Comparative Assessment of Air Quality Index (AQI) during Pre-Diwali, Diwali and Post-Diwali Periods of 2024-2025 in Delhi, India: A Case Study

Objectives: This case study presents a comparative analysis of AQI trends in some selected sampling sites of Delhi, India, focusing on pollutants CO, SO2, NO2, NH3, O3, PM10, and PM2.5 during the pre-Diwali, Diwali, and post-Diwali periods, highlighting the limited research in this area. Method: The data required for the present investigation were collected from the website of CPCB under Ministry of Environment, Forest and Climate Change, Govt. of India. The periodical variation of the average AQI values is then critically analyzed and the ambient air quality at each sampling sites are categorized. Findings: This case study shows that in October 2024, the AQI reached a highest value of 433 at Anand Vihar on 16/10/2024, dominated by PM10, followed by 392 at Rohini and 388 at Vivek Bihar on 24/10/2024, both governed by PM2.5, which indicates a very poor air quality. In December 2024, the AQI levels intensified, peaking at 485 at Nehru Nagar on 19/12/2024, with PM2.5 dominance across major stations (482 at Wazipur; 481 at Anand Vihar), reflecting a ~12% increase with severe air quality conditions. By January 2025, peak AQI marginally declined to 472 at Vivek Bihar on 10/01/2025, showing a ~3% reduction, though PM2.5-driven pollution persisted within the very poor category. The study thus revealed that AQI value increases due to probable increased emissions of various types of fire crackers along with emissions from increased number of automobiles running as well. Novelty: The study provides a unique assessment of AQI dynamics during the pre-Diwali, Diwali, and post-Diwali periods, focusing on event-specific, multi-pollutant analyses. Unlike typical research, it examines short-duration, high-intensity pollution events linked to festive activities. By evaluating major gaseous pollutants and particulate matter across multiple stations, the research reveals localized pollution variations for event-based air quality management and policy interventions in urban areas. Keywords: Air Quality, AQI, Air pollution, PM10, PM2.5