HEXAVALENT CHROMIUM QUANTIFICATION AND REMEDIATION IN SOILS AND WASTE MATERIALS

Abstract

Hexavalent chromium (Cr(VI)) is a carcinogen and a pollutant of soils and natural waters. The standard method to extract and quantify total Cr(VI) in soils and waste materials was modified to prevent method-induced reduction of Cr(VI) by not heating (95°C) but shaking (100 cycles/min) at 23°C, followed by quantification using the 1,5-diphenylcarbazide method or ion chromatography. Forms of carbon and Cr(VI) (mineralogical vs. soluble) significantly influenced method-induced reduction. The proposed method should be used with samples containing ≥ 10 g/kg organic C. The new method was used to study the reduction of Cr(VI) in soils with Fe(II), Fe(III), and organic carbon, and the Cr in remediated soils was fractionated. Fe(II) in combination with Fe(III) was the most effective at reducing Cr(VI) and immobilizing newly-reduced Cr(III). The extraction and quantification refinements are relevant to accurate and precise metrics for Cr(VI) and its remediation in soils.