Propanil in a Manitoba soil: an interactive spreadsheet model based on conventional chemical kinetics

Area of Science:

• Environmental Chemistry
• Soil Science
• Chemical Kinetics

Background:

• Pesticide sorption and degradation in soils are critical for environmental fate assessment.
• Understanding propanil's behavior in clay soils informs agricultural and environmental management.
• Quantitative models are needed to predict pesticide transformation in soil ecosystems.

Purpose of the Study:

• To develop an interactive spreadsheet model for predicting propanil sorption and reaction.
• To describe the reaction mechanism using conventional chemical kinetics.
• To provide a tool for estimating pesticide fate in Manitoba clay soil.

Main Methods:

• Developed an interactive spreadsheet model for quantitative predictions.
• Utilized experimental data on sorption sites as reactants and products.
• Employed conventional chemical kinetics, including Laidler's integral rate law for second-order kinetics.
• Applied an online HPLC extraction method to identify sorption and reaction processes.

Main Results:

• The model quantifies propanil sorption, intraparticle diffusion, and chemical reaction.
• Labile sorption follows second-order kinetics, while desorption, diffusion, and reaction follow first-order kinetics.
• Time-dependent effects of initial concentration and soil amount on these processes are predictable.

Conclusions:

• The developed model accurately predicts propanil sorption and reaction dynamics in slurried clay soil.
• The kinetic descriptions provide insights into pesticide transformation pathways.
• The model has potential applications in storm runoff analysis and hydrological fate and transport modeling.