Airshed-Based Source Apportionment of Delhi Air Pollution Using WRF-Chem and Back Trajectory Analysis
Prakriti (1*), Asfa Siddiqui (1), Hareef Baba Shaeb Kannemadugu (2), Gokul R Kamath (1), Raghavendra Pratap Singh (1), Prakash Chauhan (2)

1) Indian Institute of Remote Sensing, ISRO, Dehradun, Uttarakhand, India
2) National Remote Sensing Centre, Hyderabad, Telangana, India
*prakriti3896[at]gmail.com

Abstract

The intensification of human activities has significantly deteriorated air quality in densely populated urban centers such as Delhi, leading to severe health and urban climate challenges. While ongoing mitigation efforts aim to reduce pollutant concentrations, addressing the sources of pollution remains critical for achieving sustainable improvements. This study investigates the geographical origins and sectoral contributions of CO, NO2 and PM2.5 in Delhi. Pollutant concentration data and gridded meteorological data were utilized to identify pollution transport pathways and source regions, the study applied back trajectory analysis and the Concentration Weighted Trajectory method at 100 meters above ground level for winter, pre-monsoon, monsoon, post-monsoon season of year 2022. Airshed is delineated using back trajectory frequency analysis which extends across the Indo-Gangetic Plain, from Uttar Pradesh in India to Lahore in Pakistan. Using WRF-Chem model and emission inventories for 2022, pollutant contributions from six major sectors, namely agriculture, energy, industry, residential, transportation, and waste were estimated for 1st November 2022. Outputs were downscaled to a spatial resolution of 5 km for the regional airshed and 1 km for the local airshed. Sectoral contributions were found to be significantly higher than those estimated in earlier studies that were limited by administrative boundaries. The results show that dominant pollution sources vary by scale: for regional airshed, residential emissions contribute most to CO (55.9%), while in local airshed, transportation is the largest contributor (54.2%). Stubble burning contributed 18.01% to PM2.5, 1.43% to NO2, and 3.6% to CO in the regional airshed, higher than in the local airshed. These findings underscore the importance of adopting a regional airshed-based approach to air pollution management that considers pollutant sources beyond the administrative boundaries of Delhi.

Keywords: Airshed- Source contribution- Stubble burning- Back trajectory- WRF-Chem

Topic: Topic D: Geospatial Data Integration