Chemical Extractability of Pb in Field-Contaminated Soils: Implications for Estimating Total Pb

Lead (Pb) is frequently present in urban soils at concentrations of concern for human health. Regulations for this metal are based on total soil concentrations as determined by acid digestion, but a less expensive screening test for Pb would be useful in facilitating more thorough soil testing of urban areas if it could be shown to correlate strongly to total soil Pb. In this study, three extractants (0.1 M citrate, Modified Morgan, 1 M nitric acid) were evaluated for their ability to estimate the total Pb in contaminated soils. Nitric acid not only extracted a greater fraction of total soil Pb, but also produced the strongest correlation to total Pb and is concluded to be the superior extractant for a soil Pb screening test. As the spatial distribution of Pb was observed in selected soils to be highly heterogeneous on the micron scale, thorough soil homogenization prior to testing is recommended.