Arsenic in aquifers poisons more than 100 million people in Asia alone, as aquifers remain the primary source of water for drinking and farming. Previous studies have suggested a link between the mobilisation of arsenic in aquifers and biochemical processes. As a result of the complex interaction of microbes with arsenic bearing minerals, the relatively immobile arsenate [As(V)] is reduced to labile and more soluble arsenite [As(III)] in aquifers, resulting in elevated concentrations of the metalloid. The numerous microbial communities capable of multiple-metabolic activities colonising these arsenic impacted aquifers mean that the exact mechanism of arsenic mobilisation in aquifers remains poorly understood. To resolve this ambiguity, this study undertakes a combination of metaomic, geochemical, and statistical analyses of 75 aqueous and sediment samples (three sample sets) from 3 transects with arsenic impacted aquifers in Bangladesh and Cambodia. Key geochemical and physical properties including arsenic speciation, iron speciation, mineral and elemental compositions, pH and Eh were recorded using the state-of-the art techniques of XANES, XRF, ICP-MS and other in situ techniques. Next generation sequencing (NGS) platforms such as MiSeq, HiSeq, Nextseq and Pyrosequencing, were used to sequence and analyse DNA and RNA extracted from field samples, allowing characterisation the extent bacterial communities, including any arsenic related genes and transcripts found in these arsenic impacted aquifers. The biogeochemical findings suggest that direct As redox transformations are central to arsenic fate and transport, and that there is a residual reactive pool of both As(V) and Fe(III) in deeper sediments that could be released by microbial respiration in response to hydrologic perturbation, such as increased groundwater pumping that introduces reactive organic carbon to depth. The main findings of this molecular investigation are (i) the most abundant bacterial species belonging to the families of Comamonadaceae, Moraxellaceae, Rhodocyclaceae, Gallionellaceae etc, not known for dissimilatory arsenic reduction, might possess arrA genes and thus have the potential to mobilise arsenic through dissimilatory arsenate reduction; (ii) the bacterial community structure revealed through 16S rRNA gene based sequencing and analysis, resembles the family level community structure revealed through the WGS based community analysis; (iii) although arsenic resistant genes are found in many organisms, they are transcribed only in a few organisms; (iv) the application of O2-PLS analyses may be useful for not only identifying novel organisms associated with key biogeochemical process, but also has clear potential to predict the physical/chemical environment in situ associated with microbial samples via community profiling. In conclusion, the results obtained from this study help establish the identity of microorganisms potentially playing a role in arsenic mobilisation in aquifers, and help decipher the underpinning mechanisms. This deeper level of understanding will in turn help to better target measures that can be applied to arsenic mitigation.

Arsenic contamination of circum-Himalayan groundwater is leading to one of the greatest humanitarian disasters of modern times, poisoning at least 70 million people who are mostly poor and rural. The groundwater is hosted in Holocene aquifers consisting of Himalayan sediments deposited by the great Asian rivers in deltaic environments. Arsenic is released when organic material (OM) reacts with the iron-oxide minerals co-deposited in the sediments onto which arsenic is adsorbed. The source of OM is one of the most important questions facing researchers and policy makers. There are generally accepted to be three potential sources of OM: 1) sedimentary bound OM (SOM) co-deposited with sediments; 2) thermally mature petroleum upwelled from reservoirs below the aquifers; 3) dissolved organic carbon (DOC) some of which might be drawn in to the aquifer through modern pumping and irrigation. In this thesis the nature of organic material in the aquifer is researched and the processes and timescales which lead to arsenic release are studied. Here evidence for a new conceptual model of arsenic release is presented. Isotopic tracing combined with a new geochemical model and organic geochemical techniques, shows that OM driving arsenic release pre-dates agriculture in the region and was from natural grasslands in the early Holocene. The geochemical model utilises strontium isotopes to correct the radiocarbon age of dissolved inorganic carbon (DIC) to find only the age and isotopic signature of DIC from oxidation of organic material. This shows that DIC from oxidation of OM was from the early Holocene and had an isotopic signature consistent with the early Holocene SOM in this region. A study of the sediments in the region built upon a geomorphological history shows that the most oxidised SOM is from early Holocene sediments. Thus both techniques separately indicate that pre-agricultural organic material drove arsenic release. This conceptual model however reveals the "arsenic sand paradox", because whilst release is from early Holocene clays, today highest concentrations of arsenic are in younger sands. Explaining this paradox is the most important next step leading on from this research.

