PARENT SESSION
HA6 General and multipurpose analysis
9:00 AM to 1:30 PM, Thursday, 10 May 2001
Session Chair: P. Sorensen
Room 6

(464) Determination of Polycyclic Aromatic Hydrocarbons bioaccumulation and biotransformation in Daphnia magna using spectrofluorimetry.

Gourlay, Catherine¹, Mouchel, Jean-Marie¹, Tusseau-Vuillemin, Marie-Hélène², Garric, Jeanne³, ^{1 2 3}

ABSTRACT- A new spectrofluorimetric method is tested in order to investigate PAHs bioaccumulation in aquatic organisms. Contaminated organisms are simply sonicated in the solvent used for analysis (dichloromethane and methanol). The extract is filtrated and the emission spectrum of the filtrate is recorded. Bioaccumulation of two PAHs, fluoranthene and benzo(a)pyrene in Daphnia magna has been determined. PAHs are easily detectable in daphnia after a 4h-exposure to a 100 ng/L benzo(a)pyrene solution or to a 10 mg/L fluoranthene solution. Fluorescence response is positively correlated to exposure time. It is also well linearly related to PAH concentration in water. However, shifts in the fluorescence emission bands of B(a)P have been observed in daphnia extracts, which might suggest at least two possible conclusions : (i) bounds between absorbed B(a)P and lipidic constituents of daphnia might be too strong to be broken down by solvent extraction or (ii) absorbed B(a)P is already significantly metabolised and the modified fluorescence spectrum is in part due to metabolites. More experiments will be available in the very next future to resolve these hypothesis. As expected in presence of humic substances, a reduction of bioaccumulation of benzo(a)pyrene was observed, whereas no modification in bioaccumulation of fluoranthene was noticed. More interestingly, much less intense shifts in fluorescence were obtained when humic acids were added to the solution which suggests that not only the total amount of incorporated B(a)P is modified in presence of humic acids, but also that it is not incorporated the same way. Direct fluorescence is therefore a promising way to differentiate between various pathways for bioaccumulation or absorption of PAHs.

Key words: bioaccumulation, spectrofluorimetry, PAHs, Daphnia magna