The mechanism for dry deposition of ozone to seawater surfaces

Abstract

A simple model, in which deposition is limited by diffusion through a thin laminar film of water, has successfully described the deposition of several gases to the sea. However, the deposition velocity of ozone to seawater is 10–30 times greater than this model predicts. This enhancement is attributed to significant reactions of ozone with halides and other components of seawater within the laminar surface layer, and a modified version of the model for ozone, and possibly other reactive gases, is proposed. To test the model, comparisons were made of predicted and observed deposition velocities for ozone to solutions of sodium sulphite and nitrite. Measurements of the rate constants for the reaction of ozone with these solutions and with some components of seawater were made with a stopped flow apparatus. The reaction with iodide was too rapid for direct observation, but the rate constant was inferred from measurements of the deposition of ozone to iodide solutions. According to the model, iodide makes a substantial contribution to the deposition of ozone to seawater, but an additional, unidentified reaction is necessary to explain fully the deposition rate. A surfactant species may well be involved. The model indicates that the ozone is destroyed and the oxidation products produced in the top few microns of the sea. The production of molecular iodine at the surface may have significant geochemical consequences.

A laboratory characterisation of inorganic iodine emissions from the sea surface: dependence on oceanic variables and parameterisation for global modelling

“…However, the Arrhenius expression they reported (k = 1.44 × 10 22 exp(−73080/RT) M −1 s −1 ) contains a pre-exponential factor which is roughly 10 orders of magnitude greater than the diffusion limited reaction rate, and therefore appears to be unphysical. Hu et al (1995), using a similar droplet train technique with I − concentrations from 0.5-3 M and O 3 in the range 5 × 10 12 to 1 × 10 14 cm −3 , measured k(I − + O 3 ) = 4 × 10 9 M −1 s −1 at 277 K. Although they do not report a room temperature measurement, the room temperature value for k(I − + O 3 ) appears to be reasonably well established from a number of previous studies (Garland et al, 1980;Hoigné et al, 1985;Magi et al, 1997;Liu et al, 2001), lying in the range (1.2-2.4) × 10 9 M −1 s −1 . Thus the Hu et al (1995) result implies a slightly negative temperature dependence, although those authors state that within their experimental accuracy the reaction could have been temperature independent.…”

Ozone and aerosol tropospheric concentrations variability analyzed using the ADRIMED measurements and the WRF and CHIMERE models

“…These concentrations are usually very high in models due to a lack of deposition. This ozone deposition underestimation is rarely documented and quantified, but some previous studies showed that the dry deposition velocities used over oceans for gaseous species may be underestimated, due to a misrepresented turbulence as pointed out by Garland et al (1980), Ganzeveld et al (2009) the limitation due to the horizontal resolution, the model being not able to represent local ozone plumes as presented in Fig. 9.…”

Transformation of iodate to iodide in marine phytoplankton driven by cell senescence

“…Iodine has recently been identified as a potential key element involved in climate change, as iodide reacts rapidly with O 3 , and is believed to be a major sink for atmospheric O 3 at the sea surface (Garland et al 1980). This reaction forms HOI and I 2 , and has also been suggested as a source of organic halogens (RI) (Martino et al 2009).…”