ce dernier. La vitesse de dissolution du plagioclase, basée sur la libération de la silice, présente une variation en forme de U en fonction du pH, diminuant lorsque le pH augmente aux conditions acides mais augmentant avec le pH aux conditions alcalines. En accord avec les données de la littérature, la vitesse de dissolution du plagioclase à pH constant, en conditions acides, augmente avec sa teneur en anorthite. L'interprétation et le fit des données obtenues suggèrent que la vitesse de dissolution du plagioclase est contrôlée par la décomposition d'un complexe activé riche en silice, formé par le départ de Al de la structure du minéral. Le plus remarquable, par comparaison aux hypothèses antérieures, est que la vitesse de dissolution du plagioclase en conditions alcalines est indépendante de sa teneur en anorthite - e. G. Les vitesses de dissolution des plagioclases riches en anorthite augmentent avec le pH aux conditions alcalines. A ces conditions, il est probable que la vitesse de dissolution rapide du plagioclase domine, en raison de sa forte teneur en Ca, la libération vers la phase fluide des cations divalents du basalte cristallin. La gibbsite est généralement le premier minéral qui précipite lors de la dissolution du plagioclase. C'est un hydroxyde d'aluminium que l'on trouve dans divers sols et qui est aussi la phase principale des minerais de bauxite. Les vitesses de précipitation de la gibbsite ont été mesurées dans des réacteurs fermés, en conditions alcalines à 25 et 80°C, en fonction de l'état de saturation du fluide. Les analyses des solides après réaction ont démontré que la précipitation de gibbsite s'est produite dans toutes les expériences. L'interprétation de l'évolution dans le temps de la chimie du fluide réactif fournit des vitesses de précipitation de la gibbsite qui sont près des vitesses de dissolution du plagioclase. En plus, des vitesses de précipitation de la gibbsite diminuent plus rapidement que des vitesses de dissolution du plagioclase quand le pH descende. Ceci suggère que l'étape limitant de l'altération du plagioclase sur la surface de la terre est plutôt la consommation d'Al par formation de la gibbsite que la dissolution même du plagioclase. La kaolinite est en général le second minéral formé après la gibbsite lors de la dissolution du plagioclase à basse température. Les vitesses de précipitation de la kaolinite ont été mesurées dans des réacteurs à circulation à pH = 4 et t = 25°C, en fonction de l'état de saturation du fluide. Au total, 8 expériences de précipitation de longues durées ont été réalisées dans des fluides légèrement supersaturés par rapport à la kaolinite, en utilisant comme germes pour la précipitation une quantité connue de de kaolinite de Géorgie (KGa-1b) contenant peu de défauts et préalablement nettoyée. Les vitesses de précipitation de kaolinite mesurées sont relativement lentes comparées aux vitesses de dissolution du plagioclase. Cette observation suggère que la formation de kaolinite lors de l'altération est limitée par sa vitesse de précipitation plutôt que par que la disponibilité en Al et Si issus de la dissolution du plagioclase. L'ensemble des résultats de cette étude fournit un certain nombre de principes scientifiques de base nécessaires à la prédiction des vitesses et des conséquences de la dissolution du basalte cristallin et du plagioclase à la surface de la Terre et lors de l'injection du CO2 à proximité de la surface dans le cadre des efforts de stockage du carbone. Les résultats obtenus indiquent, bien que les vitesses de précipitation de la gibbsite soient relativement rapides, que la vitesse de précipitation relativement lente de la kaolinite peut être le processus contrôlant la formation de ce minéral à la surface de la Terre. Cette observation souligne la nécessité de poursuivre la quantification de la précipitation de ce minéral secondaire aux conditions typiques de la surface de la Terre. En outre, comme les proportions des différents métaux divalents libérés par les basaltes cristallins varient sensiblement avec le pH, la carbonatation des basaltes doit produire un changement systématique de l'identité des minéraux carbonatés et des zéolites précipités en fonction de la distance au puits d'injection. Cette dernière conclusion pourra être directement testée dans le cadre du projet CarbFix actuellement conduit à Hellisheiði en Islande
The chemical weathering of primary rocks and minerals in natural systems has a major impact on soil development and its composition. Chemical weathering is driven to a large extent by mineral dissolution. Through mineral dissolution, elements are released into groundwater and can readily react to precipitate secondary minerals such as clays, zeolites, and carbonates. Carbonates form from divalent cations (e. G. Ca, Fe and Mg) and CO2, and kaolin clay and gibbsite formation is attributed to the weathering of aluminium- rich minerals, most notably the feldspars. The CarbFix Project in Hellisheiði SW-Iceland aims to use natural weathering processes to form carbonate minerals by the re-injection of CO2 from a geothermal power plant back into surrounding basaltic rocks. This process is driven by the dissolution of basaltic rocks, rich in divalent cations, which can combine with injected CO2 to form and precipitate carbonates. This thesis focuses on the dissolution behaviour of Stapafell crystalline