Molecular halogens before and during ozone depletion events in the Arctic at polar sunrise: concentrations and sources

摘要

The molecular halogens Br_2, BrCl and Cl_2 were monitored from 9 February to 13 March 2000 as part of the ALERT 2000 campaign to investigate the causes of ozone depletion at polar sunrise. The measurements were performed over the transition period from winter to spring in the high Arctic, at Alert, on northern Ellesmere Island in Nunavut, Canada. The measurement campaign for these species covered the period from 24-h darkness, at the beginning of the campaign, to several hours of direct sunlight per day at the end of the campaign. The halogen measurements were made by atmospheric pressure ionization tandem mass spectrometry, using multiple isotopes for each species, and reporting a 20-s average for each species every 2 min.