<p> The fate of metal(loid)s in the environment depends on a variety of physical and geochemical factors. Assessing metal(loid) transport in soil solution and surface water requires detailed knowledge of the speciation, which can often control mobility, toxicity and bioavailability of a given element. The present study details the geochemical analyses of two end member types of systems: a &lsquo;pristine&rsquo; Arctic watershed and a military shooting range with an overall focus on understanding lead (Pb) and antimony (Sb) mobility in shooting range soils. The project uses bulk speciation analyses coupled with micro-scale methods to quantify variations in metal(loid) concentration as a function of environmental conditions and characterize metal(loid) speciation and distribution in relation to parent source material in order to understand the impact that metal(loid) retention versus mobilization has on a given system. </p><p> In the Arctic, stream water concentrations of Al, Ba, Fe, and Mn in Imnavait Creek were highest in the late fall (September and October). This pattern appears to correlate with the depth of the active layer throughout the watershed. Increased water infiltration at the permafrost-active layer boundary could significantly impact stream water trace metal(loid) signatures due to mineral weathering of unfrozen soil. In the central Alaskan shooting range, there were significant contributions of Pb and Sb to both the soil and soil solution as a result of the weathering of fragmented bullets. Aqueous concentrations of Sb were higher than Pb in all soil types, indicating Sb is more mobile, despite the fact that bullets introduce approximately two orders of magnitude more Pb than Sb. We observed an association of both Pb and Sb with Fe in soils, which impacts remediation scenarios for ranges as Fe treatments have potential to be effective for system-wide immobilization of major contaminants. Overall, the results from this study highlight the complexity of metal(loid) speciation, transport and mobility as a function of seasonality, soil type and environmental conditions.</p>

<p> We measured the physical, chemical and isotopic properties of groundwater, streams and Lake Chilwa in the Lake Chilwa Basin in southern Malawi. Our goal was to assess water quality and identify the hydrogeochemical processes that control water quality. Groundwater in the Lake Chilwa Basin are highly saline which has led to water shortages because of poor water quality. We hypothesized that the highly saline groundwater resulted from water-rock interaction. The objective of the study wasto assess the chemical evolution of the groundwater and surface water and their relationship to water-rock interactions. Groundwater from 16 boreholes, 5 stream water samples and 3 samples from Lake Chilwa were collected using standard methods and investigated for temperature, pH, electrical conductivity, total dissolved solids (TDS), major ions and stable isotopes of hydrogen and oxygen. Groundwater and Lake Chilwa water had higher ionic concentrations (e.g., HCO_3^&ndash;, Na⁺, Ca²⁺, Mg²⁺) than stream water. Ionic evolution models indicate weathering of silicate minerals as the major control of the ionic concentrations. The chemistry of water in the Lake Chilwa is markedly affected by evaporation. Concentrations of the TDS, HCO_3^&ndash; and Cl^&ndash; in many locations are above the recommended limits prescribed for drinking water by the World Health Organization (WHO). The results of this study show that the poor water quality is due to natural water-rock interactions. Because quality of streams water is adequate, and because base flow to perennial streams issupported by shallow groundwater, efforts should be made to map shallow fresh groundwater aquifers for domestic and industrial use.</p><p>

Analysis of nitrogen containing compounds by gas chromatography with atomic emission detection has always been problematic. Nitrogen detection has been customarily done using the 174.53 and 174.27 nm atomic lines, with very limited selectivity and sensitivity. Nitrogen can also be detected using the cyanogen (CN) molecular emission bands at 388 nm. It has been reported that a 100-fold improvement in the selectivity using this line can be reached. Therefore, in the present work, the instrument available in the laboratory was modified to allow the use of the 388 nm line for the nitrogen detection. The modification of the instrument involved the use of a mixture of reagent gases that were optimized to produce the best nitrogen emission using the 388 nm line. Figures of merit of the detection using this line, were evaluated and compared with the commonly used nitrogen line (174 nm) and the carbon detection (193 nm). The dependence of the GC-AED response with the molecular structure of the analyte, and its application in the determination of empirical formula was also evaluated, and its application for analysis of petroleum products. The second part of the present work studied the biomarkers in deep subsurface samples and their relationship with the microbial activity. Little is known of microbial community characteristics at depths larger than 50 m below surface, information that is crucial for the clean up of contaminated underground environments. The use of classical approaches to identify microbiota, often results in the characterization of less than 10% of the biota present when analyzing deep subsurface samples, therefore, the analysis of lipid content in the samples have been proposed. Microorganisms use lipids as constituent of their cell walls or as nutritional sources. Monitoring lipids can be used to develop a picture of how, when, where and under which conditions microbes are active in the subsurface. This research was focussed in the biomarker study of a shale and sandstone from Cerro Negro, New Mexico. Biomarkers were determined to study distribution, concentration and availability of resources that support life and microbial activity and their relationship with geochemical parameters.

