The use of 13C-labelled polycyclic aromatic hydrocarbons for the analysis of their transformation in soil.

The formation of non-extractable residues during biodegradation and humification processes in soils and sediments represents a major sink for organic contaminants. The mode of incorporation of polycyclic aromatic hydrocarbons (PAH) and their metabolites into macromolecular organic matter during microbial degradation was studied applying 13C-labelled compounds. Mineralisation rates were determined by measuring the 13CO2 production. An incorporation of 13C-PAH-fragments into humic material could be traced by isotopic analysis of the bulk organic matter. Furthermore, selective chemical degradation reactions were performed to analyse the precise chemical structure of covalently bound 13C-labelled PAH fragments in soil humic substances. Structural assignments by GC-MS combined with isotope measurements on the bulk organic carbon and at the molecular level (Isotope Ratio Monitoring-GC-MS) provided useful information on the fate of xenobiotics within the soil.