Trace Metal Soil Quality Criteria to Protect Ground Water

A major problem in site remediation is frequently the lack of appropriate standards for pollutants in soil. Lack of standards for an exposure route can result in subjective judgments regarding the extent of remediation needed. These problems are particularly important when considering the potential for groundwater contamination by inorganic materials. The partitioning of trace metals is highly dependent on the nature of the soil and on the solution pH. The maximum level of metal in soil for which the equilibrium soluble metal does not exceed the drinking water standard can be computed, at any pH, from the measured partition coefficient for any metal and soil.

The sorption of cadmium and lead onto major types of New Jersey soil has been determined as a function of pH. As the pH decreased, the amount of adsorbed metal decreased.

As is conventionally done, we have transformed these data into sorption coefficients (K_d) which are a function of pH. To apply such data in the decision making process, it is necessary to use the K_d and appropriate conditions of soil/groundwater in the environment. The calculation determines the maximum concentration of metal which will not result in exceedence of water quality standards. Thesecriteria can be used as a soil standard which will be protective of groundwater quality.

We developed adsorption/desorption relationships in the form of a mathematical model and computed the maximum level of metal in soil for which the equilibrium soluble metal will not exceed the drinking water standards.