The objectives achieved in this thesis are: (1) to develop a new method for measuring the most important acid buffering mechanism within a soil ecosystem-mineral weathering and (2) to test a soil acidification simulation model against actual field data to determine which soil acidifying or buffering mechanisms seem to be understood and which mechanisms need more detailed analysis. First, a new method was developed that allows for quantification of H$ sp+$ consumption due to weathering and H$ sp+$ consumption due to cation exchange. Initial results yield mineral weathering rates that are well within the range of results obtained by other workers. This technique permits the analysis of multiple soil samples in a relatively short time, allowing for better quantification of spatial variability of mineral weathering within a soil ecosystem. Secondly, it was demonstrated that the acid simulation model generally underestimates soil chemistry values for pH, base cation saturation and soil solution base cations, and overestimates soil solution nitrate concentrations. Problems with obtaining accurate measurements of atmospheric dry deposition, a lack of data on cycling of nutrient elements and the absence of a sub-model to deal with the accumulation and mineralization of organic matter are reasons thought to explain the differences between model and field results.

A novel system for leaching of reconstituted cores of soils taken from horizons of <I>Calluna</I> moorland podzol profiles derived from granites has been used to see if absolute, or at least, relative, weathering rates assessed by simple leaching techniques and by using the PROFILE model agreed. Initial base cations are first removed by leaching with ammonium acetate. Agreement was reasonable, but the results highlighted problems posed by mineralization effects in column-based procedures. A successful attempt was made to develop a procedure to overcome this problem, based upon pre-oxidation with H₂O₂. This procedure was tested on a selection of B and C horizon soils from podzol profiles, and shown to give weathering rates which correlated well with those derived using the PROFILE model. The equilibrated soil cores remaining at the end of the study were then used for testing the effect of acidification of infiltrating water upon weathering rates of base cations. Weathering rate did not increase regularly to combat the acid input. Intact soil core microcosms, fitted with rhizon samplers at three depths and subjected to appropriate simulated precipitation, have been used to elucidate how land use influences the mobility of copper and zinc. Three land uses were considered, improved pasture, semi-improved pasture, and <I>Calluna</I> moorland. Copper and zinc concentrations were also measured in river water samples collected at 59 points from throughout the River Dee network under diverse flow conditions, with a view to elucidating catchment factors influencing the mobilisation of these two elements into river water. The results demonstrated large inputs of copper arising as a consequence of arable land use, and suggested that TOC in drainage water from moorland soils mobilises copper from mineral sediments in the river network. Both zinc and copper concentrations were increased under high discharge conditions.

