Natural toxic waters of Poas Volcano, Costa Rica

Lakes within craters of active volcanoes can contain the most acidic natural waters on the Earth's surface (pH <0). At Poas Volcano acidic volcanic gases condense to form dense corrosive brines that dissolve underlying rock and seep into the Rio Agrio watershed. The environmental effects of these acidic waters are manifested in the lack of vegetation and the toxicity of surface and groundwaters as well as by the widespread precipitation of iron hydroxide at seeps and river confluences. -from Authors