Neonicotinoid concentrations in arable soils after seed treatment applications in preceding years

Area of Science:

• Environmental Chemistry
• Agricultural Science
• Ecotoxicology

Background:

• Neonicotinoid insecticides, including clothianidin, thiamethoxam, and imidacloprid, are widely used as seed dressings in agriculture.
• Understanding the environmental fate and concentration of these pesticides in soil is crucial for assessing potential ecological risks.

Purpose of the Study:

• To quantify the concentrations of clothianidin, thiamethoxam, and imidacloprid in arable soils across England.
• To investigate the distribution patterns of these neonicotinoids within agricultural fields (center vs. edge).
• To assess the relative persistence of imidacloprid compared to clothianidin and thiamethoxam in soil.

Main Methods:

• Soil samples were collected from various arable field locations in England.
• Concentrations of three neonicotinoid insecticides were determined using analytical chemistry techniques.

Main Results:

• Clothianidin concentrations ranged from 0.02 to 13.6 µg kg⁻¹, thiamethoxam from <0.02 to 1.50 µg kg⁻¹, and imidacloprid from <0.09 to 10.7 µg kg⁻¹ in field centers.
• Lower concentrations of clothianidin and thiamethoxam were observed at field edges compared to centers.
• The difference in concentration between field centers and edges was less pronounced for imidacloprid.

Conclusions:

• The study provides a clear indication of typical neonicotinoid levels in UK arable soils following standard application as seed dressings.
• Imidacloprid demonstrated greater persistence in the studied soils compared to clothianidin and thiamethoxam.
• As clothianidin and thiamethoxam have largely replaced imidacloprid in the UK, the overall measured neonicotinoid levels were lower than predicted based solely on imidacloprid data.