Mobility of nitroaromatic compounds in the sandstone after the infiltration of sulfuric acid for the in situ leaching of uranium

As a result of former in situ leaching activities with sulphuric acid, nitroaromatic compounds have invaded into cenomanian and turonian sandstone aquifers and mining waters in parts of the uranium mining of Koenigstein, Germany (Saxony). In the mining area contamination levels of nitrobenzene, mononitrotoluene and dinitrotoluene lead to a partial excess in the drinking water guide values. For environmental protection, control and remediation efforts by flooding, more knowledge about contaminant mobility in sandstone, and in intercalated clays and silts, is demanded. A selected experimental area has been flooded to realize and study transport processes under real mining conditions. In this work, we have examined the mobilization of nitroaromatic compounds by flooding waters. The interactions between the nitroaromatic compounds, which are dissolved in the mining water, and the host rocks are discussed. The existing data for strata of varying lithologic conditions suggest that the sorption processes of the compounds investigated are negligible in pure sandstone aquifer layers and significant in the lithologic conditions with a complex mixture of mudstone, siltstone and clay. Several lithologic conditions are demonstrated in contaminant sinks and sources caused by adsorption processes and mobilization of newly connected stagnant pore waters. (orig.)