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

The uptake of gas-phase SO 2, H 2 S, and CO 2 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 H 2 O and OH -, acidifying aqueous solutions. Studies yielded the reaction rates of SO 2, H 2 S, and CO 2 with OH - and the mass accommodation coefficient (α) of SO 2 on water as a function of temperature. The second-order aqueous-phase rate coefficients at 291 K for SO 2, H 2 S and CO 2 reaction with OH - are (1.1 ± 0.2) × 10 10, (1.7 ± 0.2) × 10 9, and (4.0 ± 0.7) × 10 3 M -1 s -1, respectively. As far as we can determine, the rate coefficients for SO 2 and H 2 S have been determined here for the first time. At 291 K, for SO 2, 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(−Δ G obs / RT ) with Δ H obs = −7.6 ± 0.6 kcal mol -1 and Δ S obs = −29.2 ± 2.1 cal mol -1 K -1 .