1 research outputs found
Heterogeneous reaction of ClONO with TiO and SiO aerosol particles: implications for stratospheric particle injection for climate engineering
Deliberate injection of aerosol particles into the stratosphere is a potential climate engineering scheme. Particles injected into the stratosphere would scatter solar radiation back to space, thereby reducing the temperature at the Earth's surface and hence the impacts of global warming. Minerals such as TiO or SiO are among the potentially suitable aerosol materials for stratospheric particle injection due to their greater light-scattering ability than stratospheric sulfuric acid particles. However, the heterogeneous reactivity of mineral particles towards trace gases important for stratospheric chemistry largely remains unknown, precluding reliable assessment of their impacts on stratospheric ozone, which is of key environmental significance. In this work we have investigated for the first time the heterogeneous hydrolysis of ClONO on TiO and SiO aerosol particles at room temperature and at different relative humidities (RHs), using an aerosol flow tube. The uptake coefficient, γ(ClONO), on TiO was ∼ 1.2 × 10 at 7 % RH and remained unchanged at 33 % RH, and increased for SiO from ∼ 2 × 10 at 7 % RH to ∼ 5 × 10 at 35 % RH, reaching a value of ∼ 6 × 10 at 59 % RH. We have also examined the impacts of a hypothetical TiO injection on stratospheric chemistry using the UKCA (United Kingdom Chemistry and Aerosol) chemistry–climate model, in which heterogeneous hydrolysis of NO and ClONO on TiO particles is considered. A TiO injection scenario with a solar-radiation scattering effect very similar to the eruption of Mt Pinatubo was constructed. It is found that, compared to the eruption of Mt Pinatubo, TiO injection causes less ClO activation and less ozone destruction in the lowermost stratosphere, while reduced depletion of NO and NO in the middle stratosphere results in decreased ozone levels. Overall, no significant difference in the vertically integrated ozone abundances is found between TiO injection and the eruption of Mt Pinatubo. Future work required to further assess the impacts of TiO injection on stratospheric chemistry is also discussed.Financial support provided by EPSRC grant EP/I01473X/1 and the Isaac Newton Trust (Trinity College, University of Cambridge, UK) is acknowledged. We thank NCAS-CMS for modelling support. Model integrations have been performed using the ARCHER UK National Supercomputing Service. We acknowledge the ERC for support through the ACCI project (project number: 267760). M. J. Tang would like to thank the CAS Pioneer Hundred Talents programme and State Key Laboratory of Organic Geochemistry for providing starting grants