The chemical partitioning of lead and zinc is described in contaminated soils and underlying strata at historical lead smelting sites. Sections of soil-rock cores from eight sites of age 200 to c.1900 yr were analysed using a sequential extraction procedure. Of the total amount of lead and zinc present in soils, only a small proportion is in a readily mobile form. However, this proportion increases significantly as the pH falls below 5 and for lead reaches 37 in soils at Bole A. A high proportion of lead in soils appears to be associated with the carbonate and specifically adsorbed phase. It is suggested that this is partly due to the formation of cerussite (PbCO3) in soils contaminated with calcareous slag wastes. Lead present in the residual phase in contaminated soils may be related to the presence of the element in silicate slag particles. Rapid migration of lead to a depth of 5.6 m in sandstone at Bole A was related to its high solubility in the acidic soils and rock at this site. Comparable migration at Bole C proceeds by a different mechanism, possibly with lead in association with Fe-Mn oxides and slag particles. In clay infill in fractured sandstone at Bole A, anthropogenic lead present at a depth of 4.4 m was extracted predominantly in the fraction representing Fe-Mn oxides. References: 30
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