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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.
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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.
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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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Hersey, Michelle. "Oxidation of Arsenite Via Chelator-mediated Fenton Systems." Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/HerseyMX2006.pdf.
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Radabaugh, Timothy. "Oxidation and reduction of inorganic arsenic in mammalian systems." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/280379.
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Arsenic is a toxic metalloid and is ubiquitous in our environment. In ancient cultures it was valued as a poison and today is becoming an increasing public health problem. Chronic arsenic exposure has a broad range of toxic effects including cancer. Currently millions of people are exposed to higher levels of arsenic in their food and drinking water than is considered safe by the World Health Organization. Although arsenic metabolism is not completely understood, it is known that inorganic arsenate is reduced to arsenite which can then be methylated and excreted in the urine. It is also known that some arsenic is retained in the body, presumably by binding to cellular proteins. To better understand how arsenic is metabolized, our approach was to identify and characterize proteins that are involved in arsenic metabolism. Using biochemical approaches we demonstrated that arsenate reductase activity from human liver was purine nucleoside phosphorylase (PNP). We were able to demonstrate that calf spleen PNP has arsenate reductase activity in vitro in the presence of inosine and dihydrolipoic acid, and that the reaction exhibits Michaelis-Menten kinetics. This identifies an enzymatic route for arsenate reduction. We also demonstrate that ferritin, an iron storage protein containing phosphate, can bind arsenic both in vitro and in vivo. In addition, we demonstrate that ferritin can oxidize arsenite to arsenate, and then interact with arsenate as it does with phosphate. We also establish that arsenate can inhibit ferritin's ability to store iron in vitro. Our results combined with data reported by others, suggest that DNA damage and enzyme inactivation associated with arsenic challenge may occur via reactive oxygen species generated by arsenic-iron redox reactions in ferritin, and that iron may augment arsenic toxicity. The interaction between ferritin and arsenate has two important implications. First, it suggests that iron exposure may be an important parameter to examine in epidemiological studies of arsenic sensitivity. Second, it suggests that iron chelation therapy might be beneficial in conjunction with arsenic chelation therapy for patients suffering from acute arsenic poisoning.
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Walker, Forest P. "Kinetics of Arsenopyrite Oxidative Dissolution by Oxygen." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/9881.
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The objective of this study is to use a mixed flow reactor system to determine the dissolution rate and infer potential mechanisms of arsenopyrite (FeAsS) oxidation by dissolved oxygen at 25°C and circumneutral pH. Release rates for iron, arsenic and sulfur are calculated for a variety of initial dissolved oxygen (DO) concentrations. Results indicate that the rate of arsenopyrite oxidation, represented by the rate law r = A(6.76 x 10-11) where the rate, r, is in mol/s and surface area, A, is in m2, is not significantly dependent on DO concentration. Arsenic and sulfur are released in a 1:1 molar ratio while iron is released more slowly due to precipitation of iron oxyhydroxides. Our results suggest that the rate determining step in arsenopyrite oxidation is determined by the attachment of oxygen at the anodic site in the mineral, and not the transfer of electrons from the cathodic site to oxygen, as is suggested for other sulfide minerals such as pyrite.
Previous work on FeAsS oxidation has been limited to low pH conditions with ferric iron as the oxidant. However, not all arsenopyrite weathering occurs exclusively in acidic environments. For example, at an abandoned arsenopyrite mine in Virginia, the pH of ground and surface waters is consistently between 4 and 7. Results of this study provide important insight to arsenic mobilization processes and rates, at field-relevant conditions, consequently aiding in the effort to understand arsenic release and retention in the environment.Master of Science
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Moore, Kenneth. "Treatment of Arsenic Contaminated Groundwater using Oxidation and Membrane Filtration." Thesis, University of Waterloo, 2005. http://hdl.handle.net/10012/866.
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Arsenic is a known carcinogen, causing cancers of the skin, lungs, bladder and kidney. Current research suggests that drinking water is the most common pathway for long-term low dose exposure. Arsenic contaminated drinking water has caused serious health problems in many countries including: India, Bangladesh, Argentina, Chile, Taiwan, the United States and Canada.
Nanofiltration (NF) is a promising technology for arsenic removal since it requires less energy than traditional reverse osmosis membranes. Several studies have shown that nanofiltration is capable of removing the oxidized form of arsenic [As(V)] while the reduced form of arsenic [As(III)] is poorly removed. To exploit this difference it has been suggested that a pretreatment step which oxidizes the As(III) to As(V) would improve the performance of membrane filtration, but this has never been demonstrated.
The research had three objectives: The first was to investigate the ability of NF membranes to treat arsenic contaminated groundwater and evaluate the influence of the membrane type and operating conditions. Secondly, the effectiveness of a solid phase oxidizing media (MnO2) to oxidize arsenite to arsenate was investigated. Lastly, the MnO2 was combined with NF membrane filtration to determine the benefit, if any, of oxidizing the arsenic prior to membrane filtration.
A pilot membrane system was installed to treat a naturally contaminated groundwater in Virden, Manitoba, Canada. The groundwater in Virden contains between 38 and 44 µg/L of arsenic, primarily made up of As(III), with little particulate arsenic.
In the first experiment three Filmtec® membranes were investigated: NF270, NF90 and XLE. Under all conditions tested the NF90 and NF270 membranes provided insufficient treatment of Virden's groundwater to meet Canada's recommended Interim Maximum Acceptable Concentration (IMAC) of 25 µg/L. The XLE membrane provided better arsenic removal and under the conditions of 25 Lmh flux and 70% recovery produced treated water with a total arsenic concentration of 21 µg/L. The XLE membrane is therefore able to sufficiently treat Virden's ground water. However treatment with the XLE membrane alone is insufficient to meet the USEPA's regulation of 10 µg/L or Canada's proposed Maximum Allowable Concentration (MAC) of 5 µg/L.
The effects of recovery and flux on total arsenic passage are consistent with accepted membrane theory. Increasing the flux increases the flow of pure water through the membrane; decreasing the overall passage of arsenic. Increasing the recovery increases the bulk concentration of arsenic, which leads to higher arsenic passage.
The second experiment investigated the arsenic oxidation capabilities of manganese dioxide (MnO2) and the rate at which the oxidation occurs. The feed water contained primarily As(III), however, when filtered by MnO2 at an Empty Bed Contact Time (EBCT) of only 1 minute, the dominant form of arsenic was the oxidized form [As(V)]. At an EBCT of 2 minutes the oxidation was nearly complete with the majority of the arsenic in the As(V) form. Little arsenic was removed by the MnO2 filter.
The third and final experiment investigated the benefit, if any, to combining the membrane filtration and MnO2 treatment investigated in the first and second experiments. The effect of MnO2 pretreatment was dramatic. In Experiment I, the NF270 and NF90 membranes were unable to remove any arsenic while the XLE removed, at best, approximately 50% of the arsenic. Once pretreated with MnO2 the passage of arsenic through all of the membranes dropped to less than 4 µg/L, corresponding to approximately 91% to 98% removal.
The dramatic improvement in arsenic removal can be attributed to charge. All three membranes are negatively charged. Through a charge exclusion effect the rejection of negatively charged ions is enhanced. During the first experiment, As(III) (which is neutrally charged) was the dominant form of arsenic, and was uninfluenced by the negative charge of the membrane. Once oxidized to As(V), the arsenic had a charge of -2, and was electrostatically repelled by the membrane. This greatly improved the arsenic rejection characteristics of the membrane.
Nanofiltration alone is not a suitable technology to remove arsenic contaminated waters where As(III) is the dominant species. When combined with MnO2 pre-oxidation, the arsenic rejection performance of nanofiltration is dramatically improved.
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Botfield, Andrew Civil & Environmental Engineering Faculty of Engineering UNSW. "Kinetic modelling studies of As(III) oxidation in dark pH 3 and 8 Fenton - mediated and pH 8 Cu(II) - H2O2 systems." Awarded by:University of New South Wales. School of Civil and Environmental Engineering, 2006. http://handle.unsw.edu.au/1959.4/31969.
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In this thesis, a combination of laboratory experimentation under well defined conditions coupled with a kinetic modelling approach is used to verify the existence and respective kinetic rates of previously unconfirmed or postulated mechanisms that drive and limit dark Fenton (Fe(II)/H2O2) - mediated As(III) oxidation at pH 3 and 8 and dark Cu(II) - H2O2 - mediated As(III) oxidation at pH 8. Dark Fenton - mediated oxidation of As(III) at pH 3 is first examined and the effects of the variation in the concentration of reactants (As(III), Fe(II) and H2O2), oxygen, phosphate and organics (2 - propanol, formate, and citrate) are reported and analysed. The kinetic models developed for these systems show high applicability to full scale water treatment application and key mechanistic findings include the significance of the cycling of Fe(II) / Fe(III) via HO2 ???/O2 ??????, the effects of As(IV) termination reactions in the absence of oxygen and the retarding effects of phosphate due to the postulated formation of a Fe(III) - phosphate complex (at a derived rate constant of 2.2 x 106 M-1s-1, that also appears to have negligible kinetic activity in terms of reduction to Fe(II) by HO2 ???/O2 ??????). The work also demonstrates the significance of the free radical by products of formate and citrate oxidation by ???OH (HCOO???/CO2 ?????? and 3HGA???2???). The examination of the dark Cu(II) - H2O2 - mediated oxidation of As(III) at pH 8 with variation in the concentration of reactants (As(III), Fe(II) and H2O2), carbonate and organics (2 - propanol, formate and citrate) demonstrated for the first time the high applicability of this system to the pre - oxidation of As(III) in water treatment and mechanistically that ???OH and CO3 ?????? are the dominant As(III) oxidants in this system. The As(III) oxidant CO3 ??????, is suggested to be generated by the interaction of ???OH and O2 ?????? with the carbonate matrix, at the respective rate constants of 4.9 x 107 M-1s-1 and 5.5 x 106 M-1s-1. Examination of the dark Fenton - mediated oxidation of As(III) at pH 8 and the effects of variation in the concentration of reactants (As(III), Fe(II) and H2O2), carbonate, organics (2 - propanol, formate and citrate) and Cu(II) demonstrates the varied potential mechanistic pathways in relation to the generation of As(III) oxidants from the Fenton reaction, Fe(II) + H2O2 such as Fe(IV) and CO3 ?????? and the previously dismissed ???OH, due to the presence of Fe(II) - citrate complexes. This work also demonstrates and models the enhancement of As(III) oxidation in the presence of an additional transitional metal ion, Cu(II).
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Masur, Deanne Christine. "Microbial and geochemical processes controlling the oxidation and reduction of arsenic in soils." Thesis, Montana State University, 2007. http://etd.lib.montana.edu/etd/2007/masur/MasurD0507.pdf.
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Edvardsson, Matilda. "Geochemical tracing of Arsenic sources in groundwater at the remediated Storliden mine, Skellefte district." Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-82694.
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The Swedish mining industry has changed from the historical situation with several smaller mines to the present situation with a few, bigger mines. This results in presence of abandoned mines around Sweden. Remediation of mines is regulated by legislation and the present demands are considerably higher than it was some decades ago. The Storliden mine was a Zink- and Coppermine active between 2001-2008. Storliden is located in Malå municipality, Västerbotten county, and is included in the Skellefte district, known for its sulfide mineralizations. The ore was broken underground with a technique called cut and fill mining. It was estimated that the ore was to be consumed in 2007, but due to rising ore prices, the mine was operated until 2008. Remediation was done through backfilling the mine with waste rock from Storliden and Boliden’s mines Renström, Kedträsk, and Kankberg. Also, tailings, concrete, and sludge from the sedimentation basins were backfilled. Today, the mine is filled with water. High Arsenic concentrations in water is a serious health issue in parts of the world. Bangladesh is perhaps the most common example where Arsenic in groundwater has caused health problems for millions of people. In Sweden, the Skellefte field is known for its elevated Arsenic concentrations in the bedrock, related to sulfide mineralizations. Studies confirm a correlation between Arsenic-bearing bedrock and elevated concentrations in water. This thesis work has been conducted together with the consultant company Golder Associates (Golder) in Luleå. Golder has performed environmental investigations in the Storliden area during the period 2018-2020. Installation and sampling of groundwater wells were included in this investigation. High concentrations of Arsenic was found in some of the groundwater wells. This thesis aims to review potential sources of Arsenic and their potential significance. The purposes are to be fulfilled by evaluating and interpreting the results from the sampling, Piper diagrams, ratios, and modeling in the program PHREEQC. The results indicate that the presence of Arsenopyrite in the bedrock is the most likely source of the elevated concentrations of Arsenic in deep groundwater. Oxidation of Arsenopyrite is likely caused by mainly dissolved oxygen in groundwater. Further, the water quality differs from different depths, indicating that deep groundwater and water flow from the mine via the ramp do not have any immediate connection. It is likely that remains of tailings on the industrial area cause low pH and leaching of metals locally. High concentrations of Arsenic can occur very locally, highlighting the importance of conducting sampling of groundwater used as drinking water in areas where sulfide mineralizations are confirmed or suspected. Further, a relation between the time that water is in contact with the bedrock/mineralization and the concentration of Arsenic is stated. Higher concentration HCO3- tends to correlate with elevated Arsenic concentration.Sveriges gruvindustri har förändrats i snabb takt, från ett flertal mindre gruvor till dagens läge med ett mindre antal större gruvor. Detta resulterar i förekomst av nedlagda gruvor runt om i Sverige. Efterbehandling av gruvor regleras genom lagstiftning, och kraven idag är betydligt högre än för bara något decennium sedan. Storlidengruvan var en zink- och koppargruva verksam mellan 2001–2008. Storliden ligger i Malå kommun och området ingår i Skelleftefältet, känt för sina sulfidmineraliseringar. Malmen bröts i en underjordsgruva med så kallad igensättningsbrytning, dvs. tomrum har succesivt fyllts ut med material under driften. Malmen beräknades vara förbrukad 2007, men när malmpriset ökade kunde gruvan leva vidare till 2008. Efterbehandlingen innebar att fylla igen gruvan med gråberg från Storliden men också gråberg från Bolidens gruvor Renström, Kedträsk och Kankberg. Dessutom användes anrikningssand, cement och slam från sedimentationsbassängerna för att fylla igen gruvan. Länshållning av gruvan upphörde och idag är gruvan vattenfylld. Höga arsenikhalter i vatten är ett hälsoproblem i delar av världen. Det kanske vanligaste exemplet är Bangladesh, där arsenik i grundvatten har orsakat hälsoproblem för miljontals människor. I Sverige är Skelleftefältet utmärkande för den höga arsenikhalten i berggrunden. Naturlig arsenikhalt i borrade brunnar har undersökts i flera studier som visar ett samband mellan arsenikhaltig berggrund och förhöjda halter i vatten. Examensarbetet har utförts tillsammans med konsultföretaget Golder Associates i Luleå. Golder har fått i uppdrag att utföra miljötekniska undersökningar i Storlidenområdet, bland annat ingick installation och provtagning av grundvattenrör. Denna provtagning skedde under perioden 2018–2020. I några av grundvattenrören påträffades förhöjda halter av arsenik. Detta examensarbete syftar till att utreda förekomsten av Arsenik i grundvattnet, undersöka vilka källor som kan vara orsaken till arsenikhalterna samt källornas förväntade betydelse. Detta har gjorts genom att utvärdera och tolka resultaten från provtagningarna samt användningen av Piper-diagram, geokemiska kvoter och geokemisk modellering i programmet PHREEQC. Resultaten indikerar att förekomst av arsenikkis som mineralisering i berggrunden är den mest troliga källan till de förhöjda halterna av arsenik i djupt grundvatten. Oxidationen av arsenikkis sker troligtvis främst av löst syre i grundvattnet. Vidare skiljer sig vattenkvalitén åt från olika djup och delar av området som provtagits, dvs. det verkar inte finnas någon omedelbar koppling mellan djupt grundvatten och vatten som kommer via rampen som leder till gruvan. Det är troligt att rester av anrikningssand på industriområdet orsakar lågt pH och metallutlakning lokalt. Höga arsenikhalter kan förekomma lokalt, vilket understryker vikten av att utföra provtagning av grundvatten som används för dricksvatten i områden där misstänkt eller konstaterade sulfidmineraliseringar förekommer, eftersom arsenik annars kan vara en mycket skadlig ”diffus” förorening. Vidare konstateras också samband mellan den tid som vatten är i kontakt med mineralisering och arsenikhalt. Högre halt HCO3- tenderar att korrelera med förhöjd arsenikhalt
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Rodríguez-Freire, Lucía. "The Role of Microorganisms in the Biogeochemical Cycle of Arsenic in the Environment." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/333167.
