Studies of Arctic halogen chemistry from the snowpack to the gas phase

• Main Author: Custard, Kyle D
• Other Authors: Shepson, Paul B.
• Format: Text
• Language: English
• Published: Purdue University 2015
• Subjects: Analytical chemistry|Inorganic chemistry|Organic chemistry; Arctic; Barrow; Sea ice; Alaska
• Online Access: https://docs.lib.purdue.edu/dissertations/AAI3719050

The temporary depletion of both tropospheric ozone and gaseous mercury during the Arctic springtime has been a focus of active research over the past several decades. Both of these phenomena have been linked to chemical reactions with halogen radicals. In particular, bromine atoms have been shown to act as the primary driver for these chemical depletions, although both chlorine and iodine atoms also contribute. Molecular bromine, along with its oxidation products, have been well studied in the Arctic, yet chlorine has not. Chlorine is known to impact the local oxidation capacity via its high reactivity with volatile organic compounds. Despite this understanding and the direct observations of atmospheric Cl2, the source and release mechanism has not yet been determined. This work describes experiments conducted during February 2014 in Barrow, Alaska, where in-snowpack production of BrCl and Cl2 were observed. These measurements were accompanied by vertical profile experiments to determine flux emission rates of Br2 and Cl2 from the snowpack. Furthermore, ambient chemical ionization mass spectrometer measurements of ClO, a first of their kind, are reported from the Bromine, Mercury, and Ozone Experiment (BROMEX) 2012 field campaign. This data was compared to model simulations representative of the sampling time period to investigate current understanding of the chlorine radical cycle. Finally, using data collected during the Ocean-Atmosphere-Sea Ice-Snowpack (OASIS) 2009 field campaign, we developed a model to study the impact that anthropogenic NOx emissions has on the bromine radical cycle.