Elevated arsenic concentrations have been reported in a drinking water and irrigation-supply aquifer of Stuarts Point, New South Wales, Australia. Arsenic occurrence in such aquifers is potentially a major issue due to their common use for high yield domestic and irrigation water supplies. Ten multi-level piezometers were installed to depths of approximately 30 m in the sand and clay aquifer. Sediment samples were collected at specific depths during drilling and analysed for chemical and mineralogical composition, grain size characteristics, potential for arsenic release from solid phase and detailed microscopic features. From this data, a full geomorphic reconstruction allowed the determination of source provenance for the aquifer sediments. The model proposed herein provides evidence that the bulk of the aquifer was deposited under intermittent fluvial and estuarine conditions; and that all sediments derive from the regional arsenicmineralised hinterland. More than 200 groundwater samples were collected and analysed for over 50 variables. The heterogeneity of the aquifer sediments causes redox stratification to occur, which in turn governs arsenic mobility in the groundwater. The bulk of the aquifer is composed of fluvial sand deposits undergoing reductive dissolution of iron oxides. Arsenic adsorbed to iron oxide minerals is released during dissolution but re-adsorbs to other iron oxides present in this part of the aquifer. The deeper, more reducing fluvial sand and estuarine clay groundwaters have undergone complete reductive dissolution of iron oxides resulting in the subsequent mobilisation of arsenic into groundwater. Some of this arsenic has been incorporated into iron sulfide mineral precipitates, forming current arsenian pyrite sinks within the aquifer. The extraction of groundwater from the aquifer for irrigation and drinking water supply induces seawater intrusion of arsenic-rich estuarine water, bringing further dissolved arsenic into the aquifer. A greater understanding of the source, sinks and mobilisation of arsenic in this aquifer contributes to our broad understanding of arsenic in the environment; and allows aquifer specific management procedures and research recommendations to be made. Any coastal or unconsolidated aquifer that has sediments derived from mineralised provenances should consider monitoring for arsenic, and other potentially toxic trace elements, in their groundwater systems.

Elevated arsenic concentrations have been reported in a drinking water and irrigation-supply aquifer of Stuarts Point, New South Wales, Australia. Arsenic occurrence in such aquifers is potentially a major issue due to their common use for high yield domestic and irrigation water supplies. Ten multi-level piezometers were installed to depths of approximately 30 m in the sand and clay aquifer. Sediment samples were collected at specific depths during drilling and analysed for chemical and mineralogical composition, grain size characteristics, potential for arsenic release from solid phase and detailed microscopic features. From this data, a full geomorphic reconstruction allowed the determination of source provenance for the aquifer sediments. The model proposed herein provides evidence that the bulk of the aquifer was deposited under intermittent fluvial and estuarine conditions; and that all sediments derive from the regional arsenicmineralised hinterland. More than 200 groundwater samples were collected and analysed for over 50 variables. The heterogeneity of the aquifer sediments causes redox stratification to occur, which in turn governs arsenic mobility in the groundwater. The bulk of the aquifer is composed of fluvial sand deposits undergoing reductive dissolution of iron oxides. Arsenic adsorbed to iron oxide minerals is released during dissolution but re-adsorbs to other iron oxides present in this part of the aquifer. The deeper, more reducing fluvial sand and estuarine clay groundwaters have undergone complete reductive dissolution of iron oxides resulting in the subsequent mobilisation of arsenic into groundwater. Some of this arsenic has been incorporated into iron sulfide mineral precipitates, forming current arsenian pyrite sinks within the aquifer. The extraction of groundwater from the aquifer for irrigation and drinking water supply induces seawater intrusion of arsenic-rich estuarine water, bringing further dissolved arsenic into the aquifer. A greater understanding of the source, sinks and mobilisation of arsenic in this aquifer contributes to our broad understanding of arsenic in the environment; and allows aquifer specific management procedures and research recommendations to be made. Any coastal or unconsolidated aquifer that has sediments derived from mineralised provenances should consider monitoring for arsenic, and other potentially toxic trace elements, in their groundwater systems.

Elevated arsenic concentrations have been reported in a drinking water and irrigation-supply aquifer of Stuarts Point, New South Wales, Australia. Arsenic occurrence in such aquifers is potentially a major issue due to their common use for high yield domestic and irrigation water supplies. Ten multi-level piezometers were installed to depths of approximately 30 m in the sand and clay aquifer. Sediment samples were collected at specific depths during drilling and analysed for chemical and mineralogical composition, grain size characteristics, potential for arsenic release from solid phase and detailed microscopic features. From this data, a full geomorphic reconstruction allowed the determination of source provenance for the aquifer sediments. The model proposed herein provides evidence that the bulk of the aquifer was deposited under intermittent fluvial and estuarine conditions; and that all sediments derive from the regional arsenicmineralised hinterland. More than 200 groundwater samples were collected and analysed for over 50 variables. The heterogeneity of the aquifer sediments causes redox stratification to occur, which in turn governs arsenic mobility in the groundwater. The bulk of the aquifer is composed of fluvial sand deposits undergoing reductive dissolution of iron oxides. Arsenic adsorbed to iron oxide minerals is released during dissolution but re-adsorbs to other iron oxides present in this part of the aquifer. The deeper, more reducing fluvial sand and estuarine clay groundwaters have undergone complete reductive dissolution of iron oxides resulting in the subsequent mobilisation of arsenic into groundwater. Some of this arsenic has been incorporated into iron sulfide mineral precipitates, forming current arsenian pyrite sinks within the aquifer. The extraction of groundwater from the aquifer for irrigation and drinking water supply induces seawater intrusion of arsenic-rich estuarine water, bringing further dissolved arsenic into the aquifer. A greater understanding of the source, sinks and mobilisation of arsenic in this aquifer contributes to our broad understanding of arsenic in the environment; and allows aquifer specific management procedures and research recommendations to be made. Any coastal or unconsolidated aquifer that has sediments derived from mineralised provenances should consider monitoring for arsenic, and other potentially toxic trace elements, in their groundwater systems.

