Short-term exposure testing of six different passive samplers for the monitoring of hydrophobic contaminants in water.

Passive sampling devices are increasingly relied upon for monitoring non-polar organic contaminants in water. While many types of devices are available they have seldom been evaluated alongside each other. We tested six passive sampling devices namely: Chemcatcher, two modified versions of the membrane enclosed sorptive coating (MESCO I (m) and MESCO II), silicone rod and strip and semipermeable membrane device (SPMD). Samplers spiked with a range of performance reference compounds (PRCs) were exposed (5 days) in a continuous flow-through tank using Meuse river water fortified with fluctuating concentrations (20-700 ng L(-1)) of polycyclic aromatic hydrocarbons, polychlorinated biphenyls, hexachlorobenzene and p,p'-DDE. Dissipation rates of PRCs appeared to provide reliable information on exchange kinetics even under these short-term exposure conditions. They accounted for differences between masses of contaminants accumulated by replicate samplers, indicating that the variability between replicates was in part due to differences in water turbulences and hence boundary layer thickness. In this system, resistances in the membrane and boundary layers are likely to be in the same order of magnitude for PRCs. Sampler performance was evaluated by comparing masses accumulated in the devices only for analytes for which uptake was linear (integrative) and limited by transport across the boundary layer. Consistent data were obtained across the range of samplers despite their different configurations, and the analysis being conducted in three separate laboratories. The pattern in analyte masses accumulated by Chemcatcher and MESCO II data could be explained by the extraction and analysis being conducted only on the receiving phase of the samplers and a significant impact of the lag-phase prior to obtaining a steady flux of contaminants across the polyethylene membranes.