On the vertical distribution of boundary layer halogens over coastal Antarctica: implications for O 3 , HO x , NO x and the Hg lifetime

International audience A one-dimensional chemical transport model has been developed to investigate the vertical gradients of bromine and iodine compounds in the Antarctic coastal boundary layer. The model has been applied to interpret recent year-round observations of iodine and bromine monoxides (...

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Main Authors: Saiz-Lopez, A., Plane, J. M. C., Mahajan, A. S., Anderson, P. S., Bauguitte, S. J.-B., Jones, A. E., Roscoe, H. K., Salmon, R. A., Bloss, W. J., Lee, J. D., Heard, D. E.
Other Authors: School of Chemistry, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), British Antarctic Survey (BAS), Natural Environment Research Council (NERC)
Format: Article in Journal/Newspaper
Language:English
Published: HAL CCSD 2007
Subjects:
Online Access:https://hal.science/hal-00302928
https://hal.science/hal-00302928/document
https://hal.science/hal-00302928/file/acpd-7-9385-2007.pdf
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spelling ftinsu:oai:HAL:hal-00302928v1 2023-11-12T04:07:16+01:00 On the vertical distribution of boundary layer halogens over coastal Antarctica: implications for O 3 , HO x , NO x and the Hg lifetime Saiz-Lopez, A. Plane, J. M. C. Mahajan, A. S. Anderson, P. S. Bauguitte, S. J.-B. Jones, A. E. Roscoe, H. K. Salmon, R. A. Bloss, W. J. Lee, J. D. Heard, D. E. School of Chemistry Jet Propulsion Laboratory (JPL) NASA-California Institute of Technology (CALTECH) British Antarctic Survey (BAS) Natural Environment Research Council (NERC) 2007-07-02 https://hal.science/hal-00302928 https://hal.science/hal-00302928/document https://hal.science/hal-00302928/file/acpd-7-9385-2007.pdf en eng HAL CCSD European Geosciences Union hal-00302928 https://hal.science/hal-00302928 https://hal.science/hal-00302928/document https://hal.science/hal-00302928/file/acpd-7-9385-2007.pdf info:eu-repo/semantics/OpenAccess ISSN: 1680-7367 EISSN: 1680-7375 Atmospheric Chemistry and Physics Discussions https://hal.science/hal-00302928 Atmospheric Chemistry and Physics Discussions, 2007, 7 (4), pp.9385-9417 [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere info:eu-repo/semantics/article Journal articles 2007 ftinsu 2023-10-25T16:26:26Z International audience A one-dimensional chemical transport model has been developed to investigate the vertical gradients of bromine and iodine compounds in the Antarctic coastal boundary layer. The model has been applied to interpret recent year-round observations of iodine and bromine monoxides (IO and BrO) at Halley Station, Antarctica. The model requires an equivalent I atom flux of ~10 9 molecule cm ?2 s ?1 from the snowpack in order to account for the measured IO levels, which are up to 20 ppt during spring. Using the current knowledge of gas-phase iodine chemistry, the model predicts significant gradients in the vertical distribution of iodine species. However, recent ground-based and satellite observations of IO imply that the radical is well-mixed in the boundary layer, indicating a longer than expected atmospheric lifetime for the radical. This can be modelled by including photolysis of the higher iodine oxides (I 2 O 2 , I 2 O 3 , I 2 O 4 and I 2 O 5 ), and rapid recycling of HOI and INO 3 through sea-salt aerosol. The model also predicts significant concentrations (up to 25 ppt) of I 2 O 5 in the lowest 10 m of the boundary layer, which could lead to the formation of ultrafine iodine oxide aerosols. Heterogeneous chemistry involving sea-salt aerosol is also necessary to account for the vertical profile of BrO. Iodine chemistry causes a large increase (typically more than 3-fold) in the rate of O 3 depletion in the BL, compared with bromine chemistry alone. Rapid entrainment of O 3 from the free troposphere is required to account for the observation that on occasion there is little O 3 depletion at the surface in the presence of high concentrations of IO and BrO. The halogens also cause significant changes to the vertical profiles of HO and HO 2 and the NO 2 /NO ratio. The average Hg 0 lifetime against oxidation is also predicted to be about 10 h during springtime. Overall, our results show that halogens profoundly influence the oxidizing capacity of the Antarctic troposphere. Article in Journal/Newspaper Antarc* Antarctic Antarctica Institut national des sciences de l'Univers: HAL-INSU Antarctic Halley Station ENVELOPE(-26.541,-26.541,-75.581,-75.581) The Antarctic
institution Open Polar
collection Institut national des sciences de l'Univers: HAL-INSU
op_collection_id ftinsu
language English
topic [SDU.OCEAN]Sciences of the Universe [physics]/Ocean
Atmosphere
spellingShingle [SDU.OCEAN]Sciences of the Universe [physics]/Ocean
Atmosphere
Saiz-Lopez, A.
Plane, J. M. C.
Mahajan, A. S.
