Effectiveness of gravity based particle separation and soil washing for reduction of Pb in a clay loam shooting range soil

Effectiveness of gravity based particle separation and soil
washing for reduction of Pb in a clay loam shooting range soil

A heavy particle concentrator (HPC), which can separate heavy metal particles from soil based on density, was examined for remediation of shooting range soil contaminated with lead (Pb) from a military training area. Concentrations of Pb in the stockpiles ranged between 1403 and 4300 mg/kg. The soils had high clay and silt content and were found to have relatively high exchangeable Pb, between 238 and 1480 mg/kg. After initial treatment by HPC, total Pb in the soil was reduced by 28%–56%. The fine soil fraction (<250μm) was found to still have relatively high Pb after HPC treatment. A greater removal efficiency was achieved by passing contaminated soil through the HPC a second time. Scanning electron microscopy (SEM) analysis of the treated stockpile indicated Pb present in the soil sorbed on soil particles or as very fine discrete particles (<10 - 20μm) after initial HPC treatment. The addition of a chemical washing agent, ethylenediamine-N, N’-disuccinic acid (EDDS) was effective for removal of 68% of residual Pb after a single HPC treatment and may be considered for high clay soils.