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Arsenic (As) is a highly toxic chemical that is widely distributed in groundwater around the world. As-bearing sulfide minerals (ASM) are known to contribute to high background concentrations of As in groundwater in regions where the geochemistry of the parent material is dominated by sulfide minerals. The fate of As in groundwater depends on the activity of microorganisms which can oxidize arsenite (Asᴵᴵᴵ), or reduce arsenate (Asᵛ). In oxidizing environments, Asᵛ is the predominant species, and the accumulation of As is limited by the sorption of As onto iron (Fe) oxides and hydroxides. Under reducing environments, Asᴵᴵᴵ is the predominant specie, and while the sorption strength of Asᴵᴵᴵ on the Fe-surface of Fe (oxy)hydroxides is weaker, the accumulation of As in water can be limited by the precipitation of As as part of an ASM. The main aim of this research is to study the impact of microbial activity on the mobilization and immobilization of As in the environment. The first objective of this research was to characterize the metabolic activity of three Asᴵᴵᴵ-oxidizing bacteria, Azoarcus sp. pb-1 strain EC1, Azoarcus sp. pb-1 strain EC3 and Diaphorobacter sp. pb-1 strain MC, isolated from a non-contaminated, pristine environment. These Asᴵᴵᴵ-oxidizing bacteria demonstrated a great metabolic flexibility to use oxygen and nitrate to oxidize Asᴵᴵᴵ as well as organic and inorganic substrates as alternative electron donors (e-donors) explains their presence in non-As-contaminated environments. The findings suggest that at least some Asᴵᴵᴵ-oxidizing bacteria are flexible with respect to electron-acceptors and e-donors and that they are potentially widespread in low As concentration environments. The second objective of this research was to investigate the stability of orpiment (As₂S₃) and arsenopyrite (FeAsS), at circumneutral pH and 30°C, under aerobic- and or anoxic conditions (nitrate amended as electron acceptor (e-acceptor)), in order to assess the feasibility of immobilizing As by formation of ASM as a long-term option for the bioremediation of As contamination. The percentage of As released from the minerals ranged from zero when FeAsS was biologically incubated to 87% for As₂S₃(s) under anoxic abiotic conditions. While the dissolution of ASM was greater in biological conditions, the presence of inoculum provided as sludge served as a sink for As, limiting the mobilization of As into aqueous phase. Thus, the mobilization of As from ASM can be controlled by altering the environmental conditions such as the redox conditions or by stimulating microbial activity. Further research investigated the formation of ASM catalyzed by biological reduction of Asᵛ and sulfate (SO₄²⁻). In particular, the third objective of this research was to study the effect of the pH on the removal of As due to the biological-mediated formation of ASM in an iron-poor system. A series of batch experiments were performed to study the reduction of SO₄²⁻ and Asᵛ by an anaerobic mixed culture in a range of pH conditions (6.1-7.2), using ethanol as the e-donor. A marked decrease of the total aqueous concentrations of As and S and the formation of a yellow precipitate was observed in the inoculated treatments amended with ethanol, but not in the non-inoculated controls, indicating that the As-removal was biologically mediated. The pH dramatically affected the extent and rate of As removal, as well as the stoichiometric composition of the precipitate. The precipitate was composed of a mixture of orpiment and realgar, and the proportion of orpiment in the sample increased with increasing pH. The results suggest that ASM formation is greatly enhanced at mildly acidic pH conditions. The fourth objective was to investigate the biomineralization of As through simultaneous Asᵛ and SO₄²⁻ reduction in a minimal iron environment for the As-contaminated groundwater bioremediation. A continuous bioreactor, inoculated with an anaerobic sludge was maintained at circumneutral pH (6.25-6.50) and fed with Asᵛ and SO₄²⁻, utilizing ethanol as an e-donor for over 250 d. A second bioreactor running under the same conditions but lacking SO₄²⁻ was operated as a control to study the fate of As removal. The reactor fed with both Asᵛ and SO₄²⁻ removed on the average 91.2% of the total soluble As, while less than 5% removal was observed in the control bioreactor without S. The biomineralization of As in the bioreactor was also evident from the formation of a yellow precipitate made of a mixture of As₂S₃ and AsS minerals. These results taken as a whole indicate that a bioremediation process relying on the addition of a simple, low-cost e-donor offers potential to promote the removal of As from groundwater by precipitation of ASM. The fifth objective was to evaluate the toxic impact that the exposure to soluble As or the formation of ASM could have on the anaerobic mixed culture used as inocula. The methanogenic community on the reactors was impacted by addition of As. The biogenic ASM inhibited the acetoclastic methanogens causing an accumulation of acetate. In the SO₄²⁻-free bioreactor, the methanogens were initially highly sensitive to Asᴵᴵᴵ (formed from Asᵛ reduction) but quickly adapted to its toxicity. Consequently, the formation of ASM would impact the methanogenic activity of an anaerobic biofilm, while the exposure to Asᴵᴵᴵ would not have a negative impact if the biofilm undergoes adaptation. The sixth and final objective was to study the stability of a biogenic ASM at two different pH values (6.5 and 7.5) and under different redox conditions. The long-term stability was evaluated in three different bioreactors that operated for 145 d: aerobic (R1), anoxic (nitrate as alternative e-acceptor (R2) and anaerobic (R3). The dissolution of ASM was greatly affected by the pH, and slightly by the presence and nature of the e-acceptor. The ASM was very stable at pH 6.5, however, the As mobilization rate was up to 7-fold higher at pH 7.5, likely due to the formation of thioarsenic species. The stability of ASM was also impacted by the e-acceptor present. The As mobilization rate was 77% higher under anaerobic conditions than under aerobic conditions, most likely due to the formation of secondary As-bearing minerals. Therefore, the stability of ASM depends on the conditions of the operation, and it can be controlled by altering the environmental conditions, such as the pH or the presence of the e-acceptor.
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Asta, Andrés María Pilar. "Mobilization and natural attenuation of arsenic in acid mine drainage ( AMD )." Doctoral thesis, Universitat Politècnica de Catalunya, 2009. http://hdl.handle.net/10803/22672.
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L’anomenat drenatge àcid de mina (AMD) ve generat per l’oxidació de sulfurs i és causa major de contaminació d’aigües a nivell mundial. L’arsènic és un del princiapls contaminants laconcentració del qual pot assolir centenars de mgL-1, és a dir, de 5 a 6 ordres de magnitud més gran que el límit de potabilitat per a l’aigua (10μg L-1) establert per la UE en 1998. En aquesta tesi, s’estudia l’impacte de la mobilització de l’arsènic al llarg de descàrregues de drenatge àcid de mina.
L’oxidació de sulfurs que contenen arsènic (tal com l’arsenopirita (AsFeS), la pirita rica en arsènic (FeS2) o la marcassita (FeS2) és una de les principals fonts d’alliberament d’arsènic a l’aigua. En la primera part de la tesi, s’ha estudiat la cinètica de dissolució de l’arsenopirita i de la marcassita a pHs àcids i neutre, utilitzant reactors de flux continu, i s’han valorat els efectes del pH, de l’oxigen dissolt i de la temperatura en la dissolució d’ambdós sulfurs. A partir de les velocitats en estat estacionari establertes, es proposen les respectives lleis de dissolució que tenen en compte el lleu i el fort efecte del pH i de l’oxigen dissolt, respectivament, en llur dissolució. La incorporació d’aquestes lleis cinètiques en les bases de dades del codis geoquímics i de transport reactitu permeten fer prediccions molt més realistes.
L’impacte mediambiental causat per l’arsènic alliberat a les aigües depèn de la seva atenuació natural. El principal procés que controla el destí i la mobilitat de l’arsènic aquós és l’adsorció de l’arsenat en fases de ferro precipitades. Per tant, cal tenir en compte el paper que juga l’estat d’oxidació de l’arsènic. En la segona part de la tesi, shan estudiat tant l’oxidació de l’arsènic com l’adsorció de l’arsènic. L’oxidació s’estudia en condicions abiòtiques i biòtiques a pH i composició típics d’aigües àcides de mina, fent servir experiments de tipus batch. S’hi mostra com en condicions biòtiques tenen lloc simultàniament l’oxidació de Fe(II) a Fe (III) i d’arsenit a arsenat, de manera que mentre els bacteris governen la primera, el contingut de Fe(III) domina la segona. En condicions abiòtiques, l’oxidació d’arsenit a arsenat en presència de Fe(III) és lenta, tot i que augmenta augmentant la presència de Fe(III) i de clorur amb llum de dia.
L’adsorció d’arsènic en llocs d’AMD, i per tant l’atenuació d’arsènic, ocorre mitjançant l’adsorció d’arsenat en precipitats formats per oxi-hidròxids i oxi-hidròxid-sulfats de ferro (principalment schwertmannita (Fe8O8(OH)5.5(SO4)1.25), K-jarosita (KFe3(SO4)2(OH)6) i goetita (FeOOH)). S’han estudiat les capacitats d’adsorció de la jarosita i de la goetita i s’han comparat amb la de la schwertmannita. Amb aquest propòsit es van fer experiments de tipus batch a pH molt àcid i amb mostres sintetitzades de K-jarosita i de goetita. Sense la competència d’altres anions, la capacitat de la jarosita per eliminar arsenat és més alta que la de la goetita. També s’ha vist que la força iònica té un escàs efecte en l’adsorció d’ambdós minerals, però que la presència de sulfat, que és l’anió més abundant en aigües àcides de mina, minva llurs capacitas d’adsorció.
Cal conèixer bé els mecanismes dominants que controlen el contingut d’arsènic en les aigües, no només en condicions de laboratori, sinó també en les condicions de camp. Per tant, en la tercera part de la tesi s’han estudiat el processos d’atenuació de l’arsènic en un sistema natural. Amb aquest objetiu s’han caracterizat exhaustivament l’aigua i els sediments del rieron provinent de la mina abandonada Tinto Santa Rosa, situada a la Faixa Pirítica Ibèrica (IPB). La característica dominant de l’aigua del rierol és un descens del pH aigües avall que va acompanyat d’un decreixement sistemàtic de les concentracions de ferro ferrós i de ferro total, d’arsenit i d’arsenat, així com d’arsènic total. A més a més, els sediments de llit mostren contiguts alts d’arsènic. Els principals mecanismes que dominen el destí i la mobilitat de l’arsènic en aquestes aigües de camp són l’oxidació del ferro i de l’arsènic i la precipitatió de compostos de Fe(III) que adsorbeixen l’arsenat. S’ha proposat un model unidimensional de trasnport reactiu, utilitzant el codi PHREEQC, per explicar i quantificar els processos mencionats que han estat estudiats en condicions de laboratori.Acid mine drainage (AMD) generated by sulfide oxidative dissolution is a major cause of water contamination world-wide. Arsenic is one of the main AMD pollutants whose concentration can reach up to hundreds of mg L-1, i.e. 5-6 orders of magnitude higher than the limit of 10 μg L-1 for potable water established by the European Union in 1998. This thesis is concerned with the impact of arsenic mobilization along AMD discharges. Oxidation of As-bearing sulfides such as arsenopyrite (AsFeS), As-rich pyrite (FeS2) or marcasite (FeS2) is one of the main sources of arsenic release. The first part of this thesis is focused on the dissolution kinetics of arsenopyrite and marcasite at acidic to neutral pH using long term flow-through experiments. The effects of pH, dissolved oxygen and temperature on their dissolution were assessed. The respective dissolution rate laws were proposed on the basis of the steady-state rates, taking into consideration the slight pH effect and the strong dissolved oxygen effect on dissolution. The incorporation of these rate laws into the kinetic databases of geochemical and reactive transport codes allows us to obtain better realistic simulations. The environmental impact of released arsenic into waters depends on its natural attenuation. The arsenic oxidation state is considered given that the main process that controls the fate and mobility of aqueous arsenic is arsenate sorption onto precipitated Fe-phases. The second part of the thesis discusses arsenic oxidation and arsenic sorption. Oxidation was studied by means of batch experiments under abiotic and biotic conditions at typical AMD water pH and water composition. Simultaneous oxidation of Fe(II) to Fe(III) and arsenite to arsenate occurs under biotic conditions, the former mediated by bacteria, and the latter by the presence of Fe(III). Under abiotic conditions, oxidation of arsenite to arsenate in the presence of Fe(III) is slow, but is enhanced by increasing dissolved Fe(III) and chloride concentrations in the presence of light. Arsenic sorption at AMD sites, and hence arsenic attenuation, occurs via arsenate sorption on new iron-oxyhydroxide and iron-oxyhydroxide-sulphate precipitates (mainly, schwertmannite (Fe8O8(OH)5.5(SO4)1.25), jarosite (KFe3(SO4)2(OH)6) and goethite (FeOOH)). The sorption capacity of goethite and jarosite was studied and compared with the one reported for schwertmannite. To this end, batch experiments were conducted using synthetic powders of K-jarosite and goethite at highly acidic pH. In the absence of competitive effects of other anions, K-jarosite presented better removal efficiency for arsenate, and ionic strength and pH had little effect on the sorption capacity of the two minerals. In contrast, these sorption capacities diminished considerably in the presence of sulfate, which is the main anion in AMD waters. A deeper understanding of the dominant mechanisms controlling arsenic content in waters demands the study of the processes not only under laboratory but also under natural conditions. Accordingly, the third part of this thesis deals with the arsenic attenuation processes in a natural system. To this end, the acidic water and sediments of the abandoned Tinto Santa Rosa mine discharge, located in the Iberian Pyritic Belt, were studied. The most striking feature of the water was a pH decrease accompanied by a systematic decrease in ferrous iron, total iron, arsenite, arsenate and total arsenic concentration. Additionally, bed-stream sediments showed high arsenic contents. The main processes that control the fate and mobility of arsenic in waters in the field were iron and arsenic oxidation, precipitation of Fe(III)- minerals and sorption of As(V) onto them. A 1-D reactive transport model using the PHREEQC code was used to explain and quantify the aforementioned processes that had been studied previously under laboratory conditions.
