A new representation of anoxis crises in hypertrophic lagoons

A new representation of the causes of anoxia in hypertrophic lagoons is proposed; field measurements show that, in high concentrations of organic matter and high temperature, anoxic crises may be correlated either with the anaerobic mineralization phenomena in the sediment layer or with the turbulent characteristics of the hydrodynamic field produced by external influence (wind, tide). Two different models have been developed which are able to simulate, respectively, the hydrodynamic field in the lagoon and the concentration fields of the biochemical species which are the most important in characterizing the phenomena, i.e., dissolved oxygen, organic carbon, and hydrogen sulphide. The results of the simulations are compared with field measurements to validate the representation of the phenomena. Furthermore the effect of forced recirculation by pumping, in avoiding anoxia in water, is quantified.