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N 2 O 5 uptake coefficients and nocturnal NO 2 removal rates determined from ambient wintertime measurements
Author(s) -
Wagner N. L.,
Riedel T. P.,
Young C. J.,
Bahreini R.,
Brock C. A.,
Dubé W. P.,
Kim S.,
Middlebrook A. M.,
Öztürk F.,
Roberts J. M.,
Russo R.,
Sive B.,
Swarthout R.,
Thornton J. A.,
VandenBoer T. C.,
Zhou Y.,
Brown S. S.
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.50653
Subject(s) - nitrate , aerosol , atmosphere (unit) , nocturnal , chemistry , environmental chemistry , analytical chemistry (journal) , atmospheric sciences , environmental science , meteorology , physics , astronomy , organic chemistry
Heterogeneous N 2 O 5 uptake onto aerosol is the primary nocturnal path for removal of NO x (= NO + NO 2 ) from the atmosphere and can also result in halogen activation through production of ClNO 2 . The N 2 O 5 uptake coefficient has been the subject of numerous laboratory studies; however, only a few studies have determined the uptake coefficient from ambient measurements, and none has been focused on winter conditions, when the portion of NO x removed by N 2 O 5 uptake is the largest. In this work, N 2 O 5 uptake coefficients are determined from ambient wintertime measurements of N 2 O 5 and related species at the Boulder Atmospheric Observatory in Weld County, CO, a location that is highly impacted by urban pollution from Denver, as well as emissions from agricultural activities and oil and gas extraction. A box model is used to analyze the nocturnal nitrate radical chemistry and predict the N 2 O 5 concentration. The uptake coefficient in the model is iterated until the predicted N 2 O 5 concentration matches the measured concentration. The results suggest that during winter, the most important influence that might suppress N 2 O 5 uptake is aerosol nitrate but that this effect does not suppress uptake coefficients enough to limit the rate of NO x loss through N 2 O 5 hydrolysis. N 2 O 5 hydrolysis was found to dominate the nocturnal chemistry during this study consuming ~80% of nocturnal gas phase nitrate radical production. Typically, less than 15% of the total nitrate radical production remained in the form of nocturnal species at sunrise when they are photolyzed and reform NO 2 .