basalt, which consists of three major phases (plagioclase, pyroxene, and olivine) and is rich in divalent cations. Steady-state element release rates from crystalline basalt at far-from-equilibrium conditions were measured at pH from 2 to 11 and temperatures from 5° to 75° C in mixed-flow reactors. Steady-state Si and Ca release rates exhibit a U-shaped variation with pH, where rates decrease with increasing pH at acid condition but increase with increasing pH at alkaline conditions. Silicon release rates from crystalline basalt are comparable to Si release rates from basaltic glass of the same chemical composition at low pH and temperatures =25°C but slower at alkaline pH and temperatures =50°C. In contrast, Mg and Fe release rates decrease continuously with increasing pH at all temperatures. This behaviour is interpreted to stem from the contrasting dissolution behaviours of the three major minerals comprising the basalt: plagioclase, pyroxene, and olivine. Element release rates estimated from the sum of the volume fraction normalized dissolution rates of plagioclase, pyroxene, and olivine are within one order of magnitude of those measured in this study. In addition, these experimental results show that during injection of CO2-charged waters with pH close to 3. 6, crystalline basalt preferentially releases Mg and Fe relative to Ca to the fluid phase. The injection of acidic CO2-charged fluids into crystalline basaltic rocks may therefore favour the formation of Mg and Fe carbonates rather than calcite at acidic to neutral conditions. Plagioclase is the most abundant phase in crystalline basalts and thus influences strongly its reactivity. Plagioclase dissolution rates based on Si release show a common U-shaped behaviour as a function of pH where rates decrease with increasing pH at acid condition but increase with increasing pH at alkaline conditions. Constant pH plagioclase dissolution rates increase with increasing anorthite content at acid conditions, in agreement with literature findings. Interpretation and data fitting suggests that plagioclase dissolution rates are consistent with their control by the detachment of Si-rich activated complexes formed by the removal of Al from the mineral framework. Most notably, compared with previous assumptions, plagioclase dissolution rates are independent of plagioclase composition at alkaline conditions, e. G. Anorthite-rich plagioclase dissolution rates increase with increasing pH at alkaline conditions. At such conditions rapid plagioclase dissolution rates likely dominate divalent metal release from crystalline basalts to the fluids phase due to its high Ca content. Gibbsite is commonly the first mineral formed during low temperature dissolution of plagioclase. Gibbsite is an aluminium-hydroxide that is found in various soils as well as the dominant phase in many bauxite ores. Gibbsite precipitation rates were measured in closed system reactors at alkaline condition, both at 25 °C and 80 °C as a function of fluid saturation state. Analyses of the solids demonstrate that gibbsite precipitation occurred in all experiments. The comparison of gibbsite precipitation to the dissolution rates of plagioclase at pH 11 shows that the rates are close to equal. The precipitation rates of gibbsite, however, decrease faster with decreasing pH than plagioclase dissolution rates. As such it seem likely that plagioclase dissolution is faster than gibbsite precipitation at near to neutral pH, and the relatively slow rate of gibbsite precipitation influences plagioclase weathering in many Earth surface systems. Kaolinite is commonly the second secondary mineral formed during low temperature dissolution of plagioclase. Kaolinite precipitation rates were measured in mixed flow reactors as a function of fluid saturation state at pH=4 and 25 °C. In total eight long-term precipitation experiments were performed in fluids mildly supersaturated with respect to kaolinite, together with a known quantity of cleaned low defect Georgia Kaolinite as seeds. Measured kaolinite precipitation rates are relatively slow compared with plagioclase dissolution rates. This observation suggests that kaolinite formation during weathering is limited by its precipitation rates rather than by the availability of aqueous species sourced from plagioclase dissolution. Taken together the results of this study provide some of the fundamental scientific basic for predicting the rates and consequences of crystalline basalt and plagioclase dissolution at both the Earth's surface and during the near surface injection of CO2 as part of carbon storage efforts. Results indicate that although gibbsite precipitation rates are relatively rapid, the relatively slow precipitation rates of kaolinite may be the process controlling the formation of this mineral at the Earth's surface. This observation highlights the need to further quantify this secondary mineral precipitation rates at conditions typical at the Earth's surface. Moreover, as the composition of divalent metals released from crystalline basalts varies significantly with pH, CO2 carbonation in basalt should yield a systematic variation in the identity of carbonate and zeolite minerals precipitated with distance from the injection site. This latter conclusion can be tested directly as part of the currently on-going CarbFix project in Hellisheiði, Iceland