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White, Colin P. "Molecular Microbial Ecology and Operational Evaluation of a Full-scale and Pilot-scale Biologically Active Filter for Drinking Water Treatment." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1277154047.
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West, Nicole Renee. "Arsenic Release from Chlorine Promoted Oxidation of Pyrite in the St. Peter Sandstone Aquifer, Eastern Wisconsin." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/32451.
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High arsenic concentrations (>100 ppb) have been measured in wells completed in the Ordovician St. Peter sandstone aquifer of eastern Wisconsin. The primary source of arsenic is As-bearing sulfide minerals within the aquifer. There is concern that periodic disinfection of wells by chlorination may facilitate arsenic release to groundwater by increasing the rate of sulfide mineral oxidation. Current guidance from the Wisconsin Department of Natural Resources recommends a â low-doseâ treatment of 20% of the chlorine strength and 10% of the of the contact time of chlorine treatments used in non-arsenic impacted wells for well disinfection and biofilm removal. In order to provide information pertaining to WDNRâ s recommendations, St. Peter sulfide minerals were reacted with a range of chlorine â shock-treatmentsâ similar to those occurring in wells. This study focuses on abiotic processes that mobilize arsenic from the solid phase during controlled exposure to chlorinated solutions.
Thin sections were made from aquifer material collected at Leonardâ s Michael quarry, located in Winnebago County, Wisconsin. Bulk arsenic content of this material was measured as 674 ppm. Quantitative EPMA analysis shows As zoning in pyrite grains with concentrations up to 1 wt. % As. After mineral characterization, the thin sections were exposed to solutions of 60 mg/L â free chlorine,â 1200 mg/L â free chlorine,â and nanopure water (control) at pH 7.0 and pH 8.5 for 24 hours. Thin sections were then analyzed to measure changes in the pyrite surfaces. For solution experiments, aquifer material was crushed to between 250 μm and 355 μm mesh sizes (S.A. ~ 50 cm2/g â 60 cm2/g, Foust et al. 1980) and reacted under the same conditions as the thin sections in a batch reactor. Solution samples were collected periodically during the 24 hour exposure and analyzed for arsenic, iron, and sulfate ion.
Pyrite oxidation is shown to dramatically increase with increasing chlorine concentrations as shown by measurements of released sulfate ion, used here as the reaction progress variable. EPMA maps also reveal complete oxidation of pyrite cements to Fe-oxyhydroxides at 1200 mg/L â free chlorineâ and pH 7.0. This behavior does not occur at lower concentrations or higher pH. Arsenic release to solution does not appear to be directly correlated to increasing chlorine concentrations, but is governed by Fe-oxyhydroxide nucleation, which inhibits the release of dissolved arsenic at higher concentrations of chlorine.
Master of Science
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O'Neal, Stephen Vernon. "A kinetic study of the chromium (VI) - arsenic (III) reaction in pyridine-pyridinium buffer solutions containing oxalate." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/104524.
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Malcolm, Watson. "The removal of arsenic during drinking water treatment by sorption and coagulation processes." Phd thesis, Univerzitet u Novom Sadu, Prirodno-matematički fakultet u Novom Sadu, 2016. https://www.cris.uns.ac.rs/record.jsf?recordId=101128&source=NDLTD&language=en.
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This dissertation investigates the factors which affect the removal of arsenic from groundwater by adsorption and coagulation technologies, including the interactions between As and natural organic matter (NOM). Humic acid (HA) was utilised as an NOM analogue, and was shown to be capable of both complexing and oxidising As, depending upon the prevailing conditions. The arsenic removing capabilities of three iron oxide coated sands (IOCS) were investigated, including IOCSW, a waste material from a local drinking water treatment plant generated during the removal of iron and manganese. IOCSW was highly effective at removing both As(V) and As(III) from synthetic water matrices (qmax = 78.3 µg As(V)/g and 99.1 µg As(III)/g). The negative effects of competitive anions (phosphates, silicates and HA) on arsenic removals were not significant enough to preclude the application of IOCSW for arsenic removal during drinking water treatment. The removals of both As and NOM by coagulation and enhanced coagulation with pH correction and preoxidation were also investigated. As(V) was more readily removed by coagulation than As(III), so that the most efficient coagulation treatment investigated for arsenic and NOM removal applied preozonation with subsequent combined coagulation with polyaluminium chloride and ferric chloride. Different groundwaters displayed large variations in the As and NOM removal behaviours. Response surface methodology (RSM) was therefore applied to investigate the interactions between As and NOM during ferric chloride coagulation and optimise their combined removals. Multiple interaction effects were observed during this investigation, highlighting the importance of utilizing RSM to optimise drinking water treatment technologies.Ova disertacija ispituje faktore koji utiču na uklanjanje arsena iz podzemne vode primenom adsorpcija i koagulacije, uključujući i interakcije između arsena i prirodnih organskih materija (POM). Huminska kiselina (HA) je korisćena kao model za POM, a pokazano je da može i da kompleksira i da oksiduje As, u zavisnosti od eksperimentalnih uslova. Ispitivane su mogućnosti uklanjanja arsena za tri peska obložena gvožđe oksidom (IOCS), uključujući IOCSW, koji je dobijen sa postrojenja za tretman vode za piće i potiče iz procesa uklanjanja gvožđa i mangana. IOCSW se pokazao kao visoko efikasan za uklanjanje As(V) i As(III) iz sintetičkih vodenih matriksa (qmax = 78.3 µg As(V)/g i 99.1 µg As(III)/g). Negativni efekti kompetirajućih jona (fosfata, silikata i HA) na uklanjanje arsena nisu bili dovoljno značajni da bi se isključila primena IOCSW za uklanjanje arsena tokom tretmana vode za piće. Zajedničko uklanjanje As i POM koagulacijom i unapređenom koagulacijom uz podešavanje pH i kombinovanje sa oksidacionim predtretmanima je takođe ispitivano. Bolje uklanjanje koagulacijom postignuto je za As(V) u odnosu na As(III), stoga se kao najefikasniji ispitivani koagulacioni tretman pokazalo uklanjanje arsena i POM primenom predozonizacije praćene kombinovanom koagulacijom sa polialuminijum hloridom i gvožđe hloridom. Ispitivanja na različitim podzemnim vodama, pokazala su velike varijacije u ponašanju As i POM tokom tretmana. Iz tog razloga je primenjena metodologija odzivne površine (RSM) u cilju ispitivanja interakcija između As i POM tokom koagulacije gvožđe hloridom i optimizacije njihovog kombinovanog uklanjanja. Sagledavanje većeg broja interakcija primenom metodologije odzivne površine potvrđuje važnost njegove primene pri optimizaciji tretmana vode za piće.
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Shumlas, Samantha Lyn. "Characterization of Carbon Nanomaterial Formation and Manganese Oxide Reactivity." Diss., Temple University Libraries, 2016. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/419544.
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ChemistryPh.D.
Characterization of a material’s surface, structural and physical properties is essential to understand its chemical reactivity. Control over these properties helps tailor a material to a particular application of interest. The research presented in this dissertation focuses on characterizing a synthetic method for carbon nanomaterials and the determination of structural properties of manganese oxides that contribute to its reactivity for environmental chemistry. In particular, one research effort was focused on the tuning of synthetic parameters towards the formation of carbon nanomaterials from gaseous methane and gaseous mixtures containing various mixtures of methane, argon and hydrogen. In a second research effort, photochemical and water oxidation chemistry were performed on the manganese oxide, birnessite, to aid in the remediation of arsenic from the environment and provide more options for alternative energy catalysts, respectively. With regard to the synthesis of novel carbonaceous materials, the irradiation of gaseous methane with ultrashort pulse laser irradiation showed the production of carbon nanospheres. Products were characterized with transmission electron microscopy (TEM), scanning electron microscopy (SEM), ultraviolet (UV) Raman spectroscopy, and infrared spectroscopy. Increasing the pressure of methane from 6.7 to 133.3 kPa showed an increase in the median diameter of the spheres from ~500 nm to 85 nm. Particles with non-spherical morphologies were observed by TEM at pressures of 101.3 kPa and higher. UV Raman spectroscopy revealed that the nanospheres were composed of sp2 and sp3 hybridized carbon atoms, based on the presence of the carbon D and T peaks. A 30% hydrogen content was determined from the red shift of the G peak and the presence of a high fluorescence background. Upon extending this work to mixtures of methane, argon, and hydrogen it was found that carbon nanomaterials with varying composition and morphology could be obtained. Upon mixing methane with other gases, the yield significantly dropped, causing flow conditions to be investigated as a method to increase product yield. Raman spectra of the product resulting from the irradiation of methane and argon indicated that increasing the argon content above 97% produced nanomaterial composed of hydrogenated amorphous carbon. In a second research effort, the effect of simulated solar radiation on the oxidation of arsenite [As(III)] to arsenate [As(V)] on the layered manganese oxide, birnessite, was investigated. Experiments were conducted where birnessite suspensions, under both anoxic and oxic conditions, were irradiated with simulated solar radiation in the presence of As(III) at pH 5, 7, and 9. The oxidation of As(III) in the presence of birnessite under simulated solar light irradiation occurred at a rate that was faster than in the absence of light at pH 5. At pH 7 and 9, As(V) production was significantly less than at pH 5 and the amount of As(V) production for a given reaction time was the same under dark and light conditions. The first order rate constant (kobs) for As(III) oxidation in the presence of light and in the dark at pH 5 were determined to be 0.07 and 0.04 h−1 , respectively. The As(V) product was released into solution along with Mn(II), with the latter product resulting from the reduction of Mn(IV) and/or Mn(III) during the As(III) oxidation process. Experimental results also showed no evidence that reactive oxygen species played a role in the As(III) oxidation process. Further research on the triclinic form of birnessite focused on its activation for water oxidation. Experiments were performed by converting triclinic birnessite to hexagonal birnessite in pH 3, 5, and 7 DI water with stirring for 18 hrs. Once the conversion was complete, the solid samples were characterized with TEM and x-ray photoelectron spectroscopy (XPS). The resulting hexagonal birnessites from experiment at pH 3, 5, and 7 possessed the same particle morphology and average surface oxidation states within 1% of each other. This observation supported the claim that upon transformation, Mn(III) within the sheet of triclinic birnessite migrated into the interlayer region of the resulting hexagonal birnessite. Furthermore, the migration of Mn(III) into the interlayer and formation of the hexagonal birnessite led to an increased chemical reactivity for water oxidation compared to the bulk. Electrochemical studies showed that the overpotential for water oxidation associated with the pH 3, 5, and 7 samples was 490, 510, and 570 mV, respectively. In another set of experiments, ceric ammonium nitrate was used to test birnessite for water oxidation reactivity. These experiments showed that the pH 3 birnessite produced the most O2 of all the samples, 8.5 mmol O2/mol Mn, which was ~6 times more than hexagonal birnessite which did not undergo post-synthesis exposure to low pH conditions.
Temple University--Theses
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Picquet, Isabelle. "Techniques de stabilisation physico-chimique à base de liant hydraulique appliquées aux résidus miniers sulfurés et arséniés." Vandoeuvre-les-Nancy, INPL, 1995. http://www.theses.fr/1995INPL141N.
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En alternative aux solutions les plus communes de gestion des résidus miniers sulfurés générateurs d'eaux acides (AMD), les procédés de stabilisation à base de liant hydraulique développés dans le traitement des déchets sont envisagés comme barrière contre la dissémination des éléments toxiques, voire contre la diffusion des agents oxydants. En particulier, la fixation chimique de l'arsenic est recherchée. L’expérimentation est basée sur la préparation de mortiers de stérile sulfuré et arsénié et de ciment ou de chaux. L’influence de la nature du liant utilisé et celle de la teneur en chaux sont étudiées vis à vis de la rétention de l'arsenic et de la détérioration des mortiers due à la formation de composés gonflants (ettringité). Des essais de lixiviation par extracteur de Soxhlet permettent d'évaluer l'efficacité de l'inertage sous des conditions oxydantes. L’influence de la teneur en chaux sur la fixation de l'arsenic est clairement montrée et ce quelque soit le test utilisé. L’altération accélérée des échantillons montre le départ massif de la chaux et une perte de cohésion des mortiers faiblement dosés en liant qui coïncide avec une détérioration des qualités de rétention de l'arsenic. À long terme, des phases riches en fer, en arsenic et en calcium sont identifiées comme des phases possibles de stabilisation. Les mortiers riches en ciment et en chaux assurent la meilleure rétention de l'arsenic et ce même après un an de vieillissement. Dans une dernière partie, la protection des surfaces des sulfures par des hydroxydes métalliques est envisagée pour inhiber l'oxydation
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Luukkonen, T. (Tero). "New adsorption and oxidation-based approaches for water and wastewater treatment:studies regarding organic peracids, boiler-water treatment, and geopolymers." Doctoral thesis, Oulun yliopisto, 2016. http://urn.fi/urn:isbn:9789526210797.
