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Improving predictability of sediment-porewater partitioning models using trends observed with PCB-contaminated field
Steven B Hawthorne1, Carol B Grabanski, David J Miller
1Energy and Environmental Research Center, University of North Dakota, 15 North 23rd Street, Grand Forks, North Dakota 58203, United States. shawthorne@undeerc.org
Environmental Science & Technology
|July 19, 2011
Summary
Sediment-water partitioning coefficients for polychlorinated biphenyls (PCBs) were measured in contaminated sediments. Models incorporating weathering accurately predicted PCB partitioning, outperforming traditional methods.
Area of Science:
- Environmental Chemistry
- Environmental Science
- Contaminant Hydrology
Background:
- Polychlorinated biphenyls (PCBs) are persistent organic pollutants found in sediments.
- Accurate measurement of PCB partitioning is crucial for environmental risk assessment.
- Existing models often overestimate PCB partitioning in real-world contaminated sediments.
Purpose of the Study:
- To measure sediment-water partitioning coefficients (K(TOC)) for 58 PCB congeners in 53 contaminated sediments.
- To evaluate the performance of existing and novel models in predicting PCB partitioning.
- To develop improved models for PCB partitioning in weathered sediments.
Main Methods:
- Passive sampling with polyoxymethylene to determine freely dissolved porewater concentrations.
- Measurement of over 1900 sediment-water partitioning coefficients.
- Comparison of one-carbon, two-carbon, coal-tar PP-LFER, Raoult's Law, and QSAR models.
Main Results:
- Measured K(TOC) values were significantly higher than literature values.
- No correlation found between K(TOC) and sediment organic carbon or black carbon content.
- Coal-tar PP-LFER and Raoult's Law models accurately predicted average K(TOC) values.
- A Weathering Factor (WF) improved model predictions, especially for weathered sediments.
Conclusions:
- Traditional models and carbon-based approaches are insufficient for predicting PCB partitioning in contaminated sediments.
- Noncalibrated coal-tar PP-LFER and Raoult's Law models, with a Weathering Factor, provide accurate predictions for PCB partitioning.
- These improved models are applicable to all 209 PCB congeners and can aid in environmental risk assessments.
