Investigation of PRC‐based estimates

Low-Density polyethylene (PE) sheets are used as passive samplers for aquatic environmental monitoring to measure the freely dissolved concentration (Cfree ) of hydrophobic organic contaminants (HOCs). Freely dissolved HOCs in water will partition into the PE until a thermodynamic equilibrium is achieved; that is, the HOC's activity in the passive sampler is the same as its activity in the surrounding environment. One way to evaluate the equilibrium status or estimate the uptake kinetics is by using performance reference compounds (PRCs). A fractional equilibrium (feq ) can be determined for target HOCs, under the assumption that PRC desorption from the passive sampler occurs at the same rate as the unlabeled target HOCs. However, few investigations have evaluated how effectively and accurately PRCs estimate target contaminant Cfree under in situ conditions. In this study, PE passive samplers were pre-loaded with six, (13) C-labelled PCBs as PRCs, and deployed in New Bedford Harbor, MA, USA and were collected after 30, 56, 99, and 129-day deployments. Using this unique temporal sampling design, PRC results from each deployment were fit to a diffusion model to estimate the Cfree of 27 PCB congeners and compare the results between the different deployment times. Smaller PCBs had variable concentrations over the four deployments while mid-molecular weight PCBs had consistent Cfree measurements for all deployments (relative standard deviation /= 6.5, a deployment time longer than 30 days may be prudent. This article is protected by copyright. All rights reserved.