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Speciation of arsenic under reducing conditions of organic-rich soil
Peřestá, Magdaléna ; Drahota, Petr (advisor) ; Hiller, Edgar (referee) ; Doušová, Barbora (referee)
The PhD thesis deals with arsenic speciation under reducing conditions of soil with elevated content of organic matter. This issue has been studied in two wetland soils located in two geochemical As anomalies near the villages of Mokrsko and Smolotely (CZ). Speciation and mobility of As was studied in four experiments using a range of mineralogical (XRD, SEM/EDS, EMPA, Raman microspectroscopy) and geochemical (XRF, chemical extraction, pore water analysis) methods. Other methods used in this work included S isotopes and microbial community analysis. The results indicate that the formation of authigenic As sulfides (realgar and bonazziite) is relatively common mechanism of As sequestration in reducing conditions of wetland soils. The sulfides are formed in highly reducing organic-rich microenvironments, where microbial production of dissolved sulfide is sufficiently fast compared to water flow velocity and related slow solute transport. In these microenvironments, Fe sulfides are the first precipitates; As sulfides precipitate after the depletion of Fe2+ in the pore solutions. This phenomenon was well evidenced in the long-term incubation experiment. Results of this experiment also showed that newly formed As sulfides can form in environments with variable concentrations of As and Fe in groundwater....
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Speciation of arsenic in a historical mine wastes
Peřestá, Magdaléna
There are many locations with historical mining wastes around the world that contain high concentrations of pollutants and harmful elements. Mineralogical composition of those wastes has a major impact on release and later migration of dangerous elements into surrounding environments, resulting in potential environmental risk. Goal of this master thesis is to characterize mobility and major sinks of arsenic in 50-years-old mining waste materials at Jedová mine near Vejprty and Dlouhá Ves mine near Havlíčkův Brod. For this purpose, solid waste and pore water samples were collected from both mining waste dumps. Solid samples were analysed by mineralogical (XRF, XRD, SEM-WDS and Raman microspectroscopy) and geochemical (sequential extraction) methods, while pore water samples were analysed using IPC-MS (cations), HPLC (anions) and spectrophotometry (Fe3+/Fetot species). Arsenopyrite is the primary source of As at both localities. In the mining waste at Jedová jáma mine, As precipitates predominantly as amorphous ferric arsenate (HFA) and is also accumulated in scorodite and Fe (hydr)oxide (up to 3.2 wt.% of As2O5). In Dlouhá Ves, due to weathering of large amount of sulphides (sphalerite, chalcopyrite, galena, pyrite and pyrrhotite), acidic conditions prevail (pH ~ 2.7). Under this pH, the major part...
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Speciation of arsenic in a historical mine wastes
Peřestá, Magdaléna
There are many locations with historical mining wastes around the world that contain high concentrations of pollutants and harmful elements. Mineralogical composition of those wastes has a major impact on release and later migration of dangerous elements into surrounding environments, resulting in potential environmental risk. Goal of this master thesis is to characterize mobility and major sinks of arsenic in 50-years-old mining waste materials at Jedová mine near Vejprty and Dlouhá Ves mine near Havlíčkův Brod. For this purpose, solid waste and pore water samples were collected from both mining waste dumps. Solid samples were analysed by mineralogical (XRF, XRD, SEM-WDS and Raman microspectroscopy) and geochemical (sequential extraction) methods, while pore water samples were analysed using IPC-MS (cations), HPLC (anions) and spectrophotometry (Fe3+/Fetot species). Arsenopyrite is the primary source of As at both localities. In the mining waste at Jedová jáma mine, As precipitates predominantly as amorphous ferric arsenate (HFA) and is also accumulated in scorodite and Fe (hydr)oxide (up to 3.2 wt.% of As2O5). In Dlouhá Ves, due to weathering of large amount of sulphides (sphalerite, chalcopyrite, galena, pyrite and pyrrhotite), acidic conditions prevail (pH ~ 2.7). Under this pH, the major part...
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Speciation of arsenic in fluvial systems
Jaxylykova, Anastassiya ; Drahota, Petr (advisor) ; Peřestá, Magdaléna (referee)
4 Summary This bachelor work is devoted to the distribution of the increased concentrations of arsenic in fluvial systems near the villages of Mokrsko and Smolotely in the Central Bohemian region of the Czech Republic. Arsenic in these areas is found in sulfidic minerals associated with gold- bearing mineralizations in the bedrock. Due to the toxicity of arsenic, natural weathering of the mineralized rocks represents a danger for the population of these sites. The theoretical part of the work is devoted to general concepts of the occurrence and concentrations of arsenic in different environments. In the practical part, a small separate study is presented, which studies the concentration of arsenic in fluvial sediments and stream water of the study sites. The results show that the highest arsenic concentrations in the fluvial sediments are almost the same (500- 550 mg/kg). The highest dissolved arsenic concentration was found at Mokrsko (360 g/l), while the highest aqueous arsenic at Smolotely was 160 g/l. Keywords: Arsenic, fluvial sediments, stream water, arsenic contamination
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