Diamonds are commonly present in an ore called kimberlite. Kimberlites vary extensively in mineralogy and therefore can complicate the processing and the extraction of diamonds. Weathering of kimberlite was investigated in this study and refers to the rapid physical breakdown of the kimberlite material. Kimberlite weathering by organic molecule adsorption was investigated utilising organic solutions; ethanol, formamide, n-hexane, oxalic acid, urea, pentanoic acid and acetic acid, was investigated. The extent of weathering was measured by XRD, TGA and FTIR analysis as well as by evaluating changes in the particle size distribution. The idea to predict the susceptibility of weathering of kimberlite based on TGA analysis was discredited as it was found that there was no correlation between the smectite content and the % weight loss from TGA analysis. In XRD analysis studies to relate the d-spacing to the extent of weathering, it was found that the technique was not sensitive enough to enable direct prediction of weathering behaviour. Organic solutions at 0.5 M generally did not significantly alter the d-spacing. In the case of utilising pure organic solutions, it was observed that switching from diluted to pure organic solutions did not increase the d-spacings but rather lowers the space. Cation pretreatment prior to organic weathering resulted in d-spacings up to 2 water layers (12.6 Å being equal to 1 water layer, 15.6 Å equal to 2 layers and 18.6 Å equal to 3 layer). The general trend was that the divalent cations Mg2+ and Ca2+ increased the d-spacings whereas monovalent cations Na+ and K+ decreased the spacing. In the case of pre-organic treatment prior to organic weathering, it was observed that the resulting d-spacing increased to 2 and 3 water layers. TGA analysis confirmed that the kimberlite structure did absorb organic reagents during weathering. It was observed that the amount of organic reagents adsorbed decrease in the following order: oxalic acid > urea > pentanoic acid > formamide > ethanol > n-hexane > acetic acid, with oxalic acid having been adsorbed the greatest. In addition, it was also shown that the extent of inorganic cation adsorption was more than that of organic solutions. The analysis also showed that organic pretreatments yielded promising results and the order followed was dimethyldioctadecylammonium chloride > cetylpyridium chloride > dodecylamine > pyridine in encouraging subsequent organic adsorption. FTIR analysis results indicated the mechanism by which organic molucules attached onto the mineral surface. It was observed that there was a disturbance of the bond between water in the interlayer and the silicate structure by a stronger H-bond gained through organic molecule attachment. Oxalic acid was observed to cause a structural change due to proton attack of the silicate structure. It was found that kimberlite weathering, in essence, occurred in the first 24 hours of contact with the solution. Oxalic acid was found to be the most effective weathering agent compared to the rest of the tested organic solutions. The effect of the tested solutions, at 0.5 M concentration, on kimberlite weathering followed the series Cu2+ > oxalic acid > ethanol > acetic acid > formamide > n-hexane > distilled water. This study therefore showed that the accelerated weathering of kimberlite utilising organic solutions was not as efficient as the Cu2+ solution. Comparing Cu2+ and oxalic acid treatments, results showed that 67 % of the particles passed 12 mm screen size due to Cu2+ weathering as opposed to 48 % in oxalic acid. In investigating the effects of variables, it was found that time of exposure had a small effect in the weathering of kimberlite. Increasing the organic concentration from 0.025 M to 0.5 M saw an increase in the amount of particles passing the 12 mm screen size by~20 %. There was however no improved weathering when the solution temperature was increased from approximately 25 °C to 40 °C. In the study of kinetics involved during organic weathering utilising oxalic acid and comparing with Cu2+ medium, a high mineral dissolution was observed in the first 24 hours of contact with the weathering solution. However, different weathering mechanisms were observed between Cu2+ and oxalic acid. Inorganic solutions foster weathering by interlayer cation exchange which results in the reduction of the surface energy and this encourages further crack propagation. Oxalic acid weathering mechanism was by proton attack of the structural cations which was then limited thereafter by oxalate salts precipitation. Al3+ and Mg2+ were the dominant cations in solution during weathering (reaching 40 mmol/L) at higher oxalic acid concentration. This indicated that the dissolution of the clay‟s octahedral structure occurred, making oxalic acid a more effective agent than the rest of the tested organic solutions. An alternative method to transform non-swelling clay minerals to swelling in kimberlites was highlighted. It was observed that cation exchange treatment in conjunction with acid and oxidation treatments on kimberlites containing non-swelling minerals: mica or forsterite that are at least 30 % in quantity may result in the presence of swelling clays after these treatments. Kimberlite that contained serpentine minerals was more resistant to alteration under these conditions.
Dissertation (MEng)--University of Pretoria, 2013.
gm2014
Materials Science and Metallurgical Engineering
UPonly

