Chapter 18 - Mass Independently Fractionated Ozone in the Earth's Atmosphere and in the Laboratory

Abstract

Ozone carries a large and variable mass independent isotope fractionation. Ozone is produced when an oxygen atom combines with an oxygen molecule. This chapter examines the mass independent isotope fractionation observed in ozone (O3), both in the Earth's atmosphere and in the laboratory. Measurements of mass independently fractionated (MIF) in tropospheric O3 and a recent assessment of MIF in stratospheric O3 indicates that the atmospheric variability is largely in agreement with laboratory measurements. A theoretical model is provided to understand a wide variety of laboratory results. The development of this model is timely, as it will undoubtedly contribute to the interpretation of the wide variety of natural species that have now been shown to possess a mass independent fractionation. The isotopic analysis of gases in the Earth's atmosphere provides a wealth of information regarding sources, sinks, chemical transformation, and transport processes that govern the budgets of atmospheric species. A mass dependent fractionation of oxygen isotopes results in an isotopic value that closely follows the relation δ17O =0.52δ18O. Equilibrium chemical processes such as isotope exchange, diffusion, evaporation and condensation are sensitive to isotopic mass, and different isotopes may be incorporated into the molecules at different rates.