253 lower than the evening session. It is interesting to note that PM level along the vertical depth during the afternoon session were confined within a narrow range. Afternoons are usually hot with higher atmospheric boundary layer that cause unstable atmospheric conditions and favor particle dispersion. In contrast, higher PM concentration in the evening can be attributed to the gradual accumulation of particles emitted from continuous mining operations, accompanied by a decrease in the atmospheric boundary layer height and poor vertical mixing. The temperature difference between the pit bottom and the pit top during the afternoon is significantly higher compared to the morning and evening sessions. Therefore, limited dispersion happened in the morning and evening, leading to higher PM levels along the vertical extent of the mine. 3.3 Comparison between surface iron ore and coal mine Compared to the stationary-based ground monitoring methodology followed in the surface iron ore mine, UAV based monitoring in coal mine allowed for obtaining more continuous PM concentration data along the vertical depth. Although the mean PM concentration recorded at the pit bottom of both mines is similar, there existed a significant difference in the PM concentrations at the pit top. It is interesting to note that, the PM mass concentrations recorded at each vertical depth inside the coal mine is several times higher than those recoded in the iron ore mine. The material handled in terms of coal and overburden on day-to-day operations are significantly higher in coal mines compared to the iron ore mines, which causes the higher PM pollution in the coal mine. However, the fall in PM concentration observed at the immediate level above the pit bottom in the iron ore mine is higher compared to the coal mine. The percentage fall observed in the iron ore mine for a vertical depth of 100 m is higher compared to that of 130 m deep coal mine. This can be attributed to the high-density iron ore particle that settle faster, whereas the light weight coal particle with relatively lesser density tries to escape away from the source of generation under favorable conditions. 4. POSSIBLE APPLICATIONS OF LOW-COST SENSOR AND UAV 1. One of the important applications of low-cost sensors is for personal exposure monitoring of mine workers deployed at different mining operations. As these sensors are miniature in size and can be made portable, they offer minimal discomfort when attached to miner safety helmet. Sensor scan also be deployed inside the operators’ cabin of several HEMM, for realtime and continuous monitoring of pollution exposure of operators during the working shift. 2. Low-cost sensors are several times less expensive than the regulatory instruments, hence can be used for simultaneous monitoring of multiple working locations in and around the mines. Deploying a low-cost sensor network across the surface mine gives dense information of spatial and temporal variability of PM levels. Long term spatial monitoring allows for accurate identification of mining operations of potential emission strengths and other hotspots in the mining environment. 3. The integration of wireless connectivity in low-cost air sensors enables remote, real-time monitoring of particulate matter concentrations by mining authorities and other regulatory agencies, thereby enhancing surveillance efficiency and regulatory oversight.
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