Field performance of seven passive sampling devices for monitoring of hydrophobic substances

The performance of seven passive sampling devices for the monitoring of dissolved concentrations of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), hexachlorobenzene, and p,p'-DDE was evaluated through simultaneous field exposures of 7-28 days in the River Meuse (The Netherlands). Data from the Chemcatcher, low density polyethylene membranes, two versions of the membrane-enclosed sorptive coating (MESCO) sampler, silicone rods, silicone strips and semipermeable membrane devices (SPMD) was assessed through rate of dissipation of performance reference compounds (PRCs), mass of analyte absorbed by the samplers and time-weighted average concentration (C(TWA)) data. Consistent PRC data throughout the range of samplers tested here confirmed the transition from membrane- to boundary layer-controlled exchange at log K(ow) 4.5-5.0. The comparison of sampler surface area-normalized masses absorbed for analytes under boundary layer-control showed some variability between samplers that can be attributed to the conformation and deployment of the various samplers and to the uncertainty associated with the analysis conducted in different laboratories. Despite different modes of calculation, relatively consistent C(TWA) were obtained for the different samplers. The observed variability is likely to be due to the uncertainty of sampler-water partition coefficients and the extrapolation of analyte uptake rates at the high log K(ow) range (under boundary layer-controlled exchange) from a narrow PRC data range, and these issues require further work. Finally, the usefulness of passive sampler-generated contaminant concentrations is demonstrated through the comparison with institutional monitoring and with European Water Framework Directive Environmental Quality Standards (EQS).