An investigation of contaminant metal distribution and mineral speciation in the soil near the Buick Recycling Division smelter, Iron County, Missouri

Trace metal contamination studies were conducted near the Buick Resource Recycling Division. This study used sequential extraction, total digestion, X-Ray Diffraction (XRD), and Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) to study trace metals in two soil cores. Sequential extraction analysis of the soil cores revealed that lead was associated with either iron or manganese oxides. Zinc and copper were bound to soil components, extracted mainly from organics, sulfides, and clays. Total digestion results compared favorably to the sum of the sequential extraction results for lead, thus validating the sequential extraction methodology. The highest concentration observed for lead was 4,743 parts per million (ppm) in the Oh soil horizon in the core located 0.72 km NW from the smelter. Most trace metals were concentrated in the top few inches of each core, a finding consistent with previous studies. However, nickel and copper concentrations increased from 9 to 16 inches of depth in one core. Antimony and cadmium were present in small amounts (\u3c20 \u3eppm) in the upper portion of the soil cores. Iron concentrations increased with depth in both cores. Samples were analyzed for mineral species and pH. SEM-EDS analysis revealed lead-bearing particles with a subhedral, platy habit, and a composition suggesting the presence of cerussite (PbCO₃). XRD results suggest that the majority of the clay-sized fraction of the soil is comprised of both kaolinite and illite. Smectite was present in small amounts and may influence metal immobilization. Soil acidity increased with depth, which is consistent with previous studies. The data from this study can be added to previous studies conducted in the area to provide nearly a 40 year record --Abstract, page iii