Biouptake modelling processes

The finite kinetics of the adsorption/desorption steps at the interface have been extensively studied by Hudson and Morel [13,15]. A wealth of literature is available on dealing with such interfacial processes [94-96] and its inclusion in the biouptake model should be implemented when experimental evidence of its necessity arises. 

Modelling biouptake processes helps in the understanding of the key factors involved and their interconnection [1]. In this chapter, uptake is considered in a general sense, without distinction between nutrition or toxicity, in which several elementary processes come together, and among which we highlight diffusion, adsorption and internalisation [2-4], We show how the combination of the equations corresponding with a few elementary physical laws leads to a complex behaviour which can be physically relevant. Some reviews on the subject, from different perspectives, are available in the literature [2,5-7]. 

In more traditional ecosystem modeling, it is often a goal to include as many relationships (fluxes and compartments) as possible and describe the complex relationships in a logical, causal manner. If, on the contrary, one would like to predict about one or a few y-variables, it is evident that it may be very impractical, costly and laborious to use very big ecosystem models. This mixed model has been constructed first of all to interpret the results presented for Hg and Cs. It may also be used as a tool to simulate the spread and biouptake of metals in lake ecosystems more generally. The idea is not to include every possible process, but the crucial processes. Mixed models in this context are models that are based on both dynamic characteristics and empirical relationships (Hakanson 1991). There are several ways to link these two fundamentally different model approaches, and here we will give some examples. 

---