Iodine's impact on tropospheric oxidants: a global model study in GEOS-Chem
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Published:2016-02-02
Issue:2
Volume:16
Page:1161-1186
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ISSN:1680-7324
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Container-title:Atmospheric Chemistry and Physics
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language:en
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Short-container-title:Atmos. Chem. Phys.
Author:
Sherwen T.ORCID, Evans M. J.ORCID, Carpenter L. J., Andrews S. J., Lidster R. T., Dix B.ORCID, Koenig T. K.ORCID, Sinreich R., Ortega I.ORCID, Volkamer R.ORCID, Saiz-Lopez A.ORCID, Prados-Roman C.ORCID, Mahajan A. S.ORCID, Ordóñez C.ORCID
Abstract
Abstract. We present a global simulation of tropospheric iodine chemistry within the GEOS-Chem chemical transport model. This includes organic and inorganic iodine sources, standard gas-phase iodine chemistry, and simplified higher iodine oxide (I2OX, X = 2, 3, 4) chemistry, photolysis, deposition, and parametrized heterogeneous reactions. In comparisons with recent iodine oxide (IO) observations, the simulation shows an average bias of ∼ +90 % with available surface observations in the marine boundary layer (outside of polar regions), and of ∼ +73 % within the free troposphere (350 hPa < p < 900 hPa) over the eastern Pacific. Iodine emissions (3.8 Tg yr−1) are overwhelmingly dominated by the inorganic ocean source, with 76 % of this emission from hypoiodous acid (HOI). HOI is also found to be the dominant iodine species in terms of global tropospheric IY burden (contributing up to 70 %). The iodine chemistry leads to a significant global tropospheric O3 burden decrease (9.0 %) compared to standard GEOS-Chem (v9-2). The iodine-driven OX loss rate1 (748 Tg OX yr−1) is due to photolysis of HOI (78 %), photolysis of OIO (21 %), and reaction between IO and BrO (1 %). Increases in global mean OH concentrations (1.8 %) by increased conversion of hydroperoxy radicals exceeds the decrease in OH primary production from the reduced O3 concentration. We perform sensitivity studies on a range of parameters and conclude that the simulation is sensitive to choices in parametrization of heterogeneous uptake, ocean surface iodide, and I2OX (X = 2, 3, 4) photolysis. The new iodine chemistry combines with previously implemented bromine chemistry to yield a total bromine- and iodine-driven tropospheric O3 burden decrease of 14.4 % compared to a simulation without iodine and bromine chemistry in the model, and a small increase in OH (1.8 %). This is a significant impact and so halogen chemistry needs to be considered in both climate and air quality models. 1 Here OX is defined as O3 + NO2 + 2NO3 + PAN + PMN+PPN + HNO4 + 3N2O5 + HNO3 + BrO + HOBr + BrNO2+2BrNO3 + MPN + IO + HOI + INO2 + 2INO3 + 2OIO+2I2O2 + 3I2O3 + 4I2O4, where PAN = peroxyacetyl nitrate, PPN = peroxypropionyl nitrate, MPN = methyl peroxy nitrate, and MPN = peroxymethacryloyl nitrate.
Funder
Natural Environment Research Council
Publisher
Copernicus GmbH
Subject
Atmospheric Science
Reference79 articles.
1. Ainsworth, E. A., Yendrek, C. R., Sitch, S., Collins, W. J., and
Emberson, L. D.: The effects of tropospheric ozone on net primary
productivity and implications for climate change, Annu. Rev. Plant Bio., 63,
637–661,
https://doi.org/10.1146/annurev-arplant-042110-103829,
2012. 2. Alexander, B.: Sulfate formation in sea-salt aerosols: Constraints from
oxygen isotopes, J. Geophys. Res., 110, D10307,
https://doi.org/10.1029/2004JD005659,
2005. 3. Amos, H. M., Jacob, D. J., Holmes, C. D., Fisher, J. A., Wang, Q., Yantosca,
R. M., Corbitt, E. S., Galarneau, E., Rutter, A. P., Gustin, M. S., Steffen,
A., Schauer, J. J., Graydon, J. A., Louis, V. L. St., Talbot, R. W.,
Edgerton, E. S., Zhang, Y., and Sunderland, E. M.: Gas-particle partitioning
of atmospheric Hg(II) and its effect on global mercury deposition, Atmos.
Chem. Phys., 12, 591–603, https://doi.org/10.5194/acp-12-591-2012, 2012. 4. Andrews, S. J., Jones, C. E., and Carpenter, L. J.: Aircraft measurements of
very short-lived halocarbons over the tropical Atlantic Ocean, Geophys. Res.
Lett., 40, 1005–1010,
https://doi.org/10.1002/grl.50141, 2013. 5. Andrews, S. J., Hackenberg, S. C., and Carpenter, L. J.: Technical Note: A
fully automated purge and trap GC-MS system for quantification of volatile
organic compound (VOC) fluxes between the ocean and atmosphere, Ocean Sci.,
11, 313–321, https://doi.org/10.5194/os-11-313-2015, 2015.
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