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  • Author or Editor: T. Madarász x
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Pesticides, chlorinated organic compounds and hydrocarbons are among the most threatening soil and groundwater contaminants because of their mobility and persistence in the subsurface, their widespread use, and their health effects. Hazardous chemicals getting into underground medium can be especially dangerous because they may remain persistently hidden from human eyes for a long time and their harmful impact on health may appear much later than their emission time and spatially far from the source of contamination. Development and combination of reliable and accurate geophysical methods and hydrogeological transport models with the traditional chemical analytics are greatly needed to assess the risk posed by the contamination plumes of these compounds to the subsurface.The paper presents the successful cooperation of these three disciplines in detailed characterization of subsurface hydrocarbon contaminants in a test site of Hungary. Combining the chemical analysis with high resolution geophysical methods and hydrogeological transport modeling the 4 dimensional characteristics of the contamination can be produced. The interdisciplinary research produced new developments and results in all participating fields of sciences.

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Thermally induced changes in the oxidation state of cerium(IV)

A study of carbonate and chloro complexes

Journal of Thermal Analysis and Calorimetry
Authors: J. Madarász, T. Leskelä, G. Pokol and L. Niinistö

Abstract

Cesium hexachlorocerate(IV), Cs2CeCl6 (I) and sodium pentakis(carbonato)cerate(IV), Na6Ce(CO3)5·12H2O (II) have been investigated in air by simultaneous TG/DTA, FTIR and XRD in order to follow the oxidation state of cerium during their thermal treatment. The thermal decomposition of the hexachloro compound (I) is accompanied by a double change in the oxidation state of cerium. First, in an inner reduction-oxidation reaction, chlorine is evolved and a Cs2CeCl5 phase is obtained. The immediately starting oxidation of this Ce(III) species caused various phase transitions in the CeCl3-CsCl system formed. The presence of Cs3CeCl6 above 400°C can also be assumed and finally this phase also oxidizes into CeO2 with the formation of CsCl as by-product. In the case of the pentacarbonato complex (II), no Ce(III) species were detected. The final products of its decomposition were CeO2 and Na2CO3.

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Journal of Thermal Analysis and Calorimetry
Authors: G. Pokol, F. Tóth, I. Péter, J. Madarász, T. Kocsis and S. Gál
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