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1
Rosner, Mitchell Harris. "ARSENIC METABOLITE ANALYSIS AFTER GALLIUM-ARSENIDE AND ARSENIC OXIDE ADMINISTRATION (DISTRIBUTION, EXCRETION, SOLUBILITY, HAMSTER)". Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275409.
Testo completo
2
Roberge, Jason Linscot. "Binational Arsenic Exposure Survey: Modeling Arsenic and Selenium Intake on Urinary Arsenic Biomarkers". Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/255165.
Testo completoAbstract (sommario):
Introduction: It has been reported that the principal source of exposure for humans to inorganic arsenic (As) comes from drinking water. It is known that selenium (Se) competes with the reductive metabolism and methylation of As and Se compete for the availability of glutathione. The overarching goal of this dissertation research is to assess relationships between arsenic intake from water and other fluids with urinary arsenic output and then to assess how urinary arsenic output is modified by selenium exposure. Methods: Households in the Binational Arsenic Exposure Survey (BAsES) were selected for their varying groundwater arsenic concentrations. A first morning urine void and water samples from all household drinking sources were collected for As quantification. Relationships were examined between various urinary arsenic biomarkers and estimated arsenic exposures. The association between urinary arsenic biomarkers and dietary intake and urinary output of selenium was also evaluated. Results: Arizonans reported consuming 18.5 mL/kg-day of water and 34.3 mL/kg-day from all fluids. In contrast, participants from Mexico reported 3.5 mL/kg-day of water and 12.3 mL/kg-day from all fluids. Median urinary inorganic As concentration among Arizona participants (ranging from 1.2 to 2.0 µg/L) was lower than among participants from Mexico (range 2.5 to 6.2 µg/L). Estimated arsenic intake from drinking water was associated with urinary total arsenic concentration (p<0.001), urinary inorganic arsenic concentration (p<0.001), and urinary sum of species (p<0.001). Urinary arsenic concentrations increased between 7% and 12% for each one percent increase in arsenic consumed from drinking water. No statistically significant relationships were seen between urinary methylated arsenic biomarkers with either dietary intake of selenium or the urinary selenium concentration. Conclusion: Water was the primary contributor to total fluid intake among Arizonans while Mexico participants primarily consumed carbonated beverages. Arsenic intake from water was significantly associated with urinary arsenic output; however, the concentration of arsenic consumed explained a small fraction of urinary arsenic levels. While selenium can biologically interact with arsenic in the liver, no relationship between urinary arsenic biomarkers were identified with either dietary intake of selenium or urinary output of selenium.
3
Sadee, Bashdar. "Total arsenic and arsenic speciation in indigenous food stuffs". Thesis, University of Plymouth, 2016. http://hdl.handle.net/10026.1/4583.
Testo completoAbstract (sommario):
The properties of an element are highly dependent on its chemical form, it’s called elemental speciation. This study evaluates the arsenic species found in a range of food stuffs together with growing environments and toxicity issues. Total arsenic concentrations in fish tissue and vegetable crops were determined by ICP-MS following microwave-assisted acid digestion using nitric acid/hydrogen peroxide, trypsin and cellulase enzymatic extraction procedures. The extracted arsenic species were then quantified using HPLC-ICP-MS. A dilute nitric acid (1 % (v/v)) digestion procedure was also used to extract arsenic species from rice and the different parts (root, skin, stem, leaf and grain) of a range of plant crops. The study was extended to include the aqua-regia extractable arsenic content of the soils collected from the area where the plants had been cultivated in the Kurdistan region of Iraq. Irrigation water was also investigated, but found to contain low levels of arsenic. An anion-exchange HPLC-ICP-MS method was developed, using sulphate and phosphate, for the separation and quantification of AsB, MMA, DMA, InAsIII and InAsV. The results obtained for fish samples were in the range of 3.53-98.80 µg g-1 (dry weight) with non-toxic AsB being the predominant species. The InAsV concentration was in the range of 0.1-1.19 µg g-1 for all fish species except for the John Dory which was below the limit of detection (0.027 µg g-1). Total arsenic, arsenic species, and total multi-elements (including Ag, Al, B, Ba, Be, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Se, Si, Ti, V and Zn) were determined in rice samples from Kurdistan, Iraq and other regions of geographical origin. The transport of arsenic from the soil and irrigation water into roots, stem, leaf and subsequently into the grain or bean of the plants is important when assessing the potential health risks from food crops. For the soil sample, InAsV was found to be the major species with smaller quantities of InAsIII . After applying a full BCR sequential extraction procedure to the soils, it was found that 7.87 - 21.14 % of the total arsenic was present in an easily acid-soluble extractable form. Finally, a novel method was developed to measure total arsenic and arsenic species associated with vegetative DNA. In rice plant, it was found that InAsV incorporated within the DNA molecule in which it could replace phosphate. It was also found that the concentration of InAsV associated with DNA molecule decreased with decreasing total arsenic in the rice plant from the root to the leaf.
4
Whitacre, Shane D. "Soil Controls on Arsenic Bioaccessibility: Arsenic Fractions and Soil Properties". The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1244036619.
Testo completo
5
Whitacre, Shane Dever. "Soil controls on arsenic bioaccessibility arsenic fractions and soil properties /". Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1244036619.
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6
Sun, Wenjie. "Microbial Oxidation of Arsenite in Anoxic Environments: Impacts on Arsenic Mobility". Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/194899.
Testo completoAbstract (sommario):
AbstractArsenic (As) contamination of groundwater and surface water is a worldwide problem. Exposure to arsenic in drinking water is an important current public health issue. Arsenic is well known for its carcinogenic and teratogenic effects. The U.S. Environmental Protection Agency (USEPA) has recently enacted a stricter drinking water standard for arsenic that lowers the maximum contaminant level (MCL) from 50 to 10 ug l-1.Localized elevated As concentrations in groundwater or surface water have been attributed to the natural release of As from the weathering of As bearing minerals. Microbial reduction of arsenate (As(V)) to arsenite (As(III)) and ferric (hydr)oxides to Fe(II) is hypothesized to be the dominant mechanisms of As mobilization in subsurface environments. If oxidizing conditions can be restored, As can be immobilized by the formation of As(V) and ferric (hydr)oxides. As(V) is more strongly adsorbed than As(III) at circumneutral conditions by common non-iron metal oxides in sediments such as those of aluminum. Ferric (hydr)oxides have strong affinity for both As(III) and As(V) in circumneutral environments. Oxygen can be introduced into the anaerobic zone by injection of gaseous O2 to promote oxidation reactions of As(III) and Fe(II), but O2 is poorly soluble and chemically reactive and thus difficult to distribute in the subsurface. Nitrate or chlorate can be considered as alternative oxidants with advantages over elemental oxygen due to their high aqueous solubility and lower chemical reactivity which together enable them to be better dispersed in the saturated subsurface.The objective of this study is to evaluate the importance of anoxic oxidation of As(III) to As(V) by anaerobic microorganisms such as chemolithotrophic denitrifying bacteria and chlorate respiring bacteria in the biogeochemical cycle of arsenic. This study also investigated a arsenic potential bioremediation strategy based on injecting nitrate or chlorate into contaminated groundwater and surface water under anaerobic conditions.In this study, denitrification or chlorate reduction linked to the oxidation of As(III) to As(V) was shown to be a widespread microbial activity in anaerobic sludge and sediment samples that were not previously exposed to arsenic contamination. The biological oxidation of As(III) utilizing nitrate or chlorate as sole electron acceptor was feasible and stable over prolonged periods of operation in continuous-flow anaerobic bioreactors. Evidence for the complete denitrification was demonstrated by direct measurement of N2 formation dependent on As(III) addition. Also complete chlorate reduction to chloride was attributable to the oxidation of As(III). A 16S rRNA gene clone library characterization of enrichment cultures indicated that the predominant phylotypes responsible for As(III) oxidation linked to denitrification were from the genus Azoarcus and the family Comamonadaceae. A bioremediation strategy was explored that is based on injecting nitrate to support the microbial oxidation of Fe(II) and As(III) in the subsurface as a means to immobilize arsenic. Two models were utilized to illustrate the mechanisms of As removal.1) Sediment columns packed with activated alumina were utilized to demonstrate the role of nitrate in supporting microbial As(III) oxidation and arsenic mobility in anoxic sediments containing mostly non-iron oxides;2) Sand-packed columns were used to simulate natural anaerobic groundwater and sediment systems with co-occurring As(III) and Fe(II) in the presence or absence of nitrate. Microbial oxidation by denitrifying microorganisms lead to the formation of ferric (hydroxides) which adsorbed As(V) formed from As(III)-oxidation.The studies presented here demonstrate that anoxic microbial oxidation of As(III) and Fe(II) linked to denitrification significantly enhance the immobilization of As in the anaerobic subsurface environments.
