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.

No description available.

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.

No description available.

Compacted shales cause problems because they tend to degrade with time due to weathering. Degradation results in the shale deteriorating from a hard rock-like material to a soft fine-grained soil mass with lower shear strength and high deformability. Consequently, common problems that occur in embankments constructed with compacted shales include settlement and instabilities. Therefore, accelerating weathering prior to compaction by wetting and breaking down the shales before placement can reduce the deterioration during the service life of the construction. Extensive laboratory testing was performed in order to characterize the mechanical behavior of compacted shales. Critical State theory is a clever framework that describes the mechanical behavior of soils with a simple system of equations that explains all the aspects of compression and shear of soils. NorSand is a model constructed in the framework of the Critical State theory that decouples the yield loci from the normally consolidated line. This characteristic made this model suitable for compacted shales. Also, empirical evidence showed that the plastic behavior of compacted shales is controlled by a Nova type flow rule that is a function of the mineralogical characteristics of the shales. This finding has implications in the shape of the yield loci and the hardening rule.

Everything falls apart, but some materials do it with a specific panache, and once design leaves paper to be built, no project is complete until it falls. As creatures subject to time, we identify with things in which we see ourselves, we identify with our mortal buildings. Alchemy used material transformation as an active metaphor for human betterment. This thesis will search for ways that the inevitable indexing of time on the built environment can be used to catalyze a broader understanding of time and our place in it. Sympathetic engagement with our environments can form rich internal narratives while also fostering collective memory. Four materials form the basis of these investigations: Cedar, Copper, Iron and Marble. For each material, chemical properties, history and mythology are invoked to describe their particular temporal nature, an understanding of how they come together and fall apart. The four material chapters of this thesis mean to return a sense of cognitive depth to our relationship with materials without resorting to symbolism.

The study aimed to identify deterioration problems, repair and conservation needs of andesites on the walls of the Ankara Castle. Decay forms of walls were documented by visual examination. Samples taken from the surface of the weathered andesites were examined for their basic physical, mechanical compositional and minerological properties. The bulk density and total porosity were determined as basic physical properties. The mechanical properties were expressed as ultrasonic velocity and modulus of elasticity (Emod). Compositional and mineralogical properties were determined by optical microscopy and XRD analyses. Soluble salt content of the andesite samples was determined by spot tests of anions and electrical conductivity measurements. Findings were evaluated in terms of the long-term weathering behaviour of andesites under the effect of the prevailing climate, air pollution problems of Ankara, dampness problems of the structure, previous repairs with incompatible cement mortars. The surfaces of Ankara Castle andesite blocks were heavily weathered. The results were compared with the physical and mechanical properties of fresh andesites from G&ouml / lbaSi-Ankara quarry. The surface of the andesite blocks at the Ankara Castle, had low bulk density and high porosity, low ultrasonic velocity and low Emod values. Thin section and XRD analyses supported those results by revealing the presence of physical and chemical weathering on feldspars and other main minerals of andesite, as well as the presence of amorphous minerals at the surface.

Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 44-45). / vi, 45 leaves, bound ill. (some col.) 29 cm

Honors Project--Smith College, Northampton, Mass., 2009. / Includes bibliographical references (p. 101-108).

Mémoire (M.Sc.T.)-- Université du Québec à Chicoutimi, 1992. / Bibliogr.: f. 70-77. Document électronique également accessible en format PDF. CaQCU