Hyperacid lake monitoring from Poás Volcano, Costa Rica, using UAV (Unmanned Aerial Vehicle)

Abstract Poás Volcano is a complex stratovolcano in Costa Rica’s Central Mountain Range and hosts acidic volcanic lakes. This study uses Unmanned Aerial Vehicles (UAV) to monitor the physicochemical characteristics of the hyperacid crater lake. Sampling was conducted in January and May of 2024, using a DJI Matrice 600 Pro equipped with a water collection system. The results showed extremely low pH values (as low as −1.04), high temperatures (up to 64 °C), and high concentrations of sulfate (134 877 ppm) and chloride (88 434 ppm), highlighting the influence of volcanic activity on the chemical composition of the hyperacid lake water. Sampling was marked by a decrease in rainfall patterns during the dry season and a reduction in the lake’s water volume, indicating a high evaporation rate and the release of gases and ash. The SO 4 2− /Cl − ratio was relatively constant, with no increase in activity and that meant that it was safe for tourism, based on the physicochemical characteristics of the hyperacid crater lake.