An in-situ assessment of low-density polyethylene and silicone rubber passive samplers using methods with and without performance reference compounds in the context of investigation of polychlorinated biphenyl sources in rivers
This study firstly aims to assess the field performances of low density polyethylene (LDPE) and silicone rubber (SR) samplers for the monitoring of polychlorinated biphenyls (PCBs) in water regarding the uptake, the sam- pling rate (RS) estimated by using performance reference compounds (PRCs) and the time-weighted average (TWA) concentrations. The second aim is to evaluate the efficiency of these samplers to investigate PCB sources (localization and imputation steps) using methods with and without PRCs to correct for the impact of water ve- locity on the uptake. Samplers spiked with PRCs were deployed in the outfalls of two PCB sources and at 8 river sites situated upstream and downstream of the outfalls. After 6 weeks, the uptake of PCBs in the linear phase was equivalent in LDPE and SR but 5 times lower in LDPE for PCBs approaching equilibrium. PRC-based RS and water velocity (0.08 to 1.21 m s−1) were well correlated in river (LDPE: R2 = 0.91, SR: R2 = 0.96) but not in outfalls (higher turbulences and potential release of PRCs to air). TWA concentrations obtained with SR were slightly higher than those obtained with LDPE (factor 1.4 to 2.6 in river) likely because of uncertainty in sampler- water partition coefficient values. Concentrations obtained through filtration and extraction of water samples (203 L) were 1.6 and 5.1 times higher than TWA concentrations obtained with SR and LDPE samplers, respective- ly. PCB sources could efficiently be localized when PRCs were used (increases of PCB loads in river) but the impact of high differences of water velocity was overcorrected (leading sometimes to false positives and negatives). In- creases of PCB loads in the river could not be entirely imputed to the investigated sources (underestimation of PCBs contributing to the load increases). A method without PRCs (relationship between uptake and water veloc- ity) appeared to be a good complementary method for LDPE.