Mathematical models used as field-oriented tools to predict migration rates through soils of metals contained in landfill-type leachates are explained. The concepts of the Lapidus and Amundson model were used along with actual data collected from soil column experiments. Simple equations for predicting migration rates of cadmium, nickel, and zinc contained singly and in mixed combinations in leachates through soils of varying properties are developed. The migration behavior of the metals is not significantly different whether contained singly or mixed. (7 graphs, 30 references, 1 table)

Quantitative information on the immobilization of potentially health-hazard trace elements (e.g., Cd, Co, Cr, Cu, Ni, Pb, Zn, etc.) to prevent their migration through soil to water sources is scant. Little knowledge has been generated for the development of basic management practices for trace element stabilization against migration and their ultimate movement into domestic waters and potential food channels. The research here provides "baseline" information as a beginning for the control of hazardous trace element migration through soils. The contribution of 11 U.S. soils to the mobility of some common and trace elements as influenced by four readily characterized waste stream and leachate vehicles—pure water, dilute acid, solutions resembling industrial wastes, and municipal landfill leachates—is reported. Data are presented showing that: (a) soils release potentially hazardous constituents which migrate at different rates depending on certain measurable indigenous parameters, (b) solubilizing and mobility effects are a continuing process, (c) even the cleanest aqueous vehicle can become a carrier of potentially hazardous trace elements, and (d) certain characteristics of the soil, even under the most ideal conditions, must be identified before a management plan can be developed for the control of hazardous constituents in waste disposal.

The effect of solution composition on the movement of Hg ions through soils was studied. Three solutions spiked with HgC12 were passed through four different soils. The solutions were 0.25 mM Na2 EDTA, simulated sanitary landfill effluent, and deionized water. The Hg ions were found to be more mobile in the effluent from the simulated landfill than in the other solutions. The formation of mercurous ions and the presence of organic matter seem to be the major contributing factors for Hg; movement through soils in simulated landfill effluent.

A natural leachate individually spiked with 11 trace elements (As, Be, Cd, Cr, Cu, Hg, Ni, Pb, Se, V, Zn) was used to leach 11 soils from the seven most prominent orders. Soil column effluents were continuously analyzed for the various elements and these data were correlated with soil physical and chemical properties. Although the relative mobilities of these trace elements are quite variable, data are presented showing that it should be possible to qualitatively predict the migration of an element on the basis of soil properties. Soil texture, surface area, percentage of free iron oxides, and pH provide the most useful information for estimating an element's migration. Knowledge of cation exchange capacity does not improve the ability to predict the movement of ions through these natural soils.

Ten soils were leached with a dilute solution of AICI3, and FeCl2 adjusted with HCl to pH 3.0. The effluents were analyzed for eight trace metals as well as pH, to determine the maximum contribution of the soils to the trace metal burden of the soil solution. This contribution was correlated with various soil properties to evaluate the controlling factors on the elution of certain metals. Measurable quantities of Mn, Co, Zn, Ni, Cu, and Cr were found in the soil leachates; Cd and Pb were infrequently detected. The important soil properties describing the amounts of the elements leached were the total metal originally present, the total amount of Mn, and the percentage of free iron oxides.