Jiří Mizera - Academia.edu (original) (raw)

Papers by Jiří Mizera

Journal of Environmental Radioactivity, Nov 1, 2014

Contents of uranium in coals from Ode r in the northernmost part of the Sokolov Basin, Czech Repu... more Contents of uranium in coals from Ode r in the northernmost part of the Sokolov Basin, Czech Republic, in the vicinity of the well known St. Joachimsthal uranium ore deposits, reach extremely high values. In the present work, coal samples with contents of uranium ranging from 0.02 to 6 wt.% were studied. The study employing a whole complex of analytical techniques has been aimed at identification of changes in the structure of coal organic matter, which are associated with the high contents of uranium in coal. The study includes proximate and ultimate analyses, multielement analysis by instrumental neutron and photon activation analyses, micropetrographic analysis by optical microscopy, ESEM/EDX analysis of mineral matter, infrared and Raman spectroscopies, solvent extraction followed by gas chromatography with mass spectroscopy (GC/MS), and analytical pyrolysis (Py-GC/MS). The study has confirmed previously proposed explanation of uraniferous mineralization in sedimentary carboniferous substances by the mechanism of reduction and fixation of soluble U(VI) (uranyl, UO 2þ 2) species (e.g., humic, carbonate/ hydroxo/phosphate complexes) by sedimentary organic matter under diagenetic or hydrothermal conditions, and formation of insoluble U(IV) species as phosphate minerals and uraninite. The process is accompanied with alteration and destruction of the coal organic matter. The changes in the structure of coal organic matter involve dehydrogenation and oxidation mainly in the aliphatic, aromatic and hydroxyl structures, and an increase in aromaticity, content of ether bonds, and the degree of coalification.

Meteoritics & Planetary Science, Mar 1, 2008

Twenty-three moldavites from a new locality, the Cheb Basin in Western Bohemia, were analyzed by ... more Twenty-three moldavites from a new locality, the Cheb Basin in Western Bohemia, were analyzed by instrumental neutron activation analysis for 45 major and trace elements. Detailed comparison of the Cheb Basin moldavites with moldavites from other substrewn fields in both major and trace element composition shows that the Cheb Basin is a separate substrewn field. The geochemical data obtained are discussed with respect to the source materials and processes leading to formation of moldavites. The data show that three groups of Cheb Basin moldavites exist. Ten samples of group 1 are characterized by the lowest content of Al, Fe, Na, and other elements representing phyllosilicate minerals, and by high Ca + Mg contents related probably to carbonates. They resemble the "poisonous green" moldavites, a subgroup of the Southern Bohemian moldavites. Seven samples of group 2 and 6 samples of group 3 are similar to typical moldavites of the Southern Bohemian substrewn field. These two groups differ from each other mainly in Al contents; with higher contents of Al and the elements associated with phyllosilicate minerals (namely Ba and Sr), group 3 also resembles the Moravian moldavites. Significant positive correlations between K, Ca, Mg, and Mn found in group 2 of the Cheb Basin moldavites and the enrichment in these elements observed generally in all moldavites, as well as other facts, e.g., high K/Na and K/Rb ratios and the reduced conditions during formation of moldavites, have been attributed to possible contribution to the moldavite source materials of the ash produced by burning of vegetation and soil organic matter present at the pre-impact area.

Journal of Radioanalytical and Nuclear Chemistry, Mar 1, 2007

The potential of photon activation analysis (PAA) for multielement trace analysis can hardly comp... more The potential of photon activation analysis (PAA) for multielement trace analysis can hardly compare with that of neutron activation analysis (NAA). However, PAA appears superior over NAA for the determination of a number of elements, namely C, N, O, F, Mg, Si, Ca, Ti, Ni, Sr, Y, Zr, Nb, Sn, Tl and Pb in geological, environmental and biological materials. Most

