EC-07. Mid-latitude ozone depletion and air quality impacts from industrial halogen emissions: aircraft measurements in the Great Salt Lake Basin

We report aircraft observations of very large quantities of HCl and the dihalogens Cl2, Br2, and BrCl in plumes emitted from an industrial plant near the Great Salt Lake, Utah. Complete depletion of O3 was observed concurrently with halogen emissions as a direct result of photochemically produced halogen radicals. Estimated emission fluxes for Cl2, HCl, and NOx agreed with facility-reported emissions inventories. Bromine emissions are not required to be reported in the inventory, but are estimated here as 136 Mg year-1 Br2 and 948 Mg year-1 BrCl, representing a major uncounted oxidant source. A zero-dimensional photochemical box model was used to reproduce the observed O3 depletions, and the model indicates that bromine radicals are the dominant species responsible for the rapid O3 depletion. Furthermore, the inclusion of these halogen emissions is associated with an increase in HO2, RO2, peroxides, and HNO3 + particulate nitrate by 32%, 54%, 404%, and 106%, respectively, in the plume after six hours of chemical processing. This measurement and modeling of halogen emissions and O3 depletion provides an important test for current understanding of tropospheric halogen chemistry and demonstrates the potential impact of underreported industrial bromine emissions on oxidation sources and air quality within a major urban area of the western US.