7
Senn, David B. (David Bryan) 1970. "Coupled arsenic, iron, and nitrogen cycling in arsenic-contaminated Upper Mystic Lake". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8750.
Testo completoAbstract (sommario):
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2001.Includes bibliographical references (p. 253-265).
This dissertation addresses the mechanisms controlling arsenic (As) remobilization and cycling in the hypolimnion of As-contaminated Upper Mystic Lake (UML; Winchester, MA). We conducted field and laboratory studies, and applied mass balance, surface complexation, and thermodynamic modeling to explore As cycling and its links to other elemental cycles (Fe, N, 02) in UML. Nitrate appears to control iron (Fe) and As cycling in the hypolimion of urban, eutrophic UML. In doing so, nitrate assumes the role typically taken by oxygen in the cycling of redoxactive metal(loid)s. High nitrate and ammonium inputs, combined with authigenic nitrate production in the water column (nitrification, consuming 40% of hypolimnetic oxygen), result in several months per year of anoxic, yet nitrate-rich conditions in the hypolimnion. As expected, the onset of anoxia triggers Fe and As remobilization from UML's contaminated sediments. However, despite anoxia, remobilized Fe and As accumulate in the water column primarily in their oxidized forms (Fe(IlI)-oxides and As(V)). Mass balance estimates indicate that nitrate is responsible for oxidizing the majority of the iron, which must initially have been remobilized by reductive dissolution as Fe(II). Microcosm studies confirmed this reaction's feasibility: anaerobic, biologically mediated Fe(II) oxidation occurred in nitrate-spiked microcosms with sample obtained from the sediment-water interface. Shifts in As and Fe redox chemistry toward their reduced forms (Fe(II) and As(III)) were correlated temporally and spatially with nitrate depletion. Nitrate's presence therefore appears to favor arsenic's accumulation as particle-reactive As(V) , either by directly oxidizing remobilized As(III) or indirectly by serving as a more energy-rich electron acceptor and forestalling As(V) reduction to As(III). During nitrate-rich periods, greater than 85% of remobilized arsenic was found to be particle complexed (deff > 0.05 [mu]m) at representative hypolimnetic depths by in situ filtration. Surface complexation modeling of As on Fe(III)-oxides accurately predicts As distribution between particle-complexed and dissolved phases. Thus Fe(III)-oxides appear to scavenge the vast majority of remobilized As. Through the anaerobic production of particulate Fe(III)-oxides, and by indirectly or directly causing As to accumulate as particle-reactive As(V), nitrate dominates remobilized As chemistry, and provides a continued As sink (via settling) during a large portion of anoxic periods.
by David B. Senn.
Ph.D.
8
Castlehouse, Hayley. "The Biogeochemical controls on arsenic mobilisation in a geogenic arsenic rich soil". Thesis, University of Sheffield, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515417.
Testo completo
9
Valentine, Vecorena Rominna E. "Arsenic Analysis: Comparative Arsenic Groundwater Concentration in Relation to Soil and Vegetation". CSUSB ScholarWorks, 2016. https://scholarworks.lib.csusb.edu/etd/279.
Testo completoAbstract (sommario):
Arsenic (As) is a toxic semi-metallic element found in groundwater, soils, and plants. Natural and anthropogenic sources contribute to the distribution of arsenic in the environment. Arsenic’s toxic and mobile behavior is associated with its speciation ability. There are two types of arsenic available to the environment, inorganic and organic arsenic. Of the two, inorganic arsenic is more toxic to humans and more mobile in the environment. Two inorganic compounds responsible for arsenic contamination are trivalent arsenite, As (III), and pentavalent arsenate, As (V). Trivalent arsenate is considered to be more soluble, toxic, and mobile than pentavalent arsenate. Arsenic’s absorptive properties in plant cells and ability to attach to minerals causing secondary contamination are due to environmental factors such as pH, redox potential, and solubility.
The current maximum contaminant level for arsenic in water is 10 µg/L (or ppb). Research on arsenic involving high concentrations already present in groundwater (>300ppb) are compared either with crops irrigated with such water or a human indicator (such as; hair, nails, blood, or urine) in order to determine exposure limits. In this current research, relationships between the area in the studies and the contaminated media (water, soil, vegetation) were tested to determine if arsenic in water was correlated with arsenic concentrations present in soil and vegetation. Commercially obtained ITS Quick Rapid Arsenic Test Kits were used to measure arsenic concentrations for the media tested. A method for analysis of arsenic in vegetation was developed, with an estimated 80% recovery. The pH and conductivity were also taken for water and soil samples as a means of correlative comparison. The development of faster and portable methods for arsenic concentration may provide means for predicting the relationship between all contaminated media. The purpose of the study was to determine the correlation between arsenic water concentration and pH for water, soil, or vegetation and whether it plays an overall role in the amount of arsenic present. As a result, water and soil pH played a significant role in the presence of arsenic in the water and vegetation, respectively. A moderate negative correlation between arsenic in water and water pH was discovered to have a Spearman’s rho value of -0.708 with a p ≤ 0.05. In addition, a significant negative correlation between soil pH and arsenic in vegetation was also discovered to have a Spearman’s rho of -0.628 at a p ≤ 0.05. Even though, pH was significantly correlated with arsenic concentrations in different media, there is evidence that pH plays a role also in the amount of arsenic available in the soil and vegetation. Further studies are recommended.
10
Ouypornkochagorn, Sairoong. "Uptake and biotransformation of arsenic species in various biological forms". Available from the University of Aberdeen Library and Historic Collections Digital Resources. Restricted: contains 3rd party material and therfore cannot be made available electronically, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=65766.
Testo completoAbstract (sommario):
Thesis (Ph.D.)--Aberdeen University, 2009.With: Monitoring the arsenic and iodine exposure of seaweed-eating North Ronaldsay sheep from the gestational and sucking periods to adulthood by using horns as a dietary archive / Guilhem Caumette ... et al. Environmental Science and technology 2007: 41, 8, 2673-2679. Includes bibliographical references.
11
Jeong, Yeong Nam. "Arsenic toxicity in PLHC-1 cell line and the distrbution [sic] of arsenic in central Appalachia". Huntington, WV : [Marshall University Libraries], 2007. http://www.marshall.edu/etd/descript.asp?ref=776.
