The Role of$Br_2$and BrCl in Surface Ozone Destruction at Polar Sunrise

Bromine atoms are believed to play a central role in the depletion of surface-level ozone in the Arctic at polar sunrise.$Br_2$, BrCl, and HOBr have been hypothesized as bromine atom precursors, and there is evidence for chlorine atom precursors as well, but these species have not been measured dire...

Full description

Saved in:
Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 2001-01, Vol.291 (5503), p.471-474
Main Authors: Foster, Krishna L., Plastridge, Robert A., Bottenheim, Jan W., Shepson, Paul B., Finlayson-Pitts, Barbara J., Spicer, Chester W.
Format: Article
Language:English
Subjects:
Atmospheric chemistry
Atoms
Horses
Ice
Ions
Mitochondrial DNA
Mixing ratios
Ozone
Snow
Snowpack
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Bromine atoms are believed to play a central role in the depletion of surface-level ozone in the Arctic at polar sunrise.$Br_2$, BrCl, and HOBr have been hypothesized as bromine atom precursors, and there is evidence for chlorine atom precursors as well, but these species have not been measured directly. We report here measurements of$Br_2$, BrCl, and Cl2made using atmospheric pressure chemical ionization-mass spectrometry at Alert, Nunavut, Canada. In addition to$Br_2$at mixing ratios up to ~25 parts per trillion, BrCl was found at levels as high as ~35 parts per trillion. Molecular chlorine was not observed, implying that BrCl is the dominant source of chlorine atoms during polar sunrise, consistent with recent modeling studies. Similar formation of bromine compounds and tropospheric ozone destruction may also occur at mid-latitudes but may not be as apparent owing to more efficient mixing in the boundary layer.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.291.5503.471