## 3 Results and Discussion
### Elemental Analysis
#### 3.3.2 Low-Altitude Samples  
Through the above EDX maps, it is observed that the particulates sampled at high altitudes appear much less chemically diverse than the low-altitude samples. Low-altitude samples were also observed to have a significant amount of potassium within the particulates, which is consistent with these particles coming from the gunpowder used in lift charges for smaller mortar-type fireworks or the use of potassium as oxidizers in sparkler fireworks [33].  
Figure 7(a4,c4) give EDX maps for potassium in these samples, and it is theorized that considering the closer proximity to the origin, these samples were able to capture these potassium particles much more effectively, as potassium is commonly utilized in the propellant for larger fireworks, as well as a fuel source for smaller handheld firework options. Figure 7(a1-a5) indicate that the mapped particulates are very well mixed chemically, with aluminum, oxygen, silicon, and potassium being the materials making up the particulates. This suggests that the low-altitude samples contain a mixture of elements used in various aspects of these fireworks, specifically elements tied to smaller sparklers or fountains, which is consistent with observed differences between higher and lower-altitude fireworks on the day of the celebration. The EDX spectrum seen in Figure 7(a6) has strong peaks for the elements included in the elemental maps, especially oxygen and silicon, indicating much of the imaged particulate can be silicon dioxide combined with other compounds in the particulate. The EDX maps also feature a strong correlation between sodium and chlorine in Figure 7(b2,b3), which suggests that sodium chloride was used in some of the lower fireworks that were used. This conclusion is supported by the EDX spectrum seen in Figure 7(b4), where both sodium and chlorine are the largest peaks aside from the background peaks of carbon and oxygen.  
This is also supported by the known literature, as certain sodium salts including sodium chloride are often used to create yellow effects, as would commonly be seen in fountain-style fireworks [34]. Across all samples, the presence of eight different metals are confirmed that there are either components in the fireworks' propellant or a metal used for its light properties as a part of the display. These detected elements were potassium, sodium, barium, calcium, magnesium, iron, strontium, and titanium. Each of these detected metals has a role in creating certain colors or effects in firework displays and, as a result, all are expected to be found within the collected samples [34]. Figure 7(c1-c4) indicate a different process is taking place, with a shared region of potassium and oxygen (Figure 7(c3,c4)) while there is a distinct region for aluminum as seen in Figure 7(c2). This particulate region displays a very prominent peak for potassium alongside a smaller aluminum peak which likely indicates that it originates from a gunpowder compound used in one of the low-altitude fireworks with smaller depositions (Al) on the larger existing particulate. This is more consistent with the observed patterns of Figure 6, with distinct elemental depositions on existent particulates. This theorized formation mechanism is described in the following section.