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Branch, Simon. "Arsenic speciation in food". Thesis, University of Plymouth, 1990. http://hdl.handle.net/10026.1/2138.
Testo completoAbstract (sommario):
A high performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) method has been developed for the separation and quantification of ~g kg-1 levels of arsenobetaine, monomethylarsonic acid (MMAA), dimethylarsinic acid (DMAA) , arsenite and arsenate. Using this coupling, arsenic species in fruit and vegetables grown on soils containing up to 1.4% w\w arsenic have been surveyed and DMAA, MMAA, arsenite and arsenate identified in the plants. Although extraction efficiencies were poor, typically 10%, total arsenic determinations demonstrated that arsenic uptake by the plants was low, with the highest arsenic level being 60-70 mg kg-1 dry weight in unpeeled potato. Provided the plants are washed thoroughly they pose no dietary risk. Using the same HPLC-ICP-MS coupling non-toxic arsenobetaine was identified as the major arsenic species in cod, dab, haddock, lemon sole, mackerel, plaice and whiting. Levels ranged between 1.0 mg kg-1 dry weight in the mackerel, to 187 mg kg-1 in the plaice. Mackerel also contained DMAA and possibly a lipid bound arsenic species. No degradation of arsenobetaine to more toxic species was observed when an enzymatic digestion procedure, based on the action of trypsin, was applied to fish except in the case of one of the plaice specimens for which DMAA was characterised in the digest at the mg kg-1 level. Ten volunteers participated in a dietary trial in which they were given set conventional meals. The main source of arsenic was fish and the predominant species was arsenobetaine. All of the arsenic, as arsenobetaine, was excreted in the urine within 72 hours of consumption. Urinary levels of MMAA, DMAA and inorganic arsenic were all below 10 µg. For total arsenic determination in the urine nitrogen introduction ICP-MS was used to overcome the polyatomic ion 40Ar 35Cl+. This method gave good agreement between observed and certified values for a range of reference materials.
13
Reutter, Sophia. "Arsenic in the Sugar". Wittenberg University Honors Theses / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=wuhonors1617962150790269.
Testo completo
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Ali, Waqar. "Arsenic transport in plants". Thesis, University of York, 2012. http://etheses.whiterose.ac.uk/2817/.
Testo completoAbstract (sommario):
Arsenic (As), a metalloid occurring ubiquitously in nature in organic and inorganic forms, is classified as a potent carcinogen. Among the inorganic forms which are more toxic, AsIII has a high affinity to bind with sulfhydryl groups of the amino acid cysteine, affecting many key metabolic processes such as fatty acid metabolism and glutathione production. AsV is a phosphate analogue and can substitute the inorganic phosphate affecting nucleotide synthesis and energy homeostasis of the cell. Much of the research on As in plants focuses on rice as it is the major source of dietary As intake and is often grown in areas with aquifers containing high amounts of As which are prevalent in south east Asian countries. Currently there is a great need to understand how plants deal with As, both from the perspective as potential sources of dietary As but also as potential mechanisms for phytoremediation. We are therefore using various approaches to identify and characterise plant membrane proteins involved in transport of As. NIPs (nodulin like intrinsic proteins) are a subgroup of plant aquaporins reported to be involved in bidirectional transport of AsIII. Loss of function mutants in Arabidopsis NIPs (nip5;1, nip6;1 and nip7;1) were identified and analysed for their role in As uptake, efflux and translocation. The data showed that nip5;1 and nip6;1 may be involved in the efflux of As. The data for total As concentration in root and shoot tissues showed that among these mutants only nip6;1 has a higher fraction of total As in the shoots compared to wild type. Lower efflux and more translocation suggest that this isoform (nip6;1) may be involved in vacuolar sequestration of As. Interestingly, nip7;1 showed a higher efflux of AsIII compared to other mutants and wild type. This suggests that NIP7;1 might have a role in the vacuolar sequestration or translocation because the loss of function resulted in more cytosolic AsIII due to lower sequestration or translocation, which made more AsIII available for the efflux. The Saccharomyces cerevisiae gene ACR3 is involved in AsIII efflux from the cytosol. We have transformed it into Arabidopsis and rice to assess if this can improve plant As tolerance. The results showed that expression of ACR3 affects plant growth. It appears that both in Arabidopsis and rice ACR3 may be involved in the efflux and translocation of As, as was shown by the results at the cellular, seedling and mature plant levels. ACR3 expression could be a potential means for phytoremediation of As in Arabidopsis because it increases As translocation to shoot tissue. In addition, yeast was used as a heterologous expression system to screen cDNA libraries from rice (Oryza sativa) and Arabidopsis thaliana using the yeast strains (ycf1∆ and acr3∆) to identify (new) transporters that are involved in As transport in plants. No growth tolerant/sensitive phenotype was observed in any yeast strain with both expression libraries suggesting the absence of putative new transporters/proteins involved in As transport. The information obtained from this study can be used in future research. ACR3-like genes involved in As tolerance from other organisms can be potentially useful in plants. Based on the results from NIPs, the isoforms involved in As efflux (nip5;1 and nip6;1) can be used to generate double knock out mutants to see if these have an additive/synergistic effect on As transport that will add to the knowledge of As transport in planta.
15
Schalau, Jeff. "Arsenic in Drinking Water". College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2005. http://hdl.handle.net/10150/147004.
Testo completoAbstract (sommario):
2 pp.Arsenic is the twentieth most abundant element in the earth's crust and frequently occurs in rock formations of the Southwestern United States. Arsenic remains in the environment over long periods and when it occurs in high concentrations, it can be toxic to many life forms, but it also has been shown to be an essential nutrient for many animal species and may be to humans, too. This publication provides information about the impact arsenic in drinking water has over human and plant health and the ways to remove it.
16
Healy, Sheila Marie. "Arsenic methylation in perspective". Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/289727.
Testo completoAbstract (sommario):
The following arsenite methyltransferase activities (U/mg) were measured in untreated mice: liver, 1.42 ± 0.17 (mean ± SEM); kidney, 0.62 ± 0.18; lung, 0.33 ± 0.08; testis, 1.21 ± 0.01. Arsenite methyltransferase metabolites were not detectable using guinea pig liver, kidney, lung or testis cytosol as the source of enzyme. A twofold increase in liver arsenite methyltransferase activity was observed in mice exposed to 28.6 mg sodium arsenite/L drinking water after 24 hr compared to control. Trivalent arsenic species were separated from pentavalent arsenicals in liver homogenates of hamsters injected 15 hr priorly with [⁷³As]arsenate by (CCl₄)-20 mM (DDDC) extraction and both phases analyzed by HPLC. Metabolites of inorganic arsenate were observed in the following concentrations (ng/g liver ± SEM); MMAᴵᴵᴵ, 38.5 ± 2.9; DMAᴵᴵᴵ, 49.9 ± 10.2; arsenite, 35.5 ± 3.0; arsenate, 118.2 ± 8.7; MMAᵛ, 31.4 ± 2.8; and DMAᵛ, 83.5 ± 6.7. Neither in vitro nor in vivo arsenite methyltransferase activity could be detected in S. cerevisiae . Attempting to induce enzyme activity, yeast were grown in 0-100 mM, 8 μCi [⁷³As]Na₂HAsO₄. No methylated metabolites were detected in cell lysate or media under these experimental conditions. The dissociation constants for guinea pig and rabbit cytosolic arsenite binding proteins were determined to be 59.62 ± 11.97 and 120.4 μM Asᴵᴵᴵ, respectively, and the respective specificities, 53.83 ± 3.67% and 59%. Guinea pig arsenite binding protein was fractionated using bioaffinity and size exclusion chromatography to yield partially purified protein(s) with an approximate molecular weight of 115 kDa. Arsenite methyltransferase activity was purified >7000-fold from rabbit liver and identified as 1 cys peroxiredoxin, a conserved family of antioxidant proteins characterized by non-selenium dependent glutathione peroxidase and calcium-independent phospholipase A2 activities. Murine 1 cys peroxiredoxin was cloned and expressed in E. coli and S. cerevisiae and expressed in reticulocyte lysate. Recombinant proteins had neither arsenite methyltransferase nor glutathione peroxidase activities. Antibodies directed against 1-cys peroxiredoxin immunoprecipitated a ∼29 kDa protein from guinea pig kidney cytosol which was identified as 1-cys peroxiredoxin by LC-MS/MS. Under these experimental conditions, guinea pig kidney cytosol did not catalyze the reduction of peroxides
17
Sánez, Juan. "Arsenic geochemistry and its impact in public health: the Bangladesh case". Revista de Química, 2012. http://repositorio.pucp.edu.pe/index/handle/123456789/99099.