Weathering introduces a language of durability and change throughout time. Architecture and its materials are constituents of place, as is the way they weather and age. The intent of this research is to analyze regional weathering characteristics specific to the American Southwest as a reflection of a sense of belonging that evolves over time.

It can be difficult to quickly and easily create realistic sandstone terrain. Film makers often need to generate realistic terrain for establishing the setting of their film. Many methods have been created which address terrain generation. One such method is using heightmaps which encode height as a gray-value in a 2d image. Most terrain generation techniques don't admit concavities such as overhangs and arches. We present an algorithm that operates on a voxel grid for creating 3d terrain. Our algorithm uses curvature estimation to weather away the terrain. We speed up our method using a caching mechanism that stores the curvature estimate. We generate piles of colluvium, the broken away pieces of weathered rock, with a simple deposition algorithm to improve the realism of the terrain. We explore the possibility of generating our sandstone terrain on the GPU using OpenCL. With our algorithm, an artist is able to quickly and easily create 3d terrain with concavities and colluvium.

The products of pyrite oxidation, including solution phase Fe2+, Fe3+, S2O32-, S4O62-, SO32- and SO42- and solid phase Fe(OH)3, were measured under controlled conditions in order to investigate the behavior of pyrite in calcareous and alkaline soils. The distribution of sulfur oxidation products is pH dependent and can be interpreted in terms of metastable equilibrium among thiosulfate, disulfane disulfonate and sulfite. Thisulfate and sulfite predominate in the pH range greater than about pH 7 or 8. Sulfane disulfonates are more predominant at more acid pH. Solution concentration data were consistent with the presence of Fe(OH)3. Concentrations of thiosulfate and sulfane disulfonate were consistent with a redox equilibrium among solution iron and sulfure species at pH 6 to 9. Linear or zero-order kinetics were found to be sufficient for description of pyrite oxidation in this study. Linear kinetics were observed as electrical conductivity, solution sulfur products and solution plus solid phase iron products. The measurement of solution iron plus solid-phase iron oxide is a more rigorous approach to the extent of reaction than the measurement of sulfate. The rate of pyrite oxidation is pH dependent, increasing from 10-20 pmol(Fe) m-2 s-1 to 40-60 pmol(Fe) m-2 s-1 between pH 5 and 9. This is consistent with an oxidation mechanism involving the reoxidation of solution Fe2+ via a reaction between an iron hydroxide complex and hydrated oxygen as the rate-determining step. The effect o background electrolytes on oxidation rates at low pH also supports this interpretation. Pyrite oxidation rates in the presence of calcium carbonate, sodium bicarbonate, sodium thiosulfate and calcium-saturated bentonite can be related to the pH effect. Sodium thiosulfate and DTPA appeared to have specific inhibitory effects. Column studies show that the disposal of pyritic mine spoils or tailings by mixing with calcareous material may produce thiosulfate, a good reducing agent for toxic metals. Burial of lime below pyritic materials may protect groundwater quality more effectively than application of lime to the surface.

Untreated wooden cladding has a long tradition and has in recent years become a both economically and environmentally beneficial solution in miscellaneous modern building applications. Untreated wood in cladding and similar applications represents a building part that changes its appearance rather dramatically without compromising its technical functionality. The aesthetic service life is often the decisive criterion for these applications. This thesis comprises a study on the weathering of untreated, i.e. unpainted wood. Following the service life prediction methodology suggested in the ISO 15686 standard, wood was weathered both outdoors and in two laboratory weathering apparatuses. Climate data for the test site were assessed including temperature, wind-driven rain and solar radiation. The performance of non-structural wood components in exterior above-ground applications is often closely related to the aesthetics of the wooden component in question. Hence, a method for color determination of large samples was developed, and the topic of human color perception is discussed briefly. It was found that the colonization by mold growth fungi contributes significantly to its surface appearance. Differences between materials and exposure directions were investigated. The topic of limit-state for aesthetic service life is discussed and a possible assessment method for such applications is presented. No simple dose-response relationship between solar radiation and wind-driven rain, and color response of the material could be established. Acceleration factors for the conducted laboratory weathering tests are discussed. Furthermore, color changes by outdoor versus laboratory weathering were evaluated. It was found that the conducted laboratory weathering cycles could not recreate the visual appearance of an outdoor weathered surface. In summary, the suggested bottom-up approach of the service life prediction methodology is not easily adaptive for wood in this application

A severe shortage of many, to mankind, valuable elements are to be expected in the near future. Therefor is it of utmost importance to find these deposits and a way to refine the elements with as little negative effect on the environment as possible. One deposit of valuable elements such as U, V, Mo and Sr are the so called alum shale. Alum shale is a variety of sulfidic black shale which is rich in pyrite, FeS2, and organic carbon. Primary due to its contents of hydrocarbons and uranium the alum shale has been mined at different sites throughout Sweden. One of these sites was Kvarntorp in the region of Närke. The shale which had have its contents of hydrocarbons extracted through dry distillation was dumped into a heap that is now known as Kvarntorpshögen. The remaining hydrocarbons that this processed material still contain are to this day (2011) warm, with temperatures up to some hundred degrees Celsius. Due to this heat, infiltration of rainwater is held at a minimum. What no one knows however; is for how long Kvarntorpshögen will remain warm. Once it cools; many toxic elements will leak into the surrounding environment due to natural weathering caused by precipitation and frost wedging. The study also included a heating treatment of 70°C which is a temperature that the material of Kvarntorpshögen may be capable of generating by itself. This is assumed to be a good temperature for weathering processes; because it increases the kinetics of chemical reactions but also allows the presence of water. The results of this study shows that summer will be the season that contributes the most to the leaching of elements, of which some are toxic. Newly exposed surfaces of various shale materials often contain elements that is easily leached by water. Once this coat is washed away however, further leaching of that element decreases. Exceptions from this pattern in some shale products were shown by for example vanadium and molybdenum. The digestion data show that the completely processed shale, which makes up the majority of Kvarntorpshögen, still have a high content of rare and valuable elements. Making Kvarntorpshögen itself interesting for extraction processes in the future.

