ABSTRACT
When you assess a complex system, you need to know the components of the system and how they are connected. For contaminants, the basic components are a source, a route of transport, transformation processes, receptor entities that are exposed, and affected endpoint entities. For environmental assessments, these system diagrams are commonly referred to as conceptual models. In other contexts, they have other names such as box and arrow diagrams, causal networks, or system diagrams. They are essential tools of environmental assessment. They are developed in problem formulations of environmental risk assessments (Section 4.2.4).
