A large atomic chlorine source inferred from mid-continental reactive nitrogen chemistry
Joel A Thornton1, James P Kercher, Theran P Riedel
1Department of Atmospheric Sciences, University of Washington, Seattle, Washington 98195, USA. thornton@atmos.washington.edu
Nature
|March 12, 2010
Summary
Mid-continental observations reveal nitryl chloride, a chlorine atom precursor, is produced far from coasts. This suggests a significant source of atmospheric chlorine, potentially from human-made pollution.
Area of Science:
- Atmospheric Chemistry
- Environmental Science
Background:
- Halogen atoms and oxides significantly impact atmospheric composition and chemistry.
- Chlorine atoms influence the lifetimes of mercury and methane, and affect ozone cycles.
- Gaseous chlorine precursors are typically associated with marine environments.
Purpose of the Study:
- To report mid-continental observations of nitryl chloride, a chlorine atom precursor.
- To investigate the production of nitryl chloride inland, away from coastal regions.
- To assess the contribution of anthropogenic pollutants to tropospheric chlorine.
Main Methods:
- In-situ measurements of nitryl chloride and its precursors in a mid-continental location.
- Comparison of observational data with model predictions.
- Analysis of long-term monitoring data for aerosol and precipitation composition.
Main Results:
- Persistent and significant nitryl chloride production was observed 1,400 km from the coast.
- Observed nitryl chloride production in the contiguous USA is comparable to global coastal estimates.
- A substantial portion of tropospheric chlorine atoms may originate from anthropogenic pollutants.
Conclusions:
- Nitryl chloride production is not limited to coastal or marine areas.
- Inland nitryl chloride production represents a significant, previously underestimated source of atmospheric chlorine.
- Anthropogenic pollutants may play a key role in the tropospheric chlorine cycle.
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