Anderson, P. S.
Bauguitte, S. J.-B.
Jones, A. E.
Roscoe, H. K.
Salmon, R. A.
Bloss, W. J.
Lee, J. D.
Heard, D. E.
On the vertical distribution of boundary layer halogens over coastal Antarctica: implications for O 3 , HO x , NO x and the Hg lifetime
topic_facet [SDU.OCEAN]Sciences of the Universe [physics]/Ocean
Atmosphere
description International audience A one-dimensional chemical transport model has been developed to investigate the vertical gradients of bromine and iodine compounds in the Antarctic coastal boundary layer. The model has been applied to interpret recent year-round observations of iodine and bromine monoxides (IO and BrO) at Halley Station, Antarctica. The model requires an equivalent I atom flux of ~10 9 molecule cm ?2 s ?1 from the snowpack in order to account for the measured IO levels, which are up to 20 ppt during spring. Using the current knowledge of gas-phase iodine chemistry, the model predicts significant gradients in the vertical distribution of iodine species. However, recent ground-based and satellite observations of IO imply that the radical is well-mixed in the boundary layer, indicating a longer than expected atmospheric lifetime for the radical. This can be modelled by including photolysis of the higher iodine oxides (I 2 O 2 , I 2 O 3 , I 2 O 4 and I 2 O 5 ), and rapid recycling of HOI and INO 3 through sea-salt aerosol. The model also predicts significant concentrations (up to 25 ppt) of I 2 O 5 in the lowest 10 m of the boundary layer, which could lead to the formation of ultrafine iodine oxide aerosols. Heterogeneous chemistry involving sea-salt aerosol is also necessary to account for the vertical profile of BrO. Iodine chemistry causes a large increase (typically more than 3-fold) in the rate of O 3 depletion in the BL, compared with bromine chemistry alone. Rapid entrainment of O 3 from the free troposphere is required to account for the observation that on occasion there is little O 3 depletion at the surface in the presence of high concentrations of IO and BrO. The halogens also cause significant changes to the vertical profiles of HO and HO 2 and the NO 2 /NO ratio. The average Hg 0 lifetime against oxidation is also predicted to be about 10 h during springtime. Overall, our results show that halogens profoundly influence the oxidizing capacity of the Antarctic troposphere.
author2 School of Chemistry
Jet Propulsion Laboratory (JPL)
NASA-California Institute of Technology (CALTECH)
British Antarctic Survey (BAS)
Natural Environment Research Council (NERC)
format Article in Journal/Newspaper
author Saiz-Lopez, A.
Plane, J. M. C.
Mahajan, A. S.
Anderson, P. S.
Bauguitte, S. J.-B.
Jones, A. E.
Roscoe, H. K.
Salmon, R. A.
Bloss, W. J.
Lee, J. D.
Heard, D. E.
author_facet Saiz-Lopez, A.
Plane, J. M. C.
Mahajan, A. S.
Anderson, P. S.
Bauguitte, S. J.-B.
Jones, A. E.
Roscoe, H. K.
Salmon, R. A.
Bloss, W. J.
Lee, J. D.
Heard, D. E.
author_sort Saiz-Lopez, A.
title On the vertical distribution of boundary layer halogens over coastal Antarctica: implications for O 3 , HO x , NO x and the Hg lifetime
title_short On the vertical distribution of boundary layer halogens over coastal Antarctica: implications for O 3 , HO x , NO x and the Hg lifetime
title_full On the vertical distribution of boundary layer halogens over coastal Antarctica: implications for O 3 , HO x , NO x and the Hg lifetime
title_fullStr On the vertical distribution of boundary layer halogens over coastal Antarctica: implications for O 3 , HO x , NO x and the Hg lifetime
title_full_unstemmed On the vertical distribution of boundary layer halogens over coastal Antarctica: implications for O 3 , HO x , NO x and the Hg lifetime
title_sort on the vertical distribution of boundary layer halogens over coastal antarctica: implications for o 3 , ho x , no x and the hg lifetime
publisher HAL CCSD
publishDate 2007
url https://hal.science/hal-00302928
https://hal.science/hal-00302928/document
https://hal.science/hal-00302928/file/acpd-7-9385-2007.pdf
long_lat ENVELOPE(-26.541,-26.541,-75.581,-75.581)
geographic Antarctic
Halley Station
The Antarctic
geographic_facet Antarctic
Halley Station
The Antarctic
genre Antarc*
Antarctic
Antarctica
genre_facet Antarc*
Antarctic
Antarctica
op_source ISSN: 1680-7367
EISSN: 1680-7375
Atmospheric Chemistry and Physics Discussions
https://hal.science/hal-00302928
Atmospheric Chemistry and Physics Discussions, 2007, 7 (4), pp.9385-9417
op_relation hal-00302928
https://hal.science/hal-00302928
https://hal.science/hal-00302928/document
https://hal.science/hal-00302928/file/acpd-7-9385-2007.pdf
op_rights info:eu-repo/semantics/OpenAccess
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