Geochimica et Cosmochimica Acta, Apr 1, 2016

Abstract Moldavites, tektites of the Central European strewn field, have been traditionally linke... more Abstract Moldavites, tektites of the Central European strewn field, have been traditionally linked with the Ries impact structure in Germany. They are supposed to be derived mainly from the near-surface sediments of the Upper Freshwater Molasse of Miocene age that probably covered the target area before the impact. Comparison of the chemical composition of moldavites with that of inferred source materials requires recalculation of the composition of sediments to their water-, organic carbon- and carbon dioxide-free residuum. This recalculation reflects the fact that these compounds were lost almost completely from the target materials during their transformation to moldavites. Strong depletions in concentrations of many elements in moldavites relative to the source sediments (e.g., Mo, Cu, Ag, Sb, As, Fe) contrast with enrichments of several elements in moldavites (e.g., Cs, Ba, K, Rb). These discrepancies can be generally solved using two different approaches, either by involvement of a component of specific chemical composition, or by considering elemental fractionation during tektite formation. The proposed conceptual model of moldavite formation combines both approaches and is based on several steps: (i) the parent mixture (Upper Freshwater Molasse sediments as the dominant source) contained also a minor admixture of organic matter and soils; (ii) the most energetic part of the ejected matter was converted to vapor (plasma) and another part produced melt directly upon decompression; (iii) following further adiabatic decompression, the expanding vapor phase disintegrated the melt into small melt droplets and some elements were partially lost from the melt because of their volatility, or because of the volatility of their compounds, such as carbonyls of Fe and other transition metals (e.g., Ni, Co, Mo, Cr, and Cu); (iv) large positively charged ions such as Cs + , Ba 2+ , K + , Rb + from the plasma portion were enriched in the late-stage condensation spherules or condensed directly onto negatively charged melt droplets; (v) simultaneously, the melt droplets coalesced into larger tektite bodies. Steps (iii)–(v) may have overlapped in time. The still melted moldavite bodies reaching their final size were reshaped by further melt flow. This melt flow was related to moldavite rotation and escape (bubbling off) of the last portion of gaseous volatiles during their flight in a low-pressure region above the dense layer of the atmosphere.

Journal of Hazardous Materials, 2009

The study presents results of sorption of metal ions (Pb2+, Zn2+, Cu2+, and Cd2+) onto lignite mi... more The study presents results of sorption of metal ions (Pb2+, Zn2+, Cu2+, and Cd2+) onto lignite mined in South Moravia, Czech Republic, and solid humic substances (humin and humic acid) derived from it. The efficiency of these sorbents has been studied as a function of contact time, solution pH, and metal concentration. The sorption efficiencies were higher for humin and lower for humic acid samples than for the original lignite. With its high sorption capacities of several mmol/g, particularly for Pb2+ and Cd2+, the South Moravian lignite can provide a cheap source material for preparation of sorbents utilizable in removal of toxic metals from wastewaters.

Scientific Reports, Aug 8, 2023

Geological Society of America eBooks, May 3, 2022

Actinide Speciation in High Ionic Strength Media, 1999

Page 125. DISSOCIATION CONSTANTS OF CARBOXYLIC ACIDS AT HIGH IONIC STRENGTHS Jiri Mizera, 1 Andre... more Page 125. DISSOCIATION CONSTANTS OF CARBOXYLIC ACIDS AT HIGH IONIC STRENGTHS Jiri Mizera, 1 Andrew H. Bond, 2 Gregory R. Choppin, and Robert C. Moore3 Department of Chemistry, The Florida State University ...

Scientific Reports

The parent impact crater of Australasian tektites has not been discovered so far, but a consensus... more The parent impact crater of Australasian tektites has not been discovered so far, but a consensus has been accepted on its location in a wider area of Indochina. Recently, an alternative location has been suggested in the Badain Jaran Desert (BJD), Northwest China. Employing gravity and magnetic data derived from satellites, possible presence of an impact structure in BJD is investigated. The gravity parameters include the free air gravity disturbance, its vertical derivative component and total horizontal gradient (THG), strike alignment (SA), and Bouguer anomaly with its first vertical derivative and tilt angle. The magnetic parameters include the anomalous total magnetic field (TMF), its reduced to the pole transformation (RTP), the first vertical derivative of the TMF vertical component (Bzz), tilt angle (TA), and logistic total horizontal gradient (LTHG). Both the gravity and magnetic indicators support the presence of the impact structure. Gravity parameters display typical an...

