C-Depth Method to Determine Diffusion Coefficient and Partition Coefficient of PCB in Building Materials.

Area of Science:

• Environmental Science
• Chemical Engineering
• Building Science

Background:

• Polychlorinated biphenyls (PCBs) are persistent environmental pollutants found in many buildings.
• High PCB concentrations in buildings necessitate effective exposure assessment and remediation strategies.
• Understanding PCB partitioning between sources and building materials is critical for managing contamination.

Purpose of the Study:

• To develop and validate a novel C-depth method for determining PCB diffusion (D) and partition (K) coefficients.
• To assess the performance of the C-depth method compared to existing techniques.
• To identify key factors influencing PCB partitioning in building materials.

Main Methods:

• Development of the C-depth method to calculate diffusion (D) and partition (K) coefficients.
• Application of the method to concrete as a primary building material.
• Comparison of C-depth method results with existing methods and a two-term approach.
• Sensitivity analysis to identify critical parameters for D and K determination.

Main Results:

• The C-depth method provides unique estimations for D and K without requiring assumed correlations.
• Relative standard deviations for K were 5%-22% and for D were 42%-66% across five datasets for concrete.
• Comparison with a two-term approach indicated significant uncertainty for D and smaller uncertainty for K.
• Model predictions showed good agreement with measurements, supporting engineering application.

Conclusions:

• The C-depth method offers a robust approach for determining PCB partitioning parameters (D and K).
• Effective diffusion distance, contact time, and measurement depth are critical for D.
• PCB concentration in primary sources is a critical factor for K.
• Results are acceptable for engineering applications despite inherent uncertainties.