## 3 Results and Discussion
### Proposed Growth Mechanism
This finding is supported by the same line of logic, considering that the origin of the HAS particulates was an explosive reaction intended to disperse combustible transition metals to create the glow effect that fireworks of this style are famous for [41]. Considering these two vastly different genesis processes for the particulates, the observed discrepancy in average particulate sizing between the two sample groups is a reasonable expectation and finding. The detected presence of particulates significantly varying in size is consistent with the previous literature regarding firework smoke including the article regarding Diwali Celebrations in Kolkata by [PERSON] [22]. As shown in the Supplemental Figure S1, there was an increase in the concentrations of both PM\({}_{10}\) and PM\({}_{2.5}\) around the time of the fireworks display. The data in the supplementary plots were measured optically using a Teledyne (Thousand Oaks, CA, USA) Model T640 PM mass monitor. For example, at 21:00 (9:00 PM) on 4 July, the concentration of PM\({}_{2.5}\) raised to 25 \(\upmu\) m\({}^{-3}\), up from around 8 \(\upmu\)g m\({}^{-3}\) at 18:00 (6:00 PM), with an annual average of 10.5 \(\upmu\)g m\({}^{-3}\). However, for PM\({}_{10}\), several peaks were observed at different times. Specifically, at 21:00 (9:00 PM) on 4 July, the concentration of PM\({}_{10}\) increased to 34 \(\upmu\)g m\({}^{-3}\), up from about 15 \(\upmu\)g m\({}^{-3}\) (Figure S1). The annual average for PM\({}_{10}\) is 26 \(\upmu\)g m\({}^{-3}\). Particles larger than 10 \(\upmu\)m (shapeless) are typically fugitive dust carried by winds from roadways, fields, and construction sites, and they correlate well with the morphology of particulates in the control samples. Analysis of control samples revealed airborne particulate matter on the PM\({}_{10}\) scale but not the PM\({}_{2.5}\) scale, while many particles captured during the fireworks display were on the PM\({}_{2.5}\) scale, which is consistent with studies from [PERSON] and [PERSON] [42,43]. The measured concentrations for each type of particulate matter are consistent with the observed patterns in particulate size from the day of the festival, supporting the conclusion that fireworks displays specifically increase the concentration of PM\({}_{2.5}\) in the surrounding environment. Additionally, most of the particles collected from high-altitude sampling of the fireworks have a spheroidal shape and unique chemical composition. It should be noted, however, that the PM data presented in the plot were collected approximately 10 miles away in the same metropolitan area as the firework display rather than its immediate vicinity. Previous studies of particulate matter dispersion have determined that for low wind speeds (at or below 4 km per hour), very limited particulate dispersion occurs, and pollution is likely to remain localized [44,45]. As seen in Figure S2, the wind speed was under 1 m per second (3.6 km h\({}^{-1}\)) at the time of sampling, meaning extended dispersion of particulate matter was unlikely to occur. As a result, the PM concentrations near the firework display were likely much higher than the reported values due to the limited wind speeds.