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Abstract This thesis examines three different areas of water treatment technology: the application of organic peracids in wastewater treatment; the removal of organic residues from boiler make-up water; and the use of geopolymers as sorbents. The main advantages of peracids as alternative wastewater disinfectants are their effective antimicrobial properties and high oxidation power, as well the absence of harmful disinfection by-products after their use. Performic, peracetic and perpropionic acids were compared in laboratory-scale disinfection, oxidation and corrosion experiments. From the techno-economical point of view, performic acid proved to be the most effective disinfectant against E. coli and fecal enterococci. However, in the bisphenol-A oxidation experiments, no advantages compared to hydrogen peroxide use were observed. It was also determined that corrosion rates on stainless steel 316L were negligible, while carbon steel seemed unsuitable in terms of corrosion for use with peracids even in low concentrations. Organic compounds in the boiler plant water-steam cycle thermally decompose and form potentially corrosive species. Activated carbon filtration was confirmed to be a suitable method for the removal of organic residue from deionized boiler make-up water. No significant differences in terms of treatment efficiency between commercial activated carbons were observed. However, acid washing as a pre-treatment reduced the leaching of impurities from new carbon beds. Nevertheless, a mixed-bed ion exchanger was required to remove leached impurities, such as silica and sodium. Geopolymers, or amorphous analogues of zeolites, can be used as sorbents in the treatment of wastewater. Metakaolin and blast-furnace-slag geopolymers showed positive potential in the treatment of landfill leachate (NH4+ ) and mine effluent (Ni, As, Sb)Tiivistelmä Tämä väitöskirja käsittelee kolmea erillistä vedenkäsittelyteknologian osa-aluetta: orgaanisten perhappojen käyttöä jäteveden käsittelyssä, orgaanisten jäämien poistoa suolavapaasta kattilalaitoksen lisävedestä ja geopolymeerien sovelluksia vedenkäsittelysorbentteina. Orgaanisten perhappojen pääasialliset edut verrattuna kilpaileviin tekniikoihin ovat hyvä desinfiointiteho, korkea hapetuspotentiaali ja desinfioinnin sivutuotteiden muodostumattomuus. Permuurahais-, peretikka- ja perpropaanihapon vertailu osoitti permuurahaishapon olevan kemikaaleista tehokkain E. coli - ja enterokokkibakteerien inaktivoinnissa kustannus- ja teknisistä näkökulmista. Hapetuksessa, jossa käytettiin bisfenoli-A:ta malliaineena, ei kuitenkaan havaittu etua verrattuna edullisempaan vetyperoksidiin. Ruostumattoman teräksen (316L) pinnalla ei havaittu merkittävää korroosiota, kun taas hiiliteräs ei sovellu käytettäväksi perhappojen kanssa. Orgaaniset jäämät kattilalaitoksen vesi-höyrykierrossa hajoavat termisesti pienen moolimassan hapoiksi ja aiheuttavat korroosioriskin. Aktiivihiilisuodatuksen todettiin olevan soveltuva menetelmä orgaanisten jäämien poistoon lisävedestä. Aktiivihiililaatujen välillä ei havaittu merkittäviä eroja, mutta happopesu aktiivihiilen esikäsittelynä vähensi hiilestä liukenevien epäpuhtauksien määrää. Geopolymeerit ovat zeoliittien amorfisia analogeja ja niiden ioninvaihtokykyä voidaan hyödyntää vedenkäsittelysovelluksissa. Metakaoliini- ja masuunikuonapohjaisten geopolymeerien todettiin olevan lupaavia materiaaleja malliliuosten, kaatopaikan suotoveden ja kaivoksen purkuveden käsittelyssä poistettaessa ammoniumia, nikkeliä, arseenia ja antimonia
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Pirilä, M. (Minna). "Adsorption and photocatalysis in water treatment:active, abundant and inexpensive materials and methods." Doctoral thesis, Oulun yliopisto, 2015. http://urn.fi/urn:isbn:9789526207629.
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Abstract Water contamination is a global problem and the growing utilization of limited water resources creates a need for efficient purification methods. Industrial effluents are polluting the natural waters, e.g. uncontrolled mining activities in developing countries have created numerous environmental hazards and different types of pollutants. This study focuses on novel adsorbents and photocatalytic materials in order to reach the aim of more efficient and affordable water treatment. This thesis aimed at making active, efficient, and viable adsorbents out of waste materials, as well as using photocatalysis in water treatment for organic pollutants originating from different types of industries. Local Peruvian agro-waste was used as a precursor for activated carbon that was used in adsorption studies for single (As(V) and methylene blue, MB), and multicomponent mixtures (As(V)/Pb/Cd), and real polluted river water. An industrial intermediate product, hydrous TiO2, was used for As(III)/As(V) removal. Photocatalytic materials included a commercial photoactive TiO2 (P25), and tailor-made TiO2 based nanofibers (NF) decorated with Pt/Pd. The results show that the agro-waste based activated carbons show high potential as adsorbents (e.g. ~100% As(V) removal in 2 h). With the multicomponent solution there is evidently competition for the adsorption sites; Pb was removed most efficiently. The specific surface area and pore size distribution play an important role in MB adsorption, as with As(V) the ash content is the most influential parameter. The industrial intermediate product has a high adsorption capacity towards both As(III) and As(V) (over 96% removals in 4 h), and is promising for use in natural and wastewater treatment due to its adsorption properties, availability, low cost, and non-toxicity. Photocatalysis was found to be an efficient removal method for the pollutants tested, also in the diluted industrial wastewater matrix, e.g. diuron was removed 99% in 1 h. The NFs are promising for the efficient photocatalytic degradation of organic effluents in aqueous streams such as wastewaters originating from e.g. biofuel production or fine chemicals and pharmaceutical industry. This study provides new and valuable knowledge for the purification of waters, especially when aiming at developing inexpensive water treatment materials and methods for different applicationsTiivistelmä Puhtaan veden puute on maailman laajuinen ongelma, ja raskasmetallien ja orgaanisten haitta-aineiden päätymistä ympäristöön ja luonnonvesiin voidaan vähentää hyvällä ja tehokkaalla teollisuuden jätevesien käsittelyllä. Uusia ja tehokkaita, ympäristön kannalta suotuisia ja kestäviä vedenpuhdistustekniikoita tarvitaan erityisesti kehitysmaissa, joissa esim. kontrolloimaton kaivostoiminta aiheuttaa ympäristö- ja terveyshaittoja. Työn kokeellisessa osassa valmistettiin perulaisesta maatalousjätteistä aktiivihiiltä kemiallisella aktivoinnilla, ja seurattiin niiden kykyä adsorboida haitta-aineita (As(V), Pb, Cd, metyleenisini) yksi- ja monikomponenttiliuoksista ja saastuneesta luonnonvedestä (Puyango-Tumbesjoki, Peru). Lisäksi tutkittiin teollisuuden välituotteen (TiO2) aktiivisuutta arseenin, As(III) ja As(V), adsorptiossa. Viimeisessä osiossa tutkittiin valokatalyysiä orgaanisten haitta-aineiden poistossa vesiliuoksista sekä kaupallisella TiO2 P25 -katalyytillä että kokeellisilla Pd/Pt-dopatuilla TiO2 -nanokuiduilla. Tulokset osoittavat, että paikallisesta raaka-aineesta valmistetut aktiivihiilet ovat hyvin potentiaalisia vedenpuhdistusmateriaaleja saavuttaen jopa 100% As(V) poistuman (2h). Adsorboitavien ionien välillä on nähtävissä kilpailua monikomponettiadsorptiossa; lyijyn havaittiin poistuvan tehokkaimmin tutkituissa olosuhteissa. Adsorbentin ominaispinta-ala ja huokoskokojakauma ovat tärkeitä tekijöitä metyleenisinin adsorptiossa, kun taas tuhkapitoisuudella on arseenin adsorptioon suurempi vaikutus. Teollisuuden TiO2-välituotteella havaittiin olevan korkea adsorptiokapasiteetti sekä As(III)- että As(V)-spesieksiä kohtaan saavuttaen yli 96% poistumat (4h). Se on lupaava materiaali edelleen kehitettäväksi ja käytettäväksi esimerkiksi luonnonvesien ja jätevesien puhdistuksessa johtuen sen hyvistä adsorptio-ominaisuuksista, saatavuudesta, edullisuudesta ja myrkyttömyydestä. Valokatalyysin havaittiin olevan toimiva menetelmä orgaanisten molekyylien hajottamiseen, myös laimeasta teollisuuden jätevesimatriisista, esim. diuroni poistui 99% tunnissa. Nanokuitujen tapauksessa aktiivinen metalli vaikutti merkittävämmin reaktion tehokkuuteen kuin ominaispinta-ala. Tämä työ tarjoaa uutta ja tärkeää tietoa vesien puhdistukseen kun tavoitteena on löytää tehokas ja edullinen menetelmä erityyppisiin sovelluksiin
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Phan, Thi Hai Van. "L'arsenic dans les écosystèmes du sud-est asiatique : Mekong Delta Vietnam." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAU003/document.
Full textAbstract:
On retrouve des contaminations d’aquifèr à l’arsenic dans touts les deltaï de l'Asie du Sud-Est, y compris dans le delta du Mékong, ce qui affecte la santé de millions de personnes. L’arsenic est très sensible aux fluctuations des conditions redox qui sont générés par les cycles alternés humides/secs pendant la saison de mousson. Une étude sur les caractéristiques géophysiques et chimiques du sol et des eaux souterraines dans le district de An Phu, dans le haut du delta du Mékong au Vietnam, suggère une forté contamination à l’As dans cette région. Les données chimiques et géophysiques indiquent une forte corrélation entre concentrations dans les eaux souterraines anoxiques et conductivité des sols. La liberation de l’arsenic est associée à la dissolution réductrice induih par des microorganisms des colloïdes et (oxyhydr)oxydes de fer dans des conditions d'oxydo-réduction oscillantes. La présence de bactéries sulforéductrices a le potentiel de stabiliser l’arsenic dans la phase solide et de l’atténuer dans la phase aqueuse par adsorption / désorption de l’arsenic sur les (oxyhydr)oxydes, et / ou sulfures de fer via la formation de complexes thiols. En raison de la teneur en pyrite élevée dans les sédiments, l'oxydation de la pyrite peut abaisser le pH et conduire à l'inhibition de la réduction microbienne du sulfate et aime empêcher la séquestration de l’arsenic dissous. Bien que le cycle biogéochimique de l’arsenic dans un système dynamique d’oxydoréduction soit une problématique complexe, il a été possible de renforcer notre compréhension de ce systèmeAquifer arsenic (As) contamination is occuring throughout deltaic areas of Southeast Asia, including the Mekong Delta, and affects the health of millions of people. As is highly sensitive to fluctuations of redox conditions which are generated by the alternating wet-dry cycles during the monsoonal seasons. A survey of geophysical and chemical characteristics of soil and groundwater in the An Phu district, located in the vicinity of the Mekong Delta in Vietnam, shows the occurrence high As aqueous concentration in this region. Chemical and geophysical data indicate a strong positive correlation between As concentrations in the anoxic groundwater and conductivity of soils. In addition, mechanisms of As release are shown to be associated with colloidal and iron (oxyhydr)oxides which undergo microbial mediated reductive dissolution under redox oscilatting conditions. The presence of sulfate microbial reduction potentially stabilizes As in the solid phase and diminish As in the aqueous phase through the adsorption/desorption of As onto iron (oxyhydr)oxides and/ or sulfides with formation of thiols complexes in solid phase. Because of the high pyrite content in sediment, pyrite oxidation may drop in pH values, leads to inhibition of sulfate reducing bacteria and reduces sequestration of dissolved As. Although the biogeochemical cycling of redox sensitive species such as As in dynamic systems is challenging, it has been possible to strengthen our collective understanding of such system
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Römer, Dirk. "Grundlagenuntersuchungen zur elektrochemischen Remediation von schwermetallkontaminierten Boden- /Sediment- Wassersystemen am Beispiel von Uran, Chrom, Arsen und Chlorbenzen." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2005. http://nbn-resolving.de/urn:nbn:de:swb:14-1109837957299-09232.
Full textAbstract:
In den 80-iger Jahren war die DDR hinter den USA und Kanada der drittgrößte Uranproduzent mit einer Jahresproduktion von ca. 200.000 Tonnen. Die Gewinnung erfolgte durch konventionellen Bergbau, durch in- situ- oder offene Haufenlagerung. Die Urangewinnung auf dem Territorium der ehemaligen DDR wurde nach der Wiedervereinigung eingestellt und mit der Sanierung der Altstandorte begonnen. Nach Einstellung des Uranabbaus muss die Wasserhaltung solange betrieben werden, bis eine kontrollierte Flutung der Bergbauschächte erfolgen kann. Die dabei anfallenden Grubenwässer werden je nach Schadstoffkonzentration direkt in den Vorfluter abgeleitet oder in geeigneten Aufbereitungsanlagen meist durch Flockung und Adsorption behandelt. Dieses praktisch oft angewandte Grubenwasserreinigungsverfahren bezüglich Uran und den auftretenden Begleitelementen Chrom und Arsen hat den entscheidenden Nachteil, dass die anfallenden schwermetallhaltigen Fällschlämme auf Deponien verbracht werden müssen. Durch Niederschlagsereignisse oder ansteigendes Grundwasser besteht die Gefahr, dass die Deponien wieder ausgelaugt werden und somit eine erneute Mobilisierung von Schwermetallen in die Umwelt erfolgt. Die Sanierung kontaminierter Gebiete, insbesondere Sedimente, Sondermüll-deponien, Standorte ehemaliger Galvanikbetriebe, Betriebsflächen chemischer Industriestandorte, Rieselfelder oder Orte der Klärschlammaufbereitung erfordern neue Herangehensweisen an das gegenwärtig hochaktuelle Problem der Rehabilitation. Es wurde deshalb u.a. im Rahmen dieser Arbeit ein Konzept auf Grundlage der elektrochemischen Umsetzung im "verdünnten" elektrochemischen Festbettreaktor entwickelt, das es gestattet, die mobilen Schwermetallspezies im Boden bzw. Deponiekörper in immobile Schwermetallverbindungen umzuwandeln. Damit kann die Nachsorge und Sicherung solcher Deponiekörper bezüglich einer Remobilisierung wesentlich kostengünstiger gestaltet werden. Ausgehend von diesem Konzept sollen Möglichkeiten, Einsatzbedingungen und -grenzen der Immobilisierung von Schwermetallen am Beispiel von Uran(VI), Chrom(VI), Arsen(III) und chlorierten Kohlenwasserstoffe aufgezeigt werden. Elektrochemische Verfahren zur Sanierung kontaminierter Böden, Schlämme und Sedimente befinden sich international in einer dynamischen Forschungs- und Entwicklungsphase. Sie sind einzeln und in Verfahrenskombinationen einsetzbar und werden, bei verantwortungsvoller Handhabung, in absehbarer Zeit auch als zertifizierte Verfahren in Deutschland in bestimmten Sanierungsvorhaben ihre Leistungsfähigkeit beweisen. Gegenwärtig befinden sie sich in Deutschland noch im Stadium der Forschung und Entwicklung, während international (z.B. USA, Niederlande) schon kommerzielle Anwendungen angeboten werden. Zur objektiven Beurteilung ihrer Leistungsfähigkeit und Einsatzgrenzen bedarf es spezieller Grundkenntnisse. Elektrochemische Remediationsverfahren können als ergänzende, in Einzelfällen auch als alternative Verfahren zur Sediment- und Bodensanierung angesehen werden. Sie haben dann eine Chance auf Einsatz, wenn vor Ort (in- situ) saniert werden soll. Von ihrem Prinzip her, sind sie preiswerter als Bodenaushub und Verbrennung. Das Sanierungsziel besteht in einer möglichst vollständigen Konzentrierung oder Umsetzung der Wasserschadstoffe an der Feststoffmatrix.
