Chemische Prozesse in natürlichen Gewässern

Abstract

In order to obviate nature’s complexity, simplified and manageable models (equilibrium models and steady state models) are used to illustrate the principal regulatory factors, that control the mineral composition of natural waters and in turn the composition of the atmosphere. Thermodynamic equilibrium models are shown to facilitate identification of the many variables and to establish chemical boundary conditions toward which aquatic environments must proceed, however slowly. The Gibbs phase rule is the basis for organizing and interpreting such models. The concentration of inorganic constituents in natural waters and the CO₂ pressure of the atmosphere are primarily regulated at the sea-sediment interface by reactions in which various aluminium silicates and CaCO₃ participate.
The time-invariant condition of a chemical reaction system, which is open to its environment may frequently be the idealized counterpart of a natural water, that is also an open and dynamic system with variable imputs and outputs of mass and energy. In natural waters organisms and their abiotic environments are interrelated and interact upon each other. Because of the continuous imput of solar energy (photosynthesis), necessary to maintain life, ecological systems are never in equilibrium, but in a balanced ecological system a steady state between production and destruction of organic material as well as between production and consumption of O₂ seems to be maintained, thus providing a constant surplus of O₂ in the atmosphere.
Stream pollution is interpreted as a departure from a balance between photosynthetic activity, P, and respiratory activity, R. The variations in concentrations of algal nutrients, that are observed can be explained in terms of the stoichiometry of the formal P-R reactions. In lakes, the continuous sequence of nutrient assimilation and mineralization of organic matter accompanied by the physical cycle of circulation and stagnation leads to a retention of the fertilizing constituents and to eutrophication.
Stream pollution control consists not only of waste treatment ; it is primarily necessary to attempt to restore the P R balance; among the possibilities for control in addition to chemical treatment for phosphate removal from wastes, are various physical and biological means of stream management directed toward reducing the relative detention time of fertilizing elements.