Testo completoAbstract (sommario):
Considered the king of poisons, arsenic occurs naturally in the environment being present in air, soil, water and food. Its presence in drinking water is of global concern. Initial chronic exposure is manifested by skin lesions. Additionally, arsenic consumption impairs certain visceral organs: bladder, liver, prostate, etc. More over, arsenic is a recognized carcinogenic substance.When in Bangladesh started the program to lead safe drinking water in the 60’s, they never imagined the catastrophic consequences. Water wells were drilled in the whole country. The arsenic problem was recognized recently in the 90’s. In order to understand the nature of arsenic in the environment and how it could possibly reach groundwater in Bangladesh, this work explains some chemical characteristics of arsenic, the geological formation of the basin, and its mobility.The origin of arsenic contamination in the Bangladesh Delta is due to the geologic nature of the basin rather than the possibility of an arsenic rich mineral. The profile of sediments shows that the Delta is not homogeneous, but rather heterogeneous even in closer areas. The driving process for arsenic mobility is mainly the reduction by iron oxyhydroxides coupled with organic matter, including other factors such as particle size, depth, morphology, metal content, as well
18
Simeonova, Diliana Dancheva. "Arsenic oxidation of Cenibacterium arsenoxidans : Potential application in bioremediation of arsenic contaminated water". Université Louis Pasteur (Strasbourg) (1971-2008), 2004. https://publication-theses.unistra.fr/public/theses_doctorat/2004/SIMEONOVA_Diliana_Dancheva_2004.pdf.
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Guzman, Grijalva Hector Manuel. "Arsenic Leaching from Mineral Sorbents under Landfill Conditions and Arsenic Transport by Wind". Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/347223.
Testo completoAbstract (sommario):
The capacity of four mineral sorbents to retain arsenic under simulated mature landfill conditions was tested using semi-batch and continuous flow columns. The sorbents tested were Fe-, Ti-, La-, and Zr- based oxi(hydroxides). The Fe sorbent was included as a positive control to compare the release of As from a substrate subject to reduction to those of the, non-sensitive to reduction under typical mature landfill conditions, Ti, La, and Zr media. It has been proved that under mature landfill conditions, As(V) preloaded on ferric sorbents is prompt to be released at high levels. Our results indicate that Ti, La, and Zr sorbents can release As at a similar or higher degree than a ferric sorbent. In a second phase, the capacity of the same sorbents to retain As was evaluated after being subject to polymeric encapsulation in an epoxic resin. Landfill conditions were simulated by use of semi-batch column systems packed with compost and fed with actual landfill leachate. Results obtained indicated that encapsulation highly enhanced As retention of the media under simulated landfill conditions. In our research regarding soil contamination by atmospheric transport from mine tailings, a previously developed deposition forecasting model (DFM) that is designed to model the transport of particulate As and Pb from mine tailing impoundments is verified using dust collection and topsoil measurements. The forecast deposition patterns are compared to dust collected by inverted-disc samplers through gravimetric, chemical composition and lead isotopic analysis. The DFM is capable of predicting dust deposition patterns from the tailings impoundment to the surrounding area. Finally, the bioaccessibility of As and Pb were on samples collected at Iron King Mine Tailing was evaluated through chemical extractions using simulated the gastric and the lung fluids of the human body. Results obtained indicate that extractions using simulated gastric fluid lead to As concentrations one order of magnitude higher to those obtained with lung fluid. For Pb concentration the difference was greater than 2 orders of magnitude.
20
Kurzius-Spencer, Margaret. "Modeling the Effects of Dietary Arsenic and Nutrient Intake on Urinary Arsenic Biomarkers". Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/223339.
Testo completoAbstract (sommario):
Background: Arsenic (As) is a naturally-occurring element with known toxicant effects. The primary exposure pathway is through ingestion, but the overall contribution of food versus water and the impact of specific dietary nutrients on urinary As excretion is not well understood. Methods: Secondary analyses of laboratory results from food, water and urine samples, questionnaire and anthropometric data, and dietary records were performed on four study populations: the National Health Exposure Assessment Survey (NHEXAS)-Arizona, Arizona Border Survey (ABS), the Arizona sub-group of the Binational Arsenic Exposure Survey (BAsES), and the 2003-2004 National Health and Nutrition Examination Survey (NHANES). Dietary As intake was measured in duplicate food samples and/or modeled from dietary records for each population using the U.S. Total Diet Study (TDS) arsenic residue database and a published market basket survey. Urinary total As, As⁵, As³, monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) were analyzed, and sum of species As was calculated as the sum of As⁵, As³, MMA and DMA. Regression analyses modeled the relation between urinary As biomarkers (total, sum of species, MMA:sum of species, and DMA:MMA) and dietary As, adjusted for drinking and cooking water As intake, current smoking, sex, age, ethnicity, body mass index, and nutrient intake. Results: Modeled dietary As based on TDS mean As residue data greatly underestimated exposure as compared with measured As in duplicate diet samples and estimates based on other residue data. Dietary As was a significant predictor of urinary total As in all four populations, of sum of species As in both BAsES and NHANES, and of %MMA and DMA:MMA in NHANES. Dietary protein intake was associated with decreased sum of species As in both BAsES and NHANES, but dietary folate was not. Conclusions: Dietary As contributes a markedly greater proportion of total ingested As and is a better predictor of urinary As than water As intake in the U.S. Among subjects who did not consume seafood, total As exposure from food and water exceeded the provisional tolerable daily intake of 2.1 µg/kg body weight/day in 3-15% of these study populations. Increased protein intake may mitigate the effects of As.
21
Pham, Mac Thu Trang. "Données récentes sur la toxicité de l'arsenic : son comportement dans l'environnement et ses effets biologiques chez l'homme". Paris 5, 1990. http://www.theses.fr/1990PA05P179.
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Gonzaga, Maria Isidoria Silva. "Effects of soil and plant on arsenic accumulation by arsenic hyperaccumulator Pteris vittata L". [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013732.
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Van, Wagenen Stanley Keith 1954. "DETERMINATION OF ARSENIC AND THE METABOLITES OF ARSENIC BY KINETICALLY CONTROLLED HYDRIDE GENERATION AND ATOMIZATION". Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/276365.
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Liu, Faye Fang. "Biomarkers for chronic arsenic poisoning /". [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18519.pdf.
