02 Sep 2020

02 Sep 2020

Review status: a revised version of this preprint is currently under review for the journal ACP.

PM1 composition and source apportionment at two sites in Delhi, India across multiple seasons

Ernesto Reyes-Villegas1, Upasana Panda2, Eoghan Darbyshire1,a, James M. Cash3,4, Rutambhara Joshi1, Ben Langford3, Chiara F. Di Marco3, Neil Mullinger3, W. Joe F. Acton5, Will Drysdale6, Eiko Nemitz3, Michael Flynn1, Aristeidis Voliotis1, Gordon McFiggans1, Hugh Coe1, James Lee6, C. Nicholas Hewitt5, Mathew R. Heal4, Sachin S. Gunthe2, Shivani7, Ranu Gadi7, Siddhartha Singh8, Vijay Soni8, and James D. Allan1,9 Ernesto Reyes-Villegas et al.
  • 1Department of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK
  • 2Indian Institute of Technology Madras, Chennai, 600 036, India
  • 3UK Centre for Ecology & Hydrology, EdinburghResearch Station, Penicuik, EH26 0QB, UK
  • 4School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, Edinburgh, UK
  • 5Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, UK
  • 6Wolfson Atmospheric Chemistry Laboratory, University of York, York, YO10 5DD, UK
  • 7Department of Applied Sciences and Humanities, Indira Gandhi Delhi Technical University for Women, Delhi, 110006, India
  • 8India Meteorology Department, New Delhi, 110003, India
  • 9National Centre for Atmospheric Science, University of Manchester, Manchester, M13 9PL, UK
  • anow at: The conflict and Environment Observatory, Hebden Bridge, HX7 5HZ, UK

Abstract. Air pollution in urban environments has been shown to have a negative impact on air quality and human health, particularly in megacities. Over recent decades, Delhi, India has suffered high atmospheric pollution, with significant particulate matter (PM) concentrations as result of anthropogenic activities. Organic aerosols (OA) are composed of thousands of different chemical species and are one of the main constituents of submicron particles. However, quantitative knowledge of OA composition, their sources and processes in urban environments is still limited. This is important particularly in India, as Delhi is a massive, inhomogeneous conurbation, which we would expect that the apportionment and concentrations will vary depending on where in Delhi the measurements/source apportionment is performed, indicating the need of multi-site measurements. This study presents the first multisite analysis carried out in India over different seasons, with a focus on identifying OA sources. The measurements were taken during 2018 at two sites in Delhi, India. One site was located at the India Meteorological Department, New Delhi (ND). The other site was located at the Indira Gandhi Delhi Technical University for Women, Old Delhi (OD). Non-refractory submicron aerosol (NR-PM1) concentrations (ammonium, nitrate, sulphate, chloride and organic aerosols) of four aerosol mass spectrometers were analysed. Collocated measurements of VOC, black carbon, NOx and CO were performed. Positive matrix factorization (PMF) analysis was performed to separate the organic fraction, identifying a number of conventional factors: hydrocarbon-like OA (HOA) related to traffic emissions, biomass burning OA (BBOA), cooking OA (COA) and secondary OA (SOA).

A composition-based estimate of PM1 is defined by combining BC and NR-PM1 (C-PM1 = BC + NR-PM1). No significant difference was observed on C-PM1 concentrations between sites; OD (142 ± 117 µg m−3) compared to ND (123 ± 71 µg m−3), from post-monsoon measurements. A wider variability was observed between seasons, where pre-monsoon and monsoon showed C-PM1 concentrations lower than 60 µg m−3. A seasonal variation in C-PM1 composition was observed; SO42− showed a high contribution over pre-monsoon and monsoon seasons while NO3 and Cl had a higher contribution in winter and post-monsoon. The main primary aerosol source was from traffic, which is consistent with the PMF analysis and aethalometer model analysis. Thus, in order to reduce PM1 concentrations in Delhi through local emission controls traffic emissions control offers the greatest opportunity. PMF-AMS mass spectra will help to improve future aerosol source apportionment studies. The information generated in this study increases our understanding of PM1 composition and OA sources in Delhi, India. Furthermore, the scientific findings provide significant information to strengthen legislation that aims to improve air quality in India.

Ernesto Reyes-Villegas et al.

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Ernesto Reyes-Villegas et al.

Ernesto Reyes-Villegas et al.


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Short summary
The work presented in this manuscript shows the first multisite online measurements of PM1 in Delhi, India. It covers measurements over different seasons in Old and New Delhi during 2018. OA source apportionment was performed using PMF. Traffic showed to be the main primary aerosol source for both OA and BC, as seen with the PMF analysis and aethalometer model analysis. This indicates that in Delhi control of primary traffic exhaust emissions would make a significant reduction to air pollution.