Comparison of different sampling techniques for the evaluation of pesticide spray drift in apple orchards.

An analytical method using gas chromatography-mass spectrometry has been developed for the evaluation of different sampling techniques to characterise spray drift in a commercial apple orchard. Eleven pesticides were studied (fungicides, insecticides and herbicides). A collection of airborne spray-drift pesticides released from a low-profile air-blast orchard sprayer was investigated using six types of samplers: (1) a Perkin-Elmer low volume automatic air sampler using with glass tube packed with Supelpak-2; (2) a high volume air sampler: (3, 4) an impinger containing cyclohexane that could be preceded by a glass fibre filter; and (5, 6) glass cartridges packed with Supelpak-2 that could be preceded by a glass fibre filter. Retention efficiencies of the different sampling techniques are compared, and physical forms of the retained pesticides are discussed. These techniques have allowed us to evaluate pesticide spray-drift in the orchard. Results have shown that the molecules' properties (k(H) and vapour pressure) and weather conditions (temperature and relative humidity) strongly influence pesticide gas and particles distribution. However, in the studied orchard, it is difficult to differentiate pesticide spray-drift and post-application transfers since treatment duration was > 2 days.