Fate of permethrin in model outdoor ponds

Area of Science:

• Environmental chemistry
• Ecotoxicology
• Pesticide fate and transport

Background:

• Permethrin is a widely used synthetic pyrethroid insecticide.
• Understanding its environmental persistence and degradation is crucial for ecological risk assessment.

Purpose of the Study:

• To investigate the environmental fate and persistence of 14C-permethrin in artificial pond ecosystems.
• To identify permethrin degradation products and quantify their presence in water and hydrosoil.

Main Methods:

• Application of 14C-permethrin to outdoor artificial ponds at a rate of 0.028 kg/ha (15 ug/L).
• Monitoring of permethrin uptake by duckweed and hydrosoil using direct combustion, TLC-autoradiography, HPLC, and liquid scintillation counting.
• Analysis of water and hydrosoil samples for permethrin and its degradation products over time.

Main Results:

• Rapid loss of permethrin from water, with detection of five degradation products.
• Permethrin was readily sorbed by duckweed but not persistent in vegetation.
• Hydrosoil acted as the major sink, with persistent permethrin residues detected up to 420 days post-treatment.
• Cis-permethrin exhibited greater persistence in hydrosoil compared to trans-permethrin.

Conclusions:

• Permethrin is short-lived in pond water due to rapid degradation and sorption by hydrosoil and vegetation.
• Hydrosoil is a significant long-term reservoir for permethrin residues.
• Stereoisomers of permethrin exhibit differential persistence in aquatic sediments.