The Canadian Council of Ministers of the Environment (CCME) developed guidelines for petroleum hydrocarbon (PHC) impacted field soils based on the “worst case” scenario of a fresh petroleum spill (CCME, 2001b; CCME, 2008b). Therefore, when these guidelines are applied as remedial benchmarks, they may be too conservative to be used as realistic targets as they do not account for weathering, which has been shown to decrease the toxicity of PHCs in soil. Chronic toxicity tests were performed using weathered PHC-impacted field soil from three different field sites (ON1, AB1 and BC1) and Folsomia candida. The highest PHC concentration of soil obtained from ON1 (635 mg/kg F2 and 12,000 mg/kg F3) and AB1 (610 mg/kg F2 and 2,900 mg/kg F3) did not affect F. candida survival and reproduction. However, when F. candida were exposed to PHC-impacted soil obtained from the BC1 site, a LC25 of 2,809 mg F2 + F3/kg was calculated for adult survival while an IC25 of 1,030 mg F2 + F3/kg was calculated for juvenile production. The toxicity at BC1 was postulated to be caused by the F2 concentration (it was the only site with high F2). Heat extraction and floatation methods were compared using the soil obtained from the ON1 field site. The number of adults obtained using the floatation method was always higher than the total number of adults obtained from the heat extraction method; however, only two of these results were statistically significant. This suggests that the floatation method is the best method to use to extract Folsomia candida and also indicates either method can be used with no significant effect on the conclusions. Chronic toxicity tests usually focus on measuring sub-lethal endpoints; however, only juvenile production was included in the Environment Canada protocol (Environment Canada, 2005; Environment Canada, 2007a). The endpoints of weight, length and width were added to chronic toxicity tests on AB1 and BC1 soils to determine if they were suitable endpoints. The highest concentration tested for AB1 (610 mg F2/kg and 2,900 mg F3/kg) had no effect on the weight, length or width of the adults. However, the toxicity data obtained for the BC1soils provided an EC25 of 421 mg F2 + F3/kg, 13,750 mg F2 + F3/kg and 17,425 mg F2 + F3/kg for weight, length and width, respectively. The EC25 of 421 mg F2 + F3/kg obtained for the weight of adults is lower than the IC25 of 1,030 mg F2 + F3/kg obtained for juvenile production which indicating that weight is a more sensitive endpoint than juvenile production. Avoidance-response tests involved placing a control and test soil on either side of a cylindrical container and adding 20 Folsomia candida to the midline (Environment Canada, 2007a; Liu et al., 2010). The results using soil obtained from AB1 showed no trend between soil avoidance and increasing PHC concentration. However, the avoidance-response test, using soil obtained from BC1, indicated that F. candida avoidance increased with increasing petroleum concentration. These results show that avoidance-response tests were able to predict the outcome of the chronic toxicity tests. Overall, the above results indicate that the CCME guidelines are too conservative to apply to weathered PHC-impacted field soil when the impacts are primarily F3. Results also indicate that F2 and F3 concentrations of 250 mg/kg and 2,900 mg/kg, respectively would not adversely affect F. candida adult survival, juvenile production or adult weight.

Efflorescence is the presence of insoluble salts upon the surface of concrete or masonry products. The aims of this project were to understand efflorescence and to evaluate metakaolin as an additive for efflorescence prevention. Computer modelling was used in order to simulate the effect of alkali upon relevant phases. Alkali was shown to depress the solubility of calcium hydroxide via the common ion effect, increase, in general, the solubility of calcium carbonate via the foreign ion effect and dramatically increase the solubility and rate of uptake of carbon dioxide into solution. The raindrop model is an attempt to simulate the processes leading to efflorescence. A raindrop falling onto a roof tile is assumed firstly to leach ions from the tile, secondly, to absorb atmospheric carbon dioxide and thirdly to precipitate calcium carbonate. The raindrop model calculates that the formation of efflorescence is primarily dependant upon leaching rather than drying effects. Sensitivity studies show that even when significant sulphate is leached, calcium carbonate remains the prevalent efflorescent phase. Metakaolin, a type of burnt clay pozzolan, had previously been cited as preventing efflorescence. However, this study showed that the performance of metakaolin is affected by the presence of micaceous and other impurity phases which are activated upon heating to metakaolinization temperatures, and readily release alkalis. This study found that the main products of metakaolin hydration in alkaline solutions are gehlenite hydrate and amorphous C-A-S-H gels. The latter was shown to absorb alkalis, particularly potassium, from solution. Results are presented of wet-dry and renewal of leachant leaching tests on two metakaolin blends and a neat OPC paste control. Wet-dry leaching, judged to be the most realistic leach test, produces leaching trends not noted in other leaching tests.

Includes bibliographical references. / 1 v. : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis investigates the nature and origins of minerals of a group known as layer (sheet) silicates or phyllosilicates. It consists of a collection of research papers grouped into 3 categories: modulated layer silicates, clay silicates and the weathering of rocks and minerals, including the formation of clay minerals. Central to the research has been the use of X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). All three research categories were carried out simultaneously. / Thesis (D.Sc.)--University of Adelaide, Dept. of Geology and Geophysics, 1999

Thesis (M.S.)--University of Texas at El Paso, 2008. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph.D.(Civil Engineering)) -- University of Pretoria, 2006.

Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains ix, 99 p. : ill. (some col.), maps (part col.). Includes abstract. Includes bibliographical references (p. 77-81).

Thesis (M.S.)--Montana State University--Bozeman, 2007. / Typescript. Chairperson, Graduate Committee: Mark L. Skidmore. Includes bibliographical references (leaves 69-75).

No description available.