Passive sampling to assess the availability of hydrophobic organic pollutants in fresh and matured contaminated sediments
Résumé
Dredged contaminated sediments are considered as waste. Traditional solutions to the management of these sediments are dumping at sea, disposal to landfills or use as public work materials (back-filling, noise protection slope, landscape mound). To assess its potential impacts on human health and the environment, dredged material must be characterized, particularly with respect to the emission of persistent organic pollutants in percolating water. Some questions arise concerning the effect of disposal duration on the fate and bioavailability of persistent organic contaminants. Our study aims to determine the availability of persistent organic contaminants (16 polycyclic aromatic hydrocarbons - PAHs and 40 polychlorinated biphenyls -PCBs) in 3 fresh or matured (1.5 year) dredged sediments. Sediments were characterized in terms of texture, organic carbon content, black carbon content and oil content. The free dissolved concentration of contaminants in pore water was determined by passive samplers with low-density polyethylene (LDPE). The ratio of the total concentration (determined by classical solvent extraction) with the free dissolved concentration gives the sediment-water partition coefficient (Kd) of these contaminants in fresh or matured sediment. Apparently, higher partition coefficients are observed for matured sediments. A similar conclusion emergr from complementary tests (Tenax desorption and standard percolation test) carried on fresh and matured sediments. Oxydation phenomenon of minerals, inclusion into nanopores, enhancement of weathering degree of oil and ageing phenomenon (incorporation into organic carbon matrix) could explain the higher partition coefficient for matured sediments. The suitability of LDPE passive samplers to assess the difference in sorption capacity of fresh and matured sediment will be presented.