ABSTRACT
A large lake in temperate latitude can provide the stage for dramatic and predictable changes in redox chemistry. In lakes of moderate depth, the interplay of temperature, density, and wind during the seasons of the year can produce a cycle of characteristic patterns of thermal stratification. Summer stratification can be a major problem in many lakes and reservoirs. Advective mixing across the mesolimnion is very limited during that period, and simple molecular diffusion is very slow: there is little ability for surface oxygen to move from the epilimnion into the hypolimnion. During the course of the summer, the pe and the pH will change along a track that can be plotted on a pe–pH diagram. The specific governing equations that will be solved to obtain pe and pH as they change with time will depend on how redox-active solids disappear and appear in the system.