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Römer, Dirk. "Grundlagenuntersuchungen zur elektrochemischen Remediation von schwermetallkontaminierten Boden- /Sediment- Wassersystemen am Beispiel von Uran, Chrom, Arsen und Chlorbenzen." Doctoral thesis, Technische Universität Dresden, 2003. https://tud.qucosa.de/id/qucosa%3A23840.
Full textAbstract:
In den 80-iger Jahren war die DDR hinter den USA und Kanada der drittgrößte Uranproduzent mit einer Jahresproduktion von ca. 200.000 Tonnen. Die Gewinnung erfolgte durch konventionellen Bergbau, durch in- situ- oder offene Haufenlagerung. Die Urangewinnung auf dem Territorium der ehemaligen DDR wurde nach der Wiedervereinigung eingestellt und mit der Sanierung der Altstandorte begonnen. Nach Einstellung des Uranabbaus muss die Wasserhaltung solange betrieben werden, bis eine kontrollierte Flutung der Bergbauschächte erfolgen kann. Die dabei anfallenden Grubenwässer werden je nach Schadstoffkonzentration direkt in den Vorfluter abgeleitet oder in geeigneten Aufbereitungsanlagen meist durch Flockung und Adsorption behandelt. Dieses praktisch oft angewandte Grubenwasserreinigungsverfahren bezüglich Uran und den auftretenden Begleitelementen Chrom und Arsen hat den entscheidenden Nachteil, dass die anfallenden schwermetallhaltigen Fällschlämme auf Deponien verbracht werden müssen. Durch Niederschlagsereignisse oder ansteigendes Grundwasser besteht die Gefahr, dass die Deponien wieder ausgelaugt werden und somit eine erneute Mobilisierung von Schwermetallen in die Umwelt erfolgt. Die Sanierung kontaminierter Gebiete, insbesondere Sedimente, Sondermüll-deponien, Standorte ehemaliger Galvanikbetriebe, Betriebsflächen chemischer Industriestandorte, Rieselfelder oder Orte der Klärschlammaufbereitung erfordern neue Herangehensweisen an das gegenwärtig hochaktuelle Problem der Rehabilitation. Es wurde deshalb u.a. im Rahmen dieser Arbeit ein Konzept auf Grundlage der elektrochemischen Umsetzung im "verdünnten" elektrochemischen Festbettreaktor entwickelt, das es gestattet, die mobilen Schwermetallspezies im Boden bzw. Deponiekörper in immobile Schwermetallverbindungen umzuwandeln. Damit kann die Nachsorge und Sicherung solcher Deponiekörper bezüglich einer Remobilisierung wesentlich kostengünstiger gestaltet werden. Ausgehend von diesem Konzept sollen Möglichkeiten, Einsatzbedingungen und -grenzen der Immobilisierung von Schwermetallen am Beispiel von Uran(VI), Chrom(VI), Arsen(III) und chlorierten Kohlenwasserstoffe aufgezeigt werden. Elektrochemische Verfahren zur Sanierung kontaminierter Böden, Schlämme und Sedimente befinden sich international in einer dynamischen Forschungs- und Entwicklungsphase. Sie sind einzeln und in Verfahrenskombinationen einsetzbar und werden, bei verantwortungsvoller Handhabung, in absehbarer Zeit auch als zertifizierte Verfahren in Deutschland in bestimmten Sanierungsvorhaben ihre Leistungsfähigkeit beweisen. Gegenwärtig befinden sie sich in Deutschland noch im Stadium der Forschung und Entwicklung, während international (z.B. USA, Niederlande) schon kommerzielle Anwendungen angeboten werden. Zur objektiven Beurteilung ihrer Leistungsfähigkeit und Einsatzgrenzen bedarf es spezieller Grundkenntnisse. Elektrochemische Remediationsverfahren können als ergänzende, in Einzelfällen auch als alternative Verfahren zur Sediment- und Bodensanierung angesehen werden. Sie haben dann eine Chance auf Einsatz, wenn vor Ort (in- situ) saniert werden soll. Von ihrem Prinzip her, sind sie preiswerter als Bodenaushub und Verbrennung. Das Sanierungsziel besteht in einer möglichst vollständigen Konzentrierung oder Umsetzung der Wasserschadstoffe an der Feststoffmatrix.
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Osborne, T. H. "Microbial oxidation of arsenite at low temperatures." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1335910/.
Full textAbstract:
Arsenic is toxic to most living cells and has two soluble inorganic forms: arsenite (+3) and arsenate (+5), which are ubiquitous in the environment. Microbial metabolism of arsenic in the environment, contributes to its geochemical cycling. Prokaryotic oxidation of arsenite has been reported and characterised in moderate and thermal environments but not below 10°C. Giant Mine is a discontinued gold mine located 250 miles south of the arctic circle in the Northwest Territories, Canada. 230,000 tonnes of arsenic trioxide dust are stored underground at the site and infiltrating surface waters have become contaminated with >50 mM arsenic. Several microbial biofilms were found growing on the mine walls beneath seepage points of the arsenic-contaminated water. The diversity of arsenite oxidisers in two sub-samples (which differed in arsenite concentrations) of one biofilm were compared using a functional gene approach. The diversity of the two sub-samples did not differ but the relative abundance of the three identified clades did. An arsenite-oxidising bacterium, designated GM1, was isolated from the Giant Mine biofilm. GM1 was shown to be a member of the Polaromonas genus, had a growth range of 0-25°C and oxidised arsenite in the early-log phase of growth. GM1’s arsenite oxidase was constitutively expressed. The arsenite oxidase genes were partially sequenced and their role in arsenite oxidation confirmed by mutagenesis. The arsenite oxidase of GM1 was purified and partially characterised. It consists of two subunits (88 and 15 kDa) in a α1β1 conformation, and contained Mo and Fe as cofactors. The Vmax, Kcat and Km were the highest of any known arsenite oxidase. The GM1 arsenite oxidase functioned over a broad temperature range and was more active than that of the mesophile NT-26 at low temperatures. It was also found to be less stable than that of NT-26, as observed by circular dichroism spectroscopy.
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Nagam, Satya Mohan Babu. "Effect of Thyroid Modulation on Arsenic-Induced Oxidative Stress in Zebrafish." Thesis, Southern Illinois University at Edwardsville, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1549814.
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It is well known that environmental contaminants such as arsenic can induce oxidative stress in fish. It is also known that thyroid hormone status affects susceptibility to oxidative stress. However, the effect of thyroid hormone status on pollutant- induced oxidative stress is unknown. This is significant, because such knowledge would help to assess the risk of xenobiotics such as arsenate, a prevalent contaminant in the environment. The interaction between arsenate- induced oxidative stress and altered thyroid hormones has not been elucidated thoroughly in previous studies. In order to address this, we used zebrafish (Danio rerio). There are many advantages of using this as a research model over rodents such as rats. For example, it is often used to study the effects of xenobiotic compounds such as arsenic. This xenobiotic is widespread in the environment due to human activities such as agricultural, industrial and military activities. For this purpose, it is more appropriate to use this fish as a research model. The reason for using the chemicals perchlorate and arsenic is that they occur together in the environment. Oxidative stress can be caused by environmental pollutants such as arsenic. One of the key defenses against oxidative stress is glutathione (GSH). GSH concentrations, GSSG/GSH ratios, and lipid peroxidation (TBARS) were used to assess the affect of arsenic, perchlorate and thyroxine (T4) on zebrafish (Danio rerio) liver, gills, and muscle tissue. Our results support the hypothesis that thyroid hormones modulates the toxicity of arsenic. Moreover, arsenite was found to cause oxidative stress as reflected by GSH levels, GSSG/GSH levels, and lipid peroxidation (TBARS). Although hypothyroidism caused by perchlorate did not cause any major difference on oxidative stress, but hyperthyroidism caused by treating the fish with T4 enhanced GSH levels. This shows that thyroxine is involved in response to oxidative stress. In addition, perchlorate abrogated or reversed the affects of arsenite on oxidative stress parameters. These results support the hypotheses that thyroid hormones modulate oxidative stress in general, and arsenite-mediated oxidative stress in particular.
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Matsui, Miho. "The role of oxidative DNA damage in human arsenic carcinogenesis : detection of 8-hydroxy-2'-deoxyguanosine in arsenic related Bowen's disease." Kyoto University, 1999. http://hdl.handle.net/2433/181253.
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Diaz, Heredia Zuanel. "Trolox enhances anti-leukemic effects of arsenic trioxide: the role of oxidative stress." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40699.
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Arsenic trioxide (As2O3) has considerable efficacy in the treatment of acute promyelocytic leukemia (APL), inducing partial differentiation and promoting apoptosis of malignant promyelocytes. Although initial studies focused on the role of the characteristic APL fusion protein, PML-RARα, in mediating the response to As2O3, recent investigations indicate that its cytotoxic activities are mediated by mechanisms independent of this fusion protein. As2O3 affects numerous intracellular targets mainly through the accumulation of free radicals and consequent induction of oxidative stress and causes a wide range of alterations leading to apoptosis. The intracellular oxidative status has been shown to be important for As2O3 sensitivity. Hematologic cancers other than APL and, solid tumors are less responsive to As2O3 monotherapy in part because their increased redox buffering capacity. Thus, the use of As2O3 in other malignancies is limited by the toxicity of concentrations required to induce apoptosis. The primary goal of the work presented in this thesis was a search for agents that could enhance As2O3 efficacy in malignant cells, but not in normal cells. We demonstrated that trolox (6–hydroxy–2,5,7,8–tetramethylchroman–2–carboxylic acid), a widely known antioxidant, enhances As2O3-mediated apoptosis in APL, P388 murine lymphoma, myeloma and breast cancer cells through the potentiation of As2O3-induced oxidative stress. We performed in vivo experiments in P388 tumor-bearing mice, and show that As2O3 treatment prolonged survival, and the addition of trolox provided a significant further increase in life span and decreased the number of animal with visible macrometastasis. Importantly, trolox protected normal blood mononuclear cells and non-malignant hepatocytes from As2O3-mediated cytotoxicity in vitro and protected non-tumors and tumors-bearing animals from arsenic-induced hepatotoxicity. We next investigated the mechanisms responsible for the opposite effLe trioxyde d’arsenic (As2O3) induit l’apoptose ainsi qu’une différentiation partielle des promyélocytes malins et de cette façon, il est considérablement efficace dans le traitement de la leucémie promyelocytic aigüe (APL). Les premières études sur le trioxyde d’arsenic ont mis en lumière l’importance de la protéine de fusion PML-RAR. Cependant, plusieurs études récentes démontrent que l’acitvité cytotoxiques de l’As2O3 dépend de mécanismes indépendants de PML-RAR. Entres autres, la présence d’As2O3 dans la cellule engendre une accumulation de radicaux libre qui affecte de nombreuses cibles intracellulaires et provoque une variété de changement qui vont mener à l’apoptose. L’équilibre oxydatif intracellulaire à démontré être important pour la sensibilité des cellules cancéreuse face à l’As2O3. Les cancers hématologiques autres que l’APL ainsi que les tumeurs solides semblent moins sensibles à l’As2O3 puisqu’elles possèdent une grande capacité d’oxydoréduction. L’utilisation de l’As2O3 contre plusieurs cancers est par conséquent limitée; les doses effectives pour induire l’apoptose étant toxique pour les cellules saines. L’objectif de la recherche présenté dans cette thèse est d’augmenter l’efficacité de l’As2O3 par le biais de thérapies combinatoires.Un antioxydant largement reconnu, le trolox (acide 6-hydroxy-2,5,7,8-tétraméthylchroman-2-carboxilique) augmente l’effet de l’As2O3 sur l’apoptose dans des cellules APL, de myélome, de cancer du sein en potentialisant le stress oxydatif. Par des expériences in vivo, nous observons que l’As2O3 prolonge la survie de souris possédant les tumeurs P388. De plus, la combinatoire avec le trolox augmente significativement la durée de vie de ces souris et diminue la quantité de candidats présentant des macrométastases. D’une autre part, des études in vitro montre que le trolox protège les cellules mononucl
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Bach, Griera Jordi. "Estudi in vitro del paper del dany oxidatiu com a mecanisme d’acció en la carcinogènesi associada a l’arsènic." Doctoral thesis, Universitat Autònoma de Barcelona, 2015. http://hdl.handle.net/10803/321106.
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L’arsènic inorgànic es presenta com un carcinogen molt ben establert en humans. Milions de persones es troben exposades arreu del món, fonamentalment a través de l’aigua de consum contaminada per aquest compost. Encara que existeixen múltiples mecanismes d’acció pels quals l’arsènic pot exercir els seus efectes carcinògens, la generació de dany oxidatiu en el DNA a partir de les espècies reactives d'oxigen derivades de la seva biotransformació es presenta com un dels mecanismes importants a l’hora d’explicar l’aparició dels fenòmens tumorals associats amb la seva exposició.
En aquest context, l’objectiu principal d’aquesta Tesi ha estat demostrar la connexió existent entre la presència de dany oxidatiu i la carcinogènesi associada a una exposició amb arsènic inorgànic. Per arribar a aquest objectiu s’ha implementat una estratègia innovadora de treball en el qual s’emulen les condicions d’exposició ambiental a les que es troben exposades les poblacions humanes. Concretament, aquesta estratègia es basa a desenvolupar un model d’exposició crònica in vitro a dosis subtòxiques d’arsènic inorgànic. A més, s’ha utilitzat un model cel·lular particular constituït per dues línies cel·lulars isogèniques de fibroblasts embrionaris de ratolí (MEF), una de les quals és deficient en la reparació de lesions oxidants del DNA que requereixen el mecanisme BER, exhibint un genotip knockout pel gen Ogg1, un dels gens principals de l’esmentada ruta de reparació del DNA.
Al llarg d’aquest període d’exposició crònica a dosis de 0,5, 1 i 2 µM d’arsenit sòdic, es van avaluar diferents paràmetres en ambdues línies cel·lulars, els valors dels quals van ser comparats amb els corresponents controls temporals. Dits paràmetres mesuren els nivells acumulats de dany oxidatiu (8-OH-dG), la capacitat de reparar el dany en el DNA, l’estudi de possibles mecanismes d’adaptació i, finalment, l’adquisició d’un fenotip tumoral in vitro en ambdues línies cel·lulars al llarg d’un procés d’exposició arsenit sòdic del voltant 40 setmanes.
