ChemInform Abstract: O‐ 2 Decay Catalyzed by Cu2+ and Cu+ Ions in Aqueous Solutions: A Pulse Radiolysis Study for Atmospheric Chemistry.

Abstract

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Kinetics of Heterogeneous Reactions of HO2 Radical at Ambient Concentration Levels with (NH4)2SO4 and NaCl Aerosol Particles

“…H HO 2 is Henry's law constant, and K eq HO 2 is the acid dissociation constant of HO 2 (HO 2(aq) ↔ H + (aq) + O 2 - (aq) ). H HO 2 and K eq HO 2 were 4000 (M atm -1 ) 24 and 2.1 × 10 -5 (M), respectively, and [H + ] that was estimated by the concentration in the particles was ∼10 -4.2 (M) in the range of 45−75% RH. T , D l , and ω have already been mentioned above, and α was 0.53 as determined in this study.…”

“…Because the HO 2 radical undergoes acid dissociation (HO 2 (aq) ↔ H + + O 2 - ) in the aqueous phase, there are two loss processes ((9) and (11)) to initiate catalytic consumption of HO 2 Rate constants for eqs 9−12 are 1.2 × 10 9 , 1.5 × 10 9 , 9.4 × 10 9 , and 8.0 × 10 9 M -1 s -1 , respectively. − In the case of the wet aerosol particles generated at 45−55% RH, the molarity of Cu(II) is estimated to be ∼0.5 M in the wet particles . Thus, the lifetime of HO 2 is estimated to be less than 1 ns.…”

“…In the steady-state concentration of the HO 2 between a particle surface and just inside the surface, the measured γ for the reaction on the aerosol particle is given by Hanson at al where H is the effective Henry's law constant, R is the gas constant, T is temperature, and D l is the aqueous phase diffusion coefficient, assumed to be 10 -5 cm 2 s -1 for HO 2 …”

“…Rate constants for eqs 9-12 are 1.2 × 10 9 , 1.5 × 10 9 , 9.4 × 10 9 , and 8.0 × 10 9 M -1 s -1 , respectively. [21][22][23] In the case of the wet aerosol particles generated at 45-55% RH, the molarity of Cu(II) is estimated to be ∼0.5 M in the wet particles. 13 Thus, the lifetime of HO 2 is estimated to be less than 1 ns.…”

“…25 where H is the effective Henry's law constant, R is the gas constant, T is temperature, and D l is the aqueous phase diffusion coefficient, assumed to be 10 -5 cm 2 s -1 for HO 2 . 22 k r is the first-order rate constant for the reaction of HO 2 in the bulk aqueous phase, and q is the reacto-diffusive parameter, which is the ratio of particle radius r s to the reacto-diffusive length l. This length (l) is a measure of the distance from the interface in which the reaction occurs, defined as l ) D l /k r . 25 This length may suggest reaction regimes, volume-limited reaction regime, and surface reaction regime, in the case of l .…”