Developing a consistent model for predicting equilibration in polymeric passive samplers across various HOC classes...

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Polymer Science

Background:

• Polymeric passive samplers, such as polydimethylsiloxane (PDMS) and low-density polyethylene (LDPE), are crucial for assessing hydrophobic organic compound (HOC) concentrations in aquatic environments.
• Accurate interpretation of passive sampler data relies on two key parameters: the polymer-water equilibrium partition coefficient (Kpw) and the extent of equilibration achieved during deployment.
• Existing methods for estimating Kpw and equilibration can be limited in scope and accuracy across diverse HOCs and polymer types.

Purpose of the Study:

• To develop a predictive model for extrapolating the equilibration of performance reference compounds between polymer and pore water for various HOC classes.
• To create quantitative structure-activity relationship (QSAR) models for estimating Kpw specifically for polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethanes (DDx), and dioxin/furans.
• To provide accurate Kpw estimates for the widely used PDMS and LDPE polymeric samplers.

Main Methods:

• Development of a model to predict the equilibration of performance reference compounds across different HOC classes, dependent on Kpw.
• Construction of QSAR models to estimate Kpw values for specific HOC families (PAHs, PCBs, DDx, dioxin/furans) for PDMS and LDPE.
• Validation of QSAR models using measured Kpw data for a substantial number of compounds (159 for LDPE, 131 for PDMS).

Main Results:

• The developed QSAR models demonstrate high accuracy and consistency in estimating Kpw across different HOC families for both PDMS and LDPE.
• The QSAR model for K_LDPE-w achieved a root mean square error (RMSE) of 0.226 log units.
• The QSAR model for K_PDMS-w achieved a lower RMSE of 0.184 log units, indicating high predictive performance.

Conclusions:

• The study successfully developed accurate QSAR models for estimating Kpw, essential for interpreting passive sampling data of HOCs.
• These models enhance the reliability of using PDMS and LDPE samplers for environmental monitoring of a broad range of hydrophobic contaminants.
• The findings contribute to improved quantitative risk assessment and environmental surveillance of HOCs in aquatic systems.