Emission of iodine from the sea surface in the presence of ozone

Garland, Jeffery S.; Curtis, Hilary

doi:10.1029/jc086ic04p03183

Cited by 141 publications

(134 citation statements)

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“…Correlation studies of ground-and ship-based IO and reactive iodine (IO x = IO + I) measurements with oceanic variables have shown that there is a negative correlation with Chl a and CDOM (colored dissolved organic matter), suggesting that the additional iodine production over the oceans is not biological and could be inhibited by the presence of increased biological activity or organic matter Gómez Martín et al, 2013;Großmann et al, 2013). This provides evidence for the widespread abiotic iodine source proposed by Garland and Curtis (1981): the sea surface oxidation of I − by O 3 to yield HOI and I 2 , which are then either released directly to the atmosphere or react with dissolved organic matter (Garland and Curtis, 1981;Martino et al, 2009;Carpenter et al, 2013). In addition, the correlation analysis showed significant correlations of IO x with sea surface temperature (SST) and salinity (SSS), which suggests that this abiotic mechanism will be influenced by oceanic variables.…”

Section: Introductionmentioning

confidence: 54%

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

et al. 2014

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Abstract.Reactive iodine compounds play a significant role in the atmospheric chemistry of the oceanic boundary layer by influencing the oxidising capacity through catalytically removing O 3 and altering the HO x and NO x balance. The sea-to-air flux of iodine over the open ocean is therefore an important quantity in assessing these impacts on a global scale. This paper examines the effect of a number of relevant environmental parameters, including water temperature, salinity and organic compounds, on the magnitude of the HOI and I 2 fluxes produced from the uptake of O 3 and its reaction with iodide ions in aqueous solution. The results of these laboratory experiments and those reported previously , along with sea surface iodide concentrations measured or inferred from measurements of dissolved total iodine and iodate reported in the literature, were then used to produce parameterised expressions for the HOI and I 2 fluxes as a function of wind speed, sea-surface temperature and O 3 . These expressions were used in the Tropospheric HAlogen chemistry MOdel (THAMO) to compare with MAX-DOAS measurements of iodine monoxide (IO) performed during the HaloCAST-P cruise in the eastern Pacific ocean . The modelled IO agrees reasonably with the field observations, although significant discrepancies are found during a period of low wind speeds (< 3 m s −1 ), when the model overpredicts IO by up to a factor of 3. The inorganic iodine flux contributions to IO are found to be comparable to, or even greater than, the contribution of organo-iodine compounds and therefore its inclusion in atmospheric models is important to improve predictions of the influence of halogen chemistry in the marine boundary layer.

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Section: Introductionmentioning

confidence: 54%

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

et al. 2014

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“…Therefore, during the O 3 -depleted days when [Br 2 ] and [Cl 2 ] are much reduced, iodine chemistry becomes dramatically more important in relative terms. However, laboratory studies have indicated that I 2 can be produced via O 3 oxidation of aqueous iodide (Garland and Curtis, 1981;Martino et al, 2009;Carpenter et al, 2013). If it were indeed the case that I 2 is also produced through an O 3 -mediated activation mechanism, this would likely eliminate the large difference between depleted and non-depleted days that is seen here.…”

Section: The Impact Of Iodine Chemistry and Bromine-iodine Interactionsmentioning

confidence: 75%

Interactions of bromine, chlorine, and iodine photochemistry during ozone depletions in Barrow, Alaska

et al. 2015

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Abstract. The springtime depletion of tropospheric ozone in the Arctic is known to be caused by active halogen photochemistry resulting from halogen atom precursors emitted from snow, ice, or aerosol surfaces. The role of bromine in driving ozone depletion events (ODEs) has been generally accepted, but much less is known about the role of chlorine radicals in ozone depletion chemistry. While the potential impact of iodine in the High Arctic is more uncertain, there have been indications of active iodine chemistry through observed enhancements in filterable iodide, probable detection of tropospheric IO, and recently, observation of snowpack photochemical production of I 2 . Despite decades of research, significant uncertainty remains regarding the chemical mechanisms associated with the bromine-catalyzed depletion of ozone, as well as the complex interactions that occur in the polar boundary layer due to halogen chemistry. To investigate this, we developed a zero-dimensional photochemical model, constrained with measurements from the 2009 OA-SIS field campaign in Barrow, Alaska. We simulated a 7-day period during late March that included a full ozone depletion event lasting 3 days and subsequent ozone recovery to study the interactions of halogen radicals under these different conditions. In addition, the effects of iodine added to our Base Model were investigated. While bromine atoms were primarily responsible for ODEs, chlorine and iodine were found to enhance the depletion rates and iodine was found to be more efficient per atom at depleting ozone than Br. The interaction between chlorine and bromine is complex, as the presence of chlorine can increase the recycling and production of Br atoms, while also increasing reactive bromine sinks under certain conditions. Chlorine chemistry was also found to have significant impacts on both HO 2 and RO 2 , with organic compounds serving as the primary reaction partner for Cl atoms. The results of this work highlight the need for future studies on the production mechanisms of Br 2 and Cl 2 , as well as on the potential impact of iodine in the High Arctic.

