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

BACKGROUND: Concentrations of the neonicotinoid insecticides clothianidin, thiamethoxam and imidacloprid were determined in arable soils from a variety of locations in England.
RESULTS: In soil samples taken from the central area of fields, concentrations of clothianidin ranged from 0.02 to 13.6 µg kg(-1) . Thiamethoxam concentrations were between <0.02 and 1.50 µg kg(-1) , and imidacloprid concentrations between <0.09 and 10.7 µg kg(-1) . Concentrations of clothianidin and thiamethoxam were lower in soil samples taken from the edges of fields than from the centres of fields, but this difference was less pronounced for imidacloprid.
CONCLUSION: This work gives a clear indication of the levels of neonicotinoids in arable soils after typical use of these compounds as seed dressings in the United Kingdom. There was evidence that imidacloprid was more persistent in the soils studied than clothianidin and thiamethoxam. As clothianidin and thiamethoxam have largely superseded imidacloprid in the United Kingdom, neonicotinoid levels were lower than suggested by predictions based on imidacloprid alone.