A fully automatic de-weathering system to increase the visibility/stability in surveillance applications during bad weather has been developed. Rain, snow and haze during daylight are handled in real-time performance with acceleration from CUDA implemented algorithms. Video from fixed cameras is processed on a PC with no need of special hardware except an NVidia GPU. The system does not use any background model and does not require any precalibration. Increase in contrast is obtained in all haze/rain/snow-cases while the system lags the maximum of one frame during rain or snow removal. De-hazing can be obtained for any distance to simplify tracking or other operating algorithms on a surveillance system.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1990.
Includes bibliographical references (leaves 68-76).
by Duncan Southam Fisher.
M.S.

The purpose of this research was to investigate the physical weathering of rock along the Victoria Land Coast, Antarctica. It was designed to contribute to the Latitudinal Gradient Project, a joint initiative between the New Zealand, Italian and United States Antarctic Programmes. The Latitudinal Gradient Project aims to improve our understanding of the ecosystems of the Dry Valleys and ice-free areas of the Ross Sea Region and, by using latitude as a proxy measure, identify how they might be affected by future climate change. The approach taken for this research was to use information on rock (from one rock group) temperature and moisture conditions gathered from three field locations to inform laboratory simulations. The laboratory simulations would then be used to investigate the weathering of small rock blocks and aggregates. Two temperature cycles approximating those experienced during summer and spring/autumn were identified and simulations undertaken in a specially adapted freezer. Three levels of moisture were applied: no moisture, half saturation and full saturation. Results of the laboratory simulations indicated that although rocks responded in different ways to different processes, granular disintegration took place even in the absence of additional moisture and did not require crossings of the 0 OC isotherm, nor were high levels of moisture required for across zero temperature cycling to produce weathering effects. A model that related weathering to latitude was developed and changes in climate explored. It was found that the weathering effect of summer and spring/autumn cycles was different and depended on rock characteristics rather than latitude. Increasing the ratio of summer to spring/autumn temperature cycles by 10% indicated that weathering could decrease or remain the same depending on the particular rock. Changes in temperature were found to be more important than changes in moisture. A weathering index that related local climate and rock properties to weathering was also developed and this highlighted the difficulties of using laboratory results to predict field rates of weathering. There were some surprising results from the field, including the presence of much more moisture on the surface of the rock, primarily from blowing snow, than had been predicted for this dry environment. This occurred even in the presence of negative rock surface temperatures. In addition, winter rock surface temperatures can fluctuate up to 25 OC, getting as warm as -10 OC. Macro-climate and changes in air temperature in response to foehn and katabatic winds were the drivers for these fluctuations.

Chlorite is a ferrous silicate mineral occurring as afracture filling mineral in the Swedish granite bedrock thatsurrounds the area of the candidate Swedish geologicalrepositories for nuclear waste.

To investigate the importance of chlorites as a naturalbarrier for radionuclide migration sorption of Ni(II) onto anatural chlorite was chosen as the studied system. The sorptionbehaviour was studied using batch technique under differentexperimental conditions by varying the concentration ofbackground electrolyte, pH and initial nickel concentration.Our experiments showed that sorption is dependent of pH; belowpH 4 no sorption occurs and in the pH range 7-11 the sorptionmaxima was found. The sorption shows no dependence of ionicstrength in our experiments and together with pH dependency weconclude that the sorption of nickel to chlorite is mostlyoccurring through surface complexation. The distributioncoefficient, Kd, was determined for our results and in the range formaximal sorption the Kdis approximately 10³cm³/g.

Our experimental data were described using a diffuse doublelayer model, including strong and weak surface sites, in thesoftware PHREECQ and the results obtained from PHREEQC werealso used for a fit of the data in the software FITEQL. Thesurface complexes that dominate the sorption of nickel tochlorite from our model are Chl_ONi⁺(weak) and for pH above 9 Chl_ONi(OH)^-(weak). Flow-through technique was used in ourinvestigations regarding the dissolution rate of a naturalchlorite and the experimental results show that the dissolutionrate of chlorite is strongly pH dependent and at pH 2 thehighest dissolution rate (R_Si) could be determined to 7• 10^-11mol/(m²s) based on silica data.