In this project, we have explored the possibility of growing high quality Heusler alloy thin films from multiphase targets. Bulk targets were found to be partially formed, i.e. not of homogeneous L21 structure, through x-ray diffraction measurements. Pulsed laser deposition is a technique that can provide a congruent transfer of material from the target to the substrate, even in some cases where the target is not of a single crystalline phase. It was the objective of this work to determine whether L21 structured thin films of Co2MnAsxGe(1-x) could be grown from multiphase targets. Measurements have been carried out to study the magnetic and structural properties of the Heusler alloys Co2MnAsxGe(1-x). The optimization parameters that were investigated were substrate type, growth temperature, laser parameters, film thickness, and other common deposition parameters. Temperature-dependent magneto-optic Kerr effect (MOKE) techniques were used to study the qualitative magnetic properties. Alternating current (AC) susceptibility (using a MOKE technique) measurements were made as a function of temperature to view the second-order transition and obtain the Curie temperatures. Frequency dependent AC susceptibility was measured to determine the frequency dependence of the AC susceptibility for Co2MnAsxGe(1-x).

Infrared spectroscopy was used to show that the arsenate anion is adsorbed on the surface of synthetically prepared goethite, replacing two singly coordinated (A-type) surface OH groups. In this respect, arsenate is analogous to phosphate, but its larger size causes it to interact more strongly with other OH groups that remain on the surface. This has suggested an alternative infrared band assignment for these OG groups. Potentiometric titrations performed on 'CO<SUB>2</SUB>'-free goethite gave a value for the point of zero charge (p.z.c.) of 9.15. The p.z.c. shifted to more acid values for phosphate- and arsenate-treated goethite indicating an increased negative surface charge. For sulphate-treated goethite the positive surface charge increased slightly. The results were interpreted as indicating that phosphate and arsenate were adsorbed by a chemisorption (ligand-exchange) mechanism. The exact nature of the sulphate interaction was still unclear. Solution studies on the goethite-aqueous solution interface demonstrated the adsorption of arsenate by a binuclear bridging mechanism, confirming the findings from the infrared study. The results indicated a 2:1 stoichiometry between ligands exchanged and arsenate adsorbed over the pH range 4-10. No such stoichiometry was observed for sulphate adsorption though the reaction between sulphate and goethite consumed protons (i.e. released hydroxyl). A brief study to ascertain the effect of certain competitors on arsenate adsorption was performed. Results showed considerable reduction in arsenate adsorption when vanadate ions were added simultaneously with arsenate to goethite-aqueous electrolyte suspensions. The results also indicated that goethite previously coated with small quantities of humic acid reduced arsenate adsorption. The presence of sulphate in solution at up to five times the concentration of arsenate had no effect on arsenate adsorption over the pH range 5 to 9.

