ABSTRACT
A simple model is presented to predict the long-term behavior of heavy metals in agricultural soils. The analytical solutions to the model differ in the assumed relationships between the solubility of heavy metals and their accumulated contents in soils. Four cases are distinguished: (1) precipitation and dissolution reactions determine the solubility of heavy metals in soil, (2 ) ion exchange or linear adsorption determine the solubility of heavy metals, (3) solution concen trations of heavy metals are related to their accumulated soil contents through Langmuir-or Freundlich-type adsorption equations, and (4) part of the heavy metals in an adsorbed phase is transformed into unavailable (irreversibly adsorbed) form. As an example, the model is applied to assess the long-term behavior of cadmium in agricultural soils in The Netherlands.
