1 research outputs found
A revisit of the interaction of gaseous ozone with aqueous iodide. Estimating the contributions of the surface and bulk reactions
The main source of atmospheric iodine is the heterogeneous reaction of aqueous iodide (I‐
) with ozone (O3), which takes
place in surface seawater and probably in sea‐salt aerosols. However, there are seemingly contradictory conclusions about
whether this heterogeneous reaction occurs in the bulk of the aqueous phase, via O3 dissolution, or at the aqueous surface,
via O3 adsorption. In this work, the ozone uptake coefficient has been calculated as a function of the concentration of
aqueous iodide ([I‐
]aq) and gaseous ozone near the aqueous surface ([O3]gs) by estimating parameters of the resistor model
using results of previous studies. The calculated uptake coefficients suggest that the aqueous‐phase reaction dominates at
low I
‐ concentrations (about 10 ppm), regardless
of [I‐
]aq. In contrast, the surface reaction dominates at high [I‐
]aq (about >10‐4 mol/L) as long as [O3]gs is low enough (about
<10 ppm). This trend is able to reconcile previous studies of this reaction, and is a consequence of several factors, including
the high surface excess of both reactants ozone and iodide. Given the typical O3 concentrations in the troposphere and the
possible I
‐ concentrations and O3 solubilities in sea‐salt aerosols, the surface reaction may compete with the aqueous phase
reaction in sea‐salt aerosols, unlike in surface seawater, where the aqueous‐phase reaction prevails. The rate constant of
the surface reaction has been estimated as (5‐500)10^‐13 cm2 molecule‐1 s‐1