Arsenic is a naturally occurring toxic metal and its presence in food composites could be a potential risk to the health of both humans and animals. Arseniccontaminated groundwater is often used for food and animal consumption, irrigation of soils, which could potentially lead to arsenic entering the human food chain. Its side effects include multiple organ damage, cancers, heart disease, diabetes mellitus, hypertension, lung disease and peripheral vascular disease. Research investigations, epidemiologic surveys and total diet studies (market baskets) provide datasets, information and knowledge on arsenic content in foods. The determination of the concentration of arsenic in rice varieties is an active area of research. With the increasing capability to measure the concentration of arsenic in foods, there are volumes of varied and continuously generated datasets on arsenic in food groups. Visual analytics, which integrates techniques from information visualization and computational data analysis via interactive visual interfaces, presents an approach to enable data on arsenic concentrations to be visually represented. The goal of this doctoral research in Environmental Science is to address the need to provide visual analytical decision support tools on arsenic content in various foods with special emphasis on rice. The hypothesis of this doctoral thesis research is that software enabled visual representation and user interaction facilitated by visual interfaces will help discover hidden relationships between arsenic content and food categories. The specific objectives investigated were: (1) Provide insightful visual analytic views of compiled data on arsenic in food categories; (2) Categorize table ready foods by arsenic content; (3) Compare arsenic content in rice product categories and (4) Identify informative sentences on arsenic concentrations in rice. The overall research method is secondary data analyses using visual analytics techniques implemented through Tableau Software. Several datasets were utilized to conduct visual analytical representations of data on arsenic concentrations in foods. These consisted of (i) arsenic concentrations in 459 crop samples; (ii) arsenic concentrations in 328 table ready foods from multi-year total diet studies; (iii) estimates of daily inorganic arsenic intake for 49 food groups from multicountry total diet studies; (iv) arsenic content in rice product categories for 193 samples of rice and rice products; (v) 758 sentences extracted from PubMed abstracts on arsenic in rice. Several key insights were made in this doctoral research. The concentration of inorganic arsenic in instant rice was lower than those of other rice types. The concentration of Dimethylarsinic Acid (DMA) in wild rice, an aquatic grass, was notably lower than rice varieties (e.g. 0.0099 ppm versus 0.182 for a long grain white rice). The categorization of 328 table ready foods into 12 categories enhances the communication on arsenic concentrations. Outlier concentration of arsenic in rice were observed in views constructed for integrating data from four total diet studies. The 193 rice samples were grouped into two groups using a cut-off level of 3 mcg of inorganic arsenic per serving. The visual analytics views constructed allow users to specify cut-off levels desired. A total of 86 sentences from 53 PubMed abstracts were identified as informative for arsenic concentrations. The sentences enabled literature curation for arsenic concentration and additional supporting information such as location of the research. An informative sentence provided global “normal” range of 0.08 to 0.20 mg/kg for arsenic in rice. A visual analytics resource developed was a dashboard that facilitates the interaction with text and a connection to the knowledge base of the PubMed literature database. The research reported provides a foundation for additional investigations on visual analytics of data on arsenic concentrations in foods. Considering the massive and complex data associated with contaminants in foods, the development of visual analytics tools are needed to facilitate diverse human cognitive tasks. Visual analytics tools can provide integrated automated analysis; interaction with data; and data visualization critically needed to enhance decision making. Stakeholders that would benefit include consumers; food and health safety personnel; farmers; and food producers. Arsenic content of baby foods warrants attention because of the early life exposures that could have life time adverse health consequences. The action of microorganisms in the soil is associated with availability of arsenic species for uptake by plants. Genomic data on microbial communities presents wealth of data to identify mitigation strategies for arsenic uptake by plants. Arsenic metabolism pathways encoded in microbial genomes warrants further research. Visual analytics tasks could facilitate the discovery of biological processes for mitigating arsenic uptake from soil. The increasing availability of central resources on data from total diet studies and research investigations presents a need for personnel with diverse levels of skills in data management and analysis. Training workshops and courses on the foundations and applications of visual analytics can contribute to global workforce development in food safety and environmental health. Research investigations could determine learning gains accomplished through hardware and software for visual analytics. Finally, there is need to develop and evaluate informatics tools that have visual analytics capabilities in the domain of contaminants in foods. / Environmental Sciences / P. Phil. (Environmental Science)

Ingeniera Civil / El arsénico ha sido declarado un contaminante carcinógeno y de elevada toxicidad, que afecta a más de 150 millones de personas en el mundo. En Chile se presentan altos niveles del contaminante en el agua, por causas naturales y antropogénicas, mayoritariamente en la zona centro y norte del país, donde las plantas de tratamiento usan tecnologías costosas y complejas de operación, como oxidación-filtración, osmosis inversa, procesos de membrana, entre otros. Actualmente se desarrolla el proyecto Sol-Arsenic, de remoción de arsénico con nanomateriales desarrollados especialmente. El objetivo de esta investigación, es estudiar la capacidad de adsorción y foto-oxidación de los nanomateriales desarrollados, frente a parámetros hidráulicos que rigen el comportamiento de la tecnología a implementar, en particular número de Reynolds, con el fin de potenciar la eficiencia del sistema y determinar posible desorción del arsénico adsorbido en el nanomaterial. Para esto, se realizan dos sistemas experimentales: el primero, a pequeña escala en reactor batch y el segundo, una maqueta de escala industrial en sistema continuo. De los resultados obtenidos, en ningún caso se observa desorción del contaminante desde los nanomateriales. En batch se alcanza un porcentaje de remoción del 96\%, mientras en sistema prototipo un 86\%. Por otro lado, se concluye que la adsorción de As(III) es más sensible a la velocidad de agitación del medio que la adsorción de As(V) y que el número de Reynolds debe ser turbulento para promover la mezcla. Finalmente se recomienda mejorar el sistema de agitación en tanque y ampliar el foto-reactor. / 18/01/2020