Keywords:chlorite, nickel, sorption, surfacecomplexation, dissolution rate.

Basalt and granodiorite (medium to fine sand particle size) were leached by three low molecular weight aliphatic organic acids, namely citric, oxalic and acetic acid of . 1M concentration. To evaluate the effectiveness of the organic acids in dissolving the rock samples, two control solutions, .005M HCl and distilled water were added to the number of dissolution treatments. Dissolution of ions from granodiorite, by the leaching treatment shown in parenthesis, decreased in the following order: Fe(OX) > Al(OX) ~ Si(OX) > Ca(CIT) ~ Mg(OX) ~ K(OX) > Na(OX) Dissolution of ions from basalt decreased in the following order: Fe(CIT) > Si(CIT) > Mg(CIT) > Ca(CIT) > Al(OX, ACETIC) > Na(OX) > K(HCl) Oxalic acid effectively outcompeted citric acid in the weathering of granodiorite in spite of having lower stability constants for certain elements. This was attributed to differences in pH of the solutions (affecting both concentration of H⁺ ions and anionic species), ionic competition in solution for ligand sites and geometry and oxidation state of ions in the parent mineral. There was no conclusive evidence to indicate that chelation of K⁺ or Na+ took place in any of the experiments. However, mass balance calculations revealed that oxalic acid extracted approximately 40-50% of the K from granodiorite; citric acid extracted approximately 12%. These levels were significantly higher than those extracted by non-sequestering agents. XRD analysis of granodioritic-oxalate precipitate suggested the possible formation of a K-oxalate salt. The chelating acids, citric and oxalic, greatly outcompeted acetic acid and HCl of similar pH for multivalent cations in both basalt and granodiorite. Concentrations of Fe, Al, and Si, in solution were many fold higher than calculated concentrations of those ions in equilibrium with the amorphous oxide in water. Oxalic acid and citric dissolution curves, determined from 11 weeks of leaching, showed initially increasing rates followed by declining rates which approached steady state towards the eleventh week of the experiment. Declining rates followed by steady-state rates were attributed to the presence of hyperfines the build-up of secondary precipitates, the increase of ions in solutions, and to an eroding leached surface layer. Non-chelating acids namely acetic acid, HCl and H₂O revealed dissolution curves that were approximately constant (steady-state) throughout the 11 week weathering period. XRD, XRF, SEM, and EDX analyses of weathered basalt and granodiorite as well as AA spectrophotometric solution analyses provided evidence which indicated incongruent dissolution of granodiorite and basalt by all 5 leaching treatments. SEM and XRF analyses indicated that citric acid was less effective than oxalic acid in forming precipitates from granodiorite. EDX revealed that the amorphous precipitate which did form in citric acid consisted primarily of Fe. EDX analyses of inorganic coatings indicated predominantly Si and Fe in 1:1 ratio. Although citric acid was able to extract greater amounts of Fe from basalt than granodiorite, extractable Fe, Al and Si analysis and SEM detected no organo-amorphous precipitates. Also EDX of inorganic surfaces showed no accumulation of Fe or Al. It was concluded that the Fe extracted from the basalt remained in complexed or soluble form due to the higher pH (3-5) of the basaltic solution. An amorphous precipitate formed from the leaching of granodiorite with oxalic acid. EDX analysis gave evidence that the precipitate consisted primarily of Si and Fe in a 1:1 ratio. An amorphous precipitate formed also from the leaching of basalt with oxalic acid. EDX analysis gave evidence that the precipitate consisted primarily of Mg and Fe in a 1:1 ratio. Data from molar oxide ratios and mass balance calculations as well as XRD, XRF, extractable Fe, Al and Si analyses were relied upon to determine the possible organic and inorganic components of these precipitates.
Land and Food Systems, Faculty of
Graduate

Interactions between dilute meltwater and fine-grained, freshly comminuted debris at the bed of temperate glaciers liberate significant solute. The proportions of solute produced in the subglacial environment via biotic and abiotic processes remains unknown, however, this work suggests the biotic contribution is substantial. Laboratory analyses of microbiological and geochemical properties of sediment and meltwater from the Haut Glacier d\'Arolla (HGA) indicates that a metabolically active microbial community exists in water-saturated sediments at the ice-bedrock interface. Basal sediment slurries and meltwater were incubated in the laboratory for 100 days under near in situ subglacial conditions. Relative proportions of solute produced via abiotic v. biotic mineral weathering were analyzed by comparing the evolved aqueous chemistry of biologically active (live) sediment slurries with sterilized controls. Aqueous chemical analyses indicate an increase in solute produced from mineral weathering coupled with nitrate depletion in the biologically active slurries compared with the killed controls. These results infer that microbial activity at HGA is likely an important contributor to chemical weathering associated solute fluxes from the glaciated catchment. Due to the magnitude of past glaciations throughout geologic time (e.g., Neoproterozoic and Late-Pleistocene), and evidence that subglacial microbial activity impacts mineral weathering, greater consideration needs to be given to cold temperature biogeochemical weathering and its impact on global geochemical cycles.