Els resultats obtinguts donen suport a la hipòtesi reflectida en l’objectiu principal. Així, les línies cel·lulars Ogg1 deficients (MEF Ogg1 -/-) crònicament exposades a l’arsènic mostren una acumulació progressiva de dany oxidatiu en el DNA, mentre que l’increment d’aquest dany no es detecta en la línia salvatge. Paral·lelament, l’eficiència dels mecanismes de reparació del dany induït en el DNA es veu afectada en ambdues línies cel·lulars, manifestant-se així l’activitat cocarcinògena de l’arsènic. Pel que fa referència a l’adquisició del fenotip tumoral, trobem que l’arsènic és capaç d’induir un fenotip tumoral de manera primerenca en la línia deficient, el que indicaria que el dany oxidatiu en el DNA juga un paper fonamental en la carcinogènesi associada a l’exposició. Així, les cèl·lules Ogg1 -/- manifesten un fenotip tumoral al cap de 30 setmanes d’exposició, caracteritzat per canvis morfològics, un increment en proliferació cel·lular, el descontrol en estat de diferenciació, l’ increment en la secreció de metal·loproteïnases de la matriu extracel·lular, l’adquisició de la capacitat de créixer independent d’ancoratge, i la capacitat de promoure el creixement tumoral i la invasió.
A manera de conclusió, aquesta Tesi demostra, principalment i per primera vegada, que el fons genètic referent al gen OGG1 i la inducció de 8-OH-dG són factors rellevant en el procés de carcinogènesi associada a l’arsènic. Indirectament, el treball posa de manifest el risc associat dels individus amb polimorfismes al gen OGG1, fent-los més susceptibles a l’aparició dels efectes genotòxics i carcinògens derivats de l’exposició.Inorganic arsenic is presented as a very well established human carcinogen. Millions of people around the world are exposed to this compound mainly through contaminated drinking water. Although there are multiple mechanisms of action by which arsenic may exercise their carcinogenic effects, the generation of oxidative DNA damage from reactive oxygen species derived from its biotransformation is presented as one of the most important mechanisms explaining the associated cancer phenomena. In this context, the main objective of this thesis was to demonstrate the connection between the presence of oxidative damage and carcinogenesis, linked to inorganic arsenic exposure. In order to reach this objective, we have implemented an innovative strategy plan which emulated environmental conditions in which human populations are exposed. Specifically, this strategy is based on developing an in vitro model of chronic exposure to subtoxic inorganic arsenic doses. In addition, we used a particular cell model comprising two isogenic cell lines from mouse embryonic fibroblasts (MEF), being one of them deficient in the repair of oxidative DNA lesions that require the BER mechanism, showing a knockout genotype for Ogg1, one of the major genes of this DNA repair pathway. Throughout this period, cells were exposed to 0.5, 1 and 2 µM of sodium arsenite for 40 weeks. Different parameters were evaluated in both cell lines, the values of which were compared with the corresponding time-matched controls. These parameters were the accumulated levels of oxidative damage (8-OH-dG), the ability of repairing DNA damage, the mechanisms of adaptation and, finally, the acquisition of an in vitro tumor phenotype. Results supported the main hypothesis. Thus, Ogg1 deficient cell lines chronically exposed to arsenic showed a progressive accumulation of oxidative DNA damage, whereas that increase was not detected in its wildtype counterparts. Moreover, the efficiency of DNA repair mechanisms in repairing the induced damage was affected in both cell lines, manifesting the arsenic co-carcinogen activity. Taking into account the acquisition of the tumor phenotype, we found that arsenic can induce an early tumor phenotype in the deficient Ogg1 cell line, indicating that oxidative DNA damage plays a role in carcinogenesis associated with the exposure. Thus, Ogg1 - /- cells expressed a tumor phenotype after 30 weeks of exposure, characterized by morphological changes, an increase in cell proliferation, the lack of a correct differentiation status, the increase in secretion of extracellular matrix metalloproteinases, the acquirsition of the ability to grow independent of anchor, and the acquisition of the ability to promote tumor growth and invasion. In conclusion, this thesis shows for the first time that the genetic background of the reference gene OGG1 and the induction of 8-OH-dG are key factors in the arsenic-associated carcinogenesis. Indirectly, the work highlights the associated risk of individuals carrying OGG1 gene polymorphisms, as they are expected to be more susceptible to the genotoxic and carcinogenic effects of the exposure.
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Kourelis, Maria. "Characterization of the novel arsenical darinaparsin (ZIO- 101, S-dimethylarsino-glutathione) as a more potent inducer of oxidative stress and apoptosis than arsenic trioxide in acute promyelocytic leukemia." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40780.
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Arsenic trioxide (As2O3) is an effective treatment strategy for acute promyelocytic leukemia (APL), as sensitivity to As2O3 may correlate with the induction of oxidative stress. However, the use of As2O3 in other malignancies is limited at clinically achievable doses. To expand the clinical potential of arsenic to other malignancies, a promising novel arsenical, darinaparsin (S-dimethylarsino-glutathione, ZIO-101) is more potent in vitro than As2O3 in a variety of hematopoietic malignant cell lines. At equimolar concentrations, darinaparsin is significantly more potent than As2O3 in inducing signalling pathways known to be required for arsenic-induced apoptosis. Moreover, unlike As2O3, darinaparsin is a selective inducer of Nrf2 antioxidant responses, thereby generating unopposed oxidative stress response and apoptosis in APL. Interestingly, darinaparsin does not demonstrate sensitivity to inhibition of ABCC1 (Mrp1), a known transporter involved in resistance to arsenic, suggesting that darinaparsin may be an effective treatment in tumours that overexpress ABCC1.L’anhydride arsénieux (As2O3) est un traitement efficace contre la leucémie aigue myéloide (LAM). La sensibilité envers l’As2O3 peut être attribué à l’induction de stress oxidative. Cependant, l’usage d’ As2O3 dans le cadre d’autres malignités est limité par la posologie clinique. Pour élargir le potential thérapeutique de l’arsenic, un nouveau composé arsenical, le darinaparsin (ZIO-101), est plus efficace in vitro que l’ As2O3 dans une variété de cellules hématopoïétiques malines. Dans des conditions d’équimolarité, le darinaparsin est beaucoup plus puissant que l’ As2O3 pour provoquer des voies métaboliques requises pour l’apoptose. De plus, contrairemet à l’ As2O3, le darinaparsin insite séléctivement l’antioxidant Nrf2. Ce dernier produit un stress oxidative incontesté qui permet l’apoptose dans le cadre de la LAM. Curieusement, le darinaparsin ne répond pas à l’inhibition de l‘ABCC1 (Mrp 1), un transporteur qui confère de la résistance contre l’arsenic. Ceci suggère que le darinaparsin peut être un traitement efficace contre des tumeurs qui possèdent une importante quantitée d’ABCC1.
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Hays, Allison Marie. "Arsenic Exposure: Effects on Oxidative Stress, Gene Regulation and the Extracellular Matrix in the Lung." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1403%5F1%5Fm.pdf&type=application/pdf.
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Rahman, Shaily. "Oxidation of arsenite by dissolved oxygen, manganese and iron oxyhydroxides in aqueous solutions." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80857.
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Oxidation of dissolved arsenite was studied in 0.05M and 0.7M NaCl aqueous solutions. The experimental conditions included a range of pH (3 to 9), presence and absence of ambient light, presence and absence of oxygen, and presence and absence of amorphous and crystalline Mn and Fe oxyhydroxides at (Mn - Ox and Fe-Ox) constant solid: solution ratios of 0.0002. All experiments were conducted at a temperature of 23 +/- 4°C and initial arsenite concentration of approximately 100 ppb. Arsenic speciation was determined both in the aqueous phase and in the combined solid and aqueous phases.Aqueous arsenite oxidation by oxygen alone is slow. Light, pH, and ionic strength had no effect on the oxidation rate of arsenite by dissolved oxygen. In the presence of manganese- and iron oxyhydroxides (Mn-Ox and Fe-Ox), the oxidation of arsenite is rapid: within 15 minutes, more than 80% of the initial As(III) was oxidized to As(V) by crystalline and amorphous Fe-Ox, and by amorphous Mn-Ox. In the presence of crystalline Mn-Ox, more than 20% of the initial As(III) was oxidized within the first 5 minutes of the experiment. Dissolved oxygen was not essential for the arsenite oxidation by the metal oxides. (Abstract shortened by UMI.)
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Pereira, Maria do Socorro Silva. "Especiação e remoção de arsenio de aguas utilizando voltametria de redissolução catodica e processos oxidativos avançados." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249518.
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Orientadores: Anne Helene Fostier, Susanne RathTese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
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Doutorado
Quimica Analitica
Doutor em Ciências
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Todorova, Tatina Vuilleumier Stéphane Kujumdzieva Anna. "Glutathione S-transferases and oxidative stress in Saccharomyces cerevisiae." Strasbourg : Université Louis Pasteur, 2007. http://eprints-scd-ulp.u-strasbg.fr:8080/814/01/Todorova_Tatina_2007.pdf.
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Thèse de doctorat : Aspects moléculaires et cellulaires de la biologie : Strasbourg 1 : 2007. Thèse de doctorat : Aspects moléculaires et cellulaires de la biologie : Sofia - Bulgarie : 2007.Thèse soutenue en co-tutelle. Titre provenant de l'écran-titre. Bibliogr. f. 143-155.
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Todorova, Tatina. "Glutathione S-transferases and oxidative stress in Saccharomyces cerevisiae." Université Louis Pasteur (Strasbourg) (1971-2008), 2007. https://publication-theses.unistra.fr/public/theses_doctorat/2007/TODOROVA_Tatina_2007.pdf.
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Les glutathion S-transférases répresentent une famille d'enzymes impliquée dans la détoxification de composés d’origine éxogène et endogène. Les GSTs peuvent avoir des activités péroxidase ou isomérase et également d’exprimer fonctions non-catalytiques, comme l’interaction avec differents ligands ou la modulation de la signalisation cellulaire. Un éventail des mutants de S. Cerevisiae a été choisi pour étudier le rôle des GSTs dans la réponse au peroxide et à l’arsenic. Notre criblage a montré l’existance de deux GSTs, qui peuvent avoir un rôle dans la détoxification de ces composés. Tef4p est un facteur de transduction dont le mutant correspondant est sensibile à l'As(V) et au H2O2. Au contraire, Ure2p joue un rôle dans la détoxification de l’As(III). Ce rôle, déterminé par la partie GST de la molécule est résultat de la fonction de la protéine dans la régulation du type GATA. La fonction régulatrice est dans l’origine également de la sensibilité aux oxydants du mutant ure2ΔGlutathione S-transferases are an enzyme family playing an important role in cellular detoxification of exogenous and endogenous toxic compounds. In addition, GSTs can serve as peroxidases, and isomerases or have non-catalytic functions, among which binding of non-substrate ligands and the modulation of signaling processes. A systematic approach, using defined yeast mutants, has been taken to demonstrate the connection between GSTs and the oxidative stress caused by peroxide and arsenic. This screening revealed that two yeast GSTs, Ure2p and Tef4p, may play a role in arsenic and oxidant detoxification. Tef4p is a translatation factor and the corresponding disruption mutant is sensitive to H2O2 and As(V). In contrast, Ure2p is required for the detoxification of As(III) in S. Cerevisiae. This protection role is determined by the GST domain of the molecule and is a result of the GATA repression role of Ure2p. GATA regulation is also in the origin of oxidant sensitivity of the mutant ure2Δ
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Dastidar, Aniruddha. "ARSENITE OXIDATION BY PURE CULTURES OF THIOMONAS ARSENIVORANS STRAIN B6 IN BIOREACTOR SYSTEMS." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_diss/70.
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The removal of arsenic toxicity from water is accomplished by a preliminary preoxidative step transforming the most toxic form, arsenite (As (III)), to the least toxic form, arsenate (As (V)). The potential of As (III) oxidation to As (V) was initially investigated in batch reactors using the chemoautotrophic Thiomonas arsenivorans strain b6 under varying initial As (III) and cell concentrations and at optimal pH and temperature conditions (pH 6.0 and temperature 30°C). The strain b6 completely oxidized As (III) to As (V) during exponential growth phase for lower levels of As (III) concentrations (≤ 100 mg/L) but continued into stationary phase of growth for higher levels (≥ 500 mg/L). Other important factors such as oxygen and carbon limitations during biological As (III) oxidation were also evaluated. The biokinetic parameters of the strain b6 were estimated using a Haldanesubstrate inhibition model with the aid of a non-linear estimation technique.
Microbial As (III) oxidation was further investigated in continuous-flow bioreactors (CSTR and biofilm reactor) under varying As (III) loading rates. Both the reactors achieved As (III) oxidation efficiency exceeding 99% during the steady-state conditions. The reactors were also able to recover from an As (III) overloading phase establishing the resilient nature of the microorganism. The basic mass balance expressions on As (III) and biomass along with the Monod model were used to linearly estimate the biokinetic parameters in the CSTR study. However, in the biofilm study, a steady-state flux model was used to estimate the same parameters. The performance of the model was very good in simulating the transient and steady-state conditions.
Finally, the potential application of one-stage and two-stage reactor systems was investigated for the near complete removal of arsenic. Activated alumina was used as the adsorbent for the As (V) produced by the biological oxidation of As (III). The two-stage reactor process performed better than the one-stage reactor system in lowering the arsenic level below the detection limit (1 mg/L) for at least eight days of operation. However, pH fluctuations and probable competition from ions such as PO43- , SO42-, and Cl- severely impacted the performance of the reactors. Further study is needed to improve the overall efficiency of the reactor systems for achieving complete removal of arsenic for a longer operating time.
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Macoch, Mélinda. "Impact de l’arsenic inorganique sur la physiologie in vitro des cellules dendritiques humaines." Thesis, Rennes 1, 2013. http://www.theses.fr/2013REN1B013/document.
