Bedeutung des gelösten organischen Kohlenstoffs für das Schicksal hydrophober organischer Verbindungen in ungesättigten Bodenzonen

Tne characterisation of the behaviour of hydrophobic organic pollutants is often very difficult and their fate in pedogenic and aquatic environments is also problematic. The general goal of the present work is to impart a better understanding of the complexprocesses in ecosystems and to give a feeling that these processes are interlocking in the nature. A correct interpretation for physico-chemical processes is a prerequisite in determining the mobility of hydrophobic organic pollutants in soils arid aquatic systems. In this study the interactions of acenaphthene, dibenzofuran, 4-chlorobiphenyl and the urea herbicide methabenzothiazuron with natural organic matter are studied. Specific attention is given to the characterisation of the water solubility of the selected chemicals in the presence of dissolved organic carbon, to the analysis of the interactions between hydrophobic organic chemicals and natural organic matter and to the transport of these compounds in undisturbed soil material. Recent research also showed that the nature of dissolved organic carbon plays an important role in the transport of hydrophobic organic chemicals. The chemical nature of the natural organic matter used in this study was characterised by Curie-point pyrolysis gas chromatography-mass spectrometry. Threedifferent types of natural organic matter were considered in this study: Humic acid from Aldrich, a water extractable natural organic matter from peat and the natural organic matter present in the soll water. Batch experiments with these natural organic matters and the model chemicals showed an increase of the "apparent" water solubility with increasing concentration of dissolved organic carbon. For the same dissolved concentration an aqueous peat extract had, however, a lower dissolving power than the humic acid from Aldrich. In addition, higher ionic strength of the water matrix reduced the water solubility enhancement caused by dissolved organic carbon. The sorptive behaviour of acenaphthene and dibenzofuran was described by a Freundlich isotherm. The comparison of the K$_{F}$ values in the Freundlich equation showed that dibenzofuran sorbed stronger to the soll than acenaphthene. With a higher amount of organic carbon in the soll the sorption capacity increases. The amounts of hydrophobic target compounds removed from soll by aquatic solutions of different concentrations in dissolved natural material were found to be very small