N_areas: represents the number of distinct monitoring areas that can be covered; F_responsiveness: represents the responsiveness factor of the monitoring system (0–1); R_reuse: represents the reuse rate of monitoring equipment; T_deployment: represents the average deployment time; C_displacement: represents the unit displacement cost. In the case of fixed monitoring stations, each station represents a permanent measurement point covering a limited local area; therefore N_areas=1. Their responsiveness to sudden pollution events remains limited because they cannot be easily relocated, which justifies a responsiveness factor of F_responsiveness=0.2. The reuse rate of the equipment is also limited spatially (R_reuse=0.3), since fixed stations remain installed at the same location for long periods. Installation procedures typically require approximately two to four weeks due to infrastructure preparation, calibration, and regulatory validation; therefore an average deployment time of T_deployment=21 days is considered. Finally, relocating a fixed station requires substantial logistical operations including dismantling, transportation, and recalibration, which corresponds to a high displacement cost (C_displacement=10). Using these parameters, the flexibility index for fixed stations can be estimated as:

N_areas: indicates how many separate monitoring zones can be monitored simultaneously; F_responsiveness: indicates how quickly the monitoring system can respond to changes (scale of 0-1); R_reuse: indicates what percentage of monitoring equipment can be reused; T_deployment: indicates the typical time required for system setup; C_displacement: indicates the cost per unit when moving equipment to new locations. For fixed monitoring stations, each unit functions as a stationary measurement point that monitors only its immediate surrounding area, so N_areas equals 1. These stations have poor ability to respond quickly to unexpected pollution incidents since they cannot be moved easily, resulting in a low responsiveness factor of F_responsiveness=0.2. Equipment reuse is also geographically constrained (R_reuse=0.3) because fixed stations stay in the same spot for extended periods. Setting up these stations usually takes about two to four weeks due to the need for infrastructure development, equipment calibration, and meeting regulatory requirements, leading to an average deployment time of T_deployment=21 days. Moving a fixed station to a different location involves complex logistics such as taking apart equipment, transporting it, and recalibrating everything, which results in high relocation costs (C_displacement=10). Based on these values, we can calculate the flexibility index for fixed stations as follows: