In situ Arsenic and Lead Stabilization and Remediation in Acidic Soils Using Green Chemistry and Nano Iron Welding Fumes.

Arsenic (As) and lead (Pb) are highly toxic carcinogens responsible for neurological, gastrointestinal, cardiovascular, and reproductive illnesses.  Soils with toxic accumulations of As and Pb pose a public health threat particularly to children because of their tendency to consume soil via hand-to-mouth contact and, to a lesser extent, adults with home gardens and occupational exposures. When pseudo total As contamination levels are ≤ 2000 mg kg^-1 in situ remediation with Fe amendments has been successful in preventing As leaching and may under appropriate conditions be an effective long-term strategy. Likewise, the transformation of Pb to pyromorphite at low levels of contamination by the addition of phosphorus (P) compounds has become an approved strategy to protect human health in the US.  However, the addition of P solutions is not feasible due to the risk of As leaching into ground water or streams.

The goal of this project is to demonstrate physiochemical technology responsible for the immediate in situ long-term stabilization and remediation of contaminated soils by iron (Fe) occlusion. Arsenic and Pb remediation is achieved by occlusion of As within newly precipitated Fe (hydr)oxides minerals. The risk for As leaching will be reduced or eliminated by the application of Fe nanoparticles applied to the soil with a “green” nonionic surfactant and wetting agent derived from citrus fruits.  We will present results of ligand-exchangeable and ligand-dissolvable As and Pb pools, citrate bicarbonate dithionite extractable Al, As, Fe, and Pb, as well an As and Pb X-ray Absorption Near Edge Spectroscopy.  Remediation efforts that sequester As and Pb  within recalcitrant occluded Fe minerals could give risk assessors and stakeholders confidence that the danger to human health has been significantly reduced or eliminated.  Concurrently, this remediation technology may achieve substantial cost savings in comparison to soil excavation and off site landfill deposition.