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L’arsenic inorganique est un contaminant environnemental, cancérogène pour l’homme, mais également un métalloïde étudié, aujourd’hui, dans le traitement de maladies inflammatoires chroniques. Il possède des propriétés immunosuppressives pouvant déréguler les mécanismes physiologiques de défense ou bloquer l’exacerbation de réponses inflammatoires chroniques. L’arsenic inorganique altère principalement les fonctions des lymphocytes T et des macrophages. En revanche, l’impact du métalloïde sur la physiologie des cellules dendritiques (DCs) est peu connu. Pourtant, ces cellules présentatrices d’antigène jouent un rôle fondamental dans les processus d’immunosurveillance et sont très impliquées dans la physiopathologie des maladies inflammatoires chroniques. Dans ce contexte, les objectifs de mon travail de thèse étaient d’étudier les effets de l’arsenic inorganique sur la différenciation et la maturation in vitro de DCs générées à partir de monocytes humains. Nos résultats démontrent principalement que des concentrations de métalloïde, compatibles avec les taux plasmatiques d’arsenic mesurés chez les individus exposés, répriment la capacité des DCs à sécréter différentes cytokines pro-inflammatoires jouant un rôle essentiel dans l’activation et la polarisation des lymphocytes T. En particulier, l’arsenic inhibe l’expression et la sécrétion de l’interleukine-12 par un mécanisme moléculaire impliquant le facteur de transcription Nrf2. Au total, ces travaux de thèse démontrent que l’arsenic inorganique possède des propriétés immunosuppressives sur la physiologie in vitro des DCs humaines. Cette immunotoxicité pourrait contribuer à la toxicité du métalloïde chez l’homme exposé par voie environnementale, et être prise en compte pour déterminer les effets de l’arsenic dans le traitement de certaines maladies inflammatoires chroniquesInorganic arsenic is an environmental human carcinogen, but is also studied these days because of its potential effectiveness in curing chronic inflammatory disease. Indeed, this metalloid possesses immunosuppressive properties which can dysregulate physiological mechanisms involved in immune defense, or reduce inflammation associated with those inflammatory diseases. Inorganic arsenic is known mainly to alter functions of T cells and macrophages. However, it is unknown whether arsenic targets dendritic cells (DCs). Yet, this antigen presenting cells plays a major role in the immunosurveillance, and is involved in the physiopathology of chronic inflammatory diseases. So, the aim of my thesis work was to study the effects of inorganic arsenic on in vitro differenciation and maturation of dendritic cells from human monocytes. Our results mainly shows that concentrations corresponding to those measured in environmentally exposed people, inhibits DCs secretion of proinflammatory cytokines, which plays a major role in activation and polarization of T cells. Particularly, arsenic strongly impairs expression and secretion of interleukine 12 (IL-12) by an underlying molecular mechanism involving Nrf2. Finally, this work shows that inorganic arsenic has immunosuppressive properties on the physiology in vitro of human dendritic cells. Immunotoxicity may then contribute to the metalloid toxicity in environmentally exposed people. This element could be taken into account when determining arsenic effects in curing some chronic inflammatory diseases
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Sanglard, Lílian Maria Vincis Pereira. "Impactos negativos do arsênico na fotossíntese em folhas de arroz são mitigados pela suplementação de silício, sem aumento da capacidade antioxidante." Universidade Federal de Viçosa, 2014. http://locus.ufv.br/handle/123456789/4345.
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Silicon (Si) plays important roles in alleviating various abiotic stresses, possibly by counteracting stress-induced oxidative damage. In rice (Oryza sativa), arsenic (As) is believed to cause oxidative stress and to share the Si transport pathway for entry into roots. Despite much progress in understanding the mechanisms underlying the uptake of As and how they can be affected by Si, the physiological mechanisms through which Si might alleviate As toxicity in plants remain to be elucidated. We combined gas exchange and chlorophyll fluorescence measurements with analysis of the activity of the antioxidant system to examine the effects of Si nutrition on photosynthetic performance and oxidative stress in rice plants (a wild-type cultivar and its lsi1 mutant defective in Si uptake) challenged with arsenite. Arsenite treatment led to an impairment of carbon fixation that was unrelated to stomatal and photochemical limitations but, rather, was associated with decreased mesophyll conductance. This impairment could be reverted to a considerable extent by Si in a time- and genotypedependent manner. The ameliorative effects of Si on As-treated plants were uncoupled from any noticeable up-regulation of the antioxidant capacity. We identified Si nutrition as an important target in attempts to not only decrease As concentrations but also to improve the photosynthetic performance of rice plants challenged with As, which may ultimately result in better crop yield coupled with enhanced food safety.
O silício (Si) desempenha um papel importante em mitigar vários estresses abióticos, possivelmente por minimizar o dano oxidativo induzido por estresse. Em arroz (Oryza sativa), acredita-se que o arsênio (As) possa causar estresse oxidativo compartilhando com o Si a mesma via de entrada nas raízes. Apesar dos grandes avanços na compreensão dos mecanismos de absorção de As e como estes podem ser afetados por Si, os mecanismos fisiológicos pelos quais o Si pode mitigar a toxicidade do As em plantas ainda precisam ser esclarecidos. Neste trabalho, avaliaram-se os efeitos isolados e combinados de Si e arsenito [As(III)] em plantas de arroz, usando um genótipo selvagem e o mutante lsi1 (low silicon rice 1) defectivo para a absorção de Si, no que diz respeito às trocas gasosas e parâmetros de fluorescência da clorofila a e aos danos celulares. A presença de As(III) levou a uma diminuição da fixação de carbono, fato não relacionado com limitações estomáticas e fotoquímicas, mas associada à diminuição da condutância mesofílica. Esta redução pôde ser revertida ao longo do tempo de forma considerável pela presença do Si, nos dois genótipos. Entretanto, os efeitos benéficos do Si em plantas tratadas com As(III) não apresentaram relação direta com o aumento da regulação da capacidade antioxidante. A fertilização com Si pode ser importante tanto na tentativa de diminuir as concentrações de As(III) quanto para melhorar o desempenho fotossintético de plantas de arroz contaminadas com As, o que pode resultar em uma melhor produtividade da cultura, além de promover aumento da segurança alimentar.
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Peng, Zhimin. "The Role of IκB kinase β in Redox Modulation." Cincinnati, Ohio : University of Cincinnati, 2009. http://rave.ohiolink.edu/etdc/view.cgi?acc_num=ucin1229934522.
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Thesis (Ph.D.)--University of Cincinnati, 2009.Advisors: Ying Xia PhD (Committee Chair), Howard Shertzer PhD (Committee Member), Mary Beth Genter PhD (Committee Member), Alvaro Puga PhD (Committee Member), Keith Jones PhD (Committee Member). Title from electronic thesis title page (viewed April 30, 2009). Includes abstract. Includes bibliographical references.
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Thomas, Audrey. "Effet sur le microenvironnement tumoral d’une modulation pharmacologique du stress oxydant." Thesis, Paris 5, 2012. http://www.theses.fr/2012PA05T086/document.
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Les Formes réactives de l’oxygène (FRO) ont un rôle bien établi dans l’oncogénèse en augmentant les capacités de prolifération et d’invasion des cellules tumorales. Mais les FRO exercent aussi un effet important sur le microenvironnement tumoral, en particulier en participant à l’échappement des tumeurs au système immunitaire. Une modulation pharmacologique de l’équilibre oxydo-réductif tumoral est donc susceptible d’influencer la progression tumorale. Il a été montré que l’induction pharmacologique d’un stress oxydant dans les cellules tumorales peut induire un effet cytotoxique mais ses effets sur le microenvironnement sont moins bien connus. L’objectif de nos travaux était d’étudier l’effet d’une modulation du stress oxydant sur les cellules immunitaires du microenvironnement tumoral et in fine de préciser les conséquences potentielles sur la progression tumorale. L’arsenic trioxyde (As2O3), inducteur de FRO, présentait à faible dose, dénuée d’effet cytotoxique direct sur les cellules malignes, un effet antitumoral dans un modèle de cancer colique murin. Cet effet était lié à une déplétion sélective en lymphocytes T régulateurs (Tregs) et était médié par la génération d’anions superoxyde (O2°-) et de monoxyde d’azote (NO), eux même responsables de la formation de peroxynitrite. Les Tregs présentaient un niveau basal de FRO plus élevé que les autres populations lymphocytaires, qui pourrait expliquer leur plus grande sensibilité à un surcroît de stress oxydant induit par l’As2O3. Un cytotoxique antitumoral, la vinorelbine, s’est également montré capable d’exercer un effet sur le microenvironnement tumoral. Par co-cultures, nous avons montré que la vinorelbine induisait un effet bystander toxique sur les cellules immunitaires effectrices voisines des cellules tumorales. In vivo, le prétraitement par vinorelbine de cellules malignes implantées à la souris était responsable d’une perte de la réactivité anti-tumorale des cellules mono-nuclées. Cet effet était dépendant de la production d’O2°- et de NO par les cellules malignes. Un modulateur du stress oxydant, le mangafodipir, inhibait cet effet, permettant ainsi de restaurer la réponse immunitaire antitumorale locale. Notre travail a donc permis de mettre en évidence que des modulateurs du stress oxydant peuvent agir sur le microenvironnement, et spécialement sur les cellules immunitaires. Ils pourraient être utilisés en clinique pour restaurer la réponse immunitaire antitumorale. Une meilleure compréhension du rôle du stress oxydant dans la défaillance de l’immunité antitumorale est nécessaireSeveral reports have demonstrated the involvement of reactive oxygen species (ROS) in carcinogenesis, through promotion of cancer cell proliferation and invasion. But ROS could also have consequences on non cancerous cells which are part of the tumor microenvironment, such as immune cells. Therefore, a pharmacological modulation of oxidative stress can induce a cytotoxic effect on tumor cells but its consequences on microenvironment are unknown. The aim of our studies was to evaluate the effects of a pharmacological modulation of oxidative stress on immune cells from the tumor microenvironment. At low dose, Arsenic trioxide (As203), an oxidative stress modulator, was shown to exert antitumor effects in colon tumor-bearing mice. We observed that this effect was related to As203-induced regulatory T cells (Tregs) -selective depletion in vitro and in vivo and was mediated by oxidative and nitrosative bursts. The differential effect of As203 on Tregs versus other CD4 cells was related to difference in the cells’redox status. We also observed that vinorelbine, an anticancer agent, could interfere with the antitumor immune response. We showed that vinorelbine could alter the function of immune cells surrounding tumor cells by a bystander toxic effect against tumor effector cells. In vivo experiment in A549 tumor bearing nude mice showed that adoptive transfer of A549 immune splenocytes was not able to delay tumor growth when vinorelbine-pretreated A549 cells were used for immunization. This effect was mediated by ROS and was inhibited by an oxidative stress modulator, mangafodipir, which restored antitumor immune function. Therefore, our work showed that oxidative stress modulators can influence tumor microenvironment and more specifically, immune cells. They could be used to restore antitumor immune response
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Lafleur, Gaël. "Nouvelles architectures de composants photoniques par l'ingénierie du confinement électrique et optique." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30263/document.
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Le confinement électrique et optique par oxydation des couches minces d'AlGaAs est une étape essentielle dans la réalisation des composants photoniques actifs et passifs dans la filière de matériaux GaAs. La recherche de performances ultimes sur ces composants nécessite une meilleure maîtrise du procédé d'oxydation ainsi qu'une meilleure connaissance des propriétés optiques de l'oxyde d'aluminium (AlOx). Dans cette perspective, j'ai d'abord réalisé une étude expérimentale de la vitesse d'oxydation des couches d'AlGaAs en fonction de la température du substrat, de la composition en gallium des couches étudiées, de la pression atmosphérique et de la géométrie des mesas considérés. Puis, j'ai établi un modèle anisotrope permettant une meilleure résolution spatiale et temporelle de la forme du front d'oxydation de l'AlAs. Enfin, j'ai exploité ce procédé pour réaliser des composants d'optique guidée notamment des micro-résonateurs puis réalisé des guides optiques à fente et caractérisé leurs performances optiquesOptical and electrical confinement using Al(Ga)As layer oxidation is a key milestone in the fabrication of active and passive GaAs-based photonic components. To optimize those devices, through the control of the optical and electrical confinements, a better modelling of oxidation process and a better understanding of optical properties of aluminum oxide (AlOx) is required. One part of this work is focusing on a throughout experimental study of AlGaAs oxidation kinetics, where I studied different important parameters such as wafer temperature, gallium composition, atmospheric pressure and mesa geometry. Then, I developed a new predictive model taking into account the process anisotropy, thus allowing a better temporal and spatial of AlAs oxidation front evolution. Finally, I could exploit this technological process to realize whispering gallery mode microdisks as well as slot optical waveguides, and I have characterized this latter photonic devices
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Sanville, Michael William. "Electrochemical oxidation of arsenic." 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1444624.
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Engrola, Filipa Sofia Silva. "Bacterial arsenite oxidation at the molecular level." Master's thesis, 2019. http://hdl.handle.net/10362/89008.
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According to the WHO, arsenic is one of the top 10 chemical contaminants in drinking-water worldwide and affects more than 140 million people. The arsenite oxidising enzyme (Aio), from microorganisms Rhizobium sp. NT-26 (NT-26_Aio) and Alcaligenes faecalis (A.f._Aio), and their final electron acceptors – cytochrome c552 (NT-26_cytc552) and azurin (A.f._azu), respectively – are currently being studied for their use as biosensors and in bioremediation processes. Both Aio enzymes share high structural similarity (948 matching residues with an r.m.s.d. of 1.84 Å for Cα atoms) and are composed of a large subunit (AioA) which contains a molybdenum centre and a [3Fe-4S] cluster, and a small subunit (AioB) that possess a Rieske [2Fe-2S] cluster.
Aiming to elucidate the catalysis mechanism of the enzymes, and their electron transfer to the final electron acceptors, a combination of expression and purification of the proteins, crystallisation, structural analysis, enzyme kinetics and affinity tests were conducted.
A 1.84 Å resolution structure of A.f._Aio in complex with a substrate analogue - SbV oxoanion - was determined using molecular replacement (PDB: IG8K). Additionally, a previously obtained 1.89 Å resolution structure of NT-26_Aio, containing a SbIII oxoanion near the active site, was investigated and used for comparison. Analysis of bond lengths and geometry of the ligands at the Mo active site suggests that both crystallized enzymes reveal different reaction intermediates, corresponding to different stages of the mechanism. The specific activity of two active site mutants of NT-26_Aio – D169A and E453A – determined by UV-Vis spectroscopy, revealed that these only uphold 46 and 8% of the WT enzyme efficiency, respectively. This information, together with structural analysis, strongly suggest that both amino acid residues play an essential role in substrate orientation through a complex network of hydrogen-bonds.
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Ramdial, Anusha. "Microbial oxidation of arsenite in gold mine effluent." Thesis, 2000. http://hdl.handle.net/10413/9085.
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Kuo, Hong-yi, and 郭弘億. "The Study of Arsenic Removal with Coagulation-Oxidation and PTFEHollow Fiber Microfiltration." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/44gyws.
