Articles | Volume 25, issue 22
https://doi.org/10.5194/acp-25-16009-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/acp-25-16009-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
18 Nov 2025
Research article |
| 18 Nov 2025
| 18 Nov 2025
Urban ozone trends in Europe and the USA (2000–2021)
Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
National Centre for Atmospheric Science, University of York, York, UK
Will S. Drysdale
CORRESPONDING AUTHOR
Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
National Centre for Atmospheric Science, University of York, York, UK
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Beth S. Nelson, Gareth J. Stewart, Will S. Drysdale, Mike J. Newland, Adam R. Vaughan, Rachel E. Dunmore, Pete M. Edwards, Alastair C. Lewis, Jacqueline F. Hamilton, W. Joe Acton, C. Nicholas Hewitt, Leigh R. Crilley, Mohammed S. Alam, Ülkü A. Şahin, David C. S. Beddows, William J. Bloss, Eloise Slater, Lisa K. Whalley, Dwayne E. Heard, James M. Cash, Ben Langford, Eiko Nemitz, Roberto Sommariva, Sam Cox, Shivani, Ranu Gadi, Bhola R. Gurjar, James R. Hopkins, Andrew R. Rickard, and James D. Lee
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Short summary
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Ozone production at an urban site in Delhi is sensitive to volatile organic compound (VOC) concentrations, particularly those of the aromatic, monoterpene, and alkene VOC classes. The change in ozone production by varying atmospheric pollutants according to their sources, as defined in an emissions inventory, is investigated. The study suggests that reducing road transport emissions alone does not reduce reactive VOCs in the atmosphere enough to perturb an increase in ozone production.
Ernesto Reyes-Villegas, Upasana Panda, Eoghan Darbyshire, James M. Cash, Rutambhara Joshi, Ben Langford, Chiara F. Di Marco, Neil J. Mullinger, Mohammed S. Alam, Leigh R. Crilley, Daniel J. Rooney, W. Joe F. Acton, Will Drysdale, Eiko Nemitz, Michael Flynn, Aristeidis Voliotis, Gordon McFiggans, Hugh Coe, James Lee, C. Nicholas Hewitt, Mathew R. Heal, Sachin S. Gunthe, Tuhin K. Mandal, Bhola R. Gurjar, Shivani, Ranu Gadi, Siddhartha Singh, Vijay Soni, and James D. Allan
Atmos. Chem. Phys., 21, 11655–11667, https://doi.org/10.5194/acp-21-11655-2021, https://doi.org/10.5194/acp-21-11655-2021, 2021
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This paper shows the first multisite online measurements of PM1 in Delhi, India, with measurements over different seasons in Old Delhi and New Delhi in 2018. Organic aerosol (OA) source apportionment was performed using positive matrix factorisation (PMF). Traffic was the main primary aerosol source for both OAs and black carbon, seen with PMF and Aethalometer model analysis, indicating that control of primary traffic exhaust emissions would make a significant reduction to Delhi air pollution.
James M. Cash, Ben Langford, Chiara Di Marco, Neil J. Mullinger, James Allan, Ernesto Reyes-Villegas, Ruthambara Joshi, Mathew R. Heal, W. Joe F. Acton, C. Nicholas Hewitt, Pawel K. Misztal, Will Drysdale, Tuhin K. Mandal, Shivani, Ranu Gadi, Bhola Ram Gurjar, and Eiko Nemitz
Atmos. Chem. Phys., 21, 10133–10158, https://doi.org/10.5194/acp-21-10133-2021, https://doi.org/10.5194/acp-21-10133-2021, 2021
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We present the first real-time composition of submicron particulate matter (PM1) in Old Delhi using high-resolution aerosol mass spectrometry. Seasonal analysis shows peak concentrations occur during the post-monsoon, and novel-tracers reveal the largest sources are a combination of local open and regional crop residue burning. Strong links between increased chloride aerosol concentrations and burning sources of PM1 suggest burning sources are responsible for the post-monsoon chloride peak.
