Barbora Drtinová

Cesium uptake by Ca/Mg bentonite: evaluation of sorption experiments by a multicomponent two-site ion-exchange model

Abstract Cesium sorption on Czech Ca/Mg bentonite was studied using the batch technique for a wide range of both bentonite-to-water ratios (m/V) and initial concentrations of Cs. The experiments revealed non-linear pattern of cesium sorption, which was substantially influenced by the m/V. The results of the exchange reaction between added Cs+ and Mg2+, Ca2+, Na+ and K+ ions present naturally on the bentonite sorption sites enabled to determine the appropriate selectivity coefficients. The capacity of sites with higher selectivity to cesium, which is believed to be associated with the frayed-edge sites, was measured using the AgTU method.

Mercury species in formerly contaminated soils and released soil gases

Total mercury (T-Hg), elemental mercury (Hg0), methylmercury (MeHg+), phenylmercury (PhHg+), and gaseous elemental mercury (GEM) species were determined in soils formerly contaminated by different processes from two sites in the Czech Republic. Analytical methods involved atomic absorption spectrometry (AAS) using a single-purpose Advanced Mercury Analyser AMA-254 and radiochemical neutron activation analysis (RNAA) for T-Hg determination, a thermal desorption method was used for Hg0 determination, gas chromatography coupled with atomic fluorescence spectrometry (GC-AFS) was employed for assay of MeHg+ and PhHg+, while GEM measurement was carried out using a portable Zeeman-AAS device Lumex RA-915+. The first sampling site was in the surroundings of a former PhHgCl-based fungicide processing plant next to Příbram (central Bohemia). Although the use of Hg-based fungicides as seed mordant have been banned, and their production stopped at the end of 1980s, highly elevated Hg contents in soil are still observed in the vicinity of the former plant, reaching T-Hg values >13mgkg-1. The second sampling site was an abandoned mining area named Jedová hora Hill near Hořovice (central Bohemia), where cinnabar (HgS) was occasionally mined as by-product of Fe ores hematite and siderite. Mining activities have been stopped here in 1857. Very high contents of T-Hg are still found at this site, up to 144mgkg-1. In most cases we found a statistically significant correlation between T-Hg and Hg0 values regardless of the pollution source. On the contrary, insignificant correlation was observed neither between T-Hg and GEM values, nor between GEM and Hg0. Concentrations of the investigated organomercury species were above a limit of detection (LOD) only in the most contaminated samples, where their levels were about two to three orders of magnitude lower compared to those of T-Hg.

The matrix influence on the determination of low uranium concentrations by laser induced fluorescence method

A measurement technique enabling the determination of low uranium concentration utilizing system used for time resolved laser induced fluorescence spectroscopy (TRLFS), based on a commercially available kinetic phosphorescence analysis method has been developed. The effect of the matrix, complexing agent, and the level of acidification on the fluorescence spectra and integral intensity was studied. The method is highly influenced by the sample matrix; particularly if different starting uranium salts are in the calibration solutions and in the samples. In the initial study of these effects, TRLFS measurements have been used in order to clarify this behavior.

Some approaches to remediation study of the fucoid sandstone in the Straz pod Ralskem site - Nothern Bohemia

The behaviour of acid contaminantion in fucoid sandstone was studied on samples from Straz pod Ralskem, Czech Republic. Long term leaching of solid phase cores of contaminated fucoid sandstone with very low value permeability about 0.6 mD by background groundwater from Cenomanian aquifer was performed and possible chemical reactions were proposed. Results of leaching and modified extraction method divided core samples into two groups, depending on their leaching kinetic parameter (KDM). The KDM is dependent predominantly on pore accessibility for leaching solution and dissolution of secondary minerals. Radioactive 35S and 3H were used to determine effective diffusion coefficients.

Modelling of acid-base titration curves of mineral assemblages

Abstract The modelling of acid-base titration curves of mineral assemblages was studied with respect to basic parameters of their surface sites to be obtained. The known modelling approaches, component additivity (CA) and generalized composite (GC), and three types of different assemblages (fucoidic sandstones, sedimentary rock-clay and bentonite-magnetite samples) were used. In contrary to GC-approach, application of which was without difficulties, the problem of CA-one consisted in the credibility and accessibility of the parameters characterizing the individual mineralogical components.

Characterization of Uranium Behavior in the Ruprechtov Site (CZ)

The Ruprechtov natural analogue site is being studied because its geological and geochemical conditions resemble sedimentary sequences which can cover potential host rocks for underground waste repositories. The uranium content, sorption and isotopic exchange were studied on five selected rock samples that represented i) layers with higher content of uranium and ii) neighboring layers with practically no uranium content with the aim to discuss processes influencing transport of uranium in the body. In addition, the titration curves of rock samples were determined and modeled by SCM and so called GC and CA approaches.