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

Overview

This case study examines Air Quality Index (AQI) fluctuations across selected sampling sites in Delhi during pre-Diwali, Diwali, and post-Diwali periods spanning October 2024 through January 2025. The analysis tracks seven key pollutants (CO, SO2, NO2, NH3, O3, PM10, PM2.5) to establish temporal and spatial patterns in ambient air quality, with particular emphasis on event-driven pollution dynamics associated with festive activities and seasonal meteorological conditions.

Methods and approach

Air quality data were obtained from the Central Pollution Control Board (CPCB) monitoring network under the Ministry of Environment, Forest and Climate Change. The investigation analyzed periodical variations in average AQI values across multiple sampling stations, categorizing ambient air quality conditions according to established AQI classification frameworks. Temporal comparisons were conducted across three distinct periods aligned with Diwali observance, with pollutant-specific contributions to overall AQI calculated for each monitoring site.

Results

Peak AQI values demonstrated progressive intensification from October (433 at Anand Vihar, 16 October 2024, PM10-dominated) through December 2024 (485 at Nehru Nagar, 19 December 2024, PM2.5-dominated), representing approximately 12% increase in pollution levels. Secondary peaks were recorded at Wazipur (482) and Anand Vihar (481) during December, with PM2.5 as the dominant pollutant across major stations. January 2025 observations showed marginal AQI reduction (472 at Vivek Bihar, 10 January 2025), representing approximately 3% decline, though pollution remained within very poor air quality category. Particulate matter (PM2.5 and PM10) emerged as the primary contributor to degraded air quality across the monitoring period, with localized variations observed between sampling sites.

Implications

The findings document pronounced deterioration in Delhi's ambient air quality during the festive period, with measured AQI values consistently exceeding 400 (very poor category). The temporal pattern suggests contributions from multiple anthropogenic sources including firecracker emissions coincident with Diwali observance and elevated vehicular traffic emissions. The persistence of PM2.5-driven pollution into January indicates extended air quality impacts beyond the immediate festive period, potentially reflecting atmospheric accumulation under unfavorable meteorological conditions typical of winter months in the Indo-Gangetic Plain. These results establish baseline documentation of event-specific air quality dynamics in an urban context.