Field application of a novel active-passive sampling technique for the simultaneous measurement of a wide range of contaminants in water.

A first test of the field capabilities of a novel in situ sampling technique combining active and passive sampling (APS) was conducted in the sea. The proof-of-concept device uses a pump to draw water into a diffusion cell where dissolved target substances are accumulated onto sorbents which are selective for different classes of contaminants (i.e., metal cations, polar and non-polar organic compounds), simultaneously. A controlled laminar flow established in the diffusion cell enables measurements of contaminant concentrations that are fully independent from the hydrodynamic conditions in the bulk solution. APS measurements were consistent with those obtained using conventional passive sampling techniques such as organic diffusive gradients in thin films (o-DGT) and silicone rubber (SR) samplers (generally < 40% difference), taking into account the prevailing hydrodynamic conditions. The use of performance reference compounds (PRC) for hydrophobic contaminants provided additional information. Field measurements of metal ions in seawater showed large variability due to issues related to the device configuration. An improved field set-up deployed in supplementary freshwater mesocosm experiments provided metal speciation data that was consistent with passive sampling measurements (DGT), taking into account the hydrodynamic conditions. Overall, the results indicate that the APS technique provides a promising approach for the determination of a wide range of contaminants simultaneously, and independently from the hydrodynamic conditions in the bulk solution.

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