Developing a consistent model for predicting equilibration in polymeric passive samplers across various HOC classes in sediment pore water

Abstract

The use of polymeric passive samplers (often polydimethylsiloxane, PDMS, or low-density polyethylene, LDPE) to indicate water concentrations of hydrophobic organic compounds under environmental conditions generally requires two key parameters, a compound-specific polymer-water equilibrium partition coefficient ($K_{pw}$), and the degree of equilibration achieved in a given environmental exposure scenario. Herein, we have developed model to extrapolate equilibration of performance reference compounds between polymer and pore water across different compound classes that is also dependent upon accurate estimates of $K_{pw}$. We have also developed quantitative structure-activity relationship (QSAR) models, to estimate $K_{pw}$ for PAHs, PCBs, DDx, and dioxin/furans for the two most common polymeric samplers, PDMS and LDPE. The QSAR models developed in this study provide high accuracy consistent estimates for $K_{pw}$ across the different HOC families. The root mean square error of the QSAR for $K_{LDPE-w}$ was 0.226 log units based upon measured values for 159 compounds and 0.184 log units for $K_{PDMS-w}$ based upon measured values for 131 compounds.