A negative feedback between anthropogenic ozone pollution and enhanced ocean emissions of iodine

Prados-Román, C.; Cuevas, Carlos A.; Fernández, Rafael P.; Kinnison, D. E.; Lamarque, Jean‐François; Saiz‐Lopez, Alfonso

doi:10.5194/acp-15-2215-2015

Cited by 68 publications

(83 citation statements)

References 30 publications

(41 reference statements)

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“…15. The marine boundary layer O x loss attributable to halogens is comparable to the 31 % reported by Prados-Roman et al (2015a) previously, and it is higher than the 26 % reported solely for iodine (Sherwen et al, 2016a). The inter-reaction of halogen monoxide species is found to less important here than previous studies (e.g.…”

Section: Ozonecontrasting

confidence: 47%

Global impacts of tropospheric halogens (Cl, Br, I) on oxidants and composition in GEOS-Chem

et al. 2016

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Abstract. We present a simulation of the global present-day composition of the troposphere which includes the chemistry of halogens (Cl, Br, I). Building on previous work within the GEOS-Chem model we include emissions of inorganic iodine from the oceans, anthropogenic and biogenic sources of halogenated gases, gas phase chemistry, and a parameterised approach to heterogeneous halogen chemistry. Consistent with Schmidt et al. (2016) we do not include sea-salt debromination. Observations of halogen radicals (BrO, IO) are sparse but the model has some skill in reproducing these. Modelled IO shows both high and low biases when compared to different datasets, but BrO concentrations appear to be modelled low. Comparisons to the very sparse observations dataset of reactive Cl species suggest the model represents a lower limit of the impacts of these species, likely due to underestimates in emissions and therefore burdens.Inclusion of Cl, Br, and I results in a general improvement in simulation of ozone (O 3 ) concentrations, except in polar regions where the model now underestimates O 3 concentrations. Halogen chemistry reduces the global tropospheric O 3 burden by 18.6 %, with the O 3 lifetime reducing from 26 to 22 days. Global mean OH concentrations of 1.28 × 10 6 molecules cm −3 are 8.2 % lower than in a simulation without halogens, leading to an increase in the CH 4 lifetime (10.8 %) due to OH oxidation from 7.47 to 8.28 years. Oxidation of CH 4 by Cl is small (∼ 2 %) but Cl oxidation of other VOCs (ethane, acetone, and propane) can be significant (∼ 15-27 %). Oxidation of VOCs by Br is smaller, representing 3.9 % of the loss of acetaldehyde and 0.9 % of the loss of formaldehyde.

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Section: Ozonecontrasting

confidence: 47%

Global impacts of tropospheric halogens (Cl, Br, I) on oxidants and composition in GEOS-Chem

et al. 2016

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“…Over the subtropics, IO enhancements observed below 4 km are not captured by the model. Some studies suggest that there is abiotic CH 3 I production when dust contacts seawater containing iodide (Williams et al, 2007;Puentedura et al, 2012). Implementing this chemistry into the model is out of the scope of this paper and further investigation is needed to explain whether the production of CH 3 I enhances the IO concentration or if there are other missing IO precursors.…”

Section: Gas-phase and Heterogeneous Chemistry: Brominementioning

confidence: 99%

Importance of reactive halogens in the tropical marine atmosphere: a regional modelling study using WRF-Chem