Full textAbstract:
碩士嘉南藥理科技大學
環境工程與科學系
100
Arsenic contamination in natural waters has become a worldwide issue since it is a well-known human carcinogen due to its toxicity. The maximum contaminant level of 10 μg L-1 arsenic for drinking water standard was established by WHO and USEPA as a strict guideline. Therefore, research and development on arsenic removal from natural raw waters has gained a lot of attention. In this study, the removal of arsenic from groundwater using pre-oxidation with NaOCl and hollow fiber microfiltration was investigated. The effect of coagulation using FeCl3 in combination with pre-oxidation and microfiltration on the removal efficiency of arsenic was also examined. Results showed that the removal efficiency of arsenic could be arranged in the following order: oxidation using NaOCl in combination with coagulation > coagulation alone > oxidation alone. In the sand filter, a higher dosage of coagulant applied would cause an increase in arsenic removal. However, this also leads to increase in the frequency of backwashing. The microfiltration unit provided better arsenic removal due to floc accumulation on the membrane that enhances arsenic adsorption. In addition, the microfiltration unit requires a lower dosage of coagulant and experiences lesser decline in flux in comparison to sand filtration. Membrane fouling by the microfiltration unit is prevented through a good tank mixing, which lifts and flushes away the floc film formed on the membrane. In general, the hollow fiber microfiltration unit can effectively remove arsenic from groundwater. However, due to floc formation and accumulation on the membrane that leads to the deterioration of membrane performance, replacing the microfiltration membrane is necessary. In addition, the properties and characteristics of the groundwater would also affect the frequency of changing the membrane unit. On the other hand, the microfiltration unit could be used as a tertiary treatment for drinking water, which could be installed at the end of the water purification process, in order to control the with arsenic concentration below the regulatory standards.
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Zhu, Wenyi. "Chemical and microbial control of pyrite weathering and its implications to arsenic mobility and sulfur and iron geochemistry." 2010. http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.000052172.
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Yeh, Ching-fen, and 葉錦芬. "Determination of monophosphate nucleotides, sulfur-containing amino acids, arsenic species and various oxidation states of iron, vanadium and chromium by capillary electrophoresis inductively coupled plasma mass spectrometry." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/75875427827850424034.
Full textAbstract:
博士國立中山大學
化學系研究所
93
Capillary electrophoresis (CE) is in comparison with other chromatographic techniques, CE has several advantages such as high resolving power, small sample volume requirement, minimal buffer consumption and high sample throughtput. As a detection technique, inductively coupled plasma mass spectrometry (ICPMS) provides the advantages of low detection limit, multielement detection, and element- and isotope-specific detection capabilities. Therefore, the use of CE as a high resolution separation technique with ICP-MS as a sensitive element specific detector is of growing interest for analytical research. Four studies in our research are described below, respectively. A preliminary study of a modified microconcentric nebulizer (CEI-100, CETAC) as the sample introduction device of capillary electrophoresis inductively coupled plasma mass spectrometry (CE-ICP-MS) for the determination of monophosphate nucleotides is described. The monophosphate nucleotides studied include adenosine 5’-monophosphate (AMP), guanosine 5’-monophosphate (GMP), uridine 5’-monophosphate (UMP) and inosine 5’-monophosphate (IMP). The species studied were well separated using a 70 cm length × 75 μm id fused silica capillary while the applied voltage was set at -22 kV and a 20 mmol/L ammonium citrate/citric acid buffer (pH 4.0) containing 0.1% m/v cationic polymer (hexadimethrine bromide, Polybrene) was used as the electrophoretic buffer. The electroosmotic flow was reversed by flushing the fused silica capillary with 0.2% m/v Polybrene to accelerate separation. The detection limit of various species studied was in the range of 0.036~0.054 μg P/mL, which corresponded to the absolute detection limit of 1.1~1.6 pg P based on the injection volume of 30 nl. We determined the concentrations of nucleotides in two IG-enriched monosodium glutamates purchased from the local market. The recovery was in the range of 100~112% for various species, and the concentrations of IMP and GMP in these samples were in the range of 0.15–0.18% m/m. Capillary electrophoresis dynamic reaction cellTM inductively coupled plasma mass spectrometry (CE-DRC-ICP-MS) for the determination of sulfur-containing amino acids is described. The sulfur-containing amino acids studied include L-cysteine, L-cystine, DL-homocystine and L-methionine. The species studied were well separated using a 70 cm length × 75 μm i.d. fused silica capillary while the applied voltage was set at +22 kV and a 10 mmol/L disodium tetraborate buffer (pH 9.8) containing 0.1 mmol/L EDTA and 0.5 mmol/L Triton X-100 was used as the electrophoretic buffer. The sulfur-selective electropherogram was determined at m/z 48 as 32S16O+ by using its reaction with O2 in the reaction cell. The method avoided the effect of polyatomic isobaric interferences at m/z 32 caused by 16O16O+ and 14N18O+ on 32S+ by detecting 32S+ as the oxide ion 32S16O+ at m/z 48, which is less interfered. The detection limit of various species studied was in the range of 0.047~0.058 μg S/mL, which corresponded to the absolute detection limit of 1.3~1.6 pg S based on the injection volume of 27 nl. We determined the concentrations of selected sulfur-containing amino acids in urine and nutritive complement samples. The recovery was in the range of 92~128% for various species. Capillary electrophoresis-dynamic reaction cell inductively coupled plasma mass spectrometry (CE-DRC-ICP-MS) for the speciation of iron (III/II), vanadium (V/IV) and chromium (VI/III) is described. Two different CE migration modes were employed for separating the six metal ions using pre-capillary complexation. One is counter-electroosmotic mode in which iron (III/II) and vanadium (V/IV) ions were well separated using a 60 cm × 75 μm i.d. fused silica capillary. The voltage was set at +22 kV and a 15 mmol/L tris(hydroxymethyl)aminomethane (Tris) buffer (pH 8.75) containing 0.5 mmol/L ethylenediaminetetraacetic acid (EDTA) and 0.5 mmol/L ortho-phenanthroline (phen) was used as the electrophoretic buffer. The other is co-electroosmotic mode in which chromium (VI/III) ions were well separated while the applied voltage was set at −22 kV and a 10 mmol/L ammonium citrate buffer (pH 7.7) containing 0.5 mmol/L diethylenetriaminepentaacetic acid (DTPA) and 0.01% polybrene was used as the electrophoretic buffer. The mass spectra were measured at m/z 51, 52 and 56 for V, Cr and Fe, respectively. The interfering polyatomic ions of 35Cl16O+, 40Ar12C+ and 40Ar16O+ on 51V+, 52Cr+ and 56Fe+ determination were reduced in intensity significantly by using NH3 as the reaction cell gas in the DRC. The detection limits were in the range of 0.1~0.5, 0.4~1.3 and 1.2~1.7 μg/L for V, Cr and Fe, respectively. Applications of the method for the speciation of V, Cr and Fe in wastewater were demonstrated. The recoveries were in the range of 92~120% for various species. A capillary electrophoresis-inductively coupled plasma-mass spectrometric (CE-ICPMS) method for the speciation of six arsenic compounds, namely arsenite [As(III)], arsenate [As(V)], monomethyl arsonic acid, dimethylarsinic acid, arsenobetaine and arsenocholine is described. The separation has been achieved on a 70 cm length × 75 μm ID fused-silica capillary. The electrophoretic buffer used was 15 mmol/L Tris (pH 9.0) containing 15 mmol/L sodium dodecyl sulfate (SDS), while the applied voltage was set at +22 kV. The arsenic species in biological tissues were extracted into 80% v/v methanol-water mixture, put in a closed centrifuge tube and kept in a water bath, using microwaves at 80℃ for 3 min. The extraction efficiencies of individual arsenic species added to the sample at 0.5 mg As/g level were between 96% and 107%, except for As(III), for which it was 89% and 77% for oyster and fish samples, respectively. The detection limits of the species studied were in the range 0.3~0.5 μg As/L. The procedure has been applied for the speciation analysis of two reference materials, namely dogfish muscle tissue (NRCC DORM-2) and oyster tissue (NIST SRM 1566a), and two real-world samples.
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Hsueh, An-Lun, and 薛安倫. "Urinary Arsenic Metabolites, Oxidative Stress Biomarker and Genomic Polymorphism in Arsenic-exposed Employees." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/93456415860024178048.
Full textAbstract:
碩士高雄醫學大學
公共衛生學研究所碩士班
94
Arsenic is a notorious environmental toxicant known as a carcinogen in human beings. Peoples exposed to inorganic arsenic compounds will excrete urinary arsenic metabolites via the detoxification process in the body. To understand the interindividual variability in urinary arsenic metabolites and the possible association with gene polymorphisms, this study was devoted to analyze the urinary arsenic metabolites and GSTM1, T1, O1, MTHFR gene polymorphisms in arsenic-exposed employees. In addition, to explore the possible effects of arsenic exposure on oxidative stress, this study also measured the serum malondialdehyde (MDA, a biomarker of oxidative stress) and investigated their relationship between arsenic metabolites and MDA in arsenic-exposed employees. Urine and peripheral blood samples were collected from semiconductor factory employees. The urine samples were analyzed with HPLC-HGAAS for arsenic metabolites, including arsenite (AsIII), arsenate (AsV), monomethyarsonic acid (MMAV), and dimethylarsinic acid (DMAV). Serum malondialdehyde was determined using HPLC method. DNA obtained from peripheral blood was genotyped using methods of polymerase chain reaction with restriction fragment length polymorphism (PCR-RFLP). The results indicate that no significant difference in arsenic methylation capability was observed for male and female. However, subjects with the null genotype of GST M1 have an increased inorganic arsenic/organic arsenic ratio compared to those with non-null genotype. A marked decrease in the concentrations of total arsenic and organic arsenic metabolites was found in the null genotype of GST T1 compared to those with non- null genotype. Furthermore, those with heterozygous genotype of GST O1 E155del have a decrease percentage of MMA in urine. No significant relationship between urinary arsenic metabolites and serum biomarker of oxidative stress in employees was observed in the present study.
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Chung, Chi-Jung, and 鍾季容. "Oxidative and Antioxidant Enzymes Genetic Polymorphisms and Arsenic-related Hypertension." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/47655855066558110309.
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碩士臺北醫學大學
公共衛生學系
91
To examine the association between the NAD(P)H Oxidase p22phox C242T and antioxidant enzymes (Manganese superoxide dismutase and Catalase) gene polymorphisms and arsenic-induced hypertension in the blackfoot disease endemic area. A total 292 people were recruited from the blackfoot disease (BFD) cohort randomly by who had blood and urine samples. Hypertension was defined as a systolic blood pressure of greater 140mmHg, or a diastolic blood pressure of greater 90mmHg, or have a history of hypertension and treated regularly with antihypertensive drugs. There were 79 persons diagnosed as hypertension. The demographic characteristics and other important risk factors of hypertension obtained through standardized interviews based on a structured questionnaire. Moreover, DNA was extracted from buffy coat to analyze the gene variants of oxidative and antioxidat enzymes utilizing polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). The T allele frequency of NAD(P)H Oxidase and Catalase is 0.05 and 0.04, respectively. And The C allele frequency of MnSOD is 0.17. The relative risks of NAD(P)H Oxidase CT and TT versus CC genotype, MnSOD TC and CC versus TT genotype, and Catalase CT versus CC genotype were 1.31(0.56~3.11), 1.78(0.99~3.18), and 1.07(0.35~3.22) respectively after age and sex adjustment. Body mass index, fasting serum triglyceride levels, low-density lipoprotein and cumulative arsenic exposure were all significantly positive associated with hypertension prevalence after adjusting for age and sex. After adjusted for cumulative arsenic exposure, The relative risk of MnSOD TC or CC genotype and Catalase CT and TT genotype was twice increment than the MnSOD TT genotype and Catalase CC genotype respectively. The higher the cumulative arsenic exposure was the higher the prevalence of hypertension. The results of this study suggested that long-term arsenic exposure have strong association with hypertension.
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Kofroňová, Monika. "Role sacharidového metabolismu v obraně proti oxidativnímu stresu vyvolanému působením arsenu." Doctoral thesis, 2019. http://www.nusl.cz/ntk/nusl-404722.
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Heavy metal contamination significantly reduces crop yields, causing serious problems in agriculture and having a major impact on human health if these contaminants enter the food chain. Understanding the mechanisms of plant responses could help to increase their resistance to heavy metals as well as their potential use in phytoremediation. Carbohydrates play an important role in plant growth and development as well as in defense reactions. This work summarizes the results of four publications focused on the effects of arsenic and thorium on antioxidant mechanisms in tobacco plants and horseradish root crops. Attention is paid, among other things, to the dynamics of sugar contents, which are potentially important molecules involved in the fight against oxidative stress. The first publication summarizes arsenic effects on plant physiological parameters, focusing on arsenic tolerance-enhancing mechanisms as well as summarizing the ability of plants to cope with arsenic-induced oxidative and nitrosative stress. Emphasis was placed on, among other things, a topic that was unjustly neglected in previous publications - i.e. carbohydrate metabolism. Further work was already experimental and dealt with the study of arsenic as a trigger of oxidative stress in the root culture of horseradish and...
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Chan-Wei, Yu. "Caenorhabditis elegans gcs-1 confers resistance to arsenic-induced oxidative stress." 2007. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2001200716263500.
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Yu, Chan-Wei, and 游展維. "Caenorhabditis elegans gcs-1 confers resistance to arsenic-induced oxidative stress." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/09014706117931152019.
Full textAbstract:
碩士國立臺灣大學
生物環境系統工程學研究所
95
Gamma-glutamylcysteine synthetase (γ-GCS) catalyzes the first, rate-limiting step in the biosynthesis of glutathione (GSH). To evaluate the protective role of cellular GSH against arsenic-induced oxidative stress in Caenorhabditis elegans (C. elegans), we examined the effect of the C. elegans ortholog of GCS(h), gcs-1, in response to inorganic arsenic exposure. We have evaluated the responses of wild-type and gcs-1 mutant nematodes to both inorganic arsenite (As(III)) and arsenate (As(V)) ions and found that gcs-1 mutant nematodes are more sensitive to arsenic toxicity than that of wild-type animals. gcs-1 mutant nematodes also showed an earlier response to the exposure of As(III) and As(V) than that of wild-type animals. Pretreatment with GSH significantly raised the survival rate of gcs-1 mutant worms compared to As(III)- or As(V)-treated worms alone. The intracellular GSH level increases in C. elegans exposed to As(III) and gcs-1 expression level is induced by As(III). The functional importantance of GCS-1 in C. elegans exposed to As(III) is investigated by analysis of gcs-1 transcription in transgenic C. elegans and RNAi mediated GCS-1 knock-down worms. The level of mRNA expression of several potential oxidative response gene is response to As(III) exposure was also investigated. Our results show that GCS-1 is essential for the synthesis of intracellular GSH in C. elegans and consequently that the intracellular GSH status plays a critical role in protection of C. elegans from arsenic-induced oxidative stress. Furthermore, As(III) is capable of inducing mRNA expression of oxidative stress-related genes.