Potential impacts of CF 3I on ozone as a replacement for CF 3Br in aircraft applications
Iodotrifluoromethane (CF 3I) has been considered to be a candidate replacement for bromotrifluoromethane (CF 3Br), which is used in aircraft for fuel inerting and for fire fighting. In this study, the chemical effects of aircraft-released CF 3I on atmospheric ozone were examined with the University of Illinois at Urbana-Champaign two-dimensional chemical-radiative-transport (UIUC 2-D CRT) model. Using an earlier estimate of the aircraft emission profile for tank inerting in military aircraft, the resulting equivalent Ozone Depletion Potentials (ODPs) for CF 3I were in the range of 0.07 to 0.25. As a sensitivity study, we also analyzed CF 3I emissions associated with fuel inerting if it were to occur at lower altitudes using an alternative estimate. The model calculations of resulting effects on ozone for this case gave ODPs≤0.05. Furthermore, through interactions with the National Institute of Standards and Technology (NIST), we analyzed the potential effects on ozone resulting from using CF 3I in fire fighting connected with engine nacelle and auxiliary power unit applications. The scenarios evaluated using the NIST estimate suggested that the ODPs obtained by assuming aircraft flights occurring in several different latitude regions of the Northern Hemisphere are extremely low. According to the model calculation, the altitude where CF 3I is released from aircraft is a dominant factor in its ozone depletion effects. On the assumption that the CF 3I emission profile is representative of actual release characteristics, aircraft-released CF 3I has much lower impacts than CF 3Br.