Updated Abraham solvation parameters for polychlorinated biphenyls.

Area of Science:

• Environmental Chemistry
• Physical Chemistry
• Computational Chemistry

Background:

• Polychlorinated biphenyls (PCBs) are persistent organic pollutants with significant environmental and health concerns.
• Accurate prediction of PCB partitioning behavior is crucial for environmental risk assessment and remediation strategies.
• Existing Abraham solvation parameters for PCBs show poor predictive power, particularly for highly chlorinated congeners.

Purpose of the Study:

• To develop and validate an updated set of Abraham solvation parameters for PCBs.
• To investigate the impact of ortho-chlorination on PCB physical-chemical properties.
• To improve the accuracy of predicting PCB partitioning coefficients across various environmental matrices.

Main Methods:

• Derivation of new PCB solvation parameters using four PCB properties and Abraham solvation equations.
• Investigation of ortho-chlorination effects on solvent accessible volume and surface area.
• Testing the updated parameters on partitioning between five different phase combinations.

Main Results:

• Updated PCB solvation parameters significantly improve predictions for vapor pressures, aqueous solubilities, HPLC capacity factors, and partitioning coefficients (air-n-hexadecane, air-water, organic carbon-water, n-octanol-water).
• The improved accuracy is attributed to updated McGowan specific volumes that depend on the degree of ortho-chlorination.
• No improvement was observed for partitioning between water and polydimethylsiloxane or sodium dodecyl sulfate (SDS).

Conclusions:

• The updated PCB solvation parameters provide substantially improved estimates for various partitioning processes compared to the original set.
• The dependence of specific volumes on ortho-chlorination is a key factor in the enhanced predictive capability.
• The use of updated PCB solvation parameters is recommended for more accurate environmental fate modeling of PCBs.