What does Semipermeable Membrane Device (SPMD) sampling mean? accuracy of time-weighted average concentration estimations of truly dissolved compounds

[Departement_IRSTEA]Eaux [TR1_IRSTEA]BELCAInternational audienceSPMDs1 are commonly used integrative passive samplers for hydrophobic organic compounds in water. Two major assumptions drive the interpretation of accumulated amounts of contaminants: Because of steric hindrance in the polyethylene membrane, only a fraction of dissolved organic compounds in water may be accumulated. - 1st assumption : only truly dissolved compounds are SPMD-available From the accumulated amount of a substance in SPMD, and dissipation of Performance Reference Compounds, the concentration of SPMD-available substance in water can be estimated. - 2nd assumption : the estimated SPMD-available concentration is a time-weighted average (TWA) concentration. Compiling field studies (sampling campaigns in rivers2 and wastewater treatment plants3) and using numerical simulations, we investigated the validity of these two assumption