Physico-chemical and biological aspects of Lake Albano.

Lake Albano is deep and has a small surface area, which reduces the potential for mixing across its full depth. This can lead to dangerous accumulations of carbon dioxide in the bottom waters of the lake deriving from subterranean magmatic processes. It has been proposed that limnic gas eruptions emanating from these deep waters represent the most significant present-day natural hazard of the Colli Albani volcano. Although recent evidence has shown that the lake is not meromictic and that rare full mixing events do occur, reducing to some extent the risk of limnic eruptions. At present the lake volume and water quality is rapidly decreasing due to over-abstraction and uncontrolled inputs of waste and sewage. These conditions may be responsible for large growths of toxic cyanobacteria in the lake. Lake water concentrations of microcystins (a cyanobacterial toxin) are well above the recommended limits set for drinking water, and some trace groundwater contamination has also been determined. These toxins can cause the death of animals and pose a significant risk to human health, representing a secondary hazard of the lak