Current-use and legacy pesticides' multi-annual trends in air in central Europe: primary and unidentified secondary sources

This study investigated 48 current-use pesticides (CUPs) and 30 organochlorine pesticides (OCPs) in ambient air at a rural-agricultural site in the Czech Republic, with biweekly sampling over three and 10 years, respectively. Despite being banned decades ago, OCPs persist in the atmosphere, with revolatilisation from surfaces apparent in summer. Temporal trend analysis revealed decreasing atmospheric concentrations for several OCPs, which indicate long-term diminishing reservoirs in environmental compartments, especially soil. For β- and γ-HCH, - and -DDE, -DDD, - and<br><br>-DDT, α-chlordane, and mirex, levelling off is observed, which points to recently enhanced secondary sources in the region or beyond, related to reversal of the direction of air-surface exchange in response to historic atmospheric depositions or recent mobilisation from ground compartments, such as water bodies, the cryosphere, or soils heated by wildfires.<br><br>CUP concentrations peaked during application seasons, with multi-annual trends either insignificant or declining. For compounds like chlorpyrifos and fenpropimorph, declining trends aligned with regulatory bans, though their presence in the atmosphere was evident one-year after the bans, suggesting persistence.