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| Titel |
The uptake of HO2 radicals to organic aerosols |
| VerfasserIn |
Pascale Matthews, Manuel Krapf, Josef Dommen, Ingrid George, Lisa Whalley, Trevor Ingham, Maria Teresa Baeza-Romero, Markus Ammann, Dwayne Heard |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250091783
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| Publikation (Nr.) |
 EGU/EGU2014-6094.pdf |
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| Zusammenfassung |
| HOx (OH + HO2) radicals are responsible for the majority of the oxidation in the troposphere and control the concentrations of many trace species in the atmosphere. There have been many field studies where the measured HO2 concentrations have been smaller than the concentration predicted by model calculations [1,2]. The difference has often been attributed to HO2 uptake by aerosols. Organics are a major component of aerosols accounting for 10 - 70 % of their mass [3]. However, there have been very few laboratory studies measuring HO2 uptake onto organic aerosols [4].
Uptake coefficients (γ) were measured for a range of aerosols using a Fluorescence Assay By Gas Expansion (FAGE) detector combined with an aerosol flow tube. HO2 was injected into the flow tube using a moveable injector which allowed first order HO2 decays to be measured along the flow tube both with and without aerosols. Laboratory generated aerosols were made using an atomiser or by homogeneous nucleation. Secondary organic aerosols (SOA) were made using the Paul Scherrer Institute smog chamber and also by means of a Potential Aerosol Mass (PAM) chamber. The total aerosol surface area was then measured using a Scanning Mobility Particle Sizer (SMPS).
Experiments were carried out on aerosols containing glutaric acid, glyoxal, malonic acid, stearic acid, oleic acid and squalene. The HO2 uptake coefficients for these species were measured in the range of γ < 0.004 to γ = 0.008 ± 0.004. Humic acid was also studied, however, much larger uptake coefficients (γ = 0.007 – 0.09) were measured, probably due to the fact that these aerosols contained elevated levels of transition metal ions. For humic acid the uptake coefficient was highly dependent on humidity and this may be explained by the liquid water content of the aerosols. Measurements were also performed on copper doped aerosols containing different organics. An uptake coefficient of 0.23 ± 0.07 was measured for copper doped ammonium sulphate, however, this was reduced to 0.008 ± 0.009 when EDTA was added in a 1:1 ratio with copper and 0.003 ± 0.004 when oxalic acid was added in a 10:1 ratio with copper. SOA aerosols were also investigated at PSI and HO2 uptake coefficients of γ < 0.004 and γ = 0.004 ± 0.003 were measured for alpha-pinene and trimethylbenzene derived SOA respectively.
[1] Sommariva, R. et al. Atmos. Chem. Phys.2006, 6, 1135-1153.
[2] Whalley, L.K. et al. Atmos. Chem. Phys. 2010, 10, 1555-1576.
[3] Turpin, B.J. et al. Atmos. Environ. 2000, 34, 2983–3013
[4] Taketani, F. et al Int. J. Chem. Kin. 2013, 9, 560-565. |
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