Thesis (M.Sc.)--Victoria University of Wellington, 2009. / Accompanying disc: Appendix Five. Includes bibliographical references.

<p> In this study the experiments were designed to measure the geochemical and surface charge (zeta potential) changes with time for two crushed samples of feldspar (Na-fs and K-fs) over the pH range of most natural waters (5 to 9). These experiments show: </p> <p> (a) the importance of adsorption/desorption phenomena in both short-term and long-term feldspar dissolution, and probably for chemical weathering in general; </p> <p> (b) that the generalized curve which characterizes the geochemical data (an initial rapid rise to a peak followed by a decrease to a lower, either constant or later increasing value) is consistent with a consideration of the adsorption/desorption process (i.e., the formation of the double layer) taking place at the feldspar surface and with the simple dissolution of the mineral; </p> <p> (c) that the cation-silica ratios (Na₂O/SiO₂, K₂O/SiO₂, CaO/SiO₂) of the solution compared to those in the original feldspar indicate an initially incongruent dissolution which tends towards congruency during the latter part of the experiments. </p> <p> From information in the Iiterature and the results of these experiments. it may be concluded that: </p> <p> (a) the most important or master variables in chemical weathering are abrasion, minerologic or crystallographic factors such as twinning, exsolution regions, impurities, fractures and grain size, and solution composition and concentration. pH does not appear to be a master variable in most natural waters, especially for long-term weathering, and the chemical composition of the mineral phase is also not a good criterion for predicting weathering behaviour; and </p> <p> (b) the most extreme chemical weathering should occur in a high energy environment, either for physical reasons (i.e., high abrasion due to extreme relief) or for chemical reasons (i.e., high rainfall). </p> / Thesis / Master of Science (MSc)

Thesis (M.Sc (Hons.))-- University of Western Sydney, Nepean, 1998. / Bibliography : leaves 105-106.

The aim of this study is to define mineralogical and geochemical characteristics of phlogopite-pargasite enriched ultramafic-mafic cumulate rocks from Kuran&ccedil / ali (Kirsehir) and their implications for petrology and regional geological setting. The Kuran&ccedil / ali rocks, found within an allochthonous sliver, are representative for the isolated members of the Central Anatolian Ophiolites, derived from closure of Izmir-Ankara-Erzincan branch of Alpine Neotethys. The rocks overthrust the Metamorphic Ophiolitic M&eacute / lange (the uppermost part of the Central Anatolian Metamorphics) and cut by felsic dykes of the Late Cretaceous Central Anatolian Granitoids. The Kuran&ccedil / ali rocks are unusually enriched in phlogopite and pargasite with varying crystal sizes. They are also composed of diopsidic augite, plagioclase, rutile, ilmenite, sphene, apatite and pyrite. The rocks are divided into six types / clinopyroxenite, clinopyroxenite-with-hydrous minerals-plagioclase, phlogopitite, hornblendite, layered gabbro and diorite. Evaluation of detailed EMP data from constituent minerals of different rock types showed that phlogopite with high Fe2+-Fe3+-Al[6]-Ti, diopsidic-augite with high Ca-Al(t)-Ti, Si-undersaturated pargasite with high Al[4]-K-Na-Ti-contents and intercumulus plagioclase with a wide range of composition (an%=40.61-98.58) display unusual compositions. Substitution mechanisms and elemental variations of the minerals suggest crystallization from hydrous metasomatized mantle, high water pressure and oxygen fugacities during formation of the Kuran&ccedil / ali rocks. Major oxide, trace and rare earth element abundances of the rock units were used to evaluate petrological characteristics. Chemical and tectonic discrimination diagrams, and parallel multi-element and REE patterns with highly enriched in LILE and LREE relative to HREE and HFSE show strong calc-alkaline affinity with slight alkaline features. Troughs at Nb-Ta and Ti characterize the rocks but these elements are slightly enriched than N-MORB. The rocks show high LREE/HREE ratios. Both unusual mineralogical and geochemical features of the rocks show that the rocks were generated in an arc environment. Moreover, they require a mantle wedge source strongly influenced by metasomatic components (fluid/melt) derived from subducting slab and/or OIB-like alkaline melt. Comparison of the rocks with tectonically well-defined rocks displays that they are generated in an intra-oceanic arc environment, but owe a comparison with fore-arc back-arc Central Anatolian Ophiolites within supra-subduction zone environment revealed that Kuran&ccedil / ali rocks are different and generated in an arc basement.