Chemical residues in agricultural soils in Germany between 2022 and 2024 - Analysis of neonicotinoid insecticides

Between 2022 and 2024, soil samples were taken from 101 sampling sites under agricultural use to assess residues of various compounds in a Germany-wide study. This subproject investigated residues of five neonicotinoids: Imidacloprid, thiamethoxam, clothianidin, acetamiprid, and thiacloprid. A highly sensitive analytical method was developed using quick, easy, cheap, effective, rugged, safe sample preparation and ultra‐high‐performance liquid chromatography–tandem mass spectrometry detection, achieving limits of quantification of 10 ng/kg. The contamination was examined across different agricultural uses (arable land, vineyards, orchards, and grassland), geographical distribution, soil depths (0–5 cm and 5–20 cm), and temporal trends. Results revealed widespread contamination, with detection rates (>limit of detection) of 24% (acetamiprid), 24% (thiamethoxam), 35% (thiacloprid), 72% (clothianidin), and 89% (imidacloprid) over all sampling sites. In grassland without known application of these insecticides, imidacloprid and clothianidin were also regularly detected, indicating unintended substance entries, for example, by airborne deposition, manure, or sewage sludge applications. Despite comprehensive bans on four of the substances, neonicotinoid residues remain widely present in agricultural soils. Although the calculated risk for the individual neonicotinoids remains below regulatory acceptable concentrations, cumulative risks for soil organisms may result from the presence of multiple contaminants in soils. These findings provide an important basis for assessing the actual environmental risk in light of the total chemical burden. Additionally, the findings help describe the current levels of neonicotinoid residues in soil, providing important information which should be presented to chemical regulation.