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25
Montilla, Alfonso. "Sample treatment for arsenic speciation". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0010/MQ60154.pdf.
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26
Simm, Andrew Oliver. "The electrochemical detection of arsenic". Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.433323.
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27
Sutherland, John David Wightman. "'Hidden' arsenic in estuarine systems". Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326789.
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28
Hunt, Linda Elizabeth. "Dissolved arsenic in natural waters". Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240582.
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29
Aurilio, Anna Clara. "Arsenic in the Aberjona watershed". Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/12937.
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30
Perry, Meghan Rose. "Arsenic, antimony and visceral leishmaniasis". Thesis, University of Dundee, 2014. https://discovery.dundee.ac.uk/en/studentTheses/14edf50b-4943-4ec8-8556-8aaecf3a9f49.
Testo completoAbstract (sommario):
In Bihar state, India, the cure rate of antimonial compounds in the treatment of visceral leishmaniasis (VL) has declined from over 85% to less than 50%. This has been attributed to prolonged, widespread misuse of antimonials within the Indian private healthcare system. An alternative resistance hypothesis is that exposure to arsenic in drinking water in this region has resulted in antimony-resistant Leishmania parasites. Leishmania donovani were serially passaged in mice exposed to environmentally-relevant levels of arsenic in drinking water. Arsenic accumulation in organs of these mice was proportional to exposure. After five passages, isolated parasites were refractory to SbV in drug sensitivity assays. Treatment of infected mice with SbV confirmed that these parasites retained resistance in vivo, supporting this hypothesis. A retrospective field study on a cohort of antimony treated VL patients was performed in an arsenic contaminated area of Bihar to evaluate the presence of an increased risk of treatment failure and death in those exposed to arsenic. It demonstrated a significant increased risk of death from VL in arsenic exposed patients but did not indicate a significant relationship between arsenic exposure and antimonial treatment failure. Collectively these data suggest that it is biochemically possible that arsenic contamination may have contributed to the development of antimonial resistance in Bihar although issues of underpower and the retrospective nature of our epidemiological study made it difficult to conclusively demonstrate this. Further research in to the relationships between arsenic exposure and antimonial treatment failure and death in the leishmaniases is warranted.
31
Lindsay, Emma Rebecca. "Improving arsenic tolerance in plants". Thesis, University of York, 2016. http://etheses.whiterose.ac.uk/16397/.
Testo completoAbstract (sommario):
Arsenic is a toxic metalloid contaminating soil and water supplies in many regions worldwide, and its entry into the food chain poses a serious health risk to millions of people. Arsenic is toxic to plants, lowering the rate of photosynthesis and inhibiting growth, resulting in a reduction in crop yields. Therefore, there is a pressing need to improve arsenic tolerance in plants and reduce accumulation of arsenic in crops. To this end, an arsenite efflux transporter from yeast was heterologously expressed in rice plants under the control of tissue specific promoters. Expression in different tissues led to altered arsenic tolerance and tissue distribution, indicating that this is a promising strategy for the future development of arsenic tolerant varieties. The role of NIP aquaporins in arsenic transport and tolerance in the model plant Arabidopsis was explored in Chapter 3. Group II NIPs were identified as relevant targets for engineering arsenic tolerance and reducing seed/grain arsenic accumulation in crops. Further targets for engineering arsenic tolerance were identified from a collection of T- DNA insertion mutants of Arabidopsis using forward and reverse genetic screening approaches. Two of these were further characterised for their role in arsenic tolerance and accumulation.
32
Brown, Martyn A. "Phosphorus and arsenic carbohydrate derivatives". Thesis, University of Aberdeen, 1993. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU552502.
Testo completoAbstract (sommario):
A series of O-diphenylphosphinyl monosaccharide derivatives, e.g. 1,2:5,6-di-O-cyclohexylidene-3-O-diphenyl phosphinyl--D-glucofuranose [60], has been synthesised by reaction of a free hydroxy group in a sugar with Ph_2PCl. C-Diphenylphosphinyl and diphenylarsino derivatives, e.g. methyl 4,6-O-benzylidene-3-deoxy-3-C-diphenylarsino--D-altropyranoside [89], were synthesised via reaction of Ph2PLi or Ph2AsLi with p-tosyl, mesyl, epoxy or carbonyl substituted sugar reagents. Steric factors play a large part in determining the reactivity of the precursor sugars towards the phosphorous or arsenic nucleophilic reagents. Conformations of the arsenic and phosphorus derivatives were assigned from the 13C, 1H and 31P NMR spectra. Analogous phosphinyl and arsino derivatives have the same conformations in solution. Generally, the pyranosides prefer the 4C1 conformation in solution while the furanoses and furanosides prefer a symmetrical twist. Ribofuranosides [52], [67] and [83], prefer the 2T3 conformation as to the mannofuranosides [56], [57], [58], [63] and [64], whereas xylofuranose derivatives [53] and [86] prefer the 3T2. The solid state NMR of [65] and [89] were also obtained and compared with the solution NMR. No major conformational differences were evident. The following alicyclic carbohydrate derivatives were also synthesised - 1,4:3,6-dianhydro-2,5-dideoxy-2,5-bis-C-diphenylarsino-L-iditol [99], 1,4:3,6-dianhydro-5-deoxy-5-C-diphenylarsino-2-O-p-tosyl-L-gulitol [100], 1,4:3,6-dianhydro-2-deoxy-2-C-diphenylarsino-L-iditol [97] and the 2-O- p -tosyl derivative [98] and 1,4:3,6-dianhydro-5-C-diphenyl-phosphinyl-2-O- p -tosyl-L-iditol [81]. Reactions of the carbohydrate derivatives with transition metal hexacarbonyls were also carried out. Methyl 4,6-O-benzylidene-2-deoxy-2-C-diphenylarsino--D-altropyranoside [88] gave a tetracarbonyl complex [114] on reaction with Cr(CO)_6 and two products from W(CO)_6, viz W_2(CO)_8(AsPh_2)_2 [111] and the dimer [W_2(CO)_9(H)L]. - [112]. The bridged dimer W_2(CO)_10(AsPh_2)_2 [113] was obtained from the reactions of the bis-diphenylarsino derivatives of L-iditol [99] and diisopropylidene-D-galactose [82]. The complex [Rh(1,5-cyclooctadiene)L]. &'43 BF_4. - [116] was synthesised on reaction of the chlororhodium dimer [Rh(COD)Cl]_2 with the bis-diphenylarsino-L-iditol derivative [L&'61 99].
33
Ye, Hui. "Arsenic poisoning of nickel catalysts". HKBU Institutional Repository, 1992. http://repository.hkbu.edu.hk/etd_ra/19.
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34
Farrell-Poe, Kitt. "Arsenic in Private Water Wells". College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2010. http://hdl.handle.net/10150/156928.
Testo completoAbstract (sommario):
3 pp.1. Drinking Water Wells; 2. Private Water Well Components; 3. Do Deeper Wells Mean Better Water; 4. Maintaining Your Private Well Water System; 5. Private Well Protection; 6. Well Water Testing and Understanding the Results; 7. Obtaining a Water Sample for Bacterial Analysis; 8. Microorganisms in Private Water Wells; 9. Lead in Private Water Wells; 10. Nitrate in Private Water Wells; 11.Arsenic in Private Water Wells; 12. Matching Drinking Water Quality Problems to Treatment Methods; 13. Commonly Available Home Water Treatment Systems; 14. Hard Water: To Soften or Not to Soften; 15. Shock Chlorination of Private Water Wells
This fact sheet is one in a series of fifteen for private water well owners. The one- to four-page fact sheets will be assembled into a two-pocket folder entitled Private Well Owners Guide. The titles will also be a part of the Changing Rural Landscapes project whose goal is to educate exurban, small acreage residents. The authors have made every effort to align the fact sheets with the proposed Arizona Cooperative Extension booklet An Arizona Well Owners Guide to Water Sources, Quality, Testing, Treatment, and Well Maintenance by Artiola and Uhlman. The private well owner project was funded by both the University of Arizonas Water Sustainability Program-Technology and Research Initiative Fund and the USDA-CSREES Region 9 Water Quality Program.