et al. 2019

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Abstract. This study investigates the impact of reactive halogen species (RHS, containing chlorine (Cl), bromine (Br) or iodine (I)) on atmospheric chemistry in the tropical troposphere and explores the sensitivity to uncertainties in the fluxes of RHS to the atmosphere and their chemical processing. To do this, the regional chemistry transport model WRF-Chem has been extended to include Br and I, as well as Cl chemistry for the first time, including heterogeneous recycling reactions involving sea-salt aerosol and other particles, reactions of Br and Cl with volatile organic compounds (VOCs), along with oceanic emissions of halocarbons, VOCs and inorganic iodine. The study focuses on the tropical east Pacific using field observations from the Tropical Ocean tRoposphere Exchange of Reactive halogen species and Oxygenated VOC (TORERO) campaign (January–February 2012) to evaluate the model performance. Including all the new processes, the model does a reasonable job reproducing the observed mixing ratios of bromine oxide (BrO) and iodine oxide (IO), albeit with some discrepancies, some of which can be attributed to difficulties in the model's ability to reproduce the observed halocarbons. This is somewhat expected given the large uncertainties in the air–sea fluxes of the halocarbons in a region where there are few observations of their seawater concentrations. We see a considerable impact on the inorganic bromine (Bry) partitioning when heterogeneous chemistry is included, with a greater proportion of the Bry in active forms such as BrO, HOBr and dihalogens. Including debromination of sea salt increases BrO slightly throughout the free troposphere, but in the tropical marine boundary layer, where the sea-salt particles are plentiful and relatively acidic, debromination leads to overestimation of the observed BrO. However, it should be noted that the modelled BrO was extremely sensitive to the inclusion of reactions between Br and the oxygenated VOCs (OVOCs), which convert Br to HBr, a far less reactive form of Bry. Excluding these reactions leads to modelled BrO mixing ratios greater than observed. The reactions between Br and aldehydes were found to be particularly important, despite the model underestimating the amount of aldehydes observed in the atmosphere. There are only small changes to the inorganic iodine (Iy) partitioning and IO when the heterogeneous reactions, primarily on sea salt, are included. Our model results show that tropospheric Ox loss due to halogens ranges between 25 % and 60 %. Uncertainties in the heterogeneous chemistry accounted for a small proportion of this range (25 % to 31 %). This range is in good agreement with other estimates from state-of-the-art atmospheric chemistry models. The upper bound is found when reactions between Br and Cl with VOCs are not included and, consequently, Ox loss by BrOx, ClOx and IOx cycles is high (60 %). With the inclusion of halogens in the troposphere, O3 is reduced by 7 ppbv on average. However, when reactions between Br and Cl with VOCs are not included, O3 is much lower than observed. Therefore, the tropospheric Ox budget is highly sensitive to the inclusion of halogen reactions with VOCs and to the uncertainties in current understanding of these reactions and the abundance of VOCs in the remote marine atmosphere.

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“…Recent laboratory experiments and modeling predictions have suggested that abiotic precursors would contribute to the majority of the observed global iodine oxide (IO) budget [Carpenter et al, 2013;Prados-Roman et al, 2015] (typical daytime MBL levels are~1 pptv), one of the main iodine oxidized compounds leading to particulate iodine. In addition to potential ocean abiotic iodine sources, we further show that among all biological parameters monitored in the seawater during the experiment (see supporting information), a significant correlation was found in the control mesocosm between iodine-containing species concentrations and some phytoplanktonic pigments (peridinin, chlorophyll b, and zeaxanthin) but not with the total autotrophic biomass (Chl a) (Figure 3b).…”

Section: Relationships To the Biochemical Composition Of The Seawatermentioning

confidence: 99%

Evidence of atmospheric nanoparticle formation from emissions of marine microorganisms

Sellegri

Pey

Rose

et al. 2016

Geophysical Research Letters

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Earth, as a whole, can be considered as a living organism emitting gases and particles into its atmosphere, in order to regulate its own temperature. In particular, oceans may respond to climate change by emitting particles that ultimately will influence cloud coverage. At the global scale, a large fraction of the aerosol number concentration is formed by nucleation of gas‐phase species, but this process has never been directly observed above oceans. Here we present, using semicontrolled seawater‐air enclosures, evidence that nucleation may occur from marine biological emissions in the atmosphere of the open ocean. We identify iodine‐containing species as major precursors for new particle clusters' formation, while questioning the role of the commonly accepted dimethyl sulfide oxidation products, in forming new particle clusters in the region investigated and within a time scale on the order of an hour. We further show that amines would sustain the new particle formation process by growing the new clusters to larger sizes. Our results suggest that iodine‐containing species and amines are correlated to different biological tracers. These observations, if generalized, would call for a substantial change of modeling approaches of the sea‐to‐air interactions.

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A negative feedback between anthropogenic ozone pollution and enhanced ocean emissions of iodine

Cited by 68 publications

References 30 publications

Global impacts of tropospheric halogens (Cl, Br, I) on oxidants and composition in GEOS-Chem

Global impacts of tropospheric halogens (Cl, Br, I) on oxidants and composition in GEOS-Chem

Importance of reactive halogens in the tropical marine atmosphere: a regional modelling study using WRF-Chem

Evidence of atmospheric nanoparticle formation from emissions of marine microorganisms

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