Photolytic degradation of molecular iodine adsorbed on model SiO2 particles

Abstract

A molecular derivatization method followed by gas chromatographic separation coupled with mass spectrometric detection was used to study photolytic degradation of I2 adsorbed on solid SiO2 particles. This heterogeneous photodegradation of I2 is studied at ambient temperature in synthetic air to better understand I2 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 I2 is calculated to be τ ≈ 187 min, i.e., τ ≈ 3 h. The obtained heterogeneous lifetime of I2 is shown to be considerably longer than its destruction by its principal atmospheric sink, namely, photolysis. The observed enhanced atmospheric lifetime of I2 on heterogeneous media will likely have direct consequences on the atmospheric transport of I2 that influences the toxicity or the oxidative capacity of the atmosphere.