Metals added to soil will normally be retained at the soil surface. Movement of metals into other environmental compartments, i.e. groundwater, surface water, or the atmosphere, should be minimal as long as the retention capacity of the soil is not exceeded. The extent of movement of a metal in the soil system is intimately related to the solution and surface chemistry of the soil and to the specific properties of the metal and associated waste matrix. The retention mechanisms for metals added to soil include absorption of the metal by the soil solid surfaces and precipitation. In addition to soil properties, consideration must be given to the type of metal and its concentration and to the presence of competing ions, complexing ligands, and the pH and redox potential of the soil-waste matrix. Because of the wide range of soil characteristics and various forms by which metals can be added to soil, evaluating the extent of metal retention by a soil is site/soil/waste specific. Laboratory methods for evaluating the behavior of metals in soils are available in the literature. Thermodynamic equilibrium computer models are also available to assist with the evaluation. The advantages and disadvantages of some of the available procedures and models have been presented in the document.

Caption title. Shipping list no.: 1993-0075-P. "October 1992." Includes bibliographical references (pages 20-25). "EPA/540-S-92-018."