Any concentration of a substance measured in a living or non-living system results from its distribution among all of the environmental compartments: air, water, sediments, and biota. The transfer of a substance from one compartment to another is regulated by physical forces and the chemical properties of the substance and also those of the compartments. When transfer processes are nearly constant in time, a substance will achieve predictable equilibria distributions. It is of utmost importance that students, environmental scientists, and policymakers understand the basic processes which control the distribution of a substance in order to interpret measurements obtained from within a limited number of compartments.

1 Introduction.- 2 Processes and equilibria between compartments.- 2.1 Principles.- 2.2 Phases or compartments.- 2.3 Processes and equilibria.- 3 Complexing metal- and radionuclide-sediment reactions.- 3.1 Complexation of metals by dissolved organic matter.- 3.2 Results on radionuclide sorption by marine sediments.- 4 Diffusion principles.- 4.1 Theories.- 4.2 Simple methods of determining diffusion coefficients.- 4.3 Experiments on hindrance of diffusing ions in sediments.- 4.4. Summary on effects on molecular diffusion in bottom sediments.- 5 Organochlorines.- 5.1 Introduction.- 5.2 PCB and DDT behaviour in water, PM and sediment compartments.- 5.3 The eel case.- 5.4 Pesticide use and contamination with Tambak (Indonesian brackish-water) aquaculture.- 5.5 Possible DDT and PCB partitioning between air and man.- 6 Competitive reactions and effects of conservativity.- 6.1 Introduction.- 6.4 Principles of conservativity.- 6.3 Model study of competitive processes in an estuary containing a turbidity maximum.- 6.4 Residence times of metals in an estuary.- 6.5 Sources and sinks of chemical constituents in estuaries.- 7 Examples of distribution patterns in estuaries and seas.- 7.1 Budget of plutonium and some other nuclides in an estuary.- 7.2 Metals in the Western Mediterranean.- 7.3 PCB budgets.- 7.4 The food chain accumulation paradox.- 8 Nuclear waste in the Kara Sea.- 8.1 Introduction.- 8.2 History of radioactive waste dumping in the Kara Sea.- 8.3 Inventory of dumped objects.- 8.4 Environmental concentrations of radionuclides.- 8.5 Predicting future radionuclide releases.- 8.6 Modelling radionuclide dispersion.- 8.7 Impact assessment.- 9 Globel oceanic and atmospheric stability of oxygen.- 9.1 Oxygen budgets.- 9.2 Relation to CO2 budgets.- 9.3 Time-dependent process.- 9.4 Future limit(s) of ocean pH due to fossil-fuel produced CO2.- 10 Case studies on Environmental Impact Assessment (EIA).- 10.1 Introduction.- 10.2 Techniques.- 10.3 A Delta-case EIA study.- 10.4 Assessment of diffusion of radionuclides from potential HLW disposal.- 10.5 Amoeba assessment.- 10.6 COSMO-BIO assessment.- Appendix I: Answers to a question and exercises.- Appendix II: Kara Sea box model user information.- Appendix Ills COSMO-BIO assessment.- References.