Tropospheric Mid-Latitude Halogen-Induced Ozone Depletion Observed from an Industrial Source over the Great Salt Lake

Halogen-induced ozone destruction has often been observed in the pristine Arctic, where halogen radicals are catalytically produced from marine sea salt. However, this phenomenon has rarely been seen in the midlatitudes. Presented here are estimates of the halogen emission fluxes from an industrial plant on the Great Salt Lake. During the 2017 Utah Winter Fine Particulate Study, halogen-rich plumes emanating from an industrial area on the western side of the Great Salt Lake were intercepted by the NOAA Twin Otter aircraft. In those plumes, ozone was observed to be depleted, sometimes completely. These halogen emissions and chemistry are relevant to air quality in the surrounding region, including the densely populated Salt Lake City urban area. They also provide tests of current understanding of halogen cycles and their influence on ozone in the lower atmosphere. We present results of photochemical box modeling using the Framework for 0-dimensional Atmospheric Modeling (F0AM), and illustrate the mechanism for ozone depletion by the halogen radicals Cl and Br.