Photolytic degradation of molecular iodine adsorbed on model SiO particles.

A molecular derivatization method followed by gas chromatographic separation coupled with mass spectrometric detection was used to study photolytic degradation of I adsorbed on solid SiO particles. This heterogeneous photodegradation of I is studied at ambient temperature in synthetic air to better understand I atmospheric dispersion and environmental fate. The obtained laboratory results show a considerably enhanced atmospheric lifetime of molecular iodine adsorbed on solid media. The heterogeneous atmospheric residence time (τ) of I is calculated to be τ ≈ 187 min, i.e., τ ≈ 3 h. The obtained heterogeneous lifetime of I is shown to be considerably longer than its destruction by its principal atmospheric sink, namely, photolysis. The observed enhanced atmospheric lifetime of I on heterogeneous media will likely have direct consequences on the atmospheric transport of I that influences the toxicity or the oxidative capacity of the atmosphere.