Heterogeneous uptake of ClONO₂ and N₂O₅ by sulfuric acid solutions

Abstract

Abstract. A droplet train apparatus has been used to measure the heterogeneous reactive uptake of gaseous N20 s and C1ONO2 by concentrated sulfuric acid solutions. H2SO 4 concentrations in the range of 39 to 69 wt % were investigated between 229 and 260 K. Uptake rates normalized to the gas-liquid collision frequency, 3/0, for N2Os ranged from 0.086 to 0.16, decreasing moderately with increasing temperature and decreasing H2SO 4 concentration. Uptake rates for C1ONO2, measured over a slightly narrower concentration range of 39-59 wt % H2SO4, ranged between 0.0037 and 0.056, decreasing moderately with H2SO 4 temperature but significantly with increasing concentration. Results are compared with measurements from other laboratories using different experimental techniques. In general, the data from the different groups agree well. A phenomenological model is presented which addresses the solubility, diffusion, and chemical reactivity of XNO3 (X = C1, NO2) in sulfuric acid solutions and accounts for the dependence of the observed uptake rates on H2SO 4 concentration and temperature. Two XNO3 hydrolysis pathways are proposed, one involving direct reaction with H20 and the other involving participation of H + ions to promote bond dissociation. Differences between the concentration dependencies of 3/0 for C1ONO2 and N2Os can be ascribed largely to different rates of acid-catalyzed hydrolysis. The implications of these results for the effects of lower stratospheric sulfuric acid aerosols on ozone depletion chemistry are discussed.

Knudsen cell studies of the reactions of N2O5 and ClONO2 with NaCl: development and application of a model for estimating available surface areas and corrected uptake coefficients

“…[1][2][3][4][5][6][7][8][9] The reported uptake coefficients for the reaction with solid NaCl are less consistent, ranging from less than 10 À4 to greater than 2.5 Â 10 À3 . The yield of ClNO 2 (and hence, the branching ratio between ClNO 2 and HNO 3 /HCl) is quite variable in the studies of the solids and the aerosol particles, ranging from 31 to 100%.…”

Langmuir approach in the study of interface mass transfer

“…In the works of Robinson et al [6] and Hanson and Ravishankara [7] the mass-accommodation coefficient, diffusion process into the liquid, and reaction in the bulk are connected in the frame of a ''resistor'' model. Based on the well-developed resistance model, the uptake and accommodation process are connected through Eq.…”

Direct N<sub>2</sub>O<sub>5</sub> reactivity measurements at a polluted coastal site

“…Models must parameterize the reaction probability based on laboratory studies that use highly idealized particle compositions, and then also make assumptions about the mixing state of atmospheric particles. Laboratory studies have shown that γ (N 2 O 5 ) can span several orders of magnitude depending upon particle composition and phase state (Hallquist et al, 2003;Hu and Abbatt, 1997;Kane et al, 2001;McNeill et al, 2006;Mozurkewich and Calvert, 1988;Robinson et al, 1997). Particulate water, chloride, nitrate, and organic particle coatings can all have effects on the N 2 O 5 reaction probability (Bertram and Thornton, 2009;Bertram et al, 2009b;Folkers et al, 2003;Mentel et al, 1999;Park et al, 2007;Thornton et al, 2003;Thornton and Abbatt, 2005;Wahner et al, 1998).…”