Development of soil metal criteria to preserve groundwater quality

The principal impediment in the remediation of contaminated sites and in th e protection of groundwater quality is the lack of appropriate and reasonab le standards for heavy metals in soils. There are no standards applicable t o predict the potential for groundwater contamination by heavy metals in Ta iwan. Lack of these soil standards may result in subjective judgment regard ing the remediation needed. The migration of heavy metals through the unsat urated zone to groundwater is controlled by sorption to the soil, a highly pH-dependent process, and the hydrological regime. Soil sorption behavior i s the criterion upon which to establish a standard based on a maximum permi ssible concentration in groundwater. The maximum level of metal in soil for which the equilibrium soluble metal does not exceed the Drinking Water Sta ndard can be computed, at ally pH, from the measured adsorption coefficient for any metal and soil. These metal criteria can be used as soil standards that will be protective of groundwater quality. Criteria for soil remediat ion are based on specific soil types and the effect of pH on metal sorption because the partitioning of trace metals is highly dependent on the soluti on pH and the chemical nature of the soil. (C) 1998 IAWQ. Published by Else vier Science Ltd. All rights reserved.