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Diel variations of selected elements in arsenic-rich stream at the Mokrsko
Nováková, Barbara ; Drahota, Petr (advisor) ; Skřivan, Petr (referee)
The filtration and ultrafiltration experiment was applied on the stream water at the Mokrsko gold deposit and the results revealed that most of the elements were in the dissolved form and the 0,45 or 0,1 m filters could be used. During two 24-h field experiments, water samples were collected at 1-h intervals in order to prove the diel changes in the concentration and speciation of several trace elements. The determination of sorption processes at the surface of or within the veneer of biofilm has been determined by collecting natural and artificial priphyton. The results showed regular diel changes of As, Sb and Mo with highest concentrations occurring after the moon and the lowest concentrations in the early morning. The dissolved concentrations of other elements are conservative or their values were closed to their detection limits. The diel cycles are caused by changes in adsorption/desorption equilibria induced by diel cycles of temperature. The samples of biofilm revealed increased concentrations of the elements under the study and their diel variation were significant (approximatelly 35-96%); however, biofilm-controlled diel cycles of dissolved concentrations have not been proved.
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Development of Instrumentation and Methodology for Elemental and Speciation Analysis of Arsenic Based on Hydride Generation and on Atomic Fluorescence Spectrometric Detection
Marschner, Karel ; Dědina, Jiří (advisor) ; Kanický, Viktor (referee) ; Spěváčková, Věra (referee)
(EN) The presented dissertation is devoted to hydride generation from arsenic species and its application for speciation analysis based on atomic fluorescence detection. Hydride generation from toxicologically relevant arsenic species was optimized in order to achieve a 100% efficiency. The resulted experimental setup was subsequently used for speciation analysis of arsenic in human urine by high performance liquid chromatography with detection by atomic fluorescence spectrometry. The accuracy of the developed method was verified by comparative analyses of human urine samples collected from five individuals with an independent reference method. The cleavage of As-C bond during the reaction of methylated arsenic species with tetrahydridoborate(1-) (THB) in acidic media was studied in detail. Pronounced demethylation of methylated arsenic species was found during the reaction of THB with HCl, H2SO4, and HClO4 while hydride generation from CH3COOH or TRIS buffer after prereduction with L- cysteine resulted in the exclusive formation of the corresponding hydrides. Firstly, this phenomenon can endanger the accuracy of arsenic speciation which is based on hydride generation of substituted arsanes. Secondly, the more complex arsenic species can be converted to the hydride. That was demonstrated on hydride...
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Distribution of arsenic in the soil of gold mineralizations in Central Bohemian metallogenetic zone
Řeháček, Jan ; Drahota, Petr (advisor) ; Kindlová, Helena (referee)
Univerzita Karlova v Praze Přírodovědecká fakulta Ústav geochemie, mineralogie a nerostných zdrojů Obsahy arzenu v půdách zlatonosných ložisek středočeské metalogenetické zóny Bakalářská práce Jan Řeháček Vedoucí bakalářské práce: doc. Mgr. Petr Drahota, Ph.D. Praha, 2016 Summary This bachelor thesis reviews scientific publications regarding high concentrations of arsenic in soils of natural geochemical anomalies and former gold mines in the Central Bohemian Metallogenic Zone. High concentrations of arsenic in these areas originates primarily from sulfide minerals which are associated with gold mineralization. Arsenopyrite and pyrite are the most important primary As carriers in the bedrock. Due to natural weathering of sulfide minerals hosting rocks, release of arsenic and other potentially toxic elements into the surrounding environment takes place. This presents danger not only to soil fauna and flora but also to local inhabitants as contamination may also affect water sources in the area. At the beginning of this thesis some general aspects of the presence of arsenic in the environment are described, followed by chapters about the Central Bohemian Metallogenic Zone and its sites with anomalous concentration of arsenic in soil.
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Evaluation of sequential extraction for speciation of arsenic in mining wastes
Grösslová, Zuzana ; Drahota, Petr (advisor) ; Vaněk, Aleš (referee)
ii SUMMARY This master thesis deals with selectivity assessment of an arsenic sequential extraction procedure for evaluating mobility in mine wastes. A modified sequential extraction procedure was designed on the basis of preliminary tests of extraction efficiency and selectivity for the synthetic As mineral phases (scorodite, amorphous iron arsenate, schwertmannite, goethite, jarosite) and five natural samples (Kaňk, Dlouhá Ves, Giftkies, Roudný) that were previously characterized for As concentration and speciation. The modified sequential extraction has five steps. The first leaching step was performed in nitrogen-purged deionized H2O for 10 hours; next step involved 0.01M NH4H2PO4 leaching for 16 hours. Phases in the third step were dissolved with 0.2M Tamm`s reagent in darkness for 2 hours. The fourth step was represented by 0.2M of Tamm`s reagent heated in water bath at 80řC for 4 hours. Strong acid solutions HCl/KClO3/HNO3 were used to leach sulphide phases in the last step. The testing of the sequential extraction procedure using model mixtures showed a good discrimination of several fractions: adsorbed arsenic, arsenic associated with poorly crystalline oxyhydroxide, hydroxosulfate and arsenate phases (amorphous iron arsenate, schwertmannite, ferrihydrite), arsenic associated with crystalline...
