There are numerous Cr(III)-contaminated sites on Department of Defense (DoD) and Department of Energy (DOE) lands that are awaiting possible clean up and closure. Ingestion of contaminated soil by children is the risk driver that generally motivates the likelihood of site remediation. The purpose of this study was to develop a simple statistical model based on common soil properties to estimate the hioaccessibility of Cr(III)-contaminated soil upon ingestion. Thirty-five uncontaminated soils from seven major soil orders, whose properties were similar to numerous U.S. DoD contaminated sites, were treated with Cr(III) and aged. Statistical analysis revealed that Cr(III) sorption (e.g., adsorption and surface precipitation) by the soils was strongly correlated with the clay content, total inorganic C, pH, and the cation exchange capacity of the soils. Soils with higher quantities of clay, inorganic C (i.e., carbonates), higher pH, and higher cation exchange capacity generally sequestered more Cr(III). The amount of Cr(III) bioaccessible from the treated soils was determined with a physiologically based extraction test (PBET) that was designed to simulate the digestive process of the stomach. The bioaccessibility of Cr(III) varied widely as a function of soil type with most soils limiting bioaccessibility to <45 and <30% after I and 100 d soil-Cr aging, respectively. Statistical analysis showed the bioaccessibility of Cr(III) on soil was again related to the clay and total inorganic carbon (TIC) content of the soil. Bioaccessibility decreased as the soil TIC content increased and as the clay content decreased. The model yielded an equation based on common soil properties that could be used to predict the Cr(III) bioaccessibility in soils with a reasonable level of confidence.
Seven grout formulations were tested in the laboratory for their ability to penetrate and to reduce the hydraulic conductivities of soils used as backfills for shallow land burial trenches. Soils from two sites, in Oak Ridge, TN, and Maxey Flats, KY, were used and both are classified as Typic Dystrochrepts. Three soluble grout formulations (sodium silicate, polypropenamide [polyacrylamide], and 1,3‐Benzenediol [resorcinol]‐formaldehyde) were able to both penetrate soil and sand columns and reduce hydraulic conductivities from initial values of ca. 10−4 m s−1 to < 10−8 m s−1. Three particulate grouts (lime [calcium oxide]‐fly ash, fly ash‐cement‐bentonite, and bentonite alone) could not penetrate columns; such formulations would, therefore, be difficult to inject into closed burial trenches. Field demonstrations with both sodium silicate and polyacrylamide showed that grout could be distributed throughout a burial trench and that waste‐backfill hydraulic conductivity could be reduced several orders of magnitude. Field grouting with polyacrylamide reduced the mean hydraulic conductivity of nine intratrench monitoring wells from 10−4 to 10−8 m s−1. Grouting of low‐level radioactive solid waste in situ, therefore, should be an effective technique to correct situations where leaching of buried wastes has or will result in groundwater contamination.
This report has been reproduceddlrectlyfrom the beat available copy, Available to DOE and DOE contractorsfrom the Office of Scientificand Technical Information, P.O. Box 62, Oak Ridge, TN 37831; prices available from (615) 576-8401, ITS 626-8401.
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