Integrating soil water chemistry variations at the catchment level within a cation exchange model

Abstract

The soil zone is of major importance in determining the transport of chemicals through catchments. Despite this, there is no theory that partitions the chemical transfers between the micropore and macropore soil water environments and no theory that shows how bulked chemical properties can be linked to equilibrium or kinetic-type equations. Here a method is developed that examines the relationship between the theoretical cation exchange equations and lumped chemical data for an acid soil representative of acidic and acid-sensitive areas. The method uses artificial data to examine how the lumped soil water data changes in response to changing cation exchange composition. Results indicate that for long-term studies the lumped relationships are similar to the theoretical equations. However, in the short term, i.e. for periods covering a few years or less, the changes are more difficult to describe. The relationships established are important not only from a theoretical point of view but also in relation to environmental modelling within catchment research: the work helps resolve a common discord between field evidence and modelling assumptions. © 1994.