And boundary fluxes

Internal Transport versus Reaction and Boundary Fluxes One-Dimensional Vertical (1DV) Lake Model... 

Internal Transport versus Reaction and Boundary Fluxes... 

From these semiquantitative considerations we conclude that competition between, on one hand, processes which eliminate concentration gradients like vertical mixing, and on the other hand, processes which produce concentration gradients like in-situ reactions and boundary fluxes, can be highly variable in time. Sometimes vertical mixing is intensive enough to warrant the box-model approach, other times we would need a model that allows us to describe spatially continuous concentration profiles. Sometimes we need a tool which could handle both situations. Such a model will be discussed next. 

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