Geochemistry of an acidic chromium sulfate plume

摘要: Abstract The historical disposal of acidic chromium sulfate solutions into unlined lagoons between 1953 and 1970 at an industrial site resulted in formation a dense aqueous phase liquid (DAPL) plume [specific gravity 1.11 g/cm 3 , pH 3, up to 4700 mg/L Cr(III), 90,000 mg/L SO 4 ]. DAPL sank through the shallow glacial till aquifer underlying impermeable gneissic bedrock from where it migrated downgradient along buried channels incised bedrock. Because its high density, chemistry is sharply stratified vertically. Chromium(III) predominates because excess Cr(VI) not reduced original process has been by Fe(II) derived silicates, while Cr(OH) (am) occurs as surface coatings on silicate minerals discrete particles mixed with Fe(OH) Al(OH) (am). solubility accurately describes Cr(III) concentrations nearby groundwater, Al Fe solution are also consistent solubility-controlling oxyhydroxides. these controls, metal cations attenuated relative more mobile Cl resulting chromatographic separation solutes origin. good agreement predicted observed illustrates utility equilibrium modeling when interpreting transport characteristics determining efficacy natural attenuation subsurface systems.