LIMITATIONS TO THE UNDERSTANDING OF ION-EXCHANGE AND SOLUBILITY CONTROLS FOR ACIDIC WELSH, SCOTTISH AND NORWEGIAN SITES

A summary of soilwater and streamwater data from acidic catchments in Wales, Scotland and Norway is presented. It is concluded that insufficient detail has been established to describe quantitatively the ion-exchange and weathering processes in determining streamwater chemistry: such a description is required before reliance can be placed on mathematical models describing short- and long-term changes. The need for manipulative studies is highlighted, emphasis being placed on minimizing perturbation of the system from field conditions. An appeal is made for the use of a standardized method for determining the exchangeable cations. The studies provide overwhelming evidence showing the incorrectness of the commonly used modelling assumption that Al(OH)3 solubility determines inorganic aluminium levels in the soil and streams. The importance of simple mixing of soil and ground water, in explaining streamwater aluminium-hydrogen ion relationships, is emphasized. © 1990.