Formation of bound residues in bioremediation experiments of mineral oil polluted environments

Non-extractable residues formed during biodegradation or humification processes are thought to represent a sink for contaminants but may become a source later on. The association of contaminants with macromolecular organic matter has major implications for their bioavailability, toxicity, and transport in natural environments. we studied the mode of incorporation of xenobiotics and their metabolites into macromolecular organic matter. Typical metabolites of PAHs, chemically bound to soil humic substances by ester and ether linkages, were cleaved from the macromolecular matrix by selective chemical degradation techniques including isotope labelling. Low molecular weight compounds liberated by these reactions were studied on a molecular level by GC-MS and Irm GC-MS. The results are discussed in terms of long-term risk assessment of bioremediation.