Weathering of Pb-Based Paint Chips and Other Metal Inputs in Residential Soil and Potential Bioaccessibility at the Decadal Time Scale

Lead (Pb)-based paints and other metal-bearing phases sourced from home exteriors can be added to adjacent soils, which break down over time, altering potential bioaccessibility. However, data on how particle size and morphology influence metal bioaccessibility remains limited, which was investigated in this study by using a simulated gastric acid (GA) extraction and characterization at the sub-grain scale. Soil samples were collected along horizontal transects at ~1 m intervals from three homes within the Akron metropolis, OH (USA). Each home had Pb-based paint on its exterior before recent renovations (2, 11, and 25 years ago, respectively). Soils were fractionated into sand, silt, and clay–fine silt using sieving, sedimentation, and laser scattering techniques, and analyzed by ICP-OES, XRD, and SEM-EDS. Lead content peaked within 0–2 m from the homes and declined with distance (maxima: 14,583 mg/kg, 8503 mg/kg, 2393 mg/kg at Sites 1–3, respectively), and primarily in the clay-fine silt fraction. Physical speciation of Pb at each site was invariant across the transect, but the percent Pb in the clay–fine silt Pb increased from Site 1 to Site 2, then declined at Site 3, suggesting the loss of fine particles at Site 3. Across sites 1 to 3, the paint chip abundance and size decreased, and secondary Pb-bearing phases appeared as discrete grains and secondary coatings. A similar trend is exhibited by Cu, Cd, and Zn, over time and space. These results highlight the ongoing breakdown of paint and re-sequestration of metals, which may elevate exposure risk from fine particles after housing renovations.