Atmos. Chem. Phys. Discuss., 12, 27053-27076, 2012
© Author(s) 2012. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Radical loss in the atmosphere from Cu-Fe redox coupling in aerosols
J. Mao1,2, S. Fan2, D. J. Jacob3, and K. R. Travis3
1Program in Atmospheric and Oceanic Sciences, Princeton University, Princeton, NJ 08542, USA
2Geophysical Fluid Dynamics Laboratory/National Oceanic and Atmospheric Administration, Princeton, NJ 08542, USA
3School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA

Abstract. The hydroperoxyl radical (HO2) is a major precursor of OH and tropospheric ozone. OH is the main atmospheric oxidant, while tropospheric ozone is an important surface pollutant and greenhouse gas. Standard gas-phase models for atmospheric chemistry tend to overestimate observed HO2 concentrations, and this has been tentatively attributed to heterogeneous uptake by aerosol particles. It is generally assumed that HO2 uptake by aerosol involve conversion to H2O2, but this is of limited efficacy as an HO2 sink because H2O2 can photolyze to regenerate OH and from there HO2. Joint atmospheric observations of HO2 and H2O2 suggest that HO2 uptake by aerosols may in fact not produce H2O2. Here we propose a catalytic mechanism involving coupling of the transition metal ions (TMI) Cu(I)/Cu(II) and Fe(II)/Fe(III) to rapidly convert HO2 to H2O in aerosols. The implied HO2 uptake significantly affects global model predictions of tropospheric OH, ozone, and other species, improving comparisons to observations, and may have a major and previously unrecognized impact on atmospheric oxidant chemistry.

Citation: Mao, J., Fan, S., Jacob, D. J., and Travis, K. R.: Radical loss in the atmosphere from Cu-Fe redox coupling in aerosols, Atmos. Chem. Phys. Discuss., 12, 27053-27076, doi:10.5194/acpd-12-27053-2012, 2012.
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