Flushing of a Pb(II) Contaminated Soil Using HCl, EDTA, and CaCl₂

Flushing of a Pb(II) synthetically contaminated sandy loam using 0.1 N HCl, 0.01 M EDTA, and 1 M CaCl ₂ was investigated in the continuous-flow (column) mode. Initial Pb soil concentrations ranged from 500 to 600 mg/kg. Pb-removal efficiencies (and final soil Pb concentrations) for HCl, EDTA, and CaCl ₂ were 85% (77 mg/kg Pb), 100% (≈0 mg/kg Pb), and 78% (135 mg/kg Pb), respectively. Given that HCl and CaCl ₂ could not reduce the soil Pb to background levels (≈25 mg/kg) for a synthetically contaminated soil brings into doubt their effectiveness in remediating actual contaminated soils where metal retention would be much stronger. While EDTA removed all lead (indigenous and “artificial”), its treatment and reuse and possible adverse health effects makes its use difficult. The final soil pH for HCl was near 1, raising the concern of increased contaminant mobility, decreased soil productivity, and adverse changes in the soil's chemical and physical structure due to mineral dissolution. Final soil pHs for EDTA and CaCl ₂ ranged between 4.85 and 5.2.