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Chlorine activation within urban or power plant plumes: Vertically resolved ClNO 2 and Cl 2 measurements from a tall tower in a polluted continental setting
Author(s) -
Riedel Theran P.,
Wagner Nicholas L.,
Dubé William P.,
Middlebrook Ann M.,
Young Cora J.,
Öztürk Fatma,
Bahreini Roya,
VandenBoer Trevor C.,
Wolfe Daniel E.,
Williams Eric J.,
Roberts James M.,
Brown Steven S.,
Thornton Joel A.
Publication year - 2013
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/jgrd.50637
Subject(s) - aerosol , mixing ratio , plume , chlorine , chemistry , sea salt , chloride , nox , atmospheric chemistry , sea breeze , ozone , meteorology , combustion , organic chemistry , physics
Nitryl chloride (ClNO 2 ) is a chlorine atom source and reactive nitrogen reservoir formed during the night by heterogeneous reactions of dinitrogen pentoxide on chloride‐containing aerosol particles. The main factors that influence ClNO 2 production include nitrogen oxides, ozone, aerosol surface area, soluble chloride, and ambient relative humidity. Regions with strong anthropogenic activity therefore have large ClNO 2 formation potential even inland of coastal regions due to transport or local emissions of soluble chloride. As part of the Nitrogen, Aerosol Composition, and Halogens on a Tall Tower field study, we report wintertime vertically resolved ClNO 2 and molecular chlorine (Cl 2 ) measurements taken on a 300 m tall tower located at NOAA's Boulder Atmospheric Observatory in Weld County, CO, during February and March of 2011. Gas and particle phase measurements aboard the tower carriage allowed for a detailed description of the chemical state of the nocturnal atmosphere as a function of height. These observations show significant vertical structure in ClNO 2 and Cl 2 mixing ratios that undergo dynamic changes over the course of a night. Using these measurements, we focus on two distinct combustion plume events where ClNO 2 mixing ratios reached 600 and 1300 parts per trillion by volume, respectively, aloft of the nocturnal surface layer. We infer ClNO 2 yields from N 2 O 5 ‐aerosol reactions using both observational constraints and box modeling. The derived yields in these plumes suggest efficient ClNO 2 production compared to the campaign average, where in‐plume yields range from 0.3 to 1; the campaign average yield in the boundary layer is 0.05 ± 0.15, with substantial night‐to‐night and within night variability similar to previous measurements in this region.