Geologic materials are an important source of airborne particulate matter less than 10 µm aerodynamic diameter (PM10), but the contribution of contaminated soil to concentrations of Pb and other trace elements in air has not been documented. To examine the potential significance of this mechanism, surface soil samples with a range of bulk soil Pb concentrations were obtained near five industrial facilities and along roadsides and were resuspended in a specially designed laboratory chamber. The concentration of Pb and other trace elements was measured in the bulk soil, soil size fractions, and in 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. Yields declined approximately linearly with increasing geometric mean particle size of the bulk soil. The resulting PM10 had average Pb concentrations as high as 2283 mg/kg for samples from a secondary Pb smelter. Pb was enriched in PM10 by 5.36 to 88.7 times compared with uncontaminated California soils. Total production of PM10 bound Pb from the soil samples varied between 0.012 and 1.2 mg Pb per kg of bulk soil. During a relatively large erosion event a contaminated site might contribute approximately 300 ng/m3 of PM10-bound Pb to air. Contribution of soil from contaminated sites to airborne element balances thus deserves consideration when constructing receptor models for source apportionment or attempting to control airborne Pb emissions. Thomas M. Young is an Associate Professor of Civil and Environmental Engineering at the University of California, Davis. His research examines interfacial processes in environmental systems, especially contaminant sorption to and desorption from soils, sediments and atmospheric particulate matter. Professor Young has been at U.C. Davis since receiving his Ph.D. in Environmental Engineering from the University of Michigan in 1996. Immediately before coming to Michigan, he worked in the United States Environmental Protection Agency's Office of Underground Storage Tanks in Washington, D.C. He has also received a Master's degree in Public Policy from U.C. Berkeley and a B.Ch.E. from Michigan State University.
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