Chemical controls on the uptake of ozone to the ocean

Ozone deposition to the ocean represents one of the largest sinks of ozone from the troposphere, but is highly uncertain. Chemical reactions with the sea surface drive deposition to the ocean, however the identity and contribution of different reactive compounds remains unclear. Iodide is considered one of the main drivers of ozone uptake to the ocean, however there is also an expected contribution from organic matter, the nature of which is not well characterised.
This work aimed to investigate these chemical drivers , including re-measuring the kinetics and temperature dependence of the reaction between ozone and iodide. With the ozone-iodide reaction as a baseline, ozone uptake to seawater was analysed, and the ”missing” reactivity quantified.
A method was developed, which facilitated ozone uptake measurements to iodide solutions and seawater. The rate of reaction between ozone and iodide was measured, yielding Arrhenius parameters of A = 5.4 ± 23.0 ×10^10 M−1 s−1 and Ea = 7.0 ± 10.5 kJ mol−1. This weak temperature dependence has implications for the spatial and temporal variation in ozone dry deposition to the ocean, and subsequent emissions of iodine-containing compounds.
Ozone uptake was measured to remote and coastal seawater samples. Ozone uptake to remote samples ranged from 2.97 to 6.32 ×10^−6, with 25.0 to 66.3 % of uptake attributed to iodide, while for the coastal samples ozone uptake ranged 0.87 to 4.00 ×10^−6, with 36.0 to 148.2 % predicted by iodide. Unsaturated
fatty acids were identified as a potential source of reactivity in the remote samples.
This dataset of ozone uptake measurements to authentic seawater samples, with complementary biogeochemical measurements, furthers our understanding of ozone loss from the troposphere by improved knowledge of the drivers of dry deposition to the ocean.