## 2 Materials and Methods  
To collect samples from the firework plumes, a DJI (Shenzhen, China) Mavic Pro Platinum drone and a customized mount for the drone with a particle sampling mechanism were used. The full platform is mounted on the back of the drone. This drone mount was designed using CAD software (SolidWorks 2022: Waltham, MA, USA). The particulate capture method consisted of a 3D Printed mount capable of holding 1.5-inch diameter  
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aluminum disks. These disks were coated with electrically conductive double-sided carbon tape on the outside, and just before flight, the covering of this tape was removed, allowing the airborne particulates in a plume to stick to the carbon tape for later study. The full platform also included a counterweight on the opposite side of the drone to ensure the whole system remained in balance. The isometric and top views of the sampling drone mount can be seen in Figure 1a. The exploded view with detailed components for particulate collection, including the sampling cone, is shown in Figure 1b. Figure 1c shows a photograph of the drone with the drone mount installed. Figure 1d shows the drone/sampler hovering at a low altitude, while Figure 1e depicts it during high-altitude sampling. At both altitudes, the drone/sampler remained stable.  
Samples were collected from two different types of plumes. The plume generated by professional fireworks is higher above the ground, at an altitude at or above 25 m, and is referred to as high-altitude sampling (HAS). The plume from personal fireworks is closer to the ground, at or below an altitude of 10 m, and is referred to as low-altitude sampling (LAS). The LAS plumes were formed mainly of smaller personal fireworks used by the general public in the park including sparking devices, firecrackers, and fountains while the HAS samples were primarily the larger-scale fireworks used as a part of the municipal display hosted by the city of Norman. Given the distinct nature of these two sources, one of the objectives of this study is to understand the type of particulates present in the two types of plumes emitted from these fireworks. In order to ensure particulate capture while remaining at a safe distance from the firework launch site, the drone was flown in a position downwind from the launch site, as seen in Figure 2. The plume generated by  
Figure 1: Various aspects of the experimental setup. (**a**) Isometric and top view of the sampling drone mount; (**b**) exploded view with detailed components of the sampling cone assembly; (**c**) a photograph of the actual drone and sampling platform; (**d**) drone with mounted platform hovering at low altitude; (**e**) drone with mounted platform hovering at high altitude; (**f**) example sample disk for SEM analysis with 4 samples.  
professional fireworks is higher above the ground (HAS) compared to the plume from personal fireworks that is closer to the ground (LAS). Therefore, the materials and methods required testing of the drone/collector before the firework event at various altitudes.  
Once the samples were collected, they were kept in a desiccator and consolidated onto a larger platform for Scanning Electron Microscopy analysis, as shown in Figure 1f.  
The samples underwent microscopy analysis with a Thermo-Fisher Scientific (Waltham, MA, USA) Quattro Scanning Electron Microscope (FE-ESEM) and focused primarily on conventional Everhart-Thornley (ETD, also known as Secondary Electron Imaging) and Concentric Back Scatter (CBS) methods for obtaining the physical characteristics of the sampled particulates. Prior to analysis, the samples were treated with iridium sputter-coating (Emitech K-575D, Ashford, UK) to allow for electrons to dissipate through the sample and avoid any charging artifacts that can occur in SEM samples that are not properly grounded. The microscopy analyses also included Electron Dispersal X-ray Spectroscopy (EDX) to obtain the chemical compositions of the particulates.