Analytical method for PAHs chemical speciation in sediments

The aim of this work is to optimize a method to examine the PAHs chemical speciation during the aging of sediments that is important in order to known the toxicological risk of a polluted area. In particular, we have conducted this research in order to determine if the organic contaminants fate is dependent to sediment characteristics and to study the potential role of humin and alkaline-extractable humic substances in the sequestration of PAHs in sediment. The Polycyclic Aromatic Hydrocarbons (PAHs) include molecules containing fused aromatic rings and are of special concern because of their widespread distribution throughout the environment and their often toxic and carcinogenic properties [1]. The PAHs are hydrophobic compounds and as consequence in aquatic environments, they bind tenaciously to sediment organic matter. Certain members of the PAH family even though have photolysis half-lives that are usually measured in days they are found to be preserved over geological time-scales in ancient sediments indicating that sorption onto a sediment can greatly prolong their lifetime in the environment [2]. From sediments, humic substances were fractionated into humic acids (HA) and humin-mineral fraction (HM) and after extracted, according to the method described by Nam [3]. Qualitative and quantitative determinations were carried out using a gas chromatograph coupled with a mass spectrometer. The results show the important role of humic substances in the PAHs sequestration and that the sediments characteristics influence the PAHs distribution between the labile fraction and the unavailable fraction.