Photochemically induced production of CH3Br, CH3I, C2H5I, ethene, and propene within surface snow at Summit, Greenland
Measurements at Summit, Greenland, performed from June–August 1999, showed significant enhancement in concentrations of several trace gases in the snowpack (firn) pore air relative to the atmosphere. We report here measurements of alkenes, halocarbons, and alkyl nitrates that are typically a factor...
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ftuninhampshire:oai:scholars.unh.edu:earthsci_facpub-1169 2023-05-15T16:28:28+02:00 Photochemically induced production of CH3Br, CH3I, C2H5I, ethene, and propene within surface snow at Summit, Greenland Swanson, Aaron L Blake, Nicola J Dibb, Jack E. Blake, D R Rowland, F Sherwood 2002-01-01T08:00:00Z text/html https://scholars.unh.edu/earthsci_facpub/170 https://doi.org/10.1016/S1352-2310(02)00127-9 unknown University of New Hampshire Scholars' Repository https://scholars.unh.edu/earthsci_facpub/170 http://dx.doi.org/10.1016/S1352-2310(02)00127-9 Earth Sciences Scholarship Snowpack photochemistry Methyl bromide Methyl iodide Alkenes Alkyl nitrates Atmospheric Sciences text 2002 ftuninhampshire https://doi.org/10.1016/S1352-2310(02)00127-9 2023-01-30T21:34:30Z Measurements at Summit, Greenland, performed from June–August 1999, showed significant enhancement in concentrations of several trace gases in the snowpack (firn) pore air relative to the atmosphere. We report here measurements of alkenes, halocarbons, and alkyl nitrates that are typically a factor of 2–10 higher in concentration within the firn air than in the ambient air 1–10 m above the snow. Profiles of concentration to a depth of 2 m into the firn show that maximum values of these trace gases occur between the surface and 60 cm depth. The alkenes show highest pore mixing ratios very close to the surface, with mixing ratios in the order ethene>propene>1-butene. Mixing ratios of the alkyl iodides and alkyl nitrates peak slightly deeper in the firn, with mixing ratios in order of methyl>ethyl>propyl. These variations are likely consistent with different near-surface photochemical production mechanisms. Diurnal mixing ratio variations within the firn correlate well with actinic flux for all these gases, with a temporal offset between the solar maximum and peak concentrations, lengthening with depth. Using a snow-filled chamber under constant flow conditions, we calculated production rates for the halocarbons and alkenes that ranged between 103–105 and 106 molecules cm−3 s−1, respectively. Taken together, these results suggest that photochemistry associated with the surface snowpack environment plays an important role in the oxidative capacity of the local atmospheric boundary layer, and influences post-depositional chemistry, which in turn may affect the interpretation of certain aspects of the ice core records collected previously at Summit. Text Greenland ice core University of New Hampshire: Scholars Repository Greenland Atmospheric Environment 36 15-16 2671 2682 |
institution |
Open Polar |
collection |
University of New Hampshire: Scholars Repository |
op_collection_id |
ftuninhampshire |
language |
unknown |
topic |
Snowpack photochemistry Methyl bromide Methyl iodide Alkenes Alkyl nitrates Atmospheric Sciences |
spellingShingle |
Snowpack photochemistry Methyl bromide Methyl iodide Alkenes Alkyl nitrates Atmospheric Sciences Swanson, Aaron L Blake, Nicola J Dibb, Jack E. Blake, D R Rowland, F Sherwood Photochemically induced production of CH3Br, CH3I, C2H5I, ethene, and propene within surface snow at Summit, Greenland |
topic_facet |
Snowpack photochemistry Methyl bromide Methyl iodide Alkenes Alkyl nitrates Atmospheric Sciences |
description |
Measurements at Summit, Greenland, performed from June–August 1999, showed significant enhancement in concentrations of several trace gases in the snowpack (firn) pore air relative to the atmosphere. We report here measurements of alkenes, halocarbons, and alkyl nitrates that are typically a factor of 2–10 higher in concentration within the firn air than in the ambient air 1–10 m above the snow. Profiles of concentration to a depth of 2 m into the firn show that maximum values of these trace gases occur between the surface and 60 cm depth. The alkenes show highest pore mixing ratios very close to the surface, with mixing ratios in the order ethene>propene>1-butene. Mixing ratios of the alkyl iodides and alkyl nitrates peak slightly deeper in the firn, with mixing ratios in order of methyl>ethyl>propyl. These variations are likely consistent with different near-surface photochemical production mechanisms. Diurnal mixing ratio variations within the firn correlate well with actinic flux for all these gases, with a temporal offset between the solar maximum and peak concentrations, lengthening with depth. Using a snow-filled chamber under constant flow conditions, we calculated production rates for the halocarbons and alkenes that ranged between 103–105 and 106 molecules cm−3 s−1, respectively. Taken together, these results suggest that photochemistry associated with the surface snowpack environment plays an important role in the oxidative capacity of the local atmospheric boundary layer, and influences post-depositional chemistry, which in turn may affect the interpretation of certain aspects of the ice core records collected previously at Summit. |
format |
Text |
author |
Swanson, Aaron L Blake, Nicola J Dibb, Jack E. Blake, D R Rowland, F Sherwood |
author_facet |
Swanson, Aaron L Blake, Nicola J Dibb, Jack E. Blake, D R Rowland, F Sherwood |
author_sort |
Swanson, Aaron L |
title |
Photochemically induced production of CH3Br, CH3I, C2H5I, ethene, and propene within surface snow at Summit, Greenland |
title_short |
Photochemically induced production of CH3Br, CH3I, C2H5I, ethene, and propene within surface snow at Summit, Greenland |
title_full |
Photochemically induced production of CH3Br, CH3I, C2H5I, ethene, and propene within surface snow at Summit, Greenland |
title_fullStr |
Photochemically induced production of CH3Br, CH3I, C2H5I, ethene, and propene within surface snow at Summit, Greenland |
title_full_unstemmed |
Photochemically induced production of CH3Br, CH3I, C2H5I, ethene, and propene within surface snow at Summit, Greenland |
title_sort |
photochemically induced production of ch3br, ch3i, c2h5i, ethene, and propene within surface snow at summit, greenland |
publisher |
University of New Hampshire Scholars' Repository |
publishDate |
2002 |
url |
https://scholars.unh.edu/earthsci_facpub/170 https://doi.org/10.1016/S1352-2310(02)00127-9 |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland ice core |
genre_facet |
Greenland ice core |
op_source |
Earth Sciences Scholarship |
op_relation |
https://scholars.unh.edu/earthsci_facpub/170 http://dx.doi.org/10.1016/S1352-2310(02)00127-9 |
op_doi |
https://doi.org/10.1016/S1352-2310(02)00127-9 |
container_title |
Atmospheric Environment |
container_volume |
36 |
container_issue |
15-16 |
container_start_page |
2671 |
op_container_end_page |
2682 |
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1766018119373946880 |