35
Quemeneur, Marianne Leyval Corinne Jauzein Michel. "Les processus biogéochimiques impliqués dans la mobilité de l'arsenic recherche de bioindicateurs /". S. l. : Nancy 1, 2008. http://www.scd.uhp-nancy.fr/docnum/SCD_T_2008_0088_QUEMENEUR.pdf.
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36
Kertulis-Tartar, Gina Marie. "Arsenic hyperaccumulation by Pteris vittata L. and its potential for phytoremediation of arsenic-contaminated soils". [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0010081.
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37
Lou-Hing, Daniel Edward. "Arsenic in rice : the role of phosphate in sensitivity and the genetics behind shoot arsenic". Thesis, University of Aberdeen, 2010. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=159212.
Testo completoAbstract (sommario):
Rice consumption is responsible for the largest dietary contribution of inorganic arsenic. In addition to the direct human health impact of arsenic, arsenic toxicity impacts on rice yield. Thus two issues must be addressed: rice sensitivity to arsenic and the contribution of rice towards dietary arsenic. The grass Holcus lanatus achieves arsenate tolerance through the constitutive down regulation of phosphate transporters, which facilitate arsenate uptake. To gain a better understanding of mechanisms underlying arsenic sensitivity in rice and determine if phosphate uptake was responsible for differential arsenic sensitivity between two rice cultivars (Azucena and Bala) an experiment was undertaken examining the role of phosphate in rice arsenic sensitivity. Although high phosphate treatments were found to provide protection against both arsenate and arsenite toxicity and the two cultivars were found to respond differently to phosphate induced protection, the mechanism underlying reduced arsenic sensitivity did not appear to be controlled through a reduced phosphate uptake system. Attempts to link lab-based arsenic sensitivity of various rice cultivars to published biomass and tissue arsenic concentrations of rice grown in the field is presented. No consistent trend was identified across field sites although two negative correlations at two different sites were found (grain arsenic concentrations and shoot dry weight plotted against arsenate sensitivity). These data demonstrated the importance environment influence on traits examined. These correlations suggest that breeding for more arsenic resistant rice strains may increase plant yield but inadvertently lead to an increase in grain arsenic. Finally, QTL mapping and genome-wide association mapping were used to identify genomic regions and candidates genes responsible for variations in shoot arsenic concentrations in rice. The purpose of which was to offer a better understanding of the mechanisms responsible for this variation. Unfortunately the QTLs revealed were not reproduced in the association mapping study. A list of potential positional candidate genes are summarised and functional candidates identified and discussed.
38
Cai, Lin, Guanghui Liu, Christopher Rensing e Gejiao Wang. "Genes involved in arsenic transformation and resistance associated with different levels of arsenic-contaminated soils". BioMed Central, 2009. http://hdl.handle.net/10150/610052.
Testo completoAbstract (sommario):
BACKGROUND:Arsenic is known as a toxic metalloid, which primarily exists in inorganic form As(III) and As(V)] and can be transformed by microbial redox processes in the natural environment. As(III) is much more toxic and mobile than As(V), hence microbial arsenic redox transformation has a major impact on arsenic toxicity and mobility which can greatly influence the human health. Our main purpose was to investigate the distribution and diversity of microbial arsenite-resistant species in three different arsenic-contaminated soils, and further study the As(III) resistance levels and related functional genes of these species.RESULTS:A total of 58 arsenite-resistant bacteria were identified from soils with three different arsenic-contaminated levels. Highly arsenite-resistant bacteria (MIC > 20 mM) were only isolated from the highly arsenic-contaminated site and belonged to Acinetobacter, Agrobacterium, Arthrobacter, Comamonas, Rhodococcus, Stenotrophomonas and Pseudomonas. Five arsenite-oxidizing bacteria that belonged to Achromobacter, Agrobacterium and Pseudomonas were identified and displayed a higher average arsenite resistance level than the non-arsenite oxidizers. 5 aoxB genes encoding arsenite oxidase and 51 arsenite transporter genes 18 arsB, 12 ACR3(1) and 21 ACR3(2)] were successfully amplified from these strains using PCR with degenerate primers. The aoxB genes were specific for the arsenite-oxidizing bacteria. Strains containing both an arsenite oxidase gene (aoxB) and an arsenite transporter gene (ACR3 or arsB) displayed a higher average arsenite resistance level than those possessing an arsenite transporter gene only. Horizontal transfer of ACR3(2) and arsB appeared to have occurred in strains that were primarily isolated from the highly arsenic-contaminated soil.CONCLUSION:Soils with long-term arsenic contamination may result in the evolution of highly diverse arsenite-resistant bacteria and such diversity was probably caused in part by horizontal gene transfer events. Bacteria capable of both arsenite oxidation and arsenite efflux mechanisms had an elevated arsenite resistance level.
39
Marchal, Marie. "Etude des biofilms bactériens arsénite-oxydants". Strasbourg, 2010. https://publication-theses.unistra.fr/public/theses_doctorat/2010/MARCHAL_Marie_2010.pdf.
Testo completoAbstract (sommario):
Les biofilms sont des communautés hautement organisées permettant aux cellules de se maintenir dans une niche écologique donnée. Ces structures sont capables de séquestrer des composés toxiques tels que l'arsenic. Des biofilms bactériens présentant en plus une activité d’oxydation de l’arsénite [As(III)] en arséniate [As(V)], qui est une forme moins mobile de l’arsenic, pourraient être avantageusement mis à profit dans un procédé de bioremédiation. Le but de ce travail de thèse était de caractériser les souches du genre Thiomonas, considérées comme particulièrement adaptées pour le traitement d’eaux arséniées, et d’étudier l’impact de l’As(III) sur la formation et le développement de biofilms arsénite-oxydants. La physiologie et la génomique de ces souches ont été étudiées par des analyses de protéomique différentielle et à l’aide de puces CGH (Comparative Genomic Hybridization). Ces approches ont souligné de fortes différences physiologiques entre ces souches phylogénétiquement proches, qui peuvent être expliquées en partie par la grande plasticité de leur génome qui évolue par l’acquisition d’ilots génomiques. L’impact de l’As(III) sur la cinétique de développement des biofilms a ensuite été analysé par microscopie confocale. Cette étude a mis en évidence divers mécanismes induits en présence d’As(III) et contrôlant l'initiation, la maturation et la dispersion des biofilms. Ainsi, l’As(III) retarde la formation du biofilm d’Herminiimonas arsenicoxydans en induisant la mobilité des cellules, alors qu’il favorise le développement d’un biofilm chez Thiomonas sp. CB2 en induisant la synthèse d’exopolysaccharides. Ces travaux soulignent la diversité des réponses adaptatives des souches bactériennes au stress arsénié. A terme, ils devraient faciliter la mise en œuvre d’une stratégie de bioremédiation des eaux arséniées en permettant d’anticiper le comportement de la population bactérienne d’intérêtA biofilm is a highly organized microbial community, allowing the resident cells to persist in a given ecological niche. These structures are able to trap toxic compounds such as arsenic. In addition, bacterial biofilms catalyzing arsenite [As(III)] oxidation into the more easily immobilized form arsenate [As(V)] are also of particular interest for their use in an arsenic bioremediation system. The aim of this work was to characterize strains of the Thiomonas genus, which seem to be well-suited for the treatment of arsenic contaminated waters, and to assess As(III) effects on the formation and development of arsenite oxidizing biofilms. The physiology and genomics of the Thiomonas strains were investigated using differential proteomics analyses and a comparative genomic hybridization (CGH) approach. These studies highlighted strong physiological differences between these closely related strains. These divergences may be explained, at least in part, by a high genome plasticity and the horizontal transfer of genomic islands. As(III) effects on arsenite oxidizing biofilms development were then assessed using confocal microscopy. This approach revealed various As(III) induced mechanisms affecting multiple biofilm developmental steps. Indeed, As(III) induces Herminiimonas arsenicoxydans flagellar motility what delays biofilm formation, whereas in Thiomonas sp. CB2 it promotes biofilm development through the induction of exopolysaccharides synthesis. These results highlight the high diversity existing in the bacterial adaptive responses to arsenic. Moreover, they might be helpful to develop a bioremediation process, allowing the anticipation of the bacterial population behavior
40
Buzinello, Thyalla Copetti. "Padrão de expressão de aquaporinas em plantas de arroz tolerantes e sensíveis ao arsênio". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/180584.