Steel which has no protective coating on it will struggle to survive in the environment as all that is required to initiate corrosion is water and oxygen. Coatings were therefore developed to prevent this and in doing so elongate the life of the product. British Steel use a range of products to protect their structural steel, HPS200 plastisol being the flagship coating, produced in the UK and sold around the world. Plastisol has more resistance to environmental degradation than steel but it still degrades when exposed to aggressive environments, keeping guarantees to within 30 years, the specific length depending on several predetermined factors. The degradation products are thought to be minimal and the integrity of panels already under long term test support this theory. This project was carried out with the intention of determining what concentrations of the products, if any, leach out of the plastisol systems. Model systems were placed at natural weathering sites and in accelerated weathering chambers to promote degradation of the coatings. Several standard and novel techniques have been used to monitor the physical and chemical characteristics of the coatings and hence aid the determination of the contents of the leachates. Gas analysis has been performed although not in any great depth. Results show that the coatings loose very small amounts of plasticiser and undergo cross linking. Both of these occurrences are expected to a certain extent and, within the realms of this work are not in sufficient quantities to cause concern. The leachates show metals, anions and organics present in quantities similar to those detected in the control samples. Gaseous analysis did not highlight any levels of chemical which should cause concern. The plastisols tested under these specific circumstances do not pose a threat to the environment.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2002.
Cataloged from PDF version of thesis. "The pagination in this thesis reflects how it was delivered to the Institute Archives and Special Collections. Thesis was submitted to the Institute Archives without all the required signatures"--Disclaimer Notice page.
Includes bibliographical references (page 40).
Trojan asteroids orbit at Jupiter's L4 and L5 points. They are included in the D-class of asteroids because of their steep spectral slope. According to spectra of other asteroid classes, the larger the diameter is of a D-class asteroid, the redder the asteroid should be in the visible spectrum. We examined a total of fifteen asteroids, five (from the SMASS 1 data set) were small, and ten (newly collected data) were large. The actual results did not match our expected results, most likely due to the large error bars and the small data set. Space weathering may affect Trojans in the same way as it does other asteroid classes. To know with certainty, further investigation is needed.
by April A. Deet.
S.B.

Although karst processes in south central Kentucky have been studied extensively, the Haney Limestone Member of the Golconda Formation has not been studied in detail in contrast to limestones stratigraphically below it that are thicker. In addition, the relationship between petrographic features of the Haney Limestone and the formation of caves and karst features has not been studied extensively compared to lithographic, petrographic, or structural variables Petrographic data were collected using core and surface exposures across the study area of south central Kentucky from northern Logan and Warren counties up toward the Rough Creek Graben region, and stratigraphic columns were constructed. Twenty-three petrographic thin-sections were made from samples collected at these sites, described, and photo documented. These studies have revealed that grain size and silica content play a role in how the Haney weathers both in surface exposure and in a cave setting. Petrographic thin-section analysis suggests that the Haney possesses a complex diagenetic history that involves several generations of calcite cementation, dolomitization, silicification, and pressure-dissolution features in the form of microstylolites and stylolites. A basal shale in the Big Clifty occurs commonly at the Big Clifty/Haney contact and acts as a confining hydrogeologic unit, which is favorable for the development of springs and caves. Studying the Haney Limestone petrographically provides an opportunity not only to study a lesser known unit, but also in the context of relating petrographic influences or controls on the morphology of Haney cave-passage development under both vadose and phreatic hydrologic regimens. Heretofore, the vast majority of cave morphological studies have only linked the hydrologic regimen to formation of cave passages, but such studies have not considered petrographic variance. This study not only relates karst features to petrographic variance, but also provides a petrographical description of the Haney across south central Kentucky, whereas many previous studies focused on Illinois and Indiana. Understanding Haney petrographic characteristics also provides context for potential carbonate hydrocarbon reservoirs and groundwater resources in the Illinois Basin region.

