Preprints
https://doi.org/10.5194/acp-2021-69
https://doi.org/10.5194/acp-2021-69

  04 Feb 2021

04 Feb 2021

Review status: this preprint is currently under review for the journal ACP.

Seasonal distribution and drivers of surface fine particulate matterand organic aerosol over the Indo-Gangetic Plain

Caterina Mogno1, Paul I. Palmer1,2, Christoph Knote3, Fei Yao1, and Timothy J. Wallington4 Caterina Mogno et al.
  • 1School of GeoSciences, University of Edinburgh, Edinburgh, UK
  • 2National Centre for Earth Observation, University of Edinburgh, Edinburgh, UK
  • 3Model-Based Environmental Exposure Science (MBEES), Faculty of Medicine, University of Augsburg, Germany
  • 4Research & Advanced Engineering, Ford Motor Company, Dearborn, MI, 48121-2053, USA

Abstract. The Indo-Gangetic Plain (IGP) is home to 6 % of the global population and is responsible for a large fraction of agricultural crop production in Pakistan, India, and Bangladesh. Levels of fine particulate matter (mean diameter < 2.5 microns, PM2.5) across the IGP often exceed human health recommendations, making cities across the IGP among the most polluted in the world. Seasonal changes in the physical environment over the IGP are dominated by the large-scale South Asian monsoon system that dictates the timing of agricultural planting and harvesting. We use the WRF-Chem model to study the seasonal anthropogenic, pyrogenic, and biogenic influences on fine particulate matter and its constituent organic aerosol (OA) over the IGP that straddles Pakistan, India, and Bangladesh during 2017/2018. We find that surface air quality during pre-monsoon (March–May) and monsoon (June–September) seasons is better than during post-monsoon (October–December) and winter (January–February) seasons, but all seasonal mean values of PM2.5 still exceed the recommended levels, so that air pollution is a year-round problem. Anthropogenic emissions influence the magnitude and distribution of PM2.5 and OA throughout the year, especially over urban sites, while pyrogenic emissions result in localized contributions over the central and upper parts of IGP in all non-monsoonal seasons, with the highest impact during post-monsoon seasons that correspond to the post-harvest season in the agricultural calendar. Biogenic emissions play an important role in the magnitude and distribution of PM2.5 and OA during the monsoon season, and shows a substantial contribution to secondary OA (SOA) particularly over the lower IGP. We find that the OA contribution to PM2.5 is significant in all four seasons (17–30 %), with primary OA generally representing the larger fractional contribution. We find that the volatility distribution of SOA is driven mainly by the mean total OA loading and the washout of aerosols and gas-phase aerosol precursors that result in SOA being less volatile during the pre-monsoon and monsoon season than during the post-monsoon and winter seasons.

Caterina Mogno et al.

Status: open (until 01 Apr 2021)

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Caterina Mogno et al.

Caterina Mogno et al.

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Short summary
We use a 3-D atmospheric chemistry model to investigate how seasonal emissions sources and meteorological conditions affect the surface distribution of fine particulate matter (PM2.5) and Organic Aerosols (OA) over the Indo Gangetic-Plain. We find that all seasonal mean values of PM2.5 still exceed safe air quality levels, with human emissions contributing to PM2.5 all year around, open fires during post and pre-monsoon and biogenic emissions during monsoon. OA contributes to PM2.5 up to 30 %.
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