LAUSR

Abstract Laboratory studies of HO2 uptake coefficients, γ(HO2), were conducted at room temperature using an aerosol flow tube coupled with a laser induced fluorescence (LIF) system. The measurement was conducted with atmospherically relevant HO2 concentrations (∼1 × 109 molecule/cm3) at 51% RH. The measured γ(HO2) onto aqueous (NH4)2SO4 aerosol was 0.001 ± 0.0007, which was consistent with the relatively low first-order loss rate of HO2 onto aqueous (NH4)2SO4 aerosol. The γ(HO2) was elevated with increase of Cu(II) concentrations in aqueous (NH4)2SO4 aerosol. The threshold of Cu(II) concentration was 10−3 mol/L for the dramatic increase of γ(HO2). It was found that γ(HO2) reached 0.1 when Cu(II) concentration in aerosol was larger than 10−3 mol/L, suggesting that γ(HO2) is very sensitive to concentration of transition metal ions in aerosol.