Spatial Variability in the Speciation of Lead (Pb) and Other Metals Across Urban Lawns Is Linked to Post-Deposition Weathering Reactions

The historical use of lead (Pb) poses ongoing health risks via exposure to contaminated urban soils. However, there is limited information about heterogeneity in Pb speciation and distribution at the house lot scale. This study determined highly spatially resolved Pb and other metal speciation along horizontal transects and vertical soil cores from three homes in the Akron, Ohio (USA) municipal. Solid phase characterization was coupled with a sequential extraction protocol to determine operationally defined speciation (exchangeable (MEX), reducible (MRED), oxidizable (MOX), and residual (MRES)). Lead and Zn were strongly correlated across all fractions (R2 = 0.92). Total extractable Pb and Zn were found in low weight percent concentrations nearest to the homes, and speciation was dominated by MEX and MRED. High Pb in the MEX fraction was correlated with the presence of Pb-bearing paint chips in the soil. Lead in the MEX fraction in soils near the homes decreased with increasing time due to exterior renovations coupled with increases in Pb and Zn in the MRED fraction. These results suggest that homes are the dominant source of Pb and Zn due to the weathering of exterior surfaces and highlight the acute risk of exposure to more labile Pb immediately following exterior renovations and damage to home exteriors in areas of older housing stock.