A molecular derivatization method followed by gas chromatographic separation coupled with mass spectrometric detection was used to study photolytic degradation of I2 on solid SiO2 particles. The heterogeneous photodegradation of I2 is studied at ambient temperature in synthetic air to better understand its 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 () of I2 is calculated to be 187 minutes or 3 hours. 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.