Simone T. Andersen, Lucy J. Carpenter, Beth S. Nelson, Luis Neves, Katie A. Read, Chris Reed, Martyn Ward, Matthew J. Rowlinson, and James D. Lee
Atmos. Meas. Tech., 14, 3071–3085, https://doi.org/10.5194/amt-14-3071-2021, https://doi.org/10.5194/amt-14-3071-2021, 2021
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NOx has been measured in remote marine air via chemiluminescence detection using two different methods for NO2 to NO photolytic conversion: (a) internal diodes and a reaction chamber made of Teflon-like barium-doped material, which causes a NO2 artefact, and (b) external diodes and a quartz photolysis cell. Once corrections are made for the artefact of (a), the two converters are shown to give comparable NO2 mixing ratios, giving confidence in the quantitative measurement of NOx at low levels.
Stuart K. Grange, James D. Lee, Will S. Drysdale, Alastair C. Lewis, Christoph Hueglin, Lukas Emmenegger, and David C. Carslaw
Atmos. Chem. Phys., 21, 4169–4185, https://doi.org/10.5194/acp-21-4169-2021, https://doi.org/10.5194/acp-21-4169-2021, 2021
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The changes in mobility across Europe due to the COVID-19 lockdowns had consequences for air quality. We compare what was experienced to estimates of "what would have been" without the lockdowns. Nitrogen dioxide (NO2), an important vehicle-sourced pollutant, decreased by a third. However, ozone (O3) increased in response to lower NO2. Because NO2 is decreasing over time, increases in O3 can be expected in European urban areas and will require management to avoid future negative outcomes.
Gareth J. Stewart, Beth S. Nelson, W. Joe F. Acton, Adam R. Vaughan, Naomi J. Farren, James R. Hopkins, Martyn W. Ward, Stefan J. Swift, Rahul Arya, Arnab Mondal, Ritu Jangirh, Sakshi Ahlawat, Lokesh Yadav, Sudhir K. Sharma, Siti S. M. Yunus, C. Nicholas Hewitt, Eiko Nemitz, Neil Mullinger, Ranu Gadi, Lokesh K. Sahu, Nidhi Tripathi, Andrew R. Rickard, James D. Lee, Tuhin K. Mandal, and Jacqueline F. Hamilton
Atmos. Chem. Phys., 21, 2407–2426, https://doi.org/10.5194/acp-21-2407-2021, https://doi.org/10.5194/acp-21-2407-2021, 2021
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Biomass burning releases many lower-molecular-weight organic species which are difficult to analyse but important for the formation of organic aerosol. This study examined a new high-resolution technique to better characterise these difficult-to-analyse organic components. Some burning sources analysed in this study, such as cow dung cake and municipal solid waste, released extremely complex mixtures containing many thousands of different lower-volatility organic compounds.
Gareth J. Stewart, W. Joe F. Acton, Beth S. Nelson, Adam R. Vaughan, James R. Hopkins, Rahul Arya, Arnab Mondal, Ritu Jangirh, Sakshi Ahlawat, Lokesh Yadav, Sudhir K. Sharma, Rachel E. Dunmore, Siti S. M. Yunus, C. Nicholas Hewitt, Eiko Nemitz, Neil Mullinger, Ranu Gadi, Lokesh K. Sahu, Nidhi Tripathi, Andrew R. Rickard, James D. Lee, Tuhin K. Mandal, and Jacqueline F. Hamilton
Atmos. Chem. Phys., 21, 2383–2406, https://doi.org/10.5194/acp-21-2383-2021, https://doi.org/10.5194/acp-21-2383-2021, 2021
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Mike J. Newland, Daniel J. Bryant, Rachel E. Dunmore, Thomas J. Bannan, W. Joe F. Acton, Ben Langford, James R. Hopkins, Freya A. Squires, William Dixon, William S. Drysdale, Peter D. Ivatt, Mathew J. Evans, Peter M. Edwards, Lisa K. Whalley, Dwayne E. Heard, Eloise J. Slater, Robert Woodward-Massey, Chunxiang Ye, Archit Mehra, Stephen D. Worrall, Asan Bacak, Hugh Coe, Carl J. Percival, C. Nicholas Hewitt, James D. Lee, Tianqu Cui, Jason D. Surratt, Xinming Wang, Alastair C. Lewis, Andrew R. Rickard, and Jacqueline F. Hamilton
Atmos. Chem. Phys., 21, 1613–1625, https://doi.org/10.5194/acp-21-1613-2021, https://doi.org/10.5194/acp-21-1613-2021, 2021
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We report the formation of secondary pollutants in the urban megacity of Beijing that are typically associated with remote regions such as rainforests. This is caused by extremely low levels of nitric oxide (NO), typically expected to be high in urban areas, observed in the afternoon. This work has significant implications for how we understand atmospheric chemistry in the urban environment and thus for how to implement effective policies to improve urban air quality.