Journal of Radioanalytical and Nuclear Chemistry

International Journal of Coal Geology

Radiochimica Acta, 1996

ABSTRACT

Radiochimica Acta, 2001

Experimental methods based on the radiotracer technique have been designed to study kinetic aspec... more Experimental methods based on the radiotracer technique have been designed to study kinetic aspects of the interaction of humic substances (HS) with metal ions. The rate of dissociation of Eu-HS complexes was observed via the rate of the isotope exchange in the system

DOE Scientific and Technical Information. DOE Scientific and Technical Information. ...

Water Research, 2007

Potential low-cost sorbents of metals based on combined action of coal and chitosan have been inv... more Potential low-cost sorbents of metals based on combined action of coal and chitosan have been investigated. Sorption of Cs, Co and Eu on oxidized coals in mixture with chitosan was studied as function of pH ($3-6) in batch experiments using radiotracer method. An improved sorption efficiency of the coal sorbents at neutral pH was obtained in mixture with chitosan, namely for oxihumolite at sorption of Eu and Co. Chitosan prevented deterioration of the sorption ability of coal with pH increase probably via retaining the soluble complexes with humic substances leached from coal by formation of an insoluble complex. The effect of chitosan addition was negligible or reverse in case of lignite upon acidification, where the interaction takes place preferentially on the coal surface and may restrict availability of the binding sites for metal ions.

Microchemical Journal, 2007

Despite the role of iodine for proper development of the brain and the functions of the element, ... more Despite the role of iodine for proper development of the brain and the functions of the element, the accurate data on its concentration in brain tissue are largely lacking, the main reason being analytical difficulties associated with determination of the element especially at low levels. In this work, samples from human brain regions from Hungarian patients were analyzed using epithermal and radiochemical neutron activation analysis (ENAA and RNAA, respectively). The RNAA procedure is based on alkaline-oxidative fusion followed by extraction of elemental iodine in chloroform. The results were checked by the analysis of biological standard reference materials, namely bovine liver, bone meal and diet, and by comparison with previous results obtained by a different RNAA procedure.

Journal of Radioanalytical and Nuclear Chemistry, 2005

Summary Fruitbodies of wild-growing macromycetes (mushrooms) of various genera and species colle... more Summary Fruitbodies of wild-growing macromycetes (mushrooms) of various genera and species collected in localities with different geochemical features and man-made burden in the Czech Republic were analyzed using the short-term instrumental neutron activation, with both thermal and epithermal neutrons. Analytical possibilities of these methods were compared. Na, Mg, Al, Cl, K, Ca, V, Mn, Cu, and Br were determined regularly, whereas S, Ti, Rb, Cs, Ba, and Dy were determined occasionally with thermal neutron activation at irradiation-decay-counting times mode of 1-10-10 minutes. Because of high concentration of K and P in the macromycete dry matter (2-7% and 0.5-1%, respectively) and also high Cl concentration in some genera (up to 2.5%), all “1/v” absorbers, epithermal neutron activation in Cd box (1 mm thick wall) substantially suppresses their macroactivities and enhances sensitivity in the determination of elements with significant resonance integrals. Cu, Se, Rb, Ag, Hf, and sometimes Ba are determinable in the mode of 60-30-60 seconds, while K, Cu, As, Br, Rb, In, I, U (in some species also Co, Zn, Cs, Ba, and Hg) in the mode of 1-13-13 minutes. However, Na, Mg, Al, Cl, and Mn determination is not possible this way, as the (n,p) and (n,α) interfering reactions with fast neutrons and high K, P, and other interfering elements content make great interference contributions. Information about content of the essential and toxic elements in mushrooms is important in nutritional studies, because mushrooms form a non-negligible part of diet in many countries.

Journal of Radioanalytical and Nuclear Chemistry, 2009

A specific, radium bearing type of barites has been known from the Ohře (Eger) Rift, a region of ... more A specific, radium bearing type of barites has been known from the Ohře (Eger) Rift, a region of Cenozoic volcanic activity in northwestern Bohemia, Czech Republic, since 1904. Barites from Karlovy Vary, Teplice and Děčín areas have been studied to elucidate geochemical history of these specific samples. Low background radiometric method using high-resolution gamma-ray spectrometry has shown that radioactivity of