As aquaporinas são proteínas de membrana presentes em quase todos os órgãos e tecidos de animais e plantas, onde desempenham funções que vão além do transporte de água, transportando também moléculas como ureia, ácido bórico, ácido silícico, amônia, dióxido de carbono e arsênio. Em plantas, as aquaporinas podem ser classificadas de acordo com suas sequências de aminoácidos em cinco subfamílias: proteínas intrínsecas da membrana plasmática (PIPs), proteínas intrínsecas de tonoplastos (TIPs), proteínas intrínsecas do tipo nodulina 26 (NIPs), proteínas intrínsecas pequenas (SIPs) e proteínas intrínsecas não caracterizadas (XIPs). Dados genômicos determinam o número de genes de aquaporinas em 33 para arroz, 35 para Arabidopsis, 71 para algodão e 66 para soja. Dentre as principais culturas utilizadas como alimento, o arroz é particularmente eficiente no acúmulo do semimetal altamente tóxico e carcinogênico arsênio (As), representando um risco significativo para a saúde humana Assim, o principal objetivo deste trabalho é elucidar o papel das aquaporinas no transporte de As em arroz. Utilizando cultivares que apresentam susceptibilidade diferencial ao arsênio, foi analisada a expressão dos genes de aquaporinas em resposta ao tratamento com arsenito em diferentes condições. Para a caracterização dos genes de aquaporinas diferencialmente expressos, foram realizados ensaios de complementação funcional em leveduras. Nossos resultados indicam que membros das subfamílias NIP, TIP, PIP e SIP podem estar envolvidos no transporte e metabolismo de As em arroz, dentre estes, quatro podem estar envolvidos no transporte de As para dentro da célula e seis membros podem estar envolvidos no transporte de As para os vacúolos, fazendo com que essas proteínas sejam candidatas a estratégias de melhoramento genético e fitorremediação. / Aquaporins are membrane proteins present in almost all organs and tissues of animals and plants, where they perform functions that go beyond water transport, also transporting molecules such as urea, boric acid, silicic acid, ammonia, carbon dioxide and arsenic. In plants, aquaporins can be classified according to their ami-no acid sequences into five subfamilies: plasma membrane intrinsic proteins (PIPs), tonoplast intrinsic proteins (TIPs), nodulin-26 like intrinsic proteins (NIPs), small intrinsic proteins (SIPs) and uncharacterized intrinsic proteins (XIPs). Genomic data set the number of aquaporin genes in 33 for rice, 35 for Arabidopsis, 71 for cotton and 66 for soybean. Among the main crops used as food, rice is particularly effi-cient in the accumulation of the highly toxic and carcinogenic metalloid arsenic, thus representing a significant risk to human health. Therefore, the main goal of this work is to elucidate the role of aquaporins in the transport of arsenic in rice. Using cultivars with differential susceptibility to arsenic, the expression of aquaporin genes in response to the arsenite treatment under different conditions was ana-lyzed. For the characterization of differentially expressed aquaporin genes, func-tional complementation assays were performed in yeast cells. Our results indicate that members of the subfamilies NIP, TIP, PIP and SIP may be involved in the transport and metabolism of arsenic in rice, of these, four may be involved in the transport of As into the cell and six members may be involved in transporting As to the vacuoles, making these proteins candidates to genetic improvement strategies and phytoremediation.

Made available in DSpace on 2014-10-09T12:37:23Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:08:30Z (GMT). No. of bitstreams: 1 02042.pdf: 4526500 bytes, checksum: ad7b6b77ffd93f73a1a01fc28406fb05 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

