LEAD (PB) SPECIATION AND DISTRIBUTION ACROSS URBAN HOME PROPERTIES

The historical use of lead (Pb) continues to pose a health risk via inhalation and/or ingestion of urban soils and dust. However, there is little information on Pb speciation at the local scale which is a better predictor of potential bioavailability compared to total Pb concentrations. This study investigates the speciation of Pb at the house yard-scale and the importance of deposition source(s). Samples were collected from three houses in the greater-Akron, Ohio (USA) area which were known to have used Pb-based paint in the past, in horizontal transects from the front and back of the houses and vertical cores adjacent to each house. Speciation was determined using sequential extraction to determine exchangeable (F1), reducible (F2), oxidizable (F3), and residual (F4) metal content. Solid-phase characterization was performed with XRD, XRF and SEM-EDS to determine bulk mineralogy and composition and grain-scale morphology and texture. Total extractable concentrations ([M]_T) of Pb were highest closest to the homes (21,720.2, 1,865.1, and 11,115.0 mg/kg, respectively) and decreased quickly towards the edge of the property near the road (100.5, 84.24 and 466.22 mg/kg, respectively). Most of the extractable Pb in the soil is present in the reducible fraction (avg. 51+/-13%) followed by the residual fraction (avg. 31+/-14%). The proportion of Pb in the reducible fraction decreases with an increase in the residual fraction with distance from the homes. Pearson statistical analysis indicates that Pb is correlated with Zn (0.96), Cd (0.92), and Cu (0.65). The [M]_T and maximum percentage of F1 decreased with increasing time since the last renovation of the houses for Pb and Zn. Ongoing XRD and XRF analyses will be incorporated into statistical analyses. Preliminary results indicate that potential remediation of soil can be focused on areas closest to residential buildings, but assessments of Pb speciation must be considered.