A large atomic chlorine source inferred from mid-continental reactive nitrogen chemistry.
Halogen atoms and oxides are highly reactive and can profoundly affect atmospheric composition. Chlorine atoms can decrease the lifetimes of gaseous elemental mercury and hydrocarbons such as the greenhouse gas methane. Chlorine atoms also influence cycles that catalytically destroy or produce tropospheric ozone, a greenhouse gas potentially toxic to plant and animal life. Conversion of inorganic chloride into gaseous chlorine atom precursors within the troposphere is generally considered a coastal or marine air phenomenon. Here we report mid-continental observations of the chlorine atom precursor nitryl chloride at a distance of 1,400 km from the nearest coastline. We observe persistent and significant nitryl chloride production relative to the consumption of its nitrogen oxide precursors. Comparison of these findings to model predictions based on aerosol and precipitation composition data from long-term monitoring networks suggests nitryl chloride production in the contiguous USA alone is at a level similar to previous global estimates for coastal and marine regions. We also suggest that a significant fraction of tropospheric chlorine atoms may arise directly from anthropogenic pollutants.
Thornton
Joel A
JA
Department of Atmospheric Sciences, University of Washington, Seattle, Washington 98195, USA. thornton@atmos.washington.edu
Kercher
James P
JP
Riedel
Theran P
TP
Wagner
Nicholas L
NL
Cozic
Julie
J
Holloway
John S
JS
Dubé
William P
WP
Wolfe
Glenn M
GM
Quinn
Patricia K
PK
Middlebrook
Ann M
AM
Alexander
Becky
B
Brown
Steven S
SS
D000336:Aerosols / Q000737:chemistry; D000388:Air / Q000032:analysis; D001272:Atmosphere / Q000737:chemistry*; D002713:Chlorine / Q000737:chemistry*; D003120:Colorado; D008956:Models, Chemical; D009573:Nitrites / Q000032:analysis / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry*; D009589:Nitrogen Oxides / Q000737:chemistry; D013997:Time Factors
D000336:Aerosols; D009573:Nitrites; D009589:Nitrogen Oxides; D002713:Chlorine; D009584:Nitrogen; C445660:nitryl chloride