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Effects of phosphate on the mobility of arsenic in contaminated areas
Stubbe, Petra ; Drahota, Petr (advisor) ; Hiller, Edgar (referee) ; Courtin-Nomade, Alexandra (referee)
Arsenic and phosphorus are chemical analogues, and it is proposed that they have similar chemical behaviors in environmental systems. To gain a better understanding of the geochemical processes that control the mobility and stability of arsenic and its phases exposed to low phosphate levels, a variety of environmental matrices was studied using different experimental approaches. Among the samples studied were contaminated agricultural soils, mine waste materials, streambed sediments and river waters from a contaminated fluvial system, and synthetic arsenate phases. A number of common methods and techniques used for geochemical and mineralogical investigations were chosen, such as XRD, Raman spectroscopy, ATR-FTIR, ICP-OES, or EPMA. The results obtained during my doctoral studies are presented in the form of three manuscripts. The first study explores the long-term impact of continuous input of relatively low phosphate discharged from a small- capacity wastewater treatment plant on arsenic mobility within a small fluvial system located in a natural arsenic anomaly. Here, we document a significant decrease in total arsenic concentrations and sequestration of phosphorus in sediments downstream of a treatment plant. This part of the research highlights the past and ongoing mobilization of arsenic from...
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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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Experimental in situ transformation of smelting wastes in soil systems
Jarošíková, Alice ; Ettler, Vojtěch (advisor) ; Hiller, Edgar (referee) ; Doušová, Barbora (referee)
Metallurgical activities are one of the important sources of environmental pollution, especially due to inappropriate treatment of waste materials containing potentially harmful elements. Soils in the vicinity of smelting operations are the main target reservoirs for these emitted contaminants. The aim of this study was to depict reactivity of copper smelter flue dusts and slags in aqueous and soil environments using laboratory and field experiments. Slags exhibited high concentrations of As (up to 0.95 wt.%), Cu (up to 2.4 wt.%), Pb (up to 1.02 wt.%), Sb (up to 0.37 wt.%), and Zn (up to 2.45 wt.%). Copper and other metal(loid)s were predominantly bound in sulphides, especially bornite, digenite, chalcocite, and galena. Flue dusts were mainly composed of As2O3 phase (arsenolite and claudetite), with minor amounts of gypsum, galena, quartz and covellite. The main contaminants in the dust were As (53.3 wt.%), Pb (3.41 wt.%), Sb (1.26 wt.%), Zn (1.41 wt.%), Cu (1.07 wt.%) and Bi (0.80 hm.%). The leaching tests performed in the pH range of 3-12 indicated that the release of metal(loid)s from both types of metallurgical wastes was highly pH-dependent. During the leaching in deionised water, up to 42 mg/kg As was released from slags and up to 52.6 g/kg was leached from the flue dust; the latter highly...
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Experimental in situ transformation of smelting wastes in soil systems
Jarošíková, Alice ; Ettler, Vojtěch (advisor) ; Hiller, Edgar (referee) ; Doušová, Barbora (referee)
Metallurgical activities are one of the important sources of environmental pollution, especially due to inappropriate treatment of waste materials containing potentially harmful elements. Soils in the vicinity of smelting operations are the main target reservoirs for these emitted contaminants. The aim of this study was to depict reactivity of copper smelter flue dusts and slags in aqueous and soil environments using laboratory and field experiments. Slags exhibited high concentrations of As (up to 0.95 wt.%), Cu (up to 2.4 wt.%), Pb (up to 1.02 wt.%), Sb (up to 0.37 wt.%), and Zn (up to 2.45 wt.%). Copper and other metal(loid)s were predominantly bound in sulphides, especially bornite, digenite, chalcocite, and galena. Flue dusts were mainly composed of As2O3 phase (arsenolite and claudetite), with minor amounts of gypsum, galena, quartz and covellite. The main contaminants in the dust were As (53.3 wt.%), Pb (3.41 wt.%), Sb (1.26 wt.%), Zn (1.41 wt.%), Cu (1.07 wt.%) and Bi (0.80 hm.%). The leaching tests performed in the pH range of 3-12 indicated that the release of metal(loid)s from both types of metallurgical wastes was highly pH-dependent. During the leaching in deionised water, up to 42 mg/kg As was released from slags and up to 52.6 g/kg was leached from the flue dust; the latter highly...
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