Characterization and Evaluation of Stabilized/Solidified Heavy Metal Contaminated Clays

The legacy of industrialization has resulted in a prevalence of heavy metal contamination, and sustainable redevelopment necessitates the use of effective remedial methods. Stabilization / Solidification technology has been employed in contaminated land remediation, and found to be particularly effective for heavy metal contaminants. However, uncertainties over the long term performance of the method and associated liabilities of residual contaminants on site have had detrimental implications on its employment. A careful characterization of the treated material is required to ensure efficiency and durability within the service life, and contaminant release predictions are required to improve confidence for employment. Geochemical speciation modeling provides information on partitioning and release of contaminants from the treated material, and information obtained from a carefully selected suite of leaching tests, dependent on the material can be used for a leaching assessment and subsequently model the method efficiency. LeachXS expert system and geochemical database embedded with the geochemical speciation modeling tool ORCHESTRA can be used for this assessment, providing the required information from the leaching tests have been obtained. Cement stabilized chromium contaminated kaolin clay was characterized and evaluated via these tools, using a suite of leaching tests designed for monolithic material, and the findings justify this assessment approach based on a comparison of measured and predicted release. This method of assessment provides useful information on contaminant availability, partitioning, and long term release. Information obtained can be used for performance oriented remedial design, and give an insight on the durability of the treated material based on anticipated site conditions, and ultimately lead to a better understanding of stabilized material behavior and improved confidence in designing performance oriented applications.