Seasonal Changes in Air Pollutants and Their Relation to Vegetation Over the Megacity Delhi-NCR

Delhi is one of the most densely populated megacities of the world and is experiencing deteriorating air quality due to rapid industrialization and excessive use of transportation. The limited emission control measures in Delhi have led to worsening air quality problems, which have become a serious threat to human health and the environment. In the present study, we investigate the long-term (2011-2021) interrelationship between air pollutants and vegetation index using satellite datasets. Air pollutant data viz. nitrogen dioxide (NO₂) and sulfur dioxide (SO₂) obtained from NASA’S Aura satellite called Ozone Monitoring Instrument (OMI), and carbon monoxide (CO) and particulate matter 2.5 (PM_2.5) from Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA-2) model. The vegetation indices i.e. Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Oxide (EVI) collected from the Terra Moderate Resolution Imaging Spectroradiometer (MODIS) satellite. The analysis of both data revealed higher concentrations of air pollutants in the summer months when NDVI & EVI was minimum. Further, a higher pollution load was observed in October – January months when NDVI and EVI were lower. Furthermore, we also investigated the spatial patterns of PM_2.5 and other gaseous pollutants (viz. CO, SO_2, and NO₂) and observed that they were less in the vegetated region in comparison to the sparsely vegetated area of Delhi. The present study indicates vegetation could ameliorate various air pollutants, however, it needs to validate with ground observed data.