Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 15, 10799-10809, 2015
© Author(s) 2015. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
29 Sep 2015
The NOx dependence of bromine chemistry in the Arctic atmospheric boundary layer
K. D. Custard1, C. R. Thompson1,5,b, K. A. Pratt1,2, P B. Shepson1,3, J. Liao4,5,6, L. G. Huey4, J. J. Orlando7, A. J. Weinheimer7, E. Apel7, S. R. Hall7, F. Flocke7, L. Mauldin7,a, R. S. Hornbrook7, D. Pöhler8, S. General8, J. Zielcke8, W. R. Simpson9, U. Platt8, A. Fried11, P. Weibring11, B. C. Sive10, K. Ullmann7, C. Cantrell7,a, D. J. Knapp7, and D. D. Montzka7 1Department of Chemistry, Purdue University, West Lafayette, IN, USA
2Department of Chemistry, University of Michigan, Ann Arbor, MI, USA
3Department of Earth, Atmospheric, and Planetary Sciences & Purdue Climate Change Research Center, Purdue University, West Lafayette, IN, USA
4School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
5Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO, USA
6Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO, USA
7National Center for Atmospheric Research, Boulder, CO, USA
8Institute of Environmental Physics, University of Heidelberg, Heidelberg, Germany
9Geophysical Institute and Department of Chemistry, University of Alaska Fairbanks, Fairbanks, AK, USA
10National Park Service, Air Resources Division, Lakewood, CO, USA
11Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO, USA
anow at: Atmospheric and Ocean Sciences, University of Colorado, Boulder, CO, USA
bnow at: Chemical Sciences Division, National Oceanic and Atmospheric Administration, Boulder, CO, USA
Abstract. Arctic boundary layer nitrogen oxides (NOx = NO2 + NO) are naturally produced in and released from the sunlit snowpack and range between 10 to 100 pptv in the remote background surface layer air. These nitrogen oxides have significant effects on the partitioning and cycling of reactive radicals such as halogens and HOx (OH + HO2). However, little is known about the impacts of local anthropogenic NOx emission sources on gas-phase halogen chemistry in the Arctic, and this is important because these emissions can induce large variability in ambient NOx and thus local chemistry. In this study, a zero-dimensional photochemical kinetics model was used to investigate the influence of NOx on the unique springtime halogen and HOx chemistry in the Arctic. Trace gas measurements obtained during the 2009 OASIS (Ocean – Atmosphere – Sea Ice – Snowpack) field campaign at Barrow, AK were used to constrain many model inputs. We find that elevated NOx significantly impedes gas-phase halogen radical-based depletion of ozone, through the production of a variety of reservoir species, including HNO3, HO2NO2, peroxyacetyl nitrate (PAN), BrNO2, ClNO2 and reductions in BrO and HOBr. The effective removal of BrO by anthropogenic NOx was directly observed from measurements conducted near Prudhoe Bay, AK during the 2012 Bromine, Ozone, and Mercury Experiment (BROMEX). Thus, while changes in snow-covered sea ice attributable to climate change may alter the availability of molecular halogens for ozone and Hg depletion, predicting the impact of climate change on polar atmospheric chemistry is complex and must take into account the simultaneous impact of changes in the distribution and intensity of anthropogenic combustion sources. This is especially true for the Arctic, where NOx emissions are expected to increase because of increasing oil and gas extraction and shipping activities.

Citation: Custard, K. D., Thompson, C. R., Pratt, K. A., Shepson, P. B., Liao, J., Huey, L. G., Orlando, J. J., Weinheimer, A. J., Apel, E., Hall, S. R., Flocke, F., Mauldin, L., Hornbrook, R. S., Pöhler, D., General, S., Zielcke, J., Simpson, W. R., Platt, U., Fried, A., Weibring, P., Sive, B. C., Ullmann, K., Cantrell, C., Knapp, D. J., and Montzka, D. D.: The NOx dependence of bromine chemistry in the Arctic atmospheric boundary layer, Atmos. Chem. Phys., 15, 10799-10809, doi:10.5194/acp-15-10799-2015, 2015.
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