A definition of pollution based on thermodynamic goal functions

Several functions, called 'goal functions', have been introduced at the interface between ecology and thermodynamics. Two have been chosen to study the effect of pollution on ecological systems: Exergy is related to the degree of organization of a system and represents the biogeochemical energy of a system; Emergy is defined as the total amount of solar energy directly or indirectly required to generate a product or a service. They represent two complementary aspects of a system. We previously introduced the ratio of exergy to the emergy flow to indicate the efficiency of an ecosystem in producing or maintaining its organization. If we consider the variation in time of exergy and emergy, their ratio indicates the effect of the change of available inputs in the level of organization of the system under study. This can lead to a definition of 'pollution' based on thermodynamics: we can define pollutant for a system as an input for which to an increase (decrease) in the emergy flow corresponds a loss (rise) in the exergy content of the system. A two dimensional diagram is shown in which all the possible situations are represented and discussed. (C) 1998 Elsevier Science B.V. All rights reserved.