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“…We hypothesize that iodine recycling from aerosols back to the gas phase sustains IO concentrations in the TL. Aqueous surfaces containing iodide are known to release I 2 and IO on reaction with ozone (32,35); additionally, the multiphase reaction of HOI with dissolved halides could contribute to recycling of iodine back to the gas phase, analogous to bromine chemistry (36). Iodine is also an abundant component of FT aerosols (37).…”

Section: Resultsmentioning

confidence: 99%

Detection of iodine monoxide in the tropical free troposphere

Dix

Baidar

Bresch

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

118

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Atmospheric iodine monoxide (IO) is a radical that catalytically destroys heat trapping ozone and reacts further to form aerosols. Here, we report the detection of IO in the tropical free troposphere (FT). We present vertical profiles from airborne measurements over the Pacific Ocean that show significant IO up to 9.5 km altitude and locate, on average, two-thirds of the total column above the marine boundary layer. IO was observed in both recent deep convective outflow and aged free tropospheric air, suggesting a widespread abundance in the FT over tropical oceans. Our vertical profile measurements imply that most of the IO signal detected by satellites over tropical oceans could originate in the FT, which has implications for our understanding of iodine sources. Surprisingly, the IO concentration remains elevated in a transition layer that is decoupled from the ocean surface. This elevated concentration aloft is difficult to reconcile with our current understanding of iodine lifetimes and may indicate heterogeneous recycling of iodine from aerosols back to the gas phase. Chemical model simulations reveal that the iodine-induced ozone loss occurs mostly above the marine boundary layer (34%), in the transition layer (40%) and FT (26%) and accounts for up to 20% of the overall tropospheric ozone loss rate in the upper FT. Our results suggest that the halogen-driven ozone loss in the FT is currently underestimated. More research is needed to quantify the widespread impact that iodine species of marine origin have on free tropospheric composition, chemistry, and climate.atmospheric chemistry | oxidative capacity | halogens | heterogeneous chemistry | air-sea exchange R eactive iodine impacts atmospheric chemistry in several ways. Catalytic reaction cycles involving iodine atoms and iodine monoxide (IO; I x = I + IO) destroy tropospheric ozone, which is a primary source for OH radicals (1, 2). Halogens contribute ∼45% of the ozone loss in the remote tropical marine boundary layer (MBL) (2-4). IO further affects the oxidative capacity of the atmosphere through fast reactions with HO 2 radicals and the resulting changes in HO x (HO x = OH + HO 2 ) (1, 2). Iodine also affects NO x (NO x = NO + NO 2 ) by oxidizing NO to NO 2 (1-4). Additionally, bromine atom recycling by IO increases ozone destruction and mercury oxidation rates in the MBL, resulting in higher mercury deposition rates to ecosystems and increased availability to the food chain (2, 5, 6). Finally, in coastal regions, the formation of ultrafine aerosol particles from iodine oxides can be a source of cloud condensation nuclei that can modify Earth's albedo and thus, the radiative budget of the atmosphere (2, 7).Oceans are the main source of iodine to the atmosphere. Most current knowledge of iodine sources and chemistry is based on measurements in the MBL (3,(8)(9)(10)(11)(12)(13). IO observations at coastal MBL sites primarily link iodine sources to macroalgae (8-10). More recent studies have measured IO at open ocean sites (3, 11-13), suggesting that ther...

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Emission of iodine from the sea surface in the presence of ozone

Cited by 141 publications

References 20 publications

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

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

Interactions of bromine, chlorine, and iodine photochemistry during ozone depletions in Barrow, Alaska

Detection of iodine monoxide in the tropical free troposphere

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