Thesis advisor: Rudolph Hon
Pleistocene-age terra rossa paleosols are situated on and are intercalated with eolianite and marine carbonate units across the Bermuda Islands. These clay-rich soils were originally thought to the derived from weathering of the volcanic seamount and/or from dissolution of the carbonate units, the paleosols are now believed to be primarily the result of atmospheric dust deposition from Saharan North Africa and the Sahel via long range transport, with some local inputs. If so, these soil units are mixtures of atmospheric deposition during one or more glacial- interglacial cycles. Previous investigations have been conducted on the paleosols to determine their provenance, age, and to identify unique characteristics for island wide mapping. We conducted comprehensive geochemical analyses to determine the degree of chemical weathering and diagenesis, and to identify processes responsible for their formation and development. The paleosols were found to be geochemically similar across all ages, and to show an increased degree of alteration with age rather than with their duration of subaerial exposure, indicating diagenesis by infiltrating meteoric waters as well subaerial weathering. Evidence of paleosol diagenesis suggests vadose flow across the island may not be limited to preferential pathways and that while flow through the limestones is complex, infiltrating waters appear to have allowed for additional alteration of the soils. In addition to the paleosols, clay-rich deposits with paleosol-like textures were identified during coring operations in Harrington Sound and Hungry Bay, beneath present-day sea level. The source and development histories of these materials were previously unknown. Since these clay deposits are situated beneath present-day sea level it is likely that they were deposited and chemically weathered exclusively during glacial low-sea level climate conditions. Geochemical analyses were conducted on the submarine clay samples to determine if they were related to the above-sea level paleosol and to identify their sources. Major and trace element signatures showed the submarine clay deposits to be chemically similar to the paleosols and to be derived from a similar upper continental crust-like parent. Trace element fingerprinting showed the samples to be derived from a parent similar to that of the paleosols; primarily atmospheric dust with some volcanic contributions. These findings provide additional evidence that trade wind vectors for dust transport were present during Pleistocene glacial climate conditions. Weathering indicators reveal the submarine clay samples to be somewhat less weathered than paleosols of similar age and comparable periods of exposure. Like the paleosols, the submarine clays underwent an initial period of rapid subaerial weathering which suggests warm humid climate conditions during glacial low sea level periods. However, the submarine clays did not experience extended periods of diagenesis, which may explain the somewhat lower degree of weathering. Evidence of inputs from the volcanic platform to the paleosols was limited, but comparisons with shallow volcanic rock and highly weathered volcanic residual known as the Primary Red Clay showed some similarities, suggesting that in-situ chemical weathering of the volcanic platform could produce a laterite with some characteristics similar to the Bermuda paleosols. Geochemical analysis of volcanic sands collected at Whalebone Bay showed the igneous fragments to be a result of mechanical weathering and sorting of heavy refractory minerals and we interpret these sediments to be best described as a beach placer deposit. These materials are enriched in insoluble trace elements and REE, and their contribution to the paleosols is limited
Thesis (MS) — Boston College, 2020
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Earth and Environmental Sciences

Estimates of the depth and variation of lateritic weathering profiles are especially important in tropical areas such as Oahu, HI. Shear-wave velocity data were obtained by a new application of Multi-channel Analysis of Surface Waves (MASW) to map the base of the critical zone, to show variations in the LWP, and to derive weathering rates. The MASW technique proved highly capable of imaging the base of the critical zone, confirmed by lithological well data and direct field measurements. Profile thickness can be obtained without drilling, which has applications in engineering and geochemical studies. The measured rate of advance of the weathering front derived from the thickness measured by MASW ranged from 0.019 m/ka to 0.30 m/ka in mesic zones; about 1500 mm of annual rainfall, while a zone of 800 mm of annual rain fall revealed rates ranging from 0.011 m/ka to 0.013 m/ka. These rates are comparable to geochemically derived rates in previous studies. Standard p-wave seismic reflection data were insufficient for detecting boundaries as the weathering boundaries are gradational and do not produce reflections. Shear-wave models also showed internal velocity variations that may be caused by weathering heterogeneity due to textural differences in parental lava flows. Soil chemistry revealed the nature of weathering products as enriched in Al, Fe, Ni, and Cr, and commonly contain alteration minerals such as halloysite, kaolinite, maghemite, and ferrihydrite. Imaging depth limitations were overcome by innovative experiment designs, pushing the boundaries of the current technology. Increasing offsets and combining dispersion curves allowed for a more objective picking of the dispersion curve into the lower frequency domain. Even further improvements were made from a newly developed form of the active/passive technique. These advancements in technology allowed for detailed imaging of the subsurface with greater modeling confidence. This study showed that velocity models derived from MASW are accurately able to describe laterite weathering profiles in terms of depth and variability, expanding the use of the MASW technique beyond its traditional applications and making it a potential tool of interest for many fields of geoscience.

The contribution of dissolved organic carbon (DOC) to mineral weathering was investigated under the changing Eh and pH conditions in three subarctic fens, near Schefferville, Quebec. No evidence of increased weathering rates nor different weathering patterns were found in the fen basal sediment despite DOC-rich and low Eh (0 to +200 mV) conditions.
Solutions containing 50 mg DOC/L derived from subarctic fen peat, and of 50 and 300 mg DOC/L, derived from deciduous leaf litter were used as weathering agents. Clinochlore, microcline and the Fe-rich basal till from the Schefferville fens were used as weatherable mediums. The DOC rich solutions and controls (made of distilled water buffered to the same initial pH) were used to investigate the relative weathering ability of DOC-rich waters under aerobic and anaerobic conditions. The relative ability was determined by comparing the changing cation concentrations in the solutions.