Morphology, chemical composition, and source characteristics of fine particulate pollutants emitted during firecracker burning events associated with Diwali festival in India

Abstract

This study investigates the temporal variation and physicochemical characteristics of PM_2.5 during the Diwali festival in a semi-urban region of Tamil Nadu, India. PM_2.5 samples, collected using a fine particulate sampler, were analyzed for morphology and composition. SEM identified diverse particle shapes, including spherical, hexagonal, and fractal structures, indicative of carbonaceous particles, earth crust materials, and feldspar group minerals. EDX analysis detected 18 elements, with carbon (C), nitrogen (N), and oxygen (O) as major constituents. FTIR analysis revealed ammonium ions (1420–1432 cm⁻¹) from ammonium perchlorate, sulfate compounds (612–1148 cm⁻¹) linked to firecracker fuels, and zinc oxide (550–557 cm⁻¹) from spark-producing agents. Carbonyl groups (1424–1707 cm⁻¹) highlighted emissions from fireworks and biomass burning. HYSPLIT back trajectory analysis traced pollutant-laden air masses to north-central and eastern India, traversing the Bay of Bengal. Principal component analysis (PCA) identified five key PM_2.5 sources: firecracker emissions, soil disturbances, sea salt spray, biomass burning, and industrial activities. PM_2.5 concentrations exceeded WHO and NAAQS limits, ranging from 25.05 to 137.19 µg/m³ in 2022 and 62.50–807.47 µg/m³ in 2023. During the festival period, AQI levels escalated to “Poor” in 2022 and “Severe” in 2023, while remaining “Satisfactory” before and after the festival. Health risk assessments showed minimal non-cancerous effects; however, lifetime cancer risks associated with Chromium exceeded safe thresholds, posing a significant health risk. This study highlights the substantial air quality impacts of cultural celebrations, offering critical data for source apportionment and mitigation strategies during episodic pollution events.