A global modeling study of solid rocket aluminum oxide emission effects on stratospheric ozone

Recent laboratory measurements [Molina st al. 1997] have indicated that the heterogeneous chlorine activation reaction ClONO2 + HCl --> HNO3 + Cl-2 has a reaction probability of about 0.02 on aluminum oxide particles (alumina). Since alumina is among those substances emitted by solid rocket motors (SRMs), we have assessed the heterogeneous chemical impact of SRM-emitted alumina on stratospheric ozone using the Goddard Space Flight Center two-dimensional photochemistry and transport model. Historical launch rates of the Space Shuttle, Titan III, and Titan IV rockets were used in time-dependent and steady-state model calculations. Variations in the temporal ozone decreases reflected the fluctuation in launch rate frequency. The annually averaged global total ozone (AAGTO) is computed to decrease by 0.025% by the year 1997. About one-third of this AAGTO change results from the SRM-emitted alumina while about two-thirds is due to SRM-emitted hydrogen chloride.