Elevated Tropospheric Iodine Over the Central Continental United States: Is Iodine a Major Oxidant of Atmospheric Mercury?
Abstract Previous efforts to measure atmospheric iodine have focused on marine and coastal regions. We report the first ground‐based tropospheric iodine monoxide (IO) radical observations over the central continental United States. Throughout April 2022, IO columns above Storm Peak Laboratory, Colorado (3,220 m.a.s.l.) ranged from 0.7 ± 0.5 to 3.6 ± 0.5 × 10 12 (average: 1.9 × 10 12 molec cm −2 ). IO was consistently elevated in air masses transported from over the Pacific Ocean. The observed IO columns were up to three times higher and the range was larger than predicted by a global model, which warrants further investigation into iodine sources, sinks, ozone loss, and particle formation. IO mixing ratios increased with altitude. At the observed levels, iodine may be competitive with bromine as an oxidant of elemental mercury at cold temperatures typical of the free troposphere. Iodine‐induced mercury oxidation is missing in atmospheric models, understudied, and helps explain model underestimation of oxidized mercury measurements.
Authors
- John C. Lin (ORCID: https://orcid.org/0000-0003-2794-184X)
- Christopher F. Lee (ORCID: https://orcid.org/0000-0003-3808-9859)
- Rainer Volkamer (ORCID: https://orcid.org/0000-0002-0899-1369)
- Seth N. Lyman (ORCID: https://orcid.org/0000-0001-8493-9522)
- Liji M. David (ORCID: https://orcid.org/0000-0002-0099-7715)
- Lynne E. Gratz (ORCID: https://orcid.org/0000-0002-7904-991X)
- Tyler Elgiar
- A. Gannet Hallar (ORCID: https://orcid.org/0000-0001-9972-0056)
- Viral P. Shah (ORCID: https://orcid.org/0000-0001-5547-106X)
- N. Hirshorn
- Mohamad Reza (ORCID: https://orcid.org/0000-0002-1625-2718)
- Taylor Y. Wilmot (ORCID: https://orcid.org/0000-0002-3463-1420)
- Ian B. McCubbin
Institutions
- Utah State University (US)
- Binghamton University (US)
- Cooperative Institute for Research in Environmental Sciences (US)
- University of Colorado Boulder (US)
- Colorado College (US)
- University of Utah (US)
- Science Systems and Applications (United States) (US)
- Reed College (US)
Publication Details
- Journal
- Geophysical Research Letters
- Published
- 2024-09-05
- DOI
- https://doi.org/10.1029/2024gl109247
- Citations
- 7
- Primary Topic
- Mercury impact and mitigation studies
- Type
- article
- Field-Weighted Citation Impact
- 2.20
Funders
- National Science Foundation
- National Aeronautics and Space Administration
- Goddard Space Flight Center