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Anomalous occurences of arsenic in natural waters in the Czech Republic
Rodovská, Zuzana ; Drahota, Petr (advisor) ; Redlich, Aleš (referee)
This bachelor thesis reviews the data on the distribution of arsenic in surface and underground natural waters of the Czech Republic. In addition the thesis focuses on the occurrence of anomalous arsenic concentrations and tries to detect sources of arsenic contamination. Results of the thesis suggest high quality of the surface and groundwater in the Czech Republic with respect to arsenic. Its anomalous concentrations in the natural waters in Czech Republic have been rarely documented only in areas with strong anthropogenic impact and in areas affected by historical mining operations. Keywords: Arsenic, toxicity, contamination, surface water, groundwater, Czech Republic
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Optimization of generation and atomization of arsines for speciation analysis by atomic fluorescence spectrometry
Marschner, Karel ; Dědina, Jiří (advisor) ; Komárek, Josef (referee)
Speciation analysis of arsenic based on selective hydride generation and detection by atomic fluorescence spectrometry have been studied in this work. It was found that under optimum conditions of atomization in the flame in gas shield atomizer, sensitivity was approximately twice higher and detection limit was about four times lower compared to miniature diffusion flame, which is a standard atomizer for atomic fluorescence spectrometry. The conditions to generate hydrides from both inorganic forms of the arsenic, i.e. from arsenite and arsenate, with the same efficiency have been found in the batch arrangement, by using 1 mol dm-3 hydrochlorid acid and 1% solution of tetrahydridoborate. To determine only trivalent form, TRIS buffer at pH 6.00 was used together with 1% sodium tetrahydridoborate. The detection limits found for inorganic arsenic, i.e. for arsenite and arsenate, respectively, were 15 ng dm-3 and 9 ng dm-3 . It was found that in the batch arrangement under these conditions it is possible to generate corresponding hydrides methylarsonate and dimethylarsonate with the same efficiency as from the inorganic form. Finally, it was found when slightly changing the gas-liquid separator design in order to introduce the mixture of tetrahydridoborate with hydrochloric acid to the bottom of the...
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Speciation analysis of arsenic-glutathione complexes by ion-pairing HPLC-ICP-MS
Zušťáková, Veronika ; Matoušek, Tomáš (advisor) ; Červený, Václav (referee)
The thesis has focused on the separation of arsenic-glutathione species using ion-pairing high performance liquid chromatography with detection by inductively coupled plasma mass spectrometry. Species were separated on chromatographic column Prodigy ODS (3) using an aqueous mobile phase containing 4.7mM tetrabutylammonium hydroxide (TBAH), 2mM malonic acid and 4% methanol at pH 5.85 in the isocratic mode. Simple arsenic species - arsenite (iAsIII), arsenate (iAsV) monomethylarsenic acid (MAsIII), monomethylarsenous acid (MAsV), dimethylarsenic acid (DMAsIII) and dimethylarsenous acid (DMAsV), which served as arsenic standards to determine retention times, were successfully separated under these conditions. Arsenic-glutathione complexes As(GS)3, MAs(GS)2 and DMAs (GS) were not successfully separated. These complexes provided peaks of simple arsenic species. Peak broadening was observed in the first analysis of As(GS)3 and MAs(GS)2 complexes, which disappeared in subsequent analyses. This broadening probably represents a residual of glutathion complex which disintegrated to single species. Powered by TCPDF (www.tcpdf.org)
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Arsenic determination in beer samples and raw materials for its preparation
Švadlenová, Veronika ; Hraníček, Jakub (advisor) ; Jelínek, Ivan (referee)
This thesis describes the optimization of the method for determination of arsenic by the chemical hydride generation coupled with AAS detection in beer samples and raw materials for its preparation. The beer usually contain arsenic at ultratrace level, however, it is necessary to monitor the concentration of this element in the beer. The routinely used method for determination of arsenic is determination by electrothermal atomization. This approach is time consuming, expensive and less sensitive. It has been developer suitable determination of arsenic as a faster and less expensive method. For this method there was optimized the flow rate of argon to 75 ml·min-1, the optimum flow rate for the reagents was 4.0 ml·min-1 and for the sample 5.0 ml·min-1 . 3 % NaBH4 in 0.5 % NaOH was used as the reducing agent for the determination of arsenic, and HCl diluted 1:1 with distilled water was used to acidify the sample. With this parameter LOD was 0.32 μg·l-1 and LOQ 1.05 μg·l-1 . It has been tested the arsenic determination in samples of barley, malt and potable water as beer raw materials. It has been found that the beer matrix is unsuitable for the hydride generation technique due to a stormy reaction in the gas/liquid phase separator. The effect of pretreatment, which is likely to enhance the effect of...
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