Characteristics of heavy metals in contaminated soils

Soils contaminated with lead and copper from three industrial-waste sites were characterized for particle-size distribution, heavy metal (Pb, Cu) content by particle size, sequential extraction for metal speciation, scanning electron microscopy for morphology, and energy dispersive X-ray microanalysis (SEM/EDX) for chemical composition. High concentrations of Pb and Cu were found in all size fractions of the test soils. Pb was observed to be associated primarily with the carbonate and the Fe-Mn oxide phases of the soil samples. Cu was associated with carbonate, Fe-Mn oxide, and organic fractions of the soils. In one of the test soils (Soil A), SEM/EDX analyses showed the presence of roughly spherical isolated Pb-enriched particles. In addition, a few irregularly shaped Cu-enriched particles were detected. Such particles were observed to increase with decreasing soil-particle size. The presence of small Pb particles or precipitates adhering to larger soil particles also was observed.