As aquaporinas são proteínas de membrana presentes em quase todos os órgãos e tecidos de animais e plantas, onde desempenham funções que vão além do transporte de água, transportando também moléculas como ureia, ácido bórico, ácido silícico, amônia, dióxido de carbono e arsênio. Em plantas, as aquaporinas podem ser classificadas de acordo com suas sequências de aminoácidos em cinco subfamílias: proteínas intrínsecas da membrana plasmática (PIPs), proteínas intrínsecas de tonoplastos (TIPs), proteínas intrínsecas do tipo nodulina 26 (NIPs), proteínas intrínsecas pequenas (SIPs) e proteínas intrínsecas não caracterizadas (XIPs). Dados genômicos determinam o número de genes de aquaporinas em 33 para arroz, 35 para Arabidopsis, 71 para algodão e 66 para soja. Dentre as principais culturas utilizadas como alimento, o arroz é particularmente eficiente no acúmulo do semimetal altamente tóxico e carcinogênico arsênio (As), representando um risco significativo para a saúde humana Assim, o principal objetivo deste trabalho é elucidar o papel das aquaporinas no transporte de As em arroz. Utilizando cultivares que apresentam susceptibilidade diferencial ao arsênio, foi analisada a expressão dos genes de aquaporinas em resposta ao tratamento com arsenito em diferentes condições. Para a caracterização dos genes de aquaporinas diferencialmente expressos, foram realizados ensaios de complementação funcional em leveduras. Nossos resultados indicam que membros das subfamílias NIP, TIP, PIP e SIP podem estar envolvidos no transporte e metabolismo de As em arroz, dentre estes, quatro podem estar envolvidos no transporte de As para dentro da célula e seis membros podem estar envolvidos no transporte de As para os vacúolos, fazendo com que essas proteínas sejam candidatas a estratégias de melhoramento genético e fitorremediação. / Aquaporins are membrane proteins present in almost all organs and tissues of animals and plants, where they perform functions that go beyond water transport, also transporting molecules such as urea, boric acid, silicic acid, ammonia, carbon dioxide and arsenic. In plants, aquaporins can be classified according to their ami-no acid sequences into five subfamilies: plasma membrane intrinsic proteins (PIPs), tonoplast intrinsic proteins (TIPs), nodulin-26 like intrinsic proteins (NIPs), small intrinsic proteins (SIPs) and uncharacterized intrinsic proteins (XIPs). Genomic data set the number of aquaporin genes in 33 for rice, 35 for Arabidopsis, 71 for cotton and 66 for soybean. Among the main crops used as food, rice is particularly effi-cient in the accumulation of the highly toxic and carcinogenic metalloid arsenic, thus representing a significant risk to human health. Therefore, the main goal of this work is to elucidate the role of aquaporins in the transport of arsenic in rice. Using cultivars with differential susceptibility to arsenic, the expression of aquaporin genes in response to the arsenite treatment under different conditions was ana-lyzed. For the characterization of differentially expressed aquaporin genes, func-tional complementation assays were performed in yeast cells. Our results indicate that members of the subfamilies NIP, TIP, PIP and SIP may be involved in the transport and metabolism of arsenic in rice, of these, four may be involved in the transport of As into the cell and six members may be involved in transporting As to the vacuoles, making these proteins candidates to genetic improvement strategies and phytoremediation.

Arsenic (As) exposure through water and As contaminated food in rural areas around the world is well documented. While there are accurate, precise, and even robust screening methods for on-site water analysis, the determination of toxic inorganic As (iAs, a class I carcinogen) in foodstuff has been made possible through methods based on mass spectrometry. No screening or field method for iAs in food has been established and, there is also a lack of screening and monitoring methods for human exposure to iAs. The objectives of this thesis were to develop and apply a robust, reliable and well established screening method which is field deployable for the measurement of iAs in rice and seaweed in addition to the total As metabolites in human urine resulting from exposure to inorganic As. Reported in this work is the development and application of optimised field deployable methods based on the Gutzeit reaction with the aid of a field test kit (FTK) for the determination of iAs in rice, rice-based products, edible seaweeds and seaweeds cultivated from their natural habitat. The methods involve simple sample extraction by boiling in nitric acid before analysis with the FTK. Results were obtained in under an hour with the FTK and further validated with speciation analysis by HPLC-ICP-MS (High Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry). Analysis of 30 store-bought rice samples with the field method gave good reproducibility (± 12 %) for samples with variable As concentrations. The results were comparable to those obtained by HPLC-ICP-MS with no contribution from organoarsenicals. Screening analysis with the field method based on recent regulations for inorganic arsenic in rice also gave low false positive and false negative rates ( < 10 %) for violations against these regulations, an indication that the method can accurately identify samples that are above or below the recommended maximum contaminant limits for iAs in rice. Similarly, results from the seaweed analysis with the field method were also comparable to those from speciation analysis by HPLC-ICP-MS with limited bias between the set of data from both vii methods. Optimisation of extraction methods using a subset of samples gave 80-95% iAs recovery with no contribution from the organoarsenicals present in the samples. The determination of total As metabolites in urine from the exposure to iAs could not be done directly using the FTK. In this case, the method involved the use of UV photolysis with persulphate and titanium dioxide as oxidizing agents for the conversion of methylated As species (DMA) to the inorganic form before analysis with the FTK. A partial determination of DMA with the FTK in urine matrix was demonstrated but this needs to be studied further for the development of a robust field method for monitoring human exposure to iAs.