Testo completoAbstract (sommario):
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.
41
Navrátilová, Jana. "Metody speciační analýzy sloučenin arsenu". Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2011. http://www.nusl.cz/ntk/nusl-233337.
Testo completoAbstract (sommario):
Speciační analýza arsenu v různých matricích s využitím HPLC/ICPMS byla předmětem této práce. Toxicita arsenu závisí na oxidačním stavu a formě, ve které je přítomen. Znalost zastoupení specií arsenu je nutná k hodnocení toxicity a biodostupnosti. Obecně, anorganické specie jsou více toxické než organické. V práci byla studována degradace arsenocukrů v mořských řasách za simulovaných přirodních podmínek. Původní arsenocukry byly transformovány na arseničnan a kyselinu dimethylarseničnou. Arsen vstupuje do rostlin z půdy a vody a následně může vstoupit do potravního řetězce. S ohledem na tuto skutečnost byla speciační analýza provedena u vybraných vzorcích rýže, zakoupených v české obchodní síti. Stanovený celkový obsah arsenu se pohyboval v rozmezí 36.06 µg/kg - 218.11 µg/kg a hlavními speciemi byla kyselina dimethylarseničná a anorganický arsen (54-78%). Mořské ryby a tuky obsahují významnou část arsenu ve formě zvané arsenolipidy. Část práce byla zaměřena na analýzu arsenolipidů u máslové ryby (Lepidocybium flavobrunnrum) s celkovým obsahem arsenu 1.8 mg/kg a 22% celkového arsenu bylo vyextrahováno pomocí hexanu, což potvrzuje lipofilni charakter těchto sloučenin. Hlavní specií stanovenou ve vodném extraktu byl arsenobetain, představující 89%.
42
Stuckman, Mengling Yi. "Biotic Arsenic Mobilization in Natural and Anthropogenic Systems from Redox Transformations of Arsenic, Iron and Sulfur". The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1388505419.
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43
Shan, Jilei. "Stabilization of Arsenic in Iron-Rich Residuals by Crystallization to a Stable Phase of Arsenic Mineral". Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/194711.
Testo completoAbstract (sommario):
Many water treatment technologies for arsenic removal that are used today produce arsenic-bearing solid residuals (ABSR), which are disposed in mixed solid waste landfills. It is now well established that many of these residuals will release arsenic into the environment to a much greater extent than predicted by standard regulatory leaching tests and, consequently, require stabilization to ensure benign behaviour after disposal. Conventional waste stabilization technologies, such as cement encapsulation and vitrification, are not suitable for ABSR applications due to their lack of effectiveness or high cost, thus creating a need for a more effective and low-cost treatment technology for ABSR. Arsenic Crystallization Technology (ACT) is a proposed arsenic stabilization method that involves in converting the ABSR into arsenic-bearing minerals that resemble natural materials and have high arsenic capacity, long term stability, and low solubility compared to untreated ABSR. Three arsenic minerals, scorodite, arsenate apatite and ferrous arsenate, have been investigated in this research for their potential application as ACT for ABSR stabilization. Among the three minerals, ferrous arsenate is demonstrated to be the most suitable arsenate mineral for safe arsenic disposal due to its low arsenic solubility and ease of synthesis. An innovative treatment procedure has been developed in this research for stabilization of ABSR to a stable phase of ferrous arsenate using zero-valent iron (ZVI) as the reducing agent. The procedure works at ambient temperature and pressure, and neutral pH. In addition, a modified four-step sequential extraction method has been developed as a means to determine the proportions of various arsenic phases in the stabilized as well as untreated ABSR matrices. This extraction method, as well as traditional leach and solubility tests, show that arsenic stability in the solid phase is dramatically increased after formation of crystalline ferrous arsenate.
44
Lavielle, Patricia. "Dosage de l'arsenic dans les milieux biologiques". Paris 5, 1989. http://www.theses.fr/1989PA05P081.
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45
Parmentier, Marc. "Développement d'un module microbiologique dédié à la modélisation hydrobiogéochimique et applications à la mobilité de l'arsenictitre français". Paris, ENMP, 2006. https://pastel.archives-ouvertes.fr/pastel-00002404.
Testo completoAbstract (sommario):
La géochimie est souvent influencée par l'activité biologique. Des logiciels tels que CHESS et HYTEC modélisent la plupart des processus géochimiques et hydrodynamiques et permettent d'analyser, puis de prédire, l'évolution de systèmes complexes comme les anciens sites miniers. L'objectif est d'étendre ces outils à la prise en compte de l'activité bactérienne. Dans CHESS, la méthode de Newton-Raphson, qui calcule la spéciation géochimique à l'équilibre, a été étendue à la modélisation de systèmes réactionnels composés de cinétiques biologiques (lois de Monod, d'inhibition, thermodynamique). Les autres options de cet outil comme le couplage avec le module de transport (HYTEC) ont été maintenues. L'implémentation du code a été vérifiée par la modélisation de quelques cas tirés de la littérature. L'outil a ensuite été utilisé pour la modélisation d'expériences de dissolution réductives biologiques d'hydroxydes de fer (HFO) riches en As, réalisées au BRGM. La mobilisation non congruente de Fe et As est expliquée par la sorption sur l'HFO et par les réductions biologiques de Fe et As. L'ancien site minier de Carnoulès (Gard, France) a été étudié lors d'expériences, réalisées à l'université de Montpellier, qui retracent l'évolution géochimique de l'eau acide de drainage minier. Leur modélisation prend en compte les oxydations aérobies biologiques de Fe et As et la précipitation d'une phase amorphe de FeIII et d'AsV. Les expériences ont permis de fixer les paramètres thermodynamiques et cinétiques utilisés pour la modélisation à l'échelle du terrain. Au delà de l'étude de l'interface eau-minéral, l'extension des outils CHESS et HYTEC va permettre d'étendre considérablement le champs de leurs applicationsThe geochemistry of natural system as old mine site is influenced by biological activity. Only informatics tools taking into account geochemistry, hydrodynamics and microbiology will be able to analyse, and then predict, this complex system evolution. For about ten years numerical tools, as CHESS and HYTEC, are able to take into account most of the geochemical and hydrodynamical processes present in soil. The goal of this work is to extend this tools to the microbiologic activity. CHESS calculate the geochemical equilibrium speciation using a modified Newton-Raphson process. The same method is extended to the calculation of reactions mechanisms containing biological kinetics. Most of the biological kinetic laws can now be used : Monod law, inhibition law and thermodynamical law. Moreover others options of this tools, like coupling with transport process (HYTEC), are maintained. The implementation of this code is first verified by the modelling of several cases from literature. The code is then used for the calculation of experimental study realized at the BRGM, involving a bacterial consortium responsible of a reductive dissolution of an hydrous ferric oxyde (HFO) enriched by arsenic. The non congruent mobilisation of Fe and As is explained by sorption on HFO and activity of two bacterial metabolism which degrades organic matter and reduced Fe and As. The old site mine of Carnoules (Gard, French) is studied. The experiments, realized at the university of Montpellier, permitted to study the natural biogeochemical evolution of acid mine drainage. The calculation take into account the biologic aerobic oxidation of Fe and As and the precipitation of amorphous Fe-As gel. The kinetic and thermodynamic parameter are the used on a modelling at the field scale. These applications prove the interest of the computational tools in understanding water-mineral interface, in which precipitation-dissolution can be controlled by bacterial population. Moreover, CHESS and HYTEC extension permitted to considerably extend the fields of applications
46
Molénat, Nathalie. "Etude des biotransformations de différentes formes de l'arsenic en traces et ultra traces en présence de certaines souches pures de micro-organismes". Pau, 1999. http://www.theses.fr/1999PAUU3004.
