Mriganka Sekhar Biswas1,2, Anoop S. Mahajan This email address is being protected from spambots. You need JavaScript enabled to view it.1

1 Indian Institute of Tropical Meteorology, Ministry of Earth Sciences, Pune, India
2 Savitribai Phule Pune University, Pune, India

Received: August 17, 2020
Revised: December 14, 2020
Accepted: January 22, 2021

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.

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Biswas, M.S., Mahajan, A.S. (2021). Year-long Concurrent MAX-DOAS Observations of Nitrogen Dioxide and Formaldehyde at Pune: Understanding Diurnal and Seasonal Variation Drivers. Aerosol Air Qual. Res. 21, 200524.


  • Photochemistry driven diurnal profile was observed for NO2 and HCHO over Pune city, India.
  • Winter/monsoon showed the highest/lowest NO2 and HCHO average mixing ratios, respectively.
  • Fire events outside the city led to an increase in the NO2 and HCHO over Pune city.
  • Emissions from nearby industrial areas contributed to the NO2 and HCHO load within the city.


Year-long observations of nitrogen dioxide (NO2) and formaldehyde (HCHO) using the Multi-Axis Differential Absorption Spectroscopy (MAX-DOAS) technique are reported from Pune City, India. We studied the diurnal and seasonal variations, effect of biomass burning and the weekend effect on both species. NO2 diurnal profiles displayed a traffic induced peak at ~09:00 hrs. HCHO also showed a morning peak ~10:00 hrs due to production from oxidation of VOCs in the presence of solar radiation. Both NO2 and HCHO show the highest average concentrations during the winter (October, November, December, January and February—ONDJF), with mean mixing ratios of 2.0 ± 1.4 ppb and 3.0 ± 1.4 ppb, respectively. These observations suggest that a lower boundary layer (BL) height during ONDJF leads to higher concentrations of trace gases. During June, July, August, and September (JJAS), both trace gases show a minimum in their concentrations, with average mixing ratios for NO2 and HCHO being 0.9 ± 0.6 ppb and 1.1 ± 0.7 ppb, most likely due to removal by wet deposition. There was no significant difference in both the trace gases on weekdays and weekends. Using back-trajectory analysis, we conclude that air parcels coming from regions of biomass burning increased the concentrations in Pune. Emissions from nearby industrial areas of Bhosari and Pimpri-Chinchwad increased NO2 concentrations in Pune city. Finally, we compared the observations with previous reports over India and found that both HCHO and NO2 concentrations are lower in Pune compared to the other large cities in India.

Keywords: Formaldehyde, Nitrogen dioxide, Pune city, Seasonal variation, Diurnal variation, Biomass burning

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