In situ ozone production is highly sensitive to volatile organic compounds in Delhi, India

Atmospheric Chemistry and Physics, Vol. 21 (2021)

Keywords
Authors
  • B. S. Nelson
  • Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
  • G. J. Stewart
  • Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
  • W. S. Drysdale
  • Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
  • W. S. Drysdale
  • National Centre for Atmospheric Science, University of York, Heslington, York, YO10 5DD, UK
  • M. J. Newland
  • Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
  • M. J. Newland
  • now at: ICARE-CNRS, 1 C Av. de la Recherche Scientifique, 45071 Orléans CEDEX 2, France
  • A. R. Vaughan
  • Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
  • R. E. Dunmore
  • Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
  • P. M. Edwards
  • Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
  • A. C. Lewis
  • Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
  • A. C. Lewis
  • National Centre for Atmospheric Science, University of York, Heslington, York, YO10 5DD, UK
  • J. F. Hamilton
  • Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
  • W. J. Acton
  • Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YW, UK
  • W. J. Acton
  • now at: School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK
  • C. N. Hewitt
  • Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YW, UK
  • L. R. Crilley
  • School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK
  • L. R. Crilley
  • now at: Department of Chemistry, York University, Toronto, Ontario, M3J 1P3, Canada
  • M. S. Alam
  • School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK
  • Ü. A. Şahin
  • İstanbul Üniversitesi-Cerrahpaşa Mühendislik Fakültesi Üniversite Mahallesi Bağlariçi Caddesi No:7, 34320 Avcılar, İstanbul, Turkey
  • D. C. S. Beddows
  • National Centre for Atmospheric Science, University of York, Heslington, York, YO10 5DD, UK
  • D. C. S. Beddows
  • School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK
  • W. J. Bloss
  • School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK
  • E. Slater
  • School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK
  • L. K. Whalley
  • School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK
  • L. K. Whalley
  • National Centre for Atmospheric Science, University of Leeds, Leeds, LS2 9JT, UK
  • D. E. Heard
  • School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK
  • J. M. Cash
  • UK Centre for Ecology and Hydrology, Penicuik, Midlothian, Edinburgh, EH26 0QB, UK
  • B. Langford
  • UK Centre for Ecology and Hydrology, Penicuik, Midlothian, Edinburgh, EH26 0QB, UK
  • E. Nemitz
  • UK Centre for Ecology and Hydrology, Penicuik, Midlothian, Edinburgh, EH26 0QB, UK
  • R. Sommariva
  • School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK
  • S. Cox
  • Research Software Engineering Team, University of Leicester, Leicester, LE1 7RH, UK
  • Shivani
  • Department of Applied Sciences and Humanities, Indira Gandhi Delhi Technical University for Women, Kashmere Gate, New Delhi, Delhi, 110006, India
  • Shivani
  • now at: Department of Chemistry, Miranda House, University of Delhi, New Delhi, Delhi 110007, India
  • R. Gadi
  • Department of Applied Sciences and Humanities, Indira Gandhi Delhi Technical University for Women, Kashmere Gate, New Delhi, Delhi, 110006, India
  • B. R. Gurjar
  • Indian Institute of Technology, Roorkee, Uttarakhand, 247667, India
  • J. R. Hopkins
  • Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
  • J. R. Hopkins
  • National Centre for Atmospheric Science, University of York, Heslington, York, YO10 5DD, UK
  • A. R. Rickard
  • Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
  • A. R. Rickard
  • National Centre for Atmospheric Science, University of York, Heslington, York, YO10 5DD, UK
  • J. D. Lee
  • Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
  • J. D. Lee
  • National Centre for Atmospheric Science, University of York, Heslington, York, YO10 5DD, UK

Abstract

The Indian megacity of Delhi suffers from some of the poorest air quality in the world. While ambient NO2 and particulate matter (PM) concentrations have received considerable attention in the city, high ground-level ozone (O3) concentrations are an often overlooked component of pollution. O3 can lead to significant ecosystem damage and agricultural crop losses, and adversely affect human health. During October 2018, concentrations of speciated non-methane hydrocarbon volatile organic compounds (C2–C13), oxygenated volatile organic compounds (o-VOCs), NO, NO2, HONO, CO, SO2, O3, and photolysis rates, were continuously measured at an urban site in Old Delhi. These observations were used to constrain a detailed chemical box model utilising the Master Chemical Mechanism v3.3.1. VOCs and NOx (NO + NO2) were varied in the model to test their impact on local O3 production rates, P(O3), which revealed a VOC-limited chemical regime. When only NOx concentrations were reduced, a significant increase in P(O3) was observed; thus, VOC co-reduction approaches must also be considered in pollution abatement strategies. Of the VOCs examined in this work, mean morning P(O3) rates were most sensitive to monoaromatic compounds, followed by monoterpenes and alkenes, where halving their concentrations in the model led to a 15.6 %, 13.1 %, and 12.9 % reduction in P(O3), respectively. P(O3) was not sensitive to direct changes in aerosol surface area but was very sensitive to changes in photolysis rates, which may be influenced by future changes in PM concentrations. VOC and NOx concentrations were divided into emission source sectors, as described by the Emissions Database for Global Atmospheric Research (EDGAR) v5.0 Global Air Pollutant Emissions and EDGAR v4.3.2_VOC_spec inventories, allowing for the impact of individual emission sources on P(O3) to be investigated. Reducing road transport emissions only, a common strategy in air pollution abatement strategies worldwide, was found to increase P(O3), even when the source was removed in its entirety. Effective reduction in P(O3) was achieved by reducing road transport along with emissions from combustion for manufacturing and process emissions. Modelled P(O3) reduced by ∼ 20 ppb h−1 when these combined sources were halved. This study highlights the importance of reducing VOCs in parallel with NOx and PM in future pollution abatement strategies in Delhi.

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