Uptake of gas-phase SO2, H2S, and CO2 by aqueous solutions

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 (alpha) 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) x 10(10), (1.7 +/- 0.2) x 10(9), and (4.0 +/- 0.7) x 10(3) 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, alpha = 0.175 +/- 0.015, and as in previous studies, the temperature dependence of alpha is well represented by the relationship alpha /(1 - alpha) = exp(-Delta G(obs)/RT) with Delta H-obs = -7.6 +/- 0.6 kcal mol(-1) and Delta S-obs = -29.2 +/- 2.1 cal mol(-1) K-1.