Atmospheric transport of pesticides adsorbed on aerosols I. Photodegradation in simulated atmosphere

Eight pesticides (Alachlor, Pendimethalin, Trifluralin, Malathion, Terbuthylazine, Atrazine, Isoproturon and Fenithrothion), adsorbed on kaolin and fly ash are submitted to irradiation (wavelength above 290 nm) for 40 or 80 min. The first four compounds photodegrade when they are adsorbed on fly ash. The presence of metals and metal oxides in the fly ash seem to be responsible for this rapid degradation (up to 70% in 40 min). They do not degrade, however, when they are adsorbed on kaolin. Terbuthylazine and Atrazine do not degrade significantly, at least during this short irradiation time. Weakening of the pesticide-support bonds after irradiation, promoting the extraction by organic solvents, is important for several pesticides, particularly for Alachlor and Atrazine. Isoproturon and Fenithrothion do not adsorb significantly on these two atmospheric supports and cannot be successfully submitted to irradiation. These results are used to predict the possibility of the meso-scale atmospheric transport of the pesticides from agricultural regions to non polluted areas, like alpine regions.