Dynamic changes in the characteristics of fine particles and their oxidative potential in the city of Taj (Agra, India): the untold story of fireworks display

The dithiothreitol (DTT) assay was used to investigate the oxidative potential (OP) of atmospheric fine particles (PM_2.5) during fireworks (Diwali) at Agra, India. The 12-h mean PM_2.5 was reported to be 263 ±151 μg m⁻³ during the study period. Increased levels of gaseous pollutants (NOx, SO₂, CO, and O₃) and metals Ba, Pb, Cu, Fe, Mg, K, Al, and Mn were also observed during fireworks. The results showed that the typical diurnal pattern of trace gases was observed, except their overall concentrations remained elevated during peak hours of the fireworks activity. The highest value of OP of PM was detected on the next morning of Diwali, with a volume-based DTT value (OPv) of 1.4 nmol min⁻¹ m⁻³ and a mass-based DTT value (OPm) of 11.8 pmol min⁻¹ μg⁻¹, implying higher PM-related DTT activity due to fireworks. A positive association was found between redox-active metals like Cr, Cu, Ni, and V and DTT activity which could be due to the ability of these metals to catalyze reactive oxygen species (ROS) generation in ambient air. Ba and Se concentrations in the particulate matter, which are key components of firecrackers, were likewise highly linked to DTT activity. During the daytime, ozone levels were strongly correlated (r² = 0.9) with OPv activity; this may be due to photochemical processes which may lead to the formation of tropospheric O₃. Elements C, O, Al, Si, S, K, and Ba were found to be the most prevalent in elemental mappings, which suggests that fireworks may have contributed to their abundance. A comparison of the daily OPv activity and hazard index (HI) suggests that the HI may be a poor metric for measuring the health impacts of PM exposure on human health.