1. You list copter-type UAV vertical resolution as “10 s to 100 s of m” (i.e., 10–100 m), yet later in Section 2.2.1 and Figure 3G, you present vertical profiles with much finer resolution (e.g., 10–20 m). This discrepancy undermines the core claimed advantage of UAVs. Please clarify: is the table error, or are your experimental resolutions not generally achievable?
2. Your CFD simulations recommend inlet extensions (e.g., 0.8 m for DJI M600) to keep propeller-induced wind speed <0.5 m/s. However, you provide no experimental validation of these thresholds for actual gas or particle measurements. Given that downwash turbulence can entrain surface pollutants or dilute plumes, how can readers trust that your recommended distances ensure unbiased sampling in real-world, non-laboratory conditions?
3. You state that aromatic compounds in Tedlar bags decreased to “80–90% of initial levels in the second hour.” That represents a 10–20% loss within 2 hours – a severe artifact. Yet you do not provide quantitative correction factors or recommend against Tedlar bags for aromatics. Without such guidance, how can any UAV-based VOC study using Tedlar bags be considered reliable for compounds like benzene and toluene?
4. You describe multiple flux estimation methods (mass balance, Gaussian plume, gradient transport) but provide no comparative uncertainty assessment. Given that wind speed errors of 0.5 m/s can change CH₄ flux estimates by >50%, and UAVs cannot measure 3D wind accurately near rotors, why should readers believe any absolute flux values reported from UAV platforms without simultaneous, independent validation?
5. You propose automated UAV networks and “UAV airports” for continuous operation, yet earlier (Section 4.1.2) you note strict altitude (120 m) and VLOS (visual line of sight) regulations in most regions. These regulations fundamentally prohibit beyond-visual-line-of-sight (BVLOS) autonomous swarms. How do you reconcile this future vision with current legal frameworks, and why was this contradiction not addressed?