GLOBETOX Modelling the global fate of micropollutants

GlobeTox is a multi-media box model of the so-called Mackay-type, in which the environment is modelled as a series of thirty homogeneous compartments on two spatial scales: four continental islands are nested inside a global oceanic 'background'. Each of the four continental islands comprises atmosphere, fresh surface water, sediment, natural soil, and cultivated soil as compartments ; the oceanic environment consists of seven water compartments, ice caps, sediment and atmosphere.

In GlobeTox, the 'fate' of chemicals is modelled on the basis of mass balance equations for all the compartment 'boxes' ; mass flows of a chemical to and from the compartments are written in generic mechanistic terms, on the basis of physical-chemical properties of the chemical and characteristics of the compartments. Input to GlobeTox are time series of emission rates to the continental environmental compartments and physical chemical properties (rate constants for degradation and intermedia transport).

On the basis of this input, GlobeTox simulates concentration time series of the chemical in the different compartments. GlobeTox was tested with four typical examples of toxic micropollutants, representing different origins, uses and properties: DDT, PCBs, DEHP, and lead. A first quick comparison of the simulated concentrations with easily accessible reported measured concentrations indicates that the predicted concentrations are usually in the right order of magnitude, and that trends in time appear reasonable. Further testing and validation of the model remains to be done.