Thesis (M.S.)--University of Montana, 2008. / Title from title screen. Description based on contents viewed Aug. 27, 2008. Includes bibliographical references (p. 90-94).

Thesis (M.Sc.(Environmental and Engineering Geology))--University of Pretoria, 2008. / Abstract in English. Includes bibliographical references (leaves 94-106).

Thesis (Ph. D.)--Stanford University, 2008. / Submitted to the Department of Geophysics. Copyright by the author.

Thesis (Ph.D.)--York University, 2008. Graduate Programme in Geography. / Typescript. Includes bibliographical references (leaves 255-281). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:NR51494

The early efforts of Booth, Johnson, Rubidge, Catuneanu, de Wit, Chevallier, Stankiewicz, Weckmann and many other scientists in studying the Karoo Supergroup has led to comprehensive documentation of the geology on the main Karoo Basin with regards to understanding the age, sedimentology, sedimentary facies and depositional environments. In spite of these studies, the subsurface structure, variations in thickness of various formations in large parts of the basin, the location and orientation of subsurface dolerite intrusions, and the depth to magnetic and gravity sources remains poorly documented. A geological study with the aid of geophysical techniques, magnetic and gravity, was conducted in the southwestern part of the main Karoo Basin. The objectives of the study were to construct numerous models of the main basin that image the crust to a depth of 45 km, to determine thicknesses of various formations, to relate observed geophysical anomalies with geological bodies and lineaments, to estimate the depth of existing anomalous bodies, to determine densities and porosity of various formations, as well as to determine the mineralogy of various rocks in the Karoo Basin.

xiii, 67 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / The bedrock aquifer of the Southern Willamerte Basin, Oregon, USA, is contaminated with arsenic at concentrations as high as several ppm. Single-well push-pull tests were conducted to investigate how microbial metabolisms control arsenic occurrence and levels in the aquifer. Test solutions containing ethanol were injected into the aquifer; dissolved gases, groundwater, and sediments were then sampled to monitor the speciation of carbon, iron, sulfur, and arsenic. Ethanol amendment stimulated a series of microbial metabolisms, including arsenate reduction, iron reduction, and sulfate reduction. Arsenate reduction converts arsenate to arsenite; iron reduction produces ferrous iron; sulfate reduction releases sulfide. Arsenite and ferrous iron then combine with sulfide and form arsenic sulfide and iron sulfide minerals. Results of the experiments demonstrate that the interactions among microbial metabolisms and mineral precipitation influenced arsenic contamination in the aquifer. These results shed new light on potential bioremediation strategies in the area. / Committee in Charge: Dr. Qusheng Jin, Chair; Dr. Mark Reed; Dr. Samantha Hopkins

Made available in DSpace on 2014-06-11T19:26:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-04-08Bitstream added on 2014-06-13T18:54:14Z : No. of bitstreams: 1 meaulo_fj_me_rcla.pdf: 5076114 bytes, checksum: f464c3b07acab15cd2c1d70bcf7f7943 (MD5) / Atualmente o crescimento desordenado dos centros urbanos brasileiros tem resultado em sérios problemas ambientais. Esses problemas podem ser minimizados e/ou evitados a partir de estudos específicos no meio físico. A área de estudo de 270 Km2 abrange a zona urbana e parte da zona rural do município de Araraquara (SP), região central do Estado de São Paulo. Está inserida no contexto geológico da Bacia Sedimentar do Paraná. Ocorrem litologias das formações Botucatu, Serra Geral, Adamantina, sedimentos correlatos e sistemas aqüíferos correspondentes. A estratégia metodológica adotada nesta pesquisa foi: revisão bibliográfica; trabalhos de campo; trabalho laboratorial; integração dos dados e análise dos resultados do método de mapeamento da vulnerabilidade natural de aqüíferos (FOSTER et al., 2002). Os índices de vulnerabilidade natural das formações geológicas são: Botucatu e Serra Geral (Alta), Adamantina (Baixa a Moderada) e os sedimentos recentes (Extrema). O mapa de vulnerabilidade natural à poluição dos recursos hídricos subterrâneos da área de Araraquara (SP, 1:50.000) e o ensaio de aplicação do mapa são instrumentos que reúnem um conjunto de informações capaz de subsidiar todo tipo de intervenção antrópica no meio físico, contribuindo para as tomadas de decisões governamentais e para a elaboração de programas de políticas públicas ambientais. / Currently the disorientated growth of the Brazilian urban centers has resulted in serious environmental problems. These problems can be minimized and/or be prevented by specific environmental studies. The studies developed in 270 Km2 (urban and part of the rural zone) of Araraquara city (SP), located on center region of the São Paulo State. The geologic mapping of the study area is located in the NE of the Paraná Sedimentary Basin. The litoestratigrafic and aquifers systems sequence is formed by: Botucatu Formation; Serra Geral Formation; Adamantina Formation; Cenozoic sediments. The adopted methodological strategy in this research was: bibliography revision; field works; laboratorial work; integration of the data and analysis of the results of the method of mapping of the natural vulnerability of aquifer (FOSTER et al., 2002). The natural units of vulnerability are: low to moderate (Adamantina Formation); high (formations Serra Geral and Botucatu); extreme (Cenozoic sediments). The mapping of natural vulnerability to groundwater of Araraquara area (SP, 1:50.000) and the test of application of the map are instruments that congregate a group of information capable to subsidize all type of anthropogenic intervention in the environment, contributing for governmental decisions and the elaboration of public politics to environmental programs.