Atmospheric Chemistry Program Dissertation Defense
Aircraft measurements of bromine and iodine from the sea surface to the lower stratosphere by Theodore Koenig, ANYL Student, CU Boulder, Volkamer Group
"Bromine and iodine change atmospheric oxidative capacity, deplete ozone, modify NOx = (NO2 + NO) and HOx = (OH + HO2), and in turn impact air quality and human health as well as radiative forcing and climate. The radical monoxides, BrO and IO, have large structured rovibronic absorptions in the Ultraviolet-Visible (UV-Vis) spectrum which results in rapid and active photochemistry as key intermediates in the impacts listed above, and also makes them detectable to differential optical absorption spectroscopy (DOAS). I present measurements of BrO and IO using DOAS, particularly from aircraft, from which I infer total gas-phase bromine and iodine, Bry and Iy, using chemical box-models and examine the implications of these measurements. We find active multiphase chemistry relevant from the marine boundary layer MBL where gas-phase coupling to organics modulates sea-salt aerosol debromination, to the free troposphere where we find dust initiates iodine chemistry leading to miniature ozone holes west of South America, to the upper troposphere and lower stratosphere (UTLS) where multiphase chemistry and phase partitioning around the tropopause destroy ozone and change radiative forcing in the climate relevant region."