Novel calculator for estimation of Freundlich partitioning coefficient

Area of Science:

• Environmental Chemistry
• Soil Science
• Chemical Engineering

Background:

• Accurate estimation of the Freundlich organic carbon-normalized partitioning coefficient (Kfoc) is crucial for assessing pesticide and pollutant behavior in soils.
• Existing methods for Kfoc estimation can be limited in scope or require extensive experimental data.
• The U.S. EPA pesticide registration process generates substantial batch equilibrium data suitable for developing predictive models.

Purpose of the Study:

• To present a novel estimation method for the Freundlich organic carbon-normalized partitioning coefficient (Kfoc).
• To validate the method's predictive accuracy using diverse datasets of pesticides, herbicides, Superfund Priority Pollutants, and polychlorinated biphenyls (PCBs).

Main Methods:

• Developed regression models based on batch equilibrium experiments from U.S. EPA pesticide registration data.
• Utilized subcooled liquid solubility (Sscl) as the primary predictive variable, calculated from compound solubility and melting point.
• Tested the Kfoc Estimator v0.1 method on 333 pesticides, 94 herbicides, 55 Superfund Priority Pollutants, and 22 PCBs.

Main Results:

• The estimation method achieved high accuracy for pesticides, with 43% within 2×, 65% within 3×, and 83% within 10× of published Kfoc values.
• Strong correlations (R² > 0.63) were observed between estimated and measured Kfoc values for herbicides, Priority Pollutants, and PCBs.
• Herbicides showed excellent agreement (93%-94% within 10×), while Priority Pollutants and PCBs demonstrated good to moderate agreement depending on the factor of 2×, 3×, or 10×.

Conclusions:

• The developed Kfoc estimation method provides a reliable and efficient tool for predicting pesticide and pollutant partitioning in various soil types.
• The method demonstrates broad applicability across different chemical classes, including pesticides, herbicides, and persistent organic pollutants.
• Kfoc Estimator v0.1 offers a valuable resource for environmental risk assessment and regulatory purposes, particularly when experimental data is scarce.