It is clear that there is a growing need for modeling the spread of a pollutant in the geosphere and the biosphere. However, the underlying mechanics are seldom completely understood, and environmental decision making still relies mainly on case studies. As a consequence, it is important to use sound mathematical principles in devising and using a model attempting to simulate the fate of one or more chemicals through the environment. This article tries to give an overview over standard issues of mathematical models for pollution spread. Moreover, interconnections with decision support processes are shown which might greatly increase the effectiveness of the corresponding environmental decision making processes.