Although airborne Pb levels have declined significantly in California over the past two decades, levels above 65µg/m3 are still occasionally observed. Suspension of contaminated soils by wind or mechanical abrasion is suspected as a possible source. To examine the potential significance of this mechanism, surface soil samples with a range of bulk soil Pb concentrations were obtained near eight industrial facilities and along roadsides and were resuspended in a specially designed laboratory chamber. The concentration of Pb was measured in the bulk soil, soil size fractions and in particles less than 10µm in aerodynamic diameter (PM10) generated during resuspension of soils and fractions. Average yields of PM10 from dry soils ranged from 0.169 to 0.869 mg PM10/g soil. The resulting PM10 had average Pb concentrations as high as 2,283 mg/kg for samples from a secondary Pb smelter. Concentrations of Pb in the PM10 were as much as 8 times higher than concentrations in the bulk soil. Total potential emissions of PM10 bound Pb from soil were between 0.012 and 1.2mg/kg. The results suggest that contaminated soil may be a locally important source of airborne Pb under a narrowly defined set of scenarios.
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