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[AAS11-P11] Measurement of uptake coefficient of organic peroxyl radical derived from propene onto NaCl particles by LIF technique
Keywords:peroxyl radical, uptake coefficient, LP-LIF
With the aim of establishing the measurement method of γ for R(OH)O2 radicals, this work applied the laser-pumped and laser-induced fluorescence (LP-LIF) technique (Sadanaga et al., 2004) for measurement of γ for propene derived CH3CH(OO)CH2OH onto NaCl particles. γ was determined from the decay rate of radicals measured by LP-LIF and aerosol surface concentration measured by scanning mobility particle sizer (SMPS). Particles were generated by nebulizing NaCl solution and directly measured as aqueous particles at 85% RH. We prepared three types of particles: pure (None), CuCl2 (as a transition metal ion)-doped and ascorbic acid (AA, as an antioxidant)-doped NaCl particles. We validated our experimental system by conducting measurement of γ of HO2 and by confirming that our results showed good agreement with literature value (Taketani et al., 2008).
In summary, we determined γ of CH3CH(OO)CH2OH onto pure NaCl, onto CuCl2 doped and onto ascorbic acid doped particles to be γNone=0.04±0.01, γCuCl2=0.04±0.01, and γAA=0.24±0.04, respectively. These results have shown that γ onto CuCl2 doped NaCl particles isn’t changed from γ onto pure ones, on the other hand, γ onto ascorbic acid doped ones becomes several times larger than the others. These γ values are the first experimental reports as R(OH)O2 radicals’ γ and thus no references are available.
Our result suggests that γ of R(OH)O2 onto wet particles are possibly in the range of 0.04~0.24 in the troposphere, which includes the recommended value, γ =0.1 (Jacob, 2000). However, at the same time, our results indicates that the recommended value has a large uncertainty. It is required to conduct further experiments using other types of RO2 radicals and standard aerosols, and with ambient particles.
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Sadanaga, Y., et al. (2004). Development of a measurement system of OH reactivity in the atmosphere by using a laser-induced pump and probe technique. Rev. Sci. Instrum., 75(8), 2648-2655.
Taketani, F., et al. (2008). Kinetics of Heterogeneous Reactions of HO2 Radical at Ambient Concentration Levels with (NH4)2SO4 and NaCl Aerosol Particles. J. Phys. Chem. A, 112(11), 2370–2377.