Influence of environmental conditions on the accumulation of PAHs in various passive samplers
Résumé
Over the last twenty years, several passive samplers have been developed to improve the monitoring of contaminants in aquatic systems. The amount of contaminant in situ accumulated during long periods of exposure enabled the determination of a time-weighted average concentration in water, provided exchange kinetic parameters are known. The aim of this work was to improve the knowledge of the influence of the environmental conditions on accumulation kinetics in passive samplers. The impact of the water velocity and the presence of biofilm at the surface of the sampler have been more particularly assessed. PAHs have been chosen as model hydrophobic compounds. Three passive samplers have been studied: semipermeable membranes devices (SPMDs) and polymeric membranes (LDPE and PDMS). A stainless steel channel of 6 m length has been constructed with 3 successive sections with different width and controlled velocities (0.02 to 0.09 m/s) and has been fed with wastewater at different stages of the treatment. Kinetics have been determined with passive samplers previously spiked with Performance Reference Compounds and exposed for two weeks. Dissolved concentration has been measured three times during the exposition period. A relation has been observed between the water velocity and the accumulation or elimination kinetics for all passive samplers tested regardless of the water composition. For SPMDs, the presence of biofilm at the surface has not strongly influenced exchange kinetics.