Volume 20, Issue 1 (March 1997)
Determination of Ionic Strength and Equilibrium Concentrations of Heavy Metals by the Electrical Conductivity Method
A laboratory investigation of several types of heavy metal-soil solutions was conducted to evaluate the possibility of determining ionic strength and equilibrium concentrations of heavy metals and exchangeable cations by means of the electrical conductivity method. The characteristics of the heavy metal-soil interactions including retention of metals and release of exchangeable cations by the illitic soil were examined, and electrical conductivity and pH measurements of the heavy metal-soil solutions were performed. Test results revealed that direct determination of equilibrium concentrations of certain ionic species could be realized by means of electrical conductivity measurements of soil suspensions. This laboratory technique is based on determining the relationship between the ionic strengths of the heavy metal-soil solutions and their electrical conductivity in order to derive the necessary correlations to estimate the equilibrium concentrations. The proposed technique is expected to aid in the direct calculation of equilibrium concentrations of metal ions and heavy metals from data collected during site investigation for remedial activity via electric conductivity or soil resistivity techniques.