Effects of natural and commercial dissolved organic matters (doms) on the availability of benzo(a)pyrene in spmd (semi-permeable membrane device) and daphnia magna

[Departement_IRSTEA]MA [TR1_IRSTEA]QSA / EXPERCharacteristics of the aquatic environment greatly influence the bioavailability of organic compounds. The dissolved organic matters (DOMs) may interact with hydrophobic organic compounds and this usually results in reducing their bioavailability. The assumption made is that pollutants that are bound to DOMs are too large to cross biological membranes and only the free dissolved fraction of the pollutant is avalailable for the organisms. Semi-Permeable Membrane Device (SPMD) has been developed to evaluate bioavailable fractions of hydrophobic organic compounds [1,2]. It is a polyethylene tube with 1000 Da-equivalent pore diameter containing lipid (triolein) like in biological tissues. SPMD-available fraction and Daphnia-available fraction of a selected hydrophobic pollutant, benzo(a)pyrene (BaP), have been compared in laboratory (with controlled temperature, pH and ionic strength) with various natural and commercial DOMs. In order to study the influence of the DOM properties, we tested some DOMs from various origins. Natural DOMs were previously extracted from rivers (from Suwannee river in the U.S; and Apremont, Gartempe, St Maurice, Andresy rivers in France) onto XAD-8 and XAD-4 resins and thus fractionated into a hydrophobic fraction and a transphilic fraction. Each fraction was characterized (by apparent molecular weight, elemental composition, aromaticity~). Commercial DOM-like macrolecules (cyclodextrins, macrolides, flavonoïds) were also tested. Contrary to natural DOMs which are complex mixtures of macromolecular unknown compounds, they consist of pure molecules whose chemical and physical properties are well known. Our results showed that in most cases, SPMDs are good surrogates for living organisms when considering the BaP fraction accumulated. Moreover, the influence of DOM characteristics, especially molecular weight and aromaticity, on the availability of the contaminant have been confirmed