Comparability of precipitation water, soil, and kale plants as deposition samplers for quantification of airborne pesticide deposition

Airborne pesticide transport and deposition are insufficiently studied sources of environmental pollution. A controlled experiment was conducted to examine and compare airborne deposition of pesticides in precipitation, on soil and plants. Ten relevant pesticides were analyzed by ultra-high-performance liquid chromatography-tandem mass spectrometry with limits of quantification in the low ng/L or ng/kg range. The field experiment was performed over a 28-day period in summer 2024, including a bulk sampler, a reference soil, and bioindicator plants (kale) for uptake of substances from the gas phase and deposition. Sample analysis showed that the deposited amounts were in the low ng/L or ng/kg range and could only be quantified with highly sensitive analytical methods. For comparison and interpretation of the compartments precipitation, soil (including percolate), and kale, concentrations were converted into ng/m2 deposition amounts by relation to their collection surface. Deposition reached up to 13,762 ng/m2 in the bulk sampler (propamocarb), 2571 ng/m2 in the soil compartment (terbuthylazine-desethyl), and 1231 ng/m2 in the kale compartment (terbuthylazine). The bulk sampler had 1.4 to 106 times higher deposition values than the other samplers and was found most suitable and conservative for estimating airborne pesticide deposition. These investigations provide a basis for future national monitoring of airborne pesticides in Germany and can be applied to other monitoring campaigns. The selected analytes covered a large range of chemical-physical properties of approved pesticides. These results support the estimation of pesticide residues by deposition in different environmental compartments for ecotoxicological risk assessment and estimation of crop residues for consumer protection.