Chapter 8 - Ecotoxicological Models

Abstract

Ecotoxicological models are widely applied first of all for Environmental Risk Assessment (ERA). It has given occasion to development of different types of toxic substance models. We distinguish between fate models and effect models and FTE models that are a combination of fate and effect models. The fate models may be divided into three classes focusing on a region or country, focusing on a specific case and models that are a hybrid of the two classes. The effect models are classified according to the hierarchical level of concern: an organism, a population, an ecosystem, a landscape (region), or the entire ecosphere. Most ecotoxicological models are biogeochemical models because they are based on mass conservation principles, but ecotoxicological models concerned with populations are of course population dynamic models. The characteristics of ecotoxicological models are presented and in this context we distinguish between food chain models, steady state models of toxic substance flows, toxic substance models in one trophic level, ecotoxicological models in population dynamics, and ecotoxicological models with effect components. A comprehensive overview of ecotoxicological models published the last 40 years is furthermore presented. Many toxic substance models were developed from 1980 to 2000 because the ecotoxicological problems were very much in focus. We are using in the industrialized countries about 100,000 different chemical compounds and it implies of course that we need to use a very high number of parameters to be able to develop models for all these compounds. There is therefore a need for estimation methods to estimate the parameters (the properties) for the compounds that have not been determined by measurements and it is the major number of the 100,000 compounds. An introduction to the estimation methods is included in Section 8.4 of this chapter. A case study is presented to illustrate the considerations that we have to make to model toxic substances in the environment. The last section is devoted to illustrate how models in general, but here illustrated by toxic substance models, can be used as an experimental tool.