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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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Microbial mobilization of arsenic from soil at the Mokrsko gold deposit
Redlich, Aleš ; Drahota, Petr (advisor) ; Száková, Jiřina (referee)
The Mokrsko gold deposit is characterised by high arsenic concentrations in regolith. Naturally contaminated regolith and stream sediment samples have been studied in order to determine microbially mediated processes that lead to As mobilization. Arsenic concentration in regolith and sediment were 905 mg kg-1 and 1749 mg kg-1 , respectively. The mineralogy of arsenic in the regolith is dominated by arsenic-bearing goethite and minor arseniosiderite and Ba-pharmacosiderite. In contrast, highly reducing sediments are mainly characterised by secondary realgar and less arsenic-bearing goethite and secondary arsenates. These samples were used for incubation experiments under both aerobic and anaerobic conditions. When glucose was supplied as a C source under anaerobic conditions, indigenous bacteria significantly enhanced the extent of As release from the solid samples into solution. Highly positive correlation between the extracted amount of As and Fe implied that the microbial dissolution of Fe(III)-oxides is responsible for the As release, with possible contribution of secondary arsenates dissolution. On the other side, small amount of arsenic was released from the sediment during the aerobic incubation through the microbially mediated oxidation of secondary realgar. In attempt to find some bacterial...
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Arsenic Contamination of Waters in the World
Grecká, Marie ; Bendl, Jiří (advisor) ; Drahota, Petr (referee)
Summary: In this bachelor thesis there are summarized reasons of occurrence of too high As concentration in groundwater abroad and possibilities of the water treatment. There are mentioned mainly the Asian countries, where there were proved the cases of serious diseases of inhabitants in connection with long-term consumption of the water from the shallow groundwater in the area of big river deltas. Arsenic is released to the groundwater from the iron oxides by natural process in reductive environment (due to the oxidation of organic matter). In the arid climate areas in Asia or South America, there are also localities of high As groundwater. The groundwater in these arid areas is more saline and the reason of high As concentration there is the oxidation of sulphide minerals. Then there are given the other examples of arsenic release by the oxidation of pyrite in the gold (or tin) mining areas etc. Another source of arsenic in water is a geothermal system. A suitable method for the arsenic removal from water is a coprecipitation of iron and As (V).
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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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Anomalous occurrences of arsenic in soils of the Czech Republic
Svoboda, Ondřej ; Drahota, Petr (advisor) ; Hojdová, Marie (referee)
This thesis aims to evaluate the anomalous concentrations of arsenic in soils (>30 mg/kg) of the Czech Republic. Anomalous concentrations are mainly caused by combustion of fossil fuels, mining operations and weathering of arsenic-rich rocks. The largest part of contaminated soil in CR is related to the combustion of arsenic-rich lignite, and includes, e.g., the area of Ore Mountains. The highest concentrations of arsenic in soil of CR are up to thousands of mg/kg. For example, soil adjacent to the Kutná Hora ore district contained up to 6 890 mg/kg of As. Such a high concentrations are due to mining operations. Beside anthropogenic sources, weathering of arsenic-rich rocks at Mokrsko has resulted in anomalous concentrations in soil that may attain up to 2 890 mg/kg.
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Possibilities in presentation of geological databases in Regional Geology teaching
Trubač, Jakub ; Kachlík, Václav (advisor) ; Drahota, Petr (referee)
The thesis deals with the possibilities of presentation of geological information in the field of regional geology. The main aim of the thesis is to create the proposal of On-line Textbook in Regional Geology which can be used as a learning resource for universities, experts and all interested people. There had not been paid enough attention to the geology subject within the basic and secondary schools curriculum for last years. Geology was the part of other taught subjects. Nevertheless, there were initiatives that allowed to find new space for geology subject that has been realizing especially within frame educational programme at grammar schools. There are many resources that can be used during the educational process of regional geology such as traditional textbooks, expert compendiums, but also modern aplication in the form of internet projects. Unfortunatelly, current accesible web applications are not updated and do not include modern findings and knowledge. The proposal of On-line textbook represents the core topic of the thesis. This concept is being developed with the support of the Czech Geological Survey (CGS) in collaboration with the Faculty of Science at Charles University in Prague. There is the connection with CGS portal which is the main communication interface with the user. CGS portal...
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Geochemical model of arsenic at the Mokrsko gold deposit
Drahota, Petr ; Pertold, Zdeněk (advisor) ; Száková, Jiřina (referee) ; Zeman, Josef (referee)
Geochemical model of arsenic at the Mokrsko gold deposit Dissertation of Petr Drahota 1 Abstract The dissertation contributes to the As mobility at the naturally contaminated site of Mokrsko gold deposit in Central Czech Republic. The primary goal of the dissertation is to fill some gaps in previous research carried out at the study site in order to contribute to the quantitative biogeochemical model of As in the bedrock-groundwater-soil-surface water system. In the first part, the previous research related to As environmental issues at the study site has been reviewed, discussed and evaluated. These include detail information on (i) the extent of natural As contamination in bedrock and soil, (ii) the extent of As contamination in groundwater, (iii) the primary and secondary As mineralogy in bedrock and soil, (iv) the chemical speciation of As in soil and (v) the leaching experiments of the gold ore. In the second part, the mineralogical and chemical speciation of As in soil, in stream and fishpond sediments and dissolved As concentrations in waters have been studied to determine the processes that lead to release of As into solution and control its concentration under different redox conditions at the Mokrsko gold deposit. The highest dissolved As was found in groundwater (more than 1000 g L-1 ), which...
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