Sorption kinetics and its effects on retention and leaching

Area of Science:

• Environmental Science
• Soil Science
• Agricultural Engineering

Background:

• Pesticide sorption to substrates is crucial for biopurification system efficiency.
• Fast sorption minimizes pesticide leaching, but equilibrium assumptions in transport models may not hold.
• Sorption kinetics are vital for accurate pesticide transport modeling in biopurification.

Purpose of the Study:

• Investigate batch sorption kinetics of five pesticides (linuron, isoproturon, metalaxyl, isoxaben, lenacil).
• Evaluate sorption on common biopurification substrates: manure, straw, willow, soil, coconut chips, compost, peat.
• Assess the impact of sorption kinetics on pesticide leaching using HYDRUS 1D modeling.

Main Methods:

• Batch sorption experiments were conducted for pesticide kinetic analysis.
• First-order sorption kinetics model was fitted to determine kinetic rate constants (alpha).
• HYDRUS 1D model simulated pesticide breakthrough based on estimated alpha values.

Main Results:

• Fast sorption kinetics were observed for immobile pesticides (linuron, isoxaben).
• Substrate type was less influential on sorption kinetics than pesticide mobility.
• Coconut chips, despite high organic matter, exhibited slow sorption for most pesticides.
• Differences in sorption kinetics significantly affected simulated pesticide leaching.

Conclusions:

• Sorption kinetics play a critical role in pesticide leaching in biopurification systems.
• Immobile pesticides sorbed faster, but substrate properties like coconut chips can slow kinetics.
• Accurate kinetic data are essential for predicting pesticide transport and biopurification efficacy.