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Project Number:
 
10-015
Title:
 
An Assessment of Nitryl Chloride Formation Chemistry and its Importance in Ozone Non-Attainment Areas in Texas
Lead PI:
 
James Roberts
Institution(s) Represented:
 
ENVIRON- Greg Yarwood, National Oceanic and Atmospheric Administration (NOAA)- James Roberts
AQRP Project Manager:
 
Elena McDonald-Buller
TCEQ Project Liaison:
 
Jim Neece
Awarded Amount:
 
$201,280.00

Executive Summary- Project 10-015
An Assessment of Nitryl Chloride Formation Chemistry and its Importance in Ozone Non- attainment areas in Texas
Generally urban air pollution occurs during hot, sunlit, stagnant weather when ozone and aerosols (very fine particles suspended in the air) are produced in copious amounts from the interaction of sunlight with emissions from natural sources, vehicles and industry.  However, a very different chemistry proceeds in the atmosphere in the absence of sunlight.  Indeed, at night an entirely different family of chemical species, which cannot persist in sunlight, actively modifies the composition of the urban atmosphere.  In some cases, this modified composition sets the stage to jumpstart the next day's sunlight driven chemistry, and thereby increases the amount of ozone and aerosol that are formed.  In other cases, the nighttime chemistry removes ozone and aerosol precursors and thereby reduces the next day's ozone and aerosol formation.  
Work conducted by the National Oceanic and Atmospheric Administration (NOAA) during the TexAQS 2006 study has shown that heterogeneous uptake and reaction of the important nighttime chemical species dinitrogen pentoxide (N2O5) can form the active halogen species, nitryl chloride (ClNO2), potentially in high enough abundance to impact the next day's photochemistry.  Nitryl chloride is produced when sufficient chloride-containing aerosol co-exists with high nighttime nitrogen oxides and ozone.  This process is likely particularly important in Houston due to high levels of chloride-containing aerosol from airborne sea salt, high NOx emissions, and high ozone concentrations.  This project aims to characterize nitryl chloride formation in urban areas of Texas as inferred from existing data sets from the TexAQS I, II and SHARP field campaigns in the region, and the CalNex 2010 data set conducted in another polluted coastal urban area (Los Angeles). This project will also include both box modeling of the N2O5- ClNO2-aerosol system to test and refine chemistry algorithms, and photochemical grid modeling with the CAMx model as used by TCEQ for SIP development.  
The expected outcomes of this research are improvement in our understanding of nighttime atmospheric chemistry, particularly with regard to active chlorine chemistry, and its influence on the production of ozone and aerosols in urban areas.  This improved understanding will be directly incorporated into the photochemical grid models so that more reliable SIP planning can be conducted.   

Work Plan:
 
     
Technical Report(s):
 
Technical Report(s):
 
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QAPP:
 
     
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Publications & Citations
The following papers are currently under development: Measurements of Nitryl Chloride in Several Metropolitan Areas and Comparison with Regional Models J.M. Roberts, H. Osthoff, E.J. Williams, B. Lerner, J.A. Neuman, J.B. Nowak, S.B. Brown, W.P. Dube, N.L. Wagner, T.B. Ryerson, I.B. Pollack, J.S. Holloway, A. Middlebrook, R. Bahreini, B. Koo, G. Yarwood In preparation for Journal of Geophysical Research Hydrochloric acid at the Pasadena ground site during CalNex 2010 and its role as a source of aerosol chloride J.M. Roberts, P.R. Veres, A.K. Cochran, C. Warneke, J. de Gouw, R. Weber, R. Ellis, T. Vandenboer, J. Murphy, B. Koo, G. Yarwood In preparation for Journal of Geophysical Research