Uptake of Gas-Phase SO2, H2S, and CO2 by Aqueous Solutions

Abstract

The uptake of gas-phase SO2, H2S, and CO2 by aqueous solutions was studied as a function of pH and temperature using droplet train flow reactor and bubble train reactor apparatuses. All three atmospheric species react with H2O and OH-, acidifying aqueous solutions. Studies yielded the reaction rates of SO2, H2S, and CO2 with OH- and the mass accommodation coefficient (α) of SO2 on water as a function of temperature. The second-order aqueous-phase rate coefficients at 291 K for SO2, H2S and CO2 reaction with OH- are (1.1 ± 0.2) × 1010, (1.7 ± 0.2) × 109, and (4.0 ± 0.7) × 103 M-1 s-1, respectively. As far as we can determine, the rate coefficients for SO2 and H2S have been determined here for the first time. At 291 K, for SO2, α = 0.175 ± 0.015, and as in previous studies, the temperature dependence of α is well represented by the relationship α /(1 − α) = exp(−ΔGobs/RT) with ΔHobs = −7.6 ± 0.6 kcal mol-1 and ΔSobs = −29.2 ± 2.1 cal mol-1 K-1.