CHROMIUM LEACHING VS OXIDATION-STATE FOR A CONTAMINATED SOLIDIFIED STABILIZED SOIL/

The toxicity, solubility, and mobility of chromium in soil are strongl y dependent upon its oxidation state. Solidification/stabilization (S/ S) is a potential method for preventing Cr leaching from contaminated soil. We evaluated the leaching behavior of untreated and solidified/s tabilized chromium contaminated soil samples obtained from two locatio ns al a military facility in Louisiana. The leaching of chromium, as m easured by the Toxicity Characteristic Leaching Procedure (TCLP), was expected to be dependent upon the chromium oxidation state. The pH, ca tion exchange capacity and particle size distribution were obtained fo r each sample and portions of each sample were solidified with Type I Portland cement. The oxidation state of chromium was determined by X-r ay absorption spectroscopy (XAS). The sample from Site 1 contained 478 mg kg(-1) total chromium while the sample from Site 2 contained 1272 mg kg(-1) total Cr. The TCLP chromium concentration for Site 1 untreat ed soil was 3.4 mg L-1 and 2.0 mg L-1 for the S/S treated sample. The sample from Site 2 had TCLP chromium concentrations below the analytic al detection limit (<1.0 mg L-1) for both untreated and S/S samples. T he XAS data showed the presence of the more mobile and soluble Cr+6 at Site 1 but not at Site 2, The use of Portland cement alone was not ef fective in reducing the Cr+6 to the less soluble and less mobile Cr+3, or in physically preventing leaching of Cr+6. (C) 1997 Elsevier Scien ce B.V.