ISOTOPE AND CONCENTRATION CONSTRAINED SOURCES OF PB IN FUGITIVE DUSTS FROM UNSURFACED ROADS IN SOUTHEAST, MO

The high-precision isotopic composition of Pb in fugitive dust generated by a vehicle driving on 17 unsurfaced roads in Missouri was measured to identify potential sources of Pb in dust from unsurfaced mining area roads. Recently acquired data, with an emphasis on characterizing the background Pb component in soils, suggests Pb in road dust samples is principally derived from three distinct sources: 1) Background Soil, 2) Mine Tailings, and 3) Smelter Contaminated Soil. Background Soil Pb includes natural Pb derived from bedrock mixed with Pb derived from regional aerosol deposition. Mine Tailings Pb is represented by a single tailing pile sample within central proximity to all road dust samples. Smelter Contaminated Soil is defined by samples collected within close proximity to the secondary Pb recycling smelter in Boss, MO, that has a history of contamination. The sources of Pb in Mining Road Dust samples were evaluated using a plot of ²⁰⁷Pb/²⁰⁶Pb and 1/²⁰⁶Pb ppm of partially digested samples. The distribution of Pb in Mining Road Dust samples can be represented as a variable three component mixture with 14 to 33 % of Pb derived from Background Soil, 43 to 66% derived from Mine Tailings, and 20 to 34% derived from Smelter Contaminated Soil. Labile forms of Pb as determined through sequential extraction are currently being reevaluated using this new model to determine the value of this process for characterizing human and environmental health concerns.