OH-radical reactivity of pesticides adsorbed on aerosol materials: First results of experiments with filter samples

Preliminary results of a new method to investigate the OH radical reactivity of semi-volatile organic compounds (e.g. pesticides) are presented. Terbuthylazine, simazine, sodium benzoate, and bromoxynil were adsorbed on highly disperse silicon dioxide powder as an unreactive carrier at a thickness well below one monolayer. The coated material was suspended in air as an aerosol, sampled on filters, and exposed in a 840-liter Duran chamber to OH radicals, produced by photolysis of hydrogen peroxide in the gas phase. Sunlamps on top of the chamber were used as cold light sources. OH radical concentrations were monitored in the gas phase using a set of four hydrocarbons with well-known OH reactivities as reference compounds.