Final published version
Licence: CC BY: Creative Commons Attribution 4.0 International License
Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Extreme Concentrations of Nitric Oxide Control Daytime Oxidation and Quench Nocturnal Oxidation Chemistry in Delhi during Highly Polluted Episodes
AU - Nelson, Beth S.
AU - Bryant, Daniel J.
AU - Alam, Mohammed S.
AU - Sommariva, Roberto
AU - Bloss, William J.
AU - Newland, Mike J.
AU - Drysdale, Will S.
AU - Vaughan, Adam R.
AU - Acton, W. Joe F.
AU - Hewitt, C. Nicholas
AU - Crilley, Leigh R.
AU - Swift, Stefan J.
AU - Edwards, Pete M.
AU - Lewis, Alastair C.
AU - Langford, Ben
AU - Nemitz, Eiko
AU - Shivani, null
AU - Gadi, Ranu
AU - Gurjar, Bhola R.
AU - Heard, Dwayne E.
AU - Whalley, Lisa K.
AU - Şahin, Ülkü A.
AU - Beddows, David C. S.
AU - Hopkins, James R.
AU - Lee, James D.
AU - Rickard, Andrew R.
AU - Hamilton, Jacqueline F.
PY - 2023/6/13
Y1 - 2023/6/13
N2 - 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 NOx (NO and NO2) and volatile organic compounds (VOCs) were observed, with median NOx mixing ratios of ∼200 ppbV (maximum of ∼700 ppbV). A detailed chemical box model constrained to a comprehensive suite of speciated VOC and NOx measurements revealed very low nighttime concentrations of oxidants, NO3, O3, and OH, driven by high nighttime NO concentrations. This results in an atypical NO3 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 O3 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.
AB - 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 NOx (NO and NO2) and volatile organic compounds (VOCs) were observed, with median NOx mixing ratios of ∼200 ppbV (maximum of ∼700 ppbV). A detailed chemical box model constrained to a comprehensive suite of speciated VOC and NOx measurements revealed very low nighttime concentrations of oxidants, NO3, O3, and OH, driven by high nighttime NO concentrations. This results in an atypical NO3 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 O3 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.
KW - Health, Toxicology and Mutagenesis
KW - Pollution
KW - Waste Management and Disposal
KW - Water Science and Technology
KW - Ecology
KW - Environmental Chemistry
U2 - 10.1021/acs.estlett.3c00171
DO - 10.1021/acs.estlett.3c00171
M3 - Journal article
VL - 10
SP - 520
EP - 527
JO - Environmental Science and Technology Letters
JF - Environmental Science and Technology Letters
SN - 2328-8930
IS - 6
ER -