Estimate of the life time of superoxide in seawater

The effects of ionic interactions on the dissociation of HO₂ HO₂→H⁺ + O^-₂ have been examined using the measurements of Bray et al. (1977) on the disproportionation of HO₂ HO₂ + HO₂→H₂O₂ + O₂. In NaCl solutions the values of pK*_HO2 for ionization can be accounted for by using Pitzer's equations for activity coefficients. In CaCl₂ and BaCl₂ it was necessary to account for the formation of CaO⁺₂ and BaO⁺₂ ion pairs. The values of pK_MO2 for the formation of these ion pairs (1.7 to 2.1) was of the same order of magnitude as for Mg²⁺ and Ca²⁺ interactions with F-, OH- and B(OH)-₄. These ionic interaction results have been used to estimate K*{HO₂} in seawater at 25°C. The values of t _{1 2} for the disproportionation of HO₂ in seawater estimated from these results are 3 to 5 times longer than in pure water.