James D. Lee, Will S. Drysdale, Doug P. Finch, Shona E. Wilde, and Paul I. Palmer
Atmos. Chem. Phys., 20, 15743–15759, https://doi.org/10.5194/acp-20-15743-2020, https://doi.org/10.5194/acp-20-15743-2020, 2020
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Efforts to prevent the COVID-19 virus spreading across the globe have included travel restrictions and the closure of workplaces, leading to a significant drop in emissions of primary air pollutants. This provides for a unique opportunity to examine how air pollutant concentrations respond to an abrupt and prolonged reduction. We examine how NO2 and O3 have been affected at several urban measurement sites in the UK. We look at the change in NO2 compared to previous years and the effect on O3.
W. Joe F. Acton, Zhonghui Huang, Brian Davison, Will S. Drysdale, Pingqing Fu, Michael Hollaway, Ben Langford, James Lee, Yanhui Liu, Stefan Metzger, Neil Mullinger, Eiko Nemitz, Claire E. Reeves, Freya A. Squires, Adam R. Vaughan, Xinming Wang, Zhaoyi Wang, Oliver Wild, Qiang Zhang, Yanli Zhang, and C. Nicholas Hewitt
Atmos. Chem. Phys., 20, 15101–15125, https://doi.org/10.5194/acp-20-15101-2020, https://doi.org/10.5194/acp-20-15101-2020, 2020
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Air quality in Beijing is of concern to both policy makers and the general public. In order to address concerns about air quality it is vital that the sources of atmospheric pollutants are understood. This work presents the first top-down measurement of volatile organic compound (VOC) emissions in Beijing. These measurements are used to evaluate the emissions inventory and assess the impact of VOC emission from the city centre on atmospheric chemistry.
Atallah Elzein, Gareth J. Stewart, Stefan J. Swift, Beth S. Nelson, Leigh R. Crilley, Mohammed S. Alam, Ernesto Reyes-Villegas, Ranu Gadi, Roy M. Harrison, Jacqueline F. Hamilton, and Alastair C. Lewis
Atmos. Chem. Phys., 20, 14303–14319, https://doi.org/10.5194/acp-20-14303-2020, https://doi.org/10.5194/acp-20-14303-2020, 2020
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Short summary
We collected high-frequency air particle samples (PM2.5) in Beijing (China) and Delhi (India) and measured the concentration of PAHs in daytime and night-time. PAHs were higher in Delhi than in Beijing, and the five-ring PAHs contribute the most to the total PAH concentration. We compared the emission sources and identified the major sectors that could be subject to mitigation measures. The adverse health effects from inhalation exposure to PAHs in Delhi are 2.2 times higher than in Beijing.
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Short summary
Urban O3 trends across Europe and the USA were explored between 2000–2021. Most warm season trends in high O3 in Europe were shown to be decreasing, though low values in both warm and cold seasons were increasing. Trends in the USA were similar, but showed less increasing trends low O3 in the warm season. Sites with similar trends were grouped, more different were seen in the USA, and identified ones where trends in high O3 values had started to increase later in the period.
Urban O3 trends across Europe and the USA were explored between 2000–2021. Most warm season...
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