In many urban areas, elevated soil lead (Pb) concentrations are indicators of community-level Pb exposure. Here, we examine the spatial distribution and speciation of legacy soil Pb contamination in East Chicago, Ind., an industrial center with a wide range of Pb sources including a former lead smelter. In situ X-ray fluorescence spectroscopy (n = 358) revealed widespread soil Pb contamination above the Environmental Protection Agency regulatory limit for soils. This soil contamination was heterogenous across all neighborhoods, and mostly uncorrelated with distance from the former smelting site. Soil Pb levels increased with decreasing median household income in East Chicago's nine neighborhoods (r = -0.73, p = 0.03). Extended X-ray absorption fine structure spectroscopy (n = 44) indicated that the soil Pb was primarily adsorbed to iron and manganese oxides or humic acids, and as Pb hydroxycarbonate regardless of contamination levels. Crystalline insoluble forms of Pb, like pyromorphite, were not detected in significant concentrations. Thus, the unique chemical forms of potential Pb sources to soil, such as paint, ore and slag are not persistent and instead are extensively repartitioned into acid-soluble forms of Pb with greater bioavailability. These findings have implications for remediation efforts and human health as blood Pb levels in this community are significantly elevated.
Keywords: EXAFS; Environmental Health; Heavy metals; Metal speciation; Soil contamination.
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