Effect-direct analysis of AhR-active organic compounds in industrial soils contaminated by creosote
Résumé
Contaminations of industrial soils are generally difficult to assess due to the presence of complex mixture of many pollutants. The identification of contaminants which are responsible for biological effects is an important issue for the remediation of industrial sites and soils. Effect-directed analysis (EDA) is a quite new approach which combines bioassays, chemical fractionation and chemical analysis to identify polluants having biological effects. The use of EDA to identifiy contaminants in industrial soils focuses on novel compounds that would allow to adapt soil remediation methodology based on identified molecules and to find new relevant molecules to track for soil risk assesment. The methodology should be fast, cheap and repeatable in order to interest the industrials. Here, EDA has been developped with an extraction of pollutants by pressured liquid extraction, and fractionation by normal phase HPLC. It was been applied on an industrial site contaminated by creosote, a complex mixture containing several hundreds of molecules even if PAHs present 80% of its mass. The results show that this soil is contaminated by molecules able to activate the aryl hydrocarbon receptor. The fractionation shows a good repetability and a separation of the AhR activity among different fractions. AhR activity is distributed between fractions 7 and 16 with a more important activity for fraction 7 and 8. With this fractionation methodology, PAHs are eluted between fractions 4 and 8. The activities of these fractions are responsible of 66% of total AhR activity. By using toxic equivalent factors (TEF) based on Benzo(a)pyrene, the 16 PAHs of US-EPA explain 4% and 70% of AhR activity in F7 and F8 respectively. However, majority of AhR activity is due to another molecules that 16 PAHs of US-EPA and which are not quantified for soil risk assessment. Furthermore, majority of these AhR activators are eluted with a more polar fractions involving that molecules are more hydrophilic and possibly more mobile. GC-Q/ToF analyses are under progress to identified molecules present in active fractions.