Abstract View
Heterogeneous Reactivity of HCl on CaCO3 Aerosols at Stratospheric Temperature
HAN N. HUYNH, V. Faye McNeill, Columbia University
Abstract Number: 400
Working Group: Aerosol Chemistry
Abstract
Recently proposed as a possible alternative to sulfate particles for stratospheric solar radiation management (SSRM), calcite (CaCO3) aerosols have been modeled to have minimal negative impact on both stratospheric ozone level and temperature. However, the heterogeneous chemistry of CaCO3 aerosols with relevant trace gases, such as HCl, at stratospheric conditions is still underexamined. We previously reported the heterogeneous uptake of HNO3 and HCl on CaCO3 aerosols at ambient condition as well as the role of water on increasing CaCO3 reactivity. In our recent study, we have further examined the kinetics of HCl uptake on airborne CaCO3 aerosols at stratospheric temperature, 207 ± 3 K, by performing experiments under dry conditions using an aerosol flow tube coupled with a custom-built quadrupole chemical ionization mass spectrometer (CIMS). The reactive uptake coefficient for HCl was measured to be 0.056 ± 0.005, consistent with the negative temperature dependence of gas uptake on solid surfaces in the literature. This finding suggests at least an initial strong reactive uptake of HCl gas on CaCO3 aerosols surface in the stratosphere that we expect to increase with the presence of water vapor in realistic stratospheric conditions. Additional experiments are needed to understand the change in gas uptake coefficient on CaCO3 aerosols over the aerosol lifetime in the stratosphere. Based on a recent 2020 modeling study, our result suggests that the reactions of HCl and HNO3 with calcite in the stratosphere could still lead to stratospheric ozone depletion, albeit less than sulfate particles.