Sensing dissolved sediment porewater concentrations of persistent and bioaccumulative pollutants using disposable solid-phase microextraction fibers

Polymer coated glass fibers were applied as disposable samplers to measure dissolved concentrations of persistent and bioaccumulative pollutants (PBPs) in sediment; porewater. The method is called matrix solid-phase microextraction (matrix-SPME), because it utilizes the entire sediment matrix as a reservoir for an equilibrium extraction: a glass fiber with a 15 mum coating of poly(dimethylsiloxane) (PDMS) was placed in a sediment sample until the PBPs reached their equilibrium distribution between the PDMS and the sediment matrix (1-30 days). PBP concentrations in the PDMS were determined by gas chromatography, and they were divided by PDMS water partition coefficients to derive at dissolved porewater concentrations. This approach was applied to measure porewater concentrations of spiked as well as field sediment, and several hydrophobic organic substances (log K-ow 5.2-7.5) were measured with high precision in the pg to ng/L range. Simple equilibrium partitioning is the basis for the substantial concentration factors that are built into matrix-SPME and for the low demands in materials and operation time. Matrix-SPME was in this study directed at the determination;of dissolved porewater concentrations in sediment, and it is further expected to be applicable to other environmental media, to field sampling, and to the sensing of fugacity.