Testo completoAbstract (sommario):
L'arsenic est un polluant fréquemment rencontré dans l'environnement. Son cycle est modifié par des transformations chimiques et biologiques et les différentes espèces arséniées formées sont de toxicités variables. L'objectif principal de ce travail est de mettre en évidence les biotransformations de différentes formes arséniées par des souches pures de micro-organismes. La première partie de ce mémoire est une étude bibliographique décrivant l'arsenic comme un polluant de l'environnement (origines, formes chimiques, répartition, toxicité). Dans une deuxième partie, l'optimisation d'un couplage analytique de spéciation de l'arsenic (génération d'hydrures, piégeage cryogénique, séparation chromatographique, détection par spectrométrie d'absorption atomique) est décrite. Il permet une analyse fiable et reproductible des formes minérales (AIII, ASV) et des formes méthylées (acide monométhylarsonique, acide diméthylarsinique, oxyde de triméthylarsine) avec des limites de détection comprises entre 3 et 11 Ng. L/1. De nombreux échantillons naturels (eaux, lixiviats de sols) ont également été analysés. La dernière partie de ce travail concerne l'étude des biotransformations de l'arsenic par les micro-organismes. Six champignons et cinq levures ont été cultivés en présence de 200 Ng. Ml/1 d'arsenic, sous différentes formes. Le champignon scopulariopsis brevicaulis est capable de méthyler ASIII, ASV, MMAA et DMAA en TMAO. L'effet de différents paramètres (Ph, concentration en phosphate, en arsenic) a été mis en évidence sur la méthylation. Un modèle de mécanisme pour transformer ASV en TMAO est proposé. Toutes les autres souches pures étudiées réduisent ASV en ASIII. Seulement deux champignons (aspergillus ochraceus, aspergillus fumigatus) methylent uniquement le MMAA en DMAA et TMAO. Ces résultats témoignent d'une spécificité de la methylation vis à vis de chaque souche et de chaque forme arséniée. Différents processus, probablement enzymatiques interviennent dans ces méthylations.
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Davis, Jacob. "Arsenic in Arizona: Assessing the Economic Cost and Hydrogeologic Feasibility of Nontreatment Options". Thesis, The University of Arizona, 2005. http://hdl.handle.net/10150/193305.
Testo completoAbstract (sommario):
The United States Environmental Protection Agency recently issued a new MaximumContaminant Level (MCL) for arsenic in drinking water. The new MCL lowers theacceptable level of arsenic in drinking water from 50 parts per billion to 10 parts perbillion. Treatment technologies for arsenic removal are expensive to operate.Nontreatment options pose an alternative to treatment. Nontreatment is allowed undergovernment regulation. However, such options are limited by local hydrogeologicconditions. Many areas in Arizona have favorable conditions. Estimates for the capitalcosts for several nontreatment options were collected through surveys. In a comparison ofthe capital costs of nontreatment options to treatment, nontreatment was less than half thecost of treatment. Operating costs for nontreatment are also expected to be several timessmaller than for treatment. A comparison using annualized costs shows that nontreatmentcosts less than one fifth of treatment.
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Duncan, Elizabeth Gunn. "Arsenic remediation using nanocrystalline titanium dioxide". Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=53330.
Testo completo
49
Bergqvist, Claes. "Arsenic accumulation in various plant types". Licentiate thesis, Stockholms universitet, Botaniska institutionen, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-64142.
Testo completo
50
Pillai, Jitesh Kannan. "Mechanisms of Arsenic Detoxification and Resistance". FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1699.
Testo completoAbstract (sommario):
Arsenic is a ubiquitous environmental toxic substance. As a consequence of continual exposure to arsenic, nearly every organism, from Escherichia coli to humans have evolved arsenic detoxification pathways. One of the pathways is extrusion of arsenic from inside the cells, thereby conferring resistance. The R773 arsRDABC operon in E. coli encodes an ArsAB efflux pump that confers resistance to arsenite. ArsA is the catalytic subunit of the pump, while ArsB forms the oxyanion conducting pathway. ArsD is an arsenite metallochaperone that binds arsenite and transfers it to ArsA. The interaction of ArsA and ArsD allows for resistance to As(III) at environmental concentrations.
The interaction between ArsA ATPase and ArsD metallochaperone was examined. A quadruple mutant in the arsD gene encoding a K2A/K37A/K62A/K104A ArsD is unable to interact with ArsA. An error-prone mutagenesis approach was used to generate random mutations in the arsA gene that restored interaction with the quadruple arsD mutant in yeast two-hybrid assays. Three such mutants encoding Q56R, F120I and D137V ArsA were able to restore interaction with the quadruple ArsD mutant. Structural models generated by in silico docking suggest that an electrostatic interface favors reversible interaction between ArsA and ArsD. Mutations in ArsA that propagate changes in hydrogen bonding and salt bridges to the ArsA-ArsD interface also affect their interactions.
The second objective was to examine the mechanism of arsenite resistance through methylation and subsequent volatilization. Microbial ArsM (As(III) S-adenosylmethyltransferase) catalyzes the formation of trimethylarsine as the volatile end product. The net result is loss of arsenic from cells. The gene for CrArsM from the eukaryotic green alga Chlamydomonas reinhardtii was chemically synthesized and expressed in E. coli. The purified protein catalyzed the methylation of arsenite into methyl-, dimethyl- and trimethyl products. Synthetic purified CrArsM was crystallized in an unliganded form. Biochemical and biophysical studies conducted on CrArsM sheds new light on the pathways of biomethylation. While in microbes ArsM detoxifies arsenic, the human homolog, hAS3MT, converts inorganic arsenic into more toxic and carcinogenic forms. An understanding of the enzymatic mechanism of ArsM will be critical in deciphering its parallel roles in arsenic detoxification and carcinogenesis.