TRACE-METAL SPECIATION IN A SOIL-PROFILE IRRIGATED WITH WASTE-WATERS

A chemical equilibrium computer model, GEOCHEM, was used to predict the trace metal behavior in a soil profile if subjected to a long-term irrigation with waste waters. The computations included a 10 metal - 15 ligand system with 262 soluble complex species and 21 possible solid phases. The results predicted that a major fraction of alkali elements in solution tend to be in free ionic forms, whereas, major fractions of the alkaline earths were predicted to be present in adsorbed and/or precipitated forms. In marked contrast, significant soluble fractions of transition series metals were predicted to be in adsorbed and/or complexed forms. Application of this equilibrium model appears to provide a first approximation approach to simulate the trace element behavior in soil profiles.