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Environ Sci Technol Lett

Title:		Extreme Concentrations of Nitric Oxide Control Daytime Oxidation and Quench Nocturnal Oxidation Chemistry in Delhi during Highly Polluted Episodes
Author(s):		Nelson BS; Bryant DJ; Alam MS; Sommariva R; Bloss WJ; Newland MJ; Drysdale WS; Vaughan AR; Acton WJF; Hewitt CN; Crilley LR; Swift SJ; Edwards PM; Lewis AC; Langford B; Nemitz E; Shivani; Gadi R; Gurjar BR; Heard DE; Whalley LK; Sahin UA; Beddows DCS; Hopkins JR; Lee JD; Rickard AR; Hamilton JF;
Address:		"Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, Heslington, York YO10 5DD, U.K. School of Biosciences, University of Nottingham, Sutton Bonington, Leicestershire LE12 5RD, U.K. School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham B15 2TT, U.K. National Centre for Atmospheric Science, University of York, Heslington, York YO10 5DD, U.K. Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YW, U.K. UK Centre for Ecology and Hydrology, Penicuik, Midlothian, Edinburgh EH26 0QB, U.K. Department of Applied Sciences and Humanities, Indira Gandhi Delhi Technical University for Women, Delhi 110006, India. Indian Institute of Technology, Roorkee, Uttarakhand 247667, India. School of Chemistry, University of Leeds, Leeds LS2 9JT, U.K. National Centre for Atmospheric Science, University of Leeds, Leeds LS2 9JT, U.K. Istanbul University-Cerrahpasa, Engineering Faculty, Environmental Engineering Department, Avcilar, 34320 Istanbul, Turkey. National Centre for Atmospheric Science, University of Birmingham, Birmingham B15 2TT, U.K"
Journal Title:		Environ Sci Technol Lett
Year:		2023
Volume:		20230503
Issue:		6
Page Number:		520 - 527
DOI:		10.1021/acs.estlett.3c00171
ISSN/ISBN:		2328-8930 (Print) 2328-8930 (Electronic)
Abstract:		"Delhi, India, suffers from periods of very poor air quality, but little is known about the chemical production of secondary pollutants in this highly polluted environment. During the postmonsoon period in 2018, extremely high nighttime concentrations of NO(x) (NO and NO(2)) and volatile organic compounds (VOCs) were observed, with median NO(x) mixing ratios of approximately 200 ppbV (maximum of approximately 700 ppbV). A detailed chemical box model constrained to a comprehensive suite of speciated VOC and NO(x) measurements revealed very low nighttime concentrations of oxidants, NO(3), O(3), and OH, driven by high nighttime NO concentrations. This results in an atypical NO(3) diel profile, not previously reported in other highly polluted urban environments, significantly perturbing nighttime radical oxidation chemistry. Low concentrations of oxidants and high nocturnal primary emissions coupled with a shallow boundary layer led to enhanced early morning photo-oxidation chemistry. This results in a temporal shift in peak O(3) concentrations when compared to the premonsoon period (12:00 and 15:00 local time, respectively). This shift will likely have important implications on local air quality, and effective urban air quality management should consider the impacts of nighttime emission sources during the postmonsoon period"
Keywords:
Notes:		"PubMed-not-MEDLINENelson, Beth S Bryant, Daniel J Alam, Mohammed S Sommariva, Roberto Bloss, William J Newland, Mike J Drysdale, Will S Vaughan, Adam R Acton, W Joe F Hewitt, C Nicholas Crilley, Leigh R Swift, Stefan J Edwards, Pete M Lewis, Alastair C Langford, Ben Nemitz, Eiko Shivani Gadi, Ranu Gurjar, Bhola R Heard, Dwayne E Whalley, Lisa K Sahin, Ulku A Beddows, David C S Hopkins, James R Lee, James D Rickard, Andrew R Hamilton, Jacqueline F eng 2023/06/19 Environ Sci Technol Lett. 2023 May 3; 10(6):520-527. doi: 10.1021/acs.estlett.3c00171. eCollection 2023 Jun 13"