BETTER CHARACTERIZATION OF ARSENIC AND CHROMIUM IN SOILS: A FIELDSCALE EXAMPLE

The characterization of arsenic and chromium in soil (and site remediation decisions) is commonly based on total concentration results and U.S. EPA TCLP results. Further evaluation of arsenic and chromium within the soil media by application of geostatistlcs, selective extraction laboratory procedures, and X‐ray diffraction determination of soil mineralogy provides valuable additional information. Arsenic‐and chromium‐contaminated soils at a chemical manufacturing facility represent a case study for application of this approach. From 0 to 6 ft deep, the soils are characterized by mottled, yellowish brown, silt and clay with fine sand, grading downward into light yellowish brown, sllty, micaceous, fine sand, dominated by small, gray, foliated, lithic fragments and muscovite. Total arsenic and chromium are concentrated in the upper silt and clay, but are more readily leached from the lower sandy soil, suggesting partitioning based on soil composition. Selective extraction data Indicate that arsenic is prima...