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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 1 | Copyright
Atmos. Chem. Phys., 18, 327-338, 2018
https://doi.org/10.5194/acp-18-327-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 11 Jan 2018

Research article | 11 Jan 2018

Heterogeneous reaction of HO2 with airborne TiO2 particles and its implication for climate change mitigation strategies

Daniel R. Moon1, Giorgio S. Taverna2, Clara Anduix-Canto1, Trevor Ingham1,3, Martyn P. Chipperfield2,3, Paul W. Seakins1,3, Maria-Teresa Baeza-Romero4, and Dwayne E. Heard1,3 Daniel R. Moon et al.
  • 1School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK
  • 2School of Earth and Environment, University of Leeds, LS2 9JT, UK
  • 3National Centre for Atmospheric Science, School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK
  • 4Escuela de Ingeniería Industrial, Universidad de Castilla – La Mancha, 45071 Toledo, Spain

Abstract. One geoengineering mitigation strategy for global temperature rises resulting from the increased concentrations of greenhouse gases is to inject particles into the stratosphere to scatter solar radiation back to space, with TiO2 particles emerging as a possible candidate. Uptake coefficients of HO2, γ(HO2), onto sub-micrometre TiO2 particles were measured at room temperature and different relative humidities (RHs) using an atmospheric pressure aerosol flow tube coupled to a sensitive HO2 detector. Values of γ(HO2) increased from 0.021±0.001 to 0.036±0.007 as the RH was increased from 11 to 66%, and the increase in γ(HO2) correlated with the number of monolayers of water surrounding the TiO2 particles. The impact of the uptake of HO2 onto TiO2 particles on stratospheric concentrations of HO2 and O3 was simulated using the TOMCAT three-dimensional chemical transport model. The model showed that, when injecting the amount of TiO2 required to achieve the same cooling effect as the Mt Pinatubo eruption, heterogeneous reactions between HO2 and TiO2 would have a negligible effect on stratospheric concentrations of HO2 and O3.

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One geoengineering mitigation strategy for global temperature rises is to inject particles into the stratosphere to scatter solar radiation back to space. However, the injection of such particles must not perturb ozone. We measured the rate of uptake of HO2 radicals, an important stratospheric intermediate, onto TiO2 particles. Using the atmospheric model TOMCAT, we showed that surface reactions between HO2 and TiO2 would have a negligible effect on stratospheric concentrations of HO2 and ozone.
One geoengineering mitigation strategy for global temperature rises is to inject particles into...
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