Sorption and mobility of ivermectin in different soils

Area of Science:

• Environmental Chemistry
• Soil Science
• Ecotoxicology

Background:

• Avermectins, including ivermectin, are vital veterinary antiparasitics but pose environmental risks, particularly to aquatic and soil organisms.
• Sorption processes significantly influence the environmental fate, transport, and bioavailability of ivermectin in soil ecosystems.
• Understanding ivermectin's sorption behavior is critical for accurate environmental risk assessment and management strategies.

Purpose of the Study:

• To characterize the sorption and desorption behavior of ivermectin in diverse European soil types.
• To determine key soil-water distribution coefficients (Kd, Koc, KF) for ivermectin.
• To elucidate the primary mechanisms governing ivermectin sorption in soils.

Main Methods:

• Batch equilibrium studies were conducted to measure ivermectin sorption and desorption.
• Three distinct soil types (Madrid, York, artificial) were used to assess variability.
• Sorption coefficients (Kd, Koc, KF) were calculated across a range of ivermectin concentrations.

Main Results:

• Ivermectin sorption coefficients (Kd) ranged from 57 to 396 L kg(-1), and (Koc) from 4.00 x 10(3) to 2.58 x 10(4) L kg(-1).
• Freundlich sorption coefficient (KF) indicated concentration-dependent sorption, with regression constants supporting this finding.
• Cation presence (e.g., Ca2+) decreased sorption, suggesting complexation with inorganic soil components, unlike abamectin's hydrophobic partitioning.

Conclusions:

• Ivermectin sorption is complex, likely involving interactions with inorganic soil matter, influenced by physicochemical properties and cation presence.
• Hydrophobic partitioning appears less dominant for ivermectin compared to abamectin due to differences in lipophilicity.
• Hysteresis in sorption/desorption was not observed for ivermectin in the studied soils, simplifying its environmental fate assessment.