# Development of a Robotic Airboat for Online Water Quality Monitoring in Lakes
## 7 Discussion  
Analyses can be made regarding the general situation of the lakes by comparing the average of each type of data collected with the other types. The mean temperature values of the environment varied greatly, according to the location and period of the day. The Piripau weir, on the edge of the Pacatuba Mountain, showed a higher value (33.89 \({}^{\circ}\)C after 1 pm), as it was located in a windward region. The lagoon of the condominium Jardins de Alice e Pereira showed a lower value, due to the collection time (27.11 \({}^{\circ}\)C, after 9 pm). The Cajazeiras Lagoon obtained a value of 30.93 \({}^{\circ}\)C, after 9:50 am. Figure 27 shows the averages of the environmental temperature in the three lakes analyzed. Figure 26: pH graph for the Piripau Weir. Figure 25: ORP in the Piripau weir. The average temperature of water obtained divergent results in two situations--in the lagoon of condominium Jardins de Alice e Pereira, its value in the evening was higher than the ambient temperature (28.05 \({}^{\circ}\)C), whereas in the Cajazeiras Lagoon and in the Piripau weir, the values were lower during the day, with values of 27.54 \({}^{\circ}\)C and 28.04 \({}^{\circ}\)C, respectively. Figure 28 shows the averages of water temperature in the three lakes analyzed. The Oxidation-Reduction Potential in the Piripau weir showed a good average, compared to the other two lagoons, reaching an average of 241.01 mV, while in the lagoon of condominium Jardins de Alice e Pereira, its value was 38.45 mV. In the Cajazeiras Lagoon, this value was 107.82 mV. This was due to the high rate of atmospheric oxygen and the availability of nutrients to aquatic communities, which was observed by the presence of in situ water hyacinths. Figure 29 shows the mean values of the ORP in the three analyzed lakes. Figure 28: Comparison of the lake water temperature. Figure 27: The ambient temperatures of the lagoons. Dissolved Oxygen obtained a higher value in the Cajazeiras Lagoon, with 9.1 ppm, whereas it was 7.56 ppm in the Piripau weir and 8.87 ppm in Jardins de Alice e Pereira. The amount of dissolved oxygen present in the water bodies was directly proportional to the atmospheric pressure and inversely proportional to the temperature, as observed in the Cajazeiras Lagoon, which had a higher value, and in the Piripau weir, which had a lower value. Figure 30 shows the mean values of OD in the three lakes analyzed. The Potential of Hydrogen (pH) obtained a value of 5.9 in the Piripau weir and 7.9 in the Cajazeiras lagoon. In the lagoon of the condominium Jardins de Alice e Pereira, its value was 7.6. This was due to the dissolution of rocks, absorption of gases from the atmosphere, oxidation of organic matter, and photosynthesis, as could be observed in the Cajazeiras Lagoon, where the value was higher, and in the Piripau weir, at the base of the mountain, where this value was lower. Figure 31 shows the pH averages in the three lakes analyzed. In the experiments carried out, the Airboat Vector analyzed 2 lagoons and 1 lake; 130 data collections were carried out and 15 graphs were analyzed and generated. The total time of the missions was 54 min and 25 s, in the 3 lagoons, which resulted in the following discussion parameters:  
* Dissolved Oxygen--Indicator parameter of eutrophication by domestic or industrial water pollution [29]. Values below 6 mg/L are indicators of high nutrient load, such as nitrogen and phosphorus [30], while waters with excessive growth of algae and macrophytes present values higher than 10 mg/L in the daytime period and near zero concentration, at night [31]. Such values were not reached in any of the analyzed lakes. * Potential of Hydrogen--Concentration of ions in water indicating the intensity of acidity, neutrality or alkalinity. The Resolution 357 of the National Council of the Environment  
Figure 31: Comparison of the pH of lagoons. Figure 30: Comparative of DO lagoons. (CONAMA) has established a range of 6-9 for all freshwater [32].